• Ocean Science Journal
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• v.41 no.4
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• pp.245-254
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• 2006

Long term wave climate of both extreme wave and operational wave height is essential for planning and designing coastal structures. Since the field wave data for the waters around Korean peninsula is not enough to provide reliable wave statistics, the wave climate information has been generated by means of long-term wave hindcasting using available meteorological data. Basic data base of hindcasted wave parameters such as significant wave height, peak period and direction has been established continuously for the period of 25 years starting from 1979 and for major 106 typhoons for the past 53 years since 1951 for each grid point of the North East Asia Regional Seas with grid size of 18 km. Wind field reanalyzed by European Center for Midrange Weather Forecasts (ECMWF) was used for the simulation of waves for the extra-tropical storms, while wind field calculated by typhoon wind model with typhoon parameters carefully analyzed using most of the available data was used for the simulation of typhoon waves. Design wave heights for the return period of 10, 20, 30, 50 and 100 years for 16 directions at each grid point have been estimated by means of extreme wave analysis using the wave simulation data. As in conventional methodsi of design criteria estimation, it is assumed that the climate is stationary and the statistics and extreme analysis using the long-term hindcasting data are used in the statistical prediction for the future. The method of extreme statistical analysis in handling the extreme vents like typhoon Maemi in 2003 was evaluated for more stable results of design wave height estimation for the return periods of 30-50 years for the cost effective construction of coastal structures.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.6
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• pp.581-591
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• 2016

Several attempts to construct multi-purpose tunnel for both road and waterway have been made. The multi-purpose tunnel is mainly used as a road tunnel, however it is transferred to waterway to control flood during rainy season. The planning of the multi-purpose tunnel is recognized as cost-effective way of infrastructure construction. In case of the multi-purpose tunnel constructed beneath groundwater table, seasonal fluctuation of groundwater table and repeated flow in the tunnel may cause long-term deterioration of the tunnel system. In this study, the behavior of multi-purpose tunnel in view of groundwater table or flow in the tunnel is investigated using model test and numerical modeling method. The results have shown that rising of groundwater table caused buoyant force to the tunnel and the fluctuation of rainwater in the tunnel generated loosening of surrounding ground. It is recommended to evaluate the effect of the long-term water pressure variation in the design of a multi-purpose tunnel.

• Journal of Korean Library and Information Science Society
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• v.47 no.4
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• pp.443-464
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• 2016

A great number of institutions around the world have been building digital repositories to communicate scholarly information. Meanwhile, digital repositories have been struggling with how to preserve increased volume of digital contents for the long term and how to build a sustainable information environment. The HathiTrust partnership was established to meet the need of a sustainable collaborative model of digital repositories in research libraries, mainly in North America, and has been expanded globally by signing with other libraries around the world. This paper is dealt with the establishment, operation and policy, construction status, and user service of the HathiTrust. The results presented in this paper include the benefits and potential opportunities of the HathiTrust as a participating member. Partnership in HathiTrust would allow each member institution to provide more cost-effective operations, shared management and long-term preservation of digital content, ease of copyright management, and increased accessibility. In the future it is expected to provide a shared storage of printed materials and to facilitate a big data research center.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.5
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• pp.168-177
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• 2009

This paper proposes the EAP-AKA scheme without UICC for extending its usage to existing WLAN/WiBro devices. To apply the current EAP-AKA scheme, the WLAN/WiBro devices require an external Universal Integrated Circuit Card (UICC) reader. If they don't use UICC due to cost overhead and architectural problem of device, the EAP-AKA scheme loses its own advantages in security and portability aspects. The proposed scheme uses the DH key algorithm and a password for non-UICC devices instead of using the long-term key stored in UICC. The main contribution is to maintain the security and portability of the EAP-AKA while being applied to non-3GPP network devices not equipped with UICC. Furthermore, it does not require major modifications of authentication architecture in 3GPP.

• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.118-124
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• 2017

An air cooling, open cathode type polymer electrolyte membrane fuel cell (PEMFC) has the advantages of system simplification and cost effectiveness. Open cathode PEMFC could suffer from reduced performance due to the membrane dehydration in low humidity of air. Effects of the cathode air flow rate, anode purge interval and long term storage on PEMFC performance were investigated in this work. Fan voltage is an important factor on air cooling PEMFC performance because the cathode air flow rate and stack temperature were controlled by fan voltage. The dead ended anode (DEA) method was applied to increase hydrogen usage. Periodical purge was used to discharge accumulated water and gas. The influence of long term non-operating condition on PEMFC performance degradation due to the membrane dehydration was also studied and the quick recovery method was developed.

