• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.19-20
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• 2006

The emission of particulate matter from marine diesel engines is already restricted by regional regulations in some countries, and IMO has been preparing the regulation for particulate matter from 53rd MEPC. But confusingly, the gravimetric PM measurement methods and procedures are not established clearly yet. On the other hand, smoke measurement method is set clearly, and it can also indicate PM, though it is not direct gravimetric method. As the preparing step for regulations about PM, we measured the smote density of exhaust emission from the marine four-stroke diesel engines operated in constant speed and various load steps on the test-bed, using the filter-type smoke measuring instrument. As a result, we understood the omission characteristics of smoke from the engines. Additionally, to obtain the objective reliability of our measurement data, we carried out experimental studies about various measuring parameters that could affect the smoke density.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.1940-1948
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• 2000

A design method for maximizing fatigue life of the deep groove ball bearing without enlarging mounting space is proposed by using a genetic algorithm. The use of gradient-based optimization methods for the design of the bearing is restricted because this design problem is characterized by the presence of discrete design variables such as the number of balls and standard ball diameter. Therefore, the design problem of rolling element bearings is a constrained discrete optimization problem. A genetic algorithm using real coding is used to efficiently find the optimum discrete design values. To effectively deal with the design constraints, a ranking method is suggested for constructing a fitness function in the genetic algorithm. Constrains for manufacturing are applied in optimization scheme. Results obtained for several 63 series deep groove ball bearings demonstrated the effectiveness of the proposed design methodology by showing that the average basic dynamic capacities of optimally designed bearings increased about 9-34% compared with the standard ones.

• The KIPS Transactions:PartC
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• v.10C no.1
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• pp.103-110
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• 2003

In this paper, we propose and evaluate the performance distance-based registration considering call arrival. We propose the mobility model, which can be used to analyze the performance of proposed registration schemes. Numerical results show that zone-based registration needs less number of registration than distance-based registration. On the other hand, the registration load of the distance-based registration is equally distributed to all cells in a location area. However, the registration load of the distance-based registration considering cail arrival is similar to that of zone-based registration and equally distributed to all cells in a location area. Therefore, the proposed scheme can be effectively used restricted radio resources.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.600-606
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• 2008

In closed-die hot forging, a billet is formed in dies such that the flow of metal from the die cavity is restricted. Some parts can be forged in a single set of dies, whilst others, due to shape complexity and material flow limitations, must be shaped in multi sets of dies. The purpose of a performing operation is to distribute the volume of the parts such that material flow in the finisher dies will be sound. This study focused on the design of preforms, flash thickness and land width by theoretical calculation and finite element analysis, to manufacture the super hot forging product, 70MC type piston crown used in marine engine. The optimal design of preforms by the finite element analysis and the design experiment achieves adequate metal distribution without any defects and guarantees the minimum forming load and fully filling of the cavity of the die for producing the large piston crown. The maximum loads obtained by finite element analysis are compared with the results of experiments. The loads of the analysis have good agreements with those of the experiment. Results obtained using DEFORM-2D enable the designer and manufacturer of super hot forging dies to be more efficient in this field.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.388-394
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• 2015

The inrush current of a large inductive load can be reduced with a soft starter; however, the large inrush current caused by simultaneous bulk starts (SBSs) cannot be effectively reduced. In order to reduce the high inrush current and voltage sag owing to the SBSs of large capacity inductive loads within a power network, a novel hybrid sequential start control system is proposed, implemented on embedded systems, and evaluated with a testbed in this study. From the experimental and simulation results of the proposed control system, the inrush current could be effectively restricted below the maximum current capacity of a power distributing board. Moreover, with the proposed system, power cost typically dictated by the peak power consumption can be fairly reduced, and the quality of the power system connected to the inductive loads can be efficiently increased.

• ETRI Journal
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• v.32 no.2
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• pp.292-301
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• 2010

Increasing convergence among heterogeneous radio networks is expected to be a key feature of future ubiquitous services. The convergence of radio networks in combination with dynamic spectrum allocation (DSA) could be a beneficial means to solve the growing demand for radio spectrum. DSA might enhance the spectrum utilization of involved radio networks to comply with user requirements for high-quality multimedia services. This paper proposes a simple spectrum allocation algorithm and presents an analytical model of dynamic spectrum resource allocation between two networks using a 4-D Markov chain. We argue that there may exist a break-even point for choosing whether or not to adopt DSA in a system. We point out certain circumstances where DSA is not a viable alternative. We also discuss the performance of DSA against the degree of resource sharing using the proposed analytical model and simulations. The presented analytical model is not restricted to DSA, and can be applied to a general resource sharing study.

• Journal of Welding and Joining
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• v.13 no.2
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• pp.60-67
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• 1995

The factors affecting on the fatigue strength of spot_welded specimens have been studied. The influence of initial overloads on the fatigue life of spot_welded tensile_shear specimens is investigated by considering fatigue crack initiation and crack propagation. The change of strain range and the influence of initial overload are correlated on the basis ol strain results. The results of this study are as follows. l) The initial absolute strain range decreased with initial overloads increase, and absolute strain range decreased before transformation of waveform of strain, but increased after transformation of waveform of strain. 2) In case of subsequent point of inflection of offset strain, the increment of this strain decreased with initial overload increase. 3) As initial overloads increase, the deformation behavior of spot welded parts is restricted after overloading.

• Journal of Electrical Engineering and Technology
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• v.10 no.6
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• pp.2297-2306
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• 2015

This paper presents the development of a system with a reverse matrix converter (RMC) for permanent magnet synchronous motor (PMSM) drive and its effective control method. The voltage transfer ratio of the general matrix converter is restricted to a maximum value of 0.866, which is not suitable for applications whose source voltages are lower than the load voltages. The proposed RMC topology can step up the voltage without any additional components in the conventional circuit. Its control method is different from traditional matrix converter’s one, thus this paper proposes control schemes of RMC by means of controlling both the generator and motor side currents with properly designed control loop. The converter can have sinusoidal input/output current waveforms in steady state condition as well as a boosted voltage. In this paper, a hardware system with an RMC for a PMSM drive system is described. The performance of the system was investigated through experiments

• The Transactions of the Korea Information Processing Society
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• v.5 no.6
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• pp.1468-1478
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• 1998

분산 시스템에서 부하 균형의 목적은 한 프로세서로부터 다른 프로세서로 적절히 전송함으로서 전체 시스템의 성능을 향상시키는 것이다. 본 논문에서는 수행 주기성과 탐색 한계를 이용한 제한된 부하균형 기법을 제안하였다. 본 알고리즘은 시스템에 있는 각 노드의 최신 상태를 기록하기 위해 탐색 과정에서 수집된 정보를 사용한다. 이러한 정보는 판단할 수 있어 무차별하게 탐색하는 것을 방지한다. 시뮬레이션 결과, 제안한 주기성 부하균형 알고리즘은 평균응답시간을 단축시킨다는 것과 성능이 수행 주기에 의존함을 발견하였다. 따라서, 훌륭한 수행 주기는 낮은 평균 응답시간과 부하 이주를 위한 적당한 노드가 존재한다면 그 노드를 발견할 높은 확률을 제공한다는 결론을 내렸다.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.115-117
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• 2008

Generally, because of the cost and the restricted manufacture standard, the motor control for home appliance have been used the method using hall sensors or the sensorless method. In the conventional sensorless method using home appliance, the resistor and the back-EMF coefficient are varied by the motor speed and the load torque. Therefore, these variations cause the position error when the sensorless control is operated. This paper proposes the compensation method for sensorless position error using 2-hall sensor pulse signals.