Polypyrrole nanotube modified by gold nanoparticles for improving the neural microelectrodes

Journal of Solid State Electrochemistry - High selectivity and low impedance are preferred properties for neural microelectrodes. The localized and controlled release of drugs from the...     

Skin‐worn Soft Microfluidic Potentiometric Detection System

A flexible skin‐mounted microfluidic potentiometric device for simultaneous electrochemical monitoring of sodium and potassium in sweat is presented. The wearable device allows efficient natural sweat pumping to the potentiometric detection chamber, containing solid‐contact ion‐selective Na⁺ and K⁺ electrodes, during exercise activity. The fabricated microchip electrolyte‐sensing device displays good analytical performance and addresses sweat mixing and carry‐over issues of early epidermal potentiometric sensors. Such soft skin‐worn microchip platform integrates potentiometric measurement, microfluidic technologies with flexible electronics for real‐time wireless data transmission to mobile devices. The new fully integrated microfluidic electrolyte‐detection device paves the way for practical fitness and health monitoring applications.     

Experimental investigation of paraffin nano-encapsulated phase change material on heat transfer enhancement of pulsating heat pipe

Journal of Thermal Analysis and Calorimetry - In this study, a mixture of nano-encapsulated phase change materials in water has been used as the working fluid in a pulsating heat pipe in order to...     

Numerical study of flow-induced vibrations of cylinders under the action of nonlinear energy sinks (NESs)

An isolated two-dimensional circular cylinder with two linear degrees of freedom, parallel and perpendicular to the free-stream direction, and owning a nonlinear energy sink (NES) is investigated by fluid–structure interaction (FSI) simulations to assess vortex-induced vibrations (VIV) at moderate Reynolds numbers. Subsequently, the wake-induced vibration (WIV) of a pair of identical cylinders under the action of two NES in a tandem arrangement and in a proximity–wake interference regime is explored using the same approach. The NES parameters (mass, nonlinear stiffness and damping) are investigated to determine their effects on the dynamic response of a single degree of freedom (in transverse flow direction) coupled system by a reduced-order model based on an experimentally validated van der Pol oscillator. The CFD model coupled with FSI method is also validated against VIV experimental data for an isolated cylinder in a uniform flow. The study is aimed to investigate the effect of the passive suppression NES device on VIV and WIV. The amplitude response, trajectories of cylinder motion and temporal evolutions of vortex shedding are obtained by conducting a series of numerical simulations. It is found that placing a tuned NES in the cylinders can provide good suppression effect; however, the effectiveness is function of the reduced velocity.     

Single-walled boron nitride nanotube as nano-sensor

Nowadays, the eye-catching characteristics of boron nitride nanotubes, in particular, the capability of sensing nano-objects, have opened up new prospects to develop the bio-/nano-sensing technologies. This research deals with physically affected single-walled boron nitride nanotubes (SWBNNT) as nano-sensors for sensing attached nanoscale objects. Three different boundary conditions including simply supported at both ends, clamped-free and clamped-clamped are considered to illustrate the vibrational behaviour of SWBNNTs as nano-sensor. The Rayleigh and Timoshenko beam theories are employed to model the SWBNNT. Also, the nonlocal strain gradient model is utilized to capture the size-dependent effects. One of the major factors in the scrutiny of mass nano-sensors is pertinent to the variation in frequency shift magnitudes against the number and mass weight values of attached nanoparticles. Herein, the effects of the nonlocal and material length scale parameters, the number and location of nano-objects, the rotary inertia and mass weight magnitudes of attached nanoparticles, the aspect ratio of SWBNNT, electrical potential and different boundary conditions on the variation in frequency shift and resonant frequency are analysed.     

Photoinduced Birefringence in Poly(Methyl Methacrylate) Polymeric Thin Films Doped with Di-Azo Sudan G

Photoinduced birefringence in poly(methyl methacrylate) (PMMA), polymeric thin films doped with di-azo Sudan G was investigated. A pump-probe method was used to study the dynamic behavior of the birefringence. The mechanism for the inducement of birefringence is discussed in terms of the photoisomerization of the di-azo Sudan G molecules. The results showed that the dynamic evolution of the photoinduced birefringence was such that the average birefringence increased, saturated, and then decreased with respect to the laser pump intensity. Also, an exponential-like relationship was observed between both the saturation and the isotropic states of the averaged transmitted probe beam (expressing the residual anisotropy) and the birefringence on one hand, and the intensity amplitudes of the pumping powers on the other hand.     

Intraspecific competition of predator for prey with variable rates in protected areas

Nonlinear Dynamics - In this present study, we systematically explore the periodicity (almost periodic nature) of a dynamical system in time-varying environment, which portrays a special case of...     

Modeling and active control of chatter vibrations of piezoelectric stacked machining arm in micro-turning process

Self-excited vibrations known as chatter are considered as the most detrimental issue in micro-turning processes. Occurring unpredictably, they adversely affect the tool life, productivity rate and surface quality of the machining processes. In this paper, a novel machining arm is modeled as a piezoelectric stacked rod which is subjected to a chatter force in the orthogonal micro-turning process. Due to the fact that machining processes are affected by various sources of uncertainties, H_∞ robust control approach is used to suppress the chatter vibrations of the machining arm in the presence of tool wear and dynamic model parameter variations. Also, input control force of the system is provided by exciting the input voltage of piezoelectric layers of the rod. In order to be certain that the designed controller succeeds in suppressing vibrations of the effective structural modes, behavior of the first three modes of vibrations are considered in the final response of the machining arm. In the following, performance of the robust H_∞ controller is compared with a modified PID controller. Simulation results show that the H_∞ controller improves the robustness and performance of the system against uncertainties. The PID controller extends the stability region of the sharp tool and fails to achieve this purpose for the worn tool although its performance is acceptable in suppressing chatter vibrations.