An improved dynamic model of transformer hotspot temperature based on top oil temperature

The winding hot spot temperature of the oil immersed power transformer is an important parameter. It has a great influence on the transformer insulation aging and a close relationship with the transformer top oil temperature. The changes of non linear thermal resistance, open circuit impedance, and oil viscosity and winding losses with temperature are also taken into account. An improved model added on the transformer top oil temperature to calculate transformer winding hot spot temperature by using the viscosity and loss correction factors is proposed. Model parameters are estimated by Levenberg Marquardt method. In the end, by comparing with the measured data tested under different conditions, the model shows good consistency under underload (90%), rated load (100%) and overload (110%) conditions respectively, and describes the temperature variation more accurately in the dynamic loading profiles.     

同步发电机励磁绕组匝间短路故障在线分析方法综述

励磁绕组匝间短路是同步发电机常见故障之一。为保证机组和电网的安全可靠运行,有必要对该故障进行在线分析检测。首先介绍了应用于同步发电机励磁绕组匝间短路故障在线分析的磁场-电流谐波分析法、探测线圈法、多回路法、输出电气量分析法、振动分析法等的研究现状,并对几种方法进行了比较,然后对未来在线分析方法的发展方向进行了展望,对输出电气量分析法提出了两条研究思路,最后说明了在线分析方法应具有实际可行性和多用途性。     

酥饼烤制温度的控制模型及仿真分析

金华酥饼有着千年历史,以传统的烤炉制作为主。基于现阶段酥饼生产中"烤"无法用现代技术替代,如果能将传统炉的温度控制复制到现代炉,将解决酥饼烤制的关键问题。通过对传统炉烤过程中的空气温度和炉壁温度的实测,建立烤制温度模型,利用PID控制方法,用MATLAB工具,在SIMULINK环境下进行仿真试验,经过计算和调整温度传递函数参数,得到适用于电烤温度控制的仿真曲线,为酥饼烤制的实质性研究提供条件。     

Simulation of a steady temperature field and analysis of factors affecting a worm gear

To obtain the distribution characteristic of the temperature on the surface of worm gear, a numerical simulation using heat transfer theory, tribology theory, and mesh theory is given to calculate the heat transfer coefficient and heat flux of rolling gea     

Control model for secondary cooling of continuous casting based on compensation temperature of the difference between liquidus and solidus

During continuous casting process, the composition of molten steel often varies with different heats, which leads to the big fluctuation of billet surface temperature when the traditional parameter water control model is applied to control the process. Additionally, it is difficult to keep the temperature at the straightening point of the billet within a reasonable range. Given above consideration, a new control model for secondary cooling of continuous casting based on compensation temperature of the difference between liquidus and solidus has been presented. Meanwhile, the temperature field of the billet is simulated with both the parameter water control model and the new secondary cooling control model, and the results indicate that the new control model for secondary cooling of continuous casting could perform better when it is used to control the surface temperature at straightening points of billet, thereby ensuring the quality of the billet.     

Analysis on the moisture migration of subgrade soil under effect of temperature gradient

A moisture migration test for unsaturated clayey loess along the SHERFPL is done to understand the water migration of soil under a closed system in freezing condition. The experimental data shows that the temperature decreases with the slope degrading and eventually reaches a stable temperature gradient. Temperature potential has little effect on soil’s moisture migration. The formation of the gradient of soil’s water content is mainly caused by temperature gradient. With temperature decreasing to the freezing temperature of soil, the unfrozen water content decreases quickly in frozen zone. Such decrease results in the great drop of matric potential, making unfrozen water migrate toward the lower temperature zone. Based on the model test, a coupled heat-fluid transport equation is built and simulated by a two-dimensional finite element model, from which the temperature and moisture field of the specimen under closed system are obtained. It is found that the obtained results are closely agreed with the experimental data. Therefore, the model is adapted to simulate the variations of temperature and moisture of subgrade soil during freezing process in seasonal frozen ground, which can provide the basis for inhibiting frost heave.     

Numerical Simulation of Berthing Velocity of the Ship

Based on the field data of berthing velocity for the ship (10000t-50000t), the berthing velocities have been numerically simulated by using Monte Carlo method in this paper. After statistical tests, it shows that the maximum values of the berthing velocity follow a Gumber distribution and the probability curves of failure for the means of maximum values are also obtained. The present results have been compared with the ones determined by specification of harbor engineering both at home and abroad.     

