• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.352-357
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• 2013

In this study, the pellet-type adsorbents were prepared by extrusion using water treatment sludge. Effects of binder and calcination on physical and chemical properties of pellet-type adsorbents were investigated. The porous structure and surface characteristics of the adsorbents were studied using nitrogen adsorption, compression strength, scanning electron microscope, X-ray diffraction, and infrared spectroscopy of adsorbed pyridine. With increasing of binder content to 5 wt%, the compressive strength of pellet-type adsorbent could be improved more than three times, but the surface area reduced by 30%, and thus the breakthrough time of trimethylamine was shortened. The breakthrough time of the trimethylamine, a basic gas, could be increased more than three times through calcination, which seems to be due to generation of acid sites composed of Lewis acid and Br$\ddot{o}$nsted acid sites on the adsorbent surface.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1519-1529
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• 1992

A stepped specimen which is subjected to step loading is modeled to study the initiation and growth of adiabatic shear band using explicit time integration finite element code. The material model for specimen includes effects of thermal softening, strain hardening and strain rate hardening. Various mesh sizes are tested to check whether they are small enough to model highly localized discontinuous phenomena reasonably well. It is shown that the number of adiabatic shear band depends on impact velocity and it is also shown that the initiation and growth of adiabatic shear band inversely depends on prescribed velocity at the top of specimen.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.560-567
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• 2020

Incremental Sheet Forming (ISF) is a unique sheet-forming technique. The process is a die-less sheet metal manufacturing process for rapid prototyping and small batch production. In the forming process, the critical parameters affecting the formability of sheet materials are the tool diameter, step depth, feed rate, spindle speed, etc. This study examined the effects of these parameters on the formability in the forming of the varying wall angle conical frustum model for a pure Al3004 sheet with 1mm in thickness. Using Minitab software based on Back Propagation Neural Network (BPNN) and Genetic Algorithm (GA), a second order mathematical prediction model was established to predict and optimize the wall angle. The results showed that the maximum forming angle was 87.071° and the best combination of these parameters to give the best performance of the experiment is as follows: tool diameter of 6mm, spindle speed of 180rpm, step depth of 0.4mm, and feed rate of 772mm/min.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.3
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• pp.1512-1518
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• 2013

Polycarbonates (PCs) with six different end capping agents were synthesized from melt polymerization. Chemical structure of the synthesized PC was determined by FT-IR spectroscopy. The average molecular weight and distribution, glass transition and thermal degradation temperatures were determined by GPC, DSC and TGA. Average molecular weight changed with the chemical structure of end capping agent, and 4-tert-butylphenol was estimated as the optimum end capping agent. The average molecular weights of PCs decreased with the concentration of the agent, the number average molecular weight was observed as 20,000 - 30,000 when 0.05-0.15 mol% of 4-tert-butylphenol added in PCs. The melt viscosities and glass transition temperature of the PCs decreased with molecular weight. The change for adding method of the agent affected on both the molecular weight distribution and decrease in power law index.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.5
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• pp.805-810
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• 2006

Defects in the conventional casting process of silver jewelry can result in famished products of mediocre hardness. To overcome the shortcomings of conventional methods, we proposed new press forming process, which involves applying uniaxial pressure on casting 92.5%Ag-6.5%Cu-1%Zn ring elements and shaping with a lath. We investigated Vickers hardness, density, and microstructure evolution by changing the applied uniaxial pressure. We report that our newly proposed process can increase the hardness up to 2.3 times and decrease average grain size by 50%. Our method leads to drastic mechanical property enhancements, and is thus suitable for casting tension-style jewelry.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.361-365
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• 2005

An absolute interferometer system with multiple point-sources is devised for tile 3-D measurement of rough surface profiles. The positions of the point sources are determined to be the system parameters that influence the measurement accuracy, so they are calibrated precisely prior to performing actual measurements. For the calibration, a CCD camera composed of a two-dimensional array of photo-detectors was used. Performing optimization of the cost function constructed with phase values measured at each pixel on the CCD camera, the position coordinates of each point source is precisely determined. Measurement results after calibration performed for the warpage inspection of chip scale packages (CSPs) demonstrate that the maximum discrepancy is 9.8 mm with a standard deviation o( 1.5 mm in comparison with the test results obtained by using a Form Taly Surf instrument.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.124-124
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• 2000

