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Electrick Backpack 【电子背包】
Backpacks are convenient. They can hold your books，your lunch，and a change of clothes，leaving your hands free to do other things.Someday，if you don't mind carrying a heavy load，your backpacks might also power your MP31player，keep your cell phone running，and maybe even light your way home.
Lawrence C. Rome and his colleagues from the University of Pennsylvania in Philadelphia2 and the Marine Biological Laboratory in WoodsHole3，Mass.4，have invented a backpack that makes electricity from energy produced while its wearer walks. In military actions，search-and-rescue operations，and scientific field studies，people rely increasingly on cellphones，global positioning system (GPS) 5 receivers，night-vision goggles，and other battery powered devices to get around and do their work.
The backpack’s electricity- generating feature could dramatically reduce the amount of awearer’s load now devoted to spare batteries，report Rome and his colleagues in the Sept.9 Science6.The backpack’s electricity-creating powers depend on springs used to hang a cloth pack from its metal frame.The frame sits against the wearer’s back，and the whole pack moves up and down as the person walks.A gear mechanism converts vertical movements of the pack to rotary motions of an electrical generator，producing up to 7.4 watts.
Unexpectedly，tests showed that wearers of the new backpack alter their gaits in response to the pack’s oscillations，so that they carry loads more comfortably and with less effort than they do ordinary backpacks. Because of that surprising advantage，Rome plans to commercialize both electric and non-electric versions of the backpack.
The backpack could be especially useful for soldiers，scientists，mountaineers，and emergency workers who typically carry heavy backpacks.For the rest of us，power-generating backpacks could make it possible to walk，play video games，watch TV，and listen to music，all at the same time.Electricity-generating packs aren’t on the market yet，but if you do get one eventually，just make sure to look both ways before crossing the street!
文章(16~20)
Backpacks are convenient because
Backpacks are convenient. They can hold your books，your lunch，and a change of clothes，leaving your hands free to do other things.Someday，if you don't mind carrying a heavy load，your backpacks might also power your MP31player，keep your cell phone running，and maybe even light your way home.
Lawrence C. Rome and his colleagues from the University of Pennsylvania in Philadelphia2 and the Marine Biological Laboratory in WoodsHole3，Mass.4，have invented a backpack that makes electricity from energy produced while its wearer walks. In military actions，search-and-rescue operations，and scientific field studies，people rely increasingly on cellphones，global positioning system (GPS) 5 receivers，night-vision goggles，and other battery powered devices to get around and do their work.
The backpack’s electricity- generating feature could dramatically reduce the amount of awearer’s load now devoted to spare batteries，report Rome and his colleagues in the Sept.9 Science6.The backpack’s electricity-creating powers depend on springs used to hang a cloth pack from its metal frame.The frame sits against the wearer’s back，and the whole pack moves up and down as the person walks.A gear mechanism converts vertical movements of the pack to rotary motions of an electrical generator，producing up to 7.4 watts.
Unexpectedly，tests showed that wearers of the new backpack alter their gaits in response to the pack’s oscillations，so that they carry loads more comfortably and with less effort than they do ordinary backpacks. Because of that surprising advantage，Rome plans to commercialize both electric and non-electric versions of the backpack.
The backpack could be especially useful for soldiers，scientists，mountaineers，and emergency workers who typically carry heavy backpacks.For the rest of us，power-generating backpacks could make it possible to walk，play video games，watch TV，and listen to music，all at the same time.Electricity-generating packs aren’t on the market yet，but if you do get one eventually，just make sure to look both ways before crossing the street!
文章(16~20)
Backpacks are convenient because
A they can be very large.
B they can hold as many things as you want to carry.
C your hand sare freed to do other things.
D you do not have to carry things with you.
B they can hold as many things as you want to carry.
C your hand sare freed to do other things.
D you do not have to carry things with you.
