• Journal of Biosystems Engineering
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• 제23권4호
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• pp.365-372
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• 1998

This study was carried out to develop a nutrient-solution mixing-and-supplying system, which used a low-cost metering device instead of expensive metering pumps and a fuzzy logic controller. A low cost and precise overflow-type metering device was developed and evaluated by testing the flow discharge for the automatic nutrient-solution mixing-and-supplying system for snail-scale hydroponic sewers. The fuzzy logic controllers, which could predict and meet the desired values of EC and supply rate of nutrient solution were developed and verified by simulation and experiment. this fuzzy logic controller, whose algorithm consists of four crisp inputs, two crisp outputs and nine rules, was developed to predict the desired value of EC and supply rate of nutrient solution and two crisp inputs, one crisp output and nine rules used to control EC to the desired values. The nutrient-solution mixing-and-supplying system showed satisfactory EC control performance with the maximum overshooting of 0.035 mS/cm and the maximum settling time of 15 minutes in case of increasing 0.7 mS/cm. also, the accuracy of the overflow-type metering device in terms of the full-scale error was 2.29% when using solenoid valve only and 0.2% when using solenoid valve and flow control valve together.

• 한국물환경학회지
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• 제25권5호
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• pp.764-767
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• 2009

For a more effectively designed gravity thickener, thickening experiments were conducted for residuals produced by a ceramic membrane water treatment plant (WTP). Two kinds of residuals, one from backwashing (BW) and the other from chemically enhanced backwashing (CEB) procedure, were separately collected during a pilot plant experiment and their limiting solid flux ($SF_L$) measured. Batch thickening experiments showed that the BW and CEB residual had $SF_L$ of 10 and $25kg/m^2{\cdot}d$, respectively. Continuous operation of a pilot-scale gravity thickener proved that a mixed BW and CEB residual could be successfully thickened at the solid loading rate (SLR) of $12kg/m^2{\cdot}d$, allowing the concentration of the thickened residual to be about $15kg/m^2{\cdot}d$. From the experimental results and consideration of the seasonal thickening characteristics of the residual, SLR of $15kg/m^2{\cdot}d$ was proposed as a design parameter for full-scale gravity thickeners.

• Environmental Engineering Research
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• 제11권4호
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• pp.173-180
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• 2006

Autotrophic nitrogen removal and its microbial community from a laboratory scale upflow anaerobic sludge bed reactor were characterized with dynamic behavior of nitrogen removal and sequencing result of molecular technique (DNA extraction, PCR and amplification of 16S rDNA), respectively. In the experiment treating inorganic wastewater, the anaerobic granular sludge from a full-scale UASB reactor treating industrial wastewater was inoculated as seed biomass. The operating results revealed that an addition of hydroxylamine would result in lithoautotrophic ammonium oxidation to nitrite/nitrate, and also hydrazine would play an important role for the success of sustainable nitrogen removal process. Total N and ammonium removal of 48% and 92% was observed, corresponding to nitrogen conversion of 0.023 g N/L-d. The reddish brown-colored granular sludge with a diameter of $1{\sim}2\;mm$ was observed at the lower part of sludge bed. The microbial characterization suggests that an anoxic ammonium oxidizer and an anoxic denitrifying autotrophic nitrifier contribute mainly to the nitrogen removal in the reactor. The results revealed the feasibility on development of high performance lithoautotrophic nitrogen removal process with its microbial granulation.

• Geosystem Engineering
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• 제21권5호
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• pp.282-290
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• 2018

The onset of extreme fire behaviour in a mine drift with longitudinal ventilation was analysed. A fire in a mine drift with continuous fuel load, involving several separate fires may lead to flames tilted horizontally and filling up the entire cross section. This will lead to earlier ignition, higher fire growth rate, higher fire spread rate and a severe fire behaviour. The focus has been on what changes take place at the onset and signs of the impending phenomenon. It was found that the fire gas temperature at the ceiling level provided a poor indicator. At the downstream far-field region of the fire, the sudden temperature increase at the lowest levels of the cross section and the sudden increase in flow velocities would provide signs of extreme fire behaviour. The corresponding full-scale heat release rates of the experiments at the onset of extreme fire behaviour were found to be very high for mining applications but not necessarily for tunnel fires. The heat release rate threshold for a mine drift with smaller cross-sectional dimensions would decrease considerably, increasing the likelihood of occurrence. The distance between the fuel items will play an important role during the initiation of horizontal flames.

