• 한국해양공학회지
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• 제35권4호
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• pp.296-304
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• 2021

Research on the development of marine renewable energy is actively in progress. Various studies are being conducted on the development of wave energy converters. In this study, a numerical analysis of wave-energy extraction performance was performed according to the body shape and scale of the sloped oscillating water column (OWC) wave energy converter (WEC), which can be connected with the breakwater. The sloped OWC WEC was modeled in the time domain using a two-dimensional fully nonlinear numerical wave tank. The nonlinear free surface condition in the chamber was derived to represent the pneumatic pressure owing to the wave column motion and viscous energy loss at the chamber entrance. The free surface elevations in the sloped chamber were calculated at various incident wave periods. For verification, the results were compared with the 1:20 scaled model test. The maximum wave energy extraction was estimated with a pneumatic damping coefficient. To calculate the energy extraction of the actual size WEC, OWC models approximately 20 times larger than the scale model were calculated, and the viscous damping coefficient according to each size was predicted and applied. It was verified that the energy, owing to the airflow in the chamber, increased as the incident wave period increased, and the maximum efficiency of energy extraction was approximately 40% of the incident wave energy. Under the given incident wave conditions, the maximum extractable wave power at a chamber length of 5 m and a skirt draft of 2 m was approximately 4.59 kW/m.

• Ocean Science Journal
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• 제43권2호
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• pp.67-79
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• 2008

We investigated the relationship between mesoscale spatial distribution of environmental parameters (temperature, salinity, and sigma-t), chlorophyll-a concentration and mesozooplankton in the Yellow Sea during May 1996, 1997, and 1998, with special reference to Yellow Sea Bottom Cold Water (YSBCW). Adult calanoid copepods, Calanus sinicus, Paracalanus parvus s.l., Acartia omorii, and Centropages abdominalis were isolated by BVSTEP analysis based on the consistent explainable percentage (-32.3%) of the total mesozooplankton distributional pattern. The copepods, which accounted for 60 to 87% of the total abundances, occupied 73-78% of the copepod community. The YSBCW consistently remained in the northern part of the study area and influenced the spatial distribution of the calanoid copepods during the study periods. Abundances of C. sinicus and P. parvus s.l., which were high outside the YSBCW, were positively correlated with the whole water average temperature (p<0.01). In contrast, the abundances of C. abdominalis and A. omorii, which were relatively high in the YSBCW, were associated with the integrated chl-a concentration based on factor analysis. These results indicate that the YSBCW influenced the mesoscale spatial heterogeneity of average temperature and integrated chl-a concentration through the water column. This consequently affected the spatial distribution pattern of the dominant copepods in association with their respective preferences for environmental and biological parameters in the Yellow Sea during spring.

• 한국지진공학회논문집
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• 제26권2호
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• pp.49-58
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• 2022

The 2017 Pohang earthquake caused severe damage to low-rise piloti buildings. The damage was caused mainly by column shear failure, and some core walls were as well. The damaged piloti buildings in Pohang City could be relieved if they were designed correctly according to the standards at that time. However, the post-earthquake investigation revealed design, construction, and permission problems. To solve the problems, the Piloti Building Structure Design Guidelines that include strict specifications were published in 2018. Separately, KDS 41 17 00, the seismic design standard for buildings, was enacted in 2019 and it included the guideline contents. Therefore, at least after the publication of the guidelines, piloti buildings, designed by the standard and guidelines, can be expected to possess better seismic performance than existing piloti buildings. To confirm this, the probability of exceedance for several damage state thresholds was estimated for existing and designed piloti buildings. As a result, the probability of damage of designed piloti buildings was very low compared to existing ones. Consequently, it was confirmed that the guideline and standard adequately supplement the structural fragility of existing piloti buildings.

