• 대한토목학회논문집
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• 제13권1호
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• pp.213-220
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• 1993

본 논문에서는 해마다 수 십만 개씩 발생되는 폐타이어의 열적 처리 방법인 건류 소각 처리 방법에서 발생되는 이차 오염 물질을 정량하여 폐타이어의 안전한 최종 처리 방법까지 고찰하였다. 건류-소각처리 방법에서 발생되는 배기 가스에서 이차 독성 오염 물질을 화학 평형 모델을 응용하여 예측하였고 실질적인 잔류 물질인 건류재와 소각재에서 유기성 독성 물질과 중금속을 정량하였다. 건류재에서는 폐타이어의 불완전 연소에 따른 유기성 이차 오염 물질이 다량 포함되어 있는 반면에 소각재에서는 납과 카드뮴과 같은 중금속 화합물의 함량이 높았다. 건류재 및 소각재의 안전한 최종 매립을 위하여는 서로 다른 전처리 방법이 요구된다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 자동차부품 제작기술의 진보
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• pp.97-109
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• 1996

In the present work computations are carried out for analysis of complicated sheet metal forming process such as forming of a rear hinge. Finite element formulation using dynamic explicit time integration scheme and step-wise combined Implicit/Explicit scheme are introduced for numerical analysis of sheet metal forming process. The rigid-plastic finite element method based on membrane elements has long been employed as a useful numerical technique for the analysis of sheet metal forming because of its time effectiveness. The explicit scheme in general use is based on the elastic-plastic modelling of material requiring large computation time. In finite element simulation of sheet metal forming processes, the robustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry and boundary conditions. The implicit scheme employs a more reliable and rigorous scheme in considering the equilibrium at each step of deformation, while in the explicit scheme the problem of convergency is eliminated at the cost of solution accuracy. The explicit approach and the implicit approach have merits and demerits, respectively. In order to combine the merits of these two methods a step-wise combined implicit/explicit scheme has been developed.

• 대한교통학회지
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• 제23권7호
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• pp.111-123
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• 2005

본 논문에서는 교통시설투자 의사결정을 위한 네트워크 설계 모형이 제시되었다. 모형은 사용자 평형의 통행패턴을 예측할 수 있으면서, 링크의 설치 여부를 정하는 이산형 의사결정변수를 갖는 Bi-Level Programming 형태로 구축되었다. 제시된 모형의 장점으로는 사회적 비용을 감안한 투자 결정을 묘사했다는 점과 도로와 철도로 이루어진 네트워크에서의 평형 통행패턴을 예측할 수 있다는 점이다. 정수형 변수의 Bit 구조를 이용한 효율적인 해법 알고리즘이 개발되었다. 예제를 통하여 모형과 알고리즘의 유효성을 검증하였는데, 예제 결과에서 투자의 한계효과 감소현상을 발견하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1336-1356
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• 2017

The spectrum scarcity crisis has resulted in a shortage of resources for many emerging wireless services, and research on dynamic spectrum management has been used to solve this problem. Game theory can allocate resources to users in an economic way through market competition. In this paper, we propose a bidding game-based spectrum allocation mechanism in cognitive radio network. In our framework, primary networks provide heterogeneous wireless service and different numbers of channels, while secondary users have diverse bandwidth demands for transmission. Considering the features of traffic and QoS demands, we design a weighted interference graph-based grouping algorithm to divide users into several groups and construct the non-interference user-set in the first step. In the second step, we propose the dynamic bidding game-based spectrum allocation strategy; we analyze both buyer's and seller's revenue and determine the best allocation strategy. We also prove that our mechanism can achieve balanced pricing schema in competition. Theoretical and simulation results show that our strategy provides a feasible solution to improve spectrum utilization, can maximize overall utility and guarantee users' individual rationality.

• 한국지능시스템학회논문지
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• 제11권7호
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• pp.680-688
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• 2001

In this paper, we propose a reliable method for searching the optimally performing generalized brain-state-in-a-box (GBSB) neural associative memory using an evolution program (EP) given a set of prototype patterns to be stored as stable equilibrium points. First, we exploit some qualitative guidelines necessary to synthesize the GBSB model. Next, we parameterize the solution space utilizing the limited number of parameters to represent the solution space. Then, we recast the synthesis of GBSB neural associative memories as two constrained optimization problems, which are equivalent to finding a solution to the original synthesis problem. Finally, we employ an evolution program (EP), which enables us to find an optimal set of parameters related to the size of domains of attraction (DOA) for prototype patterns. The validity of this approach is illustrated by a design example and computer simulations.

