Population dynamics of the bank vole as studied using sequence functions

Sequence functions were used to construct a simulation model of the long-term population dynamics of the bank vole in Karelia. The mechanisms of population reproduction control affect the population size if it is greater than 1 and 4 ind./100 trap-days in spring and autumn, respectively.     

Validation of a Lagrangian dispersion model implementing different kernel methods for density reconstruction

In this paper the inert version of a Lagrangian particle model named photochemical Lagrangian particle model (PLPM) is described and validated. PLPM implements four density reconstruction algorithms based on the kernel density estimator. All these methods are fully grid-free but they differ each other in considering local or global features of the particles distribution, in treating the Cartesian directions separately or together and in being based on receptors or particles positions in space. Each kernel has been shown to have both advantages and disadvantages, but the overall good performances of the model when compared with the well known Copenhagen and Kincaid data sets are very encouraging in view of its extension to fully chemically active simulations, currently under development.     

上海市郊区农业土地流转类型与土地利用变化响应差异性研究

在对农业用地流转机制进行深入分析的基础上，将农业土地流转市场划分为三种类型：政府引导型、集体推动型和农户主导型。进而结合农户调查数据，通过建立农业土地非耕地化流转的驱动力模型。分析不同类型的农业土地流转市场对于耕地利用变化的影响。模型运行结果表明：政府引导的农业土地流转导致耕地面积大幅减少，集体推动的流转有利于提高耕地利用效率。农户主导的农业土地流转促使了粮食作物种植面积的减少。最后以模型运行结果为依据，从保护农民土地权益、维持耕地总量平衡的角度提出相关建议。     

土地督察对土地市场化的影响效果评估

为评估土地督察对土地市场化的影响,论文把目标分解为两个问题:即土地督察制度的实施是否对土地市场化程度产生影响;如果有影响,影响的效果如何。论文收集了2003—2009年的省级面板数据,基于固定效应和随机效应模型估计了土地督察对土地市场化的影响。通过相关检验,采用了固定效应模型的估计结果,并在模型估计的基础上,对影响效果进行了评价。结果表明:①土地督察对土地市场化的发展有积极的促进作用,2007—2009年专项督察覆盖度每提高1%,约能促进土地市场化程度提升0.14%,例行督察覆盖度每提高1%,约能促进土地市场化程度提升1.12%;②通过实施专项督察,2007—2009年全国土地市场化程度分别提升了2.06%、 0.19%和0.55%,通过实行例行督察,2008—2009年全国土地市场化程度分别提升5.01%和12.47%;③2007—2009年通过开展土地督察,全国土地市场化程度分别提高了2.04%、 5.21%和13.02%。     

基于半经验模型对大面积染料敏化太阳电池性能影响因素的研究

以影响大面积染料敏化太阳电池性能的几个物理参量和几何参量为切入点,分析了内部电阻对电池性能的影响,针对几种构型不同的大面积电池,建立了效率的半经验模型.根据并联、串联、和各单元独立式串并联的大面积电池的相关物理参量和几何参量,对电池效率进行了计算.通过比较计算值与测试值的偏差,分析了半经验模型的适用性.在半经验模型的基础上,分析了相关物理参量和几何参量对电池性能的影响.结果表明,在实际应用中,通过半经验模型分析物理参量和几何参量的影响,可以优化大面积电池的性能.     

利用卫星资料估算我国西北地区直接辐射

在缺乏直接辐射、云量、日照时数等地面观测资料情况下,如何正确估算太阳直接辐射对太阳能合理开发利用有重要意义。利用NCEP/NCAR再分析资料、EOS-AURA卫星和FY-2C气象卫星反演资料,采用一个改进的宽带辐射传输模型对我国西北5个地面辐射站点2006年和2007年直射日曝辐量进行了估算。模型首先在Bird模型基础上对晴空条件下的太阳直接辐射进行了计算,然后结合FY-2C气象卫星总云量和云类反演数据,引入了一个线性方程,对实际天气状况下的直射日曝辐量进行了计算。结果表明:5个站点模拟的直射日曝辐量与实测值均存在较好一致性,评价效率系数NSE介于0.68~0.8,而对月均直射日曝辐量的模拟结果则显示模型在4-10月的估算精度要高于11-3月结果。     

