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新年寄语

<正>《中学生数学》和读者朋友们一起又迎来了新的一年.感谢广大读者和作者对杂志的厚爱与帮助.在过去的一年里,本刊为了更好地服务于读者,服务于社会,做了一些改进工作.在新的一年里,我们希望广大读者和作者一如既往地关心和支持《中学生数学》,在我们的共     

嘻嘻送快递

正金丝猴嘻嘻是出了名的急性子。飞毛腿快递公司的熊老板笑眯眯地对嘻嘻说:"急性子当快递员最合适啦!于是,嘻嘻就成了快递员。一天早上,熊老板指着一个大包裹(guǒ)对嘻嘻说:"这是一份加急快递,是青蛙王子送给癞(lài)蛤蟆公主的。"他又拿出几张纸,"这是到癞蛤蟆公主家的路线图。"     

螃蟹宝宝,你在哪儿

正春天来了,柳树姐姐的头发变长了,小河唱起了欢快的歌儿,勤劳的小燕子飞来飞去,忙着搭建新房子。一天下午,螃(pang)蟹(xie)妈妈领着螃蟹宝宝在河岸上急匆匆地走着,他们要在太阳落山前赶到外婆家。天色渐渐暗了下来,螃蟹妈妈和螃蟹宝宝小心翼(yi)翼地走在窄窄的田埂(geng)上。螃蟹宝宝一边走,一边吐泡泡玩,突然,他脚底一滑,"咕咚"一声,掉     

提高水分子流出纳米碳管速度的特殊水分子偶极排布研究

使用分子动力学的方法,研究了水分子进出狭窄碳纳米管的过程．发现管口处水分子的偶极垂直于碳管时容易流出碳管．根据碳管中与之相邻的水分子的偶极方向可以把这种特殊构型分为2类．虽然,这2类特殊结构的出现概率非常小,但是它们对净流过碳管水分子的贡献与其它结构的贡献基本相同．这2种偶极排布中水分子比较接近管壁、远离Lennard-Jones势的平衡位置,导致这2种偶极排布中水分子能量升高,处于相对不稳定的状态,容易流出碳管．这个发现表明可以通过调控碳纳米管内的水分偶极方向控制管内的水分子流动．     

幽你一默

结果老师:"今天我们来学减法。比方说,你哥哥有5个苹果,你从他那儿拿走3个,结果怎样?"汤姆:"结果嘛,结果他肯定会揍我一顿!"概率有问题"老师,我发现概率公式有问题!""哦?说说你的理由。""我们班共有50名同学,所以我被提问的概率是2%,可今天这一节课您几乎让我回答了所有的问题。"     

半平面上随机Dirichlet级数和Dirichlet空间

在 [1 ]的基础上 ,我们讨论了复平面上的单位圆上的Dirichlet空间和半平面上Dirichlet空间的关系 ,并找出了Dirichlet级数或一般随机Dirichlet级数属于a .s .属于Dirichlet空间和Lipr(0 相似文献   

水发汗冷却控制模型解的稳定性

本文研究了带活动边界的水发汗控制系统解对初边值条件及控制参数的连续依赖性 ,稳定性 .     

关于图Ka,b×Km,n的联结数

关于图Ｋ_（ａ，ｂ）×Ｋ_（ｍ，ｎ）的联结数张显坤（广东机械学院基础部广州５１０６４３）杨彩梅（广东民族学院应用数学系广州５１０６３３）关键词：完全偶图，笛卡尔来积；联结数ＡＭＳ（１９９１）主四分类：０５Ｃ７５．本文所讨论的都是简单图，术语和符号同０〕...     

