• 설비공학논문집
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• 제17권4호
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• pp.386-395
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• 2005

With the development of a living standard, the importance of indoor air conditioning system in all kinds of buildings and vehicles has increased. A lot of researches on energy losses in a duct and various kinds of flow pattern in branches or junctions have been carried out over many years, because the primary object of a duct system used in HVAC is to provide equal flow rate in the interior of each room by minimizing pressure drop. In this study, to get equal flow distribution in each branch, a blockage is applied to the rectangular duct system. The flow analysis for flow distribution of a rectangular duct with two branches was performed by CFD. By using SIMPLE algorithm and finite volume method, flow analysis is performed in the case of 3-D, incompressible, turbulent flow. Also, the standard $k-{\varepsilon}$ model and wall function method were used for analysis of turbulent fluid flow. The distribution diagrams of static pressure, velocity vector, turbulent energy and kinetic energy in accordance with variation of Reynolds number and blockages location in a rectangular duct show that flow distribution at duct outlets is improved by a blockage. In this rectangular duct system, mean velocity and flow rate distribution in two branch outlets are nearly constant regardless of variation of Reynolds number, and a flow pattern of the internal duct has a same tendency as well.

• 한국작물학회지
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• 제27권2호
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• pp.141-146
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• 1982

Hop의 증수를 위한 재배기술의 일환으로 적심효과를 검토하고자 무적심, 1회적심, 2회적심, 3회적심의 적심방법 시험을 1979년에 실시하였고, 무적심, 5월 14일 적심(주경 3절위 신장시), 5월 19일 적심(주경 4절위 신장시), 5월 24일 적심(주경 5절위 신장시), 5월 29일 적심(주경 6절위 신장시)의 주경적심시험을 1980년에 실시하였던 바, 그 결과를 요약하면 다음과 같다. 1. 무적심에 비하여 적심회수가 거듭되거나 적심시기가 늦어질수록 영양생장기간 및 개화기가 지연되었다. 2. 주경적심처리는 무적심보다 만장과 총측지수 적었으나 측지 생육이 촉진되어 조기 적심일수록 만중이 증가되었을 뿐만 아니라, 주경 10절위 이하에서도 구화가 착생되어 착화측지수가 증가되었다. 3. 조기적심일수록 무적심에 비하여 10절위 이상 20절위 이하의 측지장이 현저히 길어져 착화측지당구화수 및 주당 구화수가 증가되어 12-43%의 증수를 가져왔다. 4. 만기적심(5월 29일 적심)은 적심 후에서 모화기까지의 일수가 짧아 무적심보다 착화측지수가 적었고, 측지장이 짧아 주당 구화수가 적었으며 100구화중도 가벼워 무적심보다 20% 감수되었다.

• International Journal of Air-Conditioning and Refrigeration
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• 제11권2호
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• pp.51-60
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• 2003

In the nuclear power plant, emergency core coolant system (ECCS) is furnished at reactor coolant system (RCS) in order to cool down high temperature water in case of emergency. However, in this coolant system, thermal stratification phenomenon can occur due to coolant leaking in the check valve. The thermal stratification produces excessive thermal stresses at the pipe wall so as to yield thermal fatigue crack (TFC) accident. In the present study, effects of turbulence penetration on the thermal stratification into T-branches with square cross-section in the modeled ECCS are analysed numerically. Standard k-$\varepsilon$ model is employed to calculate the Reynolds stresses in momentum equations. Results show that the length and strength of thermal stratification are primarily affected by the leak flow rate of coolant and the Reynolds number of duct. Turbulence penetration into the T-branch of ECCS shows two counteracting effects on the thermal stratification. Heat transport by turbulence penetration from main duct to leaking flow region may enhance thermal stratification while the turbulent diffusion may weaken it.

• 대한치과의사협회지
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• 제50권10호
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• pp.624-629
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• 2012

This study examined the anatomical relationships along with the variability of the facial nerve trunk and its branches with an emphasis on the intraparotid connections between the divisions. And histomorphometric observations of the facial nerve branches and fascicles were performed on 40 Korean half-heads. The facial nerve trunk was bifurcated into two main divisions(35/40, 87.5%) and the other five cases were divided into a trifurcation pattern. According to the origin of the buccal branch, the branching patterns of the facia l nerve were classified into four categories. Communications between the facial and auriculotemporal nerve branches were observed in 37 out of 40 cases(92.5%). In the histological observation, the buccal branch had the greatest number of branches(3.47), however the zygomatic branch had the largest diameters(0.93mm). This detailed description of the facial nerve anatomy wi ll provide useful information for surgical procedures such as a tumor resection. a facial nerve reconstruction, autonerve graft. and facelift.

• Industrial Engineering and Management Systems
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• 제3권2호
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• pp.92-99
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• 2004

We consider the ATM switching node location problem (ANLP). In this problem, there are two kinds of facilities, hub facilities and remote facilities, with different capacities and installation costs. We are given a set of customers with each demand requirements, a set of candidate installation sites of facilities, and connection costs between facilities. We need to determine the locations to place facilities, the number of facilities for each selected location, the set of customers who are connected to each installed hub via installed remote facilities with minimum cost, while satisfying demand requirements of each customer. We formulate this problem as a general integer programming problem and solve it to optimality. In this paper, we present a preprocessing procedure to tighten the formulation and develop a branch-and-price algorithm. In the algorithm, we consider the integer knapsack problem as the column generation problem. Computational experiments show that the algorithm gives optimal solutions in a reasonable time.

