最优多用户检测问题适应值曲面分析

对于码分多址无线通信,多用户检测技术是克服多址干扰的有效手段,尽管最优多用户检测算法具有最好的检测性能,但是其计算复杂度和用户数量呈指数增长,不可能在实际系统中实现.已经证明最优多用户检测是non-deterministic potynomial(NP)完备的组合优化问题,目前还不存在有效的多项式复杂度算法来求得其精确解,而启发式方法作为求解这类问题的有效方法,可以在合理的计算时间内获得高质量的解.启发式算法性能的最重要因素是相应问题的适应值曲面特性,对特定问题的属性分析能够帮助我们理解启发式搜索算法的行为和预测其性能.本文给出了适应值曲面的概念和最优多用户检测问题的组合优化模型,指出影响启发式多用户检测算法性能的几个主要属性,定义了几个重要测度以量化这些属性并且对最优多用户检测问题的适应值曲面进行了数值仿真和分析,指出了数值仿真结果对设计高效启发式算法的指导意义.     

Global landscape of HIV-human protein complexes

Human immunodeficiency virus (HIV) has a small genome and therefore relies heavily on the host cellular machinery to replicate. Identifying which host proteins and complexes come into physical contact with the viral proteins is crucial for a comprehensive understanding of how HIV rewires the host's cellular machinery during the course of infection. Here we report the use of affinity tagging and purification mass spectrometry to determine systematically the physical interactions of all 18 HIV-1 proteins and polyproteins with host proteins in two different human cell lines (HEK293 and Jurkat). Using a quantitative scoring system that we call MiST, we identified with high confidence 497 HIV-human protein-protein interactions involving 435 individual human proteins, with ～40% of the interactions being identified in both cell types. We found that the host proteins hijacked by HIV, especially those found interacting in both cell types, are highly conserved across primates. We uncovered a number of host complexes targeted by viral proteins, including the finding that HIV protease cleaves eIF3d, a subunit of eukaryotic translation initiation factor 3. This host protein is one of eleven identified in this analysis that act to inhibit HIV replication. This data set facilitates a more comprehensive and detailed understanding of how the host machinery is manipulated during the course of HIV infection.     

Global landscape of protein complexes in the yeast Saccharomyces cerevisiae

Identification of protein-protein interactions often provides insight into protein function, and many cellular processes are performed by stable protein complexes. We used tandem affinity purification to process 4,562 different tagged proteins of the yeast Saccharomyces cerevisiae. Each preparation was analysed by both matrix-assisted laser desorption/ionization-time of flight mass spectrometry and liquid chromatography tandem mass spectrometry to increase coverage and accuracy. Machine learning was used to integrate the mass spectrometry scores and assign probabilities to the protein-protein interactions. Among 4,087 different proteins identified with high confidence by mass spectrometry from 2,357 successful purifications, our core data set (median precision of 0.69) comprises 7,123 protein-protein interactions involving 2,708 proteins. A Markov clustering algorithm organized these interactions into 547 protein complexes averaging 4.9 subunits per complex, about half of them absent from the MIPS database, as well as 429 additional interactions between pairs of complexes. The data (all of which are available online) will help future studies on individual proteins as well as functional genomics and systems biology.     

城市景观的水环境响应及景观调控研究综述?

城市化进程突出表现在不透水地面增加、绿地和水体景观减少、景观破碎和离散化等,由此引起了城市景观格局变化,导致降雨径流过程发生了质的变化,一定程度上造成了城市水体质量下降.通过对城市景观水环境响应及景观调控方法相关研究进行系统总结,得出目前研究中存在的不足之处包括:1)城市景观水环境影响研究尚不深入,基于实际的城市水环境过程的景观格局及其表征指标研究较少,缺乏城市非点源输出过程及其影响的尺度效应研究;2)城市景观水环境响应关系研究方法单一,尚少见基于城市景观格局的水环境机制模型;3)现有景观调控方法缺乏系统研究,不同尺度同时开展景观调控的研究较少,缺乏基于水环境保护的城市景观动态调控理论和技术方法.在此基础上提出未来研究的着力点.     

