Fatigue behaviour of precipitation-hardening medium C steels containing Cu

The presence of Cu precipitates counteracts the cyclic softening present in ordinary quenched and tempered steels. This is expected to result in an increase in fatigue limit. The fatigue crack propagation rate (dc/dN) at constant K in the Cu-C steels was shown to depend on heat-treatment and carbon content. To maximize yield strength and minimize ¦da/dN¦_K for tempering at 500° C, one must choose a low C content and temper for a short time; ¦da/dN¦_K in 0.28 wt % C-1.45 wt % Cu tempered for 13 min was one-third that for 0.45 wt % C-1.45 wt% Cu tempered for 200 min. There is also an advantage in adding Cu while simultaneously lowering the Ccontent. The dc/dN data are discussed in terms of the yield strength and the energy to form a unit area of fatigue crack, U, which was measured using foil strain gauges. The quantity (¦dc/dN ¦_{K y} ² U) where _y is the cyclic yield stress, was found to be nearly constant. In the 0.28 wt % C-1.45wt % Cu alloy, short ageing times at 500° C resulted in greater resistance to initiation of cracks at notches for low Ks than long ageing times.     

The Role of the Prefrontal Cortex in the Maintenance of Verbal Working Memory: An Event-Related fMRI Analysis.

Neuroimaging studies have been inconclusive in characterizing the role of the prefrontal cortex (PFC) for maintaining increasingly larger amounts of information in working memory (WM). To address this question, the authors collected event-related functional MRI data while participants performed an item-recognition task in which the number of to-be-remembered letters was parametrically modulated. During maintenance of information in WM, the dorsolateral and the ventrolateral PFC exhibited linearly increasing activation in response to increasing WM load. Prefrontal regions could not be distinguished from one another on the basis of load sensitivity, but the dorsolateral PFC had stronger functional connectivity with the parietal and motor cortex than the ventrolateral PFC. These results suggest an increasingly important role for the PFC in actively maintaining information as the amount of that information increases. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

最佳(F,K,1)光正交码的构造算法研究

(F ,K ,1)光正交码 (OOC’s)是适合于光码分多址 (OCDMA)通信的最佳地址码 ,但成功构造最佳 (F ,K ,1)光正交码十分困难。针对该问题 ,研究了一种构造算法 ,给出了构造该光正交码的具体算法及相应的计算机辅助设计方法。通过该方法可以容易地构造出最佳 (F ,K ,1)光正交码。     

原始计算对电路设计的影响

随着大型阵列型集成电路的飞速发展，电路设计的思想必然随之更新。本文从原始计算方法的角度重新审视了当前计算机技术和电路系统设计技术的发展方向，结合通用化思想和硬件软化及其网络化的发展方向，简述了算法思想对当前电路设计方法的深远影响。     

The Power of the Brown v. Board of Education Decision: Theorizing Threats to Sustainability.

Interviews with African American and White American elders capture the immediate power of the Brown v. Board of Education (1954) decision and the biography of its impact over time. This article reviews the lived experience of the decision and theorizes 3 threats to sustainability that ruthlessly undermined the decision over time: (a) the unacknowledged and enormous sacrifice endured by the African American community in the name of desegregation; b) the violent and relentless resistance to the decision by government officials, educators, and many White community members; and (c) the dramatic shrinkage of the vision of Brown from the dismantling of White supremacy to a technical matter of busing. Implications are drawn for the study of desegregation and for the study of sustainability of social justice more broadly. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

裂解C9预加氢催化剂研制

研制一种新型耐硫、抗胶质镍系加氢催化剂，在固定床液相加氢装置评价催化剂性能，考察催化剂制备方法、载体和助剂种类对裂解C₉馏分加氢性能的影响。结果表明，浸渍法制备的催化剂活性较高，添加稀土分子筛及助剂后的催化剂低温活性更好。在反应器入口温度（60～80） ℃、空速1.5 h^-1、反应压力3.0 MPa和氢油体积比500∶1条件下，对催化剂进行240 h稳定性实验，裂解C₉馏分的双烯值由5.3 g-I₂·（100g）^-1降至约0.60 g-I₂·（100g）^-1，溴值由57.2 g-Br₂·（100g）-^-1降至约25.5 g-Br₂·（100g）^-1，稳定性良好。     

