• 한국항공운항학회지
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• 제23권1호
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• pp.24-29
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• 2015

In order to increase endurance flight efficiency of long endurance electric powered UAV, main wing of UAV should have high aspect ratio and low structural weight. Since a spar which consists of thin and slender structure for weight reduction can cause catastrophic failure during the flight, it is important to develop verification method of structural integrity of the spar with the light weight design. In this paper, process of structural analysis using non-linear finite element method was introduced for the verification of structural integrity of the spar. The static strength test of the spar was conducted to identify structural characteristic under the static load. Then, the experimental result of the spar was compared to the analytical result from the non-linear finite element analysis. It was found that the developed process of structural analysis could predict well the non-linear structural behavior of the spar under ultimate load.

• Journal of Welding and Joining
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• 제17권5호
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• pp.98-106
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• 1999

In GMAW, the spatters are generated according to the variation of the arc. Of the arc is stable, Few spatters are generated. But if unstable, too many spatters are generated. So, this means the spatters are dependent on the arc state. The aim of this study is to accurately estimate the arc state. To do this, the generated spatters were captured under the some welding conditions, and the waveforms of the arc voltage and welding current were collected. From the collected signals, the waveform factors and their standard deviations were extracted. Using these factors as input parameters of multi-layer artificial neural network, the learning for the weight of the generated spatters is performed and the estimation results to the real spatter are assessed. Obtained results are as follow: the linear correlation coefficient between the estimated result and the real spatters was 0.9986. And although the average convergence error was set 0.002, the estimated error to the real spatter was within 0.1 gr/min at each welding condition. In the estimation for the weight generated spatters, the result with multi-layer neural network was far better than with multiple regression analysis. Especially, even though under the welding condition which the arc state is unstable (the spatter is generated much more), very excellent estimation performance was shown.

• 한국초지조사료학회지
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• 제7권3호
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• pp.146-152
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• 1987

Sorghum cv. Pioneer 93 1, sorghum-sudangrass hybrid cv. Sioux and maize plant cv. Blizzard were assayed for toxic concentrations of nitrate-nitrogen ($NO_3$-N) and their relationship to morphological characteristics and environmental temperature in a field and phytotron trial. In the phytotron, sorghum and maize plants ranging from emergence to heading stage, were grown under different day/night temperatures of 30125, 25/20,28/18 and 1818 degree C. Nitrate-nitrogen in sorghum and maize plants was accumulated mainly in stems. Therefore nitrate concentration in the young plants was increased as development of stalks advanced and was highest at the stage of 3-4 leaves, when the plants had a leaf weight ratio 0.78-0.80 g/g plant weight. However, nitrate concentrations of the plant decreased as morphological development progressed, especially from the stage of growing point differentiation. Correlation coefficients showed a positive correlation of nitrate concentration with leaf weight ratio, leaf area ratio and specific leaf area, while plant height, dry matter percentage and absolute growth rate showed a negative association with TEX>$NO_3$-N ($P{\le}0.1$%). Cyanogenic glycosides, total nitrogen and crude protein were close associated with nitrate accumulation, and positively significant ($P{\le}0.1$%). High temperature over 30/25^{\circ}C.$ for 3 weeks increased N-uptake and dry matter accumulation, but reduced nitrate concentration. Under cold temperature below 18/8^{\circ}C.$ concentration of nitrate-N was increased in spite of its limited nitrogen uptake and plant growth.

• 한국전산구조공학회논문집
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• 제17권2호
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• pp.171-181
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• 2004

본 연구에서는 기존의 철도차량구조에 경량소재를 적용하여 설계를 검토할 때, 각 소재의 성질이 차체구조의 경량화에 미치는 영향과 그 정도를 정량적으로 분석하여 개념설계단계에서 소재대체 설계 효과를 예측하는 방법을 개발한다. 전체 차체구조에 대해서는 굽힘변형, 압축변형, 비틀림 변형을 고려하여 소재를 변경할 때, 또 주요 골조 구조 부재에 대해서는 굽힘변형, 압축변형, 좌굴붕괴를 고려하여 소재와 단면형상을 변경할 때 경량화 특성을 분석할 수 있는 방법을 체계화였다. 차체구조 또는 골조부재의 변형 양상에 대한 강성 및 강도 조건을 경량화 지수와 연계하여 표현함으로써 각 재료와 부재의 형상이 가지는 기계적 특성과 장단점을 용이하게 분석할 수 있도록 하였다.

