• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.44 no.3
• /
• pp.9-13
• /
• 2007

This Paper deals with the synthesis of absolutely stabilizing fixed order controllers for Lure-Postnikov systems. Lure-Postnikov systems are frequently encountered in mechanical engineering applications. Analytical tools for synthesizing stabilizing fixed structure controllers, such as the PID controllers examining the absolute stability of Lure-Postnikov systems, have recently been studied in the literature. However, tools for synthesizing controllers of arbitrary order have not been studied yet. We propose a systematic method for synthesizing absolutely stabilizing controllers of arbitrary order for the Lure-Postnikov systems. Our approach is based on recent results in the literature on approximation of the set of stabilizing controller parameters that render a family of real and complex polynomials Hurwitz. We provide an example of a robotic system to illustrate the procedure developed.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.12
• /
• pp.2839-2846
• /
• 2014

New VHF band for use in VDE is determined by WRC-12 due to the overload of AIS VDL, and the system characteristics of the VDE is recommended as ITU-R M. 1842-1. CS-TDMA, a multiple access method of AIS class B, is recommended as that of the VDE. It is inefficient for CS-TDMA just applying the report interval used in AIS class B to transmit high speed data with higher payload in the aspect of efficiency. In this paper, a simulation is executed in order to determine adequate report interval according to the number of active ships that affects directly network traffic. To this end, the performance of CS-TDMA, which includes the number of received packets, reception success rate, channel utilization, and collision rate, is investigated via a simulation.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.7
• /
• pp.1547-1556
• /
• 2014

In this paper, we propose cost-effective device-to-device (D2D) advertisement scenario with properties of proximity and timeliness through the convergence of D2D communications and social commerce service. We numerically analyze advertisement dissemination effect of the proposed scenario according to the number of sectors, and demonstrate the performance of the normalized D2D coverage, the average number of D2D users, and the average D2D coverage per user via intensive simulations. We verify the accuracy of the results for our numerical analysis compared with the simulation results.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2018.11a
• /
• pp.261-262
• /
• 2018

The tasks of Vessel Traffic Services are classified according to the content of the information provided. Since the establishment of the first Vessel Traffic Service center in 1993 at Phohang harbour, it has been steadily developed and its work domain and scope have been expanded. In this paper, the importance and workload of Vessel Traffic Service operators were analyzed according to classification of the tasks. In order to measure the importance and workload, questionnaires were conducted for the operators nationwide, and conclusions were drawn using the multi-criteria decision making process. The relationship between the importance of tasks and the workload might be used as the weights for setting the service areas in the future. Furthermore, it is expected to be used as the data of changable sector operation based on the relationship between importance and workload.

• Journal of the Korea Society of Computer and Information
• /
• v.15 no.8
• /
• pp.23-30
• /
• 2010

Flash memory is non-volatile and can retain data even after system is powered off. Besides, it has many other features such as fast access speed, low power consumption, attractive shock resistance, small size, and light-weight. As its price decreases and capacity increases, the flash memory is expected to be widely used in consumer electronics, embedded systems, and mobile devices. Flash storage systems generally adopt a software layer, called FTL. In this research, we proposed a new FTL mechanism for overcoming the major drawback of conventional block mapping algorithm. In addition to the block mapping table, a index block mapping table with a small size is used to indicate sector location. The proposed indexed block mapping algorithm by adding a small size. By the simulation result, the proposed FTL provides an enhanced speed than a conventional hybrid mapping algorithm by around 45% in average, and the requirement of mapping memory is also reduced by around 12%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.254-257
• /
• 2017

As a part of the development of aircraft gas turbines, combustion performance tests have been conducted in the single combustor sector. The effects of change in the amount of air supplied to the main combustion zone to the performance of the combustor, such as a pollutant emission, a liner temperature distribution and an exit temperature patterns, were studied. Emissions of CO and NOx increased with the main air-ratio and exit temperature pattern was improved. When changing the pattern of the dilution holes, it was shown that the temperature patterns on the exit plane of the combustor and the surface of liner changed depending on the main flame structure and mixing with diluent air. These observations will be applied to combustor liner designs to improve combustor durability and emissions reduction performance.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.6
• /
• pp.681-688
• /
• 2016

