• Coupled systems mechanics
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• 제13권2호
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• pp.171-186
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• 2024

In the present paper, thermal buckling characteristics of functionally graded rectangular plates made of porous material that are integrated with surface-bonded piezoelectric actuators subjected to the combined action of thermal load and constant applied actuator voltage are investigated by utilizing a Navier solution method. The uniform temperature rise loading is considered. Thermomechanical material properties of FGM plates are assumed to be temperature independent and supposed to vary through thickness direction of the constituents according to power-law distribution (P-FGM) which is modified to approximate the porous material properties with even and uneven distributions of porosities phases. The governing differential equations of stability for the piezoelectric FGM plate are derived based on higher order shear deformation plate theory. Influences of several important parameters on the critical thermal buckling temperature are investigated and discussed in detail.

• Advances in nano research
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• 제16권5호
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• pp.489-500
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• 2024

This paper studies the free vibration analysis of the piezo-magneto-thermo-elastic FG nanobeam submerged in a fluid environment. The problem governed by the partial differential equations is determined by refined higher-order State Space Strain Gradient Theory (SSSGT). Hamilton's principle is applied to discretize the differential equation and transform it into a coupled Euler-Lagrange equation. Furthermore, the equations are solved analytically using Navier's solution technique to form stiffness, damping, and mass matrices. Also, the effects of nonlocal ceramic and metal parts over various parameters such as temperature, Magnetic potential and electric voltage on the free vibration are interpreted graphically. A comparison with existing published findings is performed to showcase the precision of the results.

• KSBB Journal
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• 제14권3호
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• pp.358-364
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• 1999

참나무의 전처리에 과산화수소가 미치는 영향을 조사하였다. 반응온도는 $170^{\circ}C$이고 전처리에 사용된 반응용액은 암모니아, 황산 그리고 순수 물이었다.10% 암모니아용액을 사용한 경우 산을 사용하는 경우에 비해 리그닌 제거율은 55%로 상당히 높았지만 헤미셀룰로오스 회수율은 26%로 상당히 낮았다. 그래서 헤미셀룰로오스 회수율을 높이기 위해 암모니아 용액에 산화제인 과산화수소를 첨가하여 반응시켰는데 과산화수소 첨가량의 증가에 따라 리그닌 제거율과 헤미셀룰로오스 회수율의 증가는 크지 않았다. 그리고 과산화수소 첨가량의 증가에 따라 액상으로 용해된 당의 분해가 증가하여 전체 헤미셀룰로오스와 셀룰로오스의 물질수지에 문제가 있었다. 반응기에 주입된 과산화수소는 주로 반응기의 전반부에 충진된 기질과 반응하는 것으로 나타났다. 헤미셀룰로오스 회수율을 높이기 위해서는 알카리용액보다 산성용액에서 기질을 전처리하는 것이 필요하였고 산보다는 물을 사용하였을 때 과산화수소의 효과가 더 컸다.

• Corrosion Science and Technology
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• 제20권5호
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• pp.289-294
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• 2021

In this study, after measuring polarization characteristics of 97.3 wt% Ag, Au-Coated 97.3 wt% Ag (ACA) and 100 wt% Au wires in 1 wt% H₂SO₄ and 1 wt% HCl electrolytes at 25 ℃, corrosion rate and corrosion characteristics were comparatively analyzed. Comparing corrosion potential (E_CORR) values in sulfuric acid solution, ACA wire had more than six times higher E_CORR value than Au wire. Thus, it seems possible to use a broad applied voltage range of bonding wire for semiconductor packaging which ACA wire could be substituted for the Au wire. However, since the E_CORR value of ACA wire was three times lower than that of the Au wire in a hydrochloric acid solution, it was judged that the use range of the applied voltage and current of the bonding wire should be considered. In hydrochloric acid solution, 97.3 wt% Ag wire showed the highest corrosion rate, while ACA and Au showed similar corrosion rates. Additionally, in the case of sulfuric acid solution, all three types showed lower corrosion rates than those under the hydrochloric acid solution environment. The corrosion rate was higher in the order of 97.3 wt% Ag > ACA > 100 wt% Au wires.

• 한국유기농업학회지
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• 제19권1호
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• pp.121-134
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• 2011

공시 농약인 "스미렉스 수화제"를 알타리무에 살포한 다음 2시간 후에 각각 지하수, 키토산 500배액, 및 목초액 1,000배액을 골고루 엽면살포하였다. 그리고 공시재료 살포 2시간 경과 후, 1일 경과 후, 7일 경과 후 및 15일 경과 후에 각각 시료를 채취하여 알타리무 체내의 procymidone 잔류농약을 분석한 결과는 다음과 같다. 1. 알타리무 체내의 procymidone의 검출농도를 측정한 결과 농약만 살포한 무처리구인 대조구에 비해 지하수, 키토산 500배액, 및 목초액 1,000배액 처리구에서 잔류농약인 procymidone의 검출농도가 낮게 나타났으며, 특히 키토산 500배액 처리구에서는 평균치 보다 낮게 나타났다. 2. 알타리무 체내의 procymidone의 분해율을 측정한 결과 키토산 500배액 처리구 및 목초액 1,000배액 처리구에서 잔류농약인 procymidone의 분해율이 비교적 높게 나타났으며, 공시 엽면처리 재료간에는 큰 차이는 없었으나 대체적으로 키토산 500배액 처리구에서 분해율이 높게 나타났으며, 시간경과에 따른 평균 분해율은 공시재료를 엽면살포하고 7일이 경과한 후에 급격히 증가하는 것으로 나타났다. 3. 지하수, 키토산 500배액 및 목초액 1,000배액을 엽면살포한 후 매일 달관조사를 하여 생육장해 및 비해조사를 한 결과 본 시험 농도에서는 비해가 없는 것으로 조사되었다.

