• 한국산림과학회지
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• 제77권3호
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• pp.294-302
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• 1988

본(本) 실험(實驗)은 낙엽송(落葉松)(Larix leptolepsis) 수피(樹皮)로부터 추출(抽出)한 수피추출물(樹皮抽出物)의 특성(特性)을 조사(調査)하고 그들 추출물(抽出物)의 접착제화(接着劑化)의 가능성(可能性)을 평가(評價)하기 위해 실행되었다. 수율(收率)과 반응도(反應度)의 측정(測定)을 통해 온도(溫度) 및 시간(時間)의 영향(影響)과 탄산화(炭酸化) 및 설폰화(化)의 효과(效果)를 조사하였다. 목재접착제(木材接着劑)로의 적용(適用) 가능성(可能性)을 구명하기 위해서는 33% 농도(濃度)에서 점도(粘度)와 겔화시간(化時間)을 측정(測定)하였다. 그 결과(結果)는 다음과 같다. 1. 수율(收率)과 반응도(反應度)가 모두 높은 $80^{\circ}C$에서 120분(分)의 추출(抽出)이 적정온도(適正溫度) 및 시간(時問)이었다. 2. 탄산화(炭酸化)는 1% $Na_2CO_3$에서 설폰화(化)는 1% $Na_2SO_3$ : $NaHSO_3$와 0.25% $Na_2SO_3$에서 가장 큰 효과(效果)를 얻었으며 이들중 0.25% $Na_2SO_3$에 의한 설폰화(化)가 수율(收率)과 반응도(反應度)를 가장 크게 증가시켰다. 3. 온수추출액(溫水抽出液)의 수율(收率)은 17.2%이며 1% NaOH와 5% NaOH 추출액(抽出液)의 수율(收率)은 각각(各各) 38.6%와 44.6%이었다. 4. 온수추출액(溫水抽出液)의 반응도(反應度)는 68.8%로 가장 높았으며 1% NaOH와 5% NaOH 추출액(抽出液)의반응도(反應度)는 각각(各各) 49.3%와 25.8%이었다. 5. 각(各) 추출액(抽出液)은 33% 농도(濃度)에서 점도변화(粘度變化)가 매우 심했다. 특히 1% NaOH 추출액(抽出液)은 점도(粘度)가 매우 높았으며 5% NaOH 추출액(抽出液)은 오히려 점도(粘度)가 낮았다. 6. 추출액(抽出液)의 겔화시간(化時間)은 pH 7-10에서 가장 낮은 값을 나타냈으며 pH 4에서 가장 높은 값을 나타냈다. 파라포름알데히드의 이용(利用)은 37% 포름알데히드보다 겔화시간(化時間)을 더 연장시켜 주었다. 7. 온수추출(溫水抽出)의 설폰화(化)와 1% NaOH 추출(抽出)의 설폰화(化)를 제외(除外)한 다른 추출방법(抽出方法)은 높은 점도(粘度)(1% NaOH 추출(抽出))와 비경화성(比硬化性)(5% NaOH 추출(抽出), 5% NaOH 추출(抽出)의 설폰화(化)) 때문에 부적합한 것으로 밝혀졌다. 8. 접착제로(接着劑)로의 이용(利用)이 적합한 것으로 나타난 추출액(抽出液) 중 온수추출(溫水抽出)과 온수추출(溫水抽出)의 설폰화(化)는 반응도(反應度)가 뛰어난 반면 1% NaOH 추출(抽出)의 설폰화(化)는 비율면(比率面)에서 유리(有利)한 것으로 나타났다.

• 한국주조공학회지
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• 제20권5호
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• pp.290-299
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• 2000

A three-dimensional model was developed in order to simulate heat and fluid flow of a continuous casting billet. The model was coded with the general-purpose CFD program FIDAP, using the finite element method. The present model consists of 2 individual calculation schemes, named model 1 and model 2. Mold region only was calculated to check the pouring stream through submerged nozzle with model 1. Entire region, which consists of mold, secondary cooling, radiation cooling was calculated to predict crater end position, temperature profile and solid shell profile(model 2). Standard $k-{\bullet}\hat{A}$ turbulence model has been applied to simulate the turbulent flow induced by submerged nozzle. Enthalpy method was adopted for the latent heat of solidification. Fluid flow in mushy zone was treated using variable viscosity approach. The more casting speed and superheat increased, the more metallurgical length increased. The shell thickness at the mold exit is proved to be mainly controlled by superheat by the present simulation. It may be concluded that the present model can be successfully applied far the prediction of heat and fluid flow behavior in the continuous casting process.

