Roles of salience and strategy in conjunction search.

In some cases, the search for a conjunction target proceeds through the smaller group of elements in a display, whereas in others, search is limited to those elements that share a particular feature with the target. In 6 experiments, participants searched for a conjunction target among displays consisting of various proportions of 2 distractor types. Smaller-group search was more prevalent than target-feature search with denser displays and with features that were highly discriminable. Explicit instructions to limit search to a specific feature affected performance only when the discriminability of the guiding feature was much greater than the other target feature. Together, these experiments show that bottom-up factors have more influence in guiding conjunction searches than previously thought. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Society Magazines Plan Coverage for 2009

In 2009, the Computer Society will offer a slate of 13 magazines covering key topics in computing.     

On the application of probabilistic risk assessment to reactors with inherently safe features

In this paper, it is shown that because of the public perception of the risk of nuclear power and the likelihood that in the event of a severe core damage accident in a reactor claimed to have a high degree of inherent safety, it is necessary to reconsider the basis for establishing safety objectives. It is shown that, if there were a large program of inherently safe reactors, the safety objectives would be determined more by investment risk than by the public health risk. These considerations lead to an objective on the order of 1 × 10⁻⁷ per r.yr (reactor year) for the probabability of a severe core damage accident. It is also shown that the introduction of inherently safe features leads to a considerable change in the allocation of the safety goal between the major safety functions. For these reactors, a major portion of the allocation shifts from the decay heat removal function to the scram function, with emphasis on insuring the integrity of critical structures.     

2009年北美轮胎生产概况

美国经济2009年1月正处于衰退期,而2010年似乎已进入了扩张期,这意味着经济衰退已经结束。2009年第3季度美国国内生产总值实现了自2008年第1季度以来首次增长。另外,申请失业救济人数和可用房源数量都呈下降趋势,预示着经济复苏的积极向好。美国国家经济研究局称,这也有可能是经济扩张中经济活动的短期逆转。     

IEEE 802.22环境下的认知无线网络功率控制研究

在主用户信干噪比(SINR)门限和认知用户总功率的限制条件下,研究了认知无线网络中的功率控制方法。主用户可容忍的干扰随通信环境的改变而不断变化,所以认知用户需根据主用户的信噪比进行严格的功率控制。仿真结果表明,该功率控制方案能最大化认知用户的传输速率和降低认知用户中断概率,同时主用户的QoS得到有效的保证。     

Bioaccumulation, biotransformation, and biochemical effects of brominated diphenyl ethers in juvenile lake trout (Salvelinus namaycush)

Juvenile lake trout (Salvelinus namaycush) were exposed to three dietary concentrations (0, approximately 2.5, and approximately 25 ng/g per BDE congener) of 13 BDE congeners (3-10 Br atoms) in the laboratory for 56 days, followed by 112 days of clean food, to examine bioaccumulation parameters and potential biochemical effects. The bioaccumulation of BDEs by the trout was highly influenced by biotransformation, via debromination, which resulted in bioaccumulation parameters that were much different than would be expected based on studies of chlorinated organic compounds (e.g., PCBs). Half-lives (t1/2's) for some BDE congeners (e.g., BDE-85 and -190) were much lower than expected based on their Kow, which was likely due to biotransformation, whereas t1/2's of other BDE congeners (e.g., BDE-66, -77, -153, and -154) were much longer than anticipated based on Kow. This was likely because the metabolites of BDE formed via debromination had the same chemical structure of these BDE congeners, which supplemented measured concentrations. The detection of three BDE congeners (an unknown penta, BDE-140, and an unknown hexa) in the fish that were not present in the food or in the control fish provide further evidence forthe debromination of BDEs. Half-lives of BDEs ranged from 38 +/- 9 to 346 +/- 173 days and biomagnification factors ranged from 1.6 (BDE-190) to 45.9 (BDE-100), but these bioaccumulation parameters need to be viewed with caution because they were highly influenced by debromination and relative abundance of individual BDEs that the fish were exposed to. CYP1A enzyme activity, measured as EROD, and free tri-iodothyronine (T3) concentrations in the plasma of lake trout varied significantly throughout the experiment but were not related to BDE exposure. In contrast, plasma levels of thyroxine levels (T4) were lower in both groups of PBDE-exposed fish compared with control fish after 56 days of exposure, and after 168 days in the high dose, suggesting that PBDEs may influence thyroid homeostasis at levels that are higher than what is normally found in the environment.