Effect of Vacuum Impregnation-Dehydration on the Mechanical Properties of Apples

The effect of sucrose solution concentration and vacuum/atmospheric pressure periods on the mechanical properties of apples (Gala var.) was studied through a stress relaxation test. The empiric model proposed by Peleg was used to fit the curves and the parameters a (level of relaxation) and b (relaxation rate) were evaluated. The experimental results obtained in this study showed that vacuum impregnation conditions had a great influence on the final mechanical properties of the apples. The Peleg model fitted well the data from the stress relaxation curves and may be useful for assessing sample deformation resulting from the vacuum impregnation process.     

Study of the Effect of High-Pulsed Electric Field Treatment on Vacuum Freeze-Drying of Apples

High-pulsed electric field pretreatment on fruits and vegetables could enable the cell to break down and increase drying rate. It is hoped that it will help in solving practical problems in vacuum freeze-drying, such as large energy consumption, high production cost, and long drying time, etc. In order to study the influence of high-pulsed electric field pretreatment on vacuum freeze-drying of apples, the drying experiments for apples pretreated by a high-pulsed electric field were carried out. The effects of high-pulsed electric field pretreatment on drying rate, drying time, productivity per unit area, and specific energy consumption were studied separately. Based on the range analysis, the optimum parameters were obtained as follows: electric field strength 1000 V · cm^?1, pulse width 120 µs, and pulse number 30 pulses. These were, in order of importance, pulse width, electric field strength, and pulse number. The comparison results showed that specific energy consumption was reduced by 20.46%, drying time was shortened by 22.50%, productivity per unit area was increased by 28.50%, and drying rate was improved by 27.02% over the results of the untreated group. Therefore, the result of complete drying of apples could be achieved by HPEF pretreatment.     

机械抽真空系统在减压蒸馏装置中的应用

在过去与现代的减压蒸馏装置中,具备一、二、三级抽空器的蒸汽抽真空系统始终占据着主导地位。而近年,一种新型的抽真空系统——机械抽真空系统正在慢慢地改变传统的抽真空方式。相对于传统的蒸汽抽真空系统,它的出现和逐步应用将会引领一场减压蒸馏中划时代的变革,通过对这两种抽真空方法的比较,浅析两种方法在减压蒸馏装置中的应用情况。     

Effect of Ozone on Fruit Quality and Fungicide Residue Degradation in Apples during Cold Storage

ABSTRACT

The potential of the ozone-enriched atmosphere for the improvement of the shelf life of apples of Gloster variety (Malus domestica) in cold storage was investigated. The storage experiment was conducted for 84 days. During that period, ozone at the concentration of 1 ppm was dosed every 12 hours for 1 minute. However, the exposure to ozone at such a concentration was unsuccessful in terms of inhibition of fungal disease development. Furthermore, the captan level in apples was reduced; therefore, they were more susceptible to fungal disease. On the other hand, the tests of the physical properties showed that utilization of ozone slowed down the ripening of apples; therefore, extending their shelf life provided that they were not infected.     

减压渣油性质对丙烷脱沥青过程的影响

研究了几种用于生产润滑油基础油的石蜡基减压渣油的性质,及其在溶剂脱沥青试验中的操作条件,并与中间基减压渣油的溶剂脱沥青实验结果相比较,分析了减压渣油在溶剂脱沥青过程中出现异常现象的原因。总结了石蜡基减压渣油的进料性质。     

Vacuum Microwave Treatment of Potato Starch and the Resultant Modification of Properties

The study focuses on the vacuum microwave treatment of low‐moisture potato starch. Typical temperature and drying profiles are presented and explained with the help of other process parameters such as sample weight, pressure, incident and absorbed microwave power. Subsequently water absorption capacity of vacuum microwave treated and conduction heated samples was investigated at 55 °C. During vacuum microwave treatment, 50 g samples were treated with incident powers of 460, 500 and 750 W at 3800 Pa for durations between 30 and 300 s. Water absorption capacity increased exponentially with the net absorbed energy but could not be functionally correlated to end temperature and incident power. During conduction heating, starch samples were treated at temperature values of 120, 130, 140, 150 and 160 °C, till constant weight. The water absorption capacity was observed to increase with increase in treatment temperature.     

