• Steel and Composite Structures
• /
• 제18권6호
• /
• pp.1541-1555
• /
• 2015

In this paper mechanical behavior of the functional gradient materials (FGM) micro-gripper under thermal load and DC voltage is numerically investigated taking into account the effect of intermolecular forces. In contrary to the similar previous works, which have been conducted for homogenous material, here, the FGM material has been implemented. It is assumed that the FGM micro-gripper is made of metal and ceramic and that material properties are changed continuously along the beam thickness according to a given function. The nonlinear governing equations of the static and dynamic deflection of microbeams have been derived using the coupled stress theory. The equations have been solved using the Galerkin based step-by-step linearization method (SSLM). The solution procedure has been evaluated against available data of literature showing good agreement. A parametric study has been conducted, focusing on the combined effects of important parameters included DC voltage, temperature variation, geometrical dimensions and ceramic volume concentration on the dynamic response and stability of the FGM micro-gripper.

• Coupled systems mechanics
• /
• 제6권3호
• /
• pp.273-286
• /
• 2017

We present a simple and easy-to-implement lumped stiffness model to elucidate the load transfer mechanism among all individual tube shells and intertube van der Waals (vdW) interactions in transversely compressed multi-walled carbon nanotubes (CNTs). Our model essentially enables theoretical predictions to be made of the relevant transverse mechanical behaviors of multi-walled tubes based on the transverse stiffness properties of single-walled tubes. We demonstrate the validity and accuracy of our model and theoretical predictions through a quantitative study of the transverse deformability of double- and triple-walled CNTs by utilizing our recently reported nanomechanical measurement data. Using the lumped stiffness model, we further evaluate the contribution of each individual tube shell and intertube vdW interaction to the strain energy absorption in the whole tube. Our results show that the innermost tube shell absorbs more strain energy than any other individual tube shells and intertube vdW interactions. Nanotubes of smaller number of walls and outer diameters are found to possess higher strain energy absorption capacities on both a per-volume and a per-weight basis. The proposed model and findings on the load transfer and the energy absorption in multi-walled CNTs directly contribute to a better understanding of their structural and mechanical properties and applications, and are also useful to study the transverse mechanical properties of other one-dimensional tubular nanostructures (e.g., boron nitride nanotubes).

• 분석과학
• /
• 제8권4호
• /
• pp.519-527
• /
• 1995

The retention mechanism of Ni(II)-${\alpha}$-isonitroso-${\beta}$-diketone imine chelates in reversed-phase HPLC has been studied by examining the effect of temperature, mobile phase composition in acetonitrile-water mixture, and molecular structure on retention. The empirical retention equation was investigated to evaluate the properties of S (hydrophilic index). The value of the S index of the Ni(II) chelates decrease with the increasing column temperature and a linear relationship between S and log $k{_w}^{\prime}$ has been found. The results showed that the S index is influenced by the interaction between Ni(II) chelates and mobile phase. Molecular properties, van der Waals molar volume, polarizability and dipole moment, of the Ni(II) chelates were calculated by Cerius 2 program and the calculations were performed at Universal Force Field (UFF) model. The S value and log $k{_w}^{\prime}$ increase with decreasing the dipole moment of Ni(II) chelates.

• Reproductive and Developmental Biology
• /
• 제28권1호
• /
• pp.45-52
• /
• 2004

To search a new porcine pheromonal odorants, this research for biostimulation and role of pheromone was augmented by means of "control system technologies" to offer a potentially useful and practical way to improve reproductive efficiency in livestock species. Therefore the 13 physicochemical parameters such as similarity indice (S), hydrophobicity (logP) and van der Waals molecule volume (MV) etc. of 54 steroid analogues, which are analogous of substrate molecules, 5$\alpha$-androst-16-en-3-one (P1) and 5$\alpha$-androst-16-en-3-ol (P2) of lipocalin as receptor of pig pheromones were calculated and discussed. The physicochemical properties of these steroid analogues were mainly followed by steric dissimilar of A and D ring in steroid nucleus. And we found that from correlation with S values and MV constants of molecules, the more MV constants are small, the more S values tend to approach 1. Based on this results, the S-values of 4-androsten-3,17-dione (P1-1) and 5 $\alpha$ -androstan-3-one (P2-1) were 1.0, respectively. The two compounds of them were chosen because they showed the same value each other at a side of hydrophobicity, molar refractivity and molecular volume. It is expected that the new two compounds will be able to substitute for P1 and P2, porcine pheromonal odorants.

