ATOM An Object-Based Formal Method for Real-time Systems 21

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关于Formal

关于Formal Charge与Partial Charge的区别要知道，⼀种不管formal charge还是partial charge都不是实际能够直接经过实验看到的原⼦性质。

实际上分⼦不是由线将点连起来的，即使是同⼀个分⼦，不⼀样价键表达⽅式下，该分⼦中的formal charge可能定位不同（⽐如去质⼦化的羧酸，可以表⽰为开库勒式与芳⾹式，两种⽅式的formal charge定位完全不同），不⼀样的partial charge计算⽅法也会给同⼀个分⼦中的同⼀个原⼦分配不⼀样的电荷，⽐如苯环可以表⽰为[cH+]1[cH-][cH+][cH-][cH+][cH-]1。

两者的区别⾸先, 出于⽤价键表征分⼦的需要，formal charge 为整数.与原⼦价、键级以及连接性⼀起定义分⼦.第⼆，partial charge为浮点数，⽤在计算化学与分⼦模拟中。

它的值⽤来表⽰电⼦分布或分⼦的波函数，⽤⼀套分布于各个原⼦的点电荷来近似地的模拟分⼦的静电场。

Partial chargePartial atomic chargesPartial charges are created due to the asymmetric distribution of electrons in chemical bonds. The resulting partial charges are a property only of zones within the distribution, and not the assemblage as a whole. For example, chemists often choose to look at a small space surrounding the nucleus of an atom: When an electrically neutral atom bonds chemically to another neutral atom that is more electronegative, its electrons are partially drawn away. This leaves the region about that atom's nucleus with a partial positive charge, and it creates a partial negative charge on the atom to which it is bonded.In such a situation, the distributed charges taken as a group always carries a whole number of elementary charge units. Yet one can point to zones within the assemblage where less than a full charge resides, such as the area around an atom's nucleus. This is possible in part because particles are not like mathematical points--which must be either inside a zone or outside it--but are smeared out by the uncertainty principle of quantum mechanics. Because of this smearing effect, if one defines a sufficiently small zone, a fundamental particle may be both partly inside and partly outside it.UsesPartial atomic charges are used in molecular mechanics force fields to compute the electrostatic interaction energy using Coulomb's law. They are also often used for a qualitative understanding of the structure and reactivity of molecules. Methods of determining partial atomic chargesDespite its usefulness, the concept of a partial atomic charge is somewhat arbitrary, because it depends on the method used to delimit between one atom and the next (in reality, atoms have no clear boundaries). As a consequence, there are many methods for estimating the partial charges. According to Cramer (2002), all methods can be classified in one of four classes: Class I charges are those that are not determined from quantum mechanics, but from some intuitive or arbitraryapproach. These approaches can be based on experimental data such as dipoles and electronegativities.Class II charges are derived from partitioning the molecular wave function using some arbitrary, orbital based scheme.Class III charges are based on a partitioning of a physical observable derived from the wave function, such as electron density.Class IV charges are derived from a semiempirical mapping of a precursor charge of type II or III to reproduceexperimentally determined observables such as dipole moments.The following is a detailed list of methods, partly based on Meister and Schwarz (1994).Population analysis of wavefunctionsMulliken population analysisCoulson's chargesNatural chargesCM1, CM2, CM3 charge modelsPartitioning of electron density distributionsBader charges (obtained from an atoms in molecules analysis)Density fitted atomic chargesHirshfeld chargesMaslen's corrected Bader chargesPolitzer's chargesVoronoi Deformation Density chargesCharges derived from density-dependent propertiesPartial derived chargesDipole chargesDipole derivative chargesCharges derived from electrostatic potentialChelpChelpG, Breneman modelMK, Merz-KollmanCharges derived from spectroscopic dataCharges from infrared intensitiesCharges from X-ray photoelectron spectroscopy (ESCA)Charges from X-ray emission spectroscopyCharges from X-ray absorption spectraCharges from ligand-field splittingsCharges from UV-vis intensities of transition metal complexesCharges from other spectroscopies, such as NMR, EPR, EQRCharges from other experimental dataCharges from bandgaps or dielectric constantsApparent charges from the piezoelectric effectCharges derived from adiabatic potential energy curvesElectronegativity-based chargesOther physicochemical data, such as equilibrium and reaction rate constants, thermochemistry, and liquiddensities.Formal chargesFormal chargeIn chemistry, a formal charge (FC) is the charge assigned to an atom in a molecule, assuming that electrons in a chemical bond are shared equally between atoms, regardless of relative electronegativity.The formal charge of any atom in a molecule can be calculated by the following equation:FC = V - N - B/2Where V is the number of valence electrons of the atom in isolation (atom in ground state); N is the number of non-bonding electrons on this atom in the molecule; and B is the total number of electrons shared in covalent bonds with other atoms in the molecule.When determining the correct Lewis structure (or predominant resonance structure) for a molecule, the structure is chosen such that the formal charge (without sign) on each of the atoms is minimized.Formal charge is a test to determine the efficiency of electron distribution of a molecule. This is significant when drawing structures.Examples:Carbon in methane: FC = 4 - 0 - (8÷2) = 0Nitrogen in NO2-: FC = 5 - 2 - (6÷2) = 0double bonded oxygen in NO2-: FC = 6 - 4 - (4÷2) = 0single bonded oxygen in NO2- FC = 6 - 6 - (2÷2) = -1An alternative method for assigning charge to an atom taking into account electronegativity is by oxidation number. Other related concepts are valence which counts number of electrons that an atom uses in bonding and coordination number, the number of atoms bonded to the atom of interest.Contents1 Examples2 Alternative method3 Formal Charge vs. Oxidation State4 References5 External linksExamplesAmmonium NH4+ is a cationic species. By using the vertical groups of the atoms on the periodic table it is possible to determine that each hydrogen contributes 1 electron, the nitrogen contributes 5 electrons, and the charge of +1 means that 1 electron is absent. The final total is 8 total electrons (1 × 4 + 5 − 1). Drawing the Lewis structure gives an sp3 (4 bonds) hybridized nitrogen atom surrounded by hydrogen. There are no lone pairs of electrons left. Thus, using the definition of formal charge, hydrogen has a formal charge of zero (1- (0 + ½ × 2)) and nitrogen has a formal charge of +1 (5− (0 + ½ × 8)). After adding up all the formal charges throughout the molecule the result is a total formal charge of +1, consistent with the charge of the molecule given in the first place.Note: The total formal charge in a molecule should be as close to zero as possible, with as few charges on the molecule as possibleExample: CO2 is a neutral molecule with 16 total valence electrons. There are three different ways to draw the Lewis structureCarbon single bonded to both oxygen atoms (carbon = +2, oxygens = -1 each, total formal charge = 0)Carbon single bonded to one oxygen and double bonded to another (carbon = +1, oxygen double = 0, oxygen single = −1, total formal charge = 0)Carbon double bonded to both oxygen atoms (carbon = 0, oxygens = 0, total formal charge =0)Even though all three structures gave us a total charge of zero, the final structure is the superior one because there are no charges in the molecule at all.Alternative methodAlthough the formula given above is correct, it is often unwieldy and inefficient to use. A much quicker and still accurate method is to do the following:Draw a circle around the atom for which the formal charge is requested (as with carbon dioxide, below)Count up the number of electrons in the atom's "circle." Since the circle cuts the covalent bond "in half," each covalent bond counts as one electron instead of two.Subtract the number of electrons in the circle from the group number of the element (the Roman numeral from the older system of group numbering, NOT the IUPAC 1-18 system) to determine the formal charge.The formal charges computed for the remaining atoms in this Lewis structure of carbon dioxide are shown below. Again, this method is just as accurate as the one cited above, but is much easier to use. It is important to keep in mind that formal charges are just that-formal, in the sense that this system is a formalism. Atoms in molecules do not have "signs around their necks" indicating their charge. The formal charge system is just a method to keep track of all of the valence electrons that each atom brings with it when the molecule is formed.Formal Charge vs. Oxidation StateThe concept of oxidation states constitutes a competing method to assess the distribution of electrons in molecules. If the formal charges and oxidation states of the atoms in carbon dioxide are compared, the following values are arrived at:The reason for the difference between these values is that formal charges and oxidation states represent fundamentally different ways of looking at the distribution of electrons amongst the atoms in the molecule. With formal charge, the electrons in each covalent bond are assumed to be split exactly evenly between the two atoms in the bond (hence the dividing by two in the method described above). The formal charge view of the CO2 molecule is essentially shown below:The covalent (sharing) aspect of the bonding is overemphasized in the use of formal charges, since in reality there is a higher electron density around the oxygen atoms due to their higher electronegativity compared to the carbon atom. This can be most effectively visualized in an electrostatic potential map.With the oxidation state formalism, the electrons in the bonds are "awarded" to the atom with the greater electronegativity. The oxidation state view of the CO2 molecule is shown below:Oxidation states overemphasize the ionic nature of the bonding; most chemists agree that the difference in electronegativity between carbon in oxygen is insufficient to regard the bonds as being ionic in nature.In reality, the distribution of electrons in the molecule lies somewhere between these two extremes. The inadequacy of the simple Lewis structure view of molecules led to the development of the more generally applicable and accurate valence bond theory of Slater, Pauling, et al., and thenceforth the molecular orbital theory developed by Mulliken and Hund.。

