On Some Aspects of the Deligne–Simpson Problem

The Deligne-Simpson problem in the multiplicative version is formulated as follows: give necessary and sufficient conditions for the choice of the conjugacy classes C _j GL(n, ), so that there exist irreducible (p + 1)-tuples of matrices M _j C _j satisfying the equality M ₁ . . . M _p+1 = I.We solve the problem for generic eigenvalues in the case where all the numbers _j,m() of Jordan blocks of a given matrix M _j with a given eigenvalue and of a given size m (taken over all j, , and m) are divisible by d > 1. Generic eigenvalues are defined by explicit algebraic inequalities of the form a 0. For such eigenvalues there exist no reducible (p + 1)-tuples.The matrices M _j are interpreted as monodromy operators of regular linear systems on the Riemann sphere.     

裂变材料中子-伽马脉冲形状甄别几何条件影响的模拟分析

快中子多重性分析技术是当前核材料衡算领域的热门研究方向。针对中子伽马脉冲形状甄别的效果在探测距离很近时明显变差的实验现象展开了研究。使用GEANT4工具箱模拟了液体闪烁体探测器测量裂变中子伽马的粒子输运过程,并基于计算机模拟数据分析了使用BC-501A液体闪烁体探测器测量裂变中子时,裂变物质与探测器的距离(几何效率)对中子-伽马甄别效果的影响。分析的结果与实验现象相符,表明在基于液体闪烁体探测器的核材料属性测量中,若单个探头的探测效率较高,裂变中子伽马脉冲叠加会严重影响甄别结果和测量计数。     

Numerical and experimental studies on the flow multiplicity phenomenon for gas-solids two-phase flows in CFB risers

The flow multiplicity phenomenon in circulating fluidized bed (CFB) risers, i.e. under the same superficial gas velocity and solids circulation rate, the CFB risers may sometimes exhibit multiple flow structures, was numerically and experimentally investigated in this study. To investigate the flow multiplicity phenomenon, the experiments of gas-solids two-phase flows in a 2-D CFB riser with different flow profiles at the inlet of the CFB riser were conducted. Specially designed gas inlet distributors with add-ons are used to generate different flow profiles at the inlet of the CFB rise. The CFD model using Eulerian-Eulerian approach with k-ε turbulence model for each phase was employed to numerically analyze the flow multiplicity phenomenon. It is experimentally and numerically proved that for gas-solids two-phase flows, the flow profiles in the fully-developed region are dominated by the flow profiles at the inlet. The solids concentration profile is closely coupled with the velocity profile, and the inlet solids concentration and velocity profiles can largely influence the fully-developed solids concentration and velocity profiles.     

GSM网络PDCH承载效率提升对用户感知影响的分析

数据业务的发展需要我们不断提高GSM PDCH信道的承载效率,但同时如何保障用户的业务感知,已是一个重要的焦点问题。本文基于现网实测数据和理论分析,分别得出了PDCH承载效率提升对话音和数据用户感知的影响;并进一步给出了工程配置的建议门限值。     

中走丝线切割多次切割跟踪式喷射流装置

随着模具加工技术迅速发展的需要及零件加工精度的不断提高,对中走丝线切割机床的加工精度和表面粗糙度提出了更高的要求.该文通过查阅相关资料和对一些重要资料进行研究和整理后设计实现了一种利用AT89C52单片机、金属传感器、步进电机以及滚珠丝杠组成的中走丝线切割多次切割跟踪式喷射流装置.该装置研究通过动态跟踪控制装置有效地控制工作液喷射压力和高度,以增强冷却和排屑效果,降低工件的表面粗糙度,进而提高工件的切割精度和切割效率.通过实际生产应用后表明,该跟踪式喷射流装置对提高零件的加工精度和切割效率具有很强的实用性.     

Child care effects in context: Quality, stability, and multiplicity in nonmaternal child care arrangements during the first 15 months of life.

Main and interactive effects of child care quality, stability, and multiplicity on infants' attachment security, language comprehension, language production, and cognitive development at 15 months were examined using data from the National Institute of Child Health and Human Development (NICHD) Study of Early Child Care. Thirty-nine percent of the infants in this sample experienced arrangement change, and 46% experienced multiple concurrent arrangements during the first 15 months. As in previous studies, concurrent quality, average quality, and quality slope significantly predicted cognitive and language development. There was some evidence that certain forms of unstable child care--including nonfamilial change, familial to nonfamilial change, and within-home to out-of-home change--were associated with poorer language development. Multiple child care arrangements involving family members positively predicted language comprehension; multiple care involving a mix of family and nonrelative caregivers negatively predicted language comprehension. Interactions among variables exhibited "effects in context." That is, under conditions of low or moderate quality in the primary care arrangement, the use of fewer multiple arrangements was associated with higher language scores; under conditions of high primary care quality, the use of more multiple arrangements was associated with higher language scores. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Designing multimedia learning environments using animated pedagogical agents: factors and issues

Animated pedagogical agents (APAs) are known to possess great potential in supporting learning because of their ability to simulate a real classroom learning environment. But research in this area has produced mixed results. The reason for this remains puzzling. This paper is written with two purposes: (1) to examine some recent research and organize the findings in terms of classroom characteristics, and (2) to discuss and reveal any uncovered issues pertaining to the findings and provide input whenever possible. A framework formed by using APA characteristics, APA presentation, and learners' characteristics is used to analyse past research findings. The findings from the analysis reveal that because APAs are regarded as social members similar to humans, they are more effective in engaging learners in environments that require social communication and interactions. They therefore produce more definitive results in terms of affective gain and group learning. But such conditions also impose greater demand on designers to create more complex learning environments that can provide interactions with several agents and yet maintain a mode of communication that is pedagogically effective. The challenges for creating such environment include using an agent's gestures to duplicate its speech in instruction, which is usually uncommon in human practice, overcoming the needs to use input–output interface for communication and taking into consideration the possible influence of the learners' characteristics such as their sensory preference. This paper suggests that APAs' application in instruction should be seen in the light of affordances and be designed within its own practical limits.     

r重正交小波的构造

首先引入r重正交小波和多尺度分析的概念，然后讨论了r重多尺度分析中闭线性子空间和尺度函数的性质，最后在最一般的情况下，给出了r重正交小波的存在性证明。     

三维三分量地震勘探观测系统设计方法

在地震勘察中，观测系统设计至关重要，本文针对转换波传播的特点，介绍了转换波最小炮检距、最大 检距和道间距的确定方法，采用常规面元尺寸对转换波覆盖次数进行了计算、分析，结果表明常规纵波面元尺寸不适合转换波，转换波面元尺寸与速度比值有关，通过分析发现，转换波覆盖次数的均匀性还受到炮点与检波点相对位置关系的影响，炮点位于接收线束两端时的覆盖次数要比炮点位于接收线束中间的覆盖次数更为均匀，在观测系统设计过程中还要考虑方位角、炮检距等分布规律的影响。