基于Verilog-A的荧光灯预热模型

提出了基于Verilog-A的荧光灯预热模型。该模型表示荧光灯管预热过程中灯丝热电阻与预热前灯丝冷电阻之比Rh/Rc的精确值。使用该模型能够方便地设计带预热功能的电子镇流器相关参数。实验过程及结果表明,该方法不但节约了设计时间,而且能够使得荧光灯预热达到最佳状态,使用寿命尽可能长。

基于自适应模糊神经网络系统的转炉终点磷的预报控制模型

根据冶炼工艺和现场数据 ,对转炉终点磷含量的预报方法进行了研究。采用自组织神经网络模式识别方法对 30 3炉现场数据进行了分类 ,分析了转炉冶炼各变量对终点磷含量的影响 ,确定了终点磷含量的控制变量 ,建立了基于自适应模糊神经网络系统的转炉终点磷含量的预报控制模型。研究表明 ,本模型能够对终点磷含量进行很好的预报和控制。模型计算值与实际值的相关性达到 0 .5 86 7;磷含量 (质量分数 ,% )控制在± 0 .0 0 3范围内的命中率达到 79.2 1%。该模型以低于目标值 0 .0 0 4 %的磷含量来对冶炼过程进行控制 ,冶炼合格率超过 91%。

沼气工程进料非稳态预热工艺设计

针对我国沼气工程普遍存在发酵温度低,冬季产气难的问题,笔者基于所在课题组开发的新型沼液换热器和现行沼气工程间歇进料的运行模式,以华东地区50~1000 m^(3)规模的沼气工程为研究对象,建立进料温度与时间相关的非稳态预热工艺。计算表明:容积产气率为0.5~1.0 m^(3)·m^(-3)d^(-1)的沼气工程所产生沼气量均能满足全年沼液预热的能耗需求;对于50 m^(3),300 m^(3),500 m^(3),1000 m^(3)的沼气工程进料预热工艺所需单根沼液换热器数量分别为串联2根、串联6根、串联5根并联2组,串联8根并联2组;对改造后的沼气工程进行效益分析,以300 m^(3)沼气工程为例,使用新型沼液换热器后冬季(11、12、1、2、3月份)所产沼气富余量约为3539~14864 m^(3)天然气,处理COD为1239~5203 kg,效益显著。该进料预热工艺可满足华东地区沼气工程的中温发酵,实现全年的高效运行,对我国沼气工程的升级改造也具有重要意义。

Relationship between Rice Planthopper Occurrence Area in China and Atmospheric Circulation Indices

[Objective] This study aimed to establish models based on atmospheric cir- culation indices for forecasting the area attacked by rice planthopper every year, and to provide guide for preventing and controlling planthopper damage. [Method] The data related to rice planthopper occurrence and atmospheric circulation were collected and analyzed with the method of stepwise regression to establish the prediction models. [Result] The factors significantly related to the area attacked by rice plan-thopper were selected. Two types of prediction models were established. One was for Sogatella furcifera （Horvath）, based on Atlantic-Europe circulation pattern W in October in that year, Pacific polar vortex area index in October in that year, North America subtropical high index in August in that year, Atlantic-Europe circulation pattern W in June in that year, northern boundary of North America subtropical high in February in that year, Atlantic-Europe polar vortex intensity index in October in that year and Asia polar vortex intensity index in November in the last year; the other type of prediction models were for Nilaparvata lugens （Stal）, based on the Eastern Pacific subtropical high intensity index in July in that year, northern hemi- sphere polar vortex area index in October in the last year, Asia polar vortex strength index in November in the last year, north boundary of North America-At- lantic subtropical high in September in that year, north boundary of North Africa-At- lantic-North America subtropical high in January in that year, sunspot in September of the last year and eastern Pacific subtropical high area index in September in that year. [Conclusion] With the stepwise regression, the forecasting equations of the rice planthopper occurrence established based on the atmospheric circulation indices could be used for actual forecast.

A new mathematical model for predicting flow stress of X70HD under hot deformation

To realize numerical simulation of rolling and obtain the hot forming process parameters for X70 HD steel, the flow stress behaviors of X70 HD steel were investigated under different temperatures（820-1100 ℃ and strain rates（0.01-10 s-1） on a Gleeble-3500 thermo-simulation machine. A new flow stress model was established. The linear and exponential relationship methods were applied to the parameters with respect to temperature and deformation rates. The rise of curve ends under certain conditions was analyzed. The flow stress of X70 HD steel predicted by the proposed model agrees well with the experimental results. So, it greatly improves the precision of the metal thermoplastic processing through finite element method and practical application of engineering.

