A comprehensive model to study nonlinear behavior of multilayered micro beam switches

A novel model to study the pull-in behavior of nonlinear electromechanically coupled systems has been developed. The proposed model is based on the multilayered cantilever and fixed–fixed micro beam type MEMS switches. Due to the complexity of the nonlinear beam mechanics, exact analytical solutions are not generally available; therefore, the derived nonlinear equation has been numerically solved fully using the nonlinear finite difference method. Furthermore, the results obtained are summarized and compared with the other existing empirical and analytical models. These results can be useful in the optimization of MEMS switch designs or other actuators. In addition, the method developed in this paper has a good potential for analyzing other types of complex MEMS devices. An erratum to this article can be found at     

Peel mechanics for an elastic-plastic adherend

The force required to propagate a 180° bend in an elastic-plastic strip has been calculated from elementary bending theory. Measured forces for Mylar strips of various thicknesses, bent to various degrees, were in good agreement with these calculated values. The corresponding additional stripping force in a peeling experiment will depend upon the thickness of the elastic-plastic adherend, becoming zero both for infinitesimally thin adherends and for those exceeding a critical thickness t_c and passing through a maximum value at intermediate thicknesses. Published data are in good agreement with these conclusions. For a strongly adhering strip, higher peel strengths are found for a peel angle of 180°, compared to 90°, and the effect is greater than can be accounted for solely by plastic yielding of the adherend. It is attributed in part to greater energy dissipation within the adhesive layer.     

Diffusion of benzene and toluene into aqueous nitric acid-sulphuric acid mixtures

Diffusion coefficients of toluene and benzene into aqueous mixtures of nitric and sulphuric acids have been measured at 30°C by use of a laminar jet technique. Equations are presented which correlate the data in terms of the acid concentrations and permit extrapolation to acid mixtures of interest for industrial mononitration reactions. The results show the expected dependence on viscosity of the acid phase and are in agreement with values predicted by the Wilke and Chang correlation.     

A multi-colony ant algorithm for optimizing join queries in distributed database systems

Distributed database systems provide a new data processing and storage technology for decentralized organizations of today. Query optimization, the process to generate an optimal execution plan for the posed query, is more challenging in such systems due to the huge search space of alternative plans incurred by distribution. As finding an optimal execution plan is computationally intractable, using stochastic-based algorithms has drawn the attention of most researchers. In this paper, for the first time, a multi-colony ant algorithm is proposed for optimizing join queries in a distributed environment where relations can be replicated but not fragmented. In the proposed algorithm, four types of ants collaborate to create an execution plan. Hence, there are four ant colonies in each iteration. Each type of ant makes an important decision to find the optimal plan. In order to evaluate the quality of the generated plan, two cost models are used—one based on the total time and the other on the response time. The proposed algorithm is compared with two previous genetic-based algorithms on chain, tree and cyclic queries. The experimental results show that the proposed algorithm saves up to about 80 % of optimization time with no significant difference in the quality of generated plans compared with the best existing genetic-based algorithm.     

A novel electrostatic based microgripper (cellgripper) integrated with contact sensor and equipped with vibrating system to release particles actively

This paper presents design and simulation of a novel electrostatic microelectromechanical systems gripper with an integrated capacitive contact sensor. Moreover, this microgripper is able to employ vibration to release micro objects (cells) actively. Lateral comb drive system is used to close the gap between the gripper arms and hold the objects while the transverse comb differential capacitances act as a contact sensor to prevent damaging the fragile micron-sized particles specifically biological cells. In addition, the capability of the microgripper in generating vibration at the end-effectors electrostatically is an advantage to facilitate releasing process by overbalancing the adhesion forces between the particle and the gripper arm. Finite element analysis based simulations are carried out to estimate the behavior of the microgripper while the standard SOI-MUMPs micromachining process is proposed for fabrication of the microgripper.     

