구조물의 최대강성 치수최적설계

신수미(Soo-Mi Shin),박현정(Hyun-Jung Park) 한국컴퓨터정보학회 2009 韓國컴퓨터情報學會論文誌 Vol.14 No.1

본 연구는 주어진 부피제약조건 하에서 최대강성을 구현하는 고층 철골 트러스 시스템의 단면치수 재조정 프로세스를 보여준다. 이러한 치수최적설계는 경사도법에 근거한 최적정 방법에 의해 수치적으로 연산된다. 전형적인 치수최적설계에서는 변위나 응력제약조건 하에서 구조물의 최소중량을 구현하지만, 본 연구에서 소개되는 치수최적설계는 이것과 반대의 프로세스를 가진다. 즉, 부피와 같은 재료제약조건 하에서 최대강성을 구현한다. 본 연구는 기존의 치수최적설계방법의 대안으로서 그 의미를 가질 수 있다. 고층 철골트러스 구조시스템의 수치 예제를 통하여 부재 단면치수 재조정 설계가 기존의 최소중량설계와 반대인 최대강성 이산화 치수최적설계를 통하여 적합하게 수행됨이 증명되었다. This study presents a structural design optimizing sizes of high-rise steel plane truss members by maximizing stiffness subjected to given volume constraints. The sizing optimum design is evaluated by using a well-known optimality criteria (OC) of gradient-based optimization methods. In typical size optimization methods, truss structures are optimized with respect to minimum weight with constraints on the value of some displacement and on the member stresses. The proposed method is an inversed size optimization process in comparisons with the typical size optimization methods since it maximizes stiffness associated with stresses or displacements subjected to volume constraints related to weight. The inversed approach is another alternative to classical size optimization methods in order to optimize members' sizes in truss structures. Numerical applications of a round shape steel pipe truss structure are studied to verify that the proposed maximum stiffness-based size optimization design is suitable for optimally developing truss members's sizes.

Algorithm Optimization of Inspection Sample Size Calculation for Improving Computation Time

Byung Hee Won,Hyun-Jo Kim,Ju-Ang Jung 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

A sample size calculation algorithm was developed in a prototype version to select inspection samples in domestic bulk handling facilities. This algorithm determines sample sizes of three verification methods satisfying target detection probability for defected items corresponding to one significant quantity (8 kg of plutonium, 75 kg of uranium 235). In addition, instead of using the approximation equation-based algorithm presented in IAEA report, the sample size calculation algorithm based on hypergeometric density function capable of calculating an accurate non-detection probability is adopted. The algorithm based the exact equation evaluates non-detection probability more accurately than the existing algorithm based on the approximation equation, but there is a disadvantage that computation time is considerably longer than the existing algorithm due to the large amount of computational process. It is required to determine sample size within a few hours using laptop-level performance because sample size is generally calculated with an inspector’s portable laptop during inspection activity. Therefore, it is necessary to improve the calculation speed of the algorithm based on the exact equation. In this study, algorithm optimization was conducted to improve computation time. In order to determine optimal sample size, the initial sample size is calculated first, and the next step is to perform an iterative process by changing the sample size to find optimal result. Most of the computation time occurs in sample size optimization process performing iterative computation. First, a non-detection probability calculation algorithm according to the sample sizes of three verification methods was improved in the iterative calculation process for optimizing sample size. A computation time for each step within the algorithm was reviewed in detail, and improvement approaches were derived and applied to some areas that have major effects. In addition, the number of iterative process to find the optimal sample size was greatly reduced by applying the algorithm based on the bisection method. This method finds optimal value using a large interval at the beginning step and reduces the interval size whenever the number of repetitions increases, so the number of iterative process is less than the existing algorithm using unit interval size. Finally, the sample sizes were calculated for 219 example cases presented by the IAEA report to compare computation time. The existing algorithm took about 15 hours, but the improved algorithm took only about 41 minutes using high performance workstation (about 22 times faster). It also took 87 minutes for calculating the cases using a regular laptop. The improved algorithm through this study is expected to be able to apply the sample size determination process, which was performed based on the approximate equation due to the complexity and speed issues of the past calculation process, based on the accurate equation.

