弯出来的量子位

在电力出现以前，最初的计算机是机械的，那是150年前Charles Babbage发明的“微分机”，它能解决对数和三角函数问题。现在，先进的量子计算机可能要重走微分机的老路，它将用数排纳米尺度的小棒作为运动机件。     

最宽的宽带

光纤已经成功地取代了大多数长途电话、有线电视公司及公用事业公司主干网络中的金属电缆，那么为什么不把光纤线路一直延伸到用户的家里去呢?这样做可能会消除所谓的“最后一英里”(1ast—mile)瓶颈问题——该瓶颈限制了用户访问因特网和使用其它服务。目前在“接入住宅”系统中，用户能以高达每秒1亿比特     

“恶意代码”混战——在这场蠕虫病毒的战争中，孰恶孰善

刚过去的八月，攻击Internet的蠕虫病毒纷纷发作，其中一种的生存伎俩不同寻常。大无极（Sobig．F)蠕虫病毒通过恶意邮件阻塞网络，冲击渡(Blaster)蠕虫病毒强迫寄主计算机每隔几分钟就要重启，但冲击波杀手     

教育领导中的范德堡评估：评价以学习为中心的领导

校长领导力的评估和评价是基于标准的问责制以及学校改进的重要部分。设计精确,执行主动,并妥善实施的评估能有效提升组织绩效并发现未来的领导者。但是,由于缺乏评估和监控领导者绩效的专门、有效的工具,优质学校领导力的发展受到严重制约。本文形成了研究基础和新的校长领导力评估研究工具的概念体系：教育领导中的范德堡评估。我们以领导力的定义和对领导力重要性的观察展开研究,进而提出校长领导力模型,本模型是在领导力评估,学校绩效和学生成功的大背景下的领导力行为概念相匹配的情况下提出的。根据对学习型领导文献的细致回顾,聚焦于论证以教学领导为主题并明确界定和衡量足以改善学习的领导行为来看教育领导中的范德堡评估模型与现有评估工具的不同之处。 这篇文章描述了概念模型和以学习为中心领导的建构为基础的研究,进而介绍了教育领导中的范德堡评估。这种新的评估工具旨在评估校长的以学习为中心的领导行为。     

蒂莉阿姨的魔法箱

大卫的父亲在他出生后不久就被派往巴西工作了。由于母亲在剧院里整天忙得四脚朝天,所以蒂莉阿姨就在这个时候走进了大卫的生活。     

Using digital images of the zebra finch song system as a tool to teach organizational effects of steroid hormones: a free downloadable module

Zebra finch song behavior is sexually dimorphic: males sing and females do not. The neural system underlying this behavior is sexually dimorphic, and this sex difference is easy to quantify. During development, the zebra finch song system can be altered by steroid hormones, specifically estradiol, which actually masculinizes it. Because of the ease of quantification and experimental manipulation, the zebra finch song system has great potential for use in undergraduate labs. Unfortunately, the underlying costs prohibit use of this system in undergraduate labs. Further, the time required to perform a developmental study renders such undertakings unrealistic within a single academic term. We have overcome these barriers by creating digital tools, including an image library of song nuclei from zebra finch brains. Students using this library replicate and extend a published experiment examining the dose of estradiol required to masculinize the female zebra finch brain. We have used this library for several terms, and students not only obtain significant experimental results but also make gains in understanding content, experimental controls, and inferential statistics (analysis of variance and post hoc tests). We have provided free access to these digital tools at the following website: http://mdcune.psych.ucla.edu/modules/birdsong.     

2002-2012年达累斯萨拉姆城市蔓延特征及影响因素

以坦桑尼亚首位城市达累斯萨拉姆2002、2007和2012年土地利用分类数据为基础,结合实地调研,运用扇形分析和同心圆分析等方法,以及用地增长弹性系数、扩展强度指数、紧凑度、分形维数等指标,研究达累斯萨拉姆近年来城市蔓延的总体态势和空间格局特征。研究结果表明：1）2002-2012年间达累斯萨拉姆城市蔓延特征明显,蔓延程度较高,蔓延速度不断加快,主要表现为非正式聚落不断增长情况下的城乡混合发展,侵占的土地类型主要为裸地,其次为植被;2）2002-2007年城市建成区主要沿交通干道以及在市中心周边进行轴线式蔓延,2007-2012年主要在交通干道间及城市边缘地区进行填充式蔓延,城市空间形态由指状向团块状演变;3）城市蔓延方向性明显,向西北、西、西南和东南扩展较多,东南方向成为新的扩展热点,且表现出明显的距离衰减特征;4）城市蔓延主要受到人口与经济增长、交通条件改善、政策变化及土地制度缺陷等因素的影响,其中交通设施起到重要的空间引导作用。     

城市物流中的内含风险

本文评述了在城市物流模型中自然和人为风险因素导致的内含风险。根据事件造成风险评估困难的来源对城市物流风险进行了分类。模拟城市货运风险的方法有：随机规划、多目标优化、稳健性优化、多代理模拟、交通仿真。关于人类安全工程的新概念的讨论主要集中在自然灾害、人为灾害、危险材料运输、交通安全和健康问题。人类安全工程很重要,它为城市货运规划体现风险提供了恰当的决策工具,风险来自于自然和人为的因素。本文对Eiichi Taniguchi,RussellG．Thompson和Tadashi Yamada的章《Incorporating risks in City Logistics》进行翻译,以期对国内城市物流的发展提供新的思路。     

Finite element modelling and experimental study of oblique soccer ball bounce

In this study, we develop a finite element model to examine the oblique soccer ball bounce. A careful simulation of the interaction between the ball membrane and air pressure in the ball makes the model more realistic than analytical models, and helps us to conduct an accurate study on the effect of different parameters on a bouncing ball. This finite element model includes a surface-based fluid cavity to model the mechanical response between the ball carcass and the internal air of the ball. An experimental set-up was devised to study the bounce of the ball in game-relevant impact conditions. Ball speed, angle, and spin were measured before and after the bounce, as well as ball deformation and the forces during the impact. The finite element model has been validated with three different sets of data, and the results demonstrate that the finite element model reported here is a valuable tool for the study of ball bounce. After validation of the model, the effect of the friction coefficient on soccer ball bounce was studied numerically. Simulation results show that increasing the friction coefficient may result in reversal of the horizontal impact force.