• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.336-339
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• 2011

In the RTLS(Real Time Location Based System), in case of existing a number of moving target, extremely complecated data flow is can be occurred. In the network where single gateway exists, various data which was collected from sensor node is transmitted along the simple route as time goes by. In case of multi-gateway configuration, the collected data is transmitted through diverse routes rather than simple route. This kind of data causes jams on nodes and this brings down the performance of the network. Different from existing studies, in this thesis, MAC (Media Access Control) protocol which minimizes data collision between nodes and guarantees QoS(Quality of Service) is suggested, in order to communicate efficiently in multi-gateway underwater sensor network environment. In the suggested protocol, source node which wants to transmit data makes a channel reservation to a number of destination node using a RTS packet. Source node reserves a channel without collision, by scheduling CTS response time using expected delay information from neighbor nodes. Once the reservation is made, source node transmit data packet without collision. This protocol analyzes/estimates the performance compared to a method provided from existing studies via simulation. As a results of the analysis, it was comfirmed that the suggested method has better performance, such as efficiency and delay.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.49-49
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• 2010

용접은 산업계의 기계 조립 및 접합을 위한 공정의 주요한 작업으로 조선, 중공업, 건설 등 산업현장에서 사람에 의한 수동적인 작업으로 대부분 수행된다. 이러한 용접 작업을 수행하는 용접 기술자는 산업 현장 훈련원과 직업 교육 학교에서 양성되지만 용접 훈련 과정은 실습 초보자에게 위험하고, 장시간 교육하기에 어려울 뿐 아니라 재료 낭비, 의사 소통의 한계, 즉석 결과 평가의 한계, 공간부족 등 다양한 문제가 있다. 그러므로, 안전하고 반복적인 실습 환경 제공하고 장시간 및 다수 교육참여 지원 등이 가능한 시스템을 구축하여 숙련된 우수 인력 조기 확보와 훈련 비용을 절감할 필요가 있다. 본 논문에서는 실제와 동일한 상호작용을 제공할 뿐만 아니라 고품질로 훈련 환경을 가시화하여 용접 상황을 동일하게 모사하는 가상 현실 기반 용접 훈련 시뮬레이터를 제시한다. 이 시스템은 용접의 형상과 환경의 고품질 가시화, 경험 DB를 통한 용접의 비드 형상 데이터 획득, 용접 토치를 이용하는 사용자 상호작용, 용접 훈련 결과 평가 및 최적 작업 가이드, 용접 콘텐츠 저작, 다양한 용접 훈련을 가시화하는 하드웨어 플랫폼으로 구성된다. 고품질 가상 용접 가시화는 경험 DB 기반 비드 형상 데이터와 신경회로망을 이용한 비드 형상 예측을 통해 실시간 비드 표현이 이루어지며 쉐이더 기반 고품질 모재 및 비드 표현, 아크 불꽃 효과 표현을 포함한다. 사용자 상호작용은 현장 작업 도구와 일치된 토치 인터페이스와 위치추적을 이용하여 토치의 작업각, 진행각, 속도, 거리 등을 반영할 수 있으며 진동과 소리 등 용접 훈련의 사실적 상호작용도 재현하였다. 용접 훈련 평가 및 최적 작업 가이드는 훈련자의 용접속도, 거리, 각도 등의 사용자 작업 결과를 그래픽으로 표현하고, 애니메이션을 통한 훈련 자세를 추후 분석할 수 있도록 하였고, 가상토치, 기준선, 수치계기 등을 이용한 최적 작업 훈련 가이드 제시하였다. 훈련 콘텐츠 저작은 메뉴UI 기반으로 용접의 전류, 전압 등의 조건과 상황을 선택하도록 제시하였고, 하드웨어 플랫폼은 워크벤치형 입체 디스플레이 방식으로 용접 환경을 가시화하였고, 위, 정면, 아래보기 등 다양한 용접 자세 변경을 지원 할 수 있도록 구축하였다. 이러한 가상현실 기반 훈련 시뮬레이터는 아크열 발생에 따른 장시간 훈련의 어려움을 극복할 수 있고, 다양한 실습 환경을 바꾸어 가며 반복적인 훈련이 가능하고, 실 재료를 사용하지 않아 재료의 낭비를 줄일 수 있는 환경 친화적인 안전하고 효율적인 훈련 실습 환경을 제공할 수 있다.

