• Journal of Advanced Navigation Technology
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• v.6 no.1
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• pp.44-51
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• 2002

This paper describes the performance evaluation and analysis of an Orthogonal Frequency-Division Multiplexing (OFDM) system having the least Inter Symbol Interference (ISI) in a multi-path fading channel environment. Wireless Local Area Network (W-LAN) in accordance with IEEE 802.11a and IEEE 802.11b provides high-speed transmission to universities, businesses and other various places. In addition, service providers can offer a public W-LAN service on restricted areas such as a subway. The proliferation of W-LAN has led to greater W-LAN service demands, but problems are also on the rise in offering a good W-LAN service. In particular, urban areas with high radio wave interference and many buildings are vulnerable to deteriorated QoS including disconnected data and errors. For example, when high-speed data is transmitted in such areas, the relatively high frequency generates ISI between Access Points (AP) and Mobile Terminals (such as a notebook computer), leading to a frequency selective fading channel environment. Consequently, it is difficult to expect a goodW-LAN service. The simulation proves that the OFDM system enables W-LAN to implement QoS in high-speed data transmission in a multi-path fading channel environment. The enhanced OFDM performance with 52 sub-carriers is verified via data modulation methods such as BPSK, QPSK and 16QAM based on IEEE 802.11a and punched convolutional codes with code rate of 1/2 and 3/4 and constraint length of 7. Especially, the simulation finds that the OFDM system has better performance and there is no data disconnection even in a mobile environment by applying a single tap equalizer and a decision feedback equalizer to a mobile channel environment with heavy fading influence. Given the above result, the OFDM system is an ideal solution to guarantee QoS of the W-LAN service in a high-speed mobile environment.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.9
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• pp.528-533
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• 2016

One of ways for effectively maintaining asbestos buildings is to select asbestos buildings to be removed firstly by manufacturing and analyzing asbestos map of various topics. Thus, in this study we manufactured asbestos map of various topics for the effective management of asbestos buildings owned by Seoul using QGIS (Quantum Geographic Information System). To select asbestos buildings likely to cause asbestos scattering problem and exposure into the air, we comprehensively took into consideration various topics such as asbestos buildings density, asbestos-area ratio, asbestos buildings distribution considering the population, first removal object, risk assessment, elapsed year. As described in this study, using the GIS may be utilized as a method for selecting asbestos buildings to be removed firstly as well as distribution of asbestos buildings. In the future, it is necessary to make assessment criteria considering diversification of property value in GIS such as the characteristics of the living environment around the asbestos buildings. This is expected to be utilized to manage the vulnerable region to asbestos exposure.

• The Journal of the Korea Contents Association
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• v.14 no.6
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• pp.417-427
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• 2014

This study was investigated on the basis of the role of housing cooperatives in sustainable regional business networks(SLEN) in regeneration of residential aged area where the urban poor live. For the analysis, input elements of human capital, social capital, financial capital and ecological capital were examine. For the process, the organization's structure, sustainable business and social networks, and for the result, the stability and community characteristics of the living and the payment possibility of housing construction cost were examined. Through this study, what kinds of issues can be from the housing coop's project in terms of sustainability, and what is the most important factor in order to overcome former mentioned issues were intended to find. For analysis literatures were reviewed and the in-depth interviews and survey were conducted with site visits. The result of this study finds that housing coop have community characteristics through active participation of residents during the regeneration process but the land, as financial and ecological capitals, and housing construction funds were poor. This was investigated that it makes groundless the sustainability of the project and the possibility of the payment. In order to overcome, land concession, inexpensive lental and active funning for housing construction to housing coop is required because housing coop is aiming to supply of social housing for low-income and vulnerable groups.

• Journal of KIISE:Computing Practices and Letters
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• v.9 no.3
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• pp.341-351
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• 2003

Digital image watermarking is the method that can protect the copyright of the image by embedding copyright information, which is called watermark. Watermarking must have robustness to intentional or unintentional data changing, called attack. The conventional watermarking schemes are robust to waveform attacks such as image compression, filtering etc. However, they are vulnerable to geometrical attacks such as rotation, scaling, translation, and cropping. Accordingly, this paper proposes new watermarking scheme that is robust to geometrical attacks by using invariant centroid. Invariant centroid is the gravity center of a central area in a gray scale image that remains unchanged even when the image is attacked by RST including cropping and proposed scheme uses invariant centroids of original and inverted image as the template. To make geometrically invariant domain, template and angle compensated Log -Polar Map(LPM) is used. Then Discrete Cosine Transform(DCT) is performed and the watermark is embedded into the DCT coefficients. Futhermore, to prevent a watermarked image from degrading due to interpolation during coordinate system conversion, only the image of the watermark signal is extracted and added to the original image. Experimental results show that the proposed scheme is especially robust to RST attacks including cropping.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.23 no.3
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• pp.445-457
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• 2013

This paper is about the study to build a quantitative methodology to assess cyber threats and vulnerabilities on control systems. The SCADA system in power industry is one of the most representative and biggest control systems. The SCADA system was originally a local system but it has been extended to wide area as both ICT and power system technologies evolve. Smart Grid is a concept to integrate energy and IT systems, and therefore the existing cyber threats might be infectious to the power system in the integration process. Power system is operated on a real time basis and this could make the power system more vulnerable to the cyber threats. It is a unique characteristic of power systems different from ICT systems. For example, availability is the most critical factor while confidentiality is the one from the CIA triad of IT security. In this context, it is needed to reflect the different characteristics to assess cyber security risks in power systems. Generally, the risk(R) is defined as the multiplication of threat(T), vulnerability(V), and asset(A). This formula is also used for the quantification of the risk, and a conceptual methodology is proposed for the objective in this study.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.692-700
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• 2007

