• Smart Structures and Systems
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• v.32 no.6
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• pp.393-402
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• 2023

Recently, hybrid and electric vehicles have been actively developed to replace internal combustion engine (ICE) vehicles. However, their vibrations and noise with complex spectra cause discomfort to drivers. To reduce the vibrations transmitted through primary excitation sources such as powertrains, structural changes have been introduced. However, the interference among different parts is a limitation. Thus, active mounting systems based on smart materials have been actively investigated to overcome these limitations. This study focuses on diminishing the source movement when a structure with two active mounting systems is excited to a single sinusoidal and a multi-frequency signal, which were investigated for source movement reduction. The overall structure was modeled based on the lumped parameter method. Active vibration control was implemented based on the modeled structure, and a multi-normalization least mean square (NLMS) algorithm was used to obtain the control input for the active mounting system. Furthermore, the performance of the NLMS algorithm was compared with that of the quantification method to demonstrate the performance of active vibration control. The results demonstrate that the vibration attenuation performance of the source component was improved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1A
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• pp.8-18
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• 2011

Visible light communication (VLC) using optical sources which can be simultaneously utilized for illumination and communication is currently an attractive option for wireless personal area network. Improving the data rate in optical wireless communication system is challenging due to the limited bandwidth of the optical sources. In this paper, we design the singular value decomposition (SVD)-based multiplexing multi-input multi-output (MIMO) system to support two data streams in optical wireless channels. In order to improve the spectral efficiency, the rate adaptation using multi-level pulse amplitude modulation (PAM) is applied according to the channel condition and we propose the method to allocate the optical power, the offset and the size of modulation scheme theoretically under the constraints of the nonnegativity of the modulated signals, the aggregate optical power and the bit error rate (BER) requirement. The simulation results show that the proposed allocation method gives the better performance than the method to allocate the optical power equally for each data stream.

• Korean Journal of Construction Engineering and Management
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• v.16 no.5
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• pp.105-113
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• 2015

In order to evaluate the energy performance of buildings, it is important to determine reliable information of energy utilization during operating phase. It is also required to establish the database which have the amounts of population deducted by objective filtering and analysis. In this study, all energy sources were applied to evaluate synthetically the energy performance of Multi-Family Housings(MFH) using district heating and the amounts of population were obtained sufficiently through data searching in Seoul and neighbor cities. Finally the database of source energy utilization and $CO_2$ emission in 325 MFH complexes were established through cross validation between data sources and statistical analysis. Additionally, further ideas have been proposed to improve existing MFH Management Information System.

• The Journal of the Korea Contents Association
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• v.16 no.3
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• pp.72-80
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• 2016

There are various methods of developing latent fingerprints from evidence found at crime scenes. Crime scene investigators should choose appropriate techniques among them depending on the conditions of the evidences. In this study, we compared the three methods using forensic light sources to develop latent fingerprints on multi-colored surfaces. We selected the various samples according to color, shape and texture of the surfaces and developed the latent fingerprints using fluorescent powder, IR(Infrared) photography and Episcopic Co-axial Illumination. Fluorescent powder was highly effective on all surfaces. IR photography was also effective, but only on the not dark surfaces. Episcopic Co-axial Illumination was effective only on the flat and polished surfaces. Although fluorescent powder was fine regardless of the characteristics of the surfaces, IR photography was better on certain surfaces.

• Nuclear Engineering and Technology
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• v.55 no.10
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• pp.3822-3830
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• 2023

The large-area Compton camera (LACC), featuring significantly high detection sensitivity, was developed for high-speed localization of gamma-ray sources. Due to the high gamma-ray interaction event rate induced by the high sensitivity, however, the multiplexer-based data acquisition system (DAQ) rapidly saturated, leading to deteriorated energy and imaging resolution at event rates higher than 4.7 × 10³ s^-1. In the present study, a new simultaneous multi-channel DAQ was developed to improve the energy and imaging resolution of the LACC even under high event rate conditions (10⁴-10⁶ s^-1). The performance of the DAQ was evaluated with several point sources under different event rate conditions. The results indicated that the new DAQ offers significantly better performance than the existing DAQ over the entire energy and event rate ranges. Especially, the new DAQ showed high energy resolution under very high event rate conditions, i.e., 6.9% and 8.6% (for 662 keV) at 1.3 × 10⁵ and 1.2 × 10⁶ s^-1, respectively. Furthermore, the new DAQ successfully acquired Compton images under those event rates, i.e., imaging resolutions of 13.8° and 19.3° at 8.7 × 10⁴ and 10⁶ s^-1, which correspond to 1.8 and 73 μSv/hr or about 18 and 730 times the background level, respectively.