超声纵振动空心变幅杆的特性

基于解析法推导了内孔分别为锥形和柱形的锥形变幅杆的频率方程及各参数表达式,利用有限元法计算了这两种变幅杆和对应空心部分填实后实心杆的应力及振动位移沿轴向分布的规律。结果表明:谐振频率和面积系数相同时,内孔为锥形杆的放大系数最大,柱孔杆次之,实心锥形变幅杆最小;各变幅杆的位移节点与应变极大位置之和近似等于其半波长谐振长度。进一步还证明了空心变幅杆与实心变幅杆具有相同的等效电路。     

基于链路预测算法分析虚假链接问题

链路预测与虚假链接是复杂网络的两大研究热点,目前为止,链路预测方法的研究已经非常成熟,而对于虚假链接的研究却仍旧没有得到太多的关注.根据链路预测与虚假链接的联系,用17种经典的链接预测算法,研究了这些算法在8个真实网络数据集中的识别虚假链接效果.实验结果表明,这些算法在识别虚假链接中的AUC值明显低于在链接预测中的AUC值;并且随着测试集比例的增加,在给定某个算法和数据集上,AUC值逐渐降低.     

一种健身发电弹簧椅的设计

目前国内市场上的健身椅多为纯机械式,其缺点是功能单一、缺乏娱乐性等,而部分健身发电椅为进口产品,价格昂贵.为此,设计了一种健身发电弹簧椅,该电弹簧椅主要由小型减速发电机、蓄电池、MP3播放板、机械装置和电控装置等组成,可以在健身的同时,将收集的能量转化为电能,驱动MP3播放板等装置,其实现原理简单、结构紧凑,与进口健身发电椅相比,价格低廉、市场前景广阔.     

The metapopulation capacity of a fragmented landscape

Ecologists and conservation biologists have used many measures of landscape structure to predict the population dynamic consequences of habitat loss and fragmentation, but these measures are not well justified by population dynamic theory. Here we introduce a new measure for highly fragmented landscapes, termed the metapopulation capacity, which is rigorously derived from metapopulation theory and can easily be applied to real networks of habitat fragments with known areas and connectivities. Technically, metapopulation capacity is the leading eigenvalue of an appropriate 'landscape' matrix. A species is predicted to persist in a landscape if the metapopulation capacity of that landscape is greater than a threshold value determined by the properties of the species. Therefore, metapopulation capacity can conveniently be used to rank different landscapes in terms of their capacity to support viable metapopulations. We present an empirical example on multiple networks occupied by an endangered species of butterfly. Using this theory, we may also calculate how the metapopulation capacity is changed by removing habitat fragments from or adding new ones into specific spatial locations, or by changing their areas. The metapopulation capacity should find many applications in metapopulation ecology, landscape ecology and conservation biology.     

密立根油滴的横向漂移对测量结果的影响

分析了密立根油滴实验中油滴的横向漂移给测量结果带来的影响，并指出了修正的方法。     

Thickness constraints on the icy shells of the galilean satellites from a comparison of crater shapes

A thin outer ice shell on Jupiter's large moon Europa would imply easy exchange between the surface and any organic or biotic material in its putative subsurface ocean. The thickness of the outer ice shell is poorly constrained, however, with model-dependent estimates ranging from a few kilometres to ten or more kilometres. Here I present measurements of depths of impact craters on Europa, Ganymede and Callisto that reveal two anomalous transitions in crater shape with diameter. The first transition is probably related to temperature-dependent ductility of the crust at shallow depths (7 8 km on Europa). The second transition is attributed to the influence of subsurface oceans on all three satellites, which constrains Europa's icy shell to be at least 19 km thick. The icy lithospheres of Ganymede and Callisto are equally ice-rich, but Europa's icy shell has a thermal structure about 0.25 0.5 times the thicknesses of Ganymede's or Callisto's shells, depending on epoch. The appearances of the craters on Europa are inconsistent with thin-ice-shell models and indicate that exchange of oceanic and surface material could be difficult.     

Cadherin 23 is a component of the tip link in hair-cell stereocilia

Mechanoelectrical transduction, the conversion of mechanical force into electrochemical signals, underlies a range of sensory phenomena, including touch, hearing and balance. Hair cells of the vertebrate inner ear are specialized mechanosensors that transduce mechanical forces arising from sound waves and head movement to provide our senses of hearing and balance; however, the mechanotransduction channel of hair cells and the molecules that regulate channel activity have remained elusive. One molecule that might participate in mechanoelectrical transduction is cadherin 23 (CDH23), as mutations in its gene cause deafness and age-related hearing loss. Furthermore, CDH23 is large enough to be the tip link, the extracellular filament proposed to gate the mechanotransduction channel. Here we show that antibodies against CDH23 label the tip link, and that CDH23 has biochemical properties similar to those of the tip link. Moreover, CDH23 forms a complex with myosin-1c, the only known component of the mechanotransduction apparatus, suggesting that CDH23 and myosin-1c cooperate to regulate the activity of mechanically gated ion channels in hair cells.     

