• Journal of Institute of Control, Robotics and Systems
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• v.14 no.4
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• pp.353-360
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• 2008

The LGP with nanometer structures resulted in enhancement of optical efficiency. Its fundamental mechanism is to recycle the polarized light via one round-trip through QWP(Quarter-Wave Plate) but the maximum efficiency to reach with this method is limited up to 2. To get the larger efficiency than this limited one a LGP with nanometer-patterned grating is suggested. For its optimum design the computer simulation is performed and suggests a grating that the spatial frequency between adjacent patterns is 500nm, its height 250nm, duty cycle 50%, and its cross section is rectangular. On the basis of simulation results the LGP with nanometer-patterned grating is fabricated and its optical properties such as angular intensity distribution and CIE color coordinates are characterized. The angles of transmitted light are nearly the same as the results expected from the generalized Snell's law. Thus the Mathematica code, developed in this experiment, will be applied to designing the optimized LGP. The LGP with nanometer-patterened grating shows the enhancement of transmitted intensity distribution up to 4.9 times.

• Journal of Welding and Joining
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• v.22 no.2
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• pp.59-68
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• 2004

Plasma transferred arc welding (PTAW) has been taken into consideration for repairing Ni-based superalloy components used gas turbine blades. Various cracks has been generally reported to be found in the base metal heat affected zone(HAZ) along grain boundary. Thus, hot cracking susceptibility of Ni-based superalloys was evaluated according to heat treatments. Hot ductility test was conducted on specimens with solution treated at 112$0^{\circ}C$ for 2 hours and aging treated at 845$^{\circ}C$ for 24hours after solution treatment. The results of the hot ductility test appeared that solution treated specimens were the highest ductility recovery rate among three conditions. The loss of ductility at high temperature in Ni-based superalloy was mainly controlled by the degree of pain boundary wetting due to constitutional liquation of MC carbide precipitates. Meanwhile, the highest ductility recovery rate in solution-treated alloys seems to be lack of M23C6, which can be dissolved during heating and then result in the local enrichment of Cr in the vicinity of the grain boundary.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.607-611
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• 2007

최근 하천변화특성에 대한 조사와 연구 없이 무분별한 하천준설로 인하여 급격한 하천지형 및 환경변화에 따른 하도의 평형, 홍수범람, 하천환경의 변화 등 이수, 치수 및 하천환경에 많은 문제점이 야기되고 있다. 따라서 준설에 따른 하천의 인위적인 손상과 이와 연관된 각종 유역 및 하천의 지배인자와의 상호연관성에 대한 학술적 고찰을 통하여 인위적인 영향을 최소화하고 국내 하천환경에 맞는 하천관리모델과 준설기법개발의 필요성이 제기되고 있다. 이에 따라 본 연구는 $\ulcorner$하도준설에 따른 하천교란 실태 조사$\lrcorner$의 일환으로 기초조사 및 후보지 현장조사 등을 통한 연구대상구간 선정을 위한 계획으로서 기 수행된 골재자원 조사결과 및 하천조사 자료 등의 관련자료 활용을 통하여 최대한 효율적으로 조사를 수행하고 최상의 연구결과 획득과 관련분야의 기술력확보를 꾀할 수 있도록 하는 것이 목적이다. 우선, 연구대상구간 선정기준(안)을 마련하고 후보지에 대한 기초조사 및 현장조사를 마친 후, 선정기준에 따라 연구내용을 최대한 만족시키는 연구대상 구간을 8개 후보지역에 대하여 검토하였다. 하천준설을 수행해 나가며 그 전 중 후의 과정을 모니터링 하여 하상변동 및 생태 환경의 변화를 관찰하고 하천환경 및 물리적 영향을 최소화 할 수 있는 연구결과를 얻기 위한 과업대상구간의 선정에는 하도준설이라는 연구특성을 만족시킬 수 있는 특화된 선정기준에 따른 평가결과, 많은 후보지들 중 낙동강수계의 감천이 최적의 대상지로 선정되었다.

• Korean Journal of Optics and Photonics
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• v.30 no.6
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• pp.230-236
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• 2019

We propose and demonstrate a searching and autoalignment method for indoor optical wireless communication, using a cost-effective retroreflective sheet and a microelectromechanical system (MEMS) mirror. We use an extremum-seeking method for a single axis and beam steering with a MEMS mirror to maintain a line of sight (LOS) with the optical link. This autoalignment method shows a receiver sensitivity of -31.87 dBm for a bit rate of 2.5 Gb/s over a 7 m communication link.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.20 no.1
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• pp.139-148
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• 1990

The purpose of this study was to investigate the effects of irradiation on the rat submandibular gland which composed of the epithelial growth factors. The experimental animals were the Sprague Dawley strain rats, which were the rats as the non-irradiated control group and the rats as the experimental group which were divided into groups as the experimental duration of 1 hour, 3 hours, 6 hours, 12 hours, 1 day, 3 days, 1 week, 2 weeks, 4 weeks. The experimental animals were singly irradiated at a dose of 8 Gray gamma ray to their head and neck region by the Co-60 teletherapy unit and sacrificed after each experimental duration. The specimens were stained with H-E and Azan stain and examined light microscopically. The results of this study were obtained as follows. 1. The all of mucous and serous acini in submandibular gland showed similar pattern of changes in structure according to the lapse of time. 2. The acinic cells started to change after 1 hour, and repaired after 12hours with mitosis and proliferation of the cells between acini. The changes were marked after 1day, and repaired gradually in course of time. 3. The duct were dilatated irregularly, and the outline of the eosinophilic stained ductal cells changed indistinctly.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.12
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• pp.2272-2293
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• 2011

