• Journal of electromagnetic engineering and science
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• v.13 no.3
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• pp.192-194
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• 2013

This paper proposes a validation model using a reverberation chamber for verification of the effectiveness and accuracy of the statistical power balance (PWB) method. The PWB method treats electromagnetic (EM) field distributions in certain environments as a representative value of an "ensemble" average, so a reverberation chamber is utilized as a testing apparatus to experimentally simulate the sets of measurement field "ensemble" inside a complex environment. Measurements are performed with various test conditions for environmental loss using flat absorbers, and front and side doors of the chamber. Comparison between the PWB analysis and the measurement results shows good agreement, indicating the usefulness of this statistical analysis method for stating the electromagnetic field inside the EM zone as a representative value to general structures.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.3
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• pp.21-27
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• 2002

In this paper, a simple test rig of high-speed crash for the front members of vehicles was developed for the improvement of crashworthiness of vehicle's side rail. The cart hanging the specimen is accelerated up to 35 mph by the traction wire and by the force of freely dropping weight and 1:3 accelerating pulleys. The cart with shock absorbers travels on the rail roads, so it does not transfer any additional vibration to the specimen. In order to measure the energy absorbed by the specimen when it collapse to the wall and during it deform, the two strain gage type load cells are used at the wall place. The test rig rated good to test the specimen like a side rail of vehicle as developing the vehicle's structures in the early design stage.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1479-1482
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• 2003

The shock absorber is a part having a direct influence on the ride comfort, stability and dynamic load prediction of a vehicle. Thus, a rationally modeled shock absorber should be required in the dynamic analysis of vehicles. This thesis presents a modified model, based on Worden's hyperbolic tangent function, in order to fit experimental data on the velocity-damping force of a shock absorber. The hyperbolic tangent function correctly indicates the characteristics of a shock absorber. and has the advantage of containing physical causality. To evaluate the method, comparative evaluations of the linear model. the 5th polynomial model and Worden's model were carried out. The function presented in this paper is not only simple but also makes it possible to estimate the function coefficients easily and visually. In addition, it has the advantage of containing physical causality. Lastly, it effectively models the damping force of a shock absorber.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.23 no.2
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• pp.109-117
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• 2017

Due to the rise of customer's alertness about fresh foods to health, in the past few years, the consumption of fresh food has increased sturdily. The use of gas scavengers is the most appropriate packaging technologies for fresh, fresh-cut produces and in ready to eat products. The gas absorber/scavenger has ability to protect or stabilize the wanted properties and shelf life of food. The success of gas absorbers in food depends on many parameters such as types of foods, storage temperature, relative humidity, initial gas concentration, and the characteristics of package materials. In this review article, we focus on the most recent research trends in gas scavenging systems used in food packaging, future trends. Intense research from industry and engineers remains important to the development of gas scavenging package that fulfill consumer requirements, enhance product quality, and offer environmentally friendly design and cost-effective application.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1156-1161
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• 2001

A significant trial has been performed for estimation of noise level of a cross flow fan for air conditioning system. In general, measurements of noise level of machinery require rigorous equipment involving an anechoic chamber with precision gauges. The apparatus is expensive to utilize and is not easy to construct. In this work, we adopt static pressure sensing from an ordinary pressure transducer for prediction of noise level of a rotating fan. The present procedure is finding sound pressure from the static pressure by manipulating Light-Curle equation depicts noisy energy in terms of pressure on surfaces of noise generators. Sound power level near core unit of the fan is evaluated with the present methodology in a normal laboratory room without any sound absorbers. The method is easy and shows good prediction results compared with precise measurements by using microphones.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.328.1-328
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• 2002

MR(Magneto-rheological) fluid is smart fluid that can change its characteristics when magnetic fields are applied. Recently, many researches are going on this MR fluid for the application in a variety of areas including automobile shock absorbers. This paper describes the design procedure of a MR damper and the analysis results of its dynamic characteristics. MR fluid in the magnetic field shows initial yield shear stress and increasing resistive viscousity with final saturation thereafter. (omitted)

• Journal of the Society of Naval Architects of Korea
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• v.38 no.1
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• pp.37-42
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• 2001

This paper proposes a new wave absorber made of flexible net structures. The motivation of this research is that the wave absorbers which already invented are not effective in small wave flume. To test the efficiency of the proposed water absorber, experiments were done for various wave length, the length of the wave absorber, and the areas of the wave absorber. The proposed new wave absorber demonstrated its efficiency when used in small-length wave flume.

• Safety and Health at Work
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• v.8 no.2
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• pp.226-230
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• 2017

The performance of sound barriers was evaluated to determine their technical effectiveness and practicality in reducing noise exposures to operating engineers in construction. Commercially purchased sound dampening mats (SDMats) were installed inside three heavy-equipment engine compartments. Sound pressure levels (SPLs) were measured before and after installing the SDMats while the equipment was on idle and full-throttle settings where it normally operates. SPLs inside the heavy-equipment operator cabs were significantly reduced by 5.6-7.6 dBA on the full-throttle setting following installation of the SDMats (p < 0.01). The evaluated engineering control intervention was simple to install, affordable, and substantially reduced the engine noise reaching the heavy-equipment operator, potentially reducing reliance on hearing-protection devices to protect construction workers from noise exposures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.925-930
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• 2004

This paper is to study vibration effects of the dynamic vibration absorber. Multi-body dynamic analysis is carried out for the vehicle driveline model using ADAMS with flexible propeller shaft attached with the vibration damper. Primary bending mode frequency of the propeller shaft is obtained from the simulation and coincides with the experimental result. Various design parameters are studied in dynamic simulation operated by the engine torque input. This paper identifies the responses of dynamic vibration absorbers in the driveline with propeller shaft, which will be used to find out optimal design parameters.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.594-599
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• 2000

Two basic acoustic quantities, the characteristic impedances and the propagation constants, of the two different ultra lightweight concrete absorbers were examined with impedance tube method. A transmission loss was tested and compared with theoretical values. The results show that these kinds of sample have proper sound absorption and transmission loss capabilities. It means that they can be used in various fields where noise proof is needed.