Research on the Real -time Simulation of Temperature Field for RCC Gravity Dam

The simulation analysis of temperature field under ideal condition can reflects the rule of true temperature field, but accidental factor during construction process will result in difference of the result. This paper studied the Baise RCC Dam with the distributed optical fiber technology and FEM technology, the numerical results were modified with the testing data and the contrastive curves can be obtained for the testing data,ideal simulation data and real -time simulation data. The results indicate that the modified real - time simulation can reflect the true temperature field ; it may serve as a guide for the temperature control.     

厅堂侧向能量因子的仿真与实测

侧向能量因子是衡量厅堂空间感的重要客观指标之一。厅堂侧向能量因子通常采用计算机仿真的方法得到。首先采用MKH800电容型传声器在实际厅堂中开展侧向能量因子测试工作。然后,通过ODEON6.5建立厅堂三维仿真模型,计算相同位置处侧向能量因子的模拟值,并将实测值与模拟值进行对比分析。研究结果表明,各点位的仿真值均大于实测值,座席区前部偏差较小,正对舞台中后部区域偏差较大。造成偏差的主要原因是由于ODEON软件中扩散系数的设置与所在面特性无关,同时,软件无法分别定义各频段的扩散系数。因此,在实际工程项目中,为了准确地预测室内音质效果,建议普遍采用缩尺模型实验测量侧向能量因子。     

Numerical Simulation on Confluence of the Two Rivers in Chongqing City

Flows of the confluence of Yangtze River and Jialing River in the city of Chongqing are numerically simulated by using Delft3D Model with staggered grids and ADI integral method. The water level, flow velocity and drogue trace are studied. Comparing the numerical results with observed data shows good agreement. Therefore the computational model and the simplified parameters are of good accuracy and have practical meaning. The results show that the contamination will linger near the Caiyuanba area and drift to Chaotianmen and the right bank of Yangtze River upstream. The results can be used to forecast flood, inspect contamination and management of riverway in the city.     

黄土高原地区玉米生产潜力模拟研究

比较了作物生产潜力常规研究方法与作物生长模拟研究方法的特点, 在玉米生长模拟模型介绍、模型验证和气候、土壤、作物数据库组建的基础上, 应用DSSAT3中的CERES-玉米模型模拟研究了黄土高原22个地点玉米光温生产潜力和气候生产潜力, 获得了各点6～15年玉米的产量潜力值, 并统计计算了研究时段内玉米生产潜力的平均值、标准     

Modeling of the Break Simulation for Both Single and Two Phase Conditions

Based on the Moody model and complied with the modular modeling ideology and principle,a general break simulation model has been proposed for both single and two phase conditions in a thermal liquid pipe.This model now is used to develop the training simulator a power plant.     

Analysis,Modeling and Simulation of the Phase shift Full Bridge Zero-Voltage-Switched PWM Converter

Based on the analysis of the phase shift Full Bridge Zero Voltage Switched PWM Converter(FB ZVS PWM converter),a smal signal model is derived,and simulation results of frequency domain and time domain are given.[WT5HZ]     

橡胶树光合与干物质积累模拟模型研究

基于单叶光合速率的光响应模型和冠层光的分布规律,通过积分形式,构建了橡胶树冠层光合作用模拟模型。模型充分量化了光通量密度、温度、叶面积指数、单叶最大光合速率、光合作用特征参数、消光系数、群体反射率等因子对橡胶树冠层光合速率的影响。在分别确定了叶片和木质器官与环境因子作用关系的基础上,构建了橡胶树的群体呼吸作用模型。在橡胶树冠层的光合作用模型和群体呼吸作用模型的基础上,整合成橡胶树干物质积累模拟模型。模型经初步检验,结果表明模拟值与观测值吻合度较好,模型不仅具有较强的机理性而且具有较高的预测性和实用性。     

同化数据在气候适宜度区域化模型中的应用

为了避免站点插值误差,实现高精度、空间分布的CLDAS同化数据在气候适宜度指标区域化中的方便高效应用,本研究利用GIS建模工具,基于内蒙古玉米日尺度动态适宜度计算方法,构造日尺度玉米温度适宜度自动化计算模型,实现了CLDAS小时数据提取、日平均气温计算、"三基点"温度计算、适宜度指标分段函数构建、误差分析等五方面功能。以2016年5月25日CLDAS融合气温产品为例,分析日尺度空间温度适宜度计算模型运行效益,结果表明:CLDAS日平均气温与站点观测值平均偏差0.57℃,CLDAS温度适宜度指标与站点适宜度平均偏差0.02,平均相对误差3.17%,空间拟合精度较高;日尺度温度适宜度指标空间化计算模型实现了适宜度指标的流程化计算,操作简便且方便推广,具有较高的实用性,达到了同化数据在气候适宜度指标区域化中的应用目的。     

