• Journal of Satellite, Information and Communications
• /
• v.6 no.1
• /
• pp.75-79
• /
• 2011

Wireless devices can communicate between each other without existing infrastructure in mobile Ad-hod network. Ad hoc networks can be used under difficult conditions, where it is difficult to construct infrastructures, such as shadowing areas, disaster areas, war area, and so on. In order to support to considerable and various wireless services, more spectrum resources are needed. However, efficient utilization of the frequency resource is difficult because of spectrum scarcity and the conventional frequency regulation. Ad-hoc networks employing cognitive radio (CR) system that guarantee high spectrum utilization provide effective way to increase the network capacity. In this paper, we simulate and compare the performance of conventional single and cooperative spectrum sensing with CR system using ad-hoc networks in additive white Gaussian noise (AWGN) and Rayleigh channel model. And we demonstrate performance improvement by analyzing the system performance.

• Proceedings of the Korean Institute Of Construction Engineering and Management
• /
• autumn
• /
• pp.581-584
• /
• 2003

Recently, construction industry has an interest on the maintenance area of construction facilities to maximize utilization of the each facility. This study suggests an interactive electronic technical manual for bridge facility to improve quality and to ensure safety of the bridge facility. The improvement method of bridge maintenance system consists of the basic information ell the facilities, maintenance manuals and measurement system. And the suggested system is based on the facilities, maintenance manuals and measurement system. And the suggested system is based on IETM (Interactive Electronic Technical Manual), and this study defines and develops a $BF\_IETM (Bridge Facility\_ITEM$ as the bridge maintenance system.

• 한국정보통신설비학회:학술대회논문집
• /
• 2007.08a
• /
• pp.181-184
• /
• 2007

Up to now, a lot of houses, roads and other urban facilities have been damaged by natural disasters such as flash floods and landslides. It is reported that the size and frequency of disasters are growing greatly due to global warming. In order to mitigate such disaster, flood forecasting and alerting systems have been developed for the Han river, Geum river, Nak-dong river and Young-san river. These systems, however, do not help small municipal departments cope with the threat of flood. In this study, a real-time urban flood forecasting service (U-FFS) is developed for ubiquitous computing city which includes small river basins. A test bed is deployed at Tan-cheon in Gyeonggido to verify U-FFS. Wireless sensors such as rainfall gauge and water lever gauge are installed to develop hydrologic forecasting model and CCTV camera systems are also incorporated to capture high definition images of river basins. U-FFS is based on the ANFIS (Adaptive Neuro-Fuzzy Inference System) that is data-driven model and is characterized by its accuracy and adaptability. It is found that U-FFS can forecast the water level of outlet of river basin and provide real-time data through internet during heavy rain. It is revealed that U-FFS can predict the water level of 30 minutes and 1 hour later very accurately. Unlike other hydrologic forecasting model, this newly developed U-FFS has advantages such as its applicability and feasibility. Furthermore, it is expected that U-FFS presented in this study can be applied to ubiquitous computing city (U-City) and/or other cities which have suffered from flood damage for a long time.

• Journal of Korean Society of Rural Planning
• /
• v.20 no.1
• /
• pp.1-12
• /
• 2014

Living environments in rural area have become deteriorated rapidly. Increase of aging population, decline in agricultural income, polarization of wealth in rural community due to rural returners have caused severe decline and imbalance of living environments in rural area. Responding to this circumstances, governments currently develop projects for improving living environments focusing on individual housing which were excluded from governmental supports because those had been regarded as private property. Nevertheless, there are still some gaps and problems in evaluating the quality of living environment and suggesting effective solutions. It would be because standards and guidelines of the projects have been based on urban housing system. In order to support the implementation of the projects, this research has developed an index for evaluating and monitoring the quality of living environments in rural area. By applying Delphi method, the index has been created in four categories of 'security', 'convenience', 'comfortability', and 'durability' 'Security' consists of structural safety, crime, disaster, accident prevention. 'Convenience' includes three divisions of living, traffic, farm working. 'Comfortability' is divided into sanitation, indoor environments, and aesthetic appreciation. Lastly, 'durability' has four divisions of energy conservation, environmental friendliness, efficiency, and economics. Each sub-division also has different items from three to twelves. In the case of an index for performance evaluation, items have been derived from energy conservation(6-items), and environmental friendliness(7-items). Items developed as an index for evaluating rural living environments in this research might be good background information for remodeling project in rural housing development.

• The Journal of the Korea Contents Association
• /
• v.17 no.4
• /
• pp.95-107
• /
• 2017

Since disasters have been getting stronger and wider according to the influence of climate change, those impacts on social and national economy have been also getting more severe in various subjects. However, as direct property damage as well as casualties are only measured in case of disasters, monetary figures on its losses are likely to be underestimated, which are known as a major barrier to both compensation for loss and making a regional disaster management plan. Thus, the main purpose of this study is to develop statistics appropriate to the direct and indirect socioeconomic losses, which have continuously been overlooked. To achieve this purpose, this study defines the scope of direct and indirect socioeconomic losses, provides a framework for developing those measurements, and determines a preliminary statistics list. Selection criteria to set the final list are decided and are then applied to the list. The result of this study can be used as basic data for further studies to estimate and calculate its socioeconomic losses from storm and flood.

