전산유체 기법을 이용한 DAF 부상조에서의 수리 특성 고찰

김성훈,유제선,김영미,박희경 대한상하수도학회 2002 상하수도학회지 Vol.16 No.4

Dissolved air flotation is a solid-liquid separation process that uses fine rising bubbles to remove particles in water. DAF is found most effective in treating algae and lower density flocs that are hard to remove in sedimentation process. Some researcher reports the results of an experimental study which examined the flow within the flotation zone of a DAF tank (ONeill at al., 1997). I would be concluded that, in general, the flow within flotation zone is robust and that differences in the performance of individual DAF tanks must be the result of processes occurring within the contact zones of these tank, not as the result of flotation processes. In this research, the authors thought that the efficiency of the DAF process is strongly related to bubble size. It means bubble rising velocity at the air injection nozzle is most important factor of DAF process. However, bubble movement in DAF tank is somewhat complicate, so it is hard to make up conceptual model through simple mass balance as other researchers did (Leppinen at. al., 2000). For the modeling of turbulent 2-phase flow in the tank, the standard k-ε model was used in CFD code because it is widely accepted and the coefficients for the model are well established. This model uses the eddy-viscosity hypothesis for the turbulence. As the result of this study, the authors concluded that bubble size and its rising velocity is very important factor of DAF process and the recycle ratio must be also consider for the flotation zone parameter. Also, For the improved model, relation between turbulent intensity and bubble-particle attachment must be studied.

폴리메틸렌 스페이서로 연결된 Cholesterol-twins의 합성과 이들의 열방성 액정의 특성

마영대,정승용,최정훈 단국대학교 2001 산업기술연구 Vol.2 No.-

Cholesterol-twins connected with central methylene chains (Cho-TW-n, where n, the number of methylene group, is 2, 4, 6, or 8) were prepared, and their thermal and mesomorphic properties were investigated. Among the samples, only Cho-TW-4 exhibited an enantiotropic cholesteric phase and the remainder a monotropic one. The monotropic isotropic-cholesteric and crystallization temperatures of the derivatives decreased irregularly with increasing n up to 6, after which they were virtually constant. All samples, which exhibit reflection colors over the full cholesteric range, formed left-handed helicoidal structures whose optical pitches (λ_ms) decrease with increasing temperature. It was also found that the temperature dependence of λ_m was virtually identical for all compounds. However, the magnitude of λ_m at the same temperature was sensitive to n.

액정질서를 지닌 O-(1,2-dlhydroxypropy) cellulose 가교필름의 열 및 팽윤특성

마영대,김장훈 단국대학교 2000 論文集 Vol.35 No.-

O-(2,3-dihydroxypropyl) cellulose (DHPC) films crosslinked with glyoxal retaining liquid-crystalline order (DHPC-GN) were prepared by casting the liquid-crystalline solution in water, and their thermotropic properties were compared with those of uncrosslinked DHPC films cast from the same solution. The swelling behaviors for DHPC-GN in water and in methanol were also investigated. Both DHPC-GN and the uncrosslinked DHPC films did not show an isotropic phase and the briefringent textures of a mosaiclike texture were maintained up to about 250℃ corresponding to the degradation temperature, showing that the mesophases of both kinds of films are very stable to heat. The weight and volume swelling ratios for DHPC-GN in both solvents decreased with increasing concentration of the crosslinker. However, the swelling ratios in water were greater than those in methanol. DHPC-GN exhibited an anisotropic swelling in both solvents. The degree of anisotropy hardly depended on the solvent and the crosslinker concentration.

LILI-128 암호의 고속화 방안 및 FPGA 구현에 관한 연구

이훈재,박영민,류명춘 경운대학교 산업기술연구소 2001 産業技術硏究論文誌 Vol.3 No.2(A)

Because LILI-128 cipher is a clock-controlled keystream generator, it makes the keystream data degrade in a speed for clock-synchronized hardware logic design: The clock-controlled LFSR_d in LILI-128 cipher requires 1∼4 times higher system clock, that is the reason why the system throughput in data rate is lower if the same clock were selected and that is the structural problem in principle. In this paper, we propose the solution to 4-bit parallel LFSR_d that each register bit has four variable data routines to feedback or shift in LFSR_d. Finally, we simulates the timing of the design on Max+plus Ⅱ of ALTERA Co., implements the logic circuit to the FPGA device (EPF10K20RC240-3), and analyses the stability on throughput to 50 Mbps rate (we choose a higher speed than T3 rate, 45 Mbps and the maximum delay routine in our design is below 20ns) under the 50㎒ system clock. For example, Lucent technologies ASIC can achieve the throughput about 500 Mbps if the maximum delay routine were 1.8㎱ at a 0.13 ㎛ semiconductor.

