Optimization of output and phosphor consumption for phosphor-converted white light-emitting diodes

Using ray-tracing simulation based on Monte Carlo method, the effects of phosphor concentration and thickness on light output and phosphor consumption of pcwLEDs were investigated in this work. The simulation was improved to comprehensively imitate the whole optical process of pc-wLEDs, including total produce of chip and phosphor light, losses in the propagation, and output.Experiments were conducted to verify the simulation.Results show that, light output changes non-monotonously over phosphor concentration and thickness, having maximum value. Experimental maximum light efficiency of158 lmáW-1was obtained at concentration of 16 wt%, 6 %higher than that of 11 wt% and 17 % higher than that of 33wt%. Phosphor consumption of pc-wLEDs increases linearly with the increase of phosphor concentration and the decrease of thickness. Experimental phosphor consumption of pc-wLEDs with concentration of 11 wt% is only 37 %of that of 33 wt%.     

基于SBM模型的中国省际全要素能源效率和污染排放效率研究

本文使用处理非期望产出的SBM模型，利用2001．2010年省际面板数据计算中国30省份的能源效率和污染排放效率及影响因素。研究结果表明，中国整体的能源效率和排放效率均在低位运行，有下滑趋势，且排放效率表现相对低落。随着时间推移，各省份和全国的能源效率和排放效率差距也有扩大趋势。整个研究期间，北京、上海、广东、海南等四地的能源效率和排放效率值均为1，实现了资源节约、环境友好的双赢局面，其他地区在节能减排上仍存在程度不一的改善空间。Tobit模型的回归结果表明，第二产业比重越高，越不利于提高各省能源效率和排放效率；政府影响力对各省能源效率和排放效率的影响为负值；贸易依存度、人口密度对各省能源效率和排放效率有正向显著影响。最后，本文提出了有关政策建议。     

Equation error versus output error methods

Abstract

For the identification of linear processes on the basis of ARX-models, equation error least squares (EELS) (often indicated as the one step ahead prediction error method) is frequently used rather than output error least squares (OELS). This is mainly because the minimum of the convex EE-criterion can easily be found, in contrast to the OE-criterion, which often displays multiple local minima. Both methods lead to the correct parameter values when the system is in the model set chosen. But in many practical situations, such as human behaviour, the real process under study will be of infinite order causing essentially different models to be found from either EE or OE criteria. Various aspects of these differences are analysed in this study. Much attention has been paid to the performance of a simulation based on a model estimated with an EELS. This simulation performance can be predicted and bounds can be given without executing the simulation itself. Furthermore the simulation performance is very poor for systems where the energy in the initial impulse response samples is very small compared with the energy in the remainder of the response. For these systems an equation error estimate cannot even provide a proper initial guess for an OELS minimization algorithm. Examples are presented that illustrate this effect.     

Actuators and regional boundary controllability of parabolic systems

The purpose of this paper is to explore the boundary regional controllability concept in connection with the choice of actuators. First, we give a definition and some properties of this concept, then we concentrate on the determination of control achieving boundary regional controllability with minimum energy. We also give an important approach that leads to numerical implementation for the computation of the optimal control.     

中国稀土永磁材料的发展现状及前景

综述了我国主要稀土永磁材料主产的原料、生产工艺、设备、产量及质量的发展。介绍了该材料的应用及在国内外市场的销售进展状况，并针对我国目前稀土永磁材料的现状提出了一些建议。     

Performance of the Zero Forcing precoding MIMO broadcast systems with channel estimation errors

In this paper, the effect of channel estimation errors upon the Zero Forcing (ZF) precoding Multiple Input Multiple Output Broadcast (MIMO BC) systems was studied. Based on the two kinds of Gaussian estimation error models, the performance analysis is conducted under different power allocation strategies. Analysis and simulation show that if the covariance of channel estimation errors is independent of the received Signal to Noise Ratio (SNR), imperfect channel knowledge deteriorates the sum capacity and the Bit Error Rate (BER) performance severely. However, under the situation of orthogonal training and the Minimum Mean Square Error (MMSE) channel estimation, the sum ca- pacity and BER performance are consistent with those of the perfect Channel State Information (CSI) with only a performance degradation.     

控制方向未知的非线性系统的自适应输出跟踪控制

针对一类含有未知控制方向和时变不确定性的本质非线性系统,应用Nussbaum-type增益技术和Adding a power integrator递推设计方法,设计了一种鲁棒自适应状态反馈拉制器．所设计的控制器能保证闭环系统所有信号全局一致有界,特别是通过适当调整控制器设计参数,可使输出跟踪误差在有限时间后变得适当小．最后通过仿真实例对算法进行验证.     

线性离散切换系统的输出调节问题

利用多Lyapunov函数方法,研究线性离散切换系统的输出调节问题．在假定每个子系统都不是输出调节问题可解的条件下,分别给出了在全息反馈控制器和误差反馈控制器作用下,这类系统输出调节问题可解的两个充分条件．同时还分别给出了相应的切换律和控制器的设计方案．最后的仿真例子进一步表明了结论的有效性．     

A comparative analysis of China and other countries in metabolic engineering: Output,impact and collaboration

In recent years, metabolic engineering has made great progress in both academic research and industrial applications. However, we have not found any articles that specifically analyze the current state of metabolic engineering in China in comparison with other countries. Here, we review the current development and future trends of global metabolic engineering, conduct an in-depth benchmarking analysis of the development situation of China’s metabolic engineering, and identify current problems as well as future trends. We searched publications in the Scopus database from 2015 to September 2020 in the field of metabolic engineering, and analyzed the output in general, including publication trends, research distribution, popular journals, hot topics and vital institutions, but also analyzed the share of citations, field-weighted citation impact, and production in collaboration with strategic countries in science and technology. This study aims to serve as a reference for later studies, offering a comprehensive view of China’s contribution to metabolic engineering, and as a tool for the elaboration of national public policy in science and technology.     

一种产量预测新方法的研究及探讨

油田产量预测在油田长远开发规划中起着至关重要的作用。以Arps递减曲线及历年新井产量组成为基础,首次建立了产量预测新模型——无因次产量组成递减率法作为产量预测的新方法,即以各年老井、新井无因次产量递减率分别作为老井、新井规划产量递减率的依据,进而达到预测老井及新井产量的目的。为验证该方法的科学合理性,将其应用于辽河油区某油田“十一五”规划中,并与典型的常规预测方法对比分析,得到了较为满意的结果。