• 대한조선학회논문집
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• 제32권1호
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• pp.103-117
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• 1995

본 논문에서는 이상화구조요소법을 적용하여 이중선체 유조선의 충돌손상 해석기법을 개발하고, 모형실험결과와의 비교를 통하여 개발한 해석기법의 정도를 검증한 뒤 4만톤급 컨테이너선의 선수가 이중선체 VLCC의 선측을 충돌할때의 손상거동을 각종설계인자(이중선측폭, 선측 부재치수등)를 변화시켜 가면서 시리즈해석을 수행하여 그 특성을 분석하였다. 본 해석법은 항복, 압괴(crushing), 파단(rupture), 국부 및 전체파손의 상관효과, 변형속도(strain-rate) 영향, gap/contact조건등을 고려하고 있으며, 소요계산시간이 유한요소법에 비해 극히 짧고 해석정도도 높으므로 실제선박의 충돌문제에 대한 구조설계 및 안전성 평가시에 유용하게 적용할 수 있는 "설계응용을 겨냥한 충돌해석방법"(design-oriented collision analysis procedure)이라 할 수 있다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.342-348
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• 2001

This study was conducted to obtain granular crystalline gypsum that can be used as raw material for plaster boards or cements from waste Plaster board. We could disintegrate preferentially gypsum to gypsum needle in 10${\mu}{\textrm}{m}$ or less size among the contents of waste plaster board (gypsum, paper, fiber, and inorganic material .etc.) by hydration afterwards the dehydration of crushed waste plaster board. In this case, the optimum conditions for minimizing the size of gypsum were dehydration rate of 75%~ 85%, hydration concentration of 10~20%, agitation speed of 250~400rpm, crushing size of 2cm or less. Gypsum of 98.21% grade was recovered with 99.0% yield from under screenings of 325mesh wet screening which followed by the dehydration-hydration process performed in the conditions of dehydration rate of 80%, hydration concentration of 15%, agitation speed of 300rpm, crushing size of 2cm or less. Subsequently, Plate-like Crystalline gypsum of is 151${\mu}{\textrm}{m}$ size and the grade of 99.49% with the Yield of 98.0% from the upper screenings of 270mesh wet screening carried out after the re-crystallization of the recovered gypsum needle slurry.

• 자원리싸이클링
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• 제10권6호
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• pp.43-52
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• 2001

This study was conducted to obtain granular crystalline gypsum that can be used as raw material for Plaster boards or cements from waste Plaster board. Gypsum could be Preferentially disintegrated to gypsum needle in $10\mu\textrm{m}$ or less size by hydration after the dehydration of crushed waste Plaster board. The finer the gypsum needle, it is easier to remove coarse impurities and to recover the gypsum needle. The optimum conditions for obtain the finer gypsum size were dehydration rate of 75~85%, solid concentration at hydration of 10~15%, agitation speed of 250~400 rpm, crushing size before dehydration of 2 cm or less. Gypsum of 98.21% grade was recovered with 99.0% yield as the undersize of 325 mesh wet screening followed by the dehydration-hydration process performed at the conditions of dehydration rate of 80%, solid concentration at hydration of 15%, agitation speed of 300 rpm, crushing size before dehydration of 2 cm or less. After the recrystallization of recovered gypsum, Plate-like gypsum of $151\mu\textrm{m}$ size with 99.49% grade was obtained as the oversize of 270 mesh in a wet screening.

• Structural Engineering and Mechanics
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• 제20권1호
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• pp.1-20
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• 2005

The present paper deals with the seismic response analysis and the evaluation of most likely failure modes for a water storage structure. For the stress analysis, a 3-D mathematical model has been adopted to represent the structure appropriately. The structure has been analyzed for both static and seismic loads. Seismic analysis has been carried out considering the hydrodynamic effects of the contained water. Based on the stress analyses results, the most likely failure modes viz. tensile cracking and compressive crushing of concrete for the various structural elements; caused by the seismic event have been investigated. Further an attempt has also been made to quantify the initial leakage rate and average emptying time for the structure during seismic event after evaluating the various crack parameters viz. crack-width and crack-spacing at the locations of interest. The results are presented with reference to peak ground acceleration (PGA) of the seismic event. It has been observed that, an increase in PGA would result in significant increase in stresses and crack width in the various structural members. Significant increase in initial leakage rate and decrease in average emptying time for the structure has also been observed with the increase in PGA.

• KSBB Journal
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• 제13권5호
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• pp.477-482
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• 1998

A biosensor with PZT piezoelectric ceramic crystal was developed for the detection of formaldehyde gas. Poled PZT piezoelectric ceramic disk was made from ZrO2, TiO2 and Nb2O5, together with the addition of PbO and polyvinyl alcohol, through various processes of mixing, calcination drying, crushing, forming, sintering, polishing, ion coating and poling. Oscillator circuit of sensor was made of operational amplifier(AD811AN). Formaldehyde dehydrogenase was immobilized onto a piezoelectic ceramic crystal, together with the cofactors, reduced glutathione and nicotinamide adenine dinucleotide. The effect of flow rate on the sensitivity was determined by varing the flow rate of carrier gas from 24.7mL/min to 111.7mL/min through detector cell. The results indicated that as the flow rate was increased, the recovery rate was increased. And a significant increase in the sensitivity was observed in enhanced flow rate of carrier gas. Frequency difference(ΔF) of immobilized PZT piezoelectic disk increased proportionally to the concentration gas and reproduced to repeated exposures of formaldehyde gas(28ppm, Δ68Hz).

