封闭系统正冻土水流的一个计算模型

A computational model of water migration flux of fine porous soil in frost heave was investigated in a closed system. The model was established with the heat-mass conservation law and from some previous experimental results. Through defining an auxiliary function an empirical function in the water migration flux, which is difficult to get, was replaced. The data needed are about the water content along the soft colunm after test with enough long time. We adopt the test data of sample soil colunms in [1] to verify the model. The result shows it can reflect the real situation on the whole.     

Iterative method on well bore boundary in numerical modeling of variably saturated flow

An iterative method was developed for incorporating the well bore boundary into the finite difference model of water flow in variably saturated porous media. Six cases were presented involving groundwater pumping or injection to demonstrate the advantages of the iterative method over the traditional method. For the iterative method, the total flux gradually approached the well discharge and the flux profile was non-uniform. And the iterative method took into account the variation of well bore water table. Compared to the traditional method, the iterative method can simulate the variably saturated flow caused by pumping or injection more realistically.     

Principal Component-Discrimination Model and Its Application

Having researched for many years, seismologists in China presented about 80 earthquake prediction factors which reflected omen information of earthquake. How to concentrate the information that the 80 earthquake prediction factors have and how to choose the main factors to predict earthquakes precisely have become one of the topics in seismology. The model of principal component-discrimination consists of principal component analysis, correlation analysis, weighted method of principal factor coefficients and Mahalanobis distance discrimination analysis. This model combines the method of maximization earthquake prediction factor information with the weighted method of principal factor coefficients and correlation analysis to choose earthquake prediction variables, applying Mahalanobis distance discrimination to establishing earthquake prediction discrimination model. This model was applied to analyzing the earthquake data of Northern China area and obtained good prediction results.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

The Verhulst model with remedy and its application in forecasting quantity of student taking entrance examination to college

The Verhulst model can be used to forecast the sequence, which is characterized as non-monotone and fluctuant sequence or saturated S-form sequence. According to the situation of national enrollment scale of college, this paper forecasts the quantity of students taking entrance examination to college with a Verhulst model with remedy based on data mining theories, and by the above model, some countermeasures are developed to the higher education of Henan province in China.     

Numerical Simulation of Land Subsidence at Tanggu District in Tianjin, China

The deep, unconsolidated sedimentary aquifersof eastern coastal China have been heavily over-exploited, which caused aquifer compaction and re-sulted in the highest rates of land subsidence in Chinaduring the past50 years. As the government and gen-eral public paid more attention to land subsidence is-sues, land subsidence monitoring networks have beenset up since the mid-1980s. However, due to lack ofgeological data as well as practical simulation meth-ods, current work focuses on routine obs…     

Pyrolysis model of single biomass pellet in downdraft gasifier

By coupling the heat transfer equation with semi-global chemical reaction kinetic equations, a onedimensional, unsteady mathematical model is developed to describe the pyrolysis of single biomass pellet in the pyrolysis zone of downdraft gasifier. The simulation results in inert atmosphere and pyrolysis zone agree well with the published experimental results. The pyrolysis of biomass pellets in pyrolysis zone is investigated, and the results show that the estimated convective heat transfer coefficient and emissivity coefficient are suitable. The mean pyrolysis time is 15.22%, shorter than that in inert atmosphere, and the pellet pyrolysis process in pyrolysis zone belongs to fast pyrolysis. Among the pyrolysis products, tar yield is the most, gas the second, and char the least. During pyrolysis, the temperature change near the center is contrary to that near the surface. Pyrolysis gradually moves inwards layer by layer. With the increase of pyrolysis temperature and pellet diameter, the total pyrolysis time, tar yield, char yield and gas yield change in different ways. The height of pyrolysis zone is calculated to be 1.51—3.51 times of the characteristic pellet diameter.     

A new equation for dielectric permittivity of saturated soils based on polarization mechanics

Based on polarization mechanisms, such as electronic, ionic and orientational polarizations, a new equation for dielectric permittivity of soil is proposed to interpret the dielectric behavior of a mixture like soil, in terms of polarization process of its components and the interactions between its components. The dielectric permittivity is expressed in terms of a fre- quency-dependent part and a frequency-independent part. These two parts correspond to polarizations occurred at different fre- quency range. It is a new volumetric mixing model with theoretical background. Based on time domain reflectometry （TDR） measurements of saturated soil samples and test data from literature, comparisons of this model with some well established mixing models show that the curves for saturated sand soils and slurries resulted from the new equation, which agree well with TDR measurements, are close to those calculated from Birchak＇s model.     