Vacuum impregnation treatment of microporous Al2O3-MgAl2O4 refractory raw materials with sub-micron pores and high strength

In the present work, we propose a novel method to decrease the pore size as well as to enhance the strength of microporous Al₂O₃-MgAl₂O₄ refractory raw materials, which were prepared by the vacuum impregnation treatment of porous Al₂O₃ powders with at MgCl₂ solution. The effect of the MgCl₂ content (0–32.5 wt%) on the phase distribution, microstructures, and physical properties of the refractory raw materials was thoroughly investigated. The results demonstrated that the sub-micron pore structure inside the pseudomorph particles was effectively preserved due to the volume expansion effect of spinel and the spinel sintering neck formation between Al₂O₃ microcrystallites. With the MgCl₂ content increasing from 0 to 11.9 wt%, the pseudomorph particles contained many sub-micron pores resulting from the introduction of the MgCl₂ solution, resulting in the decrease of the intra-particle pore size as well as the development of spinel sintering necks between pseudomorph particles. The strength of the aggregates was therefore enhanced. With a further increase of MgCl₂ content to 24.2 and 32.5 wt%, the inter-particle pore sizes increased due to the volume expansion and Kirkendall effect associated with the spinel formation between pseudomorph particles, which were responsible for the progressive decrease of the strength. Overall, the optimized samples were microporous Al₂O₃-MgAl₂O₄ refractory aggregates with the addition of 11.9 wt% MgCl₂, which exhibited an apparent porosity of 45.0%, a high compressive strength of 45.6 MPa, a median pore size of only 1.49 µm, and a high sub-micron pore volume content of 42.5 vol%. Meanwhile, it is possible to obtain the porous Al₂O₃-MgAl₂O₄ powders with a large number of sub-micron pores by crushing and sieving the optimized aggregates.     

Effect of Microwave-Assisted Vacuum Frying on the Quality of Potato Chips

We investigated the applicability of microwave-assisted vacuum frying in producing potato chips. Three microwave power levels (600, 800, 1000 W) were used for frying times of up to 360 s. The moisture loss and oil uptake histories were measured as a function of the microwave power levels. The textural crispness (breaking force) and color parameters (lightness, redness, and yellowness) were also measured as a function of microwave power levels and frying time. The application of microwave-assisted vacuum frying significantly increased the moisture evaporation and oil uptake rates in potato chips. At the same time, the amount of oil uptake was similar to that in vacuum-fried chips not assisted by microwave. The chips produced using microwave-assisted vacuum frying were crispier (lower breaking force), visually appealing, and could be produced in a shorter time.     

Effect of PCL concentration on PCL/CaSiO3 porous composite scaffolds for bone engineering

Porous polycaprolactone (PCL)-coated calcium silicate (CaSiO₃) composite scaffolds were successfully prepared by 3D gel-printing (3DGP) and vacuum impregnation technology in this study. The effect of different PCL concentration on porous CaSiO₃ scaffolds prepared by 3DGP technology was studied. The composition and morphological characteristics of PCL/CaSiO₃ scaffolds were tested by using fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS) analysis. PCL coating amount on the scaffolds surface was calculated by thermogravimetric analysis (TGA). Compressive strength was tested by a universal testing machine, and degradability was tested by immersing the scaffolds in a simulated body fluid (SBF). The results show that PCL coating thickness increased from 7.29 μm to 12.2 μm, and the compressive strength of the corresponding composite scaffolds increased from 17.15 MPa to 24.12 MPa following with PCL concentration increasing from 7.5% to 12.5%. When the porous composite scaffolds were immersed in SBF for 28 days, the degradation ratio was 1.06% (CaSiO₃), 1.63% (CaSiO₃-7.5PCL), 1.81% (CaSiO₃-10PCL) and 1.55% (CaSiO₃-12.5PCL), respectively. It is obviously that PCL/CaSiO₃ composite scaffolds, which are suitable for bone growth in bone repair engineering, are beneficial to improve the mechanical properties and biodegradability of pure CaSiO₃ scaffolds.     

