西部地方高校学习困难生的教育转化新思考

本文旨在研究西部地方高校学习困难生的教育和转化问题中新的变化,从心理学以及学生思想教育和管理角度系统分析其文化背景、形成原因、措施策略、教育转化以及相互之间的作用和联系,对学习困难生的心理特征和教育对策作了一些新的探索,以期对学习困难生起到更切实、有效的帮助,对学习困难生的人生态度、工作能力等产生积极的影响,对高校的稳定与帮助学习困难生就业具有现实意义。

一种新的帘子布返卷机的设计

本文介绍一种利用西门子s7系列PLC为主控制器设计的新的帘子布返卷机,详细的阐述了该系统的设计方案和实现方法,本针对设计的关键部分作出了详细的分析说明。

STUDY ON VIBRATION REDUCTION BEHAVIOR FOR THE HYDRAULIC ENGINE MOUNT

In this paper,the metal hydraulic engine mount (HEM) with the orifice is presented,the construction of HEM is consist of hydraulic cylinder and the spring on the bottom,its mechanical model is given and dynamics equations are set up with considering kinematics conditions and continuous of fluid,the dynamics behavior of HEM including dynamic stiffness of fluid and transferability of HEM are studied here.The example of hydraulic engine mount is calculated,it is shown that the vibration reduction performance of the hydraulic engine mount of this paper is better.The analysis method of vibration reduction behavior for HEM in this paper can be used in designing of the reduction vibration devices and the HEM in this paper can be used in the practical engineering for reduction vibration.

Comparative investigations of pressure waves induced by trains passing through a tunnel with different speed modes

Pressure waves induced by high-speed trains passing through a tunnel have adverse effects on train structures and passenger comfort. These adverse effects can be alleviated when the train passing through the tunnel with a speed mode of deceleration. Thus, to investigate the effect of speed modes on pressure waves, three-dimensional compressible unsteady Reynolds-averaged Navier-Stokes simulations and the sliding mesh are used to simulate pressure waves on train surfaces and tunnel walls when trains passing through a tunnel with three different speed modes(a constant speed at350 km/h, a uniform deceleration from 350 to 300 km/h, and another uniform deceleration from 350 to 250 km/h).Compared with the constant speed, the peak-to-peak of the train surface pressure under the other two speed modes reaches a maximum difference of 11.0%. The maximum positive pressure difference of the tunnel wall under different speed modes is caused by the different attenuation of the friction effect when the train enters the tunnel, and the maximum difference is 12.8%. The difference of the maximum negative pressure on the tunnel wall is caused by the different speed and pressure wave intensity of the train arriving at the same measuring point in different speed modes,and the maximum difference is 15.8%. Hence, it can be concluded that a speed mode of deceleration for trains passing a tunnel can effectively alleviate the aerodynamic effect in the tunnel, especially for the pressure on the tunnel wall.

Pressure-relief effect of coal rock body of long distance lower protective seam mined based on FLAC^(3D)

According to the specific geological condition, analyzed the stress distribution of the overlying strata, the displacement of pressure released seam, thickness variation and the distribution of plastic zones by FLAG3D software to simulate mining of the long-distance lower protective seam. The research results show that the distribution of vertical stress appears as a ＂Double-hump＂ within the pressure-relief range of the protected coal seam and the swelling deformation curve of coal bodies takes an ＂M＂ shape. The swelling is divided into initial swelling, swelling increase and swelling compression stability. The maximum swelling ratio of the pressure released seam is 1.84%, protection angle of the lower protective coal seam along the strike direction is about 55°, protection angle below the dip direction is about 50°, protection angle above the dip direction is about 55°, and the coal seam compression zone resembles a ＂U＂ shape.

Application of Discrete Lumped Kinetic Modeling on Vacuum Gas Oil Hydrocracking

The kinetic model of vacuum gas oil （VGO） hydrocracking based on discrete lumped approach was investigated, and some improvement was put forward at the same time in this article. A parallel reaction scheme to describe the conver- sion of VGO into products （gases, gasoline, and diesel） proposed by Orochko was used. The different experimental data were analyzed statistically and then the product distribution and kinetic parameters were simulated by available data. Fur- thermore, the kinetic parameters were correlated based on the feed property, reaction temperature, and catalyst activity. An optimization code in Matlab 2011b was written to fine-me these parameters. The model had a favorable ability to predict the product distribution and there was a good agreement between the model predictions and experiment data. Hence, the ki- netic parameters indeed had something to do with feed properties, reaction temperature and catalyst activity.

