半导体制冷式果蔬配送箱控制系统

保鲜配送环境中温度是保障果蔬品质的重要因素。以半导体制冷式果蔬配送箱为研究对象,设计基于AVR系列ATmega16微处理器为核心的控制系统。该控制系统基于ICCV7for AVR开发环境,通过C语言进行软件编程,采集果蔬配送箱的保鲜环境温度与半导体制冷器散热系统水温,使用双限值控制方法,控制半导体制冷器、风机、水泵等执行机构工作,实现对半导体制冷式果蔬配送箱保鲜环境的温度调控和散热系统高温保护。试验结果表明:该控制系统能实时获取果蔬配送箱内保鲜环境温度与半导体制冷器散热系统水温的动态变化,根据控制逻辑精确、有效地进行执行机构控制,系统工作可靠、稳定。     

制盐配电变压器经济运行分析

变压器经济运行是通过对变压器技术参数的分析计算,结合负载的特点及容量,选择合适的变压器以降低变压器损耗率和提高其运行效率。     

一种投影仪吊箱的温度场分析

温度场与流场的优化是投影仪吊箱设计中的重要问题,但优化研究既不能仅仅依靠简单的数理方程,也不能完全依赖于实验,因为实验过程中时仪器的存在会破坏流场和温度场的分布。本文采用模拟分析的方法对投影仪吊箱内温度场分布进行研究,在合理的假设条件下,建立投影仪吊箱温度场的数学模型,利用有限元分析软件Ansys计算了在投影仪工作时的吊箱的温度场,模拟了箱体内温度分布规律及变化趋势,从而可以根据结论进一步优化设计箱体散热系统,达到提高投影仪稳定性及延长使用寿命的目的。     

浅谈青海电能计量箱在居民中的具体应用

通过参加青海省输变电工程变电站、各用户及居民电能计量表箱的安装、使用和维护，进一步浅谈了青海各地区输变电工程变电站及各用户居民用计量表箱、公用变计量表箱的设计准则、技术要求、设计计算方法，为适用于新建、改建、扩建工程中的居民用计量表箱、公用变计量表箱设计、订货与验收提供一点经验和建议。     

白枇杷箱式气调保鲜技术研究

以宁海白枇杷为试材,开展气调箱保鲜试验研究。结果表明:气体变化依次为气调箱+100%封闭、气调箱+50%封闭,而对照下降最慢;气调箱+100%封闭腐烂率比对照降低73.8%;气调箱内温度平均保持5.5℃;贮藏21d,未发生木质化现象,超过28d,木质化率有所提高。     

防缩羊毛吸湿性测试的生产实践与研究

为了准确快速测量防缩羊毛的吸湿性,通过试验综合对比回潮测试烘箱法中箱内热称,箱外冷称和箱外热称3种称量方法,排除产生误差较大的箱外热称法,总结其余2种方法得出相同线密度的毛样在测试环境稳定状态下,计算箱内热称干质量与箱外冷称干质量的比值系数(含热空气上浮托力的毛样与不含上浮托力毛样的质量比值),从而通过操作简便的箱内热称法再乘比值系数得到回潮值。2组试验分别得出:实测箱内热称∶实测箱外冷称∶实测箱内热称乘以比值系数计算回潮值分别为1.12∶1∶0.98和1.06∶1∶0.98,说明实测箱内热称乘以比值系数相比实测箱内热称计算的回潮值,误差更小,精确性更高,乘以比值系数的回潮值更接近实测箱外冷称回潮值。     

浅谈220kV变电站变压器运行及继电保护措施

随着有关信息技术手段的不断发展,在电力系统当中也已经得到了大规模的应用。变电站作为对电力能源进行配置与应用的中转站点,应用以先进的技术手段将会对其功能与效率的提升起到至关重要的促进作用。文章将基于对220k V变电站变压器运行原理的分析基础上,进一步提出了变压器运行保护、状态保护以及抗干扰保护等有关继电保护措施。最终希望借助于文章的研究工作能够为有关的220k V变电站变压器运行,以及继电保护工作提供一些可供参考的内容。     

新型移动变电站用低压保护箱的研制

该移动变电站用低压保护箱为矿用隔爆兼本质安全型,额定电压分3.3kv、1.14kv/0.66kv两种,额定电流为1250A。主要介绍它的3.3kv、1.14kv/0.66kv两种电压等级的通用性、矿用隔爆型移动变电站与低压保护箱法兰接口对接的通用性、负载侧直接接线方式和采用快速电缆连接器接线方式的通用性,采用PLC保护对短路、漏电以及一些其他保护功能和本质安全型通讯的基本介绍。     