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参考解析
解析：
更多 “Electrick Backpack 【电子背包】 Backpacks are convenient. They can hold your books，your lunch，and a change of clothes，leaving your hands free to do other things.Someday，if you don't mind carrying a heavy load，your backpacks might also power your MP31player，keep your cell phone running，and maybe even light your way home. Lawrence C. Rome and his colleagues from the University of Pennsylvania in Philadelphia2 and the Marine Biological Laboratory in WoodsHole3，Mass.4，have invented a backpack that makes electricity from energy produced while its wearer walks. In military actions，search-and-rescue operations，and scientific field studies，people rely increasingly on cellphones，global positioning system (GPS) 5 receivers，night-vision goggles，and other battery powered devices to get around and do their work. The backpack’s electricity- generating feature could dramatically reduce the amount of awearer’s load now devoted to spare batteries，report Rome and his colleagues in the Sept.9 Science6.The backpack’s electricity-creating powers depend on springs used to hang a cloth pack from its metal frame.The frame sits against the wearer’s back，and the whole pack moves up and down as the person walks.A gear mechanism converts vertical movements of the pack to rotary motions of an electrical generator，producing up to 7.4 watts. Unexpectedly，tests showed that wearers of the new backpack alter their gaits in response to the pack’s oscillations，so that they carry loads more comfortably and with less effort than they do ordinary backpacks. Because of that surprising advantage，Rome plans to commercialize both electric and non-electric versions of the backpack. The backpack could be especially useful for soldiers，scientists，mountaineers，and emergency workers who typically carry heavy backpacks.For the rest of us，power-generating backpacks could make it possible to walk，play video games，watch TV，and listen to music，all at the same time.Electricity-generating packs aren’t on the market yet，but if you do get one eventually，just make sure to look both ways before crossing the street! 文章(16~20) Backpacks are convenient becauseA they can be very large. B they can hold as many things as you want to carry. C your hand sare freed to do other things. D you do not have to carry things with you.” 相关考题
考题
4． —Where is my backpack?—_________A． Yes， it isB． No， it isn’tC． It's not your backpackD． It ' s not there
考题
*部分背包问题可有贪心法求解：计算Pi/Wi数据结构：w[i]:第i个背包的重量；p[i]:第i个背包的价值；1．0-1背包： 每个背包只能使用一次或有限次(可转化为一次)：A.求最多可放入的重量。
考题
考虑一个背包问题，共有n=5个物品，背包容量为W=10，物品的重量和价值分别为：w={2，2，6，5，4}，v={6,3，5，4，6}，求背包问题的最大装包价值。若此为0-1背包问题，分析该问题具有最优子结构，定义递归式为其中c(i，j)表示i个物品、容量为j的0-1背包问题的最大装包价值，最终要求解c(n,W)。 采用自底向上的动态规划方法求解，得到最大装包价值为(62)，算法的时间复杂度为(63)。 若此为部分背包问题，首先采用归并排序算法，根据物品的单位重量价值从大到小排序，然后依次将物品放入背包直至所有物品放入背包中或者背包再无容量，则得到的最大装包价值为(64)，算法的时间复杂度为(65)。A.11B.14C.15D.16.67
考题
共用题干
第二篇Electric BackpackBackpacks are convenient. They can hold your books,your lunch,and a change of clothes,leaving your hands free to do other things.Someday,if you don't mind carrying a heavy load,your backpacks might also power your MP3 player,keep your cell phone running,and maybe even light your way home.Lawrence C.Rome and his colleagues from the University of Pennsylvania in Philadelphia and the Marine Biological Laboratory in Woods Hole,Mass.,have invented a backpack that makes electricity from energy produced while its wearer walks.In military actions,search-and-rescue operations,and scientific field studies,people rely increasingly on cell phones,global positioning system(GPS)receivers,night-vision goggles,and other battery-powered devices to get around and do their work. The backpack's electricity-generating feature could dramatically reduce the amount of a wearer's load now devoted to spare batteries,report Rome and his colleagues in the Sept.Science.The backpack's electricity-creating powers depend on springs used to hang a cloth pack from its metal frame.The frame sits against the wearer's back,and the whole pack moves up and down as the person walks.A gear mechanism converts vertical movements of the pack to rotary motions of an electrical generator, producing up to 7.4 watts.Unexpectedly tests showed that wearers of the new backpack alter their gaits in response to the pack'soscillations,so that they carry loads more comfortably and with less effort than they do ordinary backpacks. Because of that surprising advantage,Rome plans to commercialize both electric and non-electric versions of the backpack.The backpack could be especially useful for soldiers,scientists,mountaineers,and emergency workers who typically carry heavy backpacks.For the rest of us,power-generating backpacks could make it possible to walk,play video games,watch TV,and listen to music,all at the same time.Electricity-generating packs aren't on the market yet,but if you do get one eventually,just make sure to look both ways before crossing the street!What is implied in"if you do get one eventually,just make sure to look both ways before crossing the street!"?A:You will be too excited to watch the traffic.B:Enjoying electronic devices while walking may invite traffic accidents.C:It is not possible for you to get such a backpack.D:It is wise of you to have such a backpack.