Cleaning of AlN and GaN surfaces

Cleaning of AlN and GaN surfacesS.W.King,J.P.Barnak,M.D.Bremser,K.M.Tracy,C.Ronning,R.F.Davis,a)and R.J.NemanichDepartment of Materials Science and Engineering,North Carolina State University,Raleigh,North Carolina27695͑Received15June1998;accepted for publication28July1998͒Successful ex situ and in situ cleaning procedures for AlN and GaN surfaces have been investigated and achieved.Exposure to HF and HCl solutions produced the lowest coverages of oxygen on AlN and GaN surfaces,respectively.However,signiﬁcant amounts of residual F and Cl were detected.These halogens tie up dangling bonds at the nitride surfaces hindering reoxidation.The desorption of F required temperaturesϾ850°C.Remote H plasma exposure was effective for removing halogens and hydrocarbons from the surfaces of both nitrides at450°C,but was not efﬁcient for oxide removal.Annealing GaN in NH3at700–800°C produced atomically clean as well as stoichiometric GaN surfaces.©1998American Institute of Physics.͓S0021-8979͑98͒02821-7͔I.INTRODUCTIONAluminium nitride͑AlN͒,gallium nitride͑GaN͒,and in-dium nitride͑InN͒are semiconductors with band gaps of6.2,3.5,and1.9eV,respectively.1–4The recent demonstration ofa blue laser based on an InGaN quantum well structure5 highlights many of the recent advances which have been made in thisﬁeld.GaN,AlN,and their alloys are also of interest for high-power,high-frequency,and high-temperature device applications.1,2The recent observation of a negative electron afﬁnity for AlN6and Al x Ga1Ϫx N7alloys also makes these candidate materials forﬁeld emitters in cold cathode electron devices.Surface cleaning processes are the foundations on which most semiconductor device fabrication steps are built.8–10 Experience gained in silicon and gallium arsenide technol-ogy has shown that surface cleaning has a signiﬁcant inﬂu-ence on epitaxial defects,metal contact resistance/stability, and overall device quality.Thus the criteria for surface cleanliness must consider the entire electrical,structural,and physical state of the surface.This includes removal of native oxides,organic contaminants,metallic impurities,particulate contaminants,adsorbed molecules,and residual species.11–14 Studies concerning the cleaning of Si and GaAs surfaces have investigated many ex situ and in situ processes includ-ing wet chemical͑see,e.g.,Refs.8–10,14–16͒,UV/O3 oxidation,17–20thermal desorption,21and chemical beam,22,23 and atomic H cleaning.24,25There have been fewer investi-gations of methods to obtain clean AlN26–31and GaN32–52 surfaces.In theﬁrst surface cleaning study of GaN,Hedman and Martensson32used x-ray photoelectron spectroscopy͑XPS͒to examine single-crystal GaNﬁlms grown via halide vapor phase epitaxy͑HVPE͒which have been etched in H3PO4at 100°C and annealed in situ at300°C.The in situ anneal removed some oxygen and carbon contaminants;however,it was incomplete at this temperature.Subsequent investiga-tions of surface cleaning processes for GaN have only re-cently been conducted onﬁlms grown via organometallic vapor phase epitaxy͑OMVPE͒on sapphire or6H-SiC substrates.32–52Hunt et al.33investigated the efﬁcacy of the combination of sputtering with Arϩ,Xeϩ,or N2ϩions followed by thermal desorption/annealing as a cleaning procedure.Prior to pro-cessing,they observed monolayer coverages of oxygen and carbon contaminants by Auger electron spectroscopy͑AES͒with corresponding N/Ga ratios of0.47–0.57and a diffuse (1ϫ1)hexagonal reﬂection high-energy electron diffraction ͑RHEED͒pattern.Sputtering with5keV Arϩor Xeϩions resulted in an incomplete reduction of carbon and oxygen contaminants,and a simultaneous reduction in the nitrogen concentration to a N/Ga ratio of0.25.When the sputtered surfaces were annealed in UHV at500–600°C,a minor in-crease in the nitrogen surface concentration(N/Gaϭ0.5)and a disordered RHEED pattern were observed.These results suggested that nitrogen was preferentially removed from the surface by the sputtering process.This was conﬁrmed by Ma et al.34For GaN surfaces sputtered with5keV Nϩions, however,the AES results of Hunt et al.33showed only a small decrease of the nitrogen content(N/Gaϭ0.43).After annealing at500°C,the N/Ga ratio increased to0.8,and a well-deﬁned hexagonal(1ϫ1)RHEED pattern developed.Khan et al.35obtained atomically clean metalorganic chemical vapor deposition͑MOCVD͒GaN͑0001͒surfaces in a molecular beam epitaxy͑MBE͒system via either annealing in an evaporatedﬂux of Ga at600–900°C or byﬂashing off several monolayers of Ga at900°C which had been previ-ously deposited at room temperature.In situ Auger electron spectroscopy͑AES͒analysis showed the O KLL peak inten-sity to be2%of the N KLL signal while the O contamination was close to the AES sensitivity limit.Low-energy electron diffraction͑LEED͒of these surfaces displayed only unrecon-structed(1ϫ1)diffraction patterns.Kahn et al.35concluded, based on the AES ratios,that GaN samples prepared in this fashion were N terminated.a͒Electronic mail:ROBERT–DAVIS@JOURNAL OF APPLIED PHYSICS VOLUME84,NUMBER91NOVEMBER199852480021-8979/98/84(9)/5248/13/$15.00©1998American Institute of PhysicsThe technique of Kahn has since been used by Bermu-dez et al.to prepare clean GaN surfaces to study the inter-faces and interaction of GaN with Ni,36Al,37and O2.38In the latter study,Bermudez observed via XPS that for clean GaN surfaces the valence band maximum͑VBM͒lies onlyϷ2.4 eV below the surface Fermi level indicatingϷ0.9eV of upward band bending for surfaces prepared in this fashion. This has been additionally observed by King et al.39for pris-tine high quality GaN surfaces grown and analyzed in an UHV environment.Bermudez could not identify the exact origin of the surface state responsible for pinning the surface Fermi level;however,he did show that exposure of the clean GaN surface to O2decreased the band bending by0.15eV. Bermudez also found that surfaces prepared only by wet chemical cleaning in1:10NH4OH:H2O showed only a0.4Ϯ0.2eV upward band bending.A recent study by Prabhaka-ran et al.40has indicated that this etch predominantly re-moves gallium oxides(Ga2O3)from the GaN surface.Bermudez38additionally investigated the combination of N2ϩsputtering followed by in situ annealing at900°C.This technique was determined to be equivalent to the Gaﬂux technique.Surfaces prepared by N2ϩsputtering showed both the same sharp(1ϫ1)LEED patterns and theϷ0.9eV of upward surface band bending as the surface cleaned in the Gaﬂux.The latter is in sharp contrast with the results of Hunt et al.33which showed essentially no band bending for N2ϩsputtered surfaces.Bermudez has also studied the inter-action of XeF2with nitrogen ion sputter cleaned GaN surfaces.41He observed that XeF2exposure resulted in an almost complete relaxation of the band bending in compari-son to the slight0.15eV reduction for O2exposed surfaces.Nitrogen ion sputtering has also been used by Sung et al.42to examine the polarity of GaNﬁlms grown on sap-phire.Their time ofﬂight scattering and recoiling spectrom-etry͑TOF-SARS͒and classical ion trajectory simulations in-dicate that(0001)GaN/Al2O3surfaces prepared in this fashion are nitrogen terminated with Ga atoms comprising the second layer.Their results also indicated that the surface is bulk terminated with no detectable reconstruction or relax-ation within the uncertainty of their measurements and that the bulk termination is stabilized byϷ3/4ML of hydrogen atoms which terminate the outermost N atoms.This conclu-sion is in agreement with recent theoretical calculations by Rapcewicz et al.43which have indicated that a(1ϫ1)bulk surface termination with3/4monolayer͑ML͒hydrogen is energetically more stable than any of the several(2ϫ2)re-constructions that they examined.This is in contrast to the fact that(2ϫ2)reconstructions are consistently observed using RHEED during MBE growth of high quality GaN ﬁlms;whereas(1ϫ1)reconstructions are typically associ-ated with poor growth conditions.44–46Theﬁndings of Sung et al.42are also contrary to those of both Ponce et al.47and Daudin et al.48whose convergent beam electron diffraction ͑CBED͒and ion channeling diffraction techniques showed that smooth MOCVD GaNﬁlms grown on sapphire are Ga terminated,whereas rough/pyramidal GaNﬁlms are N termi-nated.Nitrogen ion sputtering and900°C annealing has also been used by Dhesi et al.49to examine the bulk and surface valence band electronic structure of GaN surfaces usingangle-resolved photoemission spectroscopy͑ARP͒.Theirstudies of this surface showedϷ0.9eV of upward bandbending and the existence of a nondispersive feature near theVBM which they attributed to a surface state.A similar non-dispersive state has also been reported from the theoreticalcalculations of Rapcewicz and appears to be related to aﬁlled dangling bond state for a nitrogen surface atom whichis not bonded to an adsorbed hydrogen atom.43A more practical approach to surface cleaning was takenby Ishikawa et al.50They investigated the inﬂuence of wetchemical treatments with HF solutions,Nϩ/Arϩion sputter-ing and annealing on the electrical properties of p-type GaN/metal interfaces.Though their XPS studies showed that awet chemical treatment with buffered(HF2NH4)HF reducedthe O1s intensity by60%for the GaN surface,their electri-cal measurements showed only a slight improvement in cur-rent injection for Ni/GaN contacts.Their XPS studiesshowed a large reduction of C and O contaminants followingthe sputter cleaning͑no annealing͒,but I/V measurementsshowed only decreased current densities for the same con-tacts.This was attributed to the generation of a large numberof surface defects by the sputtering process.Improved con-tact resistances were obtained by annealing BHF cleanedGaN/Ni interfaces at400–500°C.High-resolution transmis-sion electron microscopy͑HRTEM͒studies of the GaN/Niinterfaces with no BHF treatment or annealing showed thepresence of aϷ2nm amorphous layer between the Ni andGaN which was attributed to a contamination layer.HRTEMof GaN/Ni interfaces prepared after annealing of the GaN at400°C did not show this layer.Smith et al.51investigated cleaning of GaN surfaces us-ing HF and HCl wet chemical processes followed by in situthermal desorption.It was found that HCl:DI wet chemicalprocesses produced the lowest coverages of oxygen and car-bon contaminants,but HF wet chemistries combined withmethanol resulted in GaN surfaces which were more efﬁcientfor in situ thermal desorption of carbon and oxygen.51How-ever,complete thermal desorption of all contaminants wasnot achieved at temperatures below900°C.Recent scanningtunneling microscope͑STM͒images obtained by Packardet al.52from GaN surfaces prepared by annealing at900°Cshowed that these surfaces are highly defective exhibitingnumerous arrangements of ordered N-surface vacancies.Theobservation of a large amount of nitrogen surface vacanciesalso indicates that some type of activated nitrogen must alsobe involved to prohibit loss of nitrogen from the surface.These results clearly indicate that thermal desorption alone isnot capable of producing electronic grade atomically cleansurfaces and that more elaborate means must be used.In this study,we have investigated both ex situ and insitu cleaning of AlN and GaN surfaces using AES,XPS,UPS,LEED,and temperature programmed desorption ͑TPD͒.Oxidation via UV/O3process for ex situ carbon con-tamination removal and a variety of standard wet chemistriesand ex situ chemical vapor exposures for oxide removal wereinvestigated.Wet chemistries based on H2SO4and H3PO4solutions common in GaAs technology for chemical oxidegrowth were also investigated.14–16The in situ cleaning pro-cesses examined included thermal desorption,exposure to hydrogen plasmas and annealing inﬂuxes of Al,Ga,NH3, and SiH4.The use of GaN and In as a passivating/protective layer for AlN surfaces was additionally investigated.II.EXPERIMENTThe AlN samples were derived from͑i͒ﬁlms epitaxially grown on6H-SiC͑0001͒Si by͑a͒OMVPE53or͑b͒gas source-molecular beam epitaxy͑GSMBE͒,54or deposited via reactive ion sputtering on Si͑111͒and͑ii͒hot pressed poly-crystalline AlN wafers.The GaNﬁlms were epitaxially de-posited on AlN buffer layers grown on6H-SiC͑0001͒by OMVPE53and GSMBE.54All in situ studies were conducted in an integrated sur-face analysis and growth system previously described in Ref.55.The GSMBE system consisted of a UHV chamber hav-ing a base pressure of3ϫ10Ϫ10Torr,a residual gas analyzer ͑RGA͒and several gas dosers and Knudsen cells.The RGA was housed in a separate,differentially pumped cylindricalchamber which had a0.5cm diameter oriﬁce at the head ofthe RGA for TPD experiments.Heating proﬁles to1100°Cwere achieved using a tungstenﬁlament positioned near theback of the sample and mounted on a boron nitride disk.Athermocouple was employed to measure the temperature ofthe backside of the wafer.The actual surface/sample tem-peratures reported below were determined using an infraredpyrometer.The accuracy of the latter wasϮ25°C.Sourcematerials in the GSMBE included Al͑99.9999%͒,Ga ͑99.99999%͒,SiH4͑99.995%͒,and NH3͑99.9995%as-received and further puriﬁed via an in line metalorganic resin puriﬁer͒.CMOS grade acids and bases and high resistivity͑18.4M⍀͒de-ionized water were used in all ex situ wet chemicalcleaning processes.The wet chemical cleans investigatedincluded various mixtures of the following acids andbases:HCl,HF,NH4F,HNO3,H2SO4,H3PO4,H2O2,NH4OH,NaOH,KOH,RCA SC1and SC2͑1:1:5NH3OH:H2O2:H2O@85°C and1:1:5HCl:H2O2:H2O@85°C͒.Unless otherwise noted,AlN and GaN sampleswere rinsed in DI water and blown dry with N2after all wetchemical processes.The samples were subsequentlymounted on a molybdenum sample holder for loading intothe UHV system.The XPS and UPS experiments were performed in situ,without breaking vacuum,in a separate UHV chamber͑basepressureϭ2ϫ10Ϫ10Torr͒equipped with a dual anode͑Mg/Al͒x-ray source,a He I UV lamp,and a100mm hemispheri-cal electron energy analyzer͑VG CLAM II͒.All XPS mea-surements on AlN were obtained using Al K␣radiation (h␯ϭ1486.6eV);related spectra for GaN were acquired us-ing Mg K␣radiation(h␯ϭ1253.6eV).Calibration of the binding energy was achieved by periodically taking scans of Au4f7/2and Cu2p3/2from standard samples and corrected to83.98and932.67eV,respectively.28Sample charging was observed only in the case of polycrystalline bulk AlN wafers. This effect was corrected by assigning the C1s peak to a value of285.7eV;all other core levels͑O1s,Al2p,N1s, F1s͒were shifted accordingly.The value of285.7eV was based on the observation that adventitious carbon on thin AlN surfaces͑Ϸ30Å͒occurred at this energy.A combina-tion of Gaussian and Lorentzian curve shapes with a linear background was used toﬁt the obtained data.The AES spectra were obtained using a beam energy of 3keV,collected in the undifferentiated mode and numeri-cally differentiated.LEED pictures were obtained using an 80eV,1mA beam.The rf excited͑13.56MHz͒remote plasma cleaning sys-tem,which was connected to the same UHV transfer line, had a base pressure of4ϫ10Ϫ9Torr.The process gases ﬂowed through a quartz tube mounted at the top of the cham-ber.The samples were located40cm below the center of the rf coil.An in-line puriﬁer andﬁlter was used for the puriﬁ-cation of hydrogen and silane.Sample heating in the plasma system was achieved using a heater similar that one previ-ously described in the GSMBE system.The experimental system employed for ex situ UV/O3 exposures used to remove carbon contamination from AlN and GaN surfaces employed a high intensity Hg lamp posi-tionedϷ1cm from the samples.In some cases the UV/O3 box was purged with1L/s O2to increase the concentration of generated O3.Further details of this process have been described in Refs.56–59.III.RESULTSA.Ex situ cleaning of AlNFigure1͑a͒shows an AES spectrum of the surface of an as-received OMVPE AlN sample.Oxidation via UV/O3ex-posure was investigated initially for C removal.Both AES and XPS were used to examine an OMVPEﬁlm which had been previously cleaned in trichloroethylene,acetone,and methanol for5min in each solvent and then exposed to UV/O3for10min at room temperature.This treatment re-duced the intensity of the C KLL peak byϷ50%,as shown in Fig.1͑b͒.A similar decrease in the intensity of the C1s core level was observed in XPS.Longer UV/O3exposures of30 min–1h with or without a solvent preclean did not further appreciably decrease the surface C coverage.Figure1͑b͒also shows that the AlN surface was further oxidized by the UV/O3treatment.The XPS spectrum of the O1s corelevel FIG.1.AES survey spectra of OMVPE AlN͑a͒as-received,͑b͒solvent cleaned and20min UV/O3exposure,and͑c͒3min dip in10:1buffered HF.showed a broad peak which was deconvoluted into two peaks at 531.3and 533.0eV,as shown in Figs.2͑a ͒and 2͑b ͒.The reported binding energies of the O 1s core level from various forms of aluminum oxide have range from 530.7to 532.5eV;60–65the reported binding energies for the O 1s core level from various nitrate compounds range from 532.7to 533.6eV.65It is tempting to assign the O 1s peak at 531.3eV to Al–O bonding and the O 1s peak at 533.0eV to N–O bonding,but the second peak at 533.0eV could alter-natively be due to aluminum hydroxides.60–64The XPS stud-ies of various aluminum oxides and hydroxides ͑sapphire,gibbsite,bayerite,bauxite,boehmite,and diaspore ͒by Tsuchida and Takahashi,62have shown that the binding en-ergy of the O 1s core level of OH Ϫspecies ͑hydroxides ͒is typically 532.0–532.3eV while for O 2Ϫspecies it is typi-cally 530.7–531.5eV.Tsuchida and Takahashi 62were suc-cessful in deconvoluting the broad O 1s spectrum from boe-hmite ͓AlO ͑OH ͔͒and diaspore ͓AlO ͑OH ͔͒into two separate peaks located at 530.7and 532.2eV,respectively,which they attributed to O 2Ϫand OH Ϫspecies.Additionally,the binding energy of the O 1s core level for H 2O has been reported to be 533.3eV.65It seems,therefore,more likely that the native oxide and UV/O 3generated oxides on AlN surfaces may be composed primarily of both Al–O and AlO–OH states.The issue of N–O bonding versus AlO–OH bonding could be resolved more easily by the detection of chemically shifted Al 2p and N 1s core levels,but no chemi-cal shifts were observed in the XPS spectra.The AlN surface is reasonably inert and oxidation in a typical laboratory ambient was not observed to proceed rap-idly.Therefore,UV/O 3exposures were used to repeatedly grow a thin oxide layer with which to assess the efﬁcacy of wet chemical removal of this oxide.The 1:1HCl:DI,1:1NH 4OH:H 2O 2,RCA SC1and SC2solutions were observed to signiﬁcantly reduce the surface oxide.A comparison of the AES peak-to-peak height ͑pph ͒ratios for the various wet chemical cleans is provided in Table I.A 10:1buffered HF ͑7:1NH 4F:HF ͒process was observed to be most effective at removing the surface oxide,as shown in Fig.1͑c ͒.Close examination of this ﬁgure reveals that the Al LVV line shape changed from that typical of aluminum oxide to that of AlN after the 10:1BHF clean.51Figure 2͑c ͒also shows that the10:1BHF treatment reduced the integrated intensity of the higher binding energy (OH Ϫ)O 1s core level to about equal to that of the lower binding energy (O 2Ϫ)O 1s core level.This suggests that BHF primarily attacks hydroxide (OH Ϫ)species on AlN surfaces.Similar results were also obtained with both 10:1HF and 40%NH 4F experiments.Further examination of Table I shows that the BHF treat-ment produced AlN surfaces with the lowest carbon cover-ages for the wet chemistries examined.The RCA SC1clean produced surfaces with essentially the same carbon cover-ages as the BHF treatment but with correspondingly higher oxygen coverage.In contrast the RCA SC2clean produced surfaces with essentially the same oxygen coverage as the SC1clean but with higher carbon coverages.A small concentration of ﬂuorine was also detected in the AES spectra after the BHF clean,as shown in Fig.1͑c ͒.The presence of ﬂuorine is better illustrated in the XPS spec-trum of the F 1s region from a 30ÅGSMBE AlN ﬁlm after dipping in 10:1buffered HF ͑BHF ͒for 10min,as shown in Fig.3͑a ͒.This broad peak was deconvoluted into two lines at 686.8and 688.5eV.These lines were assigned to Al–F and N–F bonding based on previous reports of XPS from AlF 3–H 2O and NF 3.65–67The carbon contamination on the AlN surface was also studied by XPS.After an HF dip,most of the surface carbon was located at a binding energy of 285.8eV ͓full width at half maximum ͑FWHM ͒ϭ2.3eV ͒,which is typical of adventitious carbon and is indicative of a mixture of C–O and C–H bonding 65͓see Fig.4͑a ͔͒.FIG.2.XPS of the O 1s core level obtained from bulk AlN ͑a ͒as-received,͑b ͒solvent cleaned and 20min UV/O 3exposure,and ͑c ͒3min dip in 10:1buffered HF.TABLE I.O KLL /N KLL ,C KLL /N KLL ,and Al LLV /N KLL AES pph ratios from OMVPE AlN surfaces given various wet chemical treat-ments following a UV/O 3oxidation ͑uncorrected for differences in sensitiv-ity ͒.C/NO/N Al/N UV/O 30.27 2.570.6610:1BHF 0.220.120.241:1HCl:DI0.290.360.271:1NH 4OH:H 2O 20.320.580.27RCA SC10.200.210.30RCA SC20.330.210.30FIG.3.XPS of the F 1s core level from a 30ÅAlN GSMBE ﬁlm on ͑0001͒6H-SiC after ͑a ͒dipping in 10:1BHF,and annealing for 15min at ͑b ͒400°C,͑c ͒600°C,͑d ͒800°C,and ͑e ͒950°C.Other wet chemistries based on H 2SO 4,H 3PO 4,and NaOH,etc.were also investigated.Treatments in concen-trated H 2SO 4and H 3PO 4were observed to leave residual sulfate and phosphate on the surface which was related to difﬁculties in rinsing these viscous chemicals from the AlN surface.The H 2O 2:H 2SO 4͑Piranha ͒etch was observed to remove gross carbon contamination from AlN surfaces.Ex-posure to NaOH left traces of Na on the surface which were removed below the detection limits of XPS with an RCA clean.More dilute levels of H 3PO 4were moderately success-ful for oxide removal at room temperature;however,it was observed that when etching AlN in H 3PO 4at higher tempera-tures of 100–150°C,the surface roughness ͑rms ͒increased from as low as 20Åto as high as 200Å.B.In situ processing of AlNThe chemistry and thermal desorption of F,C,and O contaminants on AlN surfaces after HF processing was fur-ther examined using AES,XPS,and TPD.Figures 3͑b ͒–3͑e ͒show the F 1s core level spectra of the HF-etched AlN sur-face after subsequent in situ annealing at different tempera-tures.The two F 1s peaks became more distinguishable after annealing at 400°C ͑positions:686.7and 688.7eV ͒.The intensity of the higher binding energy line was reduced after annealing at 600°C and almost disappeared after annealing at 800°plete elimination of the low and high binding energy peak was not achieved until 950°C.The C 1s and O 1s core levels were also monitored.Figure 4shows the C 1s core level spectra as a function of annealing tempera-ture.A gradual decrease in intensity for the C 1s core level was observed over the temperature range investigated with complete removal of the adventitious carbon again occurring only after annealing at a temperature of 950°C.This is simi-lar to the dependence observed for ﬂuorine.The intensity of the O 1s peak initially decreased slightly after the 400and 600°C anneals,presumably due to desorption of water and CO.However,the O 1s intensity almost doubled after the 950°C anneal.We attribute this to the reaction of the AlN surface with water desorbing from the chamber during the heating.Temperature-dependent desorption ͑TPD ͒studies were performed on a polycrystalline AlN ﬁlm reactively sputtered on Si ͑111͒which had been subsequently dipped in 10:1BHF.Figure 5shows a strong desorption peak for m /e Ϫ16͑O ͒and 18(H 2O)at temperatures of Ͻ200°C.This is in agreement with the observed decrease in O 1s intensity in XPS.Another large TPD peak was detected for desorption of ﬂourine at m /e Ϫ19and 20͑F and HF ͒at 400°C,while a small peak for m /e Ϫ38(F 2)was detected at 500°C.This is also in agreement with the XPS data.Desorption features at 400–500°C for m /e Ϫ2,12,and 28were also detected and are related to desorption of H 2,C,and N 2or CO.Complete thermal desorption of O,C,and F contami-nants occurred only at elevated temperatures.As such in situ exposure to various different activated chemical species was investigated as a means of lowering the temperature to pro-duce atomically clean AlN surfaces.In a previous study,68we investigated remote H plasma cleaning of AlN.This tech-nique was extremely efﬁcient for removing C and F at tem-peratures as low as 400°C,however,only slight removal of oxygen was observed.Annealing in separate ﬂuxes of Al ͑0.1ML/s ͒,Ga ͑0.1ML/s ͒,and NH 3͑1–10sccm ͒was effec-tive for removing ﬂuorine and carbon at temperatures Ͻ800°C.None of these processes were effective in further removing oxygen.Exposure to silane ͑0.1–1sccm ͒at 1000°C was the only in situ process which removed appre-ciable oxygen from the AlN surfaces.However,the loss of oxygen was at the expense of some deposition of silicon onto the surface.A thin ͑Ͻ1Å͒In passivation has been successfully used to protect GaAs surfaces in air.It was subsequently ther-mally desorbed in vacuum.69As such,In was deposited on OMVPE and GSMBE AlN ﬁlms in situ immediately after growth.The In ﬁlms balled up instead of wetting the AlN surface.By contrast,complete surface coverage of the AlN with 20nm ﬁlms of GaN was achieved.Thermal desorption of the GaN occurred at Ϸ950°C and resulted in an essentially oxygen and carbon free surface,as shown in Figs.6and plete desorption of the GaN ﬁlm did not occur at this temperature as AES and XPS detected a persistent traceofFIG.4.XPS of the C 1s core level from a 30ÅAlN GSMBE ﬁlm on ͑0001͒6H-SiC after ͑a ͒dipping in 10:1BHF,and annealing for 15min at ͑b ͒400°C,͑c ͒600°C,͑d ͒800°C,and ͑e ͒950°C.FIG.5.Temperature programmed desorption ͑TPD ͒of m /e Ϫ͑a ͒18,͑b ͒20,and ͑c ͒38from a 10:1BHF dipped AlN ͑ramp:20°C/min ͒.Ga on the surface even after extended annealing at Ͼ1000°C,as shown in Fig.8.C.Ex situ cleaning of GaNFigure9displays XPS spectra of the C1s core levelfrom an OMVPE GaN surface after͑a͒solvent cleaning ͑trichloroethylene,acetone,and methanol͒followed by͑b͒UV/O3exposure.Only partial removal of the carbon con-taminants from the GaN surface by the UV/O3exposure wasachieved,similar to that for the AlN surfaces.As-receivedGaN and AlN surfaces had comparable levels of carbon con-taminants.The data of Fig.9also show that the UV/O3ex-posure shifts the peak energy of the C1s core level to ahigher binding energy͑285.3–285.8eV͒which is consistentwith oxidation of the carbon surface species.To determine if carbon removal could be enhanced byincreased oxidation of the GaN surface,the UV/O3box waspurged with1L/s of oxygen.It is anticipated that this pro-cedure will increase the concentration of ozone.A furtherdecrease in the surface carbon coverage was achieved;how-ever,complete carbon removal was not realized.The oxygenpurge did enhance the oxidation rate of the GaN surface.This was observed by an almost complete disappearance ofthe N KLL and N1s peaks.The Ga3d and N1s core levels were also observed to broaden and shift to the higher bindingenergies of20.8and398.2eV,respectively.Binding ener-gies of19.6–21.0eV65have been reported for the Ga3dcore level from Ga2O3.The reported Ga3d core levels forGaN are19.2–20.3eV.37,65The chemical shifts for the N1score level for N–Ga͑397.2eV65͒and N–O x͑400–405eV65͒bonding are much larger.A large chemically shifted N1score level atϳ405eV has been also observed for oxidizedInN which was attributed to NO and NO2species.70Sincesuch a large shift of the N1s core level was not observed inour XPS data,it appears that the oxide is composed mostlyof Ga bonded to oxygen͑Ga–O͒.No diffraction patternswere detected from this surface using LEED,which indicatesthat the O3generated oxide is likely to be amorphous.As shown in Fig.10͑a͒,only a single broad O1s corelevel(FWHMϭ3.1eV)centered at532.4–532.7eV couldbe detected from GaN surfaces after solvent cleaning andprior to the UV/O3exposure.However,after a24h UV/O3exposure,the O1s core level spectrum showed the develop-ment of a second O1s peak at531.5eV,possibly due to theformation of stoichiometric Ga2O3(O1sϭ530.8eV).65Thus,the oxides formed on UV/O3treated GaN surfaces arealso very likely composed mostly of O2Ϫand OHϪspecies.This result is similar to that for AlN surfaces͑Sec.III A͒. FIG.7.XPS of C1s core level from200ÅGaN capping layer on͑0001͒AlN buffer layer,͑a͒as-received,͑b͒after annealing at500°C,͑c͒750°C,͑d͒950°C,and͑e͒Ͼ1000°C.FIG.8.XPS of Ga2p3/2core level from200ÅGaN capping layer on͑0001͒AlN buffer layer,͑a͒as-received,͑b͒after annealing at500°C,͑c͒750°C,͑d͒950°C,and͑e͒Ͼ1000°C.FIG.9.XPS of C1s core level from͑0001͒OMVPE GaN after͑a͒ultra-soniﬁcation in trichloroethylene,acetone,and methanol,and͑b͒UV/O3exposure.FIG.6.XPS of O1s core level from200ÅGaN capping layer on͑0001͒AlN buffer layer,͑a͒as-received,͑b͒after annealing at500°C,͑c͒750°C,͑d͒950°C,and͑e͒Ͼ1000°C.。

