基于倒谱的非最小相位FIR系统自适应辨识

本文介绍了一种在高阶谱一维切片的基础上利用倒谱进行非最小相位FIR系统自适应辨识的算法。这一算法具有计算量小，不需要预先假定系统阶次的特点，而且能够自适应地分别辨识出非最小相位FIR系统的最小相位部分和最大相位部分的冲激响应，同时，系统阶次可以在自适应过程中确定。另外由于本算法利用观测信号的高阶级计量进行系统辨识，所以很好地抑制了高斯有色噪声对辨识结果的影响。数值仿真结果证明了本算法的有效性。     

一种符合EPC C1G2标准的RFID随机化密钥双向认证协议

RFID系统已广泛地应用于自动识别领域等,但RFID系统也给使用者的隐私和安全带来新的威胁.现有已提出的安全协议方案,基本上都存在着某种安全隐患或不符合EPC ClG2(electronicproduct code class1 generation2)标准要求,无法成为实际可用的RFID系统安全机制,本文在介绍了两种符合EPC ClG2标准的安全协议并分析其存在的弱点后,提出一种新的设计方案--随机化密钥双向认证协议,并分析其安全性能.     

高斯ARMA噪声中非因果非最小相位系统的辨识

本文研究在加性高斯有色噪声背景下，非因果非最小相位系统的辨识问题，提出了一种三步辨识方法。数值仿真例子证明了本文所提出方法的高分辨率性能。     

Frequency domain blind MIMO system identification based on second and higher order statistics

We present a novel frequency-domain framework for the identification of a multiple-input multiple-output (MIMO) system driven by white, mutually independent, unobservable inputs. The system frequency response is obtained based on singular value decomposition (SVD) of a matrix constructed based on the power-spectrum and slices of polyspectra of the system output. By appropriately selecting the polyspectra slices, we can create a set of such matrices, each of which could independently yield the solution, of they could all be combined in a joint diagonalization scheme to yield a solution with improved statistical performance. The freedom to select the polyspectra slices allows us to bypass the frequency-dependent permutation ambiguity that is usually associated with frequency domain SVD, while at the same time allows us compute and cancel the phase ambiguity. An asymptotic consistency analysis of the system magnitude response estimate is performed     

眼镜框架用316L不锈钢丝性能不均及模压缺陷

对企业生产的眼镜框架用316L不锈钢丝试样的微观组织、表面缺陷及夹杂物进行观察,对试样力学性能进行测试,分析模压前钢丝的头尾部性能异常以及模压后产品的表面缺陷成因。结果表明：钢丝头部试样的抗拉强度在700 MPa左右,规定塑性延伸强度为300 MPa,伸长率接近50%,而尾部试样的抗拉强度达到了900 MPa,规定塑性延伸强度达到700 MPa,伸长率在20%左右。性能差异是由于,退火初期钢丝走线速度较慢,退火过程中提高了走线速度,因而尾部钢丝退火时间较短,同时退火温度变低,使得尾部钢丝的组织内应力未完全消除,导致其强度较高,塑性较差。对模压变形后缺陷钢丝的分析表明：不合格试样的组织分布不均匀,晶粒尺寸达到29.7 μm,合格试样的晶粒尺寸为20.9 μm;不合格试样表面存在暗灰色的夹杂物,EDS分析表明,夹杂物为钙基硅酸盐及硫化物,夹杂物处容易发生点蚀,从而形成凹坑、牙齿印等缺陷。     

Categorization and communication in the face of prejudice: When describing perceptions changes what is perceived.

