• International Journal of Automotive Technology
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• 제7권3호
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• pp.283-288
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• 2006

A mathematical methodology is proposed for designing nozzle hole shapes producing controlled geometric cavitation. The proposed methodology uses an unstructured RANS flow solver, with the ability to compute sensitivity derivatives via an adjoint algorithm. The adjoint formulation for the N-S equations is presented while variation of the turbulence viscosity is not taken into account during the geometry modifications. The sensitivities are calculated in a mode independently of the shape parameterisation. The method is used to develop and evaluate conceptual shapes for nozzle hole cavitation reduction. The localized region at the hole inlet producing cavitation, is parameterised using its radius of curvature, while a cost function is formulated to eliminate the negative pressures present at this location. Sensitivity derivatives are used to assess the dependence of the localized region on the minimum pressure, and to drive the geometry to the targeted shape. The results show that the computer model can provide nozzle hole entry shapes that produce predefined flow characteristics, and thus can be used as an inverse design tool for nozzle hole cavitation control.

• International Journal of Internet, Broadcasting and Communication
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• 제14권3호
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• pp.63-68
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• 2022

Two wavelength reconfigurable optical nodes are designed. One for 20km or shorter link length, and the other for up to 60km link length. While the first one requires no dispersion compensation, the latter needs dispersion compensation fiber included in the node, which requires additional optical amplifier to compensate the insertion loss of DCF. We calculate all the optical path losses in both cases using the typical value of optical components in the market to see the feasibility of the designed optical node. The minimum received power in the node is calculated to be -21.5dBm without DCF and -12.5dBm with DCF, respectively. These received powers are above the receiver sensitivity both for OC-48 and OC-192 according to the previous work.

• Earthquakes and Structures
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• 제9권6호
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• pp.1337-1353
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• 2015

Seismic upgrading of existing structures is a technical and social issue aimed at risk reduction. Sustainable design is one of the most important challenges in any structural project. Nowadays, many retrofit strategies are feasible and several traditional and innovative options are available to engineers. Basically, the design strategy can lead to increase structural ductility, strength, or both of them, but also stiffness regulation and supplemental damping are possible strategies to reduce seismic vulnerability. Each design solution has different technical and economical performances. In this paper, four different design solutions are presented for the retrofit of an existing RC frame with poor concrete quality and inadequate reinforcement detailing. The considered solutions are based on FRP wrapping of the existing structural elements or alternatively on new RC shear walls introduction. This paper shows the comparison among the considered design strategies in order to select the suitable solution, which reaches the compromise between the obtained safety level and costs during the life-cycle of the building. Each solution is worked out by considering three different levels of seismic demand. The structural capacity of the considered retrofit solutions is assessed with nonlinear static analysis and the seismic performance is evaluated with the capacity spectrum method.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 추계학술발표대회 논문집
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• pp.99-104
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• 2011

This paper describes a design strategy at conceptual design stage using RETScreen software tool for building application of renewable energy resources. Currently, government and public buildings are required to adopt renewable energy systems with a minimum requirement for the amount of renewable energy supply. Meanwhile, there is a certificate program for private office buildings to enhance propagation of renewable energy systems. When considering application of renewable energy systems to a building, it is worthwhile developing a method to determine optimal design sizes of renewable energy systems. In the paper, a design strategy is introduced with a couple of case studies to determine optimal capacities of each renewable energy system in a building and suggest to use the method to evaluate the system for the building certificate program and the mandatory renewable target program. Objective functions considered in the study are initial system cost and reduction of CO2 emissions from the system. In the optimization study, it is assumed that solar thermal collectors are installed to satisfy solar fraction of 60%. Other renewable energy systems such as ground-source heat pump, solar PV and non-renewable systems such as electric chiller and gas-fired boiler are sized using an optimal sizing method with RETScreen suggested the authors previously.