博士研究生英语综合教程第二版

新编研究生英语系列教程博士研究生英语综合教程（第二版/教师用书）北京市研究生英语教学研究会主编陈大明徐汝舟副主编刘宁王焱华许建平编者赵宏凌邹映辉杨凤珍来鲁宁张剑柳君丽曹莉郑辉中国人民大学出版社KEY TO THE EXERCISESUnit One ScienceText 1 Can We Really Understand Matter?I. Vocabulary1. A2. B3. A4. C5. D6. B7. B8. CII. Definition1. A priority2. Momentum3. An implication4. Polarization5. the distance that light travels in a year, about 5.88 trillion miles or 9.46 trillion km.6. a contradictory or absurd statement that expresses a possible truth7. a device that speeds up charged elementary particles or ions to high energiesIII. Mosaic1. The stress: (Omitted)Pronunciation rule: An English word ended with–tion or –sion has its stress on the last syllable but one.2. molecule3. A4. B5. C6. B7. A8. AIV. TranslationA.(Refer to the relevant part of the Chinese translation)B.In September 1995, anti-hydrogen atom—an anti-matter atom—was successfullydeveloped in European Particle Physics Laboratory in Switzerland. After the startling news spread out, scientists in the West who were indulged in the research of anti-matter were greatly excited. While they were attempting to produce and store anti-matter as the energy for spacecraft, they raised a new question: Many of the mysterious nuclear explosions in the recent one hundred years are connected with anti-matter. That is to say, these hard-to-explain explosions are tricks played by anti-mat ter. They are the “destruction”phenomenon caused by the impact between matter and anti-matter.V. GroupingA.Uncertainty:what if, illusory, indescribable, puzzle, speculation, seemingly, in some mysterious wayB.Contrast:more daunting, the hardest of hard sciences, do little to discourage, from afar, close scrutiny, work amazingly wellC. Applications of Quantum mechanics:the momentum of a charging elephant, building improved gyroscopes1. probabilities2. illusory3. discourage4. scrutinyVI. Topics for Discussion and Writing(Omitted)WRITING•STRATEGY•DEFINITIONI. Complete the following definitions with the help of dictionaries.1. To bribe means to influence the behavior or judgment of others (usually in positions ofpower) unfairly or illegally by offering them favors or gifts.2. Gravity is defined as the natural force by which objects are attracted to each other,especially that by which a large mass pulls a smaller one to it.3. The millennium bug refers to the computer glitch that arises from an inability of thesoftware to deal correctly with dates of January 2000 or later.4. Globalization is understood as the development so as to make possible internationalinfluence or operation.II. Write a one-paragraph definition of the following words.1. hypothesisA hypothesis is an idea which is suggested as a possible way of explaining facts,proving an argument, etc. Through experiments, the hypothesis is either accepted as true (possibly with improvements) or cast off.2. scienceScience is defined as the intellectual and practical activity encompassing the systematic study of the structure and behavior of the physical and natural world through observation and experiment.3. superstitionSuperstition refers to a belief which is not based on reason or fact but on old ideas about luck, magic, etc. For example, it is a common superstition that black cats are unlucky.4. pessimismPessimism is a tendency to give more attention to the bad side of a situation or to expect the worst possible result. A person with pessimism is a pessimist who thinks that whatever happens is bad.5. individualismIndividualism is the idea that the rights and freedom of the individual are the most important rights in a society. It has a bad sense in that little attention is paid to the rights of the collective or a good one in that independence is emphasized rather than dependence on others.Text 2 Physics Awaits New Options as Standard Model IdlesI. Vocabulary1. C2. A3. B4. A5. C6. D7. D8. BII. Definition1. A refrain2. A spark3. A jingle4. Symmetry5. develops or studies theories or ideas about a particular subject.6. studies the origin and nature of the universe.7. studies the stars and planets using scientific equipment including telescopes.III. Mosaic1. gravity2. anti-/opposite3. D4. B5. A6. A7. B8.AIV. TranslationA.(Refer to the relevant part of the Chinese translation)B.The Standard Model of particle physics is an unfinished poem. Most of the pieces are there,and even unfinished, it is arguably the most brilliant opus in the literature of physics. With great precision, it describes all known matter – all the subatomic particles such as quarks and leptons –as well as the forces by which those particles interact with one another.These forces are electromagnetism, which describes how charged objects feel each other’s influence: the weak force, which explains how particles can change their identities, and the strong force, which describes how quarks stick together to form protons and other composite particles. But as lovely as the Standard Model’s description is, it is in pieces, and some of those pieces – those that describe gravity – are missing. It is a few shards of beauty that hint at something greater, like a few lines of Sappho on a fragment of papyrus. V. GroupingA.Particle physics:supersymmetry, equation, superpartners, stringB.Strangeness:bizarre, beyond the ken ofC.Antonyms:gravity–antigravity1. novelty2. revelatory3. Symmetry4. gravityVII. Topics for Discussion and Writing(Omitted)WRITING • STRATEGY• EXEMPLIFICATION AN D ILLUSTRATION(Omitted)Text 3 Supporting ScienceI. Vocabulary1. D2. C3. A4. C5. C6. A7. B8. A9. C 10. D 11. B 12. AII. Definition1. A portfolio2. A vista3. Cryptography4. Paleontology5. a business or an undertaking that has recently begun operation6. a group of people having common interests7. a person with senior managerial responsibility in a business organizationIII. Rhetoric1. pouring money into2. column3. unbridled4. twilight5. blossomed intoIV. Mosaic1. phenomenon criterion datum medium(because these words originated from Latin and retain their Latin plural form)2. A3. A4. B5. B6. B7. C8. BV. TranslationA.(Refer to the relevant part of the Chinese translation)B. The five scientists who won the 1996 Nobel Prize point out that the present prosperityand development are based on the fruits of basic scientific research and the negligence of basic scientific research will threaten human development of the 21st century.EU countries noticed that one of their weaknesses is “insufficient investment in research and development.” Korea and Singapore do not hesitate to pour money into research and development. The developed countries in the West have used most of the scientific and technological development resources for the research and development of new and high technology. This has become an obvious trend at present. It is evident from the experiences of various countries that new and high technology can create and form new industries, open up and set up new markets. The innovation of traditional industries with new and high technology is a key method to strengthen the competitive competency of an enterprise.VI. Grouping:A.Negligence of basic research:corporate breakups, cut back on research, ignore it, subject to a protracted dissection and review, second-guessing, dropped dramatically, subjected to a scrutiny, skirling our supportB.Significant examples of basic research:computing, biotechnology, the Internet, number theory, complex analysis, coding theory, cryptography, dinosaur paleontology, genetics research)C.Ways to intensify arguments:moved support for science from a “want to have” squarely into the “need to have”column1. resounding2. second-guessing3. downsized4. subjectedVII. Topics for Discussion and Writing(Omitted)WRITING • STRATEGY • COMPARISON, CONTRAST, AND ANALOGY (Omitted)Text 4 Why Must Scientists Become More Ethically Sensitive Than They Used to Be?I. Vocabulary1. B2. B3. A4. C5. B6. D7. D8. A9. D 10. B 11. B 12. DII. Definition1. A constraint2. Algorithm3. A prerequisite4. Ethics5. an important topic or problem for debate or discussion6. a person’s principles or standards of behaviour; one’s judgement of what is important inlife.7. a formal plan put forward for consideration to carry out a projectIII. Rhetoric1. brushed under the carpet2. smell3. hands and brains4. battle front5. module . . . moduleIV. Mosaic1. /z/ /s/ /s/ /z/ /s//s/ /iz/ /z/ /s/ /z//iz/ /z/ /s/ /z/ /z//z/ /s/ /s/ /z/ /z//s/ after voiceless consonants/z/ after voiced consonants/iz/ after a word ended with –es2. B3. D4. A5. D6. A7. CV. TranslationA.(Refer to the relevant part of the Chinese translation)B. Scientists and medical ethicists advocate the prohibition of human cloning as a way toproduce life. They all agree that human cloning exerts severe threats on human dignity.Social critics point out that cloned children will lack personality and noumenon. G. Annas, professor of health laws in Boston university, points out that “human cloning should be banned because it may fundamentally alter the definition of ourselves.”VI. Grouping:A.The change of attitudes towards ethical consideration:occupy media slots and Sunday supplements, latest battle front, can no longer be swept aside, more sensitiveB.Academic science:a worldwide institutional web, peer review, respect for priority of discovery,comprehensive citation of the literature, meritocratic preferment, smuggle ethical considerations from private life, from politics, from religion, from sheer humanitariansympathyC.Industrial science:intimately involved in the business of daily lifeD.Post-academic science:a succession of “projects”, compound moral risks with financial risks, largely the work ofteams of scientists1. individualistic2. energized3. comprehensive4. heterogeneousVII. Topics for Discussion and Writing(Omitted)WRITING • STRATEGY • CAUSE AND EFFECT(Omitted)Text 5 Beauty, Charm, and Strangeness: Science as MetaphorI. Vocabulary1. B2. A3. C4. B5. C6. B7. A8. B9. A 10. CII. Rhetoric1. pitch2. landscape3. unblinking4. yawn5. wringsIII. Mosaic1.physical poetic political scientific optical atomic2. (Omitted)3. B4. B5. A6. C7. DIV. TranslationA.(Refer to the relevant part of the Chinese translation)B. There are only two forms of human spiritual creation: science and poetry. The formergives us convenience; and the latter gives us comfort. In more common words, the former enables us to have food to eat when we are hungry; and the latter makes us aware that eating is something more than eating, and it is very interesting as well. To have science without poetry, atomic bomb will be detonated; to have poetry without science, poets will starve to death.Scientists should not despise poets; and poets should not remain isolated from scientists.If the two fields conflict each other, human beings would be on the way to doom. In fact, the greatest scientists like Newton, Einstein and Mrs. Currie were all endowed with poetic spirit.I assert that in observing the apple falling to the ground, Newton not only discovered thegravity of the earth, he also wrote a beautiful poem.V. GroupingA.Human reason:guilty of hubris, cramped imagination, commonsense logic, an ignorant manB.Differences between art and science:different in their methods and in their ends, a scientific hypothesis can be proven, new combinations of old materials, transform the ordinary into extraordinary, a practical extension into technology, the sense of an endingC.Similarities between art and science:in their origin, quest to reveal the world1. indistinguishable2. transform3. poetic4. extension5. subdueVI. Topics for Discussion and Writing(Omitted)WRITING • STRATEGY • DIVISION AND CLASSIFICATIONI. Organize the following words into groups.People: physician; driver; boxer; mother; teacherSchools: school; college; institute; kindergarten; universityColors: brown; purple; violet; black; yellowPrepositions: along; toward; upon; without; intoVerbs:listen; read; write; hear; lookII. Complete the following lists.1. College students can be classified according to:A.academic achievementB.attitude toward politics, friendship, etc.C.sexD.heightE.place of originF.value of lifeG.major2. Transportation means can be classified according to:A.speedB.sizeeD.fuelfortF.historyG.water, land, or airIII. Write a paragraph of classification on the books which you like to read.(Omitted)Text 6 Is Science Evil?I. Vocabulary1. C2. A3. D4. B5. B6.A7. C8. C9. D 10. AII. Definition1. Canon2. Validity3. A premise4. Disillusionment5. the process of establishing the truth, accuracy, or correctness of something6. a mode of thinking based on guessing rather than on knowledgeIII. Mosaic1. 1) / / illusion dis-=not -ment=noun ending2) / / science pseudo-=false3) / / conscious -ness=noun ending4) / / question -able=adjective ending5) / / extenuate -ation=noun ending6) / / indict -ment=noun ending7) / / rebut -al=noun ending8) / / perpetrate -ion=noun ending9) / / problem -ic=adjective ending10) / / dissolute -ion=noun ending2. Para. 13: Only when scientific criticism is crippled by making particulars absolute can aclosed view of the world pretend to scientific validity –and then it is a falsevalidity.Para.14: Out of dissatisfaction with all the separate bits of knowledge is born the desire to unite all knowledge.Para. 15: Only superficially do the modern and the ancient atomic theories seem to fit into the same theoretical mold.1) Para. 13: Only + adverbial clause of time + inverted orderPara. 14: Prepositional phrase + inverted orderPara. 15: Only + adverb + inverted order2) Inverted order is used to emphasize.3. C4. B5. A6. CIV. TranslationA.(Refer to the relevant part of the Chinese translation)B. At present there exist two conflicting tendencies towards the development of science andtechnology. The opponents of science hold that the development of modern science has not brought blessings to human beings, instead it has brought human beings to the very edge of disaster and peril. On the other hand, the proponents of scientific and technological progress maintains that the crises facing human beings today—such as environmental pollution, ecological unbalance, natural resource exhaustion—are the natural consequences of the development of science, and the solution to which lies in the further development of science. Both of the above tendencies are reasonable in a sense with their respective one-sided view. If we view the development of modern science and technology from the point of view of our times and with dialectic viewpoints, we can find out that the problem facing modern science and technology is not how to understand the progress of modern science and technology, but how to find out the theoretical basis for the further development of science and technology in order to meet the needs of the times.V. GroupingA.Attitudes toward science:expect to be helped by science and only by science, the superstition of science, the hatred of science, the one great landmark on the road to truthB.Characteristics of science:powerful authority, solve all problems, thoroughly universalC.Scientific knowledge:a concrete totality, cannot supply us with the aims of life, cannot lead usD.Contrast between ancient and modern science:progress into the infinite, making particulars absolute, not as an end in itself but as a tool of inquiry1. corruption2. totality3. inquiry4. superstition5. landmarkVI. Topics for Discussion and Writing(Omitted)WRITING • STRATEGY • GENERALIZATION AND SPECIFICATIONWRITING • STRATEGY • COMBINATION OF WRITING STRATEGIES (Omitted)Unit Two EngineeringText 7 Engineers’ Dream of Practical Star FlightI. Vocabulary1. D2. C3. B4. D5. A6. C7.CII. Definition1. Annihilation2. A skeptic3. A cosmic ray4. Anti-matter5. A workshop6. the curved path in space that is followed by an object going around another larger object7. any one of the systems of millions or billions of stars, together with gas and dust, heldtogether by gravitational attractionIII. Mosaic1. 闭音节, 字母u 发/ / 的音，如A, C and D.2. (Omitted)3. (Omitted)4. C5. C6. B7. A8. BIV. TranslationA.(Refer to the relevant part of the Chinese translation)B. Human beings have long been attempting sending unmanned devices, called interstellarprobes, into the outer space to understand the changes of climates, geological structures and the living beings on the stars and planets out there. A probe is usually sent into the orbit of the earth by “riding” a spacecraft or carrier rockets. After its orbital adjustments are made, the rocket engine is ignited and the probe continues its journey to the orbit of the other star or planet. With the rocket engine broken off, the probe immediately spreads its solar-cell sails and antenna, controlling its posture with sensors. When convinced that it is in the orbit of the targeted star, the probe starts its propeller and flies to the preset destination.V. GroupingA.Astronomical phenomena:interstellar medium, a wind of particles, galaxy, reserves of comets, the Kuiper Belt,orbit, Pluto, the Oort Cloud, the bombardment photonB.Space equipment:interstellar probe, gravitational lens, chemical rocket, thruster, reflective sailC.To explore the universe:scoop, bend, sampleD.Challenges and solutions in interstellar flights:carry its own supply of propellant, matter-antimatter, nuclear power1. gravitational2. propulsion3. probed4. interstellarVI. Topics for Discussion and Writing(Omitted)WRITING • RHETORIC • SIMILE AND METAPHORI. Complete the following similes with the words given, using one word once only.1. as drunk as a ___ bear 11. as cool as ___ cucumber______2. as faithful as a ___ dog_____ 12. as white as ____ snow ________3. as greedy as ____Jew_____ 13. as cunning as a ____ fox__________4. as rich as _____ king_____ 14. to fight like a ____ _lion_________5. as naked as a ___ frog_____ 15. to act like a stupid __ ass_________6. as red as a _ _lobster_ 16. to spend money like __ water_______7. as beautiful as a _ butterfly__ 17. to eat like a _ wolf________8. as busy as a ____ bee______ 18. to sleep like a _____ log ______9. as firm as a ____ rock _____ 19. to swim like a ____ fish________10. as rigid as a ___stone____ 20. to tremble like a _____ _ leaf_________II. Explain the following metaphors.1. Creaking doors hang the longest.creaking door: anything or anybody in a bad condition2. I could hardly put up with his acid comment.acid comment: bitter remark.3. Her eyes were blazing as she stormed at me.blazing: filled with angerstormed: shouted; screamed4. She burnt with love, as straw with fire flames.burnt with love: extremely excited with love5. The talk about raising taxes was a red flag to many voters.a red flag: a danger signal (that might stop the support of many voters)6. The charcoal fire glowed and dimmed rhythmically to the strokes of bellows.glowed and dimmed: became bright and gloomy7. The city is a jungle where nobody is safe after the dark.a jungle: a disorderly place8. To me he is power—he is the primitive, the wild wolf, the striking rattlesnake, thestinging centipede.the primitive, the wild wolf, the striking rattlesnake, and the stinging centipede: the most terrifying creatureText 8 Blinded By The LightI. Vocabulary1. A2. C3. A4. C5. D6. A7. BII. Rhetoric1. riveted2. pack3. pours4. creepsIII. Mosaic1. 开音节发字母读音, 如A, B and C.2. (Omitted)3. (Omitted)4. C5. D6. D7. C8. AIV. TranslationA.(Refer to the relevant part of the Chinese translation)B. The energy released from nuclear fusion is much more than that from nuclear fission, andthe radioactivity given out from fusion is only one hundredth of that from fission. The major fuel used for nuclear fusion is hydrogen and its isotopes, deuterium and tritium, among which deuterium could be directly extracted from sea water. The energy of deuterium contained in one liter of sea water is equal to 300 liters of petroleum. In the ocean there are about 35,000 billion tons of deuterium, which could be used for more than one billion years. Compared to the fission energy, the fusion energy on the earth is nearly limitless.V. GroupingA. Nuclear-fusion:the doughnut-shaped hollow, reactor, the Tokamak Fusion reactor, fusion, generate, consumeB. Verbs related to nuclear-fusion reaction:ignite, release, stickC. Excitement and cool-down:not a few tears, The experiment is an important milestone, but fusion power is still along way . . . , But no one knows for sure whether…, Even then it will take decades of engineering before…1. nuclear fusion2. repel3. blastVI. Topics for Discussion and Writing(Omitted)W RITING • R HETORIC • METONYMY AND SYNECDOCHEI. Study the uses of metonymy in the following sentences and then put them into Chinese.1.The election benched him in the district court.他在这次竞选中当上了地区法官。

