权数的评估和控制研究

用样本推断总体,权数的作用十分重要。通过权数,不仅能将样本还原到总体,还能调整样本的结构,从而提高估计的精度。但权数也是把双刃剑,如果调整后的权数差异过大有可能增大样本量的方差。本文从权数控制的角度出发,利用权效应对主观截取和计算截取两种权数控制方法进行对比研究。最后得出,主观截取对权数的控制要稍优于计算截取的效率,并且得出若采用主观截取、计算截取的方法,?(28)0.05、?(28)0.95可分别作为一般的分割点。

权数在人口抽样调查估计中的应用研究

很多全国性大型人口抽样调查项目中的核心技术包括抽样方案设计、样本单元的权数计算等。用样本数据推断总体,权数的作用很关键,尤其是抽样调查越来越难保证做到等概率抽样的情况。为此,采用第四次中国城乡老年人生活状况抽样调查中的具体调查方案和实际调查数据,系统地对抽样过程中的权数进行测算,同时根据权效应对权数进行调整和控制,利用刀切法对相关统计量的标准误差和变异系数进行对比分析,来验证权数控制在提高精度方面的有效性。结合老年人生活状况的调查数据进行实证分析,结果表明,利用刀切法计算权数截取的标准误差比未调整权数的标准误差更有效,得到变量的变异系数更小。

Model predictive flux control of permanent magnet synchronous motor driven by three-level inverter based on fine-division strategy

Aiming at the difficulty of setting the weight coefficient in the value function of model predictive torque control(MPTC)for permanent magnet synchronous motor(PMSM)driven by three-level inverter,a fine-division model predictive flux control(MPFC)method is proposed.First,establish a mathematical model between the motor torque and the stator flux linkage according to the mathematical equations of PMSM.Thus,the control of the motor torque and stator flux linkage in the MPTC is transformed into the control of a single stator flux linkage vector,omitting the cumbersome weight setting process in the traditional MPTC.The midpoint potential control strategy is proposed,which uses the characteristics of redundant small vectors to balance the midpoint potential.After that,a fine-division strategy is proposed,which effectively reduces the number of candidate vectors and the computational burden of the system.Finally,the proposed MPFC is compared with MPTC by simulation.The results show that the proposed fine-division MPFC effectively reduces the system calculation,and has the advantages of simple principle and better dynamic and steady-state control performance.The feasibility of the control strategy is verified.

Control Valve with a Constant Inner Authority Value

The aim of the article is to propose the method of designing double regulation control valves used in heating installations, allowing to obtain a constant value of the so-called inner authority and thus the constancy of the valve control characteristic, regardless of the pre-setting value set on the valve. The shape of the valve's regulation characteristics is one of the main factors determining the quality of the quantitative regulation, and thus the stability of the system's operation and overall operating costs. For this reason, the issue discussed in the article is important and can be applied in practical implementations of the valve sizing and the valve selection. The analysis was based on the relations binding the hydraulic resistances occurring inside the control valve, and the corresponding flow factors, using original author's proposal. The experimental verification was performed on a special measuring stand prepared for this purpose, measuring the values of the medium volume flow at a constant differential pressure, and then the results were converted into values of the flow factor, used in the proposed mathematical model. The results confirm the thesis put forward and the proposed mathematical model. High convergence of the results of experimental verification with the proposed mathematical model was obtained.

Network approach to understanding the organization of and the consequence of targeted leader removal on an end-oriented task

Relocation is an important event in the lives of several social insects whereby all colony members have to be transferred to a new nest when conditions in the old nest become unfavorable. In the current study, network tools were used to examine the organization of this goal-oriented task in the Indian queenless ant Diacamma indicum Which relocate their colonies by means of tandem running. Individual ants were used as nodes and tandem runs as directed edges to construct unweighted networks. Network parameters were characterized in control relocations （CRs） and in relocations where the node with the highest outdegree, that is, the Maximum tandem leader （Max TL） was experimentally removed. These were then compared to 1） randomized networks, 2） simu- lated networks in which Max TL was removed, and 3） simulated networks with removal of a random leader. Not only was there complete recovery of the task, but the manner in which it was organized when Max TL was removed was comparable to CRs. The results obtained from our empirical study were significantly different from the results predicted by simulations of leader removal. At an individual level, the Max TL had a significantly higher outdegree than expected by chance alone and in her absence the substitute Max TL did comparable work. In addition, the position of the Max TL in the pathway of information flow was conserved in control and experimentally manipulated conditions. Understanding the organization of this critical event as more than the sum of individual interactions using network parameters allows us to appreciate the dynamic response of groups to perturbations.

Watermarking Data Cubes

We propose a robust watermarking scheme and several extensions for digital right management of data cubes.The ownership information is hidden into a data cube by modifying a set of selected cell values.Its owner can use his private key to control all the watermarking parameters freely.Neither original data cube nor the watermark is required in watermark detection.Detailed analysis and extensive experiments are conducted for the proposed schemes in terms of watermark detectability,robustness and efficiency.Our results show that the scheme performs well in actual applications.