考题
共用题干
第二篇Electric BackpackBackpacks are convenient. They can hold your books,your lunch,and a change of clothes,leaving your hands free to do other things.Someday,if you don't mind carrying a heavy load,your backpacks might also power your MP3 player,keep your cell phone running,and maybe even light your way home.Lawrence C.Rome and his colleagues from the University of Pennsylvania in Philadelphia and the Marine Biological Laboratory in Woods Hole,Mass.,have invented a backpack that makes electricity from energy produced while its wearer walks.In military actions,search-and-rescue operations,and scientific field studies,people rely increasingly on cell phones,global positioning system(GPS)receivers,night-vision goggles,and other battery-powered devices to get around and do their work. The backpack's electricity-generating feature could dramatically reduce the amount of a wearer's load now devoted to spare batteries,report Rome and his colleagues in the Sept.Science.The backpack's electricity-creating powers depend on springs used to hang a cloth pack from its metal frame.The frame sits against the wearer's back,and the whole pack moves up and down as the person walks.A gear mechanism converts vertical movements of the pack to rotary motions of an electrical generator, producing up to 7.4 watts.Unexpectedly tests showed that wearers of the new backpack alter their gaits in response to the pack'soscillations,so that they carry loads more comfortably and with less effort than they do ordinary backpacks. Because of that surprising advantage,Rome plans to commercialize both electric and non-electric versions of the backpack.The backpack could be especially useful for soldiers,scientists,mountaineers,and emergency workers who typically carry heavy backpacks.For the rest of us,power-generating backpacks could make it possible to walk,play video games,watch TV,and listen to music,all at the same time.Electricity-generating packs aren't on the market yet,but if you do get one eventually,just make sure to look both ways before crossing the street!According to Paragraph 4,what does Rome plan to do?A:To make the backpack more comfortable for the wearer.B:To put the backpack on the market.C:To test the advantage of the backpack.D:To promote the backpack in a newspaper or on television.
考题
考虑下述背包问题的实例。有5件物品，背包容量为100,每件物品的价值和重量如下表所示，并已经按照物品的单位重量价值从大到小徘好序，根据物品单位重量价值大优先的策略装入背包中，则采用了（请作答此空）设计策略。考虑0/1背包问题（每件物品或者全部放入或者全部不装入背包）和部分背包问题（物品可以部分装入背包），求解该实例，得到的最大价值分别为（ ）。
A.分治
B.贪心
C.动态规划
D.回溯
考题
考虑下述背包问题的实例。有5件物品，背包容量为100,每件物品的价值和重量如下表所示，并已经按照物品的单位重量价值从大到小徘好序，根据物品单位重量价值大优先的策略装入背包中，则采用了（ ）设计策略。考虑0/1背包问题（每件物品或者全部放入或者全部不装入背包）和部分背包问题（物品可以部分装入背包），求解该实例，得到的最大价值分别为（请作答此空）。
A.605和630
B.605和605
C.430和630
D.630和430
考题
According to Paragraph 4，what does Rome plan to do?A To make the back pack more comfortable for the wearer.
B To put the backpack on the market.
C To test the advantage of the backpack.
D To promote the backpack in a newspaper or on television.
考题
What is implied in “if you do get on eventually，just make sure to take both ways before crossing the street!”?A You will be too excited to watch the traffic.
B Enjoying electronic devices while walking may invite traffic accidents.
C It is not possible for you to get such a backpack.
D It is wise of you to have such a backpack.
考题
关于0－1背包问题以下描述正确的是（）A、可以使用贪心算法找到最优解B、能找到多项式时间的有效算法C、使用教材介绍的动态规划方法可求解任意0－1背包问题D、对于同一背包与相同的物品，做背包问题取得的总价值一定大于等于做0－1背包问题
考题
对于0－1背包问题和背包问题的解法，下面（）答案解释正确。A、0－1背包问题和背包问题都可用贪心算法求解B、0－1背包问题可用贪心算法求解，但背包问题则不能用贪心算法求解C、0－1背包问题不能用贪心算法求解，但可以使用动态规划或搜索算法求解，而背包问题则可以用贪心算法求解D、因为0－1背包问题不具有最优子结构性质，所以不能用贪心算法求解
考题
举反例证明0/1背包问题若使用的算法是按照pi/wi的非递减次序考虑选择的物品，即只要正在被考虑的物品装得进就装入背包，则此方法不一定能得到最优解（此题说明0/1背包问题与背包问题的不同）。
考题
问答题举反例证明0/1背包问题若使用的算法是按照pi/wi的非递减次序考虑选择的物品，即只要正在被考虑的物品装得进就装入背包，则此方法不一定能得到最优解（此题说明0/1背包问题与背包问题的不同）。
考题
单选题关于0－1背包问题以下描述正确的是（）A
可以使用贪心算法找到最优解B
能找到多项式时间的有效算法C
使用教材介绍的动态规划方法可求解任意0－1背包问题D
对于同一背包与相同的物品，做背包问题取得的总价值一定大于等于做0－1背包问题
考题
问答题对于如下描述的背包问题，请计算最终装入背包的最大价值和以及各个物品装入背包的数量。 背包容量：C＝50千克。3件物品。物品1重20千克，价值100元；物品2重20千克，价值120元；物品3重30千克，价值90元。
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