• Solar Energy
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• v.17 no.4
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• pp.3-11
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• 1997

Because grain boundaries in polycrystalline silicon act as potential barriers and recombination centers for the photo-generated charge carriers, these defects degrade conversion effiency of solar cell. To reduce these effects of grain boundaries, we investigated various influencing factors such as thermal treatment, various grid pattern, selective wet etching for grain boundaries, buried contact metallization along grain boundaries, grid on metallic thin film. Pretreatment above $900^{\circ}C$ in $N_2$ atmosphere, gettering by $POCl_3$ and Al treatment for back surface field contributed to obtain a high quality poly-Si. To prevent carrier losses at the grain boundaries, we carried out surface treatment using Schimmel etchant. This etchant delineated grain boundaries of $10{\mu}m$ depth as well as surface texturing effect. A metal AI diffusion into grain boundaries on rear side reduced back surface recombination effects at grain boundaries. A combination of fine grid with finger spacing of 0.4mm and buried electrode along grain boundaries improved short circuit current density of solar cell. A ultra-thin Chromium layer of 20nm with transmittance of 80% reduced series resistance. This paper focused on the grain boundary effect for terrestrial applications of solar cells with low cost, large area, and high efficiency.

• Journal of East-West Nursing Research
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• v.5 no.1
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• pp.120-126
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• 2000

This study was intended to grasp the history of nursing education from the beginning to the present in Korea, and grip and look-out current diversified systems of nursing education on basis of February, 2000 through literatural review and investigation by close telephone interviews. The basic nursing educational institutions in the whole country were total 113, namely, 3 years course, 65 junior colleges of nursing, and 4 years course, 48 colleges of nursing. And there were 3 types of continuing nursing educational system: two of three were transferring to another college for gain bachelor's degree in nursing; RN-BSN programs and university of broadcasting, and the other was the system of independent learning and then examination for BSN. Total nursing graduates from junior college of nursing courses and college of nursing courses were 7,564 on February, 1999. In general graduate school, the number of master courses were 21 and Ph.D courses were 13. And the number of special graduate schools were 21, i.e., graduate school of education were 7, graduate school of administration were 2, graduate school of public health were 11 and graduate school of industry was 1. As the perspective on nursing education, we overviewed changing nursing organizational environment, increasing the system of continuing education, making standards in nursing education and systemization of nursing educational accreditation, specialization of nursing, information system in nursing education and education of graduate school. The summary of the above overviewed subjects were as follows; Every nursing educational institution needed to educate by educational criteria and standard and characteristically run BSN and graduate courses. Specialization in nursing has to develop more and more, therefore advanced education and law should be prepared appropriately. According to the age's and social needs, we have to establish counter-plan for fundamental educational environment. We have to sensitive to rapidly changing information in the era of globalization. In the level of university education, each university needs characterization of educational objectives, goals and contents, and has to replace the shortage of the number of professor. And the regulation of thesis and dissertation examinations need to be reinforced. Education in nursing should consists with specialization. Collaboration among universities will bring efficiency in the nursing education.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.41 no.1
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• pp.9-18
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• 2004

This paper presents an efficient image compression method for memory reduction in multimedia processor which can be simply implemented in hardware and provides high performance. The multimedia processor, which includes processing of high-resolution images and videos, requires large memories: they are external frame memories to store frames and internal line memories for implementing some linear filters. If we can reduce those memories by adopting a simple compression method in multimedia processor, it will strengthen its cost competitiveness. There exist many standards for efficiently compressing images and videos. However, those standards are too complex for our purpose and most of them are 2-D block-based methods, which do not support raster scanned input and output. In this paper, we propose a low-complexity compression method which has good performance, can be implemented with simple hardware logic, and supports raster scan. We have adopted 1${\times}$8 Hadamard transform for simple implementation in hardware and compression efficiency. After analyzing the coefficients, we applied an adaptive thresholding and quantization. We provide some simulation results to analyze its performance and compare with the existing methods. We also provide its hardware implementation results and discuss about cost reduction effects when applied in implementing a multimedia processor.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.1
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• pp.9-17
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• 2013

