An optimization algorithm for calculating the critical parametersof multicomponent mixture refrigerants

Aiming to calculate the true critical parameters of refrigerant mixtures, the Helmholtz free energy stability criterion for thermal systems is adopted to establish a calculation thermodynamic model of the true critical parameters. A novel optimization alg     

Calculation Model Based on Improved BP Network of Refrigerant State Parameters

BP network is improved by using Levenberg-Marquardt optimization method. Under large swatch input circumstance, more fast network constringency speed and more highly approach precision are obtained. Calculation model based on improved BP neural network of refrigerant state parameters is established. The main defect of refrigerant hot ties of matter model in existing refrigeration and air-conditioning appliances simulation system is overcome.     

An Unsteady Flow Analysis in Gas Transmission Pipeline Based on Theory of Functional Analysis

Branch -like pipeline is a common structure in gas transmission pipeline. In the light of the constituent properties of natural gas branch - like pipeline system, the system can be divided into fundamental constituent units. This paper presents a realistic unsteady flow model consisting of simple models of pipeline units and connecting conditions, boundary conditions and initial condition associated with units by using system analysis method. The solutions in wide sense are obtained by theory of functional analysis and operator series method, Such a method has the properties of both analytical solution and numerical solution methods. When the divided pipeline unit is larger, an intuitive approximate analytical solution may be obtained; while the one is smaller, a more accurate numerical solution may be acquired. Based on this, a general computer program has been developed for this model and solutions have been used successfully in a local natural gas transmission network in Sichuan. It is proved that the model and algorithm proposed in this paper are of the advantages of convenient calculation, high precision, time saving and wide application range by way of analysis and application.     

Modeling of Liquidus Temperature for Al-Si Cast Alloys with Adaptive Neuro-fuzzy Inference System

During the melting and processing practices, an accurate knowledge of liquidus temperature is necessary in the determination of process parameters relating to a given alloy. Adaptive neuro-fuzzy inference system (ANFIS) modeling method has been used to improve accuracy of prediction for liquidus temperature based on the compositions of Al-Si series cast alloys. The developed fuzzy inference system could extract Takagi-Sugeno type fuzzy rules from data directly, and has a feed-forward network structure with supervised learning capability. In order to adapt the parameters of the model, the proposed fuzzy inference system is trained over a wide range of compositions from the published data of industrial alloys. The result shows that, the developed ANFIS model can capture non-linear relationships between compositions and liquidus temperature, and then provides better prediction than the reported multiple statistic analysis. The developed model can be used to predict the liquidus temperature needed in computer modeling and thermodynamic calculation, which are needed in the aluminium alloys casting industry and research.     

Simulation of Wind Loading for Large - span Bridge Structures

Wind speed time series obtained with numerical simulation methods are adopted in structural analysis of wind - induced vibration. In this paper, based on the natural wind properties and the correlativity of nodal wind speed time series, AR model is employed to simulate wind speed time series, and the AIC rule is used to fix the rank of the AR model. Statistical analysis results of numerical wind speed time series show that AR model is efficient in simulating nodal wind speed time series which has time and space correlativity, and that the simulation precision, simulation efficiency and calculation stability answer the needs of practical engineering.     

A Theoretical Study on Thermal Dynamics Model and the Dehumidification Capacity of Hybrid Desiccant Cooling System with Condensation Heat Recovery

The structure and energy conservation characteristics of hybrid desiccant cooling system with condensation heat recovery are introduced briefly. Based on the first and second law of thermodynamics, a system thermodynamic model is established and the solution process given in a diagram. The dehumidification capacity is calculated under different exergy efficiency and indoor sensible heat conditions. The calculation results show that the desiccant wheel barely can compensate for the humidity load of outdoor air under with a ventilation rate of providing fresh air once per hour; when the fresh air rate of ventilation is limited to 0.5 times per hour, however, the desiccant wheel possess sufficient capacity under relatively large wheel exergy efficiency and high sensible heat load.     

Calculation of the Thermodynamic Properties of Mg-Zn Alloy

Getting activity of component is an important aspect of researching the thermodynamic characters of alloy. Under each model of predicting the thermodynamics characters of alloy, Miedema model has been developing as comparatively a good and accurate model in recent years. In this work, the formation enthalpy of Mg - Zn alloy has been calculated, according to the Miedema model. Further, the activity curve of Zn in Mg - Zn alloy at 1 000 K is calculated. The calculating result is that, as the formation enthalpy of Mg - Zn alloy is small, and in the procedure of calculating activity, excess entropy attributes a lot to the result, after considering excess entropy, calculating results and experimental values match each other very well.     

