• The Journal of the Acoustical Society of Korea
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• v.28 no.2
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• pp.107-111
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• 2009

Acoustic OFDM is used for audible frequency band acoustic communication which employs loudspeaker as transmitter and microphone as the receiver antenna. Since acoustic OFDM can transmit about 1 kbps using 1600 Hz band. acoustic OFDM signal is inserted into the audio signal like music or speech, However. audio quality deteriorates definitely during the inserting process. This paper introduces a reason for audio quality deterioration and discuss how to reduce this phenomenon.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.2
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• pp.153-167
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• 2024

Recently the ground settlement has been increasing in urban area according to development. And, this may attribute a groundwater level drawdown. This study presents an analysis of groundwater level drawdown for circular vertical shaft excavation of ｢◯◯◯◯ double track railway build transfer operate project｣. And, in-situ monitoring data and numerical analysis were compared. So, if we examine the groundwater level drawdown in design, ground conditions should be applied so that the site situation can be reflected. And, groundwater level should be considered a seasonal measurement in order to apply the appropriate groundwater level. It was confirmed a similar predicted value to groundwater level drawdown of in-situ monitoring data.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.3
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• pp.147-154
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• 2008

Weathered soil slope loses its shear strength if it is exposed in the air for a long time or in contact with water. And this kind of strength loss is remarkable in dam slope which has very big difference in water level according to the season. In this study, shear strength loss of weathered soil due to saturation had been found out through dryness and wetness repetition direct shear test. Also relation between penetration blow number(Nc) and shear strength parameter had been found out through small sized dynamic cone penetration test device and the correlation equation of Nc had been proposed through artificial neural network analysis to estimate shear strength parameter easily.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.181-188
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• 2013

The effect of transition metal ion exchange into UZM-9 zeolite with LTA framework on its deactivation in methanol-to-olefin (MTO) conversion was discussed. The ion exchange of copper, cobalt, nickel, and iron did not induce any notable change in the crystallinity, crystal morphology, and acidity of UZM-9. The small cage entrance of UZM-9 caused the high selectivity to lower olefins in the MTO conversion, while its large cages allowed the rapid further cyclecondensation of active intermediates, polymethylbenzenes including hexamethylbenzene, resulting in a rapid deactivation. The UZM-9 containing copper and cobalt ions showed considerably slow deactivations. The interaction between transition metal ions and polymethylbenzene cation radicals, the active intermediates, generated in the MTO conversion stabilized the radicals and slowed down the deactivation of UZM-9.

• Journal of Korea Foresty Energy
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• v.23 no.1
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• pp.19-25
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• 2004

This study was performed to investigate the growth and photosynthetic rate of ten-years old Pinus koraiensis and Pinus rigida in Banwol industrial region comparing with those of the control site in Gwangju, Gyeonggi Province. Surface soil of the damaged site in pH 4.2 was more acidic than control site in pH 4.8, assuming the accelerated soil deterioration by acid deposition. The shoot growth, needle survival rate and net photosynthetic rate of P. koraiensis and P. rigida at the damaged site were lower than at the control site. In addition, the quantum yield and chlorophyll a+b and b contents reduced in damaged treatment. These results suggest that an inhibition of photochemical reaction of P. koraiensis and P. rigida at the damaged site of Banwol industrial region could be attributed to combined influence of atmospheric pollution and soil acidification.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.6
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• pp.1083-1089
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• 2000

