Distributed control based on distributed electronic circuits: application to vibration control

This paper focuses on the design of distributed control related to distributed mechanical systems. The sensors and actuators are assumed to be numerous and periodically distributed. The problem addressed in this paper is: “Can we find a way to approximate an optimal control law with a distributed electronic circuit”. Solutions to this problem are proposed in the framework of vibration control using piezoelectric actuators and sensors.     

Analysis of the Modes of Vibration and Static Resistance of the Frame of a Stirred Tank

The present study focuses on the design and choice of materials （steels S355 and 45SCD6） of a chassis of stirred tank （with a variable filling rate） for use in the manufacturing of cosmetic products. This tank or trough will be submitted to important mechanical and thermal loads and pressure according to the various manufacturing processes. The authors propose a model of thermal and mechanical loads which takes into account the operating conditions of the tank. The analysis of the first 10 modes of vibration of the frame shows that the frequencies are much higher when the filling rate is high. They are higher for steel 45SCD6 than for the $355. The simulation results show that for a selected type of steel, the equivalent Von Mises stress increases along with increase in fill rates and thermal gradient. It appears that the influence of the thermal gradient is predominant. For both steels, the Von Mises equivalent stress is maximum in the beam 32 when the thermal gradient is at its lowest stage, and in the beam 40 for the greatest thermal gradient.     

Stability of high temperature chemical vapor deposited silicon based structures on metals for solar conversion

Highly crystallized silicon layers were grown on metal sheets at high temperature (950 degrees C) by thermal CVD from silane. An intermediate buffer layer was mandatory to prevent interdiffusion and silicide formation but also to compensate lattice parameters and thermal expansion coefficients mismatches between metal and silicon and ideally transfer some crystalline properties (grain size, texture) from the substrate to the silicon layer. After a thermodynamic study, aluminum nitride or titanium nitride diffusion barrier layers were selected and processed by CVD. The structure and the interfaces stabilities of these silicon/nitride/metal stacks were studied by field effect gun scanning and transmission electron microscopy, X-ray diffraction, Raman and energy dispersive X-ray spectroscopy. As a result, TiN deposited by CVD appears to be an efficient material as a buffer layer between steel and silicon.     

Postharvest technology for developing countries: challenges and opportunities in research, outreach and advocacy

This article discusses the needs and challenges of developing good, science-based, simple methods for postharvest handling that can be made available in developing countries. Some of the traditional challenges have been successfully met (i.e. identifying causes and sources of losses for key crops, identifying many potential postharvest technologies of practical use for reducing losses), but many challenges remain. These include the characterization of indigenous crops in terms of their unique postharvest physiology (e.g. respiration rate, susceptibility to water loss, chilling sensitivity, ethylene sensitivity), ascertaining the differences between handling recommendations made for well-known varieties and the needs of local varieties of crops, and determining cost effectiveness of scale-appropriate postharvest technologies in each locale and for each crop. Key issues include building capacity at the local level in postharvest science, university teaching and extension, and continued adaptive research efforts to match emerging postharvest technologies to local needs as these continue to change over time. Development of appropriate postharvest technology relies upon many disciplines that are relevant to the overall success of horticulture, i.e. plant biology, engineering, agricultural economics, food processing, nutrition, food safety, and environmental conservation. The expanding pool of new information derived from postharvest research and outreach efforts in these areas can lead in many directions which are likely to have an impact on relieving poverty in developing countries.     

The behaviour of some derivatives of 1,2,4-triazine toward organomagnesium halides

6-Phenyl-3,5-dioxo-2,3,4,5-tetrahydro-1,2,4-triazine 1 , 3-oxo-5,6-diphenyl-2,3-dihydro-1,2,4-triazine 3 , 3,5,6-triphenyl-1,2,4-triazine 4 , and 3-chloro-5,6-diphenyl-1,2,4-triazine 8 , react with phenylmagnesium bromide. The reactions involved are represented by scheme A. Compound 3 reacts with o- and/or p-methoxyphenylmagnesium bromide to give compounds believed to have structures like 10 and 11 respectively. Compound 1 reacts with methylmagnesium bromide and with benzylmagnesium chloride to give products believed to have structures like 12 a , b .     

