工程橡胶压缩实验和缓冲特性分析

目的研究天然橡胶、丁基橡胶和发泡橡胶等典型工程橡胶的压缩变形行为和缓冲特性。方法首先总结橡胶材料特性和工程案例,进行三类橡胶的准静态和动态压缩试验,获取材料的应力-应变关系和压缩特性。并以此为基础,给出橡胶缓冲特性表征方法,进而对比和定量分析不同橡胶的缓冲特性。结果压缩实验结果显示,不同橡胶材料的压缩变形行为基本一致。缓冲特性分析表明,在相同应变水平下,实心橡胶的缓冲吸能能力明显强于发泡橡胶,而在相同应力水平下,橡胶材料的缓冲吸能能力则与材料实际所处受力区域有关。因此,在工程中选取橡胶缓冲材料时,应当考虑其所处的应力环境。结论根据不同橡胶材料的缓冲规律给出其对应的冲击防护适用场景,以此形成判据,从而为橡胶防护结构材料的选择提供参考。     

Refrigeration waste heat utilization for drying applications: a review

ABSTRACT

Cold chain industry has a vast potential for waste heat recovery. It is a matter of importance for energy efficiency point of view, as global energy demand is increasing day by day. Ample amount of low-grade energy is either unutilized or underutilized. The heat rejected by a Heat pump or refrigeration system emerged as a promising solution for dehydration by utilizing low-grade waste heat despite higher investment. As compared to solar drying technology, heat pump drying evolved as a reliable method regarding better process control, energy efficiency, and quality of the product to be dried. Energy utilized through the refrigeration system’s waste/exhaust heat recovery in combination with or without renewable energy source enhances the overall efficiency of the system and also reduces the cost. This useful review investigated and compared the research findings of waste heat utilization through heat pump and from condenser of refrigeration system on laboratory, pilot as well as industrial scale for drying of various fruits, vegetables, and agro products. Various drying parameters like drying rate, moisture content, Specific Moisture Extraction Rate (SMER), Coefficient of Performance (COP), Exergy efficiency, and temperature as well as humidity conditions inside the drying chamber were also reviewed to promote the technological advancement of energy utilization by commercial cold storage waste heat recovery.     

A numerical model for drying of spherical object in an indirect type solar dryer and estimating the drying time at different moisture level and air temperature

A numerical model for simultaneous heat and mass transfer was developed for solar drying of spherical objects and the object considered is green peas. Solar collector outlet temperature is assumed as drying chamber temperature and justified through energy balance equations. Assumptions are imposed on heat and mass transfer governing equations without losing the physics of the problem. Discretization is performed by finite difference method with implicit scheme. To generalize, the governing equation and boundary conditions are non-dimensionalized. The set of finite difference equations was solved by Tridiagonal Matrix Algorithm and a computer code in MATLAB was developed to solve them. The drying curves showed two stages of drying, initial, and secondary drying stage. At all drying temperatures and drying time, the center moisture was maximum and it was minimum at the boundary. A percentage of 85.67 surface moisture content and 25.33% center moisture was eliminated in the first 1 hr at 348 K. The product should be dried up to 7.45, 4.74, and 3.74 hr at air drying temperatures of 318, 333, and 348 K respectively, to maintain 10% of the product’s initial moisture content. The result is compared with the experimental result from literature and they are found to be in good agreement.     

甲基汞对大鼠脑即刻早期基因c-jun mRNA表达影响

为了探讨甲基汞神经毒性早期预报指标和信息传递分子机制,本文应用RT-PCR方法研究了不同浓度甲基汞暴露不同时间后,大鼠脑中即刻早期基因c-jun mRNA表达变化(对照组为0.9%生理盐水、暴露组浓度分别为0.05、0.5、5 mg·kg^-1;取样时间分别为20、60、240、1440 min).结果表明大鼠脑c-jun mRNA表达优先于汞的蓄积,大鼠脑c-jun mRNA表达变化对于甲基汞神经毒性具有早期预报作用, 即刻早期基因c-jun参与了甲基汞对中枢神经系统损害的毒性过程.     

酸沉降对马尾松菌根共生蛋白及营养关系影响

研究模拟酸雨及不同Ｃａ／Ａｌ比对马尾松（Ｐｉｎｕｓｍ ａｓｓｏｎｉａｎａ Ｌａｍ ｂ．）菌根中真菌与植物共生及营养关系的影响,在分子水平上揭示污染对生物的作用和生物抗性机理．当ｐＨ２０ 的模拟酸雨与铝共同作用时,马尾松菌根中酸性磷酸酶、硝酸还原酶以及海藻糖酶和甘露醇脱氢酶活性明显下降,即ｐＨ２０ 的模拟酸雨及铝离子对马尾松幼苗根的磷、氮吸收以及两共生生物之间的营养物质交换过程产生了影响,且铝离子在ｐＨ值低的情况下毒性作用更强;而钙能有效地缓解铝的毒性⒚在本实验中当Ｃａ／Ａｌ比为１／１ 时,缓解能力最强;在接种外生菌根真菌彩色豆马勃（Ｐｉｓｏｌｉｔｈｕｓｔｉｎｃｔｏｒｉｕｓ）后,马尾松幼苗根部酶活性仍能保持一定水平,植物对模拟酸雨及铝毒的抗性增强．菌根形成初期,经等点聚焦电泳后分离出在植物及真菌纯培养中均不存在的共生蛋白,其等电点为４７０,经ｐＨ２０的模拟酸雨处理后该蛋白仍存在     

