C2H2-2.5O2-Ar混合气体临界管径和爆轰胞格及临界能量的实验研究

建立了C2H2-2.5O2-Ar混合气体爆轰临界管径的测试系统,其中高压电火花作为起爆源.首先分别测定了C2H2-2.5O2,C2H2-2.5O2-50%Ar,C2H2-2.5O2-70%Ar三种混合气体在不同初始压力下的爆轰临界管径.结果表明:随着氩气稀释浓度的提高,在管道直径相同的条件下,可形成球形爆轰的临界压力增加,表明物质的爆轰敏感性降低.进一步探究各种物质临界管径与爆轰胞格的关系,得到了三种物质临界管径与胞格宽度的比例系数.最后分析了三种物质的临界管径和直接起爆的临界能量的关联性,并与Lee表面积能量模型对比,实验结果与理论模型基本吻合,得出C2H2-2.5O2-Ar混合气体爆轰临界管径与临界起爆能量之间的关系为Ec=16-1πρ0v2CJIdc3.     

An improved R-tree based on childnode''''s probability

R Tree is a good structure for spatial searching. But in this indexing structure, either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R tree (PBAR tree).     

高分子土壤改良剂对种籽萌芽之影响研究

以高分子材料为土壤改良剂可使土壤团粒化，增加水份人渗效率，减少土壤冲蚀，为研究环境问题之重要课题。但此类土壤改良剂可能抑制植物种籽萌芽，为使用此种材料的一大问题。以压克力与聚乙烯醇对Bahia种籽做一系列萌芽实验探讨。实验结果发现，压克力对种籽萌芽率与萌芽势能有严重之抑制作用。但适量之聚乙烯醇添加可克服此问题。     

土工织物加筋土坡变形和破坏过程的离心模型试验

为了评价土工织物加筋土坡的稳定性,研究了土工织物对土坡变形和破坏过程的影响。在清华大学离心机上进行了自重加载条件下离心模型试验。采用离心场图像采集和非接触位移测量系统,测量了加载过程中土坡的位移场及其发展变化过程,对比了素土坡与土工织物加筋土坡的破坏模式和变形发展过程。试验结果表明:土工织物明显改变了土坡的破坏形态,滑裂面位置明显前移;土工织物的约束作用使得土体的变形趋向均匀,增强了土体的整体稳定性。     

低磁雷诺数不可压缩磁流体湍流的非线性涡黏性k-ω封闭模型

在低磁雷诺数近似下,通过逐项模化湍动能输运方程的磁流体源项,提出一个适于任意的磁场布置形式的非线性涡黏性的磁流体湍流k-ω模型.在该模型中,使用Kenjeres-Hanjalic模型和Song的非线性涡黏性模型分别模化脉动电场-速度相关量及各向异性的雷诺正应力,并采用Wilcox低雷诺数k-ω模型对层流化进行估计.通过与直接数值模拟结果和实验结果比较,表明本文模型给出的速度型误差小于5%,摩擦阻力系数误差小于10%,能够满足工程需要.     

爆轰波三波点擦除烟迹表面积碳机制

为理解三波点在壁面及端面积碳留下记录的确切机制,推动对螺旋爆轰内部结构的研究,采用端面烟熏玻璃与内壁烟膜结合的实验方法记录胞格结构,并得到不稳定、较稳定及稳定预混气的侧壁及端面爆轰记录.2H2+O2+3Ar给出了清晰精细的端面结果,其单头螺旋结果表明相对于结果近似的侧壁结果,内部螺旋结构并非固定.进而从附着碳粒的粒度尺寸分析出碳迹附着原理并结合五种预混气的反应特性,确定键能足以克服碳迹吸附在表面的力时才能擦除烟迹.另外预混气中的碳分子也会导致烟迹堆积而影响端面结果,反射激波的强度也影响记录的清晰度.最终确定烟迹擦除机制受预混气影响,应针对预混气选用表面粗糙度载体和积碳颗粒尺寸,并给出了记录爆轰结构的方法.     

Development of Virtual Equipment for a Hydraulic Mechanics Experiment

Laboratory class is very important in the education of hydraulic mechanics. However, it usually requires a high expenditure on equipment purchase and maintenance. Virtual equipment that renders the equipment in a virtual world and provides an interactive interface for users can be an ideal solution to reduce costs. In this research, we focus on developing virtual equipment for a Venturi tube experiment. We em-ployed multiple paper-prototypes to gather user feedback on the preliminary design. Following the final pro-totype, we then implemented the virtual equipment on computers. Interactive functions have been built into the virtual equipment. Users are able to manipulate the equipment and obtain real-time feedback as if they were using actual equipment. The results show that the development of the virtual equipment is technically feasible.     

基于分层制造和数控加工的复合快速成形技术

为克服现行分层制造技术(可制造的原型尺寸小、精度低、可选用材料种类有限)和数控加工(难于直接制造复杂形状、需用夹具固定工件)存在的缺点,把分层制造和数控加工的优势结合起来,研究开发了基于三维层(3D layer)的、材料堆积成形与去除成形交替并行的复合快速成形工艺,并论述了三维层的生成方法和根据三维层的特点设置必要的水平支撑来快速固定被加工工件的方法。为验证该方法的可行性,以复杂曲面组成的汽车手把为对象,进行了成形实验,其制造精度为0.05mm,整个制作过程需要5h。     

低位空调应用于住宅建筑中的节能和舒适性实验

为研究低位送风的空调形式应用于住宅建筑的节能效应及舒适性水平,在模拟卧室的实验室里分别对传统的高位空调（CAC）和低位空调（FAC）在设定室内温度相同的情况下测量其温度场和速度场,通过ADPI指标评价两种空调形式的舒适性水平;同时,对利用功率测试仪器测得的功率以及送回风的干湿球温度计算得到的两种系统不同工况下的COP值进行了比较．实验结果表明,低位空调的送风温度要高于同等工况下高位空调送风温度2．6—8.3℃,而ADPI值在大多数工况下也能满足ASHRAE要求的室内舒适性水平,尽管在实验的极端工况下略低于传统的高位空调的ADPI值．功率测试及COP计算结果表明,使用低位送风的空调系统要比使用传统的空调系统耗功平均减少14．9％,COP平均值由2．5提高到3．25,提高了29．6％．