高剪切应力下不同弹性体对ABS材料力学性能影响

采用材料在熔融挤出共混过程中提高双螺杆挤出机螺杆转速的方法,研究了较高螺杆转速条件下双螺杆挤出机的高剪切应力、不同弹性体(SEBS、POE、EVA、NBR)等对ABS材料力学性能的影响.结果表明:双螺杆挤出机的高剪切应力可促进弹性体颗粒的分散和界面结合力的增强,引起共混材料力学性能的改善;NBR、EVA等弹性体有利于ABS材料韧性的提高,POE、EVA等弹性体有利于ABS材料加工流动性的改善.在220℃的挤出温度下,当螺杆转速由240 r/min提高至1200 r/min时,其中ABS/NBR(质量比90/10)共混材料的缺口冲击强度由22.1 kJ/m2提高至28.8 kJ/m2,提高了30%,比纯ABS树脂提高一倍.     

EPS材料的力学性能试验研究

通过室内试验,在有无侧限、不同加载速率、不同控制方式和不同围压的条件下,研究了具有密闭空腔结构的成型聚苯乙烯泡沫塑料(EPS)的力学性能.结果表明:EPS材料的应力-应变曲线可分为线弹性、塑性和硬化三个阶段;应变相同时,有侧限时应力值比无侧限时略有提高,并且随着材料密度的增大,应力值不断增大,硬化点也不断提前;相同应变下的应力值会随着加载速率的增加而不断增加;另外,在同一压应力条件下,应变控制式所获曲线的应变较应力控制式时大;在同一应变条件下,材料的应力随着围压的增大而不断减小,当材料进人硬化阶段后,材料的应力却随着围压的增大而不断增大.     

Simultaneous Drying and Modification of Properties of Starch Using Vacuum Microwave Treatment

The prospect of modifying starch properties while drying was investigated. Potato starch (18% moisture, dry basis) was vacuum microwave treated for different durations (60 to 600 s) with power ratings of 600, 1,000, and 1,500 W at a reduced pressure of 5,000 Pa (absolute). The drying rate was observed to be partially constant but was accompanied by a curious rise in sample temperature. Under a polarized light microscope, reduction in granule size was noticed, which was confirmed from the bulk density measurements, and this shrinkage may be explained by the loss of constituent water. Water absorption capacity of the treated starch samples was further studied at 55°C. The results showed a sudden increase in the capacity, indicating a reduction in gelatinization temperature of starch. This may be attributed to the change in nature of starch from crystalline to amorphous as shown by X-ray diffractograms and to the cracks developed on the granule surface during treatment seen in the scanning electron microscope images. This modified starch can serve well in the paper and food industry.     

我国耐火材料真空油浸技术的现状与未来

对我国耐火材料行业的真空浸渍工艺及设备现状进行了分析,介绍了国产化真空油浸装备及工艺特点。指出今后应积极倡导推广应用高温、高压,符合环保要求的真空油浸工艺及装备。     

基于减压渣油组成及性质的连续分布模型的研究

进行了基于减压渣油组成及性质的连续分布模型研究。采用超临界流体萃取分馏技术,分别将三种减压渣油分离成若干窄馏分,并测定了各个窄馏分的性质和组成。在此基础上,建立了基于减压渣油组成及性质的连续分布模型,并利用连续分布模型对减压渣油的二次加工性能进行初步评价。再对此模型进行验证,尽管实测值与计算的KH值有一定的偏差,但是对该馏分的二次加工性能评价基本没有影响,说明该模型的应用成功。     