变压器本体与散热器上下布置的应用分析

文章根据变压器本体与散热器的三种布置方式的特点,通过对变压器油循环方式和散热器冷却方式的组合分析,结合有关制造和运行经验,论证变电站采用变压器本体与散热器上下分体式布置的可行性和优越性。     

长环蒸化箱的新型挂布杆

阐述了长环蒸化箱的成环原理。为提高生产速度，在箱内挂布杆上镶嵌了硅胶条和钢针，使挂布环长度达到4．5m。经实践，不但大大提高蒸化箱生产速度，而且对织物无不良影响。     

龙骨对体育馆用木质地板功能指标影响的初步研究

为了探求龙骨参数对体育馆用木质地板功能指标的影响情况,于2006年6月至12月在中体建科国际运动地面科学检测中心以龙骨的宽度、厚度和间距为因素进行了一次回归正交试验.通过对试验进行方差分析,得出回归方程.试验结果表明,间距是影响冲击吸收率和球反弹率最主要的因素;宽度和厚度之间普遍存在交互作用,并且该交互作用对冲击吸收率、标准垂直变形和球反弹率的影响都很显著.     

Biological variation in the colour development of Golden Delicious apples in the orchard

BACKGROUND: In managing apple orchards, crop load and rate of nitrogen (N) fertilisation are two factors with a significant influence on fruit quantity and quality, because they affect all physiological processes in the tree. Both factors are strongly related to external and internal fruit quality, especially to skin colour, sugar and acid contents and mineral composition, and consequently to the keeping quality of fruits. The aim of this study was to assess the effects of both factors (three crop load levels and two N fertilisation levels) on the colour development of Golden Delicious apples during the last month on the tree in two consecutive seasons. Data on skin colour (L*, a*, b* values) were analysed using nonlinear mixed effects modelling to extract information on the variation in biological shift factor for colour and to link this variation to the different strategies used concerning N fertilisation and crop load. RESULTS: The major source of information is contained in the a* value. The behaviour of the a* value could be described by a logistic or an exponential model depending on the season and the experimental set‐up. Nonlinear mixed effects analysis estimating the biological shift factor (maturity) for each individual fruit (random effect) while estimating the rate constant of the decolouration process in common (fixed effect) resulted in explained parts well over 95%. CONCLUSION: The variation in maturity stage between individual fruits is large. Season has the most profound effect on the estimated values, far more important than that of crop load or fertilisation level. The magnitude of variation in colour due to crop load and N fertilisation is not too large. Its effect on the maturity stage of fruits is more profound: the higher the crop load, the higher the variation. The effect of fertilisation seems to be opposite: the higher the fertilisation level, the lower the variation. Copyright © 2009 Society of Chemical Industry     

The influence of processing and refrigeration on the bacterial numbers on beef and sheep offals

An investigation was carried out in a commercial abattoir on the influence of processing and refrigeration on a variety of beef and sheep offals. The influences of the different processes and the operations, to the bacterial load before refrigeration of the product, were determined. In general all the operations in the plant had an effect on the final bacterial load. The effect of inadequate refrigeration was noteworthy in all cases and this factor alone made the most significant contribution to the products having a poor shelf-life.     

On the influence of crack closure on strength estimates of wood

Three well-known duration of load models (Gerhard, Barrett/Foschi, DVM) are considered in this note with respect to their ability to predict lifetime of wood subjected to harmonically varying loads. The result obtained is that they practically predict the same lifetime—which for low frequency loading can be considered approximately true. For higher frequencies, however, this result can be far too overestimated. The reason is that the models considered do not take into account the effect of the crack closure phenomenon (which are the main mechanisms of energy dissipation causing fatigue failure in metals). It is suggested that any of the simple models can be used in practice when low frequency load variations are considered. The DVM model, however, should be preferred because of its ability to predict residual strength, and because of its ‘build in’ flexibility with respect to wood quality and ambient climatic conditions. For high frequency load histories more refined models are required. The extended DVM model, recently developed by the author, is suggested as such a model—especially because it has the potentials of being further developed to consider arbitrary load variations (such as earthquakes). Finally, the widely spread concept of estimating long-term strength by multiplying short time strength with a codified factor (so-called k _MOD factor) is discussed. It is concluded that the k _MOD -method can be justified in practice with low frequency load variations. When high frequency load histories or unexpected peak loads are considered, the k _MOD -method may cause considerably overestimated lifetimes.     

