• Steel and Composite Structures
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• 제30권6호
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• pp.493-516
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• 2019

This paper is dedicated to nonlinear static and free vibration analysis of Uniform Distributed Carbon Nanotube Reinforced Composite (UD-CNTRC) structures under in-plane loading. The authors have suggested an efficient six-node triangular element. Mixed Interpolation of Tensorial Components (MITC) approach is employed to alleviate the membrane locking phenomena. Moreover, the behavior of the well-known LST element is considerably improved by applying an additional linear interpolation on the strain fields. Based on the rule of mixture, the properties of CNTRC are obtained. In this study, only the uniform distributed CNTs are employed through the thickness direction of element. To achieve the natural frequencies and shape modes, the eigenvalue problem is also solved. Using Total Lagrangian Principles, large amplitude free vibration is considered based on the first normalized mode shape of structure. Different well-known plane problem benchmarks and some proposed ones are studied to validate the accuracy and capability of authors' formulations. In addition, the effects of length to the height ratio of beam, CNT's characteristics, support conditions and normalized amplitude parameter on the linear and nonlinear vibration parameters are investigated.

• 한국임상수의학회지
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• 제36권3호
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• pp.176-179
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• 2019

A giant prostatic urethral calculus has not been previously reported in dogs and should be distinguished from prostatic calculus. A 7-year-old castrated male Maltese dog with a 2-month history of relapsing hematuria and urinary incontinence with slowly progressing paraphimosis was referred. On abdominal radiography and ultrasonography, there was a giant calculus in the region of prostate or urethra, one left ureteral calculus, one urinary bladder calculus, and two penile urethral calculi. On computed tomography for evaluating the accurate location and planning the surgical approach, the giant calculus was located at the prostatic urethra. The calculi in urinary bladder, prostatic and penile urethra were surgically removed. These calculi were mixed-type of calcium oxalate monohydrate, struvite and calcium phosphate carbonate. On the basis of the urolith analysis and urine bacterial culture results, antibiotics and prescription diet were adjusted. At the 3-month follow-up, there were no clinical sings but paraphimosis was still remained, and ultrasonography revealed newly-formed, small urethral calculi at the prostatic urethra. This is the first report to describe the case of a canine giant prostatic urethral calculus and its clinical signs, diagnostic imaging findings, treatment, and outcome. CT may be useful to assess the accurate location and surgical approach for such calculi.

• BMB Reports
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• 제56권9호
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• pp.488-495
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• 2023

Mitochondrial transplantation is a promising therapeutic approach for the treatment of mitochondrial diseases caused by mutations in mitochondrial DNA, as well as several metabolic and neurological disorders. Animal studies have shown that mitochondrial transplantation can improve cellular energy metabolism, restore mitochondrial function, and prevent cell death. However, challenges need to be addressed, such as the delivery of functional mitochondria to the correct cells in the body, and the long-term stability and function of the transplanted mitochondria. Researchers are exploring new methods for mitochondrial transplantation, including the use of nanoparticles or CRISPR gene editing. Mechanisms underlying the integration and function of transplanted mitochondria are complex and not fully understood, but research has revealed some key factors that play a role. While the safety and efficacy of mitochondrial transplantation have been investigated in animal models and human trials, more research is needed to optimize delivery methods and evaluate long-term safety and efficacy. Clinical trials using mitochondrial transplantation have shown mixed results, highlighting the need for further research in this area. In conclusion, although mitochondrial transplantation holds significant potential for the treatment of various diseases, more work is needed to overcome challenges and evaluate its safety and efficacy in human trials.

• Geomechanics and Engineering
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• 제35권4호
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• pp.425-436
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• 2023

An effective tool for researching actual problems in geotechnical and mining engineering is to conduct physical modeling tests using similar materials. A reliable geometric scaled model test requires selecting similar materials and conducting tests to determine physical properties such as the mixing ratio of the mixed materials. In this paper, a method is proposed to determine similar materials that can reproduce target properties using a polynomial model based on experimental results on modeling materials using a gypsum-sand mixture (GSM) to simulate rocks. To that end, a database is prepared using the unconfined compressive strength, elastic modulus, and density of 459 GSM samples as output parameters and the weight ratio of the mixing materials as input parameters. Further, a model that can predict the physical properties of the GSM using this database and a polynomial approach is proposed. The performance of the developed method is evaluated by comparing the predicted and observed values; the results demonstrate that the proposed polynomial model can predict the physical properties of the GSM with high accuracy. Sensitivity analysis results indicated that the gypsum-water ratio significantly affects the prediction of the physical properties of the GSM. The proposed polynomial model is used as a powerful tool to simplify the process of determining similar materials for rocks and conduct highly reliable experiments in a physical modeling test.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.1052-1065
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• 2024

