Orbital assembly and maintenance study

The requirements, conceptual design, tradeoffs, procedures, and techniques for orbital assembly of the support structure of the microwave power transmission system and the radio astronomy telescope are described. Thermal and stress analyses, packaging, alignment, and subsystems requirements are included along with manned vs. automated and transportation tradeoffs. Technical and operational concepts for the manned and automated maintenance of satellites were investigated and further developed results are presented

Orbital assembly and maintenance study. Executive summary

A sound, practical approach for the assembly and maintenance of very large structures in space is presented. The methods and approaches for assembling two large structures are examined. The maintenance objectives include the investigation of methods to maintain five geosynchronous satellites. The two assembly examples are a 200-meter-diameter radio astronomy telescope and a 1,000-meter-diameter microwave power transmission system. The radio astronomy telescope operates at an 8,000-mile altitude and receives RF signals from space. The microwave power transmission system is part of a solar power satellite that will be used to transmit converted solar energy to microwave ground receivers. Illustrations are included

Effects of light and phytochrome in heterotrophic growth of Lemna minor L.

Axenic cultures of Lemna minor L. were grown on a medium containing sugars and amino acids. In continuous darkness the growth rate was one-tenth of the maximum in continuous light. In darkness early death revealed a thiamine deficiency; this deficiency was counteracted, without increasing the multiplication rate, by feeding the plants thiamine or its thiazole component. The rate of cell division, the rate of frond expansion, and the frond multiplication rate were increased by illumination; at low intensities this increase was in the nature of a photostimulus effect. The increase in growth rate was accompanied by a decrease in dry weight. The sugar uptake from the medium per frond per day was constant, independent of the light intensity and multiplication rate. At intensities of above 100 μW cm -2continuous red light, the multiplication rate increased in proportion to the rate of photosynthesis.Periodic brief illuminations yielded a stimulation of the frond multiplication rate of up to 4 times the dark value. Red illuminations of 2 minutes every 48 hours were sufficient to prevent thiamine deficiency; this effect of the red illuminations was reversible by far red. Stimulation of the multiplication rate was likewise reversible by far red; the effect of continuous low intensity red light was reduced by a simultaneous far red irradiation, while the effect of brief illuminations was reduced by far red following the red. From this it was concluded that phytochrome is a photoreceptor for these light effects. The results of experiments with different far red and red illumination schedules suggested that in plants with much phytochrome only a small part of it is active but that the Pfr level in this part decreases at a rate not very different from that of the bulk phytochrome as measured by the spectrophotometer.Part of the light effect was not reversible by far red. This part increased by increasing the length of the illumination periods, the light intensity, and the number of illuminations per day. In this increase blue light was much more effective than it was in the far red reversible part of the light effect. This indicates a photoreaction different from phytochrome photoconversion.Kinetin specially increased the far red non-reversible part of the photostimulation. Together with the intensity dependency of this part of the stimulation, this gave rise to the supposition that the non-reversible part of the light effect was limited by the supply of substrates in phytochrome controlled reactions during the light periods. Thus it would seem plausible to assume that the far red non-reversible part is built up during the red and the blue light periods, whereas the reversible part is developed during the intervening dark periods

Проект топочной камеры и численное исследование топочных процессов в котле с циркулирующим кипящим слоем

Выпускная квалификационная работа имеет 109 страницы, 21 рисунок, 8 таблиц, 26 источников, 3 приложения. Ключевые слова: циркулирующий кипящий слой, численное моделирование, топочная камера, теплообменник, зола, топочные процессы. Объектом исследования являются: топочная камера с циркулирующим кипящим слоем; программный модуль для численного моделирования топочных процессов. Цель работы – отработка методики аналитического и численного расчета топочной камеры котельного агрегата с циркулирующим кипящим слоем. В процессе исследования проводились: конструкторский расчет топочной камеры и численное исследование топочных процессов в топке котла с циркулирующим кипящим слоем.Final qualifying work has 109 stranitsy, 21 picture, 8 tables, 26 sources, 3 annexes. Keywords: circulating fluidized bed, numerical simulation, combustion chamber, heat exchanger, ash, combustion processes. The object of the study are: combustion chamber with circulating fluidized bed; software module for the numerical simulation of combustion processes. The purpose of work - development of techniques of analytical and numerical calculation of the combustion chamber of the boiler unit with a circulating fluidized bed. The study was conducted with the combustion chamber design calculations and numerical study of furnace processes in the furnace of the boiler with a circulating fluidized bed

Should I go back to the roots to obtain my food? Understanding key factors driving U.S. consumers’ preferences for food foraging over buying and growing food

Alternative forms of food procurement have increased in consumer popularity since the occurrence of food price inflation and the ongoing recession in the U.S. The present study explores predictors such as food engagement, food-related COVID-19 concerns, and the importance of sustainable foraging practices as determinants for U.S. consumers’ preferences for food foraging. Two scenarios are investigated, the preference for food foraging over growing food and food foraging over regular food buying. The study is based on an online consumer survey (n = 401) and used partial least square structural equation modeling (PLS-SEM) for the data analysis. Results indicate that food engagement is the strongest predictor for both foraging over buying and foraging over growing scenarios. However, food-related COVID-19 concern appears to only be relevant for the foraging over buying scenario and the importance of sustainable growing practices is only relevant for the foraging over growing scenario. These findings are important because they indicate the attitudinal triggers of food foraging and are therefore of relevance to foraging communities and managers in municipalities, food retail, and horticultural businesses who are associated with traditional and alternative forms of food procurement

Electrical conductivity and gas-sensing properties of Mg-doped and undoped single-crystalline In2O3 thin films: Bulk vs. surface

This study aims to provide a better fundamental understanding of the gas-sensing mechanism of In2O3-based conductometric gas sensors. In contrast to typically used polycrystalline films, we study single crystalline In2O3 thin films grown by molecular beam epitaxy (MBE) as a model system with reduced complexity. Electrical conductance of these films essentially consists of two parallel contributions: the bulk of the film and the surface electron accumulation layer (SEAL). Both these contributions are varied to understand their effect on the sensor response. Conductance changes induced by UV illumination in air, which forces desorption of oxygen adatoms on the surface, give a measure of the sensor response and show that the sensor effect is only due to the SEAL contribution to overall conductance. Therefore, a strong sensitivity increase can be expected by reducing or eliminating the bulk conductivity in single crystalline films or the intra-grain conductivity in polycrystalline films. Gas-response measurements in ozone atmosphere test this approach for the real application

Electrical conductivity and gas-sensing properties of Mg-doped and undoped single-crystalline In2O3 thin films: Bulk vs. surface

This study aims to provide a better fundamental understanding of the gas-sensing mechanism of In2O3-based conductometric gas sensors. In contrast to typically used polycrystalline films, we study single crystalline In2O3 thin films grown by molecular beam epitaxy (MBE) as a model system with reduced complexity. Electrical conductance of these films essentially consists of two parallel contributions: the bulk of the film and the surface electron accumulation layer (SEAL). Both these contributions are varied to understand their effect on the sensor response. Conductance changes induced by UV illumination in air, which forces desorption of oxygen adatoms on the surface, give a measure of the sensor response and show that the sensor effect is only due to the SEAL contribution to overall conductance. Therefore, a strong sensitivity increase can be expected by reducing or eliminating the bulk conductivity in single crystalline films or the intra-grain conductivity in polycrystalline films. Gas-response measurements in ozone atmosphere test this approach for the real application