• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.17 no.5 s.122
• /
• pp.373-378
• /
• 2007

Today, the use of the sound absorptive material is increasing to improve the room acoustics in the auditorium and music hall, etc. Usually, the sound absorption materials have been used to enhance the performance of a noise barrier and improve the room acoustics in construction site. Generally, the sound absorbtion coefficients are the most important factor reflecting the sound absorbtion performance. There are two methods to measure the sound absorption coefficient. The first one is the reverberation room method, and the second is the impedance tube method. In this study, we measure the sound absorbtion coefficients using these two methods, and then we compared the results of the sound absorbtion coefficients to look into the difference of results between reverberation room method and impedance tube method. Also we compared the results of the sound absorbtion coefficients with respect to the size of sample and the volume of reverberation room. From the experiment, we could see that the sound absorbtion coefficients are measured equally for different sample size. But the sound absorbtion coefficients are measured differently according to test methods and test conditions.

• Plant Resources
• /
• v.5 no.2
• /
• pp.124-140
• /
• 2002

The effects of drying agents and ethyl alcohol treatment on the flower color of Gentiana uchiyamai. The flower color was not much changed in flower sheet, in the case of absorbtion papers only. The color was least changed in Korean and China hwasunjis, in the case of absorbtion papers and silica gel treatment. The color was less changed in flower sheets, window papers, and China hwasunjis, and was most changed in newspapers, in the case of absorbtion papers and Na$_2$SO$_4$ treatment. The color was least changed in China hwasunjis, and most changed in dampened papers, in the case of absorbtion papers and CaO treatment. The color tended to change far from the original one, as treatment time got longer, in the case of 0.01M and 0.lM of tartaric acid. The longer the treatment time and the bigger the concentration of ethyl alcohol, the bigger flower color.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.06a
• /
• pp.885-886
• /
• 2008

• Journal of radiological science and technology
• /
• v.2 no.1
• /
• pp.85-88
• /
• 1979

When X-radiation passes through the human body; some is transmitted some is truly absorbed, and some is scattered. In diagnostic radiography, scattered radiation can reach the film if no protective measures are taken. This scattered ray increased density which not necessary for image formation. We studied about absorbtion, scattered ray and the way of get rid of scatter ray according to the x-ray tube kilovoltage and obtained results as follow; 1. Absorbtion ray increased proportion to KVP. 2. Scattered ray increased at high KVP and thick object. 3. Secondary radiation of the primary increased at high KVP and thick object. 4. Remove .ate of scattered ray decreased at thick object and increase at low KVP make use of 6:1 grid ratio

• Proceedings of the KSR Conference
• /
• 2004.06a
• /
• pp.732-737
• /
• 2004

TTX(Tilting Train Express), which has improved traveling performance on curved track, is being designed in cope with future railway circumstance. Nowadays, in the world, many efforts are focussed on railway safety. Especially, a variety of researches on train crashworthiness have been conducted. As a part of these efforts, some equipments on TTX are designed to reduce fatalities and casualties in crash accidents. This paper introduces impact energy absorbtion characteristics on the initial design of the front end structure. Some comments are made briefly for improvement of initial structural design and future following researches.

• Proceedings of the KWS Conference
• /
• 2006.05a
• /
• pp.248-250
• /
• 2006

The study on a surface transformation hardening of a rod-shaped SM45C carbon steel is carried out by using CW Nd:YAG laser. Conventionally, $CO_2$ laser has been usually used as a laser source for a transformation hardening. however, it is needed to an additional absorbent coating like a colloidal graphite owing to a lower absorbtion rate. On the other hand, no cost and post-removal process of coating is required to Nd:YAG laser, due to a higher absorbtion rate relatively. Moreover, there is a merit which is capable of building up the more flexible processing system resulted from a beam delivery through a optical fiber. In this study, we were going to recognize characteristics of a transformation hardening using a optic head with a gaussian beam distribution.

• Journal of Power System Engineering
• /
• v.11 no.4
• /
• pp.72-77
• /
• 2007

It is known that elimination of ship engine room noise is impossible thing, so the working environment in the engine room is getting worse because ships are recently built with huge engines to take higher sailing power. In the yacht and cruise yacht, the engine room noise is more serious because they have bigger engines relative to their hull sizes. The noise generated from the main engine makes the employee to hearing loss and the transmitted noise make the uncomfortable conditions in the cabins of ship. The noise generated by ship engine must be attenuate for the employee and passenger. In yacht and cruise yacht, the noise levels in cabines are the most important criterions to the value of commodities. In this study, the noise absorbtion barrier which have resonators is experimentally studied by the 1/3 octave band noise elimination rates(%).

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.11a
• /
• pp.643-644
• /
• 2008

• 한국도로학회:학술대회논문집
• /
• 2009.11a
• /
• pp.303-306
• /
• 2009

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.577-580
• /
• 2008

Concrete absorbs $CO_2$ in the air because of carbonation. according to rising concern for lasting earth environment efforts of reducing greenhouse gas, especially co2, are occurred whole industry throughout the world. In this paper selected one building and computed amount of production and absorbtion of co2 during its lifecycle at concrete. In computing amount of absorbtion of co2 considered amount of absorbtion according to the area of concrete changing senarioes of servicelife(40,60,80 years) and deconstruct preiod(60,40,20 years). As a result, size of concrete and maintenance period of disused concrete work increasement of $CO_2$ as main factors. We came to the conclusion that maintenance period is more important than recycle of unused concrete as a method for reducing environmental load in architectural industry.