• 대한기계학회논문집
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• 제1권2호
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• pp.65-72
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• 1977

Major problems in the design and use of refief valve are (a) chattering because of instability, (b) excessive pressure differential which makes the valves crack far below maximum pressure diminishing useful flow in the system. In this study, A magnet-coupled relief valve is investigated theoretically and experimentally in order to improve the performance of a conventional direct type reliefvalve. A theory is developed to predict the performance, response, and stability of the magnet-coupled valve taking into account the delivery line response. In the experiment, a typical magnet-coupled relief valve is designed on the basis of the analytical results; the discharge rates are measured varying the supply pressure, and both the pressure-time curves and valve displacament-time curves are recorded providing the supply pressures greater than the setting pressure. The measured override characteristic curves are then compared with those of conventional pilot type and direct type releif valves. It is showm that the excessive pressure differential of a magnet-coupled relief valve becomes less than that of a conventional direct type valve. It is also shown that the most important chatacteristic of a magnet-coupled relief valve is to eliminate valve chattering due to instability regardless of the magnitude of setting pressures and discharge rates, which suggests wide applications of the idea of the use of a magnet in the design of hydraulic valves.

• 대한산업공학회지
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• 제31권4호
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• pp.303-315
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• 2005

In this paper we address a design problem for hub-and-spoke networks and then consider a capacitated hub locations problem with direct shipment (CHLPwD). We determine the location of hubs, the allocation of nodes to hubs, and direct shipment paths in the network, with the objective of minimizing the total cost in the network. In this paper, CHLPwD is formulated as 0-1 integer programming. We develop an evolutionary algorithm here to solve the large sized CHLPwD. To do this, we present the representation and the genetic operators suitable for the problem and propose a heuristic method for the allocation of nodes to hubs. To enhance the search capability, problem-specific information is used in our evolutionary algorithm. The proposed algorithm is compared with the heuristic method in terms of solution quality and computation time. The experimental results show that our algorithm can provide better solutions than the heuristic.

• 한국위성정보통신학회논문지
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• 제10권4호
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• pp.113-116
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• 2015

건물 외부에 설치된 각종 기상 측정센서에서 전송된 현재의 외부 기상조건과 일자별, 특수일별 건물 에너지 사용량과의 관계를 인공지능기법으로 분석하고 학습을 통한 예측기능을 갖도록 함으로써, 일자별, 특수일별, 계절별 그리고 기상조건에 따른 익일 전력 사용량을 예측하고 이에 따른 부하의 On/Off 우선순위를 결정하는 기능을 갖는 지능형 직접부하제어 시스템 구조를 설계한다.

• 전기학회논문지
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• 제67권11호
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• pp.1555-1561
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• 2018

Tracking and detecting targets by the millimeter wave seeker is affected by movement of platform. Stabilization equipments use an inertial sensor to compensate for disturbance of stabilizing gimbal or platform. In the direct line of sight stabilization system, an inertial sensor is mounted on inner gimbal to compensate the disturbance directly, so the performance is excellent and the implementation method is simple. However gimbal design requires somewhat larger volume. Since an inertial sensor is mounted on gimbal base in the indirect line of sight stabilization system, additional space of gimbal is not required for the gimbal design. However, this method does not directly compensate for the disturbance of the line of sight stabilization axis, which can degrade performance. In order to perform the tracking performance, two methods are analyzed for line of sight stabilization performance based on direct and indirect of a 2-axis gimbaled servo system for millimeter wave seeker in this study. The simulation and experimental results validate the performance comparison of two methods.

• 한국수소및신에너지학회논문집
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• 제24권5호
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• pp.401-412
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• 2013

The paper is to study on the simulation of the micro/macroscale thermo-electrochemical model of a single cell of anode-supported SOFC with direct internal reforming. The coupled heat and mass transport, electrochemical and reforming reactions, and fluid flow were simultaneously simulated based on mass, energy, charge conservation. The micro/macroscale model first calculates the detailed electrochemical and direct internal reforming processes in porous electrodes based on the comprehensive microscale model and then solve the macroscale processes such as heat and mass transport, and fluid flow in SOFCs with assumption of fully-developed flow in gas channel. The simulation results evaluate the overall performance by analyzing distributions of mole fraction, current density, temperature and microstructural design in co/counter flow configurations.

• 터널과지하공간
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• 제5권2호
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• pp.104-113
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• 1995

Shear strength of the discontinuity on which the pre-failure of rock slope was occurred during surface excavation was measured through the direct shear test using core samples obtained in-situ. Internal friction angle was increased as the roughness of discontinuity surface(JRC) was increased. Results of the tilt test using core samples of higher JRC also showed very similar trend as those of the direct shear test. When the samples replicated from natural cores were used int he tilt test, results of friction angles showed almost perfect continuation of the residual friction angles from the direct shear test. However, when the gouge material existed in the discontinuity the internal friction angle strongly depended upon the rate of filling thickness to the height of asperity irrespective of the JRC. Based on the results of both direct shear test and tilt test internal friction angle and cohesion of discontinuity, which reflect the in-situ conditions fo pre-sliding failure and also can be used for the optimum design of support system, were assessed. Two kinds of support measures which were expected to increase the stability of rock slope were considered; lowering of slope face angle and installation of rock cable. But, it was found that the first method might lead to more unstable conditions of rock slope when the cohesion of discontinuity plane was negligibly low and in that case the support systems of any kind which could exert actual resisting force were needed to ensure the permanent stability of rock slope.

