预应力薄腹梁质量事故的分析及鉴定

阐述了某工程由于施工原因，导致预应力混凝土工字形屋面梁强度不足的预制构件的检验鉴定过程和方法。采用回弹法推定混凝土实际强度；通过静载试验测试构件的实际挠度、抗裂和承载能力。分析了导致混凝土强度不足的原因。     

静压式平面空气轴承压力场的有限元分析

采用有限元理论分析了静压式平面空气轴承的压力场，并讨论了空气轴承压力场边界条件的处理。分析结果表明，空气轴承的压力场呈现尖峰状分布。分析结果已应用于三坐标测量机的空气轴承设计中，取得了令人满意的效果。     

悬挂犁传统受力分析方法的质疑和计算机辅助分析

对悬挂犁受力分析的传统方法提出了质疑，并从理论上分析了存在问题的原因。用解析方法建立了悬挂犁受力方程组，编制了计算机程序，依靠计算结果，探讨了各因素变化对悬挂犁所受作用力和力偶矩的影响。     

运用乙炔抑制-静态土柱培养法测定旱地土壤氮素反硝化损失

介绍了测定土壤反硝化作用的乙炔抑制 -静态土柱培养法 ,并就其应用中的一些条件进行了说明 ,内容包括土柱的取样深度、土柱取样量、土柱培养方式及基本操作程序等。最后阐述了这一方法在北京郊区土壤上的使用情况。     

套筒式橡胶减振器的疲劳工况试验研究

为了准确掌握金穗4SW系列马铃薯挖掘机摆动分离筛新型套筒式橡胶减振器的疲劳工况，进行了田间试验和实验室试验。试验表明，该橡胶减振器能够满足生产实际要求和对橡胶减振器的设计寿命要求。给出了符合橡胶减振器疲劳损失衡量标准的静刚度损失值，经生产实践证明，此值具有指导生产的实际意义。     

苏北不同杨树人工林经营模式下土壤呼吸日变化观测与测定方法比较

采用动态密闭气室法(IRGA)对苏北地区具有代表性的4种杨树人工林经营模式和农田对照的土壤呼吸进行了日动态观测,同时采用碱液吸收法(AA)测定土壤日呼吸速率,并把两种方法测定的结果进行了比较。结果表明:①采用动态密闭气室法(IRGA)和碱液吸收法(AA)测定土壤日呼吸速率范围分别为3 065~5 880 mgCO2-C/(m2.d)和1 060~1 697 mgCO2-C/(m2.d)。AA法测定结果均低于IRGA法,平均为IRGA法测定结果的33.8%,两者测定结果的线性相关性达到显著水平,线性关系为IRGA=3.8231A-A1118。②P1和P2模式下杨树根系呼吸分别占土壤总呼吸量的47.9%和13.5%。③土壤呼吸日变化为单峰型曲线,峰值出现在13:00~17:00,与温度变化有很好的一致性。     

DETERMINATION OF STATIC AND DYNAMIC DIFFUSION COEFFICIENTS OF MOISTURE IN PARTICLEBOARDS

The static and dynamic diffusion coefficients are important coefficients todescribe the moisture transfer processes in particleboard.In this paper,the formula ofculculating the static and dynamic diffusion coefficients were deduced.At first,the staticdiffusion coefficients of four kinds of particleboards were determined by using diffusion cupmethod.The results demonstrated that the static diffusion coefficients parallel to panelsurface were 10-20 times as large as that of perpendicular to panel surface for test boards.To determine both dynamic diffusion coefficients and surface emission coefficients ofmoisture in particleboards in one experimental period,specimens in four different thickness-es of each kind of particleboard were used in the experiment.Then the method ofregression was used and the dynamic diffusion coefficients and surface emission coefficien-ts were determined based on the slope and intercept of the regressive line.     

Dynamic excitation and static loading tests of glulam lattice floor

A wooden lattice floor with high stiffness and damping capacity has been developed to solve noise problems in wooden apartment houses. The lattice floor consisted of Douglas fir glulam beams with inserted steel plate joints and drift pins. To examine the structural performance of the floor, dynamic excitation and static loading tests were conducted on the full size floor. The first and second order resonance frequencies of the floor were 13.5Hz and 27.0Hz, respectively. These frequencies are similar to the peak frequency of a conventional wooden floor and the combined floor fabricated from glued laminated timber and iron. The maximum static load of the floor was 127kN. The apparent flexural rigidity was less than half the value of several floors studied in the past. However, it is considered that the stiffness is improved by constructing panels and this floor has almost equivalent performance. Relative deflection was not affected by the loading history.Part of this study was presented at the International Wood Engineering Conference, New Orleans, October 1996.     

Safety of the tram car for slopes examined by stress analysis of the ground structure

For monorail systems, it is very important to ensure the safety of the ground structure. We developed a tram car for slopes that utilizes the mechanism of the monorail and analyzed the stress of the ground structure that had double rails. First, we divided the ground structure into seven components, and formulated a procedure for calculating the stress of the ground structure. As a result, the stress that acts upon the main rail and the main rail connecting part was near the allowable stress, and each calculated value was within the allowable stress. We measured the stress by running the vehicle, and compared the measured values with the calculated values. As a result, some measured values were larger than the calculated values. However, the ratio of measured value to allowable stress was 90% or less. Finally, we calculated the static loading coefficient for each part, results of which were as follows: main and subrail: 1.1; rail connection part and prop foundation part: 1.0; rail installation part: 1.3. In the recalculations, it became clear that the recalculated values exceeded the allowable stresses. These results suggest that we need to review the ground structure materials.     

神农香菊花、茎和叶香气成分的组成分析

【目的】对神农香菊花、叶、茎的香气成分进行测定及比对分析,为研究和利用神农香菊独特的芳香性状提供理论基础。【方法】采用静态顶空吸附结合直接热脱附法-气相色谱/质谱联用(DTD-GC/MS)技术,对神农香菊花、叶、茎中的挥发性成分进行分析,用保留指数辅助定性及峰面积归一法对香气成分的相对含量进行测定及比对分析。【结果】神农香菊花朵中检测出的挥发物种类最多,共72种,其中同时存在于花、叶、茎香气中的挥发物有55种。萜烯类化合物含量在花、茎、叶香气中均占到总挥发物成分的80%以上,其中侧柏酮含量最高(50%),其他含量大于1%的重要成分有樟脑、桉树脑、β-石竹烯和大根香叶烯等。神农香菊花朵释放的香气量最多,茎、叶次之。【结论】神农香菊香气主要由萜烯类化合物组成,其花、茎、叶香气组成相似,但各成分含量有所差异。