Simulation of subcritical flow pattern in 180° uniform and convergent open-channel bends using SSIIM 3-D model

In meandering rivers, the flow pattern is highly complex, with specific characteristics at bends that are not observed along straight paths. A numerical model can be effectively used to predict such flow fields. Since river bends are not uniform-some are divergent and others convergent-in this study, after the SSIIM 3-D model was calibrated using the result of measurements along a uniform 180° bend with a width of 0.6 m, a similar but convergent 180v bend, 0.6 m to 0.45 m wide, was simulated using the SSI1M 3-D numerical model. Flow characteristics of the convergent 180° bend, including lengthwise and vertical velocity profiles, primary and secondary flows, lengthwise and widtbwise slopes of the water surface, and the helical flow strength, were compared with those of the uniform 180° bend. The verification results of the model show that the numerical model can effectively simulate the flow field in the uniform bend. In addition, this research indicates that, in a convergent channel, the maximum velocity path at a plane near the water surface crosses the channel＇s centerline at about a 30° to 40° cross-section, while in the uniform bend, this occurs at about the 50° cross-section. The varying range of the water surface elevation is wider in the convergent channel than in the uniform one, and the strength of the helical flow is generally greater in the uniform channel than in the convergent one. Also, unlike the uniform bend, the convergent bend exhibits no rotational cell against the main direction of secondary flow rotation at the 135° cross-section.

Smartphone use patterns and the impact on accommodation and convergence system of the eyes among Malaysian teenagers

AIM:To determine the smartphone use patterns and effects of smartphone use on accommodation and convergence system of the eyes among Malaysian teenagers.METHODS:A total of 62 participants aged between 13 and 17y were involved.A self-administered questionnaires containing 12 items was used to evaluate the smartphone usage patterns.This was followed by an eye examination,involving a battery of accommodation and convergence assessments before and after the smartphone use.The data analysis comprised descriptive statistics,paired t-test,and correlation coefficients.RESULTS:The use of smartphones is at a high level and at an optimal distance daily,with more than 6h a day watching video films,games,and completing school projects.Majority of the participants not reported eye strain factors and eye prescription changes with the use of digital devices.The use of a smartphone continuously for 30min was found to significantly decrease amplitude of accommodation,accommodative facility,and positive relative accommodation(P<0.001).Meanwhile,the lag of accommodation parameters and negative relative accommodation increased with the use of smartphones significantly(P<0.001).The near point of convergence(NPC)and distance and near negative fusional vergence decreased significantly(P<0.001).The NPC parameter was found to have a weak negative association with the frequency of smartphone use(R=-0.276,P<0.05).CONCLUSION:Frequent and continuous use of smartphones have increased visual stress and resulted in weakness of accommodation and vergence functions.Therefore,frequent break is mandatory when using a smartphone and appropriate visual hygiene,the 20-20-20 rule(every 20min,view something 20 feet away for 20s)are required during smartphone use to maintain visual function.

Global pattern of pairwise relationship in genetic network

In recent times genetic network analysis has been found to be useful in the study of gene-gene interactions, and the study of gene-gene correlations is a special analysis of the network. There are many methods for this goal. Most of the existing methods model the relationship between each gene and the set of genes under study. These methods work well in applications, but there are often issues such as non-uniqueness of solution and/or computational difficulties, and interpretation of results. Here we study this problem from a different point of view: given a measure of pair wise gene-gene relationship, we use the technique of pattern image restoration to infer the optimal network pair wise relationships. In this method, the solution always exists and is unique, and the results are easy to interpret in the global sense and are computationally simple. The regulatory relationships among the genes are inferred according to the principle that neighboring genes tend to share some common features. The network is updated iteratively until convergence, each iteration monotonously reduces entropy and variance of the network, so the limit network represents the clearest picture of the regulatory relationships among the genes provided by the data and recoverable by the model. The method is illustrated with a simulated data and applied to real data sets.

