• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2769-2774
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• 2007

In vacuum ejector-diffuser systems where a finite volume secondary chamber is used, the secondary jet exhibits transient characteristics during start-up. A steady state is achieved after some time in which mass entrainment prevails indefinitely inside the ejector, though there is no flow from the secondary chamber. An attempt is made in this work to study the infinite entrainment of secondary jet into the primary jet from a finite secondary chamber, with the help of a computational fluid dynamics method. The present study is also intended to identify the operating range of vacuum ejector-diffuser systems where the steady flow assumption can be applied without uncertainty. The results obtained show that the only condition in which an infinite mass entrainment is possible is the generation of a re-circulation zone near the primary nozzle exit. The flow in the secondary chamber attains a state of dynamic equilibrium at this point. Steady flow assumption is valid only after this point.

• 농촌지도와개발
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• 제2권2호
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• pp.163-173
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• 1995

Agricultural extension services in Korea has experienced various system changes and accomplishments. The biggest achievement of extension was rice self-suffiency in the 1970s and abundant vegetable and animal production in the 1980s. The emerging challenges of international competition and localization are contributing to significant changes such as the decentralization of activities and shared responsibilities between the central government and local governments. Change, while it threatens the status quo, is a challenge and an opportunity to review and revamp ensconced and often rigid structures. In this sense, it is time to start a new era in agricultural extension. The development of agricultural extension requires keen appraisals and cogent analysis based on the realities of each specific regional situation. In order to develop agricultural extension services, the various aspects, the synthetic identification of its environments, the clarification of the client, the program development, and the effective mechanisms between research and extension must be considered. Especially, agricultural extension systems should be flexible and adjust to changing environments and the farmers' needs.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1520-1523
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• 1997

A rigorous dynamic simulation was performed in binary gas mixture H$_{2}$/CO (70:30 vol.%) to determinate start-up operating conditions of PSA(Pressure Swing Adsorption) processes. The rigorous dynamic model for the PSA process contains an Ergun equation for expressing the pressure drop in a bed, and valve equations to compute the boundary pressure change of the bed. As the result of the continuous dynamic simulation of 100 operating cyles in various initial conditions, the unsteady-state appeared in the early period and the cyclic steady-state came out about 20th cycle in feed condition and vaccum condition, and 30th cycle in pure H$_{2}$ condition. As time goes by valve equations made change the pressure at each end of the bed in ressurization, countercurrunt-depressurization and pressure equalization steps. The H$_{2}$ purity and the recovery is 99.99% and 86.73% respectively, which is slightly higher than the experimental data. Main contributiion of this study includes supplying fundamental technologies of handling combined variables PSA processes by developing rigorous models.

• 한국해양공학회지
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• 제33권6호
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• pp.510-517
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• 2019

Efficient path planning is essential for unmanned surface vehicle (USV) navigation. The A^* algorithm is an effective algorithm for identifying a safe path with optimal distance cost. In this study, a modified version of the A^* algorithm is applied for planning the path of a USV in a static and dynamic obstacle environment. The current study adopts the A^* approach while maintaining a safe distance between the USV and obstacles. Two important parameters-path length and computational time-are considered at various start times. The results demonstrate that the modified approach is effective for obstacle avoidance by a USV that is compliant with the International Regulations for Preventing Collision at Sea (COLREGs).

• Asian Journal of Innovation and Policy
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• 제4권2호
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• pp.217-241
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• 2015

This paper, based on two engineering industry SME case studies, traces the origin and process of technological innovations enabling the development and introduction of new products leading to market expansion and enterprise growth. The study throws light on how entrepreneurs played a decisive role in recognizing market opportunities, building up crucial in-house technological capability, supplementing it with appropriate external assistance, to carry out technological innovations. A constant interaction with its customers is in-built into the system. As a result, the SMEs could achieve successful product innovations leading to their gradual growth, over time. Finally, based on the observations and inferences derived out of the two cases, a theoretical construct of the growth of innovation in SMEs is postulated. This is done linking the three stages of their development: (i) start-up and stabilizing, (ii) building up technological capability and implementing innovations; and (iii) opening up of new markets resulting in firm growth.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.518-523
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• 2001

