• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.3
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• pp.37-43
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• 2011

Reliability of piping systems is essential to the safety of any important industrial facilities. During an earthquake, damage to the piping system can occur. It can also cause considerable economic losses and the loss of life following earthquakes. Traditionally, the study of the secondary system was less important than primary structure system, however it has recently been emerging as a key issue for the effective maintenance of the structural system and to help reduce nonstructural earthquake damage. The primary objectives of this study are to evaluate seismic design requirements and the seismic performance of gas and fire protection piping systems installed in reinforced concrete (RC) buildings. In order to characterize the seismic behavior of the existing piping system in an official building, 10 simulated earthquakes and 9 recorded real earthquakes were applied to ground level and the building system by the newmark average acceleration time history method. The results developed by this research can be used for the improvement of new seismic code/regulatory guidelines of secondary systems as well as the improvement of seismic retrofitting or the strengthening of the current piping system.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.1
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• pp.61-68
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• 2010

Purpose: This article attempted to determine the factors affecting the preload and screw loosening. Methods: Available clinical studies from 1981 to 2008 from the PUBMED that presented screw loosening data and review articles regarding screw joint stability were evaluated. Eleven studies dealing the biomechanical principles of the screw mechanics were reviewed. Moreover, the results of our data were included. Results: The frequency of screw loosening was consequently reduced due to the advancement in torque tightening with torque wrench, screw material, coating technique for reducing the frictional force, and thread design, etc. If preload in the screw falls below a critical level, joint stability may be compromised, and the screw joint may fail clinically. The types of fatigue failure of screw were divided to adhesive wear, plastic deformation, and screw fracture. Conclusion: An optimum preload is essential to the success of the implant-abutment complex. To maintain optimum preload, using a torque wrench and re-tightening at recall time were needed.

• The Journal of the Acoustical Society of Korea
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• v.34 no.1
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• pp.20-35
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• 2015

Underwater acoustic channel impulse responses (CIR) are influenced by sound speed profile (SSP), and the variation of CIR has significant effects on the performance of underwater acoustic communication systems. A significant change of SSP can occur within a short period, which must be considered during the design of underwater acoustic modems. This paper statistically analyzes the effect of the variation of SSP on the long-range acoustic signal propagation in shallow-water with thermocline using numerical modeling based on the data acquired from JACE13 experiment near Jeju island. The analysis result shows that CIR changes variously according to the SSP and the depth of the transmitter and receiver. We also found that when the transmitter and receiver are deeper, the variation of sound wave propagation pattern is smaller and signal level becomes higher. All CIR obtained in this study show that a series of bottom reflections due to downward refraction and small bottom loss in the shallow water with thermocline can be very important factor for long-range signal transmission and the performance of underwater acoustic communication system in time varying ocean environment can be very sensitive to the variation of SSP even for a short period of time.

• Clinical and Experimental Reproductive Medicine
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• v.24 no.3
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• pp.335-340
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• 1997

Fluorescence in situ hybridization (FISH) techniques allow the enumeration of chromosome abnormalities and from a great potential for many clinical applications. In order to produce quantitative and reproducible results, expensive tools such as a cooled CCD camera and a computer software are required. We have developed a Chromosome Image Processing System (Chips) using FISH that allows the detection and mapping of the genetic aberrations. The aim of our study, therefore, is to evaluate the capabilities of our original system using a black-and-white video camera. As a model system, three repetitive DNA probes (D18Z1, DXZ1, and DYZ3) were hybridized to variety different clinical samples such as human metaphase spreads and interphase nuclei obtained from uncultured peripheral blood lymphocytes, uncultured amniocytes, and germ cells. The visualization of the FISH signals was performed using our system for image acquisition and pseudocoloring. FISH images were obtained by combining images from each of probes and DAPI counterstain captured separately. Using our original system, the aberrations of single or multiple chromosomes in a single hybridization experiment using chromosomes and interphase nuclei from a variety of cell types, including lymphocytes, amniocytes, sperm, and biopsied blastomeres, were enabled to evaluate. There were no differences in the image quality in accordance with FISH method, fluorochrome types, or different clinical samples. Always bright signals were detected using our system. Our system also yielded constant results. Our Chips would permit a level of performance of FISH analysis on metaphase chromosomes and interphase nuclei with unparalleled capabilities. Thus, it would be useful for clinical purposes.

