• International Journal of Reliability and Applications
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• 제13권1호
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• pp.49-56
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• 2012

Using total time on test transform (TTT), a new approach is taken for testing exponentiality versus the unknown age, exponential better than equilibrium life in convex ordering (EBELC). Selected critical values are tabulated for sample size n =2(2)50 and powers of the test are estimated for some commonly used distributions in reliability. Finally real example is presented to illustrate the theoretical results.

• 한국과학교육학회지
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• 제18권4호
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• pp.485-491
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• 1998

한국 생물 영재 학생들의 국제적 수준과 생물 영재 교육 프로그램의 필요성을 탐색하기 위하여 전국 각 고등학교 대표 학생들 중 선발된 30명과 국제생물올림피아드 참가 학생간의 성적을 비교하였다. 이론 분야를 세포 생물학, 식물 해부 및 생리학, 동물 해부 및 생리학, 행동학, 유전과 진화, 생태학, 분류학 및 미생물학 등 8개 영역으로 구분하여 1998년 1월과 3월, 2회에 걸쳐 이론 평가를 실시하였다. 그 결과 한국 생물 영재 학생들은 생물 전 영역에 걸쳐 국제생물올림피아드 참가자보다 성적이 낮은 것으로 나타났으며, 특히 행동학과 분류학 영역에서 크게 뒤떨어지는 것으로 조사되었다. 한국대표 급 상위 4명은 동메달 수상 수준에 해당하였으나, 행동학과 분류학 영역에서는 메달 수상자보다 훨씬 뒤떨어지는 것으로 나타났다. 그러므로 생물 영재 학생들을 위한 이론 강의와 탐구적 활동을 포함한 교육 프로그램이 필요하다.

• 대한조선학회논문집
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• 제50권4호
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• pp.240-247
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• 2013

Hydrodynamic characteristics of a planing craft are very sensitive to the hull form variations, especially when the craft navigates with high-speed. Therefore, we need to verify hydrodynamic performances of the craft during the process of hull form design. In this paper, motion performances of a 40ft class cruise leisure boat are evaluated by both model tests and theoretical analyses using two different methods. Model tests are carried out at calm sea and regular wave conditions using high speed towing carriage installed in SNU towing tank. Theoretical methods used are a empirical method proposed by Martin (1976) and a potential method based on Rankine panel (DNV, 2010). The results from the theoretical methods are compared with and verified by those of model tests. Results of empirical formula showed somewhat larger motion RAOs and resonant frequencies than those of model tests. Potential based method showed even larger discrepancies with the model test results. From the analyses of comparison results, we could confirm the limitation of each theoretical method and suggest the way of improvement for the better prediction of motion performances.

• 한국학교보건학회지
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• 제24권1호
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• pp.50-60
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• 2011

Purpose: This paper compares practical first aid training and theoretical first aid training in elementary schools. Methods: Research subjects were randomly selected and sorted into experimental and control groups. The former is one class (28 students) of the fifth grade students, and the latter is another class (30 students). In order to verify the effect of first aid training, we conducted theoretical as well as practical first-aid instruction about foreign body airway obstruction to the experimental group, but conducted only theoretical instruction with the control group. Data were analyzed by the ${\chi}^2$-test and t-test, one-way using the SPSS / win 12.0 program. The results were as follows (p=.05). Results: The first hypothesis was that the knowledge of an experimental group would be better than that of a control group. The analysis showed a significant difference (p=.000) between the two groups, supporting this hypothesis. The second hypothesis was that the experimental group would be more accurate than the control group. There was no because of (p=.000) between the two groups on this measure. The third hypothesis, that the two groups would vary over time on the measure of accuracy, was supported by the following observations: the experimental results were accumulated before, two days after and two weeks after the training (experimental group, p=.000, and control group, p=.000). This supports the third hypothesis that the technical performance accuracy levels of complete respiratory obstruction first aid vary over time. Conclusion: First aid training has to include practical education as well as theoretical education in the future, as part of a school's health education for elementary students. Health education classrooms should be prepared to teach first-aid theory and be supplied with equipment for practical exercises. Schools, communities, and private organizations need to carry out the practical education component periodically.

