• Environmental Engineering Research
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• 제24권2호
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• pp.220-237
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• 2019

Solid waste management (SWM) is one of the poorly rendered services in developing countries - limited resources, increasing population, rapid urbanization and application of outdated systems leads to inefficiency. Lack of proper planning and inadequate data regarding solid waste generation and collection compound the SWM problem. Decision makers need to formulate solutions that consider multiple goals and strategies. Given the large number of available options for SWM and the inter-relationships among these options, identifying SWM strategies that satisfy economic or environmental objectives is a complex task. The paper develops a mathematical model for a municipal Integrated SWM system, taking into account waste generation rates, composition, transportation modes, processing techniques, revenues from waste processing, simulating waste management as closely as possible. The constraints include those linking waste flows and mass balance, processing plants capacity, landfill capacity, transport vehicle capacity and number of trips. The linear programming model integrating different functional elements was solved by LINGO optimization software and various possible waste management options were considered during analysis. The model thus serves as decision support tool to evaluate various waste management alternatives and obtain the least-cost combination of technologies for handling, treatment and disposal of solid waste.

• Advances in environmental research
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• 제9권2호
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• pp.97-107
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• 2020

The indiscriminate growth in global population poses a threat to the world in handling and disposal of Municipal solid waste. Rapid urban growth increases the production, consumption and generation of Municipal solid waste which leads to a drastic change in the environment. The methane produced from the Municipal Solid waste accounts for up to 11% global anthropogenic emissions, which is a major cause for global warming. This study reports the methane emission estimation using IPCC default, TNO, LandGEM, EPER and close flux chamber from open dump yards at Perungudi and Kodungaiyur in Chennai, India. The result reveals that the methane emission using close flux chamber was in the range of 8.8 Gg/yr-11.3 Gg/yr and 6.1Gg/yr to 9.1 Gg/yr at Kodungaiyur and Perungudi dump yard respectively. The per capita waste generation was estimated based on waste generation and population. The waste generation potential was projected using linear regression model for the period 2017-2050. The trend of CH₄ emission in the actual field measurement were increased every year, similarly the emission trend also increased in IPCC default method (mass balance approach), EPER Germany (zero order decay model) where as TNO and Land GEM (first order decay model) were decreased. The present study reveals that Kodungaiyur dump yard is more vulnerable to methane emission compared to Perungudi dump yard and has more potential in waste to energy conversion mechanisms than compare to Perungudi dump yard.

• 자원리싸이클링
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• 제31권6호
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• pp.81-91
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• 2022

리튬이온 배터리의 사용은 전자기기 및 전기차 등의 생산량 증가로 인해 사용량이 크게 증가하고 있으며, 이와 맞물려 향후 폐배터리의 발생량 증가도 예상된다. 따라서 폐배터리를 구성하고 있는 여러 유가 자원 중 Ni, Co, Mn, Li 등이 함유되어 있는 양극 활물질이 매우 중요한 유가 자원으로, 이를 재활용하기 위한 많은 연구가 진행되고 있다. 양극 활물질 회수를 위해서 일반적으로 폐배터리로부터 블랙 매스(Black mass)를 회수하고, 이를 처리하여 주요 금속 자원을 회수한다. 블랙 매스를 회수하는 공정은 폐배터리를 수거-방전-해체-파쇄-분급의 순서로 이루어지며, 본 연구에서는 블랙 매스 회수를 위한 파쇄/분급 공정을 분석하였다. 파쇄/분급 공정을 통해 다양한 공정 산물의 입도 특성을 분석하고, 이 과정에서 생산된 산물의 입도별 형상을 현미경 및 SEM(Scanning Electron Microscopy)-EDS(Energy Dispersive Spectrometer)로 분석하였다. 분석 결과 블랙 매스로 회수되는 입자 중 74 ㎛의 미세한 입자들은 양극/음극 활물질이 전극으로부터 단체분리되어 존재하였지만, 100 ㎛ 이상의 입자들은 전극과 활물질이 붙어있는 상태에서 파쇄에 의해 입도가 감소되어 존재함을 확인하였다. 또한 배터리의 특징인 2종 혼합물(전극과 활물질)이 결합되어 있는 시료에 대해 파분쇄 특성을 모사할 수 있는 PBM(Population Balance Model) 을 개발하였으며, 2종 혼합물의 분쇄 상수를 도출하고 입도 분포 예측 성능을 검증하였다.

