制动鼓传热分析

对某重型卡车后轮制动鼓进行传热分析,模拟制动鼓的温升过程,并与三种不同改进结构的制动鼓进行对比分析,提出最优改进设计方案。     

一类不可微复合函数的二阶广义方向导数

研究一类不可微复合函数Ｃｈａｎｅｙ意义下的二阶广义方向导数,并且得到这一类不可微问题的二阶最优性条件。     

线性大系统参数稳定区域的扩大

本文利用加权V函数求解线性大系统的稳定性,得到了比较好的结果; 并指出了利用向量V函数造成亏损的实质。      

《民法典》对抵押制度的修改以及对船舶抵押权产生的影响

船舶抵押融资对造船业、航运业有着至关重要的影响,事关抵押权人、抵押人以及买受人三方之间的利益.过去的立法对抵押财产转让的条件以及正常经营活动中买受人规则的适用范围等做出了严格限制,以此来保护抵押权人的利益.2020年5月28日正式通过的《民法典》对原有抵押制度进行了一系列的修改,改善了实践中抵押权人、抵押人和买受人三方...     

杂凑算法迭代结构研究

专用Hash函数是一类目前应用比较广泛的Hash函数,随着密码分析者对基于Merkle-Damgard迭代结构构造的专用Hash函数攻击的深入,Merkle-Damgard结构逐渐显示出了它的不足。文章分析了Merkle-Damgard结构的不足,介绍了近年来密码学界针对Merkle-Damgard结构的不足而提出的新的专用Hash函数迭代结构,并对每种新迭代结构的优缺点进行了分析;最后在3C迭代结构的基础上提出了3C＋＋Hash函数迭代结构。     

THE ELASTIC FIELD CASED BY TWO INCLUSIONS WITH UNI- FORM DILATATIONAL EIGENSTRAINS IN DISSIMILAR MEDIA

IntroductionGuell and Dundurs[1] used the Papkovitch-Neuber displacementpotential and had the solutionfor a spherical inclusion in dissilmilar media whichundergoes homogeneous dilative eigenstrain. Itwas found that the displacements and stresses inthe region exterior to the sphere are the same asthose resulting from a center of dilatation of a cer-tian strength located at the center of the sphere.Using the solution of Mindlin and Cheng[2 ] inwhich the Galerkin vector was adopted and nucleiof…     

Equilibrium properties of taxi markets with search frictions

The equilibrium properties of an aggregate taxi market are investigated using a general bilateral searching and meeting function which characterizes the search frictions between vacant taxis and unserved customers. Three specific issues are analyzed for meeting functions that exhibit increasing, constant and decreasing returns to scale. Firstly, service quality in terms of customer wait/search time and average profit per taxi are examined jointly in relation to taxi fleet size, and a Pareto-improving win-win situation is identified, where an increase in taxi fleet size leads to improvements in both service quality and market profitability. Such a Pareto-improving situation is found to emerge if and only if the meeting functions show increasing returns to scale. Secondly, the properties of the socially optimal solution are examined. It is found that the taxi fleet size should be chosen such that the total cost of operating vacant taxis equals the total cost of customer waiting time multiplied by an asymmetric factor of the meeting function, and that taxi services should be subsidized at social optimum only when the meeting functions show increasing returns to scale. Thirdly, the Pareto-efficient services are examined for trade-offs between social welfare and profits in the light of partially conflicting objectives of the public sector and the private taxi firms using a bi-objective maximization approach. The taxi utilization rate and the customer wait/search time or service quality are proved to be constant along the Pareto frontier and equal to those at social optimum if the meeting functions show constant returns to scale. Extensions are made to the cases with increasing and decreasing returns to scale.     

未来的潜艇液压系统

  目的  液压油站作为液压系统的动力源,是液压系统振动、噪声产生的根源。为进一步降低液压系统的振动、噪声水平,提出一种基于模态分析与振动传递函数分析的低噪声液压油站的设计方法。  方法  建立液压油站有限元模型,在此基础上求解出油站的模态,并利用模态叠加法对油站结构及液压泵的安装位置进行优化,得到油站的最佳结构形式和液压泵最佳安装位置。基于振动传递函数分析对液压油站箱体结构进行设计,优化泵组到油站机脚的振动传递路径,进一步降低液压泵组振动噪声对液压油站的影响。  结果  油站的振动噪声测试结果表明,该设计方法显著降低了液压油站振动、噪声指标,其中液压油站振动加速度总级降低5.7 dB,空气噪声降低2 dB,  结论  为液压系统减振降噪提供了较好的方法。     

舰船主船体水线以下部分武器

采用符拉索夫计算法计算武器命中后的舰船浮态和外载荷的变化。以薄壁梁理论为基础,用迁移矩阵法计算武器命中后的舰船的内力,并以某舰船为计算模型进行了数值计算分析,找出正应力和剪应力随不同破口部位及尺寸的变化规律,从而为舰船破损后的剩余强度研究提供了依据。     

舰船通信集成交互调影响评估方法

  目的  针对多艘船舶在间歇通信环境下的编队控制问题,提出了基于反步法的协调编队控制律,并给出编队形成的充分条件以满足编队的鲁棒性。  方法  首先,利用反步法设计正常通信时段的船舶编队控制律,加入误差观测器消除外部环境带来的误差,保证船舶在正常通信时段形成理想编队。然后,对于在间歇通信中通信缺失的时段,设计控制律。此外,在船舶编队的形成以及队形保持的过程中,通信时长必须满足一定的要求,并给出在间歇通信环境下实现编队的充分条件。最后,利用李雅普诺夫理论对船舶编队控制律的稳定性进行验证,并证明该充分条件的可靠性。  结果  仿真结果表明,采用该控制律且满足给出的充分条件,船舶能够在间歇通信环境下实现编队航行。  结论  在间歇通信或类似的周期性通信缺失情况下,对船舶编队控制的设计与研究有一定的参考价值。