Fuzzy assignment of manufacturing process tolerances

The assignment of process tolerances is vital to the success of production, therefore, a systematic and reliable approach should be developed to assist the process planner in designing the tolerances. Conventional methods assign tolerances without considering the process capability of machinery, as a result, the tolerances allocated may not agreeable economically. This study proposes a new formulation to concurrently maximize the standardized process tolerances; the original multiobjective programming is consolidated into a single objective problem by using the fuzzy technique. Comparison results with other methods indicate that the presented model can design process tolerances by generating the least overall scrap rate     

Effects of manufacturing tolerances on the electrical performance of suspended and inverted microstrip lines

Effects of manufacturing tolerances in the dimensions and parameters of suspended and inverted microstrip lines on the electrical performance of these lines have been studied through sensitivity analysis. The closed-form expressions recently given by Pramanick and Bhartia for the analysis of these lines have been used to derive the mathematical expressions for various sensitivities and the dependence of sensitivities on the aspect ratios and on the substrate dielectric constant has been depicted graphically. Generally speaking, the effects of tolerances are seen to be reflected much more sharply in the sensitivities of the characteristic impedance than in those of the effective dielectric constant. Many other useful inferences are also drawn from the sensitivity graphs. The conclusions are presented in tabular form, so as to be of direct help to the user.     

On the analysis of active networks containing voltage, operational, and differential-input operational amplifiers

A method of drawing by inspection the signal-flow graph of an active network containing voltage, operational, and differential-input operational amplifiers is given and it is shown that the network functions can easily be determined from the signal-flow graph.     

空地电视制导导弹作战使用研究

研究空地电视制导导弹的作战使用,包括电视跟踪方式和电视导引头作用距离的影响因素,有利于更好地制定使用该种武器的战术,充分发挥其作战效能。通过ADC法建立的空地导弹的作战效能评估模型表明,与高炮相比,地空导弹的拦截是导弹的主要威胁,选择合适的导弹巡航高度,可以明显改善导弹的安全性能,对于提高空地电视制导导弹的作战效能提供了一种新思路。     

兵力需求的运作机理研究

兵力需求的影响因素有很多,研究这些因素之间的关系及对兵力需求的影响是一个新的课题.提出了兵力需求运作机理的研究框架,在此基础上,依照辨析关键因素、分析因果关系、评价相互影响、分析计算结果的研究步骤,采用因果关系图、层次分析法(AHP)、网络分析法(ANP)等方法,结合实例对具体问题进行了详细分析.通过研究,得出了影响兵力需求的关键因素之间的量化关系,结论具有一定的科学性.     

Refractive index of GaAs-AlAs superlattice grown by MBE

Refractive index ˉn of GaAs-AlAs superlattices grown by MBE is measured in the spectral range 1.2–1.8 eV at 300 K. Results show that for superlattices with L_B ≤ 40–50 ?, ˉn is determined by the averaged AlAs mole fraction, but that for superlattices with L_B ≥ 40–50 ?, ˉn is determined by energy separation of confined electrons and holes (E₁(e-hh)).     

直升机武器系统作战精度研究及仿真

通过对影响作战飞机的各种误差进行仿真计算,从理论上分析了各种误差因素对整个火控系统精度的影响,提出了控制误差应主要控制的参数,为整个飞机系统的设计和误差分配提供了理论依据。     

On some aspects of the high-frequency performance of operational amplifiers and current-to-voltage converters

The standard monolithic operational amplifier current-to-voltage converter will show underdamped second-order response to step inputs. This is not discussed in standard texts. It is shown that the transfer function of the amplifier must be treated as a complex variable in order to understand the response and to apply correct compensation. The response of commercial operational amplifiers is shown to fall into two categories: those which may be easily compensated and those which cannot be satisfactorily compensated.     

Specification of interval tolerances by the mapping method

This study dealt with peculiarities of specifying the rated tolerances under conditions of the interval parameter distribution law and the variation of element properties during the operation of radioelectronic devices. This paper took into account nonlinear properties of the boundaries of the workability region, interval coefficients of external inputs and the most unfavorable combination of external factors at the mounting place of radio components. The boundary operating value or the width of the operating interval of the output function has been specified and the algorithms have been used for optimizing the interval tolerances.     

