• Journal of Communications and Networks
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• 제2권1호
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• pp.5-17
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• 2000

cdma2000 offers several enhancement as compared to TIA/EIA-95, although it remains fully compatible with TIA/EIA-95 systems and allows for a smooth migration from one to the other-Major new capability include:1)connectivity to GSM-MAP in addition to IP and IS-41 networks; 2) new layering with new LAC and MAC architectures for improved service multiplexing and QoS management and efficient use of radio resource ;3) new bands and band widths of operation in support of various operator need and constraints, as well as desire for a smooth and progressive migration to cdma 2000; and 4) flexible channel structure in support of multiple services with various QoS and variable transmission rates at up to 1 Mbps per channel and 2 Mbps per user. Given the phenomenal success of wireless services and desire for higher rate wireless services. improved spectrum efficiency was a major design goal in the elaboration of cdma2000. Major capacity enhancing features include; 1) turbo coding for data transmission: 2)fast forward link power control :3) forward link transmit diversity; 4) support of directive antenna transmission techniques; 5) coherent reverse link structure; and 6) enhanced access channel operation. As users increasingly rely on their cell phone at work and at home for voice and data exchange, the stand-by time and operation-time are essential parameters that can influence customer's satisfaction and service utilization. Another major goal of cdma2000 was therefore to enable manufacturers to further optimize power utilization in the terminal. Major battery life enhancing features include; 1) improved reverse link performance (i.e., reduced transmit power per information bit; 2) new common channel structure and operation ;3) quick paging channel operation; 4) reverse link gated transmission ; and 5) new MAC stated for efficient and ubiquitous idle time idle time operation. this article provides additional details on those enhancements. The intent is not to duplicate the detailed cdma2000 radio access network specification, but rather to provide some background on the new features of cdma2000 and on the qualitative improvements as compared to the TIA/EIA-95 based systems. The article is focused on the physical layer structure and associated procedures. It therefore does not cover the MAC, LAC, radio resource management [1], or any other signaling protocols in any detail. We assume some familiarity with the basic CDMA concepts used in TIA/EIA-95.

• 대한기계학회논문집B
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• 제37권2호
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• pp.181-186
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• 2013

농업용으로 사용되는 소형트랙터 개발의 최근 이슈는 친환경과 높은 연비이다. 소형 트랙터는 비닐 하우스 등 실내에서 작업이 가능하도록 설계 되므로 최근 전기 트랙터에 대한 수요가 증가하고 있다. 그러나 전기트랙터는 배터리 등 전기에너지 저장장치의 용량 및 크기공간의 제약으로 충분한 작업시간과 성능 확보에 한계가 존재한다. 따라서 최근 전기 트랙터와 내연기관 트랙터의 특징을 결합한 플러그인 하이브리드 트랙터에 대한 개발이 진행 중이다. 트랙터는 기본 주행 능력외에 PTO 를 통한 여러 작업을 수행 할 수 있어야 하며, 플러그인 하이브리드 트랙터에서는 각각의 작업에 대한 주행전략이 필요하다. 본 연구에서는 트랙터의 작업 모드를 개발하고 그에 대한 각 작업의 작업시간 능력 등을 확인하였다.

• 한국의류산업학회지
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• 제13권5호
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• pp.806-814
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• 2011

A solar jacket, which utilizes solar energy for generating electricity, is an example of clothing developed by the fusion of multiple technologies; such fusion of technologies can lead to further developments in the clothing industry and other industries in general. Many research institutes and garment manufacturing companies in Europe and America are developing solar garments; various solar-based products manufactured using solar cells, photovoltaic batteries, etc. are being sold at high prices. The purpose of this study was to investigate the development status of solar garments and their application for generating photovoltaic energy; the study also identified the type of design and upper body clothing preferred by Korean in their early 20s. The survey participants were 188 university students aged between 20 and 25. The design of the proposed six types of solar clothing was evaluated and rated; they were then ranked on the basis of the ratings. A survey on the management of solar garments was conducted, and ratings were assigned according to a 5-point Likert scale, with 5 indicating the strong affirmation. The survey results showed that among the six types of clothing, protective clothing (50%) and sportswear (22%) were more preferable than the others (working clothes (16%), casual clothes (3%), everyday wear(6%), and suits(1%)). Among the six proposed designs, the jumper design (22%) and jean jacket design (21%) were preferred over the others (casual jacket (19%), casual jacket I (15%), classic suit (14%), and climbing jacket (9%)). Factorial analysis of the management of solar garments revealed that the most important factors were the properties of the solar cell and time required for battery charging, and the second important factors were clothing weight and comfort.