• Journal of the Korean Geotechnical Society
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• v.27 no.1
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• pp.35-40
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• 2011

Dredging and disposal is a conventional method to remove contaminated sediments. However, there are some problems in dredging and disposal, such as disturbance of contaminated sediments, disposal site determination, and high construction cost. Recently, in-situ capping which overcomes the problems of dredging and disposal is widely applied to isolate local contaminated sites. Numerical studies, which have been conducted to simulate contaminant transport during in-situ capping, have been concerned mainly with diffusive transport. However, contaminated sediments experience large strain consolidation induced by self-weight because of initially high moisture content of sediments, and contaminant transport results from advection and diffusion. Previous studies focus on contaminant transport during consolidation, but have neglected consolidation effect on long-term contaminant transport in sediments. This study presents numerical simulation results of consolidation effect on long-term contaminant transport in sediments.

• Journal of the Korean Geotechnical Society
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• v.36 no.3
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• pp.5-14
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• 2020

The railway concrete track has been increasingly adopted for high-speed train such as KTX due to its high running stability, improved ride quality for the passengers, and low maintenance cost. However, excessive settlement of the railway concrete track has been monitored at embankment sections of the ◯◯ High-speed Line, resulting in the concerns on the safety of railway operation. In order to establish an effective maintenance plan for the concrete track railway exceeding the allowable residual settlement, it is essential to reasonably predict their long-term settlement behavior during the public period. In this study, we developed a model for predicting the long-term settlement behavior of concrete track using recurrent neural network (RNN) and examined the applicability of the developed model.

• Journal of Korean Neurosurgical Society
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• v.30 no.sup2
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• pp.235-241
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• 2001

Objective : Controversy exists which surgical treatment better in lumbar grade I spondylolisthesis, decompressive laminectomy with or without lumbar instrumentation. Methods : Out of Sixty-four patients with lumbar spondylolisthesis underwent surgery, 18 patients operated with decompressive laminectomy alone and 44 patients with decompession and lumbar instrument, during recent 5-years between January, 1994 and December, 1998. The author studied a long term follow-up in the above two groups to analyzing the overall clinical outcomes in each group and to determining the incidence of pos-toperative radiologic instability. Results : 1) Overall postoperative symptoms improvement were not so different in both groups. 2) Postoperative progressive subluxation is more common after decompressive laminectomy without instrumentation than with instrumentation group. 3) Overall clinical outcomes were slightly better in decompressive laminectomy without instrumentation than with instrumentation group but there was no significant difference. 4) Postoperative radiologic changes did not seem to influence the patient-reported clinical outcomes. 5) Postoperative complications is more common in decompressive laminectomy with instrumentation group than without instrumentation group. Conclusion : In the surgical management of grade I spondylolisthesis, the efficiency and superiority of surgical treatments requires the cost effectiveness and risk/benefit analysis of decompressive laminectomy with or without instrumentation. Therefore, Further detailed studies of long term follow up in a large number of patients in each group are needed for choice of best treatment.

• Journal of Advanced Navigation Technology
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• v.26 no.2
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• pp.119-124
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• 2022

The international gnss service (IGS) provides real-time service (RTS) orbit and clock correction applicable to the broadcast ephemeris of GNSS satellites. However, since the RTS correction cannot be received if the Internet connection is lost, the RTS correction should be predicted and used when a signal interruption occurs in order to perform stable precise point positioning (PPP). In this paper, PPP was performed by predicting orbit and clock correction using a long short-term memory (LSTM) algorithm in real-time during the signal loss. The prediction performance was analyzed by implementing the LSTM algorithm in RPI (raspberry pi), the processing speed of which is not high. Compared to the polynomial prediction model, LSTM showed excellent performance in long-term prediction.

• Journal of the Korean Dietetic Association
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• v.28 no.2
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• pp.67-84
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• 2022

This study aimed to explore the status of food service outsourcing behavior of long-term care institutions (LTCIs) through a cross-sectional survey using a questionnaire administered between July 16th and August 7th, 2020. The survey respondents were either dietitians or facility managers, who worked at 731 nursing homes, 477 group homes, and 673 day-care centers. Approximately 25.9% of nursing homes, 11.7% of group homes, and 33.1% of day-care centers used a managed-services company to operate their food service units. The main reason for outsourcing food service by nursing homes was related to the staffing of dietitians and cooks, whereas group homes and day-care centers outsourced food services due to factors relating to meal costs and the cooking process. Almost all the LTCIs entered into private contracts for outsourced food services. Only a few food service contracts included the types of meals, nutrition standards such as protein and calories per meal, and the parameter or ratio of food cost. Of the respondents, 84.5% from nursing homes, 87.5% from group homes, and 87.1% from day-care centers agreed that the quality of outsourced food services of the LTCIs should be regulated. Meals are essential for maintaining the health and functional status of LTCI users. As more LTCIs outsource their food services, we suggest the following: (1) Increasing the minimum dietitian staffing standards for LTCIs as per the Welfare of Senior Citizens Act and requiring at least one dietitian for every nursing home, (2) Making it mandatory to use a standard food service contract template when drafting food service contract, and (3) Developing realistic standards for food service operations considering the size and operation type of the LTCIs.