• Bulletin of the Korean Chemical Society
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• 제11권4호
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• pp.303-306
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• 1990

Kinetic studies were carried out for the redox reaction of $[Co(NH_3)_4(C_2O_4)]^+$ with aqueous $[Fe(H_2O)_6]^{2+}$ solution in the present of $H^+$ by UV/VIS-spectrophotometric method. It was found that the order of $H^+$ for the reaction is first one in the higher $H^+$ concentration range of $1.67×10^{-1} M{\sim}1.00 M,$ while second order in the lower range of $6.30×10^{-2} M{\sim}1.67{\times}10^{-1} M.$ Reaction order of the substrates was found to be first order with respect to each of them. Accordingly overall reactions are third or fourth order. The results of calculation for the Extended Huckel Molecular Orbital theory contribute to estimate the preferred intermediates, bridging form of binuclear complex. On the basis of these results, we propose that this redox reaction proceed via inner-sphere reaction mechanism.

• 한국광학회지
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• 제4권1호
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• pp.1-8
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• 1993

축소배율(5$\times$)을 갖고, Seidel 1차 수차중 4개의 비축수차인 코마(coma), 비점수차(astigmatism), 상면만곡(field curvature) 그리고 왜곡수차(distortion)가 제거된 마이크로 리소그라피를 위한 4-구면 반사경 광학계를 해석적으로 구하였다. 이때, $t=d_1+d_2+d_3$<0, (di는 반사거울 $c_i$와 $c_{i+1}$ 사이의 거리)이고, 축상 수차인 구면수차와 잔류고차수차는 반사거울 $c_3$와 $c_4$를 비구면화 하므로서 제거하였다. 이렇게 설계된 4-반사경 광학계의 N.A.는 0.4로서 Rayleigh분해능은 0.38 $\mu\textrm{m}$이다.

• Carbon letters
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• 제8권3호
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• pp.199-206
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• 2007

The activated carbon produced from rubber wood sawdust by chemical activation using phosphoric acid have been utilized as an adsorbent for the removal of Cu(II) from aqueous solution in the concentration range 5-40 mg/l. Adsorption experiments were carried out in a batch process and various experimental parameters such as effect of contact time, initial copper ion concentration, carbon dosage, and pH on percentage removal have been studied. Adsorption results obtained for activated carbon from rubber wood sawdust were compared with the results of commercial activated carbon (CAC). The adsorption on activated carbon samples increased with contact time and attained maximum value at 3 h for CAC and 4 h for PAC. The adsorption results show that the copper uptake increased with increasing pH, the optimum efficiency being attained at pH 6. The precipitation of copper hydroxide occurred when pH of the adsorbate solution was greater than 6. The equilibrium data were fitted using Langmuir and Freundlich adsorption isotherm equation. The kinetics of sorption of the copper ion has been analyzed by two kinetic models, namely, the pseudo first order and pseudo second order kinetic model. The adsorption constants and rate constants for the models have been determined. The process follows pseudo second order kinetics and the results indicated that the Langmuir model gave a better fit to the experimental data than the Freundlich model. It was concluded that activated carbon produced using phosphoric acid has higher adsorption capacity when compared to CAC.

• 한국광학회지
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• 제4권3호
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• pp.252-259
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• 1993

극자외선 과장을 사용하는 micro-lithography를 위해 등배율을 갖는 4-반사경 holosymmetric system을 설계하였다. Holosymmetric system에서는 모든 차수의 코마와 왜곡수차가 영이 된다. 이 원리를 4-구명경계에 적용하여 등배율을 갖고 5개의 3차 수차가 모두 제거된 4-구면 반사경 holosymmetric system에 대해 유일한 해를 완전히 해석적인 표현으로 구하였다. 이 4-구면경계에 남아있는 고차 수차들을 보정하기 위해 holosymmetric 성질을 유지하면서 비구면을 채용하였고 그결과 개구수 0.33과 image field diameter 7.6mm 이내에서 극자외선 파장 $0.248{\mu}m$(KrF 엑시머 레이저 빔)에 대해 거의 회절한계의 수차성능을 갖는 비구면 4-반사경 holosymmetric system를 얻었다.

• Advances in nano research
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• 제13권1호
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• pp.29-45
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• 2022

The optimization for dynamic response associated with a cylindrical shell which is made of laminated composites embedded in a piezoelectric layer which is subjected to temperature rises and is resting on an elastic foundation is investigated for the first time. The first shear order theory (FSDT) is utilized in order to obtain the strain relations of the shell. Then, using the energy method, the equations of motions as well as boundary condition of the problem are attained. The formulation of this study together with the solution procedure which is a numerical solution method, differential quadrature method (DQM) is validated using other researches. This paper presents a thorough study on the parameters which impacts the vibration frequency of the laminated shell. The results of this paper shows that any type of laminated composite shell can reduce the vibration frequency providing that the angle related to layer are higher than 85 degrees. Also, in order to reduce the effect of temperature rises, the laminated composites instead of orthotropic one can be used.