Abstract The Tree Quorum Protocol An Efficient Approach for Managing Replicated Data

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Abstract A CONSTRAINT MONITOR ALGORITHM FOR THE CASSIN1 SPACECRA~

Abstract A CONSTRAINT MONITOR ALGORITHM FOR THE CASSIN1 SPACECRA~

A CONSTRAINT MONITOR ALGORITHMFOR THEGlennand Robert D.4800 Oak Grove Drive Pasadena, CA 91109-8099AbstractTheConstraint Monitor algorithm performs appropriate checks to ensure the legality and the realizability of the instantaneous attitude, rate, and acceleration commands.When the command is found to be unrealizable becauseof hardware limitations ortionand Science ObjectivesThecarrying a probe intended for delivery into the Titan atmosphere. The probe entry into the Titan atmospherewill occur about four months after Saturn arrival.Senior Technical Staff, Guidance and Control Analysis Group, Automation and Control Section,Member AIAASaturn’s atmospheric composition,winds and temperature,configuration and dynamics of the magnetosphere, structure and composition of the rings,characterization of the icy satellites, and Titan’s atmospheric constituent abundance. The rack mapperwill perform surface imaging and altimetry during eachTitan flyby.Flyby) andconduct scientific investigations for 120days andthe cancellation ofspacecraft. Both the high and lowprecision scan platforms and their structural booms weredeleted,the role of the observation platform and the entire spacecraft now had to turn in order to do earth pointing,star tracking, and remote science pointing. This makes the detection and avoidance of spacecraft attitudeconstraints ever more difficult since movement of oneand Modelingspacecraft with [heboom and three radio and plasma wave science antennas. The core structure of the spacecrafthouses the propulsion module which consists of twotwo1American Institute of AeronauticsFigure 1.axis. Towards theend of the Saturn tour (probe released), the mass and inertia will be reduced to 2400 kg and 6940, 5720, 3600kg-m 2. The magnetometer boom has a fundamentalfrequency at 0.65The three radio and plasma wave antennas arc much lower in mass and inertia, and have a frequency of 0.13Hz or higher and a damping of 0.2 ‘%.At the beginning of the mission, the spacecraftpropellant mass is heavier than the spacecraft dryandNitrogenconsumed by the mainengine, has a total launch mass of 3000 kg. The twolaunch mass isaxis. Each of the twoArticulation Control Subsystemspacecraft burn maneuvers, constraint violations detection and avoidance, fault protection, command processing, telemetry generation and data handling. The attitude control functional block diagram is shown inFigure 2.Diagram2American Institutenever violate a constraint regionif the ground command sequence is generateda clear understanding of the two stepsinvolved in the process -- the detection of constraint violations and, once a violation has been detected, the steps involved in the avoidance process. The avoidance step is where an acceptable alternate path is generated,In the following,underlined capital letters denotematrices, underlined()’implies transposition. The subscript b is used to denotetocoordinates.The symbol ‘x’ implies vectorcross product. Atworepresent thevector component,MonitorThe Constraint Monitorobjects, implements part ofthe AACS fault protection functions.It determines what commanded motions are acceptable, when action should bc taken to interrupt the ACM commanded pointing profile so that an unacceptable motion is notrealized, andwith the ACMcommanded motion, should the nominal path becomesmooth in attitude and rate, withintolerances (rate limited) and realizable (acceleration limited).The two functions performed by the algorithm mayThe Detection function provides the capability to detect constraint violations for ACM-commanded motions.The algorithm is capable of detecting imminent violations so that action may bc taken well in advance. The Avoidance function generates the alternate path which satisfies all constraints when ACM commanded path has been found to be in violation. The computational needs of the Avoidance algorithm are significantly greater than that of the Detection algorithm.In order to make CMT run in real-time,only the Detection algorithm isThe avoidance algorithm cm the otherhand executes in the background at a slower pace (onceevery 2 seconds). Thekinematic extrapolations, carried out every 125 rnsec,which usc the last commanded attitude and rate, and the by CMT may beclassand dynamic.Flight rulesrestricting the pointing of spacecraftcelestial objects are translated into celestial constraints enforced by the CMT. Enforcement of these constraints protect certain spacecraft fixed directions from exposure to celestial objects. There are two types of celestial constraints - non-timed and timed. A non-timedconstraint may be expressedA timed constraint, which protects certain S/C axes from extended exposure to celestial objects, may be expressed as :qThe angular separation between body vector Bfor atime period greater than T. Time is accumulated atthe rate of a 1a minimum of zero.Celestial constraints define a conical region around the celestial vector. The body vector is required to stay out of the cone for non-timed constraints and for timed constraints it is required that the body vector not stay inside the cone for longer than the specified duration.CMT also enforces dynamic constraints to ensure that the acceleration and rates commanded by the ACM are not excessive. These constraints are specified as rate and acceleration ellipsoids in the spacecraft fixed coordinates.The sizes of these ellipsoids can becontrolled via ground commands.The celestial constraints enforced by CMT are defined by ground commands and stored in a table on board (Table 1). The table is of a fixed size (20 entries) and stores all relevant attributes of celestial constraints,which are, the constraint name (unique), the name of the body object, the name of the inertial object, the spatial extent (the half-cone angle of the constraint cone ), the temporal extent (timed constraints only - the constraint is treated as a hard constraint when this attribute iszero),turned OFF (neither DETECT nor AVOID)The celestial and the body vector identifiers (C and B,respectively, in the examples above) and measuresThe appropriate vector valuesTwoseparate tables inthe appropriate vector value is returned by IVP.Once a constraint violation has been detected, theAvoidance function allows the ACM-computed attitude,rate and acceleration to be modified such that theresulting attitude,rate and accelerationAvoidance machinery does not engage unless CMT is currently in Avoidance and / or an AVOIDable celestial constraint violation or a dynamic constraint violation has been detected.When “DETECT only” celestial constraints are violated, the ACM computed attitude is not altered but such a violation is reported. The CMToutput is00AVOIDDROPSUNB37075I .0OFFDROP.1. Constraint TableDetectioncelestial constraint and dynamic constraint violations.Two types of constraints are covered:celestial constraint violations. We would like to start taking evasive action early enough so that the constraint cone is not entered for non-timed constraints and not entered for more than the allowed time for timed-constraints. This requires extrapolation of the current is lessthan the sumstoppingdistance is the predicted angular motion in the direction of the constraint under the assumption that a radialacceleration is applied away from itA closed-form solutionfor this distance is not possible. Instead a first order approximation is used. It works very well, especially for the relatively weak acceleration and rate capabilitiesofrespectively) providesthe direction (henceforth referred to as the “escape”direction) used in the evaluation of the stoppingdistance. Let theisthe normalization operator andused in this evaluation. TheAvoidance function applies maximum availableacceleration in theor is imminent (it isnot necessarily time-optimal; it would be, if all axeshad theIf the body vector is moving away from the celestialvector (else it is computed as the angular distance moved such that the application of maximum decelerationabout The prediction requires the usc of maximum available acceleration along the escape axis. The use of largest available acceleration might be optimistic since, while trying to escape, the escape direction may change as the offending body vector is pushed away from the celestial constraintit is trying to avoid. To avoid this optimism (and therefore future violations) and err on the conservativeside, the smallest available acceleration is usedused in constraint avoidance.is therefore evaluated as0.5A violation is declared imminent if the predicted future c-bseparation+is smaller than the constraintangleinside the constraint cone, the time must be accumulated. If the body vector is outside the constraint cone, the accumulated time must be reduced at the rate R specified in the constraint definition. In other wordstwhere A is the time elapsed since the last evaluation.This accumulation is bounded by O from belowentered as the S/Ca violation. If the constraint ispredicted toexited in the time5American Institute of Aeronautics and Astronauticsremaining ( acceleration then there can not be a violation imminent,otherwise an imminent violation isAvoidance machinery is invoked.acceleration commands must never lie outside theirrespective ellipsoids. A dynamic constraint violation isacceleration constraints imposed by theimminent by the Detection function.in compliance of all constraints andwhich will prevent the S/C attitude from violating celestial constraints and the rate and accelerationcommands from exceeding theDetection cycles). On initial entry intois accounted for in the avoidanceacceleration evaluation.The corrective action taken is designed to be such that the constraint in question is not violated eventually.The corrective action consists of three steps, which maybe repeated several times until the CMT commanded motion merges with the ACM commanded motion.The end goal is to always try to move constraints and is close to the ACM commanded path.When the ACM is not in violation, the goal is of course the ACM command itself. The first action takenwhen a celestial constraint violation isno longer in imminentviolation. If at this point it is possible to move along a great circle towards the goal attitude and not violate any constraint in the immediate future (next 2 seconds),aconstraints arc allowed to be penetrated (under certain conditions) but non-timed constraints arc generally followed at a fixed distance. This behavior is referred to as “... following the flow-field”. While in Circulatemode, the attitude is continually checkedfor imminent violations (transition back toEscape) or possibility ofcelestial constraints. When there are no constraint violations, the attitude and rate goals coincide with the ACM commands. When one or more celestial constraint violations arc present, the goal attitude issuch that all celestial constraints (whichhas been assumed since the attitude goal canAstronauticsexhibitare an artifact of trying tocompute the attitude goal in a finite number of steps, It makes no sense therefore to compute a rate goal consistent with the variation in the attitude goal. Only the violated constraints are considered in determining the attitude goal. The attitude goal is not “close” to the ACM command necessarily but it does satisfy all violated constraints (only in rare cases have we found the algorithm to yield a non-compliant attitude: rapidlymoving celestial constraintsfrom the goal it is tryingto attain, largest possible rate is commanded until it is in the vicinity of it where a rate proportional to thedistance from the goal is commanded.It was noted earlier that while in the Circulate mode,the constraints have to bethen i = 1, 2, 3 are theRodriguez parameters) - referred henceforth as theathe “attitude”, is required to stay outsidea collection of hyperboloids.In general the attitudevectorbe the constraint celestial vector in inertialcoordinates,S/Cw=wherex 3 identity matrix. Attitude has to “flow” a certain way around a collection of such surfacesasaxis. This argument sets the flow-field direction in a relative sense. The correct orientation (i.e. one way orthe other) isAttitudeWhen CMT is in avoidance the attitude does not wander aimlessly, it is actually trying to move towards an attitude goal as it negotiates the constraints betweenthe current attitude and the attitude goal. When the celestial constraints, the goal attitude and rate are the ACM-commanded values. The goal attitude and rate are not close, necessarily, to the ACM attitude (itis, inThe algorithm starts by accepting the ACM attitudecelestial constraintviolation (by the candidate goal attitude that is), thecandidate goal attitude is updated such (hat the offending body vector (at the modified goal) lies slightly outside the edge of the constraint cone. The movement of the offending body vector is accomplished by rotating thebody vector about the escape axisrepeated until there are no violations during an iterationor the iteration count exceeds the number of constraintsunder consideration (whichever comes first).commanded attitude.7American Institute of Aeronautics and Astronautics3.2.3.Desired Direction of MotionOnce a goal attitude is available, the direction in which CMT should try to head towards is needed. The direction is a function of’ the current state, the goal state (attitude and rate), and the location of the constraints which are to be avoided. The desired direction of motion is prescribed in terms of a rate vector which CMT should try to attain by the end of next Avoidance cycle except in Escape mode, where the desired direction is actually a direction in which to accelerate in.When in the Escape mode, the desired direction of travel is the weighted sum of all applicable escape directions and a maximum possible acceleration is commanded in this direction until either the constraints are no longer in imminent violation or the rate limit is reached.When the constraints have been exited (i.e. an Escape is no longer needed), a transition to either the Circulate or the Clear mode takes place. These modes were describedearlier. A Clear mode isbecomes a linear function of the separation from the goal.(1)+ KwherecoordinatesandThe ()* is theconjugation operation. Note that only the vector part oftheimminent had CMT tried to move towards the goal. A transition to Circulate mode is then declared until it is possible to move towards the goal (Clear mode). A desired rate vector has to be computed again. The desired rate magnitude is the largest possible when far from the goal, else the magnitude is the norm ofsum of the so-called “circulation vectors”. The weights bear an inverse square relationship to thedistance from the edge of the constraints.aboutaboutis small. Tbc attitude perturbation+where s =Clearly, aswhich implies a rotation about the directionthat is left to do is to compute therequired acceleration command. Evaluations are differentdepending onLargest possible acceleration is applied in this directionuntil the mode can be transitioned to Circulate or Clearor maximum rate is reached.For non-Escape situations, the desired rate vector (1) isused to compute the acceleration command:is the prescribed rate (1) and CMT-commanded rate in S/C coordinates. It can beshown that, inacceleration, results in a stable behavior when0<It ismust be preserved if possible. A geometric solution ispossibleis shortened such that the accelerationcommand lies on the acceleration3.2.4. Avoidancecommanded path is not in path (in attitude and rate) is close to the ACM-commanded path. The maximum rategroundbeforeattitude goal. Protection against such occurrences isprovided by another attribute of the constraints (the DROP/KEEP column in Table 1). When a situation such as the one described here arises (i.e. away from the goal attitude for too-long) all non-Sun breed constraints (i.e. constraints for which the inertial vector is not the S/C to Sun direction) and all Sun-based constraints whose DROP/KEEP attribute is DROP are marked DETECT only (i.e. the type is changed to DETECT) by CMT. No ground intervention is needed in this step.The remaining constraints which have to be negotiated are therefore all Sun-based and it can beshown that The actions of the algorithm are demonstrated below viasomeexamples. First consider a simplekept out of it isthe spacecraft x-axis. First consider a case where ACM commands a path which moves the spacecraft x-axis,initially outside, through the constraint to a final point outside the constraint.The two avoidanceexamples for this ACM command arc shown in the top two sub-plots in Figure 3. The intersections of the spacecraft x-axis with the unit celestialspherex-axis path goes from right to left and is shown as the thin solid line and the CMT action appears as a dot plotted every 2 seconds.The bard constraint is never entered and CMT rejoins with ACM after an Escape-Circulate-Clear sequence.The timeconstraint (top right) is indeed entered but for only(the bottomplots), CMT seeks the goal attitude, just outside the constraint but close to the ACM point, and comes to rest there. Again, the hard constraint is never entered but the timed constraint is entered but exited in time (0.875 seconds to spare). Note that repeated attempts arc made by CMT to approach the ACM commanded location inside the timed-constraint. This is of courseperfectly legal as long as the06 —–.03Next we consider a slightly more complicated examplewhere three constraints have to be enforced. Theconstraint table is as shown in Table 2. Three celestialNameCelestial BedyHalf Cone Max Allowable Decay Rate TypeDrop/Object, C Object, BAngle, Time, T (see)R,AVOIDKEEP 450AVOID KEEPcAVOIDKEEPAmerican Institute of Aeronautics and Astronauticsconstraints are to be enforced.The first two (A, B)). Componentsof various vectors used to define constraints A, B, Ccoordinates).Table 3. Vector Components for Constraints in Table 2The constraint cone projections and projections ofvarious axes on the unit J2000 celestial sphere arcshown in Figure 4. Constraint regions are regionsinside the dashed circles labeled A, B, C representing thethree constraints A, B, C, respectively. Theand05.e420,c,..,Figure 5. Attitude Separation and CMT ModesSummary1This the design of an autonomousboard theperformance has been very satisfying indeed.6.AcronymsThe work described in this paper was carried out by theJet Propulsion Laboratory, California Institute ofTechnology,under a contract with the NationalAeronautics and Space Administration.8. References[1]Rasmussen,Guidance and Control Conference, Keystone,Colorado, February 1-5, 199510American Institute of AeronauticsAmerican Institute of Aeronautics and Astronautics。

