• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.27 no.4B
• /
• pp.316-323
• /
• 2002

In this paper, we analyze the call control scheme that is using buffer at new call and handoff call for non-uniform traffic load distribution, the multiple cell environments and the multiple types of services such as voice and data service. Considering the facts, the call admission control method using the effective bandwidth concept is employed in this paper, The bandwidth for a new call and a handoff call is allocated by the number of mobile station and dynamically assigned by taking account of the blocking rate of new calls and the dropping rate of handoff calls. The call control procedure is experimented through a simulation study by dynamically the bandwidth to new and handoff calls based on the blocking rate and the dropping rate. The results show our call control scheme can get a good quality of service for mobile users.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.7 no.5
• /
• pp.926-929
• /
• 2006

In this paper, I propose a load balancing algorithm based on the traffic characteristics of a software streaming service, and implement the proposed algorithm on the large scale software streaming server platform which provides a software streaming service to geographically dispersed internet users. By showing that the large scale software streaming server platform fuctions correctly, we know the proposed load balancing algorithm is operating properly and efficiently.

• Proceedings of the KIPE Conference
• /
• 2012.07a
• /
• pp.13-14
• /
• 2012

본 논문에서는 정전압 제어를 위해 듀티 제어 방식을 적용한 직렬 공진형 DC/DC 컨버터 의 새로운 등가 부하 모델링을 제시함으로써 부하 변동에 따른 제어의 정밀도를 향상 시키고자 한다. PSIM 시뮬레이션 및 수식적 분석을 통해 기존 주파수 제어 방식에서의 등가 모델링과 듀티 제어 방식에서의 새로운 등가 모델링의 비교 분석을 통하여 제안한 방식의 타당성을 검증한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.14 no.5
• /
• pp.36-42
• /
• 2000

The increasing application of power electronic equipment 'especially (ASDs: adjustable speed drives)] on distribution systems has led to a growing concern for harmonic distortion and the resulting impacts on system equipment and operations. Therefore, harmonic studies have become an important aspect of power system analysis and design in recently years. Computer simulations which is related harmonic are used to quantify the distortion in voltage waveforms in a power system. Many digital computer programs are available for harmonic analysis. In frequency spectrum analysis, Simulation using SuperHarm program is superior to simulation using others. Therefore, Computer simulation using SuperHarm program is one of the effective ways to assess the harmonic effects of ASDs. The purpose of this study is to calculate the quantity of harmonic voltage by varying the ASD side load and to design the optimal harmonic filter for the elimination of harmonics.

• Journal of Advanced Marine Engineering and Technology
• /
• v.36 no.6
• /
• pp.837-843
• /
• 2012

Asynchronous motors are widely used in many fields. The various starting methods have been developed for the asynchronous motors which have large power compared to source power. The most popular ways to start the motors are to reduce the voltage of motor's stator or change the resistance fed rotor. It is needed to the specific time to reduce the voltage and change the resistance at a specific step. We call it the switching time. It is very difficult to know the switching time exactly. It varies with different types of motors as well as load characteristics. Thus, this paper focuses on the design and development for the mathematical models of motor and load. And then it is implemented in SIMULINK in order to calculate this time. The simulation results are both compared and discussed in detail so that it can be applied for new system with various motors and loads.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.29 no.6
• /
• pp.666-671
• /
• 2023

As international environmental regulations on ship emissions are gradually strengthened, interest in electric propulsion and hybrid propulsion ships is increasing, and various solutions are being developed and applied to these ships, especially stabilization of the power system and system efficiency. The direct current distribution system is being applied as a way to increase the power. In addition, verification and testing of safety and performance of marine DC distribution systems is required. As a result of establishing a DC distribution test bed, verifying the performance of the DC distribution (variable speed power generation) system, and analyzing fuel consumption, this study applied a variable speed power generation system that is applied to DC power distribution for ships, and converted the power output from the generator into a rectifier. A system was developed to convert direct current power to connect to the system and monitor and control these devices. Through tests using this DC distribution system, the maximum voltage was 751.5V and the minimum voltage was 731.4V, and the voltage fluctuation rate was 2.7%, confirming that the voltage is stably supplied within 3%, and a variable speed power generation system was installed according to load fluctuations. When applied, it was confirmed through testing that fuel consumption could be reduced by more than 20% depending on the section compared to the existing constant speed power generation system.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2009.04a
• /
• pp.340-343
• /
• 2009

u-GIS 환경에서 GeoSensor로부터 수집되는 시공간 데이터는 데이터 스트림의 특징을 포함한다. 데이터 스트림은 다양한 입력 속도로 끊임없이 입력되고, 데이터의 크기 또한 가변적이다. 이런 이유로 한정적인 메모리와 처리능력의 시스템은 과부하 현상이 발생한다. 이를 해결하기 위해 초과되는 데이터를 버려 메모리 초과를 방지하는 기법들이 연구되고 있다. 공간질의는 공간과 위치 값을 기반으로 이루어지는 연산으로 공간질의 정확도는 공간과 위치 정보를 통해 보장된다. 그러나 기존 기법인 랜덤부하제한 기법과 의미적부하제한 기법은 공간질의가 요구하는 공간과 위치 값에 대해 고려하지 않고 삭제하기 때문에 공간질의에 대한 정확도가 감소하는 문제를 갖는다. 본 논문에서는 공간의 이용도를 이용하여 차등적 비율을 적용한 부하제한 기법은 연구하였다. 이 기법은 등록된 공간질의의 영역 겹침 정도에 따라 중요 레벨을 증가시키고, 이를 토대로 시공간 데이터의 중요도를 파악하여 중요도마다 주어진 비율에 의하여 차등적으로 삭제한다. 결과적으로 기존 기법보다 다소 높은 Drop rate를 통해 질의 처리 속도를 빠르게 회복시켰으며, 중요 데이터를 최대한 유지하여 Error rate를 감소시켰다.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.20 no.5
• /
• pp.9-18
• /
• 2016

Generally the variable guide vane is used to secure the sufficient operating point in the off-design condition. In this study the inlet guide vane, 1st and 2nd stators in a multi-stage axial compressor are movable to obtain the operating range. So the effects of variable guide vane setting angle on the performance of 2.5 stage axial compressor were investigated at 70 % and 90 % conditions of nominal rotating speed in this paper. The steady-state and unsteady numerical analyses were conducted at each operating condition. The performance map, lost efficiency and flow fields were compared.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.42 no.12
• /
• pp.37-44
• /
• 2005

This paper proposes a hybrid scheme for dynamic bandwidth allocation(DBA) in Ethernet passive optical network(EPON), which combines advantages of adaptive cycle and constant cycle-based schemes. The proposed scheme is based on IPACT scheme, but it operates as adaptive cycle or constant cycle mode according to the queue status of optical line terminal(OLT) for downstream transmission. Simulation results showed that the proposed scheme could achieve a similar throughput in downstream transmission to a constant cycle-based DBA scheme, while producing a similar delay performance to the IPACT scheme in upstream transmission.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.49 no.9
• /
• pp.270-275
• /
• 2012

This paper describes design of a variable-N frequency synthesizer for RF PLL with $0.13{\mu}m$ silicon CMOS technology being used as an application of the UWB system like MBOA. To get good performance of speed and noise super dynamic circuits was used, and to get variable-N division ratio MOSFET switching circuits was used. Especially to solve narrow bandwidth problem of the dynamic circuits load resistance value of unit divider block was varied. Simulation results of the designed circuit shows very fast and wide operation characteristics as 5~26GHz frequency range.