• Journal of Radiation Protection and Research
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• v.33 no.1
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• pp.13-20
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• 2008

The flow rate measurements in a multi-phase flow pipeline were evaluated quantitatively by means of a clamp-on sealed radioisotope based on a cross correlation signal processing technique. The flow rates were calculated by a determination of the transit time between two sealed gamma sources by using a cross correlation function following FFT filtering, then corrected with vapor fraction in the pipeline which was measured by the ${\gamma}$-ray attenuation method. The pipeline model was manufactured by acrylic resin(ID. 8 cm, L=3.5 m, t=10 mm), and the multi-phase flow patterns were realized by an injection of compressed $N_2$ gas. Two sealed gamma sources of $^{137}Cs$ (E=0.662 MeV, ${\Gamma}$ $factor=0.326\;R{\cdot}h^{-1}{\cdot}m^2{\cdot}Ci^{-1}$) of 20 mCi and 17 mCi, and radiation detectors of $2"{\times}2"$ NaI(Tl) scintillation counter (Eberline, SP-3) were used for this study. Under the given conditions(the distance between two sources: 4D(D; inner diameter), N/S ratio: $0.12{\sim}0.15$, sampling time ${\Delta}t$: 4msec), the measured flow rates showed the maximum. relative error of 1.7 % when compared to the real ones through the vapor content corrections($6.1\;%{\sim}9.2\;%$). From a subsequent experiment, it was proven that the closer the distance between the two sealed sources is, the more precise the measured flow rates are. Provided additional studies related to the selection of radioisotopes their activity, and an optimization of the experimental geometry are carried out, it is anticipated that a radioisotope application for flow rate measurements can be used as an important tool for monitoring multi-phase facilities belonging to petrochemical and refinery industries and contributes economically in the light of maintenance and control of them.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1329-1337
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• 2015

By placing distributed generation power sources beside a big nonlinear load, these sources can be used as a power quality enhancer, while injecting some active power to the network. In this paper, a new scheme to use the distributed generation power source in both operation modes is presented. In this scheme, a fuzzy controller is added to adjust the optimal set point of inverter between compensating mode and maximum active power injection mode, which works based on the harmonic content of the nonlinear load. As the high order current harmonics can be easily rejected using passive filters, the DG is used to compensate the low order harmonics of the load current. Multilevel transformerless cascade inverters are preferred in such utilization, as they have more flexibility in current/voltage waveform. The proposed scheme is simulated in MATLAB/SIMULINK to evaluate the circuit performance. Then, a 1kw single phase prototype of the circuit is used for experimental evaluation of the paper. Both simulative and experimental results prove that such a circuit can inject a well-controlled current with desired harmonics and THD, while having a smaller switching frequency and better efficiency, related to previous 3-phase inverter schemes in the literature.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.112-117
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• 2004

This paper describes the analysis of the UHF signal characteristics due to the partial discharge sources which can exist in a GIS. For the experiment, a model GIS was made and 5 types of discharge source were created as follows; corona discharge, surface discharge, void discharge, discharge due to free particle, discharge from floating electrode. The frequency spectra and the phase characteristics of UHF signals were induced by UHF signal analysis. The results were quantified to systematically adapt to analyze the PD sources in the GIS and utilized as algorithm data based on the neural network for Back-Propagation Algorithm with a multi-layer structure. The perception rate of the constructed algorithm showed approximately 94[%] and 82[%] in learning and testing data, respectively.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.5
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• pp.95-106
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• 1992

Active control of acoustic noise is an application area of adaptive digital signal processing with increasingly interest along the last year. This work studies the implementation of the multichannel LMS filter and the application of this algorithm for the reduction of the noise inside a vechicle cabin using a number of 'secondary sources' drived by adaptive filtering of a reference noise source. Firstly, we propose the use of an adaptive method for the time-varient optimal convergence factor. Secondly, we propose the use of adaptive delayed inverse model to estimate the elastic-acoustic transfer function presented in vechicle cabin. The original, primary source is often periodic, with a known fundamental frequency. A suitably filtered reference signal can thus be used to drive the secondary sources. An algorithm is presented for adapting the coefficients of an FIR filter feeding such a secondary source in such a way as to minimize the output of a suitably placed microphone. In this algorithm, the coefficients of adaptive filter driving an array of secondary sources can be adapted to minimize the sum of the squares of the outputs of a number of error microphones. The multichannel LMS algorithm displays that such an algorithm is considered suitable to used for the global suppression of noise in vehicle cabin.

• The Journal of Asian Finance, Economics and Business
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• v.5 no.2
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• pp.129-137
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• 2018

The present paper study investigates the relationship between social exclusion and donation intention among specific social groups in Korea. Social exclusion refers to non-participation in social experiences by the socially disadvantaged. Data were analyzed using two sources; first was the evidence of behaviors arising from social exclusion of the university students and then socially excluded reactions of the elderly responses from the survey were compared with the first research findings. The reason of using multi-sources of data is that the outcome from the experimental design of the university student is imperative to clarify what the conclusions will be the same result with the other demographic characteristic of the elderly. The research design was three excluded elderly individuals of a self-excluded group and two other excluded groups divided such as "ignored" and "rejected" individuals to compare the differences among three groups of different sources of exclusion. The conclusion of this study is that those with high social exclusion exhibited a more negative donation intention than those with lower social exclusion, but that those who perceived themselves as self-excluded were more likely to give donations than those excluded by others, regardless of the level of their social exclusion.