• 한국수학교육학회지시리즈A:수학교육
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• 제46권1호
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• pp.53-67
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• 2007

During the recent years at a middle level Engineering School located at the local areas in Korea, more than 20 percent of freshmen had failed at their first College Mathematics. In consequence, many of them had hard time to survive at their major curriculums. The purpose of this study is to look for the main reasons of their failure and suggest an alternation of the present curriculum. Using the responses to the questionnaires and placement test scores, we studied the characteristics of the students' Mathematical abilities and analyzed how they were related to their grades of the First College Mathematics at the end of the first semester. The mathematical ability of the students at the middle level Engineering School turned out to range from bottom to top even though most of them revealed their interests towards Mathematics. The students with low scores at the placement test were more likely to fail at their first College Mathematics. Thus we suggest that the school should open a new preparation course ahead of the First College Mathematics for those who achieve low scores at the placement test and also professors should write proper books and develop ways of teaching.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.633-634
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• 2006

A new specification-based analog and mixed-signal test technique using high performance current sensors is proposed. The proposed technique using current sensors built in external ATE has little hardware overhead in circuit under test and high testability without time consuming operation of test point placement algorithm.

• 대한치과보철학회지
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• 제55권1호
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• pp.1-8
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• 2017

목적: 이 연구의 목적은 구강스캐너를 이용하여 제작된 임플란트 수술용 형판의 무치악 거리에 따른 정확성을 비교하는 것이다. 재료 및 방법: 방사선불투과성 아크릴 레진을 이용하여 상악 좌우 제2소구치, 제1대구치, 제2대구치 부위를 치아상실 상태로 5개의 상악 모형을 제작하고 각각의 모형을 구강스캐너를 이용하여 가상 모형을 획득하였다. 모형의 술전 CT DICOM file과 가상의 모형을 중첩 후 치아 상실 부위에 임플란트 식립을 계획하였고 제작된 수술용 형판을 이용하여 임플란트 식립 후 술후 CT 촬영을 시행하였다. 술전 CT와 술후 CT를 software상에서 중첩 후 X, Y, Z축을 이용하여 임플란트의 platform과 apex 부위에서, 계획된 임플란트와 실제 식립된 임플란트의 거리 및 각 오차를 측정하고 Kruskall-Wallis test와 Mann-Whitney test를 사용하여 통계분석을 시행하였다. 결과: 임플란트 식립 각도 오차는 제2소구치에서 제2대구치로 갈수록 커졌으나 통계적 차이를 보이지 않았고 platform 부위와 apex부위에서의 식립 거리 오차 또한 제2소구치에서 제2대구치로 갈수록 커지나 제2대구치에서는 통계적으로 유의성 있는 큰 오차를 보였다. 결론: 임플란트 식립 각도에서는 계획된 임플란트와 식립된 임플란트간 통계적 차이는 없었으나 platform과 apex 부위에서의 식립 거리는 제2대구치 부위의 임플란트에서 더 큰 오차를 보였으며 통계적으로 유의할 만한 차이를 보였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.219-222
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• 1999

Concrete is to be important quality in placement point and exact test method needed about early judgement method concrete on placement point. But early judgement method of concrete proposed various kind of method because the problems of accuracy and the time required of test exists, it is used within the limits. This study is to propose of early strength judgement by using microwave for accurate estimating early strength of concrete and to develop test machine. Through out this study we find that belows. 1) Strength development of concrete specimen according to the time heated by microwave showed the height strength development in 9 minutes regardless of slump and w/c. 2) As cooling time is long, strength of concrete specimen according to the time heated by microwave showed high strength development and this tendency is like regardless of heating time, w/c and slump. 3) As w/c is high, accelerating strength development according to w/c showed lower strength development and this tendency is like regardless of slump, heating time and cooling time. 4) As slump is big, compressive strength of specimen in standard curing showed lower value and as w/c is big, strength development showed lower

• Computers and Concrete
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• 제4권4호
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• pp.299-316
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• 2007

The compressive strength of concrete is a commonly used criterion in producing concrete. However, the test on the compressive strength is complicated and time-consuming. More importantly, since the test is usually performed 28 days after the placement of the concrete at the construction site, it is too late to make improvements if unsatisfactory test results are incurred. Therefore, an accurate and practical strength estimation method that can be used before the placement of concrete is highly desirable. In this study, the estimation of the concrete strength is performed using support vector regression (SVR) based on the mix proportion data from two ready-mixed concrete companies. The estimation performance of the SVR is then compared with that of neural network (NN). The SVR method has been found to be very efficient in estimation accuracy as well as computation time, and very practical in terms of training rather than the explicit regression analyses and the NN techniques.

