塔里木沙漠公路防护林土壤微生物生物量与土壤环境因子的关系

为探讨极端干旱区风沙土土壤微生物与土壤环境因子的作用规律,采用相关分析法研究了塔里木沙漠公路防护林地土壤微生物生物量与理化因子和酶活性的关系.结果表明:土壤容重和粒径减小(R0.85)时,防护林地中土壤微生物数量和生物量有增大趋势,由容重与微生物量的相关性主导;土壤养分含量与土壤微生物数量和生物量呈正相关,主要由速效养分和放线菌、微生物生物量C、P的相关性所致;土壤酶活性与土壤微生物数量和生物量的相关性差异较大,R在0.51～0.91,主要取决于蔗糖酶、磷酸酶与放线菌、微生物量C的相关;土壤盐分增加不利于土壤微生物生物量的积累(R0.63).实践中应为干旱区林地土壤微生物营造良好的土体,促进土壤物质循环

An Inverse Method for Supersonic Flowfield with Given Downstream Boundary

为了实现超声速流场出口参数的可控设计,借鉴特征线方法在古尔赛特与柯西问题两类边值条件中的应用,提出了一种根据下游边界条件求解其依赖域的逆柯西问题求解方法,并在此基础上发展了一种均匀来流条件下的超声速流场逆向求解方法。对轴对称内收缩流场、二维平面流场、轴对称外锥流场三个典型算例校核表明,逆向求解方法得到的计算结果与正向特征线方法一致,由此验证了该逆向求解方法的可行性,并有效拓展了超声速流场的设计思路。For the controllable design of exit parameters in supersonic flowfield,a new method of solving the inverse Cauchy problem,referring to the Method of Characteristics applied in the Goursat and Cauchy problems,is proposed to calculate the domain of dependence according to known downstream condition. On this basis,an inverse method for supersonic flowfield with the uniform flow condition is further developed. The validation of three typical cases(axisymmetric internal compression flowfield,two-dimensional planar flowfield and external conical flowfield) shows that results obtained by the inverse method agree well with those obtained by forward MOC,which verifies the feasibility of the inverse method and expands the thought of supersonic flowfield design effectively.国家自然科学基金(51276151;91441128);; 国防基础科研(B1420133058);; 中央高校基本科研业务费(20720140540

Conversion and Application of Streamline-Characteristic Coordinate System in Supersonic Flows

为了求解二维平面弯曲激波波后流场,讨论并发展了一系列基于流线-特征线坐标系变换的流场代数计算方法。该系列方法依据二维平面流场中气流角、静压沿特征; 线近似不变的特点,可快速求解平面弯曲激波波后流场。其中,等气流角近似法适合模拟流线轨迹,等静压近似法适合求解波后流场参数。在此基础上,又提出了一; 种改进的等气流角-等静压混合方法用于计算弯曲激波波后流场。和特征线法对比,等气流角-等静压混合法计算得到的流场基本特征与特征线法得到的结果相同,; 在来流马赫数Ma=6和Ma=4情况下误差分别仅为0.5%和0.15%,证实了该方法在求解二维平面弯曲激波流场中的适用性。In order to solve the two-dimensional planar flowfield behind the curved; shock,a series of algebraic methods are acquired at the; streamline-characteristic coordinate system. The main idea is that flow; angle and static pressure are approximately constant along each; characteristic line. In contrast to the Method of Characteristics,the; method of constant flow angle is good at calculating the streamline; trajectory while the method of constant static pressure is proper for; solving the flowfield parameters. A combined method named MCFP,Method of; Constant Flow-angle and Pressure,is afterwards proposed to better solve; the two-dimensional planar flowfield behind the curved shock. For a; relatively large Mach number range,the flowfield calculated by the MCFP; method is in good agreement with the MOC's. The error at incoming Mach; number 6 is 0.5% and the error at incoming Mach number 4 is 0.15%,which; demonstrates the applicability of the MCFP method.国家自然科学基金; 国防基础科研; 中央高校基本科研业务

城市建设中的土地污染和光污染的危害性与防治对策

【中文文摘】本文作者主要探讨了现在城市建设中往往被忽视的两种污染 ,即土地污染和光污染 ,指出了其危害性及防治对策。河南省科技攻关项目( 981140 2 10 )