• 한국구조물진단유지관리공학회 논문집
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• 제9권1호
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• pp.259-269
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• 2005

본 연구에서는 철근콘크리트 연속보의 이산최적설계를 수행하기 위해서 유전알고리즘을 적용하였다. 콘크리트, 거푸집, 주철근 및 스터럽의 경비를 포함한 경비 최소화를 목적함수로 하였고, 제약조건으로는 휨강도와 전단강도, 처짐, 균열, 철근간격, 피복두께, 철근비 상 하한치 및 단면형상에 대한 기하학적 제약조건과 더불어 주철근의 정착을 고려하였다. 보의 폭과 유효깊이, 철근량을 설계변수로 취하였으며, 설계변수 값은 실무에서 사용되는 단면치수와 철근량을 데이터베이스화한 이산집합으로부터 선택되도록 하였다. GA의 신뢰성을 검증하기 위해서 이산변수로 철근콘크리트보에 대한 최적설계를 수행한 기존 문헌과 그 결과값을 비교 검토하였으며, GA의 적용성 및 효율성을 보이기 위하여 국내 구조설계기준을 만족하는 3경간 및 5경간 철근콘크리트보에 대해 이산최적설계를 수행하였다.

• 가정과삶의질연구
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• 제23권2호
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• pp.11-22
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• 2005

The purpose of this study is 1) to clarify that the house is no long the safe place through the cases of the senior safety accidents and to argue the need for housing repair and 2) to present the minimum standards for housing repair by comparing the cases here as well as the abroad and to back up the standards with the current senior housing environment 300 people at least 60 years old living in Seoul$\cdot$Metropolitan area were interviewed using the structured questionnaire. As the result, the following conclusions were made: 1. There was high accident rates of the senior residents due to physical deficits within the house, causing excessive medical cost and decreased housing satisfaction. This problem can be sufficiently prevented by housing repair which can not only solve the safety problem but also support self sufficient living for the senior residents. 2. Proper housing repair required the architectural know how as well as the expertise knowledge of the physical characteristics of the senior people. Therefore, it is essential to secure the professional (i.e., occupational therapist) who can analyze the needs of the senior residents and evaluate and/or predict the obstacles during repair. Furthermore, development and distribution of the standardized manual are also needed. 3. The minimum standard for housing repair could be approached in view of 'barrier-free' concept. First, the bumps should be removed, slippery prevented, and safety grab-bar installed for safety. Second, the entrance should be widened and the bathroom and kitchen restructured to support for the senior residents' self sufficiency. To make housing repair policy more efficient, the legal basis is required. It can be incorporated into the existing senior citizens 'Welfare Act' or the 'Senior Residents Medical Insurance' which will be effective starting in 2007.

• Journal of Mechanical Science and Technology
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• 제18권12호
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• pp.2182-2189
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• 2004

In the recent years, environmentally conscious design and manufacturing technologies have attracted considerable attention. The coolants, lubricants, solvents, metallic chips and discarded tools from manufacturing operations will harm our environment and the earth's ecosystem. In the present work, the Tukey method of multiple comparisons is used to select the minimum level of coolant required in a turning process. The amount of coolant is varied in 270 designed experiments and the parameters cutting temperature, surface roughness, and specific cutting energy are carefully evaluated. The effects of coolant mix ratio as well as the amount of coolant on the turning process are studied in the present work. The cutting temperature and surface roughness for different quantity of coolant are investigated by analysis of variance (ANOVA) - test and a multiple comparison method. ANOVA-test results signify that the average tool temperature and surface roughness depend on the amount of coolant. Based on Tukey's Honestly Significant Difference (HSD) method, one of the multiple comparison methods, the minimum level of coolant is 1.0 L/min with 2% mix ratio in the aspect of controlling tool temperature. F-test concludes that the amount of coolant used does not have any significant effect on specific cutting energy. Finally, Tukey method ascertains that 0.5 L/min with 6% mix ratio is the minimum level of coolant required in turning process without any serious degradation of the surface finish. Considering all aspects of cutting, the minimum coolant required is 1.0 L/min with 6% mix ratio. It is merely half the coolant currently used i.e. 2.0 L/min with 10% mix ratio. Minimal use of coolant not only economically desirable for reducing manufacturing cost but also it imparts fewer hazards to human health. Also, sparing use of coolant will eventually transform the turning process into a more environment-conscious manufacturing process.

