商人渡河问题的有解性分析

"商人渡河问题"是一个传统的智力游戏问题,常常作为数学模型、数据结构与智能算法分析等学科中很重要的教学与实验案例被引用.其求解算法尚未得到很好的解决,尤其是问题解的存在性等还缺少一般性和明确的结论.对此,将主要从理论上探讨该类问题何时有解的一般性结论,并给出严格的数学证明.同时还将讨论渡船上安全策略的不同选择对问题求解的影响.     

吴家庄水库库区岩溶渗漏分析

吴家庄水库位于山西省黎城县境内 ,拟建于由西南源和北源汇合而成的浊漳河干流上 ,总库容 3.6亿 m3,属大型水利工程。坝址区基岩为震旦系串岭沟组石英砂岩 ,向上游库区依次出露寒武、奥陶系碳酸盐岩 ,其分布面积占整个库区面积的一半以上 ,岩溶渗漏是库区最主要的工程地质问题 ,它直接影响到建库规模的确定和工程的可行性 ,本文就此进行了分析、评价 ,并对建库规模提出了建议.     

长三角地区房地产市场是如何实现"去库存"的?

长三角地区在全国房地产"库存"的背景下,实现了房地产市场的不断向好.对长三角地区有关面板数据进行实证研究,实证结果表明房地产开发投资、医院床位数、工业生产总值与人均房地产成交面积呈正相关.城镇人口数,中、长期贷款利率与人均房地产成交面积呈负相关,高收入城市比低收入城市人均房地产成交面积低14.%,教育支出和城镇居民总的可支配收入对人均房地产成交面积影响不显著.     

A safe minimum standard,the elasticity of substitution,and the cleanup of the Ganges in Varanasi

Despite repeated calls for a thorough cleanup of water pollution in the Ganges river, there are only two papers in the social sciences by Batabyal and Beladi (2017, 2019) that have shed theoretical light on this cleanup problem and its connection to the sustainability of tourism in Varanasi. Hence, we extend the above‐mentioned analyses and focus on two specific questions. First, we introduce the notion of a safe minimum standard (SMS) into the study and show how to analyze a probabilistic model of the Ganges cleanup problem when the SMS is accounted for. Second, for a representative citizen of Varanasi, we study how the magnitude of the elasticity of substitution between a composite consumption good and water quality in the Ganges—modeled by the SMS—affects the tradeoff between consumption and water quality maintenance.     

覆盖数不超过3的图上渡河问题

1000多年前,英国著名学者Alcuin曾提出一个古老的渡河问题,即狼、羊和卷心菜的渡河问题。2006年,Prisner把该问题推广到任意的冲突图上,考虑了一类情况更一般的渡河运输问题。所谓冲突图是指一个图G=(V,E),这里V代表某些物品的集合,V中的两个点有边连结当且仅当这两个点是冲突的,即在无人监管的情况下不允许留在一起的点。图G=(V,E)的一个可行运输方案是指在保证不发生任何冲突的前提下,把V的点所代表的物品全部摆渡到河对岸的一个运输方案。图G的Alcuin数定义为它存在可行运输方案时所需船的最小容量。本文讨论了覆盖数不超过3的连通图的Alcuin数,给出了该类图Alcuin数的完全刻画。     

黑龙江省的界河坍塌地质灾害及其防治对策

界河坍塌是黑龙江省特殊的、主要的地质灾害,也是当前亟待解决的问题。本文总结了黑龙江省的两条主要界河—黑龙江和乌苏里江的塌岸状况;说明了界河坍塌的分布规律;论证了界河坍塌的形态类型;探讨了界河坍塌的形成机制;分析了界河坍塌的原因;最后提出了防止界河坍塌的一系列对策。     

杭州城西河网清淤优化调度

引水进入城市河网可快速提升河道水质,但也会导致泥沙淤积等问题;城市河网不仅河道众多,还有水闸等水工建筑物,使得水沙输移问题变得更为复杂.为了使泥沙尽量少淤积于不易清淤的河道,需优化河网水闸的调度.首先建立了考虑水闸的河网一维泥沙输移数学模型,利用实测水沙数据验证其精度.通过模型计算不同引水流量工况下杭州城西河网泥沙的淤积量及淤积分布,得到泥沙淤积率最低以及最利于清淤时的河网水闸优化调度方案,可为城市河网泥沙减淤及清淤提供理论依据和参考.     

