变隙式压力补偿灌水器水力特性实验研究

对自行研制的变隙式压力补偿灌水器的水力性能进行了实验研究,旨在揭示其水力特性,为改进和应用提供依据。为便于性能比较,同时测试了3种市售灌水器,包括NETAFIM、奥特普和丰霸灌水器。结果表明,变隙式灌水器的压力补偿范围为0.006-0.500MPa,额定流量为3.989L/h,流态指数为-0.002 6;0.1MPa压力点变异系数为4.64%;压力补偿范围内各压力点25个灌水器的平均流量与额定流量的平均偏差为2.81%,可用于微压滴灌和高差较大的山地滴灌系统。然而,0.1 MPa压力点的流量偏差过大,为6.14%,有待改进。

变隙宽裂隙的渗流分析

以隙宽均一单裂隙水流的立方定律及流体力学的基本方程为基础，对隙宽不均一单裂隙渗流模型进行了分析，得出了隙宽不均一单裂隙渗流量等效的等效隙宽公路；并将此公式应用于岩体裂隙网络渗透模型分析中，检验了等效隙宽公式的有效性。

弹载气流压电发电机环隙变截面进气孔

针对环隙直进气结构难以在满足气流产生旋涡脱落条件的同时满足小尺寸要求,提出了环隙变截面收缩结构。将原有的环隙直进气孔改为环隙变截面收缩孔,主要由转捩段、发展段和加速段组成。仿真表明:环隙口形成的湍流,其发展对转捩段长度不敏感,在经过直孔和收缩孔后速度分布较快地均匀和稳定,速度分布直接受孔长度影响,外径较小进气孔其速度分布发展较快。这一结论对于工程设计和结构小型化有参考价值,也为进一步的实验研究提供了依据。

单裂隙中LNAPL残留特点及残留体对水流运动的影响

轻非水相液体（LNAPL）在变隙宽裂隙中的迁移和残留机理复杂,在＂裂隙-水-LNAPL＂三相系统中,LNAPL和水流运动之间相互作用和影响,同时两者又共同受到裂隙表面和隙宽的影响和控制。采用27.4 cm×20.0 cm（长×宽）的透明仿真裂隙开展甲苯（地下水中常见的LNAPL污染物之一）迁移试验,监测并获取变隙宽裂隙中LNAPL的迁移过程与残留分布的图像,通过数学统计和数值模拟的方法,分别揭示LNAPL残留分布规律以及＂裂隙-水-LNAPL＂系统内的相互影响机制。研究结果表明：自由相的LNAPL主要沿着裂隙中的狭长通道迁移到内部,在隙宽较小的区域有少量孤立的LNAPL液滴残留。LNAPL在变隙宽裂隙中的迁移、残留与裂隙隙宽的分布密切相关,LNAPL残留的隙宽符合正态分布规律。甲苯残留的隙宽分布范围为0.01~1.40 mm,残留最多的隙宽分布在0.20~0.30 mm。LNAPL的残留增大了裂隙内水流运动的阻力,使得裂隙两端的压力差增加。LNAPL残留使裂隙内水流流速重新分布,同时也改变了裂隙原有的沟槽流分布和数量。

锥齿轮副啮合侧隙的控制——《ANSI／AGMA 2005-B88锥齿轮设计手册》的学习应用

锥齿轮的啮合侧隙是锥齿轮设计、制造和安装的重要参数之一。如何确定、控制和检验锥齿轮副的侧隙并保证在安装时达到设计规定的侧隙要求，美国国家标准《ANSI／AGMA2005-B88锥齿轮设计手册》给锥齿轮设计制造和安装人员提供了相关资料。本文作者就标准的应用谈了一些自己的看法和体会。

