• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1279-1283
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• 2010

미국의 경우 1994년 발생한 대홍수(Great Flood)에 대해 사건조사를 수행하면서 예측에 포함되는 불확실성 정도를 제공하지 못하는 확정적 예측의 위험성 및 확률유량예측에 대한 필요성이 부각되었으며, 앙상블 유량예측(Ensemble Streamflow Prediction, ESP) 기법을 활용한 확률유량예측 방안에 대해 지속적으로 연구가 수행되고 있다. 국내에서도 확률예측에 대한 필요성이 인식되면서 기존 국외 연구사례를 토대로 국내 환경에 적용 가능한 방안에 대한 연구가 진행되었으며, 중장기 앙상블 유량예측의 경우 현업에서 다양한 형태로 활용되고 있다. 앙상블 유량예측의 기본이론은 예측시점의 초기조건 하에서 예측기간에 발생 가능한 기상 앙상블 시나리오를 수문모형의 입력자료로 사용하여 불확실성 범위를 설명 가능한 유량 앙상블을 모의하는 기법이다. 이러한 이론적 단순함 때문에 쉽게 현업의 유량예측 시스템 내에서 사용할 수 있다는 장점이 있으나, 동시에 기법적 특성으로 인하여 유량예측의 신뢰도가 현업에서 활용되기 어려울 정도로 낮아지는 관계로, 이러한 한계점을 극복하기 위해 그동안 기상자료 및 수문모형으로 인한 불확실성 저감에 대한 연구가 수행되었다. 하지만 예측 및 시나리오 기간의 잘못된 설정으로 기존의 불확실성 저감을 위한 연구의 적용에도 불구하고 앙상블 유량예측의 신뢰도가 오히려 낮아질 수 있으므로, 본 연구는 시나리오 기간에 따른 오차의 양상과 예측기간의 증가에 따른 초기조건의 영향을 분석하여 앙상블 유량예측의 기법적 특성 하에서 신뢰도 높은 예측을 기대할 수 있는 예측 및 시나리오 기간을 제안하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1006-1010
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• 2010

기존의 댐에 대한 연구는 이 치수 및 전력생산, 환경문제와 같은 댐의 전통적인 기능과 그 파급효과에 대한 연구가 주로 진행되어 왔으나 댐의 친환경적 활용방안 및 댐에 서식하고 있는 동 식물 및 생태계에 대한 연구는 상당히 미흡한 실정이다. 특히, 댐 상류지역 및 주변지역에 위치하고 있는 습지는 댐의 수질개선, 희귀 동 식물의 서식처 확보 등과 같은 생태보존, 위락 경관 생태공원 등의 기능을 제공할 수 있다. 이로 인해 댐유역에 위치하고 있는 자연습지의 보전뿐만 아니라 훼손에 따른 대체습지(인공습지)의 필요성이 점증되고 있는 실정이다. 따라서 본 연구에서는 현재 운영되고 있는 댐을 대상으로 댐이 지니고 있는 습지의 역할을 검토하고자 수문지형학적 방법인 HGM 방법을 이용하여 댐습지의 기능을 평가하였다. HGM 방법을 이용하여 댐습지의 기능평가를 수행하기 위해서는 대상습지와 기준습지가 필요하며, 본 연구에서의 대상지역은 댐 유역내 습지지역이 조성되어 있는 보령댐으로 선정하였으며, 기준지역은 보전이 잘 되어 있고 람사르 협약에 등록된 우포늪으로 선정하였다. HGM 방법에서의 기능 평가는 수문학적, 생지화학적, 식물 서식처 그리고 동물 서식처 측면으로 구분하여 대상지역과 기준지역을 비교하는 방식으로 이루어진다. 그 결과, 댐습지가 지니고 있는 습지의 기능이 자연습지에 비해 평균적으로 약 50%정도의 역할을 하는 것으로 나타났다. 이는 댐습지가 습지로서의 역할을 기능적으로 100% 수행을 못하고 있지만, 댐이 습지의 기능을 어느 정도의 수준까지는 수행을 하고 있음을 알 수 있다.

