• Journal of Navigation and Port Research
• /
• v.38 no.6
• /
• pp.577-583
• /
• 2014

A ship-to-ship (STS) lightering operation takes place in order to transfer cargo (e.g. crude oil or petroleum products) between an ocean-going ship and a service ship alongside it. Instrumental measurements to accurately determine the relative speeds and distances during the approach between the vessels would benefit the operational safety and efficiency. A velocity information GPS (VI-GPS) system, which uses the instantaneous velocity measures from carrier-phase Doppler measurement, has been applied in a field observation onboard a service ship (Aframax tanker) approaching a ship-to-be-lightered (VLCC) in open waters. This article proposes to apply VI-GPS as the input sensor to a guidance and decision-support system aiming to provide accurate velocity information to the officer in charge of an STS operation. A method for precise velocity measurement using VI-GPS was described and the measurement results were compared each other with the results of Voyage Data Recorder (VDR) and VI-GPS that showed the concept of a guidance and decision-support system applying VI-GPS with the field test results during STS operations. Also, it turned out that VI-GPS has sufficient accuracy to serve as an input sensor from the field test results.

• Education of Primary School Mathematics
• /
• v.15 no.2
• /
• pp.91-106
• /
• 2012

This study reports pre-service teachers' problem solving process on the problem-based learning(PBL) employed in an elementary mathematics method course. The subjects were 6 pre-service teachers(students). The data were collected from classroom observation. The research results were described by problem solving stages. In understanding the problem stage, students identified what problem stand for and made a problem solving planned sheet. In curriculum investigation stage, students went through investigation and re-investigation process for solving the task. In problem solving stage, students selected the best strategy for solving the task and presented and shared about problem solving results.

• Journal of Internet Computing and Services
• /
• v.9 no.2
• /
• pp.83-88
• /
• 2008

Session initiation protocol (SIP) is an application-layer prolocol to initiate and control multimedia client session. When client ask to use a SIP service, they need to be authenticated in order to get service from the server. Authentication in a SIP application is the process in which a client agent present credentials to another SIP element to establish a session or be granted access to the network service. In 2005, Yang et al. proposed a key exchange and authentication scheme for use in SIP applications, which is based on the Diffie-Hellman protocol. But, Yang et al.'s scheme is not suitable for the hardware-limited client and severs, since it requires the protocol participant to perform significant amount of computations (i.e., four modular exponentiations). Based on this observation. Huang and Wei have recently proposed a new efficient key exchange and authentication scheme thor improves on Yang et al.'s scheme. As for security, Huang and Wei claimed, among others, that their scheme is resistant to offline dictionary attacks. However, the claim turned out to be untrue. In this paper, we show thor Huang and Wei's key exchange and authentication scheme is vulnerable to on offline dictionary attack and forward secrecy.

• Bulletin of the Korean Space Science Society
• /
• 2009.10a
• /
• pp.46.3-46.3
• /
• 2009

The SAR (Synthetic Aperture Radar) satellite has the advantage of implementing the imaging mission even though it is night time, cloudy weather, and all weather conditions, which is different from the satellite with the optical payload. This is the reason why the SAR satellite comes into the spotlight in the observation satellite field. The Korea Aerospace Research Institute (KARI) has been developing the first Korean SAR satellite and is currently integrating and testing the Flight Model. For the launch vehicle service, KARI finalized the selection of the launch vehicle service provider and finished Critical Design Review (CDR) of the interface between the bus and the launch vehicle. KARI and launch vehicle service provider also finished the test of the telemetry interface between the bus and the launch vehicle. The test of the telemetry interface has the purpose of checking the interface of the telemetry which is the SOH(State-of-Health) of the satellite in an early launch stage. For this test, KARI has finished the development of the spacecraft simulator which is composed of the bus simulator to generate the analog telemetry and the launch vehicle simulator to gather the telemetry. In this research, the result of the hardware implementation and the software implementation for the spacecraft simulator were described. Finally the results of the launch vehicle telemetry MUX test which were performed at the launch vehicle provider's design office by using the spacecraft simulator were summarized. It is expected that this simulator will be used in the next test after the manufacture of the launch vehicle.

• Journal of the Korean Society for Library and Information Science
• /
• v.36 no.1
• /
• pp.5-24
• /
• 2002

The purpose of this study is to find out ways for establishing the identity and for strengthening the function of Dong-office minilibraries, which are nation-widely sprouted according to the Government’s policy of converting the Dong-office’s functions. The general operating status of the minilibraries were investigated by telephone interviews with the minilibrary operators, the collection and usage status by on-site observation, and the user behaviour by user surveys. For the effective operation of the Dong-office minilibrariea they should be identified as service stations of public libraries, supported technically by the local public libraries, and connected to the local educational and social service institutions for the securance of users and volunteers. Networks among the minilibrary operators should also be established for exchanges and cooperations. Furthermore, operating models should be developed according to the library’s environments and the user’s needs.

