放射性^(125)I粒子平面永久插植布源剂量分布研究

目的利用计算机三维治疗计划系统创建125I粒子平面植入条件下剂量分布特征与等剂量分布曲线。方法利用计算机治疗计划系统创建125I粒子三角形分布、正方形分布、六边形分布、十二边形分布时剂量特征,求出1 000、3 000、6 000、9 000、12 000、15 000和20 000 cGy剂量分布曲线。计算距离平面插植中心点距离0、0.5、1.0、1.5、2.0、2.5、3.0和4.0cm处剂量分布。结果利用三维粒子治疗计划系统可以模拟出平面插值条件下等剂量曲线分布。在三角形、正方形、五边形、六边形条件下,粒子距离中心超出2.0 cm、2.5 cm、3.0 cm、4.0 cm时,中心剂量低于10 Gy,需要增加粒子,提高中心剂量。结论利用计算机三维治疗计划系统可以模拟平面条件下不同几何形状125I粒子种植分布的等剂量曲线分布,求出距离中心点不同部位的剂量,对临床具有十分重要的指导意义。

Variation in the distribution of wintering anchovy Engraulis japonicus and its relationship with water temperature in the central and southern Yellow Sea

In the present study,we investigated a shift in the spatial distribution of wintering anchovy(Engraulis japonicus)and its relationship with water temperature,using data collected by bottom trawl surveys and remote sensing in the central and southern Yellow Sea,during 2000–2015.Our results indicate that the latitudinal distribution of wintering anchovy varied between years,but there was no consistent pattern in the direction of change(north or south).Wintering anchovy did not move northward with increasing water temperature.However,the latitudinal distribution of wintering anchovy correlated well with 10°C and 11°C isotherms.The results of both a one-step and a two-step generalized additive model indicated that water temperature was associated with both presence and biomass of wintering anchovy.This paper is the fi rst to systematically examine the relationship between anchovy distribution and water temperature using a variety of techniques.All the fi ndings confi rm the impact of water temperature on wintering anchovy distribution,which has important implications for the continued management of the anchovy resource and the enhancement of marine fi shery resources in the Yellow Sea,especially as the climate changes.However water temperature only partly explains the species distribution of anchovy,and stock characteristics also aff ect fi shery distribution.Therefore,other factors should be considered in future research.

Research Progress on the Problem of Fluid,Heat and Energy Distribution near the Earthquake Source Area

As the basic problems in seismology, fluid, heat and energy distribution near earthquake sources during earthquake generation have been the leading subjects of concern to seismologists. Currently, more and more research shows fluid around earthquake source areas, which plays an important role in the process of earthquake preparation and generation. However, there is considerable controversy over the source of fluid in the deep crust. As for the problem of heat around earthquake source areas, different models have been proposed to explain the stress heat flow paradox. Among them, the dynamic weakening model has been thought to be the key to solving the heat flow paradox issue. After large earthquakes, energy distribution is directly related to friction heat. It is of timely and important practical significance to immediately implement deep drilling in-site surveying to gain understanding of fluid, friction heat and energy distribution during earthquake generation. The latest international progress in fluid, heat and energy distribution research has been reviewed in this paper which will bring important inspiration for the understanding of earthquake preparation and occurrence.

Economic Study of the Wind Energy Potential in Sahel

The wind pattern in Sahel is marked by a strong diurnal cycle as well as a strong seasonal cycle. The low level jet is blowing above the near-surface layer during nighttime and is decoupled from the surface. Nowadays, some studies showed the possibility to use the sub-jet wind at levels higher than 90 m as a source of energy in this area. In the present work, the wind turbines, with hub heights situated at 150 m and blade extremities at 150 ± 60 m, were used to make an economic study of wind energy potential in Sahel. Thus, monthly wind power was determined by two methods. The first involved the wind distributions directly observed. The second was based on the Weibull distributions which were fitted to the data. Day and night were compared. Results showed that this jet was an attractive source of energy provided if huge-capacity energy storage was used. So, the energy stored at night could be restored during the daytime, when the demand is highest. An economic study was done to estimate the number of wind turbines needed to satisfy the Niamey demand. The cost was found reasonably cheap relative to that of other renewable energy sources.

Optimum Energy Harvesting for Series-Connected Power Sources with Uniform Voltage Distribution

This paper presents a power system architecture where SIPO （series-input parallel-output） converters are controlled to achieve uniform inpt voltages across their respective series-connected power sources while also tracking the system optimum power point; the system optimum power point is the maximum power drawn from the series-connected power sources while their voltages are kept uniformly distributed. With proper uniform input voltage distribution control, near maximum use of the power sources is achieved by employing only one MPT （maximum power tracking） controller instead of multiple MPT controllers dedicated for their respective power sources. Provided that the maximum power point voltages of the input power sources are similar, the resulting system architecture offers near-maximum power transfer with a lower parts count. A feasibility study using computer simulation has successfully validated two SIPO power architectures and their control concepts for optimum power transfer.

Validating Wind Energy Probability at Ahmednagar Wind Farm

The wind speed is measured with the help of three anemometers S30, S45, S60 placed at 30 m, 45 m, and 60 m height. Mean values are recorded and stored for every hour using a data logger. For accounting wind turbine generator （WTG.） tower height, data recorded from S60 anemometer at 60 m height is used for analysis purpose. This paper analyzes the probability distribution of wind speed data recorded by maharashtra energy development agency （MEDA） wind farm at Ahmednagar （India）. The main objective is to validate the wind energy probability by using probability distribution function （PDF） of available wind potential. The energy generated from wind for any time interval is equal to the area tinder power curve multiplied by time in hours for that time interval. To estimate the wind energy probability, hourly wind speed data tbr one year interval is selected. Weibull distribution is adopted in this study to best fit the wind speed data. The scale and shape paranleters are estimated by using maximum likelihood method. The goodness of fit tests based on the probability density function （PDF） is conducted to show that the distribution adequately fits the data. It is found from the curve fitting test that, although the two distributions are all suitable for describing the probability distribution of wind speed data, the two-parameter weibull distribution is more appropriate than the lognormal distribution.

Simulation of Velocity and Temperature Distributions of Displacement Ventilation System with Single or Double Heat Sources

In order to obtain a better understanding of flow characteristics of displacement ventilation, the three-dimensional numerical models are developed using the CFD technology. The numerical simulation results are verified by experiments, based on this, the velocity and temperature distribution of three-dimensional displacement ventilation system with single and double heat sources are studied. Velocity and temperature fields under two different cases of heat source are analyzed and compared. The numerical results show that there are three layers in vertical temperature fields of displacement ventilation system with single or double heat sources, and the vertical temperature distribution of single heat source is different from that of double heat sources. When indoor load is large, the comfort requirement of people indoor can＇t be satisfied with displacement ventilation system only, thus an additional refrigeration system is necessary. Furthermore, under the condition of two heat sources, the displacement ventilation parameters can＇t be computed simply according to single heat source inlet parameters, therefore the interaction between heat sources should be considered.