Asymmetric convolution algorithm for blocking probability calculation in full-availability group with bandwidth reservation

The paper proposes a new approximate calculation method of occupancy distribution and blocking probability in the full-availability group (FAG) with multi-rate traffic streams and bandwidth reservation. The algorithm involves calculation of system state probabilities by a convolution operation. In the paper, an effective method of calculating state probabilities in a reservation space of the system is derived. The analytical results of blocking probabilities in the FAG with bandwidth reservation, obtained on the basis of the proposed analytical method, are compared with the data obtained on the basis of other known analytical methods and with the simulation results. The accuracy of the proposed method is evaluated for different multi-rate Bernoulli (Erlang), Poisson (Engset), Pascal traffic streams. The method proposed is characterised by lower complexity than the convolution algorithm for the FAG with bandwidth reservation devised earlier.     

Providing differentiated services in CDMA wireless networks

With much more advanced techniques employed, various applications can be supported by 3G CDMA-based wireless networks. Providing differentiated service over wireless networks has become a very important issue in the design of wireless networks. A new media access control protocol with a hierarchical scheduling algorithm to provide differentiated service for CDMA-based wireless networks is proposed. This protocol evolves from the distributed queuing random access protocol for CDMA wireless network. The proposed protocol has been designed to have an ability to accommodate integrated traffic in the networks with effective scheduling schemes. A series of simulation experiments have been carried out to evaluate the performance of the proposed protocol with the hierarchical scheduling algorithm. The results reveal that the proposed solution performs effectively in the integrated traffic composed of messages with or without time constraints and achieves proportional fairness among different types of traffic.     

区分服务的无线传感器网络路由协议

在优先级多路径路由协议PRIMAR（PRIoritize MultipAth Routing）的基础上,提出了NRE-PRI—MAR协议：以邻居节点剩余能量（NRE）作为衡量路径优先级大小的依据,通过建立节点的二级路由表来决定下一跳转发节点．仿真实验表明,该协议有效地提高了网络的生存期,实现了区分服务．     

铌、钽电容器性能分析

钽铌属于同族元素 都是阀金属材料,其介电常数分别为27、41,都可以用来制作电解电容器。本文使用铌和钽2种材料分别制作电解电容器,并通过容量损耗测试仪、漏电流测试仪、电子扫描电镜等分析仪器对其和始性能、偏压性能、温度特性、寿命特性及其电介质层的微观特性进行检测分析。结果表明使用铌材料同样可以得到性能较好的电解电容器。     

Analysis of gray markets in differentiated duopoly

In recent years, gray markets have become a significant phenomenon in the business practice. This paper investigates the gray markets issues in differentiated duopoly case by considering quantity competition among firms. We develop a game-theoretic model and provide equilibrium results for three scenarios, i.e. the benchmark scenario ‘no gray market’, the scenario ‘parallel imports act as a buffer against a follower’s product’ and the scenario ‘gray markets stimulate the competition’. By the analysis of the equilibrium results, some important managerial insights are obtained. Finally, by comparison of the equilibrium results among different scenarios, we study the impact of gray markets on manufacturers’ optimal strategies and profits in differentiated duopoly.     

Study of the effect of source signal bandwidth on ratiometric wavelength measurement

We derive an analytic equation for a ratiometric wavelength measurement system and analyze the influence of the optical source signal bandwidth. Our investigation shows that in a particular optical sensing system, the higher the bandwidth of the optical signal, the better resolution the system will achieve. Experiments based on two types of optical signals (output signal of a tunable laser and a fiber Bragg grating) were carried out, and experimental results verified both the simulation results and the theoretical analysis.     

A new look at the effect of bandwidth and non-normality on fatigue damage

A new attempt is made in this paper to quantify the effect of bandwidth and non‐normality in fatigue damage analysis. For the lack of actual stress history, a series of non‐Gaussian and homogeneous random processes are generated with fast Fourier transform (FFT) acceleration. A factor is defined on the basis of rain‐flow counting and Palmgren–Miner rule to correct the narrow band and normality assumption. It is revealed that the fatigue damage evaluated through the traditional method may be either conservative or rather unconservative. The upper and lower bounds of the correction factor are studied with respect to kurtosis and skewness of the generated random process and the slope of S–N curve.     