• 한국항공우주학회지
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• 제37권5호
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• pp.450-456
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• 2009

수동형 진동제어 방식과 같이 시스템이 안정되며, 수동형에 비해 높은 제진 효과가 기대되는 반능동 진동제어 방식은 시스템의 안정화가 요구되는 우주구조물의 제진방법에 유효한 진동제어 방식중 하나이다. 본 논문에서는 유연우주트러스구조물의 진동제어를 위해 고안된 반능동 댐퍼내 작동유체의 질량을 모델링에 고려했을 경우의 제진특성을 분석하였고 댐퍼내 작동유체의 점성이 부족감쇠를 유지 할 경우, 작동유체 질량 적용에 따른 반능동 댐퍼의 제진효과를 확인하였으며 이를 토대로 반능동 댐퍼의 성능향상을 위한 설계방법을 제시하였다.

• 한국전산유체공학회지
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• 제20권2호
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• pp.46-51
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• 2015

In this paper, we have developed numerical model for particulated flow through narrow slit using Eulerian-Granular method. Commercial software (FLUENT) was utilized as simulation tool and main focus was to identify the effect from various numerical options for modeling of solid particles as continuos phase in granular flow. Gidaspow model was chosen as basic model for solid viscosity and drag model. And lun-et-al model was used as solid pressure and radial distribution model, respectively. Several other model options in FLUENT were tested considering the cross related effect. Mass flow rate of the particulate through the slit was measured to compare. Due to the high volume density of the stacked particulates above the slit, effect from various numerical options were not significant. The numerical results from basic model were also compared with experimental results and showed very good agreement. The effects from the characteristics of particles such as diameter, angle of internal friction, and collision coefficient were also analyzed for future design of velocity resistance layer in solar thermal absorber. Angle of internal friction was found to be the dominat variable for the particle mass flow rate considerably. More defined 3D model along with energy equation for complete solar thermal absorber design is currently underway.

• 한국추진공학회지
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• 제15권5호
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• pp.96-106
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• 2011

젤 추진제는 젤 추진 시스템에서 액체 추진 시스템과 같이 제어의 용이성, 저장성, 취급성, 비누설성 등과 같은 장점을 포함한다. 또한, 젤 추진제는 액체 추진제와 비교했을 때 보다 높은 발열량 특성을 나타내며, 금속 입자(알루미늄, 보론)의 첨가로 높은 비추력을 얻을 수 있다. 미립화 특성과 관련하여 젤 추진제는 젤화제의 다양한 점도와 금속 입자의 첨가 정도에 따라 저조한 미립화 특성을 나타낸다. 젤 추진제의 미립화 특성 향상과 연소 효율을 증대 시키기 위해 젤화제의 함유량 변화와 금속 입자의 첨가 정도에 따른 젤 추진제 제조 기술을 바탕으로 동적 분무 특성, 연소 특성 연구를 수행하고 있으며, 이에 대한 연구동향을 소개한다.

• 한국식품조리과학회지
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• 제25권2호
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• pp.234-242
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• 2009

This study was performed to find the optimum ratio of ingredients for the manufacture of kiwifruit jam. The experiment was designed according to the D-optimal design of RSM (response surface methodology), which included 18 experimental points with 4 replicates for three independent variables (sugar $35{\sim}60%$, pectin $0.1{\sim}1.0.%$, kiwifruit paste $0.37{\sim}0.90%$). The compositional and functional properties of the prepared products were measured, and these values were applied to mathematical models. A canonical form and trace plot showed the influence of each variable on the quality attributes of the final product mixture. By use of the F-test, viscosity, color values (L, a, b), and sensory characteristics (color) were expressed by a linear model, while the L color value and select sensory characteristics (smell, taste, overall acceptance) were also expressed by a quadratic model. The optimum formulations by the numerical and graphical methods, were similar, and with the numerical method it presented as: sugar, pectin, and barley sproutling powder at 49.7%, 0.5%, and 0.6%, respectively. The above results demonstrate the feasibility of preparing kiwifruit jam added with barley sproutling powder, and therefore, the commercialization of a kiwifruit jam marketed as a functional food is deemed possible.