厌氧折流板反应器对有毒有机物冲击负荷的适应性

在厌氧折流板反应器中,以氯酚配水进行毒物冲击负荷试验,进水ＣＯＤ为１１００～１２００ｍ ｇ／Ｌ,ＨＲＴ为１ｄ 时,连续２ｄ 投加五氯酚钠１６．８３～１７．７２ｍ ｇ／Ｌ．结果表明,厌氧污泥依次经历活性抑制阶段及活性恢复阶段．毒物冲击对反应器前段影响较大,对后段危害甚小．产酸菌比产甲烷菌先恢复,污泥活性恢复期为１８～２６ｄ,污泥驯化越好,其活性恢复越快．出水挥发酸和碱度变化也可表征系统恢复的进程     

热处理对含氮活性碳纤维脱除SO2能力的影响

考察中高温热处理对含氮沥青活性碳纤维「ＰＡＣＦ（ＮＨ３）」脱除ＳＯ２的能力的影响结果表明,在９００－１１００℃尤其是在１０００℃下热处理可显著提高ＰＡＣＦ（ＮＨ３）脱除ＳＯ２的能力,当在３０℃下模拟烟气中ＳＯ２、Ｏ２和Ｈ２Ｏ的浓度分别为０．００２ｍｌ／ｍｌ,０．１ｍｌ／ｍｌ和０．１ｍｌ／ｍｌ,气休流动速率为１００ｍｌ／ｍｉｎ时,０．２５ｇ的３种不同比表面物ＰＡＣＦ（ＮＨ３）完全除去ＯＳ２的时间分别     

高效氯氰菊酯对鲤鱼的生化指标影响研究

研究了高效氯氰菊酯对鲤鱼的脑、鳃、肝和骨骼肌肉中代谢酶、RNA和蛋白质的影响.用0.356 μg/L高效氯氰菊酯处理鲤鱼21d后,其脑、腮、肝、骨骼肌肉中6-磷酸葡萄糖脱氢酶(G-6-PDH)和乳酸脱氢酶(LDH)的活性逐渐降低,酶活性降低了35.2%～48.4%,RNA质量比减少了21.55%～45.65%,蛋白质质量比减少了41.72%～49.07%;撤离高效氯氰菊酯后,鲤鱼脑、鳃、肝和骨骼肌肉中的G-6-PDH和LDH酶活性、RNA和蛋白质质量比恢复到对照水平.结果表明:高效氯氰菊酯亚致死浓度处理后的鲤鱼脑、鳃、肝和骨骼肌肉中代谢酶活性、RNA和蛋白质质量比都逐渐下降,高效氯氰菊酯对鲤鱼的生化指标影响显著.     

基因芯片筛选氯化汞对大鼠脑神经毒性差异表达基因

为了筛选汞神经毒性差异表达基因和探讨汞神经毒性分子机制,采用基因芯片技术,研究了大鼠皮下注射0.5mg/kg的HgCl₂ 1h后脑中基因表达的变化.结果表明,基因表达谱中差异表达基因共有742条,上调基因562条,下调基因180条.生物信息学分析表明,差异表达基因中有免疫应答及解毒作用相关基因、遗传信息传递与表达相关基因、细胞信号传导基因、神经传导基因、细胞增殖与分化基因、细胞调亡等多种基因.分析结果提示这些基因的差异表达可能与汞神经毒性有关.利用基因芯片技术筛选相关基因,为深入阐明汞神经毒性的作用机制提供了新思路.     

燃气轮机用YS10-021聚酰亚胺三防试验验证分析

目的 研究湿热、盐雾、霉菌环境对YS10-021聚酰亚胺材料性能的影响,为燃气轮机选材设计和定寿、延寿提供数据支撑。方法 设计开展YS10-021聚酰亚胺三防试验,定期测试试样老化后的物理性能,并对试验数据进行统计分析。结果 经3552h湿热试验后,高温拉伸强度和高温弯曲强度下降24%,仍然符合出厂指标要求;常温弯曲强度下降34%,简支梁冲击强度下降62%,超出指标要求;其他各项性能未见明显老化。经3 552 h盐雾试验后,弯曲强度下降30%,其余性能均在出厂指标要求范围以内。经84 d霉菌试验后,YS10-021聚酰亚胺各项性能均有轻微下降趋势,但老化不明显。结论 YS10-021聚酰亚胺在湿热、盐雾、霉菌环境中的耐受性良好。总体来看,湿热和盐雾环境对YS10-021聚酰亚胺力学性能的影响更大。