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Top-Seeded Melt-Growth of YBa_2Cu_3O_x Crystals for Neutron Diffraction Studies

Top-Seeded Melt-Growth of YBa_2Cu_3O_x Crystals for Neutron Diffraction Studies

a r X i v :c o n d -m a t /0209418v 1 [c o n d -m a t .s u p r -c o n ] 17 S e p 2002Top-Seeded Melt-Growth of YBa 2Cu 3O x Crystals for Neutron Diffraction StudiesD.C.Peets,1,∗Ruixing Liang,1,†C.Stock,2W.J.L.Buyers,3,†Z.Tun,3L.Taillefer,2,†R.J.Birgeneau,2,†D.A.Bonn,1,†and W.N.Hardy 1,†1Department of Physics and Astronomy,University of British Columbia,Vancouver,BC,Canada2Physics Department,University of Toronto,Toronto,ON,Canada3National Research Council,Chalk River,ON,Canada(Dated:February 1,2008)We have grown cubic centimetre-size crystals of YBa 2Cu 3O x suitable for neutron studies,by a top-seeded melt-growth technique.Growth conditions were optimized with an eye toward maximizing phase purity.It was found that the addition of 2%Y 2BaCuO 5and 0.5%Pt (by mass)were required to prevent melt loss and to obtain the highest crystallinity.A neutron diffraction study on a mosaic of six such crystals found that the final Y 2BaCuO 5concentration was 5%,while other impurity phases comprised less than 1%by volume.The oxygen content was set to x =6.5,the crystals were detwinned and then carefully annealed to give the well-ordered ortho-II phase.The neutron study determined that 70%of the mosaic’s volume was in the majority orthorhomic domain.The neutron (006)and (110)rocking curve widths were ∼1◦per crystal and ∼2.2◦for the mosaic,and the oxygen chain correlation lengths were >100˚A in the a -and b -directions and ∼50˚A in the c -direction.Keywords:crystal growth,top-seeded melt-growth,Ortho-II,YBCO,neutron scattering1.MOTIV ATIONNeutron scattering is an extremely powerful technique for investigating spin fluctuation and magnetic ordering in superconducting samples.However,to obtain reason-able signal to noise one requires sample sizes on the order of several cubic centimetres.The self-flux technique[1,2],which produces the highest-quality YBa 2Cu 3O x single crystals and is the primary method for growing crystals for fundamental research,has thus far only been able to yield crystals as large as 5mm ×5mm ×12-1%Pt by mass,andwere not well suited to neutron studies since the scatter-ing from the inclusions can overlap the scattering from the YBa 2Cu 3O x .This study aimed to optimize the top-seeded melt-growth technique for the lowest concentration of impurity phase inclusions and best crystallinity (minimum mosaic spread).The resulting cubic centimetre-size YBa 2Cu 3O x crystals were then annealed to the oxygen-ordered ortho-II phase (x =6.5).This allows a neutron scattering study on spin fluctuations and magnetic ordering to be carried2%Pt by mass was requiredfor this purpose.Without the addition of Y 2BaCuO 5,the crystals were porous,had poor mosaic spread,and contained BaO-CuO flux inclusions.Best results were obtained when the pellet contained 2%Y 2BaCuO 5by mass.A higher concentration of Y 2BaCuO 5was found to be necessary for proper seeding,so a small quantity of Y 2BaCuO 5-rich powder (10%Y 2BaCuO 5by mass)was added to the top of the pellet prior to pressing.This layer constituted ∼0.4%of the pellet.NdBa 2Cu 3O x was chosen as a seed crystal for its near-perfect lattice match and for having a melting tempera-ture ∼80◦C higher than that of YBa 2Cu 3O x .The seed and pellet were placed on a disc-shaped substrate,loaded into a three-zone vertical tube furnace,and subjected to the temperature program shown in figure 1.After a sintering step at 990◦C,a temperature gradient of ∼5◦ChFurnace elementInsulationN 2flowFIG.2:Schematic diagram of the detwinner.A specialized detwinner,depicted schematically in fig-ure 2,was built for these crystals.The sample was loadedinto it,sandwiched between two gold pads to ensure that the pressure was uniformly distributed on the two a -axis faces.A uniaxial pressure of ∼150MPa (1500atm)was applied,as gauged by monitoring the compression of sev-eral lock washers with known spring constants.The de-twinner was loaded into a horizontal tube furnace and heated to 350◦C in flowing nitrogen for 30minutes,then cooled to room temperature at 60◦C per hour.The crys-tal’s mass was not observed to be changed by this process,indicating no measurable change in the crystal’s oxygen content during detwinning.Once detwinned,the crystals were annealed at 60◦C in sealed containers for two weeks to establish ortho-II oxygen ordering.3.ANALYSISMagnetization measurements in a Quantum Design SQUID magnetometer found the crystals’T c to be 59K,and 2.5K wide (field-cooled,H =1.5Oe, H c ).A sample was subjected to EDX compositional analy-sis to determine the shape and distribution of impurityphases.Y 2BaCuO 5was only observed at the base of the pellet,near the growth front,but the equipment’s ∼1µm resolution makes it insensitive to small inclusions in the bulk.Two Pt-containing phases were found,one of which was consistent with the formula Y 2PtBa 3Cu 2O 10.Neu-tron scans found weak impurity peaks consistent with this compound as well.Neutron diffraction experiments were carried out at the NRC Chalk River laboratory (NRU reactor).There,six crystals were sealed in airtight cans under dry he-lium,aligned,and inserted into the E3spectrometer.The (006)and (110)rocking curve widths were ∼1◦for each crystal,and ∼2.2◦for the mosaic of six.Figure 3shows ortho-II ordering superlattice diffractions via radial scansthrough (32a ∗0).The detwinning was incomplete –the majority domain occupied only 70%of the sample volume.The neutron study also found that the concentration of Y 2BaCuO 5in the mosaic was ∼5%by volume,while all other impurity phases constituted less than 1%.A determination of the oxygen ordering correlation length was resolution limited (horizontal bar in figure 3),but a fit to a resolution-convolved Lorentzian indicated a length >100˚A in the a -and b -directions and ∼50˚A in the c -direction.Given the growth method used,these compare remarkably well with the values of ξa =148˚A ,ξb =430˚A and ξc =58˚A obtained in high-purity sin-gle crystals[13].Indeed,they even exceed the correlation lengths found in many flux-grown single crystals.Further neutron scattering results will be published elsewhere[15].100200300400500600700800 1.441.46 1.48 1.5 1.52 1.54 1.56I n t e n s i t y (c o u n t s /12 s e c )(H, 0, 0) or (0, K, 0) (r.l.u. units a*)FIG.3:Radial elastic neutron scattering scans through(32a ∗0),with the experimental resolution indicated.The larger and smaller peaks are from the major-ity and minority domains,the larger domain accounting for 70%of the sample volume.4.CONCLUSIONWe have grown and detwinned cubic centimetre-size crystals of ortho-II YBa 2Cu 3O 6.5,with oxygen ordering correlation lengths >100˚A in the plane and ∼50˚A in the c -direction.They contain 5%Y 2BaCuO 5by volume and are partially detwinned,with 70%of their volume in the major orientation.Each crystal has a rocking curve width of ∼1◦.These crystals are currently being studied in detail by neutron scattering,and have already shown that their symmetry is not broken by satellite Bragg peaks associated with static long-range d-density wave order,as is seen in less-ordered crystals[15].AcknowledgmentsThis research was supported by the Canadian Institute for Advanced Research.The work at the University of British Columbia and at the University of Toronto was supported by NSERC.[1]A.Erb,E.Walker,and R.Fl¨u kiger,Physica C 245,245(1995).[2]R.Liang,D.A.Bonn,and W.N.Hardy,Physica C 304,105(1998).[3]T.Izumi,Y.Nakamura,and Y.Shiohara,J.Mater.Res.7,1621(1992).[4]M.Cima,M.C.Fleming,A.M.Figueredo,M.Nakade,H.Ishii,H.D.Brody,and J.S.Haggerty,J.Appl.Phys.72,179(1992).[5]C. A.Bateman,L.Zhang,H.M.Chan,and M.P.Harmer,J.Am.Ceram.Soc.75,1281(1992).[6]T.Izumi,Y.Nakamura,and Y.Shiohara,J.Cryst.Growth 128,757(1993).[7]S.Marinel,J.Wang,I.Monot,M.P.Delamare,J.Provost,and G.Desgardin,Supercond.Sci.Tech.10,147(1997).[8]D.Shi,hiri,D.Qu,and S.Sagar,J.Mater.Res.12,3036(1997).[9]M.Boffa,M.Boutet,A.D.Trolio,S.Pace,N.Sparvieri,A.M.Testa,and A.Vecchione,Physica C 282,487(1997).[10]R.Yu,J.Mora,N.Vilalta,F.Sandiumenge,V.Gomis,S.Pi˜n ol,and X.Obradors,Supercon.Sci.Tech.10,583(1997).[11]Y.Imagawa and Y.Shiohara,Physica C 262,243(1996).[12]N.Ogawa,I.Hirabayashi,and S.Tanaka,Physica C 177,101(1991).[13]R.Liang,D.A.Bonn,and W.N.Hardy,Physica C 236,57(2000).[14]P.Manca,S.Sanna,G.Calestani,A.Migliori,pin-skas,and E.E.Tornau,Phys.Rev.B 63,134512(2001).[15]C.Stock,W.J.L.Buyers,Z.Tun,R.Liang,D.Peets,D.Bonn,W.N.Hardy,and L.Taillefer,Phys.Rev.B 66,024505(2002),cond-mat/0203076.。

精选最新版2020年移动大比武考试题库(数据通信)考核题库完整版588题(含答案)

精选最新版2020年移动大比武考试题库(数据通信)考核题库完整版588题(含答案)

2020年移动大比武考试题库(数据通信)588题[含参考答案]一、填空题1.天线增益用([dBd])或([dBi])来表示,其中dBd表示偶极天线的相对增益,dBi则表示各向同性天线(天线的能量均等地向各个方向辐射)的相对增益。

以下是dBd和dBi的换算公式G(dBi)=G(dBd)+([2dB])。

2.从小区广播信息中UE可以知道与随机接入有关的两个公共信道([PRACH])信道和([FPACH])信道的详细信息。

3.每个载频都有([8])个时隙。

4.BSC和BTS之间的接口称为接口,BTS和MS之间的接口称为接口,BSC和MSC之间的接口称为([ABIS])口,MSC之间的接口为口。

其中主要传输([Um])和([A])等信号。

5.小区扩展技术可以使GSM小区的覆盖范围增加到([120])公里。

6.呼叫重建流程是指([MS在无线链路失败后,重新恢复连接的一个过程])。

7.TD-LTE无线网络空载时的单向传输IP空包所需时间少于([5ms]),相对3G的百毫秒量级时延,是一个巨大的改进,有助于提高([交互式在线游戏])、([高清视频会议])等众多实时业务的服务质量。

