• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.1
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• pp.101-107
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• 2018

In this study, the analysis of radiation noise and chattering noise of vehicle seat recliner was conducted through testing and analysis. First, operating noise was measured by seat back frame and recliner, and chattering noise was confirmed. Next, the transient dynamic analysis was performed, and the result was mapped to the acoustic analysis. Finally, the test and analysis were compared and analyzed. The results are as follow. First, it was found that the peaks appeared in common in the range of 620~650Hz, 1,240~1,290 Hz, and 1,840~1,940 Hz. It was judged that the dynamic characteristics of the recliner system overlapped with the rotation component of the motor to cause amplification of noise and vibration. Next, as a result of imaging the radiation noise analysis, it was judged that the noise radiated in the forward and backward direction has a greater influence than the direction of the rotation axis when the ear position of the person is taken as a reference.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.938-941
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• 2004

Sound generation and radiation from the duct-rotor system are calculated numerically. The wake geometries of a two-bladed rotor are calculated by using a time-marching fiee-wake method without a non-physical model of the far wake. Acoustic free field due to a rotating rotor is obtained by Lowson's equation. Using Kirchhoff source, rotating sources are modeled as stationary ones and can be inserted in the thin body boundary element method. The Kirchhoff source is validated through calculation of acoustic pressure due to a rotating point force. The thin body boundary element method (thin body BEM) is validated through calculation of acoustic radiation of ducted dipole. Using Kirchhoff source and thin body BEM, acoustic radiation of a ducted rotating source is calculated. Acoustic shielding is observed by inserting a duct and shows different phenomena at each major frequency. Acoustic radiation of a real duct-rotor system is also calculated using this method and the ducted acoustic field is significantly different from rotor only.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.12
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• pp.1073-1081
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• 2013

The definition of the radiation efficiency is very important to estimated underwater radiated noise of a ship. Considering the structure of the ship, it can be found that the hull of a ship consists of a lot of plates supporting by longitudinal and transverse stiffener. Therefore, various modes of the hull vibration occur related to the combination of these plates including stiffeners. In this paper, the method to define the radiation efficiency is suggested considering the vibration mode of the hull based on Uchida's experimental equation of the radiation efficiency. The suggested method is verified by the experiments with various kinds of naval vessels.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2041-2043
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• 1999

In order to investigate the radiation characteristics of unmixed line noise from overhead high voltage AC transmission lines, a gap noise generator was manufactured. Disk size which decides capacitance between the noise generator and earth was selected through preliminary indoor experiments and analysis by charge simulation method. The capacitance is one of principal parameters related to inject a proper noise current into lines. The field experiments were performed with the noise generator installed in Kochang 765 kV full scale test line. As the results, the useful data which can be used to analysis the radiation characteristics of noise from transmission lines was obtained. Those are lateral profiles the directivity of antenna toward lines, frequency spectra and so on.

• International Journal of Railway
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• v.7 no.4
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• pp.109-116
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• 2014

For optimization of a low-noise track system, rail vibration and noise radiation needs to be investigated. The main influencing parameters for the noise radiation and the quantitative results of every track system can be obtained using a calculation model of generation and radiation of railway noise. This kind of model includes contact modeling and the calculation model of the dynamic properties of the wheel and the rail. This study used a nonlinear wheel/rail interaction model in the time domain to investigate the excitation of the rolling noise. Wheel/rail response is determined by time integrating Green's function of the rail together with force impulses from the wheel/rail contact. This model and the results of the study can be used for supporting calculation with the conventional model by an addition of the contributions due to nonlinearities to the roughness spectrum.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.332.1-332
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• 2002

The study was performed as reduction method using finite and boundary element analysis on structure-borne noise radiated by dash panel of a real car. The radiation efficiency is used to estimate sound noise of dash panel. Curvature and edges of dash panel have effect on radiation efficiency. The simulation results of dash panel was ensured by comparison between experimental results and simulation results of a simple rectangular plate. (omitted)

