• 정보처리학회논문지C
• /
• 제16C권6호
• /
• pp.717-724
• /
• 2009

IPTV 서비스의 품질은 IPTV 서비스가 성공적으로 정착되기 위한 가장 중요한 요소라 할 수 있다. 본 논문에서는 IPTV 서비스가 전달되는 계층적인 구조에 있어서 각 계층을 대표하는 서비스 품질 지표들을 선정하고 이들 간의 상관관계를 분석한다. 이를 위하여 IPTV 서비스가 전달되는 과정을 최대한 실제와 가깝게 구현하기 위한 시험 네트워크를 구축하고 선정된 품질 지표들에 대한 반복적인 측정을 수행한다. 측정을 통한 분석 결과 네트워크 계층의 대표적인 서비스 품질 지표 가운데 패킷손실률이 지연이나 지터에 비해 IPTV 서비스의 비디오 품질에 더 큰 영향을 미친다는 점을 보인다.

• 한국항행학회논문지
• /
• 제21권4호
• /
• pp.359-364
• /
• 2017

현재 아날로그 방식의 마을방송 시스템은 기술 적용의 문제 및 시설 노후화로 인한 성능 저하 등의 문제로 인하여 무선 디지털 시스템으로의 전환과 이에 따른 시스템 표준이 요구되고 있다. 그러나 주파수 부족으로 인해 효율적인 디지털 무선 마을 방송 시스템의 구축을 위해서는 이웃마을간의 간섭분석이 중요하므로 여기서는 대표적인 간이무선국 dPMR(digital private mobile radio) 및 DMR(digital mobile radio) 방식을 고려하여 동일채널 간섭과 인접채널 간섭에 대한 시뮬레이션을 수행하였다. 동일채널 간섭분석에서는 마을간 이격거리와 인접채널 간섭분석에서는 주파수 오프셋을 사용하여 주파수 재사용 및 채널분리에 대한 본 논문의 결과는 향후 마을방송 표준개발과 시범 사업화를 위한 자료로 활용될 것이다.

• 한국소음진동공학회논문집
• /
• 제20권8호
• /
• pp.734-741
• /
• 2010

In this paper, an intake RCV system for low noise turbo engine was developed through optimization process of a geometric path of compressor housing and an open rate of recirculation valve. At first, the critical customer requirement from voice of customer was defined and quality function deployment of an intake RCV system was executed. And then, the renovative concept design using pugh matrix method was selected as final concept for satisfaction of requirement. Simultaneously, system analysis was carried by function diagram and fishbone diagram. Next, control factors and levels for the optimal design were performed. And, the optimal design of an intake RCV system was studied using design of experiment. Conclusively, we achieved not only cancellation tip-out noise at the driving condition but also improvement of NVH commodity through optimization process of an intake RCV system, which is optimal configuration of compressor housing and recirculation valve.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 춘계학술대회 논문집
• /
• pp.1664-1667
• /
• 2005

The main function of Ball-Stop part is to operate power shift for vehicle with more than 5 ton when a driver changes gear using suitable force. This paper presents the implementation of a DFSS(Design For Six Sigma) for robust design of Ball-Stop part of power shift. The factors influencing Ball-Stop part performance is derived to find control factor. Based on this factor, contact force between head and detent pin analysis is performed to get optimal factor is analyzed and compared with contact force test result to verify reliability of design. This makes clear the reason why the proposed one is necessary and the role of DFSS.

• 한국지구과학회지
• /
• 제26권2호
• /
• pp.129-136
• /
• 2005

Continued observation of ARGO floats for years(about 4 years) makes the conductivity sensor more vulnerable to fouling by marine life and associated drift in salinity measurements. In this paper, we address this issue by making use of floats deployed in different years. Floats deployed in the East Sea and the Indian Ocean are examined to find out float-to-float match-ups in such a way that an older float pops up simultaneously with a newer deployment (with tolerable space-time difference). A time difference of less than five days and space difference of less than 100km are considered for the match-up data sets. For analysis of the salinity drift under the stable water mass, observations of the floats from deepest water masses have been used. From the cross-check of ARGO floats in the East Sea and the Indian Ocean, it is found that there is a systematic drift in the older float compared to later deployments. All drift results, consistently show negative bias indicating the typical nature of drift from fouled sensors. However, the drift is much less than 0.01, the specified accuracy of ARGO program.