节流性能优异的新型液体静压支承节流器

传统的液体静压支承节流器存在严重缺陷 ,性能不佳 ,不能消除支承间隙随外加载荷增加而剧减的缺点 ,严重影响其实际应用。新型节流器节流变量指数b≥ 3,能够保持节流器进油与油囊排油速度接近一致。此外 ,当有外加载荷作用于支承时 ,油囊压力会升高 ,迫使节流变量产生附加增量 ,从而弥补了因油囊压力升高而减少供油量与油囊增加的排油量。因此 ,新型节流器能够保证在有外加载荷作用时支承间隙变化很小或近于不变。新型节流器节流性能优良 ,结构简单 ,成本低廉 ,体积较小 ,具有实用价值。

基于Skewed Miura构型的周期可展结构变带隙分析研究

基于折纸构型的周期结构在一定条件下具有带隙特性,能阻止特定频率的弹性波在结构中传播,这种带隙特征可以调节,为减振结构的开发提供了新思路.对基于Skewed Miura折纸构型的周期性可展结构变带隙机理进行研究.推导了Skewed Miura折纸构型的几何关系,并利用布洛赫波分析框架研究了该构型的带隙情况.将Skewed Miura单元的几何形状和折纸构型的折叠状态作为设计变量,找出该构型的最大带隙值和相应的折展状态.对比发现,Skewed Miura构型带隙的数量及大小明显大于Miura构型,且带隙位置所处频率范围较低.本研究为减振结构的开发提供了新的结构形式.

6BX-40型苎麻剥制机设计

提出了基于变隙定压原理的旋切式苎麻剥制机的设计思路和技术方案,分析了弧形变隙定压双支点浮动式旋转切削机构的工作原理和技术特点。依据旋转切削机构的受力条件,对影响苎麻剥制质量的相关工艺参数进行了试验和测定,在此基础上对旋转切削机构及其主要参数进行了设计和计算,并对其力学模型的动力和运动参数进行了理论研究和分析。通过6BX-40型样机试验表明：剥制效率比传统方法提高2~3倍,纤维胶质含量25.8%,纤维含杂率4.6%,纤维损失率4.3%,剥制质量达到国家相关标准要求。

采用平衡摇臂悬架的移动平台稳定性分析

设计了一种带平衡摇臂悬架且具备变轮距变地隙功能的移动平台(VII-HPC)。在传统分析的基础上,针对平台的变地隙、变轮距和变姿态工况进行了研究,总结出质心高度变化趋势、侧滑和侧翻、纵滑和纵翻的计算公式、边界条件和相应曲线,并对横向行驶变姿态工况下平台的稳定性作了分析和评价,同时通过对采用平衡摇臂悬架结构的平台与普通拖拉机的稳定性对比仿真,验证了其稳定性。

集束弹在轨道内动力分析

建立了一种新型电磁轨道炮用集束穿甲弹物理模型,这种集束结构在轨道内由电枢推动,产生动能。在脱离炮口时速度达到2000m/s以上的发射条件时,该结构受力条件极为严苛。为了提高整体的发射强度,通过采用变齿隙技术改进弹托与弹芯的齿间啮合方式,并使用Ls-Dyna软件对齿间强度进行数值模拟。模拟结果表明:与传统啮合方式相比,使用变齿隙技术设计的间隙方案,可以有效的降低弹托和弹芯危险齿面的最大等效应力,提高整体发射强度。

表面键合对硅(111)量子面电子结构的影响

将纳米硅薄膜看成理想的一维限制的量子面结构,通过第一性原理计算研究了不同厚度的硅(111)量子面的能带结构及态密度。随着量子面厚度的变化,在Si—H键钝化较好的量子面结构上,其带隙宽度变化主要遵循量子限制效应规律。当在表面掺杂时,模拟计算表面含Si—N键的硅(111)量子面的结果表明:在一定厚度范围内,带隙宽度主要由量子限制效应决定;超过这个厚度,带隙宽度同时受量子限制效应和表面键合结构的影响。保持量子面厚度不变,表面掺杂浓度越大则带隙变窄效应越明显。同样,模拟计算含Si—Yb键的硅(111)量子面的结果也有同样的效应。几乎所有的模拟计算结果都显示:量子面的能带结构均呈现出准直接带隙特征。