• 한국강구조학회 논문집
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• 제23권3호
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• pp.337-347
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• 2011

본 논문에서는 콘크리트 채움 U형 강재보와 강재 H단면 기둥으로 구성된 접합부의 내진 성능을 평가하였다. 접합부 내진성능을 평가하기 위하여 세 개의 보-기둥 접합부 실험체를 반복주기하중에 대하여 실험하였다. 합성보는 콘크리트 슬래브와 스터드를 이용하여 일체화 되었으며, 슬래브에는 부모멘트를 위한 철근이 배치되었다. 접합부 상세를 실험 변수로 하였으며, 보 접합부의 강화방안 및 약화방안, 합성효과의 정도를 고려하였다. 합성보의 춤은 슬래브 두께를 포함하여 600mm이며, 강재보와 슬래브의 철근은 H형강 기둥과 용접을 통해 접합하였다. 접합부 강화방안은 합성보 플랜지에 덧댐플레이트를 용접하였으며, 약화방안으로서 소성힌지 발생지점에 채움콘크리트 안에 스티로폼을 삽입하였다. 실험 결과 완전합성 실험체는 강도와 변형능력, 에너지 소산에 있어서 우수한 성능을 보여주었다. 변형능력은 특수모멘트골조 기준인 4% 이상의 회전각을 발휘하였다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.493-500
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• 2003

The effect of reductive treatment with elemental iron on the extent of mineralization by Fenton oxidation was studied for the explosive 2,4,6-trinitrotoluene (TNT) and hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX) using a completely-stirred tank reactor (CSTR). The results support the hypothesis that TNT and RDX are reduced with elemental iron to products that are oxidized more rapidly and completely by Fenton's reagent. Iron pretreatment enhanced the extent of TOC removal by approximately $20\%\;and\;60\%$ for TNT and RDX, respectively. Complete TOC removal was achieved for TNT and RDX solutions with iron pretreatment under optimal conditions. On the other hand, without iron pretreatment, complete mineralization of TNT and RDX solutions were not achieved even with much higher $H_2O_2$ and $Fe^{2+}$ concentrations. The bench-scale iron treatment-Fenton oxidation integrated system showed more than $95\%$ TOC removal for TNT and RDX solutions under optimal conditions. The proposed zero-valent iron-Fenton process was evaluated with pink water from the Iowa Army ammunition plant. Results from batch and column experiments show that TNT, RDX, and octahydro-l,3,5,7-tetranitro-l,3,5,7-tetrazocine (HMX) were completely removed from the pink water and that triaminotoluene (TAT) and ${NH_4}^+$ were recovered as products in reduction with zero-valent iron. By using an integrated system, $83.3\pm4.2\%$ of TOC was removed in a CSTR with 10 mM of $Fe^{2+}$ and 50 mM of $H_2O_2$. These results suggest that the reduction products of TNT and RDX are more rapidly and completely mineralized by Fenton oxidation and that a sequential iron treatment-Fenton oxidation process may be a viable technology for pink water treatment.

• Korean Chemical Engineering Research
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• 제48권3호
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• pp.342-349
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• 2010

젖산은 식품, 화학 및 의약 산업에서 널리 이용되며 생분해성 고분자인 폴리젖산(poly lactic acid)의 원료로서 요구량이 증대되고 있다. 합성에 의한 생산 방법에서 환경 친화적이고 경제적인 발효에 의한 생산 방법으로 바뀌는 추세이다. 그러나 발효에 의해 생성된 생산물은 과량의 물과 고비점 부산물을 포함하고 있다. 고비점 물질의 존재와 젖산의 비휘발성은 젖산 분리 및 정제를 어렵게 만든다. 또한 정제 및 분리 공정은 많은 투자 비용과 에너지 소모를 요구한다. 반응증류 공정은 기존 공정과 비교하여 높은 선택도와 수율을 얻을 수 있다. 분리벽형 반응 증류탑과 같이 새롭게 통합된 공정은 투자 비용과 에너지 비용을 줄일 수 있고 순수한 젖산을 회수할 수 있다. 본 연구에서는 젖산의 분리 및 정제를 위한 설계구조들을 제안하였다. 제안된 설계구조들은 SQP 방법에 의해 최적화되었으며 최적화된 설계 구조들 사이의 에너지 소모량 및 생산물 순도를 비교하였다. 그리고 공정 성능과 최적화된 공정에 대한 주요 공정 변수들의 영향을 조사하였다.