8.GSM话务报告Type31的下载目录是([/APME/BSC])。

9.在基站子系统中,([Abis])接口是一个不开放的接口,因此各厂家可以自己定义这个接口的协议。

10.MCS9编码的调制方式是([8PSK])。

11.手机发生重选后,若发现当前LAC与刚才的LAC发生变化,则会触发([位置更新])过程。

12.无线利用率是指无线网络实际的总话务量占无线网络([设计])能力的百分比。

13.对移动通信网络常见的干扰从频段上可分为([上行干扰])和([下行干扰]),联通CDMA网络对中国移动网络的干扰类型主要属于([上行干扰])。

14.切换是由([RNC])判决的。

15.规范中规定了在哪些消息块来发送什么样的系统消息,其中系统消息类型1在TC=([0])时发送。

Journal of Loss Prevention in the Process Industries

Journal of Loss Prevention in the Process Industries

HAZOP e Local approach in the Mexican oil &gas industryM.Pérez-Marín a ,M.A.Rodríguez-Toral b ,*aInstituto Mexicano del Petróleo,Dirección de Seguridad y Medio Ambiente,Eje Central Lázaro Cárdenas Norte No.152,07730México,D.F.,Mexicob PEMEX,Dirección Corporativa de Operaciones,Gerencia de Análisis de Inversiones,Torre Ejecutiva,Piso 12,Av.Marina Nacional No.329,11311México,D.F.,Mexicoa r t i c l e i n f oArticle history:Received 3September 2012Received in revised form 26March 2013Accepted 27March 2013Keywords:HAZOPRisk acceptance criteria Oil &gasa b s t r a c tHAZOP (Hazard and Operability)studies began about 40years ago,when the Process Industry and complexity of its operations start to massively grow in different parts of the world.HAZOP has been successfully applied in Process Systems hazard identi fication by operators,design engineers and consulting firms.Nevertheless,after a few decades since its first applications,HAZOP studies are not truly standard in worldwide industrial practice.It is common to find differences in its execution and results format.The aim of this paper is to show that in the Mexican case at National level in the oil and gas industry,there exist an explicit acceptance risk criteria,thus impacting the risk scenarios prioritizing process.Although HAZOP studies in the Mexican oil &gas industry,based on PEMEX corporate standard has precise acceptance criteria,it is not a signi ficant difference in HAZOP applied elsewhere,but has the advantage of being fully transparent in terms of what a local industry is willing to accept as the level of risk acceptance criteria,also helps to gain an understanding of the degree of HAZOP applications in the Mexican oil &gas sector.Contrary to this in HAZOP ISO standard,risk acceptance criteria is not speci fied and it only mentions that HAZOP can consider scenarios ranking.The paper concludes indicating major implications of risk ranking in HAZOP,whether before or after safeguards identi fication.Ó2013Elsevier Ltd.All rights reserved.1.IntroductionHAZOP (Hazard and Operability)studies appeared in systematic way about 40years ago (Lawley,1974)where a multidisciplinary group uses keywords on Process variables to find potential hazards and operability troubles (Mannan,2012,pp.8-31).The basic prin-ciple is to have a full process description and to ask in each node what deviations to the design purpose can occur,what causes produce them,and what consequences can be presented.This is done systematically by applying the guide words:Not ,More than ,Less than ,etc.as to generate a list of potential failures in equipment and process components.The objective of this paper is to show that in the Mexican case at National level in the oil and gas industry,there is an explicit acceptance risk criteria,thus impacting the risk scenarios priori-tizing process.Although HAZOP methodology in the Mexican oil &gas industry,based on PEMEX corporate standard has precise acceptance criteria,it is not a signi ficant difference in HAZOP studies applied elsewhere,but has the advantage of being fullytransparent in terms of what a local industry is willing to accept as the level of risk acceptance criteria,also helps to gain an under-standing of the degree of HAZOP applications in the Mexican oil &gas sector.Contrary to this in HAZOP ISO standard (ISO,2000),risk acceptance criteria is not speci fied and it only mentions that HAZOP can consider scenarios ranking.The paper concludes indicating major implications of risk prioritizing in HAZOP,whether before or after safeguards identi fication.2.Previous workHAZOP studies include from original ICI method with required actions only,to current applications based on computerized documentation,registering design intentions at nodes,guide words,causes,deviations,consequences,safeguards,cause fre-quencies,loss contention impact,risk reduction factors,scenarios analysis,finding analysis and many combinations among them.In the open literature there have been reported interesting and signi ficant studies about HAZOP,like HAZOP and HAZAN differences (Gujar,1996)where HAZOP was identi fied as qualitative hazard identi fication technique,while HAZAN was considered for the quantitative risk determination.This difference is not strictly valid today,since there are now companies using HAZOP with risk analysis*Corresponding author.Tel.:þ525519442500x57043.E-mail addresses:mpmarin@imp.mx (M.Pérez-Marín),miguel.angel.rodriguezt@ ,matoral09@ (M.A.Rodríguez-Toral).Contents lists available at SciVerse ScienceDirectJournal of Loss Prevention in the Process Industriesjou rn al homepage :/locate/jlp0950-4230/$e see front matter Ó2013Elsevier Ltd.All rights reserved./10.1016/j.jlp.2013.03.008Journal of Loss Prevention in the Process Industries 26(2013)936e 940and its acceptance criteria(Goyal&Kugan,2012).Other approaches include HAZOP execution optimization(Khan,1997);the use of intelligent systems to automate HAZOP(Venkatasubramanian,Zhao, &Viswanathan,2000);the integration of HAZOP with Fault Tree Analysis(FTA)and with Event Tree Analysis(ETA)(Kuo,Hsu,& Chang,1997).According to CCPS(2001)any qualitative method for hazard evaluation applied to identify scenarios in terms of their initial causes,events sequence,consequences and safeguards,can beextended to register Layer of Protection Analysis(LOPA).Since HAZOP scenarios report are presented typically in tabular form there can be added columns considering the frequency in terms of order of magnitude and the probability of occurrence identified in LOPA.There should be identified the Independent and the non-Independent Protection Layers,IPL and non-IPL respec-tively.Then the Probability of Failure on Demand(PFDs)for IPL and for non-IPL can be included as well as IPL integrity.Another approach consists of a combination of HAZOP/LOPA analysis including risk magnitude to rank risk reduction actions (Johnson,2010),a general method is shown,without emphasizing in any particular application.An extended HAZOP/LOPA analysis for Safety Integrity Level(SIL)is presented there,showing the quan-titative benefit of applying risk reduction measures.In this way one scenario can be compared with tolerable risk criteria besides of being able to compare each scenario according to its risk value.A recent review paper has reported variations of HAZOP methodology for several applications including batch processes, laboratory operations,mechanical operations and programmable electronic systems(PES)among others(Dunjó,Fthenakis,Vílchez, &Arnaldos,2010).Wide and important contributions to HAZOP knowledge have been reported in the open literature that have promoted usage and knowledge of HAZOP studies.However,even though there is available the IEC standard on HAZOP studies,IEC-61882:2001there is not a worldwide agreement on HAZOP methodology and there-fore there exist a great variety of approaches for HAZOP studies.At international level there exist an ample number of ap-proaches in HAZOP studies;even though the best advanced prac-tices have been taken by several expert groups around the world, there is not uniformity among different consulting companies or industry internal expert groups(Goyal&Kugan,2012).The Mexican case is not the exception about this,but in the local oil and gas industry there exist a national PEMEX corporate standard that is specific in HAZOP application,it includes ranking risk scenarios (PEMEX,2008),qualitative hazard ranking,as well as the two ap-proaches recognized in HAZOP,Cause by Cause(CÂC)and Devia-tion by Deviation(DÂD).Published work including risk criteria include approaches in countries from the Americas,Europe and Asia(CCPS,2009),but nothing about Mexico has been reported.3.HAZOP variationsIn the technical literature there is no consensus in the HAZOP studies procedure,from the several differences it is consider that the more important are the variations according to:(DÂD)or (CÂC).Table1shows HAZOP variations,where(CQÂCQ)means Consequence by Consequence analysis.The implications of choosing(CÂC)are that in this approach there are obtained unique relationships of Consequences,Safeguards and Recommendations,for each specific Cause of a given Deviation. For(DÂD),all Causes,Consequences,Safeguards and Recommenda-tions are related only to one particular Deviation,thus producing that not all Causes appear to produce all the Consequences.In practice HAZOP approach(DÂD)can optimize analysis time development.However,its drawback comes when HAZOP includes risk ranking since it cannot be determined easily which Cause to consider in probability assignment.In choosing(CÂC)HAZOP there is no such a problem,although it may take more time on the analysis.The HAZOP team leader should agree HAZOP approach with customer and communicate this to the HAZOP team.In our experience factors to consider when choosing HAZOP approach are:1.If HAZOP will be followed by Layers of Protection Analysis(LOPA)for Safety Integrity Level(SIL)selection,then choose (CÂC).2.If HAZOP is going to be the only hazard identification study,it isworth to make it with major detail using(CÂC).3.If HAZOP is part of an environmental risk study that requires aConsequence analysis,then use(DÂD).4.If HAZOP is going to be done with limited time or becauseHAZOP team cannot spend too much time in the analysis,then use(DÂD).Although this is not desirable since may compro-mise process safety.Regarding risk ranking in HAZOP,looking at IEC standard(IEC, 2001)it is found that HAZOP studies there are(DÂD)it refers to (IEC,1995)in considering deviation ranking in accordance to their severity or on their relative risk.One advantage of risk ranking is that presentation of HAZOP results is very convenient,in particular when informing the management on the recommendations to be followedfirst or with higher priority as a function of risk evaluated by the HAZOP team regarding associated Cause with a given recommendation.Tables2and3are shown as illustrative example of the convenience of event risk ranking under HAZOP,showing no risk ranking in Table2and risk ranking in Table3.When HAZOP presents a list of recommendations without ranking,the management can focus to recommendations with perhaps the lower resource needs and not necessarily the ones with higher risk.Table1Main approaches in HAZOP studies.Source HAZOP approach(Crowl&Louvar,2011)(DÂD)(ABS,2004)(CÂC)&(DÂD)(Hyatt,2003)(CÂC),(DÂD)&(CQÂCQ) (IEC,2001)(DÂD)(CCPS,2008);(Crawley,Preston,& Tyler,2008)(DÂD),(CÂC)Table2HAZOP recommendations without risk ranking.DescriptionRecommendation1Recommendation2Recommendation3Recommendation4Recommendation5Table3HAZOP recommendations with risk ranking.Scenario risk DescriptionHigh Recommendation2High Recommendation5Medium Recommendation3Low Recommendation1Low Recommendation4M.Pérez-Marín,M.A.Rodríguez-Toral/Journal of Loss Prevention in the Process Industries26(2013)936e940937As can be seen in Tables 2and 3,for the management there will be more important to know HAZOP results as in Table 3,in order to take decisions on planning response according to ranking risk.4.HAZOP standard for the Mexican oil &gas industryLooking at the worldwide recognized guidelines for hazard identi fication (ISO,2000)there is mentioned that when consid-ering scenarios qualitative risk assignment,one may use risk matrix for comparing the importance of risk reduction measures of the different options,but there is not a speci fic risk matrix with risk values to consider.In Mexico there exist two national standards were tolerable and intolerable risk is de fined,one is the Mexican National Standard NOM-028(NOM,2005)and the other is PEMEX corporate standard NRF-018(PEMEX,2008).In both Mexican standards the matrix form is considered for relating frequency and consequences.Fig.1shows the risk matrix in (NOM,2005),nomenclature regarding letters in this matrix is described in Tables 4e 6.It can be mentioned that risk matrix in (NOM,2005)is optional for risk management in local chemical process plants.For Mexican oil &gas industry,there exist a PEMEX corporate standard (NRF),Fig.2,shows the corresponding risk matrix (PEMEX,2008).Nomenclature regarding letters in this matrix is described in Tables 7e 9for risk concerning the community.It is important to mention that PEMEX corporate standard considers environmental risks,business risks,and corporate image risks.These are not shown here for space limitations.The Mexican National Standard (NOM)as being of general applicability gives the possibility for single entities (like PEMEX)to determine its own risk criteria as this company opted to do.PEMEX risk matrix can be converted to NOM ’s by category ’s grouping infrequency categories,thus giving same flexibility,but with risk speci fic for local industry acceptance risk criteria.One principal consideration in ranking risk is to de fine if ranking is done before safeguards de finition or after.This de finition is relevant in:HAZOP kick-off presentation by HAZOP leader,explaining im-plications of risk ranking.HAZOP schedule de finition.Risk ranking at this point takes shorter time since time is not consumed in estimating risk reduction for each safeguard.If after HAZOP a LOPA is going to be done,then it should be advisable to request that HAZOP leader considers risk ranking before safeguards de finition,since LOPA has established rules in de fining which safeguards are protections and the given risk reduction.Otherwise if for time or resource limitations HAZOP is not going to be followed by LOPA,then HAZOP should consider risk ranking after safeguards de finition.Therefore,the HAZOP leader should explain to the HAZOP team at the kick-off meeting a concise explanation of necessary considerations to identify safeguards having criteria to distinguish them as Independent Protection Layers (IPL)as well as the risk reduction provided by each IPL.In HAZOP report there should be make clear all assumptions and credits given to the Protections identi fied by the HAZOP team.Figs.3and 4,shows a vision of both kinds of HAZOP reports:For the case of risk ranking before and after safeguards de finition.In Figs.3Fig.1.Risk matrix in (NOM,2005).Table 5Probability description (Y -axis of matrix in Fig.1)(NOM,2005).Frequency Frequency quantitative criteria L41in 10years L31in 100years L21in 1000years L1<1in 1000yearsTable 6Risk description (within matrix in Fig.1)(NOM,2005).Risk level Risk qualitative descriptionA Intolerable:risk must be reduced.B Undesirable:risk reduction required or a more rigorous risk estimation.C Tolerable risk:risk reduction is needed.DTolerable risk:risk reduction not needed.Fig.2.Risk matrix as in (PEMEX,2008).Table 7Probability description (Y -axis of matrix in Fig.2)(PEMEX,2008).Frequency Occurrence criteria Category Type Quantitative QualitativeHighF4>10À1>1in 10yearsEvent can be presented within the next 10years.Medium F310À1À10À21in 10years e 1in 100years It can occur at least once in facility lifetime.LowF210À2À10À31in 100years e 1in 1000years Possible,it has never occurred in the facility,but probably ithas occurred in a similar facility.Remote F1<10À3<1in 1000years Virtually impossible.It is norealistic its occurrence.Table 4Consequences description (X -axis of matrix in Fig.1)(NOM,2005).Consequences Consequence quantitative criteriaC4One or more fatalities (on site).Injuries or fatalities in the community (off-site).C3Permanent damage in a speci fic Process or construction area.Several disability accidents or hospitalization.C2One disability accident.Multiple injuries.C1One injured.Emergency response without injuries.M.Pérez-Marín,M.A.Rodríguez-Toral /Journal of Loss Prevention in the Process Industries 26(2013)936e 940938and4“F”means frequency,C means consequence and R is risk as a function of“F”and“C”.One disadvantage of risk ranking before safeguards definition is that resulting risks usually are found to be High,Intolerable or Unacceptable.This makes difficult the decision to be made by the management on what recommendations should be carried outfirst and which can wait.One advantage in risk ranking after safeguards definition is that it allows to show the management the risk scenario fully classified, without any tendency for identifying most risk as High(Intolerable or Unacceptable).In this way,the management will have a good description on which scenario need prompt attention and thus take risk to tolerable levels.There is commercial software for HAZOP methodology,but it normally requires the user to use his/her risk matrix,since risk matrix definition represents an extensive knowledge,resources and consensus to be recognized.The Mexican case is worldwide unique in HAZOP methodology, since it uses an agreed and recognized risk matrix and risk priori-tizing criteria according to local culture and risk understanding for the oil&gas sector.The risk matrix with corresponding risk levels took into account political,economical and ethic values.Advantages in using risk matrix in HAZOP are:they are easy to understand and to apply;once they are established and recognized they are of low cost;they allow risk ranking,thus helping risk reduction requirements and limitations.However,some disad-vantages in risk matrix use are:it may sometimes be difficult to separate frequency categories,for instance it may not be easy to separate low from remote in Table7.The risk matrix subdivision may have important uncertainties,because there are qualitative considerations in its definition.Thus,it may be advantageous to update Pemex corporate HAZOP standard(PEMEX,2008)to consider a6Â6matrix instead of the current4Â4matrix.5.ConclusionsHAZOP studies are not a simple procedure application that as-sures safe Process systems on its own.It is part of a global design cycle.Thus,it is necessary to establish beforehand the HAZOP study scope that should include at least:methodology,type(CÂC,DÂD, etc.)report format,acceptance risk criteria and expected results.Mexico belongs to the reduced number of places where accep-tance risk criteria has been explicitly defined for HAZOP studies at national level.ReferencesABS.(2004).Process safety institute.Course103“Process hazard analysis leader training,using the HAZOP and what-if/checklist techniques”.Houston TX:Amer-ican Bureau of Shipping.CCPS(Center for Chemical Process Safety).(2001).Layer of protection analysis: Simplified process risk assessment.New York,USA:AIChE.CCPS(Center for Chemical Process Safety).(2008).Guidelines for hazard evaluation procedures(3rd ed.).New York,USA:AIChE/John Wiley&Sons.CCPS(Center for Chemical Process Safety).(2009).Guidelines for Developing Quan-titative Safety Risk Criteria,Appendix B.Survey of worldwide risk criteria appli-cations.New York,USA:AIChE.Crawley,F.,Preston,M.,&Tyler,B.(2008).HAZOP:Guide to best practice(2nd ed.).UK:Institution of Chemical Engineers.Crowl,D.A.,&Louvar,J.F.(2011).Chemical process safety,fundamentals with ap-plications(3rd ed.).New Jersey,USA:Prentice Hall.Table8Consequences description(X-axis of matrix in Fig.2)(PEMEX,2008).Event type and consequence categoryEffect:Minor C1Moderate C2Serious C3Catastrophic C4 To peopleNeighbors Health and Safety.No impact on publichealth and safety.Neighborhood alert;potentialimpact to public health and safety.Evacuation;Minor injuries or moderateconsequence on public health and safety;side-effects cost between5and10millionMX$(0.38e0.76million US$).Evacuation;injured people;one ormore fatalities;sever consequenceon public health and safety;injuriesand side-consequence cost over10million MX$(0.76million US$).Health and Safetyof employees,serviceproviders/contractors.No injuries;first aid.Medical treatment;Minor injurieswithout disability to work;reversible health treatment.Hospitalization;multiple injured people;total or partial disability;moderate healthtreatment.One o more fatalities;Severe injurieswith irreversible damages;permanenttotal or partial incapacity.Table9Risk description(within matrix in Fig.2)(PEMEX,2008).Risk level Risk description Risk qualitative descriptionA Intolerable Risk requires immediate action;cost should not be a limitation and doing nothing is not an acceptable option.Risk with level“A”represents an emergency situation and there should be implements with immediate temporary controls.Risk mitigation should bedone by engineered controls and/or human factors until Risk is reduced to type“C”or preferably to type“D”in less than90days.B Undesirable Risk should be reduced and there should be additional investigation.However,corrective actions should be taken within the next90days.If solution takes longer there should be installed on-site immediate temporary controls for risk reduction.C Acceptablewith control Significant risk,but can be compensated with corrective actions during programmed facilities shutdown,to avoid interruption of work plans and extra-costs.Solutions measures to solve riskfindings should be done within18months.Mitigation actions should focus operations discipline and protection systems reliability.D ReasonablyacceptableRisk requires control,but it is of low impact and its attention can be carried out along with other operations improvements.Fig.3.Risk ranking before safeguard definition.Fig.4.Risk ranking after safeguards definition.M.Pérez-Marín,M.A.Rodríguez-Toral/Journal of Loss Prevention in the Process Industries26(2013)936e940939Dunjó,J.,Fthenakis,V.,Vílchez,J.A.,&Arnaldos,J.(2010).Hazard and opera-bility(HAZOP)analysis.A literature review.Journal of Hazardous Materials, 173,19e32.Goyal,R.K.,&Kugan,S.(2012).Hazard and operability studies(HAZOP)e best practices adopted by BAPCO(Barahin Petroleum Company).In Presented at SPE middle east health,safety,security and environment conference and exhibition.Abu Dhabi,UAE.2e4April.Gujar,A.M.(1996).Myths of HAZOP and HAZAN.Journal of Loss Prevention in the Process Industry,9(6),357e361.Hyatt,N.(2003).Guidelines for process hazards analysis,hazards identification and risk analysis(pp.6-7e6-9).Ontario,Canada:CRC Press.IEC.(1995).IEC60300-3-9:1995.Risk management.Guide to risk analysis of techno-logical systems.Dependability management e Part3:Application guide e Section 9:Risk analysis of technological systems.Geneva:International Electrotechnical Commission.IEC.(2001).IEC61882.Hazard and operability studies(HAZOP studies)e Application guide.Geneva:International Electrotechnical Commission.ISO.(2000).ISO17776.Guidelines on tools and techniques for hazard identification and risk assessment.Geneva:International Organization for Standardization.Johnson,R.W.(2010).Beyond-compliance uses of HAZOP/LOPA studies.Journal of Loss Prevention in the Process Industries,23(6),727e733.Khan,F.I.(1997).OptHAZOP-effective and optimum approach for HAZOP study.Journal of Loss Prevention in the Process Industry,10(3),191e204.Kuo,D.H.,Hsu,D.S.,&Chang,C.T.(1997).A prototype for integrating automatic fault tree/event tree/HAZOP puters&Chemical Engineering,21(9e10),S923e S928.Lawley,H.G.(1974).Operability studies and hazard analysis.Chemical Engineering Progress,70(4),45e56.Mannan,S.(2012).Lee’s loss prevention in the process industries.Hazard identifica-tion,assessment and control,Vol.1,3rd ed.,Elsevier,(pp.8e31).NOM.(2005).NOM-028-STPS-2004.Mexican National standard:“Norma Oficial Mexicana”.In Organización del trabajo-Seguridad en los procesos de sustancias químicas:(in Spanish),published in January2005.PEMEX.(2008).Corporate Standard:“Norma de Referencia NRF-018-PEMEX-2007“Estudios de Riesgo”(in Spanish),published in January2008. Venkatasubramanian,V.,Zhao,J.,&Viswanathan,S.(2000).Intelligent systems for HAZOP analysis of complex process puters&Chemical Engineering, 24(9e10),2291e2302.M.Pérez-Marín,M.A.Rodríguez-Toral/Journal of Loss Prevention in the Process Industries26(2013)936e940 940。

抗自适应泄漏的基于身份加密方案

抗自适应泄漏的基于身份加密方案
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义 了 自适应泄漏攻击下 I E的安全性 ;利用基于身份 的散列证明系统 (B— S B I HP )和提取器 ,提 出了抗 自适应泄漏 的 I E方案 ;并对其进行实例 化,构建 了基于 qT B E假 设的抗 自适应泄漏 的 IE方案 。安全性分析表明, B -A DH B 设计 的 I E方案是选择明文攻击安全 的,它不仅能够有效地抵抗 自适应泄漏 ,而且 能够容忍较大 的密钥泄漏量 。 B 关键词 : 自适应泄漏;基于身份 的加密 ;熵抗泄漏 ;qT B HE假设 —A D
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CCNASecurityChap2答案

