• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.50 no.3
• /
• pp.107-114
• /
• 2001

Electro-mechanical battery (EMB) consists of a high-speed fly wheel with an integral motor/ generator suspended on magnetic bearings and in an evacuated housing. Permanent magnet (PM) machines as the EMB motor/ generator are a popular choice, since there are no excitation losses which means substantial increase in the efficiency. In this paper we present the comparison of conventional slotted and slotless ring-wound types, aimed at EMB and other high-speed drives. We firstly discuss the topology of each machine for this particular application. these machines are primarily designed as 1kW two-pole PM generator with the rated speed of 40000 rpm. the motoring torque of 0.51 Nm has to be enough to accelerate the flywheel to the rated speed. We then present the comparison of the open-circuit field, the armature reaction field and winding inductance. next we analyze the induced voltage and the developed torque per unit stack length and unit weight of different machines. Finally, we estimate and compare the losses and the efficiency at motoring and generating modes.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.53 no.4
• /
• pp.27-34
• /
• 2016

In the train system, railway vehicles are connected in a line. Therefore, this feature should be considered in composing network topology in a train system. Besides, inter-car communication should be distinguished from in-car communication. As for the inter-car communication, the hybrid topology was proposed to use rather than the conventional ring, star, daisy-chain, and bus topologies. In the hybrid topology, a number of cars are bound to be a group. Then star topology is used for the communication in a group and daisy-chain topology is used for the communication between groups. Hybrid topology takes the virtue of both star and daisy-chain topologies. Hence it maintains communication speed with reducing the number of connecting cables between cars. Therefore, it is important to choose the number of cars in a group to obtain higher performance. In this paper, we focus on the optimization of hybrid topology for railway cars. We first assume that the size of data and the frequency of data production for each car is identical. We also assume that the importance for the maximum number of cables to connect cars is variable as well as the importance of the communication speed. Separated weights are granted to both importance and we derive the optimum number of cars in a group for various number of cars and weights.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• v.9 no.2
• /
• pp.131-134
• /
• 2005

This paper describes the efficient peer-to-peer migration method of Grid service agent on the mobile agent based P-Grid. The migration mechanism for transmitting service agent upon the service request is based on the peer's logic network topology. The network topologies that this system uses are organized as star topology, ring topology and tree topology, and agents are migrated by the master/slave method and serial/parallel method. The migration method of services is chosen based on the execution range and characteristic of the requested service. Also, the entire execution time of service is affected by the performance of peer that is a part of network topology, and the migration order, Therefore, the system monitors the performance of peers, and determines the migration priority based on analyzing and learning history. The system can reduce service execution time efficiently with decisions of migration method for service agent and priority of peers.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.1767-1770
• /
• 2003

This paper proposes an efficient network architecture for reflective memory system (RMS). Using this architecture, the time for broadcasting a shared-data to all nodes can be significantly shortened. The device named topology conversion switch (TCS) is implemented to realize the network architecture. The implemented TCS is applied to the ethernet based real time control network (ERCnet) to evaluate the performance.

• Proceedings of the Korean Information Science Society Conference
• /
• 2005.11a
• /
• pp.847-849
• /
• 2005

인터넷 사용자의 요청이 점차 증가함에 따라, 여러 웹 서버들이 하나의 클러스터를 이루어 사용자 요청을 더욱 효율적으로 처리하는데 않은 연구가 이루어지고 있다. 이러한 연구들 중에는 클러스터내의 최대 효율을 위하여 웹 서버들간의 부하를 분산시키는 기법들에 대한 다양한 기법들이 연구되고 있다. 이에, 본 논문에서는 DNS를 기반으로 하는 부하 분산 기법을 적용하되, 각 웹 서버들에 의해 수집된 부하정보를 바탕으로 추가적인 부하 분산을 하고자 한다. 이 기법은 실험에 의해 기존의 부하 분산 기법에 비해 웹 서버들간의 부하가 더욱 균등하게 분산됨을 보이고 있다.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.1322-1327
• /
• 2005

This paper presents a single-stage ZVT full-bridge AC/DC converter for aerospace applications. The detailed operating principle and design consideration of this soft-switched converter are analyzed and described. The proposed circuit topology and control scheme are proposed to exhibit optimum performances (i.e. high power factor, high efficiency, ring-free and low EMI features). A laboratory prototype, 500W 5V/100A AC/DC converter was implemented. The simulation and experimental waveforms verify the feasibility of the proposed design.

• Journal of the Korean Mathematical Society
• /
• v.42 no.4
• /
• pp.621-634
• /
• 2005

Let$P{\rightarrow}M$ be an oriented $S^2-fiber$ bundle over a closed manifold M and let Q be its associated SO(3)-bundle, then we investigate the ring structure of the cohomology of the total space P by constructing the coupling form TA induced from an SO(3) connection A. We show that the cohomology ring of total space splits into those of the base space and the fiber space if and only if the Pontrjangin class $p_1(Q)\;{\in}\;H^4(M;\mathbb{Z})$ vanishes. We apply this result to the twistor spaces of 4-manifolds.

• Journal of Information Processing Systems
• /
• v.16 no.6
• /
• pp.1447-1458
• /
• 2020

This paper describes a structured overlay network scheme based on multiple different time intervals. Many types of data (e.g., sensor data) can be requested at specific time intervals that depend on the user and the system. These queries are referred to as "interval queries." A method for constructing an overlay network that efficiently processes interval queries based on multiple different time intervals is proposed herein. The proposed method assumes a ring topology and assigns nodes to a keyspace based on one-dimensional time information. To reduce the number of forwarded messages for queries, each node constructs shortcut links for each interval that users tend to request. This study confirmed that the proposed method reduces the number of messages needed to process interval queries. The contributions of this study include the clarification of interval queries with specific time intervals; establishment of a structured overlay network scheme based on multiple different time intervals; and experimental verification of the scheme in terms of communication load, delay, and maintenance cost.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2009.11a
• /
• pp.187-188
• /
• 2009

최근 무선 센서 노드를 이용하여 다양한 환경 정보를 수집하고 처리할 수 있는 기술들이 활발히 연구되고 있다. 무선 센서 네트워크는 제한적인 컴퓨팅 자원을 가진 소형의 센서 노드들로 구성된다. 무선 센서 네트워크에서 중요한 이슈중 하나는 모든 노드가 게이트웨이인 싱크 노드를 통해 정보수집 네트워크를 효율적으로 구성하는 것이다. 기존의 무선 센서 네트워크에서는 싱크 노드와 센서 노드들간의 데이터 통신에 있어서 한 싱크 노드가 다운되면 통신경로가 상실되는 문제점을 가지고 있다. 이를 해결하기 위해 본 논문에서는 무선 슬롯 링 방식을 제안한다. 무슨 슬롯 링 방식은 기존의 트리형 혹은 클러스터형과 달리 센서 노드로 링형 네트워크를 구성하고 한 노드를 통해 데이터를 싱크노드로 전송하는 통신 기법을 제안한다.

• Kyungpook Mathematical Journal
• /
• v.55 no.2
• /
• pp.259-266
• /
• 2015

Let G be a group with identity e. Let R be a G-graded commutative ring and M a graded R-module. In this paper, we introduce the concept of graded quasi-prime submodules and give some basic results about graded quasi-prime submodules of graded modules. Special attention has been paid, when graded modules are graded multiplication, to find extra properties of these submodules. Furthermore, a topology related to graded quasi-prime submodules is introduced.