• 한국가족관계학회지
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• 제22권3호
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• pp.73-101
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• 2017

Objectives: This study is to understand the experiences of overcoming pain of loss of family survivors in Suicide Bereavement Support Group(SBSG). Method: Experiential data was collected by in-depth interview(FGI, individual) to 10 family survivors(over 19) who having an experience participating in SBSG over 5months and analyzed using qualitative methodology. Results: We drew the result that 'SPACE model' which structuralize by 5 stages of suicide survivors' experience of SBSG of time path. SPACE model configured as follow: Stage1, Space in vacuum, the time to feel a sense of overwhelming feeling like pain, fear, alienation after loss of suicide, Stage2, Probing, when to find informations and resources to help survivors themselves, Stage3, Acclimation, having experiences empathy and healing as in SBSG, Stage4, Composure, accepting SBSG meaning as a part of their lives, loss of my family by suicide, and the beginning of bereavement, Stage5, Endurance, overcoming suffering through SBSG and try to help other survivors. Conclusions: SBSG is the opportunity for family survivors to overcome the pains from loss of suicide, shock, anger, grief, etc., and to empower them to help other suicide survivors.

• 신재생에너지
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• 제3권3호
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• pp.14-19
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• 2007

A flow channel model of a bipolar plate with varying cross-sectional area was newly designed for improving performance and efficiency of a PEM fuel cell stack. As a result, the varying cross-sectional area model showed poor uniformity in velocity distribution, however, maximum velocity in the flow path is about 30% faster than that of the uniform cross-sectional area model. The proposed varying cross-sectional area model is expected to diffuse operating fluids more easily into diffusion layer because it has relatively higher values in pressure distribution compared with other flow channel models. It is expected that the implementation of the varying cross-sectional area model can reduce not only the mass transport loss but also the activation loss in a PEM fuel cell, and open circuit voltage of a fuel cell can thus be increased slightly.

• Journal of Communications and Networks
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• 제5권3호
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• pp.230-239
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• 2003

In this paper, we propose a framework to study how to route packets efficiently in multipath communication networks. Two traffic congestion control techniques, namely, flow assignment and packet scheduling, have been investigated. The flow assignment mechanism defines an optimal splitting of data traffic on multiple disjoint paths. The resequencing delay and the usage of the resequencing buffer can be reduced significantly by properly scheduling the sending order of all packets, say, according to their expected arrival times at the destination. To illustrate our model, and without loss of generality, Gaussian distributed end-to-end path delays are used. Our analytical results show that the techniques are very effective in reducing the average end-to-end path delay, the average packet resequencing delay, and the average resequencing buffer occupancy for various path configurations. These promising results can form a basis for designing future adaptive multipath protocols.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.154-160
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• 2003

Multi-path ultrasonic flowrate measuring technology is being received much attentions from a variety of industrial fields to exactly measure the flowmeter. Multi-path ultrasonic flowmeter has much advantage since it has no moving parts and not occurred pressure loss. It offers good accuracy, repeatability, linearity and Tum-down ratio can measure over 1:50. The present study investigates flowrate integration errors using weighting factors. A theoretical flow model uses power law to describe a fully developed velocity profiles and wall roughness changes. The methods of weighting factor simulate three configurations of measuring location of gaussian, chebyshev and tailor method. The obtained results show that many chord arrangements are not affected for wall roughness changes and can measure accurate flowrate.

• Spatial Information Research
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• 제19권1호
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• pp.1-11
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• 2011

최근 도시지역은 국지성 호우로 인한 범람의 빈도가 증가하고 있다. 이 연구에서는 HECRAS 모형을 이용하여 중량천 수계에 대한 홍수범람모의를 수행하였다. 분석은 1m 간격의 LiDAR 자료를 기반으로, 하천 정보를 위해 HEC-GeoRAS를 이용하여 Geometry 자료를 구축하여 활용하였다. 홍수에 대한 가상시나리오를 홍수량이 100년 빈도일 경우 200년 빈도일 경우, PMF일 경우로 작성하여 침수 취약지역을 분석하였고, 이를 구역화하고 대피소까지의 대피경로를 분석하였다. 분석 결과 인구가 밀집된 시가화 지역의 면적 비율이 범람지역의 약 70%를 차지하고 있어 홍수 시 상당한 인명 및 재산피해가 예상되었다. 범람지역에서 대피소까지의 최단거리 대피경로는 평균거리 1,000m로 대피 경보에 따라 피해를 최소화 할 수 있음을 알 수 있었다. 이 연구에서 제시한 방법은 향후 도식지역의 홍수대피 계획 수립에 많은 도움이 될 것이다.