Determination of Trace Elements in Marine Cetaceans by ICP-MS and Health Risk AssessmentSCIEI北大核心CSCD

The liver, kidney and muscle samples from seven cetaceans were digested by microwave digestion, and trace elements amounts of V, Cd, Cu, Zn, As, Cr, Ni, Mn, Se, Hg and Pb were determined by inductively coupled plasma mass spectrometry (ICP-MS), and the health risk assessment for Zn, Cu, Cd, Hg, Se in the liver was conducted. The results of international lobster hepatopancreas standard (TORT-2) showed acceptable agreement with the certified values, and the relative standard deviation (RSD) of eleven kinds of trace elements were less than 3.54%, showing that the method is suitable for the determination of trace elements in cetaceans. The experimental results indicated that different tissues and organs of the dolphins had different trace elements, presenting the tissue specificity. There is a certain inter-species difference among different dolphins about the bioaccumulation ability of the trace elements. The distribution of trace elements in whales presented a certain regularity: the contents of most elements in liver, kidney were much higher than the contents of muscle tissues, Cu, Mn, Hg, Se, and Zn exhibit the higher concentrations in liver, while Cd was mainly accumulated in kidney. And according to the health risk assessment in liver, the exceeding standardrate of selenium and copper in seven kinds of whales was 100%, suggesting that these whales were suffering the contamination of trace elements. The experimental results is instructive to the study of trace elements in cetaceans, while this is the first report for the concentrations in organs of Striped dolphin, Bottlenose dolphin, Fraser's Dolphin and Risso's dolphin in China, it may provide us valuable data for the conservation of cetaceans.     

Stable H and O isotope-based investigation of moisture sources and their role in river and groundwater recharge in the NE Carpathian Mountains,East-Central Europe†

The region situated between the mountain area and the lowlands in NE Romania (East-Central Europe) is experiencing increased competition for water resources triggered by a growing population, intensification of agriculture, and industrial development. To better understand hydrological cycling processes in the region, a study was conducted using stable isotopes of water and atmospheric trajectory data to characterize regional precipitation and vapour sources derived from the Atlantic Ocean, Mediterranean and Black Seas, as well as recycled continental moisture, and to assess and partition these contributions to recharge of surface and groundwater. Atmospheric moisture in the lowlands is found to be predominantly delivered along easterly trajectories, while mountainous areas appear to be dominated by North Atlantic Ocean sources, with moisture transported along mid-latitude, westerly storm tracks. Large-scale circulation patterns affect moisture delivery, the North Atlantic Oscillation being particularly influential in winter and the East Atlantic pattern in summer. Winter precipitation is the main contributor to river discharge and aquifer recharge. As winter precipitation amounts are projected to decrease over the next decades, and water abstraction is expected to steadily increase, a general reduction in water availability is projected for the region.     

Spatiotemporal patterns of stable isotopes and hydrochemistry in springs and river flow of the upper Karkheh River Basin,Iran

Karst springs of the Zagros Mountains contribute a significant amount to agricultural and human water demands of western and south-western Iran. For an adequate management of available water resources in semi-arid and arid regions, sufficient hydrological monitoring is needed, and hydro-chemical and isotope hydrological data provide important additional information. About 350 water samples were collected from precipitation, river water, and karst springs of the upper part of the Karkheh River Basin (20,895 km²) located between 33°35^′ and 34°55^′ North and 46°22^′ and 49°10^′ East with elevations ranging from 928 to 3563 m above sea level. Sampling was conducted in monthly time resolution from August 2011 to July 2012. All samples were analysed for hydro-chemical parameters (pH, electrical conductivity, and major ions) and stable isotopes (deuterium, oxygen-18). Isotope values of precipitation indicate a local meteoric water line (Zagros MWL δ²H=6.8 δ¹⁸O+10.1; R²=0.99) situated between the Mediterranean MWL and Global MWL. Spring and river water isotope values vary between?7.1 and?4.1 ‰, and?38 and?25 ‰ for δ¹⁸O and δ²H, respectively, responding to winter snowmelt and evaporation. This work implements stable isotopes and hydro-chemical information of springs and river water to understand hydrological and hydro-geological interrelations in karstic semi-arid areas and helps to improve the current water resources management practices of western Iran.