Correlation between process parameters and primary dendrite arm spacing in laser welding of Cu and Al

A combined numerical model of thermal field and the primary dendrite arm spacing （PDAS） was proposed to correlate the process parameters and PDAS in laser welding of Cu and A1. The solidification parameters simulated by the finite volume method with commercial software ANASYS FLUENT were applied in the PDAS model to predict the dendrite arm spacing of fusion zone. Dendrite was also examined by the metallographic method to validate the model. Results indicate that the calculated PDAS agrees with metallographic measurements reasonably, especially the Hunt model. PDAS increases apparently with increasing laser power while decreases slightly with increasing welding speed. Increasing laser power increases the secondary dendrite and increasing welding speed increases the microporosity in dendrite.     

Benefit evaluation of the Three-Gorges Reservoir migration by an assessment index model based on analytic hierarchy process

An assessment index model was established to evaulate the benefit of the Three-Gorges Reservoir migration through the analytical hierarchy process. Totally 43 indicators were selected to assess the impact of migration on the economic, social and ecological environmental aspects of the migration communities, with the data of the indicators of the years 1992, 1998, 2002 which represented the period of premigration, the end of the first phase migration and the end of the second phase migration, respectively. The evaluation matrix is sufficiently consistent, with a consistency ratio CR equal to 0.086 3. The assessment turned out a benefit value for the economic subsystem in the year 2004 larger than triple the value in the year 1992, indicating a remarkable economic growth in the Reservoir area. The constantly increasing value for the social subsystem reflects the stable social situations. There is a slight decline in the assessment outcome of the ecological subsystem for the year 1998, which implies enviromental conservation was given insufficient importance during that period. On the whole, the implementation of the migration project is favorable to the Reservoir region, as confirmed by the stably increasing overall evaluation value from 42.22% in 1992 to 68.81% in 2002. However, there is still much room to improve from the status quo to the target criteria.     

An Approach to the Estimation of the Packing Efficiency by Considering Gas and Uquid Axial Mixings

To evaluate the influence of gas and liquid axial mixings on the separation efficiency of packed column, an approximate mathematical solution of HETP (equivalent height to a theoretical plate) under continuous operation has been proposed based on the mixing pool model. The mass transfer and hydrodynamic data of structured packing, Mellapak 350Y, obtained in a high pressure tower have been used to test the validity of the proposed model. Compared with the SRP model and the Gualito model, it is found that for high pressure distillation process the present mathematical prediction shows a mean relative error of about 10% to the experimental data,the accuracy of which is the same as that by the Gualito model but better than that by the SRP model.     

Studies on parallel seismic testing for integrity of cemented soil columns

The principle and process of parallel seismic (PS) testing for the integrity testing of cemented soil columns are in- troduced in this paper. A three-dimensional (3D) finite element model (FEM) for the pile-soil system is established for impulse responses. Under saturated soil or unsaturated soil condition, several vibrating velocity-time histories at different depths in parallel hole are obtained based on the numerical simulation. It shows that the length of the pile and the one-dimensional (1D) P-wave velocity in the pile can be determined easily from the features of the mentioned velocity-time histories. By examining the slopes of the first arrival time plotted versus depth or the depth where the amplitude of the first arrival significantly decreases, the length of the pile can be determined. The effects of the 3D P-wave propagation through the saturated soil and the defect of the cemented soil column on the velocity-time histories are also investigated.     

The Advantages and the Application of the CAI Courseware in English Teaching

By the end of last century,the computer has been more and more widely used in our delay life.Computer has come to pervade every aspect of our lives--including education.This article talks about the advantages of the Computer-Assisting Instruction courseware(CAI courseware)during the college English teaching.It can be used to optimize the English teaching model,teachers' teaching and students' study during the class.It also talks about the methods of using CAI courseware in college English teaching:teachers should know students' condition and use the CAI courseware ingeniously and timely.When the teachers design the CAI courseware,they should select the materials suitably.Furthermore,it predicts that the CAI courseware will have good prospects in the college English teaching.     

Experimental Study on Cyclic Mechanics Characteristic of Saturated Soft Clay Strata

Failure criterion of saturated soft clay is studied under cyclic loads through different experiments. A large number of cyclic torsional shear and cyclic triaxial tests on saturated soft clay under unconsolidated undrained condition are conducted. From the test result analysis, it is seen that the failure of saturated soft clay under static and cyclic loads satisfies Mises criterion. The result from different test stress states is not related to the test stress states or confining pressures. It can be applied in general stress states. Then according to the Mises criterion, the equivalent relationship on failure moment between the test stress state and the general stress state can be established. So the cyclic mechanics characteristics of saturated soft clay at failure moment are clarified in this paper. Furthermore, a theory basis is provided for using pseudo-static elasto-plastic cyclic strength model to evaluate cyclic bearing capacity.     