Several VHF bands for the use in analog communications has been changed to those for the use in new maritime digital communications by WRC-12. ITU-R M. 1842-1 has been also standardized, recommending the characteristics of maritime digital communication systems. In addition, a Shipborne Ad-hoc Network (SANET) has been introduced by IMO in order to provide ships, which cannot be connected to a shore directly, with maritime digital data exchange services with the help of ad-hoc communication. In this paper, several functionalities of the SANET, including channel access, route determination to a shore, and data exchange, are verified via sea trials. It is expected that the SANET can be applicable to collecting and analyzing maritime information, facilitating the entry and departure of vessels, and the communication infrastructure of e-navigation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.11A
• /
• pp.844-851
• /
• 2009

Handover is needed in multi-hop relay systems to support mobility. The main purpose of handover is to provide the continuous connection when a MS migrates from the air-interface of one BS to another air-interface provided by another BS. Especially the handover between different systems is essential to next generation network. Vertical Handover technology in Mobile WiMAX MMR system is very useful for operators to introduce to Mobile WiMAX system in an overlaid cell environment. This technology will be applied to technology which hands MRS(Mobile Relay Station) over to different systems for system performance enhancement in Ubiquitous environment overlaid between Micro ce11(Frequency 1,FA1) and Macro cell(Frequency 2,FA2). In this paper, FA1 and FA2 are used in order to perform Vertical Handover of MRS(Mobile Relay Station) according to suggested conditions. interferences from neighboring BS or other sectors of 6 macro cells surrounding center Macro cell are analyzed and throughputs are measured according to suggested conditions.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39B no.3
• /
• pp.151-161
• /
• 2014

3GPP LTE-Advanced (Release 10) system specifies carrier aggregation (CA) to enable high data rate on using multiple frequency bands, including the variout CA-specific deployment scenarios. Considering one of those scenarios in which the different directional sector antenna is employed by each frequency band, we propose a per-carrier cell selection scheme that can improve the average throughput of the cell-edge users by allowing each user equipment (UE) to select the frequency band of the adjacent cell. Furthermore, a distributed algorithm for inter-cell copperative scheduling in this scheme is proposed to support proportional fairness among the cells. It has been shown that the proposed scheduling algorithm for the per-carrier cell selection scheme improves the cell-edge user throughput roughly by 50% over that of the conventional scheme.

• Proceedings of the Korean Information Science Society Conference
• /
• 2005.07a
• /
• pp.826-828
• /
• 2005

이동 기기의 저장 장치로 플래시 메모리가 널리 사용되고 있으며 고정 하드 디스크를 대체하는 저장 매제로 부상하고 있다. 그러므로 플래시 메모리의 특성을 잘 이해하고, 최대한 효율적으로 플래시 메모리를 사용할 필요성이 있다. 이러한 역할을 해주는 것은 플래시 내부의 시스템 소프트웨어인 FTL(Fiash Translation Layer)이다. FTL은 운영체제가 디스크에 전달하는 블록을 물리적인 플래시 메모리에 맵핑하는 역할을 한다. 그러므로 플래시 메모리의 성능은 FTL 알고리즘이 결정한다. 플래시를 대체한 플래시 디스크에서는 기존의 파일 시스템이 탑재되며 간단한 섹터 기반외 이동형 기기에서와는 다른 특성을 가진다. FTL 성능을 평가하기 위해서는 실제적으로 플래시 메모리가 장착된 제품들이 동작하는 시스템에서 실험을 해야 한다. 많은 플래시 디스크는 윈도우즈에서 동작하므로 윈도우즈의 디스크 I/O를 추출하여 실험을 해야만 한다. 본 논문에서는 윈도우즈에서 물리적인 디스크 I/O 패턴을 추출하여 FTL 알고리즘의 성능을 평가하기 위한 도구 개발에 대하여 설명하고 이에 대한 간단한 결과를 보인다.