CCNASecurityChap2答案

Which three services on a router does Cisco SDM One-Step Lockdown enable? (Choose three.)SNMPTCP interceptsSSH access to the routerCisco Discovery Protocolpassword encryption servicefirewall on all outside interfacesWhich statement describes the operation of the Cisco SDM Security Audit wizard?The wizard configures a router to prevent unauthorized access.The wizard compares a router configuration against recommended settings.The wizard monitors network data and logs possible unauthorized or malicious traffic.The wizard logs the effectiveness of network security measures for baselinecomparisons.Which service is enabled on a Cisco router by default that can reveal significant information about the router and potentially make it more vulnerable to attack?HTTPCDPFTPNTPTFTPRefer to the exhibit. What two facts can be determined from the output? (Choose two.)The Cisco IOS image and configuration files have been properly secured.ROMmon mode will be inaccessible upon entering the privileged EXEC reloadcommand.The Cisco IOS Resilient Configuration feature is enabled.The Cisco IOS Resilient Configuration feature has detected an image versionmismatch.The Cisco IOS configuration files have been erased.An administrator needs to create a user account with custom access to most privileged EXEC commands. Which privilege command is used to create this custom account?privilege exec level 0privilege exec level 1privilege exec level 2privilege exec level 15What is the minimum recommended modulus key length for keys generated to use with SSH?25651276810242048Which three options can be configured by Cisco AutoSecure? (Choose three.)CBACSNMPsyslogsecurity bannerinterface IP addressenable secret passwordWhich three commands are required to restore a primary bootset from a secure archive on a router on which Cisco IOS resilience is enabled? (Choose three.)Restart the router in ROM monitor mode and display the secure bootset Cisco IOS image name using the dir command.Restart the router, enter privileged EXEC mode, and display the secure bootset Cisco IOS image name using the show flash command.Boot the secure bootset Cisco IOS image using the boot command with the filename.Copy the secure bootset Cisco IOS image to flash using the copy IOS-backup-image flash command.Restore the secure configuration file using the copy config-backup flash command.Restore the secure configuration file using the secure boot-config restore filename command.Refer to the exhibit. Routers R1 and R2 are connected via a serial link. One router is configured as the NTP master, and the other is an NTP client. Which two pieces of information can be obtained from the partial output of the show ntp associations detail command on R2? (Choose two.)Both routers are configured to use NTPv2.Router R1 is the master, and R2 is the client.Router R2 is the master, and R1 is the client.The IP address of R1 is 192.168.1.2.The IP address of R2 is 192.168.1.2.What are two characteristics of SNMP community strings? (Choose two.)A vulnerability of SNMPv1, SNMPv2, and SNMPv3 is that they send the communitystrings in plaintext.Commonly known community strings should be used when configuring secure SNMP.If the manager sends one of the correct read-only community strings, it can getinformation and set information in an agent.SNMP read-only community strings can be used to get information from anSNMP-enabled device.SNMP read-write community strings can be used to set information on anSNMP-enabled device.What are three requirements that must be met if an administrator wants to maintain device configurations via secure in-band management? (Choose three.)network devices configured to accommodate SSHa separate network segment connecting all management devicesat least one router acting as a terminal serverencryption of all remote access management trafficconnection to network devices through a production network or the Internetdirect access to the console ports of all network devicesIf AAA is already enabled, which three CLI steps are required to configure a router with a specific view? (Choose three.)assign a secret password to the viewassign commands to the viewassign users who can use the viewassociate the view with the root viewcreate a superview using the parser view view-name commandcreate a view using the parser view view-name commandWhich two characteristics apply to Role-Based CLI Access superviews? (Choose two.)CLI views have passwords, but superviews do not have passwords.Users logged in to a superview can access all commands specified within the associatedCLI views.A single superview can be shared among multiple CLI views.Commands cannot be configured for a specific superview.Deleting a superview deletes all associated CLI views.Refer to the exhibit. Based on the output of the show running-config command, which type of view is SUPPORT?secret view, with a level 5 encrypted passwordroot view, with a level 5 encrypted secret passwordsuperview, containing SHOWVIEW and VERIFYVIEW viewsCLI view, containing SHOWVIEW and VERIFYVIEW commandsRefer to the exhibit. Which statement regarding the JR-Admin account is true?JR-Admin can issue show, ping, and reload commands.JR-Admin can issue ping and reload commands.JR-Admin can issue only ping commands.JR-Admin can issue debug and reload commands.JR-Admin cannot issue any command because the privilege level does not match one ofthose defined.Which recommended security practice prevents attackers from performing password recovery on a Cisco IOS router for the purpose of gaining access to the privileged EXEC mode?Keep a secure copy of the router Cisco IOS image and router configuration file as abackup.Disable all unused ports and interfaces to reduce the number of ways that the router canbe accessed.Configure secure administrative control to ensure that only authorized personnel canaccess the router.Locate the router in a secure locked room that is accessible only to authorized personnel.Provision the router with the maximum amount of memory possible.An administrator defined a local user account with a secret password on router R1 for use with SSH. Which three additional steps are required to configure R1 to accept only encrypted SSH connections? (Choose three.)configure the IP domain name on the routerenable inbound vty Telnet sessionsgenerate the SSH keysconfigure DNS on the routerenable inbound vty SSH sessionsgenerate two-way pre-shared keysBy default, how many seconds of delay between virtual login attempts is invoked when the loginblock-for command is configured?onetwothreefourfiveWhich set of commands are required to create a username of admin, hash the password using MD5, and force the router to access the internal username database when a user attempts to access the console?R1(config)# username admin password Admin01pa55R1(config)# line con 0R1(config-line)# login localR1(config)# username admin password Admin01pa55R1(config)# line con 0R1(config-line)# login internalR1(config)# username admin Admin01pa55 encr md5R1(config)# line con 0R1(config-line)# login localR1(config)# username admin secret Admin01pa55R1(config)# line con 0R1(config-line)# login localR1(config)# username admin secret Admin01pa55R1(config)# line con 0R1(config-line)# login internalWhich three areas of router security must be maintained to secure an edge router at the network perimeter? (Choose three.)physical securityflash securityoperating system securityremote access securityrouter hardeningzone isolationRefer to the exhibit. What two pieces of information can be gathered from the generated message? (Choose two.)This message is a level five notification message.This message appeared because a minor error occurred requiring further investigation.This message appeared because a major error occurred requiring immediate action.This message indicates that service timestamps have been globally enabled.This message indicates that enhanced security was configured on the vty ports.Refer to the exhibit. Which two statements describe the current SDM logging setup? (Choose two.)Buffered logging will be enabled on the router for Logging Level 7 messages.Buffered logging will be enabled on the syslog server for Logging Level 7 messages.All messages with a trap level of 4 and higher (less critical) will be logged.All messages with a trap level of 4 and lower (more critical) will be logged.The router interface IP address that is connected to the syslog server is 192.168.1.3.The syslog server IP address is 192.168.1.3.Refer to the exhibit. What is the significance of secret 5 in the generated output?The ADMIN password is encrypted using DH group 5.The ADMIN password is encrypted via the service password-encryption command.The ADMIN password is hashed using MD5.The ADMIN password is hashed using SHA.Which two operations are required to implement Cisco SDM One-Step Lockdown? (Choosetwo.)Choose the One-Step Lockdown feature.Apply the documented network policies.Deliver the configuration changes to the router.Compare the router configuration against recommended settings.Select the Firewall and ACL task on the SDM Configuration screen.Which statement matches the CLI commands to the SDM wizard that performs similar configuration functions?aaa configuration commands and the SDM Basic Firewall wizardauto secure privileged EXEC command and the SDM One-Step Lockdown wizardclass-maps, policy-maps, and service-policy configuration commands and the SDM IPSwizardsetup privileged EXEC command and the SDM Security Audit wizardWhat are two characteristics of the SDM Security Audit wizard? (Choose two.)It uses interactive dialogs and prompts to implement AAA.It automatically enables Cisco IOS firewall and implements Cisco IOS IPS security configurations to secure the router.It displays a screen with Fix-it check boxes to let you choose which potential security-related configuration changes to implement.It requires users to first identify which router interfaces connect to the inside network and which connect to the outside network.It is initiated from CLI and executes a script in which the managment plane functions and forwarding plane services are tested against known vulnerabilities.。

错失恐惧对上海市大学生高危性行为的影响

错失恐惧对上海市大学生高危性行为的影响

【社会医学】中国卫生事业管理2021年1月第38卷第1期(总第391期)错失恐惧对上海市大学生高危性行为的影响郭佩佩姜茂敏A(上海工程技术大学管理学院,上海201620)[摘要]目的.•了解上海市大学生高危性行为现状,探析错失恐惧对上海市大学生高危性行为的影响,为大学生性 健康教育提供参考依据。

方法:采用分层抽样法选取上海市不同类型的高校,通过自制问卷及特质-状态错失恐惧量表 (T- S FOMOS)对4244名大学生进行调查,根据logistic回归分析错失恐惧对不同性取向的大学生高危性行为的影响。

结果:过去半年发生过高危性行为的大学生约占调查对象的33. 7%(1429/4244),错失恐惧总得分为44.45 ±4.22分,各 维度的错失恐惧得分依次为:特质错失恐惧17.82 ±2. 45分、状态错失恐惧26. 63 ±2.34。

logistic回归结果显示大学生的 错失恐惧对其高危性行为有着显著影响其中,错失恐惧中的特质错失恐惧对非异性恋患者高危性行为有正向预测作用 (P<0.05);状态错失恐惧对全体大学生均有正向预测作用(p<0.05)。

结论:上海市大学生存在明显的错失恐惧心理,且大学生的高危性行为尤其是临时性行为较为突出,错失恐惧和大学生高危性行为存在关联。

相关部门可从缓解大学生 错失恐惧出发,调节大学生社交网络中的心理状态,以期减少大学生高危性行为的发生,实现性健康促进。

[关键词]高危性行为;错失恐惧;大学生;性健康教育[中图分类号]R193 [文献标志码]A[文章编号]10044663(2021 )01-71 -05Studying on The Influence of Fear of Missing out on High -Risk Sexual Behaviors among College Students in Shanghai. /G uo Peipei, et al. //T h e Chinese Health Service Management.Abstract Objective To understand the status of high- risk sexual behaviors among college students in Shanghai,analyze the impact of missing fear on high - risk sexual behaviors,and provide references for sexual health education on college students.Methods4244 college students were chosen from colleges and universities in Shanghai by stratified sampling method,and surveyed with self-m ade questionnaire and trait- state loss fear scale(TS FOMOS).Binaiy logistic regression analysis was used to ana­lyze the influence of missed fear on high- risk sexual behaviors of college students with different sexual orientations.Results The percentage of college students who had high- risk sexual behaviors in the past six months was33. l°/c(1429/4244) ,whose total score of missed fear was44. 45 ± 4.22,and the scores of missed fear in each dimension were 17.82 ± 2.45 in trait missed fear, and26. 63 ± 2.34 in state loss fear.The result of binary logistic regression showed that fear of missing out had significant influ­ence on high- risk sexual behaviors of college students,in which the trait of missed fear has a positive predictive effect on the high -risk sexual behaviors of non- heterosexual patients (p< 0.05) ,and the state of missed fear has a positive predictive effect on all college students (p<0. 05). Conclusion There had obvious fear of losing in college students in Shanghai.The high- risk sex­ual behaviors,especially temporary behaviors,were more prominent.There had a correlation between missing fear and high- risk sexual behaviors among college students.It is suggested for relevant departments to start from alleviating the fear of missing out in college students,and adjust the psychological state of college students in social networks,which can reduce the occurrence of high -risk sexual behaviors and promote sexual health.Author’s address School of Management,Shanghai University of Engineering Science,Shanghai,P.R.China.Key words high- risk sexual behavior;fear of missing out;college students;sexual health education.近年来,性传播已经成为我国艾滋病(AIDS)疫情增长最快 的传播途径:1]。

专家系统

专家系统

Using fuzzy method to evaluate safety condition of big diesel engineLiang Wei *,Zhang Lai-bin,Wang Zhao-hui,Duan Li-xiangResearch Center of Oil and Gas Safety Engineering Technology,China University of Petroleum,Beijing 102249,Chinaa r t i c l e i n f oArticle history:Received 10August 2007Received in revised form 7July 2009Accepted 7July 2009Keywords:Fuzzy diagnosis Safety evaluation Diesel enginea b s t r a c tBig diesel engine is one of the most important equipments in industry,and its safety condition plays a great role in oil production.This paper presents a fuzzy method to monitor the safety state of the big diesel.Six useful diagnostic characteristic parameters have been selected to diagnose safety condition of the big diesel engine.The standard fuzzy vector was obtained by using statistical method,so the status of big diesel’s safety condition can be determined by calculating the fuzzy distance between the fuzzy vector and standard fuzzy vector.This fuzzy method has been successfully used on PZ12V190diesel engine.Ó2009Elsevier Ltd.All rights reserved.1.IntroductionBig diesel engine is important equipment in oil filed,and its safety condition plays a great role in oil production.Its reliability and safety working have been of increasing concern in recent years.Many methods have been proposed on fault diagnosis and condi-tion monitoring for safety evaluation of diesel engine.Pontoppidan,Sigurdsson,and Larsen (2005)has discussed diesel engine’s safety monitoring based on mean field independent components analysis of acoustic emission energy signals.Kimmich,Schwarte,and Isermanm (2005)has presented a systematic development of fault detection and diagnosis methods for two system components of diesel engines,the intake system and the injection system together with the combustion process.Yang,Pu,and Wang (2005)has introduced instantaneous angular speed to diagnose the faults of fuel leakage,valve leakage,etc.These methods mentioned above have resolved some practical problems of diesel engine.However,diesel engine is a complex system which includes many compo-nents.Evaluating the diesel’s safety condition needs many related parameters.To analyze safety condition of big diesels only by running time or distance is not enough,and may leads to mistakes in production and maintenance.So it is necessary to search a method to analyze the safety condition in all aspects for more accurate results.Because of the complicated connections between diagnostic characteristic parameters and diesel engine’s parts,assemblies and whole diesels (Xu,Tang,&Xie,2002),there are few definite connections but more fuzzy connections.Therefore,toanalyze safety condition of large diesel engines needs fuzzy methods (Dinca &Aldemir,1999).This paper presents six fault characteristic parameters of diesel engine,and use fuzzy method to analyze diesel’s safety condition by integrating the parameters.This article comprises of the following parts:Section 3gives six fault characteristic parameters and their corresponding membership functions.Section 4intro-duces the fuzzy method which is used to determine safety condi-tion.Section 5presents the field experimental analysis and gives the level of safety condition.Section 6ends with the conclusion of this study.2.Background knowledge2.1.Introduction to PZ12V190B diesel machinePZ12V190B diesel plays an important role of the drilling process at oilfields.Its basic type is Z12V190B,shown as Fig.1.The PZ12V190B diesel engine is added up a base,a wind cooling system and an intake and exhaust pipes.2.2.Fault analysis of PZ12V190B dieselOne of the most important tasks of fault diagnosis is to reveal the connection between fault symptom and the causes.The major fault symptoms and the causes of PZ12V190B diesel are analyzed,shown as Table 1.2.3.Theory of fuzzy C -means cluster algorithmIt is a method for finding clusters of a data set with most simi-larity in the same cluster and most dissimilarity between different*Corresponding author.Fax:þ861089733203.E-mail address:lweimm@ (L.Wei).Contents lists available at ScienceDirectJournal of Loss Prevention in the Process Industriesjournal homepage:/locate/jlp0950-4230/$–see front matter Ó2009Elsevier Ltd.All rights reserved.doi:10.1016/j.jlp.2009.07.002Journal of Loss Prevention in the Process Industries 22(2009)928–933clusters.Cluster criterion is a function that expresses quality of cluster.The similarity among samples is measured by distance.Feature space,there are mixed-density function,can be divided into several sub-regions.Density function of every sub-region has only one peak value.Accordingly,eigenvectors that belong to the same class are close,and linear scale between different eigenvectors is far.Fuzzy C means is established on the criterion of square sum of error,and the distance between the sample and certain class is embodied by grade of membership that can describe the sample belonging to certain class.Above all,by initially dividing into sample set,average position of certain group is calibrated by cluster,and every sample is endowed with membership degrees that corre-spond to all kinds of class.By iterative calculation,cluster andmembership degree are updated,leaving the minimum error sum is minimum for sample set (Kimmich et al.,2005;Yang et al.,2005).Assume X ¼{x 1,x 2,.,x k ,.,x n }is eigenvector,where n is the number of samples,x k is the k th sample,and k ¼1,2,.,n .In order to cluster X into C types,assume u ik is the fuzzy distance between k th sample and i th cluster center.So adds up all the elements u ik will make the fuzzy matrix U ¼(u ik )c Ân ˛B cn .Where B cn is the space of c Ân .Every element of the matrix U is followed by:ð1Þu ik ˛½0;1ð2ÞX c i ¼1u ik ¼1ð3ÞX c k ¼1u ik >0Assume V i ,i ¼1,2,.,C be the i th cluster center.The optimizedfunction can be estimated by the following formulae:J m ðU ;V Þ¼Xn k ¼1X c i ¼1ðu ik Þm k x k ÀV i k 2;ð1 m N Þ(1)u ik ¼1P cj ¼1Âk x k ÀV i k k x k ÀV j ki 2(2)V i ¼P n k ¼1ðu ik Þmx kP n k ¼1ðu ik Þm ;i ¼1;2;/;C (3)where k k presents the distance of Euclidean space.3.Selection of characteristic parameters 3.1.Traditional parameters for diesel diagnosisThere are lots of parameters influences the running state of diesel.Some traditional parameters to monitor the state of PZ12V190B diesel engine can be classified by the followings.(1)Fixed parameterIt refers to the parameters which are almost invariant after assembly of diesel,such as compression ratio,etc.(Xu et al.,2002)(2)Routine parametersIt refers to some parameters that related to running state of diesel,such as speed,oil temperature,water temperature,pressure and cumulative runtime,etc.(3)Limited control parameterIt refers to limited parameters which will lead to fault when safety range is beyond the normal operation of diesel.It generally uses warning,unloading,and stopping,etc.(Dinca &Aldemir,1999)to process automatically.Such as the device will stop automatically when oil pressure islow.Fig.1.Z12V190B diesel engine.1–Exhaust manifold;2–turbocharger;3–outlet pipe;4–cylinder head;5–shock absorber;6–oil pan hot joint;7–fuel drain valve;8–one-way pressure regulating valve;9–oil pan;10–inlet pipe;11–cylinder block;12–panel;13–starting gear;14–oil filter;15–intakepipe.L.Wei et al./Journal of Loss Prevention in the Process Industries 22(2009)928–933929(4)Main performance parametersIt refers to parameters that closely related to working perfor-mance of diesel,which includes speed,power,specific fuel consumption,explosion pressure,intake and exhaust temperature,and pressure of diesel and turbocharger,etc.(5)Abrasion parametersThrough regularly sample analyzing,accessory abrasion degree of movement can be determined and predicted.Besides,abrasion between cylinder liner and piston,main bearing lining and crank shaft can be determined by collecting and analyzing cylinder head signal of diesel.3.2.The selection of fault characteristic parametersSafety condition of diesel engine depends on each assembly,while assembly condition depends on each part (Xu et al.,2000).So in the course of analyzing diesel’s safety condition,not only the whole diesel’s parameters but also the parameters of each part must be taken into account.Some traditional indexes like maximum value are lack of validity to diagnose the faults of diesel engine.So some new indexes are going to be introduced,as follows:3.2.1.The crank wearing valueForm a one-dimension time series of vibration data of tested diesel engine:x ¼f x i ;i ¼1;2;.n g (4)where n is the number of data x .Fig.2shows a time vibration signal divided into three sections by low,middle and high wave threshold.L ,M and H represent bottom,middle,high wave threshold respectively.The wear of connection crank is also called ‘‘machine knock’’.The parameter Middle wave amplitude Pm can reflect the crank wear condition.Middle wave amplitude Pm is a value of wave amplitude abso-lute value large than L less than M ,and is defined as:Pm ¼1Xnm i ¼1j x ij ;L j x i j M(5)where nm is the length x i matching L j x i j M .When the crank’s wear is great,the value in the middle wave of the vibration will obviously increase.Therefore,the bigger the Pm value is,the more serious the connection rod wear is.Its membership function is designed as:S m ¼Pm max ÀPm max min(6)where S m is subjection value,Pm is the measured crank wear value,Pm max is the maximum crank wear value,Pm min is the minimum crank wear value.3.2.2.The cylinder knocks valueThe cylinder knock is caused by fuel combustion or mechanical knock.When the cylinder knock happens,the peak value of the vibration will distinctly increase.So the parameter high wave amplitude Ph can reflect the proportion of the high peak value in the whole data.High wave amplitude Ph is an absolute average value of wave absolute value large than M less than H ,and defined as:X High ¼1Xnh i ¼1j x ij ;M j x i j H(7)where nh is the length x i matching M j x i j H .The value of Ph indicates the serious degree of cylinder knock.The greater the value is,the more serious of cylinder knock.Its membership function is designed as:S h ¼1ÀPh max ÀPh Ph max ÀPh min(8)where S h is subjection value,Ph is the measured cylinder knock value,Ph max is the maximum cylinder knock value,Ph min is the minimum cylinder knock value.3.2.3.Power of diesel enginePower is the best parameter to reflect the condition of diesel,and a lot of attention has been paid to it.For the same type of diesel engine,the output power in good condition is more than that in bad condition.PZ12V190B diesel engine’s rating power is 882kW,and if its power is lower than 500kW,it does not work any more.Then based on the importance of power and the change of power with engines running time,its membership function is designed as:S p ¼1ÀP max ÀP P max ÀP min(9)where S p is subjection value,P max is the max power;P min is minimum power,P is the real power.3.2.4.Lubrication pressureLubrication pressure can reflect the lubrication system’s working condition,and can also tell that wearing condition of all wearing parts,such as the piston and crock.The increase of friction can lower the oil pressure.The diesel engine cannot be used if the oil pressure is lower than its rated value Pr min .So its membership function is designed as:S L ¼k1ÀPr max ÀPrPr max ÀPr min(10)where S L is subjection value,Pr max is the maximum pressure,Pr min is the minimum pressure,Pr is the real pressure,k is factor,its value depends on diesel engine’s wearing condition.3.2.5.Intake pressureIntake pressure of diesel engine reflects the working state of a supercharger and the leakage condition of an intake pipe.AstheFig.2.Low,middle and high wave threshold.L.Wei et al./Journal of Loss Prevention in the Process Industries 22(2009)928–933930intake pressure directly affects the sufficient degree of the fuel’s combustion condition,the intake pressure is considered as an important index of working condition of the whole machine.Its membership function is designed as:S I¼1ÀPi maxÀPiPi maxÀPi min(11)where S I is subjection value,Pi max is the maximum intake pressure, Pi min is the minimum intake pressure,Pi is the measured value of intake pressure.3.2.6.Thefluctuation value of speedIf the combustion state of some cylinders is poor or the leakage of some cylinders is big,the diesel engine will be in the bad tech-nical condition,and the rotating speed of the whole machine will fluctuate.So thefluctuating value of the rotating speed is consid-ered as an important index of the whole diesel’s technical state. The technology subjection value can be directly gained by the collected data by sensor,which is between0and1.The diesel engine safety condition can be evaluated through the above parameters.The level of diesel engine’s safety condition can be calculated through fuzzy analysis.ing a fuzzy method to determine diesel-working condition4.1.The main steps of FCM algorithmStep1:Let C be cluster number.Set l¼0,and initial classification matrix UðlÞcÂn can satisfyX c i¼1uðlÞik¼1(12)Step2:Computing cluster center eigenvector V i of initial classifi-cation by formula(3).Let the weighted index m¼2.Step3:renewing each element to the membership of each cluster uðlþ1Þikby formula(2).uðlþ1Þik ¼1P cj¼1h k XkÀVðlÞikk X kÀVjk!(13)Step4:Discriminating convergence precision.Let the convergence discrimination precision3>0,if k Uðlþ1ÞÀUðlÞk<3not satisfied,go back to step2,iterating until satisfying.The key numbers of FCM algorithm:(1)Determination of cluster number C.Because the cluster result is very sensitive to the value of C, different values of C lead to different cluster learning results,how to select the appropriate value of C becomes a difficulty to cluster algorithm.The technical condition of equipment generally can be divided into‘‘optimal,good,medium,and poor’’.As a result,C can be4for the PZ12V190B diesel engine.(2)Selection of fuzzy weighted index m.Fuzzy weighted index m controls the distribution of member-ship and fuzzy degree of cluster,if FCM algorithm is used to analyze data,appropriate value of m must be selected.As a result,m can be 2for the PZ12V190B diesel engine.4.2.Modeling of the diesel-working conditionIn the given domain U,there are n standard fuzzy subsets:A1,A2, .,A n,and there is another fuzzy subsets B.Provided:1i n,Making N(B,Ai)¼max(B,A j),1j n.According to a closing recognition method(Adachi&Kotani, 1994),vector B is considered most close with vector A j,and vector B should be attributed to mode A j.According to the accumulating of data acquisition on the basis of the diesel,the standard fuzzy subsets A j are established, 1i n.Suppose establishing the n kinds of state,and the fuzzy subsets B is obtained on the basis of the fault diagnosis of the diesel,then the closing degree of the B and A j can be calculated.So the current state of the diesel is made,and whether repair or scrap of the diesel engine is decided.4.3.Deciding the standard fuzzy vectorFor the PZ12V190B diesel engine,the parameter of standard fuzzy vector is determined according to the current runtime of the diesel engine.For example,state A degree is the runtime below 2000h,state B degree is that from2000to4000h,state C degree is that from4000to7000h,state D degree is over7000h,then the standard fuzzy vector A j of the diesel with different state degrees can be gained by the data accumulation.4.4.Evaluating the diesel statusBy calculating the acquired data of the diesel,the current state fuzzy vector B of the diesel engine can be gotten.Then the closing degrees between the applied vectors and the standard fuzzy vector can be calculated.So the closest standard vector to B can be found and the state degree can be determined.5.Thefield experimental examplesAccording to the above method,a series of tests have been made,and the results of the collected data by sensor are shown as Table2in Appendix A.According to formulae(6)–(11),the collected data of each diesel can be changed into corresponding subjection value,show as Table3in Appendix A.And four standard vectors are obtained by calculating matrix V,shown as Table4in Appendix A. The safety evaluation results of the eleven diesel engines are listed in Table5.And the safety evaluation result of the above diesel accord with the applied situation very well.6.ConclusionsAs the status of the diesel engine is a fuzzy notion,the safety classification is under the consideration of accuracy by using the fuzzy method.In the process of the above test and calculation, the safety classification of the PZ12V190B diesel is basically realized.This has played an important role forfield maintenance of diesel engines.However,some diagnostic characteristic parameters are affected by the objective conditions.Moreover, more data are needed to build an optimizing standard vector, and the method needs to be further studied and improved.L.Wei et al./Journal of Loss Prevention in the Process Industries22(2009)928–933931AcknowledgmentsThe project supported by the National High Technology Research and Development Program of China (Grant No.2008AA06Z209)and supported by Special Items Fund of Beijing Municipal Commission of Education ofChina.Appendix ATable 1Table 2Table 3L.Wei et al./Journal of Loss Prevention in the Process Industries 22(2009)928–933932ReferencesAdachi,M.,&Kotani,M.(1994).Identification of chaotic dynamical systems withback-propagation neural networks.IEICE Transactions on Fundamentals of Elec-tronics,Communications and Computer Sciences,77-A ,324–334.Dinca,L.,&Aldemir,T.(1999).Fault detection and identification in dynamic systemswith noisy data and parameter/modeling uncertainties.Reliability Engineering and System Safety,65,17–28.Kimmich,F.,Schwarte,A.,&Isermanm,R.(2005).Fault detection for modern dieselengines using signal-and process model-based methods.Control Engineering Practice,13,189–203.Pontoppidan,N.H.,Sigurdsson,S.,&Larsen,J.(2005).Condition monitoring withmean field independent components analysis.Mechanical Systems and Signal Processing,19,1337–1347.Shayler,P.J.,&Goodman,M.(2000).The exploitation of neural networks in auto-motive engine management systems.Engineering Applications of Artificial Intelligence,13,147–157.Xu,K.,Tang,L.C.,&Xie,M.(2002).Fuzzy assessment of FMEA for engine systems.Reliability Engineering and System Safety,75,17–29.Yang,J.,Pu,L.,&Wang,Z.(2005).Fault detection in a diesel engine by analysing theinstantaneous angular speed.Mechanical Systems and Signal Processing,15,549–564.Table 5Table 4L.Wei et al./Journal of Loss Prevention in the Process Industries 22(2009)928–933933。

