• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 춘계학술대회논문집
• /
• pp.1081-1085
• /
• 2002

A modeling is developed to predict the isolation performance of sound barrier systems under the sound pressure radiated from excited by point impact. The predicted results are compared with the measured results obtained by using APAMAT II. This instrument provides a combination of structure-borne noise and air-borne noise, which corresponds to rolling noise, by applying the excitation system projected steel balls against the steel sheet.

• 한국소음진동공학회논문집
• /
• 제15권9호
• /
• pp.1108-1117
• /
• 2005

A robust damage detection method using short-time Fourier transform and beating phenomena is presented as an estimating tool of the healthiness of large structures. The present technique makes use of beating phenomena that manifest themselves when two signals of similar frequencies are added or subtracted. Unlike most existing methods based on vibration signals, the present approach does not require an analytic model for target structures. Furthermore, the main advantage of the proposed method compared to the competing diagnostic method using vibration data is its robustness. The proposed method is not affected by the amplitude of exciting signals and the location of exciting points. From a measuring view point. the location of sensing point have no influence on the performance of the present method. With a view to verifying the effectiveness of this method. a series of experiments are made and the results show its possibility as a robust damage diagnostic method.

• International Journal of Automotive Technology
• /
• 제2권1호
• /
• pp.33-38
• /
• 2001

The noise generated from a treadband mechanism of a tire has been the subject of this research. In particular, the treadband has been treated as an infinite tensioned beam resting on an elastic foundation which includes damping. The main objective is here to predict the sound power generated from a system mentioned above by locating harmonic point forces representing the excitation of treadband at the contact patch. It is possible to predict the sound power radiated from this structure by wavenumber transformation techniques. To find out the minimum radiated sound power, All parameters were varied. Thus this model can be used as a tire design guide for selecting parameters which produce the minimum noise radiation.

• 한국세라믹학회지
• /
• 제40권11호
• /
• pp.1062-1066
• /
• 2003

Design of a piezoelectric actuator for the ultrasonic motor must ensure that contact point has elliptic trajectory of movement. The new idea of an elliptic trajectory formation of the piezoelectric actuator is investigated in the paper. Shaking beam for the piezoelectric linear ultrasonic motor was introduced to realize this new idea. The principle is based on the excitation of longitudinal and flexural vibrations of the actuator by using two sources of longitudinal mechanical vibrations shifted by $\pi$/2. Mode-frequency and harmonic response analyses of the actuator based on FEM have been carried out. The moving trajectory of the contact point has been defined. Finally, The experimental research of shaking beam has been confirmed an opportunity of the elliptic trajectory reception with the help of one stable mode of the vibrations.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2001년도 추계학술대회논문집 II
• /
• pp.1089-1092
• /
• 2001

In order to measure the vibration of a ribbed clindrical shell, the principle of reciprocity has been implemented. An accelerometer was fixed at the position defined as the excitation point. An impact hammer was used to tap at the response array points (64 points) located along the circumference of the shell. The frequency response function was reciprocally measured at each point in turn. The response data was processed to obtain the frequency/wavenumber spectrum. From the spectrum the characteristics of wave propagation on the ribbed cylindrical shell have been observed.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2005년도 추계학술대회논문집
• /
• pp.844-848
• /
• 2005

A method to predict the strain responses from the measurements of displacement responses is considered. The method uses a transformation matrix which is composed of a displacement modal matrix and a strain modal matrix. The method can predict strains at points where displacements are not measured as well as at displacement measuring points. One of the drawbacks of the strain prediction method is that the displacement responses must be measured at many points on a structure simultaneously. This difficulty can be overcome by measuring the FRFs between displacements at a reference point and other point in sequence with a two channel measuring equipment This procedure is based on the assumption that the characteristics of excitation applied to the structure do not vary with time.

• 대한화학회지
• /
• 제47권4호
• /
• pp.325-333
• /
• 2003

1,2-와 1,3-dioxetane$(C_2O_2H_4)$, 그리고 1,3-cyclodisiloxane$(Si_2O_2H_4)$에 대하여 높은 이론 수준에서 분자구조, 진동주파수, 그리고 에너지 등을 계산하였다. 위의 모든 분자들에 대하여 TZ2P CCSD(T)의 이론 수준까지 분자구조를 최적화 하였으며. 진동주파수는 여러 basis set에서 SCF 방법으로 계산하였다. 본 연구에서 최적화된 분자구조들에 대한 진동주파수가 모두 실수(real number)로 예측됨으로서, 제안된 모든 분자구조가 local minimum 구조임을 확인하였다. 1,2- 및 1,3-dioxetane들과 cyclodisiloxane이 두 분자의 aldehyde와 silanone으로 해리 될 때의 중합에너지를 zero-point vibrational energy(ZPVE)를 고려하여 계산하고, 안정성을 비교하였다.

