• International Journal of Highway Engineering
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• v.7 no.4 s.26
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• pp.31-39
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• 2005

Tests are conducted to analyze the compaction characteristics of domestic river sand used frequently for backfill in construction of electrical pipeline. As a result of test, the range of specific gravity of sand is found to be in between 2.63 and 2.67, and of maximum dry weight of sand is in between $1.70g/cm^3\;and\;1.86g/cm^3$. Also, the optimum moisture content is found to be in between 11.3% and 13.8%. The variability of compaction degree with respect to compaction energy is well captured by hyperbolic function.

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.166-174
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• 2014

This research investigated the aging properties of the $B-KNO_3$ system as the igniter. The $B-KNO_3$ system showed the degradation in ignition properties depending on the method and period of storage. It should be found out the cause of the degradation to predict the reliability of the igniters. The changes of the properties by the degradation after aging tests were analyzed by microstructure analysis, XRD analysis and thermal analysis using DSC. It was found out that the lattice parameters of the $KNO_3$ as the oxidizer in the ignition system was changed into the JCPDS values as the aging time increased. Conclusively, the changes of the crystal structure of oxidizer affected the activation energy increasing as aging time increased.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.819-827
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• 1992

Investigations of the fatigue damage of roughing mill roll and experimentally. By the computer simulation for analysing the stresses on the roll surface and experimental hot rolling, the following results were drawn : The crakcs observed on the roll surface were initiated thermally in the initial stage of the rolling and propagated by repeated thermal and bending stresses. The size of the roll surface cracks smaller than 4.87mm could avoid the occurrence of tiny scab, surface defect of hot steel strip. Since the size of surface cracks observed on the roughing mill roll was very small, the fatigue damage of roll surface was found not to be the major factor for the formation of the scab.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.04a
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• pp.11-15
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• 1994

헤어드라이기, 자동차용 진공청소기, 면도기, 쥬서/믹서기등과 같은 소형 가 전제품은 사용시, 제품과 소비자사이의 거리가 짧아 진동/소음에 관한 인식이 대형 가전제품에 비해 크다. 과거에는 가전제품의 경우, 기본성능 및 각 회사만이 갖고 있는 독자적인 성능과 디자인을 최우선적으로 고려하여 설계하였다. 소음/진동에 관한 문제는 제품이 제작된 후에 필요에 따라 고려되었기 때문에 주어진 조건하에서 저진동/저소음을 위한 대책에는 한계가 있었다. 근래에는 진동/소음에 대한 관심이 증가하면서 제품의 설계단계부터 저진동/저소음 제품을 설계하기 위한 노력이 점차로 증가하고 있다. 본 연구는 이러한 추세의 한 예로서 헤어드라이기에 대해 결정된 디자인 및 성능이 크게 변경되지 않는 범위내에서 진동/소음이 적은 구조를 설계하는데 목적이 있다. 먼저, 헤어드라이기의 소음원 및 특성을 간단히 규명한 뒤, 벨마우스(bellmouth) 이용등과 같이 일반적으로 잘 알려진 소음저감법을 소음원에 대해 적용하였다. 헤어드라이기의 경우 소음원이 몸체에 삽입되는 순간 특정 주파수대역에서 소음이 증가하는 현상이 발생하는데, 헤어드라이기의 몸체에 대한 음향학적 특성을 수치해석 및 실험을 통해 파악함으로써 이에 대한 원인을 규명하였다. 이를 바탕으로 몇가지의 변경된 구조에 대해 소음에 관련된 현상을 고찰해 봄으로써 저소음을 위한 헤어드라이기의 설계방법을 제안하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.223-223
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• 1999

