分子进化中性理论的进展

中性理论与达尔文的自然选择进化论有明显的差别。中性论认为在分子水平上覆盖着多数的进化改变，是在连续产生突变时，由于选择中性（即选择相等），使突变得到随机的固定（即小群体内，样本的随机漂变）。还认为在分子水平上，大多数的种内变异（如蛋白质和ＤＮＡ多态）是选择中性或近于中性，它们能够保持在种内是由于突变的产生和随机消失之间的平衡引起的。近年来，ＤＮＡ顺序的研究资料，都有力地支持中性论，如鼠的拟球蛋白基因、鼹鼠的αＡ－晶状体蛋白、流行性感冒Ａ病毒基因，果蝇的核和线粒体基因等。所以，从地球上生命的历史来看，中性进化的改变至少在数量上已超过达尔文自然选择进化的改变。     

Migration rates of human populations from surname distributions

Migration is an important factor in the biological evolution of human populations, and surnames provide one of the simplest records of identification. The distribution of surnames can supply quantitative information on the structure of human populations. Surnames considered as alleles of a gene transmitted only by the male line can be assumed to be neutral markers and therefore satisfy the expectations of the neutral theory of evolution, which is entirely described by random genetic drift, mutation and migration. As data on surnames are easier to collect than those from genes, the information yield is potentially increased, but the validity of the conclusions must be tested in actual samples. The purpose of this report is to compare the estimates of migration rates in Italy, as inferred by the surname distribution found in the telephone directories and other sources, with the corresponding estimates from official demographic sources. Our findings show that in these samples the ratio of surnames to individuals makes it possible to calculate reliable estimates of migration rates.     

A neutral point potential drift control method for NPC three-level inverter

The output current harmonic distortion of a three-level inverter is less than the traditional twolevel inverter.The voltage stress of the semiconductor switch is low.A neutral point potential drift control method is proposed to solve the problem of the neutral point potential drift of the three-level inverter.The interaction mechanism between the neutral point potential and the space voltage vector is presented.The small vector output by the inverter is found to be the root cause of the midpoint potential drift.It is found that the fluctuation of the midpoint potential could be suppressed by increasing the capacitance value of the inverter bus voltage stabilizing capacitor.Furthermore,it inhibits the fluctuation of the midpoint potential.The experimental results verify the efficiency and precision of the proposed method.     

A test of the unified neutral theory of biodiversity

One of the fundamental questions of ecology is what controls biodiversity. Recent theory suggests that biodiversity is controlled predominantly by neutral drift of species abundances. This theory has generated considerable controversy, because it claims that many mechanisms that have long been studied by ecologists (such as niches) have little involvement in structuring communities. The theory predicts that the species abundance distribution within a community should follow a zero-sum multinomial distribution (ZSM), but this has not, so far, been rigorously tested. Specifically, it remains to be shown that the ZSM fits the data significantly better than reasonable null models. Here I test whether the ZSM fits several empirical data sets better than the lognormal distribution. It does not. Not only does the ZSM fail to fit empirical data better than the lognormal distribution 95% of the time, it also fails to fit empirical data better even a majority of the time. This means that there is no evidence that the ZSM predicts abundances better than the much more parsimonious null hypothesis.     

追踪事件微博报道:一种流的动态话题模型

为了解决微博中存在的话题漂移和大量噪声问题,提出了基于动态话题模型和微博信息熵相结合的流的动态话题模型。首先利用动态话题模型在整个追踪过程,从正反两个方面增强对追踪话题的描述,进一步克服了话题漂移问题。但由于微博中存在大量中间类微博,所以定义并使用微博信息熵来衡量一条微博对于话题报道的重要性,并将其扩展到动态话题模型中,用于区分新闻类和中间类微博。在超过17万用户的1 200万条微博上进行了话题追踪,实验结果表明,本文算法较之传统的动态话题模型更有效,追踪结果包含更少噪声。     

电离层F层动力学数值模拟

中、低纬电离层Ｆ层动力学的数值模拟通过研究等离子体的连续性方程和运动方程进行，等离子体的输运过程顺电磁漂移的运动坐标系中运算。计及双极扩散、温度、中性风、电磁漂等影响。     

Field parameterization and experimental test of the neutral theory of biodiversity

Ecologists would like to explain general patterns observed across multi-species communities, such as species-area and abundance-frequency relationships, in terms of the fundamental processes of birth, death and migration underlying the dynamics of all constituent species. The unified neutral theory of biodiversity and related theories based on these fundamental population processes have successfully recreated general species-abundance patterns without accounting for either the variation among species and individuals or resource-releasing processes such as predation and disturbance, long emphasized in ecological theory. If ecological communities can be described adequately without estimating variation in species and their interactions, our understanding of ecological community organization and the predicted consequences of reduced biodiversity and environmental change would shift markedly. Here, I introduce a strong method to test the neutral theory that combines field parameterization of the underlying population dynamics with a field experiment, and apply it to a rocky intertidal community. Although the observed abundance-frequency distribution of the system follows that predicted by the neutral theory, the neutral theory predicts poorly the field experimental results, indicating an essential role for variation in species interactions.     