数据结构英文教程

数据结构英文教程

数据结构英文教程Data structures are an essential concept in computer science. 数据结构在计算机科学中是一个基本概念。

They are used to organize, store, and manipulate data efficiently. 它们用于高效地组织、存储和操作数据。

By understanding different data structures, programmers can optimize their algorithms and improve the performance of their applications. 通过了解不同的数据结构,程序员可以优化他们的算法,并提高他们应用程序的性能。

There are various types of data structures, such as arrays, linked lists, stacks, queues, trees, and graphs. 有各种各样的数据结构,比如数组、链表、栈、队列、树和图。

Each type has its own strengths and weaknesses, making them suitable for different tasks. 每种类型都有其优点和缺点,使它们适用于不同的任务。

One of the most basic data structures is an array. Arrays are used to store a collection of elements of the same data type in contiguous memory locations. 一个最基本的数据结构是数组。

数组用于在连续内存位置中存储相同数据类型的元素的集合。

They provide fast access to elements based on their index and are suitable for tasks that require random access to elements. 它们根据索引快速访问元素,适用于需要对元素进行随机访问的任务。

《数据结构(Java版)(第4版)》样卷及答案

《数据结构(Java版)(第4版)》样卷及答案
public static StringBuffer trim(StringBuffer s)
//将 s 中所有空格删除,返回操作后的 s 串
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//i 记住第 1 个空格下标
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String target="aababbabac", pattern="ab", str="aba";
System.out.println("\""+target+"\".replaceAll(\""+pattern+"\", \""+str+"\")=\""+
target.replaceAll(pattern,str)+"\"");
5. mat+(i*n+j)*4=1000+(4*8+5)*4=1148 6. n*(n-1)/2 7. {43,61*,72,96};{43,17,20,32}。解释见《习题解答》第 54 页习 8-9。 8. 见《数据结构(Java 版)(第 4 版)习题解答》第 57 页习 9-4。
二、 问答题(50 分=5 分×10 题)

2020年智慧树知道网课《数据结构(全英文)》课后章节测试满分答案

2020年智慧树知道网课《数据结构(全英文)》课后章节测试满分答案

第一章测试1【单选题】(10分) ThealgorithmandflowchartcanhelpustoA.TostorethedataB.ToknowthememorycapacityC.IdentifythedatatypeofavariableD.Specifytheproblemcompletelyandclearly2【单选题】(10分) TherhombusordiamondshapeinflowchartingdenotesA.DecisionB.InputC.InitializationD.Output3【单选题】(10分) Whichofthefollowingisnotanadvantageofaflowchart?A.EfficientcodingB.BettercommunicationC.SystematictestingD.Improperdocumentation4【单选题】(10分) Theflowchartsymbolsusedforstartandstopoperationsarecalledas_______.A.decisionB.processingC.terminalsD.connectors5【单选题】(10分)TheformulaF n=F n-1+F n-2willproduceA.FibonacciNumberB.RamanujanNumberC.PrimeNumberD.EulerNumber6【单选题】(10分) ThemainmeasuresfortheefficiencyofanalgorithmareA.ComplexityandcapacityB.ProcessorandmemoryC.TimeandspaceD.Dataandspace7【单选题】(10分) WhichoneofthefollowingistheconstanttimecomplexityintermsofBig-OhnotationA.O(1)B.O(n2)C.O(n3)D.O(n)8【单选题】(10分)Whatisthetimecomplexityofthefollowingcode?inta=0;for(i=0;i<n;i++){for(j=n;j>i;j--){a=a+i+j;}}A.O(nlog n)B.O(n)C.O(n2)D.O(1)9【单选题】(10分) Whichoneofthefollowingisanexampleforexponentialtimecomplexity?A.O(n2)B.O(2n)C.O(n)D.O(1)10【单选题】(10分)Forlargervaluesof n,whichonerepresentstheslowesttime?A.O(n2)B.O(2n)C.O(n)D.O(n!)第二章测试1【单选题】(10分) Deletionofanelementfromthearrayreducesthesizeofarrayby___________.A.threeB.twoC.zeroD.one2【单选题】(10分)Assumingthatint isof4bytes,whatisthesizeof intarr[10];?A.30B.10C.40D.3【单选题】(10分) Twodimensionalarraysareusefulwhentheelementsbeingprocessedaretobearran gedintheformof___________.A.NoneoftheaboveB.Both(a)and(b)C.rowsD.columns4【单选题】(10分)Inthepolynomial,A(x)=3x2+2x+4,thedegreeofthispolynomialisA.3B.1C.D.5【单选题】(10分)Inthepolynomial,A(x)=3x2+2x+4,coefficientoffirsttermisA.2B.1C.D.36【单选题】(10分) Amatrixhavingalargernumberofelementswithzerovaluesthanthenumberofnon-zeroelem entsissaidtobea_____________.A.triangularmatrixB.zeromatrixC.diagonalmatrixD.sparsematrix7【单选题】(10分)WhilerepresentingthesparsematrixA(m×n)withtnon-zerotermsin3-tuplesform,the sizeofthematrixbecomesA.t×nB.m×nC.3×tD.(t+1)×38【单选题】(10分)Consideringasparseof m×n matrixwith t non-zeroterms,in FAST_TRANSPOSE algorithm,thesi zeofone-dimensionalarray(SorT)isequalto:A.n+tB.mC.nt9【单选题】(10分)Consideringasparseof m×n matrixwith t non-zeroterms,thetimecomplexityof TRANS POSE algorithmis:A.O(n*t)B.O(n+t)C.O(n t)D.O(n-t)10【单选题】(10分)Whichofthefollowingstatementistrueregarding TRANSPOSE and FAST_TRANSPOSE algorit hms.A.NoneoftheaboveB.The TRANSPOSE algorithmisslowerthan FAST_TRANSPOSEC.TheTRANSPOSEalgorithmisfasterthanFAST_TRANSPOSETimecomplexitiesofTRANSPOSEandFAST_TRANSPOSEaresame第三章测试1【单选题】(10分) Theelementisinsertedfirstandwillberemovedlastin_____________.A.queueB.stackC.noneoftheaboveD.linkedlist2【单选题】(10分)Theexpression1*2^3*4^5*6isevaluatedas(^isforpower,asin a^b=a b):A.49152B.173458C.162^30D.32^303【单选题】(10分) Thedatastructurerequiredtocheckwhetheranexpressioncontainsbalancedparenthesisis?A.TreeB.ArrayC.QueueD.Stack4【单选题】(10分)Thepostfixformof A*B+C/D is?A.AB*CD/+B.ABCD+/*C.A*BC+/DD.5【单选题】(10分) Whichdatastructureisneededtoconvertinfixnotationtopostfixnotation?A.StackB.BranchC.QueueD.Tree6【单选题】(10分) Transformthefollowinginfixexpressiontoprefixform.((C*2)+1)/(A+B)A./+*C21+ABB.AB+12C*+/C.NoneoftheaboveD.7【单选题】(10分)Transformthefollowinginfixexpressiontopostfixform.(A+B)*(C-D)/EA.AB+CD-*E/B.AB*C+D/-C.AB+CD*-/ED.ABC*CD/-+8【单选题】(10分) Astackisadatastructureinwhichallinsertionsanddeletionsaremaderespectivelyat:A.atanypositionB.boththeendsC.inthemiddleD.oneend9【单选题】(10分) Whichofthefollowingapplicationsmayuseastack?:A.AlloftheaboveB.SyntaxanalyzerforacompilerC.AparenthesisbalancingprogramD.Keepingtrackoflocalvariablesatruntime10【单选题】(10分) Whichofthefollowingstatementiscorrect.A.NoneoftheaboveB. ApostfixexpressionismerelythereverseoftheprefixexpressionC.PostfixandprefixexpressionsuseparenthesisD. Apostfixexpressionisnotthereverseoftheprefixexpression第四章测试1【单选题】(10分) Aqueueisadatastructureinwhichallinsertionsanddeletionsaremaderespectivelyat:A.rearandfrontB.frontandrearC.rearandrearD.frontandfront2【单选题】(10分) Thefollowingdatastructureisusedforschedulingofjobsduringbatchprocessingincomputer s.A.stackB.queueC.linkedlistD.tree3【单选题】(10分) Inaqueuethedeletionsaretakeplaceat_________.A.NoneoftheaboveB.topC.frontD.rear4【单选题】(10分) Inaqueuetheinsertionsaretakeplaceat_________.A.rearB.topC.NoneoftheaboveD.front5【单选题】(10分)Incircularqueue,thefrontwillalwayspointtooneposition__________fromthefirstelementint hequeue.A.leftB.clockwiseC.counterclockwiseD.right6【单选题】(10分)Whichofthefollowingisnotthetypeofqueue.A.priorityqueueB.doubleendedqueueC.circularqueueD.singleendedqueue7【单选题】(10分)Oneoftheadvantageofcircularqueueis_____________.A.NoneoftheaboveB.effectiveuseofmemoryC.easiercomputationsD.deletingelementsbasedonpriority8【单选题】(10分) Whatisthetimecomplexityofalinearqueuehaving n elements?A.O(nlogn)B.O(logn)C.O(1)D.O(n)9【单选题】(10分)Whatisadequeue?A.AqueueimplementedwithadoublylinkedlistB.Aqueuewithinsert/deletedefinedforfrontendofthequeueC.Aqueuewithinsert/deletedefinedforbothfrontandrearendsofthequeueD. Aqueueimplementedwithbothsinglyanddoublylinkedlist10【单选题】(10分) Onedifferencebetweenaqueueandastackis:A.Queuesrequiredynamicmemory,butstacksdonot.B.Stacksrequiredynamicmemory,butqueuesdonot.C.Stacksusetwoendsforaddinganddeleting,butqueuesuseone.D.Queuesusetwoendsforaddinganddeleting,butstacksuseone.第五章测试1【单选题】(10分) Alinearlistofdataelementswhereeachelementcallednodeisgivenbymeansofpointeriscalle dA.nodelistB.linkedlistC.queueD.stack2【单选题】(10分)Consideranimplementationofunsortedsinglylinkedlist.Supposeithasrepresentationwhich aheadpointeronly.Giventherepresentation,whichofthefollowingoperationcanbeimpleme ntedinO(1)time?(I).Insertionatthefrontofthelinkedlist.(II).Insertionattheendofthelinkedlist.(III).Deletionofthefrontnodeofthelinkedlist.(IV).Deletionofthelastnodeofthelinkedlist.A.IandIIIB.I,II,andIIIC.I,II,andIVD.IandII3【单选题】(10分) Whatisthetimecomplexitytocountthenumberofelementsinthelinkedlist?A.O(1)B.O(n2)C.O(logn)D.O(n)4【单选题】(10分) InwhichofthefollowinglinkedliststherearenoNULLlinks?A.DoublylinkedlistB.NoneoftheaboveC.SinglylinkedlistD.Circularlinkedlist5【单选题】(10分)Indoublylinkedlists,traversalcanbeperformed?A.OnlyinforwarddirectionB.InbothdirectionsC.NoneD.Onlyinreversedirection6【单选题】(10分)Whatkindoflistisbesttoanswerquestionssuchas:“Whatistheitematposition n?”A.Singly-linkedlistsB.NoneoftheaboveC.Doubly-linkedlistsD.Listimplementedwithanarray7【单选题】(10分) Inasinglylinkedlistwhichoperationdependsonthelengthofthelist.A.DeletethelastelementofthelistB.AddanelementbeforethefirstelementofthelistC.DeletethefirstelementofthelistD.Interchangethefirsttwoelementsofthelist8【单选题】(10分)Thelinkfieldinanodecontains:A.dataofcurrentnodeB.addressofthenextnodeC.dataofnextnodeD.dataofpreviousnode9【单选题】(10分)Linkedlistdatastructureoffersconsiderablesavingin:A.SpaceutilizationB.ComputationaltimeC.SpaceutilizationandcomputationaltimeD.Noneoftheabove10【单选题】(10分) Alinearlistinwhicheachnodehaspointerstopointtothepredecessorandsuccessorsnodesis calledas:A.CircularlinkedlistB.Singly-linkedlistsC.Doubly-linkedlistsD.Linearlinkedlist第六章测试1【单选题】(10分) Torepresenthierarchicalrelationshipbetweenelements,whichdatastructureissuitable?A.treeB.arrayC.stackD.queue2【单选题】(10分) Whatisthemaximumnumberchildrenthatabinarytreenodecanhave?A.1B.C.2D.33【单选题】(10分) TheinordertraversaloftreewillyieldasortedlistingofelementsoftreeinA.NoneoftheaboveB.BinarysearchtreesC.BinarytreesD.Heaps4【单选题】(10分) Ifwestorethenodesofabinarytreeinanarraywithindexstartingfromzero,therightchil dofanodehavingindex n canbeobtainedat:A.2n+2B.n+1C.(n-1)/2D.2n+15【单选题】(10分) WhichofthefollowingtraversaloutputsthedatainsortedorderinaBST?A.InorderB.PostorderC.PreorderD.Levelorder6【单选题】(10分)Toobtainaprefixexpression,whichofthefollowingtraversalsisused?A.LevelorderB.InorderC.PostorderD.Preorder7【单选题】(10分) Themaximumnumberofnodesinatreeforwhichpostorderandpreordertraversalsmaybeequ altois_______.A.B.3C.2D.18【单选题】(10分)Supposethenumbers7,5,1,8,3,6,0,9,4,2areinsertedinthatorderintoaninitiallyempty BinarySearchTree.TheBinarySearchTreeusestheusualorderingonnaturalnumbers.What istheinordertraversalsequenceoftheresultanttree?A.024*******B.7510324689C.0123456789D.98642301579【单选题】(10分)Afullbinarytreeisatreewhere________________.A.eachnodehasexactlyzeroortwochildren.B.eachnodehasexactlytwochildrenC.alltheleavesareatthesamelevel.D.eachnodehasexactlyoneortwochildren.10【单选题】(10分) Acompletebinarytreeisatreewhere________________.A. everylevelofthetreeiscompletelyfilledexceptthelastlevelB.eachnodehasexactlytwochildrenC. eachnodehasexactlyzeroortwochildrenD. eachnodehasexactlyoneortwochildren。