Spatio-temporal Pattern and Driving Forces of Comprehensive Agricultural Productivity in Jilin Province,China

Improving comprehensive agricultural productivity is an important measure to realize agricultural modernization.Based on the data from Jilin Statistical Yearbook,this study analyzed the spatial and temporal characteristics of comprehensive agricultural productivity discrepancy in the main agricultural production areas of Jilin Province,China.The comprehensive agricultural productivity of 25 county-level administrative units were evaluated by a comprehensive index system based on five aspects which included 20 indicators from 2004 to 2017.The pattern of the discrepancy was analyzed by the spatial differentiation indices and spatial convergence theory.The results were as follows:1) the overall comprehensive agricultural productivity was in a ’W-type’ rising trend;2) the discrepancy was in’inverted W-type’ trend;3) the spatial distribution characteristics were mainly discrete plaque and ’inverted V-type’;4) the formation of differences was forced by a combination of internal and external driving forces.Our study demonstrates the effectiveness of rising agricultural productivity and the level of economic and social developments in different counties in Jilin Province.

黄河流域水生态文明建设水平的时空格局及空间收敛性

水生态文明建设是实现黄河流域生态保护和高质量发展的重要支撑。基于2010—2021年黄河流域地级市面板数据,采用时空极差熵值法、核密度估计法、探索性空间数据分析和空间面板模型对黄河流域水生态文明建设水平的时空格局及收敛性进行了实证分析。研究发现:黄河流域及上中下游城市水生态文明建设水平均呈现稳步提升态势,但水节约、水生态和水环境建设仍为主要短板;全流域及上中下游水生态文明建设水平的演进脉络各异,但极化趋势日益加剧;全流域水生态文明建设水平呈现显著的正向空间外溢效应和空间格局锁定特征,高高集聚区集中在下游城市,低低集聚区集中在上游城市;全流域及上中下游水生态文明建设水平均存在显著的绝对β收敛和条件β收敛,中游绝对β收敛最快,上游条件β收敛最快;人口密度、人力资本、经济发展水平、产业结构和城镇化水平对水生态文明建设水平的收敛性有显著影响,但存在明显的区域异质性。上述发现为协同推进黄河流域水生态文明建设提供了决策参考和经验证据。

时空矢量场下人群活动聚散模式提取与分析

由于传统方法缺乏顾及人群在区域间的动态流动而无法反映人群在未来(下一时刻)的活动聚散趋势,因此,文中借助时空矢量场来建模人群活动的趋向性,通过矢量场理论中的散度算子来定量计算人群活动聚散强度,将人群活动聚散模式提取问题转化为时间序列聚类问题识别出主要聚散模式。在海口市滴滴出行数据集上进行实验,选取角度偏态系数证明了主体方向计算方法的有效性,提取出了4种主要人群活动聚散模式,并结合POI类型的分布情况对4种模式进行了语义解释,为探索人类移动性提供研究思路和方法支持。

黄河流域制造业高质量发展的空间格局演化、地区差异及收敛性分析

基于2010-2020年黄河流域73个地市面板数据,通过AHP-熵值法测算各地市制造业高质量发展水平,综合运用标准差椭圆、Dagum基尼系数及β收敛模型考察流域内制造业高质量发展的空间格局演化、地区差异及其空间收敛特征.研究结果表明:1)黄河流域制造业高质量发展水平呈波动上升趋势,但存在显著的空间非均衡性,始终保持“下强上弱”的空间分布格局.2)制造业高质量发展的重心向西南方向偏移,并表现为东西向集聚、南北向扩散趋势.3)制造业高质量发展的总体差异略有增加,组间差异是总体差异的主要来源.4)流域整体及上、下游地区支持条件β收敛和绝对β收敛机制,但不同地区的收敛速度和影响因素存在差异.基于实证结果,从提升黄河流域制造业高质量发展水平、缩小地区差距、促进区域差异化发展等方面提出建议.

Finite Convergence of On-line BP Neural Networks with Linearly Separable Training Patterns

In this paper we prove a finite convergence of online BP algorithms for nonlinear feedforward neural networks when the training patterns are linearly separable.