Advanced Pressurized Water Reactors (APWRs) and Boiling Water Reactors (BWRs) employ a suppression pool as a heat sink to prevent containment overpressure. Steam can be discharged into the pool through multi-hole spargers or blowdown pipes in both normal and accident conditions. Direct Contact Condensation (DCC) creates sources of momentum and heat. The competition between these two sources determines the development of thermal stratification or mixing of the pool. Thermal stratification is of safety concern as it reduces the cooling capability compared to a completely mixed pool condition. In this work we develop a scaling approach to prediction of the thermal stratification in a water pool induced by steam injection through spargers. Experimental data obtained from large-scale pool tests conducted in the PPOOLEX and PANDA facilities, as well as simulation results obtained using validated codes are used to develop the scaling. Two injection orientations, namely radial injection through multi-hole Sparger Head (SH) and vertical injection through Load Reduction Ring (LRR), are considered. We show that the erosion rate of the cold layer can be estimated using the Richardson number. In this work, scaling laws are proposed to estimate both the (i) transient erosion velocity and (ii) the stable position of the thermocline. These scaling laws are then implemented into a 1D model to simulate the thermal behavior of the pool during steam injection through the sparger.

• Asia pacific journal of information systems
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• 제34권2호
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• pp.421-446
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• 2024

Through Information and Communication Technology (ICT), the growth of music streaming platforms has revolutionized music consumption. "Digital Shadow Work" (DSW) refers to unpaid labor in digital spaces, with some prior research on its aspects. However, a comprehensive understanding is hindered by limitations in existing studies such as a lack of universality and dynamic exploration. To address these gaps and enable a comprehensive investigation into the role of DSW within highly versatile digital applications such as digital streaming platforms, this study employs a grounded theory methodology, a qualitative approach well-suited for exploring the intricacies of DSW among users of Chinese music streaming applications over a two-month period, involving longitudinal interviews with nine participants. The study findings elucidate the dynamic nature of DSW perceptions, which fluctuate across different stages of use and change in intensity over time. This study uncovers mixed attitudes towards DSW tasks, and observes a waning enthusiasm for social features over time, prompting some users to consider switching platforms. This study highlights the importance of thoughtful and user-centric feature development to enhance user satisfaction and the understanding of DSW, providing practical design and enhancement implications for music streaming applications.

• 지능정보연구
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• 제19권4호
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• pp.55-79
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• 2013

본 연구에서는 집중형 센터를 가진 역물류네트워크(Reverse logistics network with centralized centers : RLNCC)를 효율적을 해결하기 위한 혼합형 유전알고리즘(Hybrid genetic algorithm : HGA) 접근법을 제안한다. 제안된 HGA에서는 유전알고리즘(Genetic algorithm : GA)이 주요한 알고리즘으로 사용되며, GA 실행을 위해 0 혹은 1의 값을 가질 수 있는 새로운 비트스트링 표현구조(Bit-string representation scheme), Gen and Chang(1997)이 제안한 확장샘플링공간에서의 우수해 선택전략(Elitist strategy in enlarged sampling space) 2점 교차변이 연산자(Two-point crossover operator), 랜덤 돌연변이 연산자(Random mutation operator)가 사용된다. 또한 HGA에서는 혼합형 개념 적용을 위해 Michalewicz(1994)가 제안한 반복적언덕오르기법(Iterative hill climbing method : IHCM)이 사용된다. IHCM은 지역적 탐색기법(Local search technique) 중의 하나로서 GA탐색과정에 의해 수렴된 탐색공간에 대해 정밀하게 탐색을 실시한다. RLNCC는 역물류 네트워크에서 수집센터(Collection center), 재제조센터(Remanufacturing center), 재분배센터(Redistribution center), 2차 시장(Secondary market)으로 구성되며, 이들 각 센터 및 2차 시장들 중에서 하나의 센터 및 2차 시장만 개설되는 형태를 가지고 있다. 이러한 형태의 RLNCC는 혼합정수계획법(Mixed integer programming : MIP)모델로 표현되며, MIP 모델은 수송비용, 고정비용, 제품처리비용의 총합을 최소화하는 목적함수를 가지고 있다. 수송비용은 각 센터와 2차 시장 간에 제품수송에서 발생하는 비용을 의미하며, 고정비용은 각 센터 및 2차 시장의 개설여부에 따라 결정된다. 예를 들어 만일 세 개의 수집센터(수집센터 1, 2, 3의 개설비용이 각각 10.5, 12.1, 8.9)가 고려되고, 이 중에서 수집센터 1이 개설되고, 나머지 수집센터 2, 3은 개설되지 않을 경우, 전체고정비용은 10.5가 된다. 제품처리비용은 고객으로부터 회수된 제품을 각 센터 및 2차 시장에서 처리할 경우에 발생되는 비용을 의미한다. 수치실험에서는 본 연구에서 제안된 HGA접근법과 Yun(2013)의 연구에서 제안한 GA접근법이 다양한 수행도 평가 척도에 의해 서로 비교, 분석된다. Yun(2013)이 제안한 GA는 HGA에서 사용되는 IHCM과 같은 지역적탐색기법을 가지지 않는 접근법이다. 이들 두 접근법에서 동일한 조건의 실험을 위해 총세대수 : 10,000, 집단의 크기 : 20, 교차변이 확률 : 0.5, 돌연변이 확률 : 0.1, IHCM을 위한 탐색범위 : 2.0이 사용되며, 탐색의 랜덤성을 제거하기 위해 총 20번의 반복실행이 이루어 졌다. 사례로 제시된 두 가지 형태의 RLNCC에 대해 GA와 HGA가 각각 실행되었으며, 그 실험결과는 본 연구에서 제안된 HGA가 기존의 접근법인 GA보다 더 우수하다는 것이 증명되었다. 다만 본 연구에서는 비교적 규모가 작은 RLNCC만을 고려하였기에 추후 연구에서는 보다 규모가 큰 RLNCC에 대해 비교분석이 이루어 져야 할 것이다.

