• 한국구조물진단유지관리공학회 논문집
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• 제17권3호
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• pp.20-27
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• 2013

본 논문에서는 고유진동수를 구하기 Simple Iteration Method을 제시하였다. 이 방법은 임의의 단면과 지점을 갖고 임의의 하중을 받는 보나 탑의 진동모드와 관련된 고유진동수를 간편하면서도 정확하게 계산할 수 있는 획기적인 방법이다. 이 방법에는 공진상태에서 관성력에 기인한 부재의 처짐 모드를 구하게 된다. 진동해석을 위하여 처짐의 영향을 고려한 다양한 방법이 검토되었다. 이러한 목적으로 본 논문에서는 유한차분법을 사용하였다. 고유진동수에 대한 $D_{22}$ 휨강성의 영향을 철저하게 검토하였다. 본 논문에서는 구조 요소의 하중 분포 또는 상이한 단면에 따른 고유진동수에 대한 영향을 연구하였으며 그 결과를 제시하였다. 이 방법은 첨단복합재료를 포함한 2차원 문제에도 적용할 수 있다.

• 전기학회논문지
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• 제56권2호
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• pp.355-360
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• 2007

The recent TFT-LCD Trend that is done large size gradually. As size of monitor great, though problem happens, it is that consumer's request which it makes monitor combined TV function. Monitor and TV are no difference externally greatly, but define difference happens as for backlight. An external electrode fluorescent lamp (EEFL) has an advantage of a long lifetime in the early stages of the study on plasma discharge, interest in the lamp continues. Researches on the operation of external electrode fluorescent lamps have focused mainly on its use of a type of high frequency (MHz). By performing high Luminance using a square wave operation method with the low frequency below 100kHz, which is applied to a narrowed tube type lamp that has several mm of lamp diameter, EEFL presented the possibility of using it as a light source for back-lights. However, because EEFL generates plasma using wall charges, which considers the impedance characteristics of glass based on the structural principle in discharge, it can be significantly affected by frequency. Thus, this study verified the change in the characteristics of electromagnetic fields according to the change in frequency through a Maxwell electromagnetic field simulation and examined the relationship between the change in the EEFL frequency and Luminance by measuring the optical characteristics.

• Advances in nano research
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• 제10권2호
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• pp.175-189
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• 2021

In this article, frequency characteristics, and sensitivity analysis of a size-dependent laminated composite cylindrical nanoshell under bi-directional thermal loading using Nonlocal Strain-stress Gradient Theory (NSGT) are presented. The governing equations of the laminated composite cylindrical nanoshell in thermal environment are developed using Hamilton's principle. The thermodynamic equations of the laminated cylindrical nanoshell are obtained using First-order Shear Deformation Theory (FSDT) and Fourier-expansion based Generalized Differential Quadrature element Method (FGDQM) is implemented to solve these equations and obtain natural frequency and critical temperature of the presented model. The novelty of the current study is to consider the effects of bi-directional temperature loading and sensitivity parameter on the critical temperature and frequency characteristics of the laminated composite nanostructure. Apart from semi-numerical solution, a finite element model was presented using the finite element package to simulate the response of the laminated cylindrical shell. The results created from finite element simulation illustrates a close agreement with the semi-numerical method results. Finally, the influences of temperature difference, ply angle, length scale and nonlocal parameters on the critical temperature, sensitivity, and frequency of the laminated composite nanostructure are investigated, in details.

• 경영과정보연구
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• 제2권
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• pp.237-266
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• 1998