陀螺随机漂移的神经网络预报方法研究

针对惯性导航系统中陀螺仪的漂移特性,在时间序列分析及神经网络理论的基础上提出了一种时间序列神经网络结构,并采用此种网络模型对某捷联惯导系统中所用的陀螺仪漂移数据进行了预报。预测结果表明,这种预测方法对于陀螺漂移建模及预报是可行的。     

解析式直流辉光放电等离子体理论模型的改进

对作者前期建立的自洽、解析式直流辉光放电等离子体理论模型进行了改进。考虑到电子能量分布，认为电子碰撞电离速率系数ｆ取决于电子的迁移速度ＶＥ和扩散速度ＶＤ，而不象以前假设电离速率系数ｆ为一常数。另外，不再将形式为（Ｃ１ｃｏｓｍｚ＋Ｃ２ｓｉｎｍｚ）的通解简化为形式为Ｃ（ｃｏｓｍｚ＋ｓｉｎｍｚ）的特解，改进后的理论模型仍为自洽的解析式理论模型，它的适用范围更广，与实验结果更为接近。     

中性风对暴时电离层影响的研究

从电离层等离子体动力学方程出发,研究了磁暴期间中性风对中低纬度电离层的影响.通过计算机模拟发现:中性风能够对暴时电离层等离子体的垂直向上漂移产生抑制作用,并延迟电离层F层底部"抛空"的形成;不论采用哪种中性风模式,磁暴都会对较低纬度的电离层产生更大的影响.     

行星际磁场扰动下极区热层中性风对夜侧离子拖曳的响应

离子拖曳可以对极区的高层大气中性风场产生强烈影响。行星际磁场(interplanetary magnetic field,IMF)扰动期间,通过全天空法布里-帕罗干涉仪(all-sky Fabry-Perot interferometer,all-sky FPI)的观测数据,分析了2012年1月21日21:21UT~2012年1月22日00:11 UT期间北极黄河站(78.92°N,11.93°E)上空630.0 nm氧原子辐射高度的中性风视线风场。行星际扰动数据与同时期离子风数据的对比分析表明,行星际磁场扰动使得Super DARN监测到的F层夜侧离子运动加速,高速运动的离子与中性风发生耦合,离子以传送动力给中性大气并向其运动方向拖曳的方式改变中性风的风场形态。     

On the origin of species by sympatric speciation.

Understanding speciation is a fundamental biological problem. It is believed that many species originated through allopatric divergence, where new species arise from geographically isolated populations of the same ancestral species. In contrast, the possibility of sympatric speciation (in which new species arise without geographical isolation) has often been dismissed, partly because of theoretical difficulties. Most previous models analysing sympatric speciation concentrated on particular aspects of the problem while neglecting others. Here we present a model that integrates a novel combination of different features and show that sympatric speciation is a likely outcome of competition for resources. We use multilocus genetics to describe sexual reproduction in an individual-based model, and we consider the evolution of assortative mating (where individuals mate preferentially with like individuals) depending either on an ecological character affecting resource use or on a selectively neutral marker trait. In both cases, evolution of assortative mating often leads to reproductive isolation between ecologically diverging subpopulations. When assortative mating depends on a marker trait, and is therefore not directly linked to resource competition, speciation occurs when genetic drift breaks the linkage equilibrium between the marker and the ecological trait. Our theory conforms well with mounting empirical evidence for the sympatric origin of many species.     

高稳定度电源设计的关键因素

通过传递函数，从7个方面系统分析了影响电源高稳定度的各种因素，讨论了电源基本参数及它们之间的关系，得出影响电源稳定度的直接因素是基准电压的稳定度、分流器阻值随温度的变化、放大器输入端电压的漂移，间接因素是放大器本身参数的变化、放大器输入端内阻漂移、负载电阻随温度的变化、交通电网的波动以便为研制和设计高稳定度电源提供理论依据。     

Stability of forest biodiversity

Two hypotheses to explain potentially high forest biodiversity have different implications for the number and kinds of species that can coexist and the potential loss of biodiversity in the absence of speciation. The first hypothesis involves stabilizing mechanisms, which include tradeoffs between species in terms of their capacities to disperse to sites where competition is weak, to exploit abundant resources effectively and to compete for scarce resources. Stabilization results because competitors thrive at different times and places. An alternative, 'neutral model' suggests that stabilizing mechanisms may be superfluous. This explanation emphasizes 'equalizing' mechanisms, because competitive exclusion of similar species is slow. Lack of ecologically relevant differences means that abundances experience random 'neutral drift', with slow extinction. The relative importance of these two mechanisms is unknown, because assumptions and predictions involve broad temporal and spatial scales. Here we demonstrate that predictions of neutral drift are testable using palaeodata. The results demonstrate strong stabilizing forces. By contrast with the neutral prediction of increasing variance among sites over time, we show that variances in post-Glacial tree abundances among sites stabilize rapidly, and abundances remain coherent over broad geographical scales.     