NOMENCLATURE

NOMENCLATURE

Abstract Providing reliable group communication is an ever recurring topic in distributed settings. In mobile ad hoc networks, this problem is even more significant since all nodes act as peers, while it becomes more challenging due to highly dynamic and unpredictable topology changes. In order to overcome these difficulties, we deviate from the conventional point of view, i.e., we “fight fire with fire”1 , by exploiting the nondeterministic nature of ad hoc networks. Inspired by the principles of gossip mechanisms and probabilistic quorum systems, we present in this paper P ILOT (ProbabilistIc Lightweight grOup communication sysTem) for ad hoc networks, a two layer system consisting of a set of protocols for reliable multicasting and data sharing in mobile ad hoc networks. The performance of P ILOT is predictable and controllable in terms of both reliability (fault tolerance) and efficiency (overhead). We

抽象类英语作文模板

抽象类英语作文模板

抽象类英语作文模板英文回答:Abstract Classes。

An abstract class in Java is a class that is declared abstract—it may or may not include abstract methods. Abstract classes cannot be instantiated, but they can be subclassed. When an abstract class is subclassed, the subclass usually provides implementations for all of the abstract methods in its parent class. However, if it does not, then the subclass must also be declared abstract.Syntax。

The syntax for an abstract class in Java is:```。

public abstract class ClassName {。

// Abstract methods and/or concrete methods。

}。

```。

Abstract Methods。

An abstract method is a method that is declared without an implementation. The syntax for an abstract method is:```。

public abstract void methodName();```。

Concrete Methods。

A concrete method is a method that is implemented in the abstract class. The syntax for a concrete method is:```。

哈夫曼编码课件

哈夫曼编码课件

哈夫曼编码与哈夫曼树
➢ 哈夫曼编码和哈夫曼树
二叉树与编码
➢ ASCII码和二叉树
二叉树与编码
➢ Morse码和二叉树
ASCII码传输优缺点
➢ ASCII码优点是编码长度固定,可省去传输字符之间 的间隔;缺点是未考虑(英文)字符出现的频率,编码 效率不高。
字母频率与传统加密
➢ 英文字母的频率作为例子引入权重概念。《跳舞的 人》中福尔摩斯利用英文字母频率解开跳舞小人的 秘密,语言的Zipf定律等实用知识进行介绍。
Morse码传输优缺点
➢ Morse码优点是考虑到字符出现的频率,编码效率较 高;缺点是传输间隔非常重要,否则会产生歧义。
无前缀编码
是否存在无歧义的不等长编码?无歧义=无前缀 无前编码
哈夫曼编码结合了ACSII码和Morse码的优点
例如:tree
ASCII码:1110100111001011001011100101
例:thethreethetreethe
t5 h4 r2 e7
哈夫曼编码 e:0 t:10 r:110 h:111
0
1
7
e
0
1
5
t
01
2
4
r
h
哈夫曼树及哈夫曼编码的构造演示
哈夫曼编码的故事
1951年,哈夫曼还是一名学生,他的老师法 诺教授正思考信息传送中的编码问题,他和申农 已想到一个编码,但不知是不是最有效的,于是 他把寻找最有效编码的问题作为论文题目留给学 生,但没有告诉学生问题的背景,完成论文的学 生可以不参加期末考试。哈夫曼在即将承认失败 将所有努力扔进废纸篓之际突发灵感,从而得到 了哈夫曼编码。
二叉树的应用
哈夫曼编码

川大软院计网选择题答案Chapter5(含答案)

川大软院计网选择题答案Chapter5(含答案)

1. A ( D) protocol is used to move a packet over an individual 独立link.A. application-layerB. transport-layerC. network-layerD. link-layer2. Which of the following services can not offered by a link-layer protocol? ( )A. congestion controlB. Link AccessC. Error controlD. FramingHint:framing, link access,reliable delivery,flow control,error detection,error correction,half-duplex and full-duplex3. ( B ) protocol serves to 为……服务coordinate 协调the frame transmissionsof the many nodes when multiple nodes share a single broadcast link.A. ARPB. MACC. ICMPD. DNS4. Consider CRC error checking approach, the four bit generator G is 1011, andsuppose that the data D is 10101010, then the value of R is ( A).A. 010B. 100C. 011D. 1105. In the following four descriptions说明about random access protocol, whichone is not correct? ( A )A. In slotted ALOHA, nodes can transmit at random time.B. CSMA/CD cannot be implemented on a wireless channel.C. The maximum efficiency of a slotted ALOHA is higher than a pure ALOHA.D. In CSMA/CD, one node listens to the channel before transmitting.6. In the following descriptions about MAC address, which one is not correct? ( D )A. The MAC address is the address of one node’s ada pter.B. No two adapters have the same MAC address.C. The MAC address doesn’t change no matter where the adapter goes.D. MAC address has a hierarchical structure分层结构.MAC:flat structureIP:hierarchical structure7. The ARP protocol can translate ( ) into ( ). ( C )A. host name, IP addressB. host name, MAC addressC. IP address, MAC addressD. broadcast address, IP address8. The value of Preamble field in Ethernet frame structure is ( C)A. 10101010 10101010……10101010 11111111B. 10101011 10101011……10101011 10101011C. 10101010 10101010……10101010 10101011D. 10101010 10101010……10101010 101010109. In CSMA/CD, the adapter waits some time and then returns to sensing thechannel. In the following four times, which one is impossible? ( D)A. 0 bit timesB. 512 bit timesC. 1024 bit timesD. 1028 bit times10. The principal components of PPP include but not( D ).A. framingB. physical-control protocolC. link-layer protocolD. network-layer protocol11. Consider the data D is 01110010001, if use even parity checking approach, theparity bit is( ① ), if use odd parity checking approach, the parity bit is( ② ). ( D )A. ① 0 ② 1B. ① 0 ② 0C. ① 1 ② 1D. ① 1 ② 012. In the following four descriptions, which one is not correct? (B )A. Switches can interconnect different LAN technologies.B. Hubs can interconnect different LAN technologies.C. There is no limit to how large a LAN can be when switches are used tointerconnect LAN segments.D. There is restriction on the maximum allowable number of nodes in a collisiondomain when hubs are used to interconnect LAN segments.13. Which of the following devices is not a plug and play device? ( B )A. hubB. routerC. switchD. repeater14. Which device has the same collision domain? ( A )A. HubB. SwitchC. RouteD. Bridge15. In data link-layer, which protocol is used to share bandwidth? ( D)A. SMTPB. ICMPC. ARPD. CSMA/CD16. When two or more nodes on the LAN segments transmit at the same time, therewill be a collision and all of the transmitting nodes well enter exponential back-off, that is all of the LAN segments belong to the same( A ).A. collision domainB. switchC. bridgeD. hub17. In the following four descriptions about PPP, which one is not correct? ( D )A. PPP is required to detect and correct errors.B. PPP is not required to deliver frames to the link receiver in the same order inwhich they were sent by the link sender.C. PPP need only operate over links that have a single sender and a single receiver.D. PPP is not required to provide flow control.18. For ( A ) links that have a single sender at one end of the link and a single receiverat the other end of the link.A. point-to-pointB. broadcastC. multicastD. all of the above19. With(B )transmission, the nodes at both ends of a link may transmit packets at thesame time.A. half-duplexB. full-duplexC. simplex(单工)D.synchronous20. Which of the following is wrong? ( A )A. ARP table is configured by a system administratorB. ARP table is built automaticallyC. ARP table is dynamicD. ARP table maps IP addresses to MAC addresses21. In LAN, if UTP is used, the common connector is (C ).A. AUIB. BNCC. RJ-45D. NNI22. Which of the following four descriptions about MAC addresses is wrong? ( C )A. a MAC address is burned into the adapter’s ROMB. No two adapters have the same addressC. An adapter’s MAC address is dynamicD. A MAC address is a link-layer address23. In the CSMA/CD protocol, what condition on the transmission delay and thepropagation delay has to be satisfied to guarantee that a node always detects a collision? BA. B.C. D.。

ACM-GIS%202006-A%20Peer-to-Peer%20Spatial%20Cloaking%20Algorithm%20for%20Anonymous%20Location-based%

ACM-GIS%202006-A%20Peer-to-Peer%20Spatial%20Cloaking%20Algorithm%20for%20Anonymous%20Location-based%

A Peer-to-Peer Spatial Cloaking Algorithm for AnonymousLocation-based Services∗Chi-Yin Chow Department of Computer Science and Engineering University of Minnesota Minneapolis,MN cchow@ Mohamed F.MokbelDepartment of ComputerScience and EngineeringUniversity of MinnesotaMinneapolis,MNmokbel@Xuan LiuIBM Thomas J.WatsonResearch CenterHawthorne,NYxuanliu@ABSTRACTThis paper tackles a major privacy threat in current location-based services where users have to report their ex-act locations to the database server in order to obtain their desired services.For example,a mobile user asking about her nearest restaurant has to report her exact location.With untrusted service providers,reporting private location in-formation may lead to several privacy threats.In this pa-per,we present a peer-to-peer(P2P)spatial cloaking algo-rithm in which mobile and stationary users can entertain location-based services without revealing their exact loca-tion information.The main idea is that before requesting any location-based service,the mobile user will form a group from her peers via single-hop communication and/or multi-hop routing.Then,the spatial cloaked area is computed as the region that covers the entire group of peers.Two modes of operations are supported within the proposed P2P spa-tial cloaking algorithm,namely,the on-demand mode and the proactive mode.Experimental results show that the P2P spatial cloaking algorithm operated in the on-demand mode has lower communication cost and better quality of services than the proactive mode,but the on-demand incurs longer response time.Categories and Subject Descriptors:H.2.8[Database Applications]:Spatial databases and GISGeneral Terms:Algorithms and Experimentation. Keywords:Mobile computing,location-based services,lo-cation privacy and spatial cloaking.1.INTRODUCTIONThe emergence of state-of-the-art location-detection de-vices,e.g.,cellular phones,global positioning system(GPS) devices,and radio-frequency identification(RFID)chips re-sults in a location-dependent information access paradigm,∗This work is supported in part by the Grants-in-Aid of Re-search,Artistry,and Scholarship,University of Minnesota. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on thefirst page.To copy otherwise,to republish,to post on servers or to redistribute to lists,requires prior specific permission and/or a fee.ACM-GIS’06,November10-11,2006,Arlington,Virginia,USA. Copyright2006ACM1-59593-529-0/06/0011...$5.00.known as location-based services(LBS)[30].In LBS,mobile users have the ability to issue location-based queries to the location-based database server.Examples of such queries include“where is my nearest gas station”,“what are the restaurants within one mile of my location”,and“what is the traffic condition within ten minutes of my route”.To get the precise answer of these queries,the user has to pro-vide her exact location information to the database server. With untrustworthy servers,adversaries may access sensi-tive information about specific individuals based on their location information and issued queries.For example,an adversary may check a user’s habit and interest by knowing the places she visits and the time of each visit,or someone can track the locations of his ex-friends.In fact,in many cases,GPS devices have been used in stalking personal lo-cations[12,39].To tackle this major privacy concern,three centralized privacy-preserving frameworks are proposed for LBS[13,14,31],in which a trusted third party is used as a middleware to blur user locations into spatial regions to achieve k-anonymity,i.e.,a user is indistinguishable among other k−1users.The centralized privacy-preserving frame-work possesses the following shortcomings:1)The central-ized trusted third party could be the system bottleneck or single point of failure.2)Since the centralized third party has the complete knowledge of the location information and queries of all users,it may pose a serious privacy threat when the third party is attacked by adversaries.In this paper,we propose a peer-to-peer(P2P)spatial cloaking algorithm.Mobile users adopting the P2P spatial cloaking algorithm can protect their privacy without seeking help from any centralized third party.Other than the short-comings of the centralized approach,our work is also moti-vated by the following facts:1)The computation power and storage capacity of most mobile devices have been improv-ing at a fast pace.2)P2P communication technologies,such as IEEE802.11and Bluetooth,have been widely deployed.3)Many new applications based on P2P information shar-ing have rapidly taken shape,e.g.,cooperative information access[9,32]and P2P spatio-temporal query processing[20, 24].Figure1gives an illustrative example of P2P spatial cloak-ing.The mobile user A wants tofind her nearest gas station while beingfive anonymous,i.e.,the user is indistinguish-able amongfive users.Thus,the mobile user A has to look around andfind other four peers to collaborate as a group. In this example,the four peers are B,C,D,and E.Then, the mobile user A cloaks her exact location into a spatialA B CDEBase Stationregion that covers the entire group of mobile users A ,B ,C ,D ,and E .The mobile user A randomly selects one of the mobile users within the group as an agent .In the ex-ample given in Figure 1,the mobile user D is selected as an agent.Then,the mobile user A sends her query (i.e.,what is the nearest gas station)along with her cloaked spa-tial region to the agent.The agent forwards the query to the location-based database server through a base station.Since the location-based database server processes the query based on the cloaked spatial region,it can only give a list of candidate answers that includes the actual answers and some false positives.After the agent receives the candidate answers,it forwards the candidate answers to the mobile user A .Finally,the mobile user A gets the actual answer by filtering out all the false positives.The proposed P2P spatial cloaking algorithm can operate in two modes:on-demand and proactive .In the on-demand mode,mobile clients execute the cloaking algorithm when they need to access information from the location-based database server.On the other side,in the proactive mode,mobile clients periodically look around to find the desired number of peers.Thus,they can cloak their exact locations into spatial regions whenever they want to retrieve informa-tion from the location-based