• Journal of Communications and Networks
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• 제7권4호
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• pp.401-407
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• 2005

Simulations are currently an essential tool to develop and test wireless sensor networks (WSNs) protocols and to analyze future WSNs applications performance. Researchers often simulate their proposals rather than deploying high-cost test-beds or develop complex mathematical analysis. However, simulation results rely on physical layer assumptions, which are not usually accurate enough to capture the real behavior of a WSN. Such an issue can lead to mistaken or questionable results. Besides, most of the envisioned applications for WSNs consider the nodes to be at the ground level. However, there is a lack of radio propagation characterization and validation by measurements with nodes at ground level for actual sensor hardware. In this paper, we propose to use a low-computational cost, two slope, log-normal path­loss near ground outdoor channel model at 868 MHz in WSN simulations. The model is validated by extensive real hardware measurements obtained in different scenarios. In addition, accurate model parameters are provided. This model is compared with the well-known one slope path-loss model. We demonstrate that the two slope log-normal model provides more accurate WSN simulations at almost the same computational cost as the single slope one. It is also shown that the radio propagation characterization heavily depends on the adjusted model parameters for a target deployment scenario: The model parameters have a considerable impact on the average number of neighbors and on the network connectivity.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권5호
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• pp.2453-2467
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• 2017

Wireless communication is a telecommunication technology, which enables wireless transmission between the portable devices to provide wireless access in all types of environments. In this research, the measurements and various empirical models are analysed and compared in order to find out a suitable propagation model to provide guidelines for cell planning of wireless communication systems. The measured data was taken in urban region with low vegetation and some trees at 900 MHz frequency band. Path loss models are useful planning tools, which permit the designers of cellular communication to obtain optimal levels for the base station deployment and meeting the expected service level requirements. Outcomes show that these empirical models tend to overestimate the propagation loss. As one of the key outputs, it was observed that the calculations of Weissberger model fit with the measured data in urban environment.

• 한국인터넷방송통신학회논문지
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• 제14권3호
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• pp.51-56
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• 2014

TETRA(TErrestrial Trunked RAdio)는 디지털 TRS(Trunked Radio System)의 유럽 표준으로 재난통신에 특화된 서비스를 제공한다. 특히 TETRA에서 제공하는 DMO(Direct Mode Operation) 기능은 기지국 중계 없이 단말기간 직접통신이 가능하여 기지국 전파가 도달되지 않는 음영지역에 효과적으로 활용된다. 하지만 사용자들이 DMO기능을 보다 효과적으로 활용하기 위해서는 전파도달범위 예측 정보가 제공되어야 한다. 따라서 본 논문에서는 국내에 보급되어 운용 중인 TETRA DMO 단말기의 링크버짓을 계산하고 이를 경로손실 모델에 적용시켜 지역 환경별 전파도달 거리를 예측하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 추계종합학술대회
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• pp.457-461
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• 2007

In many applications, received signal strength indicator is used for location tracking and sensor nodes localization. For location finding, the distances between sensor nodes can be estimated by converting received signal's power into distance using path loss prediction model. Many researches have done the analysis of power-distance relationship for radio channel characterization. In indoor environment, the general conclusion is the non-linear variation of RSSI values as distance varied linearly. This has been one of the difficulties for indoor localization. This paper presents works on indoor RSSI characterization based on statistical methods to find the overall trend of RSSI variation at different places and times within the same room From experiments, it has been shown that the variation of RSSI values can be determined by both spatial and temporal factors. This two factors are directly indicated by the two main parameters of path loss prediction model. The results show that all sensor nodes which are located at different places share the same characterization value for the temporal parameter whereas different values for the spatial parameters. Using this relationship, the characterization for location estimation can be more efficient and accurate.

• 한국전자파학회논문지
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• 제17권3호
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• pp.259-266
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• 2006

본 논문에서는 인체 모델 시뮬레이터를 이용해 인체 내부에 소스를 인가한 경우에 대한 전파 특성을 제시하였다. 시뮬레이터는 인체 캐드 및 조직 데이터로 구성된 인체 자료에 FDTD 기법을 적용하였다. 시뮬레이터에 대한 정확성을 검증한 후, 전계 소스가 소장 중앙에 인가된 경우에서 소화관 중 소장을 포함하는 수평층의 수신파를 계산하였다. 시뮬레이션 결과로부터 다양한 수신 지점에 대해 단위 길이 당 경로 손실을 구함으로써 인체전파 특성을 보였다.