• Journal of Satellite, Information and Communications
• /
• v.10 no.4
• /
• pp.146-150
• /
• 2015

The COSPAS-SARSAT committee decides MEOSAR (Medium-Earth Orbit for search and rescue) service development for installing 406MHz SAR instruments on their respective MEO navigation satellite system of the United States, EU, and Russia, since 2000. The transmitted beacon signal is separately arrived by satellites with different FOA (Frequency of Arrival) and TOA (Time of Arrival). It is directly transferred to MEOLUT. In MEOLUT, a LUT track at least 3 or 4 satellites simultaneously and estimate location of beacon using time difference of arrival (TDOA) and frequency difference arrival (FDOA). But the transmitted distress signals may be overlapped each other because the distress beacons transmit signal on mean interval of 50 seconds in arbitrary time. It's difficult that simultaneously estimate location of beacon by current scheme for several overlapped distress signal. So we use cross ambiguity function (CAF) Map algorithm and present Multi-CAF MAP scheme in order to satisfy performance requirement of system. The performance is analyzed for COSAPS-SARSAT MEOSAR.

• Journal of the Korean Society of Industry Convergence
• /
• v.23 no.3
• /
• pp.411-417
• /
• 2020

Therefore, it was agreed that an earthquake monitoring station should be set up within the site of Handong University by analyzing drilling data and Disaster such as earthquakes is urgently needed to prepare for earthquakes in that people's lives and national development depend on the nation's ability to manage disasters. Many experts say that the Korean Peninsula is also under the influence of earthquakes and is not a safe zone for earthquakes. A seismological observatory will be established in Pohang to monitor ground sensors and study seismic characteristics through the task of "Development of Smart Sensor-based Intelligent Information Platform in Earthquake Region." Therefore, it was agreed to set up a seismological observatory within the site of Handong University by analyzing drilling data and conducting on-site surveys in northern Pohang, which were heavily damaged by liquefaction and earthquakes. In this study, it was decided to make a comprehensive judgment by considering the geological characteristics of the site, whether it can perform functions, and the convenience of construction and maintenance for the final site of the seismological observatory discussed with Handong University. After completing a feasibility review on selecting a site for Handong University, we will establish a seismological observatory and actively utilize it for seismic research using data from alarm issuance and seismic data in the event of a future earthquake.

• Wind and Structures
• /
• v.26 no.4
• /
• pp.191-204
• /
• 2018

This article presents a study of the largest-ever (height = 220 m) cooling tower using the large eddy simulation (LES) method. Information about fluid fields around the tower and 3D aerodynamic time history in full construction process were obtained, and the wind pressure distribution along the entire tower predicted by the developed model was compared with standard curves and measured curves to validate the effectiveness of the simulating method. Based on that, average wind pressure distribution and characteristics of fluid fields in the construction process of ultra-large cooling tower were investigated. The characteristics of fluid fields in full construction process and their working principles were investigated based on wind speeds and vorticities under different construction conditions. Then, time domain characteristics of ultra-large cooling towers in full construction process, including fluctuating wind loads, extreme wind loads, lift and drag coefficients, and relationship of measuring points, were studied and fitting formula of extreme wind load as a function of height was developed based on the nonlinear least square method. Additionally, the frequency domain characteristics of wind loads on the constructing tower, including wind pressure power spectrum at typical measuring points, lift and drag power spectrum, circumferential correlations between typical measuring points, and vertical correlations of lift coefficient and drag coefficient, were analyzed. The results revealed that the random characteristics of fluctuating wind loads, as well as corresponding extreme wind pressure and power spectra curves, varied significantly and in real time with the height of the constructing tower. This study provides references for design of wind loads during construction period of ultra-large cooling towers.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.59 no.4
• /
• pp.65-74
• /
• 2017

North Korea is one of the high vulnerable countries facing the threat of natural disaster and has experienced more frequent disasters in recent years. These disasters have significantly led to food shortages and large reductions in crop yields. In 2015, both North Korean officials and international agencies had identified the extreme drought event, the worst in one hundred years according to the North Korean government. The objective of this study was an assessment of the extreme drought events in 2014~2015, and to apply climatic drought indices for drought monitoring in North Korea. Characteristics of the extreme drought in North Korea are examined by using the weekly-based Standardized Precipitation Evapotranspiration Index (SPEI). The drought characteristics illustrated by the SPEI results are compared with a Standardized Precipitation Index (SPI) results and drought impact information to understand how these indices can explain the drought conditions within the country. These results demonstrated that the SPEI could be an effective tool to provide improved spatial and temporal drought conditions to inform management decisions for drought policy.

• Journal of Satellite, Information and Communications
• /
• v.9 no.1
• /
• pp.107-114
• /
• 2014

The satellite 2.1 GHz frequency bands, 1980-2010 MHz and 2170-2200MHz are allocated for mobile satellite service including satellite IMT, while it does not preclude the use of these bands for mobile services. The concept of an integrated satellite/terrestrial network has been introduced in worldwide because the terrestrial use in these bands adjacent to existing terrestrial IMT bands is attractive to provide mobile broadband services. The integrated satellite/terrestrial infrastructure with a high degree of spectrum utilization efficiency has the ability to provide both multimedia broadband services and public protection and disaster relief solutions. In addition, it is required to consider interference issues between the terrestrial and satellite components in order to reuse the same frequency band to both satellite and terrestrial component. This paper analyzes the interference for satellite uplink in the satellite/terrestrial integrated system and the interference reduction scheme for satellite uplink interfered by terrestrial user equipment.