• 한국항공우주학회지
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• 제37권9호
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• pp.923-930
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• 2009

본 논문에서는 위성의 개념설계와 교육목적에 활용할 수 있는 위성 시스템 개념설계 소프트웨어 개발에 관한 내용을 담고 있다. 이 소프트웨어는 상용도구인 MATLAB, STK, Excel을 이용하여 구성되었다. MATLAB은 기본연산, GUI 구성, 엑셀 데이터베이스 관리 및 STK의 제어를 담당한다. AGI사에서 개발한 궤도 시뮬레이션 소프트웨어인 STK는 위성의 정밀 궤도정보의 산출을 담당한다. 마이크로소프사의 엑셀은 기존 위성들의 데이터 베이스 와 본 개념설계 소프트웨어의 임시적 및 최종 결과의 저장장소로 사용된다. 위성의 개념설계는 위성의 대략적인 전력시스템과 질량계를 추정하는 것이다. 전력시스템 설계과정에서는 태양전지판과 배터리의 크기를 결정한다. 기존 위성들의 데이터베이스를 기반으로 목표 위성의 부시스템의 질량 분할을 추정할 수 있다. 개발된 소프트웨어의 입증을 위해 아리랑 1호 및 2호에 대한 개념설계결과를 포함하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권2호
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• pp.484-503
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• 2016

Mobile cloud computing has recently become a new paradigm for the utilization of a variety of shared mobile resources via wireless network environments. However, due to the inherent characteristics of mobile devices, a limited battery life, and a network access requirement, it is necessary for mobile servers to provide a dynamic approach for managing mobile resources efficiently in mobile cloud computing environments. Since on-demand job requests occur frequently and the number of mobile devices is drastically increased in mobile cloud computing environments, a different mobile resource management method is required to maximize the computational power. In this paper, we therefore propose a cooperative, mobile resource sharing method that considers both the inherent properties and the number of mobile devices in mobile cloud environments. The proposed method is composed of four main components: mobile resource monitor, job handler, resource handler, and results consolidator. In contrast with conventional mobile cloud computing, each mobile device under the proposed method can be either a service consumer or a service provider in the cloud. Even though each device is resource-poor when a job is processed independently, the computational power is dramatically increased under the proposed method, as the devices cooperate simultaneously for a job. Therefore, the mobile computing power throughput is dynamically increased, while the computation time for a given job is reduced. We conduct case-based experiments to validate the proposed method, whereby the feasibility of the method for the purpose of cooperative computation is shown.

• Journal of Communications and Networks
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• 제14권6호
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• pp.662-671
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• 2012

Plug-in hybrid electric vehicles (PHEVs) will be widely used in future transportation systems to reduce oil fuel consumption. Therefore, the electrical energy demand will be increased due to the charging of a large number of vehicles. Without intelligent control strategies, the charging process can easily overload the electricity grid at peak hours. In this paper, we consider a smart charging and discharging process for multiple PHEVs in a building's garage to optimize the energy consumption profile of the building. We formulate a centralized optimization problem in which the building controller or planner aims to minimize the square Euclidean distance between the instantaneous energy demand and the average demand of the building by controlling the charging and discharging schedules of PHEVs (or 'users'). The PHEVs' batteries will be charged during low-demand periods and discharged during high-demand periods in order to reduce the peak load of the building. In a decentralized system, we design an energy cost-sharing model and apply a non-cooperative approach to formulate an energy charging and discharging scheduling game, in which the players are the users, their strategies are the battery charging and discharging schedules, and the utility function of each user is defined as the negative total energy payment to the building. Based on the game theory setup, we also propose a distributed algorithm in which each PHEV independently selects its best strategy to maximize the utility function. The PHEVs update the building planner with their energy charging and discharging schedules. We also show that the PHEV owners will have an incentive to participate in the energy charging and discharging game. Simulation results verify that the proposed distributed algorithm will minimize the peak load and the total energy cost simultaneously.