• Geophysics and Geophysical Exploration
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• v.7 no.3
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• pp.164-173
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• 2004

To delineate geothermal water movement at the Pohang geothermal development site, Self-Potential (SP) survey and monitoring were carried out during pumping tests. Before drilling, background SP data have been gathered to figure out overall potential distribution of the site. The pumping test was performed in two separate periods: 24 hours in December 2003 and 72 hours in March 2004. SP monitoring started several days before the pumping tests with a 128-channel automatic recording system. The background SP survey showed a clear positive anomaly at the northern part of the boreholes, which may be interpreted as an up-flow Bone of the deep geothermal water due to electrokinetic potential generated by hydrothermal circulation. The first and second SP monitoring during the pumping tests performed to figure out the fluid flow in the geothermal reservoir but it was not easy to see clear variations of SP due to pumping and pumping stop. Since the area is covered by some 360 m-thick tertiary sediments with very low electrical resistivity (less than 10 ohm-m), the electrokinetic potential due to deep groundwater flow resulted in being seriously attenuated on the surface. However, when we compared the variation of SP with that of groundwater level and temperature of pumping water, we could identify some areas responsible to the pumping. Dominant SP changes are observed in the south-west part of the boreholes during both the preliminary and long-term pumping periods, where 3-D magnetotelluric survey showed low-resistivity anomaly at the depth of $600m\~1,000m$. Overall analysis suggests that there exist hydraulic connection through the southwestern part to the pumping well.

• The Transactions of the Korea Information Processing Society
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• v.1 no.3
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• pp.367-379
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• 1994

This paper describes scheduling algorithms of the UNIX operating system and shows an analytical approach to approximate the average conditional response time for a process in the UNIX operating system. The average conditional response time is the average time between the submittal of a process requiring a certain amount of the CPU time and the completion of the process. The process scheduling algorithms in thr UNIX system are based on the priority service disciplines. That is, the behavior of a process is governed by the UNIX process schuduling algorithms that (ⅰ) the time-shared computer usage is obtained by allotting each request a quantum until it completes its required CPU time, (ⅱ) the nonpreemptive switching in system mode and the preemptive switching in user mode are applied to determine the quantum, (ⅲ) the first-come-first-serve discipline is applied within the same priority level, and (ⅳ) after completing an allotted quantum the process is placed at the end of either the runnable queue corresponding to its priority or the disk queue where it sleeps. These process scheduling algorithms create the round-robin effect in user mode. Using the round-robin effect and the preemptive switching, we approximate a process delay in user mode. Using the nonpreemptive switching, we approximate a process delay in system mode. We also consider a process delay due to the disk input and output operations. The average conditional response time is then obtained by approximating the total process delay. The results show an excellent response time for the processes requiring system time at the expense of the processes requiring user time.

• Journal of Food Hygiene and Safety
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• v.32 no.2
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• pp.107-113
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• 2017

To understand of the present state for temperature management of cold and frozen food transportation vehicles, we surveyed and measured the temperatures of eight transportation vehicles (including 3 small & medium and 5 large businesses) in Jeonbuk province, Korea. In the transportation vehicles of small & medium businesses, the mean temperature of cold and frozen foods was $8.35{\pm}5.72^{\circ}C$ and $-3.45{\pm}16.88^{\circ}C$; in large businesses, $3.92{\pm}1.44^{\circ}C$ and $-15.38{\pm}2.98^{\circ}C$, respectively. In the difference of temperature by the locations within transportation vehicles, the difference in each cold and frozen was $2.40{\pm}1.45^{\circ}C$ and $2.37{\pm}2.52^{\circ}C$, as a mean. But there was not statistically significant difference in locations between cold and frozen (p > 0.05). In the difference of surface temperatures on various foods before and after door opening during the loading, the temperatures of cold and frozen foods increased by $0.55^{\circ}C$ and $1.18^{\circ}C$, as means, respectively. The temperature of foods over time and placement of cold and frozen foods in transportation vehicles were not consistently maintained at optimal values in distribution. Therefore, the development of time-temperature history (TTH) system technology at the distribution level for cold and frozen foods is required.

• The Journal of Engineering Geology
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• v.15 no.2 s.42
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• pp.213-227
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• 2005

This study aims to assess the problems with investigation method and to suggest the complementary solutions by comparing the predicted data from surface investigation with the outcome data from underground cavern. In the study area, one(NE-1) of 6 fracture zones predicted during the surface investigation was only confirmed in underground caverns. Therefore, it is necessary to improve the confidence level for prediction. In this study, the fracture classification criteria was quantitatively suggested on the basis of the BHTV images of NE-1 fracture zone. The major orientation of background fractures in rock mass was changed at the depth of the storage cavern, the length and intensity were decreased. These characteristics result in the deviation of predieted predicted fracture properties and generate the investigation bias depending on the bore hole directions and investigated scales. The evaluation of hydraulic connectivity in the surface investigation stage needs to be analyze by the groundwater pressures and hydrochemical properties from the monitoring bore hole(s) equipped with a double completion or multi-packer system during the test bore hole is pumping or injecting. The hydraulic conductivities in geometric mean measured in the underground caverns are 2-3 times lower than those from the surface and furthermore the horizontal hydraulic conductivity in geometric mean is six times lower than the vertical one. To improve confidence level of the hydraulic conductivity, the orientation of test hole should be considered during the analysis of the hydraulic conductivity and the methodology of hydro-testing and interpretation should be based on the characteristics of rock mass and investigation purposes.