• The Journal of the Acoustical Society of Korea
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• v.23 no.1
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• pp.54-60
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• 2004

In order to mitigate the problems in storage space and network bandwidth for the full CD quality audio, current digital audio is always restricted by sampling rate and bandwidth. This restriction normally results in low sample rate audio or calls for the data compression scheme such as MP3. However, they can only reproduce a lower frequency range than a regular CD quality because of the Nyquist sampling theory. Consequently they lose rich spatial information embedded in high frequency. The propose of this paper is to propose efficient high frequency enhancement of low sample rate audio using n adaptive filtering and DWT analysis and synthesis. The proposed algorithm uses the LMS adaptive algorithm to estimate the missing high frequency contents in DWT domain and it then reconstructs the spectrally enhanced audio by using the DWT synthesis procedure. Several experiments with real speech and audio are performed and compared with other algorithm. From the experimental results of spectrogram and sonic test, we confirm that the proposed algorithm outperforms the other algorithm and reasonably works well for the most of audio cases.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.2
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• pp.51-58
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• 2001

Supersonic, axisymmetric, jets issuing from several kinds of dual, coaxial, nozzles were experimentally investigated. Four different kinds of coaxial, dual nozzles were employed to characterize the major. features of the supersonic, coaxial, dual jets. Two convergent-divergent supersonic nozzles with different impinging angle on the jet axis of were designed to have the Mach number 2.0 and used to compare the coaxial jet flows with those discharging from two sonic nozzles. The primary pressure ratio was changed in the range from 4.0 to 10.0 and the assistant jet ratio from 1.0 to 4.0. The results obtained show that the assistant jets from the annular. nozzle affect the coaxial jet flows and an increase of both the primary jet pressure ratio and assistant jet pressure ratio lead to a longer supersonic length of the dual, coaxial jet.

• Journal of the Korea Computer Graphics Society
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• v.15 no.1
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• pp.25-34
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• 2009

Sound is very important element to enhance and reinforce reality and immersion of users in virtual reality and computer animation. Recently, significant researches about sound modeling are presented in computer graphics community. In this article, main subjects are explained and major researches are reviewed based on the sound papers presented in computer graphics community. Specially, several papers about following two subjects are reviewed in this paper: 1) synthesing sound using physically-based laws and generating sound synchronized with graphics. 2) spatializing sound and modeling sonic environment. Many research about sound modeling have been focused on more efficient modeling of real physical law and generate realistic sound with limited resources. Based on this concept, various papers are introduced and the relationship between researches about sound and graphics is discussed.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.6
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• pp.149-156
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• 2008

SLAM(Simultaneous Localization and Mapping) system is to find a global position and build a map with sensing data when an unmanned-robot navigates an unknown environment. Two kinds of system were developed. One is used distance measurement sensors such as an ultra sonic and a laser sensor. The other is used stereo vision system. The distance measurement SLAM with sensors has low computing time and low cost, but precision of system can be somewhat worse by measurement error or non-linearity of the sensor In contrast, stereo vision system can accurately measure the 3D space area, but it needs high-end system for complex calculation and it is an expensive tool. In this paper, we implement the SLAM system using a single camera image and a PSD sensors. It detects obstacles from the front PSD sensor and then perceive size and feature of the obstacles by image processing. The probability SLAM was implemented using the data of sensor and image and we verify the performance of the system by real experiment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.7
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• pp.625-638
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• 2014

In this study, the uncertainties in the critical flow functions (CFFs) calculated by the AGA8-dc equation of state were estimated. To this end, the formulas for enthalpy, entropy, and speed of sound, which are used in calculating the CFF, were expressed in the form of dimensionless Helmholtz free energy and its derivatives, and the uncertainty in Helmholtz free energy was inferred. To consider the variations in the compressibility-dependent variables induced by the variation (i.e., uncertainty) in compressibility, the form of the AGA8-dc equation was modified to have a deviation equal to the uncertainty under each flow condition. For each independent uncertainty component of the CFF, a model for uncertainty contribution was developed. All these changes were applied to GASSOLVER, which is KOGAS's thermodynamic database. As a result, the uncertainties in the CFF were estimated to be 0.025, 0.055, and 0.112 % at 10, 50, and 100 bar, respectively, and are seen to increase with the increase in pressure. Furthermore, these results could explain the deviations in the CFFs across the different labs in which the CFF international comparison test was conducted under the ISO management in 1999.

