• 한국정보통신학회논문지
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• 제21권1호
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• pp.180-186
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• 2017

본 논문에서는 무선 센서 네트워크의 센서 노드들로부터 전송되는 데이터 트래픽에 따라 낮은 지연과 높은 데이터 효율을 지원하는 새로운 MAC 프로토콜을 제안한다. 본 논문에서 제안하는 TADW-MAC은 기존의 멀티 홉 전송에서 해당 Sleep 구간에서 오직 하나의 패킷 전송만을 스케줄할 수 있는 DW-MAC의 문제점을 해결하며, 물체 트래킹(object tracking)이나 화재 감시 시스템 등의 응용에 적합한 duty cycling 메커니즘을 가진다. 이러한 응용에서는 평소에는 데이터 전송이 이루어지지 않지만, 물체의 나타남과 화재 발생 등 이벤트가 발생하는 경우에는 많은 데이터를 전송해야 하며, 낮은 지연을 요구한다[6-8]. 따라서 TADW-MAC에서는 이러한 이벤트가 발생하였을 경우에 duty cycle을 조절함으로 보다 높은 효율과 적은 에너지를 소모할 수 있다. 여러 시뮬레이션을 통해 TADW-MAC은 기존의 RMAC이나 DW-MAC에 비해 에너지 효율과 전송 지연 면에서 더 나은 성능을 보여준다.

• 한국통신학회논문지
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• 제34권6A호
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• pp.506-514
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• 2009

센서 네트워크를 위한 MAC 프로토콜들은 전력 소모를 최소화하기 위해 낮은 듀티 사이클(Duty Cycle)을 사용한다. 그 중에서 RMAC [4]의 경우 Pioneer(PION) 프레임을 이용하여 한 주기 내에 여러 홉을 전송한다. 본 논문에서는 HE-MAC(Hop-Extended MAC)이라는 홉 연장 프로토콜을 제안한다. HE-MAC의 데이터 전송은 기존 RMAC과는 달리 한 주기 내에 전달될 수 있는 최대 홉 수 정보가 포함된 Explorer(EXP)를 이용하여 이루어진다. EXP의 정보와 Ready-to-Receive(RTR) 상태를 이용하여 RMAC에 비해 2홉을 늘림으로써 평균 전송 지연 시간을 감소시킨다. 또한, 적응적 슬립을 통하여 불필요한 전력 소모를 최소화할 뿐만 아니라 RMAC에서 나타나는 잦은 트래픽(Traffic)으로 인한 패킷 역전 문제를 해결한다. HE-MAC의 패킷 전송 지연시간을 수학적으로 분석하였으며, ns-2를 이용한 모의실험을 통해 성능평가를 하였다. 300개의 노드가 배치된 랜덤 토폴로지에서 HE-MAC은 RMAC에 비해 전력 소모량과 평균 전승 지연 시간을 14%, 20%만큼 감소시킨다.

• 한국안전학회지
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• 제5권2호
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• pp.66-75
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• 1990

This study is conducted to establish the structural standard of tube and coupler scaffold which is suitable for our present stuation through the comparison analysis for domestic and foreign standards as well as measurement of field survey. The results of this study are as follows ： 1) The load is classified by three categories, light-duty(equal and lower than 150kg/m$^2$), medium-duty(150-250 kg/m$^2$), heavy-duty(250-350kg/m$^2$), and the equivalent horizontal length of side posts is each, 1.5-1.8m, 1.2-1.5m, equal and lower than 1.2m, and the equivalent horizontal length between front and rear posts is each 1.2-1.5m, 0.9-1.2m, equal and lower thatn 0.9m, in accordance with the load classification. 2) The height between upper and lower runner is equal and lower than 1.5m, and the brace across the width of scaffold should be installed within 15m in horizontal direction at 45 degree angle. 3) The entire scaffold should be securely tied to the wall of permanent structure with uslng anchor and bolt at intervals not to exceed 6m in case of non-connection and 4.5m in case of connection in both horizontal and vertical direction. 4) The post should be installed on the sound foundation tied to lumber footing with using base plate, and standard platform plank should be produced in the factory and widely used in the construction field.

• 대한안전경영과학회지
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• 제14권3호
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• pp.183-191
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• 2012

Since June 25th 1950, the beginning of the cold war (Korean war), Korean peninsula is still in a state of war. Officially South and North Korean government call a truceafter three years from the beginning day, however both countries are still having several combats in these days. So every Korean citizen male has duty for serving military duty and this lasts even after the serving regular military force, as reserved military. Although South Korea is very small country, the size of military is very large so informing all reserved military takes some time. Since this nation is confronting the enemy and considering the global potential threat, South Korean military needs expedite informing system to call up the reserved military to active duty. In this project, the current informing system has been analyzed and compared with the new method which is using social network service such as Twitter. However mobilization order is very critical. So in our new model there are two ways combined. Using twitter to inform and then use traditional ways to finish the order. This method will provide more efficient and accurate way to cover the call ups.

