• Earthquakes and Structures
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• 제20권4호
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• pp.405-415
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• 2021

Following the dynamic property analysis and elaboration, linear response spectrum analysis (RSA) and response history analysis (RHA) were conducted on a representative hyperbolic cooling towers (HCT) in present study. The seismic responses in tower shell were illustrated in detail, including the internal force amplitude, modal contribution, influence from damping ratio, comparison of results got from RSA and RHA and especially the latitude distributions of internal forces. The results show that the eigenmodes could be classified in a new method into four types according to their mode shapes and only the lateral bending modes and vertical stretching modes are meaningful for horizontal and vertical earthquake correspondingly. The bending modes and seismic deformation display the same feature which is global lateral bending accompanied by minute circular flow displacement of section. This feature also decides the latitude distributions of internal forces as sine or cosine. Moreover, the following method is also proposed for approximate estimation of internal force amplitudes without time-consuming response history analysis: getting the response spectrums of the selected ground accelerations and then comparing values of response spectrums at the natural period of first lateral bending mode because it is always prime dominant for horizontal seismic responses.

• 한국소음진동공학회논문집
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• 제26권4호
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• pp.398-405
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• 2016

A shape of loop-pipe in a compressor affects the vibration of compressor. In this paper, optimal design of shape of loop-pipe to decrease the stress was carried out. Body and shell were assumed to be rigid, while loop-pipe is considered to be flexible. The finite element model was derived and programmed. Genetic algorithm was used for optimization. Locations of 18 point in loop-pipe were considered as shape variables, while the shapes of loop-pipe were interpolated as polynomials or ellipses. Maximum stress of loop-pipe was used as a fitness function for optimization. The spatial constraints and acceleration response of shell were also considered in optimization. The maximum stress and acceleration could be reduced by 79 % and 49 % respectively.

• 한국토양비료학회지
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• 제47권6호
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• pp.398-405
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• 2014

Salt accumulation at soil surface is one of the most detrimental factors for crop production in reclaimed tidal land. This study was conducted to investigate the effect of capillary barriers beneath the soil surface on dynamics of soil salts at coarse-textured reclaimed tidal land. A field experiment was conducted at Saemangeum reclaimed tidal land for two years (2012-2013). Capillary barriers ($3.5{\times}12m$) were treated with crushed-stone, oyster shell waste, coal briquette ash, coal bottom ash, rice hull and woodchip at 40-60 cm depth from soil surface. Silage corn (Zea mays) was cultivated during the experimental period and soil salinity was monitored periodically. Soil salinity was significantly reduced with capillary barrier compared to that of control. Oyster shell waste was one of the most effective capillary barrier materials to control soil salinity at Saemangeum reclaimed tidal land. At the first growing season capillary barrier did not influence on corn growth regardless of types of the material, but plant biomass and withering rate of corn were significantly improved with capillary barrier at the second growing season. The results of this study showed that capillary barrier was effective on the control of soil salinity and improvement of corn growth, which indicated that capillary barrier treatment can be considered one of the best management practices for stable crop production at Saemangeum reclaimed tidal land.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.405-408
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• 2002

A high speed feeding type laser cutting UC is developed for the precise cutting of sheet metal. The M/C is a flying optics type one with specified functions of movability and strength in order to increase workability. The gantry frame should be moved with a certain velocity within a relatively short time for the proper cutting of object materials. The gantry is actuated by rack and pinion. In this paper, modal and structural analysis for a laser culling M/C, is carried out in development of the machine The machine is modeled by placing proper shell and solid finite elements and fictitious mass properties to represent the real one.

• Structural Engineering and Mechanics
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• 제31권4호
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• pp.393-405
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• 2009

The Purpose of this paper is to show the applicability of a methodology, developed by the authors, with which to perform the mechanical optimization of space truss structures strongly restricted. This methodology use a parameter call "Volumetric Displacement", as the Objective Function of the optimization process. This parameter considers altogether the structure weight and deformation whose effects are opposed. The Finite Element Method is employed to calculate the stress/strain state and the natural frequency of the structure through a structural linear static and natural frequency analysis. In order to show the potentially of this simple methodology, its application on a large diameter telescope structure (10 m) considering the strongly restriction that became of its use, is presented. This methodology, applied in previous works on continuous structures, such as shell roof and fluid storage vessels, is applied in this case to a space truss structure, with the purpose of generalize its applicability to different structural topology. This technique could be useful in the morphology design of deployable and retractable roof structures, whose use has extensively spread in the last years.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1998년도 제10회 학술강연회논문집
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• pp.31-31
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• 1998

