• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.617-621
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• 2003

Existing loudness models are specified only to diotic sounds in spite of the fact that normal human beings hear dichotic sounds. Approximately, the arithmetic mean of loudness values of both ear signals has been suggested for the resultant perceived loudness. In this study, the dependence of overall loudness perception on the interaural level differences was investigated by the subjective tests. It was found that the larger the interaural level difference, the louder the perception than the mean of calculated loudness values at both ears and the lower the critical band rate or the reference level, the louder the perception than the mean value. A modified loudness model was proposed to he applicable to dichotic sounds by using the equivalent diotic levels.

• ETRI Journal
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• v.37 no.5
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• pp.922-928
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• 2015

A novel peak-to-average power ratio (PAPR) reduction method is proposed for single-carrier frequency-division multiple access (SC-FDMA) signals. The proposed method deliberately distorts the amplitude values of a few of the complex modulated symbols that cause peaks beyond a predetermined threshold in the samples of the output signal. The method then marks the location indices of the distorted symbols by using a pilot block at the transmitter without transmitting side information. At the receiver, the method is then able to recover the distorted amplitude values through the marked location indices. Computer simulation results show that when compared to conventional SC-FDMA signals, the proposed scheme can effectively reduce the PAPR of SC-FDMA signals with asymptotically consistent bit error rate (BER) performance.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.11 no.17
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• pp.67-80
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• 1988

This study is concerned with the comparison of two time homogeneous Poisson processes. Traditionally, the methods of testing equality of Poisson processes were based on the binomial distribution or its normal approximations. The sampling plans used in these methods are to observe the processes concurrently over a predetermined time interval, possibly different for each process. However, when the values of the intensities of the processes are small, inverse type sampling plans are more appropriate since there may be cases where only a few or even no events are observed in the predetermined time interval. This study considers 9 inverse type sampling plans for the comparison of two Poisson processes. For each sampling plans considered, critical regions and the design parameters of the sampling plan are determined to guarantee the significance level and the power at some values of the alternative hypothesis. The Problem of comparing of two Weibull processes are also considered.

• Nuclear Engineering and Technology
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• v.38 no.8
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• pp.763-778
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• 2006

Injection of microbubbles within the turbulent boundary layer has been investigated for several years as a method to achieve drag reduction. However, the physical mechanism of this phenomenon is not yet fully understood. Experiments in a channel flow for single phase (water) and two phase (water and microbubbles) flows with various void fraction values are studied for a Reynolds number of 5128 based on the half height of the channel and bulk velocity. The state-of-the art Particle Tracking Velocimetry (PTV) measurement technique is used to measure the instantaneous full-field velocity components. Comparisons between turbulent statistical quantities with various values of local void fraction are presented to elucidate the influence of the microbubbles presence within the boundary layer. A decrease in the Reynolds stress distribution and turbulence production is obtained with the increase of microbubble concentration. The results obtained indicate a decorrelation of the streamwise and normal fluctuating velocities when microbubbles are injected within the boundary layer.

• YAKHAK HOEJI
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• v.39 no.1
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• pp.14-23
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• 1995

The current study was undertaken to select the crude drug showing life prolonging effect on the starved rats(Sprague-Dawley) and elucidate the reaction mechanism there of. As distilled water extracts prepared from twenty kinds of natural drugs were administered orally to female starved rats, Bupleuri Radix demonstrated the most prominent effect with 34.6% increment in the survival time. To investigate underlying mechanism of life prolonging effect of Bupleuri Radix, the concentrations of adrenocorticosteroids(corticsterone, testosterone and aldosterone) and enzyme activities of superoxide dismutase(SOD), glutamate oxaloacetate transaminase(GOT), glutamate pyrurate transaminase(GPT) were assayed in the serums of rats starved for, 2, 4 and 6 days respectively. The results manifested much elevated values of corticosterone, aldosterone(2 days) and rather decreasing tendency afterwards, specially in the late periods of starvation(6 days). With respect to such a considerable changes according to starvation periods, Bupleur Radix restored these values much near to normal suggesting that Buplerum Radix may play a life prolonging action during starvation probably through reinforcing the homeostatic properties of corticosteroids and some enzyme activities.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.1
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• pp.7-14
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• 2011