中立型变时滞随机微分方程数值解的强收敛性

讨论中立型变时滞随机微分方程改进的修正截断Euler-Maruyama （EM）方法的q阶矩强收敛性，并得到收敛速度。结果表明此方法适用于高度非线性的漂移项和扩散项，且相较于隐式的修正截断EM方法计算量更小，适用范围更广。     

基于可靠度理论的下向进路胶结充填技术分析

为探索下向进路胶结充填采矿法充填技术经济分析的科学方法，通过建立下向进路力学模型求出承载层应力分布规律及最危险点的位置，确定该种采矿方法充填体稳定性评判依据，并在此基础上，应用可靠度理论建立承载层稳定性极限状态方程，以及承载层稳定性可靠度不变时充填成本与进路宽度、承载层厚度之间的关系方程。结合某矿山实际情况，得出该矿山下向进路胶结充填采矿法承载层稳定性可靠概率为90％和在不同进路宽度条件下承载层厚度与充填成本之间的关系方程。研究结果表明，增加承载层厚度、减少承载层的灰砂比，既可保证承载层的稳定性，又可降低充填成本。对不同进路宽度的承载层厚度与充填成本之间的关系对比分析结果表明，当该矿山进路宽度增加到5．5m和6．0m，承载层稳定性可靠度达到90％时，充填成本将分别增加3．5％和7．7％，采场的生产能力提高10％～20％。     

电磁式静电除尘空气净化机理的研究

提出了电磁式静电除尘空气净化法。从带电粒子的电漂移理论出发，阐明了加平行磁场较加垂直磁场能得到更高的净化效率的理论依据。在更深一步的试验研究基础上，提出粒子初速存在着一个提高净化效率的最佳值，并应用带电粒子电漂移理论解释了一定的集尘板间距内加垂直磁场后，净化效率低于不加磁场情况下的净化效率这一特殊现象，完善了这一新技术。     

同时监控过程均值和方差漂移的VSI EWMA平均损失控制图设计

结合WLE控制图和VSI EWMA控制图,提出了基于田口损失函数下的可变抽样区间的EWMA控制图（简称VSI EWMA平均损失控制图）,它是一种在抽样区间可以变化的条件下能够同时检测过程均值和方差漂移的控制图;同时构造的新控制图通过添加控制限区分漂移类型,即在过程失控状态下区分是过程均值发生了漂移还是方差发生了漂移,或者两者都发生了漂移.通过与FP EWMA平均损失控制图及X-～S控制图进行比较,得出新构造的控制图对过程漂移具有更好的敏感性.     

Adaptive protein evolution at the Adh locus in Drosophila

Proteins often differ in amino-acid sequence across species. This difference has evolved by the accumulation of neutral mutations by random drift, the fixation of adaptive mutations by selection, or a mixture of the two. Here we propose a simple statistical test of the neutral protein evolution hypothesis based on a comparison of the number of amino-acid replacement substitutions to synonymous substitutions in the coding region of a locus. If the observed substitutions are neutral, the ratio of replacement to synonymous fixed differences between species should be the same as the ratio of replacement to synonymous polymorphisms within species. DNA sequence data on the Adh locus (encoding alcohol dehydrogenase, EC 1.1.1.1) in three species in the Drosophila melanogaster species subgroup do not fit this expectation; instead, there are more fixed replacement differences between species than expected. We suggest that these excess replacement substitutions result from adaptive fixation of selectively advantageous mutations.     

无底柱分段崩落法进路宽度的优化确定

进路宽度是反映无底柱分段崩落法技术经济效益的重要技术指标,为确定无底柱分段崩落法最优进路宽度,以新疆某铁矿为工程背景,基于随机介质放矿理论、wilson弹塑性理论、FLAC3D数值模型,通过矿柱稳定性分析提出了进路极限宽度公式,并得到该矿的进路极限宽度为7m。结合技术经济分析,采用最高积分法对7种进路宽度进行优化。优化结果表明,最优进路宽度为6.6m,除了可获得良好的放矿效果外,还可使每一进路增加60万元收益。该进路宽度综合考虑了安全、技术、经济等因素,既保证了采场的安全性、掘支技术的可行性,又降低了矿石的贫损指标,提高了回采的经济效益,研究成果对矿山生产具有实际指导意义。