Analytical Model for Predicting the Heat Loss Effect on the Pyrolysis of Biomass Particles

This paper presents the combined influence of heat-loss and radiation on the pyrolysis of biomass particles by considering the structure of one-dimensional, laminar and steady state flame propagation in uniformly premixed wood particles. The assumed flame structure consists of a broad preheat-vaporization zone where the rate of gas-phase chemical reaction is small, a thin reaction zone composed of three regions: gas, tar and char combustion where convection and the vaporization rate of the fuel particles are small, and a broad convection zone. The analysis is performed in the asymptotic limit, where the value of the characteristic Zeldovich number is large and the equivalence ratio is larger than unity(i.e.u≥1). The principal attention is made on the determination of a non-linear burning velocity correlation. Consequently, the impacts of radiation, heat loss and particle size as the determining factors on the flame temperature and burning velocity of biomass particles are declared in this research.

Effect of double ageing on performance and establishment of prediction model for 6005 aluminum alloy

In the present investigation, the relation of pre-ageing temperature and pre-ageing time to mechanical properties was studied, and a model was established to predict the mechanical properties of AA6005 Al alloy. Compared with the experimental results, the deviation of the proposed model was limited to 8.1%, which showed reasonable accuracy of forecasting. It was found that the performance of AA6005 alloy was better at higher pre-ageing temperature with shorter pre-ageing time than that at T6 temper. The microstructure of the alloy was observed by transmission electron microscopy, and the results showed that high dislocation density and precipitate density existed at 160 ℃ and 200 ℃ pre-ageing, which were in good agreement with the model.

Projected Changes of Palmer Drought Severity Index under an RCP8.5 Scenario

The potential change of drought measured by the Palmer Drought Severity Index （PDSI） is projected by using a coupled climate system model under a Representative Pathway 8.5 （RCP8.5） scenario.The PDSI changes calculated by two potential evapotranspiration algorithms are compared.The algorithm of Thomthwaite equation overestimates the impact of surface temperature on evaporation and leads to an unrealistic increasing of drought frequency.The PM algorithm based on the Penman-Monteith equation is physically reasonably and necessary for climate change projections.The Flexible Global Ocean-Atmosphere-Land System model,Spectral Version 2 （FGOALS-s2） projects an increasing trend of drought during 2051-2100 in tropical and subtropical areas of North and South America,North Africa,South Europe,Southeast Asia,and the Australian continent.Both the moderate drought （PDSI ＜-2） and extreme drought （PDSI ＜-4） areas show statistically significant increasing trends under an RCP8.5 scenario.The uncertainty in the model projection is also discussed.

Microstructure evolution,mechanical properties and tailoring of coefficient of thermal expansion for Cu/Mo/Cu clad sheets fabricated by hot rolling

The law of microstructure evolution and mechanical properties of hot roll bonded Cu/Mo/Cu clad sheets were systematically investigated and the theoretical prediction model of the coefficient of thermal expansion(CTE)of Cu/Mo/Cu clad sheets was established successfully.The results show that the deformation of Cu and Mo layers was gradually coherent with an increase in rolling reduction and temperature and excellent interface bonding was achieved under the condition of a large rolling reduction.The development of the microstructure and texture through the thickness of Cu and Mo layers was inhomogeneous.This phenomenon can be attributed to the friction between the roller and sheet surface and the uncoordinated deformation between Cu and Mo.The tensile strength of the clad sheets increased with increasing rolling reduction and the elongation was gradually decreased.The CTE of Cu/Mo/Cu clad sheets was related to the volume fraction of Mo.The finite element method can simulate the deformation and stress distribution during the thermal expansion process.The simulation result indicates that the terminal face of the clad sheets was sunken inward.

THE APPLICATION OF TIDAL SIGNAL EXCLUSION SCHEME FROM INITIALIZATION IN A GENERAL CIRCULATION MODEL

In this paper, some corrections was made to the assumption that the forcing is quasi-static, which is the basis of the nonlinear diabatic initialization scheme adopted by a global model T106L19. Thus the tidal signal is expressed and excluded from the initialization scheme. It shows that the new scheme captures the semi-diurnal pressure variation and is much closer to the uninitialized field. Compared with the standard initialization scheme, both the anomaly correlation coefficients and RMS of 500 hPa geopotential height simulated under the new scheme have improved significantly.

