• 펄프종이기술
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• 제30권3호
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• pp.74-83
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• 1998

The phenomenon of decrease in sizing efficiency when the stock temperature is increased is well recognized as summer sizing, and this is believed to be caused by uneven distribution of sizing agents on paper surface most often incurred by coagulation of sizing agents. When unevenly sized paper is used as coating base stock, nonuniform consolidation of the coating layer may result, which, in turn, causes uneven distribution of binder on coating surface. This causes nonuniform ink absorption to produce print mottle. In this study the effects of simple or polymeric electrolytes, storage temperature and time on the coagulation of cationic dispersed rosin size were investigated using a turbidity measurement method which was verified to correlate well with the particle size of rosin emulsion or its coagulates. Handsheets sized with rosin dispersions coagulated under various conditions were prepared and their sizing degree and coated paper properties including gloss and ink density were examined. The relationship between the sizing nonuniformity of coated papers and its ink absorption property was evaluated. Turbidity of rosin emulsion increased as the storage temperature and time were increased. Addition of simple or polymeric electrolytes caused reduction in $zeta$ -potential of the rosin dispersion and accelerated the coagulation tendency substantially. Reversion of the $zeta$ -potential of rosin dispersion, however, did not occur when coagulation was induced with simple electrolytes. On the other hand, addition of an anionic polyelectrolyte reversed the $zeta$ -potential of the flocculated rosin dispersion. This indicated that electrical double layer compaction and bridging flocculation were coagulation mechanisms for simple and polymeric electrolytes, respectively. Sizing degree decreased as coagulation of rosin was increased. Paper gloss, ink gloss and ink density were increased when sizing degree of base stock was increased most probably due to prevention of base paper swelling and increased binder migration to coating surface. This suggested that uneven printing ink density occurred when uneven sizing development was induced by coagulation of rosin particles.

• Archives of Pharmacal Research
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• 제9권1호
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• pp.39-43
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• 1986

Bovine serum albumin microspheres containing cytarabine were prepared using cross-linking agent, formaldehyde. The shape and the size distribution of them were observed. The shape of them was spherical and the susrface was compact and smooth. The size distribution of them was affected by dispersion forces during emulsfication. The release of cytarabine from albumin microspheres was dependent upon cross-linking time, amount of cross-linking agent and drug/albumin ratio. However, the difference of drug release by the dispersion forces was not great. After release test, the shape of albumin microspheres was nonspherical and the albumin matrix seemed to be a little relaxed. The degradation tests of albumin microspheres by the proteolytic enzyme showed that albumin microspheres were progressively digested according to the cross-linking degree.

• 반도체디스플레이기술학회지
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• 제12권3호
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• pp.1-6
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• 2013

In many technical fields including electronics and display manufacturing processes, properties of coating liquids could be greatly enhanced by adding nanopowders and it requires efficient mixing techniques to achieve uniform dispersion of nanoparticles in liquids. This paper presents the three-dimensional CFD simulations on the flowfields of a highly viscous liquid in the large scale industrial mixer of impeller type. The effects of several important design and operation parameters such as impeller geometry, rotational speed, and degree of liquid viscosity are investigated to appreciate the mixing performance by examining the computational results for flow pattern of rotationally stirred liquid of high viscosity in the mixer.

• Korean Journal of Hydrosciences
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• 제5권
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• pp.85-97
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• 1994

A hybrid finite difference method for the longitudinal dispersion equation, which is based on combining the Holly-Preissmann scheme with fifth-degree Hermite interpolating polynomial and the generalized Crank-Nicholson scheme, is described and comparatively evaluated with other characteristics-based numerical methods. Longitudinal dispersion of an instantaneously-loaded pollutant source is simulated, and computational results are compared with the exact solution. The present method is free from wiggles regardless of the Courant number, and exactly reproduces the location of the peak concentration. Overall accuracy of the computation increases for smaller value of the weighting factor, $\theta$of the model. Larger values of $\theta$ overestimates the peak concentration. Smaller Courant number yields better accuracy, in general, but the sensitivity is very low, especially when the value of $\theta$ is small. From comparisons with the hybrid method using cubic interpolating polynomial and with splitoperator methods, the present method shows the best performance in reproducing the exact solution as the advection becomes more dominant.

• 반도체디스플레이기술학회지
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• 제22권4호
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• pp.1-6
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• 2023

In CO₂ laser surface machining of plastic films in modern display manufacturing, scattering of fume particles could be a major source of well-recognized film surface contamination. This computational fluid dynamics research investigates the suction air flow patterns over a film surface as well as the dispersion of micron-sized fume particles with low-Reynolds number particle drag model. The numerical results show the recirculatory flow patterns near laser machining point on film surface and also over the surface of vertical suction slot, which may hinder the efficient removal of fume particles from film surface. The dispersion characteristics of fume particles with various particle size have been tested systematically under different levels of suction flow intensity. It is found that suction removal efficiency of fume particles heavily depends on the particle size in highly nonlinear manners and a higher degree of suction does not always results in more efficient particle removal.