Materials Hydrogen Storage V3TiNi0.56Al0.2 by Self-propagating High-temperature synthesis

With the help of the calculation of adiabatic temperature and thermodynamic analysis of the reactive system the autaurs discuss possibility about system of V 2O 5-TiO 2-Al by Self-propagating High-temperature synthesis(SHS).Hydrogen Storage V 3TiNi 0.56 Al 0.2 by SHS is studied by XRD,SEM and scanning electron microscopy.The experiment result indicates that it has same microstructure between synthesization by SHS and other ways.PCT curve indicated that alloy has certain hydrogen storage capability,saturated capacity of hydrogen storage is 0.092 L/g,which is a little lower than alloy by other ways.     

牛初乳液态奶和牛初乳粉的加工工艺探讨

在查阅大量资料的基础上,结合乳品厂工作的实践经验,探讨牛初乳液态奶和牛初乳粉的加工工艺,结果表明,牛初乳的加工工艺与常乳大体相同,只是由于牛初乳的热稳定性差,其杀菌、干燥、浓缩等工艺条件与常乳不同。通常条件下,牛初乳的杀菌温度为60℃,时间为30min,也可以用辐照等高科技技术手段杀菌,辐照杀菌采用~(60)Co,剂量≤8.4kGy;真空浓缩压力>81kPa,温度≤60℃,浓缩后的奶液干物质含量达到40%～60%;干燥可以采用冷冻真空干燥或低温真空喷雾干燥法,前者用小于规模干燥,真空度为0.3～0.8MPa,料液受热温度<65℃,热蒸汽温度控制在70～75℃。     

DIGITAL SIMULATION OF HIGH VOLTAGE AC/DC PARALLEL SYSTEMS

The method of companion model is applied to the digital simulation of high voltage hybrid AC/DC systems for the first trme in this thesis.The mathematical model of the digital simulation of hybrid AC/DC systems is represented. This method can model the normal states, faults and games of faults of any hybrid AC/DC systems. The method has a series of advantages : saving the computation and the amounts of memory, high precision and fast calculation and it can be used with convenience. The simulation results of a hybrid AC/DC system arc in consistent with that of theoretical analysis. It shows that the mathematical model, the simulation method and the program in this thesis are correct.     

Application of Meshless Method in Dynamic Mechanics

As a new type of meshless method which has appeared in recent years, the Reproducing Kernel Particle Method has such meshless features as the need for nodes only without classified units, and is advantageous in the process of calculation. The present study introduces the Reproducing Kernel Particle Method and applies it to the research of nonlinear dynamic mechanics. The dynamic process involves different kinds of nonlinearity. The study assumes that deformation of dynamic analysis belongs to small one and that the material nonlinearity has been taken into account. When under small strain, the increment constitutive law and the total Lagrangian model of calculation are adopted to deduce the dynamic control equation by the Reproducing Kernel Particle Method. The instances of calculation demonstrate that this method is effective in the analysis of dynamic problems.     

Experimental Research on the Application of Enviromental Protection Refrigerants in the Large-scale Screw-Refrigerator

On the research of alternative refrigerants, because of their advantageous thermal characters and unparalleled prepondrance of environmental protection, kinds of HCs substance have taken more and more scholars attention. At the base of full demonstration, the HCs is applied on large-scale screw-refrigerator for the first time. The result indicate that, although the autlwrs do not make any better about the system, the energy-efficiency-ratio(EER) of R290 system is equally matched R22 system. So R290 can alternate R22 in the refrigerant system and can works well. If some improvements are maken on the system against the flammability of HCs, then the large-scale refrigerant system with HCs as the refrigerant could march to the markets, and make immense social and economic benefits.     

A FAST ALGORITHM FOR DIGITAL SIMULATTON OF HVDC SYSTEMS

After considering the features of the differential equations which have described the dynamic behaviours of HVDC systems, a fast algori -thm is presented for these equations. Compared with the fourth Runge-Kutta Method,this method has less amount of calculation with the same precision, numerical stability and other properties. Therefore, the use of the method has greatly increased the speed of the digital simulation of HVDC systems.In this paper an example of calculation is given, and the results obtained hv using this example are compared with the results obtained by calculating with the fourth Runge-Kutta Method. The speed of simulation by using this method is about 1.8 timss as fast as that by using the fourth Runge-Kutta Method.     