Volume change of macropores of titanium foams during sintering

The porosity of titanium foams obtained from the space holder technique was theoretically analyzed in the cases of volume shrinking, retaining and expanding during sintering. The relationship between porosity and spacer content was compared under different conditions. The kind of volume change of macropores during sintering was discussed. The results indicate that the relationship between porosity and spacer content depends on the decreased volume of macropores and the volume of micropores in cell-walls in the first case, while the porosity will be greater than the spacer content for the other two cases. It proves that the volume change of macropores during sintering decreases based on theory and practice.

APPLICATION OF THE MULTI-SLIT METHOD IN THE RESEARCH ON THE MECHANICAL PROPERTIES OF RABBIT AORTAS

n the research on the mechanical properties of the blood vessel, it is necessary to measure three-dimensional deformation of the blood vessel. This paper presents a non-contact optical method for measuring these deformation in vitro or in vivo, and the data-processing procedure for the three-dimensional coordinate reconstruction of the aorta surface. The accuracy of this method is tested with a known cylinder. This method has been used in the study of the rabbit aorta and the result shows that it is valuable in the research on the mechanical properties of the blood vessel.

Characteristics of Soil Porosity and Changes of Soil Water Content in Eucalyptus Plantation

Objective] This study almed to investigate the characteristics of soiI total porosity （STP） and various factors affecting soiI water content （SWC） in eucalyptus pIantation （EP）, thereby providing references for soiI water utiIization in eucalyptus pIanting in the red soiI hiI y region of South China. [Method] In the same cIimatic region, soiI sampIes were coI ected from surface soiI Iayer （A）, iI uvial horizon （B） and parent material horizon （C） in the upper sIope, middIe sIope and Iower sIope of eucalyptus pIantation, native forest and pine forest, respectiveIy, to determine the soiI porosity and soiI water content and analyze changes and various infIuencing factors of soiI water content in horizontal and vertical direction. [Result] Average soiI porosity in eucalyptus pIantation, native forest and pine forest was 45.9%, 41.4%and 55.3%, respectiveIy; soiI water content in these three forest stands was 13.3%, 13.4% and 15.5%, respectiveIy. In addition, soiI water content in these three forest stands exhibited no significant differences （P＆gt;0.05） among different soiI profiIes and sIope positions, but soiI water content in surface soiI Iayer varied significantIy （P＆lt;0.05） among different forest stands; in the horizontal direction, soiI water content exerted an extremeIy significant positive correIation with total coverage. [Conclusion] Total coverage of canopy Iayer, herb and Iitter Iayer is one of the most critical fac-tors affecting the changes of soiI water content in surface soiI Iayer of forest stands.

Correction of seabed layer thickness in processing subbottom profile data

The subbottom profiling is an important means of marine engineering survey, hazardous geology study and continental shelf scientific research. The accuracy of subbottom profile data interpretation has a direct impact on the research and investigation results. Because some of profilers’ transducer and hydrophone are separately installed, when the survey area is very shallow, distortion of shallow layers will be caused if it is seen as a self-excited and self-collected single-channel seismic system. According to the principle of subbottom profiler, the distortion correction formula is deduced and analyzed, providing actual value to using C-View software to interpret such subbottom profile data more accurately. In addition, the seabed sediments sound velocity is one of the key parameters when acquiring and processing the subbottom profile data. On the basis of comparing some sound velocity forecasting empirical equations, the LU Bo’s equation was considered the most appropriate to predict the seabed sediments, sound velocity at near-shore of China. In a survey of an artificial island site, the LU Bo’s equation and the porosity data obtained from geological drilling were utilized to predict the sediments sound velocity, and the sound velocity structure profile was plotted, which was applied in processing the subbottom profile data of the artificial island investigation. The method of using porosity data to predict sediments sound velocity in processing subbottom profile data can improve the interpretation accuracy and it’s of practical significance.