database server.In general,the contributions of this paper can be summarized as follows:1.We introduce a distributed system architecture for pro-viding anonymous location-based services (LBS)for mobile users.2.We propose the first P2P spatial cloaking algorithm for mobile users to entertain high quality location-based services without compromising their privacy.3.We provide experimental evidence that our proposed algorithm is efficient in terms of the response time,is scalable to large numbers of mobile clients,and is effective as it provides high-quality services for mobile clients without the need of exact location information.The rest of this paper is organized as follows.Section 2highlights the related work.The system model of the P2P spatial cloaking algorithm is presented in Section 3.The P2P spatial cloaking algorithm is described in Section 4.Section 5discusses the integration of the P2P spatial cloak-ing algorithm with privacy-aware location-based database servers.Section 6depicts the experimental evaluation of the P2P spatial cloaking algorithm.Finally,Section 7con-cludes this paper.2.RELATED WORKThe k -anonymity model [37,38]has been widely used in maintaining privacy in databases [5,26,27,28].The main idea is to have each tuple in the table as k -anonymous,i.e.,indistinguishable among other k −1tuples.Although we aim for the similar k -anonymity model for the P2P spatial cloaking algorithm,none of these techniques can be applied to protect user privacy for LBS,mainly for the following four reasons:1)These techniques preserve the privacy of the stored data.In our model,we aim not to store the data at all.Instead,we store perturbed versions of the data.Thus,data privacy is managed before storing the data.2)These approaches protect the data not the queries.In anonymous LBS,we aim to protect the user who issues the query to the location-based database server.For example,a mobile user who wants to ask about her nearest gas station needs to pro-tect her location while the location information of the gas station is not protected.3)These approaches guarantee the k -anonymity for a snapshot of the database.In LBS,the user location is continuously changing.Such dynamic be-havior calls for continuous maintenance of the k -anonymity model.(4)These approaches assume a unified k -anonymity requirement for all the stored records.In our P2P spatial cloaking algorithm,k -anonymity is a user-specified privacy requirement which may have a different value for each user.Motivated by the privacy threats of location-detection de-vices [1,4,6,40],several research efforts are dedicated to protect the locations of mobile users (e.g.,false dummies [23],landmark objects [18],and location perturbation [10,13,14]).The most closed approaches to ours are two centralized spatial cloaking algorithms,namely,the spatio-temporal cloaking [14]and the CliqueCloak algorithm [13],and one decentralized privacy-preserving algorithm [23].The spatio-temporal cloaking algorithm [14]assumes that all users have the same k -anonymity requirements.Furthermore,it lacks the scalability because it deals with each single request of each user individually.The CliqueCloak algorithm [13]as-sumes a different k -anonymity requirement for each user.However,since it has large computation overhead,it is lim-ited to a small k -anonymity requirement,i.e.,k is from 5to 10.A decentralized privacy-preserving algorithm is proposed for LBS [23].The main idea is that the mobile client sends a set of false locations,called dummies ,along with its true location to the location-based database server.However,the disadvantages of using dummies are threefold.First,the user has to generate realistic dummies to pre-vent the adversary from guessing its true location.Second,the location-based database server wastes a lot of resources to process the dummies.Finally,the adversary may esti-mate the user location by using cellular positioning tech-niques [34],e.g.,the time-of-arrival (TOA),the time differ-ence of arrival (TDOA)and the direction of arrival (DOA).Although several existing distributed group formation al-gorithms can be used to find peers in a mobile environment,they are not designed for privacy preserving in LBS.Some algorithms are limited to only finding the neighboring peers,e.g.,lowest-ID [11],largest-connectivity (degree)[33]and mobility-based clustering algorithms [2,25].When a mo-bile user with a strict privacy requirement,i.e.,the value of k −1is larger than the number of neighboring peers,it has to enlist other peers for help via multi-hop routing.Other algorithms do not have this limitation,but they are designed for grouping stable mobile clients together to facil-Location-based Database ServerDatabase ServerDatabase ServerFigure 2:The system architectureitate efficient data replica allocation,e.g.,dynamic connec-tivity based group algorithm [16]and mobility-based clus-tering algorithm,called DRAM [19].Our work is different from these approaches in that we propose a P2P spatial cloaking algorithm that is dedicated for mobile users to dis-cover other k −1peers via single-hop communication and/or via multi-hop routing,in order to preserve user privacy in LBS.3.SYSTEM MODELFigure 2depicts the system architecture for the pro-posed P2P spatial cloaking algorithm which contains two main components:mobile clients and location-based data-base server .Each mobile client has its own privacy profile that specifies its desired level of privacy.A privacy profile includes two parameters,k and A min ,k indicates that the user wants to be k -anonymous,i.e.,indistinguishable among k users,while A min specifies the minimum resolution of the cloaked spatial region.The larger the value of k and A min ,the more strict privacy requirements a user needs.Mobile users have the ability to change their privacy profile at any time.Our employed privacy profile matches the privacy re-quirements of mobiles users as depicted by several social science studies (e.g.,see [4,15,17,22,29]).In this architecture,each mobile user is equipped with two wireless network interface cards;one of them is dedicated to communicate with the location-based database server through the base station,while the other one is devoted to the communication with other peers.A similar multi-interface technique has been used to implement IP multi-homing for stream control transmission protocol (SCTP),in which a machine is installed with multiple network in-terface cards,and each assigned a different IP address [36].Similarly,in mobile P2P cooperation environment,mobile users have a network connection to access information from the server,e.g.,through a wireless modem or a base station,and the mobile users also have the ability to communicate with other peers via a wireless LAN,e.g.,IEEE 802.11or Bluetooth [9,24,32].Furthermore,each mobile client is equipped with a positioning device, e.g.,GPS or sensor-based local positioning systems,to determine its current lo-cation information.4.P2P SPATIAL CLOAKINGIn this section,we present the data structure and the P2P spatial cloaking algorithm.Then,we describe two operation modes of the algorithm:on-demand and proactive .4.1Data StructureThe entire system area is divided into grid.The mobile client communicates with each other to discover other k −1peers,in order to achieve the k -anonymity requirement.TheAlgorithm 1P2P Spatial Cloaking:Request Originator m 1:Function P2PCloaking-Originator (h ,k )2://Phase 1:Peer searching phase 3:The hop distance h is set to h4:The set of discovered peers T is set to {∅},and the number ofdiscovered peers k =|T |=05:while k <k −1do6:Broadcast a FORM GROUP request with the parameter h (Al-gorithm 2gives the response of each peer p that receives this request)7:T is the set of peers that respond back to m by executingAlgorithm 28:k =|T |;9:if k <k −1then 10:if T =T then 11:Suspend the request 12:end if 13:h ←h +1;14:T ←T ;15:end if 16:end while17://Phase 2:Location adjustment phase 18:for all T i ∈T do19:|mT i .p |←the greatest possible distance between m and T i .pby considering the timestamp of T i .p ’s reply and maximum speed20:end for21://Phase 3:Spatial cloaking phase22:Form a group with k −1peers having the smallest |mp |23:h ←the largest hop distance h p of the selected k −1peers 24:Determine a grid area A that covers the entire group 25:if A <A min then26:Extend the area of A till it covers A min 27:end if28:Randomly select a mobile client of the group as an agent 29:Forward the query and A to the agentmobile client can thus blur its exact location into a cloaked spatial region that is the minimum grid area covering the k −1peers and itself,and satisfies A min as well.The grid area is represented by the ID of the left-bottom and right-top cells,i.e.,(l,b )and (r,t ).In addition,each mobile client maintains a parameter h that is the required hop distance of the last peer searching.The initial value of h is equal to one.4.2AlgorithmFigure 3gives a running example for the P2P spatial cloaking algorithm.There are 15mobile clients,m 1to m 15,represented as solid circles.m 8is the request originator,other black circles represent the mobile clients received the request from m 8.The dotted circles represent the commu-nication range of the mobile client,and the arrow represents the movement direction.Algorithms 1and 2give the pseudo code for the request originator (denoted as m )and the re-quest receivers (denoted as p ),respectively.In general,the algorithm consists of the following three phases:Phase 1:Peer searching phase .The request origina-tor m wants to retrieve information from the location-based database server.m first sets h to h ,a set of discovered peers T to {∅}and the number of discovered peers k to zero,i.e.,|T |.(Lines 3to 4in Algorithm 1).Then,m broadcasts a FORM GROUP request along with a message sequence ID and the hop distance h to its neighboring peers (Line 6in Algorithm 1).m listens to the network and waits for the reply from its neighboring peers.Algorithm 2describes how a peer p responds to the FORM GROUP request along with a hop distance h and aFigure3:P2P spatial cloaking algorithm.Algorithm2P2P Spatial Cloaking:Request Receiver p1:Function P2PCloaking-Receiver(h)2://Let r be the request forwarder3:if the request is duplicate then4:Reply r with an ACK message5:return;6:end if7:h p←1;8:if h=1then9:Send the tuple T=<p,(x p,y p),v maxp ,t p,h p>to r10:else11:h←h−1;12:Broadcast a FORM GROUP request with the parameter h 13:T p is the set of peers that respond back to p14:for all T i∈T p do15:T i.h p←T i.h p+1;16:end for17:T p←T p∪{<p,(x p,y p),v maxp ,t p,h p>};18:Send T p back to r19:end ifmessage sequence ID from another peer(denoted as r)that is either the request originator or the forwarder of the re-quest.First,p checks if it is a duplicate request based on the message sequence ID.If it is a duplicate request,it sim-ply replies r with an ACK message without processing the request.Otherwise,p processes the request based on the value of h:Case1:h= 1.p turns in a tuple that contains its ID,current location,maximum movement speed,a timestamp and a hop distance(it is set to one),i.e.,< p,(x p,y p),v max p,t p,h p>,to r(Line9in Algorithm2). Case2:h> 1.p decrements h and broadcasts the FORM GROUP request with the updated h and the origi-nal message sequence ID to its neighboring peers.p keeps listening to the network,until it collects the replies from all its neighboring peers.After that,p increments the h p of each collected tuple,and then it appends its own tuple to the collected tuples T p.Finally,it sends T p back to r (Lines11to18in Algorithm2).After m collects the tuples T from its neighboring peers, if m cannotfind other k−1peers with a hop distance of h,it increments h and re-broadcasts the FORM GROUP request along with a new message sequence ID and h.m repeatedly increments h till itfinds other k−1peers(Lines6to14in Algorithm1).However,if mfinds the same set of peers in two consecutive broadcasts,i.e.,with hop distances h and h+1,there are not enough connected peers for m.Thus, m has to relax its privacy profile,i.e.,use a smaller value of k,or to be suspended for a period of time(Line11in Algorithm1).Figures3(a)and3(b)depict single-hop and multi-hop peer searching in our running example,respectively.In Fig-ure3(a),the request originator,m8,(e.g.,k=5)canfind k−1peers via single-hop communication,so m8sets h=1. Since h=1,its neighboring peers,m5,m6,m7,m9,m10, and m11,will not further broadcast the FORM GROUP re-quest.On the other hand,in Figure3(b),m8does not connect to k−1peers directly,so it has to set h>1.Thus, its neighboring peers,m7,m10,and m11,will broadcast the FORM GROUP request along with a decremented hop dis-tance,i.e.,h=h−1,and the original message sequence ID to their neighboring peers.Phase2:Location adjustment phase.Since the peer keeps moving,we have to capture the movement between the time when the peer sends its tuple and the current time. For each received tuple from a peer p,the request originator, m,determines the greatest possible distance between them by an equation,|mp |=|mp|+(t c−t p)×v max p,where |mp|is the Euclidean distance between m and p at time t p,i.e.,|mp|=(x m−x p)2+(y m−y p)2,t c is the currenttime,t p is the timestamp of the tuple and v maxpis the maximum speed of p(Lines18to20in Algorithm1).In this paper,a conservative approach is used to determine the distance,because we assume that the peer will move with the maximum speed in any direction.If p gives its movement direction,m has the ability to determine a more precise distance between them.Figure3(c)illustrates that,for each discovered peer,the circle represents the largest region where the peer can lo-cate at time t c.The greatest possible distance between the request originator m8and its discovered peer,m5,m6,m7, m9,m10,or m11is represented by a dotted line.For exam-ple,the distance of the line m8m 11is the greatest possible distance between m8and m11at time t c,i.e.,|m8m 11|. Phase3:Spatial cloaking phase.In this phase,the request originator,m,forms a virtual group with the k−1 nearest peers,based on the greatest possible distance be-tween them(Line22in Algorithm1).To adapt to the dynamic network topology and k-anonymity requirement, m sets h to the largest value of h p of the selected k−1 peers(Line15in Algorithm1).Then,m determines the minimum grid area A covering the entire group(Line24in Algorithm1).If the area of A is less than A min,m extends A,until it satisfies A min(Lines25to27in Algorithm1). Figure3(c)gives the k−1nearest peers,m6,m7,m10,and m11to the request originator,m8.For example,the privacy profile of m8is(k=5,A min=20cells),and the required cloaked spatial region of m8is represented by a bold rectan-gle,as depicted in Figure3(d).To issue the query to the location-based database server anonymously,m randomly selects a mobile client in the group as an agent(Line28in Algorithm1).Then,m sendsthe query along with the cloaked spatial region,i.e.,A,to the agent(Line29in Algorithm1).The agent forwards thequery to the location-based database server.After the serverprocesses the query with respect to the cloaked spatial re-gion,it sends a list of candidate answers back to the agent.The agent forwards the candidate answer to m,and then mfilters out the false positives from the candidate answers. 