作物生长期水分条件对大连地区粮食产量的影响

利用1961～2000年大连主要产粮地区旅顺、金州、瓦房店、普兰店、庄河粮食产量资料和5个不同时段的水分条件指数资料。分析了粮食作物生长期水分条件对大连地区粮食气象产量的影响关系。结果表明，偏湿年份利于粮食增产，偏干年份粮食减产。     

稻飞虱的发生发展与气象条件的关系

稻飞虱是水稻生产中的主要害虫之一。近几年来,稻飞虱在大连地区的危害有明显加重的趋势。因此,研究稻飞虱的发生发展规律并提出相应的防治措施,是目前大连地区水稻生产中亟待解决的问题。稻飞虱属热带昆虫,具有迁飞特性。在我国北方每年所发生稻飞虱的虫源都是由南方逐次迁飞而来的。稻飞虱的迁飞与气象条件密切相关,其起飞、高空飞行、降落等过程,必须依赖于地面上升气流、高空气流、当地的下沉气流或降水来完成。因此,本文从气象角度来研究稻飞虱的高空飞行及降落与气象条件的关系,并找出相应的气象指标。1稻飞虱迁入的气候规律1…     

Simulation of Surface Wave with Large Eddy Simulationin in δ-Coordinate System

A three-dimensional numerical model in the δ-coordinate system is developed to study the problem of waves. Turbulence effects are modeled by a subgfid-scale (SGS) model with the concept of large eddy simulation (LES). The δ-coordinate transformation is introduced to map the irregular physical domain of the wavy free surface and uneven bottom onto the regular computational domain of the shape of rectangular prism. The operator splitting method, which splits the solution procedure into the advection, diffusion, and propagation steps, is used to solve the modified Navier-Stokes Equation.The model is used to simulate the propagation of solitary wave and wave passing over a submerged breakwater. Numerical results are compared with available analytical solutions and experimental data in terms of velocity profiles, free surface displacement, and energy conservation. Good agreement is obtained. The method is proved to be of high accuracy and efficiency in simulating surface wave propagation and wave-structure interaction. It is suitable for the large and irregular physical domain, and requiring the non-uniform grid system. The present work provides a foundation for further studies of random waves, wave-structure interaction, wave-discharge interaction, etc.     

Numerical Study of Submerged Vertical Plane Jets Under Progressive Water Surface Waves

When wastewater is discharged into a coastal area through an ouffall system, it will always be subjected to the action of waves. It is important to study and quantify the mixing of the discharge with the ambient water so that accurate environmental impact assessment can be made for such discharge conditions. The present work aims to study the phenomenon of a plane jet discharged into water environment with regular waves. A 3D numerical model based on the full Navier- Stokes equations （NSE） in the a-coordinate is developed to study the present problem. Turbulence effects are modeled by a subgrid-scale （SGS） model using the concept of large eddy simulation （LES）. The operator splitting method is used to solve the modified NSE. The model has been applied to the simulation of three different eases of submerged plane jets with surface waves： jet with strong waves, jet with weak waves and jet without waves. Numerical results show that the waves enhance the mixing of the jet with the ambient fluid, and cause a periodic deflection of the jet. The size of the recirculation is about 1.5- 2.4 h （water depth） . The velocity profile of the jet is serf-similar in the zone of established flow for both the pure jet and jet in wave circumstances. The spreading characteristic constant a is 0. 100 and 0. 105 for pure momentum jets with Re numbers 1025 and 2050. The value of a increases from 0. 130 to 0. 147 for a jet in weak and strong wave circumstances, showing that waves have an obvious effect on the mixing and dilution properties of jets. Numerical results are in good agreement with the experimental data for the cases of pure jets and jets with waves.     

Simulation of Surface Wave with Large Eddy Simulation in σ-Coordinate System

1 .IntroductionInthepastdecades,thepropagationofwaveswaswidelystudiedbecausemanyindustrialanden vironmentalproblemsincoastalengineeringcouldbecategorizedaswavesorinteractionbetweendis chargeandwaves.Forexample,whenwastewaterisdischargedintoacoastalareathroughanoutfallsystem ,itwillalwaysbesubjectedtotheactionofwaves.Itisimportanttostudyandquantifythisphenomenonsothatanaccurateenvironmentalimpactassessmentcanbemadeforsuchdischargecon ditions.Asafirststep ,thepresentworkaimstostudyanefficientmet…     

大连地区冬季气温异常与前期印度洋海温的关系

利用近40a全球海温、500hPa高度场、300hPa纬向风场和海平面气压场月平均资料以及大连地区冬季的气温资料,分析了大连地区冬季气温异常的变化特征,探讨了大连地区冬季气温异常与前期印度洋海温异常的相互联系。结果发现:影响大连地区冬季气温的海温异常关键区位于5°S~5°N、60°~75°E,关键影响时段为当年的4~7月;长时间的海气相互作用使前期的海温异常影响了后期的大气环流,在关键海区冷、暖水年,海平面气压距平场、500hPa高度距平场、300hPa纬向风距平场都存在着显著的差异;其中西伯利亚高压、极涡的位置、东亚大槽的强弱、极锋急流都差异显著,从而导致大连地区冬季气温的异常。     

大连地区主汛期多、少雨年同期大气环流场的差异

大连地区主汛期降水异常是该地区大气环流异常直接影响的结果,本文用1961~2000年各层大气环流场资料来分析对比多、少雨年同期大气环流的情况。揭示出大连地区主汛期多雨年和少雨年同期的海平面气压场、850 hPa大气环流场、500 hPa西风带槽脊和高度场都存在显著差异。多雨年较少雨年该地区低层的辐合上升运动加强,850 hPa盛行西南气流,水汽输送旺盛。同时,500 hPa西风带的槽脊波动加深,高空西风急流增强。     

大连地区伏期旱涝指数EOF分析和预测

从大连地区气候规律及农业生产实际出发，制定出客观定量表征伏期旱涝特征的旱涝指数；用EOF方法对大连地区1961～2000年伏期旱涝指数进行了分析，在此基础上提出一种伏期旱涝预测方法。     

黄河三角洲湿地保护与恢复的现状、问题与建议

黄河三角洲湿地是中国暖温带保存最完整、最广阔和最年轻的湿地生态系统,其原始性、脆弱性和作为珍稀濒危鸟类重要栖息地的作用在国际上备受关注。着眼于当前黄河三角洲湿地的生态问题及变化趋势,分析了黄河三角洲湿地保护与恢复的现状、问题和发展趋势,阐明了黄河三角洲湿地保护与恢复的基本框架和关键技术,明确了下一步黄河三角洲湿地保护与恢复的主要任务,并从区域可持续发展角度提出了黄河三角洲湿地保护与恢复的措施与建议。     

浅析企业价值最大化的理财目标

从对公司理财目标的认识出发,提出企业价值最大化是最为科学的公司理财目标,围绕实现这个财务管理的根本目标,认为企业实现价值最大化的途径是提高企业盈利能力与降低风险;通过对企业盈利能力、风险的因素分析,提出企业的营业决策、筹资决策、投资决策、风险控制管理决策对企业实现价值最大化理财目标的影响及相应对策.