导电剂对氧化钌基超级电容器电极材料性能的影响

采用液相共沉积法合成了RuO2/AC复合电极材料,用扫描电镜对不同导电剂材料的形貌进行表征,进而通过循环伏安法、恒流充放电、交流阻抗谱研究了不同导电剂对RuO2/AC复合电极材料超级电容器性能的影响。结果表明,在38%(质量分数)的H2SO4溶液中,电流密度为2 m A/cm2,以CNTs、AB、KS6、Super PLi为导电剂时比容量和ESR分别为689,556,574和512 F/g,0.19,0.36,0.32和0.41Ω。     

单光纤光栅实现窄带全光纤反射器的分析

提出了一种由单个光纤光栅和一个光纤方向耦合器组成的新型全光纤反射器,推导出了当光栅为均匀 Bragg 光栅、器件任意端口输入时,任何一端口的输出解析式。分析表明器件具有法布里-珀罗腔干涉仪的特点,耦合器的耦合比系数类似于法布里-珀罗腔的反射率, 耦合比系数越大,输出光谱半高全宽度(FWHM)越窄, 消光比越好。当耦合比系数大于 0.8 时,FWHM 可以窄到0.02nm,消光比大于 0.9。如果光栅是“强”耦合,器件具有均匀分布的多通道梳状输出特性;光栅为“弱”耦合时,则能实现 FWHM 小于 0.02nm 的单频输出。器件只需单个光栅,克服了制作两个完全相同光栅的困难。     

Analysis of excess water impact on the structural performance of flexible pavements

Excess water in pavement foundations is one of the major factors contributing to pavements deterioration. In recent years, a number of research studies have been carried out to understand the water movement into pavements and to assess its detrimental effects on the mechanical response of the foundations. However, these studies do not quantify the impact of suction reduction or pore pressure buildup in the foundations on the pavement response. In this paper, coupled finite element analyses are carried out to investigate the effect of the excess water in the granular foundations on the structural performance of flexible pavements. The coupled analyses simulate critical features governing the foundations' hydromechanical response including the transient unsaturated flow and porous nonlinear behaviour of the foundations under moving wheel loads. Furthermore, a parametric study that examines the influences of various loading and foundation parameters on the performance of pavements subjected to excessive moisture scenarios is carried out. The numerical analysis results obtained in this paper are qualitatively in line with the empirical observations reported in the literature.     

Widely tunable optical filter with variable bandwidth based on the thermal effect on cholesteric liquid crystals

A widely tunable optical filter with variable bandwidth has been demonstrated based on the thermal effect on cholesteric liquid crystals. The central wavelength can be widely tuned from 826 to 517?nm and the bandwidth can be varied from 10 to 70?nm. It will have potential applications in many fields, especially in telecommunications and multi-spectral/hyper-spectral imaging systems.     

硫酸钡填允改性对PTFE密封材料性能的影响

采用冷压和自由烧结工艺制备硫酸钡填充改性聚四氟乙烯(PTFE)密封材料。实验研究了硫酸钡表面处理方法、颗粒粒径及其体积含量对材料性能的影响,并对改性机理进行了分析。研究结果表明,采用钛酸酯偶联剂NDZ-401可以较好地改善填料颗粒和PTFE基体间的界面结合度,有利于提高材料性能;采用小粒径硫酸钡填充PTFE材料可有效降低材料的应力松弛率,但拉伸强度下降明显;大粒径硫酸钡的填充改性效果优于小粒径,且当其体积含量约为26%时,可获得综合性能较好的PTFE密封复合材料。     

三层板压印接头力学性能分析

本文的研究目的是分析三层板不同搭接方式的压印接头的力学性能,主要采用试验方法对其进行研究,具体方法如下:首先对1.5 mm AA5052+1.5 mm SPCC+1.5 mm AA5052三层板不同配置方式下的压印接头进行静态力学性能测试,分析三层板压印接头的静态失效模式及其静强度;再对静态力学性能最优组进行动态疲劳性能测试,分析疲劳失效模式及其疲劳强度,并采用最小二乘法拟合获得接头力-寿命(F-N)方程.试验结果表明:静态失效为上板颈部断裂、中板内锁拉脱和混合失效三种模式;T-A型接头静强度最低,T-C型接头静强度最高.其中,T-C型接头疲劳失效模式为上板颈部先断裂,之后下板出现裂纹导致接头失效;T-C型接头上板颈部疲劳性能较差,当应力水平为静强度40%时,疲劳循环最多只能达到15 965次,但是中板与下板连接可达到200万次.     

潮流能柔性叶片水轮机水动力学特性分析

提出了一种新型海洋潮流能获取装置--潮流能柔性叶片水轮机.其叶片采用柔性材料,可适应流体发生形变,从而它能自动调节攻角,能充分利用流体的升力效应和阻力效应做功,具有独特的水动力学特性.以柔性叶片水轮机获能系数(Cp)为主要研究目标,通过水槽模型实验对其影响因素进行了研究.实验证实了该柔性叶片水轮机的独特水动力学特性,而且证明,叶片形状和水轮机结构形式是其性能的主要影响因素,并通过分析得到了具有较佳水动力学特性的水轮机的叶片形状和水轮机结构形式.     