PZT(PbZr1-xTixO3) 박막은 고유전율과 같은 remanent polarization을 가져서 고집적 소자의 커패시터 유전율층 또는 비휘발성 메모리 소자의 제조에 이용되고 있으나, fatigue 와 aging 문제로 인하여 새로운 물질의 개발이 필요한데, 그 대표적으로 연구되고 있는 것이 PMN-PT(Pb(Mg1/3Nb2/3)O-PbTiO3) 이다. 본 실험에서는 sol-gel 법에 의하여 제조된 PMN-PT막을 ICP(Inductively coupled plasma)에 의하여 식각하였고 mask층으로는 PR을 사용하였다. 식각 가스로는 Ar, Cl, BCl를 단독 또는 혼합하여 사용하였으며, 식각 특성을 보기 위하여 RF Power, Substrate bias, Operation pressure, Substrate temperature를 변화시켰다. 식각속도는 stylus profiler를 이용하여 측정하였고, 단면 profile은 scanning electron microscopy (SEM)를 이용하여 관찰하였다. 식각 메커니즘을 규명하고자 식각된 박막의 표면을 X-ray photoelectron spectroscopy (XPS)로 관찰하였고, optical emission spectroscopy (OES)로 플라즈마 특성을 규명하고자 하였다. 식각속도는 Ar 또는 Cl2 플라즈마에 BCl3 가스를 혼합하였을 경우 증가되었고, BCl3 가스를 단독으로 사용하여도 높은 식각속도를 나타내었으며, BCl3의 첨가량이 늘어날수록 PR의 식각속도는 감소하여 높은 선택비를 보였다. 90% BCl3/10%Cl2 플라즈마에서 2800$\AA$/min의 식각속도 그리고 1.37:1의 PR 선택비를 얻을 수 있었다. Power나 기판 bias 증가에 따라 식각속도는 증가하였으나 기판 온도변화에는 민감하지 않았다. BCl3 rich에서의 식각속도 증가와 선택비 증가는 B2O3의 형성에 의한 것으로 생각된다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11B
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• pp.1225-1233
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• 2009

ISPs and Enterprises are equipping their networks with sufficiently high speed facilities and provide large bandwidths members. However the high speed enterprise network does not have satisfying end-to-end network performance within the network in spite of under utilization. The root cause of this performance degradation is a micro-congestion, which is a short-live event of traffic congestion. A micro-congestion causes packet loss, delay and packet reodering, and finally results in end-to-end network performance degradation. In this paper, we propose a micro-congestion detection method and find out the characteristics of performance degradation by analyzing traffic archives which is collected from a network link when a micro-congestion occurs.

• The Korean Journal of Zoology
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• v.33 no.3
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• pp.303-309
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• 1990

In order to have a handle on the availability of eukarvotic peptide hormone precursors, a cDNA encoding angler fish prepro-SRIF I was manipulated so that it can be produced in large quantity from heterologous E. coli cells. Using T7 overexpression system, fusion constructs between the T7 phage coat protein Sl0 and the prepro-SRIF were made and modified as desired. From the host E. coli strain, BL21 DE3, harboring these plasmid constructs, three different SRIF related polypeptides were expressed in large amount and characterized. The results confirm the exact construction and authenticity of the overexpressed proteins from E. coli cells. The importance of this heterologous overexpression in hard to get peptide hormone precursors as well as the suitability of the target peptide hormone SRIF for this approach are discussed.

• Geophysics and Geophysical Exploration
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• v.9 no.4
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• pp.255-260
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• 2006

Measurements in two adjacent (about 1.5 m separation) boreholes reveal that there is a significant degree of variations in the width and property (permeability) of shear zones in the granitic rock. A high frequency (>10 kHz) cross-well seismic tomography was conducted to characterize the features of permeability distribution at the shear zones in the inter-well region. At the shear zones, the correlation between the permeability at the well location and the velocity pattern shown in the cross-well velocity tomogram suggests that a high resolution velocity tomogram may provide useful information for the shear zone characteristics, such as permeability, fracture density, width, and length.

• Journal of the Korean Society for Railway
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• v.14 no.2
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• pp.160-166
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• 2011

It is difficult to clarify the dynamic response characteristics of trackbed because of various environmental conditions. However, track irregularity be affected by ununiformed bearing capacity and its dynamic response, study for dynamic response characteristics is required to investigate the cause of track irregularity and countermeasure. In this paper, the response variation for dominant frequency and vibration energy by trackbed structure and material stiffness are investigated. The analysis section is two layered ground structure that is comprised of trackbed and soft rock. This structure amplifies the energy of dominant range easily. It is evaluated to affect track irregularity on comparing by theoritical, analytical and empirical method for dynamic response of the trackbed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.517-527
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• 1989

A theoretical analysis for the characteristics of pyrolysis and combustion of solid fuel was carried out in the present study. The hollow cylindrical combustion model including gas phase and solid fuel at inside and outside respectively was developed for the numerical analysis and parametric studies. The effects of volatile contents in the porous solid fuel and Reynolds number at inlet of gas phase on the characteristics of pyrolysis and combustion such as the radial, axial and time variations of volatile mass flux through porous solid fuel, temperature, mass fractions of gaseous fuel and oxidizer, and flame shape were investigated in the parametric studies. The results of the present study show that the flame produced by the volatiles moves to the downstream of fuel with accelerating velocity with time until extinction is occurred resulting from the completion of pyrolysis. When flame is employed with smaller amount of volatiles content in the solid fuel, the flame sheet exists closer to the inner wall of solid fuel. As Reynolds number at inlet increases, the flame sheet moves to the inner wall due to effect of convection even though the volatiles by pyrolysis increases.