Asynchronous cooperative communication systems:A survey on signal designs

Cooperative communications is a promising technique for future high speed wireless communications.These systems may be formulated as virtual multi-input multi-output (MIMO) systems where spatial/cooperetive diversity is a key advantage. However,different from MIMO systems,one of the major chal- lenges for cooperative communications systems is that the cooperative transmissions in cooperative systems may be neither time nor frequency synchronized,since the transmissions are from multiple cooperative nodes at...     

射频板条CO2激光器整形光路自适应调节研究

为了解决射频板条CO2激光器因安装或腔镜热畸变造成的光路偏移问题,采用外光路偏移补偿的方法对其进行校正。研究了基于压电陶瓷的偏移补偿装置,设计了压电陶瓷驱动电路,并分析了控制精度和自适应控制方法。结果表明,通过偏移补偿装置,激光输出功率在任何占空比下均可达到或超过标准参考功率值,并通过对比有无自适应调节,激光输出功率最大相差100W,且可保持激光输出功率在2h运行中波动小于2%。此项研究可保证激光器高效运行,提高激光器的输出功率和模式的稳定性,具有较大的实用价值。     

Irrelevance of interface defects to heterojunction band offsets

We present a photoemission measurement of the valence band discontinuity, ΔE_v, and the Fermi level, E_F, position at the interface between different surface reconstructions of GaAs(100) and Ge. GaAs(100) exhibits a number of surface reconstructions that differ in their As content and bonding configuration. The initial and final Fermi level position is observed to move toward the conduction band as the As content of the starting surface increases. The observed change in the final E_F due to the variation in surface As content is 0.3 eV. The band offsets are the same (0.46±0.05) regardless of the starting surface. The addition of As during the interface formation causes the Fermi level position to further move toward the conduction bands of Ge and GaAs; however, it doesnot change the band offsets. We conclude that deposition-induced defects do not occur in sufficient density across the interface to play a primary role in determining the GaAs/Ge(100) heterojunction potential step.     

频偏稳健的分级调制分类算法

通过对观测样本进行非线性变换,提出了一种基于高阶累积量分级调制分类算法,有效解决了频偏引起的相位旋转问题.仿真表明,在归一化频偏小于0.2时,算法具有较好的分类性能.理论分析和仿真结果均证明了算法的正确性和有效性.     

零内错回采巷道围岩变形机理及控制研究

针对大同四台矿14#煤层81005工作面回采巷道支护问题,从实际地质条件出发,进行了场论分析。研究了近距离煤层零内错回采巷道围岩变形的影响因素,结合FLAC数值模拟,得出了较为合理的巷道支护方案,以工业性实验进行了验证,取得了较好的成果,为确定近距离煤层零内错回采巷道支护方案的选择提供了强有力的支撑手段。     

CMOS运算放大器失调电压消除设计

基于直流对称偏置技术、版图的对称布局布线和先进的CMOS工艺技术。文中设计了一种低失调电压的高性能运算放大器。测试结果表明,在负载电容100 pF和电阻10 kΩ的情况下,最大失调电压＜2 mV;开环增益为98 dB;单位增益带宽达到10.4 MHz;相位裕度为55°;电源抑制比为-87 dB。该电路可广泛用于高性能数模混合电路、高性能模拟、计算、控制等系统中。     

Verification of a Continuous Guidance Procedure of Xenon Oscillation Control

A new method for controlling axial spatial xenon oscillations in large PWRs has been proved to be effective. The method is based on two additional newly defined axial offsets, AOi and AOX together with the conventional axial offset of power distribution AOp. AOi and AOx are the axial offsets of power distributions which would give the current iodine and xenon distributions under equilibrium conditions, respectively. Further efforts have been continued to establish a new control concept which can give continuous and clear guidance on a display to the operator for xenon oscillation control. The new concept uses information from AOi, AOx and AOp to display the trajectory of (AOp-AOx, AOi-AOx) in the X-Y plane. The trajectory shows a very characteristic behavior. With these simple characteristics in mind the xenon oscillation can be controlled quite easily. In other words, to eliminate the xenon oscillation, we watch the trajectory and use the control rods to lead the plot to the origin where three AOs are identical.

Verification of the concept was carried out based on the full record of the axial offset during a xenon oscillation in an actual reactor and good results were obtained.     

Optimal Control Timing Search of Xenon Oscillations in Large PWRs Using a Characteristic Ellipse Trajectory Based on Three Axial Offsets

We have proposed a simplified control procedure for axial xenon oscillations in large PWRs based on a characteristic ellipse trajectory method. However, this procedure cannot guarantee that the desired control rod position can be achieved when the xenon oscillation is terminated. In a previous paper, we proposed an innovative and very simple procedure to generate the trajectory for the predicted oscillation behavior, which can be expressed by trigonometric functions multiplied by an exponential function. By using this prediction capability, it is shown that the optimal control timing can be easily determined to terminate the xenon oscillation at the desired control rod position. The optimal timing is obtained at the intersection or, cross point, of two predicted trajectories, the forward trajectory beginning from the current position and the backward trajectory that is generated based on the desired control rod position. Since the trajectories are calculated by simple trigonometric functions and an exponential function, the prediction takes only a few seconds using a PC.     

Integrating carbon market uncertainties into a sustainable manufacturing investment decision: a Bayesian NPV approach

Net present value (NPV) is a widely used technique in capital budgeting. In this paper, we develop a Bayesian NPV framework using a Gibbs sampler. This approach allows decision-makers to integrate their knowledge, past experience, and uncertain and volatile cash flows from carbon emissions credits into decisions dealing with energy efficient, sustainable manufacturing equipment. The results indicate NPV is highly dependent on the nature of volatility and uncertainty of the cash flows. Without inclusion of this information through the Bayesian framework results, NPV becomes overstated, and thus it may provide biased guidance for the investment. The results developed in this paper further show that the frequency of very high and low cash flows and to a lesser degree their variability adversely impacts NPV. The results may also explain reasons for the economic phenomenon known as the energy efficiency gap.