• Geomechanics and Engineering
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• 제15권4호
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• pp.997-1004
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• 2018

The brine leakage is a tough problem in artificial freezing engineering. This paper takes the common soft clay in Wujiang District as the study object, and calcium chloride solutions with six salinity levels were considered. The 'classic' cooling curve method was employed to measure the freezing point of specimens after freeze-thaw. Results indicate that four characteristic stages can be observed including supercooling, abrupt transition, equilibrium and continual freezing, strongly dependent on the variation of unfrozen water content. Two characteristic points were found from the cooling curves, i.e., freezing point and initial crystallization temperature. A critical value for the former exists at which the increment lowers. The higher the saline content approximately linearly, lower the freezing point. In the initial five cycles, the freezing point increases and then stabilizes. Besides, the degree of supercooling was calculated and its correlations with water, salt and freeze-thaw cycles were noted. Finally, an empirical equation was proposed for the relationship of freezing point and three main factors, i.e., water content, saline content and freeze-thaw cycles. Comparison of calculated and measured data proves that it is reliable and may provide guidance for the design and numerical analysis in frozen soil engineering.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.270-274
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• 2001

With Increasing importance of electroless nickel plating technology in many fields such as electronic and automobile industries, the treatment of the spent baths is becoming a serious problem. These spent baths contain iron and zinc as impurities, organic acids as complexing reagents, and phosphonate ions as oxidized species of tile reducing reagent. as well as several grams per liter of nickel. The spent baths are currently treated by conventional precipitation method. but a mettled with no sludge generation is desired. This work aims at establishing a recycling process of nickel from tile spent baths using solvent extraction. Extraction behaviors of nickel. iron. and zinc in various 쇼pes of real spent baths are investigated as a function of pH using LIX841, di (2-ethylhexyl)phosphoric acid (D2EHPA), and PC88A as tile extractants. Nickel is extracted by LIX84I at the equilibrium pH of more than 6 with high efficiency. For the weakly acid baths. iron and zinc are extracted by D2EHPA or PC88A without adjusting the pH of the baths leaving nickel in the aqueous phase. Stripping of nickel from LIX84I with sulfuric acid is also investigated. It is shown that concentrated nickel sulfate solution (> 100 ㎏-Ni/㎥) is obtained. This solution can be reused in the electroless plating process. Based on these findings, flow sheets for recovering nickel from the spent baths are proposed.

• 한국전산구조공학회논문집
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• 제18권2호
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• pp.141-149
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• 2005

본 논문에서는 유연체 동역학해석을 위하여 유한회전을 표현하는데 있어, 4원법의 대수학적인 표현을 도입하여 운동방정식이 에너지보존 조건을 만족하도록 이산화된 에너지 평형식으로 정식화되었다. 여기서 사용된 유한회전의 4원법은 로드리게스 매개변수를 이용하도록 하였으며, 구속력에 대한 일이 제거되도록 하였다. 수치해석의 예를 통하여 제안된 방법이 사다리꼴 방법과 비교할 때 비선형 문제에서도 무조건적으로 안정조건을 보장함을 검증하였으며, 향후 유연한 관절로 연결된 3차원 유연다물체에 대한 동역학 해석을 확장할 수 있는 토대를 마련하였다.

• 한국컴퓨터정보학회논문지
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• 제19권8호
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• pp.55-62
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• 2014

게임이론을 적용하여 에너지 효율적인 전송률 스케줄링 방안을 제안한다. 먼저, 개별 단말의 효용함수를 정의하고, 효용함수를 최적화하도록 에너지를 결정하는 비협력적 전송률 게임을 모델링한다. 여기서, 효용함수는 개별 단말이 데이터 전송시 소모하는 전송 에너지이다. 특히, 개별 단말의 효용함수가 Convex 함수임을 이용하여 에너지 효율적인 전송률 스케줄링 문제가 나쉬 평형이 존재함을 증명하고, 이를 기반으로 비협력적 스케줄링 알고리즘을 제안한다. 또한, 에너지 효율의 개선을 위해서 개별 단말의 효용함수의 합을 최적화하는 협력적 스케줄링 알고리즘도 제안한다. 성능 분석을 위하여 비협력적 알고리즘과 협력적 알고리즘의 수렴도 결과와 에너지 효율성 결과를 제시한다.

• Nuclear Engineering and Technology
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• 제33권5호
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• pp.468-482
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• 2001

As a process of Direct Containment Heating (DCH) issue resolution for Korean Standard Nuclear Power Plants (KSNPs), a containment load/strength assessment with two different approaches, the probabilistic and the deterministic, was performed with all plant-specific and phenomena-specific data. In case of the probabilistic approach, the framework developed to support the Zion DCH study, Two-Cell Equilibrium (TCE) coupled with Latin Hypercubic Sampling (LHS), provided a very efficient tool to resolve DCH issue. In case of the deterministic approach, the evaluation methodology using the sophisticated mechanistic computer code, CONTAIN 2.0 was developed, based on findings from DCH-related experiments or analyses. For three bounding scenarios designated as Scenarios V, Va, and VI, the calculation results of TCE/LHS and CONTAIN 2.0 with the conservatism or typical estimation for uncertain parameters, showed that the containment failure resulted from DCH loads was not likely to occur. To verify that these two approaches might be conservative , the containment loads resulting from typical high-pressure accident scenarios (SBO and SBLOCA) for KSNPs were also predicted. The CONTAIN 2.0 calculations with boundary and initial conditions from the MAAP4 predictions, including the sensitivity calculations for DCH phenomenological parameters, have confirmed that the predicted containment pressure and temperature were much below those from these two approaches, and, therefore, DCH issue for KSNPS might be not a problem.