• Structural Engineering and Mechanics
• /
• 제75권6호
• /
• pp.747-769
• /
• 2020

This paper provides a semi-analytical approach to investigate the variations of 3D displacement components, electric potential, stresses, electric displacements and transverse vibration frequencies in laminated piezoelectric composite plates based on the scaled boundary finite element method (SBFEM) and the precise integration algorithm (PIA). The proposed approach can analyze the static and dynamic responses of multilayered piezoelectric plates with any number of laminae, various geometrical shapes, boundary conditions, thickness-to-length ratios and stacking sequences. Only a longitudinal surface of the plate is discretized into 2D elements, which helps to improve the computational efficiency. Comparing with plate theories and other numerical methods, only three displacement components and the electric potential are set as the basic unknown variables and can be represented analytically through the transverse direction. The whole derivation is built upon the three dimensional key equations of elasticity for the piezoelectric materials and no assumptions on the plate kinematics have been taken. By virtue of the equilibrium equations, the constitutive relations and the introduced set of scaled boundary coordinates, three-dimensional governing partial differential equations are converted into the second order ordinary differential matrix equation. Furthermore, aided by the introduced internal nodal force, a first order ordinary differential equation is obtained with its general solution in the form of a matrix exponent. To further improve the accuracy of the matrix exponent in the SBFEM, the PIA is employed to make sure any desired accuracy of the mechanical and electric variables. By virtue of the kinetic energy technique, the global mass matrix of the composite plates constituted by piezoelectric laminae is constructed for the first time based on the SBFEM. Finally, comparisons with the exact solutions and available results are made to confirm the accuracy and effectiveness of the developed methodology. What's more, the effect of boundary conditions, thickness-to-length ratios and stacking sequences of laminae on the distributions of natural frequencies, mechanical and electric fields in laminated piezoelectric composite plates is evaluated.

• 접착 및 계면
• /
• 제9권1호
• /
• pp.22-27
• /
• 2008

아크릴 점착제의 점착력을 목표 수준으로 향상시키기 위해 실험계획법을 이용하여, 2-ethyl hexyl acrylate (2-EHA), ethyl acrylate (EA), metha acrylic acid (MAA), acryl amide (AAm)를 라디칼 용액 중합하여 점착력을 측정하였다. 실험계획법은 반응표면분석법의 하나인 혼합물 설계를 이용하여 특수 3차 모형으로 분석하였으며, 그 적용은 상용프로그램인 MINITAB을 사용하였다. 수립된 실험계획에 의해 실험하고 분석한 결과, 목표하는 점착력을 얻기 위한 단량체 조성은 2-EHA (0.8861), EA (0.0639), MAA (0.03), AAm (0.02)로 나타났으며, 그 회귀분석 식은 다음과 같았다. $$y=54.8816x_1+80.7067x_2-44.4700x_3-99.0288x_1x_2+60.7706x_1x_3-441.030x_2x_3+974.341x_1x_2x_3$$.

• Elastomers and Composites
• /
• 제44권3호
• /
• pp.232-243
• /
• 2009

근래 고성능 친환경 타이어의 개발요구에 의하여 경제성(낮은 회전 저항)과 안전성(wet traction) 및 내마모성면에서 균형있는 특성을 가지는 타이어 트레드 고무의 합성 제조 기술이 중요하게 대두된다. 이를 위하여 다양한 기능성 용액중합 SBR의 개발과 함께 고무/충전제 간의 상호작용 증진 기술이 학술적으로나 산업적으로 활용되고 있다. 본 고에서는 기존의 카본블랙 고무와 함께 최근 green tire로서 각광 받는 실리카 충전 고무에서 충전제와 상호반응이 가능한 화학적 변성 SBR과 커플링제를 이용한 고성능 타이어 트레드 고무의 합성 제조 기술에 대하여 최근 연구 방향과 함께 작용 메카니즘에 대하여 고찰하였다.

