蚁群算法解决TSP问题的研究

蚁群算法是一种用于解决复杂问题的新的启发武算法，它是通过信息素的积累和更新收敛于最优路径上，隶解速度慢，而遗传算法具有快速随机的局部搜索能力。将遗传算法和蚁群算法融合，给出一种求解TSP问题的改进的算法。     

一般含时线性势的量子解及有关问题

对于一般形式的含时线性势, 通过假设波函数形式的方法得到了Schr?dinger方程的精确和完备解. 同时指出, 用两个波函数φ(t)〉和ψ(t)〉定义的坐标和动量的矩阵元〈φ(t)xψ(t)〉和〈φ(t)pψ(t)〉满足经典形式的运动方程. 按照量子力学的系综理论, 这样的经典形式的运动方程实际上是流体方程. 进一步研究发现, 对于任意形式的线性系统有类似的结论.     

Cooperative solution of constraint satisfaction problems

It is widely believed that a group of cooperating agents engaged in problem solving can solve a task faster than either a single agent or the same group of agents working in isolation from each other. Nevertheless, little is known about the quantitative improvements that result from cooperation. A number of experimental results are presented on constraint satisfaction that both test the predictions of a theory of cooperative problem solving and assess the value of cooperation for this class of problems. These experiments suggest an alternative methodology to existing techniques for solving constraint satisfaction problems in computer science and distributed artificial intelligence.     

Analytic and algorithmic solution of random satisfiability problems

We study the satisfiability of random Boolean expressions built from many clauses with K variables per clause (K-satisfiability). Expressions with a ratio alpha of clauses to variables less than a threshold alphac are almost always satisfiable, whereas those with a ratio above this threshold are almost always unsatisfiable. We show the existence of an intermediate phase below alphac, where the proliferation of metastable states is responsible for the onset of complexity in search algorithms. We introduce a class of optimization algorithms that can deal with these metastable states; one such algorithm has been tested successfully on the largest existing benchmark of K-satisfiability.     

城市环境与城市生态面临的问题和出路

20世纪70年代以来，城市环境污染严重程度已经倍受关注，人类通过对环境问题的认真思考，选择了正确的发展现——可持续发展。正确的发展战略，新的产业结构，文明的生态意识，使人们对新世纪的未来充满了希望。然而，20世纪产生的许多重大的环境问题并没有消失。人类要生存，经济要发展，环境要保护，三者依然存在很多矛盾。城市作为发展的先驱，其面临的机遇和挑战是并存的。本文以理论为指导拟对我国城市居民面临的环境状况。城市中人们面临的污染以及提出面对和解决这些问题的设想。     

玉米覆膜播种中存在的两个问题及解决方法

针对现行玉米覆膜播种机因采用平直型种植垄面播种玉米造成幼苗的灼烧 ,及利用圆柱型垂直窝眼式圆盘排种器使种子破碎率高的问题 ,运用分析、试验的方法 ,提出玉米覆膜播种中以 W型种植垄面替代平直型种植垄面 ,及以 V形窝眼式圆盘排种器替代圆柱型垂直窝眼式圆盘排种器的改进措施 ,消除了烧苗现象 ,使种子破碎率降低到 0 .5 2 % ,穴粒数合格率提高到 98.95 % ,空穴率降为 1.0 4%。     

河北省城市化问题分析与对策

河北省城市化进程已进入了加速发展的中期阶段,但城市化水平低于全国水平,与发达省份的差距在不断加大。通过分析河北省城市化现状及问题,提出了解决河北省城市化问题的对策。     

农业推广硕士专业学位研究生教育存在的问题及对策

文章对农业推广硕士专业学位研究生在招生和培养上存在的问题做了具体分析，并从7个方面提出了保证农科专业学位质量的对策及建议：端正农科专业学位教育思想；严格入学资格审查；入学考试全部实行全国统考；健全招生管理，完善招生指标分配制度；认真执行培养方案，严格教学管理；健全规章制度；建立质量评估体系和监督机制。     