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.568-574
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• 2024

The development of radiation-tolerant radio-frequency (RF) systems can be a solution for applications in extreme radiation environments, such as nuclear power plant monitoring and space exploration. Among the crucial components within an RF system, the low noise amplifier (LNA) stands out due to its vulnerability to TID effects, mainly relying on transistors as its main devices. In this study, the TID effects in the LNA using standard 0.18 ㎛ complementary metal oxide semiconductors (CMOS) technology are estimated and analyzed. The results show that the LNA can withstand absorbed radiation up to 100 kGy. The S₂₁, S₁₁, noise figure (NF), stability (K), and linearity of the third input intercept point (IIP3) slightly shifted from the initial values of 0.8312 dB, 0.793 dB, 0.00381 dB, 1.34406, and 2.36066 dBm, respectively which are still comparable to the typical performances. Moreover, the standard 0.18 ㎛ technology has demonstrated its radiation tolerance, as it exhibits negligible performance degradation in the conventional LNA even when exposed to radiation levels up to 100 kGy. In this context, simulation approach offers a means to predict the TID effects and estimate the radiation exposure limit for electronic devices, particularly when transistors are used as the primary RF components.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.11
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• pp.1222-1230
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• 2009

A theoretical model was developed to compute the effect of a bubble layer in reducing the radiation noise generated by a force applied on an infinite flat plate considering the noise of multi-bubbles. Using the model, the effectiveness of a bubble layer in reducing the structure-borne noise of the plate was evaluated to consider various parameters such as the source noise levels, the thickness of bubble layers, the volume fractions and the frequency characteristics of bubbly fluids. Considering the noise of multi-bubbles, the actual reduction effect of radiation noise using a bubble layer was expected in cases of high source levels, high volume fractions of bubbles and large thickness of the bubble layer above the resonance frequency of the bubble layer. Accordingly, it is recommended that the thickness of a bubble layer, the source noise level and the characteristics of bubbly fluids should be optimized cautiously to maximize noise reduction effects.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.973-979
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• 1995

The input equivalent noise charge (ENC) of hydrogenated amorphous silicon radiation detector diodes was measured and analyzed. The noise sources of amorphous silicon diodes were analyzed into three sources; shot noise, flicker noise and thermal noise from the contact resistance. By comparing the measured ENC with the calculated signal charge in uniform generation case, the signal-to-noise ratio (S/N) for the sample diodes is estimated as a function of the detector bias and the shaping time of Gaussian pulse shaper. The maximum S/N occurred at the bias level just above the full depletion voltage for shaping time of 2∼3 ${\mu}$sec. The developed method is useful in optimum design or amorphous silicon p-i-n diodes for charged particulate radiation spectroscopy.

• Journal of Radiation Protection and Research
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• v.37 no.2
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• pp.84-89
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• 2012

The purpose of this study was to compare radiation dose and image quality between low-dose (LDP) and standard-dose protocol (SDP). LDP (120 kVp, 30 mAs, 2-mm thickness) and SDP (120 kVp, 180 mAs, 1.2-mm thickness) images obtained from 61 subjects were retrospectively evaluated at level of carina bifurcation, using multi-detector CT (Brilliance 16, Philips Medical Systems). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated at ascending aorta and infraspinatus muscle, from CT number and back-ground noise. Radiation dose from two protocols measured at 5-point using acrylic-phantom, and CT number and noise measured at 4-point using water-phantom. All statistical analysis were performed using SPSS 19.0 program. LDP images showed significantly more noise and a significantly lower SNR and CNR than did SDP images at ascending aorta and infraspinatus muscle. Noise, SNR and CNR were significantly correlated with body mass index (p<0.001). Radiation dose, SNR and CNR from phantom were significant differences between two protocols. LDP showed a significant reduction of radiation dose with a significant change in SNR and CNR compared with SDP. Therefore, exposure dose on LDP in clinical applications needs resetting highly more considering image quality.