• Journal of Magnetics
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• 제18권3호
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• pp.365-369
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• 2013

Coal ash is known to contain a noticeable amount of valuable elements, including transition metals and lanthanides. Therefore it is quite actual problem to extract them for metallurgy and other applications. This paper presents the results of high gradient magnetic and mechanical separation, microscopy, element analyses and optical spectroscopy of brown coal ash taken from the combustion camera and chimney-stalk of Angren thermal power station. The separated magnetic fraction was 3.4 wt.%, where the content of Fe in ferrospheres increased to 58 wt.%. The highest contents of Fe and rare earth elements were found in the fine fractions of $50-100{\mu}m$. Optical absorption spectroscopy of water solutions of the magnetic fractions revealed $Fe^{2+}$ and $Fe^{3+}$ ions in the ratio of ~1:1. The separated coal ash could be used for cleaning of technological liquid waste by means of the high gradient magnetic field.

• Archives of Pharmacal Research
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• 제5권2호
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• pp.61-70
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• 1982

Sulfisoxazole, a chemotherapeutic agent, was microencapsulated with ethylcellulose by means of phase separation form cyclohexane by temperatture change. The size distribution was determined by use of standard sieves and the effect of core to wall ratio was noted. To examine their shapes and usrface characteristics, the microcapsules were observed with a scanning electron microscope. Release of the drug from microcapsules into pH 7.5 buffer medium was studied. The release pattern was found to have similar properties to the release of a drug from an insoluble porous matrix reported. The apparent diffusion coefficient of sulfisoxazole was measured for the transport of the drug from the core of microcapsules into the surronding sink condition. The apparent diffusion coefficient increased with increasing capsule size.

• Journal of Positioning, Navigation, and Timing
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• 제10권1호
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• pp.21-28
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• 2021

In order to develop a Korea Positioning System (KPS) as part of key national infrastructure, independent navigation signal design is essential. The designed signal candidates must coexist with existing or planned GNSS signals within the limited frequency band. This requires a RF compatibility assessment, which can be performed using the Spectral Separation Coefficient (SSC) and Effective Carrier to Noise Density Ratio (Effective C/N0), for navigation signals. Thus, in this paper, the analysis of RF compatibility between the designed signal candidates and the existing GNSS signals is carried out based on analytical and numerical techniques.

• Korean Chemical Engineering Research
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• 제51권4호
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• pp.476-481
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• 2013

본 연구에서는 물리적 특성이 유사한 에틸벤젠과 파라자일렌의 혼합물을 분리하고자 MFI형 제올라이트(TS-1, ZSM-5, Silicalite-1) 분리막을 제조하였으며 이를 이용하여 기상에서 분리 실험을 진행하였다. 제올라이트 입자가 코팅된 분리막을 제조함에 있어서 마이크로웨이브 합성 방법을 사용하여 합성 시간을 단축하였으며, 500 nm 내외의 균일한 입자를 튜브타입의 지지체 막에 안착시켜 제올라이트 입자가 $3{\sim}4{\mu}m$ 두께로 치밀하게 코팅된 분리막을 제조하였다. 제조한 분리막으로 에틸벤젠/파라자일렌 혼합물 원료의 혼합비를 변경하여 투과 분리한 결과 에틸벤젠:파라자일렌=5:5 비율에서 가장 높은 분리도를 가짐을 알 수 있었다. 세 종류의 서로 다른 제올라이트 물질(TS-1, ZSM-5, Silicalite-1)을 각각 코팅하여 제조된 분리막을 이용하여 $160{\sim}220^{\circ}C$의 실험온도에서 에틸벤젠/파라자일렌을 투과 실험을 실시한 결과, TS-1 분리막이 $1,666mol/m^{2*}s^*Pa$의 가장 높은 투과 플럭스를, Silicalite-1 분리막이 1.73의 가장 높은 분리도를 $200^{\circ}C$의 온도에서 각각 보임을 확인할 수 있었다.

• 대한원격탐사학회지
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• 제32권3호
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• pp.245-251
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• 2016

황사의 주요 발원지인 중국 북부 둔황지역에 선포토미터를 설치하여 440, 675, 870 그리고 1020 nm 채널에서 황사의 파장별 입자편광소멸도를 산출하였다. 이와 함께 발원한 황사가 장거리 수송과정에 위치한 제주 고산과 일본 오사카에 설치된 선포토미터를 함께 분석하였다. 황사 발원지에서 1020 nm 파장에서 입자편광소멸도가 0.34로 가장 높은 수치를 보였다. 또한, 초미세먼지농도가 증가하는 경우 입자편광소멸도는 감소하는 경향을 보였다. 우리는 본 연구에서 선포토미터의 입자편광소멸도 산출을 통해 에어로졸에서 황사의 구성 비율이 변화함을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.131-134
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• 2002