은행의 대형화가 경영효율성에 미치는 영향: 상대적 규모를 중심으로

김은석,최종범 한국기업경영학회 2013 기업경영연구 Vol.20 No.6

본 연구는 은행의 대형화가 수익성, 리스크 및 비용효율성에 미치는 영향을 43개국 2,153개 은행을 대상으로 분석한 것이다. 실증분석 결과는 다음과 같다. 첫째, 은행이 대형화될수록 절대규모나 시스템 위험규모와 관계없이 수익성이 하락하고, 자본적정성이 악화되는 음(-)의 효과와 자산건전성은 개선되고, 비용효율성도 개선되는 양(+)의 효과가 존재하는 이중적인 효과가 있다. 둘째, 은행 대형화가 리스크에 미치는 영향은 국가별로, 규모별로, 리스크 종류별로 다르다. 소형은행의 경우, 대형화에 따라 수익성이 감소하고 자본적정성이 악화되지만 자산건전성과 비용효율성이 개선되는 효과는 얻을 수 있으나, 대형은행이 초대형화 되는 경우에는 수익성의 증가를 수반하지 않으면서 리스크만 커지는 결과를 초래하는 것으로 나타났다. 셋째, 절대규모를 기준으로 볼 때, 은행 대형화에 따른 규모의 경제효과는 존재하는 것으로 보이나, GDP 대비 80%를 초과할 정도의 초대형화의 경우 오히려 규모의 비경제가 나타났다. 은행의 대형화로 인해 리스크가 감소하는 효과는 모든 리스크 종류에 무관하게 항상 존재하는 것은 아니며, 특히 시스템 위험의 규모가 매우 큰 초대형은행의 경우 자본적정성 하락효과가 매우 큰 것으로 나타났다. 따라서, SIFI 등 바젤 III의 추가 자본규제는 필요하나, 시스템 위험규모를 기준으로 실시하는 것이 타당하며, 국가별 GDP 대비 60%∼80% 수준에서 수익성 하락을 최소화 하면서 리스크를 최소화 시킬 수 있는 최적자산규모가 존재할 수 있다. The existence of economies of scale implies that banks will be more profitable and less risky as they get larger in size. In the context of modern portfolio theory, one can reasonably expect that banks with large and diversified portfolios can save costs and afford to put less capital at risk. Extant literature, however, lacks definitive evidence demonstrating that economies of scale exist in the banking industry. In this paper, we empirically re-examine whether economies of scale exist in the banking industry. We add more risk measures to the z-score which was used commonly in the literature. Our measures of bank risks include capital adequacy, asset soundness, and liquidity. We also analyze the effects of relative bank size and absolute bank size. To incorporate each bank’s systemic risk into our analysis, we utilize global data on banks, and divide our sample banks into five groups. We sort each group by their asset size relative to the size of the GDP of each of the countries they belong to. Our sample period begins in 1997 and ends in 2012. Our sample covers data for a total of 2,153 banks operating in 43 countries. We employ panel regression methodology with the country fixed effects and the year fixed effects. The dependent variables used in this paper include return on asset, non-performing loan ratio, loan-reserve ratio, capital ratio, liquidity ratio and cost ratio. Our main independent variables include total assets, systemic asset size calculated by total asset divided by GDP, asset growth rate, GDP growth rate, and inflation rate. Our results can be summarized as follows. First, bank profitability measured by ROA (return on asset) decreases as asset size gets bigger, regardless of whether we use absolute size or relative systemic size. Second, we find mixed effects of bank size on risk measures. As a bank gets bigger, its capital adequacy ratio decreases, but other ratios, such as asset soundness ratio, liquidity ratio and cost ratio are increasing irrespective of whether size is measured by its total asset or systemic size. Third, the effects of bank size on the bank’s risks differ across countries. More importantly, they differ according to the bank’s systemic size. In the case of smaller banks, asset growth improves asset soundness and liquidity. However, in the case of systemically large banks whose asset size exceeds 80% of the GDP of its country, bank size growth increases bank risk while decreasing profitability. Fourth, economies of scale exist in all countries for all size groups of the sample banks except for systemically large banks, i.e., biga100 (which belong to the largest systemic size group and account for more than 80% of the GDPs of their respective countries). Systemically large banks (biga100) exhibit no economies of scale. In summary, we find that there are both positives and negatives resulting from growth in bank assets. As the size of bank assets grows, both the asset soundness ratio and liquidity ratio improve with a saving in cost, but the profitability ratio and capital adequacy ratio deteriorate. However, asset growth in systemically large banks is associated with increased risks, without achieving higher profits. Our results also imply that there exists an optimal asset size which can maximize profit and minimize risk. Our results indicate that the optimal asset size will lie somewhere between 60% and 80% of the GDP of the country to which a bank belongs. Investigating which factors result in cross-country differences is left for future research.