Optical bandwidth and fabrication tolerances of multimodeinterference couplers

Analytical expressions are derived which relate the optical bandwidth and the fabrication tolerances of multimode interference (MMI) couplers to their most important design parameters. These expressions compare adequately with mode analysis simulations. For strong guided structures, the optical bandwidth is shown to he inversely proportional to the number of input and output ports N and to the length of the device. The fabrication tolerances are independent of N and proportional to the output channel separation D. Measurements on MMI couplers in InP/InGaAsP corroborate the theoretical predictions     

考虑天气因素的飞机作战效能对数模型

近来世界范围内的几场战争表明,现代高科技条件下的战争中,由于大量精确制导武器的应用,战争的进程更加依赖于天气.为了满足在天气因素影响下的飞机作战效能评估需要,阐述了天气对作战效能的显著影响,将天气因素引入到效能评估的对数模型当中.为保持模型的简洁性,采用系数修正法,结合雷达波、红外线、激光在各种天气条件下的传播特性,对相关参数进行了天气修正,使对数模型的适用范围更加广泛.评估结果显示,天气对飞机作战效能影响显著,考虑天气因素之后的作战效能评估结果更能反映客观实际.     

On fault tolerance in manufacturing systems

The physical and control structure of manufacturing systems is described, and a hierarchical model for supporting fault tolerance is proposed. The main advantage of the model is that it allows different fault tolerance and recovery techniques to be used in different segments of the network. To help in the choice of specific techniques in particular network segments, a set of metrics to evaluate fault tolerance techniques is presented along with preliminary ideas about integrating the different techniques. Design issues in applying the model to a given manufacturing system are discussed     

试论手工雪茄卷制工厂的智能制造改造

智能制造已经成为全球性的制造业进步的风潮,手卷雪茄的加工周期长,手工工艺复杂,手工作业很难被机械化替代。在手卷雪茄如何实现智能制造,制造的柔性、订单的响应及时性、人力调度优化和生产计划的科学性如何保证,是一个有行业代表性的命题。利用CPS概念,全面规划和改造雪茄烟的智能制造实践,通过物料标识全面应用物联网采集,实现手工为主的作业的数字化车间和数字化工厂。     

Dispersion and modulation of the linear optical properties of GaAs-AlAs superlattice waveguides using quantum-well intermixing

We report on the large modulation of the optical properties of a 14:14 monolayer GaAs-AlAs superlattice waveguide following quantum-well intermixing. Low-temperature photoluminescence measurements illustrate a large 169-meV differential blue-shift obtained between the disordering-suppressed and disordering-enhanced materials. Effective index measurements are presented as a function of polarization, for both the as-grown and disordered material for near-bandedge and half-bandedge wavelengths, which is the wavelength range 775-1550 nm. The largest effective refractive index shift observed was 9/spl times/10/sup -2/ which exceeds that previously reported for disordered AlGaAs ternary multilayer structures, and illustrates the potential of the superlattice for the fabrication of etch-free, planar optical components with large index contrast.     

Surface roughness and tolerances in model scattering experiments

A problem of importance in model scattering work is the extent to which requirements on tolerance and surface finish can be relaxed before affecting the accuracy of measured scattering data. The consequences of minor shape perturbations are examined by considering several different types of scattering contribution, and a brief discussion of roughness is presented. The results are translated into criteria on tolerance and surface finish and it is concluded that accuracies of10^{-3}of a wavelength should be sufficient for all practical purposes. Some experimental data on spheres and cone-spheres of varying degrees of roughness are presented for comparison.     

Effect of tolerances on the performance of microstrip parallel-coupled bandpass filters

The response of microstrip parallel-coupled bandpass filters has been calculated, and the effect of the tolerances on a microstrip realisation on the response given. It is shown that the substrate thickness and the relative electrical lengths of each section are the most critical. A method of compensating for the reduction in bandwidth due to losses is also described.     

On the design of highly linear CMOS digitally programmable operational transconductance amplifiers for low and high-frequency applications

This paper proposes a novel highly linear digitally programmable fully differential operational transconductance amplifier (DPOTA) circuit. Two versions of the proposed DPOTA structure are designed. The first version is optimized for high-frequency operation with current division networks designated to 3-bit control code words. On the other hand, the second version is optimized for low-frequency operation with 4-bit control code words. The third-order harmonic distortion (HD3) of the first DPOTA version remains below ? 66 dB up to 0.4 V differential input voltage at 10 MHz frequency. The second DPOTA version achieved HD3 of ? 70 dB with an amplitude of 20 mV_p–p and at 100 Hz frequency. The proposed circuits are designed and simulated in 90 nm CMOS model, BSIM4 (level 54) under a balanced 1.2 V supply voltage.     

Dispersion-determined limits on production tolerances of single-mode fibres

For single-mode fibres the standard deviation of dispersion at the nominal zero-dispersion wavelength depends strongly on the dispersion slope. For dispersion-shifted fibres, optimum values of the slope as a function of production tolerances on core radius and index difference are found, and for dispersion-flattened fibres maximum allowable production tolerances are given.     

MPLS运营问题的探讨

在A TM 热过之后，M P LS 成为备受关注的网络技术，作者以最终用户、运营商、设备供应商的各自利益为着眼点，探讨了MPLS 的运营前景。