Coal-gas interaction： implications of changes in texture and porosity

Transient sorption and desorption of helium and carbon dioxide in Upper Freeport coal powder and lumps were analyzed. Differences in texture and porosity between the powder and lumps may affect the transport and interaction of the penetrant and coal. In this work, we address macroscopic and mesoscopic structural differences between powdered and non-powdered coals that influence the rates of the gas transport kinetics and changes in coal texture （swelling, shrinkage, and changes in the pore structure and interconnectivity） and the reciprocal free-phase pressure decay （relaxation）. Com- parison of the multi-exponential relaxation time constants as a function of pressure, for CO2 and inert gas （helium）, allows us to postulate several mechanisms responsible for observed pressure decay patterns.

Design and Dynamics Simulation of a Novel Double-Ring-Plate Gear Reducer

A patented double-ring-plate gear reducer was designed and its dynamic performance was simulated. One unique characteristic of this novel drive is that the phase angle difference between two parallelogram mechanisms is a little less than 180 degree and four counterweights on two crankshafts are designed to balance inertia forces and inertia moments of the mechanisms. Its operating principle, advantages, and design issues were discussed. An elasto-dynamics model was presented to acquire its dynamic response by considering the elastic deformations of ring-plates, gears, bearings, etc. The simulation results reveal that compared with housing bearings, planetary bearings work in more severe conditions. The fluctuation of loads on gears and bearings indicates that the main reason for reducer vibration is elastic deformations of the system rather than inertia forces and inertia moments of the mechanisms.

Numerical simulation on pressure-relief deformation characteristics of underlying coal-rock mass after upper protective layer excavation

Based on the occurrence features of Group B coal-seams at a coal mine in the Huainan coal mining area, the elasto-plastic mechanical damage constitutive functions and numerical model for the protective layer excavation were established. With the UDEC2D computer program, after the upper protective layer was mined, the stress field change trends, crack development, and expansion deformation trends of underlying coal rock seams in the floor of the working face were simulated and analyzed. The simulation results show the stress changes in coal rock seams, the evolution process of pre-cracks during the process of upper protective layer mining, the caved zone and fractured zone of the underlying coal rock seams. At the same time, the results from the actual investigation and analysis of protected layer deformation match the simulation values, which verifies the validity and accuracy of numerical simulation results. The study results have an important guiding significance for gas management in low permeability and high gas coal seams with similar mining conditions.

Pneumatic resistance network analysis and dimension optimization of high pressure electronic pneumatic pressure reducing valve

The structure and working principle of a self-deigned high pressure electronic pneumatic pressure reducing valve (EPPRV) with slide pilot are introduced.The resistance value formulas and the relationship between the resistance and pressure of three typical pneumatic resistances are obtained.Then,the method of static characteristics analysis only considering pneumatic resistances is proposed,the resistance network from gas supply to load is built up,and the mathematical model is derived from the flow rate formulas and flow conservation equations,with the compressibility of high pressure gas and temperature drop during the expansion considered in the model.Finally,the pilot spool displacement of 1.5 mm at an output pressure of 15MPa and the enlarging operating stroke of the pilot spool are taken as optimization targets,and the optimization is carried out based on genetic algorithm and the model mentioned above.The results show that the static characteristics of the EPPRV are significantly improved.The idea of static characteristics analysis and optimization based on pneumatic resistance network is valuable for the design of pneumatic components or system.

Effects of axial static stress on stress wave propagation in rock considering porosity compaction and damage evolution

A wave equation of rock under axial static stress is established using the equivalent medium method by modifying the Kelvin-Voigt model.The analytical formulas of longitudinal velocity,space and time attenuation coefficients and response frequency are obtained by solving the equation using the harmonic method.A series of experiments on stress wave propagation through rock under different axial static stresses have been conducted.The proposed models of stress wave propagation are then verified by comparing experimental results with theoretical solutions.Based on the verified theoretical models,the influences of axial static stress on longitudinal velocity,space and time attenuation coefficients and response frequency are investigated by detailed parametric studies.The results show that the proposed theoretical models can be used to effectively investigate the effects of axial static stress on the stress wave propagation in rock.The axial static stress influences stress wave propagation characteristics of porous rock by varying the level of rock porosity and damage.Moreover,the initial porosity,initial elastic modulus of the rock voids and skeleton,viscous coefficient and vibration frequency have significant effects on the P-wave velocity,attenuation characteristics and response frequency of the stress wave in porous rock under axial static stress.

