集合包装水果的差压预冷研究进展

目的综述国内外关于集合包装水果差压预冷的研究,并分析了存在的问题。方法从差压预冷技术在果品保鲜领域的应用背景出发,分析预冷的基本原理、特点及意义,归纳了目前差压预冷果品在理论和实验两方面的研究内容及成果。结果水果差压预冷的研究主要集中在包装箱内水果预冷的数值模型、送风工艺参数及通气包装结构设计等方面,包装箱上的开孔对调节预冷气流,促进热质交换具有重要的作用。结论果品预冷数学模型的系统性、可靠性及新型实验验证技术的精准性有待进一步研究,送风工况、预冷包装系统的结构及适用性须兼顾经济、强度因素进行优化。     

果蔬差压通风预冷冷却均匀性研究

对于差压通风预冷除了冷却速度,包装箱内果蔬冷却的均匀性直接影响到其保鲜品质.提出基于方差分析的评价冷却均匀性的指标——均匀度.建立了果蔬差压通风预冷试验台,对黄金梨在不同送风速度、包装箱开孔形状、开孔面积、及箱内排列方式等工况下的差压预冷过程进行了试验测试.分析了相关参数对包装箱内黄金梨冷却均匀性的影响.结果表明,箱内黄金梨直排摆放工况下的流场比较均匀,冷风送风速度在1.5～2m/s时,圆形开孔包装箱且开孔直径45mm左右,黄金梨的冷却均匀性较好,均匀度σ在0.15左右.     

差压预冷外部遮挡开孔方式数值研究及实验验证

为解决目前果蔬差压预冷的存在的降温不均匀性,设计了五种不同的外部遮挡开孔方式,包括32个均匀孔、32个非均匀孔、28个孔、40个孔及50个孔,建立了物理和数值模型,利用计算流体动力学(CFD)软件对土豆分别进行了五种开孔方式的数值模拟研究.对比分析了五种开孔方式的预冷模拟结果,预冷降温速率最快和均匀性最好的是32个非均匀孔的,并对此进行了实验验证,二者基本吻合.为差压通风预冷的外部遮挡或包装的开孔设计提出了建议:靠近压差风机处的开孔率要低以阻挡靠近差压风机侧气流,远离差压风机处开孔率要高,最底部的孔径应稍大于上部的.     

甘蓝通风预冷实验研究

本文分析了甘蓝预冷的必要性,探讨了适合于甘蓝的预冷方法。对强制通风预冷、差压通风预冷的冷却过程进行了实验测试,并对二者的冷却效果进行了比较,重点分析了差压通风预冷包装箱开孔大小以及通风量的选择,为甘蓝差压通风预冷技术的普及应用奠定了基础。     

不同压力下具有内热源的包装箱内传热特性

目的研究具有内热源的某产品包装箱在不同压力下的传热特性。方法搭建具有内热源的某产品包装箱传热特性实验系统,对不同压力下内部具有热源的某产品包装箱内的温度场进行测量,讨论产品各部件的传热特性,并基于计算结果,拟合各部件的传热关联式。结果常压状态下各测点温度较低压状态更易达到平衡,箱体内温度场的分布符合被加热物四周热边界层厚度分布规律。包装箱内对流传热能力随着压强的增大而增强,且箱内压强处于较小范围时,压强的增加对于箱内各部的冷却效果更加显著。结论正常工作的温度范围内,该产品包装箱内传热能力的强弱主要受对流传热影响,对流传热能力随着压强的增大而增强;得到了各部件壁面传热关联式,误差在5%以内。     

葡萄差压通风预冷实验研究

本文根据差压通风预冷的原理建立了实验台,对一定位置圆形开孔的葡萄差压预冷包装箱在五种不同开孔面积、5种不同压差工况下的葡萄冷却速度分别进行了测试,并绘制了2.5h内的葡萄温降曲线.结果表明,合理地选择压差以及包装箱开孔大小对葡萄的冷却速度、冷却均匀性起着关键的作用.     

基于有限元法的果蔬保鲜包装箱通风孔设计

通过建立不同通风孔设计的果蔬保鲜包装箱有限元模型,模拟分析了其应力分布云图,探讨了果蔬保鲜包装箱通风孔设计的主要参数。分析结果表明,长圆形、靠近纸箱中部且对称分布的偶数个通风孔设计,能有效减少应力集中,避免纸箱压缩强度的大幅下降。为实际应用中果蔬保鲜包装箱通风孔结构设计提供参考。     

结球白菜干耗的真空预冷实验研究

以天津产高桩型结球白菜作为实验的对象,研究结球白菜处理量与预冷时间之间的关系,总结出结球白菜处理量与干耗损失之间的经验公式。用保鲜膜把结球白菜密封,置于两侧开孔的包装箱内,与未加包装的结球白菜进行不同位置的温度和干耗的对比分析,得出包装对结球白菜真空预冷效果的影响。根据捕水理论计算,拟合出结球白菜干耗计算的理论公式,并由实验验证了合理性。     

苹果差压预冷包装箱的传热数值计算与实验研究

针对苹果差压预冷问题，建立了预冷过程包装箱的传热模型，分别采用数值计算和实验的方法进行了研究。实验表明，本文建立的传热模型是可靠的。这种数值计算方法为实际工程苹果差压预冷系统的优化设计提供了理论依据。     

葡萄差压预冷保鲜技术的实验研究

通过对不同开孔直径、不同压差工况下和多列码垛葡萄包装箱的冷却速度进行实验测试,得到葡萄冷却速度随时间的变化曲线,获得了适宜的葡萄差压预冷保鲜时间、差压和包装箱开孔直径.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Study on Bond Ability of Arc-Spraying Coatings with Different Surface Pretreatment on Cast-Iron

Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.