• 한국식품저장유통학회지
• /
• 제15권3호
• /
• pp.396-404
• /
• 2008

반응표면분석법을 이용하여 홍삼 지근의 볶음 온도와 시간에 따른 추출물의 기능성 성분을 모니터링하고 최적 볶음조건을 예측하였다. 그 결과 가용성 고형분, 총 페놀함량 및 항산화성은 볶음 온도와 시간이 증가함에 따라 그 값이 증가하는 경향을 나타내었으며, 산성다당체 함량은 볶음시간보다 볶음온도에 더 크게 영향을 받는 것으로 나타났다. 이로써 홍삼 지근의 기능성 관련 성분을 고려한 최적 볶음조건은 볶음온도 $194.5{\sim}210.9^{\circ}C$와 볶음시간 $13.8{\sim}20.0$분으로 예측되었다.

• 대한영양사협회학술지
• /
• 제24권1호
• /
• pp.19-30
• /
• 2018

The primary objective of this study was to develop an optimal composite recipe for ginger extract candy with Salicornia herbacea L., for consumption during the first trimester of pregnancy. The secondary objective was to examine quality characteristics of the candy. The physical and mechanical properties and sensory properties for pregnant women in were measured, and these values were applied to mathematical models. Time of stirring water solution, saltiness, pH, and redness of the candy increased as concentrations of ginger juice did, but variations in pH were not significant. The hardness values of the candy ranged from 3,063.90 to $5,681.65dyne/cm^3$. The average values of sweetness and time stirring the water solution were 5.36% and 14.1 minutes, respectively. However, hardness and sweetness stirring water solution were not significant. The range of sensory values of color (P<0.01), flavor (P<0.05), sweetness, saltiness, spiciness, and overall quality (P<0.05) ranged from were 3.73~5.32, 4.05~5.05, 3.67~5.14, 3.59~5.09, 3.55~5.15, and 3.32~5.45, respectively. Results suggest that ginger extract candy with Salicornia herbacea L. should be comprised of 7.37 g of ginger juice and 1.77 g of salt. Consequently, it could be a functional candy for pregnant women.

• 해양환경안전학회지
• /
• 제7권3호
• /
• pp.17-28
• /
• 2001

The wheelhouse front glass of a Fore-Bridge-Ship (Ro-Ro Ship) was broken by the shipping of water in rough seas, and then the flooding of seawater into the wheelhouse caused the uncontrollable condition of the ship. The hull which was entered into the floating condition rolled severely, and the heavy rolling caused secondary damage such as the collapse of a lot of cargo. It was an incredible accident because the height of bow freeboard was about 2.5 times higher than the standard height of minimum bow freeboard regulated by the International Load Line Convention(1966). And it would be also difficult for navigators to imagine a great deal of seawater flooding into the wheelhouse because the front glass was positioned at about 20m height above the sea surface. In this paper, we carried out the evaluation for the safety navigation of the Fore-Bridge-Ship numerically against ship's speed and encountering angle to the wave in each sea state of rough sea, by using the integrated seakeeping performance index (ISPI) which is able to evaluate synthetically the safety operation of ships. And then the problem on the application of the past criteria proposed as the safety navigation of a merchant ship was clarified by inquiring the dangerousness of the shipping of water at her bow deck, which caused the breakage of the wheelhouse front glass.

• 한국식품과학회지
• /
• 제32권1호
• /
• pp.117-124
• /
• 2000

인삼 성분의 열불안정성과 실용성을 고려하여 상압 조건에서 마이크로웨이브 추출실험을 실시하면서 반응 표면분석에 의해 추출조건의 최적화 및 추출특성을 모니터링하였다. 가용성 성분의 수율은 에탄올 농도가 낮고 microwave power가 높을수록, 조사포닌 함량은 에탄올 농도가 높을수록 증가하였다. 그리고 추출물의 가용성성분 함량, 조사포닌 함량, 페놀성화합물 함량, 전자공여작용 등의 추출물 특성을 모두 만족시키는 최적 추출조건을 예측하여 보았을 때, 에탄올 농도 $54{\sim}60%$ 범위, microwave power $41{\sim}90$ W 범위, 추출 시간 4분 이내로 나타났다. 예측회귀식의 신뢰성을 확인하기 위하여 예측된 추출조건의 임의의 최적점에서 실제 추출실험을 실시해 본 결과, 각 반응변수들의 예측값은 실제값과 유사하였다.