中国数字经济发展水平的时空分异化及其收敛性研究

在数字经济发展的背景下,探究数字经济发展的时空格局和收敛性问题,对于促进地区协调发展具有重要的现实意义。文章基于选取的2011-2021年我国30个省份的面板数据,采用熵权法构建了中国数字经济综合指数,并利用核密度估计考察了中国数字经济的地区非均衡性及动态演化规律,同时采用变异系数法与空间计量模型检验了数字经济的收敛特性。研究发现:中国数字经济的发展呈现出以东部沿海省份为核心,中西部内陆省份为外围的“核心-边缘”结构,“数字鸿沟”特征明显;“H-H”集聚与“L-L”集聚构成了中国数字经济发展的主要格局,呈现出一定的极化特征,并且随着时间的推移极化特征有所减弱,非对称结构趋于缓解。计量结果显示:中国数字经济发展水平具有δ收敛、 β收敛以及俱乐部收敛特征,但在不同地区收敛速度存在差异,相对于东部地区而言中西部具有明显的“赶超效应”,收敛速度在省际间呈现“分化特征”。为此,政府应该遵循协同思维把握中国数字经济发展的时空演变规律与区域结构优化,从而实现区域间的共同发展。

混合模式搜索差分进化算法研究及其在高压容器概率优化中的应用

为求解高压容器的概率优化问题,提升差分进化算法的收敛速度,提出一种基于模式搜索算法的混合差分进化算法。该算法在差分进化算法的后期,引入模式搜索算子,以当前群体最优点作为模式搜索算子的基点进行模式搜索。仿真结果表明该混合算法收敛速度明显要优于差分进化算法。最后建立高压容器的概率优化设计模型,利用混合算法求解高压容器优化问题的确定型优化模型及概率优化模型,结果表明概率优化模型的优化结果更合理可靠。

基于混合灰狼算法的阵元失效校正方法

针对经典灰狼算法在处理复杂非线性优化问题时存在搜索不均衡、易陷入局部最优而出现早熟、寻优精度低等缺点,提出一种基于非线性双收敛因子策略与局部跳出机制相结合的混合灰狼算法,用于解决阵元失效校正问题。首先,依据平均适应度值将种群分为侦察狼和捕猎狼,两类狼依据不同的非线性递减收敛因子寻优来平衡算法的全局勘探和局部挖掘能力;其次,引入一种基于Sine混沌函数的跳出机制,提高了头狼个体的局部抗停滞能力,提升了算法的种群多样性。算法在目标函数中设计增加公共激励约束条件来降低天线系统的维护成本、提高系统的稳定性。对比现有基于群智能算法的校正技术,在更为苛刻的约束条件下,算法综合所得公共激励占比由0分别上升至10.7%,且校正前后方向图的辐射特性有一定提升,证明了所述算法的有效性。

遗传算法的一个调节算子研究

虽然遗传算法在许多领域获得了成功应用 ,但它本身存在不成熟的过早收敛问题是影响其发展的中的课题 .本文通过对遗传算法机理的分析和认识 ,给出了遗传算法早熟现象产生的原因是模式缺少 ,并提出了一个在遗传算法中基于模式抽取和模式补偿的调节算子以解决早熟现象 。

塔里木荒漠绿洲过渡带主要种群生态位与空间格局分析

于新疆塔里木盆地荒漠绿洲过渡带设置3条样带（长900 m×宽50 m）进行植物群落调查,运用生态位测度指标和点格局法对种群空间格局、空间关联性及生态位特征进行研究。结果显示,胡杨（Populus euphratica Oliv.）、多枝柽柳（Tamarix ramosissima Ledeb.）和甘草（Glycyrrhiza inflate Bat.）具有较大的重要值和生态位宽度,对其它生态位较窄的物种具有资源竞争和扩张优势,生态适应能力强,对群落结构和环境变化起决定性作用;生态过渡带植物的种间生态位重叠普遍较高,尤其是草本植物间更明显,此分配格局反映出荒漠植物长期适应旱化生境而发生趋同适应,生态位分化程度低,种间资源竞争激烈;优势种群空间格局呈明显的空间变异性,0-25 m尺度内多枝柽柳和甘草分别呈随机分布和聚集分布,胡杨种群在≤5 m尺度内呈聚集分布,并随尺度增大转为随机分布;胡杨与多枝柽柳、胡杨与甘草、多枝柽柳与甘草分别在〈4 m、≤16 m和≤25 m尺度内呈显著空间负关联,种间相互排斥。表明在匮乏环境资源条件下植物趋同适应与资源竞争是驱动荒漠植物群落演替和限制物种共存的主要原因。

基于改进粒子群算法的天线方向图综合技术

针对基本粒子群算法的早熟收敛、易收敛于局部极值的特点,提出一种改进的粒子群优化算法,采用对全局最佳微扰和惯性权重跳变阈值的设置改善了算法的优化速度和收敛精度。经过对一系列测试函数的计算,证明该方法具有良好的优化效果。最后,给出了该方法应用于阵列天线方向图综合中的模型和仿真实例。

