分形理论在煤层气非平衡吸附模型中的应用

传统的煤层气动力学模型均是建立在欧几里得几何基础上的,难以描述煤层孔隙结构的复杂性及形状的不规则性。本文以分形理论为基础,通过引入分形维数来刻画煤层孔隙结构的复杂性并考虑煤层的吸附特性、双重介质特征及介质的变形,建立基于Fick第二定律的分形介质煤层气非稳态渗流数学模型。由于流动方程的强非线性,结合各类边界条件用正则摄动法和Laplace变换得到模型在拉氏空间上的近似解析解,再利用Laplace数值反演求得实空间上的数值解。对参数进行敏感性分析并绘制了典型压力曲线,这些结果为煤层气开采提供了理论依据和试井方法。     

聚酰胺氨类树枝形聚合物插入式自组装膜的制备与摩擦学性能：小分子链长的影响

在硅基片上制备了聚酰胺氨类树枝形聚合物与不同链长的脂肪酸小分子复合自组装单层膜,用椭圆偏振光测厚仪、DSA 100接触角测量仪、X 射线光电子能谱（XPS）和原子力显微镜（AFM）对所制备的薄膜结构进行了表征,并分别考察了薄膜的纳米摩擦学性能和宏观摩擦学性能。结果表明：C18和C12成功组装到了PAMAM单层膜上PAMAM分子间的空白处。小分子的插入减小了PAMAM自组装膜表面的摩擦力和摩擦系数,提高了PAMAM自组装膜的承载能力。小分子链长的差别对复合薄膜的结构及摩擦学性能影响的差别不明显。     

无网格方法在平面粘弹性力学问题中的应用

本文综合应用无网格方法(EFGM)、线性粘弹性与弹性力学之间的对应原理,Laplace变换和逆变换等方法求解了拟静态平面弹性和粘弹性力学问题。首先,利用Laplace变换和逆变换推导了平面问题的粘弹性本构关系,建立了拟静态粘弹性平面问题的边值问题;其次,利用粘弹性与弹性力学之间的对应原理得到了Laplace变换域中平面问题的基本方程,在Laplace变换域中建立了相应的泛函,并得到了用无网格方法离散的控制方程;同时,求解了几个拟静态弹性和粘弹性平面问题,给出了它们的表达式和数值结果;最后,采用Laplace逆变换和数值逆变换,得到了粘弹性力学平面问题在物理空间中的解,并比较了由解析解和无网格数值方法所得到的数值结果,可以看到它们是非常吻合的。说明本文方法的正确性和有效性。     

Characterization of the bubbling fluidization of nanoparticles

The dynamic features of an agglomerate bubbling fluidization of nanoparticles were investigated through the analysis of pressure fluctuations. Experiments were carried out in a lab-scale fluidized bed at ambient conditions using 10-15 nm silica nanoparticles without any surface modification. Pressure fluctuation signals were processed in both frequency and time-frequency domains to characterize the behavior of various scales of phenomena （i.e.. macro-, meso-, and micro-structures） during fluidization. Due to the aggregation of nanoparticles, three separate broad peaks were observed in the frequency spectra of the pressure signals measured in the bubbling fluidized bed of nanoparticles. A non-intrusive method based on the decoupling of pressure fluctuations recorded simultaneously in the plenum and in the bed was used to determine the approximate size of the bubbles in the bed.     

Dynamics Analysis of Ground Contact Pressure of English Pointer Dogs

In this study force sensing resistors were used to determine thepressure on the central area of each of the weight bearing pads of thefore and hind paws of dogs at the walk. Six adult normal healthy EnglishPointer dogs were used in this project. Pressure data were collected byaffixing a force sensing resistor to the central area of the groundcontact surface of each weight bearing paw pad of the right fore andhind limbs. Pressure signal data from stance phase during walking wereanalyzed. Within paw pads, the pressure graphs were consistent in formand magnitude. Within paws, there were significant pressure differencesamong pads on both fore and hind limbs. The coefficient of restitution,the embedding dimension, and the Lyapunov exponents were calculated. Theability to measure and analyze pressure on individual paw pads providesinsight into soft tissue stresses on the palmar/plantar surface of thepaw. Pressure at a wound site on the pads has a detrimental effect onwound healing and a better understanding these stresses will be ofbenefit when suturing and bandaging pad wounds. Such information isespecially important in athletic and working dogs, e.g. search andrescue dogs.     