Bending load capacity of carbon fiber reinforced concrete beams as a function of fiber performance index (FPI)

Over the past several decades, textile reinforced concrete (TRC) materials have been developed due to their superior mechanical properties, corrosion resistance, lightweight application, and high load-bearing capacity. In this study, the effect of three main factors on bending load capacity of carbon fiber reinforced concrete (CFRC) beams is investigated; the number of reinforcements (carbon-fiber rovings), penetration of the cement within the fibers, and the post-cracking factor. The second and third factors are defined as the fiber performance index (FPI) for evaluating bending load capacity of CFRC beams. The best FPI for a different number of reinforcements was estimated using empirical values of bending load capacity of CFRC beams. The results were indicative of the efficiency and accuracy of the proposed FPI for a wide range of roving numbers, namely 2–24 with 800 tex as the titer. The post-cracking factor was suggested as 2.67 for TRCs and CFRCs materials, which are reinforced by rovings. In order to improve the FPI, the roving was impregnated partially with epoxy, which increased the maximum load capacity and displacement of the beams up to 26.68 and 23.24%, respectively. In addition, the impacts of roving numbers, the first factor, on the failure mode, load-bearing capacity, ductility, and toughness of the CFRC beams were investigated.     

棉纺织厂空调节能分析

从空调系统设计、系统运行和空调设备的选型等方面，根据棉纺织厂空调能耗的特点，提出了在空调设计中应推广采用冷负荷系数法计算冷负荷，合理确定温湿度基数、新风负荷，并认真作好冷冻水管的保温；在设备选型中注意选用流体动力式喷水室、蒸发冷却技术和喷雾轴流风机等有关降低空调能耗的节能措施。     

Monte Carlo Simulation to establish the effect of pH, temperature and heating time on the final load of Bacillus stearothermophilus spores

Bacillus stearothermophilus heat treatment studies at different pH levels were carried out in order to predict the final microbiological load as affected by the temperature and pH treatment. For that, distribution functions were obtained for the initial number of microorganisms, the decimal reduction coefficient, the z _T and the z _pH parameters, and Monte Carlo Simulation was used as a tool to determine this microbial load after a heat treatment introducing in this way the variability and uncertainty. The mean value of the predictions made by Monte Carlo Simulation, when compared with independent data, rendered Accuracy Factors close to 1, values close to 1 indicated good predictions. Bias values were close to 1, but some values were below 1 and others above 1. The tornado graphs indicated that the main factor contributing to the final load after the heat treatment was the initial number of microorganisms followed by the temperature and pH.     

制备低反式酸氢化葵花油的研究

采用自制的负载型钯氧化铝催化剂,以反式脂肪酸含量为考察目标,通过单因素实验,研究了不同反应温度、反应压力、催化剂用量等条件对氢化油(氢化油碘值为75)中反式酸含量的影响。在单因素实验的基础上,采用响应面实验优化了氢化工艺参数,并进行了重复验证实验,得出低反式酸氢化葵花油反应的最佳工艺条件为:反应温度为52℃,反应压力为1.9MPa,催化剂用量为170mg/kg,此时的反式酸含量为10.59%。     

PTT/毛混纺织物的回弹性能

实测了PTT／毛混纺织物弹性产品在定伸长率为10％时及定负荷为10N时的弹性回复率及织物的应力松弛。分析了织物弹性回复率与伸长率之间的关系、经纬向紧度和组织等因素对弹性回复率的影响及织物应力松弛特征。     

织机四连杆打纬机构对主墙板的动应力分析

 织机的墙板具有尺寸大、结构复杂的特点。四连杆打纬机构的往复摆动特性使得墙板受到较大的冲击,是机器振动的主要来源。针对四连杆的两个固定孔承受的支撑力,建立了相应的运动学和动力学公式。通过对两固定孔相对位置的承载力计算和分析,结果显示两孔各自承受的作用力在不同的主轴转角具有不同的数值和作用方向,并且在两孔不同的安装角度下,墙板受到的冲击载荷也是变化的,当打纬角确定时,能够计算出不同安装角度下的最大总支撑力,选取最小值进行孔位设计就能取得墙板较好的振动和寿命要求。