• Journal of Korean Society of Steel Construction
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• v.15 no.6 s.67
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• pp.603-610
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• 2003

A damage identification technique using static displacement data is developed to asses s the structural integrity of bridge structures.As such, the relationship between static displacement and stiffness is derived, and the optimization technique utilized.Comparisons with numerical and experimental tests are performed to investigate the practical applicability of the proposed method.Various damage scenarios are considered by varying damage-width as well as damage-degree. The influence of noise in identifying the damage is also numerically investigated.Finally, the applicability and limitation of the proposed method are discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.175-178
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• 2008

Spray characteristics for the simplex atomizer are investigated. The atomizer was tested with kerosene which is generally used as a fuel for gas turbine engines. But it is very difficult and dangerous to measure spray performance. So water is used as a working fluid for measuring the droplet information. In this study, spray visualization was performed by using ND-Yag Laser and droplet size was measured by using PDPA system by using two different working fluid such as water and test fluid # 2 which has similar characteristics of the kerosene. The test results show that SMD of water bigger than test fluid # 2 about 5$\sim$15 mm because surface tension of water is higher by a factor of 3. But the spray angles and the spray shapes have similarity

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.305-312
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• 2014

Purpose : The purpose of this study is to analyze the mechanical and leaf speed accuracy of the dynamic multileaf collimator (DMLC) and determine the appropriate period of quality assurance (QA). Materials and Methods : The quality assurance of the DMLC equipped with Millennium 120 leaves has been performed total 92 times from January 2012 to June 2014. The the accuracy of leaf position and isocenter coincidence for MLC were checked using the graph paper and Gafchromic EBT film, respectively. The stability of leaf speed was verified using a test file requiring the leaves to reach maximum leaf speed during the gantry rotation. At the end of every leaf speed QA, dynamic dynalog files created by MLC controller were analyzed using dynalog file viewer software. This file concludes the information about the planned versus actual position for all leaves and provides error RMS (root-mean square) for individual leaf deviations and error histogram for all leaf deviations. In this study, the data obtained from the leaf speed QA were used to screen the performance degradation of leaf speed and determine the need for motor replacement. Results : The leaf position accuracy and isocenteric coincidence of MLC was observed within a tolerance range recommanded from TG-142 reports. Total number of motor replacement were 56 motors over whole QA period. For all motors replaced from QA, gradually increased patterns of error RMS values were much more than suddenly increased patterns of error RMS values. Average error RMS values of gradually and suddenly increased patterns were 0.298 cm and 0.273 cm, respectively. However, The average error RMS values were within 0.35 cm recommended by the vendor, motors were replaced according to the criteria of no counts with misplacement > 1 cm. On average, motor replacement for gradually increased patterns of error RMS values 22 days. 28 motors were replaced regardless of the leaf speed QA. Conclusion : This study performed the periodic MLC QA for analyzing the mechanical and leaf speed accuracy of the dynamic multileaf collimator (DMLC). The leaf position accuracy and isocenteric coincidence showed whthin of MLC evaluation is observed within the tolerance value recommanded by TG-142 report. Based on the result obtained from leaf speed QA, we have concluded that QA protocol of leaf speed for DMLC was performed at least bimonthly in order to screen the performance of leaf speed. The periodic QA protocol can help to ensure for delivering accurate IMRT treatment to patients maintaining the performance of leaf speed.