• 콘크리트학회논문집
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• 제17권6호
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• pp.1075-1084
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• 2005

The compressive strength of concrete is commonly used criterion in producing concrete. However, the tests on the compressive strength are complicated and time-consuming. More importantly, it is too late to make improvement even if the test result does not satisfy the required strength, since the test is usually performed at the 28th day after the placement of concrete at the construction site. Therefore, accurate and realistic strength estimation before the placement of concrete is being highly required. In this study, the estimation of the compressive strength of concrete was performed by probabilistic neural network(PNN) on the basis of concrete mix proportions. The estimation performance of PNN was improved by considering the correlation between input data and targeted output value. Improved probabilistic neural network was proposed to automatically calculate the smoothing parameter in the conventional PNN by using the scheme of dynamic decay adjustment (DDA) algorithm. The conventional PNN and the PNN with DDA algorithm(IPNN) were applied to predict the compressive strength of concrete using actual test data of two concrete companies. IPNN showed better results than the conventional PNN in predicting the compressive strength of concrete.

• 한국군사과학기술학회지
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• 제26권5호
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• pp.400-408
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• 2023

The tracking accuracy of buoy-based LBL(Long Base Line) systems can be significantly influenced by sea environmental conditions. Particularly, the position of buoys that may have drifted due to sea currents. Therefore it is necessary to predict and optimize the drifted-buoy positions in the deploying step. This research introduces a free-drift simulation model using ocean data from the European CMEMS. The simulation model's predictions are validated by comparing them to actual sea buoy drift tracks, showing a substantial match in averaged drift speed and direction. Using this drift model, we optimize the initial buoy layout and compare the tracking performance between the center hexagonal layout and close track layout. Our results verify that the optimized layout achieves lower tracking errors compared to the other two layout.

• The Korean Journal of Pain
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• 제22권2호
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• pp.124-129
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• 2009

Background: The "gold standard" for proper epidural catheter positioning is a clinical response, as assessed by a pinprick test. Yet it may take time or it may be difficult to perform this test after epidural catheter placement in sedated or uncooperative patients or during general anesthesia. We assessed the usefulness of aspirating injected air via an epidural catheter as an indicator of correct epidural catheter placement. Methods: We surveyed 200 patients who underwent surgery under general or epidural anesthesia. A Tuohy needle was inserted into the epidural space with using the hanging drop technique. After placement of the epidural catheter, 3 ml of air was injected via the catheter, and then the volume of aspirated air was measured. Results: The mean volume of aspirated air was $2.3{\pm}0.7ml$ (75% of the injected air volume) and this ranged from 0 to 3 ml. Conclusions: Aspiration of injected air is a simple alternative method for identifying the appropriate placement of epidural catheters in the epidural space.

• 응용통계연구
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• 제29권7호
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• pp.1411-1419
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• 2016

랜덤화 블록 계획법을 검정하는 비모수적 방법에는 일반적인 대립가설에서 Friedman (1937)이 제안한 검정법이 있다. 이 방법은 처리 효과의 차이를 알아보기 위한 검정법으로 블록 내 순위를 사용해 검정함으로써 블록 간 정보의 손실이 있을 수 있다. 본 논문에서는 Hodges와 Lehmann (1962)이 제안한 정렬방법을 이용하여 블록 간 정보 손실을 줄이고, Jo와 Kim (2013)이 제안한 랜덤화 블록 계획법의 결합위치 방법을 확장하여 결합위치에 점수함수를 적용한 새로운 비모수적 방법을 제시하였다. 또한 Monte carlo simulation을 통하여 기존의 검정 방법과 제안한 검정법의 검정력을 비교하였다.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.474-486
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• 2015

This paper proposes a multi-objective optimal placement method of Phasor Measurement Units (PMUs) in large electric transmission systems. It is proposed for minimizing the number of PMUs for complete system observability and maximizing measurement redundancy of the buses, simultaneously. The measurement redundancy of the bus indicates that number of times a bus is able to monitor more than once by PMUs set. A high level of measurement redundancy can maximize the system observability and it is required for a reliable power system state estimation. Therefore, simultaneous optimizations of the two conflicting objectives are performed using a binary coded firefly algorithm. The complete observability of the power system is first prepared and then, single line loss contingency condition is added to the main model. The practical measurement limitation of PMUs is also considered. The efficiency of the proposed method is validated on IEEE 14, 30, 57 and 118 bus test systems and a real and large- scale Polish 2383 bus system. The valuable approach of firefly algorithm is demonstrated in finding the optimal number of PMUs and their locations by comparing its performance with earlier works.