由景观的实质探悉南疆绿洲城市景观设计

运用调查研究、比较研究、历史研究的方法对南疆绿洲城市的景观资源进行了总结归纳分类,通过对景观本质的挖掘,探悉了南疆绿洲城市特色的主要表现手法。结果表明,从景观的实质出发,演绎南疆绿洲城市的历史和文化。景观的实质是当地居民真实生活的写照,它需要人们去参与、去演绎,它反映了当地的历史、文化和人们的精神风貌。南疆绿洲城市的景观设计的主题是南疆各族人民团结一致,屯垦戍边,共同追求美好幸福生活。     

含随机分布散射颗粒的吸波体设计和性能分析

单层致密平板吸波材料除几个特殊的吸收峰外,很难在较宽的频段达到理想的吸收效果．通过在吸波体内导电媒质的“孤岛”化设计,制备了单层非连续体平板吸波材料．测试结果表明,在8～18GHz频段内,热压平板媒质只出现两个特征吸收峰值,含炭20％吸收效果最好,但超过10dB的有效频段只有约1GHz．而非连续体平板吸波材料由于和空间波阻抗的良好匹配以及内部“孤立”颗粒对电磁波的散射和吸收衰减,其反射损耗有较大提高;而且随着平板试样中“孤立”颗粒炭含量的增加,平板对电磁波的反射损耗也增加,当炭含量达到30％时,平板的反射损耗在8．5～18GHz宽频范围内都超过10dB,有效频段在10GHz以上．     

The limits of the nuclear landscape

In 2011, 100 new nuclides were discovered. They joined the approximately 3,000 stable and radioactive nuclides that either occur naturally on Earth or are synthesized in the laboratory. Every atomic nucleus, characterized by a specific number of protons and neutrons, occupies a spot on the chart of nuclides, which is bounded by 'drip lines' indicating the values of neutron and proton number at which nuclear binding ends. The placement of the neutron drip line for the heavier elements is based on theoretical predictions using extreme extrapolations, and so is uncertain. However, it is not known how uncertain it is or how many protons and neutrons can be bound in a nucleus. Here we estimate these limits of the nuclear 'landscape' and provide statistical and systematic uncertainties for our predictions. We use nuclear density functional theory, several Skyrme interactions and high-performance computing, and find that the number of bound nuclides with between 2 and 120 protons is around 7,000. We find that extrapolations for drip-line positions and selected nuclear properties, including neutron separation energies relevant to astrophysical processes, are very consistent between the models used.     

武汉市湿地景观格局的变化与城市景观建设

选择武汉市城市发展较快的时间段(1996～2001年)的遥感图片作为信息源提取湿地景观信息,采用部分景观格局指标评价5年间景观格局的变化;利用马尔科夫矩阵计算湿地景观与非湿地景观的转化概率,再据此分析湿地景观格局变化与城市建设之间的关系;根据分析结果提出湿地景观的保护与城市景观建设的协调,使得湿地景观成为城市景观的重要组成部分,突现湿地景观与城市景观部分与整体的不可分割的密切关系.     

佛山市禅城区景观格局粒度效应分析Ⅰ——景观制图与景观指数选取

以佛山市禅城区作为研究对象,在其土地利用分类基础上,利用GIS软件、景观格局分析软件（Fragrats3.3）和Excel软件,从景观水平和斑块类型水平上分析了粒度变化对禅城区、老城区和南庄镇3类景观格局的影响,并对比分析南庄镇和老城区在不同粒度下的尺度效应,寻找不同景观的适宜分析粒度,从而为选择适宜粒度进行景观指数的计算和尺度转换提供理论依据。结果表明,景观指数具有粒度效应：在景观水平上,禅城区的适宜尺度为5、20～40和120～140 m区间,老城区的适宜尺度为10、20～40和120～140 m区间,南庄镇的适宜粒度为5、70、110 m;在斑块类型水平上,禅城区和老城区的适宜粒度均为10或120～140 m区间,南庄镇的适宜粒度大致是粒度为10、20或120～150 m区间。     

论全民健身体育人才的培养

从体育事业发展、体育整体功能发挥和民族体育３个方面论述了全民健身体育人才培养的必要性;指出发展学科建设、设置相应专业、构建与城乡协调配套的社区体育人才体系以及加强竞技人才的学历教育等,是加快全民健身体育人才培养的必要途径．     

田径运动在全民健身中的作用

田径运动作为各项运动的基础 ,它在全民健身运动中有着良好的群众基础 ,具有易普及、花费和投资小、经济实用以及健身作用价值大的优势 ,有着其他运动项目无法比拟的作用