• 한국기계가공학회지
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• 제15권2호
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• pp.1-8
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• 2016

Generally, electrical circuits are fabricated as Printed Circuit Boards (PCBs) and mounted on the casing of the product. Additionally, this requires many other parts and some labor for assembly. Recently, molding technology has increasingly been applied to embed simple circuits in plastic casing. The technology is called a Molded Interconnected Device (MID). By using this technology, PCB fabrication can be replaced by molding, and much of the corresponding assembly process for PCBs can be eliminated if the circuit is simple enough for molding. Furthermore, as the improvement of conductive materials and printing technologies of simple electric circuits can be printed directly on the casing part, this also reduces the complexity of the product design and production cost. Therefore, this paper introduces a new MID fabrication process using direct 3D printing technology. Additionally, it is applied to an automotive part of a cruise control switch. The methodology and design are shown.

• 한국의류학회지
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• 제45권5호
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• pp.741-757
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• 2021

In addition to direct sales to consumers, the direct-to-consumers (D2C) strategy, which provides specialized experiences and services, communicates closely with a consumer's perspective. This tendency is related to the recent trend wherein the luxury fashion system is being transformed into a new luxury. Therefore, this study analyzes the development of online D2C platforms and investigates the characteristics of new luxury from the functional, symbolic, and experiential dimension perspectives based on mobile apps, which is becoming increasingly important among online D2C platforms. Based on the study results, the premium of new luxury fashion displayed in Louis Vuitton's mobile D2C platform in terms of product utility and functionality is newly defined as a usable luxury experience. Moreover, from the heritage perspective, based on the cultural sympathy of the brand contents, we determine that an attachment can be formed between new luxury fashion consumers and brands. Additionally, the personalization service and experiential content on the D2C platform can directly afford emotional and bonding induced brand immersion in a playful way.

• 대한치과보철학회지
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• 제14권1호
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• pp.66-71
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• 1976

The purpose of this investigation was to evaluate the mouth preparation and design of removable partial dentures. A total of 187cases for the prefabricated partial denture frameworks in both maxillary and mandibular semi-dentulous situations (66 cases and 203 cases) was selected from this study. The evaluations of mouth preparation and design observed here involved the classification of edentulous spaces, status of abutment splinting with location, design of direct retainer and structure of maxillary major connector according to the incidence of both dental arches, ages, sexes and segment of semidentulousness. The analyzed results were as follows: 1) The order of frequency rate in removable partial denture construction was Class II (50.27%), Class I (36. 90%), Class III (10.69%), and Class IV (2.14 %). 2) The distribution on design of maxillary removable partial denture prosthesis was 33.22% and 64.11% in mandibular removable partial denture prosthesis. 3) The age distribution of removable partial denture prosthesis was prominent after40 years (41.71%). 4) The design pattern of maxillary major connectors was in order of anteroposterior bar, single palatal bar, palatal strap, U-shape connector. 5) The design pattern of direct retainer was in order of Aker's clasp, I-bar clasp, backaction clasp, cuspid universal clasp. 6) The abutment for partial denture clasp splinted between premolar and premolar and its frequency rate revealed 53.44%. 7) It seemed that the location and design of the indirect retainer showed accepatble limit.

• 물과 미래
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• 제9권2호
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• pp.76-86
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• 1976

The 30-year design flood hydrograph for the Musim Representative Basin, one of the study basins of the International Hydrological Program, is synthesized by the method of unit hydrograph. The theory of unit hydrograph has been well known for a long time. However, the synthesis of flood hydrograph by this method for a basin with insufficient hydrologic data is not an easy task and hence, assumptions and engineering judgement must be exercized. In this paper, the problems often encountered in applying the unit hydrograph method are exposed and solved in detail based on the theory and rational judgement. The probability rainfall for Cheonju Station is transposed to the Musim Basin since it has not been analyzed due to short period of rainfall record. The duration of design rainfall was estimated based on the time of concentration for the watershed. The effective rainfall was determined from the design rainfall using the SCS method which is commonly used for a small basin. The spatial distribution of significant storms was expressed as a dimensionless rainfall mass curve and hence, it was possible to determine the hyetograph of effective design storm. To synthesize the direct runoff hydrograph the 15-min. unit hydrograph was derived by the S-Curve method from the 1-hr unit hydrograph which was obtained from the observed rainfall and runoff data, and then it was applied to the design hyetograph. The exsisting maximum groundwater depletion curve was derived by the base flow seperation. Hence, the design flood hydrograph was obtained by superimposing the groundwater depletion curve to the computed direct runoff hydrograph resulting from the design storm.