Reduced Expanding Load Method for Simulation-Based Structural System Reliability Analysis

The current situation and difficulties of the structural system reliability analysis are mentioned. Then on the basis of Monte Carlo method and computer simulation, a new analysis method reduced expanding load method (RELM) is presented, which can be used to solve structural reliability problems effectively and conveniently. In this method, the uncertainties of loads, structural material properties and dimensions can be fully considered. If the statistic parameters of stochastic variables are known, by using this method, the probability of failure can be estimated rather accurately. In contrast with traditional approaches,RELM method gives a much better understanding of structural failure frequency and its reliability index β is more meaningful.To illustrate this new idea, a specific example is given.

Peristaltic flow with convective mass condition and thermal radiation

The primary objective of present investigation is to introduce the novel aspects of convective mass condition and thermal radiation in the peristaltic transport of fluid. Magnetohydrodynamic(MHD) fluid was considered in a symmetric channel. Heat and mass transfer characteristics were analyzed in the presence of Soret and Dufour effects, and the results were presented via two forms of thermal radiation. The temperature, concentration and pressure rise per wavelength were examined. It is observed that the velocity slip and magnetic field parameters have opposite effects on the pressure rise per wavelength. Temperature of fluid is a decreasing function of the radiation parameter. Further, the temperature of fluid decreases by increasing the heat transfer Biot number. It is notified that the heat transfer rate at the wall is a decreasing function of radiation parameter.

A numerical simulation of the influence initial temperature has on the propagation characteristics of, and safe distance from, a gas explosion

A model roadway with a cross-sectional area of 80 mm 80 mm and a length of 100 m was used to estimate the overpressure, the temperature, the density, and the combustion rate during an explosion. Auto-ReaGas software was used for the calculations and the initial temperatures were 248, 268, 308, or 328 K. The methaneair mixture had a fuel concentration of 9.5% and the tunnel had a filling ratio of 10%. The results show that the safe distance necessary to avoid harm from the shock wave increases with increasing initial temperature. The distance where the peak overpressure begins to rise, and where the maximum value occurs, increases as the initial temperature increases. These are almost linear functions of the initial temperature. At locations before shock wave attenuation has occurred increasing the initial temperature linearly increases the maximum temperature at each point following along the tunnel. At the same time, the peak overpressure, the maximum density, and the maximum combustion rate decrease linearly. How-ever, after the shock wave has attenuated the attenuation extent of the peak overpressure decreases with an increase in initial temperature. The influence of the initial temperature on the explosion propagation depends on the combined effects of inhibiting and enhancing factors. The research results can provide a theoretical guidance for gas explosion disaster relief and treatment in underground coal mines.

Fluid structure interaction for circulation valve of hydraulic shock absorber

Based on the working principle and the damping characteristic of hydraulic shock absorber, a fluid structure interaction method was presented, which was used to analyze the microcosmic and high-frequency processing mechanism of fluid structure interaction between circulation valve and liquid of hydraulic shock absorber. The fluid mesh distortion was controlled by the CEL language, and the fluid struc^tre interaction mathematical model was established. The finite element model was established by ANSYS CFX software and was analyzed by dynamic mesh technique. The local sensitive computational area was meshed by prismatic grid, which could reduce the negative volume problem during the simulation. The circulation valve and liquid of hydraulic shock absorber were simulated and analyzed under the condition of sinusoidal inlet velocity loads. Flow characteristic and dynamics characteristic were obtained. The pressure distribution and the displacement of circulation value were obtained, and the acceleration curve of circulation valve was simulated and analyzed. The conformity of the final simulation results with the experimental datum indicates that this method is accurate and reliable to analyze the dynamics characteristic between circulation valve and liquid of hydraulic shock absorber, which can provide a theoretical foundation for optimizing hydraulic shock absorber in the future.