三质体声共振混合机的动力学特性及其性能分析

为研究三质体声共振混合机的动力学特性,建立了三质体声共振混合机的动力学模型,进而分析了系统物理参数对动力学特性的影响,阐明了物料质量和阻尼变化对声共振混合机动力学响应的影响规律,提出了系统在共振频率附近工作的振幅控制策略。进一步分析了典型声共振混合机在额定载荷下的对地动载荷和所需激振力,并与额定载荷所需的最大推力进行了比较。结果表明,通过选择合理的系统物理参数,三质体声共振混合机在三阶共振频率附近工作,其振幅变化较平缓、负载质体和激振质体的运动相位相反,系统能够兼具能量转换率高、对地动载荷小且激振力小等优点。所得结论有助于进一步提高声共振混合机的工作性能和设计水平。     

空分设备余能利用分析与应用

从节能降耗的角度分析了空分设备运行过程中余能的利用,对可利用的各种热能、气体等余能提出应用方案。     

NaOH活化法中碱炭比对孔结构和电化学性能的影响

采用沥青焦为原料,以NaOH化学活化法制备出不同碱炭比(R)系列活性炭.用氮气吸附和脱附等温线计算出BET比表面积、DFT孔径分布及孔容,并且通过直流循环充放电、循环伏安等表征方法研究了其电化学性能.实验结果表明,R值对活性炭的BET比表面积、DFT孔径分布及孔容有良好的调控作用:当R=5时,其最大BET比表面积为1089m2/g,孔容达0.53cm3/g,当R=3时,其孔径分布在1.0-2.0nm百分比达36.2%;其直流循环充放电曲线较好,循环伏安曲线也近似矩形,表明具有良好双电子层电容器电极材料特性,在3mol/L的KOH电解液体系中,最大质量比电容、体积比电容、单位面积比电容分别达202F/g、143F/cm3、32.9μF/cm2;在1mol/L(C2H5)4NBF4/Propylene Carbonate(PC)电解液体系中,最大质量比电容、体积比电容、单位面积比电容分别达149F/g、107.3F/cm3、20μF/cm2.对KOH和(C2H5)4NBF4/PC电解质吸附的最佳孔径分别为1.3nm,1.5nm左右.     

HEMA-NVP共聚物表面性能研究

室温下,以质量分数为0.2%的2-羟基-甲基苯基丙烷-1-酮(1173)为引发剂,0.5%的二乙二醇甲基丙烯酸酯(EGDMA)为交联剂,在紫外光照下合成了甲基丙烯酸2-羟基乙酯(HEMA)-N-乙烯吡咯烷酮(NVP)二元共聚物水凝胶.探讨了共聚物表面的润湿性、脱水性及对牛血清蛋白(BSA)的吸附性.试验表明,材料薄膜表面接触角随着NVP含量增大及接触时间的延长而减小;BSA通过物理作用吸附于水凝胶薄膜表面,BSA吸附量随时间延长及吸附液初始浓度升高而增大;随着共聚物中NVP含量的增大,BSA吸附量增大,而释放量减小;脱水试验表明水凝胶薄膜的脱水速率随NVP及交联剂含量的增大而减小.     

孔隙率对碳纤维/尼龙6复合材料湿热性能影响的数值模拟研究

孔隙在复合材料制造过程中广泛存在,在湿热环境下孔隙的存在会改变应力场和水分场,进而影响复合材料的吸湿性能与力学老化性能。对碳纤维/尼龙6(Carbon fiber reinforced polyamide 6,CF/PA6)复合材料在不同温度浸水环境下吸湿老化后的力学性能测试,研究了温度与吸湿量对其力学性能的影响及强度与模量等力学参数的演化规律,建立吸湿参数与力学参数的关联函数。基于随机顺序吸附法算法(Random sequential adsorption,RSA),建立了纤维、界面和孔隙随机分布的代表性体积单元(Representative volume element,RVE)模型。在本构模型中引入依赖于吸湿量的退化因子,研究了孔隙含量对复合材料横向拉伸、压缩、剪切强度和模量的影响,揭示了湿热老化前后不同的失效机制。结果表明：在热湿老化前,由于应力集中,孔隙会导致复合材料力学性能下降,孔隙率含量每增加1%,横向拉伸强度降低6.4%;湿热老化后,基体吸湿塑化效应是复合材料力学性能降低主要因素,对应降低率为3.86%。