美国普通化学笔记5

ChemistryChapter 8∙In 1864, English chemists john newlands noticed that when the known elements were arranged in order of atomic mass, every eighth element hadsimilar properties. Newlands referred to this peculiar relationship as thelaw of octaves. Howe ver, this “law” turned out to be inadequate forelements beyond calcium, and newland’s work was not accepted by thescientific community.∙Representative elements are the elements in groups 1A through 7A, all of which have incompletely filled s or p subshells of the highest principalquantum number. With the exception of helium, the noble gases (thegroup 8A elements) all have a completely filled p subshell. The transitionmetals are the elements in groups 1B and 3B through 8B, which haveincompletely filled d subshells or readily produce cations withincompletely filled d subshells (these metals are sometimes referred to asthe d-blok transition elements). The group 2B elements are Zn, Cd, andHg, which are neither representative elements nor transition metals. Thelanthanides and actinides are sometimes called f-block transition elementsbecause they have incompletely filled f subshells∙The outer electrons of an atom, which are those involved in chemical bonding are often called the valence electrons. Having the same number ofvalence electrons accounts for similarities in chemical behavior among theelements within each of these groups.∙Ions, or atoms and ions, that have the same number of electrons and hence the same ground-state electron configuration are said to be isoelectronic.∙Atomic radius of a metal is one-half the distance between the two-nuclei in two adjacent atoms. For elements that exist as diatomic molecules, theatomic radius is one-half the distance between the nuclei of the two atomsin a particular molecule.∙When looking at a periodic table:o The elements are increasing as in atomic radius as you go fromright to left, and from up to down. ****∙Ionic radius is the radius of a cation or an anion. Ionic radius affects the physical and chemical properties of an ionic compound.∙When a neutral atom is converted to an ion, we expect a change in size. If the atoms forms an anion, its size increases, because the nuclear chargeremains the same but the repulsion resulting from the additional electronenlarges the domain of the electron cloud. On the other hand, a cation issmaller than the neutral atom, because removing one or more electronsreduces electron-electron repulsion but the nuclear charge remains thesame, so the electron cloud shrinks.∙Focusing on isoelectronic cations, we see that the radii of tripostive ions (that is, ions that bear three positive charges) are smaller than those ofdipositive ions (that is, ions that bear two positive charges) which in turnare smaller than unipositve ions (that is, ions that bear one positive charge).∙Ionization energy – is the minimum energy required to remove an electron from a gaseous atom in its ground state. The magnitude of ionizationenergy is a measure of the effort required to force an atom to give up anelectron, or of how “tightly” the electron is held in the atom., the higherthe ionization energy the more difficult it is to remove the electron.∙For a many-electron atom, the amount of energy required to remove the first electron, from the atom in its ground state:o Energy + X(g) -> X+(g) + e-o Is called the first ionization energy (I1). In this equation Xrepresent a gaseous atom of any element and e- is an electron.Unlike an atom in the condensed liquid and solid phases, an atomis the gaseous phase is virtually uninfluenced by its neighbors.o Energy + X+(g) -> X2+(g) + e- Second ionizationo Energy + X2+(g) -> X3+(g) + e- Third Ionization∙When a electron is removed from a neutral atom, the repulsion among the remains electrons decreases. Because the nuclear charge remains constant,more energy is needed to remove another electron from the positivelycharged ions. Thus for the same element ionization energies alwaysincrease in this order:o I1<I2<I3<….∙Another property that greatly influences the chemical behavior of atoms is their ability to accept one or more electrons. This ability is called electronaffinity, which is the negative of the energy change that occurs when anelectron is accepted by an atom of an element in the gaseous stateo X(g) + e- -> X-(g) deltaH = -XXXkJ▪If delta h has a positive value (ie. 390 kj/mol) means thatthe process is exothermic▪If delta h has a negative value, that means that the processis endothermic∙Another trend in chemical behavior of the representative elements is the diagonal relationship. Diagonal relationship refers to similarities that existbetween pairs of elements in different groups and period of the periodictable. Specifically the first three members of the second period (Li, Be andB) exhibit many similarities to the elements located diagonally belowthem in the periodic table.If you would like to further understand this chapter, I suggested reading the summary. Or if you would like to learn more about the individual group elements, then I suggest reading the last few pages of this chapter.Chapter 9∙Lewis dot symbol – consists of the symbol of an element and one dot for each valence electron in an atom of the element.∙Covalent bond – a bond in which two electrons are shared by two atoms.Covalent compounds are compounds that contain only covalent bonds.∙Lone pairs – pairs of valence electrons that are not involved in covalent bond formation (ie. F2)∙Lewis structures is a representation of covalent bonding in which shared electron pairs are shown either as lines or as pairs of dots between two atoms, and lone pairs are shown as pairs of dots on individual atoms. Only valence electrons are shown in a Lewis structure.∙Octet rule – an atom other than hydrogen tends to from bonds until it is surrounded by eight valence electrons. In other words, a covalent b ond forms when there are not enough electrons for each individual atom tohave a complete octet. By sharing electrons in a covalent bond, theindividual atoms can complete their octets. The requirement for hydrogen is that it attains the electron configuration of helium, or a total of twoelectrons.o The octet rule works mainly for elements in the second period of the periodic table.∙Atoms can form different types of covalent bonds. In a single bond – two atoms are held together by one electron pair. Many compounds are held together by multiple bonds, that is, bonds formed when two atoms shre two or more pairs of electrons. If two atoms share two pairs of electrons, the covalent bond is called a double bond.∙ A triple bond arises when two atoms share three pairs of electrons, (N2) ∙Bond length – is defined as the distance between the nuclei of two covalently bonded atoms in a molecule.∙The bond HF is called a polar covalent bond, or simply a polar bond, because the electrons spend more time in the vicinity of one atom than the other. The HF bond and other polar bonds can be though of as beingintermediate between a (nonpolar) covalent bond, in which the sharing of electrons is exactly equal, and an ionic bond, in which the transfer of the electron(s) is nearly complete.∙ A property that helps us distinguish a nonpolar covalent bond from a polar covalent bond is electronegativity, the ability of an atom to attract toward itself the electrons in a chemical bond. Elements with highelectronegativity have a greater tendency to attract electrons than doelements with low electronegativity.o Electronegativity is related to electron affinity and ionization energy.o Electronegativity is a relative concept, mea ign tha t an element’s ectronegativity can be measured only in relation theelectronegativity of other elements.o Linus Pauling devised a method for calculating relativeelectronegativities of most elements.∙There is no sharp distinction between a polar bond and an ionic bond, but the following rule is helpful in distinguishing between them. An ionicbond forms when the electronegativity difference between the twobonding atoms is 2.0 more. This rule applies to most but not all ioniccompounds. Sometimes chemists use the quantity percent ionic characterto describe the nature of a bond. A purely ionic bond would have 100percent ionic character, although no such bond is known, whereas anonpolar or purely covalent bond has 0 percent ionic character.∙Electronegativity and electron affinity are related but different concepts.Both indicate the tendency of an atom to attract electrons. However,electron affinity refers to an isolated atom’s attraction for an additionalelectron, whereas electronegativity signifies the ability of an atom in achemical bond (with another atom) to attract the shared electron.Furthermore, the electron affinity is an experimentally measurablequantity, whereas electronegativity is an estimated number that cannot be measured.∙An atom’s formal charge is the electrical charge difference between the valence electrons in an isolated atom and the number of electrons assigned to an atom in a lewis structure.∙To assign the number of electrons on an atom in a lewis structure, we proceed as:o All the ato m’s nonbonding electrons are assigned to the atomo We break the bond(s) between the atom and other atom(s) and assign half of the bonding electrons to the atom∙When you write formal charges, these rules are helpful:o For molecules, the sum of the formal charges must add up to zero because they are electrically neutral species.o For cations, the sum of the formal charges must equal the positive chargeo For anions, the sum of the formal charges must equal the negative charge∙Keep in mind, that formal charges do not represent actual charge separation within the molecule.∙Resonance structure – one of two or more lewis structures for a single molecule that cannot be represented accurately by only one lewis structure.The double-headed arrow indicates that the structures shown areresonance structures.∙The term resonance itself means the use of two or more lewis structures to represent a particular molecule.∙Exceptions to the octet rule:o The incomplete octet:▪In some compounds the number of electrons surround thecentral atom in a stable molecule is fewer than eight.▪Elements in group 3A, particularly boron and aluminum,also tend to form compounds in which they are surroundedby fewer than eight electrons.∙ A resonance structure with a double bond betweenB and F can be drawn that satisfies the octet rule forB.▪The B-N bond is different from the covalent bondsdiscussed so far in the sense that both electrons arecontributed by the N atom. A covalent bond in which oneof the atoms donated both electrons is called a coordinatecovalent bond. Although the properties of a coordinatecovalent bond do not differ from those of a normal covalentbond (because all electrons are alike no matter what theirsource), the distinction is useful for keeping tack of valenceelectrons and assigning formal charges)o Odd-Electron Molecules▪Some molecules contain an odd number of electrons.Among them are nitric oxide (NO) and nitrogen dioxide(NO2)▪Because we need an even number of electrons for completepairing (to reach eight) the octet rule clearly cannot besatisfied for all the atoms in any molecule that has an oddnumber of electronso The expanded octet:▪In a number of compounds there are more than eightvalence electrons around an atom. These expanded octetsare needed only for atoms of elements in and beyond thethird period of the periodic table.∙ A measure of the stability of a molecule is its bond energy, which is the enthalpy change required to break a particular bond in 1 mole of gaseousmolecules. (bond energies in solids and liquids are affected byneighboring molecules.)∙In many cases, it is possible to predict the approximate enthalpy ofreaction by using the average bond energies. Because energy is alwaysrequired to break chemical bonds and chemical bond formation is alwaysaccompanied by a release of energy, we can estimate the enthalpy of areaction by counting the total number of bonds broken and formed in thereaction and recording all the corresponding energy changes. The enthalpyof reaction in the gas phase is given by:o deltaH o = sigma(BE(reactants)) – sigma(BE(products))o where be stands for average bond energy and sigma is thesummation signTo further understand Bond energies, and Lewis dot structures and resonance I suggest taking a deeper look into the textbook.。

Contributions

A Proof Environment for Specifications
March th,

/ in a Nutshell
e Object Constraint Language ()
Textual extension of the Allows for annotating diagrams In the context of class–diagrams:
invariants preconditions postconditions
Practice:
A machine checked semantics for .
Achim D. Brucker ( Zurich)
A Proof Environment for Specifications
March th,

/ in a Nutshell
context Account inv: 0 <= id
Account balance:Integer id:Integer 1..* getId():Integer accounts getBalance():Integer deposit(a:Integer):Boolean withdraw(a:Integer):Boolean
Achim D. Brucker ( Zurich)
A Proof Environment for Specifications
March th,

/ in a Nutshell
The Object Constraint Language ()
e Object Constraint Language ()
Outline

化学成键英文版

Basic Chemical Bonding
9
Electron Density of a Polar Bond Li–H
Li → H dipole moment
Basic Chemical Bonding 10
Writing Lewis Dot Structures
Show all valence electrons. Each bond represents two electrons. All electrons are paired, usually (exceptions). Each atom acquires 8 valence electrons, usually (exceptions). Multiple bonds are needed sometimes. Show class how to write Lewis structure for CF4, (CX4, SiX4), NH3, H2O, HF C2H5OH, HC≡N, H3PO4, O=N=O
Basic Chemical Bonding
7
Periodic Table of Electronegativity
Basic Chemical Bonding
8
Covalent and Ionic Bonds
The ionicity of a bond depends on the difference in electronegativity. A difference of 1.7 is given as 50% ionic, and usually considered ionic. Analyze these
1
Looking Back at Chemical Bonding

