• Journal of Mechanical Science and Technology
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• 제19권6호
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• pp.1378-1389
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• 2005

This work provides the fundamental knowledge of energy transport characteristics during very short-pulse laser heating of semiconductors from a microscopic viewpoint. Based on the self-consistent hydrodynamic equations, in-situ interactions between carriers, optical phonons, and acoustic phonons are simulated to figure out energy transport mechanism during ultrafast pulse laser heating of a silicon substrate through the detailed information on the time and spatial evolutions of each temperature for carriers, longitudinal optical (LO) phonons, acoustic phonons. It is found that nonequilibrium between LO phonons and acoustic phonons should be considered for ultrafast pulse laser heating problem, two-peak structures become apparently present for the subpicosecond pulses because of the Auger heating. A substantial increase in carrier temperature is observed for lasers with a few picosecond pulse duration, whereas the temperature rise of acoustic and phonon temperatures is relatively small with decreasing laser pulse widths. A slight lagging behavior is observed due to the differences in relaxation times and heat capacities between two different phonons. Moreover, the laser fluence has a significant effect on the decaying rate of the Auger recombination.

• 대한기계학회논문집B
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• 제26권10호
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• pp.1427-1435
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• 2002

The main aim of the present article is numerically to investigate the micro-scale heat transfer phenomena in a silicon microstructure irradiated by picosecond-to-femtosecond ultra-short laser pulses. Carrier-lattice non-equilibrium phenomena are simulated with a self-consistent numerical model based on Boltzmann transport theory to obtain the spatial and temporal evolutions of the lattice temperature, the carrier number density and its temperature. Especially, an equilibration time, after which carrier and lattice are in equilibrium, is newly introduced to quantify the time duration of non-equilibrium state. Significant increase in carrier temperature is observed for a few picosecond pulse laser, while the lattice temperature rise is relatively small with decreasing laser pulse width. It is also found that the laser fluence significantly affects the N 3 decaying rate of Auger recombination, the carrier temperature exhibits two peaks as a function of time due to Auger heating as well as direct laser heating of the carriers, and finally both laser fluence and pulse width play an important role in controlling the duration time of non-equilibrium between carrier and lattice.

• 유기물자원화
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• 제16권4호
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• pp.57-63
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• 2008

본 연구에서는 돈분을 이용한 열분해공정(pyrolysis)에 의한 바이오오일의 특성을 분석하여 보고하였다. 기본적으로 bio-oil 생산을 위한 pilot auger형 반응기는 $400^{\circ}C{\sim}600^{\circ}C$의 고온을 유지하였다. 바이오오일의 특성은 수질분석, 열량가, 원소분석, GC/MS를 이용한 마이오일의 원소, $^1H$ NMR분광기에 의한 functional group 구명 등을 포함한다. 돈분시료를 이용한 바이오오일 생산량은 pilot auger 반응기의 온도가 $550^{\circ}C$일 때 바이오일 생산율은 질량의 21%로서 최대를 나타내었다. 이 결과는 본 연구에서 연속 auger형 반응기의 이송이 편리하고 bio-oil 생산량이 적지 않아 대체 축분처리기술의 하나로 검토할 수 있음을 보였다. 그러나 auger 반응기의 원료로의 열전도가 유동상 반응조보다 낮아서 향후 이를 개선하기 위한 연구가 성공적으로 수행되면 바이오오일 생산량을 제고시킬 수 있을 것으로 판단된다.

• 청정기술
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• 제24권1호
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• pp.70-76
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• 2018

오거 반응기를 이용하여 해조류 바이오매스인 다시마로부터 열분해 오일 제조 실험을 수행하였으며, 열분해 오일의 물리화학적 특성을 살펴보았다. 주요 공정 변수인 열분해 온도 및 오거 컨베이어 속도의 최적 조건은 각각 $412^{\circ}C$, 20 rpm이었으며, 이 때 열분해 오일의 최대 수율은 32 wt%이었다. 낮은 탄소 함량 및 높은 산소 함량으로 인해, 다시마 유래 열분해 오일의 발열량($23.6MJ\;kg^{-1}$)은 기존 화석연료의 약 60% 이었다. 열분해 오일의 GC/MS 분석 결과, 1,4-Anhydro-d-galactitol, dianhydromannitol, 1-hydroxy 2-propanone, isosorbide 등이 주요 화합물로 확인되었다. 촤는 탄소 함량이 낮고 산소함량이 높아 발열량($13.0MJ\;kg^{-1}$)이 낮으며 다량의 무기 성분 및 황을 포함하고 있는 것으로 확인되었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.167-171
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• 2009

We conducted performance test of a 350 kW class wood pellet boiler installed at a dormitory whose total area is $1,354\;m^2$. The maximum heating capacity of the boiler is 350 kW(300,000 kcal/kg). The wood pellet boiler consists of 3 parts; boiler, hot water storage tank and wood pellet storage tank. In testing the boiler, we shut off hot water utility supply and open up floor heating water system in order to measure exact value of the heating output of the wood pellet boiler. To determine the efficiency and heating output of the wood pellet boiler, we measured mass flow rate of wood pellet, the lower heating value(LHV) of the wood pellet, mass flow rate and temperature of water for floor heating and so on. We measured the mass flow rate of fuel, wood pellet with respect to rotational speed of auger, wood pellet feeding screw. We also measured the flue gas concentration of the wood pellet boiler by using a gas analyser. The result shows that the efficiency of the wood pellet boiler is 80.6% based on lower heating value at 124 kW of heating output. At this condition, O2 concentration of the flue gas is 6.0%, CO and NOx concentrations are 85 and 102 ppm.