Potential application of particle based simulations in reservoir security management

In order to model the movement progress in case of risks such as dam collapse and coastal inundation, particle-based simulation methods, including the discrete-element method and smoothed particle hydrodynamics, which have specific advantages in modeling complex three-dimensional environmental fluid and particulate flows, are adopted as an effective way to illustrate environmental applications possibly happening in the real world. The theory of these methods and their relative advantages compared with traditional methods are discussed. Examples of 3-D flows on realistic topography including the flooding of a river valley as a result of a dam collapse and coastal inundation by a tsunami are introduced. Issues related to validation and quality data availability are also discussed. The results show that the simulations provide a valuable insight in a given situation for the security management of reservoir dams. Validation can only be performed where both the initial and final states can be very well characterized.     

Research on Action Learning of Teachers in Higher Vocational Colleges

Action learning refers to that man try everything to find out the new pattern of action in similar situations of the future by introspection and comprehension about past and present experience （affairs） in order to achieve a certain purpose or solve a certain problem. Compared with the traditional vocational teachers＇ training model, the action learning model based on ＂experience-introspection-action＂ is better to promote and enhance the practical knowledge growth and personal theory construction of vocational teachers. Action learning can simultaneously promote mutual development of individuals and learning groups （organizations）.     

Application of Holter ECG Signal Analysis Based on Wavelet and Data Mining Technique

A new model based on dyadic differential wavelet was developed for detecting the R peak in Holter ECG signal according to the design of data mining. The Mallat recursive filter algorithm was introduced to calculate wavelet and optimize the detection algorithm which is based on the equivalent filter technique. The detection algorithm has been verified by MIT arrhythmia database with a high efficiency of 99％. After optimization, the algorithm was put into clinical experiment and tested in the Air Force Hospital in Tianjin for about two months. After about 108 hearts beating test of more than 100 patients, the total efficient detection rate has reached 97％，Now this algorithm module has been applied in business software and shows perfect performance under the complex conditions such as the inversion of heart beating, the falling off of the electrodes, the excursion of base line and so on.     

The Role of Social Capital/Guanxi in Students’ Decision-Making about Postgraduate Education in China: An Explorative Case Study

This paper explores how the concept of social capital developed by Bourdieu and Coleman as well as the Chinese concept of guanxi (关系) or relationships facilitates students’ access to postgraduate education in a case study of a university in southeast China. The study comprises an initial survey of 381 first-year postgraduate students and a series of interviews with 30 participants. Social capital and guanxi inform analysis of the data. The results reveal that students from different social backgrounds employ different forms of social capital and guanxi networks in their decision-making about postgraduate education. They contribute to conceptualizations of how social capital is generated through guanxi in the Chinese educational context.     

Application of three-dimensional visual simulation in tidal defense engineering

Any tidal defense engineering involves the collection and analysis of massive information about engineering structures and their surrounding environment. Traditional method, which is carried out mainly by means of twodimensional drawings and textures, is not efficient and intuitive enough to analyze the whole project and reflect its spatial relationship. Three-dimensional visual simulation provides an advanced technical means of solving this problem. In this paper, triangular irregular network (TIN) model simplified by non-uniform rational B-splines (NURBS) technique was used to establish the digital terrain model (DTM) of a super large region. Simulation of dynamic water surface was realized by combining noise function with sine wave superposition method. Models of different objects were established with different modeling techniques according to their characteristics. Application of texture mapping technology remarkably improved the authenticity of the models. Taking the tidal defense engineering in the new coastal region of Tianjin as a case study, three-dimensional visual simulation and dynamic roaming of the study area were realized, providing visual analysis and visible demonstration method for the management and emergency decision-making associated with construction.     

University students＇ conceptions about the concept of gene： Interest of historical approach

Concepts of genetics are often difficult to teach, specifically the central concept of gene. Even the scientists disagree when defining this concept. This paper investigates university students＇ understanding about the gene and its functions. The results show the dominance of two conceptions of the gene： the Neoclassical model and the Mendelian model. The existence of hybrid conceptions and the lack of the modern model show that students are unable to mobilize the knowledge taught in biology. These results suggest to improve the teaching methods of genetics, for instance, by developing activities that bring students face to face with their conceptions.