最全编程常用英语词汇

最全编程常⽤英语词汇打开应⽤保存⾼清⼤图其实在国内，绝⼤部分⼯作并不真的要求你英语多好，编程也⼀样。

如果只是做到平均⽔准或者⽐较好，都未必要英语很熟。

但是⼀般我还是会建程序员们好好学英语，迈过这个坎，你会发现完全不⼀样的世界，你会明⽩以前这个困惑真的是……下⾯是编程常⽤的英语词汇，赶紧收藏吧。

按字母索引A英⽂译法 1 译法 2 译法 3a block of pointers ⼀块指针⼀组指针abbreviation 缩略语abstract 抽象的abstract syntax tree, AST 抽象语法树abstraction 抽象abstraction barrier 抽象屏障抽象阻碍abstraction of function calls 函数调⽤抽象access 访问存取access function 访问函数存取函数accumulator 累加器activate 激活ad hoc 专设adapter 适配器address 地址algebraic data type 代数数据类型algorithm 算法alias 别名allocate 分配配置alternative 备选amortized analysis 平摊分析anaphoric 指代annotation 注解anonymous function 匿名函数antecedent 前提前件先决条件append 追加拼接application 应⽤应⽤程序application framework 应⽤框架application program interface, API 应⽤程序编程接⼝application service provider, ASP 应⽤程序服务提供商applicative 应⽤序argument 参数⾃变量实际参数/实参arithmetic 算术array 数组artificial intelligence, AI ⼈⼯智能assemble 组合assembly 汇编assignment 赋值assignment operator 赋值操作符associated 关联的association list, alist 关联列表atom 原⼦atomic 原⼦的atomic value 原⼦型值attribute 属性特性augmented 扩充automatic memory management ⾃动内存管理automatically infer ⾃动推导autometa theory ⾃动机理论auxiliary 辅助B英⽂译法 1 译法 2 译法 3backquote 反引⽤backtrace 回溯backward compatible 向下兼容bandwidth 带宽base case 基本情形base class 基类Bayes' theorem 贝叶斯定理best viable function 最佳可⾏函式最佳可⾏函数Bezier curve 贝塞尔曲线bignum ⼤数binary operator ⼆元操作符binary search ⼆分查找⼆分搜索⼆叉搜索binary search tree ⼆叉搜索树binary tree ⼆叉树binding 绑定binding vector 绑定向量bit 位⽐特bit manipulation 位操作black box abstraction ⿊箱抽象block 块区块block structure 块结构区块结构block name 代码块名字Blub paradox Blub 困境body 体主体boilerplate 公式化样板bookkeeping 簿记boolean 布尔border 边框bottom-up design ⾃底向上的设计bottom-up programming ⾃底向上编程bound 边界bounds checking 边界检查box notation 箱⼦表⽰法brace 花括弧花括号bracket ⽅括弧⽅括号branch 分⽀跳转breadth-first ⼴度优先breadth-first search, BFS ⼴度优先搜索breakpoint 断点brevity 简洁buffer 缓冲区buffer overflow attack 缓冲区溢出攻击bug 臭⾍building 创建built-in 内置byte 字节bytecode 字节码C英⽂译法 1 译法 2 译法 3cache 缓存call 调⽤callback 回调CamelCase 驼峰式⼤⼩写candidate function 候选函数capture 捕捉case 分⽀character 字符checksum 校验和child class ⼦类choke point 滞塞点chunk 块circular definition 循环定义clarity 清晰class 类类别class declaration 类声明class library 类库client 客户客户端clipboard 剪贴板clone 克隆closed world assumption 封闭世界假定closure 闭包clutter 杂乱code 代码code bloat 代码膨胀collection 收集器复合类型column ⾏栏column-major order ⾏主序comma 逗号command-line 命令⾏command-line interface, CLI 命令⾏界⾯Common Lisp Object System, CLOS Common Lisp 对象系统Common Gateway Interface, CGI 通⽤⽹关接⼝compatible 兼容compilation 编译compilation parameter 编译参数compile 编译compile inline 内联编译compile time 编译期compiled form 编译后的形式compiler 编译器complex 复杂complexity 复杂度compliment 补集component 组件composability 可组合性composition 组合组合函数compound value 复合数据复合值compression 压缩computation 计算computer 计算机concatenation 串接concept 概念concrete 具体concurrency 并发concurrent 并发conditional 条件式conditional variable 条件变量configuration 配置connection 连接cons 构造cons cell 构元 cons 单元consequent 结果推论consistent ⼀致性constant 常量constraint 约束constraint programming 约束式编程container 容器content-based filtering 基于内容的过滤context 上下⽂语境环境continuation 延续性continuous integration, CI 持续集成control 控件cooperative multitasking 协作式多任务copy 拷贝corollary 推论coroutine 协程corruption 程序崩溃crash 崩溃create 创建crystallize 固化curly 括弧状的curried 柯⾥的currying 柯⾥化cursor 光标curvy 卷曲的cycle 周期D英⽂译法 1 译法 2 译法 3dangling pointer 迷途指针野指针Defense Advanced Research Projects Agency, DARPA 美国国防部⾼级研究计划局data 数据data structure 数据结构data type 数据类型data-driven 数据驱动database 数据库database schema 数据库模式datagram 数据报⽂dead lock 死锁debug 调试debugger 调试器debugging 调试declaration 声明declaration forms 声明形式declarative 声明式说明式declarative knowledge 声明式知识说明式知识declarative programming 声明式编程说明式编程declarativeness 可声明性declaring 声明deconstruction 解构deduction 推导推断default 缺省默认defer 推迟deficiency 缺陷不⾜define 定义definition 定义delegate 委托delegationdellocate 释放demarshal 散集deprecated 废弃depth-first 深度优先depth-first search, BFS 深度优先搜索derived 派⽣derived class 派⽣类design pattern 设计模式designator 指⽰符destructive 破坏性的destructive function 破坏性函数destructuring 解构device driver 硬件驱动程序dimensions 维度directive 指令directive 指⽰符directory ⽬录disk 盘dispatch 分派派发distributed computing 分布式计算DLL hell DLL 地狱document ⽂档dotted list 点状列表dotted-pair notation 带点尾部表⽰法带点尾部记法duplicate 复本dynamic binding 动态绑定dynamic extent 动态范围dynamic languages 动态语⾔dynamic scope 动态作⽤域dynamic type 动态类型E英⽂译法 1 译法 2 译法 3effect 效果efficiency 效率efficient ⾼效elaborateelucidatingembedded language 嵌⼊式语⾔emulate 仿真encapsulation 封装enum 枚举enumeration type 枚举类型enumrators 枚举器environment 环境equal 相等equality 相等性equation ⽅程equivalence 等价性error message 错误信息error-checking 错误检查escaped 逃脱溢出escape character 转义字符evaluate 求值评估evaluation 求值event 事件event driven 事件驱动exception 异常exception handling 异常处理exception specification 异常规范exit 退出expendable 可扩展的explicit 显式exploratory programming 探索式编程export 导出引出expression 表达式expressive power 表达能⼒extensibility 可扩展性extent 范围程度external representation 外部表⽰法extreme programming 极限编程F英⽂译法 1 译法 2 译法 3factorial 阶乘family （类型的）系feasible 可⾏的feature 特⾊field 字段栏位file ⽂件file handle ⽂件句柄fill pointer 填充指针fineo-grained 细粒度firmware 固件first-class 第⼀类的第⼀级的⼀等的first-class function 第⼀级函数第⼀类函数⼀等函数first-class object 第⼀类的对象第⼀级的对象⼀等公民fixed-point 不动点fixnum 定长数定点数flag 标记flash 闪存flexibility 灵活性floating-point 浮点数floating-point notation 浮点数表⽰法flush 刷新fold 折叠font 字体force 迫使form 形式form 表单formal parameter 形参formal relation 形式关系forward 转发forward referencesfractal 分形fractions 派系framework 框架freeware ⾃由软件function 函数function literal 函数字⾯常量function object 函数对象functional arguments 函数型参数functional programming 函数式编程functionality 功能性G英⽂译法 1 译法 2 译法 3game 游戏garbage 垃圾garbage collection 垃圾回收garbage collector 垃圾回收器generalized 泛化generalized variable ⼴义变量generate ⽣成generator ⽣成器generic 通⽤的泛化的generic algorithm 通⽤算法泛型算法generic function 通⽤函数generic programming 通⽤编程泛型编程genrative programming ⽣产式编程global 全局的global declaration 全局声明glue program 胶⽔程序goto 跳转graphical user interface, GUI 图形⽤户界⾯greatest common divisor 最⼤公因数Greenspun's tenth rule 格林斯潘第⼗定律H英⽂译法 1 译法 2 译法 3hack 破解hacker ⿊客handle 处理器处理程序句柄hard disk 硬盘hard-wirehardware 硬件hash tables 哈希表散列表header 头部header file 头⽂件heap 堆helper 辅助函数辅助⽅法heuristic 启发式high-order ⾼阶higher-order function ⾼阶函数higher-order procedure ⾼阶过程hyperlink 超链接HyperText Markup Language, HTML 超⽂本标记语⾔HyperText Transfer Protocol, HTTP 超⽂本传输协议I英⽂译法 1 译法 2 译法 3identical ⼀致identifier 标识符ill type 类型不正确illusion 错觉imperative 命令式imperative programming 命令式编程implement 实现implementation 实现implicit 隐式import 导⼊incremental testing 增量测试indent 缩排缩进indentation 缩排缩进indented 缩排缩进indention 缩排缩进infer 推导infinite loop ⽆限循环infinite recursion ⽆限递归infinite precision ⽆限精度infix 中序information 信息information technology, IT 信息技术inheritance 继承initialization 初始化initialize 初始化inline 内联inline expansion 内联展开inner class 内嵌类inner loop 内层循环input 输⼊instances 实例instantiate 实例化instructive 教学性的instrument 记录仪integer 整数integrate 集成interactive programming environment 交互式编程环境interactive testing 交互式测试interacts 交互interface 接⼝intermediate form 过渡形式中间形式internal 内部internet 互联⽹因特⽹interpolation 插值interpret 解释interpreter 解释器interrupt 中⽌中断intersection 交集inter-process communication, IPC 进程间通信invariants 约束条件invoke 调⽤item 项iterate 迭代iteration 迭代的iterative 迭代的iterator 迭代器J英⽂译法 1 译法 2 译法 3jagged 锯齿状的job control language, JCL 作业控制语⾔judicious 明智的K英⽂译法 1 译法 2 译法 3kernel 核⼼kernel language 核⼼语⾔keyword argument 关键字参数keywords 关键字kludge 蹩脚L英⽂译法 1 译法 2 译法 3larval startup 雏形创业公司laser 激光latitudelayout 版型lazy 惰性lazy evaluation 惰性求值legacy software 历史遗留软件leverage 杠杆 (动词)利⽤lexical 词法的lexical analysis 词法分析lexical closure 词法闭包lexical scope 词法作⽤域Language For Smart People, LFSP 聪明⼈的语⾔library 库函数库函式库lifetime ⽣命期linear iteration 线性迭代linear recursion 线性递归link 链接连接linker 连接器list 列表list operation 列表操作literal 字⾯literal constant 字⾯常量literal representation 字⾯量load 装载加载loader 装载器加载器local 局部的局域的local declarations 局部声明local function 局部函数局域函数local variable 局部变量局域变量locality 局部性loop 循环lvalue 左值Mmachine instruction 机器指令machine language 机器语⾔machine language code 机器语⾔代码machine learning 机器学习macro 宏mailing list 邮件列表mainframes ⼤型机maintain 维护manifest typing 显式类型manipulator 操纵器mapping 映射mapping functions 映射函数marshal 列集math envy 对数学家的妒忌member 成员memorizing 记忆化memory 内存memory allocation 内存分配memory leaks 内存泄漏menu 菜单message 消息message-passing 消息传递meta- 元-meta-programming 元编程metacircular 元循环method ⽅法method combination ⽅法组合⽅法组合机制micro 微middleware 中间件migration （数据库）迁移minimal network 最⼩⽹络mirror 镜射mismatch type 类型不匹配model 模型modifier 修饰符modularity 模块性module 模块monad 单⼦monkey patch 猴⼦补丁monomorphic type language 单型语⾔Moore's law 摩尔定律mouse ⿏标multi-task 多任务multiple values 多值mutable 可变的mutex 互斥锁Multiple Virtual Storage, MVS 多重虚拟存储N英⽂译法 1 译法 2 译法 3namespace 命名空间native 本地的native code 本地码natural language ⾃然语⾔natural language processing ⾃然语⾔处理nested 嵌套nested class 嵌套类network ⽹络newline 换⾏新⾏non-deterministic choice ⾮确定性选择non-strict ⾮严格non-strict evaluation ⾮严格求值nondeclarativenondestructive version ⾮破坏性的版本number crunching 数字密集运算O英⽂译法 1 译法 2 译法 3object 对象object code ⽬标代码object-oriented programming ⾯向对象编程Occam's razor 奥卡姆剃⼑原则on the fly 运⾏中执⾏时online 在线open source 开放源码operand 操作对象operating system, OS 操作系统operation 操作operator 操作符optimization 优化optimization of tail calls 尾调⽤优化option 选项optional 可选的选择性的optional argument 选择性参数ordinary 常规的orthogonality 正交性overflow 溢出overhead 额外开销overload 重载override 覆写P英⽂译法 1 译法 2 译法 3package 包pair 点对palindrome 回⽂paradigm 范式parallel 并⾏parallel computer 并⾏计算机param 参数parameter 参数形式参数/形参paren-matching 括号匹配parent class ⽗类parentheses 括号Parkinson's law 帕⾦森法则parse tree 解析树分析树parser 解析器partial application 部分应⽤partial applied 分步代⼊的partial function application 部分函数应⽤particular ordering 部分有序pass by adress 按址传递传址pass by reference 按引⽤传递传引⽤pass by value 按值传递传值path 路径patternpattern match 模式匹配perform 执⾏performance 性能performance-criticalpersistence 持久性phrenology 相⾯physical 物理的pipe 管道pixel 像素placeholder 占位符planning 计画platform 平台pointer 指针pointer arithmetic 指针运算poll 轮询polymorphic 多态polymorphism 多态polynomial 多项式的pool 池port 端⼝portable 可移植性portal 门户positional parameters 位置参数precedence 优先级precedence list 优先级列表preceding 前述的predicate 判断式谓词preemptive multitasking 抢占式多任务premature design 过早设计preprocessor 预处理器prescribe 规定prime 素数primitive 原语primitive recursive 主递归primitive type 原⽣类型principal type 主要类型print 打印printed representation 打印表⽰法printer 打印机priority 优先级procedure 过程procedurual 过程化的procedurual knowledge 过程式知识process 进程process priority 进程优先级productivity ⽣产⼒profile 评测profiler 评测器性能分析器programmer 程序员programming 编程programming language 编程语⾔project 项⽬prompt 提⽰符proper list 正规列表property 属性property list 属性列表protocol 协议pseudo code 伪码pseudo instruction 伪指令purely functional language 纯函数式语⾔pushdown stack 下推栈Q英⽂译法 1 译法 2 译法 3qualified 修饰的带前缀的qualifier 修饰符quality 质量quality assurance, QA 质量保证query 查询query language 查询语⾔queue 队列quote 引⽤quoted form 引⽤形式R英⽂译法 1 译法 2 译法 3race condition 条件竞争竞态条件radian 弧度Redundant Array of Independent Disks, RAID 冗余独⽴磁盘阵列raise 引起random number 随机数range 范围区间rank （矩阵）秩排名rapid prototyping 快速原型开发rational database 关系数据库raw 未经处理的read 读取read-evaluate-print loop, REPL 读取-求值-打印循环read-macro 读取宏record 记录recursion 递归recursive 递归的recursive case 递归情形reference 引⽤参考referential transparency 引⽤透明refine 精化reflection 反射映像register 寄存器registry creep 注册表蠕变regular expression 正则表达式represent 表现request 请求resolution 解析度resolve 解析rest parameter 剩余参数return 返回回车return value 返回值reuse of software 代码重⽤right associative 右结合Reduced Instruction Set Computer, RISC 精简指令系统计算机robust 健壮robustness 健壮性鲁棒性routine 例程routing 路由row-major order 列主序remote procedure call, RPC 远程过程调⽤run-length encoding 游程编码run-time typing 运⾏期类型runtime 运⾏期rvalue 右值S英⽂译法 1 译法 2 译法 3S-expression S-表达式save 储存Secure Sockets Layer, SSL 安全套接字层scaffold 脚⼿架鹰架scalar type 标量schedule 调度scheduler 调度程序scope 作⽤域SCREAMING_SNAKE_CASE 尖叫式蛇底⼤写screen 屏幕scripting language 脚本语⾔search 查找搜寻segment of instructions 指令⽚段semantics 语义semaphore 信号量semicolon 分号sequence 序列sequential 循序的顺序的sequential collection literalsserial 串⾏serialization 序列化series 串⾏级数server 服务器shadowing 隐蔽了sharp 犀利的sharp-quote 升引号shortest path 最短路径SICP 《计算机程序的构造与解释》side effect 副作⽤signature 签名simple vector 简单向量simulate 模拟Single Point of Truth, SPOT 真理的单点性single-segment 单段的sketch 草图初步框架slash 斜线slot 槽smart pointer 智能指针snake_case 蛇底式⼩写snapshot 屏幕截图socket 套接字software 软件solution ⽅案source code 源代码space leak 内存泄漏spaghetti ⾯条式代码意⾯式代码spaghetti stack 意⾯式栈⾯条式栈spam 垃圾邮件spec 规格special form 特殊形式special variable 特殊变量specialization 特化specialize 特化specialized array 特化数组specification 规格说明规范splitter 切分窗⼝sprite 精灵图square 平⽅square root 平⽅根squash 碰撞stack 栈stack frame 栈帧stakeholderstandard library 标准函式库state machine 状态机statement 陈述语句static type 静态类型static type system 静态类型系统status 状态store 保存stream 流strict 严格strict evaluation 严格求值string 字串字符串string template 字串模版strong type 强类型structural recursion 结构递归structured values 结构型值subroutine ⼦程序subset ⼦集substitution 代换substitution model 代换模型subtype ⼦类型superclass 基类superfluous 多余的supertype 超集support ⽀持suspend 挂起swapping values 交换变量的值symbol 符号symbolic computation 符号计算syntax 语法system administrator 系统管理员system administrator disease 系统管理员综合症System Network Architecture, SNA 系统⽹络体系T英⽂译法 1 译法 2 译法 3(database)table 数据表table 表格tag 标签标记tail-recursion 尾递归tail-recursive 尾递归的TAOCP 《计算机程序设计艺术》target ⽬标taxable operators 需节制使⽤的操作符taxonomy 分类法template 模版temporary object 临时对象testing 测试text ⽂本text file ⽂本⽂件thread 线程thread safe 线程安全three-valued logic 三值逻辑throw 抛出丢掷引发throwaway program ⼀次性程序timestamp 时间戳token 词法记号语义单位语元top-down design ⾃顶向下的设计top-level 顶层trace 追踪trailing space ⾏尾空⽩transaction 事务transition network 转移⽹络transparent 透明的traverse 遍历tree 树tree recursion 树形递归trigger 触发器tuple 元组Turing machine 图灵机Turing complete 图灵完备typable 类型合法type 类型type constructor 类构造器type declaration 类型声明type hierarchy 类型层级type inference 类型推导type name 类型名type safe 类型安全type signature 类型签名type synonym 类型别名type variable 类型变量typing 类型指派输⼊U英⽂译法 1 译法 2 译法 3user interface, UI ⽤户界⾯unary ⼀元的underflow 下溢unification 合⼀统⼀union 并集universally quantify 全局量化unqualfied 未修饰的unwindinguptime 运⾏时间Uniform Resource Locator, URL 统⼀资源定位符user ⽤户utilities 实⽤函数V英⽂译法 1 译法 2 译法 3validate 验证validator 验证器value constructor 值构造器vaporware 朦胧件variable 变量variable capture 变量捕捉variadic input 可变输⼊variant 变种venture capitalist, VC 风险投资商vector 向量viable function 可⾏函数video 视频view 视图virtual function 虚函数virtual machine 虚拟机virtual memory 虚内存volatile 挥发vowel 元⾳W英⽂译法 1 译法 2 译法 3warning message 警告信息web server ⽹络服务器weight 权值权重well type 类型正确wildcard 通配符window 窗⼝word 单词字wrapper 包装器包装What You See Is What You Get, WYSIWYG 所见即所得What You See Is What You Want, WYSIWYW 所见即所想Y英⽂译法 1 译法 2 译法 3Y combinator Y组合⼦Z英⽂译法 1 译法 2 译法 3Z-expression Z-表达式zero-indexed 零索引的专业名词英⽂译法 1 译法 2 译法 3The Paradox of Choice 选择谬论。

