• 한국식품과학회지
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• 제24권4호
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• pp.301-305
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• 1992

원심식 박막증발기를 이용해 마늘 착즙을 농축한 경우 가열 매체 및 증발온도가 농축비, 총괄열전달계수, 증발속도 등에 대해 미치는 영향에 대하여 조사하였다. 마늘착즙의 급액속도와 증발온도가 일정할 때 가열증기의 온도가 높을수록 농축비, 증발속도, 및 총괄열전달계수는 증가하였으나, 가열증기의 온도가 $110^{\circ}C$ 이상이 되면 이들 값의 증가가 현저하게 둔화되었다. 증기온도 $100^{\circ}C$ 이하에서는 증발온도가 증가함에 따라 농축비, 증발속도, 총괄열전달계수는 감소하였다. 그러나 그 이상의 온도에서 어느 일정 증발온도까지는 이들 값이 증가하다가 다시 감소하는 경향을 나타내었다. 급액속도가 일정할 때 증기의 온도와 증발온도와의 차이가 $70^{\circ}C$가 될 때까지는 농축비, 증발속도 및 총괄열전달계수는 모두 증가하였다. 그러나 온도 차이가 $70^{\circ}C$ 이상이 되면 이들 값의 증가가 둔화되거나 감소하였다.

• 정보저장시스템학회논문집
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• 제1권1호
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• pp.58-66
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• 2005

Pseudo-Near Field Recording (Pseudo-NFR) system is proposed to prevent contamination and oxidation of media surface occurred in conventional NFR systems. To solve these critical problems of the NFR systems, we investigate the optimal thickness of cover layer for Pseudo NFR. This paper presents the theoretical analysis for cover layer thickness based on the measured length of dust particle and numerical simulation for the temperature distribution using Finite Difference Time Domain (FDTD) method and heat conduction equation. To verify the simulation results, we conduct and compare simulation results in case of far field MO recording and near field MO recording. A measured dust particle length in general environment was mostly less than $20{\mu}m$, and the optimal thickness of cover layer is $30{\mu}m$ in this case. Based on the designed optimal cover layer thickness, temperature distribution is simulated to have $800{\~}850^{\circ}C$.

• 한국수소및신에너지학회논문집
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• 제19권4호
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• pp.299-304
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• 2008

Thermal decomposition of Ammonia Borane have been investigated with various analytical methods including TGA, TP-MS, DSC. By-products such as aminoborane and borazine were identified during hydrogen release by TGA, TP-MS analysis. $H_2$ release amount was measured at each temperature isothermally, which resulted in 7 wt% $H_2$ release at 130$^{\circ}C$. Moreover, higher temperature enhanced hydrogen release kinetics leading to shortened induction period from 20 min at 95$^{\circ}C$ to 0 min at 130$^{\circ}C$. Melting and decomposition at close temperature (4$^{\circ}C$ difference) caused the formation of thin foam during hydrogen release. Suppression of by-products and thin foam formation during hydrogen release is suggested as critical issues to realize chemical hydrogen storage system with ammonia borane.

• Biomaterials and Biomechanics in Bioengineering
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• 제2권1호
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• pp.15-22
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• 2015

Poly(ethylene glycol) end-capped with pentafluorophenyl group(s) in ABA (FP-PEG-FP) and AB (mPEG-FP) types were prepared. Even though they were similar in composition, the lower critical solution temperature (LCST) of FP-PEG-FP was observed at $23^{\circ}C$, whereas that of mPEG-FP was observed at $65^{\circ}C$. To understand the large difference in solution behaviour of the two polymers, UV-VIS spectroscopy, microcalorimetry, 1H-NMR spectroscopy, and dynamic light scattering were used. FP-PEG-FP has two hydrophobic pentafluorophenyl groups at the ends of hydrophilic PEG (1000 Daltons), whereas mPEG-PF has a highly dynamic PEG (550 Daltons) block that are anchored to a hydrophobic pentafluorophenyl group. PF-PEG-PF not only has a smaller conformational degree of freedom than mPEG-PF but also can form extensive intermolecular aggregates, therefore, PF-PEG-PF exhibits a significantly lower LCST than mPEG-PF. This paper suggests that topological control is very important in designing a temperature-sensitive polymer.

• 한국세라믹학회지
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• 제27권6호
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• pp.799-807
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• 1990

In this study, effects of oxide additives on mechanical properties and microstructure of A1N and A1N polytype ceramics were investigated. Fine A1N powder was synthesized by nitriding alumiuim hydroxide prepared from Al-isopropoxide, at 1350$^{\circ}C$ for 10h in N2 atmosphere. By adding 3w/o Y2O3, 0.56w/o CaO, and 10w/o SiO2 to AlN powder, AlN and AlN polytype ceramics were prepared by hot-pressing under the pressure of 30 MPa at 1800$^{\circ}C$ for 1h. AlN ceramics with no additives formed considerable amount of AlON phase, while AlN ceramics doped with Y2O3 or CaO decreased AlON phase and formed Y-Al or Ca-Al oxide compound. AlN＋10w/o SiO2(＋3w/o Y2O3) composition produced AlON and AlN polytype compound having 21R as a major phase. Room temperature flexural strength of AlN ceramics with no additive was 246MPa, and room temperature flexural strength and critical temperature difference by thermal shock(ΔTc) of AlN ceramics dooped with Y2O3 or CaO were 532MPa/340$^{\circ}C$ and 423MPa/300$^{\circ}C$, respectively. Y2O3 and CaO used as sintering agent played roles of densification and oxygen removal of AlN ceramics, and affected grain growth/grain morphologies of AlN ceramics.