• 한국환경과학회지
• /
• 제25권5호
• /
• pp.737-744
• /
• 2016

For electrolysis process using an insoluble electrode, electrochemical performance was greatly affected by the manufacturing method and procedure, such as the firing temperature, pre-treatment, type of precursor solution, coating method, electrode material, etc. Components of the electrode therein is one of the most important factors in electrochemical reaction. To achieve such characteristics, a appropriate ratio of the electrode material should be carefully chosen. The aim of this research was to apply experimental design method in the optimization of electrode component for the maximum generation of oxidants in electrochemical oxidation process. Mixture design, especially expanded simplex lattice design, in DOME (design of mixture experiments) with Design Expert - commercial software - was used to analyze the data. Analysis of variance (ANOVA) showed a high coefficient of determination ($R^2$) value of 0.9470, thus ensuring a satisfactory adjustment of the $3^{rd}$ order special cubic regression model with the experimental data. The application of response surface methodology (RSM) yielded the following regression equation, which is an empirical relationship between the TRO generation concentration and independent variables(mol ratio of 3 electrode components) in a real unit: TRO generation concentration $(mg/L)=TRO\;conc.=98.25{\times}[Ir]+49.71{\times}[Sn]+95.29{\times}[Sb]-16.91{\times}[Ir]{\times}[Sn]-29.47{\times}[Ir]{\times}[Sb]-22.65{\times}[Sn]{\times}[Sb]+703.19{\times}[Ir]{\times}[Sn]{\times}[Sb]$. The optimized formulation of the 3 component electrode for an high TRO (total residual oxidants) generation was acquired at mol ratio of Ir 0.406, Sn 0.210, Sb 0.384 (desirability d value, 1).

• Journal of Microbiology and Biotechnology
• /
• 제21권7호
• /
• pp.739-745
• /
• 2011

During the production of grape wine, the formation of thick leathery pellicle/bacterial cellulose (BC) at the airliquid interface was due to the bacterium, which was isolated and identified as Gluconacetobacter hansenii UAC09. Cultural conditions for bacterial cellulose production from G. hansenii UAC09 were optimized by central composite rotatable experimental design. To economize the BC production, coffee cherry husk (CCH) extract and corn steep liquor (CSL) were used as less expensive sources of carbon and nitrogen, respectively. CCH and CSL are byproducts from the coffee processing and starch processing industry, respectively. The interactions between pH (4.5-8.5), CSL (2-10%), alcohol (0.5-2%), acetic acid (0.5-2%), and water dilution rate to CCH ratio (1:1 to 1:5) were studied using response surface methodology. The optimum conditions for maximum BC production were pH (6.64), CSL (10%), alcohol (0.5%), acetic acid (1.13%), and water to CCH ratio (1:1). After 2 weeks of fermentation, the amount of BC produced was 6.24 g/l. This yield was comparable to the predicted value of 6.09 g/l. This is the first report on the optimization of the fermentation medium by RSM using CCH extract as the carbon source for BC production by G. hansenii UAC09.

• 대한환경공학회지
• /
• 제36권6호
• /
• pp.429-433
• /
• 2014

본 연구에서는 음식물퇴비에서 발생되는 악취물질 중 암모니아 가스를 탈취제를 사용하여 제거하는 실험을 진행하였다. 이를 위해 탈취제로 죽초액(bamboo smoke distillate, BSD)을 사용하여 첨가량과 반응시간에 따른 변화를 반응표면분석법을 통해 최적점을 도출하였다. 그 결과 본 연구에서 사용한 분석 범위내에서는 음식물퇴비(food waste compost, FWC) 600 g 당 죽초액 74 mL (0.123 mL BSD/g FWC)를 첨가하고 3시간 반응하였을 때 제거량(8.47 ppm $NH_3$/600g FWC)이 가장 높았다. 탈취제로 식초를 사용하였을 때의 암모니아 제거량보다 죽초액을 사용하였을 때 암모니아 제거량이 높았다(p < 0.05).