Study of Oil/Water Interfacial Tension of Vacuum Residual Fractions from Iranian Light Crude Oil

The vacuum residual from Iranian Light crude oil are separated into a series of 16 narrow fractions according to the molecular weight by the supercritical fluid extraction and fractional (SFEF) technology. The chemical element and the UV spectrum of each fraction are analyzed. The effects of several factors on the interfacial tension are investigated, which are the fraction concentration in oil phase, the ratio of oil component, the salts dissolved in the water phase and the pH value. The interfacial tension decreases rapidly as the concentration of the residual fraction in the oil increases, showing a higher interfacial activity of the fraction. The interfacial tension changes, as the amount of absorption or the state of the fractions in the interface changes resulting from different ratios of oil, different kinds or concentrations of salts in water, and different pH values. It is concluded that the interfacial tension changes regularly, corresponding to the regular molecular parameters of the vacuum residual fractions.

Parametric design of an electrorheological shock absorber with the mixed-mode

A mathematical model based on an electrorheological (ER) shock absorber with the mixed-mode is presented. Its application to the parametric design of an electrorheological fluid shock absorber with the simulation calculation performed by program MATLAB demonstrates that the model can predict the behavior of ER shock absorbers satisfactorily, shorten the design period of an electrorheological shock absorber, and reduce the cost in the prototype manufacturing. The strength analysis based on a three-dimensional finite element model for the electrorheological shock absorber confirm that the structure design of the ER shock absorber is reasonable, and the stress distribution is uniform.

Numerical simulation of flow field of single-hole oxygen lance jet

The numerical simulation of jet flow field in Laval tube was carried out first by commercial software CFX4.4, and it is used to determine inlet pressure condition out of nozzle in order to its numerical simulation. The decay rule of jet middle line velocity of axial symmetry turbulence jet and cross section＇s expand situation out of the tube in different stagnation pressure and surrounding temperature were analyzed systematically. The result showed that K-e model is suitable for numerical simulation. The conclusion will have important guide and referent function to research of two important craft parameters, impact depth and the impact area which are related to steel-making production practice.

Co-processing Vacuum Residue with Waste Plastics in a Delayed Coking Process:Kinetics and Modeling

Thermal upgrading of vacuum residue mixed with waste plastics was studied in a laboratory scale delayed coking unit.The model of feed thermal decomposition was set up and the first order reaction kinetics was used to predict products distribution during the coking process.The distillate yield was higher(70%) for the vacuum residue/polystyrene(VR/PS) feed system and the vacuum residue/low density polyethylene(VR/LDPE) feed system.The resulted distillate yield was separated into fractions according to their boiling points,with gasoline and diesel being our fractions of concern.The activation energy was higher for gasoline production(around 60 kcal/mol) varying with the type of feed system,while it was 33 kcal/mol for diesel fraction.The regression coefficient R was 0.990.

一种用于治疗脊柱侧弯的脊柱减压牵引系统的研究

现代社会由于青少年爱玩游戏、运动减少、缺乏睡眠等其他不健康的生活习惯以及遗传等因素造成其脊柱侧弯的发病率越来越高、越来越年轻化。引起了国家相关部门各高度重视;因此把脊柱侧弯和肥胖、近视并列为危害青少年健康成长的三大“杀手”。它的危害包括会引起脊柱本身和脊柱两侧的受力不平衡;影响儿童的身体发育;如果不干预治疗;随着年龄的增加;侧弯程度会加重;渐渐出现腰背疼痛的症状;严重的会压迫脊髓或神经;引起截瘫或椎管狭窄。所以;脊柱侧弯不仅影响青少年的心理;最终对其生活和工作都会造成不可逆的严重影响。加上特发性脊柱侧弯是青少年最常见的一种侧弯;目前还找不到明确的具体发病原因;前期很难进行针对性的预防;其自然发病趋势又是不可逆的。因此;脊柱侧弯应该早发现;早治疗;脊柱脊柱侧弯的治疗目的是矫正侧弯畸形且制止其进一步进展。治疗方法分为非手术治疗和手术治疗两大类。由于人体脊柱结构复杂;周围神经丰富;因此手术难度极大;风险极高;术后会有一些后遗症;因此只有重度脊柱侧弯;才推荐进行手术治疗。非手术治疗主要包含药物治疗、针灸、按摩、穿戴支具、传统牵引等治疗方法;但是这些方法面临治疗周期长、效果缓慢、容易复发等缺点。我们研究出了一款脊柱定位周期减压牵引系统;该系统通过伺服控制系统按照设定的非线性对数曲线进行周期性间歇加载施力;通过角度调节装置配合智能分离床体进行定位病变部位完成脊柱侧弯的治疗;实验结果表明;具有较好的临床使用价值。