• 대한전자공학회논문지
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• 제24권5호
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• pp.740-746
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• 1987

In calculating resonant frequencies of a microstrip resonator the effect of the stray field at resonator edges has been neglected in most publications. The formula for resonant frequencies therefore provided inaccurate results. In the paper the effective dimension and the dynamic dielectic constant of a resonator are defined and obtained for more accurate resonant frequencies and qualty factor by including the effect of stray fields. Theoretical results obtained from the new formula show good agreement with experimental results. In addition, the effect on resonant modes of the distance and coupling angle between the microstrip line and the resonator is also observed.

• 한국의사학회지
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• 제28권1호
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• pp.135-141
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• 2015

The purpose of this study is to analyze vocabulary found in "Donguibogam", one of the medical books in mid-Chosun, through Corpus-based analysis, one of the text analysis methods. According to it, Donguibogam has total 871,000 words in it, and Chinese characters used in it are total 5,130. Among them, 2,430 characters form 99% of the entire text. The most frequently appearing 20 Chinese characters are mainly function words, and with this, we can see that "Donguibogam" is a book equipped with complete forms of sentences just like other books. Examining the chapters of "Donguibogam" by comparison, Remedies and Acupuncture indicated lower frequencies of function words than Internal Medicine, External Medicine, and Miscellaneous Diseases. "Yixuerumen (Introduction to Medicine)" which influenced "Donguibogam" very much has lower frequencies of function words than "Donguibogam" in its most frequently appearing words. This may be because "Yixuerumen" maintains the form of Chileonjeolgu (a quatrain with seven Chinese characters in each line with seven-word lines) and adds footnotes below it. Corpus-based analysis helps us to see the words mainly used by measuring their frequencies in the book of medicine. Therefore, this researcher suggests that the results of this analysis can be used for education of Chinese characters at the college of Korean Medicine.

• Smart Structures and Systems
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• 제3권3호
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• pp.341-356
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• 2007

A good understanding of normal modal variability of civil structures due to varying environmental conditions such as temperature and wind is important for reliable performance of vibration-based damage detection methods. This paper addresses the quantification of wind-induced modal variability of a cable-stayed bridge making use of one-year monitoring data. In order to discriminate the wind-induced modal variability from the temperature-induced modal variability, the one-year monitoring data are divided into two sets: the first set includes the data obtained under weak wind conditions (hourly-average wind speed less than 2 m/s) during all four seasons, and the second set includes the data obtained under both weak and strong (typhoon) wind conditions during the summer only. The measured modal frequencies and temperatures of the bridge obtained from the first set of data are used to formulate temperature-frequency correlation models by means of artificial neural network technique. Before the second set of data is utilized to quantify the wind-induced modal variability, the effect of temperature on the measured modal frequencies is first eliminated by normalizing these modal frequencies to a reference temperature with the use of the temperature-frequency correlation models. Then the wind-induced modal variability is quantitatively evaluated by correlating the normalized modal frequencies for each mode with the wind speed measurement data. It is revealed that in contrast to the dependence of modal frequencies on temperature, there is no explicit correlation between the modal frequencies and wind intensity. For most of the measured modes, the modal frequencies exhibit a slightly increasing trend with the increase of wind speed in statistical sense. The relative variation of the modal frequencies arising from wind effect (with the maximum hourly-average wind speed up to 17.6 m/s) is estimated to range from 1.61% to 7.87% for the measured 8 modes of the bridge, being notably less than the modal variability caused by temperature effect.

• 한국소음진동공학회논문집
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• 제19권6호
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• pp.607-613
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• 2009

A new formulation of NDIF method to the algebraic eigenvalue problem is introduced to efficiently extract natural frequencies of arbitrarily shaped plates with the simply supported boundary condition. NDIF method, which was developed by the authors for the free vibration analysis of arbitrarily shaped membranes and plates, has the feature that it yields highly accurate natural frequencies compared with other analytical methods or numerical methods(FEM and BEM). However, NDIF method has the weak point that it needs the inefficient procedure of searching natural frequencies by plotting the values of the determinant of a system matrix in the frequency range of interest. A new formulation of NDIF method developed in the paper doesn't require the above inefficient procedure and natural frequencies can be efficiently obtained by solving the typical algebraic eigenvalue problem. Finally, the validity of the proposed method is shown in several case studies, which indicate that natural frequencies by the proposed method are very accurate compared to other exact, analytical, or numerical methods.

• 대한기계학회논문집
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• 제13권3호
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• pp.385-396
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• 1989

본 논문에서는 차륜과 레일의 접촉부에서 발생하는 크리프힘과 크리프모멘트 를 결합시키고 이들이 병진스프링과 비틀림스프핑에 의해서 연성되었을때 생기는 고유진동수의 특성을 차륜과 레일의 직교성을 이용하여 수치해석하고 모델실험을 통하여 연구하였다.