大跨度非对称酿热温室热环境及节地增产效果分析

【目的】设计一种大跨度非对称酿热温室(GH-F),探究其保温蓄热性能,为未来温室设计提供新思路和理论依据。【方法】GH-F依据传统日光温室采光保温原理设计,东西走向,南北非对称,跨度17.0 m,其南部10.0 m,北部7.0 m,北部底端内侧根据温室长度配置30.0 m×1.0 m×1.0 m的农业废弃物发酵酿热槽。以传统日光温室(GH-P)和大跨度双层内保温大棚(GH-D)为对照,采用理论分析的方法比较3种温室在最大采暖负荷(室内外温差20℃)下的散热量,通过试验测定3种温室冬季晴天光照强度日变化及冬季典型晴天、典型阴天、典型雪天条件下的保温蓄热性能,并对3种温室建造的投资成本与节地增产效益进行计算。【结果】根据温室热负荷静态模拟理论,在夜间室内外温差20℃条件下,GH-F、GH-D和GH-P室内散热量分别为51.21,45.99,41.86 W/m~2。GH-F的保温性能低于GH-D和GH-P,故建造酿热槽来弥补其保温蓄热性能的不足。实测结果表明,在2016-01-01-2016-01-31,酿热槽1月份平均温度高出室内气温24.7℃,可有效向外界释放热量。在冬季典型晴天条件下,GH-F、GH-D及GH-P夜间平均气温和地温分别为7.9,5.0,8.0℃和12.0,10.4,10.7℃;典型阴天条件下,室内夜间平均气温和地温分别为8.7,5.8,7.3℃和11.3,9.1,10.9℃;典型雪天条件下,室内夜间平均气温和地温分别为8.9,6.5,7.1℃和11.6,9.8,9.3℃。GH-F的日平均气温分别比GH-D和GH-P高2.1～3.0和0.7～2.1℃;GH-F的日平均地温分别比GH-D和GH-P高1.4～2.0和0.5～2.2℃;在室外最低气温为-14.3℃的极端天气下,GH-F夜间最低气温为5.3℃,比GH-D和GH-P分别高出3.8和0.8℃。统计结果表明,GH-F实际建造成本为180.06元/m~2,比GH-D及GH-P分别低59.97和170.02元/m~2;与GH-P相比,GH-F土地利用率提高29.93%,番茄产量提高1.80 kg/m~2。【结论】大跨度非对称酿热温室冬季温度、土地利用率和实际种植效益均优于传统日光温室,适合在黄河中下游及淮河流域类似气候条件的地区推广应用。     

高校教师素质存在的问题与破解之策

本文分析了高校师资队伍存在的主要问题,认为提高高校教师队伍的整体素质应主要从两方面入手:一是教师队伍要转换教育思想和教育观念,自觉进行知识更新与重组;二是各级教育行政部门和高等学校要采取多种措施,提高教师素质。     

具有非局部反应项的非线性抛物方程解的整体存在性与爆破问题

研究了满足Dirichilet零边界条件的具有非局部反应项的非线性抛物方程解的整体存在性与爆破问题.     

浅析林权证登记管理工作中存在的问题及解决途径

林权证是林业产权制度不断完善的产物,也是依法严格保护林权,维护其合法权益的根本保证.林权证的全面实施与发放,关系到森林、林木及林地资源的合理经营与可持续发展,对保护和发挥我国现有森林资源的综合价值与潜在实力,调动社会各方面造林、护林、营林的科学性和积极性,促进林业更好更快发展的有着重要的意义.对林权证的法律效应及发放意义、林权证管理的关键环节及在发证工作中暴露出的几个问题做出阐述,并就今后如何进一步加强林权登记管理工作提出了几点建议.     

政和县村级财务管理存在的问题及解决途径

重点分析当前农村财务管理上存在的财务管理不规范等问题,并提出解决当前这些问题的途径。     

Current status of asymmetric synthesis

In the last 30 years the subject of asymmetric synthesis has grown from a little studied academic niche in organic chemistry to an intensely investigated field of commercial importance and heightened general interest. Impressive advances have been made in several areas, notably catalytic asymmetric homogeneous hydrogenation, catalytic asymmetric epoxidation of allyl alcohols and stereochemical control of carbon-carbon bond-forming reactions. Asymmetric synthesis must now be deliberately considered along with other available methods as a practical strategy for the synthesis of any chiral compound.     

