Parametric Study of High-Intensity Ultrasound in the Atmospheric Freeze Drying of Peas

Atmospheric freeze drying (AFD) is a dehydration process that can be used to produce high-end products for the food, pharmaceutical, and biological industries. Evaporation or sublimation at the drying temperatures used for these processes is generally low. Airborne ultrasound can be used to increase drying rates. This parametric study investigates the influence of the drying temperature, drying time, and ultrasonic power for atmospheric freeze drying in the presence of an airborne ultrasonic field. Accelerated effective diffusion of up to 14.8% was obtained for atmospheric freeze drying with a fluid bed. The faster drying in ultrasonic-assisted atmospheric freeze drying is assumed to be due to a higher mass transfer rate at the solid-gas interface, caused by a reduced boundary layer due to a higher turbulent interface. Thus high intensity, airborne ultrasound used with modern drying systems has great potential to accelerate drying, reduce investment and production costs, and improve product quality.     

Effects of Drying Methods on Functionality of a Native Potato Protein Concentrate

Pulp and dilute fruit water (PFW) are by-products from the potato starch processing industry. Potato protein obtained from an expanded bed adsorption (EBA) process is a value-added protein concentrate that can offer special technical properties in food systems. The influence of drying techniques on the physiochemical, quality, and functional properties (color, water content, bulk density, rehydration properties, sorption isotherms, specific enzyme activity, solubility, protein denaturation) of dehydrated potato water effluent was investigated. The results indicate that atmospheric freeze drying (AFD) is a more gentle drying process than spray drying and vacuum freeze drying. Both enthalpy measurements and sorption isotherms indicate reduced protein denaturation of AFD samples, while specific enzyme activity is at the same level for all dried samples.     

CFD Model of Apple Atmospheric Freeze Drying at Low Temperature

An Internet-controlled atmospheric freeze dryer was designed, built, and tested in the Department of Heat and Mass Transfer, Technical University of ?ód?. A film sublimation-based CFD model was developed and verified using Fluent 6.1 commercial CFD software. The model enables the simulation of phase change and water vapor diffusion process within porous media. Transport of non-condensable species can be calculated with species transport inbuilt model of Fluent 6.1 and used to predict sublimation rate under given conditions. Results were compared with AFD experimental data of 10-mm Idared apple cubes. The viability of applying the film sublimation model to atmospheric freeze-drying process was demonstrated. Higher mass flux was found on the leading edge, relatively uniform mass flux within the porous zone illustrates that vapor diffusion dominates atmospheric freeze drying process at low temperature (below 0°C). CFD results for apple cubes show a predomination of diffusional resistance of porous tissue.     

Synergetic Effect of Grit-Blasting and Atmospheric Cold Plasma Pretreatments on the Surface Free Energy of a Fibreglass/Epoxy Vinyl Ester Composite

For the first time, the efficiency of different surface pretreatment approaches prior to adhesive bonding of a fibreglass-reinforced epoxy vinyl ester thermoset composite has been investigated. It was found that grit-blasting generally had a negligible effect on the surface free energy (SFE) calculated using the Owens, Wendt, Rabel, and Kaelble method, as well as the Lifshitz–van der Waals/acid-base (LWAB) approach. However, contrary to abrading, grit-blasting has shown its efficiency to flatten sharp surface irregularities and introduce surface roughness features suitable to adhesive bonding processes. With or without a previous grit-blasting step, argon gas atmospheric cold plasma treatment has shown a slight to moderate efficiency in increasing the SFE polar component of the composite. However, it was found that the addition of 0.07% oxygen to the argon plasma readily allows an important gain in the SFE polar component. Indeed, when processed at a speed of 30 m/min on a previously grit-blasted composite surface, the Ar/O₂ atmospheric cold plasma treatment increases the surface free energy to values >73 mJ/m², making the surface condition optimized for structural adhesive bonding. An oxidation mechanism of the composite surface exposed to atmospheric cold plasma was suggested on the basis of correlations established between the polar part of SFE obtained from the Owens et al. method, acid/base components calculated using the LWAB approach, and ATR infrared spectroscopy signatures obtained for a model polyolefin material.     