玻璃-陶瓷基支撑点对真空玻璃力学性能及热导的影响

近几年真空玻璃产业发展迅速,而支撑物作为真空腔体的支撑材料直接影响真空玻璃的透明度、受力、热导等性能.本文制备了一种弹性模量适中、热变形可调的玻璃-陶瓷基真空玻璃支撑点,研究了其制备工艺以及工艺对玻璃力学性能及热导的影响.结果 表明:制备的支撑物材料粉体粒径分布范围集中在0.5～10 μm之间,采用点胶工艺可制备高度在0.2～0.35 mm之间,直径在0.5～1.0 mm之间,尺寸可控的支撑点矩阵;支撑点在经过物理钢化后有晶体析出,为玻璃-陶瓷结构,提高了支撑点的强度;支撑点由“点接触”改为“面接触”可以有效避免支撑点的破碎和玻璃微裂纹的产生;适当调整支撑点的尺寸和间距可以在保证力学性能的基础上使玻璃同时具有低的热导.     

Effect of Ultrasound Pretreatment on Vacuum Drying of Chinese Catalpa Wood

Ultrasound pretreatment of wood prior to drying was examined as a method to increase the effective water diffusivity, reduce drying time, and improve product quality of Chinese Catalpa wood. Pretreatment tests were carried out at three pretreatment durations, three absolute pressure levels, and three ultrasonic intensities. All specimens were then dried at 60°C and the absolute pressure level of 0.02 MPa to determine the effects of pretreatment parameters on vacuum drying characteristics. A microscopic analysis was carried out to visualize the formation of microchannels and view any other changes to wood tissue structure that occurred. Results showed that ultrasound pretreatment prior to vacuum drying enhances the effective water diffusivity; the higher the ultrasound power level, the longer the pretreatment time, and the lower the absolute pressure, the shorter is the drying time. Ultrasound creates micro channels within the tissue of wood during pretreatment. However, the pretreatment time should not be too long when the ultrasound is high.     

真空高压气淬炉齿啮式快开结构应力有限元计算

利用ANSYS中接触单元法 ,采用面 面接触模型对齿啮式快开结构齿间的接触行为进行数值模拟 ,对有限元计算结果选出高应力区进行应力线性化处理 ,应力评定结果表明各应力值均在许用范围之内。采用电阻应变仪测量布点应力 ,实测值与计算值较吻合。     

真空连续干燥系统抽气量的计算

介绍了真空连续干燥装置真空系统—抽气量的计算方法,通过与实际实验装置操作情况的比较,验证了该计算方法的可行性。     

连续碳纤维增强PA66复合材料的结晶与力学性能

采用熔融浸渍法制备了连续碳纤维（CF）增强聚酰胺66（PA66）浸渍带,用万能材料试验机、X射线衍射仪、差示扫描量热仪、扫描电子显微镜、动态热力学分析以及热重分析仪等研究了纤维含量对复合材料结晶与力学性能的影响。结果表明,CF的加入改变了PA66的α晶型的晶态结构,促进PA66异相成核,导致结晶温度升高;CF的加入使得PA66的双重熔融现象变得愈加明显,其高温熔融温度先减后增,这是由于CF对PA66具有诱导、促进成核作用,过多的晶核生长不完善,出现晶粒细化现象,其熔融温度降低;进一步增加纤维含量,其对成核的促进作用达到了饱和,晶粒逐步生长趋于完善,其熔融温度升高;浸渍带随着纤维含量的增加,其拉伸强度、储能模量、损耗模量以及玻璃化转变温度都有所提高。     

粮食真空低温干燥新技术的优势

真空低温干燥技术是近年来被广泛应用的一项新技术。就近年来真空低温干燥技术在东北玉米干燥方面的应用研究及其进展作了综述。探讨了真空干燥技术在玉米方面的应用前景。