• 수산해양기술연구
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• 제34권3호
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• pp.259-273
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• 1998

The hydroacoustic surveys to provide the essential information for the assessment, management and utilization of fishery resources in the southern waters of Korea were carried out during five research cruises between October 1996 and October 1997 by the training ship KAYA of Pukyong National University. These hydroacoustic investigations were designed to obtain more precise estimates of the geographic distribution, absolute abundance and biological characteristics of the fishery resources, and the vertically integrated densities of fish in terms of volume backscattering strength(SV) by survey region and depth bins, such as the entire water column and the 0~ 10 m from bottom fraction, were measured separately. Hydroacoustic data were collected by using a Simrad EK 500 Scientific echo sounder operating at two frequencies of 38kHz and 120kHz and the data stored in field were later processed on a HP PC using a Simrad EP 500 echo integration and target strength analysis system. The biological compositions of echo signal were identified and sampled using a demersal trawl during daylight hours. The mean target strength to scale the echo integration data for hydroacoustic surveys was derived from the relationship between the SV and the weight of trawl catch per unit volume of the water column sampled by demersal trawls. The results obtained can be summarized as follow : 1. The mean volume backscattering strength for the entire water column in the southern waters of Korea between 1996 and 1997 were -67.2 dB and -70.9 dB at two frequencies of 38 kHz and 120 kHz , respectively, and for the bottom layer of the 0-10 m from bottom friction were -68.8 dB, -70.2 dB, respectively. That is, the volume backscattering strength for the entire water column at low frequency was higher than that at high frequency. 2. The relationship between the mean backscattering strength (〈SV〉, dB) for the depth strata of trawl hauls and the weight (C, kg/m3) per cubic meter of the catch sampled by bottom trawling in the southern waters of Korea in January and July 1997 were expressed by the following equations: 38 kHz : 〈SV〉= -28.2 + 10 log(C), 120 kHz : 〈SV〉= -32.4 + 10 log(C). The mean weight -normalized target strengths derived from these equitions were -28.2 dB/ kg, -32.4 dB/ kg at 38 kHz and 120 kHz , respectively. That is, the mean weight -normalized target strength at 38 kHz was 4.2 dB higher than that at 120 kHz. 3. The distribution density of fish in terms of biomass per unit volume in the southern waters of Korea were estimated to be 125.9 $\times$ 10-6 kg/m3 and 141.3 $\times$ 10-6 kg/m3 at 38 kHz and 120 kHz , respectively.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.472-477
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• 2004

A new earthquake design method performing iterative calculations with secant stiffness was developed. Since basically the proposed design method uses linear analysis, it is convenient and stable in numerical analysis. At the same time, the proposed design method can accurately estimate the inelastic strength and ductility demands of the structural members through iterative calculations. In the present study, the procedure of the proposed design method was established, and a computer program incorporating the proposed method was developed. The proposed method, as an integrated analysis and design method, can directly address the earthquake design strategy intended by the engineer, such as limited ductility of member and the concept of strong column - weak beam. Through iterative calculations on a structural model with member sizes preliminarily assumed, the strength and ductility demands of each member can be determined so as to satisfy the given design strategy. As the result, structural safety and economical design can be achieved.

• 한국실내디자인학회논문집
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• 제19호
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• pp.30-37
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• 1999

This study presents a methods on the construction of integrated system for the purpose of automation of design plans, calculation of quantity of materials and estimation by abstracting information on building materials which is produced on the course of three dimension modeling by using computer. Therefore, an object oriented methodology is introduced to compose design informations in three dimension, space for unifying building informations, and expressing properties of building factors and materials, and to construct a database for computers to recognize architecture informations. An object indicates a conceptual individual existing in real world or existence of individual and necessity in composing a building could be called as objects such as column, wall, beam, slab, door and window and these contain materiality and immateriality. It is systemized to which properties of these building's objects are installed by the user of computer and by API(Application Programming Interface), chosen informations automatically converse to each unit work such as design plan structure plan, calculation of amount of materials, etc.

• Structural Engineering and Mechanics
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• 제44권2호
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• pp.163-178
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• 2012

A strut-and-tie model is introduced in this paper to predict the ultimate shear strength of non-seismically detailed columns. The validity and applicability of the proposed strut-and-tie model are evaluated by comparison with available experimental data. The model was developed based on visible crack patterns observed on the test specimens. The concrete contribution is integrated into the strut-and-tie model through a concept of equivalent transverse reinforcement. To further validate the model a full-scale non-seismically detailed reinforced concrete column was tested to investigate its seismic behavior. The specimen was tested under the combination of a constant axial load, $0.30f_c{^{\prime}}A_g$ and quasi-static cyclic loadings simulating earthquake actions. Quasi-static cyclic loadings simulating earthquake actions were applied to the specimen until it could not sustain the applied axial load. The analytical results reveal that the strut-and-tie method is capable of modeling to a satisfactory accuracy the ultimate shear strength of non-seismically detailed columns subjected to reserved cyclic loadings.