口型模拟技术及其在网络课程中的应用探索

口型模拟是一种人工智能技术,目前已在多个领域得到应用。文章在介绍口型模拟技术的基础上,比较了两款典型软件的特点,并探讨了该技术在网络课程制作中的应用。通过实验证明,在网络课程中采用口型模拟技术生成动画来讲解理论性知识,与真实教师视频讲解的教学效果基本接近,二者在测验成绩和认知负荷方面未呈现显著差异。

A plasticity model for sand-structure interfaces

The predictive capacity of numerical analyses in geotechnical engineering depends strongly on the efficiency of constitutive models used for modeling of interfaces behavior.Interfaces are considered as thin layers of the soil adjacent to structures boundary whose major role is transferring loads from structures to soil masses.An interface model within the bounding surface plasticity framework and the critical state soil mechanics is presented.To this aim,general formulation of the interface model according to the bounding surface plasticity theory is described first.Similar to granular soils,it has been shown that the mechanical behavior of sand-structure interfaces is highly affected by the interface state that is the combined influences of density and applied normal stress.Therefore,several ingredients of the model are directly related to the interface state.As a result of this feature,the model is enabled to distinguish interfaces in dense state from those in loose state and to provide realistic predictions over wide ranges of density and normal stress values.In evaluation of the model,a reasonable correspondence between the model predictions and the experimental data of various research teams is found.

Simulated circulations off the Changjiang (Yangtze) River mouth in spring and autumn

The circulations off the Changjiang mouth in May and November were simulated by a three dimension numerical model with monthly averaged parameters of dynamic factors in this paper. The area covers the East China Sea (ECS), Yellow Sea and Bohai Sea. Simulated results show that the circulation off the Changjiang mouth in spring and autumn is mainly the Changjiang runoff and Taiwan Warm Current (TWC). The Changjiang discharge is much larger in May than in November, and the wind is westward in May, and southward in November off the Changjiang mouth. The runoff in May branches in three parts, one eastward flows, the other two flow northward and southward along the Subei and Zhejiang coast respectively. The Changjiang diluted water expands eastward off the mouth, and forms a strong salinity front near the mouth. Surface circulation in autumn is similar to that in winter, the runoff southward flows along the coast, and the northward flowing TWC becomes weaker compared to that in spring and summer. The bottom circulations in May and November are mainly the runoffnear the mouth and the TWC offthe mouth, and the runoff and TWC are greater in May than in November.

Delamination analysis of woven fabrication laminates using cohesive zone model

A new test method was proposed to evaluate the cohesive strength of composite laminates. Cohesive strength and the critical strain energy for Mode-II interlamiar fracture of E-glass/epoxy woven fabrication were determined from the single lap joint(SLJ) and end notch flexure(ENF) test, respectively. In order to verify their adequacy, a cohesive zone model simulation based on interface finite elements was performed. A closed form solution for determination of the penalty stiffness parameter was proposed. Modified form of Park-Paulino-Roesler traction-separation law was provided and conducted altogether with trapezoidal and bilinear mixed-mode damage models to simulate damage using Abaqus cohesive elements. It was observed that accurate damage prediction and numerical convergence were obtained using the proposed penalty stiffness. Comparison between three damage models reveals that good simulation of fracture process zone and delamination prediction were obtained using the modified PPR model as damage model. Cohesive zone length as a material property was determined. To ensure the sufficient dissipation of energy, it was recommended that at least 4 elements should span cohesive zone length.

Flow field simulation and establishment for mathematical models of flow area of spool valve with sloping U-shape notch machined by different methods

Precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke was derived. The computational fluid dynamics was used to analyze the flow features of the sloping U-shape notch on the spool, such as mass flow rates, flow coefficients, effiux angles and steady state flow forces under different operating conditions. At last, the reliability of the mathematical model of the flow area for the sloping U-shape notch orifice on the spool was demonstrated by the comparison between the orifice area curve derived and the corresponding experimental data provided by the test. It is presented that the bottom arc of sloping U-shape notch （ABU） should not be omitted when it is required to accurately calculate the orifice area of ABU. Although the theoretical flow area of plain bottom sloping U-shape notch （PBU） is larger than that of ABU at the same opening, the simulated mass flow and experimental flow area of ABU are both larger than these of PBU at the same opening, while the simulated flow force of PBU is larger than that of ABU at the same opening. Therefore, it should be prior to adapt the ABU when designing the spool with proportional character.

