• Ocean Systems Engineering
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• 제4권3호
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• pp.201-213
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• 2014

Wave run-up is an important issue in offshore engineering, which is tightly related to the loads on the marine structures. In this study, a series of physical experiments have been performed to investigate the wave run-up around a vertical cylinder in transitional water depth. The wave run-ups of regular waves, irregular waves and focused waves have been presented and the characteristics in frequency domain have been investigated with the FFT and wavelet transform methods. This study focuses on the nonlinear features of the wave run-up and the interaction between the wave run-up and the cylinder. The results show that the nonlinear interaction between the waves and the structures might result wave run-up components of higher frequencies. The wave run-ups of the moderate irregular waves exhibit 2nd order nonlinear characteristics. For the focused waves, the incident waves are of strong nonlinearity and the wavelet coherence analysis reveals that the wave run-up at focal moment contains combined contributions from almost all the frequency components of the focused wave sequence and the contributions of frequency components up to 4th order harmonic levels are recommended to be included.

• 대한한방내과학회지
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• 제21권1호
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• pp.135-145
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• 2000

Objective : This study has been made to analysis of clinical type of vertigo prodromic Cerebral Vascular Disease in stroke patients who admitted to sangji oriental hospital department of circulatoty internal medicine in the period from July. 1999 to October 1999. Methods : A Questionaire was done after explanationin details to patients and agreement of patients. The inquire was done as follows. Sex and age, risk factor of stroke, type of stroke, existence of vertigo last three years before stroke attack, the beginning age of vertigo and period of prevalence, frequency, continuance time of vertigo, predilection season and time, factor of causing vertigo, accompanying symptoms of vertigo, severity of vertigo. Result and Conclusion : The existence of Rotation sense(Rotation group and non-Rotation group) and the type of Stroke is no difference significantly but the Rotation vertigo group and non-Rotation vertigo group is difference significantly in distribution. The sixties in age of vertigo attack, previous vertigo before 3 year Stroke attack, irregular in predilection season of vertigo, have a high frequency significantly in distribution and previous period of vertigo has no significantly difference in distribution. One or two per a month in frequency of vertigo, below 5 minute in continuance time of vertigo, irregular in predilection time of vertigo, stand up and sit down in causing vertigo position have a high frequency significantly in distribution.

• Wind and Structures
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• 제13권3호
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• pp.235-256
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• 2010

The aeroelastic stability of bridge decks equipped with multiple tuned mass dampers is studied. The problem is attacked in the time domain, by representing self-excited loads with the aid of aerodynamic indicial functions approximated by truncated series of exponential filters. This approach allows to reduce the aeroelastic stability analysis in the form of a direct eigenvalue problem, by introducing an additional state variable for each exponential term adopted in the approximation of indicial functions. A general probabilistic framework for the optimal robust design of multiple tuned mass dampers is proposed, in which all possible sources of uncertainties can be accounted for. For the purposes of this study, the method is also simplified in a form which requires a lower computational effort and it is then applied to a general case study in order to analyze the control effectiveness of regular and irregular multiple tuned mass dampers. A special care is devoted to mistuning effects caused by random variations of the target frequency. Regular multiple tuned mass dampers are seen to improve both control effectiveness and robustness with respect to single tuned mass dampers. However, those devices exhibit an asymmetric behavior with respect to frequency mistuning, which may weaken their feasibility for technical applications. In order to overcome this drawback, an irregular multiple tuned mass damper is conceived which is based on unequal mass distribution. The optimal design of this device is finally pursued via a full domain search, which evidences a remarkable robustness against frequency mistuning, in the sense of the simplified design approach.

• Fibers and Polymers
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• 제3권1호
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• pp.31-37
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• 2002

Most fibers are irregular, and they are often subjected to combined loading conditions during processing and enduse. In this paper polyester and wool fibers under the combined tensile and torsional loads have been studied for the first time using the finite element method (FEM). The dimensional irregularities of these fibers are simulated with sine waves of different magnitude and frequency. The breaking load and breaking extension of the fibers at different twist or torsion levels are then calculated from the finite element model. The results indicate that twist and level of fiber irregularity have a major impact on the mechanical properties of the fiber and the effect of the frequency of irregularity is relatively small.