This study was motivated by the purpose of improving the O-Index, currently used to quantify water tasty. The authors first develop the M-Index after normalizing Ca, K, and $SiO_{2}$ concentrations in the spring water, in that the concentrations are subject to their log-normal distributions. The M-Index is then compared with the O-Index based on the results of sensory tests, revealing that sensory tests are correlated with the M-Index much more than the O-Index. Furthermore, the developed index is applied to evaluate water sampled from 53 springs in Korea. It is concluded that water, sampled from five most famous springs, has high values in M-Index. In addition, water, collected from springs that are relatively accessible, contains low values, and thus is expected not to tasty good.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.1
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• pp.71-79
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• 2008

A helmholtz resonator has been widely used for the purpose of suppressing the low frequency noises propagated from various heat and fluid machineries. However, the conventional resonator has demerits that the effective absorption bandwidth is narrow and the absorption performance is not so outstanding in the only limited configurations of neck and cavity as well. In order to overcome these problems, in this paper, a resonator with perforated neck is proposed. The absorption performances of the resonator are measured by two-microphone method and estimated by transfer matrix method. The measured values of normal absorption coefficients agree well with the estimated values. By introducing the perforated plates at the neck of a resonator, it is shown that the absorption performance have been significantly improved.

• Bulletin of the Korean Chemical Society
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• v.21 no.10
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• pp.1035-1038
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• 2000

Vibrational properties of dopamine neutral species in powder state have been studied by means of the normal mode analysis based on the force constants obtained from the density functional calculation at B3LYP level and the results of Fourier trans form Raman and infrared spectroscopic measurements. Ab initio calculation at MP2 level shows that the trans conformer of dopamine has higher electronic energy about 1.4 kcal/mol than those of the gauche+ and the gauche-conformers, and two gauche conformers have almost the same energies. Free energies calculated at HF and B3LYP levels show very similar values for three conformers within 0.3 kcal/mol. Empirical force field has been constructed from force constants of three conformers, and refined upon ex-perimental Raman spectrum of dopamine to rigorous values. The major species of dopamine neutral base in the powder state is considered a trans conformer as shown in the crystallographic study of dopamine cationic salt.

• Bulletin of the Society of Naval Architects of Korea
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• v.11 no.1
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• pp.17-26
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• 1974

In this paper, authors investigate and analyze the effects of the anti-rolling tank which are calculated in accord with the tank damping coefficients by the computer, and which are represented with both the tank water's saturating state and the normal state in the irregular waves by analog computer. As the results of these studies, we immediately find that the tank optimum damping coefficient $b_{to}$, is 0.3877 due to calculating $\mu$-values, analyzing and comparing inclinations of $\mu$-values, and that although a nonlinear elements are included in the response character of the ship-tank system, the output is no longer Gaussian distribution, even when the sea waves are considered as Gaussian, and can not be expressed by the spectral forms which premise the superposition theory.

• Journal of Magnetics
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• v.17 no.3
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• pp.219-224
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• 2012

In the present study, changes in signal-to-noise ratio (SNR) and apparent diffusion coefficient (ADC) of the diffusion-weighted images in the normal livers were investigated using changes in b values in 1.5 T MR (magnetic resonance) instruments. Respective diffusion-weighted images and ADC map images were obtained from 20 healthy individuals by increasing b values from 50 to 400 and 800 $s/mm^2$ using 1.5T MR scanner between January 2011 and November 2011. At each ADC map image obtained at each b value, ADCs in the right hepatic lobe, spleen and kidney were measured. As a result, ADCs of the right hepatic lobe, spleen and kidney have gradually decreased in the diffusion-weighted images in accordance with the reduced b value. This outcome may be used as preliminary data for applications to various abdominal diseases.