101种防御机制布莱克曼 英文版

101种防御机制布莱克曼 英文版

101种防御机制布莱克曼(Blackman)英文版引言在网络安全领域,防御机制是保护信息系统免受恶意攻击和未经授权访问的重要手段。

Blackman是一种广泛使用的防御机制,它以其全面性、灵活性和高效性而受到普遍认可和采用。

本文将介绍101种Blackman防御机制及其功能,以帮助读者更好地理解和应用此机制。

基本概念Blackman是一种综合性防御机制,它结合了传统的防火墙、入侵检测系统(IDS)和入侵防御系统(IPS)等技术。

其基本目标是通过实时监控和分析网络流量,检测潜在的安全漏洞和攻击,并采取相应的防御措施来保护系统的完整性和可用性。

Blackman的主要特点1.多层次防御:Blackman采用多种技术对网络进行综合防御,包括网络层、传输层和应用层等各个层次。

这样可以在不同的攻击场景下提供更加全面和灵活的防御策略。

2.实时监控:Blackman能够实时监控网络流量,及时发现和回应潜在的安全威胁。

这种实时性可以大大缩短系统受到攻击后的响应时间,有效减少损失。

3.智能化分析:Blackman利用机器学习和人工智能等技术,对网络流量进行智能分析和识别。

基于历史数据和模型训练,它可以准确地判断网络流量中的异常行为,并作出相应的防御措施。

Blackman的功能以下是Blackman的101种防御机制及其功能的详细介绍:网络层防御1.防火墙:限制对系统的非授权访问,并过滤恶意流量和网络威胁。

2.路由控制:通过设置路由策略,限制来自特定IP地址或网络的访问。

3.虚拟专用网络(VPN):通过加密网络通信,保护数据传输的安全和隐私。

4.网络隔离:将网络划分为多个虚拟网络,隔离不同安全级别的系统和用户。

传输层防御1.数据包过滤:根据特定的规则和策略,对传输层数据包进行过滤和检查。

2.状态检测:监测传输层连接的状态,及时发现异常行为和恶意攻击。

3.连接限制:限制特定IP地址或用户的同时连接数,防止DoS和DDoS攻击。

第10章教材配套课件

第10章教材配套课件

Unit10 Images and Televisions
When two images are added or subtracted, the resultant matrix will frequently contain illegal gray scale values. For example, when a pixel in one 17-bit image has the gray scale level 129 and the corresponding pixel in a second 17-bit image has the gray scale level 201, the sum pixel is 129+201=330. This is outside the legal range for an 17-bit image, which may only contain gray scale levels between 0 and 255. When the same two images are subtracted, the difference pixel is 129201= -72, again a value outside the legal range.
Unit10 Images and Televisions
The transition between source and destination images is then accomplished by smoothly transforming not only the control element locations, but also their colors. The locations and colors of pixels not explicitly marked as control elements are determined by the locations and colors of the control elements that are nearest.

chap10[1]

chap10[1]
15
The Role of Government: Medicare
• Approximately 40 million enrollees • Not means-tested • Program divided into three parts:
– Part A: Hospital insurance (HI) – Part B: Supplementary medical insurance (SMI) – optional, but 99% of elderly take it up – Part C: Medicare+Choice – optional, a managed care arrangement where elderly get certain additional benefits like prescription drug coverage and have restricted choice of providers
5
What’s Special About Health Care?
• Assumes that demand for health care downward sloping (e.g., health care use is elastic with respect to the price). • Assumed coinsurance rate of 20% -- the amount the insured person pays out of pocket. • Social experiments find that the elasticity of demand for health care is -0.20.
6

experiments on learning by back propagation

experiments on learning by back propagation
2. Early Experiments:
Early experiments on back propagation began in the late 1970s and early 1980s. One of the groundbreaking experiments was conducted by David E. Rumelhart, Geoffrey E. Hinton, and Ronald J. Williams. They applied back propagation totrain a multi-layer perceptron network for learning handwritten characters. The experiment demonstrated the ability of back propagation to recognize different handwriting styles and paved the way for further research in the field.
6. Transfer Learning:
Transfer learning is the process of usingknowledge learned from one task to improve the performance on another related task. Back propagation plays a crucial role in transfer learning experiments. By fine-tuning pre-trained networks on new datasets, researchers have achieved state-of-the-art results on various challenging tasks. Transfer learning experiments utilizing back propagation have significantly reduced the training time and data requirements for developing models in new domains.

计量经济学(庞皓)_课后习题答案

计量经济学(庞皓)_课后习题答案

Yˆ2005 = −3.611151 + 0.134582 × 3600 = 480.884 (亿元)
区间预测:
∑ 平均值为:
xi2
=
σ
2 x
(n
−1)
=
587.26862
× (12
−1)
=
3793728.494
( X f 1 − X )2 = (3600 − 917.5874)2 = 7195337.357
1.138
18
2.98
1.092
试建立曲线回归方程 yˆ = a ebx ( Yˆ = ln a + b x )并进行计量分析。
2.7 为研究美国软饮料公司的广告费用 X 与销售数量 Y 的关系,分析七种主要品牌软饮
料公司的有关数据2(见表 8-1)
表 8-1
美国软饮料公司广告费用与销售数量
品牌名称
449.2889
1994
74.3992
615.1933
1995
88.0174
795.6950
1996
131.7490
950.0446
1997
144.7709
1130.0133
1998
164.9067
1289.0190
1999
184.7908
1436.0267
2000
225.0212
1665.4652
2 i
=
3134543
∑Yi2 = 539512
(1)作销售额对价格的回归分析,并解释其结果。 (2)回归直线未解释的销售变差部分是多少?
∑ XiYi = 1296836
2.9 表中是中国 1978 年-1997 年的财政收入 Y 和国内生产总值 X 的数据:

Probiotics as prevention and treatment for diarrhea

Probiotics as prevention and treatment for diarrhea

Probiotics as prevention and treatment for diarrhea Alfredo Guarino,Andrea Lo Vecchio and Roberto Berni CananiIntroductionProbiotics may have preventive or therapeutic effects on diarrhea of various etiologies.However,not all probiotics are effective and physicians must select preparations with proven efficacy.Here,we critically appraise recent data on the prevention and treatment of diarrhea in relation to cause.We also briefly discuss new data impinging on the mechanisms governing the effects of probiotics.The role of probiotics in diarrhea associated with inflammatory bowel diseases and irritable bowel syndrome is not taken into account in this review.Primary preventionAs diarrhea is a very frequent problem in young infants and children,probiotics have been proposed for the prevention of community-acquired diarrhea.Six randomized controlled trials(RCTs)are available. The probiotics tested were Lactobacillus GG(LGG), Streptococcus thermophilus in association with Bifidobacter-ium breve or with Bifidobacterium lactis,ctis alone, Lactobacillus casei DN-114and Lactobacillus reuteri.The results were not always statistically significant and were of questionable clinical relevance.A double-blind RCT performed in a large pediatric population in France reported fewer episodes of dehydration,medical consul-tation and need for formula shift in infants fed probiotic-supplemented formula,although the incidence of diar-rhea was similar to that of the control group[1].A smaller RCT in Israel found a reduction in the frequency and duration of diarrhea in treated children[2].These trials provided evidence of a modest protective effect of specific strains.Indirect evidence that targeting intesti-nal microecology is effective in preventing diarrhea is the finding of fewer intestinal infections in a cohort of healthy infants fed prebiotics in thefirst year of life [3].The cost efficacy of such interventions remains to be established.Secondary preventionSecondary prevention involves selected conditions, limited in duration,that are associated with an increased risk of diarrhea rather than with host-related factors.Department of Pediatrics,University of Naples‘Federico II’,Naples,ItalyCorrespondence to Alfredo Guarino,Professor of Pediatrics,University of Naples‘Federico II’,Via Pansini 5,Naples,ItalyTel:+390817464232;e-mail:alfguari@unina.it Current Opinion in Gastroenterology2008, 25:18–23Purpose of reviewTo critically appraise evidence on probiotic use for prevention and treatment of diarrhea in children and adults.RecentfindingsSeveral randomized controlled trials and meta-analyses suggested that probiotics are effective in primary and secondary prevention of gastroenteritis and its treatment. Selected Lactobacillus strains had a modest,although significant effect in primary prevention.Saccharomyces boulardii was effective in antibiotic-associated and in Clostridium difficile diarrhea.There is evidence that it might prevent diarrhea in day-care ctobacillus rhamnosus GG was associated with reduced diarrheal duration and severity,more evident in case of childhood Rotavirus diarrhea.Similar,although weaker,evidence was obtained with S.boulardii.Both strains are included in evidence-based recommendations for gastroenteritis management in children.Data on other Lactobacillus strains are preliminary.Probiotic efficacy was related to cause,early administration and bacterial load,and their mechanisms were associated with antiinfectious action in the intestine or,indirectly,to modulation of innate and adaptive immunity.SummaryProbiotics have gained a role as adjunctive treatment of infantile gastroenteritis together with rehydration.Their efficacy is less convincing in adults,but promising in antibiotic-associated diarrhea.However,evidence of efficacy is limited to a few strains.Keywordsgastroenteritis,guidelines,Lactobacillus,probioticsCurr Opin Gastroenterol25:18–23ß2008Wolters Kluwer Health|Lippincott Williams&Wilkins0267-13790267-1379ß2008Wolters Kluwer Health|Lippincott Williams&Wilkins DOI:10.1097/MOG.0b013e32831b4455Antibiotic-associated diarrheaAntibiotic-associated diarrhea(AAD)occurs in about 5–25%of adult patients and11–40%of children upon administration of broad-spectrum antibiotics.Clostri-dium difficile is a major agent,although diarrhea may be related to general changes in intestinal microflora.A systematic review[4]and a meta-analysis of RCTs[5] provided evidence of a moderate beneficial effect of LGG,Saccharomyces boulardii and a combination of B. lactis and S.thermophilus in preventing AAD.A recent Cochrane review of10RCTs carried out in1015treated and971control children reported a significant reduction in the incidence of AAD[Relative risk(RR)0.49;95% confidence interval(CI)0.32–0.74],confirming the efficacy of LGG and S.boulardii[6 ].The subgroup analyses provided evidence that probiotic dose may be responsible for the observed clinical and statistical heterogeneity of results.Interestingly,of the eight studies that provided dosage information,five studies in which children received5–40billion bacteria/yeast/ day showed that probiotics had preventive effects(RR 0.35;95%CI0.25to0.47),whereas the combined results of three studies using less than5billion col-ony-forming unit(CFU)bacteria/yeast/day were not significant(RR0.89;95%CI0.53to 1.48, I2¼61.4%).The number-needed-to-treat was between seven and10.As suggested by the Cochrane review, more data are needed to consider the routine use of probiotics to prevent AAD in children started on large spectrum antibiotics.In particular,cost-benefit data are strongly needed.Two recent double-blind RCTs suggested that other strains were effective in preventing AAD.Thefirst, conducted on135adults,showed that a drink containing L.casei,Lactobacillus bulgaricus and S.thermophilus twice daily prevented AAD and diarrhea caused by C.difficile (number-needed-to-treatfive and seven,respectively) [7].The second was a pediatric trial in which Lactobacillus rhamnosus(strains E/N,Oxy and Pen)reduced the risk of any diarrhea in children undergoing antimicrobial therapy for common infectious diseases[8 ].The role of probiotics in C.difficile-associated diarrhea is still unclear.S.boulardii was found to be significantly effective in treating C.difficile diarrhea[9].The benefit of probiotics in C.difficile diarrhea was mostly seen in adults and,particularly,in subgroups characterized by severe disease[10].Despite the moderate evidence obtained in adults,the use of probotics to specifically treat or prevent C.difficile diarrhea has not been evaluated in a RCT in children.A recent meta-analysis showed that LGG and S. boulardii might be useful in treating or preventing recur-rences of C.difficile diarrhea[11].Nonetheless,the heterogeneity of the studies makes it difficult to draw definite conclusions.Nosocomial and day-care center diarrheaNosocomial diarrhea may prolong hospital stay and increase medical costs.It is commonly caused by Rota-virus and less frequently by C.difficile.Earlier and incon-sistent data suggesting that probiotics may reduce the risk of nosocomial diarrhea were summarized in a recent review,and the conflicting results may have been related to the strain and dose of probiotic used[12 ].Five RCTs have been published on the prevention of diarrhea in day-care centers.The probiotics tested were LGG,ctis (alone or combined with S.thermophilus)and Lactobacillus thermophilus.Efficacy was modest and inconsistent and was detected for some strains only.A narrative review[12 ]and a recent systematic review[13]agreed thatevidence in favor of probiotics for prevention of diarrhea in day-care centers and for nosocomial diarrhea is not sufficient to recommend their routine use.Traveler’s diarrheaTravel is a risk factor for infectious gastroenteritis.A recent meta-analysis revealed evidence of a protective effect by S.boulardi and by mixture of Lactobacillus acidophilus and Bifidobacterium bifidum[14].However, evidence of the efficacy of probiotics in the prevention of traveler’s diarrhea is preliminary.Diarrhea related to nonantibiotic treatmentDrugs and other treatment administered for noninfec-tious diseases such as cancer may induce diarrhea.A novelfield of application of probiotics is prevention of iatrogenic diarrhea related to treatment ctic acid producing bacteria reduce the risk of radiation-induced diarrhea.Prophylactic administration of VSL#3(a mixture of four species of lactobacilli,three species of bifidobacteria and S.thermophilus)reduced the incidence of radiation-associated enteritis in a placebo-controlled trial that included500patients who underwent postoperative radiation therapy[15].Some probiotic strains were found to be beneficial in cancer drug-induced diarrheas,namely,VSL#3prevented irinote-can-related diarrhea(in rats)and LGG reduced the frequency of severe diarrhea caused by5FU-based che-motherapy[16].Treatment of intestinal infectionsAlthough the standard treatment of acute diarrhea remains to be an oral rehydration solution(ORS),pro-biotics have gained an important role as adjuvant therapy.A large number of trials,including randomized andcontrolled,and several accurate meta-analyses reported that probiotics exerted antidiarrheal effects particularly in children.A wide pattern of strains,schedules,doses and conditions have been tested.The outcomes most widely considered were duration of diarrhea,duration of hospi-talization and severity of diarrhea,with some trials eval-uating ORS intake,number of vomiting episodes and Probiotics as prevention and treatment for diarrhea Guarino et al.19stool volumes.Despite the broad spectrum of design and conditions,nearly all studies showed some positive effects on diarrhea,with statistically significant benefits or moderate clinical benefits mainly in infants and young children.A number of strains have been tested,but proof of efficacy is compelling only for a few.LGG and S.boulardii are the strains most widely tested and also are the most effective.The efficacy of LGG as an adjunctive treatment of diarrhea is now considered conclusive.A recent meta-analysis of RCTs [17 ]showed that LGG is associated with a reduced duration of diarrhea,particu-larly that induced by Rotavirus.LGG also reduced the risk of persistent diarrhea (lasting >7days)and shortened the duration of hospitalization compared with placebo.Interestingly,probiotic administration is generally effec-tive in a population irrespective of the cause of diarrhea.However,when the cause of diarrhea is known,the efficacy tends to be confined to viral diarrhea and,less commonly,to ‘unknown etiology’,whereas it does not extend to bacterial diarrhea.An exception is a recent double-blind RCT conducted in parallel with an exper-imental study of L.acidophilus strain LB,which showed a reduction by 1day of bacteria-induced diarrhea [18].This trial was performed with a probiotic preparation contain-ing heat-killed strains.Five RCTs testing S.boulardii in a total of 619patients were included in a recent meta-analysis [19 ],and the authors concluded that S.boulardii exerts a moderate clinical benefit by significantly reducing the duration of diarrhea and the risk of diarrhea longer than 1week.Other strains have been tested including Lactobacillus reuteri ,L.acidophilus LB,a mixture of S.thermophilus ,Lactobacillus bulgaricus and others.Two recent multicen-ter RCTs,each of which included more than 100children treated with Escherichia coli strain Nissle 1917,reported a significant reduction of the duration of acute diarrhea [20,21].The only head-to-head comparative trial performed with different strains was a single-blind RCT performed in Italy on children aged from 3to 36months with acute gastroenteritis [22 ].The trial compared the effects of five probiotic preparations,namely,LGG,S.boulardii ,Bacillus clausii ,a mixture of L.bulgaricus ,S.thermophilus ,L.acidophilus and B.bifidum and finally Enterococcus faecium SF68.The control group received oral rehydra-tion solution only.Diarrhea duration and severity were significantly reduced after the administration of LGG and the mix of four strains versus children who received ORS alone (Fig.1).LGG was more effective than the mix,but the difference was not significant.The other three preparations did not affect symptom duration.These results confirm that the efficacy of probiotics is related to the strain,however,dosage is also important.An early meta-analysis reported dose-related efficacy for lactobacilli preparations against gastroenteritis [23].This important concept emerged again from a recent review [12 ].Probiotic efficacy was correlated in a linear fashion with bacterial load,the minimal effective dose being at least 10billions CFU/day.An example of the importance of the dose comes from a RCT conducted in India [24],in which a dose of only 60million CFU of LGG,one of the lowest ever used in a clinical trials,was administered twice a day and did not affect the fre-quency and duration of diarrhea or vomiting in children with acute diarrhea.However,interestingly,the same dose significantly reduced the risk of persistent diar-rhea,thus showing that efficacy is not merely a matter of dose,but also depends on the outcome parameter considered [25].In conclusion,data from several meta-analyses show that the effects of probiotics in acute diarrhea in children are strain-dependent and dose-dependent,being generally greater with doses more than 1010–1011CFU,highly significant for watery diarrhea and viral gastroenteritis,but not for invasive bacterial diarrhea,more evident when treatment is initiated early in the course of disease and more evident in children in developed than in developing countries.20Gastrointestinal infectionsFigure 1Effects of different probiotic strains on the duration of acute diarrhea inchildrenüP <0.001compared with oral rehydration solution alone (Mann–Whitney U test).The figure shows the effects on the duration of diarrhea of five different probiotic preparations administered in addition to oral rehydration solution.The control group received oral rehydration solution only.The total duration of diarrhea is significantly lower in children receiving Lactobacillus rhamnosus GG (group 1)and in those receiving the bacterial mix (group 4)than in patients receiving oral rehydration solution alone.These results demonstrate that not all commercially available probiotic preparations are effective in children with acutediarrhea.,Oral rehydration solution (ORS)alone;,Lactobacillus casei subsp.rhamnosus GG;,Saccharomyces boulardi;,Bacillus clausii;,Lactobacillus delbrueckii var.bulgaricus ,Lactobacillus acid-ophilus ,Streptococcus thermophilus ,Bifidobacterium bifidum;,Enterococcus faecium Sf 68.Reproduced with permission [22 ].In May2008,probiotics were included in a guideline document,namely the Guidelines For the Manage-ment of Acute Gastroenteritis produced by a joint committee from the European Society for Pediatric Gastroenterology,Hepatology and Nutrition(ESP-GHAN)and the European Society for Pediatric Infec-tious Disease(ESPID)[26 ].The document was developed through an evidence-based systematic review approach that incorporated tables of evidence with their grading.The guidelines state that‘probiotics may be an effective adjunct to the management of diarrhea.However,because of the lack of efficacy for many preparations,only the use of probiotic strains with proven efficacy and in appropriate doses is suggested for the management of acute diarrhea in European children as an adjunct to rehydration therapy’.The evidence of efficacy for LGG was rated as IA,which is the maximum,and that for S.boulardii IIB,corresponding to a strong level of evidence based on meta-analysis of RCTs and properly designed RCTs of appropriate size,respectively.A similar con-clusion appears in the recent recommendations for the clinical use of probiotics based on the Yale University Workshop update of2007in which the recommen-dations were graded‘A’,‘B’,‘C’or no category,based on expert opinion[27].Probiotics have also been tested in HIV/AIDS patients, many of whom suffer from debilitating infectious and noninfectious diarrhea.Although probiotics did not sig-nificantly affect gastrointestinal symptoms in a well designed RCT that included HIV-infected patients undergoing antiretroviral therapy[28],a recent clinical trial showed that probiotic yogurt containing some Lac-tobacilli strains resolved moderate diarrhea and increased CD4cells/m l in HIV/AIDS patients[29].Safety issuesProbiotics are generally regarded as being safe,and side effects in ambulatory care have rarely been reported. Safety issues are related to bacterial translocation and sepsis,and to the risk of carrying antibiotic resistance transposons that may spread resistance to antibiotics.The latter has been reported for some probiotics,among which are L.reuteri ATCC55730and Enterococcus faecium [30,31].Mechanisms of action of probioticsThe rationale for using probiotics is based on the assumption that they modify the composition of colonic microflora and counteract enteric pathogens. However,there are two main views as to how probiotics counteract diarrhea.According to one theory,probiotics act locally(at intestinal level).According to the other theory,probiotics act by modulating the immune response.At local level,probiotics:(1)compete with pathogens for nutrients and receptors[32];(2)induce hydrolysis of toxins and receptors[32];(3)induce production of antimicrobial substances(including peptides of the innate immune system)[32];(4)induce production of organic acids and modulation ofnitric oxide synthesis[32];(5)regulate intestinal permeability by modulating theepithelial tight junctions[33];(6)exert a trophic action on the intestinal mucosa,whichleads to brush border enzyme activation,stimulationof glucose absorption and antiapoptotic effects on theenterocyte[34];(7)inhibit selected intracellular mechanisms involved inviral replication(such as MEK,PKA,p38MAPK)[34].On the other hand,an increasing body of evidence supports the concept that probiotics modulate the immune response.Dendritic cells and toll-like receptor molecules are crucial factors in this process.These cells receive signals from structural lipopolysaccharides,gly-copeptides and CpG DNA of probiotic strains and trans-duce them in order to regulate the production of innate immunity peptides that,in turn,exert antimicrobial activity or modulate adaptive immunity[35 ].Selected probiotics promote specific antibody responses against given pathogens.This is the case of S.boulardii that,apart from producing a54-kD protease that hydrolyzes the A and B toxins of C.difficile and their intestinal receptors, also stimulates the production of specific IgG and IgA antitoxin A produced by the same pathogen[35 ].LGG increases the mucosal production of specific antirotavirus sIgA and modulates the mucosal inflammatory response to pathogens by stimulating the production of anti-inflammatory IL-10and IL-4and by inhibiting the pro-duction of proinflammatory TNF-a,IL-6and IFN-g[36 ].This process affects transepithelial ionfluxes,and hence diarrhea,as proinflammatory cytokines inducea potent ion secretory effect at intestinal level and theirinhibition reducesfluid losses in children with inflam-matory diarrhea.Specific Lactobacillus strains activate muciparous cell genes,which leads to an increase in the thickness of the enterocyte mucus layer,thereby preventing the adhesion of pathogenic E.coli.LGG negatively modu-lates Shiga toxin2A production by enterohemorrhagic E.coli(EHEC)0157:H7through a mechanism that involves pH changes mediated by the production of organic acids[37].Finally,strains of the same probiotic species mayhave different mechanisms of action depending on the pathogen.Probiotics as prevention and treatment for diarrhea Guarino et al.21Most probiotic effects have been demonstrated in exper-imental studies and only a few in clinical studies.How-ever,it remains to be established whether the antidiar-rheal effects of different probiotic strains are governed by a single mechanism.ConclusionThe evaluation of the effects of probiotics has progressed from empiricism to science,and the efficacy of specific strains in acute gastroenteritis is demonstrated in several RCTs and meta-analyses.The increasing use of probio-tics is linked to the concept of‘naturality’,which fulfills the desire of customers to take medicines free from side effects that is largely true for probiotics.Novelfields of application for probiotics may emerge,including func-tional bowel disorders and inflammatory or allergic dis-eases that are responsible for chronic,potentially severe diarrhea in both adults and children.This is likely to support the concept of using specific strains for specific conditions.AcknowledgementsWe are grateful to Jean Ann Gilder for editing the text. References and recommended readingPapers of particular interest,published within the annual period of review,have been highlighted as:of special interestof outstanding interestAdditional references related to this topic can also be found in the Current World Literature section in this issue(p.77).1Thibault H,Aubert-Jacquin C,Goulet O.Effects of long-term consumption of a fermented infant formula(with Bifidobacterium breve c50and Streptococcus thermophilus065)on acute diarrhea in healthy infants.J Pediatr Gastro-enterol Nutr2004;39:147–152.2Weizman Z,Asli G,Alsheikh A.Effect of a probiotic infant formula on infections in child care centers:comparison of two probiotic agents.Pedia-trics2005;115:5–9.3Bruzzese E,Volpicelli M,Squaglia M,et al.Impact of prebiotics on human health.Dig Liver Dis2006;38(Suppl2):S283–S287.4Szajewska H,Setty M,Mrukowicz J,et al.Probiotics in gastrointestinal diseases in children:hard and not-so-hard evidence of efficacy.J Pediatr Gastroenterol Nutr2006;42:454–475.5Szajewska H,Ruszczynski M,Radzikowski A.Probiotics in the prevention of antibiotic-associated diarrhea in children:a meta-analysis of randomized controlled trials.J Pediatr2006;149:367–372.6 Johnston BC,Supina AL,Ospina M,et al.Probiotics for the prevention of pediatric antibiotic-associated diarrhea.Cochrane Database Syst Rev2007; 2:CD004827.A recent and complete systematic review that reports the efficacy of selected probiotics in the prevention of antibiotic-associated diarrhea and underlines the important role of the dose-response effect.7Hickson M,D’Souza AL,Muthu N,et e of probiotic Lactobacillus preparation to prevent diarrhoea associated with antibiotics:randomised double blind placebo controlled trial.BMJ2007;335:80.8 Ruszczynski M,Radzikowski A,Szajewska H,et al.Clinical trial:effectiveness of Lactobacillus rhamnosus(strains E/N,Oxy and Pen)in the prevention of antibiotic-associated diarrhoea in children.Aliment Pharmacol Ther2008; 28:154–161.A well designed randomized controlled trial that demonstrates thebeneficial effects of new probiotic strains for the prevention of antibiotic-associated diarrhea in children. 9Czerucka D,Piche T,Rampal P.Review article:yeast as probiotics–Saccharomyces boulardii.Aliment Pharmacol Ther2007;26:767–778.10Dendukuri N,Costa V,McGregor M,et al.Probiotic therapy for the prevention and treatment of Clostridium difficile disease:a systematic review.CMAJ 2005;173:167–170.11Segarra-Newnham M.Probiotics for Clostridium difficile-associated diarrhea: focus on Lactobacillus rhamnosus GG and Saccharomyces boulardii.Ann Pharmacother2007;41:1212–1221;Review.12Guandalini S.Probiotics for children with diarrhea:an update.J Clin Gastro-enterol2008;42(Suppl2):S53–S57.A complete and useful review that focuses on the efficacy of probiotics for diarrhea of different etiologies in children in different settings.13Mrukowicz J,Szajewska H,Vesikari T.Options for the prevention of rotavirus disease other than vaccination.J Pediatr Gastroenterol Nutr2008;46(Suppl2):S32–S37.14McFarland LV.Meta-analysis of probiotics for the prevention of traveler’s diarrhea.Travel Med Infect Dis2007;5:97–105.15Delia P,Sansotta G,Donato V,et e of probiotics for prevention of radiation-induced diarrhea.World J Gastroenterol2007;13:912–915.16Osterlund P,Ruotsalainen T,Korpela R,et ctobacillus supplementation for diarrhoea related to chemotherapy of colorectal cancer:a randomised study.Br J Cancer2007;97:1028–1034.17Szajewska H,Skorka A,Ruszczynski M,et al.Meta-analysis:Lactobacillus GG for treating acute diarrhoea in children.Aliment Pharmacol Ther2007;25:871–881.A complete meta-analysis of the role of LGG in the therapy of acute diarrhea in children.18Lievin-Le Moal V,Sarrazin-Davila L,Servin AL.An experimental study and a randomized,double-blind,placebo-controlled clinical trial to evaluate the antisecretory activity of Lactobacillus acidophilus strain LB against nonrota-virus diarrhea.Pediatrics2007;120:e795–e803.19Szajewska H,Skorka A,Dylag M.Meta-analysis:Saccharomyces boulardii for treatingacutediarrhoea inchildren.AlimentPharmacolTher2007;25:257–264.A complete meta-analysis on the role of S.boulardii in the therapy of acute diarrhea in children.20Henker J,Laass M,Blokhin BM,et al.The probiotic Escherichia coli strain Nissle1917(EcN)stops acute diarrhoea in infants and toddlers.Eur J Pediatr 2007;166:311–318.21Henker J,Laass M,Blokhin BM,et al.Probiotic Escherichia coli Nissle1917 versus placebo for treating diarrhea of greater than4days duration in infants and toddlers.Pediatr Infect Dis J2008;27:494–499.22Canani RB,Cirillo P,Terrin G,et al.Probiotics for treatment of acute diarrhoea in children:randomised clinical trial offive different preparations.BMJ2007;335:340.The only head-to-head trial with different probiotic preparations.It shows that many probiotic strains are effective and not all probiotics are interchangeable in their efficacy.23Van Niel CW,Feudtner C,Garrison MM,et ctobacillus therapy for acute infectious diarrhea in children:a meta-analysis.Pediatrics2002;109:678–684.24Basu S,Chatterjee M,Ganguly S,et al.Efficacy of Lactobacillus rhamnosus GG in acute watery diarrhoea of Indian children:a randomised controlled trial.J Paediatr Child Health2007;43:837–842.25Basu S,Chatterjee M,Ganguly S,et al.Effect of Lactobacillus rhamnosus GG in persistent diarrhea in Indian children:a randomized controlled trial.J Clin Gastroenterol2007;41:756–760.26Guarino A,Albano F,Ashkenazi S,et al.European Society for Paediatric Gastroenterology,Hepatology,and Nutrition/European Society for paediatric infectious diseases evidence-based guidelines for the management of acute gastroenteritis in children in Europe:executive summary.J Pediatr Gastro-enterol Nutr2008;46:619–621.This is the most recent and complete evidence-based document for the manage-ment of acute gastroenteritis in pediatric age and thefirst guideline to recommend probiotics as an effective adjunct to the management of diarrhea.27Floch MH,Walker A,Guandalini S,et al.Recommendations for probiotic use-2008.J Clin Gactroenterol2008;42(Suppl2):S104–S108.28Salminen MK,Tynkkynen S,Rautelin H,et al.The efficacy and safety of probiotic Lactobacillus rhamnosus GG on prolonged,noninfectious diarrhea in HIV Patients on antiretroviral therapy:a randomized,placebo-controlled, crossover study.HIV Clin Trial2004;5:183–191.29Anukam KC,Osazuwa EO,Osadolor HB,et al.Yogurt containing probiotic Lactobacillus rhamnosus GR-1and L.reuteri RC-14helps resolve moderate diarrhea and increases CD4count in HIV/AIDS patients.J Clin Gastroenterol 2008;42:239–243.30Egervarn M,Danielsen M,Roos S,et al.Antibiotic susceptibility profiles of Lactobacillus reuteri and Lactobacillus fermentum.J Food Prot2007;70:412–418.22Gastrointestinal infections。

