基于MFSK的多载波水声通信系统及实验研究

本文在深入研究水声通信信道特性及多载波关键技术的基础上,设计并研制了基于M FSK的高速自适应多载波水声通信系统,并进行了湖上实验。理论分析、仿真及湖上试验结果表明:基于M FSK的多载波水声通信系统,多径抑制有效,对同步的精确度要求不高,性能稳健,更适合于恶劣水声通信环境下、中距离(10~30km)较高数据率多载波通信系统,易于工程实现,具有良好的应用前景。     

DDS+PLL系统的频谱分析

简要介绍了 ＤＤＳ＋ＰＬＬ频率合成的原理，分析了在 ＤＤＳ没有相位截断误差时，ＤＤＳ＋ＰＬＬ输出信号的杂散抑制度，并讨论了杂散抑制度与环路参数的关系。     

石油工程项目管理机制

为了妥善处理石油工程项目中的委托-代理关系,研究了委托-代理模型和石油工程项目管理中的激励约束机制,分析了激励机制、监督机制和选择机制在石油工程项目运行管理中的重要性.只有用有效的契约去激励技术服务公司,才能使服务公司在追求自身效益最大化的同时也为实现石油公司的最大效益而尽最大努力;只有对技术服务公司的作业实施监督,才能形成对技术服务公司的有效约束;采用激励性承包方式、实施综合性评标和组建工程项目动态联盟能够防止逆向选择.分析表明,在最优激励安排下,激励强度与项目面临的不确定性、承包商的边际成本及其风险规避系数负相关,与承包商的边际生产率正相关,还与其他可观测变量相关.在最优监督水平下,作业公司的边际生产率越高,边际成本越低,越容易监督,监督带来的边际收益越高.对于那些监督比较困难的项目,可以通过加强惩罚力度的方式弥补难以有效监督的不足.激励性承包方式可以减小逆向选择造成的危害,组建动态联盟可以进一步加强激励作用,降低道德风险,解决逆向选择问题.参8     

Axial vibrations of U-shaped bellows with elastically restrained end conditions

Previous work by Li et al. in the area of axial vibrations of bellows dealt with fixed end conditions. However, it is seen on several occasions that bellow ends are welded to a small pipe spool that has a lumped mass such as a valve or an instrument. Hence, the present paper aims at finding out the effect of elastically restrained ends on the axial natural frequencies. The analysis considers finite stiffness axial restraints on the bellows, i.e. solving the set of equations with non-homogeneous boundary conditions. Two bellow specimens are considered for comparison having the same dimensions as taken by Li in his analysis. The transcendental frequency equation deduced is accurate as the first, second and third mode frequencies computed are in close agreement to the ones obtained by Li.     

工业自动化控制系统的抗干扰技术分析

分析了干扰感应模型,指出常见的工业自动化控制系统的干扰源包括辐射干扰、传导干扰和设计施工引起的干扰,分析了这些干扰的产生机理;指出应从设计和现场施工两方面采取抗干扰措施,设计阶段要考虑电源设计、接地系统设计、管线设计、器件选择、软件设计等因素,并给出了常见的抗干扰措施;以某燃气站控制系统为例介绍了抗干扰措施在实际工业现场中的应用方案,验证了合理的抗干扰措施可有效降低干扰,保证工业自动化控制系统的可靠运行。     

Reliability-based robust assessment for multiobjective optimization design of improving occupant restraint system performance

Optimal performance of vehicle occupant restraint system (ORS) requires an accurate assessment of occupant injury values including head, neck and chest responses, etc. To provide a feasible framework for incorporating occupant injury characteristics into the ORS design schemes, this paper presents a reliability-based robust approach for the development of the ORS. The uncertainties of design variables are addressed and the general formulations of reliable and robust design are given in the optimization process. The ORS optimization is a highly nonlinear and large scale problem. In order to save the computational cost, an optimal sampling strategy is applied to generate sample points at the stage of design of experiment (DOE). Further, to efficiently obtain a robust approximation, the support vector regression (SVR) is suggested to construct the surrogate model in the vehicle ORS design process. The multiobjective particle swarm optimization (MPSO) algorithm is used for obtaining the Pareto optimal set with emphasis on resolving conflicting requirements from some of the objectives and the Monte Carlo simulation (MCS) method is applied to perform the reliability and robustness analysis. The differences of three different Pareto fronts of the deterministic, reliable and robust multiobjective optimization designs are compared and analyzed in this study. Finally, the reliability-based robust optimization result is verified by using sled system test. The result shows that the proposed reliability-based robust optimization design is efficient in solving ORS design optimization problems.     

削弱或抑制抗氧剂、光稳定剂作用的有关因素

介绍了削弱或抑制抗氧剂、光稳定剂作用的常见因素及实例，分析了防老化塑料制品发生提前老化现象的可能性和原因。     

复杂电磁暂态下变压器差动保护异常动作行为分析及对策

随着电力系统结构与组成的复杂性增加,变压器差动保护发生原因不明的误、拒动作几率明显上升,给电网安全带来隐患,也影响工业生产的正常运行.分析变压器经历外部故障切除、有载合闸、非线性负荷投入、换流变合闸等复杂电磁暂态过程时基于二次谐波制动的差动保护误动的机理,指出TA局部暂态饱和、非线性特性元件的相互作用是造成上述保护误动的根本原因.并对换流变压器差动保护在故障情况下长延时动作的原因进行分析,基于相电压突变量和差流突变量的时差,提出一种能有效解决上述问题的变压器差动保护判据。在任何非故障的异常情况下,该时差总是存在,而内部故障时该时差很小,可以将变压器故障和其经历的异常运行状态相区分.通过大量的试验对该判据的可行性和有效性进行验证.     

混凝土底板温度及温度应力影响参数分析

借助参数化设计语言(APDL)分析了水泥品种及标号、结构尺寸、外界约束对混凝土底板温度及温度应力的影响.结果表明:与普通硅酸盐水泥525相比,普通硅酸盐水泥425、矿渣水泥425可使底板最大拉应力分别减低约21%、37%;底板平面尺寸增大,压应力几乎保持不变,拉应力增大,发展较为平缓;底板厚度越大,出现最高温度的龄期越晚,底板降温时持续高温时间更长,且温度应力随厚度增大而增大.