• 생물환경조절학회지
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• 제26권4호
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• pp.402-410
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• 2017

본 연구에서는 실대형 실험과 구조해석을 통하여 현장에서 사용되는 기둥-서까래-도리, 기둥-도리-방풍벽 접합부를 적용한 강관 골조 플라스틱 연동온실의 정적 구조성능을 분석하였다. 실대형 재하실험 결과는 접합부를 강접합으로 가정한 구조해석 결과와 비교하여 구조물의 횡방향 강성과 각 부재의 하중분담률에서 많은 차이를 보였다. 동고 높이에서 측정한 수평변위는 실험과 구조해석의 차이가 40%이었고 수직변위는 89%의 차이를 보였다. S3 부재의 발생응력을 기준으로 한 각 부재별 하중분담률을 비교한 결과 실험과 구조해석에서 두 배 이상의 차이를 보이는 부재가 있었으며, 하부측벽이음(S2), 기둥 상부(S7) 등 주요 부재의 실험결과가 구조해석의 하중분담률을 재현하지 않았다. 현장에서 사용하는 접합부가 충분한 강성을 확보하지 않음으로써 구조물에 작용하는 외력을 각 부재에 적절하게 전달하지 못했으며 이로 인해 구조물의 강성이 저하되는 현상이 나타났다. 설계 단계에서 일반적으로 구조해석에 의해 결정되는 구조성능의 신뢰도는 접합부의 특성을 보다 면밀하게 고려했는지 여부에 따라 좌우 될 수 있다. 따라서 온실 구조 성능에 대한 신뢰성을 높이기 위해서는 온실에 사용되는 다양한 접합부를 고려할 수 있는 구조해석 기술의 개발이 필요하며 설계 기준에서 상세 설계 방법을 보다 명확히 규정해야 할 것으로 판단된다.

• 한국시뮬레이션학회논문지
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• 제28권2호
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• pp.1-14
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• 2019

고에너지 구성 요소 시스템의 설계를 위하여 고폭화약의 폭발 반응을 엄밀하게 모사할 수 있는 실제 규모의 하이드로다이나믹 해석을 수행하였다. 폭발성능 정밀 해석 SW는 고에너지 물질의 충격 민감도를 정량화하기 위한 반응 유동 모델을 검증하고 일련의 화약 트레인을 통과하는 충격파 전달을 예측하기 위해 개발되었다. 파이로테크닉 장치는 여폭약(HNS+HMX), 격벽(STS), 수폭약(RDX), 파이로테크닉 추진제(BPN)로 구성된다. 추진제 연소로 인하여 생성된 고압의 연소 가스는 충격파와 저밀도파 간 간섭에 의해 유도된 고유의 진동 유동 특성을 파악하기 위하여 10 cc 밀폐형 챔버에 유입된다. 특정 주파수(${\omega}_c=8.3kHz$)에서의 피크 특성을 검증하기 위하여 실험 및 계산으로 측정된 압력 진동을 비교하였다. 본 연구에서는 고폭화약의 폭발반응과 추진제의 폭연반응, 비-반응 금속의 변형에 관하여 단계별 수치해석 기법들을 충격 물리 해석 SW로 구현함으로써 고에너지 물질 시스템에 대한 대규모 하이드로다이나믹 시뮬레이션을 용이하게 하였다. 개발된 고폭화약 폭발성능 정밀 해석 SW를 고에너지 구성 요소 시스템의 파이로테크닉 연소 반응 M&S에 적용하여 실험 결과와 비교함으로써 검증하였다.

• Steel and Composite Structures
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• 제49권5호
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• pp.517-532
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• 2023

Tower structures have been widely used in communication and transmission engineering. The failure of joints is the leading cause of structure failure, which make it play a crucial role in tower structure engineering. In this study, the aluminum alloy three tube tower structure is taken as the prototype, and the middle joint of the tower was selected as the research object. Three different stainless steel-aluminum alloy composite joints (SACJs), denoted by TA, TB and TC, were designed. Finite element (FE) modeling analysis was used to compare and determine the TC joint as the best solution. Detail requirements of fasteners in the TC stainless steel-aluminum alloy composite joint (TC-SACJ) were designed and verified. In order to systematically and comprehensively study the mechanical properties of TC-SACJ under multi-directional loading conditions, the full-scale experiments and FE simulation models were all performed for mechanical response analysis. The failure modes, load-carrying capacities, and axial load versus displacement/stain testing curves of all full-scale specimens under tension/compression loading conditions were obtained. The results show that the maximum vertical displacement of aluminum alloy tube is 26.9mm, and the maximum lateral displacement of TC-SACJs is 1.0 mm. In general, the TC-SACJs are in an elastic state under the design load, which meet the design requirements and has a good safety reserve. This work can provide references for the design and engineering application of aluminum alloy tower structures.

