PPO/PA6合金改性技术的研究

为了使聚酰胺6(PA6)、聚苯醚(PPO)的性能互补,采用共混改性的方法制备综合性能优异的PPO/PA6合金,并对PPO/PA6共混改性技术进行研究。结果表明,苯乙烯系产品(SEBS)不仅可以提高PPO/PA6合金体系的相容性,而且同时还能起到增韧作用。     

RDX基发射药相容性和安定性的研究

为了解由黑索今(RDX)、聚氨酯黏合剂、硝化棉等组分组成的发射药的相容性和安定性,采用差示扫描量热法(DSC)进行测定。根据不同加热速率下的峰温,进而求得加热速率趋于零时试样的峰温TP0、单独体系相对于混合体系分解峰温的改变量ΔTP及表观活化能改变率ΔE:Ea,考察了不同单独体系下的发射药的相容性和安定性。研究结果表明,以单基发射药作为单独体系,新型发射药的相容性较好;以RDX或聚氨酯作为单独体系,新型发射药的相容性均较差;新型发射药的安定性低于RDX,高于硝化棉。     

Self-tuning adaptive neurocontroller for brushless DC motors

This paper describes a self-tuning adaptive neurocontroller for brushless DC motors. Nonlinear and unknown motor dynamics are identified by using a multilayer neural network and the control input for the motor is derived from the identified model. The effect of the load torque on the control system is damped by filtering the control input. Simulation and experimental results show that the self-tuning adaptive neurocontrol has a good tracking performance but needs an adaptive filter and a parallel PI controller in the case of disturbances.     

Spread spectrum in three-phase inverter by an optimised dual randomised PWM technique

Randomised pulse width modulation (RPWM) technique has become a viable alternative to deterministic pulse width modulation (DPWM). By spreading the power spectrum in a continuous noise, this new technique better complies with electromagnetic compatibility (EMC) requirements for conducted electromagnetic interferences (EMI) and allows reducing the emitted acoustic noise in variable speed drives (VSDs). The most popular RPWM schemes are randomised pulse position modulation (RPPM) and randomised carrier frequency modulation (RCFM). The combination (RCFM-RPPM) or dual RPWM (DRPWM) has also been proposed. In this article, we propose an optimised DRPWM (ODRPWM) for the three-phase inverter. First, the modulating principle is proposed, and then, a mathematical model of power spectral density (PSD) of the output voltage is developed and validated for the three schemes, namely RPPM, RCFM and RCFM-RPPM. PSD analysis shows that the proposed scheme is more effective on spreading PSD. Moreover, this analysis reveals optimal parameters of randomisation for a maximum spread of the PSD. The optimisation problem is then modelled and solved using two powerful non-linear methods.     

A controllable resistance sheet using rectifying diodes

A controllable resistance sheet consists of an array of contiguous diode-loaded dipoles. A design method is described for the control of the RF resistance by an off-array DC resistor. These ‘rectifying sheets’ find application as high-power smart absorbers and dissipative frequency selective surfaces, beam transmittance controllers and spatial strong-signal suppressors.     

Electrical Conductivity and Dielectric Behavior of Some Poly(Alkyl Methacrylate)s/Polyvinylpyrrolidone Blends

A systematic dielectric study over a frequency range of 100 Hz up to 100 k Hz was carried out on some poly(alkyl methacrylate)s: poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(butyl methacrylate) (PBMA) blended with polyvinylpyrrolidone (PVP). The compatibility investigation, which was tested by using the dielectric method and confirmed by viscosity technique, led to a conclusion that both PMMA/PVP and PEMA/PVP blends are incompatible while PBMA/PVP blends are compatible. Tetrachlorophthalic anhydride (TCPA) was chosen to be added in increasing quantities (0%–30% by weight) to the investigated blends. Ten percent of such anhydride was found to solve the problem of phase separation between both incompatible blends. Moreover, the electrical conductivity of the investigated blends was found to increase linearly, in the semilogarithmic scale, by increasing TCPA content (10^?12 to 10^?5 S^?1 cm^?1). After subtraction of the losses due to dc conductivity, the dielectric data reveal a lower frequency absorption region, which is found to be unchanged by increasing either the blend ratio or the content of TCPA. This region ascribes the Maxwell-Wagner effect due to the difference in the permittivity and conductivities in polymeric materials. The higher values of ?″ in the higher frequency range for all the blends indicates a higher frequency absorption region with maximum frequency out of the available range of frequencies. The addition of TCPA shifts this maximum towards lower frequencies. This shift indicates an increase in the molar volume of the rotating units and consequently an increase in the relaxation time.     

助磨剂组分对水泥与减水剂相容性的影响及机理分析

通过试验,研究不同的助磨剂组分对水泥与减水剂相容性的影响,并对其作用机理进行分析。结果表明,助磨剂会改变水泥的吸附性能、颗粒大小、水化速度等,从而影响水泥与减水剂的相容性。明显提高标准稠度用水量或促进早期水化的助磨剂组分（如丙三醇、三乙醇胺）容易引起水泥与减水剂相容性不良;明显降低标准稠度用水量或延缓早期水化的助磨剂组分（如三聚磷酸钠、六偏磷酸钠）可以改善水泥与减水剂相容性;憎水性的硅油使水泥浆体严重泌水;其他大多数助磨剂组分对标准稠度用水量、水化速度等影响较小（如乙二醇、二乙醇胺、糖蜜、木钙、木钠）,基本上不会影响水泥与减水剂的相容性。此外,有些助磨剂组分对水泥与减水剂相容性的影响因减水剂不同而有所差别,如二甘醇、三异丙醇胺。     

基于机制设计理论的用户需求订购模型

在实施激励性补偿驱动的需求响应项目过程中,由于信息不对称,传统的基于历史数据的用户基准负荷估计会导致操纵问题,从而会影响需求响应项目的经济效率。采用机制设计理论,引入用户类型参数来描述不同用户的不同用电需求意愿,提出了信息不对称环境下,供电公司考虑用户参与约束和激励相容约束的需求订购模型,并给出了求解方法。该模型解决了需求订购中用户真实基准负荷的自愿披露问题,算例仿真验证了模型的有效性和合理性。     

基于LTCC多层基板技术的宽带T/R组件设计

介绍了一种基于低温共烧陶瓷(LTCC)多层基板工艺的宽带发射/接收(T/R)组件的设计,详细论述了组件的电路布局和装配工艺,给出了具体的测试数据。T/R组件的体积为65mm×29mm×9mm,连续波输出功率大于25W,均方根移相误差小于3°,已达到工程应用要求。     

中国联通WCDMA3G国土资源监控解决方案

介绍利用WCDMA3G无线通信网络和视频监控技术进行国土资源监控的解决方案,该方案主要用于解决传统卫星遥感成像技术不能及时发现问题的弊端,为耕地保护工作提供一种新型、高效、可行的技术手段。