In the face of prejudice against an ingroup, common ground for communication exists when people use similar social categories to understand the situation. Three studies tested the hypothesis that describing perceptions of prejudice can fundamentally change those perceptions because communicators account for the common ground in line with conversational norms. When women (Study 1), African Americans (Study 2), and Americans (Study 3) simply thought about suspected prejudice against their ingroup, categorization guided their perceptions: Participants assimilated their views of the prejudiced event toward the perceptions of ingroup members but contrasted away from the perceptions of outgroup members. Conversely, when participants described their perceptions, they contrasted away from the given category information and actually arrived at the opposite perceptions as those who merely thought about the prejudiced event. Study 3 identified an important qualification of these effects by showing that they were obtained only when participants could assume their audience was familiar with the common ground. Implications are discussed for understanding the role of communication in facilitating and inhibiting collective action about prejudice. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Validity of personnel decisions: A conceptual analysis of the inferential and evidential bases.

Issues common to both the process of building psychological theories and validating personnel decisions are examined. Inferences linking psychological constructs and operational measures of constructs are organized into a conceptual framework, and validation is characterized as the process of accumulating various forms of judgmental and empirical evidence to support these inferences. The traditional concepts of construct-, and content-, and criterion-related validity are unified within this framework. This unified view of validity is then contrasted with more conventional views (e.g., Uniform Guidelines, 1978), and misconceptions about the validation of employment tests are examined. Next, the process of validating predictor constructs is extended to delineate the critical inferences unique to validating performance criteria. Finally, an agenda for programmatic personnel selection research is described, emphasizing a shift in the behavioral scientist's role in the personnel selection process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

面向对象设计中的O/R映射架构

O／R映射是当前基于关系型数据库应用的面向对象系统设计中的新问题,关系型数据库在一定程度上制约了应用系统面向对象设计的架构和灵活性。文中结合已有应用设计架构提出改进的缓冲工作元(Cache Worker)架构,用它可以在兼顾性能的基础上屏蔽关系型数据存储方式给面向对象系统设计带来的障碍,给系统设计更大的灵括性。     

Evaluation of two stormwater infiltration trenches in central Copenhagen after 15 years of operation

Two stormwater infiltration trenches were installed in 1993 in an area in central Copenhagen. The system was monitored continuously for almost three years after establishment, and a small reduction in performance over that time, possibly due to clogging, was noted. A new study was conducted in 2009 to see whether the reduction in performance has continued and to determine how the system performs today. Water levels in the trenches were monitored for almost 4 months, and from this period seven events were selected to analyse the infiltration rate. A comparison with similar analyses on storm sequences from the first 3 years of operation shows that the infiltration has decreased since the establishment of the system 15 years ago. The decrease is statistically significant (p<0.01). A clogging model was fitted to the data and predictions were made for future performance. The results show that the system will discharge around 10 times more annual overflow to the sewers after 100 years of operation compared to the initial volumes, if clogging continues at current rates. This corresponds to 60% of the total runoff from the area. The results show that clogging and proper maintenance are important factors to consider when implementing stormwater infiltration trenches.     

气井泡排后气液分离不充分分析及措施研究

目前靖边气田在未采取泡沫排水采气措施的情况下,集气站气液分离状况良好,脱水撬运行平稳。但采取泡沫排水采气措施后,相应站内气液分离不够充分,严重影响脱水撬的高效、平稳运行。分析气液分离不充分的原因,并确定气液高效分离的措施对于提高靖边气田的开发具有重要意义。本文通过对生产动态与起泡剂和消泡剂作用特点的分析研究,以及对携液流动时间和破泡时间的分析计算,结合对丝网捕雾器液泛速度的分析,找到了气液分离不充分的原因:产量的波动导致携带泡沫液的天然气从进站加入消泡剂到进入分离器入口前的流动时间短于消泡剂的破泡时间,致使泡沫在破泡不够充分的情况下就进入了分离器;泡排后地层水变为泡沫液,密度大为降低,而破泡不充分使相对较多的残余液沫进入分离器中的丝网捕雾器,大幅降低了丝网的波泛速度,致使液沫容易被气流二次夹带。在对现场实际情况分析的基础上,提出了在泡沫排水采气措施后提高气液分离效率的措施与建议。