점성·비점성 유동장에서의 Solution-Adaptive Grid 기법연구

오동훈,임영택,김문상 한국항공대학교 항공우주산업기술연구소 2002 航空宇宙産業技術硏究所 硏究誌 Vol.12 No.-

유동장 해석에 있어 격자가 얼마나 잘 구성되어 있는가는 해의 정확도와 수렴성에 큰 영향을 미친다. 가장 이상적인 격자는 모든 격자점에서 오차가 같은 값으로 분배되어 있어야한다. 그러기 위해서는 오차가 크게 생길만한 충격파나 경계층 등에서는 그만큼 많은 수의 격자가 필요하게 된다. 그러나 이를 미리 예측하고 격자를 만들기가 어렵기 때문에 Solution-adaptive grid 생성방법이 사용된다. 이것은 해의 변화가 심하게 나타나 오차가 큰 곳에 격자를 모아주고 상대적으로 오차가 작은 곳은 격자를 펴줌으로써 같은 수의 격자로 효율적인 격자를 생성하는 방법이다. 본 논문은 Elliptic Type의 격자생성법을 이용한Solution-adaptive Grid 방법과 Parameter 영역을 이용한 Solution-adaptive grid 방법을 이용하여 유동장을 계산하였다. One of the most important things for improving solution accuracy and convergency is grid refinements. Ideal grids make the same error distributions in all grid points. For this reason, grid rearrangement is sometimes necessary in some cases. If the flow fields have shock waves or boundary layers, there may be a lot of errors in those regions. Therefore, we should have more grid points in those regions to overcome this defect. Unfortunately, it is very difficult to estimate the regions which needs more grid points unless we have a final solution. So solution-adaptive grid methods are introduced. It is one of the grid refinement methods for making an effective grid in the flow fields. It makes grids be denser in the larger flow gradient regions and be coarser in smaller regions. Generally, two solution-adaptive grid methods are very popular. One of these is a solution adaptive grid generation method using elliptic type partial differential equation and the other is a solution adaptive grid generation methods using bilinear interpolation between physical domain and parametric domain.

化學蒸着法에 의한 Fe,Ni의 Cr 被覆에 關하여

梁薰永,崔鎭一 연세대학교 산업기술연구소 1979 논문집 Vol.11 No.1

Applications of chromium diffusion coating on nickel and iron were studied by chemical vapour deposition(CVD) process. Effects of various treating conditions such as HCl and H₂flow rate, time, temperatute, and carbon content of iron were investigated with separate two chambers; vapourizing and reaction chambers. Weight increase of iron was not noticeable compared with nickel, since both exchange and reducing reaction were occured in the former. When nickel and iron is charged in reaction chamber simultaneously, nickel is effectively coated, while iron is attacked by HCl generated by reducing reaction. Less weight increase with higher carbon content of iron was resulted, since the active site for adsorption of reactant was decreased with higher carbon steel.

電解 Boronizing에서 Al-B合金 添加의 影響과 耐高溫酸化性에 對하여

양훈영,유병돈,김문철 연세대학교 산업기술연구소 1980 논문집 Vol.12 No.1

To investigate the effect of Al-B alloy addition on the boride thickness, hardness, wear and heat-resistance of the boride layer, an electrolytic boronizing with various amount of Al-B alloy in the electrolyte has been carried out at the current density of 0.5A/ ㎠ and in the temperature range of 800~1,000℃. Also aluminizing was conducted to the boronized specimen in order to find out whether aluminium would penetrate into the boride layer and improve the heat resisting property. From the experimental work, following results were obtained. 1) Increased thickness of boride layer and hardness were resulted with increased addition of Al-B alloy. Excess addition of the alloy, however, inhibited the boronizing because of the increasing viscosity of electrolyte. 2) Thickness of the boride layer increased rapidly with increasing temperature which improves the fluidity of electrolyte and diffusion rate. 3) Wear resistance improved markedly by boronizing and better result obtained by Al-B alloy addition. 4) Aluminium diffused into the boride layer by aluminizing of the boronized specimen, showing excellent heat resistivity even at 1,000℃.In this case,however, decreasing wear resistance was inevitable.