Multi-objective particle swarm optimization with dynamic population size

Shu Xiaoli,Liu Yanmin,Liu Jun,Yang Meilan,Zhang Qian 한국CDE학회 2023 Journal of computational design and engineering Vol.10 No.1

There are many complex multi-objective optimization problems in the real world, which are difficult to solve using traditional optimization methods. Multi-objective particle swarm optimization is one of the effective algorithms to solve such problems. This paper proposes a multi-objective particle swarm optimization with dynamic population size (D-MOPSO), which helps to compensate for the lack of convergence and diversity brought by particle swarm optimization, and makes full use of the existing resources in the search process. In D-MOPSO, population size increases or decreases depending on the resources in the archive, thereby regulating population size. On the one hand, particles are added according to local perturbations to improve particle exploration. On the other hand, the non-dominated sorting and population density are used to control the population size to prevent the excessive growth of population size. Finally, the algorithm is compared with 13 competing multi-objective optimization algorithms on four series of benchmark problems. The results show that the proposed algorithm has advantages in solving different benchmark problems.

케미컬 탱커선 운항노선별 최적선형에 관한 연구

김재호,김택원,우수한 한국항해항만학회 2015 한국항해항만학회지 Vol.39 No.6

This study objects to find characteristics in chemical tanker markets and to determine optimal chemical tanker size using a total shipping cost in main trading route of asia chemical tankers .Precedent studies of determination of the optimal ship size and case studies about chemical tankers was carried out and tried to introduce a cost model which is applicable to chemical tanker. This study is dependant on numerical analysis and involves scenario analysis to minimize sensitivity of results. This analysis shows as follows. First, 12,000DWT tanker is an optimal size on the 'Far East-Middle East' services, 9,000DWT tanker is a most competitive on the 'Far East-South East Asia' services and 3,000DWT tanker is a most economic size on the 'Inner Far East' services at average market situation. Second, the bigger size of chemical tanker, the more competitive advantage the tanker will obtain when bunker fuel prices rise. Small size ship gets more competitive during bunker prices down. Third, market fluctuation of time charter rate for chemical tanker is less than 20% against its average time charter hire which means less volatile. And tanker's competitiveness per each size is remained mostly same when time charterer rates rise at same proportion. Fourth, bigger size chemical tankers have cost advantages when tanker's quantity of each part cargo increase. And small-sized tanks are more competitive when part cargo scales decrease. For the last, ship's port stay strongly influences on the determination of the optical tanker size. When vessel has shorter port stay, bigger-sized tanker will be more competitive and even can be competitive if applies in short voyage as well. 본 연구는 아시아 케미컬 탱커 시장을 구성하는 수요 및 공급적 특성을 알아보고 케미컬 탱커선의 주요 비용을 파악하여 탱커시장의 주요 노선별로 최적선형을 제시하는 것이다. 따라서 본 연구는 선박 운항 상 비용분석에 관한 선행연구사례를 파악하고 케미컬 탱커 관련 연구를 통해 케미컬 탱커선에 적용 가능한 비용모델을 파악하였다. 또한 각 비용요소에 해당하는 데이터를 수치해석(Numerical Analysis)하고 연구결과의 민감도를 최소화하기 위해 시나리오 분석을 시행하였다. 그 결과 다음과 같이 다섯 가지의 시사점을 도출할 수 있다. 첫째, 연구대상 선형에서 평균적인 마켓상황을 가정했을 때, ‘극동-중동 노선’에서는 12,000DWT급 선형, ‘극동-동남아시아 노선’에서는 9,000DWT급 선형, 극동지역 내 에서는 3,000DWT급이 비용측면에서 경쟁력을 보일 수 있다. 둘째, 케미컬 탱커의 선박 사이즈가 커질수록, 연료의 가격이 상승함에 따른 경쟁우위가 높아지고 작은 사이즈의 경우 연료가격이 하락할 경우 경쟁우위가 높아지는 것으로 나타났다. 셋째, 케미컬 탱커의 용선료 변동은 호황기와 불황기의 표준편차가 20%미만으로 시황의 영향을 덜 받는 것으로 나타났으며, 비슷한 비율로 상승 시 사이즈별 경쟁력에는 큰 차이가 없는 것으로 나타났다. 넷째, 케미컬 탱커의 Parcelling의 규모가 커질수록 큰 사이즈의 케미컬 탱커가 경쟁력을 가지며 반대의 경우 작은 탱커의 경쟁력이 상승하는 것으로 나타났다. 마지막으로, 케미컬 탱커의 재항시간은 선박의 비용측면에 큰 영향을 미치는데 재항시간이 감소할 경우 큰 사이즈의 선박 경쟁력이 더욱 상승하여 보다 짧은 루트에 투입하여도 경쟁력이 있는 것으로 나타났다.