위성체의 보조추진시스템은 임구궤도까지의 궤도진입 및 임무궤도상에서의 속도 또는 자세제어에 필요한 임펄스를 제공한다. 단일하이드라진 추력기는 하이드라진(H$_2$H$_4$)과 자발적 촉매(Shell 405)의 발열 및 흡열 열분해 반응에 의해 발생하는 질소($N_2$), 수소(H$_2$), 암모니아(NH$_3$), 혼합가스를 노즐을 통해 방출하므로써 요구되는 impulse를 얻는다. 단일하이드라진 추력기 설계는 주입기, 촉매대, 노즐과 기타 설계 형태에 따른 다지관, 링, 스크린, 지지판 등의 부수적인 부품으로 구성된다. 추력기 제작 과정은 크게 piece-parts 기계가공, HEA(Head End Assembly)와 TCA(Thrust Chamber Assembly)로 구성되고 각 세부공정마다 전수시험 및 검사를 가진다. 연소시험설비는 최소 모사진 공 수준이 고도 100,000 ft(8.4 torr)를 만족시킬 수 있는 진공설비, 시험제어부, 성능변수 측정 및 처리부, 추진제 가압 공급부, 기타 환경 안전 및 부대 설비로 구성된다. 추력기 연소성능시험 절차는 추진제 충전 및 오염 여부 표본 검사, 가압 및 공급 라인 이상여부 확인, 추력기 장착, 추진제 가압 및 공급, 시험장치 보정, 진공 모사 및 연소성능시험, data 처리 등으로 구성된다.

• Fisheries and Aquatic Sciences
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• 제24권12호
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• pp.400-405
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• 2021

In this study, the relationship between the growth of abalone and the presence of epibionts was investigated in abalone cultured in Goheung, Jeollanam-do, where there are severe problems high water temperatures and attachment. The experiment was conducted for eight months (May-December 2020), and 40 abalone were collected every month. Water temperature was at its highest at a range of 13.5℃-26.6℃ and dissolved oxygen levels were at their lowest at a range of 4.0-10.2 ㎍/L in August. The shell height (mm) of abalone grew to 117.7% (81.8 ± 1.9 mm) in cultures where epibionts were removed (ER) and 111% (77.4 ± 3.3 mm) where they were not (non-epibionts, NER). Their total weight (TW) and body weight increased significantly and steadily with ER, whereas the TW increased sharply after August with NER. In the condition index, no significant difference was observed between ER and NER. The monthly proportion of epibionts increased significantly in July, accounting for the value of 69.9% reached in December.

• 한국지구과학회지
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• 제38권6호
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• pp.405-420
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• 2017

미국 Lick 천문대에서 위상이 다른 세 시기에 공생별 AG Peg을 분광 관측하고 방출선 H I, He II, O III를 조사하였다. 6개의 O III Bowen 선의 FWHM과 선세기를 측정하고 형광 기작 효율을 연구하였다. 세 시기의 O III 일반선과 Bowen 선의 평균 FWHM은 큰 차이가 없었으나 선세기 비는 약 4.0 배 정도로 O III Bowen 선이 높았다. O III Bowen 선의 이론적 세기 비와 관측 세기 비를 비교한 결과, O III ${\lambda}$ 3759.87만 제외하고 관측한 세기가 이론적 세기보다 크다는 사실을 알았다. O III ${\lambda}$ 3791.26과 3754.67의 선세기 비는 세 시기 중에서 2001년도만이 Saraph and Seaton(1980)의 모델과 잘 일치하였다. 다른 두 시기는 AG Peg의 효율(R)을 구할 수 없었으나 2002년은 R=0.47을 얻었다. 이 때문에, 2002년 효율 결과를 기초로 He II ${\lambda}$ 4685.68에 대한 O III 일반선과 Bowen 선의 세기 비를 구하여 시기에 따른 효율 변화를 알아보았다. 그 결과 AG Peg의 효율은 1998년이 가장 높았고 2001년이 가장 낮았다. 결론적으로, 위상에 따른 효율 변화는 이온화된 가스의 전자 온도 변화에 기인하는데, AG Peg의 효율은 전자 온도가 증가함에 따라 증가하고 있다. 우리 연구 결과는 선세기 비 및 효율의 경향성 파악과 공생별에서 이온화된 껍질의 물리적 조건을 이해하는데 사용될 수 있다.

• 한국수산과학회지
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• 제32권3호
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• pp.290-294
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• 1999

참전복의 성장을 증진시키거나 품질을 개선시킬 수 있는 첨가제를 탐색하기 위해, 오징어분 $5\%$, 먹이유인물질 $0.5\%$, 한약제$1\%$ 및 lecithin $0.5\%$를 각각 첨가한 배합사료를 설계하여 외국에서 수입된 상품사료와 비교하였다. 평균체중 150mg의 참전복 치패를 대상으로 각 사료당 4반복으로 18주간 사육 실험한 결과, 최종 평균체중은 한약제를 첨가한 실험구가 720mg으로 가장 높았고, lecithin를 첨가한 실험구가 610mg으로 가장 낮았으며 (P<0.1), 상품사료는 660 mg이었다. 생존율과 가식부의 일반성분은 사료구간에 유의적인 차이가 인정되지 않았다 (P>0.1). 증체율은 한약제 첨가 사료가 $405\%$로 가장 높아 오징어분 첨가구, lecithin 첨가구 및 상품사료의 $320\~329\%$ 보다 높았다 (P<0.1). 이와 같이 한약제 첨가구가 오징어 분말, lecithin 및 상품사료보다 성장이 개선되는 경향이 있어, 한약제의 첨가가 성장개선에 도움이 될 것으로 보이며, 금후 이에 대한 연구가 계속 수행되어야 할 것이다.