다이아몬드에 버금가는 높은 경도뿐만 아니라 높은 화학적 안정성 및 열전도성 등 우수한 물리화학적 특성을 가진 입방정 질화붕소(cubic boron nitride)는 마찰.마모, 전자, 광학 등의 여러 분야에서의 산업적 응용이 크게 기대되는 재료이다. 특히 탄화물형성원소에 대해 안정하여 철계금속의 가공을 위한 공구재료로의 응용 또한 크게 기대된다. 이 때문에 각종의 PVD, CVD 공정을 이용하여 c-BN 박막의 합성에 대한 연구가 광범위하게 진행되어 많은 성공사례들이 보고되고 있다. 그러나 c-BN 박막의 유용성에도 불구하고 아직 실제적인 응용이 이루어지지 못한 것은 c-BN 박막의 증착직후 급격한 박리현상 때문이다. 본 연구에서는 평행자기장을 부가한 ME-ARE(Magnetically Enhanced Activated Reactive Evaporation)법을 이용한 c-BN 박막의 합성에서 적용한 증착공정 인자들의 변화에 따른 박리특성 고찰과 함께 다층박막화 및 제 3원소 혼입 방법을 적용하여 박리특성 향상 정도를 조사하였다. BN 박막합성은 전자총에 의해 증발된 보론과 (질소+아르곤) 플라즈마의 활성화반응증착(Activated Reactive Evaporation)에 의해 이루어졌다. 기존의 ARE 장치와 달리 열음극(got cathode)과 양극(anode) 사이에 평행자기장을 부가하여 플라즈마의 증대시켜 반응효율을 높였다. 합성실험용 모재로는 p-type으로 도핑된 (100) Si웨이퍼를 30$\times$40mmzmrl로 절단 후, 10%로 희석된 완충불산용액에 10분간 침적하여 표면의 산화층을 제거한 후 사용하였다. 박막실험실에서의 주요공정변수는 기판바이어스 전압, discharge 전류, Ar/N2가스유량비이었다. 합성된 박막의 결정성 분석을 FTIR을 이용하였으며, BN 박막의상 및 미세구조관찰을 위해 투과전자현미경(TEM;Philips EM400T) 분석을 병행하였고, 박막의 기계적 물성 평가를 위해 미소경도를 측정하였다. 박리특성의 고찰은 대기중에서의 자발적 박리가 일어나 90%이상의 박리가 진행된 시점까지의 시간을 측정하였고, 증착직후 박막의 잔류응력 변화와 연관하여 고찰해 보았다.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.6
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• pp.501-510
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• 2000

Recently, advanced signal analysis which is called "time-frequency analysis" has been used widely in nondestructive evaluation applications. Wavelet transform(WT) and Wigner Distribution are the most advanced techniques for processing signals with time-varying spectra. Wavelet analysis method is an attractive technique for evaluation of material characterization nondestructively. Wavelet transform is applied to the time-frequency analysis of ultrasonic echo waveform obtained by an ultrasonic pulse-echo technique. In this study, the feasibility of noise suppression of ultrasonic flaw signal and frequency-dependent ultrasonic group velocity and attenuation coefficient using wavelet analysis of ultrasonic echo waveform have been verified experimentally. The Gabor function is adopted the analyzing wavelet. The wavelet analysis shows that the variations of ultrasonic group velocity and attenuation coefficient due to the change of material characterization can be evaluated at each frequency. Furthermore, to assure the enhancement of detectability and naw sizing performance, both computer simulated results and experimental measurements using wavelet signal processing are used to demonstrate the effectiveness of the noise suppression of ultrasonic flaw signal obtained from austenitic stainless steel weld including EDM notch.

• Korean Journal of Food Science and Technology
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• v.46 no.3
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• pp.364-368
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• 2014

This study investigated the antioxidant activity of onion peels extracted from onion byproducts by hot water treatment. Hot water extraction of freeze dried onion peel powder was analyzed for total polyphenol content, 2,2'-diphenyl-1-picryllhydrazyl (DPPH), and 2,2'-azino-bis(3-ehtylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activities, reducing power, oxygen radical absorbance capacity (ORAC). Total polyphenol content was the highest (233.90 mg/g) in onion peel extract mix with ethanol (OPME-1). The DPPH radical scavenging activity ($IC_{50}$), reducing power, and ORAC obtainbed from onion peel extract mix with ethanol precipitation (OPMPE-1) were the highest at 1.15 mg/mL, 1.69 $A_{700}$, and $318,509{\mu}M\;TE/mL$, respectively. The ABTS radical scavenging activity was the highest at 432.78 mg amino acids (AA) eq/g in the OPM. The results of this study suggest that onion peel extracts have marked antioxidant activity, which can have significant health benefits.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.615-620
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• 2008

We fabriacted thermal evaporated $10nm-Ni_{1-x}Co_x$(x=0.2, 0.6, and 0.7) films on 70 nm-thick polysilicon substrate with $0.5{\mu}m$ line width. NiCo composite silicide layers were formed by rapid thermal annealing (RTA) at the temperatures of $700^{\circ}C$ and $1000^{\circ}C$. Then, we checked the microstructure evaluation of silicide patterns. A FIB (focused ion beam) was used to micro-mill the interconnect patterns with low energy condition (30kV-10pA-2 sec). We investigated the possibility of selective removal of silicide layers. It was possible to remove low resistance silicide layer selectively with the given FIB condition for our proposed NiCo composite silicides. However, the silicides formed from $Ni_{40}Co_{60}$ and $Ni_{30}Co_{70}$ composition showed void defects in interconnect patterns. Those void defects hinder the selective milling for the NiCo composite silicides.