• 한국콘텐츠학회논문지
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• 제5권3호
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• pp.193-199
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• 2005

휴리스틱 알고리즘 연구에 있어서 중요한 분야 중 하나가 강화와 다양화의 조화를 맞추는 문제이다. 개미 집단 시스템은 최근에 제안된 조합 최적화문제를 해결하기 위한 메타 휴리스틱 기법으로, 그리디 탐색과 긍정적 보상에 의한 접근법으로 순회 판매원 문제를 풀기 위해 처음으로 제안되었다. 본 논문에서는 기존 개미집단 시스템의 성능을 향상시키기 위해 강화 전략과 다양화 전략으로 나누어진 엘리트 전략을 통해 집단간 긍정적 부정적 상호작용을 수행하는 다중 집단 개미 모델을 제안한다. 그리고, 이 제안된 엘리트 전략에 의한 다중 집단 상호작용 개미 모델을 순회판매원문제에 적용해 보고 그 성능에 대해 기존 개미집단 시스템과 비교한다.

• Advances in Computational Design
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• 제8권1호
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• pp.37-59
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• 2023

Squat reinforced concrete (SRC) shear walls are a critical part of the structure for both office/residential buildings and nuclear structures due to their significant role in withstanding seismic loads. Despite this, empirical formulae in current design standards and published studies demonstrate a considerable disparity in predicting SRC wall shear strength. The goal of this research is to develop and evaluate hybrid and ensemble artificial neural network (ANN) models. State-of-the-art population-based algorithms are used in this research for hybrid intelligence algorithms. Six models are developed, including Honey Badger Algorithm (HBA) with ANN (HBA-ANN), Hunger Games Search with ANN (HGS-ANN), fitness-distance balance coyote optimization algorithm (FDB-COA) with ANN (FDB-COA-ANN), Averaging Ensemble (AE) neural network, Snapshot Ensemble (SE) neural network, and Stacked Generalization (SG) ensemble neural network. A total of 434 test results of SRC walls is utilized to train and assess the models. The results reveal that the SG model not only minimizes prediction variance but also produces predictions (with R²= 0.99) that are superior to other models.

• 대한간호학회지
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• 제35권7호
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• pp.1285-1294
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• 2005

Purpose: This study was done to evaluate the predictive value of aspects of the Transtheoretical model (TTM) of behavior change as applied to smoking cessation in a rural population. Method: A convenience sample was recruited from a public health center in a community. A total of 484 participants were recruited, including 319 smokers, 116 ex-smokers and 49 non-smokers. A cross-sectional and descriptive design was used in this study. Data was analyzed using descriptive statistics, frequency statistics, ANOVA and Logistic regression. Result: The major findings were 1) The participants were assessed at baseline for their current Stage of Change resulting in a distribution with $42.1\%$ in Precontemplation, $24.1\%$ in Contemplation, $9.7\%$ in Preparation, $6.2\%$ in Active, and $17.9\%$ in the Maintenance stage. 2) There were statistically significant differences of processes of change, decisional balance and situational temptation across the stages of change. 3) The main factors that affect smoking cessation were age, number of years smoking, age when began smoking, self-liberation and negative/affective situations, which combined explained $33.2\%$ of the smoking cessation. Conclusion: TTM variables measured prior to a smoking cessation program added little predictive value for cessation outcome beyond that explained by demographic and smoking history variables.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.1002-1012
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• 2024

To remove insoluble fission products, which could possibly cause reactor instability and significantly reduce heat transfer efficiency from primary system of molten salt reactor, a helium bubbling method is employed into a passive molten salt fast reactor. In this regard, two-phase flow behavior of molten salt and helium bubbles was investigated experimentally because the helium bubbles highly affect the circulation performance of working fluid owing to an additional drag force. As the helium flow rate is controlled, the change of key thermal-hydraulic parameters was analyzed through a two-phase experiment. Simultaneously, to assess the applicability of numerical model for the analysis of two-phase flow behavior, the numerical calculation was performed using the OpenFOAM 9.0 code. The accuracy of the numerical analysis code was evaluated by comparing it with the experimental data. Generally, numerical results showed a good agreement with the experiment. However, at the high helium injection rates, the prediction capability for void fraction of helium bubbles was relatively low. This study suggests that the multiphaseEulerFoam solver in OpenFOAM code is effective for predicting the helium bubbling but there exists a room for further improvement by incorporating the appropriate drag flux model and the population balance equation.