板分析的滑动最小二乘插值函数残值法

利用滑动最小二乘插值数作为加权残值法中试函数，对试函数中的基函数的以及权函数的选取提出了建议；分析了形函数的特性；对试函数拟合原函数的效果进行了分析，进而提出了权函数及相应的影响半径的取值；采用最小二北配点法求解定解问题的近似解；利用该试函数对矩形薄板和L形板的弯曲进行了数值计算，并与理论结果和有限元数值结果进行对比，结果表明，该试函数适用于多种边值问题，且精度高。该法简化了选择试验的过程，尤其适用于工程中的各种数值计算。     

Simulation of unsteady laminar flow in models of terminal aneurysm of the basilar artery

Blood flow dynamics play an important role in the pathogenesis and treatment of intracranial aneurysms. The evaluation of the velocity field in the aneurysm dome and neck is important for the correct placement of endovascular coils, in addition the temporal and spatial variations of wall shear stress in the aneurysm are correlated with its growth and rupture. The present numerical investigation describes the hemodynamics in two models of terminal aneurysm of the basilar artery. Aneurysm models with an aspect ratio of 1.0 and 1.67 were studied. Each model was subject to a steady, sinusoidal and physiologically representative waveform of inflow for a mean Reynolds number of 560. Symmetric and asymmetric outflow conditions in the branches were also studied.

The three-dimensional continuity and the Navier-Stokes equations for incompressible, unsteady laminar flow with Newtonian properties were solved with a commercial software using non structured grids with 61334 and 65961 cells for models 1 and 2, respectively. The grids were primarily composed of tetrahedral elements.

The intra-aneurysmal flow was unsteady for all input conditions and in both models, the flow always showed a complex vortex structure. The inflow and outflow zones in the aneurysm neck were determined. The wall shear stress on the aneurysm showed large temporal and spatial variations. The asymmetric outflow increased the wall shear stress in both models.     

高校既有建筑地面抗滑性能试验研究

在滑倒摔伤事故中地面光滑是1个关键因素,以往许多研究都是在实验室内进行的,而本研究是用建筑地面抗滑性能测定仪对大学校园的干燥和潮湿2种地面条件进行了实地检测,考虑了不同湿水时间、不同测试方向以及橡胶机械磨损对地面摩擦系数的影响。通过对某食堂地面的测定来说明不同测试位置对地面摩擦的影响,并比较了潮湿条件下的摩擦损失值。为了确定静摩擦系数和动摩擦系数可能的相关性,对所测得的数据进行了线性回归分析。     

Stress analysis of HNPF loading-face shield

Experimental stress analysis was performed on design aspects of the loading-face shield not amenable to theoretical analysis. Strain and load data obtained from deflection tests of an aluminum model were used to derive bending-stress coefficients for different sections of the shield; maximum strains were recorded at inner edges of moderator-removal holes. Concrete specimens in which process-tube hole patterns were reproduced were tested in compression; strain-concentration factors as high as eight were recorded. Sleeves of practical proportions were found to be ineffectual in reducing diametric shortening of the holes. Transverse deflections of a plaster scale model were found to be 2 1/2 times greater than predicted by plate theory. On the basis of these investigations, maximum stresses in loading-face-shield concrete and steel were determined and factors of safety were calculated. Results of this analysis indicate that the shield will fulfill service requirements.     