• Journal of Periodontal and Implant Science
• /
• v.52 no.3
• /
• pp.194-205
• /
• 2022

Purpose: This study aimed to determine the long-term outcomes after peri-implantitis treatment and the factors affecting these outcomes. Methods: This study included 92 implants in 45 patients who had been treated for peri-implantitis. Clinical data on the characteristics of patients and their implants were collected retrospectively. The change in the marginal bone level was calculated by comparing the baseline and the most recently obtained (≥3 years after treatment) radiographs. The primary outcome variable was progression of the disease after the treatment at the implant level, which was defined as further bone loss of >1.0 mm or implant removal. A 2-level binary logistic regression analysis was used to identify the effects of possible factors on the primary outcome. Results: The mean age of the patients was 58.7 years (range, 22-79 years). Progression of peri-implantitis was observed in 64.4% of patients and 63.0% of implants during an observation period of 6.4±2.7 years (mean±standard deviation). Multivariable regression analysis revealed that full compliance to recall visits (P=0.019), smoking (P=0.023), placement of 4 or more implants (P=0.022), and marginal bone loss ≥4 mm at baseline (P=0.027) significantly influenced the treatment outcome. Conclusions: The long-term results of peri-implantitis treatment can be improved by full compliance on the part of patients, whereas it is impaired by smoking, placement of multiple implants, and severe bone loss at baseline. Encouraging patients to stop smoking and to receive supportive care is recommended before treatment.

• Korean Journal of Human Ecology
• /
• v.21 no.2
• /
• pp.197-211
• /
• 2012

This purpose of this study was to explore the meaning and significance of experiences encountered by preservice teachers' during their observational practicum at day care centers. This study involved one cohort of 32 junior students who were majoring in early childhood education at a 4-year university. Data was analyzed using qualitative research methodology. The findings were as follows: 1) the meaning and significance of students'experiences related to observing children was to develop a trusting relationship with children and a cooperative relationship with teachers in an unfamiliar context. 2) the meaning and significance of students'experiences in observing children was to understand the children and their circumstance. 3) the meaning and significance of students'experience in observing children was to understand the importance of listening in child-teacher spoken interaction.

• Wind and Structures
• /
• v.12 no.4
• /
• pp.349-381
• /
• 2009

Since 1998, several institutions have deployed mobile instrumented towers to collect research-grade meteorological data from landfalling tropical cyclones. This study examines the wind flow characteristics from seven landfalling tropical cyclones using data collected from eight individual mobile tower deployments which occurred from 1998-2005. Gust factor, turbulence intensity, and integral scale statistics are inspected relative to changing surface roughness, mean wind speed and storm-relative position. Radar data, acquired from the National Weather Service (NWS) Weather Surveillance Radar - 1988 Doppler (WSR-88D) network, are examined to explore potential relationships with respect to radar reflectivity and precipitation structure (convective versus stratiform). The results indicate tropical cyclone wind flow characteristics are strongly influenced by the surrounding surface roughness (i.e., exposure) at each observation site, but some secondary storm dependencies are also documented.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2006.04a
• /
• pp.235-241
• /
• 2006

The demand of 3D terrain mapping techniques is increasing in many application fields such as CNS(Car Navigation System), web service system, DMB(Digital Multimedia Broadcasting) systems and etc To construct a 3D terrain map, it is a pre-requite step that register data collected from different surveying sources. This Paper Present the methodology to register airborne photo, LIDAR data, and digital map, which are major data sources to create a 3D terrain mao. For this purpose, we developed the generally applicable algorithm that uses linear features to register airborne photos and digital maps to LIDAR data. The algorithm explicitly formulates step-by-step methodologies to establish observation equations for transformation. The results clearly demonstrate the proposed algorithm is appropriate to register these data sources.

• Proceedings of the KSRS Conference
• /
• 2005.10a
• /
• pp.112-115
• /
• 2005

Communication Ocean Meteorological Satellite (COMS) for the hybrid mission of meteorological observation, ocean monitoring, and telecommunication service is planned to be launched onto Geostationary Earth Orbit in 2008. The meteorological payload of COMS is an imager which will monitor meteorological phenomenon around the Korean peninsular intensively and of Asian-side full Earth disk periodically. The meteorological imager (MI) of COMS has 5 spectral channels, I visible channel with the resolution of I km at nadir and 4 infrared channels with the resolution of 4 km at nadir. The characteristics of the COMS MI are introduced in the view points of user requirements, hardware characteristics, and operation features.