• 대한음성학회:학술대회논문집
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• 대한음성학회 2006년도 춘계 학술대회 발표논문집
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• pp.113-116
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• 2006

This research was investigate to understand how moderate bilingual subjects represent the lexicon in second language. Although most researches have focused only on high proficient bilinguals, we analysed how moderate bilinguals who have learned English mostly in school represent the prototype of verb and its inflected form of verb. Results of lexical decision task showed that moderate bilingual subjects used different mental representation depending on whether the verb have regular or irregular conjugation. With regular verbs, the identification of an inflected form was affected by both the frequency of its prototype and that of inflected form, but with irregular verbs, it is affected only by the frequency of inflected form.

• 산업기술연구
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• 제15권
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• pp.169-174
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• 1995

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross-sections and with arbitrary boundary conditions was developed and reported by D. H. Kim in 1974. IN this paper, the result of application of this method to the laminated plates with axial forces and with attached point mass/masses is presented. Both $N_x$ and $N_y$ forces are considered. The solution for the laminated plates with arbitrary boundary conditions and irregular section can be obtained by simply obtaining the deflection influence coefficients by any method. The effect of neglecting the mass of the plates on the natural frequency, as the ratio of the point mass/masses to the plate mass increases, is thoroughly studied. The influence of $N_x$ and $N_y$ is also carefully investigated.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.297-313
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• 2020

An Arctic Spar is characterized by its conical shape near the waterline. In this case, the nonlinear effects from its irregular hull shape would be significant if there is either a large amplitude floater motion or steep wave conditions. Therefore, in this paper, the nonlinear effects of an Arctic Spar are numerically investigated by introducing a weakly nonlinear time-domain model that considers the time dependent hydrostatic restoring stiffness and Froude-Krylov forces. Through numerical simulations under multiple regular and irregular wave conditions, the nonlinear behavior of the Arctic Spar is clearly observed, but it is not shown in the linear analysis. In particular, it is found that the nonlinear Froude-Krylov force plays an important role when the wave frequency is close to the heave natural frequency. In addition, the nonlinear hydrostatic restoring stiffness causes the structure's unstable motion at a half of heave natural period.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.198-203
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• 2002

A fuzzy logic controller design technique is proposed to apply for the control of flexible system under irregular disturbance. The fuzzy rules of $\ulcorner$Mode Selecting Fuzzy Controller$\lrcorner$ are constructed using displacement, velocity information and modal characteristics of the system. The frequency information of flexible system is picked up from $\ulcorner$Mode Selecting Unit$\lrcorner$ based on Fast-Fourier transform algorithm. Experiment is conducted to verify the proposed theoretical approach, Piezo ceramic and laser accelerometer are used as actuator and sensor in the experiments respectively

• 수산해양기술연구
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• 제44권1호
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• pp.46-56
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• 2008

A numerical model analysis was performed to analyze the motion and mooring tension response of submersible fish cage systems in irregular waves and currents. Two systems were examined: a submersible cage mooring with a single, high tension mooring and the same system, but with an additional three point mooring. Using a Morison equation type model, simulations of the systems were conducted with the cage at the surface and submerged. Irregular waves(JONSWAP spectrum) with and without a co-linear current with a magnitude of 0.5m/s were simulated into the model as input parameters. Surge, heave and pitch dynamic calculations were made, along with tension responses in the mooring lines. Results were analyzed in both the time and frequency domains and linear transfer functions were calculated.

• 한국정보처리학회논문지
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• 제5권7호
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• pp.1943-1950
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• 1998

본 논문에서는 평판 플라즈마 표시장치(PDP)의 휘도를 개선할 수 있는 방법으로서 불규칙 어드레싱 방식을 제안하고 있다. 종래의 계조 조정 방식에서 주사 전극의 선택이 한 가지 순열조합에 의해 순차적으로 일어나는 것에 반하여 불규칙 어드레싱에서는 화소의 발광시간을 90%이상으로 늘릴 수 있도록 비순차적으로 주사 전극을 선택한다. 이 방식은 PDP의 물리적 구조에 무관하며 구동 전압이나 전류 등을 바꾸지 않고도 구현이 가능한 장점을 가진다.