• Structural Engineering and Mechanics
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• 제74권6호
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• pp.809-819
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• 2020

For the first time, the influence of in-plane magnetic field on wave propagation of Graphene Nano-Platelets (GNPs) polymer composite nanoplates is investigated here. The impact of three- parameter Kerr foundation is also considered. There are two different reinforcement distribution patterns (i.e. uniformly and non-uniformly) while the material properties of the nanoplate are estimated through the Halpin-Tsai model and a rule of mixture. To consider the size-dependent behavior of the structure, Eringen Nonlocal Differential Model (ENDM) is utilized. The equations of wave motion derived based on a higher-order shear deformation refined theory through Hamilton's principle and an analytical technique depending on Taylor series utilized to find the wave frequency as well as phase velocity of the GNPs reinforced nanoplates. A parametric investigation is performed to determine the influence of essential phenomena, such as the nonlocality, GNPs conditions, Kerr foundation parameters, and wave number on the both longitudinal and flexural wave characteristics of GNPs reinforced nanoplates.

• Advances in Energy Research
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• 제5권2호
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• pp.129-145
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• 2017

In this study, the use of a micro gas turbine system using biogas to supply heating, cooling and electricity loads of a rural building located in rural area around Tehran has been studied. Initially, the amount of energy needed by the farmhouse was calculated and then the number of needed microturbines was determined. Accordingly, the amount of substances entering biogas digester as well as tank volume were determined. The results of this study showed that village house loads including electrical, heating and cooling and hot water loads can be supplied by using a microturbine with a nominal power of 30 kW and $33.5m^3/day$ of biogas. Digester tank and reservoir tank volumes are $67m^3$ and $31.2m^3$, respectively. The cost of electricity produced by this system is 0.446 US$/kWh. For rural area in Iran, this system is not compatible with micro gas turbine and IC engine system use urban natural gas due to low price of natural gas in Iran, but it can be compatible by wind turbine, photovoltaic and hybrid system (wind turbine& photovoltaic) systems.

• 대한기계학회논문집A
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• 제34권2호
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• pp.191-201
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• 2010

본 연구는 비스플라인 근사기법을 사용한 분지한계법 기반의 새로운 전역 최적화 알고리즘에 관한 것이다. 본 연구에서는 알고리즘 구성 요소 및 이들의 구현 내용에 관한 상세히 설명한다. 핵심 요소로서, 상호분리되는 부공간으로의 설계 공간의 분할 작업이 있고, 이들 분할 부공간의 한계값 계산 작업이 있는데, 이들 모두는 실수형 비스플라인 볼륨모델에 의해 구현된다. 본 연구 알고리즘은 다양한 테스트 문제들을 가지고 해의 정확성, 함수호출 회수, 알고리즘 수행시간, 메모리 사용량, 알고리즘 수렴성 등 그 계산 성능들을 평가한다. 이러한 평가 결과는 제안 알고리즘이 직관에 의존하지 않는 완전 알고리즘이며, 대용량의 최적화 문제에도 높은 가능성이 있음을 보여주는 것이다.

• Journal of Mechanical Science and Technology
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• 제20권7호
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• pp.1030-1042
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• 2006

An experimental study has been performed to investigate the off-take phenomena at the header-feeder systems (horizontal header pipe with multiple feeder branch pipes) in a CANDU (CANadian Deuterium Uranium) reactor with the branch orientation varies ${\pm}36^{\circ}\;or\;{\pm}72^{\circ}$. In order to evaluate the applicability of the conventional correlations used in the safety analysis code, RELAP5-Mod3, the test facility is designed with the 1/2 scale of the. CANDU 6. It was found that the data set for the top, bottom and side branches are in a good agreement with the correlations used. However, for the specific angled branches, ${\pm}36^{\circ}\;and\;{\pm}72^{\circ}$, the onsets of off-take data and quality data showed large deviation with the conventional model inside RELAP5-MOD3. Furthermore, based on the uncertainty analysis, the conventional 2.5 power law needs to be modified. The present experimental data set can be useful for the construction of the general correlation considering the arbitrary branch orientation.

• Steel and Composite Structures
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• 제28권6호
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• pp.681-690
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• 2018

This paper highlights results of some experimental work that deals with strengthening of bolted shear joints in thin-walled ferrocement structure where steel wires, bent into U-shape are considered as simple inserts around the bolt hole. The parameters investigated include the number of layers of wire mesh, edge distance of bolt hole, size and location of the inserts. Test results have shown that for small edge distance, failure occurred either in cleavage or shearing mode, and the strength of the joint increased with an increase in the edge distance. This continued up to an upper limit set by either tension or bearing failure. The experimental study further revealed that for a given edge distance the strength of a joint can significantly be enhanced by using U-inserts. The equations developed for predicting joint strength in ferrocement composites can also be modified to include the effects of the inserts with a good level of accuracy.