• Korean Chemical Engineering Research
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• 제52권5호
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• pp.652-656
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• 2014

소형형광등(Compact fluorescent Lamp; CFL) 3종류를 파쇄할 때 발생하는 수은의 기상농도와 대기로 방출되는 수은 양을 평가하였다. CFL 파쇄 시 배출되는 수은 농도는 초기에 매우 급격하게 감소되었으나 24시간 이후에는 수은농도의 변화가 점차 작아졌으며, 이 후 42시간까지 일정 농도를 유지되었다. 이러한 일정한 농도를 안정화 농도(Stabilized concentration)로 나타내었고 안정화 농도는 기체상 수은이 거의 배출되어 파쇄장치에 잔류하는 액체상 수은이 온도와 기압에 의한 영향으로 기화되어 배출되는 것으로 판단되었다. 소형형광등에서 발생되는 수은농도는 회사별로 A사 < B사 < C사 순으로 나타났으며, 회사별로 수은의 안정화 농도와 안정화 시간은 A사 < B사 < C사 순으로 높았다. 공기유량이 증가함에 따라 수은 부분압은 감소하였으며, 이는 대기 중 수은의 양이 낮아짐을 의미하고 안정화 농도도 감소하는 것으로 나타났다. CFL 파쇄 시 초기의 수은 농도는 공기유량에 관계없이 $0.1mg/m^3$인 지정시설의 환경기준보다 매우 높으므로 소형형광등을 파쇄할 때 기상의 수은을 관리하는 것이 절대적으로 필요하다.

• Steel and Composite Structures
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• 제50권2호
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• pp.159-181
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• 2024

In the present study, the effect of geometrical parameters of two different types of aluminum thin-walled structures on energy absorption under three-bending impact loading has been investigated experimentally and numerically. To evaluate the effect of parameters on the specific energy absorption (SEA), initial peak crushing force (IPCF), and the maximum crushing distance (δ), a design of experiment technique (DOE) with response surface method (RSM) was applied. Four different thin-walled structures have been tested under the low-velocity impact, and then they have simulated by ABAQUS software. An acceptable consistency between the numerical and experimental results was obtained. In this study, statistical analysis has been performed on various parameters of three different types of tubes. In the first and the second statistical analysis, the dimensional parameters of the cross-section, the number of holes, and the dimensional parameter of holes were considered as the design variables. The diameter reduction rate and the number of sections with different diameters are related to the third statistical analysis. All design points of the statistical method have been simulated by the finite element package, ABAQUS/Explicit. The final result shows that the height and thickness of tubes were more effective than other geometrical parameters, and despite the fact that the deformations of the cylindrical tubes were around forty percent greater than the rectangular tubes, the top desirability was relevant to the cylindrical tubes with reduced cross-sections.

• Computers and Concrete
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• 제32권5호
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• pp.499-511
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• 2023

Anchor channels are commonly used for façade, tunnel, and structural connections. These connections encounter various types of loadings during their service life, including high rate or impact loading. For anchor channels that are placed close and parallel to an edge and loaded in shear perpendicular to and towards the edge, the failure is often governed by concrete edge breakout. This study investigates the transverse shear behavior of the anchor channels under quasi-static and high rate loadings using a numerical approach (3D finite element analysis) utilizing a rate-sensitive microplane model for concrete as constitutive law. Following the validation of the numerical model against a test performed under quasi-static loading, the rate-sensitive static, and rate-sensitive dynamic analyses are performed for various displacement loading rates varying from moderately high to impact. The increment in resistance due to the high loading rate is evaluated using the dynamic increase factor (DIF). Furthermore, it is shown that the failure mode of the anchor channel changes from global concrete edge failure to local concrete crushing due to the activation of structural inertia at high displacement loading rates. The research outcomes could be valuable for application in various types of connection systems where a high rate of loading is expected.

• Journal of Advanced Marine Engineering and Technology
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• 제28권5호
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• pp.773-781
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• 2004

This research was Performed to raise grade efficiency of Sturtevant type air classifier. to treat powder less than $74\mu\textrm{m}$ particle produced at the crushing process of the dry aggregates manufacturing system or concrete wastes recycling system. The experimental conditions were in the ranges. 0.85 to 5.15 $m^3$/s of primary air flow rate. 0.005 to 0.015 $m^3$/s of secondary air flow rate $30^{\circ}$ to $70^{\circ}$ of auxiliary blades angle. respectively. for 1.7~3.3 kg/min of the powder feed rate. It was found that the grade efficiency of the air classifier was increased as the baffle plate was attached at the expansion region. and the optimal operating conditions of the air flow rates and the blade angle were obtained. The fractional recovery curves from the experiments were well agreement with the theoretical one of Molerus model.

• 한국임상수의학회지
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• 제15권2호
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• pp.358-363
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• 1998

These studies were performed to investigate what genital diseases could be diagnosed by ultrasonography in the mares associated with infertility. Of 159 thoroughbred breeders(4 to 18 years old), 31 mares which had been considered as the mares with reproductive disorders were examined by ultrasonography during the breeding season. 1. Hematoma in ovarian disordersl endometritis and pyometra in uterine disorders could be diagnosed by ultrasonography. 2.The rate of infertility was 19.5% out of 159 breeders and the rate of uterine disordres was 71.0% among the whole reproductive disorders. 3.Of 31 mares considered as the mares with infertilityi 26 mares were diagnosed by ultrasonography denoting 83.9% of diagnosis rate. 4.The highest average age of mares among the mares with reproductive disorders was 11.7 years in the mares with uterine disorders. The average age of the mares diagnosed as concepted was 7.5 years, which was much lower than that of the mares with reproductive disorders.5.Crushing one of twin vesicles was confirmed by ultrasonography. In conclusions ultrasonography was feasible for diagnosis of the mares with reproductive problems.