刨花板吸水和吸湿特征及其对力学性能的影响

对刨花板的吸水性、吸湿性及其对力学性能的影响进行测定,结果表明,浸泡时间、试件大小和水的温度,对吸水特征均有明显影响,在吸水厚度膨胀率和吸水率之间,存在线性相关关系;相对湿度的变化,对刨花扳的吸湿厚度膨胀率和平衡含水率亦有明显影响。特别是相对湿度达到65%以上时,影响更为显著,并导致其静曲强度和平面抗拉强度显著降低。     

Field assessment of crusting on a tilled sandy clay loam

Nine different techniques were used to record the initial change in the physical and hydrological properties of a freshly tilled soil surface following successive cycles of wetting and drying. The study was made in the field on a sandy clay loam soil ploughed and harrowed and then exposed to three simulated rainfall events of 76 mm/h for 15 minutes. Although the degradation of the soil surface increased with each successive rainfall, the most significant changes were observed after the first rainfall. Qualitative observations of clod size distribution and crust development provide a good indication of the early stages of soil surface degradation. Complementary physical data were quickly obtained using a hand held shear vane. These techniques are simple and robust enough that they can be used in on-farm research programmes, where resources, both human and technical are at a premium. Tension infiltrometry provided hydrological information that complemented the physical information provided by the above techniques, but is not as simple.     

泗水裘皮羊鞣后羔皮的物理性能

系统研究了山东泗水裘皮羊4个年龄组，即2－5日龄（小毛）、10－25日龄（中毛）、30－60日龄（大毛）、6月龄共24只个体鞣后羔皮的主要物理性能指标。结果表明，皮板的抗张强度为8．68－14．86N/mm^2撕裂强度为22．62－55．45N/mm，规定负荷（试受到5N/mm^2拉力）伸长率44．67－72．33％，崩裂强度为360．65－344．77N/mm，收缩温度为65．90－90．77℃；皮重为140．00－416．33g，皮厚为0．94－1．23mm，总面积为1690．67．3418．67cm^2。有花面积占总面积的84．44％－99．86％。以上各物理性能指标，除皮板的规定负荷伸长率随年龄增长而下降外，其余各指标均随年龄增长而增加。小毛、大毛、6月龄羔皮的皮厚部位差均较小（P＜0．05）。     

车用散热器结构强度的有限元分析

建立了管带式车用散热器的有限元模型，对其动强度进行了计算分析，得出了散热器应力场分布及其危险位置，并在MTS振动台上进行了试验验证。结果表明，有限元计算结果可靠，此模型可为散热器结构参数的改进提供理论依据。     

冷冻鱼圆质地的研究

本文以添加不同淀粉量的5种自制冷冻鲢鱼圆和6种市售冷冻小包装鱼圆为研究对象，对反映冷冻鱼圆质地特性的硬度和弹性作感官评定和仪器测定，并进行质地嗜好性试验。根据5种自制冷冻鱼圆和6种市售冷冻鱼圆的质地嗜好性试验结果表明，嗜好性评分高的冷冻鱼圆，其质地特性主要力学参数的范围是硬度150～270g，弹性（凝胶强度）140～220g·cm。自制冷冻鲢鱼圆淀粉的添加量直控制在5％～10％左右。冷冻鱼圆硬度和弹性的感官评分与仪器测定值之间存在着显著的相关关系（P＜0，01）。     

空间钢框架结构的几何与材料非线性分析

本文采用有限变形理论及内力屈服面塑性流动理论对空间钢框架的极限承载力进行了弹塑性在形全过程分析。理论与算例都表明，本文方法精度较高，而计算又不过于复杂。     

高强度铝钒土型壳的溃散性试验研究

用"P"盐对低密度(<1.28克/厘米~3)水玻璃改性处理,可使精铸型壳残留强度σ弯稳定在(9～15)×10~5Pa范围内,初步解决了推广这一新工艺的难题.     

