Percussion Laser-Drilled Holes: Characteristics and Characterization Procedure

Percussion laser drilling, being a thermal process, produces holes having widely differing characteristics than that of the mechanically drilled holes. In the present study, on the percussion laser drilling of through holes in a nickel-based superalloy (SUPERNI 263A), 21 characteristics were identified, and the methods of their determination were proposed. The effect of peak power of laser pulses on the identified hole characteristics were studied.     

Cryobank of plant genetic resources in Russian Academy of Sciences

Cryopreservation is the most reliable method for long-term storage of plant genetic resources. A review of cell injury by ice crystals and dehydration during a freeze–thaw cycle is given. For successful regeneration of plants and cultures after cryopreservation of their cells, the development of reliable cryopreservation procedure is required including preliminary cultivation, treatment by cryoprotectors, freezing by different methods, thawing and recultivation. Up to now 27 cell lines successfully resumed their growth after storage in liquid nitrogen and preserved their specific features and biosynthetic potential. Besides, shoot tips of 40 cultivars of potato, rose, strawberry and raspberry regenerated plants both in vitro and in vivo after cryopreservation. The longest storage duration was 25 years. Now in liquid nitrogen we continuously store 24 cell strains of rare medicinal plants, shoot tips of seven cultivars of strawberry and raspberry and seeds of 250 endangered plant species collected over all Russian territory.     

Study on high performance ice slurry formed by cooling emulsion in ice storage (discussion on adaptability of emulsion to thermal storage material)

This study focuses on an emulsion as a new thermal storage material for ice storage. Two types of emulsions were formed using an oil–water mixture with a small amount of additive. A silicone, light and lump oils were used. The water contents of the emulsions were 70, 80 and 90%. The additive was an amino group modified silicone oil. No depression of freezing point was observed for the emulsions because of their hydrophobic properties. In order to determine the structure of the emulsions, their electrical resistances were measured. Moreover, components of the liquids separating from the emulsions were analyzed. The results indicated that one emulsion was a W/O type emulsion, while the other was an O/W type. Finally, adaptability of the two emulsions to ice storage was discussed, it was concluded that a high performance ice slurry could be formed by the W/O type emulsion.     

Modelling of food transportation systems – a review

In 2002, over a million refrigerated road vehicles, 400,000 refrigerated containers and many thousands of other forms of refrigerated transport systems are used to distribute chilled and frozen foods throughout the world. All these transportation systems are expected to maintain the temperature of the food within close limits to ensure its optimum safety and high quality shelf life.Increasingly, modelling is being used to aid the design and optimisation of food refrigeration systems. Much of this effort has concentrated on the modelling of refrigeration processes that change the temperature of the food such as chilling, freezing and thawing. The purpose of a refrigerated transport system is to maintain the temperature of the food and appears to have attracted less attention from modellers. This paper reviews the work that has been carried out specifically on the modelling of food temperature, microbial growth and other parameters in the transportation of food.     

Thermal performance indicators for refrigerated road vehicles

An experimental evaluation of insulation effectiveness, pull-down times and effectiveness of a mechanical refrigeration unit was performed on five refrigerated panel vans. Additionally, a mapping of temperature variability in the cargo space was carried out during a simulated journey encompassing several door openings. The temperature variability measured in the vans was neither correlated to the effectiveness of the insulation nor the time required to achieve complete cooling of the cargo space. These criteria are common thermal performance indicators used to evaluate refrigerated vehicles in international standards. The efficiency of insulation was correlated to the pull-down times, presenting the possibility of calculating the former as a function of the latter. The temperature variability was correlated with the time required for the unit to recover temperature control after a door opening and the difference between the maximum and minimum temperatures reached during a door opening cycle.     

Development and validation of “grey-box” models for refrigeration applications: A review of key concepts

“Grey-box” modelling combines the use of first-principle based “white-box” models and empirical “black-box” models, offering particular benefits when: (a) there is a lack of fundamental theory to describe the system or process modelled; (b) there is a scarcity of suitable experimental data for validation or (c) there is a need to decrease the complexity of the model. The grey-box approach has been used, for example, to create mathematical models to predict the shelf life of chilled products or the thermal behaviour of imperfectly mixed fluids, or to create models that combine artificial neural networks and dynamic differential equations for control-related applications. This paper discusses the main characteristics of white-box, black-box and their integration into grey-box models, the requirements and sourcing of accurate data for model development and important validation concepts and measures.     

Filtered vacuum arc deposition of transparent conducting Al-doped ZnO films

Transparent conducting ZnO:Al and ZnO films of 380-800 nm thickness were deposited on glass substrates by filtered vacuum arc deposition (FVAD), using a cylindrical Zn cathode doped with 5-6 at.% Al or a pure Zn cathode in oxygen background gas with pressure P = 0.4-0.93 Pa. The crystalline structure, composition and electrical and optical properties of the films were studied as functions of P. The films were stored under ambient air conditions and the variation of their resistance as function of storage time was monitored over a period of several months.The Al concentration in the film was found to be 0.006-0.008 at.%, i.e., a few orders of magnitude lower than that in the cathode material. However, this low Al content influenced the film resistivity, ρ, and its stability. The resistivity of as-deposited ZnO:Al films, ρ = (6-8) × 10^− 3 Ω cm, was independent of P and lower by a factor of 2 in comparison to that of the ZnO films deposited by the same FVAD system. The ρ of ZnO films 60 days after deposition increased by a factor of ∼ 7 with respect to as-deposited films. The ZnO:Al films deposited with P = 0.47-0.6 Pa were more stable, their ρ first slowly increased during the storage time (1.1-1.4 times with respect to as-deposited films), and then stabilized after 30-45 days.     

Characterization of low refractive index SiOCF:H films designed to enhance the efficiency of light emission

An anti-reflection (AR) coating was deposited on the surface of flat panel displays to increase the efficiency of the light emission. The use of low reflective index material can decrease the thickness of the optical coating layer. In this work, low refractive index SiOCF:H films were deposited on P-type (100) Si and glass substrates by the plasma enhanced chemical vapor deposition (PECVD) method using an SiH₄, CF₄ and N₂O gas mixture. The refractive index of the SiOCF:H film continuously decreased with increasing deposition temperature and rf power, exhibiting a minimum value of 1.3854. As the rf power was increased, the fluorine content of the film increased linearly to 5.41% at an rf power of 180 W. The rms surface roughness decreased to 1.0 nm with increasing rf power, with the optimum conditions being observed for the film deposited at an rf power of 140 W.     

UPS并机数字锁相误差分析

针对不间断电源(UPS)并联系统同步问题,进行锁相误差分析,并探讨了减少锁相误差的措施和方案。通过在两台30kVA样机上进行并联实验,验证了方案的正确性。     

学生成绩评定方法研究

分别用x2拟合检验法、直方图和Q-Q分布图从直观和理论两方面出发验证学生成绩是否呈正态分布,通过图象与应用概率统计知识有机结合,运用数学软件对数据进行处理,达到验证研究的目的。