Model of critical strain for dynamic recrystallization in 10%TiC/Cu-Al_2O_3 composite

Using the Gleeble-1500 D simulator, the hot deformation behavior and dynamic recrystallization critical conditions of the 10%Ti C/Cu-Al2O3(volume fraction) composite were investigated by compression tests at the temperatures from 450 °C to 850 °C with the strain rates from 0.001 s-1 to 1 s-1. The results show that the softening mechanism of the dynamic recrystallization is a feature of high-temperature flow true stress-strain curves of the composite, and the peak stress increases with the decreasing deformation temperature or the increasing strain rate. The thermal deformation activation energy was calculated as 170.732 k J/mol and the constitutive equation was established. The inflection point in the lnθ-ε curve appears and the minimum value of-(lnθ)/ε-ε curve is presented when the critical state is attained for this composite. The critical strain increases with the increasing strain rate or the decreasing deformation temperature. There is linear relationship between critical strain and peak strain, i.e., εc=0.572εp. The predicting model of critical strain is described by the function of εc=1.062×10-2Z0.0826.

Simulation of the Microphysical Processes and Effect of Latent Heat on a Heavy Rainfall Event in Beijing

An extraordinary rainstorm that occurred in Beijing on 21 July 2012 was simulated using the Weather Research and Forecasting model. The results showed that:(1) The two precipitation phases were based on a combination of cold cloud processes and warm cloud processes. The accumulated conversion amount and conversion rate of microphysical processes in the warm-area phase were all much larger than those in the cold front phase.(2) 72.6% of rainwater was from the warm-area phase. Rainwater mainly came from the melting of graupel and the melting of snow, while the accretion of cloud water by rain ranked second.(3) The net heating rate with height appeared as an overall warming with two strong heating centers in the lower and middle layers of the troposphere and a minimum heating center around the melting layer. The net heating effect in the warm-area phase was stronger than that in the cold front phase.(4) Warm cloud processes contributed most to latent heat release, and the thermal effect of cold cloud processes on the storm in the cold front phase was enhanced compared to that in the warm-area phase.(5) The melting of graupel and snow contributed most to latent heat absorption, and the effect of the evaporation of rainwater was significantly reduced in the cold front phase.

Dynamic Model for Evaluation of Risk Factors During Work in Hot Environment

Mathematical model is developed for prediction of physiological changes in man during work in hot environment taking into consideration intensity of work, clothing and environment. To evaluate human functional state the heat stress index was calculated. Modeling researches made the conclusion that the main risk factor during work in hot environment is water losses that happens through thermoregulatory sweat evaporation. Modeling showed that in humid environment man wearing protective clothing has short time to work as water losses became more than 2% of human weight that means body dehydration. Preliminary model prediction can be used as preventive method to avoid hazard of human health.

Modeling Thermal Protective Performance of Multilayer Fabrics for Firefighters

This paper is to report a prediction model for thermal protective performance of multilayer fabrics based on Matlab neural network toolbox. Then a back propagation (BP) neural network model is developed to predict thermal protective performance of multilayer fabrics for firefighters. The network consists of twelve input nodes, six hidden nodes, and one output node. The inputs are weight, thickness, density of warp and weft, limited oxygen index (LOI), and heat conductivity of each-layer fabric. Thermal protective performance (TPP) rating of multilayer fabrics is the output. In this paper, the data from the experiments are used as learning information for the neural network to develop a reliable prediction model. Finnally the model performance is verified, and the proposed model can be applied to predict the thermal protective performance of multilayer fabrics for firefighters.

Towards Modeling Rutting for Asphalt Pavements in Hot Climates

Rutting is a chronic disease in asphalt pavements despite several mitigation measures. Although many attempts have been made by both researchers and practitioners to develop rutting prediction models, each model, however, has certain inherent limitations due to assumptions and data used during the development of the model. Placement of an asphalt overlay is the most common method used in Zambia to rehabilitate existing asphalt pavements. The objective of this research is to go towards developing a national rutting prediction model for use in tropical hot climates based on default finite element creep and elasto-visco-plastic analysis tools in ABAQUS. Dynamic modulus and repeated load tests are conducted on overlay mixtures designed based on the pavement residual structural adequacy from deflection tests to provide material properties for the constitutive rutting model. Unified, three dimensional linear viscoelastic boundary value problems were formulated for each five national representative pavement sections. In general, the FE （finite element） creep and elasto-visco-plastie rutting evolutions were in agreement with the measured laboratory scaled one third mobile load simulators. Performance ranking of the validated models revealed optimal pavement system combination suitable for calibration. The study recommends future directions for local adoption of the South African mechanistic-empirical design method currently being developed.