Simple Atoms, Quantum Electrodynamics and Fundamental Constants

a r Xi v:h ep-ph/3525v119May23Simple Atoms,Quantum Electrodynamics and Fundamental Constants Savely G.Karshenboim Max-Planck-Institut f¨u r Quantenoptik,85748Garching,Germany D.I.Mendeleev Institute for Metrology (VNIIM),St.Petersburg 198005,Russia Abstract.This review is devoted to precision physics of simple atoms.The atoms can essentially be described in the framework of quantum electrodynamics (QED),however,the energy levels are also aﬀected by the eﬀects of the strong interaction due to the nuclear structure.We pay special attention to QED tests based on studies of simple atoms and consider the inﬂuence of nuclear structure on energy levels.Each calculation requires some values of relevant fundamental constants.We discuss the ac-curate determination of the constants such as the Rydberg constant,the ﬁne structure constant and masses of electron,proton and muon etc.1Introduction Simple atoms oﬀer an opportunity for high accuracy calculations within the framework of quantum electrodynamics (QED)of bound states.Such atoms also possess a simple spectrum and some of their transitions can be measured with high precision.Twenty,thirty years ago most of the values which are of interest for the comparison of theory and experiment were known experimentally with a higher accuracy than from theoretical calculations.After a signiﬁcant theoretical progress in the development of bound state QED,the situation has reversed.A review of the theory of light hydrogen-like atoms can be found in [1],while recent advances in experiment and theory have been summarized in the Proceedings of the International Conference on Precision Physics of Simple Atomic Systems (2000)[2].Presently,most limitations for a comparison come directly or indirectly fromthe experiment.Examples of a direct experimental limitation are the 1s −2s transition and the 1s hyperﬁne structure in positronium,whose values are known theoretically better than experimentally.An indirect experimental limitation is a limitation of the precision of a theoretical calculation when the uncertainty of such calculation is due to the inaccuracy of fundamental constants (e.g.of the muon-to-electron mass ratio needed to calculate the 1s hyperﬁne interval in muonium)or of the eﬀects of strong interactions (like e.g.the proton structure for the Lamb shift and 1s hyperﬁne splitting in the hydrogen atom).The knowledge of fundamental constants and hadronic eﬀects is limited by the experiment and that provides experimental limitations on theory.This is not our ﬁrst brief review on simple atoms (see e.g.[3,4])and to avoid any essential overlap with previous papers,we mainly consider here the2Savely G.Karshenboimmost recent progress in the precision physics of hydrogen-like atoms since the publication of the Proceedings[2].In particular,we discuss•Lamb shift in the hydrogen atom;•hyperﬁne structure in hydrogen,deuterium and helium ion;•hyperﬁne structure in muonium and positronium;•g factor of a bound electron.We consider problems related to the accuracy of QED calculations,hadronic eﬀects and fundamental constants.These atomic properties are of particular interest because of their appli-cations beyond atomic physics.Understanding of the Lamb shift in hydrogen is important for an accurate determination of the Rydberg constant Ry and the proton charge radius.The hyperﬁne structure in hydrogen,helium-ion and positronium allows,under some conditions,to perform an accurate test of bound state QED and in particular to study some higher-order corrections which are also important for calculating the muonium hyperﬁne interval.The latter is a source for the determination of theﬁne structure constantαand muon-to-electron mass ratio.The study of the g factor of a bound electron lead to the most accurate determination of the proton-to-electron mass ratio,which is also of interest because of a highly accurate determination of theﬁne structure con-stant.2Rydberg Constant and Lamb Shift in HydrogenAboutﬁfty years ago it was discovered that in contrast to the spectrum predicted by the Dirac equation,there are some eﬀects in hydrogen atom which split the 2s1/2and2p1/2levels.Their splitting known as the Lamb shift(see Fig.1)was successfully explained by quantum electrodynamics.The QED eﬀects lead to a tiny shift of energy levels and for thirty years this shift was studied by means of microwave spectroscopy(see e.g.[5,6])measuring either directly the splitting of the2s1/2and2p1/2levels or a bigger splitting of the2p3/2and2s1/2levels(ﬁne structure)where the QED eﬀects are responsible for approximately10%of the ﬁne-structure interval.The recent success of two-photon Doppler-free spectroscopy[7]opens an-other way to study QED eﬀects directed by high-resolution spectroscopy of gross-structure transitions.Such a transition between energy levels with dif-ferent values of the principal quantum number n is determined by the Coulomb-Schr¨o dinger formula(Zα)2mc2E(nl)=−,(2)2hSimple Atoms,QED and Fundamental Constants31s 2s 1/23/2Fig.1.Spectrum of the hydrogen atom (not to scale).The hyperﬁne structure is neglected.The label rf stands for radiofrequency intervals,while uv is for ultraviolet transitionswhere h is the Planck constant.Another problem in the interpretation of optical measurements of the hydrogen spectrum is the existence of a few levels which are signiﬁcantly aﬀected by the QED eﬀects.In contrast to radiofrequency mea-surements,where the 2s −2p splitting was studied,optical measurements have been performed with several transitions involving 1s ,2s ,3s etc.It has to be noted that the theory of the Lamb shift for levels with l =0is relatively simple,while theoretical calculations for s states lead to several serious compliﬁcations.The problem of the involvement of few s levels has been solved by introducing an auxiliary diﬀerence [8]∆(n )=E L (1s )−n 3E L (ns ),(3)for which theory is signiﬁcantly simpler and more clear than for each of the s states separately.Combining theoretical results for the diﬀerence [9]with measured frequencies of two or more transitions one can extract a value of the Rydberg constant and of the Lamb shift in the hydrogen atom.The most recent progress in determination of the Rydberg constant is presented in Fig.2(see [7,10]for references).Presently the optical determination [7,4]of the Lamb shift in the hydrogen atom dominates over the microwave measurements [5,6].The extracted value of the Lamb shift has an uncertainty of 3ppm.That ought to be compared with the uncertainty of QED calculations (2ppm)[11]and the uncertainty of the contributions of the nuclear eﬀects.The latter has a simple form∆E charge radius (nl )=2(Zα)4mc 22δl 0.(4)To calculate this correction one has to know the proton rms charge radius R p with suﬃcient accuracy.Unfortunately,it is not known well enough [11,3]and leads to an uncertainty of 10ppm for the calculation of the Lamb shift.It is likely4Savely G.KarshenboimDate of publicationR y − 10 973 731.568 [m −1]Fig.2.Progress in the determination of the Rydberg constant by two-photon Doppler-free spectroscopy of hydrogen and deuterium.The label CODATA,1998stands for the recommended value of theRydberg constant (Ry =10973731.568549(83)m −1[10])Fig.3.Measurement of the Lamb shift in hydrogen atom.Theory is presented accord-ing to [11].The most accurate value comes from comparison of the 1s −2s transition at MPQ (Garching)and the 2s −ns/d at LKB (Paris),where n =8,10,12.Three re-sults are shown:for the average values extracted from direct Lamb shift measurements,measurements of the ﬁne structure and a comparison of two optical transitions within a single experiment.The ﬁlled part is for the theorythat a result for R p from the electron-proton elastic scattering [12]cannot be improved much,but it seems to be possible to signiﬁcantly improve the accuracy of the determination of the proton charge radius from the Lamb-shift experiment on muonic hydrogen,which is now in progress at PSI [13].Simple Atoms,QED and Fundamental Constants 53Hyperﬁne Structure and Nuclear EﬀectsA similar problem of interference of nuclear structure and QED eﬀects exists for the 1s and 2s hyperﬁne structure in hydrogen,deuterium,tritium and helium-3ion.The magnitude of nuclear eﬀects entering theoretical calculations is at the level from 30to 200ppm (depending on the atom)and their understanding is unfortunately very poor [11,14,15].We summarize the data in Tables 1and 2(see [15]1for detail).Hydrogen,1s 1420405.751768(1)[16,17]1420452-33Deuterium,1s 327384.352522(2)[18]327339138Tritium,1s 1516701.470773(8)[19]1516760-363He +ion,1s -8665649.867(10)[20]-8667494-213Table 1.Hyperﬁne structure in light hydrogen-like atoms:QED and nuclear contri-butions ∆E (Nucl).The numerical results are presented for the frequency E/hThe leading term (so-called Fermi energy E F )is a result of the nonrelativistic interaction of the Dirac magnetic moment of electron with the actual nuclear magnetic moment.The leading QED contribution is related to the anomalous magnetic moment and simply rescales the result (E F →E F ·(1+a e )).The result of the QED calculations presented in Table 1is of the formE HFS (QED)=EF ·(1+a e )+∆E (QED),(5)where the last term which arises from bound-state QED eﬀects for the 1s state is given by∆E 1s (QED)=E F × 32+α(Zα)23ln 1(Zα)26Savely G.Karshenboim+4ln2−28115ln2+34π .(6)This term is in fact smaller than the nuclear corrections as it is shown in Table2 (see[15]for detail).A result for the2s state is of the same form with slightly diﬀerent coeﬃtients[15].Hydrogen23-33Deuterium23138Tritium23-363He+ion108-213π (Zα)m R cSimple Atoms,QED and Fundamental Constants7 In the next section we consider the former option,comparison of the1s and2s hyperﬁne interval in hydrogen,deuterium and ion3He+.4Hyperﬁne Structure of the2s State in Hydrogen, Deuterium and Helium-3IonOur consideration of the2s hyperﬁne interval is based on a study of the speciﬁc diﬀerenceD21=8·E HFS(2s)−E HFS(1s),(9) where any contribution which has a form of(7)should vanish.D21(QED3)48.93711.3056-1189.252D21(QED4)0.018(3)0.0043(5)-1.137(53)D21(nucl)-0.0020.0026(2)0.317(36)Table 3.Theory of the speciﬁc diﬀerence D21=8E HFS(2s)−E HFS(1s)in light hydrogen-like atoms(see[15]for detail).The numerical results are presented for the frequency D21/hThe diﬀerence(9)has been studied theoretically in several papers long ago [28,29,30].A recent study[31]shown that some higher-order QED and nuclear corrections have to be taken into account for a proper comparison of theory and experiment.The theory has been substantially improved[15,32]and it is summarized in Table3.The new issues here are most of the fourth-order QED contributions(D21(QED4))of the orderα(Zα)3,α2(Zα)4,α(Zα)2m/M and (Zα)3m/M(all are in units of the1s hyperﬁne interval)and nuclear correc-tions(D21(nucl)).The QED corrections up to the third order(D21(QED3))and the fourth-order contribution of the order(Zα)4have been known for a while [28,29,30,33].For all the atoms in Table3the hyperﬁne splitting in the ground state was measured more accurately than for the2s state.All experimental results but one were obtained by direct measurements of microwave transitions for the1s and 2s hyperﬁne intervals.However,the most recent result for the hydrogen atom has been obtained by means of laser spectroscopy and measured transitions lie in the ultraviolet range[21,22].The hydrogen level scheme is depicted in Fig.4. The measured transitions were the singlet-singlet(F=0)and triplet-triplet (F=1)two-photon1s−2s ultraviolet transitions.The eventual uncertainty of the hyperﬁne structure is to6parts in1015of the measured1s−2s interval.8Savely G.Karshenboim1s2s F = 0 (singlet)Fig.4.Level scheme for an optical measurement of the hyperﬁne structure (hfs )in the hydrogen atom (notto scale)[22].The label rf stands here for radiofrequency intervals,while uv is for ultraviolet transitions21Fig.5.Present status of measurements of D 21in the hydrogen atom.The results are labeled with the date of the measurement of the 2s hyperﬁne structure.See Table 1for referencesThe optical result in Table 1is a preliminary one and the data analysis is still in progress.The comparison of theory and experiment for hydrogen and helium-3ion is summarized in Figs.5and 6.Simple Atoms,QED and Fundamental Constants9Fig.6.Present status of measurements of D21in the helium ion3He+.See Table1for references5Hyperﬁne Structure in Muonium and Positronium Another possibility to eliminate nuclear structure eﬀects is based on studies of nucleon-free atoms.Such an atomic system is to be formed of two leptons.Two atoms of the sort have been produced and studied for a while with high accuracy, namely,muonium and positronium.•Muonium is a bound system of a positive muon and electron.It can be produced with the help of accelerators.The muon lifetime is2.2·10−6sec.The most accurately measured transition is the1s hyperﬁne structure.The two-photon1s−2s transition was also under study.A detailed review of muonium physics can be found in[34].•Positronium can be produced at accelerators or using radioactive positron sources.The lifetime of positronium depends on its state.The lifetime for the1s state of parapositronium(it annihilates mainly into two photons)is1.25·10−10sec,while orthopositronium in the1s state has a lifetime of1.4·10−7s because of three-photon decays.A list of accurately measuredquantities contains the1s hyperﬁne splitting,the1s−2s interval,2s−2pﬁne structure intervals for the triplet1s state and each of the four2p states,the lifetime of the1s state of para-and orthopositronium and several branchings of their decays.A detailed review of positronium physics can be found in[35].Here we discuss only the hyperﬁne structure of the ground state in muonium and positronium.The theoretical status is presented in Tables4and5.The theoretical uncertainty for the hyperﬁne interval in positronium is determined only by the inaccuracy of the estimation of the higher-order QED eﬀects.The uncertainty budget in the case of muonium is more complicated.The biggest10Savely G.KarshenboimE F 1.000000000 4.459031.83(50)(3)a e0.0011596525170.926(1)QED2-0.000195815-873.147QED3-0.000005923-26.410QED4-0.000000123(49)-0.551(218)Hadronic0.000000054(1)0.240(4)Weak-0.000000015-0.065Table 4.Theory of the1s hyperﬁne splitting in muonium.The numerical results are presented for the frequency E/h.The calculations[36]have been performed for α−1=137.03599958(52)[37]andµµ/µp=3.18334517(36)which was obtained from the analysis of the data on Breit-Rabi levels in muonium[38,39](see Sect.6)and precession of the free muon[40].The numerical results are presented for the frequency E/hE F 1.0000000204386.6QED1-0.0049196-1005.5QED20.000057711.8QED3-0.0000061(22)-1.2(5)Table5.Theory of the1s hyperﬁne interval in positronium.The numerical results are presented for the frequency E/h.The calculation of the second order terms was completed in[41],the leading logarithmic contributions were found in[42],while next-to-leading logarithmic terms in[43].The uncertainty is presented following[44] source is the calculation of the Fermi energy,the accuracy of which is limited by the knowledge of the muon magnetic moment or muon mass.It is essentially the same because the g factor of the free muon is known well enough[45].The uncer-tainty related to QED is determined by the fourth-order corrections for muonium (∆E(QED4))and the third-order corrections for positronium(∆E(QED3)). These corrections are related to essentially the same diagrams(as well as the D21(QED4)contribution in the previous section).The muonium uncertainty is due to the calculation of the recoil corrections of the order ofα(Zα)2m/M [42,46]and(Zα)3m/M,which are related to the third-order contributions[42] for positronium since m=M.The muonium calculation is not completely free of hadronic contributions. They are discussed in detail in[36,47,48]and their calculation is summarizedSimple Atoms,QED and Fundamental Constants11∆ν(h a d r V P ) [k H z ]Fig.7.Hadronic contributions to HFS in muonium.The results are taken:a from [50],b from [51],c from [52]and d from [36,47]1s hyperfine interval in positronium [MHz]Fig.8.Positronium hyperﬁne structure.The Yale experiment was performed in 1984[53]and the Brandeis one in 1975[54]in Fig.7.They are small enough but their understanding is very important because of the intensive muon sources expected in future [49]which might allow to increase dramatically the accuracy of muonium experiments.A comparison of theory versus experiment for muonium is presented in the summary of this paper.Present experimental data for positronium together with the theoretical result are depicted in Fig.8.12Savely G.Karshenboim6g Factor of Bound Electron and Muon in MuoniumNot only the spectrum of simple atoms can be studied with high accuracy.Other quantities are accessible to high precision measurements as well among them the atomic magnetic moment.The interaction of an atom with a weak homoge-neous magneticﬁeld can be expressed in terms of an eﬀective Hamiltonian.For muonium such a Hamiltonian has the formH=e2m Ng′µ sµ·B +∆E HFS s e·sµ ,(10)where s e(µ)stands for spin of electron(muon),and g′e(µ)for the g factor ofa bound electron(muon)in the muonium atom.The bound g factors are now known up to the fourth-order corrections[55]including the term of the orderα4,α3m e/mµandα2m e/mµand thus the relative uncertainty is essentially better than10−8.In particular,the result for the bound muon g factor reads[55]2g′µ=g(0)µ· 1−α(Zα)2m e2 m e12πm e108α(Zα)3 ,(11)where g(0)µ=2·(1+aµ)is the g factor of a free muon.Equation(10)has been applied[38,39]to determine the muon magnetic moment and muon mass by measuring the splitting of sublevels in the hyperﬁne structure of the1s state in muonium in a homogeneous magneticﬁeld.Their dependence on the mag-neticﬁeld is given by the well known Breit-Rabi formula(see e.g.[56]).Since the magneticﬁeld was calibrated via spin precession of the proton,the muon magnetic moment was measured in units of the proton magnetic moment,and muon-to-electron mass ratio was derived asmµµp µp1+aµ.(12)Results on the muon mass extracted from the Breit-Rabi formula are among the most accurate(see Fig.9).A more precise value can only be derived from the muonium hyperﬁne structure after comparison of the experimental result with theoretical calculations.However,the latter is of less interest,since the most important application of the precise value of the muon-to-electron mass is to use it as an input for calculations of the muonium hyperﬁne structure while testing QED or determining theﬁne structure constantsα.The adjusted CODATA result in Fig.9was extracted from the muonium hyperﬁne structure studies and in addition used some overoptimistic estimation of the theoretical uncertainty (see[36]for detail).Simple Atoms,QED and Fundamental Constants13Value of muon-to-electron mass ratio mµ/m eFig.9.The muon-to-electron mass ratio.The most accurate result obtained from com-parison of the measured hyperﬁne interval in muonium[38]to the theoretical calcu-lation[36]performed withα−1g−2=137.03599958(52)[37].The results derived from the Breit-Rabi sublevels are related to two experiments performed at LAMPF in1982 [39]and1999[38].The others are taken from the measurement of the1s−2s interval in muonium[57],precession of a free muon in bromine[40]and from the CODATA adjustment[10]7g Factor of a Bound Electron in a Hydrogen-Like Ion with Spinless NucleusIn the case of an atom with a conventional nucleus(hydrogen,deuterium etc.)an-other notation is used and the expression for the Hamiltonian similar to eq.(10) can be applied.It can be used to test QED theory as well as to determine the electron-to-proton mass ratio.We underline that in contrast to most other tests it is possible to do both simultaneously because of a possibility to perform experiments with diﬀerent ions.The theoretical expression for the g factor of a bound electron can be pre-sented in the form[3,58,59]g′e=2· 1+a e+b ,(13) where the anomalous magnetic moment of a free electron a e=0.0011596522 [60,10]is known with good enough accuracy and b is the bound correction.The summary of the calculation of the bound corrections is presented in Table6. The uncertainty of unknown two-loop contributions is taken from[61].The cal-culation of the one-loop self-energy is diﬀerent for diﬀerent atoms.For lighter elements(helium,beryllium),it is obtained from[55]based onﬁtting data of [62],while for heavier ions we use the results of[63].The other results are taken from[61](for the one-loop vacuum polarization),[59](for the nuclear correction14Savely G.Karshenboimand the electric part of the light-by-light scattering(Wichmann-Kroll)contri-bution),[64](for the magnetic part of the light-by-light scattering contribution) and[65](for the recoil eﬀects).4He+ 2.0021774067(1)10Be3+2.0017515745(4)12C5+ 2.0010415901(4)16O7+ 2.0000470201(8)18O7+ 2.0000470213(8)M iB(14)and the Larmor spin precession frequency for a hydrogen-like ion with spinless nucleusωL=g be2= Z−1 m eωc(16) or an electron-to-ion mass ratiom eZ−1g bωL.(17)Today the most accurate value of m e/M i(without using experiments on the bound g factor)is based on a measurement of m e/m p realized in Penning trap [66]with a fractional uncertainty of2ppm.The accuracy of measurements ofωc andωL as well as the calculation of g b(as shown in[58])are essentially better. That means that it is preferable to apply(17)to determine the electron-to-ion mass ratio[67].Applying the theoretical value for the g factor of the bound electron and using experimental results forωc andωL in hydrogen-like carbonSimple Atoms,QED and Fundamental Constants15Value of ptoron-to-electron mass ratio m p/m eFig.10.The proton-to-electron mass ratio.The theory of the bound g factor is taken from Table6,while the experimental data on the g factor in carbon and oxygen are from[68,69].The Penning trap result from University of Washington is from[66] [68]and some auxiliary data related to the proton and ion masses,from[10],we arrive at the following valuesm p16Savely G.Karshenboim8The Fine Structure ConstantTheﬁne structure constant plays a basic role in QED tests.In atomic and particle physics there are several ways to determine its value.The results are summarized in Fig.11.One method based on the muonium hyperﬁne interval was brieﬂy discussed in Sect.5.A value of theﬁne structure constant can also be extracted from the neutral-heliumﬁne structure[70,71]and from the comparison of theory [37]and experiment[60]for the anomalous magnetic moment of electron(αg−2). The latter value has been the most accurate one for a while and there was a long search for another competitive value.The second value(αCs)on the list of the most precise results for theﬁne structure constant is a result from recoil spectroscopy[72].Value of the Inverse fine structure constant α-1Fig.11.Theﬁne structure constant from atomic physics and QED We would like to brieﬂy consider the use and the importance of the recoil result for the determination of theﬁne structure constant.Absorbing and emit-ting a photon,an atom can gain some kinetic energy which can be determined as a shift of the emitted frequency in respect to the absorbed one(δf).A mea-surement of the frequency with high accuracy is the goal of the photon recoil experiment[72].Combining the absorbed frequency and the shifted one,it is possible to determine a value of atomic mass(in[72]that was caesium)in fre-quency units,i.e.a value of M a c2/h.That may be compared to the Rydberg constant Ry=α2m e c/2h.The atomic mass is known very well in atomic units (or in units of the proton mass)[73],while the determination of electron mass in proper units is more complicated because of a diﬀerent order of magnitude of the mass.The biggest uncertainty of the recoil photon value ofαCs comes now from the experiment[72],while the electron mass is the second source.Simple Atoms,QED and Fundamental Constants17 The success ofαCs determination was ascribed to the fact thatαg−2is a QED value being derived with the help of QED theory of the anomalous mag-netic moment of electron,while the photon recoil result is free of QED.We would like to emphasize that the situation is not so simple and involvement of QED is not so important.It is more important that the uncertainty ofαg−2originates from understanding of the electron behaviour in the Penning trap and it dom-inates any QED uncertainty.For this reason,the value ofαCs from m p/m e in the Penning trap[66]obtained by the same group as the one that determined the value of the anomalous magnetic moment of electron[60],can actually be correlated withαg−2.The resultα−1=137.03600028(10)(22)Cspresented in Fig.11is obtained using m p/m e from(18).The value of the proton-to-electron mass ratio found this way is free of the problems with an electron in the Penning trap,but some QED is involved.However,it is easy to real-ize that the QED uncertainty for the g factor of a bound electron and for the anomalous magnetic moment of a free electron are very diﬀerent.The bound theory deals with simple Feynman diagrams but in Coulombﬁeld and in partic-ular to improve theory of the bound g factor,we need a better understanding of Coulomb eﬀects for“simple”two-loop QED diagrams.In contrast,for the free electron no Coulombﬁeld is involved,but a problem arises because of the four-loop diagrams.There is no correlation between these two calculations.9SummaryTo summarize QED tests related to hyperﬁne structure,we present in Table7the data related to hyperﬁne structure of the1s state in positronium and muonium and to the D21value in hydrogen,deuterium and helium-3ion.The theory agrees with the experiment very well.The precision physics of light simple atoms provides us with an opportunity to check higher-order eﬀects of the perturbation theory.The highest-order terms important for comparison of theory and experiment are collected in Table8.The uncertainty of the g factor of the bound electron in carbon and oxygen is related toα2(Zα)4m corrections in energy units,while for calcium the crucial order is α2(Zα)6m.Some of the corrections presented in Table8are completely known,some not.Many of them and in particularα(Zα)6m2/M3and(Zα)7m2/M3for the hyperﬁne structure in muonium and helium ion,α2(Zα)6m for the Lamb shift in hydrogen and helium ion,α7m for positronium have been known in a so-called logarithmic approximation.In other words,only the terms with the highest power of“big”logarithms(e.g.ln(1/Zα)∼ln(M/m)∼5in muonium)have been calculated.This program started for non-relativistic systems in[42]and was developed in[46,8,74,31,15].By now even some non-leading logarithmic terms have been evaluated by several groups[43,75].It seems that we have reached some numerical limit related to the logarithmic contribution and the calculation18Savely G.KarshenboimHydrogen,D2149.13(15),[21,22]48.953(3) 1.20.10Hydrogen,D2148.53(23),[23]-1.80.16Hydrogen,D2149.13(40),[24]0.40.28Deuterium,D2111.16(16),[25]11.3125(5)-1.00.493He+ion,D21-1189.979(71),[26]-1190.072(63) 1.00.013He+,D21-1190.1(16),[27]0.00.18parison of experiment and theory of hyperﬁne structure in hydrogen-like atoms.The numerical results are presented for the frequency E/h.In the D21case the reference is given only for the2s hyperﬁne intervalof the non-logarithmic terms will be much more complicated than anything else done before.Hydrogen,deuterium(gross structure)α(Zα)7m,α2(Zα)6mHydrogen,deuterium(ﬁne structure)α(Zα)7m,α2(Zα)6mHydrogen,deuterium(Lamb shift)α(Zα)7m,α2(Zα)6m3He+ion(2s HFS)α(Zα)7m2/M,α(Zα)6m3/M2,α2(Zα)6m2/M,(Zα)7m3/M2 4He+ion(Lamb shift)α(Zα)7m,α2(Zα)6mN6+ion(ﬁne structure)α(Zα)7m,α2(Zα)6mMuonium(1s HFS)(Zα)7m3/M2,α(Zα)6m3/M2,α(Zα)7m2/MPositronium(1s HFS)α7mPositronium(gross structure)α7mPositronium(ﬁne structure)α7mPara-positronium(decay rate)α7mOrtho-positronium(decay rate)α8mPara-positronium(4γbranching)α8mOrtho-positronium(5γbranching)α8m。