海南甜瓜的主要病毒病及其防控措施

海南甜瓜的主要病毒病及其防控措施

中国瓜菜2023,36(3):15-20收稿日期:2022-10-11;修回日期:2023-01-29基金项目:国家西甜瓜产业技术体系(CARS-25);海南省农业科学院科技创新团队稳定引导经费(HAAS2022TDYD03);广西壮族自治区八桂学者项目(2016A11)作者简介:王敏,男,研究员,主要从事西甜瓜栽培育种。

E-mail :130****************共同第一作者:邱艳红,女,助理研究员,主要从事植物病毒研究。

E-mail :********************通信作者:柳唐镜,男,正高级农艺师,主要从事瓜类作物种质创新与遗传改良研究工作。

E-mail :*****************海南作为中国唯一的热带海岛地区,在秋冬季与冬春季具有得天独厚的气候优势。

经过多年产业发展与技术提升,海南陵水县、三亚市、乐东县、东方市近200km 海岸线附近已经形成了全球最大最集中的甜瓜产区。

海南甜瓜的年播种面积超过3.34万hm 2,产量达到101亿t [1],成为仅次于杧果的第二大高效园艺作物,已成为海南农民致富和乡村振兴的重要产业。

然而,多年的连作种植导致病毒病问题日益突出,病毒种类越来越多,发生范围越来越广。

病毒病的防控主要依赖于防治传播病毒的昆虫介体,而常年化学药剂的使用又导致虫害抗药性增强,进一步加剧了病害的传播扩散。

因此,加强甜瓜病毒病害的监测,做好田间传播介体防控,创制抗病品种海南甜瓜的主要病毒病及其防控措施王敏1,邱艳红2,古勤生3,陈建军1,王锋1,徐秀兰2,李茂营2,许勇2,叶云峰4,柳唐镜4(1.海南省农业科学院三亚研究院海南三亚572000;2.北京市农林科学院蔬菜研究所北京100097;3.中国农业科学院郑州果树研究所郑州450009;4.广西壮族自治区农业科学院园艺研究所南宁530007)摘要:甜瓜是我国重要的蔬菜作物,海南是我国重要的甜瓜产区,而病毒病的发生严重影响了海南甜瓜的生产。

武汉大学金融专业保险学原理(学生版)

武汉大学金融专业保险学原理(学生版)

保险历史回顾
本章主要内容
保险思想的萌芽 近代保险业的发展 现代保险制度的建立与发展 中国保险史
4
保险历史回顾
以时间为主线,可分为
原始(古代)保险思想萌芽(公元14世纪以前) 近代保险的发展(公元14~18世纪) 现代保险制度的形成与发展(公元18世纪~ )
5
保险历史回顾
原始保险阶段(公元14世纪之前)
结论(2)
保险制度形成的前提条件:自 然灾害、意外事故的客观存在 保险制度形成的可能条件:剩 余产品的出现,后备物质或基 金的形成 保险制度形成的理论条件:以 生命表诞生为代表的理论基础
14
保险历史回顾
中国保险的出现及其发展
中国古代几种典型的仓储制度 中国古代商业保险的萌芽 中国民族保险业的诞生与兴起 社会主义保险业的建立与发展
所谓社会风险,是指由于个人行为的失常或不可预测的团体行为引 起的风险,如民风危险。 所谓经济风险,是指企业在生产经营过程中由于各种相关因素的变 动而导致赢利的减少、企业亏损甚至破产倒闭的风险。 所谓政治风险,是指政治的原因或源于种族、宗教信仰之间的冲突、 叛乱或者战争引起的各种风险。
32
风险与保险
36
风险与保险
按风险承担的主体分类 个人/家庭风险 企业风险 国家风险
所谓个人或家庭风险,是指家庭收入的潜在波动,这种波动表现为 收入的减少或是支出的增加。 所谓企业风险,指的是任何原因引起的企业价值可能的减少都可以 被定义为企业风险。 国家风险,是指那些由于战争、国际关系变化、政权更迭或政策变 化而导致国家资产或利益受到损害的风险。国家风险通常包括政治 风险、社会风险和经济风险三种。
所谓人身风险,是指人们因生、老、病、死、残等原因而产生的经 济风险。 所谓责任风险,是指因人们的过失行为、侵权行为或违约责任依法 应对他人造成的人身伤害、财产损失承担民事赔偿责任的风险。 信用风险,是指债权人的债务因债务人违约而不能收回或者不能及 时收回,因此给债权人带来的损失。信用风险具有不对称性、累计 性、内源性和行为因素等特点。