• Asia-Pacific Journal of Atmospheric Sciences
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• 제54권4호
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• pp.527-544
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• 2018

This paper presents a nighttime sea fog detection algorithm incorporating unsupervised learning technique. The algorithm is based on data sets that combine brightness temperatures from the $3.7{\mu}m$ and $10.8{\mu}m$ channels of the meteorological imager (MI) onboard the Communication, Ocean and Meteorological Satellite (COMS), with sea surface temperature from the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA). Previous algorithms generally employed threshold values including the brightness temperature difference between the near infrared and infrared. The threshold values were previously determined from climatological analysis or model simulation. Although this method using predetermined thresholds is very simple and effective in detecting low cloud, it has difficulty in distinguishing fog from stratus because they share similar characteristics of particle size and altitude. In order to improve this, the unsupervised learning approach, which allows a more effective interpretation from the insufficient information, has been utilized. The unsupervised learning method employed in this paper is the expectation-maximization (EM) algorithm that is widely used in incomplete data problems. It identifies distinguishing features of the data by organizing and optimizing the data. This allows for the application of optimal threshold values for fog detection by considering the characteristics of a specific domain. The algorithm has been evaluated using the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) vertical profile products, which showed promising results within a local domain with probability of detection (POD) of 0.753 and critical success index (CSI) of 0.477, respectively.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4431-4446
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• 2023

A Multiphysics coupling framework, MPCORE, has been developed to analyze safety parameters using the best estimate codes. The framework contains neutron kinetics (NK), thermal hydraulics (TH), and fuel performance (FP) codes to analyze fuel burnup, radial power distribution, and coolant temperature (T_bc). Shuffling and rotation capabilities have been verified on the Watts Bar reactor for three cycles. This study focuses on two coupling approaches for TH and FP modules. The one-way coupling approach involves coupling the FP code with the NK code, providing no data to the TH modules but getting T_bc as boundary condition from TH module. The two-way coupling approach exchanges information from FP to TH modules, so that the simplified heat conduction solver of the TH module is not used. The power profile in both approaches does not differ significantly, but there is an impact on coolant and cladding parameters. The one-way coupling approach tends to over-predict the cladding hydrogen concentration (CHC). This research highlights the difference between one-way and two-way coupling on critical boron concentration, T_bc, CHC, oxide surface temperature, and pellet centerline temperature. Overall, MPCORE framework with two-way coupling provides a more accurate and reliable analysis of safety parameters for nuclear reactors.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.13-18
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• 2007

When triple flames propagated in a diverging channel, the effects of fuel dilution on the lift-off characteristics of triple flames were investigated. A multi-slot burner was used to stabilize the lift-off flame especially at weak fuel concentration gradients. It was reported that there is a maximum propagation velocity at a critical concentration gradient in an open jet regardless of fuel dilution. The enhancement of a diffusion flame affected to increase the propagation velocity around critical concentration gradients. However, the influence of a confined channel on the structure of triple flames according to fuel dilution needs to be investigated compared with an open jet case. This study aimed to examine the effect of a confined channel on the structure and the propagation velocity of the triple flames according to fuel dilution. Lift-off height and propagation velocity of triple flames were investigated by employing three kinds of fuel compositions diluted by nitrogen (0%, 25%, 50% $N_2$), Fuel dilution reduced the propagation velocity of triple flame in a confined channel mainly due to the decrease of flame temperature in premixed branch. Despite the difference in fuel dilution, the propagation velocity has a maximum value at a specific fuel concentration gradient even though the critical concentration gradient increases with fuel dilution. And the critical concentration gradient in a confined channel is larger than that in an open jet due to enhancement of convective diffusion.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.475-481
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• 2017

본 실험에서는 추진기관 연료의 주 성분으로 사용되는 액체 탄화수소 화합물의 초임계 분사 거동 특성을 분석하기 위해서 고속카메라 이미지를 활용한 실험을 수행하였다. 케로신의 구성성분 중 임계점의 차이가 있는 Decane과 Methylcyclohexane (MCH)를 실험 유체로 선정하였으며, 분석을 위해 Shadowgraphy 기법을 사용하였다. 제트 분사 시 임계온도 조건 하에서 각 유체의 환산압력에 따라 케이스를 나누었다. 아임계 조건의 동일한 인젝터 초기상태에서 기화가 발생하기까지 온도변화량의 차이에 따라 Decane과 MCH는 서로 다른 거동을 보였다. 하지만 초임계 조건에서는 같은 온도변화량이 필요하더라도 임계점 부근에서는 증발엔탈피가 0에 가까워져 기화과정이 아닌 초임계 유체로의 상변화가 일어나고 급격한 밀도변화가 없어 Decane과 MCH 모두 원기둥 형상의 액주가 관측되었다.

• 한국추진공학회지
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• 제20권4호
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• pp.26-33
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• 2016

추진기관의 주요 연료로 사용되는 액체 탄화수소 연료의 초임계 천이특성을 분석하기 위해서 Methylcyclohexane (MCH)의 상변화 가시화 및 MCH와 Decane의 포화곡선 측정실험을 수행하였다. 압력 정체구간은 임계점 부근에서 급격한 비열의 상승으로 존재하며, 정체구간이 종료되는 시점부터 임계점까지 임계단백광이 관측되었다. 또한, 초임계로 완전히 천이되면서 상의 경계가 사라지고 강한 밀도 구배를 관측할 수 있었다. 실험 포화온도 곡선과 수치적 데이터를 비교한 결과 단일 탄화수소계열 연료는 실험과 수치데이터가 거의 일치하는 경향을 보였으나, 혼합탄화수소계열연료의 임계점 예측에서는 다소 차이를 보였다.