• Korea journal of population studies
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• v.28 no.2
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• pp.131-164
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• 2005

The central focus of this research paper is to explore the recent structural core empirical unemployment reason of IT new professional manpower who graduated in higher education level in Korea. The final goal of this issue is to estimate and analyze rambling impediment in IT manpower labor market between 26 detail occupations and between detail occupations and 3 educational levels of new graduates and entrants who entered in IT 6 occupational groups composing 26 particular occupations. This study uses the 2004 data published by the Ministry of ICT and relies upon both one-way analysis of variance and two-way analysis variance to tackle the issue. According to the ANOVA results, 2 main points were delineated In the one-way analysis of variance method. the total sum of squares (SST) is decomposed into two major components: within sum of squares (SSW) (6 detail occupations, 85%) and between sum of squares (SSG) (26 detail occupation, 15%) The other major finding is that total sum of squares (SST) is decomposed into three major components: between detail occupations (SSG) (19.3%), between educations (SSB) and errors (SSE) (56%) in IT SIW development design group.

• Korea journal of population studies
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• v.28 no.2
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• pp.205-217
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• 2005

Purpose: To evaluate the factors affecting hospital utilization for respiratory diseases by ecological study design and GIS tool. To raise the social concern for respiratory disease by the result. Methods: Hospital admission data supported by national health insurance cooperation were transformed to spread sheet data format and combined with air monitoring dataset. Air pollution data were collected from the annual report of air monitoring published by Korea Ministry of Environment. Socioeconomic statistics including population density, age distribution, forest ratio etc.. were filed using Korea National Statistical Office database. Multiple linear regression analysis was performed to evaluate the factors affecting hospital utilization for respiratory diseases. Analytical unit was 52 cities. Results: The factors affecting hospital utilization for respiratory diseases were the proportion of population 60 years and over, seaside city, $O_3$ level, smoking rate. Conclusions: However, outdoor pollutants monitoring data and smoking rate have weakness in reflecting individual exposure. Further research is required to propose more illustrative means to evaluate causal relationship between air pollution and respiratory health effect factors.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.6
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• pp.794-802
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• 2018

The ice resistance series charts for icebreaking ships were developed through a series of systematic model tests in the ice tank of the Korean Research Institute of Ship and Ocean Engineering (KRISO). Spencer's (1992) component-based scaling system for ship-ice model tests was applied to extend the model ship correlations. Beam to draft ratio (B/T), length to beam ratio (L/B), block coefficient ($C_B$) and stem angle (${\alpha}$) were selected as geometric parameters for hull form development. The basic hull form (S1) of twin pod type with B/T of 3.0, L/B of 6.0, $C_B$ of 0.75 and stem angle of $25^{\circ}$ was generated with a modern hull design concept. A total of 13 hulls were designed varying the geometric parameters; B/T of 2.5 and 3.5, L/B of 5.0 and 7.0, $C_B$ from 0.65 to 0.85 in intervals of 0.05, and 5 stem angles from $15^{\circ}$ to $35^{\circ}$. Ice resistance tests were first carried out with the basic hull form in level ice with suitable speed. Four more tests for $C_B$ variations from 0.65 to 0.85 were conducted and two more for beam to draft and length to beam ratios were also performed to study the effect of the geometric parameters on ice resistance. Ice resistance tests were summarized using the volumetric coefficient, $C_V$ ($={\nabla}/L^3$), instead of L/B and $C_B$ variations. Additional model tests were also carried out to account for the effect of the stem angle, ice thickness and ice strength on ice resistance. In order to develop the ice resistance series charts with a minimum number of experiments, the trends of the ice resistance obtained from the experiments were assumed to be similar for other model ship with different geometric parameters. A total of 18 sheets composed of combinations of three different beam to draft ratios and six block coefficients were developed as a parameter of $C_V$ in the low speed regions. Three correction charts were also developed for stem angles, ice thickness and ice strength respectively. The charts were applied to estimate ice resistance for existing icebreaking ships including ARAON, and the results were satisfactory with reasonable accuracy.

