• 한국연소학회:학술대회논문집
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• 한국연소학회 2001년도 제22회 KOSCI SYMPOSIUM 논문집
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• pp.127-132
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• 2001

A numerical study was carried out to investigate the combustion phenomena in a model Scramjet engine, which had been experimentally studied in the University of Tokyo using a high-enthalpy supersonic wind tunnel. The main airflow was 2.0 in Mach number and the total temperature of hot flow was 1800K. Equivalence ratio was set to be rather higher value of 0.26 than that of experiment to investigate the effect of strong precombustion shock. The results showed that self-ignition occurred at the rear bottom wall of the combustor and combined with the shear layer flame between fuel jet and main airflow. Then, precombustion shock was generated at the step location and reversely enhanced the mixing and combustion process behind the shock. Due to the high equivalence ratio, the precombustion shock moved upstream of the step compared with that of experiment.

• 펄프종이기술
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• 제36권2호
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• pp.1-9
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• 2004

Structure and strengths of paper have been studied by analyzing fibers characteristics depending on refining methods. In those studies stock preparation aspect of softwood and hardwood fibers mixing and fibers characteristics was focused for paper quality improvement. In this study drainage of fibers were analyzed to improve the production efficiency and paper product's quality. Fiber properties by one and two-step refining processes were compared. By applying two-step refining processes($2.8kg_f$ and $5.6kg_f$ of refining load), refining efficiency, drainage, and strengths could be improved at specific extent of refining.

• 상하수도학회지
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• 제20권5호
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• pp.691-700
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• 2006

This study conducted to optimize the design and operation of orifice typed distribution channels which were generally constructed to link the rapid mixing process and flocculation/sedimentation basin. To accomplish the goal of this study, programming step method using FORTRAN 90, was applied it to simulate the performance of existing distribution channel in the selected S DWTP (Drinking Water Treatment Plant). The proposed step method program was validated in terms of the feasibility with comparison between the measurement and prediction value in each orifice. From the evaluation results of the current conditions with the design and operation, it was revealed that the existing gradient of the tapered channel is not appropriate. Also, we suggested that in the case of the inlet width being 3.5m, reducing the downstream width by about 0.5m would make more equitable distribution flow in the channel. Consequently, dealing with various conditions of the design and operation with distribution channel, we could conclude that for the parallel typed channel, as the width is wider and the diameter of orifice is smaller, the more equitable distribution occur. In addition, the inlet flowrate and the number of orifice can affect the flow velocity in the channel.

• 한국의류산업학회지
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• 제13권6호
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• pp.972-982
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• 2011

The purpose of this study is to improve the method of color developing with alkali solution as a promotor of color developing for feasible use. Cotton fabric was dyed with persimmon extract ranged with 0~3% alkali component with 5 types of strong to mild alkali solution. Heat treatment for color developing was applied to fabric dyed with persimmon extract and alkali mixing solution. Tests were carried out to analyze the change of surface color, ${\Delta},Ea^*b^*$, and water repellent of the dyed cotton fabric. The alkali mixing sample showed higher ${\Delta},Ea^*b^*$ value than control one without alkali mixing on the base of dyed fabric due to high color developing by alkali in the initial step of dyeing process. As alkali concentration increased, deeper dark color appeared on the fabric. The fabric color was changed to more dark in the application of sodium hydroxide, sodium carbonate, potassium carbonate in the initial step of dyeing process but color was not changed by increased heating time. However, the fabric showed a slight dark color with sodium acetate and more color change than that of the fabric dyed with persimmon extract without alkali. Therefore, sodium acetate seemed to a suitable promotor for color developing in persimmon extract dyeing. Property of water repellent was showed after color developing by heating with low concentration of alkali treatment.

• 한국추진공학회지
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• 제11권5호
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• pp.51-59
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• 2007

충돌형 산화제 주입기를 사용한 end-burning 하이브리드 연소기의 혼합특성을 선행 연구되었던 접선형 주입기와 비교 분석하였다. 충돌형 주입기를 사용한 연소유동장이 접선형 주입기에 비해 축방향 및 반경방향으로 월등한 혼합특성과 연소효율을 보였다. 충돌효과와 선회효과를 동시에 발생시키는 파생형 주입기를 사용한 결과, 보다 넓은 연소실 영역에서 혼합효율이 증대되었으며 연료 표면의 연소 균일도가 향상될 수 있음을 확인하였다. 충돌로 인한 축방향 운동량과 선회유동이 체류시간과 난류강도를 증가시켜 혼합을 촉진시키는 주요 인자로 판단되었으나 연소실의 기하학적 형상변화를 꾀한 step의 유무는 난류혼합 증진에 있어서 중요한 변수가 아님을 확인할 수 있었다.

• 한국분말재료학회지
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• 제25권6호
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• pp.487-493
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• 2018

The impact of different mixing methods and sintering temperatures on the microstructure and piezoelectric properties of PZNN-PZT ceramics is investigated. To improve the sinterability and piezoelectric properties of these ceramics, the composition of $0.13Pb((Zn_{0.8}Ni_{0.2})_{1/3}Nb_{2/3})O_3-0.87Pb(Zr_{0.5}Ti_{0.5})O_3$ (PZNN-PZT) containing a Pb-based relaxor component is selected. Two methods are used to create the powder for the PZNN-PZT ceramics. The first involves blending all source powders at once, followed by calcination. The second involves the preferential creation of columbite as a precursor, by reacting NiO with $Nb_2O_5$ powder. Subsequently, PZNN-PZT powder can be prepared by mixing the columbite powder, PbO, and other components, followed by an additional calcination step. All the PZNN-PZT powder samples in this study show a nearly-pure perovskite phase. High-density PZNN-PZT ceramics can be fabricated using powders prepared by a two-step calcination process, with the addition of 0.3 wt% MnO2 at even relatively low sintering temperatures from $800^{\circ}C$ to $1000^{\circ}C$. The grain size of the ceramics at sintering temperatures above $900^{\circ}C$ is increased to approximately $3{\mu}m$. The optimized PZNN-PZT piezoelectric ceramics show a piezoelectric constant ($d_{33}$) of 360 pC/N, an electromechanical coupling factor ($k_p$) of 0.61, and a quality factor ($Q_m$) of 275.

• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.2179-2188
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• 2015

Recently, many researches have been done to solve the challenging problem of Blind Source Separation (BSS) problems in the underdetermined cases, and the “Two-step” method is widely used, which estimates the mixing matrix first and then extracts the sources. To estimate the mixing matrix, conventional algorithms such as Single-Source-Points (SSPs) detection only exploits the sparsity of original signals. This paper proposes a new underdetermined mixing matrix estimation method for time-delayed mixtures based on the receiver prior exploitation. The prior information is extracted from the specific structure of the complex-valued mixing matrix, which is used to derive a special criterion to determine the SSPs. Moreover, after selecting the SSPs, Agglomerative Hierarchical Clustering (AHC) is used to automaticly cluster, suppress, and estimate all the elements of mixing matrix. Finally, a convex-model based subspace method is applied for signal separation. Simulation results show that the proposed algorithm can estimate the mixing matrix and extract the original source signals with higher accuracy especially in low SNR environments, and does not need the number of sources before hand, which is more reliable in the real non-cooperative environment.

• 자원리싸이클링
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• 제24권6호
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• pp.61-68
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• 2015

본 연구에서는 천연수경성석회(NHL) 모르타르에 바잘트 섬유를 혼합하여 섬유혼합에 따른 강도특성을 연구하고자 하였다. 건식 및 습식 4가지로하여 혼합방법에 따른 물리적 특성발현을 확인하였으며, 압축강도 및 휨강도 등을 고려하여 강도 특성이 최대로 발현되는 혼합방법 한 가지를 선택하였다. 실험결과 물성 발현은 습식혼합보다 건식혼합에서 더 우수하였으며, 건식혼합 중 바인더(NHL)와 섬유를 pre-mixing 한 후 물과 골재를 순차적으로 혼합하여 섬유의 분산력을 높여주는 혼합방법을 선택하였다. 이후 섬유 길이에 따른 물리적 특성 발현성을 확인하였다. 바잘트 섬유 길이에 따른 압축강도 및 휨강도 측정결과, Plain 샘플 대비 섬유 혼합에 따라 압축강도는 감소하는 경향성을 보였으며, 휨강도는 증가하는 경향을 나타내었다. 또한 섬유를 혼합한 샘플 중에서 섬유길이 6 mm일 때 가장 우수한 강도 특성을 나타내었다.

• 한국세라믹학회지
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• 제40권2호
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• pp.132-138
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• 2003

출발물질의 종류와 몰비 혼합 방법, 숙성, 결정화 온도와 결정화 시간 등 제올라이트 입자를 합성하는 조건이 FAU 형 제올라이트의 입자크기에 미치는 영향을 연구하였다. 동일한 출발물질이라도 혼합 경로에 따라 생성물의 결정상이 달랐다. 일반적으로 숙성과정을 거친 경우, 특히 숙성온도가 낮은 쪽이 입자 크기가 작았다. 2단계의 혼합겔 제조 방법을 거치는 경우 결정화 기간은 크게 단축되고 입자 크기도 작아졌으나. 1단계에서 제조된 2종의 혼합겔을 모두 숙성하지 않는 경우에는 결정화 시간은 단축되지만, 입자크기는 작아지지 않았다. 액상규산나트륨과 알루민산나트륨, 수산화나트륨을 출발물질로 하여. 저농도와 고농도의 혼합겔을 1차 제조하고, 이 혼합겔을 각각 숙성하고 다시 혼합하여 숙성하는 방법으로 결정화 시간을 단축하고 평균입경 0.4$\mu$m. 비표면적 838 $m^2$/g의 우수한 특성을 가지는 FAU혈 제올라이트를 합성하였다.

• 한국항해항만학회지
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• 제28권10호
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• pp.947-953
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• 2004

연안에서 대규모 항만개발이 단계적으로 진행되고 항만 부근역에서의 인구가 더욱 더 증가되면서 항만의 오폐수 및 도시하수의 처리방안에 대한 문제가 관심을 끌고 있다. 오폐수를 1차 또는 2차 처리한 후 수중 방류관을 통해 해안이나 심해 또는 그 중간지점에서 방류하는데, 오폐수가 방류되면 주변 해수를 연행하여 플룸, 제트 또는 부양성 제트의 형태로 해수면까지 상승하면서 크게 희석된다. 본 연구는 효율적인 해양방류시스템의 설계시 간과되어온 계절적, 공간적인 해수온도의 변화에 따른 플룸의 거동 및 희석 특성에의 영향을 다루고자 한다. 방류수의 수온 뿐 아니라 방류지점의 계절적 주변수의 온도변화를 고려하여 CORMIX-GI을 적용하였다. 결과를 방류수의 혼합역 특성을 평가하는데 사용시에는 주의하여야 한다. 이 연구가 방류관의 효율적 운영, 바람직한 방류관의 설계, 수질보호, 발전소의 온배수 방류문제 등에 도움이 되기를 바란다.