• Advances in concrete construction
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• 제13권4호
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• pp.327-337
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• 2022

This paper is concerned with the vibration analysis of middle layer cylindrical shell made of functionally graded material. The outer layers and inner layer are composed of functionally graded and isotropic material respectively. The Rayleigh Ritz method is applied to solve the presented shell dynamics equations. Two configurations are constructed with layers distributions. Fundamental natural frequencies of the three layered cylindrical shell is plotted against the circumferential wave number with different power law exponents. The frequency decreases with the increase of power law exponent. The fundamental natural frequencies first decreases and fall down to its minimum value, after frequencies increases with circumferential wave number. This is due to change in the magnitude of extensional and bending energies of the cylindrical shells. The computer software MATLAB has been employed for the computation of presented frequencies and tested the results obtained in order to assess the accuracy and validity of the cylindrical shell model for predicting the vibration frequencies of cylindrical shell.

• 한국전산구조공학회논문집
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• 제15권3호
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• pp.399-407
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• 2002

속이 빈 축대칭 회전체인 두꺼운 쉘의 정확한 고유진동수와 모우드형상을 결정하기 위해서 3차원적인 해석방법이 사용되었다. 이 축대칭 회전쉘의 모선을 직선으로 한정하지 않았으며, 쉘의 두께 또한 일정한 것으로 제한하지 않았다. 이 쉘의 중앙면은 임의의 곡율을 가지며, 쉘의 두께도 임의적으로 변한다. 자오선방향, 두께방향, 원주방향으로의 변위 성분인$U_\Phi, U_z, U_\theta$는 시간반응의 정현성(sinusoidal)과$\theta$방향으로의 주기성을 지니며,$\Phi$와 z 방향으로는 대수다항 식의 형태로 가정되었다. 이 쉘의 변형률에너지와 운동에너지를 공식화하였으며, 진동수의 최소화를 통해 상위경계치의 진동수를 구하고 다항식의 차수를 증가시켜 엄밀해에 수렴된 진동수를 구할 수 있다. 선형적으로 두께가 변하는 두꺼운 원추형쉘과 구형쉘에 대한 예를 통하여 하위 다섯 개의 진동수에 대해서 유효 숫자 4자리까지의 정확한 수렴성연구가 이루어졌다. 이 해석 방법은 두께가 매우 두꺼운 쉘 뿐만이 아니라 얇은 쉘에도 적용이 가능하다

• 한국소음진동공학회논문집
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• 제23권4호
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• pp.301-307
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• 2013

MRU(motor reduction unit) for KTX is a assembled complex structure that is equipped with a lot of parts at the express train KTX and that is the core power source operating variable speeds. This study is recorded the dynamic characteristics analysis results tested by EMA which is done through the parts and assembly test, transient analysis and stoped train test in order to design the online monitoring system for KTX MRU. And the mode shapes result from critical vibration frequency explain the relation with variable speeds of express train over 250 km/hr. Also these variable speeds make variable operational frequencies at pinion, axle gear mesh frequency and normal bearing fault frequencies. As the specified speed can make resonance with natural frequencies of the MRU, for the train operating stability, this study also presents the MRU's critical speeds calculated by the each train speed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.919-924
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• 2004

A CFA(Cooling Fan Assembly) is composed of a fan, motor and shroud, which is at the back of the automotive radiator. By forcing the wind to pass, the CFA controls the cooling performance of the radiator. The noise and vibration of the CFA may be primarily due to the resonance between the CFA and engine. The Interference among the fan, shroud and radiator by deformation is considered when the CFA is designed. In this paper, in order to analyze the structural vibration of the CFA for automobiles, a finite element model of the CFA is established by using a commercial FEM code. After the finite element modeling, the natural frequencies and the mode shapes are obtained from the FE analysis. The natural frequencies are obtained from the vibration test as well. Then, the results of the vibration test are compared with those of the FE analysis. The natural frequencies obtained by experiment have a great similarity to the results from FE model. We have confirmed the validity of the FE model and verify the structural safety for the resonance. The stress and displacements are obtained from FE analysis. We have confirmed the safety for the interference and failure.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.401.2-401
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• 2002

An unconstrained tuning fork with a 3-D model has been numerically analyzed by Finite Element Method (FEM) and Boundary Element Method (BEM). The first three natural frequencies were calculated by the FEM modal analysis. Then the change of the modal frequencies was examined with the variation of the tuning fork length and width. (omitted)