北祁连山加里东期聚敛作用的构造转换及其成矿响应

北祁连造山前的构造聚敛样式的诸多争议 ,主要源于北祁连山东西段的巨大差异。甘肃肃南白泉门以东主要表现为 ,自北而南发育有弧后、岛弧和洋中脊、洋岛海相火山岩系 ,产出岛弧裂谷白银厂式 (黑矿型 )和弧后扩张脊石居里沟式 (塞浦路斯型 )块状硫化物矿床 ,少见陆壳基底碎块 ,花岗岩侵入体不发育 ;而西段以镜铁山微地块为特点 ,岛弧钙碱性火山岩系发育 ,分布有大面积花岗质岩基 ,产出夕卡岩型钨矿床。这种东西段区域岩石组合和成矿特征上的差异 ,反映了早古生代北祁连洋盆在中奥陶世—早志留世向北俯冲消减构造聚敛上的不同 ,东段为洋—洋俯冲的马里亚纳型的沟—弧—盆系大陆边缘 ,西段则转换为洋—陆俯冲的智利型活动大陆边缘 ,并由于深部消减物质的差异而形成不同的碰撞岩浆作用形式和相应的成矿组合。

基于改进模式提取变异算子的遗传算法

在经典遗传算法的基础上 ,提出了一种基于改进模式提取 ( Algorithm of pattern extrac-tion,Alopex)的变异算子 ,种群个体的连续进化方向作为当前代个体的变异方向 ,并利用自适应来调整变异步长 ,通过控制参数来控制变异方向的概率从而跳过局部最优值 .对几种典型函数的测试结果表明 ,基于该变异算子的遗传算法能较好地避免收敛到局部最优 。

长三角区域一体化背景下城乡收入格局演变研究

以长江三角洲地区74个县级地域单元1989-2011年城镇居民人均可支配收入、农村居民人均纯收入为资料，采用变异系数和马尔科夫链等方法分析长江三角洲地区收入格局的时空演变特征。结果表明：1989年以来，城镇收入的整体区域差异水平先升后降，农村收入区域差异则持续降低；城镇收入格局由以上海为中心的核心一边缘结构，转变为从沿海到内陆收入递减的地带式结构，一体化发展以后俱乐部增长趋同现象明显；农村收入格局渐趋均衡，高收入极化现象有所缓解，但低收入俱乐部向上移动困难；农村收入增长依托于城市，但增长速度相对落后，导致城乡差距持续拉大。

造山带汇聚板块边缘沉积盆地的鉴别与恢复

大洋俯冲和大陆碰撞是板块汇聚过程中的有机连续过程,也是造山带形成的两种基本造山作用方式。不同的造山作用过程形成不同类型的沉积盆地和填充序列,沉积盆地性质的改变和沉积物源区变化是造山作用方式和时限的最直接体现。沉积盆地是造山带重要大地构造相单元之一,完整记录了板块边缘动力学过程和构造演化以及造山作用方式和时限。沉积盆地构造原型鉴别与恢复是造山带结构-属性解剖的重要内容之一。视沉积盆地与相邻大地构造相的演化为统一整体,以填充物和沉积物源区作为链接沉积盆地和造山带的纽带,系统地精细解剖填充物组成和沉积相以及沉积物源区时空变化系列,准确鉴别并恢复造山带沉积盆地构造原型,是获取大陆碰撞方式和时限的沉积-地层判别标志的有效方法之一。

中国CO时空分布的遥感诊断分析

利用2010年9月AIRS(Atmospheric InfraRed Sounder)传感器的CO柱密度数据及地面CO小时浓度监测资料进行对比分析,结果表明,二者具有时间同步特征,相关系数为0.63(显著性水平95%),AIRS观测数据反映了地面CO的污染。通过2004-2010年CO柱密度数据,研究了中国CO的时空分布特征,平均CO柱密度由重至轻依次为华北、长三角、华中、珠三角、东北、四川及新疆地区,各区域在3月和4月达到CO污染峰值,且7年的CO柱密度较稳定。CO的空间分布具有显著汇聚带的特征,结合气象资料发现,反气旋系统中部及后部覆盖的均压场是形成显著汇聚带系统的主要背景场。