Simulation of Spread of Infectious Diseases and Population Mobility in a Deterministic Epidemic Patch Model

Computer simulation models are widely applied in various areas of the health care sector, including the spread of infectious diseases. Patch models involve explicit movements of people between distinct locations. The aim of the present work has been designed and explored a patch model with population mobility between different patches and between each patch and an external population. The authors considered a SIR （susceptible-infected-recovered） scheme. The model was explored by computer simulations. The results show how endemic levels are reached in all patches of the system. Furthermore, the performed explorations suggest that the people mobility between patches, the immigration from outside the system and the infection rate in each patch, are factors that may influence the dynamics of epidemics and should be considered in health policy planning.

FEM simulation of aluminum extrusion process in porthole die with pockets

In order to investigate the effects of pockets in the porthole die on the metal flow,temperature at the die bearing exit and the extrusion load were contrasted with the traditional die design without the pockets in the lower die.Two different multi-hole porthole dies with and without pockets in lower die were designed.And the extrusion process was simulated based on the commercial software DEFORM-3D.The simulation results show that the pockets could be used to effectively adjust the metal flow and especially benefit to the metal flow under the legs.In addition,the maximum temperature at the die bearing and the peak extrusion load decrease,which indicates the possibility of increasing the extrusion speed and productivity.

Water Quality Evaluation in Tidal River Reaches of Liaohe River Estuary, China Using a Revised QUAL2K Model

Rivers in the Liaohe River Estuary area have been seriously polluted by discharges of wastewater containing petroleum pol- lutants and nutrients. In this paper, The Enhanced Stream Water Quality Model （QUAL2K） and its revised model as well as One-dimensional Tide Mean Model （1D model） were applied to predict and assess the water quality of the tidal fiver reach of the Liaohe River Estuary. Dissolved oxygen （DO）, biochemical oxygen demand （BODs）, ammonia nitrogen （NH3-N） and total phosphorus （TP） were chosen as water quality indices in the two model simulations. The modelled results show that the major reasons for degraded rivers remain petroleum and non-point source pollution. Tidal water also has a critical effect on the variation of water quality. The sensitivity analysis identifies that flow rate, point load and diffuse load are the most sensitive parameters for the four water quality indices in the revised QUAL2K simulation. Uncertainty analysis based on a Monte Carlo simulation gives the probability distribution of the four wa- ter quality indices at two locations （6.50 km and 44.84 km from the river mouth）. The statistical outcomes indicate that the observed data fall within the 90% confidence intervals at all sites measured, and show that the revised QUAL2K gives better results in simulating the water quality of a tidal fiver.

Relationship between trawl selectivity and fish body size in a simulated population

Trawl is a main fishing gear in Chinese fishery,capturing large fish and letting small ones at large.However,long-term use of trawl would result in changes of phenotypic traits of the fish stocks,such as smaller size-at-age and earlier age-at-maturation.In this study,we simulated a fish population with size characteristics of trawl fishing and the population produces one generation of offspring and lives for one year,used trawl to exploit the simulated fish population,and captured individuals by body size.We evaluated the impact of the changes on selectivity parameters,such as selective range and the length at 50% retention.Under fishing pressure,we specified the selectivity parameters,and determined that smaller selection rates and greater length at 50% retention were associated with an increased tendency towards miniaturization.

Dental Arch3D Direct Detection System from the Patient＇s Mouth and Robot for Implant Positioning

This paper describes a three-dimensional structured light scanning system to generate a virtual model of a dental arch, from the patient＇s mouth, and the scheme ofa 2 ＋ 1 DOF （degree of freedom） parallel/serial Robot for implant positioning, both positioned on a platform held in a fixed position with respect to the patient＇s head. Presently, dental prosthesization requires quite a long time to be completed. This process, in fact, involves the detection of the shape of the dental arch, its plaster model generation, scanning of it, prosthesis preparation and its implant. The procedur＇e is even longer when use of dental implants is required, while early loading of the implants is considered a positive solution. Current research effort is focused on the development of devices for the direct intra-oral determination of the shape of dental prostheses and inserts. These devices, however, are able to detect limited portions of the dental arch, since they must be hand-held by the doctor without external supports, and this may produce relatively large errors due to the sum of relatively small ones. Furthermore, to place an implant correctly, the doctor can use a new system to guide the implant position, but this requires sending the information in Sweden to obtain a special mask in return.