The Structure of an Atom英语翻译

Assignment for Week 1:The Structure of an AtomAtoms are made of smaller particles, called electrons, protons, and neutrons. An atom consists of a cloud of electrons surrounding a small, dense nucleus of protons and neutrons. Electrons and protons have a property called electric charge, which affects the way they interact with each other and with other electrically charged particles. Electrons carry a negative electric charge, while protons have a positive electric charge. The negative charge is the opposite of the positive charge, and, like the opposite poles of a magnet, these opposite electric charges attract one another. Conversely, like charges (negative and negative, or positive and positive) repel one another. The attraction between an atom’s ele ctrons and its protons holds the atom together. Normally, an atom is electrically neutral, which means that the negative charge of its electrons is exactly equaled by the positive charge of its protons.The nucleus contains nearly all of the mass of the atom, but it occupies only a tiny fraction of the space inside the atom. The diameter of a typical nucleus is only about 1/100,000 of the diameter of the entire atom. The electron cloud makes up the rest of the atom’s overall size. If an atom were magnified until it was as large as a football stadium, the nucleus would be about the size of a grape.原子的结构原子是由名叫电子、质子和中子这些更小的微粒构成。

化学英语课件

( )：
[ ]： { }：
rounds brackets, parenthese
square brackets braces
a>>b: a is much greater than b ab： a is greater than or equal to b
ab： a varies directly as b
P-block Element
IIIA B: boron Al: Aluminium Ga: Gallium In: Indium Tl: Thallium
IVA C: Si: Ge: Sn: Pb:
VA
Carbon Silicon Germanium Tin Lead
N: P: As: Sb: Bi:
3. fundamental constants
Symbol Quantity
e
F g
elementary charge
Faraday‘s constant gravitational acceleration
h
k NA R Vm
Planck‘s constant
Boltzmann‘s constant Avogadro‘s number molar gas constant gas molar volume
Nitrogen Phosphorus Arsenic Antimony Bismuth
P-block Element
VIA O: S: Se: Te: Po:
VIIA Oxygen Sulfur Selenium Tellurium Polonium
F: Fluorine Cl: Chlorine Br: Bromine I: Iodine At: Astatine

原子吸收光谱法的英文

原子吸收光谱法的英文Title: Atomic Absorption Spectroscopy: Principles and ApplicationsAtomic absorption spectroscopy (AAS) is a powerful analytical technique used to determine the concentration of specific elements in various samples, including metals in environmental, biological, and industrial contexts. This method is widely valued for its sensitivity, precision, and ability to analyze complex mixtures.The principle of atomic absorption spectroscopy is based on the absorption of light by free atoms in the gaseous state. The process begins with the atomization of the sample, which can be achieved through techniques such as flame atomization or graphite furnace atomization. In flame atomization, the sample is introduced into a flame, where it is vaporized and atomized. In graphite furnace atomization, a small amount of the sample is placed in a graphite tube, where it is heated to high temperatures to produce atoms.Once the sample is atomized, a light source, typically a hollow cathode lamp, emits light at a specific wavelength corresponding to the element being analyzed. As the light passes through the vaporized sample, some of it is absorbed by the atoms, leading to a decrease in the intensity of the transmitted light. This decrease is measured using a spectrometer, and the absorbance is directly related to the concentration of the element in the sample.AAS has numerous applications across various fields. In environmental analysis, it is used to detect heavy metals in water and soil, ensuring compliance with safety regulations. In clinical laboratories, AAS helps in determining trace elements in biological fluids, which is crucial for diagnosing health conditions. Additionally, it is widely used in metallurgy and food safety to analyze the composition of alloys and food products.Despite its advantages, AAS also has some limitations.It can only analyze one element at a time, which can be time-consuming when multiple elements need to be measured. Additionally, the presence of interfering substances can affect the accuracy of the results.In conclusion, atomic absorption spectroscopy is an invaluable tool in analytical chemistry, providing accurate and reliable data for various applications. Its ability to detect trace elements with high sensitivity makes it essential in fields ranging from environmental science to healthcare. As technology advances, AAS continues to evolve, promising even more efficient and comprehensive analysis in the future.。

范德瓦尔相互作用采取atom-based方法处理

范德瓦尔相互作用采取atom-based方法处理社会物理学中，范德瓦尔相互作用被认为是自然界中的一种势能，它是由于相邻分子之间的极化和磁化而产生的相互作用。

原子之间相互作用是研究分子和固体性质的基础，同时也是许多现代技术的基础。

目前，处理范德瓦尔相互作用的方法主要有两种，分别是基于能量的方法和基于原子的方法。

基于能量的方法是研究范德瓦尔相互作用的传统方法，它基于二体范德瓦尔解析式，将分子作为两体问题处理，并利用公式计算其势能。

这种方法的优点是计算简单，能够处理大型分子和高密度系统。

但是，这种方法的局限性在于它无法处理特殊性质，比如极化和双极分子相互作用，以及长程效应和晶体环境中的相互作用。

基于原子的方法则是新近发展起来的处理范德瓦尔相互作用的方法。

它将范德瓦尔相互作用看作原子之间的相互作用，并基于该原则建立了一种新的计算方法，即地毯式计算法。

这种方法的特点是注重原子之间的相互作用，利用原子之间的感应极化和互感应作用共同处理相邻原子之间的相互作用，得到了比较准确的结果。

地毯式计算法的核心思想是将分子表面覆盖成一张无数细小区域的地毯，每一小块地毯的大小都是一个原子的大小。

当计算相互作用时，先确定两个原子之间的位置关系，然后确定相邻原子之间的相互作用。

如果两个原子间的距离很大，相互作用被认为很小，可以忽略不计。

但是，当两个原子距离很近时，相互作用将是很强烈的，可通过一种数学方法计算得出。

在整个计算中，每个原子的电子云都被视为等同的，以简化计算。

总之，地毯式计算法是目前范德瓦尔相互作用研究中的新技术，它的发展为分子动力学和分子机器的研究提供了新思路和新方法，对于理解范德瓦尔相互作用具有重要意义。

原子吸收光谱法重金属

原子吸收光谱法重金属英文回答：Atomic absorption spectroscopy (AAS) is a widely used analytical technique to determine the presence and concentration of heavy metals in various samples. It relies on the principle of light absorption by atoms in the ground state, which is specific to each element.In AAS, a sample is atomized and introduced into a flame or graphite furnace. The light source used is typically a hollow cathode lamp, which emits a characteristic wavelength of light that corresponds to the element of interest. This light is then passed through the sample, and the amount of light absorbed by the atoms is measured using a detector.The absorption of light by the atoms is directly proportional to the concentration of the element in the sample. By comparing the absorption of light by the sampleto that of a calibration standard, the concentration of the element can be determined. This is usually done by measuring the absorbance or the percentage of light transmitted through the sample.AAS offers several advantages for heavy metal analysis. Firstly, it is a highly sensitive technique, capable of detecting trace amounts of metals in a sample. Secondly, it is a selective technique, as the characteristic wavelengthof the light source allows for the specific determinationof a particular element. Lastly, AAS is a relatively simple and cost-effective method, making it widely used in various fields such as environmental monitoring, pharmaceutical analysis, and industrial quality control.To illustrate the application of AAS, let's considerthe analysis of lead (Pb) in drinking water. Drinking water contaminated with lead can have detrimental health effects, so it is crucial to monitor its concentration. By using AAS, we can accurately determine the level of lead in the water.In this case, a water sample is collected and preparedfor analysis. The sample is then atomized and introduced into the flame or graphite furnace. A hollow cathode lamp emitting light at the characteristic wavelength of lead is used as the light source. The light passes through the sample, and the amount of light absorbed by the lead atoms is measured.By comparing the absorbance of the sample to that of a calibration standard, the concentration of lead in the water can be determined. If the concentration exceeds the permissible limit set by regulatory agencies, appropriate actions can be taken to ensure the safety of the drinking water.中文回答：原子吸收光谱法（AAS）是一种广泛应用于分析化学的技术，用于确定不同样品中重金属的存在和浓度。

冷原子光谱法英语

冷原子光谱法英语Okay, here's a piece of writing on cold atom spectroscopy in an informal, conversational, and varied English style:Hey, you know what's fascinating? Cold atom spectroscopy! It's this crazy technique where you chill atoms down to near absolute zero and study their light emissions. It's like you're looking at the universe in a whole new way.Just imagine, you've got these tiny particles, frozen in place almost, and they're still putting out this beautiful light. It's kind of like looking at a fireworks display in a snow globe. The colors and patterns are incredible.The thing about cold atoms is that they're so slow-moving, it's easier to measure their properties. You can get really precise data on things like energy levels andtransitions. It's like having a super-high-resolution microscope for the quantum world.So, why do we bother with all this? Well, it turns out that cold atom spectroscopy has tons of applications. From building better sensors to understanding the fundamental laws of nature, it's a powerful tool. It's like having a key that unlocks secrets of the universe.And the coolest part? It's just so darn cool! I mean, chilling atoms to near absolute zero? That's crazy science fiction stuff, right?。

科技英语综合教程练习答案

Keys:第一章科技英语阅读第一节科技英语主要特点I.1.The first three sentences in Passage One are all constructed with passive voice while thefirst three sentences in Passage Two are constructed with active voice. Therefore, the language in Passage One sounds more formal and objective than that of Passage Two.2.The words spoken by Sheila in Passage Two are informal. Examples: "There's Ravi atthe home of that American doctor." (Contracted form); "A wonderful guy." (Incomplete sentence); "Ravi looks sweet, doesn 't he?" (Question tag).3.In the second paragraph of Passage One, "it" refers to "to use insecticide regularly, on avery large scale."4.In the second paragraph of Passage Two, "through" means "finish" or "complete."5.Passage One is written for academic purpose and Passage Two mainly for entertainment. II.Passage OneA blast of hot air is sent into the bottom of the furnace to make the coke burn fiercely. It is blown into the furnace through pipes. These pipes are installed around the circumference of the blast furnace eight feet above the bottom.While the coke is burning and iron is melting, gas is formed at the top of the chamber. This is led off from the top of the furnace to be used. It contains carbon monoxide, which is combustible. Part of this gas is used for making the air blast hot. It is led off into stoves.Passage TwoAll elements are composed of discrete units called atoms, which are the smallest particles that exhibit the characteristics of the element. Atoms are tiny units of matter composed of positively charged protons, negatively charged electrons, and electrically neutral neutrons. Protons and neutrons, which have approximately the same mass, are clustered in the nucleus in the center of the atom. Electrons, which are tiny in comparison to the other units, orbit the nucleus at high speed. Atoms that have an equal number of electrons and protons are electrically neutral. Those that have gained or lost electrons, and therefore are positively or negatively charged, are called ions.第二节科技、半科技英语专业术语I.1. D (自动驾驶仪)2. F (生物钟)3. I (热核的)4. G (地热的)5. B (微波)6. J (放射疗法)7. E (光周期)8. A (超导体)9. H (远距离操纵器) 10. C (超显微/滤过性病毒)II.1. 一位从事航空医学研究的医生2. 防止计算机犯罪的措施3. 一种新型除霜器4. 一个用光电池驱动的玩具5. 一辆装有自动报警器的汽车6. 隔音材料7. 一种广泛使用的杀虫剂（农药）8. 用放射性碳做的试验9. 电信业的发展10. 一台通用机床III.1. in-(Inorganic)2. radio- (radioactive)3. hydro- (Hydrotherapy)4. -free (caffeine-free)5. infra- (infrared) / ultra- (ultrared)6. mono- (monorail)7. aero- (Aerodynamics) 8. -fold (33-fold)9. geo- (geocentric) 10. -proof (weatherproof)11. bio- (biotechnology) 12. anti- (antibiotic)IV. 发电站 2. 矿物燃料 3. 太阳黑子 4. 航天探测器 5. 滚珠轴承6. 涡轮7. 航天飞机8. 树木的年轮9. 离心调速器10. 心肌功能V.1. flow2. laws3. law4. conserved5. transferred6. transformed7. bond8. thermodynamics9. work 10. law 11. degraded 12. work13. law 14. state 15. disorder 16. energy17. law 18. biological 19. metabolically 20. cellVI.1.很明显，许多家用电器的加热和照明作用都依靠电阻。

吸附模型综述EST

Department of Energy, Environmental and Chemical Engineering, Washington University, St. Louis, Missouri, United States ABSTRACT: The inclusion of multidentate adsorption reactions has improved the ability of surface complexation models (SCM) to predict adsorption to mineral surfaces, but variation in the mass action expression for these reactions has caused persistent ambiguity and occasional mishandling. The principal diﬀerences are the exponent (α) for the activity of available surface sites and the inclusion of surface site activity on a molar concentration versus fraction basis. Exempliﬁed by bidentate surface complexation, setting α at two within the molar-based framework will cause critical errors in developing a self-consistent model. Despite the publication of several theoretical discussions regarding appropriate approaches, mishandling and confusion has persisted in the model applications involving multidentate surface complexes. This review synthesizes the theory of modeling multidentate surface complexes in a style designed to enable improvements in SCM practice. The implications of selecting an approach for multidentate SCM are illustrated with a previously published data set on U(VI) adsorption to goethite. To improve the translation of theory into improved practice, the review concludes with suggestions for handling multidentate reactions and publishing results that can avoid ambiguity or confusion. Although most discussion is exempliﬁed by the generic bidentate case, the general issues discussed are relevant to higher denticity adsorption.