Environmental effects induced by excavation

Based on 3D Biot’s consolidation theory and nonlinear Duncan-Chang’s model, a 3D FEM (finite element method) program is developed considering the coupling of groundwater seepage and soil skeleton deformation during excavation. The comparison between the analysis result considering the variation of water head difference and that without considering it shows that the porewater pressure distribution of the former is distinctly different from that of the latter and that the foundation pit de- formations of the former are larger than those of the latter, so that the result without considering the variation of water head dif- ference is unreliable. The distribution rules of soil horizontal and vertical displacements around the pit and excess porewater pressure are analyzed in detail in time and space, which is very significant for guiding underground engineering construction and ensuring environment safety around the pit.

A novel method to predict static transmission error for spur gear pair based on accuracy grade

This paper proposes a novel method to predict the spur gear pair’s static transmission error based on the accuracy grade,in which manufacturing errors(MEs),assembly errors(AEs),tooth deflections(TDs)and profile modifications(PMs)are considered.For the prediction,a discrete gear model for generating the error tooth profile based on the ISO accuracy grade is presented.Then,the gear model and a tooth deflection model for calculating the tooth compliance on gear meshing are coupled with the transmission error model to make the prediction by checking the interference status between gear and pinion.The prediction method is validated by comparison with the experimental results from the literature,and a set of cases are simulated to study the effects of MEs,AEs,TDs and PMs on the static transmission error.In addition,the time-varying backlash caused by both MEs and AEs,and the contact ratio under load conditions are also investigated.The results show that the novel method can effectively predict the range of the static transmission error under different accuracy grades.The prediction results can provide references for the selection of gear design parameters and the optimization of transmission performance in the design stage of gear systems.

Deformation transition of intact coal induced by gas injection

Gas migration in coal bed is a multiple-physical process, of which not only includes gas desorption/diffusion through coal matrix and gas Darcy flow through the cleat system, but also results in deformation of solid coal. Especially for enhanced coal bed methane(ECBM) and CO2 capture and sequestration(CCS), gas injection is mainly controlled by the gas diffusivity in the coal matrix and coal permeability.Although the relevant coal permeability models have been frequently developed, how the dual-porosity system of coal affects gas adsorption/diffusion is still poorly understood. In this paper, a series of experiments were carried out in order to investigate deformation evolution of intact coal subjected to hydrostatic pressure of different gases(including pure H2, N2 and CO2) under isotherm injection. In the testing process, the coal strain and injected gas pressure were measured simultaneously. The results show that the pressure of non-adsorptive helium remained unchanged throughout the isothermal injection process, in which the volumetric strain of the coal shrinked firstly and maintained unchanged at lower isobaric pressure. With the injected pressure increasing, the coal volume underwent a transition from shrinking to recovery(still less than initial volume of the coal). In contrast, N2 injection caused the coal to shrink firstly and then recover with decreasing gas pressure. The recovery volume was larger than the initial volume due to adsorption-induced swelling. For the case of CO2 injection, although the stronger adsorption effect could result in swelling of the solid coal, the presence of higher gas pressure appears to contribute the swelling coal to shrink. These results indicate that the evolution of coal deformation is time dependent throughout the migration of injected gas. From the mechanical characteristics of poroelastical materials, distribution of pore pressure within the coal is to vary with the gas injection,during which the pore pressure in the cleats will rapidly increase, in contrast, the pore pressure in the matrix will hysteretically elevate. Such a difference on changes of pore pressure between the cleats and the matrix will contribute to the shrinkage of the matrix as a result of initially greater effective stress.Besides, both gas-adsorption-induced swelling and decreasing effective stress also control the coal deformation transition. This work gives us an insight into investigation on influence of effective stress on coal-gas interaction.