轴心受压H型截面钢柱火灾行为的试验研究

本文对4根H型截面钢柱进行了火灾行为的试验研究。全部火灾试验采用自行研制的火灾试验炉,试验结果表明炉子性能稳定,使用方便。试验采用足尺试验形式,柱长3300mm。钢柱轴心受压,其中两个限制轴向变形,另两个不限制轴向变形。柱两端采用单向刀口支座,允许钢柱绕强轴转动。钢柱试验中考虑荷载大小和是否限制轴向变形两个因素。通过试验,得出了钢柱在火灾下的侧向变形和轴向变形随温度变化情况。试验证明:钢柱受火时,轴向变形明显的分为膨胀阶段和压缩阶段。压缩阶段很短,一旦进入压缩阶段,钢柱很快破坏。钢柱受到的外加荷载越大,其极限温度越低。限制轴向变形的钢柱极限温度降低。试验研究为今后钢结构火灾行为研究提供了依据。     

Experiments of free vibration of shells of revolution

This paper presents experimental techniques used in and results obtained during a series of experiments performed to investigate the free-vibration behavior of 15-in. base-diameter spherical and paraboloidal shell models of various geometric parameters and boundary conditions. The models were manufactured from polyvinyl-chloride (P.V.C.) sheets by a thermo-vacuum process using special molds and templates. To provide the necessary excitation power, a variable control amplitude/frequency audio oscillator was used to drive a loudspeaker which was mounted underneath the models. A recently developed noncontact fiber-optics instrument, referred to as the “Fotonic Sensor”, was employed in determining the motion of the models. Thirty-two models of different configurations and boundary conditions were tested in the series. The natural frequencies were observed for all models, while the mode shapes associated with the first four-to-six resonant frequencies were mapped only for some of the models, using special scanning devices.     

Prediction of impacts of wheeled vehicles on terrain

Traffic of off-road vehicles can disturb soil, decrease vegetation development, and increase soil erosion. Terrain impacts caused by wheeled off-road vehicles were studied in this paper. Models were developed to predict terrain impacts caused by wheeled vehicles in terms of disturbed width and impact severity. Disturbed width and impact severity are not only controlled by vehicle types and vehicle dimensions, but also influenced by soil conditions and vehicle dynamic properties (turning radius, velocity). Field tests of an eight-wheeled vehicle and a four-wheeled vehicle were conducted to test these models. Field data of terrain–vehicle interactions in different vehicle dynamic conditions were collected. Vehicle dynamic properties were derived from a global position system (GPS) based tracking system. The average prediction percentage error of the theoretical disturbed width model is less than 20%. The average absolute error between the predicted impact severity and the measured value is less than an impact severity value of 12%. These models can be used to predict terrain impacts caused by off-road wheeled vehicles.     

Influence of non-uniform flow distribution on overall heat transfer in convective bundle of circulating fluidized bed boiler

In the paper the results of comparative investigations on heat transfer performance of boiler convective bundle and its additional surface, i.e. membrane water wall are presented. For this purpose the non-uniform flow field was modelled in an isothermal test stand operated in self-modeling mode. Then the heat transfer characteristics of such arrangement were estimated by means of naphthalene heat/mass transfer analogy technique. The bundle samples in the shape of round bars (rods) were cast with naphthalene and placed in 27 locations in the bundle while water-wall-modeling samples were coated with naphthalene by painting. Both types of samples were exposed to cold air flow. The results were then compared to the mean heat transfer performance of the same bundle exposed to uniform flow field. The differences of approximately 10% were noticed. Moreover, the heat transfer coefficients for additional surface were even three times lower than those of the bundle. In view of results obtained in the work, the commonly made assumption of equality of heat transfer coefficients for both the bundle and its additional surface may lead to certain errors in heat transfer calculations and discrepancies between the calculated values of heating surfaces area and later operational needs of steam generator.     

初始堆积对发射药床底部挤压应力的影响

为给发射装药发射安全性的评估提供关键数据,对不同初始堆积发射药床进行了挤压破碎实验,测得了发射药床底部的挤压应力。利用离散单元法,建立了发射装药挤压破碎动力学模型,对发射药床的挤压应力进行了计算。实验结果和计算结果吻合较好。随机堆积药床底部的挤压应力较一致,竖排堆积药床底部的挤压应力差异较大。     

Experimental investigation of normal perforation of projectiles in metallic plates

This paper describes an experimental program on ballistic perforation of metallic plates. Three kinds of rifles and various steel and aluminum target plates were used. Measurements were made of the initial and post-perforation velocities and in some cases of the time duration of perforation. High speed photographs were taken during the perforation process and detailed studies were made on sections of the perforated target plates. The examination of the physical process of perforation served to motivate aspects of the analytical treatment presented in an associated paper. The experimental results, i.e. post-perforation velocities and duration times, were found to be in good agreement with predictions of the associated analysis.     