• Earthquakes and Structures
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• 제23권2호
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• pp.169-181
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• 2022

To research the dynamic response of the high-rise structure under the rocking ground motion, which we believed that the effect cannot be ignored, especially accompanied by vertical ground motion. Theoretical analysis and shaking table seismic simulation tests were used to study the response of a high-rise structure to excitation of a H-V-R ground motion that included horizontal, vertical, and rocking components. The use of a wavelet analysis filtering technique to extract the rocking component from data for the primary horizontal component in the first part, based on the principle of horizontal pendulum seismogram and the use of a wavelet analysis filtering technique. The dynamic equation of motion for a high-rise structure under H-V-R ground motion was developed in the second part, with extra P-△ effect due to ground rocking displacement was included in the external load excitation terms of the equation of motion, and the influence of the vertical component on the high-rise structure P-△ effect was also included. Shaking table tests were performed for H-V-R ground motion using a scale model of a high-rise TV tower structure in the third part, while the results of the shaking table tests and theoretical calculation were compared in the last part, and the following conclusions were made. The results of the shaking table test were consistent with the theoretical calculation results, which verified the accuracy of the theoretical analysis. The rocking component of ground motion significantly increased the displacement of the structure and caused an asymmetric displacement of the structure. Thus, the seismic design of an engineering structure should consider the additional P-△ effect due to the rocking component. Moreover, introducing the vertical component caused the geometric stiffness of the structure to change with time, and the influence of the rocking component on the structure was amplified due to this effect.

• 전기전자학회논문지
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• 제13권2호
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• pp.220-223
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• 2009

A simple measurement system is built to estimate the dual-antenna diversity gain at 2.4GHz easily in open lab environment. To obtain multipath fading propagation channel, the system consists of two transmission horn that placed on opposite direction and a rotating stage mechanically changing the position of test dual-antenna with time over distance greater than one wavelength. Estimated diversity is nearly same as theoretical value such that measured diversity gain of 30mm separated is about 6dB similar to theoretical value of 5.7dB and increases monotonically with the increasing separation distance as predicted by the theory. Proposed measurement system that is simple enough to fit in a small space can evaluate the performance of various dual-antennas with a reasonable accuracy with lower 5% difference between the ten sets of measured waveform distribution and theoretical Rayleigh cumulative distribution.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제25회 춘계학술대회
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• pp.253-259
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• 1997

A software for design of turbine bearings has been developed based on both the theoretical analysis and experimental investigation. Static and dynamic performance, i.e. load capacity, frictional loss, temperature distribution, stiffness and damping coefficients, stability etc., can be obtained by using this software taking into account the effects of three dimensional variation of lubricant viscosity, turbulence and inlet pressure. A performance test rig was developed by self-design and technology, which was used to verify static and dynamic characteristics and to investigate the proper boundary conditions for theoretical analysis. Consequently HANJUNG has developed the self-design technology for design of turbine bearings for power plants.

• 한국세라믹학회지
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• 제27권3호
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• pp.321-328
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• 1990

For the reliability analysis of Sin/Hip silicon nitride, such as Weibull modulus m, scale parameter $\sigma$0, and Batdorf crack density coefficient kB were obtained by 4-point MOR test. And its theoretical failure probabilities under arbitrary stress state were predicted using finite element analysis and KARA II reliability analysis program, which was programmed for both surface adn volume flaws. For the verification of this theoretical results, the experimental failure probabilities were measured using ring-to-ring tests at room temperature as well as 4-point MOR tests at 100$0^{\circ}C$, and were compared with theoretical failure probabilities.

• 한국정밀공학회지
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• 제28권5호
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• pp.551-558
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• 2011

To analyze the effect of wear of wheel profile on the running stability of rolling-stock, theoretical and experimental studies were conducted on the profiles used in conventional lines. In experiment using 1/5 scale model to verify the results of the theoretical analysis, the test results of the critical speed for worn wheel profile samples show similar trend. In case of the conical type wheel profile(Profile 40), the equivalent conicity is increased with flange wear. But in case of the arc type wheel profile(Profile 20h), the equivalent conicity is decreased with flange wear. And the critical speed of the bogie was inverse proportion to the equivalent conicity. It is shown that the variation of the critical speed with the wheel wear could be changed according to the design concept and wear pattern of wheel profile. Results of the theoretical and experimental studies are discussed here.

• Structural Engineering and Mechanics
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• 제55권5호
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• pp.931-951
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• 2015

To improve the durability and service life of reinforced concrete column such as bridge piers, an advanced composite column made of Ultra High Performance Cementitious Composites (UHPCC) permanent form is proposed. Based on elasticity plasticity theory, axial compression behavior of the composite column was studied theoretically. The first circumferential cracking load and ultimate limit loading capacity are derived for the composite column. Short composite column compression tests and numerical simulations using FEM method were carried out to justify the theoretical formula. The effects of UHPCC tube thickness on the axial compression behavior were studied. Using the established theoretical model and numerical simulation, the large dimension composite columns are calculated and analyzed with different UHPCC tube thickness. These studies may provide a reference for advanced composite column design and application.