Influence of Particle Damper Configurations on the Dynamic Characteristic for Gear Transmission System

齿轮传动正朝着高速、重载和高精度方向发展,对其动态性能要求越来越高。颗粒阻尼通过颗粒间、颗粒与阻尼器壁间的非弹性碰撞和摩擦作用耗能,具有减振效果; 显著、耐高温、各向同性、对原结构改动小等优点。利用有限元法对齿轮进行了有预应力的模态分析,通过齿轮系统动力学分析,研究单双齿啮合激励对齿轮传动的; 影响;同时建立齿轮传动离心场中颗粒系统耗能模型,将离散元法计算颗粒系统耗能和试验测试对比,分析阻尼器配置对齿轮传动系统动特性的影响。结果显示,阻; 尼器配置方案是影响齿轮传动系统动特性的一个重要因素,在阻尼孔中填充一定数量的颗粒,当阻尼器总体积相同且齿轮结构静刚度相差不大时,阻尼器个数越多颗; 粒系统能耗越大;当阻尼孔直径相同时,阻尼孔个数越多颗粒系统总能耗越小;当阻尼孔个数相同时,阻尼孔直径越大颗粒系统能耗越小。通过试验和仿真对比验证; 了模型的正确性,为颗粒阻尼在离心场中的应用提供重要的理论依据。The gear transmission is advancing towards high speed, heavy load and; high precision. The requirements for the dynamic performance of gear; system are urgently proposed. The particle damping dissipates mechanical; system energy through inelastic collisions and friction between; particles. It is an effective and simple measure for vibration; reduction. It has many advantages, such as isotropy, high temperature; resistance and less modification to the original structure. This paper; has conducted the prestressed modal analysis of gear system by the; finite element method. Based on the dynamics analysis of gear system,; the effect of single tooth and double teeth meshing incentive on gear; transmission has been analyzed. The energy dissipation model of particle; damping for gear transmission in centrifugal field has been established.; By contrasting theoretical analysis and the test, the effect of damper; configuration on dynamic characteristic of gear transmission system is; analyzed. The results show that damper configuration is an important; factor of the dynamic characteristic for gear transmission system.; Filling a certain number of particles, when the gears static stiffness; are similar and the total dampers volume are equal, the more damping; hole, the greater the total energy loss. When the damping holes diameter; are the same, the more number of damping hole, the smaller the total; energy loss. When the damping hole number is the same, the bigger the; diameter, the less the total energy loss. Experimental results are; consistency with the theoretical analysis. These results can provide; guidelines for the application of particle damping in centrifugal field.国家自然科学基金; 福建省重点科技专项; 中央高校基本科研业务费专项资金; 福建省高端装备制造协同创新中心资助项

塔里木沙漠公路防护林生态工程的综合生态环境效应

为了探讨重大工程的生态环境效应,从风沙环境、土壤环境、小气候、生物多样性和地下水环境5个方面对塔里木沙漠公路防护林工程的综合生态环境效应进行了研究.结果表明:(1)防护林改变了近地表风沙运动过程,防沙体系内风速、输沙率降低幅度分别达64%~80%和87.45%~99.02%,风沙流结构、沙物质粒度、地表蚀积状况也发生了明显变化;(2)与自然流沙地相比,防护林土壤容重减小,全盐含量、总孔隙度和含水量增大,土壤肥力质量明显提高,其变化基本呈现"先快后慢"的规律;(3)防护林对于小环境改善作用明显,距地面6m范围内,林地不同高度的空气温度普遍低于自然流沙地,而空气湿度则高于自然流沙地,林地土壤温度也低于自然流沙地;(4)随着防护林内生境的变化,土壤微生物种类显著增加,但不同种类微生物的种群分布并不均匀;(5)目前防护林灌溉抽水对地下水位、地下水矿化度的影响不大,水位在厘米级范围波动,矿化度的变化幅度在±1g·L-1左右,且没有明显的变化趋势

双伺服电动机控制万向指示器的设计

万向指示器在机电一体化演示系统、检测与自动控制系统中有广泛的用途,本文采用两台伺服电动机控制万向指示器的水平转动与垂直转动,通过两种转动的合成来达到任意方向精确指向的目的。实验结果表明,本系统实时性好,反应敏捷。而且体积小、重量轻、造价低,易于实现