Pilot study of high‐performance air filtration for classroom applications

A study was conducted to investigate the effectiveness of three air purification systems in reducing the exposure of children to air contaminants inside nine classrooms of three Southern California schools. Continuous and integrated measurements were conducted to monitor the indoor and outdoor concentrations of ultrafine particles (UFPs), fine and coarse particulate matter (PM_2.5 and PM₁₀, respectively), black carbon (BC), and volatile organic compounds. An heating, ventilating, and air conditioning (HVAC)‐based high‐performance panel filter (HP‐PF), a register‐based air purifier (RS), and a stand‐alone air cleaning system (SA) were tested alone and in different combinations for their ability to remove the monitored pollutants. The combination of a RS and a HP‐PF was the most effective solution for lowering the indoor concentrations of BC, UFPs, and PM_2.5, with study average reductions between 87% and 96%. When using the HP‐PF alone, reductions close to 90% were also achieved. In all cases, air quality conditions were improved substantially with respect to the corresponding baseline (preexisting) conditions. Data on the performance of the gas‐absorbing media included in the RS and SA unit were inconclusive, and their effectiveness, lifetime, costs, and benefits must be further assessed before conclusions and recommendations can be made.     

Children's emotional competence and attentional competence in early elementary school.

The current study examined the relations between two aspects of emotional competence--emotion knowledge and emotion expression, and children's attentional competence during one school year. Participants were 263 first- and second-grade students at two rural elementary schools. A multiple regression analysis showed that emotion knowledge predicted attentional competence while controlling for age, gender, verbal ability, and initial levels of attentional competence. Multiple regression analyses examining predictors of peer nominations of emotion expression showed that attentional competence predicted peer nominations of happiness, sadness, and anger expression, and emotion knowledge predicted peer nominations of anger expression. Potential improvements for prevention programs and the importance of the findings for school personnel are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

聚醚固体电解质锂电池放电性能研究

利用氧亚甲基连接的聚氧乙烯-聚氧丙烯多嵌段共聚物或氧亚甲基连接的聚氧乙烯多嵌段共聚物与高氯酸锂的络合物作电池的电解质,锂片作负极,几种含钒的化合物作正极,组装了全固态二次锂电池.研究了不同正极材料、不同电解质和不同温度对电池短路放电性能的影响以及电池的重复短路放电性能.研究表明,正极材料V_6O_(13)的性能优于Na_(1+x)V_3O_8;电解质(PEO)_n·LiClO_4的性能优于(PEO-PPO)_n·LiClO_4,这与它们的电导率分别为3.2×10~(-3)S·cm~(-1)和2.2×10~(-3)S·cm~(-1)是一致的.     

湍流强度对激光大气传输及其自适应光学校正的影响

利用激光大气传输及其相位校正四维程序,计算了不同的发射和传输条件对平台聚焦光束水平大气传输及其自适应光学校正的影响。结果表明:自适应光学系统开环时,在弱湍流效应条件下,以D／r_0为特征参量可以很好地表征湍流效应的强弱,SR值满足关系式SR=exp[-0．2(D／r_0)2],不考虑系统像差时,光束质量因子满足关系式β2=1 1．2(D／r_0)2;随着湍流强度或传输距离的增加,要考虑闪烁效应和相位不连续性对光束质量的影响,以D／r_0为特征参量就不足以表征湍流效应的强弱。另外,对于不同的发射和传输条件,自适应光学系统对激光大气传输的校正范围是不同的,且存在一阈值,条件不同其阈值是不同的。