Effect of cold work on anodic polarization of low carbon steel

Carbon steel nails prepared by deep drawing exhibit grains elongated in the direction of swaging. They are also characterized by high corrosion rates, as measured potentiodynamically in 0.1 M H₂SO₄. Normalization of grain dimensions and reduction in the corrosion rate are achieved through annealing. Treatment at 750? C for 2 h is effective in producing strain-free specimens with rounded grains. Extended heat treatment at this temperature causes the development of larger grains and the improvement in the corrosion behaviour of the alloy. “As-received” and strain-free specimens are subjected to controlled tensile or torsional cold work. In all cases deformation results in an increase in the susceptibility of the alloy to undergo attack. The rate of corrosion increases greatly when the deformed steel corrodes in Cl^? ion containing media. Both general and pitting corrosion are operative.     

Eco Insulation Materials： Reduction of Cooling Loads of a House Made of Breeze Block or Laterite in a Dry Tropical Climate

In this paper, we study the influence ofeco materials for roof insulation and fiber-reinforced mortar coatings on cooling loads of a home in dry tropical climate. The walls of the house are made of cinderblock or laterite and the insulating material of a roof panel is made with lime （24%）, cement （6%）, water （50%） of vegetable fibers hibiscus sabdariffa （16%）, tree widespread in Burkina Faso and sugar cane bagasse （4%）. This panel roof insulation and the fiber-reinforced mortar were characterized at the Laboratory of Physics and Chemistry of the environment by the hot plate method. The building is modeled in TRNSYS using climate data from the city of Ouagadougou. The results obtained show that in the warmer months of the year, that is to say in March and April, the relative differences between heat gains the configurations ＂breeze block-coating mortar and roof not insulated＂ and ＂laterite- fiber-reinforced mortar coating and insulated roof＇ vary between 15.6% and 16.8%. The configuration ＂laterite-fiber-reinforced mortar coating and insulated roof allows a reduction of annual heat gains of 15.5% compared to the configuration ＂breeze block-coating mortar and roof not insulated＂.     

Flavor quality of fruits and vegetables

Fruits and vegetables are important sources of vitamins, minerals, dietary fiber, and antioxidants. The relative contribution of each commodity to human health and wellness depends upon its nutritive value and per capita consumption; the latter is greatly influenced by consumer preferences and degree of satisfaction from eating the fruit or vegetable. Flavor quality of fruits and vegetables is influenced by genetic, preharvest, harvesting, and postharvest factors. The longer the time between harvest and eating, the greater the losses of characteristic flavor (taste and aroma) and the development of off‐flavors in most fruits and vegetables. Postharvest life based on flavor and nutritional quality is shorter than that based on appearance and textural quality. Thus, it is essential that good flavor quality be emphasized in the future by selecting the best‐tasting genotypes to produce, by using an integrated crop management system and harvesting at the maturity or ripeness stage that will optimize eating quality at the time of consumption, and by using the postharvest handling procedures that will maintain optimal flavor and nutritional quality of fruits and vegetables between harvest and consumption. Copyright © 2008 Society of Chemical Industry     

消除相间电容电流影响的故障分量综合阻抗计算方法

分析了区内、区外故障时,线路相间电容对故障分量综合阻抗的影响,并提出了消除相间电容电流影响的故障分量综合阻抗计算方法。在各相的故障分量差动电流中减去该相流向其他两相线路的电容电流,计算结果仅取决于线路对地电容。使用EMTP数据对该方法进行了仿真,结果表明,采用新方法后,计算结果更稳定,整定时仅需考虑线路对地电容,整定原则更加明确,定值裕度大。