• Computers and Concrete
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• 제3권2_3호
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• pp.79-90
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• 2006

This paper describes the results of an investigation into high mass-low velocity impact behaviour of reinforced concrete beams. Tests have been conducted on fifteen 2.7 m or 1.5 m span beams under drop-weight loads. A high-speed video camera has been used at rates of up to 4,500 frames per second in order to record the crack formation, propagation, particle spallation and scabbing. In some tests the strain in the reinforcement has been recorded using "Durham" strain gauged bars, a technique developed by Scott and Marchand (2000) in which the strain gauges are embedded in the bars, so that the strains in the reinforcement can be recorded without affecting the bond between the concrete and the reinforcement. The impact force acting on the beams has been measured using a load cell placed within the impactor. A high-speed data logging system has been used to record the impact load, strains, accelerations, etc., so that time histories can be obtained. This research has led to the development of computational techniques based on combined continuum/discontinuum methods (finite/discrete element methods) to permit the simulation of impact loaded reinforced concrete beams. The implementation has been within the software package ELFEN (2004). Beams, similar to those tested, have been analysed using ELFEN a good agreement has been obtained for both the load-time histories and the crack patterns.

• 대한인간공학회지
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• 제18권1호
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• pp.71-90
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• 1999

This study was conducted to examine the comfortability of wearing pantyhose in summer. To satisfy this purpose. 4 types of pantyhose were chosen from the market: a Mono type(M), a Wooly type(W), and two Support types(Sl, S2), were chosen. After the performances of samples were measured, these were worn by 8 healthy adult women. Under the summer field environment, psychological comfort ability was examined through the 5 steps of SD method. Physiological comfort ability was examined by measuring the body reactions(clothing pressure, skin temperature, total body weight loss, rectal temperature, pulse rates, and blood pressure), under the artificial environment($28.5{\pm}0.5^{\circ}C$, $82{\pm}3%$). The results of this examination were as follows : The order of comfortability which people felt in the field was W>M>S1>S2. The number of items which showed the highest correlation with comfort ability decreased and the correlation was lowered on the whole as time went by. There was positive high correlation between the performances of samples and comfort ability in compressibility, air permeability, water vapor permeability, while a negative high correlation in thickness, weight, compressional resiliency, strain (course) and moisture regain. The mean skin temperature was in the comfort zone, and rectal temperature, pulse rates, blood pressure were mostly in the normal range. Also it was showed that the correlation between the performance of samples and body reactions, except total body weight loss, was low.

• Steel and Composite Structures
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• 제12권3호
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• pp.207-230
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• 2012

Nowadays CFRP (Carbon Fiber Reinforced Polymer) became widely used materials for the strengthening and retrofitting of structures. Many experimental and analytical studies are encountered at literature about strengthening beams by using this kind of materials against static loads and cyclic loads such as earthquake or wind loading for investigating their behavior. But authors did not found any study about strengthening of RC beams by using CFRP against low velocity impact and investigating their behavior. For these reasons an experimental study is conducted on totally ten strengthened RC beams. Impact loading is applied on to specimens by using an impact loading system that is designed by authors. Investigated parameters were concrete compression strength and drop height. Two different sets of specimens with different concrete compression strength tested under the impact loading that are applied by dropping constant weight hammer from five different heights. The acceleration arises from the impact loading is measured against time. The change of velocity, displacement and energy are calculated for all specimens. The failure modes of the specimens with normal and high concrete compression strength are observed under the loading of constant weight impact hammer that are dropped from different heights. Impact behaviors of beams are positively affected from the strengthening with CFRP. Measured accelerations, the number of drops up to failure and dissipated energy are increased. Finite element analysis that are made by using ABAQUS software is used for the simulation of experiments, and model gave compatible results with experiments.