英文翻译

英文翻译

Seismic vulnerability of gas and liquid buried pipelinesnzano a ,E.Salzano b ,*,F.Santucci de Magistris a ,G.Fabbrocino aa University of Molise,Di.Bi.T.Department,StreGa Laboratory,Termoli,CB,ItalybIstituto di Ricerche sulla Combustione,CNR,Via Diocleziano 328,80124Napoli,Italya r t i c l e i n f oArticle history:Received 20February 2013Received in revised form 23March 2013Accepted 24March 2013Keywords:Pipelines EarthquakeSeismic vulnerability Na-Tech Fragilitya b s t r a c tLifelines play a crucial and essential role in human life and in economic development.The resilience of those systems under extreme events as earthquakes is a primary requirement,especially when large amount of toxic and flammable material are transported.In this work,the seismic vulnerability of buried gas and liquid pipelines has been analyzed,starting from a large number of damage data to pipelines collected from post-earthquake reconnaissance reports.Seismic fragility formulations and threshold values for the earthquake intensity with respect to the release of content from different types of pipelines have been derived.The main outcome of the work is therefore a novel seismic assessment tool which is able to cover the needs of industrial risk assessment procedures and land use planning requirements.Ó2013Elsevier Ltd.All rights reserved.1.IntroductionA primary requirement for the industrial installations and their fundamental components is the adequate structural safety level with respect to natural hazard and particularly to earthquakes,especially when large amount of toxic and flammable substances are stored or manipulated.Among the very large number of structural and non-structural components of the industrial plants,the pipeline system needs special attention.Indeed,the multiple interactions among the soil,the structure itself and the contained fluid during seismic events is not negligible for this class of structures.Therefore,in addition to the structural earthquake engineering,the key contribution of geotechnical and hydraulic engineering is required and a multidisciplinary effort is recommended.In the past,pipelines have shown to suffer heavy damages when loaded by seismic actions,as in the recurrent and catastrophic earthquakes of California (San Francisco,1906;earthquake of San Fernando,1971;Northridge,1994)and Japan (Kobe,1995).How-ever,despite the evolution in the anti-seismic techniques and the progress in the seismic design,relevant damages to pipelines have been still observed during recent earthquakes occurred in Italy (earthquake of L ’Aquila,2009;earthquake of Emilia,2012),New Zealand (Dar field,2010),Chile (2010),Japan (Tohoku,2011).Pipelines are frequently buried for two main reasons:first,the land fill protects the pipeline from above ground damaging events,either natural or anthropical.Moreover,the lateral con finement given by the surrounding soil,which increases with depth,miti-gates the inertial seismic effects.The present paper reports fragility curves,probit functions and threshold values for the structural damage of buried pipelines containing gases or liquids as function of a basic parameter of the earthquake motion.The data and the function can be pro fitably used in existing tool for the Quantitative Risk Analyses (QRA)which includes natural-technological risks (Na-Tech issue)(Campedel,Cozzani,Garcia-Agreda,&Salzano,2008;Fabbrocino,Iervolino,Orlando,&Salzano,2005),in Land Use Planning methodologies and more in general for the procedures activated by the public awareness with respect to the risks related to the transportation,transmission and distribution of hazardous substances,when loaded by natural events (seismic Na-Tech accidents (Krausmann,Cozzani,Salzano,&Renni,2011;Salzano et al.,2013)).1.1.Earthquake intensity measureThe first important aspect related to the seismic response of civil and industrial constructions is the proper measurement of the shaking level at the site of interest.Before quantitative seismology was developed,the seismic intensity was estimated only on the basis of the destructive effects on built environment and people perceptions.That led to observational scales as the Modi fied*Corresponding author.Tel.:þ390817621922;fax:þ390815704105.E-mail addresses:salzano@r.it ,ernesto.salzano@tiscali.it (E.Salzano).Contents lists available at SciVerse ScienceDirectJournal of Loss Prevention in the Process Industriesjou rn al homepage :/locate/jlp0950-4230/$e see front matter Ó2013Elsevier Ltd.All rights reserved./10.1016/j.jlp.2013.03.010Journal of Loss Prevention in the Process Industries 28(2014)72e 78Mercalli one (MMI or Macroseismic Intensity),that is still used nowadays for its practical implications.Actually,governmental agencies give the Macro-seismic Intensity maps for many historical and recent earthquakes.On the basis of historical data only,many empirical relations,developed to describe the performance of the structures during the earthquakes,were expressed as a function of MMI.This applies also to the seismic vulnerability of pipelines [Eguchi,1991;O ’Rourke,Toprak,&Sano,1998].More recently,instead,the deployment of seismic stations in seismic areas has led to the more common use of basic parameters obtained from the field measurements.The most signi ficant seismic instrumental parameters for structural applications are the Peak Ground Acceleration (PGA)and the Peak Ground Velocity (PGV),which are respectively the peak of the horizontal acceleration and velocity time history obtained from accelerometer measurements.Quite clearly,these parameters are only concise descriptions of the seismic motion and do not give a complete information of the local ground motion,in terms of fre-quency content and signal duration,which are important param-eter for the structural response.Despite of these limitations,due to their simplicity,the above cited parameters are currently the most used indexes in order to relate structural damage and seismic in-tensity,including pipelines,and will be used in this work.1.2.Seismic behavior of pipelinesPipelines for the transportation of fluids are widely used for industrial and civil purposes.These structures,having a predomi-nant one-dimensional development,are commonly addressed as lifelines and are often dislocated over wide areas.Few and only general provisions are given in the current relevant codes con-cerning the seismic behavior of these structures.In particular,the Eurocode 8part 4(EN 1998-4,2006)provides only general prin-ciples to ensure earthquake protection.The most relevant pre-scriptions in the context of the present paper may be summarized as follows:i)each structure,including pipelines,tanks and silos,must beveri fied for ultimate limit state;ii)at least one of two damage limitation states needs to besatis fied:full integrity and minimum operating level.In the latter case,a certain level of damage is allowed,on the basis of a possible loss consequences of fluid or functionality;iii)the principal safety hazard directly associated with thepipeline rupture under a seismic event is related to explo-sions and fires,particularly with regard to gas pipelines.The distance of the location and the size of the population that isTable 1Structural aspects in the seismic behavior of pipelines.Pipelines UseMaterialsJointsDamage patternContinuous (CP)Natural gas OilPetroleum Water SteelPolyethylene (HDPE)Polyvinyl chloride (PVC)Ductile ironWelded jointsMechanical or flange joints Special seismic joints Tension cracksCompression cracks Local buckling Beam buckling Segmented (SP)WaterWastewaterAsbestos cement Reinforced Concrete Polyvinyl chloride (PVC)Vitri fied clay Cast ironCaulked joints Bell endSpigot joints.Axial pull-outCrushing of bell endCrushing of spigot joints Circumferential failure Flexuralfailure.Fig.1.Summary of strong ground shaking and ground failure interaction mechanisms (adapted after O ’Rourke &Liu,1999).nzano et al./Journal of Loss Prevention in the Process Industries 28(2014)72e 7873exposed to the impact of rupture shall be considered in establishing the level of protection;iv)for buried pipelines,the soil/structure interaction is always not negligible;v)the hydrodynamic effects in the structures which contains fluid should be considered accounting all the component of the motion;however,as observed for horizontal tanks,“when H/R(the ratio betweenfilling level H and section radius R) exceeds1,6”,the pipeline“should be assumed to behave as if it were full,i.e.,with the total mass of thefluid acting solidly”with the pipeline;vi)the use of continuous pipelines for systems which treat flammable and pollutant material is mandatory.Damage patterns occurred in the pipelines are various and largely dependent on a number of features related to the properties of the material and the joint detailing.Table1summarises all the most relevant aspects from the structural perspective and shows all the possible combinations of material and joints.The table also shows the main transportationfluids used in each structural type.In Table1,two significant categories for the seismic damage are reported:1)Continuous pipelines(CP);2)Segmented pipeline(SP). The hazardous,toxic andflammable,fluids must be transported only in continuous pipelines,which have high strength and large deformations before structural break and consequentfluid release. It is worth noting that a similar approach has been already adopted in the context of HAZUS(FEMA,1999),where the pipelines are classified as brittle(SP)and ductile(CP),depending on the seismic performance measured in terms of pre-failure strain levels.HAZUS software is the geographic information system-based natural haz-ard loss estimation software package developed by the Federal Emergency Management Agency(FEMA),which is an agency of the United States Department of Homeland Security.The performance of the buried pipeline structure is strongly related to the geotechnical effects.Based on experience and data collected during past earthquakes,these dynamic effects can be divided in two categories[O’Rourke&Liu,1999]:the strong ground shaking(SGS),which is the transient deformation of the soil due to wave passage(Fig.1a),and the ground failure(GF),that is the permanent deformation of the surrounding soil due to co-seismic failure phenomena.The ground failure mechanisms appear only in specific geotechnical conditions;hence they are site dependent and may be summarized in:active fault movement(Fig.1b), liquefaction(Fig.1c)and earthquake-induced landslides(Fig.1d).The Eurocode8provided a simplified analytical formulation to evaluate the maximum strains and curvatures induced in contin-uous pipelines by wave passage for transient deformations as presented by Newmark(1967).The soil deformation,for each type and orientation of transient waves,is measured in terms of PGV.This approach is different from that employed for aboveground structures,as buildings,for which the structural response is directly related to the PGA because the importance of inertial effects in the seismic loadings.In Eurocode8,however no methodology is given for the evaluation of permanent deformations(except for some indications for the design of crossing fault pipelines),in spite of the fact that several references are given in the literature for this evaluation.An example of the available proposed correlations and related authors are reported in Table2.These studies proposed different input parameters for the seismic intensity:the moment magnitude of the earthquake M w,which is a unique measurement of the seismic size,the distance of the pipeline site from the earthquakeTable2Empirical correlations for Permanent Ground Displacement(d¼PGD).Ground failure Seismic parameters Correlations ReferenceActive fault M w log d¼À4.8þ0.69M w Wells&Coppersmith,1994 Lateral spread M w,R ep log(d hþ0.01)¼À7.28þ1.017M wÀ0.278log RÀ0.026Rþ0.497log Yþ0.454log Sþ0.558log T15Bardet,Mace&Tobita,1999Landslide PGAlog d¼2:3À3:3PGAcAmbraseys&Menu,1988Seismic settlement PGA d¼0:3H1PGAþ2Takada&Tanabe,1988Table3Empirical pipelines SGS fragility expressions based onEq.(1).S:steel;DI:ductile iron;CI:cast iron;AC:asbestos cement;C:concrete;WJ:welded joints;FJ:flange joints;CJ:caulked joints;D:diameter.IM a(∙10À4)b ReferenceCP SPPGA e 1.698∙10(CI) 6.06Isoyama&Katayama,1982PGV0.3 1.0 2.25O’Rourke&Ayala,1993PGV0.83(S,WJ small D)0.25(S,WJ,large D)0.5(DI,FJ)1.33(CI,CJ,small D)0.83(CI,FJ,small D)0.83(AC,FJ,small D)1.66(AC,CJ,small D)3.32(AC,CJ,large D)1.66(C,WJ,large D)3.32(C,CJ,large D)1.98Eidinger,1998PGV14.5(S,WJ,small D)3.62(S,WJ,large D)16.9(S,FJ,small D)12(DI,FJ,small D)24.2(CI,CJ,small D)19.3(CI,FJ,small D)12(AC,FJ,small D)24.2(AC,CJ,small D)16.9(C,WJ,large D)24.2(C,CJ,large D)19.3(C,FJ,large D)1ALA,2001E7.24∙1040.92O’Rourke&Deyoe,2004Table4Empirical GF fragility expressions for pipelines based on Eq.(1).(S:steel;DI:ductile iron;CI:cast iron;AC:asbestos cement;C:concrete;WJ:welded joints;FJ:flange joints;CJ:caulked joints;D:diameter).IM A b ReferenceCP SPPGD 2.187.820.56Honegger&Eguchi,1992PGD 3.55(S,WJ)16.57(S,FJ)7.10(DI,FJ)23.67(CI,CJ)16.57(CI,FJ)23.67(AC,CJ)18.94(AC,FJ)18.94(C,WJ)23.67(C,CJ)0.53Eidinger&Avila,1999PGD 1.68(S,WJ)7.85(S,FJ)5.61(DI,FJ)11.22(CI,CJ)8.98(CI,FJ)11.22(AC,CJ)8.98(AC,FJ)6.73(C,WJ)11.22(C,CJ)7.85(C,FJ)0.32ALA,2001PGD e 3.21(PVC)0.41Terzi,Alexoudi,&Hatzigogos,2007nzano et al./Journal of Loss Prevention in the Process Industries28(2014)72e78 74epicenter,R ep,and the PGA.Moreover,the correlations are based also on topographical(as Y and S),geometrical(T15and H1)and soil strength parameters(a c and N).Special correlations,commonly called GMPEs(Ground Motions Prediction Equations),give an estimation of some seismic site dependent parameter(i.e.PGA and PGV)mainly based on M w and R ep(Douglas,2004).The PGA and PGV are difficult to determinis-tically retrieve and a direct measurement is available only for the instrumented sites,which generally is not the same of the site of interest.In this way,the GMPEs were used to estimate the reference seismic parameters in each site of damaged pipelines.Similarly to MMI,governmental agencies released the maps for peak ground acceleration and velocity,on the basis of deterministic measure-ments and attenuation laws implementation,for many historical and recent earthquakes.These maps are commonly called Shaking maps(see for instance Wald,Worden,Quitoriano,&Pankow,2006).In the next sections the seismic vulnerability of pipelines under ground failure will be expressed as a function of PGA,The choice is not a limitation of this study for two main reasons:most of the empirical formulation for PGD estimation are directly or indirectly (through GMPEs)related to PGA;and the wide use of PGA as seismic intensity measurement,especially from National Authorities,en-sures a direct and easy access to the required territorial data.2.Seismic performance in terms of repair rateThe seismic damages of the pipelines are generally described through curves reporting a performance indicator as a function of a seismic intensity measure.These curves are mainly derived as best fitting of the available data coming from post-earthquake recon-naissance.In general,the performance indicator is the repair rate, RR,which gives the numbers of repairs after an earthquake for a unit length of pipeline.The functional form of the curves is usually given by:RR Àn repairs=kmÁ¼a$IM b(1)where a and b are two are constants which depend on pipeline design and characteristic as reported in Table2and the term IM is an intensity indicators for the seismic action,which is mainly based on the geotechnical aspects.These empirical formulations for damage estimation are opti-mized to provide consequence assessment results mainly in terms of repair expenditures.More interesting are the fragility functions providing the probability of exceedance of a given damage state as a function of a demand parameter correlated to the seismic ground motion.Therefore,in order to assess the damage probability,in the HAZUS approach,a Poisson probability distribution was used:PðN¼nÞ¼eÀRR$L$ðRR$LÞn(2)where P is the probability of having n pipe breaks or leaks in a pipe segment of length L.Assuming that the pipe fails when at least one break along its length has occurred,the probability of failure P f is then:P f¼1ÀPðN¼0Þ¼1ÀeÀRR$L(3) An interesting overview of the existing vulnerability curves for pipelines in terms of RR was given by Tromans(2004),which focused the attention on pipelines subjected to transient de-formations(SGS).These formulations are mainly based on PGV as seismic intensity indicator.However,other relations that adopt PGA,MMI,PGV2/PGA(Pineda-Porras&Ordaz,2010),or even formulation based on the transient deformation of the surrounding ground(ε),are available.Table3provides some empirical SGS fragility formulations.The empirical formulation proposed by O’Rourke and Ayala (1993)has been also adopted by HAZUS.The expressions by Eidinger(1998)and ALA(2001)include an additional classification based on material,joints and tube diameter.The fragility formulations for ground failure are fewer and formally similar to SGS i.e.,the functional relationship is givenTable5Damage states DS for pipelines.States Hazard Patterns(structural damage)DS0Slight Investigated sections with negligible damage;pipe bucklingDS1Significant Longitudinal and circumferential cracks;compression joint break.DS2Severe Tension cracks for continuous pipelines;jointloosening in the segmented pipelines.Table6Risk States RS for pipelines(F¼equivalent diameter).States Hazard Patterns(loss of containment)Gas/Vapor/Liquefied gas LiquidRS0Null No losses Limited lossRS1Low Very limited losses:-Toxic(F<1mm/m)-Flammable(F<10mm/m)Limited,time-distributed lossof hazardous substance:multiple losses(F<10mm/m)RS2High Non-negligible losses Large loss(e.g.entire tube surface)or multiple losses(F>10mm/m)Table7Events used for the construction of the fragility curves.Earthquake Country Year M w MMI PGA(g)PGV(cm/s)San Francisco U.S.19067.8VIII e IX0.44e0.6440e56 Long Beach U.S.1933 6.3VI0.107Kern County U.S.19527.7VII e IX0.17e0.5726e112 Kern County U.S.1954 5.9VI e VII0.12e0.297e28 Anchorage(Alaska)U.S.19649.2VII0.2018San Fernando U.S.1971 6.7VIII e IX0.32e0.640e94 Imperial Valley U.S.1979 6.5IX0.36e0.4060e80 Michoacan Mexico19858.0V e VI0.08e0.1014e34 Whittier Narrows U.S.1987 5.9a VII0.28e0.3618e24 Loma Prieta U.S.1989 6.9VII e VIII0.16e0.240e50 Erzincan Turkey19927.0VIII e IX0.28e0.4248e74 Kushiro-Oki Japan19937.5VIII0.28e0.3036e39 Northridge U.S.1994 6.7V e X0.08e0.764e164 Kocaeli Turkey19997.4VIII0.36e0.456e60Chi e Chi Taiwan19997.7IX0.4496 Qinghai-Xinjiang China20017.8X0.64308 Achaia-Ilia Greece2008 6.5VIII0.3438L’Aquila Italy2009 6.3VIII0.24e0.3624e31 Maule Chile20108.8VII e VIII0.16e0.2822e28Darfield New Zealand20107.1VI e VII0.16e0.2016e20a Local Magnitude.Table8Fragility coefficients for pipelines under SGS.IM¼PGV expressed in cm/s. Structural aspects Class Fragility Correlation coefficientRisk state,RS m(cm/s)bCP!RS145.220.390.996CP¼RS271.160.200.987SP!RS121.800.260.886nzano et al./Journal of Loss Prevention in the Process Industries28(2014)72e7875again in Eq.(1).They are essentially based on Permanent Ground Displacement,PGD,induced by the co-seismic GF phenomena (Table 4).The empirical formulation for Ground Failure proposed by Honegger &Eguchi (1992)has been also adopted by HAZUS.Despite of the various aspects accounted in the fragility formula-tions,these existing curves are generally based on few data,except for ALA (2001).Moreover,the repair rate RR may not be an objec-tive parameter,because it depends on the reference length of pipeline,which could be not uniform and comparable among the different formulations.Finally,it is easy to recognize that either qualitative or quantitative risk assessment of industrial facilities and pipeline infrastructures (transportation risk)needs fragility formulations based on different performance indicators which take into account the structural damage and the corresponding loss of content,particularly when the pipelines carry hazardous liquids or gases.An approach based on such paradigm is introduced in the following section.3.ResultsAn alternative description of pipeline seismic performance is recommended whenever attention is paid to consequence of failures different from extension of repair interventions and related costs.This is the case of quantitative risk analysis of industrial facilities,which requires an estimation of released hazardous content.In such context,an option is the construction of pipeline fragility on the analogy with the seismic damage estimation of above groundindustrial structures developed by Salzano,Iervolino,and Fabbrocino (2003;2009)and more recently by Lanzano,Salzano,Santucci de Magistris,and Fabbrocino (2012,2013).The method requires the creation of a thoughtful database founded on the classi fication in signi ficant construction classes for pipelines and on the de finition of Damage State (DS)and Risk State (RS)indicators.The Damage State refers to type of structural damage to pipeline (Table 5),whereas the Risk States (RS)were quali fied on the basis of the possible negative effects on the external environment or population,i.e.on the possible harmful effects derived from the release of content from the damaged pipe (Table 6).Quite clearly,the indicators have been distinguished on the basis of the transported fluid.In order to correlate the structural damage to the release of containment,an equivalent diameter F of a crack in the pipelines has been de fined.The RS levels for pipelines transporting gas,vapour and lique-fied gas were organized in order to match the corresponding damage states.The RS0corresponds to DS0,in which the damage type,even if severe,did not cause any loss of containment.The RS1was formulated considered a very limited amount of loss,however distinguishing between toxic and flammable substances.Finally,the RS2has the highest level of risk and accounts for the release of large amount of fluid in a very short time interval.Similar risk states RS were formulated for liquid transporting pipelines.Differently from the previous classes,the RS0level allows very limited loss of liquid.The RS1accounts limited release,but time-distributed,0%10%20%P e r c e n t a m o u n t o f d a t aDS0DS1DS2Fig.2.Percent amount of data for earthquakes and DS.39%8%25%27%CP-SGS SP-SGS CP-GF SP-GFFig.3.Percent amount of data for each class.020*********PGV (cm/s)020406080100L i m i t s t a t e p r o b a b il i t y (%)0.20.40.60.81PGA (g)20406080100Fig.4.Fragility curves for buried pipelines,under Strong Ground Shaking (a)and Ground Failure (b),in terms of limit state probability (%)for the RS state.,:CP RS !RS1;>:CP RS ¼RS2;B :SP RS !RS1;6:SP RS ¼RS2.nzano et al./Journal of Loss Prevention in the Process Industries 28(2014)72e 7876whereas the RS2involves the cases in which the pipe section has completely failed.An extensive review of case-histories of damages for buried pipelines was carried out and a large database populated.The dataset is composed of 335samples,coming from edited books,papers and post-earthquake reports.The earthquakes analyzed for the construction of pipelines fragility curves,are given in Table 7.In the table,some seismic features,in terms of range of local synthetic parameters,are shown.In Table 8,20earthquakes were considered signi ficant for pipelines damage having,in most of the cases,moment magnitude M w >6.The range of the intensity parameter can be very large like in Northridge (1995)and San Fernando (1971)earthquakes.The same data were plotted in a histogram graph (Fig.2)in order to show the relative amount of data for the most important earth-quakes,taking into account the DS level reported in Table 5.Most of the available data came from the Californian Earthquake of San Fernando 1971(about 35%);most of the data are relative to DS2class (about 55%)and the smallest amounts are relative to DS0(about 14%).Based on such a large database and on the observed behavior of buried pipelines,four possible classes of fragility curves have been then assumed:a)continuous pipelines under strong ground shaking;b)continuous pipelines under ground failure;c)segmented pipelines under strong ground shaking;d)segmented pipelines under ground failure.As previously discussed,the reference intensity parameter is PGV for SGS cases and PGA for GF.Accordingly,the database has been divided into 4classes,accounting both structural (CP or SP)and geotechnical aspects (SGS and GF).The relative amount of each class is given in Fig.3,where it is clear that most of the data are relative to continuous pipelines subjected to transient deformations;instead the corresponding amount of data of segmented pipelines is the smallest,including about 25damage cases.Based on this historical data and the given de finition of damage state DS and risk state RS,a uni-modal distribution of the damage states versus the intensity measure has been observed.Finally,the data have been fitted by a cumulative log-normal distribution:P ðDS !DS i or RS !RS i Þ¼1 1þerf ln IM Àln mb ffiffiffi2p !(4)where m and b are respectively the median and the shape param-eter of the best-fitting distribution.Results of the RS fragility for the four above-mentioned classes are reported in Fig.4.Tables 8and 9reports the corresponding calculated values of the median and shape parameters.Moreover,the correlation coef ficients between experimental data and the cumulative distribution has been also given;in most of the cases the factors are very close to unity.In the case of segmented pipelines under strong ground shaking the sample data were small (cfr.Fig.3)and the correlation co-ef ficients are lower compared to those retrieved from other classes;in particular,for the cases RS ¼RS2,a reasonable cumulative dis-tribution was not obtained.Furthermore,the fragility curves obtained for the ground failure are practically coincident between the RS !RS1and RS ¼RS2datasets:it means that the RS1data are not signi ficant for fragility estimation.This consideration,however,is in agreement to the HAZUS indication on ground failure damage,which is almost totally related to high damage (breaks).Also,coherently to seismic per-formance of segmented pipelines,the value of median m is lower than the corresponding values of continuous pipelines.Finally,the value of b is higher for SGS classes,compared to GF.Following the procedure given by Salzano et al.(2003;2009),in order to obtain univocal threshold values both for PGV and PGA with reference to RS states,the seismic vulnerability of the pipe-lines has been evaluated by using the classical probit analysis.The probit variable Y is expressed in the Eq.(5),as a dose e response model:Y is the measure of a certain damage possibility as a func-tion of a variable “dose ”IM (Intensity Measure).Y ¼k 1þk 2ln IM(5)Details on this classical statistical method can be found else-where in the technical literature (Finney,1971).The resulting probit functions are shown in Fig.5.The calculated probit coef ficients k 1e k 2for the signi ficant RS classes are then given in Tables 10and 11,where the cut-off value of the intensity measure parameters,IM 0,has also been reported.This is the value of Y providing a value of the dose equal to 2.71,which corresponds to zero probability.This threshold value could be considered as a strength intrinsic parameter,signi ficant for the pipeline structural performance and for the soil/structure interaction during the seismic events;the physical meaning of IM 0is de fined as the limit value of the seismic parameter,to above which a certain level of damage should be considered in the Risk Analyses of the pipeline network.Table 9Fragility coef ficients for pipelines under GF.IM ¼PGA expressed in g.Structural aspects Class FragilityCorrelation coef ficient Risk state,RS m (g)bCP !RS10.580.170.998CP ¼RS20.560.180.999SP !RS10.370.230.996SP¼RS20.370.190.9972345LN(PGV)3456Y (-)72055148PGV (cm/s)-3-2-1LN(PGA)34560.10.41.0PGA (g)Fig.5.Probit curves for buried pipelines under Strong Ground Shaking (a)and Ground Failure (b).,:CP RS !RS1;>:CP RS ¼RS2;B :SP RS !RS1;6:SP RS ¼RS2.Table 10Probit coef ficients for pipelines under SGS.Structural aspectsRisk state,RSProbit parameters Threshold,IM 0k 1k 2(cm/s)CP RS !RS1À4.12 2.4117.05RS ¼RS2À5.95 2.6426.58SPRS !RS1À0.361.795.50Table 11Probit coef ficients for pipelines under GF.Structural aspectsRisk state,RSProbit parameters Threshold,IM 0k 1k 2(g)CP ¼RS2 6.97 2.540.20SP¼RS27.792.590.14nzano et al./Journal of Loss Prevention in the Process Industries 28(2014)72e 7877。

PTN中级试题

PTN中级试题

PTN中级试题一、单选题1、关于 PTN 隧道线性保护的倒换,其中优先级最低的是( A )A 、人工倒换B 、保护信号失效C 、工作信号失效D 、工作信号劣化2、对于ZXCTN6300在扩缩环操作的时候,对于 1:1线性保护,手工切换保护组的时候,只在一端进行切换,另一端则会( A )A 、同时也会自动切换B 、不会自动切换,需要手工进行切换C 、状态未知D 、延迟1分钟之后再切换3、对于伪线双归保护的倒换机制,下列哪项的优先级最高( B )A 、人工倒换B 保护闭锁C 、强制倒换4、PTN 隧道线性保护,优先级最低的是(D ) A 、保护闭锁B 、保护信号失效C 、强制倒换5、下列对LAG 保护分类的叙述中,错误的是( A )A 、根据成员端口上是否启用了LACP 协议,可将链路聚合分为静态聚合和动态聚合两种模式B 、动态LAG 保护方式分类为:主备方式和负载均衡方式C 、动态LAG 保护链路聚合协商模式(LACP_Activity )有两种模式:主动协商模式( Active )和被动协商模式( Passive )D 、动态LAG 保护超时模式分为:长超时和短超时6、对于 6300 设备,从标签及性能考虑,建议隧道总数不用超过( B )A 、 1KB 、 2KC 、 4KD 、 8K 7、为了保障设备的正常运行,主控板的温度要求低于(B ) A 、50C B 、60CC 、70CD 、80C8、 ZXCTN610C 设备为根节点配置 EPTREE 业务时,最多支持配置(D )个叶子节点 A 、 8 B 、 16C 、 32D 、 649、 Y.1731 OAM 中CV 包检测功能选择启用时,其支持设置的CV 包发送周期不包括下面哪一项( C ) 10、 Y.1731 OAM 标准中,连续性检查可应用于故障管理、性能监视或保护倒换。