• 한국수자원학회논문집
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• 제49권5호
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• pp.431-438
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• 2016

역삼투 해수 담수화 공법의 주요 단점으로 여겨지고 있는 에너지 소비량을 줄이기 위한 방편으로 해안선을 통하여 바다로 유출되는 담수 지하수를 활용하여 낮은 염도의 원수를 확보하는 방안을 제시하였다. 저 염도 지하 염수는 담수화 비용 뿐 아니라 표류 해수 취수의 알려진 단점을 극복하는 데도 유리하다. 지하 염수의 염도는 해안선을 통하여 바다로 유출되는 담수 지하수량의 영향을 크게 받는다. 본 연구에서는 담수화 시설에 필요한 수량을 최저 염도로 충족시킬 수 있는 지하 염수 관정의 위치 및 양수량 분포를 산정할 수 있는 최적 전산설계모델을 개발하였다. 해안 지역에서 지하 염수를 개발하면 대수층으로 해수가 추가 침투하여 다른 사용자의 지하수 관정을 오염시킬 수 있다. 본 모델은 지하 염수 관정의 최적 설계 시에 기존 지하수 관정을 해수 침투로부터 보호할 수 있도록 구성되었다.

• Current Research on Agriculture and Life Sciences
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• 제21권
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• pp.23-29
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• 2003

Worldwide consumption of vegetable soybean bas been increasing recently, hence it is necessary to produce good quality of soybean in our farms. In the process of vegetable soybean production threshing and seperation work accounts for about 80% of overall labor. Therefore, developing of the vegetable soybean thresher is necessary to reduce the cost of labor. The purpose of this study is to acquire the basic informations to design of the vegetable soybeans-thresher. We make the experimental system which measure the physical properties and investigate the detachment forces. Also, We calculated the minimum speed of threshing cylinder. The result are as follows; 1. The average length of soybean stem is 68.2cm. 2. The length of soybean pods are seen as 61.3mm for 3 grain, 52.6mm fer 2 grains and 41.0mm fer 1 grain 3. The widths of soybean pods are seen as 14.1mm fer 3 grain, 13.8mm fer 2 grains and 13.4mm fer 1 grain. 4. The weights of soybean pods are seen as 4.1grams for 3 grains, 2.7grams for 2 grains and 1.4grams for 1 grain. 5. The average detachment forces of pods are seen as 1.5kgf for 3 grains, 1.2kgf for 2 grains and 0.8kgf for 1 grain respectively For 1 grain, the detachment force of pods ranges from 0.2kgf to 1.4kgf. For 2 grains, the minimum detachment force of pods is seen as 0.6kgf and the maximum one is seen as 2.5kgf. For 3 grains, the minimum detachment force of pods is seen as 0.7kgf and the maximum one is seen as 2.7kgf. 6. The minimum speed of threshing cylinder is shown 6.83m/s.

• 조명전기설비학회논문지
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• 제24권8호
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• pp.40-47
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• 2010

Micro Grid(MG)는 새로운 개념의 전력시스템으로 Smart Grid 기술의 일환으로 관심을 받고 있다. 기본적인 MG의 개념은 신/재생에너지를 포함한 분산전원의 도입 및 효율적인 계통운영이지만 여기에는 전력공급의 신뢰성과 경제성이 배제될 수 없는 요소임은 확실하다. MG라는 새로운 계통의 개념을 도입하는데 있어서 기존 전력계통(Utility Grid)과의 간섭, 신뢰도 및 전력품질의 문제들이 해결해야 하는 숙제로 떠오르고 있는데 이에 대한 대안 중 하나가 에너지저장기술이다. 그러나 본 기술은 아직까지는 초기투자비 및 운영유지비가 매우 높은 수준이기 때문에 MG의 설계에 있어서 신뢰도와 경제성을 함께 고려한 Energy Storage System(ESS)의 설치방법이 필요로 된다. 이에 본 논문에서는 공급신뢰도기준을 충족할 수 있는 ESS의 최소필요용량 및 적정투자시점을 결정하는 확률론적 방법을 제안하고 이에 대한 사례연구를 수행하였다.