4.3Modes of OperationsThe P2P spatial cloaking algorithm can operate in twomodes,on-demand and proactive.The on-demand mode:The mobile client only executesthe algorithm when it needs to retrieve information from the location-based database server.The algorithm operatedin the on-demand mode generally incurs less communica-tion overhead than the proactive mode,because the mobileclient only executes the algorithm when necessary.However,it suffers from a longer response time than the algorithm op-erated in the proactive mode.The proactive mode:The mobile client adopting theproactive mode periodically executes the algorithm in back-ground.The mobile client can cloak its location into a spa-tial region immediately,once it wants to communicate withthe location-based database server.The proactive mode pro-vides a better response time than the on-demand mode,but it generally incurs higher communication overhead and giveslower quality of service than the on-demand mode.5.ANONYMOUS LOCATION-BASEDSERVICESHaving the spatial cloaked region as an output form Algo-rithm1,the mobile user m sends her request to the location-based server through an agent p that is randomly selected.Existing location-based database servers can support onlyexact point locations rather than cloaked regions.In or-der to be able to work with a spatial region,location-basedservers need to be equipped with a privacy-aware queryprocessor(e.g.,see[29,31]).The main idea of the privacy-aware query processor is to return a list of candidate answerrather than the exact query answer.Then,the mobile user m willfilter the candidate list to eliminate its false positives andfind its exact answer.The tighter the spatial cloaked re-gion,the lower is the size of the candidate answer,and hencethe better is the performance of the privacy-aware query processor.However,tight cloaked regions may represent re-laxed privacy constrained.Thus,a trade-offbetween the user privacy and the quality of service can be achieved[31]. Figure4(a)depicts such scenario by showing the data stored at the server side.There are32target objects,i.e., gas stations,T1to T32represented as black circles,the shaded area represents the spatial cloaked area of the mo-bile client who issued the query.For clarification,the actual mobile client location is plotted in Figure4(a)as a black square inside the cloaked area.However,such information is neither stored at the server side nor revealed to the server. The privacy-aware query processor determines a range that includes all target objects that are possibly contributing to the answer given that the actual location of the mobile client could be anywhere within the shaded area.The range is rep-resented as a bold rectangle,as depicted in Figure4(b).The server sends a list of candidate answers,i.e.,T8,T12,T13, T16,T17,T21,and T22,back to the agent.The agent next for-(a)Server Side(b)Client SideFigure4:Anonymous location-based services wards the candidate answers to the requesting mobile client either through single-hop communication or through multi-hop routing.Finally,the mobile client can get the actualanswer,i.e.,T13,byfiltering out the false positives from thecandidate answers.The algorithmic details of the privacy-aware query proces-sor is beyond the scope of this paper.Interested readers are referred to[31]for more details.6.EXPERIMENTAL RESULTSIn this section,we evaluate and compare the scalabilityand efficiency of the P2P spatial cloaking algorithm in boththe on-demand and proactive modes with respect to the av-erage response time per query,the average number of mes-sages per query,and the size of the returned candidate an-swers from the location-based database server.The queryresponse time in the on-demand mode is defined as the timeelapsed between a mobile client starting to search k−1peersand receiving the candidate answers from the agent.On theother hand,the query response time in the proactive mode is defined as the time elapsed between a mobile client startingto forward its query along with the cloaked spatial regionto the agent and receiving the candidate answers from theagent.The simulation model is implemented in C++usingCSIM[35].In all the experiments in this section,we consider an in-dividual random walk model that is based on“random way-point”model[7,8].At the beginning,the mobile clientsare randomly distributed in a spatial space of1,000×1,000square meters,in which a uniform grid structure of100×100cells is constructed.Each mobile client randomly chooses itsown destination in the space with a randomly determined speed s from a uniform distribution U(v min,v max).When the mobile client reaches the destination,it comes to a stand-still for one second to determine its next destination.Afterthat,the mobile client moves towards its new destinationwith another speed.All the mobile clients repeat this move-ment behavior during the simulation.The time interval be-tween two consecutive queries generated by a mobile client follows an exponential distribution with a mean of ten sec-onds.All the experiments consider one half-duplex wirelesschannel for a mobile client to communicate with its peers with a total bandwidth of2Mbps and a transmission range of250meters.When a mobile client wants to communicate with other peers or the location-based database server,it has to wait if the requested channel is busy.In the simulated mobile environment,there is a centralized location-based database server,and one wireless communication channel between the location-based database server and the mobile。

一种改良型检测群体感应信号分子的tlc方法

一种改良型检测群体感应信号分子的tlc方法
Acyl - homoserine lactonesꎬ AHLs) 的研究最为广泛ꎮ 以往针对 AHLs 的检测主要是传统的薄层色谱法( Thin Layer
chromatographꎬTLC) ꎬ即采用报告菌株、显色剂 X - gal 以及半固体培养基三者混合后平铺于 TLC 板上ꎬ通过生物显
色反应来进行定性判断ꎮ 但这一方法在实际操作中存在一些不足ꎬ包括显色不均匀、蓝色斑点发散、以及分辨率不
nals and regulates the expression of many physiological characteristic in Gram negative bacteria. The traditional dection method main de ̄
pends on thin ̄layer chromatography ( TCL) . Howeverꎬ some shortcomings still exist in this classical methodsꎬ including uneven pig ̄
高等问题ꎬ因此该方法还具有很大的改进空间ꎮ 利用根癌农杆菌( Agrobacterium tumefaciens) A136 ( pCF218) 建立了
一种改良型的 TLC 方法ꎬ主要包括设计一套简易型的制胶板、改变铺板程序以及节省 X - gal 用量等ꎮ 结果表明ꎬ改
良后的方法使得显色斑点更聚焦ꎬ显色强度和线性迁移率效果更好ꎬ检测分辨率更高ꎬ更适合混合型样本ꎮ 同时该
Shenzhen 518055ꎻ 3. Graduate School at Shenzhenꎬ Tsinghua Universityꎬ Shenzhen 518055ꎬ China)
Abstract Quorum sensing ( QS) is the uniqueꎬ diverse group behavior phenomenon occurred when the bacterium grows to a certain

基于二叉排序树的缓冲机制在污染源监控系统中的研究

基于二叉排序树的缓冲机制在污染源监控系统中的研究
7 0
基 于 二 叉 排序 树 的缓 冲 机 制在 污 染 源 监 控 系统 中 的研 究
基于二叉排序树的缓冲机制在污染源监控系统中的研究
Mo i r g S se nt i y t m F r P l t n S u c s Ba e n u f r g W i n r o tT e on o ol i o r e s d o B f i t Bia y S r r e uo e n h
放 于 数 据 库服 务 器 的时 间延 迟 , 高 了数 据检 索 效 率 , 且 降低 了 时 间复 杂度 。 通过 实验 测 试 发 现 该 方法 对 污 染 源 在 线 自 提 而 动 监 控 系统 的 整体 性 能 有 明 显 的 改善 作 用 。
关 键 词 : 又排 序树 , 衡 二 叉树 , 冲机 制 , 整 算 法 二 平 缓 调
王 鑫 宁 魏振 钢 ( 中国海洋大学信息科学与工程 学院, 山东 青岛 2 6 0 ) 6 1 0
李 崇
( 中国海洋大学工程学院, 山东 青岛 260 ) 6 10
摘 要
针 对 污 染 源在 线 自动 监 控 系统 , 出 了二 叉排 序 树 的 数 据缓 冲机 制 的 方 案 , 计 树 形 存 储 结 构 , 其 进 行 平 衡 化 处理 , 提 设 将 完 成 结 构 化缓 冲存 储 , 实现 了基 于二 叉排 序 树 的数 据 缓 冲 机 制 的 污 染 源在 线 自动监 控 系统 。 机 制 不 仅 避 免 了数 据 直 接 存 该
染 源 在 线 自动 监 控 系统 , 高 监 测 污 染 物 的 效 率 , 提 降低 查 询 时 间
复杂 度 。 形 目录 的 存储 结 构 比线 性 表 结 构 的组 织 形 式 更 灵 活 , 树 所 以对 于 数 据 量 大 的信 息 通 常采 用 树 形 结 构 存 储 。污 染 物 数 据 存 储 于 关 系 数 据库 中 , 询 时需 要 频 繁 地 访 问 数 据 库 。 数 据 库 查 从

用树数据结构求解的经典应用

用树数据结构求解的经典应用

用树数据结构求解的经典应用【中英文版】英文文档:Tree data structure is a fundamental concept in computer science that is widely used to solve various problems.Some classic applications of tree data structure include:1.Depth-First Search (DFS): DFS is a traversal algorithm that explores as far as possible along each branch before backtracking.It is commonly used to solve pathfinding and connectivity problems.2.Breadth-First Search (BFS): BFS is another traversal algorithm that explores all the vertices of a graph in breadth-first order.It is often used to find the shortest path in a graph.3.Binary Search: Binary search is an efficient algorithm for finding an item from a sorted list of items.It works by repeatedly dividing in half the portion of the list that could contain the item and comparing the value with the item you are searching for.4.binary tree traversal: There are three common traversal methods for binary trees: pre-order, in-order, and post-order.These methods are used to traverse the nodes of a binary tree and can be used to solve various problems related to binary trees.5.spanning tree: A spanning tree of an undirected graph is a subgraph that includes all the vertices of the graph but contains nocycles.Spanning trees are used in various applications, such as network design and clustering.6.decision tree: A decision tree is a flowchart-like tree structure where an internal node represents a feature, and each branch represents a possible value of that feature.Decision trees are commonly used for classification and regression tasks.7.B-tree: B-tree is a self-balancing tree data structure that maintains sorted data and allows searches, sequential access, insertions, and deletions in logarithmic time.B-trees are widely used in database systems and file systems.8.Red-Black Tree: Red-black tree is a type of self-balancing binary search tree, where each node contains an extra bit for denoting the color of the node, either red or black.Red-black trees are used in various applications, such as data compression and sorting.9.AVL Tree: AVL tree is another type of self-balancing binary search tree, where the difference between the heights of left and right subtrees cannot be more than one for all nodes.AVL trees are used in applications that require high performance, such as dictionary implementations.10.Trie: Trie, also known as prefix tree, is a type of search tree used to store a dynamic set or associative array where the keys are usually strings.Tries are widely used in applications like spell checkers, autocorrect, and search engines.These are some of the classic applications of tree data structure that demonstrate its importance and versatility in solving various problems in computer science.中文文档:树数据结构是计算机科学中的基本概念,广泛用于解决各种问题。

叙述几种生成树协议的基本原理

叙述几种生成树协议的基本原理

叙述几种生成树协议的基本原理英文回答:Spanning Tree Protocols (STPs) are used in computer networks to ensure that there is only one active path between any two network devices. This is important to prevent loops, which can cause broadcast storms and other network problems.There are several different STP algorithms, but the most common one is the IEEE 802.1D Spanning Tree Protocol (STP). STP works by electing a single root bridge for the network. The root bridge then sends out messages to all other bridges in the network, telling them which ports to block and which ports to forward. This creates a spanning tree, which is a loop-free path between all the network devices.Other STP algorithms include:Rapid Spanning Tree Protocol (RSTP): RSTP is a faster and more efficient version of STP.Multiple Spanning Tree Protocol (MSTP): MSTP allows for multiple spanning trees to be created, which can be useful for load balancing and redundancy.FabricPath: FabricPath is a more advanced STP algorithm that is designed for use in large and complex networks.中文回答:生成树协议 (STP) 用于计算机网络中,以确保任意两个网络设备之间只有一条活动路径。

多叉树线索化算法的改进

多叉树线索化算法的改进

TECHNOLOGY AND INFORMATION科学与信息化2022年5月下 67多叉树线索化算法的改进马乐 李晨志 马尧四川大学/公共管理学院 四川 成都 610000摘 要 多叉树作为二叉树的延伸,在管道、网络等规划方面具有重要作用。

而线索多叉树充分利用了空置链域,大大提高了空间利用率。

本文借鉴重新定义Ltag域和Rtag域的方法,简化树的线索化过程,将其推广至多叉树的线索化并以三叉树为例给出具体代码。

关键词 多叉树;线索多叉树;遍历;数据结构Improvement on Threaded Multi-branch Tree Algorithm Ma Le, Li Chen-zhi, Ma YaoSchool of Public Administration, Sichuan University, Chengdu 610000, Sichuan Province, ChinaAbstract As the extension of binary tree, multi-branch tree plays an important role in pipeline and network planning. The threaded multi-branch tree makes full use of the empty chain domain, which greatly improves the spatial utilization. In this article, the method of redefining Ltag domain and Rtag domain is used to simplify the process of tree threading, which is extended to the threading of multi-branch tree and the specific code is given by taking the ternary tree as an example.Key words multi-branch tree; threaded multi-branch tree; traversal; data structure引言在经典的二叉树线索化算法改进方面,费洪晓、杨彦等人在改进二叉树线索化方面取得了相应成果,简化了二叉树遍历流程,但是并没有将该改进方法推广至多叉树。

关于红黑树的参考文献

关于红黑树的参考文献

关于红黑树的参考文献红黑树是一种自平衡的二叉搜索树,其在计算机科学中扮演着重要的角色。

它在很多应用中都有广泛的应用,例如在操作系统的调度算法、数据库索引以及编译器的符号表等方面。

为了深入了解红黑树的相关内容,我们可以参考以下几篇经典的学术文献。

这些文献涵盖了红黑树的原理、性质和算法分析等方面的内容,对于学习和理解红黑树非常有帮助。