Prediction Model for Cooling of an Electrical Unit with Time-Dependent Heat Generation

The satisfactory performance of electrical equipments depends on their operating temperature. In order to maintain these devices within the safe temperature limits, an effective cooling is needed. High heat transfer rate of compact in size and reliable operation are the challenges of a thermal design engineer of electronic equipment. Then, it has been simulated the transient a three-dimensional model to study the heating phenomenon with two assumption values of heat generation. To control for the working of this equipment, cooling process was modeled by choosing one from different cooling technique. Constant low speed fan at one direction of air flow was used for cooling to predict the reducing of heating temperature through working of this equipment. Numerical Solution of finite difference time domain method （FDTD） has been utilized to simulate the temporal and spatial temperature profiles through two processes, which would minimize the solution errors.

THE OBJE CTIVE ANALOGUE PREDICTION MODEL FOR TROPICAL CYCLONE TRACK WITH COMPREHENSIVE ASSESSMENT OF THE ENVIRONMENT

An objective analogue prediction model for tropical cyclone (TC) track is put forward that comprehensively assesses the environmental field. With the parameters of the tropical cyclone and environmental field at initial and future time, objective analogue criteria are set up in the model. Analogous samples are recognized by comprehensive assessment to historical TC cases for similarity with multivariate criteria,using non-linear analogue indexes especially defined for the purpose. When the historical tracks are coordinateconverted and weighted with reference to analogue indexes,forecast tracks are determined. As shown in model verification and forecast experiments, the model has forecasting skill.

A Study on Simple Prediction Method of Heat Load： A Use of Linear Approximation Indicial Response in Basements

This study was conducted to establish a predictable method for a heat load of an underground structure with sufficient accuracy. As the first step, our previous paper reported the measurement results of field experiments on an underground experimental basement under internal heat generation conditions. Also, it presented the results of numerical analyses on the heat and moisture behavior and the influence of internal heat generation of the experimental basement and ground. However, it is practically impossible to utilize the model of simultaneous heat and moisture transfer at the design phase because the prediction by the model of simultaneous heat and moisture transfer requires a long calculation time. In this paper, the authors present the simple load calculation technique, using a linearized approximation indicial response of the inner surface heat flux in a basement to outdoor air temperature change. In addition, the approximation indicial responses for each part of the single-walled concrete drawn using this technique are arranged. The heat load calculation example of application to the basement of the optional size by this technique is shown.

Mathematical Model Prediction of Heat Losses from a Pilot Sirosmelt Furnace

A mathematical model was developed for simulating heat transfer through the sidewall, bottom and top of a pilot scale TSL （Top-Submerged-Lance） Sirosmelt furnace. With a feed rate of about 50 kg/h, the furnace has been used for investigating the technical feasibility of a variety of pyrometallurgical processes for smelting nonferrous and ferrous metals and for high temperature processing of solid wastes including electronic scraps, etc. The model was based on numerical solution of energy transport equations governing heat conduction in multi-layered linings in the sidewall, bottom and top lid of the furnace as well as convection and radiation of heat from the furnace outer surfaces to the ambient. Imperfect contacts between two neighboring solid lining layers due to air gap formation were considered. Temperature profiles were determined across the furnace bottom, top lid and three sections of the furnace sidewall, from which the heat loss rates through the corresponding parts of the furnace were calculated. The modelling results indicate that approximately 88% of heat is lost from the furnace sidewall, 7-8% from the bottom and 4-5% from the top lid. With increasing melt bath temperature, the proportion of total heat loss from the bottom decreases whereas that from the top lid increases and that from the sidewall is little changed. For a bath temperature of 1,300℃, total absolute heat loss rate from the furnace was found to be close to 12 kW.

Prediction of Thermal Behavior of Pyrolyzed Wet Biomass by Means of Model with Inner Wood Structure

A simplified one-dimensional transient model for biomass pyrolysis in a fixed bed cylindrical reactor has been formulated and experiments have been carded out to verify the calculation results regarding temperature distribu- tion. The mathematical model accounts for mass, momentum and heat transfer, including moisture evaporation and convection of pyrolysis gases. Numerical simulation has allowed to predict temperature and heat flux distri- bution, and the dynamics of feedstock devolatilization. Special attention has been devoted to the analysis of the effect of biomass moisture content on the pyrolysis process. The model of moisture vaporization in biomass bed was proposed, which included structure of surface of biomass particles. Assuming that vaporization occurs on the border of the dry and wet areas of the bed, the flux of water vaporization depends on the specific surface area of the particles and overall heat flux.