본 연구는 에탄올의 급여수준과 금주 후 회복이 체내항산화비타민 상태에 미치는 영향을 조사하고자 평균 체중이 200g인 Dprague-dawley 종 숫쥐 50마리를 사용하여 혈장 및 간조직의 비타민 A 및 E 의 함량을 비교.분석하였다. 실험식이라는 에탄올 액체식이형태로 만들어 공급하였으며, 이때 식이는 mL당 1 kacal의 열량을 공급할 수 있도록 조제하였다. 각 실험군의 식이구성은 에탄올을 첨가하는 대신 dextrin-maltose를 급여한 C군, 전체 칼로리의 10%를 에탄올로 첨가하는 LE 군 , 20%를 첨가하는 ME 군, 30%를 첨가하는 HE군 , 30%의 에탄올을 5주간 공급한 후 다시 2주간 정상식이를 급여한 회복군(HR)으로 설정하여 실험식이를 공급하였다. 혈자에서의 retinol 함량은 에탄올 급여수준에 따른 유의적인 차이는 나타나지 않았다. 간조직 중의 retinol 함량은 20% 이상의 에탄올 군에서 대조군에 비해 유의적으로 감소되었고, 30% 에탄올군인 HE 군에서는 현저하게 저하되었다. 30% 에탄올 급여후 2주간 정상식이를 회복시킨 군에서도 간조직의 retinol의 함량은 그대로 저하된 상태를 유지하였다. 간조직의 retinyl palmitate 함량은 에탄올 급여수준이 높을수록 감소되는 경향이었으며, 30% 에탄올군에서는 대조군에 비해 유의적으로 감소되었다. 회복군의 경우에도 이러한 저하현상은 더욱 심화되었다. 혈장의 $\alpha$-tocopherol 함량은 에탄올 급여량에 따라 별다른 차이를 나타내지 않았다. 간조직에서 10% 에탄올군에서도 대조군에 비해 유의적으로 감소되었으며, 에탄올 급여수준이 증가될수록 현저하게 저하되었다. 그러나 회복군에서는 $\alpha$-tocopherol의 함량이 10% 에탄올군의 수준까지 회복되었다. 이상의 결과에서와 같이 만성적인 에탄올의 섭취는 대체로 열량의 20% 이상을 에탄올로 급여하였을대 섭취수준이 증가함에 따라 흰쥐의 간조직에서 비타민 A와 $\alpha$-tocopherol으 lgkafid이 저하되었다. 이는 에탄올의 섭취를 중단하고 정상식이를 일정기간 급여하여도 특히 비타민 A 함량은 회복되지 않는 경향을 보여 만성적인 에탄올 섭취자들에게 비타민 A영양상태의 문제를 예방할 수 있는 방안이 강구되어야 함을 나타낸다.

• Journal of Digital Convergence
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• v.12 no.2
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• pp.587-594
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• 2014

This study was carried out to look into the cognitive function of the elderly in community and investigate the factors affecting their cognitive decline provide preliminary data so as to help develop a program to maintain and promote cognitive function. With 481 senior citizens aged over 65 in J. city, a survey was conducted on their demographic characteristics, health-related characteristics and depression using structured questionnaires from September 1 through 7, 2011. The collected data were analyzed by descriptive statistics, Chi-square test and logistic regression analysis using IBM SPSS Statistics V. 20. As a result of this study, 40.1% of the subjects showed cognitive decline and the factors related to their cognitive decline turned out to be the level of education (p<.001), age (p=.000), depression and exercise (p<.05). Therefore, intervention programs on depression or exercise should be implemented intensively and in particular, various programs and educations should be provided considering individual differences according to the level of education and age.

• Tunnel and Underground Space
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• v.21 no.2
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• pp.138-144
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• 2011

Mine closure does often accompany the flooding of mine galleries due to ceasing a pumping operation. When a mine gallery is flooded, rocks around the gallery are fully saturated and the gallery is subject to a water pressure. The uniaxial unconfined compressive strength of a rock depends on its water content and decreases as the water content increases. A water pressure may originate the crack growth of a rock or the discontinuity growth of rock mass. Although the water in a gallery will give some support pressure inside the gallery, the degradation of rock mass properties caused by a water pressure will reduce the stability of the gallery. In this study, 2-dimensional discontinuous and 3-dimensional continuous numerical analyses have been conducted to evaluate an effect that a reduction of rock mass properties around the gallery induced by a water pressure has on the stability of mine gallery. The numerical analyses show that a reduction of rock mass properties caused by a water pressure increases displacements of rock mass around mine gallery. 2-dimensional model is found to give larger values of displacement than 3-dimensional model.

• Journal of Korean Society of Steel Construction
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• v.15 no.4 s.65
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• pp.359-368
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• 2003

Design and detailing requirements of seismic provisions for Concentrically Braced Frames (CBF) were specified based on the premise that bracing members with large KL/r and low b/t have superior seismic performance. However, relatively few tests have been done to investigate the cyclic behavior of CBF. Therefore, the question lies on whether the compression member of CBF plays as significant a role as what has been typically assumed by design providers. In this paper, existing experimental data were reviewed to quantify the extent of hysteretic energy achieved by bracing members in past compression tests as well as the extent of degradation of the compression force given repeated cycling loading.

• Journal of Korean Society of Transportation
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• v.23 no.5 s.83
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• pp.105-112
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• 2005

This paper not only tests VIDS(Video Image Detection System) performance by vehicle speed group but also suggests optimal VIDS height considering road and cost condition. The VIDS spreads over freeway and national highway and plays an important role in ITS(Intelligent Transportation Systems). As a result, speed data accuracy drops form 50kph vehicle speed and volume and occupancy data accuracy drop from 30kph. Lowest speed data accuracy is only 88%, but volume and occupancy accuracy are 75% and 77% respectively. The reason VIDS data accuracy drop by vehicle speed is gap distance decrease between vehicles. Therefore, this paper suggests $17m{\sim}21m$ for optimal VIDS height considering road and cost condition.