1.《Introduction to Algorithms》第三版(CLRS)这本著名的教材由Thomas H. Cormen、Charles E. Leiserson、Ronald L. Rivest 和Clifford Stein共同编写,被广泛认可为计算机科学领域的经典教材。

第十三章讲述了红黑树的原理和算法,以及与其他自平衡二叉搜索树的比较。

这本书系统地介绍了算法和数据结构的基本概念,并且提供了深入的理论分析和实践指导。

2.《Data Structures and Algorithms in Java》(Robert Lafore)这本书以Java作为实现语言,详细介绍了各种数据结构和算法的原理和实现方法。

其中第11章专门讨论了红黑树,通过分析红黑树的旋转操作和插入、删除操作的实现细节,帮助读者深入理解红黑树的工作原理。

此外,书中也提供了丰富的示例代码和练习题,有助于读者加深对红黑树的理解和应用。

3.《Introduction to the Design and Analysis of Algorithms》(Anany Levitin)这本书着重介绍了算法的设计、分析和实现。

第十章详细探讨了平衡搜索树的设计和性能分析,并着重讨论了红黑树。

该书以清晰的语言和例子解释了红黑树的实现和特性,同时还介绍了红黑树在应用中的广泛应用,为读者提供了深入理解的途径。

4.《Algorithms》第四版(Robert Sedgewick和Kevin Wayne)这本书致力于介绍算法的设计和分析方法,并提供了丰富的实际例子和代码实现。

一种针对树形拓扑网络的混合MAC协议

一种针对树形拓扑网络的混合MAC协议

一种针对树形拓扑网络的混合MAC协议刘广钟;徐艺原【摘要】在树形拓扑水声传感网络中,时分多址(TDMA)机制存在信道利用率低的问题.为此,提出一种轻量级的流量自适应随机访问与TDMA的混合MAC协议.该协议在网络流量较低时采用S-ALOHA竞争机制提高信道利用率,运用最优化算法计算分配给簇内子节点的最大发送概率,通过流量自适应的灵活时隙分配机制以适应不同的网络流量.实验结果表明,该协议不仅能够提高树形拓扑网络中节点的通信效率,能减少子节点的等待时间.%Aiming at the problem of low utilization ratio of the channel in the Time Division Multiple Access(TDMA) mechanism in the tree topology underwater acoustic sensor network,this paper proposes a hybrid MAC protocol based on improved lightweight traffic adaptive random medium access mechanism and TDMA mechanism:TAST-MAC.It adopts S-ALOHA competition mechanism effectively to improve the channel utilization when the network traffic is low.This protocol uses an optimization algorithm to calculate the maximum transmission probability table values which are assigned to the cluster sub nodes,and uses a flexible traffic adaptive slot allocation mechanism to adapt different network traffic situation.Experimental results show that TAST-MAC not only improves the communication efficiency in the tree topology networks,but also reduces the waiting time of the sub nodes.【期刊名称】《计算机工程》【年(卷),期】2017(043)011【总页数】8页(P32-39)【关键词】树形拓扑;水声传感网络;轻量级随机访问;时分多址;最优化算法【作者】刘广钟;徐艺原【作者单位】上海海事大学信息工程学院,上海201306;上海海事大学信息工程学院,上海201306【正文语种】中文【中图分类】TP391目前,水下无线通信仍是具有较为挑战性的研究领域。

川大软件数据结构选择题库

川大软件数据结构选择题库

_______________________________ 少年易学老难成,一寸光阴不可轻-百度文库一Chapter 1 Data Structures and Algorithms: Instructor's CD questions1.The primary purpose of most computer programs isa)to perform a mathematical calculation.*b) to store and retrieve information.c)to sort a collection of records.d)all of the above.e)none of the above.2.An integer is aa)) simple typeb)aggregate typec)composite typed)a and be)none of the above3.A payroll records is aa)simple typeb)aggregate typec)composite type*d) a and b e) none of the above4.Which of the following should NOT be viewed as an ADT?a)listb)integerc)array*d) none of the above5.A mathematical function is most like a*a) Problemb)Algorithmc)Program6.An algorithm must be or do all of the following EXCEPT:a)correctb)composed of concrete steps*c) ambiguousd)composed of a finite number of stepse)terminate7.A solution is efficient ifa.it solves a problem within the require resource constraints.b.it solves a problem within human reaction time.1_______________________________ 少年易学老难成,一寸光阴不可轻-百度文库_______ c.it solves a problem faster than other known solutions.d.a and b.*e. a and c.f. b and c.8.An array isa)A contiguous block of memory locations where each memory location storesa fixed-length data item.b)An ADT composed of a homogeneous collection of data items, each data item identified by a particular number.c)a set of integer values.*d) a and b.e)a and c.f)b and c.9.Order the following steps to selecting a data structure to solve a problem.(1)Determine the basic operations to be supported.(2)Quantify the resource constraints for each operation.(3)Select the data structure that best meets these requirements.(4)Analyze the problem to determine the resource constraints that anysolution must meet.a)(1, 2, 3, 4)b)(2, 3, 1, 4)c)(2, 1, 3, 4)*d) (1, 2, 4, 3)e) (1, 4, 3, 2)10.Searching for all those records in a database with key value between 10 and 100 is known as:a) An exact match query.*b) A range query.c)A sequential search.d)A binary search.Chapter 2 Mathematical Preliminaries: Instructor's CD questions1.A set has the following properties:a)May have duplicates, element have a position.b)May have duplicates, elements do not have a position.c)May not have duplicates, elements have a position.*d) May not have duplicates, elements do not have a position._______________________________ 少年易学老难成,一寸光阴不可轻-百度文库2.A sequence has the following properties:a)) May have duplicates, element have a position.b)May have duplicates, elements do not have a position.c)May not have duplicates, elements have a position.d)May not have duplicates, elements do not have a position.3.For set F, the notation |P| indicatesa)) The number of elements in Pb)The inverse of Pc)The powerset of F.d)None of the above.4.Assume that P contains n elements. The number of sets in the powerset of P isa)nb)n A2*c) 2A nd)2A n - 1e) 2A n + 15.If a sequence has n values, then the number of permutations for that sequence will bea)nb)n A2c)n A2 - 1d)2A n*e) n!6.If R is a binary relation over set S, then R is reflexive if*a) aRa for all a in S.b)whenever aRb, then bRa, for all a, b in S.c)whenever aRb and bRa, then a = b, for all a, b in S.d)whenever aRb and aRc, then aRc, for all a, b, c in S.7.If R is a binary relation over set S, then R is transitive ifa)aRa for all a in S.b)whenever aRb, then bRa, for all a, b in S.c)whenever aRb and bRa, then a = b, for all a, b in S.*d) whenever aRb and aRc, then aRc, for all a, b, c in S.8.R is an equivalence relation on set S if it isa)) reflexive, symmetric, transitive.b)reflexive, antisymmetric, transitive.c)symmetric, transitive.少年易学老难成,一寸光阴不可轻-百度文库d)antisymmetric, transitive.e)irreflexive, symmetric, transitive.f)irreflexive, antisymmetric, transitive.9.For the powerset of integers, the subset operation defines *a) a partial order.b)a total order.c)a transitive order.d)none of the above.10.log nm is equal toa) n + m*b) log n + log mc)m log nd)log n - log m11.A close-form solution isa) an analysis for a program.*b) an equation that directly computes the value of a summation.c) a complete solution for a problem.12.Mathematical induction is most likea) iteration.*b) recursion.c)branching.d)divide and conquer.13.A recurrence relation is often used to model programs witha)for loops.b)branch control like "if" statements.*c) recursive calls.d) function calls.14.Which of the following is not a good proof technique.a) proof by contradiction.*b) proof by example.c) proof by mathematical induction.15.We can use mathematical induction to:a) Find a closed-form solution for a summation.*b) Verify a proposed closed-form solution for a summation.c) Both find and verify a closed-form solution for a summation._______________________________ 少年易学老难成,一寸光阴不可轻-百度文库一Chapter 3 Algorithm Analysis: Instructor's CD questions1.A growth rate applies to:a)the time taken by an algorithm in the average case.b)the time taken by an algorithm as the input size grows.c)the space taken by an algorithm in the average case.d)the space taken by an algorithm as the input size grows.e)any resource you wish to measure for an algorithm in the average case.*f) any resource you wish to measure for an algorithm as the input size grows.2.Pick the growth rate that corresponds to the most efficient algorithm as n gets large:a) 5n*b) 20 log nc)2nA2d)2A n3.Pick the growth rate that corresponds to the most efficient algorithm when n =4.a)5nb)20 log nc)2nA2*d)2A n4.Pick the quadratic growth rate.a)5nb)20 log n*c) 2nA2d) 2An5.Asymptotic analysis refers to:a) The cost of an algorithm in its best, worst, or average case.*b) The growth in cost of an algorithm as the input size grows towards infinity.c)The size of a data structure.d)The cost of an algorithm for small input sizes6.For an air traffic control system, the most important metric is:a)The best-case upper bound.b)The average-case upper bound.c)) The worst-case upper bound.d)The best-case lower bound._______________________________ 少年易学老难成,一寸光阴不可轻-百度文库__________e)The average-case lower bound.f)The worst-case lower bound.7.When we wish to describe the upper bound for a problem we use:a)) The upper bound of the best algorithm we know.b)The lower bound of the best algorithm we know.c)We can't talk about the upper bound of a problem because there can alwaysbe an arbitrarily slow algorithm.8.When we describe the lower bound for a problem we use:a)The upper bound for the best algorithm we know.b)the lower bound for the best algorithm we know.c)The smallest upper bound that we can prove for the best algorithm that could possibly exist.*d) The greatest lower bound that we can prove for the best algorithm that could possibly exist.9.When the upper and lower bounds for an algorithm are the same, we use:a)big-Oh notation.b)big-Omega notation.*c) Theta notation.d)asymptotic analysis.e)Average case analysis.f)Worst case analysis.10. When performing asymptotic analysis, we can ignore constants and low order terms because:*a) We are measuring the growth rate as the input size gets large.b)We are only interested in small input sizes.c)We are studying the worst case behavior.d)We only need an approximation.11.The best case for an algorithm refers to:a) The smallest possible input size.*b) The specific input instance of a given size that gives the lowest cost.c)The largest possible input size that meets the required growth rate.d)The specific input instance of a given size that gives the greatest cost.12.For any algorithm:a)) The upper and lower bounds always meet, but we might not know what they are.少年易学老难成,一寸光阴不可轻-百度文库b)The upper and lower bounds might or might not meet.c)We can always determine the upper bound, but might not be able to determine the lower bound.d)We can always determine the lower bound, but might not be able to determine the upper bound.13.If an algorithm is Theta(f(n)) in the average case, then it is: a) Omega(f(n)) in the best case.*b) Omega(f(n)) in the worst case.c) O(f(n)) in the worst case.14.For the purpose of performing algorithm analysis, an important property ofa basic operation is that:a)It be fast.b)It be slow enough to measure.c)Its cost does depend on the value of its operands.*d) Its cost does not depend on the value of its operands.15.For sequential search,a) The best, average, and worst cases are asymptotically the same.*b) The best case is asymptotically better than the average and worst cases.c)The best and average cases are asymptotically better than the worst case.d)The best case is asymptotically better than the average case, and the average case is asymptotically better than the worst case.Chapter 4 Lists, Stacks and Queues: Instructor's CD questions1.An ordered list is one in which:a) The element values are in sorted order.*b) Each element a position within the list.2.An ordered list is most like a:a)set.b)bag.c)) sequence.3.As compared to the linked list implementation for lists, the array-based listimplementation requires:a)More spaceb)Less space*c) More or less space depending on how many elements are in the list._______________________________ 少年易学老难成,一寸光阴不可轻-百度文库4.Here is a series of C++ statements using the list ADT in the book.L1.append(10);L1.append(20);L1.append(15);If these statements are applied to an empty list, the result will look like:a)< 10 20 15 >*b) < | 10 20 15 >c)< 10 20 15 | >d)< 15 20 10 >e)< | 15 20 10 >f)< 15 20 10 | >5.When comparing the array-based and linked implementations, the array-based implementation has:a)) faster direct access to elements by position, but slower insert/delete from the current position.b)slower direct access to elements by position, but faster insert/delete from the current position.c)both faster direct access to elements by position, and faster insert/delete from the current position.d)both slower direct access to elements by position, and slower insert/delete from the current position.6.For a list of length n, the linked-list implementation's prev function requiresworst-case time:a)O(1).b)O(log n).*c) O(n).d) O(n A2).7.Finding the element in an array-based list with a given key value requiresworst case time:a)O(1).b)O(log n).*c) O(n).d) O(n A2).8.In the linked-list implementation presented in the book, a header node isused:*a) To simplify special cases._______________________________ 少年易学老难成,一寸光阴不可轻-百度文库一b)Because the insert and delete routines won't work correctly without it.c)Because there would be no other way to make the current pointer indicatethe first element on the list.9.When a pointer requires 4 bytes and a data element requires 4 bytes, thelinked list implementation requires less space than the array-based list implementation when the array would be:a)less than 1/4 full.b)less than 1/3 full.*c) less than half full.d)less than 第full.e)less than 34 fullf)never.10.When a pointer requires 4 bytes and a data element requires 12 bytes, thelinked list implementation requires less space than the array-based list implementation when the array would be:a)) less than 1/4 full.b)less than 1/3 full.c)less than half full.d)less than 2/3 full.e)less than 34 fullf)never.11.When we say that a list implementation enforces homogeneity, we meanthat:a) All list elements have the same size.*b) All list elements have the same type.c) All list elements appear in sort order.12.When comparing the doubly and singly linked list implementations, we findthat the doubly linked list implementation*a) Saves time on some operations at the expense of additional space.b)Saves neither time nor space, but is easier to implement.c)Saves neither time nor space, and is also harder to implement.13. We use a comparator function in the Dictionary class ADT:a)to simplify implementation.*b) to increase the opportunity for code reuse.c) to improve asymptotic efficiency of some functions.14.All operations on a stack can be implemented in constant time except:少年易学老难成,一寸光阴不可轻-百度文库a) Pushb)Popc)The implementor's choice of push or pop (they cannot both be implementedin constant time).