• Applied Chemistry for Engineering
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• v.20 no.4
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• pp.430-436
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• 2009

Deactivated three-way catalysts which had been exposed to gasoline engine exhaust for a long time were remanufactured by ultra sonic cleaning with distilled water, sulfuric acid solution and impregnation with precious metals (Pt, Pd, Rh). The catalytic properties as well as conversion reactivity of CO, THC and NOx about fresh, aged and remanufactured catalysts were examined. Most of the pollutants deposited on the aged three-way catalysts were removed in the remanufacturing process of those catalysts. At the same time a little amount of precious metals like Pt and Pd were removed in the remanufacturing process. Under the experimental condition used in this study, in the case of the remanufactured catalysts with impregnation of precious metals, the catalytic activities were recovered to almost the same level, or higher level of that of the fresh catalyst.

• The Journal of Korean Physical Therapy
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• v.13 no.2
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• pp.433-444
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• 2001

This review highlights the ontogenesis and the differentiation of motor neuron in spinal cord, and introduce the survival motor neuron(SMN) which is associated with growth and survival of motor neurons. The differentiation of floor plate cells and motor neurons in the vertebrate neural tube appears to be induced by signals from the notochord. This signal is Sonic hedgehog(Shh). The early development of motor neurons involves the inductive action of Shh. The SMN gene is essential for embryonic viability. SMN mRNA is also expressed in virtually all cell types in spinal cord, including large motor neurons. The SMN protein is involved in RNA processing and during early embryonic development is necessary fer cell survival. Two SMN genes are present in 5q 13 in humans: the telomeric gene(SMNt), which is the SMA-determining gene, and the centromeric analog gene(SMNc). The majority of transcripts from the SMNt gene are full length but, major transcripts of the SMNc gene have a high degrees of alternative splicing and tend to have little or no exon 7. The SMN is involved in the RNA processing(the biogenesis of snRNPs and pre-mRNA splicing), the anti-apoptotic effects, and regulating gene expression.

• Journal of Korea Water Resources Association
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• v.51 no.2
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• pp.109-120
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• 2018

In this study, we conducted flume experiments to investigate the three-dimensional flow structures around a half-submerged spur dike in a straight open channel flume. The experiments were carried out under the two different Froude numbers, 0.10 and 0.18. The results were compared with the previous experimental result conducted for non-submerged spur dike. Three-dimensional instantaneous velocities were measured using Acoustic Doppler Velocimetry (ADV) and water elevation data were collected using ultra sonic distance sensor. The results show that submergence conditions of the spur dike largely influence the three-dimensional flow structures around a spur dike.

• Polymer(Korea)
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• v.29 no.2
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• pp.216-220
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• 2005

A new type of polymer gel electrolyte was prepared from poly(ethylene glycol) diacrylate(PEGDA) and 1-butyl-3-methylimidazolium bis((trifluorornethyl) sulfonyl) amide$(BuMeIm^+Tf_2N^-)$ ionic liquid. The effect of the ionic liquid on ionic conductivity of the gel polymer electrolyte was investigated. It was observed that the gel polymer electrolyte having the ionic liquid exhibited higher ionic conductivity $(ca.\;10^{-3}S/cm)$ as well as electrochemical stability than that using organic solvent.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.2
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• pp.129-136
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• 2005

The movement ranges and diurnal behavior of the rockfish (Sebastes schlegeli) sonic tagged externally were measured by the acoustic telemetry in the marine ranching area of Tongyoung on 20 to 26 March and 4 October to 3 November, 2003. The results of study are as follows: 1. Two cage cultured fishes (body length: $30-34{\cal}cm$) were released the point where located approximately $250{\cal}m$ from the caught point on 30 March, 2003. They moved to the south $500{\cal}m$ away Sojangdudo and stayed within a $500{\cal}m$ radius of the position during the study. 2. Three wild fishes (body length: $28-32{\cal}cm$) were released around the caught point on 4 and 8 October, 2003. It was often measured that tagged fishes moved out the $500{\cal}m$ radius of released point for a week after release. After several days, the movement range tended to be reduced. Finally, they stayed within the $250{\cal}m$ radius of released point. 3. There was no significant difference of diurnal behavior of the rockfish between the cage cultured and the wild fishes. The movement range, however, for the night-time was a little wider than for the day-time.