Effects of school choice on the margin: The cream is already skimmed

Critics of school choice argue that cream-skimming will worsen outcomes for those left behind in public schools. Since “high ability” families may have already sorted themselves out of the schools in question, this paper will examine whether existing within-school heterogeneity leaves any scope for cream-skimming to operate. It asks, “given the current level of within-school heterogeneity, how strong would peer effects have to be to significantly worsen outcomes for those left behind?” In order for cream-skimming to lower math test scores by one half-year's progress, the peer effect would have to be as strong as increasing class sizes by 8–20 students, or cutting per-student funding by $400–2000. These results indicate that current levels of within-school heterogeneity are so low that peer effects would have to be unrealistically strong to give cream-skimming any bite.     

关于《恋爱中的女人》“死亡”主题的思考

《恋爱中的女人》是英国现代小说家劳伦斯的一部重要作品。在这部作品中,劳伦斯对西方工业文明的抨击达到了极至。他认为现代工业文明破坏了自然环境和人类本身,使得人类世界蒙上了死亡的阴影;劳伦斯在小说中主张以死亡消除死亡;但是小说的这个主题本身带有很大的局限性。     

中央企业A＋H同步IPO模式分析

虽然A＋H同步IPO模式目前尚不具备常态化操作的条件,但相对于早期的先H后A,对于尚未在香港上市的中央企业而言至少具备7大优点：一是两地同时上市,有利于扩大新股发行影响,提高资金募集效率;二是可以避开其中某一个市场出现不稳定市况的影响,降低首次公开发行的风险;三是能够使企业获得更优的发行价,而此前香港市场的发行市盈率和二级市场市盈率都要低于内地市场,同时以A＋H同步IPO,企业投资者基础更加广泛,这会有利于公司价值得到深入挖掘;四是可以使上市公司充分利用国际和国内两个资本市场的优势,尤其是利用香港市场监管国际化的优势提升企业市场化和规范化经营;五是同步发行A股、H股将发行影响扩大到全球范围,能极大地提升公司的市场形象和国际知名度;六是对于企业再融资也带来便利条件;七是上市前期工作也可以相互利用,募集资金到位更加及时。此外,中央企业A＋H同步整体上市对于资本市场而言,也具有许多优点。     

时滞不确定系统的H∞控制器设计

针对多时滞不确定系统,用Riccati和LMI相结合的方法设计了一个H∞控制器。该方法的要旨在于只要相应的ARE和LMI存在正定解,就能设计出H∞控制器。同时用仿真验证了该H∞控制器不但保证了闭环系统鲁棒渐近稳定,而且对于所有容许的不确定性,其H∞范数小于某一常数r,并且其系统响应都趋向稳定。     

论知识论与社会学在图书馆学中结合——基于对谢拉“社会知识论”的考察

图书馆知识性和社会性的统一要求知识论和社会学在图书馆学中的结合,并形成两种基于不同中心的结合模式。谢拉的“社会知识论”以社会学为中心,知识论在其中尽管具有重要的实践意义,却局限于传统立场。他的理论因此在实质上接近于“知识社会学”。引入个体知识论或社会学的规范性不能使之转变为社会知识论,应采取以知识论为中心,在其规范性中包含社会学因素的结合模式。     

A Comparison of H. D. Thoreau's View of Nature and Traditional Chinese Perspectives on Human and Nature

This paper involves several typical scholars in Chinese history of literature,and it emphasizes the analysis of their typical works,which are compared with Thoreau's view of nature again and again. In spite of their differences and similarities,beauty and cherishment are the same; and there is a hope that we could grip the nature of these authors and their works after these analyses.     

（H-η）-增生算子在一类集值拟变分包含中的应用

在Banach空间中引进一类H-增生算子,并给出了一类新的（H-η）-增生算子的概念,及相关的预解式算子R^H,ηM,λ,利用新的预解式算子技巧得出一系列广义集值拟变分包含问题的逼近解。     

教学中海洋化学一类离子聚变引起的深思

地球大气的物理变化与海洋的物理化学变化是相互关联的。大气中氢离子的失衡导致氢氧根离子、氯离子等一类的极大饱和,使海洋中的盐碱浓度增大,从而致使海洋中某些生物（例如恐龙）无法生存最后灭绝。这也是引起地球温室效应的一个很重要原因,特别是太阳的剧烈活动是地球变暖的根本所在。     

Parallel processing architecture of H.264 adaptive deblocking filters

In H.264, computational complexity and memory access of deblocking filters are variable, dependent on video contents. This paper proposes a VLSI architecture of deblocking filters with adaptive dynamic power, which avoids redundant computations and memory accesses by precluding the blocks that can be skipped. The vertical and horizontal edges are simultaneously processed in an advanced scan order to speed up the decoder. As a result, dynamic power of the proposed architecture can be reduced adaptively （up to about 89%） for different videos, and the off-chip memory access is improved when compared to previous designs. Moreover, the processing capability of the proposed architecture is in particular appropriate for real-time deblocking of high-definition television （HDTV, 1920× 1080 pixels/frame, 60 frames/s video signals） video operation at 62 MHz. Using the proposed architecture, power can be reduced by up to about 89% and processing time by from 25% to 81% compared with previous designs.     

Dominant edge direction based fast intra mode decision in the H.264/AVC encoder

The H.264/AVC video coding standard uses an intra prediction mode with 4×4 and 16×16 blocks for luma and 8×8 blocks for chroma. This standard uses the rate distortion optimization （RDO） method to determine the best coding mode based on the compression performance and video quality. This method offers a large improvement in coding efficiency compared to other compression standards, but the computational complexity is greater due to the various intra prediction modes. This paper proposes a fast intra mode decision algorithm for real-time encoding of H.264/AVC based on the dominant edge direction （DED）. The DED is extracted using pixel value summation and subtraction in the horizontal and vertical directions. By using the DED, three modes instead of nine are chosen for RDO calculation to decide on the best mode in the 4×4 luma block. For the 16×16 luma and the 8 × 8 chroma, only two modes are chosen instead of four. Experimental results show that the entire encoding time saving of the proposed algorithm is about 67% compared to the full intra search method with negligible loss of quality.