지방자치단체 적정규모에 대한 논의

김성희 ( Seong Hee Kim ) 한국정책연구원 2006 한국정책논집 Vol.6 No.-

효율성에 초점을 둔 지방정부 적정규모 논의에서 가장 일반적인 것이 최소비용접근이다. 최소비용접근에 따라 기능별, 지방자치단체 유형 별로 지방정부의 적정규모를 산출하여 보았다. 그 결과 첫째, 지방정부의 최소비용규모, 즉 적정규모는 지방정부규모의 평균적 규모보다는 큰 것으로 나타났으나 전반적으로 적용할 수 있는 적정규모는 확인하기 어려웠다. 둘째, 지방정부가 수행하는 많은 기능들의 적정규모는 제각기 다르게 나타났으며 각 기능들의 하위기능들도 최소비용을 가지는 규모가 각기 다르게 나타났다. 셋째, 지방자치단체 유형별로, 즉 시ㆍ군ㆍ구별로 적정인구규모는 현저하게 다르게 나타났으며 도시형인 시가 가장 큰 적정규모를 그 다음으로는 구(區)가, 농촌형인 군의 경우에는 적정규모가 상대적으로 작았다. 또한 농촌형의 지방자치단체에서는 기능별 적정규모의 차이가 작았으나 도시형의 자치단체인 시에서는 기능별 적정규모의 차이가 크게 나타났다. 따라서 효율성, 그 중에서도 규모의 경제라는 측면만을 고려한다면 지방자치단체의 규모를 현재 수준보다 광역화하는 것은 고려해 봄직한 대안이 될 수 있을 것이다. 그렇지만 자치단체 유형별로, 기능별로 적정규모가 다양하게 나타나고 있음을 감안할 때 지방자치단체간의 기능별로 행정적 협력 체제를 구축하는 것이 하나의 대안이 될 수 있을 것이다. 농촌형의 지방자치단체의 적정규모가 상대적으로 도시의 그것보다 작게 나타나고 도시형의 지방자치단체의 기능별 적정 규모의 차이가 크게 나타난다는 사실에서 적정규모에 관한 논의는 지역적 특성에 맞추어서 접근하여야 한다. 최소비용 접근은 일률적으로 적용하기에는 많은 한계를 가진 방법으로 적정규모를 산출하는 여러 요소 중 하나일 뿐이다. 적정규모의 파악은 지역의 기능, 생활의 질, 도시의 계층 등 다원적인 접근으로 이루어져야 한다. 일단 적정규모가 산정되더라도 이를 구체화하는 데는 지역 주변 환경과 역사ㆍ사회적 상황을 고려한 입지적 측면의 분석이 필요하다. This study aims at estimating optimal size of local governments. Through the minimum costs approach (economy of scale), optimal sizes are estimated. The results of study are as follows. First, Optimal sizes estimated are larger than average size of local governments. But it is not confirmed that one optimal size will be able to apply with the most of the governments, Second, each function that local governments carry out has different optimal size. Subfunctions that consist of each function have different optimal size. Third, All the types of local governments is different in the minimum cost of government services. So optimal sizes are different from each other. The optimal size Si(City) government is the largest. Gu(sub metropolitan area) has larger size than Gun(rural area). This analysis suggests expansion of local government area. But as optimal size is different in type of governments and functions, we suggest local government cooperation system that carries out each specific function. And determining optimal size of local governments, we should examine many factors such as functions of region, quality of life, class of cities.