• Imaging Science in Dentistry
• /
• 제52권3호
• /
• pp.259-266
• /
• 2022

Purpose: This study aimed to evaluate the clinical usefulness of magnetic resonance (MR) neurography using the 3-dimensional double-echo steady-state with water excitation (3D-DESS-WE) sequence for the preoperative delineation of the facial and lingual nerves. Materials and Methods: Patients underwent MR neurography for a tumor in the parotid gland area or lingual neuropathy from January 2020 to December 2021 were reviewed. Preoperative MR neurography using the 3D-DESS-WE sequence was evaluated. The visibility of the facial nerve and lingual nerve was scored on a 5-point scale, with poor visibility as 1 point and excellent as 5 points. The facial nerve course relative to the tumor was identified as superficial, deep, or encased. This was compared to the actual nerve course identified during surgery. The operative findings in lingual nerve surgery were also described. Results: Ten patients with parotid tumors and 3 patients with lingual neuropathy were included. Among 10 parotid tumor patients, 8 were diagnosed with benign tumors and 2 with malignant tumors. The median facial nerve visibility score was 4.5 points. The distribution of scores was as follows: 5 points in 5 cases, 4 points in 1 case, 3 points in 2 cases, and 2 points in 2 cases. The lingual nerve continuity score in the affected area was lower than in the unaffected area in all 3 patients. The average visibility score of the lingual nerve was 2.67 on the affected side and 4 on the unaffected side. Conclusion: This study confirmed that the preoperative localization of the facial and lingual nerves using MR neurography with the 3D-DESS-WE sequence was feasible and contributed to surgical planning for the parotid area and lingual nerve.

• Bulletin of the Korean Chemical Society
• /
• 제33권3호
• /
• pp.933-940
• /
• 2012

Recently, it has been shown that quantum coherence appears in energy transfers of various photosynthetic lightharvesting complexes at from cryogenic to even room temperatures. Because the photosynthetic systems are inherently complex, these findings have subsequently interested many researchers in the field of both experiment and theory. From the theoretical part, simplified dynamics or semiclassical approaches have been widely used. In these approaches, the quantum-classical Liouville equation (QCLE) is the fundamental starting point. Toward the semiclassical scheme, approximations are needed to simplify the equations of motion of various degrees of freedom. Here, we have adopted the Poisson bracket mapping equation (PBME) as an approximate form of QCLE and applied it to find the time evolution of the excitation in a photosynthetic complex from marine algae. The benefit of using PBME is its similarity to conventional Hamiltonian dynamics. Through this, we confirmed the coherent population transfer behaviors in short time domain as previously reported with a more accurate but more time-consuming iterative linearized density matrix approach. However, we find that the site populations do not behave according to the Boltzmann law in the long time limit. We also test the effect of adding spurious high frequency vibrations to the spectral density of the bath, and find that their existence does not alter the dynamics to any significant extent as long as the associated reorganization energy is changed not too drastically. This suggests that adopting classical trajectory based ensembles in semiclassical simulations should not influence the coherence dynamics in any practical manner, even though the classical trajectories often yield spurious high frequency vibrational features in the spectral density.

• Structural Engineering and Mechanics
• /
• 제75권4호
• /
• pp.435-444
• /
• 2020

Ultrasonic guided wave testing is a very promising non-destructive testing method for rails, which is of great significance for ensuring the safe operation of railways. On the basis of the semi-analytical finite element (SAFE) method, a analytical model of 59R2 grooved rail was proposed, which is commonly used in the ballastless track of modern tram. The dispersion curves of ultrasonic guided waves in free rail and supported rail were obtained. Sensitivity analysis was then undertaken to evaluate the effect of rail elastic modulus on the phase velocity and group velocity dispersion curves of ultrasonic guided waves. The optimal guided wave mode, optimal excitation point and excitation direction suitable for detecting rail integrity were identified by analyzing the frequency, number of modes, and mode shapes. A sinusoidal signal modulated by a Hanning window with a center frequency of 25 kHz was used as the excitation source, and the propagation characteristics of high-frequency ultrasonic guided waves in the rail were obtained. The results show that the rail pad has a relatively little influence on the dispersion curves of ultrasonic guided waves in the high frequency band, and has a relatively large influence on the dispersion curves of ultrasonic guided waves in the low frequency band below 4 kHz. The rail elastic modulus has significant influence on the phase velocity in the high frequency band, while the group velocity is greatly affected by the rail elastic modulus in the low frequency band.