• Geomechanics and Engineering
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• 제14권2호
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• pp.115-129
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• 2018

This paper presents a set of results of plate load tests that imposed incremental cyclic loading to a sandy soil bed containing multiple layers of granulated rubber-soil mixture (RSM) at large model scale. Loading and unloading cycles were applied with amplitudes incrementally increasing from 140 to 700 kPa in five steps. A thickness of the RSM layer of approximately 0.4 times the footing diameter was found to deliver the minimum total and residual settlements, irrespective of the level of applied cyclic load. Both the total and residual settlements decrease with increase in the number of RSM layers, regardless of the level of applied cyclic load, but the rate of reduction in both settlements reduces with increase in the number of RSM layers. When the thickness of the RSM layer is smaller, or larger, settlements increase and, at large thicknesses may even exceed those of untreated soil. Layers of the RSM reduced the vertical stress transferred through the foundation depth by distributing the load over a wider area. With the inclusion of RSM layers, the coefficient of elastic uniform compression decreases by a factor of around 3-4. A softer response was obtained when more RSM layers were included beneath the footing damping capacity improves appreciably when the sand bed incorporates RSM layers. Numerical modeling using "FLAC-3D" confirms that multiple RSM layers will improve the performance of a foundation under heavy loading.

• 한국환경과학회지
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• 제7권2호
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• pp.171-176
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• 1998

This study was conducted to evaluate water quality utilizing principal component analysis in the Nakdong River Estuary. From the results of analysis, water quality in the Nakdong River Estuary could be explained up to 65.3 Percente by three factors which were Included In river loadlnwastes from the Nakdong River and rainfalls : 39.1%1, sediment resuspension(13.7BS) and metabolism(12.5%). In the eastern part of estuary In flowing the Nakdong River, river loading factor score(factor 1 Pas higher than that In western part. Sediment resuspension factor score(factor 2) was high in shallow water, while metabolism factor score(factor 3) was high in deeper water. For seasonal variations of factors score, factor 1 was h19h- 1y related to rainfall season.

• 한국전자파학회논문지
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• 제23권4호
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• pp.468-474
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• 2012

본 논문은 기판 직접형 도파관(SIW)에 complementary split ring resonator(CSRR)이 탑재된 저위상 잡음 발진기를 제안한다. SIW 캐비티의 unloaded Q-factor는 CSRR을 삽입하여 높아졌고, 그 값은 1960을 나타내고 있다. 높은 Q-factor를 나타내는 SIW 캐비티 공진기에 대한 이론적인 분석과 설계 과정이 제시되어 있으며, 설계된 회로가 11.3 dBm의 출력 파워와 1-MHz 오프셋에서 -127.9 dBc/Hz의 위상 잡음을 갖는 9.3 GHz의 신호를 발생시킴을 실험적으로 보여주고 있다.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1126-1139
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• 2016

In this research, for the first time, a new optimization method, i.e., strength Pareto evolutionary algorithm II (SPEA-II), is developed for the burnable poison placement (BPP) optimization of a nuclear reactor core. In the BPP problem, an optimized placement map of fuel assemblies with burnable poison is searched for a given core loading pattern according to defined objectives. In this work, SPEA-II coupled with a nodal expansion code is used for solving the BPP problem of Kraftwerk Union AG (KWU) pressurized water reactor. Our optimization goal for the BPP is to achieve a greater multiplication factor ($K_{eff}$) for gaining possible longer operation cycles along with more flattening of fuel assembly relative power distribution, considering a safety constraint on the radial power peaking factor. For appraising the proposed methodology, the basic approach, i.e., SPEA, is also developed in order to compare obtained results. In general, results reveal the acceptance performance and high strength of SPEA, particularly its new version, i.e., SPEA-II, in achieving a semioptimized loading pattern for the BPP optimization of KWU pressurized water reactor.

• Nuclear Engineering and Technology
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• 제49권4호
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• pp.663-667
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• 2017

Delayed hydride cracking (DHC) was first observed in pressure tubes in Canadian CANDU reactors. In light water reactors, DHC was not observed until the late 1990s in high-burnup boiling water reactor (BWR) fuel cladding. In recent years, the focus on DHC has resurfaced in light of the increased interest in the cladding integrity during interim conditions. In principle, all spent fuel in the wet pools has sufficient hydrogen content for DHC to operate below $300^{\circ}C$. It is therefore of importance to establish the critical parameters for DHC to operate. This work studies the threshold stress intensity factor ($K_{IH}$) to initiate DHC as a function of temperature in Zry-4 for temperatures between $227^{\circ}C$ and $315^{\circ}C$. The experimental technique used in this study was the pin-loading testing technique. To determine the $K_{IH}$, an unloading method was used where the load was successively reduced in a stepwise manner until no cracking was observed during 24 hours. The results showed that there was moderate temperature behavior at lower temperatures. Around $300^{\circ}C$, there was a sharp increase in $K_{IH}$ indicating the upper temperature limit for DHC. The value for $K_{IH}$ at $227^{\circ}C$ was determined to be $2.6{\pm}0.3MPa$ ${\surd}$m.

