• Elastomers and Composites
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• v.22 no.4
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• pp.333-339
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• 1987

A modern kinetic evaluation method for nonisothermal reactions measured with Differential Scanning Calorimetry(DSC) is presented. It is based on multiple linear regression analysis using a number of curve points in a selectable range of conversion. The obtained kinetic data are the basis to compute a reaction process under any condition e.g. isothermal or adiabatic. The DSC measurements was performed on a Mettler TA3000 SYSTEM with the built in evaluation software. Mainly the following reactions are discussed: vulcanization of natural rubber compounds containing vulcanizing accelerators. The purpose of this work is to analyse the vulcanization kinetics of typical NR vulcanization systems using DSC. These systems were chosen because they are typically reactive elastomer and are commercially important.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.221-225
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• 2004

Evaluation of turbulence models is performed for a better prediction of thermal stratification in an upper plenum of a liquid metal reactor by applying them to the experiment conducted at JNC. The turbulence models tested in the present study are the two-layer model, the $\kappa-\omega$ model, the v2-f model and the low-Reynolds number differential stress-flux model. When the algebraic flux model or differential flux model are used for treating the turbulent heat flux, there exist little differences between turbulence models in predicting the temporal variation of temperature. However, the v2-f model and the low-Reynolds number differential stress-flux model better predict the steep gradient o( temperature at the interface of thermal stratification, and only the v2-f model predicts properly the oscillation of temperature. The LES Is needed for a better prediction of the amplitude and frequency of the temperature fluctuation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.10
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• pp.884-888
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• 2007

It is necessary to evaluate periodically the performance of the AOV(air-operated valve) which is used for controlling flow and pressure in nuclear power plant. The required thrust for actuating valve and available thrust of actuator are calculated with conditions of flow through a valve in this study and operating performance is analyzed through comparing two thrusts. In general, differential pressure is increased according to increase the flow rate and differential pressure affects the required thrust of valve. We found the fact that it is possible not to close the valve perfectly because required thrust becomes bigger than available thrust of actuator.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.7
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• pp.29-35
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• 1994

The performance of continuous phase modulation signals is well known for the coherent demodulation. But the carrier recovery circuits of the coherent receiver have long acquisition time and the receiver experiences high error floors for fading channels. In this paper, we propose the differential demodulation of 2-h continuous phase modulation signals. The sets of modulation indices of 2-h phase codes adequate to the differential demodulation for differentially encoded input are obtained and the average bit error probability in Additive White Gaussian Noise environments is derived and analyzed.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2008.04a
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• pp.251-254
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• 2008

The fact that the major cases of life casualties are from smoke in the fire accidents and the expected steep increase of skyscrapers, huge spaces, multiplexes and huge scaled underground spaces demand establishment of efficient smoke countermeasure. The field experiments on two high buildings of 20 stories and 21 stories are carried out to evaluate the field performance of pressure differential systems for smoke management and the results of experiments are presented.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.6
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• pp.403-410
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• 2006

Eddy current testing (ECT) signals produced by a differential bobbin coil probe vary according to probe design parameters such as the number of turns, geometry and coil gap size. In the present study, the characteristics of a differential bobbin coil probe signals are investigated by numerical simulation in order to determine the optimum coil gap. For verification of numerical simulation accuracy, a specially designed bobbin probe of which the coil gap can be adjusted is fabricated and a series of experiments to acquire signals from two kinds of standard tubes with the variation in coil gap is performed. Then, the experimental signals are compared to the simulation results. Based on this investigation, a decision on the optimum range of coil gap is made. The theoretically predicted signals agree very well to the experimental signals. In fact, this excellent agreement demonstrates a high potential of the simulation as a design optimization tool for ECT bobbin probes.

• Geomechanics and Engineering
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• v.34 no.3
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• pp.329-339
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• 2023

The objective of this study is to develop a Stability Evaluation System for retaining walls to assess their safety in real-time during excavation. A ground investigation is typically conducted before construction to gather information about the soil properties and predict wall stability. However, these properties may not accurately reflect the actual ground being excavated. To address this issue, the study employed a differential evolution algorithm to estimate the soil parameters of the actual ground. The estimated results were then used as input for an artificial neural network to evaluate the stability of the retaining walls. The study achieved an average accuracy of over 90% in predicting differential settlement, wall displacement, anchor force, and structural stability of the retaining walls. If implemented at actual excavation sites, this approach would enable real-time prediction of wall stability and facilitate effective safety management. Overall, the developed Stability Evaluation System offers a promising solution for ensuring the stability of retaining walls during construction. By incorporating real-time soil parameter analysis, it enhances the accuracy of stability predictions and contributes to proactive safety management in excavation projects.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.6
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• pp.2005-2013
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• 1996

Particle paths and flow fields in a prototype differential mobility analyzer (DMA) were numerically analyzed solving Navier-Stokes equation, electric field equation and particle motion considering viscous drag force, Coulomb force and polarization force. Analytically predicted particle diameters for the prototype DMA are in good agreement with the measured particle diameters within $\pm$1%. And the analytically predicted particle diameters are also in good agreement with numerical results for the prototype DMA.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.8
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• pp.626-631
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• 2002

A modified equation for the evaluation of discomfort of a seated human body exposed to differential vibration at the seat and the floor was proposed in this paper. Through the review and analysis of the preceding studies, effect of phase difference between the seat and the floor vibration on discomfort were quantitatively identified. The phase effect was shown to be governed by not only phase difference between the two vibrations but both their frequency and the magnitude, which means the present equation for the evaluation of perceptual amount of vibration provided by ISO 2631-1 should be modified. The proposed equation was developed such that the correction function was multiplied to the present equation. The correction function consisted of three parts, each of them represented the effect by phase difference, frequency and vibration magnitude on discomfort respectively.

• Journal of the Korean Institute of Landscape Architecture
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• v.23 no.3
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• pp.155-166
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• 1995

The aim of this paper was to investigate images of neighborhood parks and pergola facilities. 280 individuals responded to the 19 semantic differential pollar terms for all four parks. A 7-point semantic differential scale was used. Results from the data analysis suggest several important findings; 1. Mean scores were significantly different in most of S.D.scales according to park and pergola facilities types. As compared with park, S.D.scales values of pergola varied with its visual identity in the spatial composition of park. 2. Data from the factor analysis revealed that four dimensions appeared for all park and pergola types : "Evaluation ", "Potentiality", "Variety", and "Familiarity". 3. In terms of the "Familiarity" dimension, Omok park and its pergola were viewed a ssignificantly more familiar than any of the other three areas. 4. Parks were perceived more positive than pergolas images in the dimensions of "Evaluation ", "Variety", and "Familiarity". 5. Regression analysis showed that "Evaluation "and "Variety" dimensions were mainly related to visual preference.