• 공업화학
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• 제33권3호
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• pp.322-327
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• 2022

Fucoidans were degraded by hydrogen peroxide under the electron beam (2.5 MeV) with various radiation doses (5 kGy, 10 kGy, 15 kGy, and 20 kGy) at room temperature. The degradation property was analyzed with a gel permeation chromatography (GPC-MALLS) method. An average molecular weight of fucoidan decreased from 99,956 at the irradiation dose of 0 kGy to 6,725 at the irradiation dose of 20 kGy. The solution viscosity of fucoidans showed a similar pattern to the molecular weight change. The number of chain breaks per molecule (N) increased with increasing the irradiation dose and concentration of hydrogen peroxide. The radiation yield of scission value markedly increased with increasing the irradiation dose up to 15 kGy. Also a 10% hydrogen peroxide concentration was more efficient than that of 5%. The structures of degraded fucoidan samples were studied with Fourier transform infrared spectroscopy (FT-IR). The results showed that the degradation process did not significantly change the chemical structure or the content of sulfate group. The sulfur content of each sample was determined with an Elemental Analyzer. With increasing the concentration of hydrogen peroxide, the ratios of sulfur/carbon, hydrogen/carbon, and nitrogen/carbon slightly decreased. The antioxidant activities of fucoidans were investigated based on hydroxyl radical scavenging activities. The ability of fucoidan to inhibit the hydroxyl radical scavenging activity was depended on its molecular weight.

• Journal of Biosystems Engineering
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• 제33권2호
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• pp.106-114
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• 2008

This study was performed to analyze the distribution of air current speed, $CO_2$ concentration, and photosynthetic photon flux (PPF) in a closed transplants production system (CTPS) for producing quality transplants. And the effect of PPF on the growth of potato (Solanum tuberosum L. cv. Dejima) plug seedlings was analyzed. Uniformity of the air current speed in CTPS was improved by installing perforated floors in duct for air circulating and by adjusting of air flow rate of the fan connected to air conditioning unit used in this study, Measured $CO_2$ concentrations were measured $409{\pm}13$, $950{\pm}25$, and $1,550{\pm}35\;{\mu}mol{\cdot}mol^{-1}$ for setting values of 400, 950, and $1,550\;{\mu}mol{\cdot}mol^{-1}$, respectively. Uniformity of PPF by adding each one the single fluorescent lamp of 20 W at both ends of the single fluorescent lamps of 40 W was highly improved. While the average PPF measured under the twin fluorescent lamps of 55 W installed at regular intervals of 10 cm was decreased by increasing the vertical distance from the lighting sources, the ratio of average PPF measured at both ends to PPF measured in the center was 74-79%. Five levels ($100{\pm}9$, $150{\pm}14$, $200{\pm}17$, $250{\pm}24$ and $300{\pm}31{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$) of PPF were provided to investigate the effect of PPF on plant height, fresh weight and dry weight of potato plug seedlings produced in CTPS. Plant height was decreased by increasing PPF. Maximum fresh weight and dry weight were shown under PPF of $250{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. Thus PPF of $250\;{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ was enough to produce quality potato transplants under air temperature, photoperiod, and relative humidity of $20^{\circ}C$, 16/8 h, and 70%, respectively. It was concluded that quality indices such as plant height, fresh weight and dry weight could be improved by illuminating of adequate PPF from artificial lighting sources.

• 생물환경조절학회지
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• 제29권1호
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• pp.1-8
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• 2020

고구마 바이러스 무병묘의 기내급속증식을 위한 적정 생장 조절물질 및 sucrose 농도, 최소생장 기내보존(15℃)에 미치는 광의 영향과 생존율 및 기내생장 특성 등을 조사하였다. 고구마 무병묘의 마디배양은 0.2 mg·L^-1 BA 첨가배지에서 줄기신장, 줄기직경, 잎수, 뿌리수, 생체중 및 건물중 등이 가장 양호하였다. 배양부위 및 배지물리성에 따른 적정 sucrose 농도는 마디배양은 5% sucrose를 첨가한 고체배지에서, 정단배양은 3% sucrose를 첨가한 액체배지에서 줄기두께, 잎수, 뿌리수, 뿌리길이, 생체중 및 건물중 등의 생육에 가장 효과적이었다. 15℃ 저온항온기에서 고구마 무병묘의 최소생장 기내보존은 암상태에서는 3개월 내에 모두 고사하였으나, 적색:청색(7:3) 혼합 LED (150±5 μmol·m^-2·s^-1 PPFD)에서는 5개월까지 100% 생존하였다. 따라서 고구마 무병묘의 최소생장 기내보존에는 광이 필요하며, 샬레에 밀식(10 개체/샬레)할 경우, 좁은 공간에서 대량보존이 가능하였다.