集成材胶合工艺的研究

以水曲柳、核桃楸和长白鱼鳞云杉为试验用材,采用水性高分子聚合物异氰酸酯作胶黏剂,以单位压力、加压时间和涂胶量为试验因子进行集成材的胶合试验,并对其胶合性能进行检验。通过试验结果分析,得出较优的胶合工艺条件为：单位压力2．0MPa(水曲柳、核桃楸)、1．5MPa(长白鱼鳞云杉),加压时间为60min．涂胶量为250g／m^2。     

Mechanical testing of a steel-reinforced epoxy resin bar and clamp for external skeletal fixation of long-bone fractures in cats

AIMS: To provide veterinarians with confidence when using a commercially available epoxy resin in external skeletal fixators (ESF), testing was conducted to determine exothermia during curing of the epoxy resin compared to polymethylmethacrylate (PMMA), the hardness of the epoxy resin as a bar over 16 weeks, and the strength of the epoxy resin bar compared with metal clamps in similarly constructed Type 1a ESF constructs simulating the repair of feline long bone fractures.

METHODS: Exothermia of the epoxy resin during curing was tested against PMMA with surface temperatures recorded over the first 15 minutes of curing, using four samples of each product. The hardness of 90 identical epoxy resin bars was tested by subjecting them to cyclic loads (1,000 cycles of 20.5?N, every 7 days) over a 16-week period and impact testing 10 bars every 2 weeks. Ten bars that were not subjected to cyclic loads were impact tested at 0 weeks and another 10 at 16 weeks. Strength of the epoxy resin product, as a bar and clamp composite, was tested against metal SK and Kirschner-Ehmer (KE) clamps and bars in Type 1a, tied-in intramedullary pin, ESF constructs with either 90° or 75° pin placement, subjected to compressive and bending loads to 75?N.

RESULTS: The maximum temperature during curing of the epoxy resin (min 39.8, max 43.0)°C was less than the PMMA (min 85.2, max 98.5)°C (p<0.001). There was no change in hardness of the epoxy resin bars over the 16 weeks of cyclic loading (p=0.58). There were no differences between the median strength of the epoxy resin, SK or KE ESF constructs in compression or bending when tested to 75?N (p>0.05). Stiffness of constructs with 75° pin placement was greater for SK than epoxy resin constructs in compression (p=0.046), and was greater for KE than epoxy resin constructs in bending (p=0.033).

CONCLUSIONS: The epoxy resin tested was found to be less exothermic than PMMA; bars made from the epoxy resin showed durability over an expected fracture healing timeframe and had mechanical strength characteristics comparable to metal bar and clamp ESF constructs.

CLINICAL RELEVANCE: The epoxy resin ESF construct tested in this study can be considered a suitable replacement for SK or KE ESF constructs in the treatment of feline long-bone fractures, in terms of mechanical strength.     

Tibiotarsus bone characteristics and tibial dyschondroplasia incidence of broilers fed diets supplemented with leucine and valine

Two experiments were conducted to study the effect of standardized ileal digestible (SID) leucine and valine levels on tibiotarsus bone characteristics and the incidence of tibial dyschondroplasia of broilers from day 1 to 21 (Experiment I) and day 21 to 42 post‐hatch (Experiment II). Each experimental phase was evaluated independently. In both experiments, a total of 1,500 one‐day‐old Cobb 500 male broiler chickens were distributed in a completely randomized design 5 × 5 factorial arrangement for a total of 25 treatments. The SID leucine and valine levels were ranged from 10.0 to 19.6 g/kg, and 6.0 to 12.0 g/kg from day 1 to 21 post‐hatch, respectively, while day 21 to 42 post‐hatch ranged from 10.0 to 18.0 g leucine/kg, and 5.2 to 11.2 g valine/kg. Serum calcium and phosphorus, bone concentrations of calcium, phosphorus and ash, diameter and Seedor index of the tibiotarsus were not affected (p > .05) by the treatments at 21 or 42 days of age. There was an interaction (p ≤.06) between the SID levels of leucine and valine on tibiotarsus breaking strength at 21 days, but not at 42 days of age (p > .05). Tibiotarsus breaking strength was maximized in broilers from day 1 to 21 with the dietary levels of leucine and valine at 14.2 and 9.0 g/kg respectively. Dietary leucine levels reduced linearly (p < .05) the hypertrophic zone of tibiotarsus cartilage at 21 days of age. Therefore, leucine and valine supplementation interact positively on bone strength of broilers from day 1 to 21 post‐hatch. Leucine can be a useful amino acid for reducing the hypertrophic cartilage zone in broilers from day 1 to 21, but not from day 21 to 42 post‐hatch.