• 대한지리학회지
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• 제49권3호
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• pp.423-437
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• 2014

구획화는 인간 활동에 영향을 미치는 새로운 지역적 틀을 만들어내는 공간 의사결정 과정이다. 그러나 구역 내 포함되어 있는 자연적 장애물은 재조직화된 구역 내에서 이루어지는 인간 활동의 효율성을 떨어뜨릴 수 있다. 이는 구획화 과정에서 경계의 특성, 즉 고도와 같은 자연적 특성, 상호작용과 같은 관계적 특성을 고려할 필요가 있음을 의미한다. 본 연구의 목적은 이러한 경계 특성을 반영하는 새로운 구획모델을 고안하는 것이다. 경계를 '결합' 혹은 '분리'와 같이 이분법적으로 간주하기 보다는 인접한 두 공간 단위 사이의 길이, 고도 편차, 상호작용과 같은 여러 경계 특성을 바탕으로 평가된 결합의 가능성을 나타내는 연속적 함수로 간주하고 목적함수 형태로 모델에 반영한다. 모델은 인구, 면적과 같은 수요 균형을 부여하는 제약조건뿐만 아니라 명시적인 연접성 제약조건을 갖는다. 경계 속성을 자연적 특성과 관계적 특성으로 구분하고, 이와 관련된 다양한 요인들에 대하여 적합도 분석을 수행하여 인접한 두 기본 공간 단위 사이의 결합 가능성을 평가한다. 행정구역 재설정문제에 고안된 모델 및 경계 특성 분석 방법을 적용한다. 분석 결과는 혼합정수계획법의 틀로 다양한 경계 특성을 고려한 구획화가 가능함을 보여준다.

• 한국가시화정보학회지
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• 제17권3호
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• pp.24-31
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• 2019

Recently, an air-lift bio-reactor operated by micro bubbles has been utilized to product hydrogen fuel. To enhance the performance, characteristics of hydrodynamics inside the bio-reactor were analyzed using a numerical simulation for two-phase flow. An Eulerian model was employed for both of liquid and gas phases. The standard k-ε model was used for turbulence induced by micro bubbles. A Population Balance Model was employed to consider size distribution of bubbles. A hollow cylinder was introduced at the center of the reactor to reduce a dead area which disturbs circulation of CO bubbles. An appropriate diameter of the draft tube and hollow cylinder were optimized for better performance of the bio-reactor. The optimum model could be obtained when the cross-sectional area ratio of the hollow cylinder to the reactor, and the width ratio of the riser to the downcomer approached 0.4 and 3.5, respectively. Consequently, it is expected that the optimum model could enhance the performance of the bio-reactor with the homogeneous distribution and higher density of CO, and more effective mixing.

• Asian-Australasian Journal of Animal Sciences
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• 제33권10호
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• pp.1573-1578
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• 2020

Objective: Milk fatty acid (FA) is a main nutritional component that markedly effects human health. Intentional modification of the FA profile has the potential to improve milk quality. This study aimed at the factors affecting elevated FA levels and the estimation of the genetic parameters for milk FAs in the Korean Holstein population. Methods: Total 885,249 repeated test-day milk records including, milk yield, saturated fatty acids (SFA), polyunsaturated fatty acids (PUFA), monounsaturated fatty acids (MUFA), total unsaturated fatty acids (TUFA), fat and protein percentages were analyzed using CombiFoss FT+ system (Foss Analytical A/S, Denmark). Genetic parameters were estimated by the restricted maximum likelihood procedure based on the repeatability model using the Wombat program. Results: The FA profile varies along with the lactation and the energy balance (EB). With the negative EB in early lactation, mobilization of body fat reserves elevates the desirable FA levels. As a result of that, milk quality is increased by means of nutritionally and usability aspects during the early lactation. Moreover, heritability estimates for SFA, MUFA, PUFA, TUFA were 0.33, 0.42, 0.37, 0.41 respectively. According to the parity wise heritability analysis, first parity cows had relatively lower heritability for SFAs (0.19) than later parities (0.28). Conclusion: Genetic parameters indicated that FAs were under stronger genetic control. Therefore, we suggest implementing animal breeding programs towards improving the milk FA profile.