预扭转钨合金杆弹侵彻能力的细观研究

对预扭转和未扭转钨合金杆弹弹道实验后的残余弹体和碎片进行了细观金相分析 ,发现钨合金预扭转后钨晶粒变形方向与最大剪应力方向接近 ,因此在弹靶冲击过程中有利于绝热剪切变形和剪切破坏的发生。钨弹残余弹头上观察到的绝热剪切带说明 ,预扭转弹在侵彻过程中要比未扭转弹更易于自锐 ,这是预扭转杆弹侵彻能力得到提高的根本原因。     

三种粘结固体润滑涂层微动磨损性能比较研究

采用Deltalab-Nene型微动摩擦磨损试验机和UMT-2型通用摩擦磨损试验仪对比考察了42CrMo钢基体表面MoS2基、石墨基、PTFE基粘结固体润滑涂层的微动磨损性能及其同涂层划痕临界载荷的相关性；基于微动损伤表面和截面扫描电子显微分析以及涂层原始表面和微动磨损表面X射线衍射分析，探讨了几种涂层的微动损伤机理．结果表明：3种涂层的减摩抗磨性能并不简单取决于其同基体的结合强度，而是同时与涂层本身的机械力学性能和微结构密切相关；涂层在微动早期经历较轻微的塑性变形和流动，并可沿滑动方向发生晶粒择优取向，进而在偶件磨损表面形成转移膜，从而有效地起到减摩抗磨作用；涂层的失效主要归因于往复疲劳应力作用下的裂纹萌生、扩展以及层状剥落．     

An experimental study of cyclic deformation of extruded AZ61A magnesium alloy

Thin-walled tubular specimens were employed to study the cyclic deformation of extruded AZ61A magnesium alloy. Experiments were conducted under fully reversed strain-controlled tension-compression, torsion, and combined axial-torsion in ambient air. Mechanical twinning was found to significantly influence the inelastic deformation of the material. Cyclic hardening was observed at all the strain amplitudes under investigation. For tension-compression at strain amplitudes higher than 0.5%, the stress-strain hysteresis loop was asymmetric with a positive mean stress. This was associated with mechanical twinning in the compression phase and detwinning in the subsequent tension phase. Under cyclic torsion, the stress-strain hysteresis loops were symmetric although mechanical twinning was observed at high shear strain amplitudes. When the material was subjected to combined axial-torsion loading, the alternative occurrence of twinning and detwinning processes under axial stress resulted in asymmetric shear stress-shear strain hysteresis loops. Nonproportional hardening was not observed due to limited number of slip systems and the formation of mechanical twins. Microstructures after the stabilization of cyclic deformation were observed and the dominant mechanisms governing cyclic deformation were discussed. Existing cyclic plasticity models were discussed in light of their capabilities for modeling the observed cyclic deformation of the magnesium alloy.     

Method of equilibrium differential equation for analysis of strength of large deflection drill string

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挡板尺寸对电弧离子镀TiAlN涂层微观结构和摩擦学性能的影响

利用电弧离子镀技术,采用Ti50Al50合金靶,在304不锈钢基体上沉积TiAlN涂层.在Ti50Al5合金靶和基体挂架中间设置直径分别为80、100和120 mm圆形挡板,并与无挡板沉积的TiAlN涂层对比,采用SEM/EDS、XRD研究挡板尺寸对涂层微观结构、成分的影响,通过显微硬度计、划痕仪和摩擦磨损试验研究挡板尺寸对TiAlN涂层力学性能及摩擦学性能的影响.结果表明：随着挡板尺寸增大,TiAlN涂层中Ti含量逐渐降低,Al含量逐渐升高,涂层表面熔滴数量显著减少,沉积速率降低.增大挡板尺寸后,涂层硬度下降,膜基结合力减小.添加挡板后TiAlN涂层表面凹坑缺陷增多,摩擦系数增大,与无挡板的TiAlN涂层相比,耐磨性显著提高.