Vortex methods were originally conceived as a tool to model the evolution of unsteady, incompressible, high Reynolds number flows of engineering interest. Recently various methods have been proposed for simulating the diffusion in vortex methods for two-dimensional incompressible flows. We test the diffusion schemes of vortex methods. In this paper we directly compare the particle strength exchange scheme with the vorticity redistribution scheme in tenus of their accuracy and computational efficiency. Comparisons between both viscous models described are presented for short-time runs of impulsively started flows past a circular cylinder for Reynolds number of 60. The particle strength exchange scheme has been shown more accurate and efficient than the vorticity redistribution scheme.

• 전자공학회논문지S
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• 제35S권2호
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• pp.50-57
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• 1998

In this paper, we propoe a log N-stage ATM concentator. ATM concentrator is used in the ATM access network to concentrate the traffic offered at UNI, so that high utilization of the newtork rewources is achieved. The concetrator may be used as a construction block in the design of ATM switch. We define abasic element, named equalizer, and decribe its function and theory to construct an efficient concentrator using the element. In addition, a control scheme to enhance the concentrator to a superconcentrator is presented, which enables the concentration to start from an arbitrary output. This scheme makes it possible to construct an efficient ditributior or a barrel shifter which are often used in ATM switch and other application. The proposed concentrator has a low hardware complexity of O(N log N), thus it is economical to implement. Also, the time complexity of proposed concentrator for determining the rouging is O(N log N), which is faster than that of the existing ones.

• 산업경영시스템학회지
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• 제20권41호
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• pp.157-166
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• 1997

Classical SPC charting methods such as (equation omitted), R, S charts assume high volume manufacturing processes where at least 25 or 30 calibrate samples of size 4 or 5 each can be gathered to estimate the process parameters before on-line charting actually begines. However, for many processes, especially in a job-shop setting, production runs are not necessarily long and charting technique are required that do not that depend upon knowing the process parameters in advance of the run. In this paper, using modifying statistics, we give a method for constructing control charts for the process mean when the measurements are from a normal distribution. In this case, consider that smaller weight being assigned to the older data as time process and properties and taking method of exponential smoothing constant$(\lambda)$ are suggested.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2003년도 ISIS 2003
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• pp.166-169
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• 2003

Reinforcement learning if a kind of machine learning. It aims to adapt an agent to a given environment with a clue to a reward and a penalty. Q-learning [8] that is a representative reinforcement learning system treats a reward and a penalty at the same time. There is a problem how to decide an appropriate reward and penalty values. We know the Penalty Avoiding Rational Policy Making algorithm (PARP) [4] and the Penalty Avoiding Profit Sharing (PAPS) [2] as reinforcement learning systems to treat a reward and a penalty independently. though PAPS is a descendant algorithm of PARP, both PARP and PAPS tend to learn a local optimal policy. To overcome it, ion this paper, we propose the Multi Best method (MB) that is PAPS with the multi-start method[5]. MB selects the best policy in several policies that are learned by PAPS agents. By applying PS, PAPS and MB to a soccer game environment based on the SoccerBots[9], we show that MB is the best solution for the soccer game environment.

• 대한치과의사협회지
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• 제53권2호
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• pp.103-110
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• 2015

The dental accidents and disputes among Korean dentists have been on the increase with time. The main purpose of this study is to figure out the actual status of the dental accidents and malpractice disputes based on a questionnaire survey. The findings showed that 64.8% of respondents had been experienced the dental accidents, and 52.9% of respondents had been locked into the disputes. Within 5 years from the start of dental practice, the nearly half of the dentists responded the experience of the dental accidents and disputes. The amount of compensation for dental accidents and disputes wereindentalimplant, prosthodontics, and oral surgery treatments in descending order. The highest incident type was wrong process/treatment/procedure problem in clinical process/procedure.