Physical and Numerical Modelling Applied to a Major New Port Development and Impacts of Its Deep Navigational Channel

This paper describes the use of a numerical and physical modelling study in the design of large breakwaters for a new port and dry dock complex on the southern coast of Oman. The numerical modelling was carried out to optimise the entrance channel layout with respect to wave penetration into the port and to refine design conditions for the sizing of the primary armour on the breakwaters. Wave conditions inside and outside of the port have been assessed using the 2-dimensional numerical wave penetration model MIKE21 EMS （Elliptic Mild-Slope）. As part of the design process, 3D physical modelling studies were also undertaken at Delft Hydraulics in the Netherlands to confirm the stability of the armour on the trunk and roundhead of the breakwaters and to verify the influence of the deep approach channel on stability. The opportunity was taken to extend the physical model tests to assess the influence of the deep channel on wave penetration through the port entrance. The paper focuses on the influence of the deep channel on wave conditions in the entrance to the port and compares the results from the numerical and physical modelling.

Control of Water Supply in Pipe Networks Nonlinear Case

The paper deals with control of supply in pipe networks based on so-called Dynamic Virtual Distortion Method. Making use of the analytical network model of this installation and using presented below, the so-called Virtual Distortion Method （VDM）, the control of water supply can be performed. Minimization of supply pressure in inlets to the network, subject to inequality constraints imposed on outlet pressure （in chosen nodes） is discussed. Taking advantage of pre-computed influence vectors, the real-time control strategy can be realised with small computational effort and therefore, can be managed with use of hardware-based controllers. Non-linear constitutive relation （water flow vs. pressure head） has been assumed.

Impacts of wind stress on saltwater intrusion in the Yangtze Estuary

The observation at the Chongxi gauging station indicated the salinity of saltwater spilling over from the North Branch to the South Branch increased abnormally from November 10 to 12 in 2009 (during neap tide) and from February 11 to 12 in 2010 (during moderate tide).We found for the first time that the strong northerly wind was responsible for the above abnormal salinity increase.Previous studies indicated that the saltwater intrusion in the Yangtze Estuary is influenced mainly by the river discharge,the tide,and the wind stress,but the impacts of variations of wind speed and direction on it have not been investigated.In this study the impacts of wind stress on the saltwater intrusion were numerically simulated and the associated mechanisms were analyzed.The model results were consistent with the observed data obtained at six gauging stations during February and March in 2007 and four gauging stations in March 2008,and the abnormal salinity risings were well captured.Meanwhile,if the wind speed is reduced by half,the salinity there will be significantly decreased.Driven by the monthly mean river discharge of 11000 m 3 /s and northerly wind of 5 m/s from January to February,the model simulated the temporal and spatial variation of saltwater intrusion.The wind-driven circulation,as well as the net water and salt fluxes from the North Branch into the South Branch,was calculated and analyzed in the cases of different wind speeds and directions.The results indicated that the intensity of the saltwater intrusion in the Yangtze Estuary is significantly influenced by the wind speeds and directions.

Chinese urbanization 2050： SD modeling and process simulation

Is Chinese urbanization going to take a long time, or can its development goal be achieved by the government in a short time? What is the highest stable urbanization level that China can reach? When can China complete its urbanization? To answer these questions, this paper presents a system dynamic(SD) model of Chinese urbanization, and its validity and simulation are justified by a stock-flow test and a sensitivity analysis using real data from 1998 to 2013. Setting the initial conditions of the simulation by referring to the real data of 2013, the multi-scenario analysis from 2013 to 2050 reveals that Chinese urbanization will reach a level higher than 70% in 2035 and then proceed to a slow urbanization stage regardless of the population policy and GDP growth rate settings; in 2050, Chinese urbanization levels will reach approximately 75%, which is a stable and equilibrium level for China. Thus, it can be argued that Chinese urbanization is a long social development process that will require approximately20 years to complete and that the ultimate urbanization level will be 75–80%, which means that in the distant future, 20–25% of China's population will still settle in rural regions of China.

Performance Prediction of a Multi-Stage Wind Tower for Indoor Cooling

A theoretical model is developed to establish an indepth understanding of the performance of a three-stage wind tower with a bypass system for indoor cooling in rural dry and hot climates. Model simulations are presented for a wide range of ambient conditions that include inlet wind speed, inlet temperature and relative humidity. Simulation results provide an insight into the desirable water flow rates and air-to-water loadings for comfort zone tem-peratures and relative humidity levels at the exit of the wind tower. Simulations show wind towers with variable cross-sections provide an increase in the cooling power for the same inlet wind speed, inlet air temperature and relative humidity when compared to wind towers with a constant cross-section. The study shall lead to a better understanding to designing wind towers that are both environmentally friendly and energy efficient.