In this study, an efficient analytical model for the dynamic analysis of tall buildings with a shear wall-frame structural system has been proposed. A shear wall-frame structural system usually consists of a core wall showing flexural behavior and a frame presenting shear behavior. Therefore, the deformed shape of the shear wall-frame structural system is shown by the combination of flexural mode and shear mode. These characteristics should be considered when an efficient analytical model is developed. To this end, the effect of shear wall and frame on the dynamic behavior of a tall building with a dual system has been separately investigated. In this study, the structural characteristics of a separated individual shear wall model and the frame model without shear wall has been evaluated. In order to consider the effect of the shear wall in the frame model without shear wall, a rigid body was used instead of the shear wall. Each equivalent model for the separated shear wall part and frame part has been independently developed and two equivalent models were then combined to create an efficient analytical model for tall buildings with a shear wall-frame structural system. In order to verify the efficiency and accuracy of the proposed method, time history analyses of tall buildings with a shear wall-frame system were performed. Based on analytical results, it has been confirmed that the proposed method can provide accurate results, requiring significantly reduced computational time and memory.

• Korean Journal of Agricultural and Forest Meteorology
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• v.14 no.1
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• pp.28-38
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• 2012

This study was conducted to investigate growth performance, photosynthesis, water use efficiency (WUE), and stomatal conductance ($g_s$) of container seedlings of Liriodendron tulipifera and Zelkova serrata growing under three different irrigation periods (1 time/1 day, 1 time/2 days and 1 time/3 days) for high seedling quality. The root collar diameter and height of L. tulipifera and Z. serrata seedlings were highest with 1 time/1 day irrigation, whereas they were lowest with 1 time/3 days irrigation. The two species showed low drought tolerance. As irrigation period was shortened, biomass and seedling quality index (SQI) of the two species increased. The ratio of height to root collar diameter (H/D) and the ratio of below to aboveground biomass (T/R) of the two species were lower with 1 time/3 days than at other irrigation periods. L. tulipifera and Z. serrata seedlings showed significantly higher photosynthetic capacity with 1 time/1 day irrigation. As irrigation period was shortened, $g_s$ of two species increased, while their WUE decreased significantly (P<0.05) These results show that 1 time/1 day irrigation provides the most optimal water condition for container seedling production of two species and irrigation controlling is very important for growth and quality of container seedlings.

• Journal of the Korean GEO-environmental Society
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• v.9 no.2
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• pp.39-46
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• 2008

Due to the growth in industrialization, potential hazards in subsurface environments are becoming increasingly significant. The extraction of the contaminant from the soil and movement of the water are restricted due to the low permeability and adsorption characteristics of the reclaimed soils. There are a number of approaches to in-situ remediation that are used in contaminated sites for removing contaminants. These include soil flushing, dual phase extraction, and soil vapor extraction. Among these techniques, soil flushing was the focus of the investigation in this paper. Incorporated technique with PVDs has been used for dewatering from fine-grained soils for the purpose of ground improvement by means of prefabricated vertical drain systems. The laboratory model tests were performed by using the flushing tracer solutions for silty soils and recorded the tracer concentration changes with the elapsed time and flow rates. The modeling was intended to predict the effectiveness and time dependence of the remediation process. Modeling has been performed on the extraction, considering tracer concentration and laboratory model test characteristics. The computer model used herein are SEEP/W and CTRAN/W, this 2-D finite element program allows for modeling to determine hydraulic head and pore water pressure distribution, efficiency of remediation for the subsurface environment. It is concluded that the coefficient of permeability of contaminated soil is related with vertical velocity and extracted flow rate. The vertical velocity and extracted flow rate have an effect on dispersivity and finally are played an important role in-situ soil remediation.