• 한국전자파학회논문지
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• 제14권7호
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• pp.741-749
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• 2003

광섬유의 색 분산과 자기 위상 변조 외에 상호 위상 변조 효과에 의해 왜곡된 WDM 채널 신호가 MSSI (Mid-Span Spectral Inversion) 기법을 통해 보상되는 정도를 다양한 광섬유 분산 계수를 고려하여 분석해 보았다. 본 연구에서 고려된 시스템은 120 Gbps (3$\times$40 Gbps) 강도 변조 직접 검파 방식의 WDM 시스템이다. 또한 전체 전송로의 중간에 비선형 매질로 HNL-DSF(Highly nonlinear dispersion shifted fiber)를 갖는 광 위상 공액기를 두고, 광 위상 공액기를 중심으로 첫 번째 전송 구간에서의 평균 강도와 두 번째 전송 구간에서의 평균 강도를 같게 하는 PAIA(Path Averaged Intensity Approximation) 방식 의 MSSI 기법을 채택한 시스템이다. 채널별 보상 특성의 분석은 1 dB 기준 눈 열림 패널티(Eye Opening Penalty)를 이용했다. 색 분산과 비선형 효과에 의한 채널 신호 왜곡이 유도될 수 있는 장거리 WDM 시스템에 MSSI 기법을 적용하면 전송 거리와 전송 품질을 단일 채널 전송 이상으로 개선시킬 수 있고, 상호 위상 변조에 의한 왜곡의 보상 측면에서 MSSI 기법은 광섬유의 분산 계수가 비교적 큰 WDM 시스템에 더욱 유효하다는 것을 확인할 수 있었다.

• 폴리머
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• 제27권1호
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• pp.75-83
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• 2003

다이시아네이트-점토 나노복합재료(dicyantate-clay nanocomposite)를 개질제의 종류와 cation exchange capacity (CEC)의 차이에 따라 용융 in-situ법에 의하여 제조하였고 이들의 물성과 분산을 측정하였다. 다양한 층간 삽입물을 함유하여 다양한 층간거리와 적층밀도를 갖는 montmorillonite (MMT)에 따라 다양한 구조의 나노복합재가 제조되었다. 사용된 다이시아네이트와 점토는 각각의 친화성에 따라 실리케이트 내부로의 삽입정도가 달라졌다. 다이시아네이트-점토 나노복합재료의 분산은 CEC와 개질제의 지방족 사슬길이에 의존하였으며 더 낮은 CEC를 가지고 지방족 사슬의 길이가 짧은 것이 좀 더 분산된 구조를 가지는 것으로 측정되었다. 또한 사용된 개질제에 고분자와의 반응성이 부여되면 층간 삽입이 더욱 용이한 것으로 나타났다. 다이시아네이트 나노복합재료의 전단탄성율은 반응성을 가지며 박리된 구조를 가지는 경우에 더 향상된 물성을 가지는 것으로 나타났다.

• Advances in nano research
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• 제12권1호
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• pp.1-23
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• 2022

To date, nondestructive tests (NDT) applications and advances in detecting the dispersion and defections of the nano concrete (NC) materials fields are very limited. The current paper provides a review of the dispersion efficiency of nanomaterials in cement-based materials and how NDT can be efficiently used in detecting and visualizing the defections and dispersions of NC. The review identifies the characteristics of different types of nanoparticles used in NC. Nanomaterials influences on concrete characteristics and their dispersion degree are presented and discussed. The main aim of this article is to present and compare the common NDT that can be used for detecting and visualizing the defections and dispersions of different kinds of nanomaterials utilized in NC. The different microscopy and X-ray methods are explicitly reviewed and compared. Based on the collected data, it can be concluded that the fully detecting and visualizing of NC defections and dispersions have not been fully discovered and that needs further investigations. So, the distinction of this paper lies in defining NDT that can be employed for detecting and/or visualizing NC defections and dispersions.

• 폴리머
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• 제31권6호
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• pp.543-549
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• 2007

폴리우레탄의 우수한 기계적 물성에 전기 전도성을 가질 수 있도록 은 입자와의 복합체를 제조하였다. 균일하고 우수한 물성을 나타내기 위해서는 고른 분산성이 중요하게 되는데 폴리우레탄의 hard segment와 soft segment를 바꿔가며 가장 열적 안정성이 뛰어나고 은 입자를 균일하게 분산시킬 수 있는 폴리우레탄의 구조를 파악하였다. 열적 안정성은 방향족 증가와 사슬의 hard segment 비율 증가에 따라 높아짐을 알 수 있었고 분산성에서는 hard segment의 방향족이 포함된 것이 지방족보다 우수한 분산성을 가졌다. 또한 soft segment에 따라서는 낮은 분자량에서 사슬의 motility로 인해 좋은 분산성을 나타내었다. 하지만 전기 전도성에서는 고른 분산성보다도 입자간의 inter-connection을 이룰 수 있는 형태가 가장 낮은 저항값을 나타내었으며. NDI와 낮은 분자량의 PEG로 이루처진 복합체가 가장 좋은 물성을 나타내었다.

• 공업화학
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• 제18권1호
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• pp.64-70
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• 2007

분산성이 우수한 carbon-slurry 연료의 제조와 특성 분석을 하였다. Carbon-slurry 연료는 액체연료(Jet A-1)와 탄소 입자 그리고 적당한 첨가제를 혼합하여 얻었다. Carbon-slurry 연료의 분산성은 교반 온도, 탄소 입자의 특성 그리고 첨가제의 양과 종류 등에 따라서 달라진다. 특히 첨가제의 종류가 slurry 연료의 안정성에 가장 중요하였다. 다양한 음이온성, 양이온성, 비이온성 형태의 첨가제를 사용하여 carbon-slurry 연료의 분산성을 분석하였고, 이 결과 나트륨 염의 형태를 가진 음이온성 첨가제를 사용하였을 경우 carbon-slurry 연료의 분산성이 가장 우수하였음을 확인하였다. Carbon-slurry 연료의 분산성은 빛이 투과되는 광도 값을 측정하여 분석하였다.