水稻脱粒破碎率与脱粒元件速度关系研究

脱粒元件的冲击是水稻脱粒谷粒损伤的主要原因。该文基于碰撞理论和能量平衡原理对单个、多个谷粒和脱粒元件的碰撞过程进行了理论分析。建立了圆形截面脱粒元件线速度和脱粒破碎率之间的数学模型。在自制的脱粒分离性能试验台上对水稻进行了脱粒性能试验,通过试验确定了数学模型中的待定系数,验证了数学模型的正确性。为脱粒装置的设计、优化提供了理论依据。     

自然吸气与增压中冷柴油机气缸套应变对比

采用应变片测试技术,对自然吸气和增压中冷柴油机湿式缸套在外特性工况下工作时的周向应变进行了动态测试,拟合出缸套工作时的周向变形曲线,对比分析了不同机型湿式气缸套工作变形的特点以及主要影响因素。研究结果表明,随转速的提高,自然吸气柴油机缸套主推力面应变随之增加,逐渐呈现一种振动特性;而转速提高对增压中冷柴油机缸套周向应变影响不明显,缸套主推力面应变最大值出现在各作用力对缸套壁面作功最多的额定扭矩工况。     

梯形防渗渠道塑膜铺衬机的试验

借助均匀设计理论和软件对防渗渠道塑膜铺衬机进行了试验研究。提出了渠道塑膜铺衬效果的评价方法,分析了机器前进速度、展膜刷后倾角、展膜刷高度对铺膜效果的影响规律,并对设计参数进行了优化,证明主动同步放膜、展膜刷随动展膜的铺膜机构适于渠道空间铺膜作业。     

涡流室柴油机燃烧过程模拟

利用FLUENT软件构建了描述S195型涡流室单缸柴油机燃烧过程的三维数学物理模型,并对气体在涡流室内的运动情况进行了数值模拟分析,获得了缸内气体的压力变化、温度变化以及碳烟排放的情况。实测结果表明,该模型能够比较准确地模拟涡流室柴油机的燃烧过程。     

柔性坐标测量机参数辨识方法

设计了一种六自由度关节式柔性坐标测量机,并对该测量机测量方程中的参数进行了辨识,提出了一种快速简易的单点锥窝标定方法。该方法基于单点锥窝提供的空间单点基准,利用非线性最小二乘中的高斯-牛顿法,求解测量机测量方程的参数值。实验结果表明,该方法能够有效提高测量机的整体精度,且操作简单、计算效率高。     

甘蔗收割机单圆盘根切器虚拟样机研究

为了研究收割机单圆盘根切器运动、几何参数对甘蔗切割质量、收获损失的影响,使用ObjectARX在AutoCAD平台上建立根切器虚拟样机,对其工作过程进行了研究。研究表明:切割过程中存在多刀切割和重复切割甘蔗现象,该现象通过高速摄影试验得到了验证。给出了甘蔗受到多刀切割和重复切割刀数的计算公式,出现多于两刀切割的现象主要是由于刀盘转速、收获机前进速度和刀片数之间的匹配问题,是可以避免的。刀片安装角度影响刀片切入甘蔗所经历的路程,并且相当于改变了实际切入甘蔗的刀片厚度。甘蔗和根切器的相对位置影响根茬与刀片之间的作用力。     

并联混合动力飞机牵引车控制系统设计与试验

分析了并联混合动力飞机牵引车的动力系统结构及工作模式,对目前主要的两种并联混合动力控制策略进行了分析比较,详细阐述了控制系统硬件及软件系统的设计方法,该控制系统在模拟工况测试试验中达到了预期的控制效果。     

互插式连栋温室风压分布模拟分析

以CFD理论为基础,建立了互插式连栋温室周围空气绕流的数学模型,设定了流体的边界条件,运用Fluent软件对互插式连栋温室的风压分布进行模拟分析。模拟结果表明,风力对温室作用主要是向上的升力;风压系数沿温室跨度方向分布的数值模拟结果与风洞试验结果基本吻合;上风向和下风向风压系数沿温室高度方向呈二次曲线分布,相关系数分别为0.975和0.990;最后将模拟得到的风压系数转换成相应的风载体型系数,为结构优化设计提供参考。     

电涡流缓速器对车辆制动稳定性的影响分析

修正车辆理想制动力分配曲线使之适用于装用电涡流缓速器的车辆,对装用电涡流缓速器的车辆制动稳定性进行了定性分析,并且提出了增加前后制动器制动力的分配系数来提高装用缓速器后的车辆制动稳定性的技术措施.对给定参数的车辆的定量分析表明,提出的技术措施能扩大车辆同步附着系数的范围,降低车辆后轮先抱死的可能性,提高车辆的制动稳定性.     

Effects of dietary vitamin E and fat supplementation in growing-finishing swine fed to a heavy slaughter weight of 150 kg: II. Tissue fatty acid profile,vitamin E concentrations,and antioxidant capacity of plasma and tissue

The study aimed to assess the effects of vitamin E (VE) supplementation and fat source on fatty acid (FA) composition, VE concentrations, and antioxidant capacity in plasma and tissues of pigs fed to a heavy slaughter weight (150 kg). A total of 64 pigs (32 barrows, 32 gilts; 28.41 ± 0.83 kg) were blocked by sex and weight, and randomly assigned to one of eight dietary treatments (n = 8 per treatment) in a 4 × 2 factorial arrangement. Fat sources included corn starch (CS), 5% tallow (TW), 5% distiller’s corn oil (DCO), and 5% coconut oil (CN); VE supplementation levels were 11 and 200 ppm. Five-phase diets were formulated to meet requirement estimates of NRC (2012) and fed to pigs for each period of 25 kg from 25 to 150 kg. Increasing VE supplementation level increased C16:1 (P < 0.05) content but decreased C20:0 (P < 0.05) content in backfat and belly fat, while in liver, it increased C17:0 (P < 0.05) but decreased C18:0 (P < 0.05). Compared to the pigs fed the CS diet, the pigs fed the CN diet had greater (P < 0.05) content of total saturated FA, the pigs fed the DCO diet had greater (P < 0.05) content of total polyunsaturated FA content and iodine value, and the pigs fed the TW diet had greater (P < 0.05) content of total monounsaturated FA in backfat, belly fat, and liver. Plasma VE concentrations increased linearly (P < 0.05) with increasing length of feeding but faster (P < 0.05) in the pigs fed the CN and TW diets compared with the CS and DCO diets within the 200 ppm VE level; the pigs fed the DCO diet had the highest plasma VE concentrations (P < 0.05) from Phase 2 to Phase 5 within the 11 ppm VE level. The VE concentrations in liver and loin muscle (P < 0.05) increased with increasing dietary VE level from 11 to 200 ppm, but it was not affected by dietary fat source. There was no effect of VE supplementation and fat source on antioxidant capacity in plasma and liver except that pigs fed the DCO diet had greater liver SOD activity (P < 0.05) than the pigs fed the CN diet. In conclusion, dietary VE supplementation did not affect FA profile in backfat, belly fat, and liver consistently, while dietary FA composition with different fat sources affected much of the FA profile in backfat, belly fat, and liver. The higher level of VE supplementation increased liver and muscle VE concentrations and dietary fat sources affected plasma VE concentrations differently (P < 0.05), wherein the TW and CN diets increased the VE absorption greater than the DCO diet.