柱型水力旋流器对硅切割废砂浆分离性能的研究

为了研究废砂浆中碳化硅粉和硅粉的分离情况,选用混合模型对柱型水力旋流器多相流流场进行数值模拟。模拟结果表明:柱型水力旋流器的分离效率与入口速度、进口浓度等因素有关,并分析出一定条件下当主、次相的入口速度均为1.1m/s时颗粒分离效果较好,分离效率较高,实验检测分离性能较好,为进一步实验研究提供一定的指导。     

Three-dimensional hydrodynamic and water quality model for TMDL development of Lake Fuxian, China

Lake Fuxian is the largest deep freshwater lake in China. Although its average water quality meets Class I of the China National Water Quality Standard (CNWQS), i.e., GB3838-2002, monitoring data indicate that the water quality approaches the Class II threshold in some areas. Thus it is urgent to reduce the watershed load through the total maximum daily load (TMDL) program. A three-dimensional hydrodynamic and water quality model was developed for Lake Fuxian, simulating flow circulation and pollutant fate and transport. The model development process consists of several steps, including grid generation, initial and boundary condition configurations, and model calibration processes. The model accurately reproduced the observed water surface elevation, spatiotemporal variations in temperature, and total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) concentrations, suggesting a reasonable numerical representation of the prototype system for further TMDL analyses. The TMDL was calculated using two interpretations of the water quality standards for Class I of the CNWQS based on the maximum instantaneous surface and annual average surface water concentrations. Analysis of the first scenario indicated that the TN, TP and COD loads should be reduced by 66%, 68% and 57%, respectively. Water quality was the highest priority; however, local economic development and cost feasibility for load reduction can pose significant issues. In the second interpretation, the model results showed that, under the existing conditions, the average water quality meets the Class I standard and therefore load reduction is unnecessary. Future studies are needed to conduct risk and cost assessments for realistic decision-making.     

全国大气扩散输送模态与区划研究

基于NCEP再分析气象资料,使用HYSPLIT模式对我国大陆区域进行了一整年的连续轨迹计算.轨迹以1°×1°的网格化经纬度分辨率进行计算.考虑气候、地理及经济因素,将全国计算区域分为10个大区,分别统计各大区出发的轨迹在全国的分布频率.根据全年和各季的轨迹统计结果,分析我国不同区域的大气输送扩散特征以及区域间大气环境的相互影响潜势.结果表明,全国10个大区的大气扩散输送模态可分为特性不同的7大类,其中以西北方向的3个大区为一类,西南高原的2个大区为另一类,其它各区自成一类.10个大区大气扩散物质的累积效应差异显著且季节变化特征各异.全国以西南区(XN)东部大气累积效应最强,东北区(DB)累积效应最弱.     

近17年鄱阳湖区生态系统健康时空变化研究

以遥感影像和社会统计数据为基础,构建基于压力-状态-响应(P-S-R)概念模型的鄱阳湖区生态系统健康评价指标体系,并建立湖区生态系统健康评价模型,通过对生态系统健康指数的计算与分析,揭示鄱阳湖区生态系统健康的时空变化特征.研究结果表明,在人类生产活动的影响下,近17年鄱阳湖区生态系统结构渐趋不合理,生态系统功能有所减弱,虽然湖区生态系统健康总体处于一般水平,但人类活动干扰的不断加强,导致湖区生态系统健康正逐步向着恶化方向发展.湖区生态系统健康在空间分布上呈现出南北分异的特点,南部工业化、城镇化水平较高的地区生态系统健康状况较差,经济发展水平较低的北部地区,生态系统健康状况则相对较好.