• 산업경영시스템학회지
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• 제39권2호
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• pp.28-36
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• 2016

Recently, owing to the development of ICT industry and wide spread of smart phone, the number of people who use car sharing service are increased rapidly. Currently two-way car sharing system with same rental and return locations are mainly operated since this system can be easily implemented and maintained. Currently the demand of one-way car sharing service has increase explosively. But this system have several obstacle in operation, especially, vehicle stock imbalance issues which invoke vehicle relocation. Hence in this study, we present an optimization approach to depot location and relocation policy in one-way car sharing systems. At first, we modelled as mixed-integer programming models whose objective is to maximize the profits of a car sharing organization considering all the revenues and costs involved and several constraints of relocation policy. And to solve this problem efficiently, we proposed a new method based on particle swarm optimization, which is one of powerful meta-heuristic method. The practical usefulness of the approach is illustrated with a case study involving satellite cities in Seoul Metrolitan Area including several candidate area where this kind systems have not been installed yet and already operating area. Our proposed approach produced plausible solutions with rapid computational time and a little deviation from optimal solution obtained by CPLEX Optimizer. Also we can find that particle swarm optimization method can be used as efficient method with various constraints. Hence based on this results, we can grasp a clear insight into the impact of depot location and relocation policy schemes on the profitability of such systems.

• 한국정보시스템학회지:정보시스템연구
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• 제29권1호
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• pp.75-91
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• 2020

Purpose Retrofit, defined to be addition of new technologies or features to the old system to increase efficiency or to abate GHG emissions, is considered as an important alternative for the old coal-fired power plant. The purpose of this study is to propose mathematical method to model multiple alternative retrofit in Generation Capacity Expansion Planning(GCEP) problem, and to get insight to the retrofit patterns from realistic case studies. Design/methodology/approach This study made a multi-alternative retrofit GECP model by adopting some new variables and equations to the existing GECP model. Added variables and equations are to ensure the retrofit feature that the life time of retrofitted plant is the remaining life time of the old power plant. We formulated such that multiple retrofit alternatives are simultaneously compared and the best retrofit alternative can be selected. And we found that old approach to model retrofit has a problem that old plant with long remaining life time is retrofitted earlier than the one with short remaining life time, fixed the problem by some constraints with some binary variables. Therefore, the proposed model is formulated into a mixed binary programming problem, and coded and run using the GAMS/cplex. Findings According to the empirical analysis result, we found that approach to model the multiple alternative retrofit proposed in this study is comparing simultaneously multiple retrofit alternatives and select the best retrofit satisfying the retrofit features related to the life time. And we found that retrofit order problem is cleared. In addition, the model is expected to be very useful in evaluating and developing the national policies concerning coal-fired power plant retrofit.

• 한국태양에너지학회 논문집
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• 제38권1호
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• pp.45-55
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• 2018

Environmentally benign lead-free solder coated ribbon (e. g. SnCu, SnZn, SnBi${\cdots}$) has been intensively studied to interconnect cells without lead mixed ribbon (e. g. SnPb) in the crystalline silicon(c-Si) photovoltaic modules. However, high melting point (> $200^{\circ}C$) of non-lead based solder provokes increased thermo-mechanical stress during its soldering process, which causes early degradation of PV module with it. Hence, we proposed low-temperature conductive paste (CP) based tabbing method for lead-free ribbon. Modules, interconnected by the lead-free solder (SnCu) employing CP approach, exhibits similar output without increased resistivity losses at initial condition, in comparison with traditional high temperature soldering method. Moreover, 400 cycles (2,000 hour) of thermal cycle test reveals that the module integrated by CP approach withstands thermo-mechanical stress. Furthermore, this approach guarantees strong mechanical adhesion (peel strength of ~ 2 N) between cell and lead-free ribbons. Therefore, the CP based tabbing process for lead free ribbons enables to interconnect cells in c-Si PV module, without deteriorating its performance.