A Novel Atmospheric Freeze-Drying System Using a Vibro-Fluidized Bed with Adsorbent

Atmospheric freeze drying (AFD) in a vibro-fluidized bed dryer coupled with an adsorbent and multimode heat input is proposed for dehydration of food products at lower cost than the traditional freeze-drying process under vacuum. The aim of this project is to study the proposed AFD system using a vortex tube to produce low-temperature dry air, an alternative for producing dried food products of high quality. An experimental setup was designed and built to permit simultaneous application of convection, conduction, and radiation heat input to the drying material above its freezing point to ensure sublimation. A parametric evaluation over a broad range of possible parameter values was carried out using cubic-shaped potato and carrot as model heat-sensitive products. The influence of various system parameters on drying kinetics, quality, and functional properties of the dried products (color, rehydration properties, and morphology) were investigated. Comparison between physical quality and drying characteristics of the AFD system with AFD using fixed bed, fluidized bed dryer, and also with traditional vacuum freeze drying were carried out to investigate the viability of this new system. Results indicate that proposed system is an alternative to reduce the process time as well as to maintain the product quality at lower cost.     

影响沿海地区储罐腐蚀的因素分析

沿海地区是指介于大陆与海洋之间的过渡地区。由于紧邻海洋，空气潮湿，雨量丰富，并且海风中夹杂着大量的盐类颗粒，所以建于这一地区的储罐的腐蚀速度非常快，给生产的安全进行带来许多隐患。本文对沿海这一特殊腐蚀环境中影响金属腐蚀的因素作了简要拼提出相应的防护方法。     

差频延时法测距的大气折射误差

给出了用差频延时法测距的距离谢误差的计算公式，在电离层内，连续波ｃｏｓ２πｆ２ｔ与ｃｏｓ２πｆ２ｔ以相速传播，但它们的差频信号ｃｏｓ［２π（ｆ１－ｆ２）ｔ］等效用频率√ｆ１ｆ２以群速传播。     

The evolution of outdoor copper patina

A general reaction scheme has been deduced which describes the evolution of the copper patina, including altogether eight compounds, formed upon exposure to outdoor atmospheric environments. The scheme is based on data obtained from altogether 39 exposure sites, using a recently developed method for quantitative X-ray powder diffraction analysis of up to 8 year old patina still adhering to the copper substrate. In all cases, cuprite forms initially and continuously throughout the atmospheric exposure. Three main sequences have been identified on sheltered copper, representing different reaction routes in sulfur- or chlorine-dominated environments. In less sulfur-polluted environments, posnjakite forms on the cuprite as a precursor to brochantite. In more sulfur-polluted environments, strandbergite is a precursor to antlerite. Both reaction routes may operate simultaneously and the main route may change from the more sulfur-polluted to the less polluted route, as a result of decreased pollutant levels. In chlorine-dominated environments the initial cuprite formation is followed by nantokite and atacamite. By far the most dominating sequence on unsheltered copper includes cuprite, followed by posnjakite and brochantite formation.     

Soybean oil triacylglycerol analysis by reversed-phase high-performance liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry

Soybean oil triacylglycerols from genetically modified soybean lines were conclusively identified by reversed-phase high-performance liquid chromatography coupled with mass spectrometry with atmospheric pressure chemical ionization. Atmospheric pressure chemical ionization is a soft ionization technique which gives simple spectra for triacylglycerols. Spectral identification of the triacylglycerols was based on the molecular [M+1]⁺ ion and the 1(2)-, 2(3)- and 1(3)-diacylglycerol fragments. Triacylglycerols identified in high-stearic and high-palmitic soybean varieties were quantitated by reversed-phase high-performance liquid chromatography with flame-ionization detection. There was excellent agreement between the fatty acid composition calculated from the triacylglycerol composition and the fatty acid composition obtained by gas chromatography of the transmethylated oils. The oils of the modified soybean varieties, compared to typical soybean oil, contained increased content of triacylglycerols known to be more oxidatively stable, such as linoleoyloleoylstearoyl, linoleoylpalmitoylstearoyl, and linoleoyldipalmitoyl glycerols, and less triacylglycerols like trilinoleoylglycerol, known to decrease oxidative stability. This study showed that the atmospheric pressure chemical ionization technique is suitable for mass spectral identification of neutral molecules, such as triacylglycerols, which do not contain a chargeable functional group.     

受大气湍流影响的光学波前模拟

大气湍流对光学波前的影响可以用Ｚｅｒｎｉｋｅ模式分析，由于Ｚｅｒｎｉｋｅ模式并非统计独立，需要转而寻找一种称为Ｋａｒｈｕｎｅｎ－Ｌｏｅｖｅ（简称Ｋ－Ｌ）函数的系数，它们统计独立，而且可以展开为Ｚｅｒｎｉｋｅ多项式的形式。本文介绍的就是用Ｋ－Ｌ函数构造随机波前的原理和仿真构造尝试。