Suppressing wall turbulence by means of a transverse traveling wave

Direct numerical simulations of wall-bounded flow reveal that turbulence production can be suppressed by a transverse traveling wave. Flow visualizations show that the near-wall streaks are eliminated, in contrast to other turbulence-control techniques, leading to a large shear stress reduction. The traveling wave can be induced by a spanwise force that is confined within the viscous sublayer; it has its maximum at the wall and decays exponentially away from it. We demonstrate the application of this approach in salt water, using arrays of electromagnetic tiles that produce the required traveling wave excitation at a high efficiency.     

Educated consumers don't believe artificial meat is the solution to the problems with the meat industry

The production of in vitro meat by cell culture has been suggested by some scientists as one solution to address the major challenges facing our society. Firstly, consumers would like the meat industry to reduce potential discomfort of animals on modern farms, or even to avoid killing animals to eat them. Secondly, citizens would like meat producers to reduce potential environmental deterioration by livestock and finally, there is a need to reduce world hunger by increasing protein resources while the global population is predicted to grow rapidly. According to its promoters, artificial meat has a potential to make eating animals unnecessary, to reduce carbon footprint of meat production and to satisfy all the nutritional needs and desires of consumers and citizens. To check these assumptions, a total of 817 educated people(mainly scientists and students) were interviewed worldwide by internet in addition to 865 French educated people. We also interviewed 208 persons(mainly scientists) after an oral presentation regarding artificial meat. Results of the three surveys were similar, but differed between males and females. More than half of the respondents believed that artificial meat was feasible and realistic. However, there was no majority to think that artificial meat will be healthy and tasty, except respondents who were in favour of artificial meat. A large majority of the respondents believed that the meat industry is facing important problems related to the protection of the environment, animal welfare or inefficient meat production to feed humanity. However, respondents did not believe that artificial meat will be the solution to solve the mentioned problems with the meat industry, especially respondents who were against artificial meat. The vast majority of consumers wished to continue to eat meat even they would accept to consume less meat in a context of increasing food needs. Only a minority of respondents(from 5 to 11%) would recommend or accept to eat in vitro meat instead of meat produced from farm animals. Despite these limitations, 38 to 47% of the respondents would continue to support research on artificial meat, but a majority of them believed that artificial meat will not be accepted by consumers in the future, except for respondents who were in favour of artificial meat. We speculated that the apparent contradictory answers to this survey expressed the fact that people trust scientists whoare supposed to continuously discover new technologies potentially useful in a long term future for the human beings, but people also expressed concern for their health and were not convinced that artificial meat will be tasty, safe and healthy enough to be accepted by consumers.     

Experimental observation of nonlinear traveling waves in turbulent pipe flow

Transition to turbulence in pipe flow is one of the most fundamental and longest-standing problems in fluid dynamics. Stability theory suggests that the flow remains laminar for all flow rates, but in practice pipe flow becomes turbulent even at moderate speeds. This transition drastically affects the transport efficiency of mass, momentum, and heat. On the basis of the recent discovery of unstable traveling waves in computational studies of the Navier-Stokes equations and ideas from dynamical systems theory, a model for the transition process has been suggested. We report experimental observation of these traveling waves in pipe flow, confirming the proposed transition scenario and suggesting that the dynamics associated with these unstable states may indeed capture the nature of fluid turbulence.     

Mechanism and stereoselectivity of asymmetric hydrogenation

Rhodium complexes containing chiral phosphine ligands catalyze the hydrogenation of olefinic substrates such as alpha-aminoacrylic acid derivatives, producing chiral products with very high optical yields. Elucidation of the mechanisms of such reactions leads to the conclusion that the stereoselection is dictated not by the preferred initial binding of the substrate to the chiral catalyst, but rather by the much higher reactivity of the minor diastereomer of the catalyst-substrate adduct corresponding to the less favored binding mode.