板栗切口对微波干燥工艺的影响研究

板栗的切口有利于在干燥过程中进行开壳脱衣。本文分析了板栗的切口形式、切口的放置方向、切口数目和切口长度对干燥效果产生的影响,获得了板栗干燥的最佳工艺参数。试验为板栗切口机械的研制提供了依据,也为后续的机械脱壳去衣创造了条件。     

机械破壳机结构、工作原理及应用

脱壳率和碎仁率是带壳物料破壳的2个关键指标,机械破壳则是提高上述关键指标的重要途径之一。文章分析了常见的带壳物料机械破壳方式、机械破壳类型、机械破壳原理及发展现状,总结了机械破壳设备的优缺点,并对目前机械破壳应用过程中所存在的问题提出了建议。     

含碳量对车轮材料磨损影响的试验研究

为研究车轮剥离失效的影响因素，为车轮的选材提供依据，通过选择儿种不同含碳量的钢材，研究了含碳量对磨损及剥离的影响。研究结果表明：含碳量的改变，对材料的摩擦因数基本没有影响，但可以改变材料的磨损机制；材料的抗磨损能力随含碳量增加而迅速增大。     

基于TRIZ的新型长生果柔性去壳机设计

目的 针对市场上现有的长生果去壳设备在粒度相差较大时,壳和仁分离不完全、剥净率低等问题,对其进行创新性改进设计。方法 基于TRIZ理论,对市场上应用最广泛的长生果去壳机的工作原理进行分析,对其存在的问题进行分析,利用发明问题解决理论,通过宏观的矛盾矩阵法,得到相对应的创新设计原理。结果 根据选取的最优原理,解决了设计过程中出现的4个主要技术冲突。利用参数变化原理,将Ⅰ级去壳装置中起碾压作用的工作板改成连续变化的斜面,解决了脱壳效率低的问题;利用分割原理和动态特性原理,将驱动曲柄设计成长度可调的形式,使生产节拍可调,实现了柔性生产;利用有效运动的连续性原理,通过增加专门用于小果、秕果的碾压装置,提高了剥净率及设备的自动化程度;利用多用性原理,用Ⅲ级去壳装置的动力源代替果壳收集装置的动力源,使设备结构更加紧凑。结论 实验结果表明,新型长生果柔性去壳机可实现大白沙剥净率达到97.6%,四粒红剥净率达到98.2%,均高于现有去壳设备;大白沙破损率为1.97%,四粒红破损率为1.18%,均低于现有去壳设备。设计结果对类似去壳设备的设计研究奠定了一定的理论基础。     

橡胶果碾搓式脱壳试验机设计

试验机装置主要由驱动传动、碾搓单元、控制电机自动正反转的电器元件、机架等组成。采用往复式摩擦、挤压的原理使橡胶果在摩擦力和挤压力的双重作用下实现壳仁分离。试验结果表明:该机工作性能良好,操作简便,脱壳率可达到78.3%,可进行橡胶果脱壳效果试验和破壳机理的研究。该装置可为研制高效率低损伤的橡胶果脱壳机提供技术基础。     

Effects of thermal load on wheel–rail contacts: A review

This article presents a technical review on the effects of thermal loads evolved at the wheel–rail–brake contact interfaces. These dynamic contact interfaces develop heat transfer conditions of widely varied thermal level. Their modeling to identify the sources for a variety of defect formation, observable on wheel tread or rail surface, is very important. The railway system, in general, has to bear axle load, friction load, and thermal load arising from their contact conditions in addition to traction and dynamic loads. The defects arising from the interaction of thermal load and other loadings may be identified as hot spots, shelling, spalling, rolling contact fatigue (RCF), and corrugation. The mechanisms for the formation of such defects are pivoted over the existing thermal environment of dynamic interacting surfaces. This review summarizes the works of early investigations and recent advances in modeling the heat transfer conditions required to estimate the temperature distribution at the contact zone. The heat partitioning method for both drag and stop braking conditions, in the presence of rail chill effect, is emphasized. Thermal gradient, introduced by localized temperature rise in the contact zone, in the presence of variable friction coefficient, promotes the RCF process. These alter the residual stresses in the contact region to cause a structural shakedown, aggravate plastic flow and activates ratchetting phenomenon in rails. The evolution of thermomechanical surface and subsurface fatigue cracks are also discussed for the completeness of this article. The effect of all such defect formation, emerging from thermal loading condition, and their countermeasures for defect mitigation are presented in this review. This abridged technical documentation envisions attracting more research in the area to improve wheel–rail set design and performance standards to extend enhanced safety and comfort to rail transport operation. It is opined that the thermomechanical loading, their effects on promoting defect formation and propagation should be studied in combination instead of the current practice of treating them separately.     

Defects in rails

The performance of rails in service is greatly influenced by the presence of metallurgical defects. Hydrogen-induced shatter crack is the most prominent among these and has been discussed in detail. Principal causes of rail failure have been outlined and different types of defects leading to failure of rails during service have been documented. Wear of rails which accounts for reduced life has been considered. Influence of microstructure on wear rate has been described.     

雷达天线阵面及天线座炮振响应分析

为了保证天线阵面和天线座在炮击振动下的位移响应满足天线指向的精度要求,应力响应满足强度要求,加速度响应满足模块的设计要求,固有频率满足伺服系统带宽的要求,对雷达天线阵面和天线座的炮振响应进行仿真计算,得到仿真模型的固有模态和固有频率,以及模型的位移响应、应力响应和加速度响应,然后将仿真结果和各项要求进行对比分析,证明了天线阵面和天线座的结构设计合理,雷达在炮振条件下可以正常工作.     

Timing and rate of nitrogen application influence grain quality and yield in maize planted at high and low densities

BACKGROUND: Efficient use of nitrogen (N) is considered one of the most important inputs needed for increasing grain quality and crop productivity. Hypothesis was that grain quality and yield of maize (Zea mays L.) in north‐west Pakistan are enhanced by increasing the rate of N, and that response to applied N is greater with an increase in the number of N split applications at high plant density compared to low density. RESULTS: Field experiments were carried out on maize (cv. Azam) in summer 2002 and 2003 consisting of two planting densities and three N rates as main plots, and six split N applications as sub‐plots. Year 1 had higher shelling percentage and stover yield (SY). Harvest index (HI) decreased but SY increased with increase in plant density. Increase in N rate and number of split N applications increased grain weight and protein content, HI and SY. CONCLUSION: The highest N rate in four to five split applications increased maize grain quality and yield at both densities. Maize response to the interactive effect of year × plant density, year × N rate, and year × N timing suggests zonal specific effective N management practices for sustainable maize production in different agro‐ecological zones. Copyright © 2009 Society of Chemical Industry     

四点挤压式核桃破壳机的设计与试验

针对于现有核桃破壳机两点受力破壳原理易造成破壳率低,高路仁率低的现象,研制"四点挤压式"核桃破壳机,并进行了"四点受力破壳"和"两点受力破壳"的对比试验,以及四点挤压式破壳机的初步试验。试验结果表明:"四点挤压式"核桃破壳机的破壳效果明显优于两点受力破壳,且可适用于不同尺寸大小的核桃。破壳效果和挤行程有很大关系,但和核桃本身大小尺寸关系并不明显。核桃的含水率为10%的条件下,当挤压行程为6 mm时,核桃的破壳效果最好,破壳率为100%,高路仁率为96.8%。