• Wind and Structures
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• 제28권6호
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• pp.381-388
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• 2019

This paper described the application of Geospatial Analysis in determining mean wind speed, $V_h$ for wind load calculation imposed to electrical transmission tower structural design. The basic wind speed data on available station obtained from Malaysian Meteorology Department is adjusted by considering terrain and ground roughness factor. The correlation between basic wind speed, terrain factor and ground roughness stated in EN-50341-1 is used to obtain the $V_h$ for overhead transmission line elements 50 m above ground. Terrain factor, $k_r$ and ground roughness, $z_0$ in this study are presented by land use types of study area. Wind load is then calculated by using equation stated in design code EN-50341-1 by using the adjusted mean wind speed. Scatter plots of $V_h$ for different $k_r$and $z_0$ are presented in this paper to see the effect of these parameters to the value of $V_h$. Geospatial analysis is used to represent the model of $V_h$. This model can be used to determine possible area that will subject to wind load which severe to the stability of transmission tower and transmission line.

• 한국수자원학회논문집
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• 제31권2호
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• pp.155-165
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• 1998

생활수준 향상과 식생활 변화로 인하여 생활용수 소비량이 증가함에 따라 일상생활에서 배출되는 오수의 양도 증가할 것으로 예측된다. 아파트 단지내 오수정화시설 및 하수처리장의 설계를 위해서는 먼저 인구에 근거한 오수량의 발생원단위를 알아야 한다. 이러한 자료는 하수처리의 운전이나 수질관리 계획 수립을 위해서도 꼭 필요한 것이다. 따라서 본 연구에서는 주택공사의 123개 관리소에 2년간의 급수량을 취합하여 거주인구에 따른 급수량을 분석하였고 그 중에 수도권 1개 단지와 지방권 1개 단지를 선정하여 시간별, 일별, 요일별, 계절별의 오수유입량을 직접 실측함으로써 실제 급수량과 비교를 통하여 오수유입 총량 및 거주인구에 따른 원단위를 계산하였다.

• 한국통신학회논문지
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• 제28권5B호
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• pp.448-456
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• 2003

본 논문에서는 음성신호 전송을 위한 ATM 서비스 중 ABR에 대한 새로운 체증제어 알고리즘을 제시한다. 제시하는 알고리즘에서는 기존의 방법들과는 달리 네트워크의 혼잡 정도를 측정하기 위하여 스위치의 버퍼레벨뿐만 아니라 버퍼레벨의 변화율을 측정하여 보다 유연하게 네트워크의 상황에 대처하도록 하였다. 또한, 음성신호 송신원의 셀 전송속도가 다른 음성신호 송신원에 비해 상대적으로 작아지거나 커지는 불평등을 해소하기 위하여 Loading Factor를 도입하여 전송속도의 증감율을 조정하였다. 본 논문에서 제시하는 알고리즘이 기존의 다른 방법에 비해 우수하다는 것을 입증하기 위하여 7개의 음성 신호 송신원과 4개의 스위치를 갖는 네트워크 모델을 제시하여 모의실험 하였다. 네트워크 모델은 페트리 네트를 통해 구현하였으며 모의실험 도구로는 ExSpect가 사용되었다. 모의실험 결과 본 논문에서 제안하는 알고리즘을 사용하면 기존의 방법에 비해 네트워크의 효율과 음성신호 송신원들의 불평등이 많이 개선됨을 알 수 있다.

• 한국전산구조공학회논문집
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• 제34권6호
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• pp.393-401
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• 2021

본 논문에서는 폭발하중을 받는 부재의 저항성능 평가를 위한 모멘트-곡률 관계 기반 수치해석 기법을 소개한다. 직접전단 파괴 모드를 고려하기 위하여 경험적인 직접전단응력-슬립양 관계를 기반으로 하는 무차원 스프링 요소를 도입하였다. 재료에 대해 정의된 동적증가계수 식을 바탕으로 단면의 모멘트-곡률 관계에 직접적으로 적용가능한 단면의 곡률 변화율에 따른 동적증가계수 식을 제작하였다. 또한 부착슬립의 영향을 고려하기 위하여 소성힌지영역 내에 등가 휨강성을 도입하였다. 제안된 수치해석 모델의 타당성 검증을 위하여 실험결과와의 비교연구를 수행하였으며, 단자유도계 모델의 해석결과와의 비교를 통해 본 수치해석 모델의 우수성을 확인하였다. P-I 선도를 제작하여 부재의 휨 파괴 및 직접전단 파괴에 대한 저항성능을 평가하였으며, 매개변수 연구를 수행하여 P-I 선도 및 저항성능의 변화를 확인하였다.

• 한국해양공학회지
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• 제5권2호
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• pp.207-207
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• 1991

The crack length measurements by electrical potential(EP) method for 1% Cr-Mo-V and 12%Cr steel of 0.5T-CT specimen were performed at $500^{\circ}C, 600^{\circ}C 700^{\circ}C$, and an applicability of stress intensity factor($K_I$), net section stress($\sigma_{net}$), $C^*$-ingegral and $C_t$ parameter was studied to measure creep crack growth rate(da/dt) with side groove and without side groove under static and cyclic loading condition. The experimental result could be summarized as follows: 1) Crack measurement by EP method was available and coincided with the Johnson,s analytical equation. 2) da/dt by $K_I$ and $\sigma_{net}$ was not adequate because of the wide scatter band according to load and temperature, but $C^*$-integral, except for transition region, was adequate. 3) $C_t$ parameter showed the best fitted line through total creep region without relating with both temperature and load condition. 4) Under the cyclic loading condition, $C_t$ parameter was proper to extimate da/dt. And it was shown that da/dt for 1% Cr-Mo V steel under the static condition(R=1) was 1.16 times faster than the case under cyclic loading(R=0), and for 12% Cr steel, 1.43 times.