• 한국항만경제학회지
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• 제19권1호
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• pp.89-112
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• 2003

In this article, 1'd like to analyse the principal distinctions between the duty of disclosure and warranty which are based on the same legal principles, utmost good faith(uberrima fides). Although the duty of disclosure and warranty have a same legal principle to protect insurance contract, they have several difference in appliance actually. Through these comparative analysis, 1 want to reveal the character of warranty which is unfamiliar to us under our commercial law. Warranty has some peculiarity, these are (a)A warranty does not have to be material to the risk, (b)A warranty must be exactly complied with, (c)It is impossible to defence for a breach of warranty, the breach of warranty is irremediable, and A casual connection between breach and loss needs not be shone, (d)A breach of a warranty may be waived by insurer. Sometimes in Korea like those stringent principles of warranty make Korean's small fishing or shipping company suffer from difficult because of insistence of discharge from liability by insurer. So I expect that all of them acknowledge the character of warranty and can make them protect their insurance money by themselves.

• 한국항만경제학회:학술대회논문집
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• 한국항만경제학회 2003년도 정기학술대회지
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• pp.271-294
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• 2003

In this article, 1'd like to analyse the principal distinctions between the duty of disclosure and warranty which are based on the same legal principles, utmost good faith(uberrima fides). Although the duty of disclosure and warranty have a same legal principle to protect insurance contract, they have several difference in appliance actually. Through these comparative analysis, I want to reveal the character of warranty which is unfamiliar to us under our commercial law. Warranty has some peculiarity, these are (a)A warranty does not have to be material to the risk, (b)A warranty must be exactly complied with, (c)It is impossible to defence for a breach of warranty, the breach of warranty is irremediable, and A casual connection between breach and loss needs not be shone, (d)A breach of a warranty may be waived by insurer. Sometimes in Korea like those stringent principles of warranty make Korean's small fishing or shipping company suffer from difficult because of insistence of discharge from liability by insurer. So I expect that all of them acknowledge the character of warranty and can make them protect their insurance money by themselves.

• Journal of Information Processing Systems
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• 제14권4호
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• pp.948-960
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• 2018

Many mobile sensing frameworks have been developed to help researcher doing their mobile sensing research. However, energy consumption is still an issue in the mobile sensing research, and the existing frameworks do not provide enough solution for solving the issue. We have surveyed several mobile sensing frameworks and carefully chose one framework to improve. We have designed an adaptive sampling module for a mobile sensing framework to help solve the energy consumption issue. However, in this study, we limit our design to an adaptive sampling module for the location and motion sensors. In our adaptive sampling module, we utilize the significant motion sensor to help the adaptive sampling. We experimented with two sampling strategies that utilized the significant motion sensor to achieve low-power consumption during the continuous sampling. The first strategy is to utilize the sensor naively only while the second one is to add the duty cycle to the naive approach. We show that both strategies achieve low energy consumption, but the one that is combined with the duty cycle achieves better result.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권12호
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• pp.3046-3060
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• 2012

Low power listening (LPL) MAC protocols based on duty-cycling mechanism have been studied extensively to achieve ultra low energy consumption in wireless sensor networks (WSNs). Especially, recent ACK-based LPL schemes such as X-MAC employ strobe preambles and an early ACK, and show fair performances in communications and energy efficiencies. However, the state-of-the-art ACK-based LPL scheme still suffers from collision problems due to the protocol incompleteness. These collision effects are not trivial and make WSNs unstable, aggravate energy consumptions. In this paper, we propose two novel schemes; (i) ${\tau}$-duration CCA to mitigate the collision problem in ACK-based LPL MAC protocols. (ii) Short Preamble Counter (SPC) to conserve more energy by reducing unnecessary overhearing. We demonstrate the performance improvement of our scheme via a mathematical analysis and real-time experiments. Both analysis and experimental results confirm that our proposed scheme saves energy by up to 36% compared to the naive ACK-based LPL MAC protocol thanks to ${\tau}$-duration CCA and SPC.

• 한국항공운항학회:학술대회논문집
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• 한국항공운항학회 2016년도 춘계학술대회
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• pp.89-94
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• 2016

This paper is to investigate how each cases(recurrent cases) is to be classified and what each parties should prepare to solve their cases by civil law system and so on. We could find the increased volume (or quantity) of transportation by air recently and have to worry about the sky-rocketed cases of unfulfilled navigation management(aviation service) proportionately inevitably. So we knew that some cases of disputes are solved by unreasonable demand, unilateral concession or irrational decision without any logical or legal criterion, because both sides(passenger and carrier) do not recognize the situation correctly and have any preparation for the legal settlement. Therefore we should prepare the classification work and comprehend about the legal effect(fulfillment retardation of duty, fulfillment impossibility of duty and imperfect fulfillment in our civil law system) of each cases. We can grasp the legal relationship with a carrier and a passengers by the legal analysis more efficiently and save (or help) energy and time of concerned parties.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 전력전자학술대회 논문집
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• pp.154-157
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• 1998

In this paper, the inverter TIG(Tungsten Inert Gas) welding system with high power efficiency by means of pulse current control of welding process is presented. In TIG welding, pulse current control is utilized in order to attain less apatter and high welding performance. The four factors which determine the welding performance of the pulse current are frequency, base current, peak current, and peak current duty current, and peak current duty ratio. In this paper, we analyze these factors should be controlled to achieve minimum power input. To demonstrate the practical significance of our results, we present some experimental results as well as simulation results.