Quick Modifying Method of NURBS Curve

Although there are modifying modules in the most CAD software, the parameters of entire curve must be computed again as the tiny local curve changed. The modification are not local and spending long time and difficult as the eurve is complex or large. A method can be applied to engineering designer easily has been proposed. There are only four segments have been ehanged along with the moving of a given point, and the speed is fast. It ean be used to CAD software and generalize the method to surface easily.     

Production of mahogany sawdust reinforced LDPE wood-plastic composites using statistical response surface methodology

We produced wood–plastic composite board by using sawmill wastage of mahogany(Swietenia macrophylla) wood and low density polyethylene.We used multi-response optimization to optimize the process parameters of composite board production including mixing ratio,fire retardant(%) and pressing time(min).We investigated the effects of these three process parameters in the mechanical and physical properties of the composite board.Afterwards,Box–Behnken design was performed as response surface methodology with desirability functions to attain the optimal level of mixing ratio,fire retardant and pressing time(min).The maximum modulus of elasticity(MOE) and modulus of rupture(MOR) were achieved at the optimal conditions of wood plastic mixing ratio of60:40,pressing time of 9 min and zero fire retardant percentage.The optimized MOR and MOE were 13.12 and1,781.0 N mm-2,respectively.     

包膜对越冬期苹果枝条内源脱落酸和赤霉素含量变化的影响

用气相色谱法和高效液相色谱法测定了越冬期间不同处理苹果枝条内源脱落酸和赤霉素的含量变化.结果表明:①越冬前期包膜和露地枝条皮层的脱落酸含量高,2月20日开始迅速下降,包膜枝条下降快,3月5日至4月5日显著低于露地枝条(P<0.05);②包膜枝条营养芽内源脱落酸1月20日达1.47×10~(-3)mg·g~(-1)高峰值,在其后15d中脱落酸含量迅速下降,3月5日至4月5日维持低而稳定的水平;③越冬期间两个处理营养芽内源赤霉素呈上升趋势,包膜枝条上升快,其含量始终高于露地枝条,分别于2月5日和3月20日出现明显高峰,包膜枝条4月5日显著高于露地枝条(P<0.01).     

The Effect of Water-Cement Ratio on the Plastic Shrinkage Cracking of Lightweight Aggregate Concrete

In this paper, the characteristic of the plastic shrinkage cracking of the lightweight aggregate concrete (LWAC) was studied under the condition of prescribed quantity of cement and aggregate and was compared with that of the normal aggregate concrete (NC) with the same proportion of materials for the LWAC. The results suggested that the water evaporation quantity in the concrete became larger with the increase of w/c, and water evaporation velocity reached maximum value around two hours. When the water-cement ratio was low, the area of the plastic shrinkage cracking of LWAC was large and when w/c was 0.40, the area reached the maximum value and then became smaller with the increase of w/c.     

辽西半干旱地区春播前土壤墒情变化的研究

试验监测了不同种植茬口和玉米地秋后不同处理下土壤含水量变化情况,监测结果表明,春播前玉米地表层土壤含水量分别比谷子和大豆地表层土壤含水量低55%,52%,其他土层深度的土壤含水量也均为玉米地最低,谷子和大豆地较高;秋后玉米地的4种处理方式中,土壤含水量高低依次为覆膜＞灭茬＞刨茬＞留茬,其覆膜处理的表层土壤含水量达到11.76%,覆膜和灭茬处理的土壤含水量随监测时间的延长变化不大,刨茬和留茬处理土壤含水量都随监测时间的延长而下降.     

日光暖棚畜舍的设计及其环境评价

根据不同季节的太阳高度角随地理纬度变化这一原理，确定畜舍塑料暖棚面与地面的最佳夹角，使冬季大寒(最冷)这天正午时分，太阳辐射的入射角与塑料棚面垂直，以其充分利用太阳的辐射热能，提高畜舍内的温度。通过对地处北纬46°霍林郭勒市牧民一户牛舍和一户羊舍的温热环境和舍内空气质量的测定表明，大寒这天舍外气温-24～-10℃下，牛舍内的温度平均8.2℃，羊舍内的温度平均6.1℃，空气质量在卫生要求的范围内，达到了防寒抗灾的目的。     

基于改进AquaCrop模型的覆膜栽培玉米水分利用过程模拟与验证

为应用AquaCrop模型模拟覆膜玉米水分利用与产量形成过程,该文根据玉米发育阶段生长度日恒定原理,利用地积温对气积温的补偿效应,改进AquaCrop模型对覆膜玉米的气温计算方法,并根据2011年的生育期、耗水量和产量实测数据对改进模型参数进行校正,依据2012年与2013年的冠层覆盖度、土体贮水量、产量与水分利用效率试验数据对改进模型验证。结果表明,玉米地膜覆盖地积温对气积温的量化补偿系数（Cm）：播种-出苗为1.356,出苗-抽雄前为0.635;校正改进的AquaCrop模型能够较好地模拟覆膜与裸地玉米生育天数、作物耗水量、籽粒产量,相对误差（Pe）、模型效率（CE）、残差系数（CRM）变幅分别为：-4%0.88,CE>0.87,0.09相似文献   

滑动接触失效判据的适用性研究

界面温度是影响滑动摩擦副失效的重要因素。该文在考虑热源强度的非均匀性和表面膜影响的基础上对微凸体滑动接触时的界面瞬时温度进行了研究,并通过量纲分析给出了计算混合润滑状态下微凸体滑动接触界面瞬时温度的近似公式。针对滑动接触失效时普遍存在的塑性变形特征,以该公式为基础并综合考虑表面膜丧失对微凸体塑性变形的影响,对摩擦副失效的温度判据——Blok闪温理论、临界速度和临界PV值等判据的适用性问题进行了分析。指出对于不同的微凸体几何特征、压力、速度组合,发生失效时的界面温度可低于或高于Blok闪温,并据此给出了Blok闪温理论的适用范围。