• Journal of Bio-Environment Control
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• v.21 no.4
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• pp.459-465
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• 2012

This study analyzed the effect of semi-rigid rafter-purlin cross-linking connection and driven steel pipe base on the static behavior of plastic greenhouse (PG). To promote the time and cost efficiency of the assembly process, each cross-linking connections of space arch type grid that consists of rafter and purlin is linked with steel-wire buckles, and each end of the rafters was driven directly to the ground to support the PG structure. However, in the design process, cross-linking connections and bases are idealized by being categorized as fully rigid or frictionless pinned, which does not appropriately reflect actual conditions. This study takes a full-scale loading test of PG and analyzes the effect of member cross-linking connections and driven steel pipe base on the behavior of a structure. The analysis provided a basis for determining the rigidity factor of member cross-linking nodes needed for finite element analysis, and the reliability of the result regarding the static behavior of PG.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.2
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• pp.229-242
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• 2006

Statement of problem: In order to increase preload with reducing the friction coefficient, abutment screws coated with pure gold and Teflon as dry lubricant coatings have been introduced. But the reported data indicate that if screw repeated tightening and loosening cycle, an efficiency of increasing preload was decreased by screw surface wearing off. Purpose: This study was to evaluate the influence of tungsten carbide/carbon coating, which has superior hardness and frictional wear resistance, on the preload of abutment screws and the stability of coating surface after repeated closures. Material and method: The rotational values of abutment screws and the compressive forces between abutment and fixture were measured in implant systems with three different joint connections, one external butt joint and two internal cones. Moreover the stability and the alteration of coating surface were examined by comparison of the compressive force and the removable torque values during 10 consecutive trials, observation with scanning electron microscope and analyzed the elemental composition with energy dispersive x-ray spectroscopy Results and conclusion: 1. Application of coating resulted in significant increase of compressive force in all implant systems(P<.05). The increasing rate of compressive force by coating in external butt joint was gloater than those in internal cones (P<.05). 2. Coated screw showed the significant additional rotation compared to non-coated screw in all implant systems (P<.05). There were no significant differences in the increasing rate of rotation among implant systems (P>.05). 3. Removable torque values were greater with non-coated screw than that with coated screw (P<.05). 4. Coated screw showed insignificant variations in the compressive forces during 10 consecutive trials(P>.05) 5. After repeated trials, the surface layer of coated screw was maintained relatively well. However surface wearing and irregular titanium fragments were found in non-coated screw.

• Journal of Animal Science and Technology
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• v.46 no.2
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• pp.173-182
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• 2004

The effect of dietary Antartic krill(Euphausia Superba) meal on the performance of broiler chicks during the acute phase responses was studied. One d-old male broiler chicks(Avian) were fed on the experimental basal (0.0 % krill meal), and 0.5 and 1.0 % krill meal diets, and then the acute phase response were activated by injecting Salmonella typhymurium lipopolisaccharide(LPS) three times i. p. at 8, 10 and 12 day of age. The 1.0% krill meal diet group had reduced daily gain and feed efficiency during the acute phase response of the 2nd week of age, while during recovery from the acute phase response of the 3rd week of age the lowered performance disappeared. The acute phase response increased the relative weight of liver and spleen, and dietary krill meal enhanced the activities of MnSOD and Cu/ZnSOD in liver and erythrocyte cytosols during the acute phase response, although neither the acute phase response or dietary krill meal affected significantly PHA-p hypersensitivity. The results indicated that dietary krill meal affected the performance and SOD activity of broilers chicks during the acute phase response.

• Journal of Broadcast Engineering
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• v.17 no.1
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• pp.73-80
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• 2012

Recently, medical equipments are developed and used for diagnosis or studies. In addition, demand of techniques which automatically deal with three dimensional medical images obtained from the medical equipments is growing. One of the techniques is automatic bone segmentation which is expected to enhance the diagnosis efficiency of osteoporosis, fracture, and other bone diseases. Although various researches have been proposed to solve it, they are unable to be used in practice since a size of the medical data is large and there are many low contrast boundaries with other tissues. In this paper, we present a fast and accurate automatic framework for bone segmentation based on multi-resolutions. On a low resolution step, a position of the bone is roughly detected using constrained branch and mincut which find the optimal template from the training set. Then, the segmentation and the registration are iteratively conducted on the multiple resolutions. To evaluate the performance of the proposed method, we make an experiment with femur and tibia from 50 test knee magnetic resonance images using 100 training set. The proposed method outperformed the constrained branch and mincut in aspect of segmentation accuracy and implementation time.