• 한국통신학회논문지
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• 제31권2B호
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• pp.80-90
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• 2006

USN(Ubiquitous Sensor Network)은 감지기능을 수행하기 위해서는 센서노드에서 싱크로의 라우팅 기법이 반드시 필요하다. 본 논문에서는 데이터의 전달을 위한 경로설정시 에너지의 효율성 및 균일성을 제공하는 제어메시지의 확률적 플러딩을 제안하며 에너지의 소모를 되도록이면 균일하도록 유도하는 에너지확률을 이용하고 경로를 은닉할 수 있는 분산 라우팅기법을 제안하였다. 에너지효율성을 측정하기 위하여 수학적 모델링과 NS-2 시뮬레이터를 이용하였다. 각 기법은 기존의 관련연구와 비교분석하여 본 논문에서 제안한 기법이 우수함을 증명하였다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 추계학술대회
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• pp.318-321
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• 2017

대부분의 웨어러블 플랫폼(예, 삼성 기어, 안드로이드 웨어)의 기능은 모바일 플랫폼의 기능을 수정 없이 사용하고 있다. 그러나 웨어러블 디바이스는 웨어러블 형태, 작은 배터리, 스크린 모양, 열악한 네트워크 성능, 상대적으로 짧지만 자주 사용하는 사용자 인터페이스 등의 이유로 독특한 특성을 가지고 있다. 일반적으로 웨어러블 디바이스는 모바일 디바이스와 연결을 위해 어플리케이션 또는 서비스 등을 가지고 있는데, 이는 디바이스 모델 이름, 네트워크 능력(3G, LTE, Wi-Fi 등), 제조사, 지원하는 언어 리스트 등의 정보 교환하는 프로토콜을 사용하고 있다. 즉, 웨어러블 디바이스는 연결된 단말(예, 폰, 태블릿 등)에 깊이 의존하고 있고, 따라서 웨어러블 플랫폼은 이를 고려해야만 한다. 본 논문에서는 사용자 편의성과 웨어러블 플랫폼의 성능 하락(Sluggish) 문제를 해결하기 위해서 웨어러블 플랫폼의 특성을 고려한 효율적인 어플리케이션 관리 방안을 제시한다.

• Safety and Health at Work
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• 제12권4호
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• pp.462-470
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• 2021

Background: Fatigue is pervasive, under-reported, and potentially deadly where flight operations are concerned. The aviation industry appears to lack a standardized, practical, and easily replicable protocol for fatigue risk assessment which can be consistently applied across operators. Aim: Our paper sought to present a framework, supported by real-world data with subjective and objective parameters, to monitor aircrew fatigue and performance, and to determine the safe crew configuration for commercial airline operations. Methods: Our protocol identified risk factors for fatigue-induced performance degradation as triggers for fatigue risk and performance assessment. Using both subjective and objective measurements of sleep, fatigue, and performance in the form of instruments such as the Karolinska Sleepiness Scale, Samn-Perelli Crew Status Check, Psychomotor Vigilance Task, sleep logs, and a wearable actigraph for sleep log correlation and sleep duration and quality charting, a workflow flagging fatigue-prone flight operations for risk mitigation was developed and trialed. Results: In an operational study aimed at occupational assessment of fatigue and performance in airline pilots on a three-men crew versus a four-men crew for a long-haul flight, we affirmed the technical feasibility of our proposed framework and approach, the validity of the battery of assessment instruments, and the meaningful interpretation of fatigue and work performance indicators to enable the formulation of safe work recommendations. Conclusion: A standardized occupational assessment protocol like ours is useful to achieve consistency and objectivity in the occupational assessment of fatigue and work performance.

• 경영정보학연구
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• 제18권4호
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• pp.1-15
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• 2016

전기자동차는 화석연료 사용으로 인한 대기오염을 줄여 삶의 질을 개선하고, 신규 사업을 창조하여 경제적 발전에 역할을 할 것으로 기대된다. 그러나 이러한 기대와는 달리 전기자동차의 보급은 쉽지 않다. 주요한 이유 가운데 하나는 화석연료를 사용하는 자동차에 비해 충전이 늦거나 불편하다는 것이다. 전기자동차가 보급되지 않은 상황에서 선제적으로 충전소를 확보하는 일은 비용부담과 관리의 어려움을 야기할 수 있어 주의해야 한다. 본 연구는 디자인 과학 연구법을 활용하고 전기자동차 충전소 결정 문제를 정보시스템 관점에서 해석한다. 주행 범위 불안감을 이론적 근거로 삼아 여정 설계 알고리즘을 제안하고 네비게이션 사용자 데이터를 분석함으로써 서울시 충전소의 위치 선정의 문제점을 확인한다. 또한 여정 설계 디자인의 적용 가능성을 검토하고 시사점을 도출한다.