*d) None of the above.15.Recursion is generally implemented usinga) A sorted list.*b) A stack.c) A queue.Chapter 5 Binary Trees: Instructor's CD questions1.The height of a binary tree is:a)The height of the deepest node.b)The depth of the deepest node.*c) One more than the depth of the deepest node.2.A full binary tree is one in which:*a) Every internal node has two non-empty children.b) all of the levels, except possibly the bottom level, are filled.3.The relationship between a full and a complete binary tree is:a)Every complete binary tree is full.b)Every full binary tree is complete.*c) None of the above.4.The Full Binary Tree Theorem states that:a)) The number of leaves in a non-empty full binary tree is one more than the number of internal nodes.b)The number of leaves in a non-empty full binary tree is one less than the number of internal nodes.c)The number of leaves in a non-empty full binary tree is one half of the number of internal nodes.d)The number of internal nodes in a non-empty full binary tree is one half of the number of leaves.5.The correct traversal to use on a BST to visit the nodes in sorted order is:a) Preorder traversal.*b) Inorder traversal.c) Postorder traversal.6. When every node of a full binary tree stores a 4-byte data field,10少年易学老难成,一寸光阴不可轻-百度文库two 4-byte child pointers, and a 4-byte parent pointer, theoverhead fraction is approximately:a)one quarter.b)one third.c)one half.d)two thirds.*e) three quarters.f) none of the above.7.When every node of a full binary tree stores an 8-byte data field and two 4-byte child pointers, the overhead fraction is approximately:a)one quarter.b)one third.*c) one half.d)two thirds.e)three quarters.f)none of the above.8.When every node of a full binary tree stores a 4-byte data field and theinternal nodes store two 4-byte child pointers, the overhead fraction is approximately:a)one quarter.b)one third.*c) one half.d)two thirds.e)three quarters.f)none of the above.9.If a node is at position r in the array implementation for a complete binarytree, then its parent is at:a)) (r - 1)/2 if r > 0b)2r + 1 if (2r + 1) < nc)2r + 2 if (2r + 2) < nd)r - 1 if r is evene)r + 1 if r is odd.10.If a node is at position r in the array implementation for a complete binarytree, then its right child is at:a)(r - 1)/2 if r > 0b)2r + 1 if (2r + 1) < n*c) 2r + 2 if (2r + 2) < nd)r - 1 if r is evene)r + 1 if r is odd.11_______________________________ 少年易学老难成,一寸光阴不可轻-百度文库—11.Assume a BST is implemented so that all nodes in the left subtree of agiven node have values less than that node, and all nodes in the rightsubtree have values greater than or equal to that node. Whenimplementing the delete routine, we must select as its replacement:a) The greatest value from the left subtree.*b) The least value from the right subtree.c) Either of the above.12.Which of the following is a true statement:a)In a BST, the left child of any node is less than the right child, and in a heap, the left child of any node is less than the right child.*b) In a BST, the left child of any node is less than the right child, but in a heap, the left child of any node could be less than or greater than the right child.c)In a BST, the left child of any node could be less or greater than the right child, but in a heap, the left child of any node must be less than the right child.d)In both a BST and a heap, the left child of any node could be either less than or greater than the right child.13.When implementing heaps and BSTs, which is the best answer?a)The time to build a BST of n nodes is O(n log n), and the time to build a heap of n nodes is O(n log n).b)The time to build a BST of n nodes is O(n), and the time to build a heap of n nodes is O(n log n).*c) The time to build a BST of n nodes is O(n log n), and the time to build a heap of n nodes is O(n).d) The time to build a BST of n nodes is O(n), and the time to build a heap of n nodes is O(n).14.The Huffman coding tree works best when the frequencies for letters area) Roughly the same for all letters.*b) Skewed so that there is a great difference in relative frequencies for various letters.15.Huffman coding provides the optimal coding when:a)The messages are in English.b)The messages are binary numbers.*c) The frequency of occurrence for a letter is independent of its context within the message.d) Never.12_______________________________ 少年易学老难成,一寸光阴不可轻-百度文库一Chapter 6 Binary Trees: Instructor's CD questions1.The primary ADT access functions used to traverse a general tree are: a) left child and right siblingb) left child and right child*c) leftmost child and right siblingd) leftmost child and next child2.The tree traversal that makes the least sense for a general treeis:a) preorder traversal*b) inorder traversalc) postorder traversal3.The primary access function used to navigate the general tree when performing UNION/FIND is:a)left childb)leftmost childc)right childd)right sibling*e) parent4.When using the weighted union rule for merging disjoint sets, the maximum depth for any node in a tree of size n will be:a) nearly constant*b) log nc)nd)n log ne)n A25.We use the parent pointer representation for general trees to solve which problem?a)Shortest pathsb)General tree traversal*c) Equivalence classesd) Exact-match query6. When using path compression along with the weighted union rule for merging disjoint sets, the average cost for any UNION or FIND operation in a tree of size n will be:*a) nearly constantb)log nc)nd)n log n13_______________________________ 少年易学老难成,一寸光阴不可轻-百度文库一7.The most space efficient representation for general trees will typically be:a) List of children*b) Left-child/right siblingc) A K-ary tree.8.The easiest way to represent a general tree is to:a) convert to a list.*b) convert to a binary tree.c) convert to a graph.9.As K gets bigger, the ratio of internal nodes to leaf nodes:a)) Gets smaller.b)Stays the same.c)Gets bigger.d)Cannot be determined, since it depends on the particular configuration of the tree.10.A sequential tree representation is best used for:*a) Archiving the tree to disk.b)Use in dynamic in-memory applications.c)Encryption algorithms.d)It is never better than a dynamic representation.Chapter 7 Internal Sorting: Instructor's CD questions1.A sorting algorithm is stable if it:a) Works for all inputs.*b) Does not change the relative ordering of records with identical key values.c) Always sorts in the same amount of time (within a constant factor) for a given input size.2.Which sorting algorithm does not have any practical use?a) Insertion sort.*b) Bubble sort.c)Quicksort.d)Radix Sort.e)a and b.3.When sorting n records, Insertion sort has best-case cost:a)O(log n).14_______________________________ 少年易学老难成,一寸光阴不可轻-百度文库*b) O(n).c)O(n log n).e)O(n!)f)None of the above.4.When sorting n records, Insertion sort has worst-case cost:a)O(log n).b)O(n).c)O(n log n).*d) O(n A2)e)O(n!)f)None of the above.5.When sorting n records, Quicksort has worst-case cost:a)O(log n).b)O(n).c)O(n log n).*d) O(n A2)e)O(n!)f)None of the above.6.When sorting n records, Quicksort has average-case cost:a)O(log n).b)O(n).c)) O(n log n).d)O(n A2)e)O(n!)f)None of the above.7.When sorting n records, Mergesort has worst-case cost:a)O(log n).b)O(n).*c) O(n log n).d)O(n A2)e)O(n!)f)None of the above.8.When sorting n records, Radix sort has worst-case cost:a)O(log n).b)O(n).c)O(n log n).d)O(n A2)e)O(n!)15少年易学老难成,一寸光阴不可轻-百度文库*f) None of the above.9.When sorting n records with distinct keys, Radix sort has a lower bound of:a)Omega(log n).b)Omega(n).*c) Omega(n log n).d)Omega(n A2)e)Omega(n!)f)None of the above.10.Any sort that can only swap adjacent records as an average case lower bound of:a)Omega(log n).b)Omega(n).c)Omega(n log n).*d) Omega(n A2)e)Omega(n!)f)None of the above.11.The number of permutations of size n is:a)O(log n).b)O(n).c)O(n log n).d)O(n A2)*e) O(n!)f)None of the above.12.When sorting n records, Selection sort will perform how many swaps in the worst case?a) O(log n).*b) O(n).c)O(n log n).d)O(n A2)e)O(n!)f)None of the above.13.Shellsort takes advantage of the best-case behavior of which sort?*a) Insertion sortb)Bubble sortc)Selection sortd)Shellsorte)Quicksortf)Radix sort16_______________________________ 少年易学老难成,一寸光阴不可轻-百度文库_______________14.A poor result from which step causes the worst-case behavior for Quicksort?*a) Selecting the pivotb)Partitioning the listc)The recursive call15.In the worst case, the very best that a sorting algorithm can do when sorting n records is:a)O(log n).b)O(n).*c) O(n log n).d)O(n A2)e)O(n!)f)None of the above.Chapter 8 File Processing and External Sorting: Instructor's CD questions1.As compared to the time required to access one unit of data frommain memory, accessing one unit of data from disk is:a)10 times faster.b)1000 times faster.c)1,000,000 time faster.d)10 times slower.e)1000 times slower.*f) 1,000,000 times slower.2.The most effective way to reduce the time required by a disk-based program is to:a) Improve the basic operations.*b) Minimize the number of disk accesses.c)Eliminate the recursive calls.d)Reduce main memory use.3.The basic unit of I/O when accessing a disk drive is:a)A byte.*b) A sector.c)A cluster.d)A track.e)An extent.4.The basic unit for disk allocation under DOS or Windows is:a)A byte.b)A sector.*c) A cluster.17少年易学老难成,一寸光阴不可轻-百度文库d) A track.e) An extent.5.The most time-consuming part of a random access to disk is usually: *a) The seek.b)The rotational delay.c)The time for the data to move under the I/O head.6.The simplest and most commonly used buffer pool replacement strategy is:a)First in/First out.b)Least Frequently Used.*c) Least Recently Used.7.The C++ programmer's view of a disk file is most like:a)) An array.b)A list.c)A tree.d)A heap.8.In external sorting, a run is:a)) A sorted sub-section for a list of records.b)One pass through a file being sorted.c)The external sorting process itself.9.The sorting algorithm used as a model for most external sorting algorithms is:a)Insertion sort.b)Quicksort.*c) Mergesort.d) Radix Sort.10.Assume that we wish to sort ten million records each 10 bytes long (for a total file size of 100MB of space). We have working memory of size 1MB, broken into 1024 1K blocks. Using replacement selection and multiway merging, we can expect to sort this file using how many passes through the file?a)About 26 or 27 (that is, log n).b)About 10.c)4.*d) 2.Chapter 9 Searching: Instructor's CD questions18少年易学老难成,一寸光阴不可轻-百度文库1.Which is generally more expensive?a) A successful search.*b) An unsuccessful search.2.When properly implemented, which search method is generally the most efficient for exact-match queries?a)Sequential search.b)Binary search.c)Dictionary search.d)Search in self-organizing lists*e) Hashing3.Self-organizing lists attempt to keep the list sorted by:a) value*b) frequency of record accessc) size of record4.The 80/20 rule indicates that:a) 80% of searches in typical databases are successful and 20% are not.*b) 80% of the searches in typical databases are to 20% of the records.c) 80% of records in typical databases are of value, 20% are not.5.Which of the following is often implemented using a self-organizing list? *a) Buffer pool.b)Linked list.c)Priority queue.6.A hash function must:a)) Return a valid position within the hash table.b)Give equal probability for selecting an slot in the hash table.c)Return an empty slot in the hash table.7.A good hash function will:a)Use the high-order bits of the key value.b)Use the middle bits of the key value.c)Use the low-order bits of the key value.*d) Make use of all bits in the key value.8.A collision resolution technique that places all records directlyinto the hash table is called:a)Open hashing.b)Separate chaining.*c) Closed hashing.d) Probe function.19少年易学老难成,一寸光阴不可轻-百度文库9.Hashing is most appropriate for:a)In-memory applications.b)Disk-based applications.*c) Either in-memory or disk-based applications.10.Hashing is most appropriate for:a)) Range queries.b)Exact-match queries.c)Minimum/maximium value queries.11.In hashing, the operation that will likely require more record accesses is: *a) insertb) deleteChapter 10 Indexing: Instructor's CD questions1.An entry-sequenced file stores records sorted by:a)Primary key value.b)Secondary key value.*c) Order of arrival.d) Frequency of access.2.Indexing is:a) Random access to an array.*b) The process of associating a key with the location of a corresponding data record.c) Using a hash table.3.The primary key is:a)) A unique identifier for a record.b)The main search key used by users of the database.c)The first key in the index.4.Linear indexing is good for all EXCEPT:a)Range queries.b)Exact match queries.*c) Insertion/Deletion.d)In-memory applications.e)Disk-based applications.5.An inverted list provides access to a data record from its:a) Primary key.20______________________________ 少年易学老难成,一寸光阴不可轻-百度文库*b) Secondary key.c) Search key.6.ISAM degrades over time because:a) Delete operations empty out some cylinders.*b) Insert operations cause some cylinders to overflow.c) Searches disrupt the data structure.7.Tree indexing methods are meant to overcome what deficiency in hashing? *a) Inability to handle range queries.。

国际会议词汇

国际会议词汇