Fe₃O ₄-Al₂O ₃-CaO系 鑛球의 還元에 關한 硏究

양훈영,이승원,김진호,은일상 연세대학교 산업기술연구소 1975 논문집 Vol.6 No.1

Reduction of coke mixed magnetite ore pellets containing alumina and/or lime has been carried out in a fixed bed with coke powder in the temperature range of 1,100-1,250℃. Degree of metallization of the reduced pellets was obtained from the chemical analysis, and volume change of the reduced pellets was evaluated by measuring pellet diameter before and after reduction. Phase change during the reduction was also investigated by microscopic observation. The results obtained are summurized as follows. (1) As the Al₂O ₃content increases, degree of metallization of the ore pellets decreases and shrinkage of the reduced pellets also decreases. (2) Addition of 5% CaO to the 5% Al₂O ₃ pellets improves the degree of metallization and increases shrinkage of the reduced pellets, especially within the temperature range of 1,200-1,250℃. In the case of 10% CaO addition to the same pellets, however, both degree of metallization and shrinkage decrease. (3) CaO addition to the 10% Al₂O ₃ pellets showed the similar effect to that of 5% Al₂O ₃ pellets on the degree of metallization and shrinkage, showing no conspicuous effect of lime addition. (4) While Al₂O ₃ in the pellets is inhibitive to the reducibility as well as agglomeration, CaO is promotive to the above properties.

남녀 유아의 체격과 체력과의 상관 : 유아스포츠단 6세를 중심으로

이정우,김영훈 한국유아체육학회 2003 한국유아체육학회지 Vol.4 No.-

본 연구는 경남 스포츠 아카테미 유아스포츠단에 입단한 6세(만 4년 4개월 ∼ 5년 : 3월 기준) 남녀를 대상으로, 체격에서 2개 항목과 체력에서 5개 종목을 측정하여 체격과 체력의 성적을 남녀별로 분석하고 상관관계를 알아 본 결과는 다음과 같다. 1. 신장과 체력과의 상관관계에서 남자는 3월에 25M 달리기(- .294)에서 약간 상관이 있었으며, 11월에 25M 달리기( .377), 윗몸 일으키기( .309)에서 약간 상관이 있었다. 여자는 3월에 25M 달리기(- .625) 한발 중심잡기(- .531), 제자리멀리뛰기( .684), V자 앉기(- .480)에서 확실한 상관이 있었으며, 11월에 25M 달리기(- .412), V앉기(- .313)에서 약간 상관이 있었다. 2. 체중과 체력과의 상관관계에서 남자는 3월에 25M 달리기(- .301), 윗몸 일으키기(. 312), V자 앉기( .331)에서 약간 상관이 있었으며, 11월에 한발 중심잡기( .306)에서 약간 상관이 있었다. 여자는 3월에 25M 달리기(- .491), 한발 중심잡기( .434), 제자리멀리뛰기( .472), V자 앉기(- .452)에서 확실한 상관이 있었으며, 11월에 한발 중심잡기(- .409), 윗몸 일으키기(- .474) V자 앉기(- .621)에서 확실한 상관이 있었다. Selecting, at my option, 44 male children and 33 female children at Kyung-nam Sports Academy kindergarten sports club in Chang-won city. I conducted a survey into correlation between 2 items of physique and 5 items of physical strength. And the results are as follow : 1. On height of physique male children' height show 3.33cm increase as average 101.70cm in March to average 111.03mn in November, whereas female children' height show 4.43cm increase as average 103.70cm in March to average 108.13cm. It means that female's growth is faster than male's one. 2. On weight of physique male children' weight show 1.73kg increase as average 18.68kg in March to average 20.41 in November. Whereas female children' weight show 1.73kg increase as average 17.91kg in March to average 19.64kg in November. 3. On physical strength, male children made an excellent 25m run, sit-ups, standing broad jump, V-form sitting, but female children made an excellent foot balance. 4. On correlation between height and physical strength for male children 25m run(.294) in March and 25m run(.377), sit-ups(.309) in November have a little correlation. For female children, in March 25m run(-.626), foot balance(-.531), standing long jump(.684), V form-sit(-.480) have a distinctive correlation whereas in November 25m run(-.412) and V form-sit (-.313) have a little correlation. 5. On correlation between weight and physical strength for male children 25m run(-.301), sit-ups(.312), V form-sit(.331) in March have a little correlation and foot balance(.306) in November have a little correlation. For female children, 25m run(-.491), foot balance(.434), standing long jump(.472), V form-sit(-.452) in March have a distinctive correlation, also foot balance(-.409), sit-ups(.47), V4 form-sit (-.621) in November have a little correlation.

알루미나 적층복합체에서 Fe_2O_3 첨가가 알루미나의 입자배향에 미치는 영향

송준호,박훈,정용빈,박상업 국립7개대학공동논문집간행위원회 2001 공업기술연구 Vol.1 No.-

Alumina laminate composites with alternating layers of textured and untextured were fabricated by continuous tape casting and pressureless sintering with the addition of Fe_2O_3 known to be influencing on the abnormal grain growth of alumina. Alumina grains in textured layer were aligned with (006) and (1010) plane, and the addition of Fe_2O_3 was influencing on the abnormal grain growth in untextured layer rather than texutured layer. The efffective control of crack propagation was possible through the grain orientation from the observation of crack path between textured and untextured layer.