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ATOM:An Object-Based Formal Method for Real-time SystemsHussein Zedan1),Antonio Cau,Zhiqiang Chen,Hongji YangSoftware Technology Research Laboratory,SERCentre,De Montfort University,The Gateway,Leicester LE19BH,England,/STRL/June25,19991)The author wishes to acknowledge the funding received from the U.K.Engineering and Physical Sciences Research Council (EPSRC)through the Research Grant GR/M/02583E-mail:zedan@AbstractAn object based formal method for the development of real-time systems,called ATOM,is presented.The method is an integration of the real-time formal technique TAM(Temporal Agent Model)with an industry-strength structured methodology known as HRT-HOOD.ATOM is a systematic formal approach based on the reﬁnement calculus.Within ATOM,a formal speciﬁcation(or abstract description statement)contains Interval Temporal Logic (ITL)description of the timing,functional,and communication behavior of the proposed real-time system.This formal speciﬁcation can be analyzed and then reﬁned into concrete statements through successive applications of sound reﬁnement laws.Both abstract and concrete statements are allowed to freely intermix.The semantics of the concrete statements in ATOM are deﬁned denotationally in speciﬁcation-oriented style using ITL.keywords:object-based,wide-spectrum language,reﬁnement calculus,Temporal Agent Model,HRT-HOOD,Interval Temporal LogiciiZedan,Cau,Chen and Yang,ATOM:An Object-Based Formal Method for Real-time Systems1 1INTRODUCTIONThe‘correctness’of real-time systems’design not only depends on satisfying functional requirements,as in most information processing systems,but also on non-functional requirements,such as timing,limited resources and dependability.The development of a real-time system has been traditionally a somewhat ad-hoc affair.A system is designed from an informal requirements speciﬁcation as a number of tasks with associated deadlines,execution periods,and resource requirements.The worst-case execution time is calculated for those tasks,and a resource allocation and schedule is computed which guarantees deadlines.Worst-case execution time,allocation,and scheduling are all complex procedures and research is still active in these areas;in the two latter cases the problems are known to be NP-complete.Correctness of systems developed in this way can only be performed by testing and detailed code inspection.However,when the consequence of system failure is catastrophic such as loss of life and/or damage to the environment,testing and code inspection can not alone be relied upon.Therefore,there is clearly scope for formalizing some of the development process,particularly in the area of requirements speciﬁcation and design[Fraser et al.1991].For this purpose,a large number of formalisms have been developed,for example RTL[F.Jahanian and A.Mok1986],Timed CSP[Davies1991],RTTL[Ostroff and Wonham 1985],MTL[Koymans1990],XCTL[Harel et al.1990],ITL[Moszkowski1985],TAM[Scholeﬁeld et al.1993; Scholeﬁeld et al.1994b;Scholeﬁeld et al.1994a;Lowe and Zedan1995;He and Zedan1996],TCSP[Schneider et al.1992],TCCS[Yi1991],TACP[Bergstra and Klop1984]and time Petri Nets[Petri1962;Merlin and Segall 1976;Ramchandani1974].However,we have shown[Chen1997]that there are a signiﬁcant number of limitations with existing real-time development formalisms.Most important of these is the lack of method or guidance on how to use a formalism for both speciﬁcation writing and proving correctness.In addition,it is not clear how such formalisms can cope with the development of large scale real-time systems.In real-time systems development we would beneﬁt from a method which assists in the derivation of concrete designs from informal requirements speciﬁcations through a‘temporal’reﬁnement notion.A number of reﬁnement calculi already exist for real-time systems,but they are either incomplete or use an unrealistic computational model.PL time[He1991]is a real-time design language which consists of a CSP-like syntax with extensions for real-time.However,the formalism is based on the maximal-parallelism hypothesis(i.e.,the assumption that there are always sufﬁcient resources available)which is too restrictive for most real time systems.In addition,since PL time does not provide a separate speciﬁcation statement as a syntactic entity,the reﬁnement remains purely in the concrete domain.Similarly,RT-ASLAN[Auernheimer and Kemmerer1986]is a reﬁnement calculus which reﬁnes a speciﬁcation into concrete code,but this again relies on the maximal parallelism model.The Duration Calculus[Zhou et al.1991](and to some extend timed Z[Hayes and Utting1998]and B-method[Abrial et al.1991]2Zedan,Cau,Chen and Yang,ATOM:An Object-Based Formal Method for Real-time Systemsin recent attempts),on the other hand,is a formalism based on ITL[Moszkowski1985]and provides rules which are only applicable at the logical level of development.Furthermore,with the advent of Object-Oriented(OO)paradigm,as a powerful approach in modeling and developing large-scale and complex software systems,research in object-oriented formalism has increased.This has ranged from extending process-oriented formalisms to cater for object structure(e.g.,Z++[Lano1990]and VDM++ [Lano1995])to the development of new formal OO models(e.g.,HOSA[Goguen and Diaconescu1994;Malcom and Goguen1994],Maude[Meseguer and Winkler1992;Meseguer1993],CLOWN[Battiston and Cindio1993;Battiston et al.1995;Battiston et al.1996],CO[Bastide1992;Bastide and Palanque1993],COOPN/2[Biberstein et al.1996; Biberstein et al.1997],TRIO+[Morzenti and Pietro1994]and OO-LTL[Canver and von Henke1997]).Although the use of formal methods in the development of real-time systems have their beneﬁts,turning them into a sound engineering practice has proved to be extremely difﬁcult.Some“pure”formal methods may keep practically-oriented software engineers from employing their beneﬁts.This has led to investigating the inte-gration of formal methods with well established structured techniques used by industry(e.g.,System Analysis and Design Methodology(SSADM)[Meldrum and Lejk1993],Yourdon[Yourdon1989]and Jackson[Jackson1983], for non-real-time systems,and ROOM[Celic et al.1994]and HRT-HOOD[Burns and Wellings1995]for real-time applications).As a result,in[Mander and Polack1995;Semmens and Allen1991],both SSADM and Yourdon were integrated with the formal notation Z respectively.An attempt to incorporate Dataﬂow diagrams into the for-mal speciﬁcation notation VDM was done in[Fraser et al.1991;Plat et al.1991].Recently,Liu,et al[Liu et al. 1998],provided a method that integrates both formal techniques,structured methodologies and the Object-Oriented paradigm.However,they still lack mechanisms for the systematic development of concrete design/code from formal speciﬁcation.This has provisionally been addressed in[Chen et al.1999].The main objective of this paper is to provide a formal development technique whose underlying computational model is realistic and supports the development of large-scale systems.By realistic we take the view that it must reﬂect the basic developer’s intuition about the target application area and that the resulting system can be analyzed for schedulability.In addition,to support large-scale system development,the computational model should adopt features advocated to in the OO paradigm.The systematic derivation of a concrete design from an abstract speciﬁcation requires that the formal devel-opment technique to be based on a wide-spectrum language in which concrete and abstract constructs can be freely intermixed.Further,a set of sound reﬁnement laws must be provided enabling the software developers to transform a requirement speciﬁcation into an executable program.In this paper,we present a formal development technique ATOM.The formal language of ATOM contains both abstract and concrete statements.The development technique uses a reﬁnement calculus to get from an abstract statement to a concrete statement.The concrete statements in the language include those of the Temporal AgentZedan,Cau,Chen and Yang,ATOM:An Object-Based Formal Method for Real-time Systems3Model(TAM)[Scholeﬁeld et al.1993;Scholeﬁeld et al.1994b;Scholeﬁeld et al.1994a;Lowe and Zedan1995]. The underlying computational structure of ATOM is an extension of TAM to cater for objects.The object structure in ATOM is based on that found in the industry strength structured technique known as HRT-HOOD[Burns and Wellings 1995].HRT-HOOD is a real-time extension to HOOD[Robinson1992].The abstract statements in the language are Interval Temporal Logic[Moszkowski1985](ITL)formulae.ITL is also used to give a denotational semantics to the concrete statements so that abstract and concrete statements can be freely intermixed.The reﬁnement calculus of ATOM is an extension of that of TAM to cater for the reﬁnement into objects.In Section2,we introduce Interval Temporal logic.The computational object model of ATOM is detailed in Sect.3.The syntax and informal semantics of the ATOM language are given in Sect.4.The reﬁnement calculus of ATOM is presented in Sect.5.The systematic development technique is the outlined in Sect.6and illustrated with a small case-study in Sect.7.2INTERV AL TEMPORAL LOGICWe base our work on Interval Temporal Logic and its programming language subset Tempura[Moszkowski 1985].ITL will be used both as our abstract speciﬁcation language and to deﬁne the speciﬁcation-oriented semantics of the concrete statements in ATOM.Our selection of ITL is based on a number of points.It is aﬂexible notation for both propositional andﬁrst-order reasoning about periods of time.Unlike most temporal logics,ITL can handle both sequential and parallel composition and offers powerful and extensible speciﬁcation and proof techniques for reasoning about properties involving safety,liveness and projected time.Timing constraints are expressible and furthermore most imperative programming constructs can be viewed as formulas in a slightly modiﬁed version of ITL[Cau and Zedan1997]. Tempura provides an executable framework for developing and experimenting with suitable ITL speciﬁcations.2.1SyntaxAn interval is considered to be a(in)ﬁnite sequence of states,where a state is a mapping from variables to their values.The length of an interval is equal to one less than the number of states in the interval(i.e.,a one state interval has length0).The syntax of ITL is deﬁned in Table1whereµis an integer value,a is a static variable(doesn’t change within an interval),A is a state variable(can change within an interval),v a static or state variable,g is a function symbol,p is a predicate symbol.The informal semantics of the most interesting constructs are as follows:ıa:f:the value of a such that f holds.4Zedan,Cau,Chen and Yang,ATOM:An Object-Based Formal Method for Real-time SystemsTable1:Syntax of ITLSkip:unit interval(length1).f1;f2:holds if the interval can be decomposed(“chopped”)into a preﬁx and sufﬁx interval,such that f1holds over the preﬁx and f2over the sufﬁx,or if the interval is inﬁnite and f1holds for that interval.f:holds if the interval is decomposable into aﬁnite number of intervals such that for each of them f holds,or the interval is inﬁnite and can be decomposed into an inﬁnite number ofﬁnite intervals for which f holds.These constructs enables us to deﬁne programming constructs like assignment,if then else,while loop etc.In table2 some frequently used abbreviations are listed.2.2Data RepresentationIntroducing type system into speciﬁcation languages has its advantages and disadvantages.An untyped set theory is simple and is moreﬂexible than any simple typed formalism.Polymorphism,overloading and subtyping can make a type system more powerful but at the cost of increased complexity.While types serve little purpose in hand proofs,they do help with mechanized proofs.There are two basic inbuilt types in ITL(which can be given pure set-theoretic deﬁnitions).These are integers N(together with standard relations of inequality and quality)and Boolean(true and false).In addition,the executable subset of ITL(Tempura)has basic types:integer,character,Boolean,list and arrays.Further types can be built from these by means of and the power set operator,P(in a similar fashion as adopted in the speciﬁcation language Z).For example,the following introduces a variable x of type Tx:T f x type T fHere type T denotes a formula describing the desired type.For example,type T could be0x7and so on.Although this might seem to be rather inexpressive type system,richer type can be added following that of Spivey[Spivey1996].Zedan,Cau,Chen and Yang,ATOM:An Object-Based Formal Method for Real-time Systems5Table2:Frequently used abbreviations3OBJECT-BASED COMPUTATIONAL MODELIn this section we present our object-based model which is a conservative extension to that adopted in the Temporal Agent Model(TAM)[Scholeﬁeld et al.1993;Scholeﬁeld et al.1994b;Scholeﬁeld et al.1994a;Lowe and Zedan1995].TAM was developed to be a realistic formal software development method for real-time systems.Such an extension is based on an industry-strength structured methodology known as HRT-HOOD[Burns and Wellings 1995].A real-time system is viewed as a collection of concurrent activities which are initiated either periodically or sporadically with services which can be requested by the execution of the activities.The operations of the activities and services,as threads and methods,are allocated to the corresponding objects(an encapsulated operation environment for the thread or methods)according to their functional and temporal requirements and the relationships between them.6Zedan,Cau,Chen and Yang,ATOM:An Object-Based Formal Method for Real-time Systems3.1Object StructureIn ATOM we can identifyﬁve types of objects.These are deﬁned as follows.1.sporadic object—deﬁnes a unique thread which activates an operation sporadically by response to externalevents.The thread can not be requested and executed by other methods’invocations,however,it can invoke methods provided by other objects.The thread may be concurrent with other activities in the system.A mini-mum interval can be speciﬁed to restrain responses to continuous event occurrences.Sporadic objects are used to model entities in a system which are involved in random activities.2.cyclic object—is similar to a sporadic object except that its thread speciﬁes an operation which is executedperiodically.A cyclic object deﬁnes a period to specify how often the operation is and it isﬁxed.Every execution of the operation must be terminated within this period.Cyclic objects are used to model entities in a system which are involved in periodic activities.3.protected object—deﬁnes services which can be invoked.The services are implemented by methods whichcan be requested by others for execution.The methods can be requested arbitrarily,but their executions must be mutually exclusive.The execution order of invocations depends on their times of request.A method in a protected object can only request the methods which are(in)directly implemented by passive objects.Protected objects are used to model shared critical resources accessed by different objects or methods.4.passive object—is similar to a protected object except there are no constraints on invocations of its methods.Amethod in a passive object can be arbitrarily requested and immediately executed as a part of its client whenever being requested.A method in a passive object can only request the methods which are(in)directly implemented by other passive objects.Passive objects are used to deﬁne non-interfering operations on resources.5.active object—deﬁnes a framework for a number of related objects which are referred to as its child objects.An active object can be viewed as an independent system or subsystem.It encapsulates the methods of its child objects.Any object outside an active object can not request the methods deﬁned in its child objects directly but through a method deﬁned by it.The signature of a method deﬁned in an active object must be consistent with that of its counterpart except its name.An active object can not include itself as a child object directly or indirectly and an object can not be a child object of different objects.The environment of a non-active object is a set of data over which the methods of the object execute for computations and communications.The data include constants,variables and shunts.For cyclic and sporadic objects, an activation period and a minimum activation interval are speciﬁed in the environment declaration respectively.We use ObjEnv o to denote the environment set of an object o.Zedan,Cau,Chen and Yang,ATOM:An Object-Based Formal Method for Real-time Systems7Threads/methods are agents as deﬁned in TAM.Threads activate and terminate with the corresponding objects and are concurrent with each other.Methods are activated by invocations and their executions may be either concurrent or sequential.Invocations of methods can be either asynchronous or synchronous.Recursive invocations between methods are prohibited,neither directly nor indirectly.3.2Agent StructureAn agent is described by a set of computations,which may transform a local data munication is asynchronous via time-stamped shared data areas called shunts.Shunts are passive shared memory spaces that contain two values:theﬁrst gives the time at which the most recent write took place,and the second gives the value that was most recently written.Systems themselves can be viewed as single agents and composed into larger systems.At any time,a system can be thought of having a unique state,deﬁned by the values in the shunts and local variables.The computation may be nondeterministic.In particular:Time is global,i.e.,a single clock is available to every agent and shunt.The time domain is discrete,linear,and modeled naturally by the natural numbers.No state change may be instantaneous.An agent may start execution either as a result of a write event on a speciﬁc shunt,or as the result of some condition on the current time:these two conditions model sporadic and periodic tasks respectively.An agent may have deadlines on computations and communication.Deadlines are considered to be hard,i.e., there is no concept of deadline priority,and all deadlines must me met by the run-time system.We are currently investigating the inclusion of prioritized deadlines into the language.A data space is created when an agent starts execution,with nondeterministic initial values;the data space isdestroyed when the agent terminates.No agent may read or write another agent’s local data space.A system has a static conﬁguration,i.e.,the shunt connection topology remainsﬁxed throughout the lifetime ofthe system.An agent’s output shunts are owned by that agent,i.e.,no other agent may write to those shunts,although many other agents may read them.Shunt writing is destructive,but shunt reading is not.8Zedan,Cau,Chen and Yang,ATOM:An Object-Based Formal Method for Real-time Systems4ATOM LANGUAGEATOM has the following syntactic form.An object consists of a declaration and method(s)in a structure.The declaration presents the deﬁnitions of attributes and/or an execution environment for methods deﬁned in the object. The attributes of an object include:object type—indicates the object is either active,sporadic,cyclic,protected or passive.provided methods—signatures of the methods provided by the object for other objects.We use ProvidedMethods o to denote the provided method set of an object o where o is sometimes dropped if no confusion is caused.The signatures must be accordant with their deﬁnitions.They are declared in the form of m in out,where m is a method name which is free in the object.in and out are sets which present parameters transfered between m and its clients.card in0and card out0(where card denotes cardinality of the set).We use in m and out m to denote them.used methods—declare the methods invoked by the object and the objects which provide the methods.We use UsedMethods o to denote the used method set of an object o where o is sometimes dropped if no confusion is caused.The elements of the set UsedMethods o take the form of o m,where m is a method to be invoked by o and is deﬁned in edMethods o deﬁnes use relationships between o and objects in UsedMethods o.Such relationships specify controlﬂows between objects and together with in m and out m, dataﬂows are also speciﬁed.Other attributes vary with the type of objects:the activation interval of the thread for a cyclic object.the minimum activation interval of the thread for a sporadic object.the child object set for an active object.We use ChildObjects o to denote the child object set of o if o is an active object.ChildObjects o speciﬁes an include relationship between o and its child objects based on which the decomposition process is achieved.The syntax of the ATOM language is deﬁned in Table3where A is a TAM agent;ProvidedMethods is a set of provided methods;Ev is a shunt;P,t and T are time variables;S a shunt name;w a set of computation variables and shunts;f an ITL formula;x a variable;e an expression on variables;I someﬁnite indexing set;g i a boolean expression;and n a natural number.Informally,the agents in Table3have the following meaning:Table3:Syntax of ATOM languagew:f is a speciﬁcation statement.It speciﬁes that only the variables in the frame w may be changed,and the execution must satisfy ITL formula f.The agent Skip may terminate after any delay.The agent∆t terminates after t time units.x:e evaluates the expression e,using the values found in variables at the start time of the agent,and assigns it to x.The expression e may not include the values held in shunts:it may only use the values held in variables.x s performs an input from shunt s,storing the value in x;the type of x must be a time–value pair.e s writes the current value of expression e to shunt s,time-stamping it with the time of the write.A;A performs a sequential composition of A and A.var x:T in A deﬁnes x to be a new local variable of type T within A;its initial value is chosen nondeterministi-cally.shunt s:T in A deﬁnes s to be a new local shunt of type Time T within A;its initial value is chosen nondeter-ministically,but it is time-stamped with the time of its declaration.t A gives agent A a duration of t:if the agent terminates before t seconds have elapsed,then the agent should idle toﬁll this interval;if the agent does not terminate within t seconds,then it is considered to have failed.if t i I g i then A iﬁevaluates all the boolean guards g i,and executes an A i corresponding to a true guard;if all the guards evaluate to false,then the agent terminates correctly.The evaluation of the guards should take precisely t time units;if necessary,the agent should idle toﬁll this interval.We shall sometimes omit theparameter t if we do not want to specify it.We shall sometimes write this construct as if t g1then A1g2then A2g n then A nﬁ.A A forms a nondeterministic choice between A and A.A s t A monitors shunt s for t time units:if a write occurs within this time,then it executes A;otherwise ittimes-out and executes A.A A executes the two agents concurrently,terminating when both agents terminate.loopfor n period t A executes A n times,giving each a duration of t.We note here that no agent may share its local state space with concurrently executing agents,and only one concurrent agent may write to any given shunt:these restrictions allow the development of a compositional semantics and reﬁnement calculus.The formal semantics of the concrete part of the ATOM language is presented in Sect.A.5ATOM REFINEMENT CALCULUSThe reﬁnement relation is deﬁned on a component(agent,method and object)in a similar fashion to that of TAM.A component X is reﬁned by the component Y,denoted X Y,if and only if Y X.A set of sound reﬁnement laws are derived to transform an abstract speciﬁcation into concrete objects.The following are some useful reﬁnement laws.The soundness of these laws follows from the deﬁnition of the reﬁnement relation.The following law states that the operators in ITL are monotonic w.r.t.the reﬁnement relation.Monotonicity means that the ATOM reﬁnement calculus is compositional.Law1(Monotonicity)Let f i be an ITL formula then1If f0f1and f1f2then f0f22If f0f1and f2f3then f0f2f1f33If f0f1and f2f3then f0f2f1f34If f1f2then f0;f1f0;f25If f1f2then f1;f0f2;f06If f0f1then f0f17If f0f1then v f0v f1The following law states that any interval of length1can be reﬁned into the Skip statement.Law2(Skip)len1SkipThe following law states that any interval of length t can be reﬁned into the delay statement∆t.Law3(Delay)len t∆tThe following law states that when variable x gets the value of exp in the next state of an interval this can be reﬁned into the assignment x:exp.Law4(Assignment)If x w thenw:x exp x:expThe following law states that shunt reading corresponds to reading of the stamp and the value of the shunt.Law5(Shunt read)If x w thenw:x1s x2read s x sThe following law states that shunt writing is like assignment but that also the stamp is increased by1.Law6(Shunt read)If x w thenw:s s1x x sThe following law states that sequential composition is associative and distributes over the.Law7(Sequential composition)f0;f1;f2f0;f1;f2f0;f1;f2f0;f1;f2f0;f1f2f0;f1f0;f2f0;f1f0;f2f0;f1f2The following law is for the introduction of a variable v.Law8(New variable)w:f var v in w v:fThe following law is for the introduction of a new shunt.Law9(New shunt)w:f shunt s in w s:s0fThe following law is for the introduction of the deadline.Law10(Deadline)∆t f;true f len t t fThe alternation is introduced with the following law.Law11(Alternation)f0f1f2f3if f0then f1f2then f3ﬁThe following law states that the nondeterministic choice corresponds to the of ITL. Law12(Nondeterministic choice)f0f1f0f1The timeout is introduced with the following law.Law13(Timeout)∆t stable s;f0∆t stable s;f1f0s t f1The following law introduces the parallel composition.Law14(Parallel composition)If w0w1/0,thenw0w1:f0f1w0:f0w1:f1This law will introduce the loop.Law15(Loop)t f n loopfor n period t fThe following5laws is for the introduction of the ATOM objects.Law16(Cyclic object)ﬁnite len P f;true cyclic Object name thread on P do f endLaw17(Sporadic object)ﬁnite stable Ev;Skip Ev Ev;f;true len Tsporadic T Object name thread on Ev do f endLaw18(Protected object)LetMutΣi Status i Act1Ifm i Status i Req stable Status i;Skip;Status i Act stable Status i f m i;Skip;Status i Idle stable Status ithenﬁnite i m i Mut protected Object name ProvidedMethods m1m n endLaw19(Passive object)Ifm i Status i Req stable Status i;Skip;Status i Act stable Status i f m i;Skip;Status i Idle stable Status ithenﬁnite i m i passive Object name ProvidedMethods m1m n endLaw20(Active object)Let ProvidedMethods o/0.o i active Object name ProvidedMethods o1o n endi6ATOM DEVELOPMENT TECHNIQUEIn order to derive a concrete design from an abstract speciﬁcation,a reﬁnement calculus was developed.In theﬁrst stage,the designer builds a system model and states the system’s requirements(or‘expectation’)along with assumptions/constraints of the ing HRT-HOOD such system’s requirement may be decomposed into sub-requirement.Each sub-requirement is formalized,using the speciﬁcation statement which is subsequently reﬁned into objects using the reﬁnement laws.A development method is therefore suggested:Given an informal requirement REQ of a system.。