排序方式: 共有143条查询结果,搜索用时 250 毫秒
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在不确定需求下研究易逝品零售商面对具有异质性策略消费者的两阶段定价问题.考虑零售商两阶段定价是否采用提供保价险的价格承诺策略,分别构建了无价格承诺、在第1阶段和在第2阶段进行价格承诺的零售商收益模型.运用均衡理论和逆向归纳法分析了降价期价格、购买均衡和全价期价格的收益情形,研究结果表明:在这几种情况下,采用价格承诺策略... 相似文献
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介绍了采用基于组合公钥(CPK)技术的认证原理,提出一种简化或取消第三方CA机构或证明,减少庞大的支持机构和维护量,从而达到简化IPSec协议的实现过程和提高认证效率。 相似文献
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Remote user authentication is essential in distributed network environment to protect unauthorized access of a networked system. However, most of those existing remote user authentication schemes have not provided the user identity anonymity, while user anonymity is particularly important in some practical applications. Therefore, based on self-encryption mechanism, a new remote user authentication scheme was proposed. The scheme not only has no need of maintaining a password table at the remote server, but also can protect the user's anonymity. 相似文献
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Introduction Remoteuserauthenticationschemesarevery usefulindistributedsystemssincetheycanguar-anteeonlythelegalusershaverighttovisitthere-sourcesprovidedbytheremoteservers.There-fore,overthepastyears,manyremoteuserau-thenticationschemes[1-8]havebeenproposed.In1981,Lamport[1]proposedthefirstwell-known passwordauthenticationschemeusingapassword tabletoachieveuserauthentication.However,Lamport'sschemesuffersfromtheriskofamodi-fiedpasswordtableandthecostofprotectingand maintainingthepasswordtabl… 相似文献
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VGT叶片开度对二级增压柴油机高海拔低速匹配特性的影响 总被引:1,自引:0,他引:1
基于二级可调增压柴油机高海拔性能模拟试验平台,研究了不同海拔条件下 VGT 叶片开度对高压共轨柴油机二级可调增压系统低速匹配特性的影响。研究结果表明:不同海拔下,随着 VGT 叶片开度的减小,高压级涡轮的涡轮膨胀比和压气机压比、绝热效率逐渐提高,而低压级涡轮膨胀比及压气机效率变化则趋于平缓,因此两级压气机总压比、总效率和总功率的变化趋势与高压级压气机一致;柴油机进气流量及空燃比随着 VGT 叶片开度的减小而增大,动力性及经济性也随之升高;海拔0~4500 m ,高压级压气机匹配状况良好,联合运行线均位于高效率区内。 相似文献
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二级可调增压器旁通阀与喷油参数调节规律的仿真分析 总被引:3,自引:0,他引:3
利用Wave仿真软件建立了某二级可调增压V型8缸电控单体泵柴油机的仿真分析模型,应用台架试验数据对模型进行了标定,以最佳燃油经济性为目标,计算了外特性条件下排气旁通阀开度与喷油提前角对柴油机性能的影响规律,得到两者的优化匹配规律。计算结果表明:旁通阀阀门开度及喷油参数直接影响二级可调高增压柴油机系统的燃烧和换气过程;高转速高负荷工况时需要打开排气旁通阀,并适当增加喷油提前角以降低过高的排气背压,减少泵气损失,且转速越高放气阀开度越大、喷油提前角越大;中低转速高负荷工况时,排气背压低于进气压力,泵气损失功小,不需要打开排气旁通阀,并且应适当减小喷油提前角。 相似文献
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The estimation of semi-compensatory models is gaining momentum in transport planning in recent years. However, traditional survey methodologies focus on collecting solely compensatory choice data, which leads to information loss when semi-compensatory models are estimated. The present study proposes a novel web-based survey that enables collecting data about the entire semi-compensatory choice process. The web-based environment allows seamless tracking of semi-compensatory choice protocols without interfering with the natural choice process and without introducing problems related to comprehension bias, narrative inconsistency and misinterpretation of the choice protocols. The procedure is applied to rental apartment choice by students and results shed light on semi-compensatory choice by: (1) demonstrating the importance of choice set formation; (2) unravelling the distribution of threshold selection across the population; (3) revealing the linkage between the viable choice-set and the choice. 相似文献