不同食用植物油微量成分及其自由基清除能力的比较

本文对不同种植物油中的雏生素E和植物甾醇等可能的抗氧化成分做了定性定量分析。并结合自由基清徐试验和加速氧化试验。探讨了这些微量物质在油脂氧化过程中的作用。结果表明:不同的植物油中微量物质的种类和含量都存在一定的差异,而这种差异也导致了植物油抗氧化能力各异。比如月见革油和玉米油都有着较好的由由基清除能力。而油茶籽和松子油的则相对弱一些。多酚含量最高的橄榄油的氧化诱导时间长达14h。     

Drying of shiitake mushroom by combining freeze-drying and mid-infrared radiation

Mid-infrared drying (MIRD) was applied before or after freeze-drying (FD) of shiitake mushroom to shorten the drying time, to enhance the rehydration, and to better preserve the aroma compounds and color. The effect of application of MIRD before freeze drying (MIRD–FD) and after freeze drying (FD–MIRD) on drying time, color, rehydration ratio, apparent density, microstructure and aroma compounds was measured, explained and compared with the effect of FD on these parameters. The results showed that the combination of FD (for 4 h) followed by MIRD saves 48% time compared to FD while keeping the product quality at an acceptable level. The MIRD–FD combination was found to be inferior compared to the FD–MIRD as the former tended to produce products with a collapsed surface layer and poor rehydration capability. The combination of MIRD with FD had a significant effect on aroma retention and caused an increase of sulfur compounds such as dimethyl, trisulfide and 1,2,4-trithiolane.     

舰船摇摆环境飞机牵引车牵引特性仿真分析

为了研究舰船摇摆环境下飞机牵引车的牵引特性,通过对一辆舰载牵引车的实际测试,基于Virtual.Lab Motion软件平台建立了该牵引车的多体动力学模型.经过各种仿真试验,从牵引速度、牵引力及附着力3个主要方面分析了舰船摇摆运动对牵引车牵引特性的影响规律,初步掌握了舰船横摇、纵摇和垂荡及舰船摇摆中心、幅值和周期等因素...     

声发射技术在热障涂层失效机理研究中的应用

模拟高温下的实际工况并研究高温下热障涂层的失效机理对热障涂层的研究具有积极意义。在自主研制的热循环试验机中引进声发射技术,对涂层高温性能进行了研究和试验,初步对声发射信号特征与涂层寿命之间的关系进行了探索性研究,实现了对裂纹的实时、动态监测,而且能够得到与理论上疲劳裂纹扩展速率曲线相似的结果。通过大量数据分析,证明利用声发射技术研究热障涂层失效机理是可行的。     

盐雾腐蚀条件下Ti合金表面功能薄膜的摩擦磨损性能

目的研究Ti6Al4V合金、铬掺杂类金刚石(Cr-DLC)薄膜、钨掺杂类金刚石(W-DLC)薄膜和氮化钛(TiN)薄膜,在干摩擦和盐雾腐蚀气氛摩擦条件下的摩擦磨损性能。方法在商用Ti6Al4V合金表面通过非平衡磁控溅射制备Cr-DLC薄膜和W-DLC薄膜,通过多弧离子镀技术制备TiN薄膜。利用扫描电镜、显微硬度计、摩擦磨损试验机、白光干涉扫描轮廓仪,对薄膜的形貌、硬度、干摩擦和腐蚀摩擦性能、磨痕形貌进行测试分析。结果干摩擦条件下,Ti6Al4V合金表面沉积Cr-DLC、W-DLC和TiN三种薄膜的摩擦系数均比Ti6Al4V合金低;Ti6Al4V合金及其表面制备的三种薄膜在盐雾腐蚀气氛条件下的摩擦系数都比干摩擦条件下有所增加。与Ti6Al4V合金相比,Cr-DLC、W-DLC和TiN三种薄膜在干摩擦和盐雾腐蚀气氛摩擦条件下均减小了磨损体积。干摩擦条件下,W-DLC薄膜的磨损体积为0.0017 mm~3,耐磨性最好;盐雾腐蚀气氛摩擦条件下,TiN薄膜的磨损体积为0.0028 mm~3,表现出最佳的耐腐蚀磨损性能。通过磨痕形貌可以得出,盐雾腐蚀气氛摩擦条件下,Ti6Al4V合金表面制备的金属掺杂类金刚石薄膜的磨损受到磨粒磨损和腐蚀磨损双重机制的影响。结论三种表面功能薄膜在盐雾腐蚀气氛摩擦条件下都较好地保护了Ti合金,极大地减少了磨损损失。     

Performance evaluation of the double screw conveyor in radio frequency systems: Heating uniformity and quality of granular foods

Non-uniform heating is a major challenge for commercial applications of radio frequency (RF) technology in the food industry. To improve the RF heating uniformity of granular foods, a double screw conveyor was designed and used to investigate effects of conveying direction, screw rotation speed, filling ratio, and electrode gap on the heating rate and uniformity of jujubes. The results showed that there was no significant (p > 0.05) difference between forward and backward conveying directions both in heating rate and uniformity, while the RF heating uniformity gradually improved with the increased screw rotation speed. RF heating rate increased gradually with the increase of filling ratio or decrease of electrode gap. Except for the significantly higher λ value found in the filling ratio of 80%, no significant (p > 0.05) changes were observed between 20 and 60%. Furthermore, the λ values also increased with decreasing electrode gap. Quality evaluation indicated that there were no significant (p > 0.05) differences in the color values, texture properties, ascorbic acid, and moisture content between control and samples treated by RF heating under the double screw conveying. Overall, the results obtained from this study demonstrate that as a simultaneous mixing and moving equipment, the screw conveying can be considered as a promising approach in improving the RF heating uniformity of granular foods for industrial applications.     

橘子皮对水溶液中活性艳蓝的吸附研究

采用静态吸附方式研究了农业废弃物橘子皮对水溶液中活性艳蓝X-BR的吸附特性.探讨了吸附剂量、溶液pH、吸附时间、染料初始浓度等参数对吸附的影响,并讨论了吸附过程的动力学和热力学特征.结果表明,橘子皮吸附剂对活性艳兰X-BR的吸附平衡时间为90 min;酸性条件下有利于吸附实验的进行.当吸附剂用量为8 g/L时,水溶液中活性艳蓝X-BR的吸附量可达12.98 mg/g;用Langmuir和Frendlich两种等温吸附模型对废弃果皮吸附染料的数据进行了拟合分析,结果表明,橘子皮对活性艳蓝X-BR吸附更好的符合Frendlich等温式.     

干燥方法对白牛肝菌和鸡枞菌品质特性的影响

本研究以白牛肝菌和鸡枞菌为原料,采用微波-热风联合干燥、热风干燥和真空冷冻干燥三种方法对菌菇进行处理,研究干燥方法对菌菇色泽、复水率、质构特性及微观结构等品质特性的影响。结果表明:色泽方面,真空冷冻干燥和微波-热风联合干燥优于热风干燥;复水性方面,真空冷冻干燥法优于微波-热风联合干燥法和热风干燥法,又以鸡枞菌的复水性最佳;质构方面,不同方法干燥后,菌菇硬度、弹性和咀嚼性变化规律相同,各指标强度大小排序为热风干燥 > 微波热风联合干燥 > 真空冷冻干燥;微观结构方面,微波-热风联合干燥和真空冷冻干燥后的菌菇截面呈多孔状,热风干燥菌菇的多孔网状结构不明显。综合考虑,白牛肝菌和鸡枞菌的干燥方法首选真空冷冻干燥,其次为微波-热风联合干燥,不宜选择热风干燥。