• Journal of Advanced Navigation Technology
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• 제21권3호
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• pp.279-286
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• 2017

The international maritime organization(IMO) has defined performance requirements for future maritime navigation through IMO resolution A.915(22) in 2001. Many DGPS systems currently providing DGPS services do not meet the performance requirements specified in IMO resolution A.915(22). The use of SBAS is considered as one of the DGPS replacement and supplementary system for coping with the increase in demand performance and providing safe positioning service. In particular, since a large amount of budget is required to rearrange the existing DGPS reference stations, a method which transmits differential corrections generated by using SBAS message has been proposed. In this paper, we compare and analyze the performance of NDGPS which is operated by the National Maritime PNT Office of the ministry of oceans and fisheries(MOF) in Korea and MSAS in Japan. Also, we verify that SBAS, as alternative and complementary system, meets the performance requirement specified in IMO resolution A.915(22).

• Journal of the Korea Institute of Information and Communication Engineering
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• 제9권3호
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• pp.638-646
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• 2005

In recent wireless communications, direct conversion transceiver or If sampling SDR-based receivers have being designed as an alternative to conventional transceiver topologies. In direct conversion receiver a.chitectu.e, the 1.equency/phase offset between the RF input signal and the local oscillator signal is a major impairment factor even though the conventional AFC/APC compensates the service deterioration due to the offset. To rover the limited tracking range of the conventional method and effectively aid compensation scheme in terms of I/Q channel imbalances, the frequency/phase offset compensation in RF-front end signal stage is proposed in this paper. In RF-front end, the varying phase offset besides the fixed large frequency/phase offset are corrected by using early-late phase compensator. A more simple frequency and phase tacking function in digital signal processing stage of direct conversion receiver is effectively available by an ingenious frequency/phase offset tracking method in RF front-end stage.

• Journal of Broadcast Engineering
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• 제16권2호
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• pp.305-318
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• 2011

Since switched digital video (SDV) provides specific programs only to the subscribers who request the programs, SDV has attracted considerable interest of MSOs for bandwidth efficiency. In North America, MSOs service over 2.3 million households with the SDV for cable networks. In Korea, since demand of HD program, high-speed Internet, VoD, and VoIP is noticeably rising, the SDV is considered as the alternative for bandwidth saving and efficient managing. In this paper, the characteristics, operating structure, and bandwidth saving of the SDV are discussed and technical requirements for the SDV are also introduced. The channel switching performance and stability of the SDV are analyzed through the test-bed.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제11권1호
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• pp.130-140
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• 2010

SIP (Session Initiation Protocol) is a signaling protocol to provide IP-based VoIP (Voice over IP) service. However, many security vulnerabilities exist as the SIP protocol utilizes the existing IP based network. The SIP Malformed message attacks may cause malfunction on VoIP services by changing the transmitted SIP header information. Additionally, there are several threats such that an attacker can extract personal information on SIP client system by inserting malicious code into SIP header. Therefore, the alternative measures should be required. In this study, we analyzed the existing research on the SIP anomaly message detection mechanism against SIP attack. And then, we proposed a Co-occurrence based SIP packet analysis mechanism, which has been used on language processing techniques. We proposed a association rule generation and an attack detection technique by using the actual SIP session state. Experimental results showed that the average detection rate was 87% on SIP attacks in case of using the proposed technique.

• Journal of Digital Convergence
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• 제18권10호
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• pp.479-490
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• 2020

The purpose of this study was to examine the perceptions of vocational rehabilitation practitioners in mental rehabilitation facilities related to their services, then it was intended to suggest the strategic plans for the services. To this purpose, data related to vocational rehabilitation services provided by mental rehabilitation facilities were collected, and a focus group interview(FGI) was conducted for the practitioners in charge of vocational rehabilitation services. And this data was analyzed to results. The research results are as follows. First, the related manuals and guidelines should be created to clarity the role and function of the facilities, that is the detailed standards are necessary for the workers participating in vocational rehabilitation services. Second, they expect that people with mental illness must be treated equally with other people with disabilities and the vocational rehabilitation services should be supported according to their disability characteristics. Based on the results of these studies, specific strategic plans for vocational rehabilitation services were suggested.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 한국환경독성학회 2003년도 추계국제학술대회
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• pp.91-93
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• 2003