Quantitative analysis of photoacoustic spectroscopy detection for dissolvedgas in transformer oil based on least squares regression

Current solutions solve each component's gas concentration by multi equation inverse calculation, which has disadvantage of introducing parameter errors like noise, constant pool, etc. Based on the photoacoustic spectroscopy detection principle, a novel method for photoacoustic spectroscopy quantitative analysis is proposed using least square regression, and a quantitative analysis model is constructed. Using this method in inverse calculation of the gas concentration can avoid introducing parameter errors. The analysis model is verified by the experiment on the acetylene and methane dissolved in the transformer oil.     

EQUIVALENT CIRCUIT METHOD FOR DYNAMIC DIGITAL SIMULATION OF HVDC CONVERTERS

This paper presents a transient mathematical model of the HVDC converters-Equivalent Circuit Method(ECM), which can describe all possible states of converter valves in a simple and explicit way. With the converter model, programs have been implemented for single and double bridge HVDC systems. The results of simulation to the normal and fault operation of HVDC system show that the method is flexible and reliable, and has the advantages of small calculation amount and less computer storage requirments. The programs based on this paper provide convenient, inexpensive and feasible tools for computer dynamic or transient analysis of the HVDC systems.     

大跨度PC连续刚构桥徐变预测模型

为了能准确预测混凝土收缩徐变,提出了一系列徐变预测模型,但传统的徐变理论研究主要是针对普通混凝土进行的,所提出的徐变模型并不能完全适用于高强混凝土。对各徐变预测模型进行分析比较,最终参考了日本混凝土示方书建议模型,并在高强混凝土徐变试验的基础上,提出了一个适用于高强混凝土的徐变预测模型。基于Abaqus平台,使用Python语言进行二次开发,定义了修正模型的徐变规律,并采用修正后的模型计算牛角坪大桥的徐变应变。结果表明,修正模型的精度,能很好的满足工程需求。     

Dropwise Condensation Heat Transfer Coefficient on the Horizontal Circular Surface with Radial Gradient Surface Energy

A theoretical model is developed for the dropwise condensation heat transfer on the horizontal circular surface with radial gradient surface energy based on the heat transfer model of individual condensate drop and the size distribution model of condensate drop on homogeneous condensation surface.The effect of variation of contact angle on the gradient surface on condensation heat transfer and condensate drop size distribution is taken account of in this model.The theoretical calculation method was obtained to predict the dropwise condensation heat transfer coefficient on the horizontal circular surface with radial gradient surface energy under various wall subcooled temperature,contact angle profile on wall surface,and working fluid.The effects of surface energy gradient,wall subcooled temperature,and thermophysical properties of condensate on the condensation heat transfer are discussed respectively.The calculation results show that the condensation heat transfer coefficient increases slightly with the increase of wall subcooled temperature.As latent heat and surface tension increasing,the condensation heat transfer coefficient increases.A larger surface energy gradient induces a larger condensation heat transfer coefficient.     

The Model of Water and Steam to Real-time Simulation for Supercritical Fossil Power Unit

Based on the general thermodynamic theory,a mathematical model for thermodynamic parameters of hot-shot steam is derived,it includes the formula of specific enthalpy,specific volume,specific heat at constant pressure and specific entropy.The specific enthalpy formula of steam with a pressure range from 0 MPa to 90 MPa and the specific volume formula of steam with a pressure range from 0 MPa to 40 MPa within permission error of the International Steam Skeleton Tables in 1985,and that all the model with a temperature range from 273.15 K to 1 073.15 K.The model is applied to real-time simulation for supercritical fossil power unit and convenience in application of engineering.     

冷冻羊腿几种解冻方法比较

用绵羊后腿为解冻材料,进行微波解冻、空气解冻和水解冻。通过测定其解冻至0℃所需的时间和解冻后羊腿的质量损失率进行比较,以及解冻后羊腿品质分析,表明微波解冻效果明显。     

CAPM模型在降雨量预测中的应用

降雨是影响农业生产的一个重要因素,如何预测降雨量以及所得结果对农业生产具有重要的指导意义。本研究基于降雨量变化与资产价格变化的相似性,将资本资产定价模型（CAPM）的建模思想,应用到降雨量的预测中,建立了降雨量的CAPM模型。用该模型预测的结果比较合理,而且计算方法简单,易于掌握。