• Journal of Korea Water Resources Association
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• v.39 no.2 s.163
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• pp.139-150
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• 2006

In recent, increasing of the impervious area gives rise to short concentration time and high peak discharge comparing with natural watershed and it is a cause of urban flood damage. Therefore, we have performed for structural and non-structural plans to reduce the damage from inundation. The Gulpo-cheon basin had been frequently inundated and damaged due to the water level of Han river. So, the Gulpo-cheon floodway was constructed with 20 meters width for flood control in the basin but it was not enough for our expectation and now we have a plan to expand the floodway to 80 meters. We use a XP-SWMM model developed based on EPA-SWMM version for analyzing the capacity of flood conveyance by the expansion of Gulpo-cheon floodway with the same 100 years return period design storm and the same tidal conditions of the Yellow sea. The flood conveyance after the expansion of floodway becomes three times comparing it with before the expansion. Also we simulate the flood discharge at the diversion point of Gulpo-cheon for the expanded condition of floodway and know that the discharge of about 300 m3/sec is flowing backward to the expanded floodway. Therefore we may need some kinds of hydraulic structures to prevent the back water.

• Journal of Korea Water Resources Association
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• v.44 no.6
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• pp.497-510
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• 2011

A levee height is determined by adding a deterministic freeboard to a flood water level in Korea. In the USA, a levee height is determined by choosing a value conditionally among the freeboard criteria and the levels resulted from a probabilistic method. The probabilistic method adopts a conditional non-exceedance probability (CNP) which is the probability that the target stage will not be exceeded given a specific flood event. The purpose of the study is to compare Korean criterion for levee height estimation with that of the USA. Levee heights were determined according to the above two criteria at twenty-five cross sections in five streams. The results show that Korean criterion on average yields levee heights 20 cm higher than those calculated by the criterion of the USA. The larger the flood discharges become, the higher the levee height differences are usually. It is caused by the freeboard estimation criterion of Korea that the larger design flood is, the higher freeboard is given. Korean criterion, however, resulted in lower levee heights for smaller streams than those by the criterion of the USA. To sum it up, the Korean levee height criteria can result in overestimation or underestimation depending on flood discharge amount, being compared with the criteria of the USA. The Korean freeboard especially needs to be increased for smaller flood discharges.

• Journal of Korea Society of Industrial Information Systems
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• v.22 no.4
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• pp.117-129
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• 2017

The Purpose of this Study is to Identify the Learning Modules of the National Competency Standard (NCS) Related to the Information Systems Development Curriculum of 4-year Colleges, to Explore the Possibility of Applying NCS to the Curriculum, and to Examine Implications. The Importance of 26 Competency Units in the Applied SW Engineering of NCS was Compared by Area Experts Composed of 14 Information Systems Developers and Professors of 7 Universities who Teach Software Engineering Subjects Through the Hierarchical Analysis Process (AHP). The Results of the Study as Follows. First, the Relative Importance of the Competency Elements was in order of 'Confirming the Requirements', 'Checking the UI Requirements', 'Designing the Physical Data Repository', 'Testing Developer Integration', and 'Fixing Developer Defects'. Second, while the Entry and Intermediate Level Developer Group Determined that the Competency Elements Related to the IS Development Implementation Stage is more Important, the Advanced IS Developer Groups Consider the Competency Elements Related to the Theory-oriented Design Stage as Important Competency. In Addition, the Group of College Professors was Found to Choose all the Practical and Theoretical Competency Elements that Two Developers Groups Considered Important. Implications of the Study Suggested that the Job Performance Competence and Quality of Education Related to IS Development can be Enhanced.