• 한국전기전자재료학회논문지
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• 제24권2호
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• pp.147-151
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• 2011

We were analyzed the piezoelectric characteristic for electronics printing to inkjet printing system. These applications were possible use to Actuator, MEMS, FPCB, RFID, Solar cell and LCD color filter etc. Piezoelectric print head is firing from ink droplet control consideration ink viscosity properties. At this time, micro pattern for PCB metal printing was possible by droplet control of piezoelectric driving. These driving characteristics are variable voltage pulse waveform. We are used the piezoelectric analysis software of Finite Element Method (FEM), Piezoelectric design parameters are acquired from piezoelectric analysis, and measurement of piezoelectric. It designed for piezoelectric head to possible electric print pattern of inkjet printing system. For this validity we were established through in comparison with simulation and measurement. Designed piezoelectric specification obtained voltage 98V, firing frequency 10 kHz, resolution 360dpi, drop volume 20pl, nozzle number 256, and nozzle pitch 0.33 mm.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.748-752
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• 2004

Fluid dynamic bearings (FDBs) have been replacing ball bearings of the HDD spindle motor very rapidly. But there are several demerits of HDB, such as high friction torque, variable viscosity of the fluid lubricant depending on operating temperature, low stiffness, and etc. Eccentricity is one of the major parameters which affects the static and dynamic characteristics. As the static eccentricity is larger, the stiffness and the damping coefficients become bigger. But friction torque is relatively unaffected by the static eccentricity. This research proposes a new type of journal bearing with asymmetric journal grooves which results in better dynamic characteristics. The static and dynamic characteristics of the new journal bearing are investigated by solving the Reynolds' equation with FEM, and the transient analysis is performed to predict the dynamic behavior of rotor by solving the equations of motion of a HDD spindle system with Runge-Kutta method. The result shows that the proposed Journal bearings have much bigger stiffness and damping coefficients compared with the conventional symmetric ones. And consequently, it has smaller whirl radius and tilting angle.

• 한국소음진동공학회논문집
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• 제12권9호
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• pp.717-724
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• 2002

In this study, a numerical analysis for the piston secondary dynamics of small refrigeration reciprocating compressors is performed. In general, the length of cylinder in this class of compressors is shortened to diminish the frictional losses of the piston-cylinder system. So, the contacting length between piston and cylinder wall is in variable with the rotating crank angle around the BDC of the reciprocating piston. In the problem formulation of the piston dynamics, the change in bearing length of the piston and all corresponding forces and moments are considered in order to determine the piston trajectory, velocity and acceleration at each step. A Newton-Raphson procedure was employed in solving the secondary dynamic equations of the piston. The developed computer program can be used to calculate the entire piston trajectory and the hydrodynamic force and moment as functions of crank angle under compressor running conditions. The results explored the effects of the radial clearance, lubricant viscosity, length of the cylinder wall, and pin location on the stability of the piston.

• 대한전자공학회논문지
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• 제22권5호
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• pp.75-82
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• 1985

Weighted Least Square(W.L.S.)알고리즘을 통한 계수식별 이론과 출력 증차를 최소로 하기위해 한단계 앞서서 제어입력을 결정하는 제어이론을 결수한 기준 모델 통용제어를 응용한 연료펌프 시스템을 설계하였다. 시스템의 성능에 관계되는 샘플링 이기 7, 비중계수 공및 State Yarlable Filter(5. Y. F.)의 릴터계수의 값은 컴퓨터 시뮬레이션을 통해 결정했으며, 특히 주독온도의 변화로 인해 연료의 점성도가 변하므로서 공정의 동특성을 나타내는 공량계수가 변하는 것에 대한 제어시스템의 적응도를 레팔레이션(regu lation)과 추종(tracking)관점에서 고찰하였다.