Unidirectional fiber–polymer composites: Swelling and modulus anisotropy

The solvent swelling of unidirectional rubber–fiber composites was studied. The amount of matrix swelling was constrained to the extent that would be predicted from the thermodynamic theories of elasticity and polymer–solvent interaction. The geometry of swelling was found to be orthotropic in nature. A simple trigonometric function was derived to relate linear deformation due to swelling to the angle which the direction of its measurement makes with the fiber direction. The validity of the derivation was demonstrated experimentally. Considering swelling to be the imposition of tensile forces of equal magnitude in all directions, and considering a swelling-induced linear deformation to be analogous to a tensile compliance, a simple set of relationships between elastic parameters and their direction of measurement was derived: where E_θ, G_θ, v_θ, and η_θ are Young's modulus, shear modulus, Poisson's ratio, and the shear coupling ratio measured in a longitudinal transverse plane at an angle with the fiber direction, respectively, and E_L, G_LT, and θ_LT are the longitudinal Young's modulus, the longitudinal transverse shear modulus, and the longitudinal transverse Poisson ratio, respectively. Further simplifying the case of combined transverse isotropy and special orthotropy was the conclusion that 1/G_LT = 1/E_T + (1 + 2v_LT)/E_L. The relationships for G and E were experimentally demonstrated.     

Poly(Ethylene-co-Vinylacetate) Based Hot Melt Adhesives: I. Relating Adhesive Rheology to Peel Adhesion

The successful selection of bonding conditions for hot melt adhesives depends on melt morphology and rheological properties. Rheological properties were determined for model poly(ethylene-co-vinylacetate) hot melt adhesives. T-Peel fracture energies of joints consisting of two polypropylene films bonded with these adhesives were determined. Rheological data suggest that the EVA and its blends form homogeneous melts. Tackifiers and wax lower melt viscosity and elasticity but increase the activation energy for melt flow. Adhesives with higher melt activation energy, as well as lower elasticity and viscosity, show little dependence of peel strength on bonding temperature and require little time to reach the equilibrium bond strength. The equilibrium T-Peel strengths of adhesives containing wax are almost independent of bonding temperature. This may result from the existence of a weak boundary layer of wax or to their high flowability.     

Novel surfactants for ultralow interfacial tension in a wide range of surfactant concentration and temperature

This work investigates the possibility of injecting dilute aqueous solutions of novel surfactants into the Yibal field (Sultanate of Oman). This was accomplished through an experimental protocol based on the following criteria: (i) compatibility of the surfactants with the high-saline reservoir water (∼200 g/L); (ii) low interfacial tension (IFT) between crude oil and reservoir water (less than 10⁻² mN m⁻¹); and (iii) maintaining the low IFT behaviour during the entire surfactant flooding. Novel surfactants selected in this study consist of a series of ether sulfonates (AES-205, AES-128, AES-506, and 7–58) and an amphoteric surfactant (6–105). These surfactants were found to be compatible with reservoir water up to 0.1% surfactant concentration, whereas 6–105 and 7–58 showed compatibility within the full range of surfactant concentration investigated (0.001–0.5%). All surfactant systems displayed dynamic IFT behavior, in which ultralow transient minima were observed in the range 10⁻⁴–10⁻³ mN m⁻¹, followed by an increase in the IFT to equilibrium values in the range 10⁻³–10⁻¹ mN m⁻¹. The results also showed that with respect to concentration (0.05–0.5%) and temperature (45–80°C), AES-205 and 7–58 surfactants exhibit a wide range of applicability, with the IFT remaining below 10⁻² mN m⁻¹, as required for substantial residual oil recovery. In addition, ultralow IFT were obtained at surfactant concentrations as low as 0.001%, making the use of these surfactants in enhanced oil recovery extremely cost-effective.     

High sensitive photonic crystal ring resonator structure applicable for optical integrated circuits

Quality factor and refractive sensitivity are significant parameters in designing optical devices such as filters, demultiplexers, switches and sensors. In this paper, we proposed a novel structure for photonic crystal ring resonator with octagon-shaped core. The transmission efficiency of the proposed ring resonator at \(\lambda =1551\,\hbox {nm}\) is about 99.6 % with bandwidth and quality factor values equal to 0.3 nm and 5170. The proposed structure is very sensitive upon the variation of refractive index of total structure and core part of the resonator, such that the refractive index sensitivity to the refractive index of total structure and the resonant ring core is \(\Delta \lambda /\Delta \lambda =3.1\,\hbox {nm}\,/\,0.01\) and \(\Delta \lambda /\Delta \hbox {n}=2.9\,\hbox {nm}\,/\,0.01\), respectively.