A trial run of locally-developed tilting train has been in process on Chungbuk line since the test vehicle was first produced. For the system stabilization, interface verification among the systems including track, structure, catenary and signaling system, not to mention the rolling stock, is very crucial. In the area of wayside structure, the stability of track structure and train run shall be evaluated through the review of impact by increased speed by developed train on track structure. The study thus was intended to evaluate the impact on track while a tilting train is running the curve section, which is vulnerable to accelerated train speed. The analysis of tilting train test running the part of Chungbuk line and Honam line was conducted to identify the impact on existing track performance by tilting train. To identify the movement behavior of each part of track while tilting train, high speed train and traditional train (Mugunghwa and freight train) were running the existing line, wheel load, lateral wheel load, rail bending stress, vertical and lateral displacement of rail and vertical displacement of sleeper were compared and analyzed so as to evaluate the expected impact by tilting train for improving the train speed.

• The Korean Journal of Applied Statistics
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• v.27 no.7
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• pp.1243-1255
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• 2014

This study is aimed at developing an index and indicator in the light of social factors by analyzing the basic materials on Korean working conditions survey to make it possible to grasp various working environment factors consequent on business type and to judge the industrial safety & health policy of the related area. For the purpose of developing an index, this study was conducted by benchmarking the OECD-suggested index development guidelines and overseas cases of index development. This study suggested indexes related to health by benchmarking OECD's press-state-response model. The press-state health-related indexes specified in Korean working condtions survey were found to consist of physical risk environment, working hours, business environment, and social environment, and its consequent 'state' items were comprised of mental health, physical health, absence from work due to health problems and work satisfaction as health-related items. As a result, it was found that the 'press-state index' for wage worker, regular employee, manager, clerks, expert & related personnel involved, and workers aged under 50 was relatively good; in contrast, the 'press-state index' for people aged over 50, owner-operator, daily job, skilled position in agriculture & fisheries, simple labor service, and apparatus & machines assembly worker was found to be relatively vulnerable.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.5
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• pp.711-716
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• 2012

Due to the climate change in South Korea the annual total precipitation will increase by 17 percent by 2100. Rainfall is concentrated during the summer in South Korea and the landslide of farmland by heavy rain is expected to increase. Because regional torrential rains accompanied by a storm continue to cause the damage in farmland urgent establishment of adaptation plant for minimizing the damage is in need. In this study we assessed vulnerability of landslide of farmland by heavy rain for local governments. Temporal resolution is 2000 year and the future 2020 year, 2050 year, 2100 year via A1B scenario. Vulnerability of local government were evaluated by three indices such as climate exposure, sensitivity, adaptive capacity and each index is calculated by selected alternative variable. Collected data was normalized and then multiplied by weight value that was elicited in delphi investigation. Current vulnerability is concentrated in Jeju island and Gyeongsangnam-do, however, it is postulated that Kangwon-do will be vulnerable in the future. Through this study, local governments can use the data to establish adaptation plans for farmland landslide by climate change.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.1
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• pp.17-30
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• 2018

Currently, the global climate change response paradigm has been changed to a universal response system in which all nations, not the developed countries, participate. Korea has also set a target of 25.9 million tons of transportation greenhouse gas reduction targets by 2030. Korean society is expected to enter the super aging society in 2026. In this study, to reduce the greenhouse gas emissions in public transport and to improve the convenience of transportation vulnerable, we estimate the willingness to pay(WTP) and social benefits assuming that the existing feeder buses are replaced with medium-sized low floor electric buses. To this end, survey was conducted on bus users in the metropolitan area and WTP was estimated by using contingent valuation method(CVM), which is one of the non-market value evaluation methods. As a result of estimation of WTP, the average WTP is 51.4 (won / time person), estimated the economic benefits were 50 million won on weekdays and 40 million won on weekends in Gyeonggi Province in 2014.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.1
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• pp.34-39
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• 1993

A nutrition survey of 99 children, 3 to 6 years old and their mothers, in the day care center, situated in Kamman-dong of Pusan, as the location of one of the socioeconomically vulnerable groups, was undertaken between July 1 and 14, 1992, to investigate the effect of nutrition knowledge and nutrition attitude of the mothers. The results are summarized as follows. Nutrition attitude of the mother was tend to be higher score with increasing nutrition knowledge score. The scores of nutrition knowledge and nutrition attitude were affected by the mother's education level. There was a significant positive correlation between mother's employment and nutrition knowledge, but the nutrition attitude had no significant correlation with mother's employment. The intake of protein, lipid, Ca, niacin were significant correlation with maternal education level. The better the maternal nutrition attitude, the higher nutrient intakes of the children. But, there was negative significant correlation between nutrient intake of the children and mother's employment. The physical growth was affected more maternal nutrition attitude than education level and nutrition knowledge, whereas had negative correlation with maternal employment. There was negative correlation between mother's employment and food diversity of the children.