三维海洋水动力计算σ坐标转换存在的问题及改进方法

三维水动力模型在准确模拟海洋物理特性中起着重要的作用,传统的σ坐标转换由于当时计算机能力所限,舍去了复杂的高阶项,在实际复杂地形（或水深变化）环境下,会带来一定的误差或计算失真等问题.由此,为了适应高精度计算结果的需求,对原有σ坐标三维水动力模型进行了重新修正.在改进后的模型中,综合考虑了经σ坐标变换引入的与流速、水位、地形相关的复杂高阶项,选用特定的插值函数,利用有限元和差分相结合的方法,进行求解σ坐标下的完整三维浅水模式方程.相比原模型,改进的模型对底坡、水深、潮汐振幅等变化适用范围更为广泛,能更好地模拟出复杂水深变化下的垂向流动分布特征,计算结果具有更高的精确度;改进的模型针对一些极端水位条件（潮汐振幅与水深比大于0.15）,其计算误差同样可保持在一个较低的范围内;同时,改进的模型只需更短的时间就可运行至稳定状态.     

Application of nonlinear optimization to water quality

Two formulations for nonlinear optimization (minimize variance and fractile programming formulations) are presented for the solution of water quality planning problems. The optimization algorithms are applied to the problem of determining the optimal waste removal to mitigate the deleterious impacts of the waste discharges on the dissolved oxygen concentration in a water body. The pollutant loading and transport in the stream are considered as random variables with the first two moments of the resulting distributions included in the models.     

基于粒子群算法的水稻用水的优化配置

本文旨在实现水稻用水资源的优化配置.早稻、一季稻和晚稻等不同类型水稻的用水,以及同一类型的水稻在不同的生长阶段,均存在着用水优化配置的问题.粒子群优化算法比较容易操作,在计算方面具有效率和精度高的优点,可以应用于水稻用水的优化配置模型的求解.以衡阳县高炉村的水稻用水优化配置为具体算例,验证了算法的可行性.     

大型海湾水交换计算中随机游动方法的应用研究

水交换矩阵是反映大型海湾不同子区域之间水交换关系的有效工具,该文对随机游动方法在水交换矩阵计算中的应用进行了研究．通过与对流扩散模型的对比,指出用随机游动方法计算水交换矩阵比用对流扩散方程求解更快更灵活．同时,为了对不同区域之间的水交换特性进行长期快速预测,采用了Thompson提出的预测矩阵方法．通过理论分析得出,影响该矩阵预测效果的因素主要有:粒子数目、分区数和预测矩阵取值时间．以一个矩形海湾为例,将数值模拟结果和预测矩阵预测结果进行对比,分析了以上各因素对预测效果的影响．结果表明,粒子数目越多,预测矩阵取值时间越长,预测矩阵的预测效果越好．在粒子数目足够多的情形下,分区数越多,预测效果越好．相反,粒子数目如果较少,过多的分区数将可能导致预测矩阵效果太差而不可用．     

EFFICIENCY IN GREAT BARRIER REEF WATER POLLUTION CONTROL: A CASE STUDY FOR THE DOUGLAS SHIRE

ABSTRACT. . Despite the lack of adequate economic evidence, water pollution from economic activities in Great Barrier Reef (GBR) catchments is often regarded excessive. In this paper marginal benefits from terrestrial (agricultural) water pollution and associated marginal marine costs from GBR degradation are estimated and used in an optimal control approach to determine optimal levels of water quality. Results, for a case study in the Wet Tropics in Australia, show that locally optimal levels of (fine sediment) water pollution are close to current levels, indicating that increased rates of (agricultural) water pollution lead to a decrease in local economic welfare. Globally optimal levels of water pollution are, however, below current levels, indicating that (inter‐) national compensation for beneficial spillovers from reduced GBR degradation can increase global economic welfare.     

A multi-objective optimal allocation model for irrigation water resources under multiple uncertainties

This paper proposed a multi-objective optimal water resources allocation model under multiple uncertainties. The proposed model integrated the chance-constrained programming, semi-infinite programming and integer programming into an interval linear programming. Then, the developed model is applied to irrigation water resources optimal allocation system in Minqin’s irrigation areas, Gansu Province, China. In this study, the irrigation areas’ economic benefits, social benefits and ecological benefits are regarded as the optimal objective functions. As a result, the optimal irrigation water resources allocation plans of different water types (surface water and groundwater) under different hydrological years (wet year, normal year and dry year) and probabilities are obtained. The proposed multi-objective model is unique by considering water-saving measures, irrigation water quality impact factors and the dynamic changes of groundwater exploitable quantity in the irrigation water resources optimal allocation system under uncertain environment. The obtained results are valuable for supporting the adjustment of the existing irrigation patterns and identify a desired water-allocation plan for irrigation under multiple uncertainties.     