• Korean Chemical Engineering Research
• /
• 제53권2호
• /
• pp.193-198
• /
• 2015

Polycaprolactone, Dichloromethane, 이산화탄소로 구성된 3성분계 고압 시스템의 상거동 측정 실험은 가변 부피 셀 장치를 이용해서 측정했다. 실험의 온도범위는 313.15 K에서 353.15 K, 압력은 약 300 bar까지 측정했으며 실험결과는 Polycaprolactone의 질량 분율이 1.0%, 2.0%, 3.0%일 때 온도와 이산화탄소/Dichloromethane의 질량 분율로 정리했다. 또한 실험 결과는 hybrid 상태방정식 (Peng-Robinson 상태방정식과 SAFT 상태방정식의 혼합형태) 을 이용하여 열역학적으로 검증하였으며, 혼합규칙은 반데르 발스의 단일 유체 혼합규칙을 사용했다. 이 다성분계 시스템에서 이원 상호 작용 파라미터 등, 각종 파라미터는 심플렉스 알고리즘을 통해 최적화했다.

• 유기물자원화
• /
• 제30권3호
• /
• pp.13-22
• /
• 2022

수계에 오염된 색도 물질을 더욱 효율적으로 처리하고자 버려지는 폐자원을 이용하여 흡착제인 바이오차를 제조하고 적용하는 방안을 모색하고자 하였다. 이에 가로수 전정부산물이나 폐목재를 활용하여 넓은 비표면적을 가지고 있는 바이오차를 제조하고 이를 이용하여 색도물질 제거에 적용하였다. 대표적인 가로수 전정부산물(플라타너스, 은행나무, 참나무)과 폐목재를 산소가 없는 조건에서 열분해하여 바이오차를 제조하였으며, 제거대상 물질로는 방향족 고리를 가지고 있어서 생물학적 분해가 어렵고, 물리적 처리와 화학적 처리시 제거효율이 떨어지는 것으로 알려져 있는 녹청색의 유기염료로 주로 인피섬유에 사용되며, 종이, 가죽과 면의 매염에 사용되기도 하는 메틸렌블루(MB)를 선정하였다. 실험결과 플라타너스 기반 바이오차가 제일 높은 흡착능을 보였으며, Langmuir 모델식을 이용하여 구한 q_max 값은 78.47 mg/g으로 나타났다. 또한 물리적 흡착과 화학적 흡착을 구별하는데 사용되는 Dubinin-Radushkevich(D-R) 모델식을 이용하여 흡착에너지(E) (kJ/mol)를 구한 결과 MB에 대한 흡착에너지(E) 값은 4.891 kJ/mol로 8 kJ/mol(물리흡착과 화학흡착의 기준 값) 보다 작았으며, 이는 바이오차와 MB 염료 사이에 van der Waals와 같은 약한 결합이 존재하는 물리흡착임을 알 수 있었다. 반응온도 변화에 따른 흡착실험을 통해 얻은 ∆G의 값은 -3.67~7.68 kJ/mol으로서 물리적 흡착반응 영역에 해당함을 확인하여, 본 연구에서 제조된 플라타너스 기반 바이오차의 MB 흡착메커니즘은 넓은 비표면적을 이용한 물리적 흡착임을 제시할 수 있었다. 또한 타 연구에서 제시된 상업용 활성탄과 비교하여도 동등 이상의 흡착능력을 보였다.