• Information Systems Review
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• v.10 no.2
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• pp.253-267
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• 2008

As the importance of information security becomes a major concern, there has been growing effort to educate information security professionals. This study aims to analyze the level of required knowledge and skills for four information security skills groups: strategy and planning; research and development; system management and operation; and accident control. For this study, we selected 55 critical knowledge and skills for information security professionals by literature review and Delphi method, and we conducted a survey of information security knowledge and skills requirements for information security professionals to perform their jobs. As a result, we analyzed the current status of the information security professionals' knowledge and skills level and suggested some guidelines for establishing the demand-based curriculum for training information security professionals.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.3
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• pp.339-344
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• 2008

Titanium dioxide nanotubes were fabricated by self-organized electrochemical potentiostatic anodization of titanium thin film with an electrolyte solution of sodium sulfate 1M and sodium flouride 0.5wt% aqueous solution at 20$^{\circ}C$ for 20min. Field Emmision Scanning Electron Microscopy(FE-SEM) and X-ray Diffractometer(XRD) were used to evaluate the micromorphology and crystalline structure of the titanium dioxide nanotube thin film. Titanium dioxide nanotube were fabricated with diameters approx. 100nm and tube length from appox. 1 $\mu$m. Titanium dioxide films formed through anodization and annealing process at 450$^{\circ}C$ contained a phase of anatase. Also, this study was performed to evaluate the application of titanium dioxide thin film for treating humic acid dissolved in water. The reaction tended to follow the Langmuir-Hinshelwood kinetics with zero order. Comparative experiments with thin film and anatase powder showed the same zero order kinetics when 0.3g of powder had been used.

• Journal of Korean Home Economics Education Association
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• v.15 no.4
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• pp.1-22
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• 2003

The purpose of this study was to general needs and identify the educational needs for teaching competency of home economics teachers. based on their perception on teaching competency revealed in Previous studies. Data were collected from 1,104 schools selected by stratified sampling. based on school district, ranking and size. The 616 items of survey materials were collected from 417 schools and the levels of importance and performance were measured on Likert scale with 7- and 5- points, respectively. The analysis reveled that the educational needs for improving teaching competency were high in the following three areas out of seven areas. 1) interfacing ability with the local community and diverse human resources. 2) ability managing space and materials for learning 3) ability diversifying lesson development and evaluation ability. In addition. diversifying and professionalizing present development program for home economics teachers made higher score than improving education program for home economics teachers. These two needs of teachers showed significant differences according to their educational experiences and foundation types of their schools.

• School Mathematics
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• v.14 no.3
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• pp.357-375
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• 2012

This research intends to examine how 6th graders (age 12) generalize various increasing patterns. In this research, 6 problems corresponding to the ax, x+a, ax+c, ax2, and ax2+c patterns were given to 290 students. Students' generalization methods were analysed by the generalization level suggested by Radford(2006), such as arithmetic and algebraic (factual, contextual, and symbolic) generalization. As the results of the study, we identified that students revealed the most high performance in the ax pattern in the aspect of the algebraic generalization, and lower performance in the ax2, x+a, ax+c, ax2+c in order. Also we identified that students' generalization methods differed in the same increasing patterns. This imply that we need to provide students with the pattern generalization activities in various contexts.

• The KIPS Transactions:PartD
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• v.9D no.1
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• pp.11-20
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• 2002

We propose a new concurrency control algorithm for enhancing the degree of parallelism of the transactions in fully replicated databases designed to improve the availability and the reliability. The update transactions can be logically decomposed of a read-only transaction and a write-only transaction. In our algorithm, a set of read operations of an update transaction is treated as a read-only transaction and the read-only transaction reads data items in the site to which it is submitted. And a set of write operations of the update transaction is treated as a write-only transaction and it is submitted to all corresponding sites after the update transaction has been completed. By using the proposed update protocol, all write-only transactions can execute at all sites atomically. The proposed algorithm can have transactions execute concurrently at the site to which they are submitted and, after the completion of each transaction, the update protocol is performed for updating their data items and checking their serializability. Therefore, the degree of parallelism of the transactions can be improved. Especially, if the probability of conflict among transactions is low, we can expect the higher degree of their parallelism.