基于二层规划的流域水资源交易决策模型

对于一个流域而言,解决水资源短缺及污染最为有效的经济手段是建立以流域统一管理为基础,兼顾水权交易和排污权交易的市场体系.在水交易市场运作过程中存在着流域管理机构和具体用户之间的利益矛盾,为此本文构建了以流域管理机构作为流域水资源系统整体计划、控制和协调中心的上层决策者,各用户作为具有相对自主权的下层决策者的决策管理机制,并利用二层规划方法对流域水资源的交易进行建模研究,期望实现流域水资源的最优分配.最后,应用算例验证了模型及求解方法的可行性和有效性.     

A DISTRIBUTED PARAMETER CONTROL SYSTEMS APPROACH TO THE ANALYSIS OF WATER ALLOCATION

The optimal diversion and consumption of water is examined in a framework acknowledging both diversionary water demands and instream water demands. Return flow relationships among a basin's water users recommends that optimization be conducted over time and space domains jointly. The distributed parameter control methodology is employed to satisfy this need in a generalized model. Results demonstrate the power of the method and identify how attention to instream demands influences optimal water use by the basin's diverters.     

多水库水资源系统的随机动态运行模型

具有多个水库的水资源系统是一种随机动态系统。研究这种系统的运行管理的目的是要确定一年内各时段中最优运行的策略。在建立优化运行模型时要解决两个问题。一是对于作为系统输入的天然迳流序列和作为系统约束的用水序列的处理方法；二是应用多维动态规划法推求优化运行模型的方法。     

DEVELOPMENT OF AN OPTIMAL WATER ALLOCATION DECISION TOOL FOR THE MAJOR CROPS DURING THE WATER DEFICIT PERIOD IN THE SOUTHEAST UNITED STATES

ABSTRACT. We developed a dynamic economic model to optimize irrigation water allocations during water deficit periods for three major crops grown in the humid southeastern United States. Analysis involved the use of crop simulation models to capture (a) the yield water relationship and (b) soil moisture dynamics from one week to another week. A hy‐drological model was used to find the water supply; combinations of hydrological and simulation models were used to find the optimal water allocation during each week in corn, cotton and peanuts. Results indicated that farmers should irrigate the most valuable crop first (peanuts) before applying water to other crops (corn and cotton). Results also showed that, because of restriction on total water supply, an increase in crop acreage did not increase the net revenue of the farm in a proportionate amount. Results should provide guidelines to water managers, engineers, policy makers, and farmers regarding an optimal amount of water allocation that will maximize net returns when water shortage is a serious concern.     

努拉里边底水油气藏提高采收率注采制度优化方法

开发边底水油气藏关键因素是抑制边底水锥进,延长油井无水采油期以提高油藏采收率,因此需要设置合理的开采速度和油水井注采制度.为深入了解不同井网系统和注采参数对边底水油气藏开发效果的影响程度,针对努拉里边底水油气藏开展研究.对边底水影响程度进行研究,得到各井在改变水体倍数后,以含水率差值4%为界限定义受边底水影响程度强弱,差值超过4%则定义为强水侵井,反之则为弱水侵井.在此基础上,采用油藏工程和数值模拟方法优选了注采参数,得出最优井距为1000m,最佳日注水量为30m³/d,最佳采液速度为4.75%-5%,并对优化参数进行了模拟预测,优化后累计产油量增加1.98×10⁴t,采收率达到54.7%.运用油藏工程方法对优化后的开发方式调整进行了分析,结果表明:可采储量采出程度小于62.78%时应以扩大波及体积为主,大于62.78%后应以增加驱油效率为主,目标区块优化后可采储量采出程度达到71.3%,相对潜力值i=0.81<1,处于开发后期,此时开发方式应以提高驱油效率为主.研究成果为同类边底水油气藏前期开发和后期措施调整提供了理论指导和借鉴.