Communication technology of future networks is predicted to provide a large variety of services including WiFi service in vehicular network. In this paper, we assume that vehicles are embedded with WiMAX antenna and in-vehicle terminals receive WiMAX traffic through WiFi interface. This assumption will impose severe performance degradation due to interference among mobile BSSs when WiFi access points (APs) are densely located. Existing interference avoidance techniques cannot properly resolve the above problems and do not cope with dynamically moving vehicular scenario since they focus only on the fixed network topology. In this paper, we propose a mobility-aware interference avoidance scheme for WiFi services. The proposed scheme computes the interference duration by exploiting mobility vector and location information of neighboring APs. If the interference duration is not negligible, our scheme searches for another channel in order to avoid interference. However, if the interference duration is negligible, our scheme continues to use the channel to reduce switching overhead. To measure the effectiveness of the proposed scheme against other existing techniques, we evaluated performance by using OPNET simulator. Through the simulation, we obtained about 60% reduction in the maximum interference frequency and about 67% improvement in throughput. Furthermore, our scheme provides fair channel usage.

• Journal of Photoscience
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• v.4 no.2
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• pp.31-34
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• 1997

The rapid and spontaneous interaction between superoxide anion radical and nitric oxide to yield the potent oxidants. peroxynitrite artion and peroxynitrous acid, was investigated in phorbol myristate acetate(PMA)-stimulated RAW264.7 macrophases by means of lucigenin- or luminol-enhanced chemiluminescence method. When RAW264.7 macrophages were stimulated by PMA. peroxynitrite-induced chemiluminescence was clearly observed. To prove observed chemiluminescencc due to the reaction between superoxide anion radical and nitric oxide produced by RAW264.7 macrophases, N-nitrosoglutathione (GSNO), a nitric oxide-releasing compound. superoxide dismutase(SOD), an enzyme removing superoxide anion radical by dismutating superoxide artion radical to hydrogen peroxide, and N-acethyl cysteine(NAC), a scarvenging reagent both superoxide artion radical and nitric oxide, were added in the cell system. Peroxynitrite- induced chemilumincscence was increased by exogenous addition of GSNO. whereas observed chemiluminescence was decreased by SOD and NAC. These results suggest that PMA-stimulated RAW264.7 macrophages produce both superoxide anion radical and nitric oxide to form peroxynitrite.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.21 no.2
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• pp.377-392
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• 1991

The aim of this study was to investigate the thickness of alveolar lamina dura and alveolar bone height by the change of periodontal status. The periapical radiograms of the 853 cases were taken by paralleling technique. The conclusions from this study were as follows: 1. In the normal periodontal status, the alveolar lamina dura was the thickest at alveolar crest, followed by apex, midroot, and the average thickness of the posterior teeth was thicker than that of the anterior teeth. 2. In Russel's Periodontal Index 0 and 1, no significant differences of thickness were found to be 3 areas. In Russel's Periodontal Index 2 and 6, the thickness of alveolar lamina dura at alveolar crest was decreased, only. 3. In Russel's Periodontal Index 0 and 1, distance from the cemento-enamel junction to the alveolar crest was within 1.5㎜. In Russel's Periodontal Index 2 and 6, the distance was 3. increased over 1.5㎜.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 1999.10a
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• pp.121-130
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• 1999

The objective of this paper is to apply Extended AND-OR Graph (EAOG)-related techniques to extract knowledge from a specific problem-domain and perform analysis in complicated decision making area. Expert systems use expertise about a specific domain as their primary source of solving problems belonging to that domain. However, such expertise is complicated as well as uncertain, because most knowledge is expressed in causal relationships between concepts or variables. Therefore, if expert systems can be used effectively to provide more intelligent support for decision making in complicated specific problems, it should be equipped with real-time inference mechanism. We develop two kinds of EAOG-driven inference mechanisms(1) EAOG-based forward chaining and (2) EAOG-based backward chaining. and The EAOG method processes the following three characteristics. 1. Real-time inference : The EAOG inference mechanism is suitable for the real-time inference because its computational mechanism is based on matrix computation. 2. Matrix operation : All the subjective knowledge is delineated in a matrix form, so that inference process can proceed based on the matrix operation which is computationally efficient. 3. Bi-directional inference : Traditional inference method of expert systems is based on either forward chaining or backward chaining which is mutually exclusive in terms of logical process and computational efficiency. However, the proposed EAOG inference mechanism is generically bi-directional without loss of both speed and efficiency.

• Journal of Korean Academy of Nursing Administration
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• v.20 no.2
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• pp.215-226
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• 2014

Purpose: This study was done to suggest policies for nurse workforce based on patient safety. Methods: The two steps in developing the items were items related to what would be desirable policies and items on how the policies should be developed for patient safety regarding nurse workforce. A literature review was done and suggestions from experts through two rounds using the Delphi technique were outlined. The fifteen experts who participated in this study were six representatives of service consumers and nine representatives of service providers (four medical doctors and fives nurses). Results: To guarantee patient safety, accreditation of nursing practice and nursing education were found to be necessary, and to prevent medical and nursing accidents in clinical practice, the professional judgement of the nurses was found to be pivotal to the provision of safe nursing services. Conclusion: Polices on nursing for the nurse workforce based on patient safety in clinical settings should be established to ensure that nursing care is provided according to the nurses' clinical judgements based on their professional knowledge and assessment skills.