It has been estimated that the equivalent of approximately $US 50 billion has been spent on research on the behavior and fate of pesticides in the environment since Rachel Carson published “Silent Spring” in 1962. Much of the resulting knowledge has been summarized explicitly in computer algorithms in a variety of empirical, deterministic, and probabilistic simulation models. These models describe and predict the transport, degradation and resultant concentrations of pesticides in various compartments of the environment during and after application. In many cases the known errors of model predictions are large. For this reason they are typically designed to be “conservative”, i.e., err on the side of over-prediction of concentrations in order to err on the side of safety. These predictions are then compared with toxicity data, from tests of the pesticide on a series of standard representative biota, including terrestrial and aquatic indicator species and higher animals (e.g., wildlife and humans). The models' predictions are good enough in some cases to provide screening of those compounds which are very unlikely to do harm, and to indicate those compounds which must be investigated further. If further investigation is indicated a more detailed (and therefore more complicated) model may be employed to give a better estimate, or field experiments may be required. A model may be used to explore “what if” questions leading to possible alternative pesticide usage patterns which give lower potential environmental concentrations and allowable exposures. We are currently at a maturing stage in this research where the knowledge base of pesticide behavior in the environmental is growing more slowly than in the past. However, innovative uses are being made of the explosion in available computer technology to use models to take ever more advantage of the knowledge we have. In this presentation, current developments in the state of the art as practiced in North America and Europe will be presented. Specifically, we will look at the efforts of the ‘Focus’ consortium in the European Union, and the ‘EMWG’ consortium in North America. These groups have been innovative in developing a process and mechanisms for discussion amongst academic, agriculture, industry and regulatory scientists, for consensus adoption of research advances into risk management methodology.

• Journal of Korean Society of Rural Planning
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• 제15권4호
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• pp.199-211
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• 2009

The aim of this paper is to investigate the applicability of high spatial resolution remote sensing images for conducting the rural amenity resources survey. There are a large number of rural amenity resources and field reconnaissance without a sufficient preliminary survey involves a big amount of cost and time even if the data quality cannot always be satisfied with the advanced study. Therefore, a new approach should be considered like the state-of-the-art remote sensing technology to support field survey of rural amenity resources as well as to identify the spatial attributes including the geographical location, pathway, area, and shape. Generally high-resolution satellite or aerial photo images are too expensive to cover a large area and not free of meteorological conditions, but recently rapidly-advanced internet-based image services, such as Google Earth, Microsoft Bing maps, Bluebirds, Daum maps, and so on, are expected to overcome the handicaps. The review of the different services shows that Google Earth would be the most feasible alternative for the survey of rural amenity resources in that it provides powerful tools to build spatial features and the attributes and the data format is completely compatible with other GIS(Geographic information system) software. Hence, this study tried to apply the Google Earth service to interpret the amenity resources and proposed the reformed work process conjugating the internet-based high-resolution images like satellite and aerial photo data.

• Korean Journal of Remote Sensing
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• 제27권4호
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• pp.421-433
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• 2011

The importance of acquisition of road information has recently been increased with a rapid growth of spatial-related services such as urban information system and location based service. This paper proposes an automatic road extraction method using object-based approach which was issued alternative of pixel-based method recently. Firstly, the spatial objects were created by MSRS(Modified Seeded Region Growing) method, and then the key road objects were extracted by using properties of objects such as their shape feature information and adjacency. The omitted road objects were also traced considering spatial correlation between extracted road and their neighboring objects. In the end, the final road region was extracted by connecting discontinuous road sections and improving road surfaces through their geometric properties. To assess the proposed method, quantitative analysis was carried out. From the experiments, the proposed method generally showed high road detection accuracy and had a great potential for the road extraction from high resolution satellite images.

• Journal of Society of Preventive Korean Medicine
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• 제17권1호
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• pp.149-162
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• 2013

Objectives : This study was conducted to estimate the future demand and supply of physicians for korean medicine from 2016 year to 2026 year in order to make an adequate manpower policy in a way of keeping a balance between demand and supply. Methods : Baseline projection method and trend analysis(a polynomial log power equation model) were used in the estimation of future supply and demand respectively. We used data about the amount of oriental doctors from Ministry of Health and Welfare Statistics Yearbook and the treatment days from HIRA Statistics Yearbook. Results : It was projected that the total number of physician of Korean medicine will be 25,178 registered and 18,967 available in clinical setting. According to polynomial equation model which explained the trend of demand and had the highest score of $R^2$ among the equation models, 3,800~5,600 physician in Korean medicine will be oversupplied in 2016 year, 9,000~10,700 physicians in 2021 year and 15,700~17,000 persons in 2026 year depends on annual working days which is 265days, 255days or 239days. Log equation model also showed that overall excess supply of physician manpower in Korean medicine. Conclusions : Alternative manpower policies for Korean medicine doctors should be implemented in a way of both dwindling supplies and growing demand in Korean medical service in terms of Korean medical services utilization and improving physician's productivity.

• Journal of the Korean Society for Nondestructive Testing
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• 제21권4호
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• pp.415-424
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• 2001

The destructive method is reliable and widely used for the estimation of material degradation but, it have time-consuming and a great difficulty in preparing specimens from in-service industrial facilities. Therefore, the estimation of degraded structural materials by nondestructive evaluation is strongly desired. In this paper, the use of guided wave was suggested for the evaluation on thermally damaged 2.25Cr-1Mo steel as an alternative way to compensate for limitations of fracture tests. The observation of microstructure variations of the material including carbide precipitation increase and spheroidization near grain boundary was conducted and the correlation with the guided wave features such as energy loss ration and group velocity changes was investigated. Through this study, the feasibility of ultrasonic guided wave evaluation for thermally damaged materials was explored.