会议相关词汇A. 会议的类型TYPES OF MEETINGS群众大会Mass meeting大会Assembly全国代表大会(美) Convention (USA)大会General meeting会议,大会Conference外交代表会议Diplomatic conference区域会议Regional conference大会、国会(美)Congress理事会Board of governors干事会,理事会,董事会Board of directors委员会Committee委员会(指比较大型有固定性的)Commission小组委员会Sub-committee代表团团长委员会Committee of heads of delegations财务委员会Finance committee预算委员会Budget committee(财务)审核委员会Auditing committee资格审查委员会Credentials committee决议委员会Resolutions committee起草委员会Drafting committee接待委员会Hospitality committee/ Reception committee专家委员会Committee of experts联络委员会Liaison committee工作人员委员会,职员委员会Staff committee协调委员会Coordination committee圆桌会议Round table meeting专家小组会议Panel meeting座谈会,学术报告会Symposium研究小组,讨论会Study group, Seminar(USA)讨论小组Discussion group, colloquium研究小组Study group工作组Working party定期开会To meet periodically每隔一定时间开会To meet at regular intervals休会期间Between sessions与别的会议重叠Overlapping with other meetings设立一个委员会To set up, to establish a committee指派一个委员会To appoint a committee将…委托给一个委员会,把一个任务To entrust a committee with (to assign a task 交给一个委员会to) assign a task to) a committeeB. 会议的筹备工作PREPARATION OF THE MEETING1. 邀请和召集1. Invitations and Convocations发出邀请参加会议的信件(邀请信) To address (to send, to send out)a (letter or) convocation (an invitation)邀请派遣代表To invite to be represented召开(紧急地) To convene, to summon, to convoke, to call (urgently)向大会报到To register at the congress委派…为代表(观察员) To appoint as delegate (observer)奉命代表… To be instructed to represent…派遣一个重要的代表团To send an important delegation随带专家To bring (along*) experts只同意(接受)以观察员身份参加To agree (accept) to attend only as (in the capacity of) observer本届会议(开始时,终了时)被替换(指代表) To be replaced for (at the beginning, the end of) the session…不能参加… … is unable to take part in (to attend to…)…拒绝参加会议To refuse (to decline) to take part in ameeting2. 会议进行的条件2. Conditions under which the Meeting is held邀请委员会在(某地)…召开下届会议The committee is invited to hold its next session at …委员会接受…政府的邀请The committee a ccepts the invitation of the … Government下届会议的日期和地点将由负责人员The date and place of the next session will(局)同秘书处商洽决定be fixed by the Officers (the Bureau) in consultation with the Secretariat东道国Host country邀请国Inviting country一切费用可以报销All expenses paid一切包括在内All-inclusive按照一次总付的办法On a lump sum basis(费用)由会议负担At the expense of the conference按日(每天)Per diem生活津贴Subsistence allowance住房津贴Accommodation allowance偿付旅费Refunding of travel expensesC. 文件DOCUMENTS1. 基本文件1.Basic Documents最后决议,总结文件Final act盟约,公约,约章Covenant条约Treaty公约Convention宣言Declaration附加议定书Additional protocol协定(双边,多边)Agreement (bilateral, multilateral)议定书Protocol法典,准则Code规则,法规Rules2. 议程,决议,日程等2. Agenda, Resolutions, Programmes, etc.临时议程Provisional agenda(最后)审定(通过)的议程Approved agenda见于议程To appear on the agenda列入议程To include in the agenda议程项目Item on the agenda其他事项(Any) other business工作日程Programme of work会议日程表Daily programme of meetings (sittings)时间表,日程表Time-table, schedule决议,提案Resolution(联合)决议草案Draft (joint) resolution草案初稿First draft, preliminary draft其他供选择的(反)建议Alternative (counter-) proposal建议Recommendation3. 报告,备忘录等3. Reports, Memoranda, etc.最后(总结)报告Final report初步报告Preliminary report临时报告Provisional report临时报告Interim report总、月度、季度、半年、年度报告General, monthly, quarterly, six-monthly, annual report多数(少数)报告Majority, minority report行政工作报告Administrative report财务报告Financial report情况报告Information report事实报告Factual report专家报告Expert report工作进展情况报告Progress report备忘录Memorandum备忘录Aide-mémoire工作文件Working paper声明,发言Statement摘要Abstract参考意见(咨询意见)Advisory opinion意见,评论Comment, commentary机密文件Confidential document私人文件Private document档案Archives4. 会议记录,公报,新闻稿,记录4. Minuses, Bulletins, Press releases, Records 做记录To keep, to draw up the minutes截(列)入记录,记录在案To place on record in the minutes(每日)公报(Daily) Bulletin会议的正式记录Official records of the Conference新闻稿,公报Press release, communiqué通知,通函Circular letter通函(通知)各代表团To circularize delegations摘要记录(纪要)Summary record逐字记录Verbatim recordD. 表决和选举VOTES AND ELECTIONS1. 表决或选举的目的和条件1. Purpose and Conditions of a Vote or an Election 把问题交付表决、进行表决To put a question to the vote, to proceed to a vote请表明态度Please signify宣布表决(投票)开始To declare that the voting has begun参加表决、投票、选举To take part in a vote, a ballot, a poll(我们)已足法定人数The quorum is reached, we have a quorum检查是否已足法定人数To ascertain that there is a quorum指派正式成员、代理人To appoint a regular member, a substitute补缺To fill a vacancy授命连任To renew the term of office, the appointment延长任期To extend the term of office接受连任To accept the renewal of one’s term of office提议分开(分别)表决To move that a separate vote be taken要求逐条表决To ask for a vote article by article表决整个动议To vote on the motion as a whole2. 表决的方式和方法,选举的程序2. Forms and Methods of Voting, and Electoral Procedure表决,投票,参加选举To vote, to cast a vote, to take part in an election弃权To abstain赞成票Affirmative vote反对票Negative vote投反对(不同意)票To cast a dissenting vote一致同意Unanimous vote一致通过Carried unanimously不经辩论的表决Vote without debate鼓掌通过Approval by acclamation举手表决Vote by show of hands口头表决Vote by “yes” and “no”起立表决Vote by sitting and standing, rising vote (USA)无记名投票Secret ballot唱名表决Vote by roll call唱名表决(须登台表示意见) A vote by roll call at the rostrum代理投票Vote by proxy通信投票Vote by correspondence组成一个选举团To be constituted as an electoral college表决票,选票Voting slip, voting paper, ballot paper投票入票箱To deposit a voting paper in the ballot box必要的多数The requisite majority以特定的多数(四分之三,三分之二To elect by a qualified majority (three多数)选出fourths, two thirds majority)以绝对(简单)多数选出To elect by an absolute (a simple) majority以相对的多数选出To elect by a relative majority(按特殊票权)分配(所得)多数Distributed majority出席并投票的会员的多数The majority of members present and voting大会会员的多数The majority of the members of the assembly就单个侯选人进行选举Voting (ballot) for a single candidate就整个侯选人名单进行选举Voting (ballot) for a list of candidates按比例的代表Proportional representation当选票额Electoral quotient一次投票Single ballot连续投票Successive ballots不投票的主席Non-voting Chairman有表决权,有权投票To be entitled to vote, to have the right to vote被取消表决(投票)权To be deprived of the right to vote行使表决(投票)权To exercise the right to vote对所投的票加以说明To explain one’s vote担任侯选人To stand for election提名To nominate …支持某一个提名,支持(某人)的侯选资格To support a nomination, a candidature 保持、撤销某人的侯选资格To maintain, to withdraw one’s candidature同意担任侯选人,接受提名To agree to be a candidate, to accept nomination送交提名名单To present a panel of nominees声明某一侯选提名是可以接受的,不可以To declare a candidature receivable,接受的(符合规则,不符合规则)irreceivable (in order, out of order)有被选权,有被连选权,无被选权Eligible, re-eligible, ineligibility有被选权,无被选权Eligibility, ineligibility与职务不相称Incompatibility of duties3. 表决或选举终了3. Conclusion of the Vote or Election指派计票人To appoint tellers实行表决To go back upon a vote停止、延期、中断表决(投票)To defer, postpone, interrupt a vote (a ballot)宣布表决(投票)结束To declare the vote (ballot) closed改投他票To change one’s vote经声明的弃权也将计算在内Declared abstentions will be reckoned, taken into account 未填写的选票(无效的选票)将不计算在内Voting papers left blank (null and void)will not be reckoned, taken into account点票,计算票数To count the votes检查表决结果To check the result of the voting否决,行使否决权To veto, to impose a veto4. 宣布结果4. Announcement of the Result报到(登记)的会员Registered members投票的会员Members voting票数Number of votes已投的票votes cast有效票Valid ballot papers空白票Blank ballot papers, voting papers无效的票,废票Ballot papers null and void宣布当选To declare elected以年长当选Elected on grounds of seniority抽签To draw lots票选无结果The ballot is inconclusive票数相等Equality of votes, a draw, a tie无结果的表决Inconclusive vote动议是以12票对9票通过,2票弃权The motion is adopted, carried, by 12 votes to 9 with 2 abstentions动议被否决The motion is rejected, lost获得多数The majority is obtained第一次投票表决First ballot第二次投票表决Second ballot再次投票表决Additional ballot宣布除两票外以一致同意当选To declare unanimously elected less two votes宣布以绝对(简单)多数当选To declare elected by an absolute (a simple) majority 5. 表决(选举)的后果5. Consequences of the Voting (the Election)接受当选To accept an election不接受委任、职务To refuse an appointment让给… To yield in favor of …请把你的票改投… Please transfer your votes to …质问表决结果To challenge a result取消所投的票To cancel a vote使有效,使无效To validate, to invalidate调查选举时的情况To investigate the circumstances of an election结果是最后的,不能改变的The result is final, definitive认定表决、投票、选举为有效To confirm a vote, a ballot, an election宣布某次表决、投票是最后的To declare a vote, a ballot, to be finalE. 辩论DEBATES1. 辩论开始1. Opening of the Debate现在开会了The sitting is open, is called to order委员会在开会The committee is in session, is holding a sitting, is sitting开会To be sitting in session开始讨论,进行讨论To take up, to come to the discussion, to initiate a discussion 宣布讨论开始To declare the discussion open复会,继续开会To resume a sitting继续辩论To resume a debate2. 主席2. Chairmanship担任主席To take, to occupy the Chair继续担任主席To resume the chairmanship放弃、辞去主席的职务To give up, to renounce, the office of chairman请发言人不要离开本题To request the speaker to keep to the point under discussion 征求与会者的意见To take the sense (the consensus of opinion) of the meeting征求与会者的意见To consult the meeting接受主席的决定、裁定To accept the chairman’s decision, ruling尊重主席的决定To bow to the chairman’s decision对主席的裁定、决定提出异议To challenge the chairman’s ruling, decision驳回,宣布无效To overrule3. 动议和决定7. Motions and Decisions提出提案、对案To make, to move, to table (UK) a proposal, a counterproposal提出决议草案To submit a draft resolution实质性动议Substantive motion替代的决议Substitute resolution提出修正案、提案草案、对案To present an amendment, a draft proposal, a counter-proposal附议,支持一个提案To second, to support a proposal反对一个修正案、决议、提案To oppose an amendment, a resolution, a proposal延期决定,暂不决定To postpone, to adjourn, to put off a decision接受一个修正案(决议,提案)To accept an amendment (a resolution, a proposal) 把几个修正案(决议草案)合并起来To merge together several amendments (draft resolutions)撒回提案To withdraw a proposal无限期搁置动议To table a motion (USA)4. 辩论结束9. Closure of the Debate决定延期、休会To decide to postpone, to adjourn动议结束辩论To move the closure就结束辩论作出决定To decide on the closure of the debate结束辩论To close the debate闭幕词Closing speech大会申谢Vote of thanks(最后)闭会To adjourn (finally) the meeting。

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However, complex and expensive despite failures. synchronization protocols [Giffg, BG87, ES83, DB85, JM87, PL88] are needed to maintain the replicas. There has been a considerable research effort to reduce the cost of executing operations while maintaining data availability in replicated databases. A common approach is to use network configuration information [ESC85, Her87, ET89]. This information is used to allow operations to adapt to changes in the network configuration. In this paper, we present a replica control protocol that reduces the cost of executing operations without the need for reconfiguration. This is achieved by imposing a logical tree structure on the set of copies of each object. We describe a protocol that operates by reading one copy of an object while guaranteeing faulttolerance of write operations and still does not require any reconfiguration on account of a failure and subsequent recovery. The protocol provides a compara ble degree of data availability as other replica control protocols [GiflS] at substantially lower costs. Furthermore our approach is fault-tolerant, and exhibits the property of graceful degradation [MS85]. In a failurefree environment, the communication costs are minimal and as failures occur the cost of replica control may increase. However, when failures are repaired the protocol reverts to its original mode without undergoing any reconfiguration. In the next section, we present the model of a distributed replicated database. Section 3 motivates the usefulness of logical structures for replica control. The
243
2
Model
3
Motivation
A distributed system consists of a set of distinct sites that communicate with each other by sending messages over a communication network. No assumptions are made regarding the speed, connectivity, or reliability of the network. We assume that sites are faiJ-slop [SSSZ] and communication links may fail to deliver messages. Combinations of such failures may lead to partilioning failures [DGMS85], w h ere sites in a partition may communicate with each other, but no communication can occur between sites in different partitions. A site may become inaccessible due to site or partitioning failures. A distributed database consists of a set of objects stored at several sites in a computer network. Users interact with the database by invoking transaclion pre grams. A transaction is a partially ordered sequence of read and write operations that are executed atomically. The execution of a transaction must appear atomic, i.e., a transaction either commits or aborts. A commonly accepted correctness criteria in distributed databases is the serializable execution of transactions [EGLT76]. The serializable execution is guaranteed by employing a concurrency control mechanism, e.g., twophase locking, timestamp ordering, or an optimistic concurrency control protocol. In a replicated database, copies of an object may be stored at several sites in the network. Multiple copies of an object must appear as a single logical object to the transactions. This is termed as one-copy equivalence [BG87] and is enforced by the replica control protocol. The correctness criteria for replicated databases is one-copy serializability [BG87], which ensures one-copy equivalence and serializable execution of transactions. In order to ensure one-copy equivalence, a replicated object z may be read by reading a read quorum of copies, and it may be written by writing a write quorum of copies. The following restriction is placed on the choice of quorum assignments:
*This research is supported by the NSF under grant numbers CCE8809387 and IRI-8809284. Permission to copy without fee all or part of is granted provided that the copies are not tributed for direct commercial advantage, the right notice and the title of the publication appear, and notice is given that copying is by the Very Large Data Base Endowment. or to republish, requires a fee and/or from the Endowment. this material made or disVLDB copyand its date permission of
The Tree Quorum
Protocol:
An Efficient
Approach
for Managing
Replicated
Data*
A. El Abbadi D. Agrawal Department of Computer Science University of California Santa BБайду номын сангаасrbara, CA 93106
Abstract In this paper, we present an efficient algorithm for managing replicated data. We impose a logical tree structure on the set of copies of an object. In a failurefree environment the protocol executes read operations by reading one copy of an object while guaranteeing fault-tolerance of write operations. It also exhibits the property of graceful degradation, i.e., communication costs are minimal in a failure-free environment but may increase as failures occur. This approach in designing distributed systems is desirable since it provides faulttolerance without imposing unnecessary costs on the failure-free mode of operations. 1 Introduction
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