• Journal of Biosystems Engineering
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• 제28권2호
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• pp.97-106
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• 2003

One of the obstructing factors against managing dairy fm has been heavy labor requirement for feeding dairy cows. A Power-tiller TMF mixer was developed to reduce the cost and to provide economic benefit. The TMF mixer was desisted by the feeding capacity of 20∼30 heads at a batch with various functioning systems of auger type mixer, delivery conveyer, weighing console, pipe heater type heating system, power transmission train and mounting trailer. According to the study resulted, it showed that 1,200rpm, 1,600rpm, 2,000rpm and 2,300rpm were 6ps. Bps, lops and 12ps respectively. and that reduced shaft output by 15%. On the fodder mixer attached powertiller, initial output was necessary large torque. And the heating system was maintaining uniform temperature 60$^{\circ}C$ relatively.

• 대한전자공학회논문지
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• 제27권9호
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• pp.1386-1392
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• 1990

Characteristics of the direct thermal nitrided films by RF induction heating has been studied. The nitrided films on Si were prepared at 1000-1200\ulcorner in ammonia gas ambient. The nitrided films were analyzed by ellipsometry an Auger electron spectroscopy. I-V and C-V characteristics of MIS capacitors fabricated using nitrided film were investicated. The nitrided films were grown up mostly within initial thirty minutes and no significant growth was observed thereafter. Etch rates of films were about 1\ulcornermin in diluted HF (HF:H2O= 1:50). The nitrided films were resistant to dry and wet oxidations at temperatures below 1000\ulcorner and 900\ulcorner, respectively.

• 대한금속재료학회지
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• 제50권7호
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• pp.539-544
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• 2012

Thermal shock behavior of TiN-coated SUS 304 substrate was investigated using a laser ablation method. By short surface ablation with a pulse Nd-YAG laser, considerable surface crack and spalling were observed, whereas there were few oxidation phenomena, such as grain growth of TiN crystallites, nucleation and growth of $TiO_2$ crystallites, which were observed from the coatings quenched from $700^{\circ}C$ in a chamber. The oxygen concentration of the ablated coating surface with the pulse laser also had a lower value than that of the quenched coating surface by Auger electron spectroscopy and electron probe micro analysis. These results were attributed to the fact that the properties of the pulse laser method have a very short heating time and so the diffusion time for oxidation was insufficient. Consequently, it was verified that the laser thermal shock test provides a way to evaluate the influence of the thermal shock load reduced oxidation effect.

• 열처리공학회지
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• 제22권1호
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• pp.3-7
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• 2009

Variation in oxidation behavior with heat treatment temperature is investigated for a Ni-Ti alloy using X-ray diffraction, DSC (differential scanning calorimetry) and Auger electron spectroscopy. And the effect of oxidation on transformation behavior and superelasticity is characterized. A cold-worked 50.6Ni-Ti alloy is oxidized at 300-$700^{\circ}C$ for 1 hr in the air atmosphere. With an increase in heating temperature, the structure of $TiO_2$ changes from amorphous (300 and $400^{\circ}C$) to anatase ($500^{\circ}C$), and to rutile ($700^{\circ}C$). Activation energy of oxidation for NiTi is measured to be 51 Kcal/mol when heating temperature is $500^{\circ}C$ or above. Since Ti reacts preferably with oxygen, Ni content increases between matrix and oxide, forming $Ni_{3}Ti$ compounds. The resultant of oxidation decreases significantly $M_s$ and $A_s$ temperature in the specimen oxidized at $900^{\circ}C$ with $B_2{\rightarrow}M$ transformation path. An extra is found on cooling between two peaks in the specimen with $B_2{\rightarrow}R{\rightarrow}M$ one which is oxidized at $900^{\circ}C$ and aged at $500^{\circ}C$. Oxidation deteriorates superelasticity due to formation of Ni-rich compound.

• 분석과학
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• 제6권2호
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• pp.217-223
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• 1993

저항가열식 진공중착기를 이용하여 실온(ambient temp.)과 $250^{\circ}C$에서 알루미나 기판 위에 Au/Cr, Au/Ni/Cr 및 Au/Pd/Cr 박막을 제조하였으며, 공기 중에서 $300^{\circ}C$, $450^{\circ}C$, $600^{\circ}C$의 온도로 각각 1시간 동안 열처리하였다. Au, Ni(또는 Pd) 및 Cr 박막의 두께는 각각 $1000{\AA}$, $300{\AA}$, 및 $50{\AA}$이었다. 박막 제조시 기판의 온도와 박막 제조 후 열처리 온도는 각 층의 상호확산으로 인하여 박막의 면저항값에 영향을 주었다. Auger depth profile 분석결과, Au/Cr 시스템에서는 기판의 온도는 $250^{\circ}C$로 하여 박막을 제조할 때 이미 Cr은 Au 표면으로 확산되었으며, 열처리 후에는 Au의 분포도만 변화하였다. Au/Ni/Cr과 Au/Pd/Cr 시스템의 경우 Ni와 Pd 모두 확산현상이 발견되었으며, 특히 Ni(약 45 at.%)는 Au 박막 표면으로 확산되어 산화되었다.