当 MEP 接收到一个CV/CC 帧,帧中的MEL 低于目的MEP 的MEL,且MEG ID 也不同,那么这时产生的告警是( B ) A 、错误合并缺陷B 错误MELC 错误MEPD 、连续性丢失11、在Y.1731标准中,如何标示一个报文是TMP 隧道层的OAM 报文(B )A 、隧道层的标签为13B 、隧道层的内一层标签为 13C 、隧道层外一层标签为 20D 、隧道层标签为2012、关于 OAM 类故障处理,下列说法正确的是(C )A 、若A 网元报TMC-LOC,而Z 网元无告警,可能是 A 网元下发异常,PW 和隧道未绑定导致B 、若A 网元报TMP/TMC-RDI,而Z 网元无告警,A 可能是误告警,可以通过环回检测确认C 、若A 向Z 做LB 检测通,说明 A 与Z 间的基础数据无任何问题D 、当出现不期望 UNPhb,UNPeriod,UNMep 等时,一定是两端 MEP 配置不一致导致的13、在 6000 1.1 以及 9000 32 平台版本,为避免网管断链、防止因产生大量空闲 telnet 链接D 、信号失效 D 、工作信号失效A 、 3.3msB 、 100msC 、 3.3sD 、 10ms导致的TCP 链接资源消耗,需要在设备上配置 tel net 最大空闲超时时间,其值为( C )A 、10 分钟B 、15 分钟C 、30 分钟D 、 60 分钟14、新配置一条隧道,发现隧道一端上报 LOC 告警,分析原因不可能是(A )A 、隧道两端 PE OAM channel type 参数不一致B 、基础数据配置错误C 、某段链路光功率异常D 、 oam 参数两端不一致15、为了检查ROS 平台和age nt 数据库的一致性,需要如何处理(B )17、对于OSPF 协议特点,下列说法错误的是(D )A 、快速收敛,通过快速扩散链路状态更新确保数据库的同步,并同步计算路由表B 、无路由环路,通过最短路径优先( SPF )算法,确保不会产生环路C 、路由聚合,减小路由表压力D 、使用广播方式发送更新18、对于OSPF 支持的网络类型,下边说法错误的是( E )A 、支持广播网络B 、支持非广播多路访问网络C 、支持点对点网络D 、支持点对多点网络E 、不支持虚链路19、下面对于CES 业务伪线控制字中的R 比特描述错误的是哪一项(B ) A 、本地PSN 处于包丢失状态时,置位 R 比特 B 、若PSN 迁出包丢失状态时,需要清除 R 比特置位C 、本地TDM AC 出现故障需要置位 R 比特D 、远端出现包丢失状态后,向本端发送的伪线控制字中的 R 比特置位20、关于PTN 与CE 的相同点,下列说法错误的是(B )A 、我司当前大部分场景,两类组网的管理平面路由协议均使用OSPF 或DCNB 、两者的控制平面协议均为 OSPF 或ISISC 、两者均支持链路捆绑功能(LAG )D 、两者均支持L2/L3VPN 桥接技术21、下面对于E1-AIS 告警的解释描述正确的是(B ) A 、帧丢失告警,连续收到 3个不正确的FAS 信号B 、告警指示信号,对 E1信号在连续512bit ( 2帧)中监测到0的个数少于等于2个C 、对E1信号在连续2个或5个双帧,检测到帧头的 Abit 为1D 、 CRC 复帧丢失告警22、对于CES 报文封装格式,下列哪一项是非必选的( D )A 、L2 HeaderB 、MPLS 标签C 、控制字(CW )D 、RTP 头23、关于PTN 与CE 的不同点,下列说法错误的是( C )A 、当前MPLS-TP 中一般不需要单独部署控制平面A 、DBCheck 工具检查B 、数据上载比较C 、使用设备巡检工具16、根据区域层次的划分, D 、 agent 信息收集工具 IS 设备不可以工作在(D )层次A 、 level-1 :区域内设备B 、level-2 :区域间设备C 、level-1-2 :区域内和区域间设备D 、level-0 :区域内设备B、当前主流 MPLS-TP中隧道标签由网管分配C 、 PTN 中Tunnel 两条单向组成, CE 中Tunnel 为一条双向的D 、 PTN 中的检测机制为 OAM, CE 中一般用BFD24、 Z XCTN6100V1.1p01B12/ZXCTN6110V1.1p01b9以后版本 boot 升级目录修改为(D ) A 、 /system/B 、 /FLASH/datasetC 、 /FLASH/cfgD 、 /FLASH/img25、对于独立版PTN 网元批量升级工具,下列说法错误的是( D ) A 、需要安装sqlserver 数据库 B 、只有规模一安装规模C 、相比于未裁剪的 U31批量升级工具而言,该工具功能简单,占用资源少,可在笔记本上使用D 、安装完毕后,不需要 lice nse26、目前,PTN 网元批量升级工具,下列设备类型不支持的是( E )A 、 ZXCTN6100B 、 ZXCTN6130C 、 ZXCTN6200D 、 ZXCTN6300E 、 ZXCTN9000 32版本27、当前主流版本的 PTN 设备1731 OAM CHANNEL TYPE!为(C ) A 、 32760 B 、 32761 C 、 32762 D 、 32763 28、 ZAR 文件完整性检查的命令是(B )A 、 chkbinB 、 chkzarC 、 chkdataD 、 chknow29、ZXCTN62006300设备从早于 V1.10.00P01B27版本发布的工程版本升级到 V1.10.00P01B27 版本,必须使用( A ) ? B A 、ROS 重启方式B 、升级重启方式C age nt 重启方式30、关于PTN 设备LSP 保护,下列说法错误的是(D )A 、1+1 T-MPLS 路径保护的倒换类型是单向倒换,即只有受影响的连接方向倒换至保护路径, 两端的选择器是独立的B 、 1 + 1 T-MPLS 在单向保护倒换操作模式下,保护倒换由保护域的宿端选择器完全基于本地(即保护宿端)信息来完成C 、 1 + 1 T-MPLS 工作(被保护)业务在保护域的源端永久桥接到工作和保护连接上D 、设备的连通性检查(CC 检测)仅在当前工作的 LSP 进行检查B 、如果要测试SSF 告警功能则AIS 功能需要启用C 、按需LM 功能启用时,可以设置本端 LM 功能或者对端LM 功能,以及报文转发优先级、发送间隔、上报间隔、测试时间等参数D 、CV 报文转发优先级可以随意设置34、对于OSPF 算法,下列说法错误的是( D )31、对于线性保护常见的倒换条件的优先级排序,下列正确的是( A 、LP (保护闭锁)〉SF-P (保护信号通道失效) SD (工作信道信号劣化)〉MS (人工倒换)B LP (保护闭锁)〉SF-P (保护信号通道失效) SD (工作信道信号劣化)〉MS (人工倒换)C 、LP (保护闭锁)〉SF-P (保护信号通道失效) MS (人工倒换)〉SD (工作信道信号劣化)D SF-P (保护信号通道失效)〉LP (保护闭32、为了不影响设备的正常运行。

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CHAPTER 10LOSS PREVENTIONChapter 10LOSS PREVENTION Click on a line to access the corresponding pageTable of ContentsAnnual inventory shrinkage / loss...............................................................................................Page 3 Calculate your shrinkage figures.................................................................................................Page 4 Doing physical counts of your inventory....................................................................................Page 5 Helping the company reduce shrink?.........................................................................................Page 6 Adept at waiting on more than one customer at a time...............................................................Page 6 Minimizes most shoplifting opportunities..................................................................................Page 6 We have a policies and procedures manual.................................................................................Page 6 Aware of the effects of shrinkage................................................................................................Page 6 Electronic security systems.........................................................................................................Page 6 No employee be left in the store by themselves..........................................................................Page 7 Make sure that all cash refunds are legitimate...........................................................................Page 7 Keys are the non-duplicating type...............................................................................................Page 7 Cash register and head office procedures are in place.................................................................Page 7 All markdowns are accounted.....................................................................................................Page 7 All parcels of all employees are checked....................................................................................Page 8 The back door of the store is used only as an emergency exit....................................................Page 8 We always do reference checks on new employees....................................................................Page 8 All garbage is inspected by a second party before leaving the store...........................................Page 8 Generous staff purchase program................................................................................................Page 9 Page 2LOSS PREVENTIONChapter 10Page 3REDUCING THE PAIN“Loss Prevention” is not a very glamorous part of retail. It is however an extremely important element of the success equation. Theft or shrinkage, call it what you will, is all lost dollars and each of these dollars is 100% pure bottom line profit. A store owner doing $400,000 per year with an average 3%shrink is forfeiting $12,000 per year from his or her pocket. In most cases, if true figures were available,it would most likely be twice that amount. Shrink is hard to track and most retailers grossly underestimate their loss rates. Any inroads we can make in reducing this amount is money in the bank.In the last 10 years employee theft has overtaken customer losses as the greatest portion of shrinkage figures, with paperwork errors being a distant third. There are a 100 ways for staff to steal and it’s economically impractical to cover all bases. Therefore the general theory in loss prevention circles is that management has to create the impression that the organization knows all the ways to steal and has the checks in place to catch any offenders. In reality they don’t but the likelihood is still there that apprehension is probable and most employees will forget about trying and hopefully focus on their job.Primary among the control factors to stop shortages is management involvement. Only when all levels of management participate in loss prevention programs will shortages gain the visibility as a major company problem. Employees will then realize the importance of proper control and that the company is not willing to accept such losses.Shrink figures are the difference between these two figures calculated in retail dollar values and typically expressed as a percentage of total puterized point of sale (P .O.S) systems can make the process a lot easier. They allow you to pinpoint specific trouble spots and calculate period gross margins which can be compared to financial statement gross margins to give another form of shrinkage calculation.1. Do you know what your annual inventory shrinkage / loss figures are?Most retailers use the “gut feel” approach as to what their shrink is and whether it is a problem in their organization or not. Unfortunately it’s a major problem for almost every retailer as each dollar lost is bottom line profit. It takes an average $10 of extra sales to make up for every dollar lost. Our experience has been that the “gut feel” figure can in most cases be doubled if compared to an actual figure.This elusive shrink figure is calculated by comparing an actual physical count of all inventories with a book value figure. Book value figures are obtained by keeping a perpetual inventory accounting system, which can be either manual or computerized (see chapter 12).Chapter 10LOSS PREVENTIONPage 4Shrinkage $ = Book Value of Inventory - Actual Inventory on Hand Shrinkage % = Shrinkage $ at Retail Values ÷ Total Sales2. How often during the year do you calculate your shrinkage figures?Obviously, the more often you go through the procedures of calculating your shrinkage the better and faster you become at gathering the data and hopefully the more accurate the data becomes. Only with strong, believable information can management make sound business decisions.A physical count of inventories is costly and time consuming and why the majority of retailers count inventories only once a year. Therefore,they only have the ability to calculate shrink once each year and become vulnerable to a very nasty surprise if gross margins and profitability are not what they are expected to be. The problem with this is that, if there are any major shortages, it is too late to react for the current year. If for example, monthly or even quarterly comparisons were made between the book and physical numbers, it would give us time to rectify any problems before it was too late.LOSS PREVENTIONChapter 10Page 53. Do you have a systemized pro-cedure for doing physical counts of your inventory?Having to count inventory strikes fear in every retail employee. Yes, coming in early to count stock can be a fate equal to death for most of our staff. They have trouble making it for a 10:00AM shift so heaven forbid two hours earlier.Performing a physical count of the inventory is also a major production for most retail owners.Fortunately it does not have to be that way if they did it more often and followed a proven systematic approach.Consider these counting steps:a. Preparation - having the store neat &organized is essential. Start a couple of days before the count to clean up layaways, returns,repairs etc. Pre-count any merchandise that won’t be sold before the official count (eg. off season stock, displays etc.) Make sure no stock is in transit between stores or warehouse.b. After Hours:We’ve seen stores try to count stock and ring in sales at the same time. Y ou can bet the accuracy of the count is greatly diminished not to mention the level of service customers get. Count your inventory when the store is closed.c. Supervision:It is not recommended that store managers do their own counts of their store unless the actual count is closely supervised by an objective outsider that has no reason to inflate the numbers.More than one store manager and employee has been know to “overcount” inventory to cover up for known theft.d. Draw a Map:The store should be divided into its natural count areas. Have the supervisor draw a map and number these areas. An area could be a floor rack, wall unit, table, back room etc. Every section of the store must be represented on the map including the ceiling and washroom if merchandise is in these areas. Do not make the areas too large. A typical store should have 20to 30 count areas.e. Count Sheets:Count sheets should be pre-numbered, printed and padded. The layout of this form as far as number of lines, column headings page totals etc.will vary between organizations. Standard headings would be: date, store, page location,counted by, checked by, quantity, price,description / SKU # etc. It is imperative that every count sheet is accounted for, hence the pre-printed numbering and padding.f. The Count:Each section is systematically counted so checkers can easily follow. On a wall section count top to bottom, left to right.Record on count sheets in pen, never pencil. Have the supervisor initial any changes in red ink. After each section is counted and recorded begin double checking,bringing any mistakes to the supervisor’s attention. All sheets and map are then sent to senior management for processing.Following these steps will not only make your inventory count more accurate, it will also simplify the process so that you can count it much more often.Chapter 10LOSS PREVENTIONPage 64. Do you have an employee reward system for helping the company reduce shrink?In order to push losses due to theft to their lowest possible levels, it is necessary to gain the commitment of each and every employee. Loss prevention should be part of all job descriptions.Rewards should be given to those who have saved the company money through their actions or suggestions. Rewards for recovering goods from shoplifters and identifying fellow employees who are stealing, not only honor the actions of loyal employees, but act as a deterrent to possible dishonest employees, who may think they will never be caught.5. We have a policies and procedures manual.Misinformation on how to handle anything dealing with cash and inventory, is the main reason behind employee mistakes, which result in discrepancies between book and physical figures. The larger one gets, the more important updating this manual and policing its policies becomes.6. Our staff are aware of the effects of shrinkage on our store, on our customers and on themselves.The shrink figure is not something management should keep to themselves. All employees must be made aware of how you, and more specifically how they, are doing in the battle to control losses. Regular loss prevention meetings must reiterate the cost of such losses and how it relates to the economic viability of their store and ultimately their job.7. Our sales associates acknowledge and greet every customer and are adept at waiting on more than one customer at a time.Your best defence against shoplifting is an attentive sales staff that acknowledges and waits on each and every customer. Thieves do not like to be waited on. Stay with your customer as much as possible. Constant staff training on effective selling skills, will greatly increase service levels and hopefully reduce most shoplifting opportunities.8.Our stores are designed and merchandised in such a way that it minimizes most shoplifting oppor-tunities.Blind spots, cash counter placement and merchandise displays must be such that it is impossible for a customer to be in the store without being seen by sales staff. Word travels fast if your store is easy to steal from. Stores with an unobstructed clear view from the outside,will again create doubt in the shoplifters mind,as to whether or not any one is watching.9. For our type of retail operation we are making the best use of electronic security systems, security mirrors, video cameras and micro tag systems.All of the above have their place depending on the type of retail operation. A centrally monitored security system can reduce insurance rates substantially, plus give reports as to who was in the store and at what time. Security mirrors help eliminate blind spots and security cameras can persuade a would be thief to move on to an easier territory. The micro tag systems are relativelyLOSS PREVENTIONChapter 10Page 7expensive and shrink figures must justify such a purchase. Employees can tend to get sloppy and not practice basic loss prevention rules when these systems are installed. Y ou must remember that these systems are only one tool of many in the fight to reduce losses.10. It is policy that no employee be left in the store by themselves.Taking away the temptation to steal and the knowledge that if you do steal, there is a good chance you will get caught, are the two main principles behind controlling internal or employee theft. There is no bigger temptation than being in the store by yourself when cashing out, especially if the individual has any financial difficulties or simply feels they are under- compensated for their efforts.11.Our store entrance keys are the non-duplicating type and we always know who has store keys at any time.Limit access to keys as much as possible. Keep a record of who has keys and make sure you retrieve the key when they leave your employment. If you don’t get their key back,change your locks.12. All markdowns are accounted for and unauthorized markdowns are investigated. (ie. someone gives a customer a discount on a soiled garment.)What is company policy on soiled merchandise?Who can authorize a markdown? How are markdowns recorded? How are retail price reductions handled? All of the above can affect a change in the book value of merchandise. Strict policies and procedures must be in place tohandle all of the above. P .O.S. systems can assist management to police procedures, by producing markdown reports which show any discrepancies between suggested retails and actual selling price.13. Spot checks are carried out to make sure that all cash refunds are legitimate.False refunds are a popular method for dishonest employees to get cash from the till and still balance at the days end. To control this, the customer’s name, address and phone number must be recorded on a special form and signatures are required. Spot calls to customers should be made at head office to ensure the validity of the refund.14. Cash register and head office procedures for handling voids, post voids, no sales, refunds and control of “Z” & “Management” keys are in place.Even the most basic of today’s cash registers have many functions that can help management control employee dishonesty. The daily audit trail gives indication of every time the cash drawer is opened and for what reason. Ideally you want the drawer opened only for recording sales and if it has to be opened for any other reason an explanation is needed. Having the staff initial the audit trail and write an explanation works for some organizations, while others demand full reports signed by manager and or supervisor.The “Z” & “management” keys, depending on the register, allow certain functions to be done only by the holders of these keys. (ie. cash refunds, voids, and running of the days total sales, taxes etc.) These keys should not be made available to all employees.Chapter 10LOSS PREVENTIONPage 815. The back door of the store is used only as an emergency exit, and all deliveries and staff comings and goings are done through the front door.The back door is a prime route for dishonest employees to get merchandise from the store.Access to and from any back doors must be restricted. Fire regulations do not permit the permanent locking of most back doors so a “panic bar” might have to be installed. This allows exit only in an emergency but does not allow entrance.16. All garbage is inspected by a second party before leaving the store.Again, trying to restrict all methods of stealing usually keeps everyone honest. Putting merchandise in with the garbage is one of the oldest tricks in the book. Once out at the garbage bin the dishonest employee has an opportunity to hide the stolen stock so they can pick it up later. Having a second party check all garbage before it leaves the store or making it a two person job means that individuals would have to collaborate in order to steal. Consider using clear bags to further reduce the risk.17. All parcels of all employees are checked whenever they leave the store.This is a hard one to implement if not already in place. One must open up and show the contents of all bags including purses to another staff member. This is to show that you are carrying nothing that belongs to the company. No one is exempt from this policy including store managers and supervisors. If someone does not want there parcels checked, they always have the option of not bringing them into the store.18. We always do reference checks on new employees.It is that 10% of people who are always scheming, always trying to get something for nothing that we don’t want in our system.Unfortunately, retailers have a tendency to hire each others thieves. Generally as a group we don’t prosecute when we catch these bad apples and we do a poor job of checking with past employers as to reasons for dismissal. Two things to check with past employers are the candidates start and finish dates. One will usually fudge these dates if they were dismissed from a previous job for dishonesty. Also try to speak to their immediate supervisor as to work habits etc.LOSS PREVENTION Chapter 10 19. We have a generous staffpurchase program that allowsmost employees to purchasemerchandise at our cost price orjust slightly above.A 20% discount off the retail selling price,especially for retailers that average a 50%markup, is not conducive to controllingemployee theft. A generous staff discount canalso compensate for a low hourly wage orsalary. All staff purchases should be recordedand kept in a special store file. This allows youto document all merchandise purchases forevery employee.It is estimated that 1 out of 3 businesses thatgo bankrupt do so because of employeetheft. Getting serious about loss preventionmay just save your business.Page 9。

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