Parameter Design for the Power Train and Simulation of the Dynamic Performance of Elctrical Vehicle

The method and principle of the parameter design for the power train of EV is explored and discussed,then the parametersof EV. based on SC7101 are reasonably selected.The method of calculating the SOC of Lead_acid battery is provided and the relation among the electromotive force,the interior resistance, the polarized resistance and the SOC are analyzed. The capacity is compensated according to the relation between the capacity and the temperature, which is the basis on which the energy management system is designed and improved. The dynamic model which reflects the dynamic characteristics of the power train is established,then the dynamic performance of the EV based on SC7101 is simulated, and the factors that affect the continuous mileage of EV are analyzed,the measures to increase the continuous mileage are provided.The result shows that the analysis of the electric characteristics of battery and the dynamic model are correct,and the dynamic performance perfectly meets the need of the design target.     

Numerical Simulation of Temperature Field during the Dissolution-Diffusion Bonding Process to Mending Iron Casting Defects

The common finite element method microcomputer software for simulation of the temperature field is developed by authors. It is used for calculating the temperature field duringthe mending process of iron casting defects by means of the dissolution-diffusion bonding technology. The correctness has been proved by testing results. This software has been used to analyse thecaused of hardness rising in heat effecting zone,and also find out the approach for solving the problem.     

温室甜瓜果实糖酸积累模拟模型研究

通过不同类型温室春、秋茬甜瓜栽培,基于有效积温、日温差积与甜瓜果实蔗糖、柠檬酸间关系的回归分析,建立了甜瓜果实蔗糖、柠檬酸及糖酸比及有效积温与日温差积的模拟模型.结果表明,甜瓜果实蔗糖、柠檬酸及糖酸比均随有效积温与日温差累积的增加呈logistic曲线函数变化,但不同栽培茬口函数模型的常数项有差异,它与日温差累积呈线性关系.验证试验结果表明:该模型能较好地模拟甜瓜果实蔗糖、柠檬酸积累过程与糖酸比变化,可精确预测甜瓜果实的成熟特性,因而在确定甜瓜优质采收期中具有很好的应用价值.     

Modeling and simulation of the upper limb artery system using three section electric network model

A three section electric network model is built for human upper limb arterial system according to the Windkessel model. Blood pressure waveform of brachial artery is inputted into the electric network model. The state space equations of the electric network model are refined by using the state space analysis and solved numerically by the fourth order Runge Kutta method to obtain the blood pressure and flow waveform of radial artery. Effects of changes of the electric network model’s parameters on the blood pressure and flow waveform are also analyzed in normal and different pathological conditions(arteriosc lerosis and hypertension). The results of simulation show that the parameters of the model can well reflect the physiological significations of the upper limb arterial system; the analytic and computational methods are of fairly high precision and fast convergence for the model; and the model can simulate effectively the hemodynamic characteristics of upper limb arteries under normal and different pathological conditions.     

Estimation of Crown Temperature of Winter Wheat and the Effect on Simulation of Frost Tolerance

Accurate estimation of winter wheat frost kill in cold‐temperate agricultural regions is limited by lack of data on soil temperature at wheat crown depth, which determines winter survival. We compared the ability of four models of differing complexity to predict observed soil temperature at 2 cm depth during two winter seasons (2013‐14 and 2014‐15) at Ultuna, Sweden, and at 1 cm depth at Ilseng and Ås, Norway. Predicted and observed soil temperature at 2 cm depth was then used in FROSTOL model simulations of the frost tolerance of winter wheat at Ultuna. Compared with the observed soil temperature at 2 cm depth, soil temperature was better predicted by detailed models than simpler models for both seasons at Ultuna. The LT50 (temperature at which 50 % of plants die) predictions from FROSTOL model simulations using input from the most detailed soil temperature model agreed better with LT50 FROSTOL outputs from observed soil temperature than what LT50 FROSTOL predictions using temperature from simpler models did. These results highlight the need for simpler temperature prediction tools to be further improved when used to evaluate winter wheat frost kill.