Nonlinear analysis of nuclear coupled density wave instability in time domain for a boiling water reactor core undergoing core-wide and regional modes of oscillations

The objective of the paper is to develop a nuclear coupled thermal-hydraulic model in order to simulate core-wide (in-phase) and regional (out-of-phase) stability analysis in time domain within the limitation of desktop research facility for a boiling water reactor subjected to operational transients. The integrated numerical tool, which is a combination of thermal-hydraulic, neutronic and fuel heat conduction models, is used to analyze a complete boiling water reactor core taking into account the strong nonlinear coupling between the core neutron dynamics and primary circuit thermal-hydraulics via the void-temperature reactivity feedback effects. The integrated model is validated against standard benchmark and published results. Finally, the model is used for various parametric studies and a number of numerical simulations are carried out to investigate core-wide and regional instabilities of the boiling water reactor core with and without the neutronic feedback effects. Results show that the inclusion of neutronic feedback effects has an adverse effect on boiling water reactor core by augmenting the instability at lower power for same inlet subcooling during core-wide mode of oscillations, whereas the instability is being suppressed during regional mode of oscillations in presence of the neutronic feedback. Dominance of core-wide instability over regional mode of oscillations is established for the present case of simulations which indicates that the preclusion of the former will automatically prevent the latter at the existing working condition.     

Fatigue behavior of aluminum alloys under biaxial loading

The biaxiality effect, especially the effect of non-singular stress cycling, on the fatigue behavior was studied, employing cruciform specimens of aluminum alloys 1100-H14 and 7075-T651. The specimens, containing a transverse or a 45^o inclined center notch, were subjected to in-phase (IP) or 100% out-of-phase (hereinafter referred to as “out-of-phase or OP”) loading of stress ratio 0.1 in air. The biaxiality ratio λ ranged from 0 to 1.5, and 3 levels of stress were applied. It was observed that: (1) at a given λ, a lower longitudinal stress induced a longer fatigue life under IP and OP loading, and the fatigue life was longer under IP loading, (2) the fatigue crack path profile was influenced by λ, phase angle (0^o or 180^o), and initial center notch (transverse or 45^o inclined); (3) the fatigue crack path profiles, predicted analytically and determined experimentally, had similar features for the specimens with a transverse center notch under IP loading; and (4) the fatigue crack growth rate was lower and the fatigue life longer for a greater λ under IP loading, whereas it changed little with change in λ under OP loading. These results demonstrate that non-singular stress cycling affects the biaxial fatigue behavior of aluminum alloys 1100-H14 and 7065-T651under IP and OP loading.     

一种简易的电机软启动与节能控制装置

利用价廉的集成运算放大器芯片LM324来实现电机软启动与节能运行控制.介绍设计与实现的有关原理控制装置的特点:结构简单,易于工程实现,造价低廉,在功能方面具备基于单片机技术的电机软启动控制装置的相应功能.图5参4     

Joint estimation of carrier frequency offset, dc offset and I/Q imbalance for OFDM systems

Orthogonal frequency division multiplexing (OFDM) systems with direct-conversion receiver (DCR) are vulnerable to carrier frequency offset (CFO), dc offset (DCO) and in-phase/quadrature (I/Q) imbalance. In this paper, we propose blind estimator for joint estimation of CFO, DCO and I/Q imbalance in OFDM systems with DCR. Simulation results show that performance of proposed estimator approaches Cramér-Rao lower bound (CRLB) asymptotically, which demonstrates its effectiveness.     

基于闭环多分配网络重叠的噪声注入校正方法

提出了一种闭环多噪声网络重叠注入的干涉式综合孔径辐射计校正方法,该方法采用多个1?4噪声注入网络闭环重叠来实现1?10噪声注入网络;然后对其鲁棒性分析,分析结果表明在不可分离误差小于1°,正交残余误差小于0.5°,输出测量值随机误差为2%时,通道相位差估计精度不大于2.3°;与开环噪声网络重叠注入法相比,该方法能达到更高的校正精度。     

On the quadrature accuracy of in-phase coupled quadrature LC oscillator

In this article, closed-form equations are proposed for phase and amplitude errors of an in-phase coupled quadrature LC oscillator. First of all, the injected current from coupling network to switching one is analytically calculated in a novel approach. Then, fundamental equations are obtained to derive phase and amplitude errors which are results of mismatches of the tank's inductors, capacitors and resistors. The analysis shows that the LC tank's phase of this oscillator has a negligible deviation from zero that is desirable and causes low phase noise. Also, the study indicates that in-phase coupling of this structure generates an injection current that reduces the output current magnitude. In the following, a mechanism is proposed to compensate the phase error, using intentional mismatch in tail currents. Moreover, In contrast to previous works, there is not a considerable trade-off between phase error and phase noise; meaning phase noise is almost stable while phase error dramatically decreases. Next, Many simulations have been done in TSMC 0.18 μm to evaluate the proposed analytical equations and efficiency of the presented approach. Finally, all of these tests confirm the high accuracy of equations and capability of the mentioned technique.     

Comments on the application of bifurcation analysis in BWR stability analysis

Currently, BWR stability analysis is most often performed by the application of system codes which provide the time evolution of the neutron flux or thermal power at a defined operational point (OP) after imposing a system parameter perturbation. However, in general it is impossible to understand the real stability state of the BWR at a specific OP by the application of system code analysis alone. Hence, we are exploring methods developed in the nonlinear dynamics field in order to reveal the nature of the BWR stability states when power oscillations are observed. A powerful method is bifurcation analysis. In order to motivate this “nonlinear thinking” versus “linear thinking”, in this paper we will demonstrate some examples of phenomena which can only be understood in nonlinear terms by application of bifurcation theory and where linear interpretation leads to incorrect conclusions.     

支持动态联盟的工作流管理及应用

敏捷制造的组织形式为动态联盟,是面向任务而形成的虚拟企业。联盟企业间的工作流管理是企业经营成功的保障和衡量企业敏捷性的重要标志。现分析了动态联盟的特点及其对工作流管理的要求,阐述了一种基于 Ｐｅｔｒｉ 网的工作流模型,并结合定做式人工关节这一个性化产品的需要,组建动态联盟及具体的工作流。     

瞬态阵列电磁脉冲同相合成特性研究

根据电磁理论和光栅方程给出线源天线能量辐射的解析公式,得到波的矢量积分的最大值与阵元数目的平方成正比。并在不同实验条件下测试天线阵列在轴向的电场强度和能量密度,在实验误差范围内可以得出,电场强度与天线单元数成正比,能量密度与天线单元数的平方成正比。这说明瞬态阵列电磁脉冲可以很好的实现同相合成。     

集成运算放大器同相和反相形式的E_n-I_n噪声分析和比较

本文通过分析和比较同相和反相放大器E_n-I_n噪声的特点,给出了若干新结果。本文方法在低噪声运放电路设计和运放噪声参数提取中都具有十分重要的意义。