고층 트러스 철골구조 시스템의 단면치수 재조정 최대강성 이산화 최적설계

이동규(Lee Dong-Kyu),신수미(Shin Soo-Mi),박성수(Park Sung-Soo) 대한건축학회 2009 大韓建築學會論文集 : 構造系 Vol.25 No.6

This study presents a structural design optimizing sizes of high-rise steel plane truss members by maximizing stiffness subjected to given volume constraints. The sizing optimum design is evaluated by using a well-known optimality criteria (OC) of gradient-based optimization methods. In typical size optimization methods, truss structures are optimized with respect to minimum weight with constraints on the value of some displacement and on the member stresses. The present method is an inversed size optimization in comparisons with the typical size optimization methods since it maximizes stiffness associated with stresses or displacements subjected to volume constraints related to weight. The inversed approach is another alternative to classical size optimization methods in order to optimize members' sizes in truss structures. Numerical applications of a round shape steel pipe truss structure are studied to verify that the proposed maximum stiffness-based size optimization design is suitable for optimally developing truss members's sizes.

고층 트러스 구조물의 최대강성 치수최적설계

신수미(Shin Soo-Mi),오주연(Oh Joo-Yeon),박성수(Park Sung-Soo),이동규(Lee Dong-Kyu) 대한건축학회 2007 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.27 No.1

This study presents a structural design optimizing sizes of high-rise steel plane truss members by maximizing stiffness subjected to given volume constraints. The sizing optimum design is evaluated by using a well-known optimality criteria (OC) of gradient-based optimization methods. In typical size optimization methods, truss structures are optimized with respect to minimum weight with constraints on the value of some displacement and on the member stresses. The present method is an inversed size optimization in comparisons with the typical size optimization methods since it maximizes stiffness associated with stresses or displacements subjected to volume constraints related to weight. The inversed approach is another alternative to classical size optimization methods in order to optimize members' sizes in truss structures. Numerical applications of a round shape steel pipe truss structure are studied to verify that the proposed maximum stiffness-based size optimization design is suitable for optimally developing truss members's sizes.

Optimization of spatial truss towers based on Rao algorithms

Maksym Grzywiński 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.81 No.3

In this study, combined size and shape optimization of spatial truss tower structures are presented by using new optimization algorithms named Rao-1, and Rao-2. The nodal displacements, allowable stress and buckling for compressive members are taken into account as structural constraints for truss towers. The discrete and continuous design variables are used as design variables for size and shape optimization. To show the efficiency of the proposed optimization algorithm, 25-bar, and 39-bar 3D truss towers are solved for combined size and shape optimization. The 72-bar, and 160-bar 3D truss towers are solved only by size optimization. The optimal results obtained from this study are compared to those given in the literature to illustrate the efficiency and robustness of the proposed algorithm. The structural analysis and the optimization process are coded in MATLAB programming.

Optimization and Performance Evaluation of the Median Modified Wiener Filter Algorithm in Breast Electromagnetic X-ray Image

Yunhee Mo,Seong-Hyeon Kang,Youngjin Lee 한국자기학회 2023 Journal of Magnetics Vol.28 No.4

The mask size of the median modified Wiener filter (MMWF) algorithm was optimized for application to digital mammographic phantom images obtained under different tube currents to obtain an optimal image by removing noise with a minimal dose of radiation. A simulation was conducted using the Female Adult Mesh (FASH) phantom to optimize the mask size of the MMWF algorithm. The optimal mask size was determined by measuring various evaluation factors and applying different mask sizes to the noisy image of the various evaluation phantom. An American College of Radiology (ACR) phantom image was obtained per milliamperes using digital mammography equipment to evaluate the MMWF algorithm with the optimal mask size. Based on the noise level and similarity evaluation factors, the optimal mask size for the MMWF algorithm was 7 × 7. The results of the experiment indicated that improvements in the noise level evaluation factors were most noticeable for the MMWF, followed by the median, Gaussian, and Wiener filters. Overall, we confirmed that the optimal mask size for the MMWF algorithm was 7 × 7 for application to digital mammographic images, and its effectiveness was proven through a comparative evaluation with conventional filters.