• 한국재난정보학회 논문집
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• 제20권2호
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• pp.329-338
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• 2024

연구목적: 본 연구는 긴장방식을 복합적으로 적용한 세그멘탈 PSC U형 거더에 대한 해석적 거동을 기반으로 실대형 실험체의 휨 거동 결과를 평가하여 거동의 안전성을 검증하고자 한다. 연구방법: 도로교설계기준 한계상태설계법의 사용한계 및 극한한계상태 설계 결과를 바탕으로 40m 실대형 실험체의 가력하중을 산정하고 이에 대한 4점재하방식 정적 하중재하 실험을 수행하였다. 연구결과: 설계하중, 균열하중 및 극한하중이 작용할 때 해석적 처짐값 대비 97.1%, 98.5% 그리고 79.0%에 해당하는 실험체 처짐이 발생하였다. 설계하중, 균열하중 및 극한하중이 작용할 때 균열계는 각 연결부에서 0.009~0.035mm, 0.014~0.050mm, 6.383~5.522mm로 계측되었다. 결론: 균열하중 재하시까지 실험체는 탄성적으로 거동하였고 균열발생 후 극한하중까지 변형율-경화현상을 보이며 작용하중에 대하여 휨 저항 거동이 뚜렷이 나타났음을 확인하였다. 실대형 실험체 연결부(Dry Joint) 균열은 시설물 상태평가 B등급 기준 25% 미만의 결과로써 연결부의 탄성적 거동을 확인하였고 극한하중 제거 후 최종적 잔류 변형은 0.114mm로써 세그먼트 연결부의 안정적 거동을 확인하였다.

• 한국환경농학회지
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• 제19권5호
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• pp.433-441
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• 2000

A feasibility study was performed to examine the agronomic application of treated sewage on paddy rice culture by field experiment for two consecutive years. The domestic sewage was treated by the constructed wetland system which was in subsurface flow type and consisted of sand and macrophyte. The effluent of the wetland system was used for irrigation water. The effluent was diluted to maintain the total nitrogen concentration below $26mg{\cdot}L^{-1}$ in the first year and used without dilution in the second year experiment. Growth components and yields were compared against the CONTROL plot where conventional method was applied. And also, soil characteristics of the plots before and after reclaimed sewage irrigation were analyzed. Generally, addition of the treated sewage to the irrigation water showed no adverse effects on paddy rice culture, and even enhancement was noticed in both growth and yield. Irrigation of treated sewage after concentration adjusted with conventional fertilization showed the better result, and the yield exceeded that of CONTROL case where clean water was irrigated. Soil characteristics changed after irrigation, and significant EC increasing was observed for the reclaimed sewage irrigation plots. From this study, it appears that reuse of treated sewage, as supplemental irrigation water could be a feasible and practical alternative. For full-scale application, further study is recommended on the specific guideline of major water quality components in treated sewage for irrigation and public health.

• 한국화재소방학회논문지
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• 제11권2호
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• pp.25-33
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• 1997

화재 위험성올 조사하기위해 우리나라의 주거형태에서 가장 보편적인 공동주태을 사용하여 실물 화 재실험을 하였다. 화재 실험에서는 우리나라의 실제 생활에 사용되는 가구와 가연성물질풍을 사용하여 우리나라의 현실에 적합한 화재 위험성을 명가해 보았다. 이 실험에서 얻은 결과를 C-FAST라는 해석 모텔올 사용하여 얻은 예측치와 비교하였다. C-F AST의 제한성때문에 거실에서 발생한 화재에 대해서 만 결과를 비교해보았다. 실물 화재실험에서는 flash-over가 약 380초 경에 Zone-Model에서는 약 420 초 경에 발생하는 것으로 예측되었다. 그 외의 모든 실험 결과와 예측 결과에 의해 피난시간을 도출하 면 화재 실험과 Zone-Model 모두에서 250초 이내에 피난해야 한다는 결론을 얻었다.