The purpose of this study was to analyze the differences of application level the computer programming languages in major. The method of this study is the empirical method based on theoretical one with the previous bibliographical suduies. The sample consists of 268 listed university disclosing over the period of Dec. 1. 1997 to Du. 15. 1997. The samples were 10 university in university of Seoul, Pusan, Masan City, Korea. The data were collected by questionnaire research through interview with each person. The analysis data was carried to 268 samples by using SPSS/PC for Windows Version 7.5 statistical package. Statistical methods such as frequency analysis, chi-square test, ANOVA test, correlation analysis were used to test the research questions. This paper focuses on the design of the hypothesis test show that the 2 type are significantly different in major of university students. Before the test of research questions performed it frequency analysis by using the factor score that bring each items. The research type of 2 guoups, that is, BA Group(business administration group) and NBA Group(non-business administration guoup). To summarize the result of this study is as follows ; (1) Hypothesis 1 : Concerning about computer programming language in major, the significant difference is application the present condition. (2) Hypothesis 2 : Concerning about computer programming language in major, the significant difference is application level. (3) Hypothesis 3 : Concerning about each application software in major, the significant difference is application level. According to the results of this study, it is found that (1) Hypothesis 1 related In application the present condition of computer programming language was accepted its all at 0.05 % significance level. (2) Hypothesis 2 related to application level of computer programming language was accepted its all at 0.05 % significance level. (3) Hypothesis 3 related to application level of each application software was rejected its all. at 0.05 % significance level.

• 방송공학회논문지
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• 제11권2호
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• pp.222-228
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• 2006

이 논문에서는 동일채널 간섭이 존재하는 채널 환경에서 OFDM(Orthogonal Frequency Division Multiplexing) 시스템의 수신 다이버시티 결합 방법을 제시한다. 제시한 방법에서 각 수신 안테나로부터의 수신 신호는 주파수 영역에서 부반송파 단위로 결합하며, 잡음과 간섭 전력을 고려한 MRC(Maximum Ratio Combining)를 적용한다. 잡음과 간섭 전력은 채널의 제한된 지연 확산에 기인하는 주파수 대역에서의 상관특성(coherency)을 이용하여 상관성이 큰 일정구간 이내의 부채널에 대해 잡음과 간섭 전력의 평균을 취함으로써 더 정확한 추정치를 얻는다. IEEE 802.11a 무선 LAN 규격에서 모의실험한 결과 제안방법은 간섭전력을 이용하지 않는 방식에 비해 신호대잡음비를 2-3.5dB 개선하였으며, 정확하게 잡음 및 간섭 전력을 추정한 경우에 대해 1dB 이내로 접근하는 결과를 나타내었다.

• Journal of Mechanical Science and Technology
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• 제19권11호
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• pp.2032-2039
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• 2005

The lattice Boltzman method (LBM) and the finite difference-based lattice Boltzmann method (FDLBM) are quite recent approaches for simulating fluid flow, which have been proven as valid and efficient tools in a variety of complex flow problems. They are considered attractive alternatives to conventional finite-difference schemes because they recover the Navier-Stokes equations and are computationally more stable, and easily parallelizable. However, most models of the LBM or FDLBM are for incompressible fluids because of the simplicity of the structure of the model. Although some models for compressible thermal fluids have been introduced, these models are for monatomic gases, and suffer from the instability in calculations. A lattice BGK model based on a finite difference scheme with an internal degree of freedom is employed and it is shown that a diatomic gas such as air is successfully simulated. In this research we present a 2-dimensional edge tone to predict the frequency characteristics of discrete oscillations of a jet-edge feedback cycle by the FDLBM in which any specific heat ratio $\gamma$ can be chosen freely. The jet is chosen long enough in order to guarantee the parabolic velocity profile of a jet at the outlet, and the edge is of an angle of $\alpha$=23$^{o}$. At a stand-off distance w, the edge is inserted along the centerline of the jet, and a sinuous instability wave with real frequency is assumed to be created in the vicinity of the nozzle exit and to propagate towards the downstream. We have succeeded in capturing very small pressure fluctuations resulting from periodic oscillation of the jet around the edge.