• 한국멀티미디어학회논문지
• /
• 제13권6호
• /
• pp.911-923
• /
• 2010

In wireless sensor networks (WSNs), cluster based data routing protocols have the advantages of reducing energy consumption and link maintenance cost. Unfortunately, most of clustering protocols have been designed for uniformly distributed sensor networks. However, some urgent situations do not allow thousands of sensor nodes being deployed uniformly. For example, air vehicles or balloons may take the responsibility for deploying sensor nodes hence leading a normally distributed topology. In order to improve energy efficiency in such sensor networks, in this paper, we propose a new cluster formation algorithm named DAEEC (Density Aware Energy-Efficient Clustering). In this algorithm, we define two kinds of clusters: Low Density (LD) clusters and High Density (HD) clusters. They are determined by the number of nodes participated in one cluster. During the data routing period, the HD clusters help the neighbor LD clusters to forward the sensed data to the central base station. Thus, DAEEC can distribute the energy dissipation evenly among all sensor nodes by considering the deployment density to improve network lifetime and average energy savings. Moreover, because the HD clusters are densely deployed they can work in a manner of our former algorithm EEVAR (Energy Efficient Variable Area Routing Protocol) to save energy. According to the performance analysis result, DAEEC outperforms the conventional data routing schemes in terms of energy consumption and network lifetime.

• 정보보호학회논문지
• /
• 제28권5호
• /
• pp.1209-1223
• /
• 2018

안드로이드 앱은 바이트코드로 구성되어 있어 역공학으로부터 취약하며, 이를 보완하기 위해 앱을 강건하게 재구성해주는 보호 서비스들이 등장하였다. 암호 알고리즘과 다르게, 이런 보호 서비스의 강건함은 보호 방식을 감추는 것에 상당 부분 의존하고 있다. 그러므로 보호 서비스의 파훼 기법은 다양하더라도 보호 방식에 대한 체계적인 논의가 거의 없으며, 개발자의 직감에 따라 구현되고 있다. 정적 또는 동적분석을 방해하는 기술의 간단한 배치보다는, 강건한 보안 체인을 위한 체계적인 보호 구조에 대한 논의가 필요하다. 본 논문에서는 이를 위해, 대표 상용 안드로이드 앱 보호 서비스인 방클(bangcle)을 분석하여 보호 구조와 취약한 요소를 살펴본다. 그리고 이를 통해 강건한 구조를 위해 요구되는 사항과 보호 구조 원칙을 제안한다.

• 한국군사과학기술학회지
• /
• 제16권5호
• /
• pp.666-674
• /
• 2013

This paper studied about the design and implementation of tactical communication network simulator in order to obtain tactical communication network parameter, such as link capacity and routing plan, and a number of exceptional cases that may occur during actual deployment by conducting simulation of a large-scale tactical communication networks. This tactical communication network simulator provides equipment models and link models of commercial OPNET simulator for tactical communication network. In addition, 6 types of simulation scenario writings convenience functions and traffic generation models that may occur in situations of tactical communication network environment were implemented in order to enhance user friendliness. By taking advantages of SITL(System-In-The-Loop) function of OPNET, the tactical communication network simulator allows users to perform interoperability test between M&S models and actual equipment in operating simulation of tactical communication network, which is run on software. In order to confirm the functions and performance of the simulator, small-scale of tactical communication network was configured to make sure interoperability between SITL-based equipment and a large-scale tactical communication network was simulated and checked how to cope with traffic generated for each network node. As the results, we were able to confirm that the simulator is operated properly.

• 전기학회논문지
• /
• 제64권6호
• /
• pp.864-871
• /
• 2015

Recently, one of the main research on the power distribution system is the microgrid. The microgrid is a combination of power sources and loads, which is controllable and has separable connection. The main objective of microgrid is the deployment of the renewable clean energy and the enhancement of load-side reliability. The modern power sources and loads have DC I/O interfaces, which is the major advantage of DC microgrid compared to the conventional AC grid. The components in the microgrid have diverse features, so there is need of proper coordination control. For achieving economic feature, the active power of renewable energy resources is regarded as major control parameter and the whole operation modes of DC microgrid are defined, and the proper operations of each component are described. From the inherent characteristics of DC, there are two control variables: voltage and active power. Through analysis of operation modes, it is possible to determine exact control objectives and optimized voltage & power control strategy in each mode. Because of consideration of whole operation modes, regardless of the number and capacity of components, this coordination control method can be used without modification. This paper defines operation mode of DC microgrid with several DC sources and suggests economic and efficient coordinated control methods. Simulation with PSCAD proves effectiveness.

• 산업공학
• /
• 제18권1호
• /
• pp.104-116
• /
• 2005

In this paperm we provide a plan of construction, employment and management of the Korean postal address database and discuss the design of to-be models for it. For the purpose, we adopt and modify the information strategy planning methodology to fit it into our study. We examine the managerial environments and limitations of the postal services and define the requirements as a result. The U.S. Postal Service (USPS) was chosen as the best practice for a benchmarking and gap analysis with its advanced management of address information. After analyzing the current status of the postal business processes and information systems used, we classify the products and the services of USPS by the process to which they are applied and propose a deployment plan. In order to design a to-be model, we define the operating and managing functions for the address database and specify the scenario according to the functions. By managing the address database and supporting the postal services, it could be possible to make the business competitive and satisfy the customer demands.