Compressible gas flow through a convergent-divergent nozzle is choked at the nozzle throat under a certain critical pressure ratio, and then being no longer dependent on the pressure change in the downstream flow field. In practical, the flow field at the divergent part of the critical nozzle can affect the effective critical pressure ratio. In order to investigate details of flow field through a critical nozzle, the present study solves the axisymmetric, compressible, Wavier-Stokes equations. The diameter of the nozzle throat is D=8.26mm and the half angle of the diffuser is changed between $2^{\circ}\;and\;10^{\circ}$ Computational results are compared with the previous experimental ones. The results obtained show that the divergence angle is significantly influences the critical pressure ratio and the present computations predict the experimented discharge coefficient and critical pressure ratio with a good accuracy. It is also found that a nozzle with the half angle of $4^{\circ}$ nearly predicts the theoretical critical pressure ratio.

• 천문학회지
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• 제42권3호
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• pp.39-45
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• 2009

We investigate the degeneracy in the pattern of central microlensing perturbations of a pair of planetary systems where the planets are located from the primary with projected separations in units of the Einstein radius s and $s^{-1}$, respectively. From this, we confirm the fact that although alike, the patterns of central perturbations induced by a close (s < 1) planet and a wide (s > 1) planet are not identical and the degree of difference depends on the planet/primary mass ratio and the planet-primary separation. We find that the difference can be greater than 5% for planetary systems with lensing parameters located in the parameter space of (1/1.8 < |s| < 1.8, q > $5{\times}10^{-3}$), (1/1.3 < |s| < 1.3, q > $1{\times}10^{-3}$), and (1/1.2 < |s| < 1.2, q > $5{\times}10^{-4}$), where q represents the planet/primary mass ratio. Although this range occupies a small fraction of the entire parameter space of planetary systems, we predict that the chance of resolving the close/wide degeneracy would not be meager considering that the planet detection efficiency is higher for planets with resonant separations (s $\sim$ 1) and heavier masses. We also find that the differences between the perturbation patterns are basically caused by the effect of the planetary caustic. This explains the tendency of the perturbation difference where (1) the difference increases as the planet/primary mass ratio increases and the separation approaches the Einstein radius, (2) the region of major difference is confined within the region around the line connecting the central and the planetary caustics, and (3) a wide (close) planetary system has a more extended central perturbation region toward the (opposite) direction of the planet.

• 멤브레인
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• 제7권2호
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• pp.75-83
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• 1997

직선형(Type 1), 곡선형(Type 2) 및 병렬형 (Type 3) baffle을 설치한 역삼투용 판틀형 모듈을 설계 제작하였으며 NaCl과 sucrose 용액을 각각의 모듈에 공급하여 용액농도 및 운전압력등이 분리특성에 미치는 효과를 측정하고 각 모듈의 특성치를 비교하였다. 운전압력 35bar, 원료 공급유량 6 l/min 이내의 운전조건에서 Type 3가 투과선속 및 배제율 측면에서 가장 우수하였다. NaCl 수용액의 경우, Type 1에 대한 Type 2 및 3의 투과선속 향상율은 운전압력이 증가함에 따라서 감소하였다: 1wt% NaCl 수용액에 대한 Type 3 투과선속 향상율은 10bar 근처에서 약 100%이었으나 35bar에서는 약 10%로 감소하였다. 그러나 sucrose 수용액에 대한 Type 2 및 3의 투과선속 향상율은 농도 및 운전압력에 따라서 크게 변화하였다. 또한 Type 3의 경우, 원료용액의 공급속도 변화에 따른 투과선속의 의존성은 거의 선형적으로 나타났으며 이는 baffle이 존재하지 않는 난류영역에서 보다 큰 값이었다.

• International Journal of Air-Conditioning and Refrigeration
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• 제13권3호
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• pp.145-151
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• 2005

A thermally asymmetric straight rectangular fin is analysed and optimized using the two-dimensional separation of variables method. The optimum heat loss is presented as a function of bottom to top Biot number ratio, fin base length and top Biot number. Decreasing rate of the optimum fin length with the increase of the fin base length is listed. The optimum fin tip length is shown as a function of bottom to top Biot number ratio, fin base length and tip to top Biot number ratio. One of the results shows that the optimum heat loss and the actual optimum fin length decrease while the optimum fin tip length increases as the fin base length increases.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 가을 학술논문 발표대회
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• pp.166-167
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• 2021

The purpose of this study is to evaluate the viscosity and flowability of polymer-cement composites for repairing cracks of RC structures. The viscosity and flowability of the polymer cement composites differed greatly depending on the type of polymer and the polymer cement ratio, and the polymer cement composites could be produced that could repair fine cracks in the RC structure without material separation by adjusting the proper water-cement ratio. In particular, the mixing of high viscosity EVA-modified polymer composites could be adjusted.