• Journal of Periodontal and Implant Science
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• 제39권sup2호
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• pp.269-278
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• 2009

Purpose: The aim of this study was to investigate matrix metalloproteinase 1 (MMP-1) gene polymorphism (1G/2G at -1607 and A/G at -519) in Korean subject and to assess the association between polymorphism and periodontal status. Methods: Forty nine generalized aggressive periodontitis (GAP) patients and 57 periodontally healthy children were recruited and genomic DNA was extracted from buccal swab. The polymorphisms of MMP-1 promoter genes were determined by polymerase chain reaction and restriction fragment length product (PCR-RFLP) method. The distribution of genotype and allele frequency was compared between 2 groups by ${\chi}^2$ test. Results: There was a significant difference in the distribution of genotypes and frequency of alleles between the GAP and reference groups at the position - 519 of MMP-1 gene promoter (P<0.05). Allele G carrier rate was significantly lower in GAP group than that of the reference group (P< 0.001). At the position -1607 of MMP-1 gene promoter, genotype distribution and allele frequency showed no statistically significant difference between the groups. However, in the female group, a significant difference was observed between the groups for the genotype distribution, allele frequency and allele 1G carrier rate (P< 0.05). Conclusions: The DNA polymorphism at the MMP-1 gene promoter might be associated with GAP in Korean.

• Journal of Chest Surgery
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• 제19권2호
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• pp.232-237
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• 1986

The intraventricular conduction disturbances have been documented after correction of ventricular septal defects by any surgical route but debated its etiology. And so the frequency of conduction disturbances following right ventriculotomy, right atriotomy and pulmonary arteriotomy for closure of ventricular septal defects was compared in various conditions. The present series consists of 218 patients with ventricular septal defects. They had the surgical repair at the Seoul National University Hospital from January 1983 to October 1984. Conduction disturbances were studied with conventional 12 leads electrocardiogram. Of the 218 VSD`s 139 patients were repaired via vertical right ventriculotomy, 45 patients via right atriotomy, 34 patients via pulmonary arteriotomy. 1] Of 218 patients the frequency of RBBB was 26.1% and the frequency of RBBB + LAH was 6.0%. 2] There is no statistical difference between right ventriculotomy group [30.2%] and right atriotomy group [24.4%]. But there is significant difference between right ventriculotomy group and pulmonary arteriotomy group [11.8%] [P<0.05]. 3] In respect to anatomical classification by Kirklin`s method, the frequency of RBBB was higher in type II [32.1%] than in type I [14.9%]. [P<0.05] But in each anatomical type, there is no influence of the various surgical approach on the incidence of postoperative RBBB. 4] The frequency of RBBB was 31.8% in patch closure group and 14.3% in direct closure group. [P<0.05] Although the result suggests that there is no significant difference in various surgical approaches on the incidence of postoperative conduction disturbances, it may be reduced by a new-ventricular approach or a limited incision at right ventricular outflow tract in right ventricular approach.

• 지구물리와물리탐사
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• 제5권2호
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• pp.99-107
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• 2002

표면파 기법(SASW, Spectral Analysis of Surface Waves)을 지반공학 분야에 효율적으로 적용하기 위해 모형 응답 알고리듬을 해석적으로 도출하였다. 이 논문에서는 이론적인 분산 곡선 응답 반응을 Aki and Richard에 의해 제안된 운동 응력 벡터(motion stress vector)를 이용하여 미분 방정식을 구성한 후 차분 전개를 통하여 구함으로서 동적 강성도 법이나 전파 행렬법에 비해 간단하고 빠르게 구할 수 있었다. 차분 전개를 통한 이론 분산 곡선 응답 반응 알고리즘으로 2개의 지구 모형에 대해 이론 분산 곡선을 구하여 타당성을 검증하였다. 또한 모형 응답 계산 과정에서 고려하여야 할 주파수 대역에 따른 적절한 모형의 크기에 대하여 고찰한 결과 각 파장의 $1.5\~2$배 이내로 모형의 크기를 결정할 때 경제적이고 안정적인 결과를 얻을 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.341-344
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• 1988

This paper derives a condition foe constant voltage i constant frequency generation of doubly-fed induction generator. The condition is varied by the magnitude of output voltage, load current and its power factor, slip of the machine. Magnitude of output voltage is controlled by exiting voltage which is caculated by derived equation from operating condition. frequency of output voltage is controlled by injecting slip frequency to the rotor which is the difference between wanted output frequency and rotor frequency.