Analytical study of pulsatile mixed electroosmotic and shear-driven flow in a microchannel with a slip-dependent zeta potential

The escalation of zeta potential by the influence of wall slip for the electrokinetically modulated flow through a microchannel motivates to consider the impact of hydrodynamic slippage upon the zeta or surface potential.The reported study undergoes an analytical exploration of the pulsatile electroosmosis and shear-actuated flow characteristics of a fluid with a Newtonian model through a microchannel with parallel plates by invoking the reliance of a zeta or surface potential on slippage.The linearized Poisson-Boltzmann and momentum equations are solved analytically to obtain the explicit expression of the electrical potential induced in the electrical double layer(EDL),the flow velocity field,and the volumetric flow rate for an extensive span of parameters.The velocity field proximal to the microchannel wall is observed to enhance by an apparent zeta potential,and is further escalated for a thinner EDL and an oscillating electric field with a higher amplitude.However,near the core region of the microchannel,the flow velocity becomes invariant with the EDL thickness.The result shows that the lower wall velocity contributes to the flow velocity along with the electroosmotic body force and the impact of the velocity of the wall underneath diminishes proximal to the upper wall.Moreover,the volumetric flow rate increases when the thickness of the EDL decreases,owing to the influence of the wall slip.However,for thinner EDLs and medium and higher oscillating Reynolds numbers,the volumetric flow rate varies non-monotonously,correlative to the slip-free and slip cases.

A new four-dimensional chaotic system with first Lyapunov exponent of about 22,hyperbolic curve and circular paraboloid types of equilibria and its switching synchronization by an adaptive global integral sliding mode control

This paper presents a new four-dimensional（4 D） autonomous chaotic system which has first Lyapunov exponent of about 22 and is comparatively larger than many existing three-dimensional（3 D） and 4 D chaotic systems.The proposed system exhibits hyperbolic curve and circular paraboloid types of equilibria.The system has all zero eigenvalues for a particular case of an equilibrium point.The system has various dynamical behaviors like hyperchaotic,chaotic,periodic,and quasi-periodic.The system also exhibits coexistence of attractors.Dynamical behavior of the new system is validated using circuit implementation.Further an interesting switching synchronization phenomenon is proposed for the new chaotic system.An adaptive global integral sliding mode control is designed for the switching synchronization of the proposed system.In the switching synchronization,the synchronization is shown for the switching chaotic,stable,periodic,and hybrid synchronization behaviors.Performance of the controller designed in the paper is compared with an existing controller.

An experimental study on ballistic impact response of jute reinforced polyethylene glycol and nano silica based shear thickening fluid composite

The present study aims at assessing the ballistic impact behaviour of jute reinforced polyethylene glycol(PEG)and nano silica based shear thickening fluid(STF).Preparation of STF is achieved by dispersing the nano silica particles at different weight percentage loadings of 10%,20%,30%and 40%in PEG and the effect of various weight percentages loading of nano silica particles on ballistic performance of the proposed composites is studied experimentally.Rheological studies of the prepared STF’s showed that at all nanosilica loading shear thickening occurred and also the shear thickening was highest at higher loading of nano silica at lower rate of shear.The study reveals that the ballistic performance of the jute fabric is enhanced with impregnation of STF.The ballistic results indicate that energy absorption of the proposed composites is enhanced with increased loading of nano silica particles and at the same time,the effect of STF was reduced.Specific energy absorption(SEA)of the neat fabric and the proposed composites was made use of for the purpose of comparing the energy absorption capabilities.It is found that the SEA of proposed composites with 10%nano silica loading is lesser than the neat fabric both in case of 3 layers and 6 layers.It was also found that proposed composite with 40%nano silica loading exhibits highest SEA compared to neat fabric and its counterparts with its SEA being 3.21 and 3.76 times highest compared to three and six layers of neat fabrics respectively.

Investigation of current collapse and recovery time due to deep level defect traps inβ-Ga2O3 HEMT

In this paper,drain current transient characteristics ofβ-Ga2O3 high electron mobility transistor(HEMT)are studied to access current collapse and recovery time due to dynamic population and de-population of deep level traps and interface traps.An approximately 10 min,and 1 h of recovery time to steady-state drain current value is measured under 1 ms of stress on the gate and drain electrodes due to iron(Fe)–dopedβ-Ga2O3 substrate and germanium(Ge)–dopedβ-Ga2O3 epitaxial layer respectively.On-state current lag is more severe due to widely reported defect trap EC–0.82 e V over EC–0.78 e V,-0.75 e V present in Iron(Fe)-dopedβ-Ga2O3 bulk crystals.A negligible amount of current degradation is observed in the latter case due to the trap level at EC–0.98 e V.It is found that occupancy of ionized trap density varied mostly under the gate and gate–source area.This investigation of reversible current collapse phenomenon and assessment of recovery time inβ-Ga2O3 HEMT is carried out through 2 D device simulations using appropriate velocity and charge transport models.This work can further help in the proper characterization ofβ-Ga2O3 devices to understand temporary and permanent device degradation.

Structural, electronic, and mechanical properties of cubic TiO_2:A first-principles study

We present an analysis of structural, electronic, and mechanical properties of cubic titanium dioxide （TiO2） using an all electron orthogonalzed linear combinations of atomic orbitals （OLCAO） basis set under the framework of density functional theory （DFT）. The structural property, especially the lattice constant a, and the electronic properties such as the band diagram and density of states （DOS） are studied and analyzed. The mechanical properties such as bulk moduli, shear moduli, Young＇s Moduli, and Poison＇s ratio are also investigated thoroughly. The calculations are carried out on shear moduli and anisotropy factor for cubic TiO2. The Vickers hardness is also tested for fluorite and pyrite cubic-structured TiO2. Furthermore, the results are compared with the previous theoretical and experimental results. It is found that DFT- based simulation produces results which are approximation to experimental results, whereas the calculated elastic constants are better than the previous theoretical and experimental values.

Assessment of self-reacting bobbin tool friction stir welding for joining AZ31 magnesium alloy at inert gas environment

Research work presented in this study has the primary target of exploring joint attributes of AZ31 magnesium alloys using friction stir welding process with a modified tool referred as bobbin tool.Effects of inert and open atmosphere on mechanical properties are evaluated over a wide range of welding speed and tool rotation speed.Comparison of the research findings from the inert atmosphere bobbin tool were made with the traditional process of friction stir welding.The results depicted improved joint properties for inert atmosphere welding.Low and intermediate range of tool rotational speed is found to be favorable for bobbin tool friction stir welding without and with an inert medium,respectively.Controlled atmosphere due to inert medium leads to less oxidation of the AZ31 Mg alloy leading to superior joint properties.Microstructural investigations are also made with the aim of evaluating the impact of bobbin tool and inert medium on joint properties.In each aspect for joining of AZ31 Mg alloy,bobbin tool with inert medium is found to be an effective solution for joining with improved mechanical properties compared to without inert bobbin tool as well as conventional tool friction stir welding.

Gap acceptance behavior of drivers at uncontrolled T-intersections under mixed traffic conditions

Explicit traffic control measures are absent in uncontrolled intersections which make them susceptible to frequent conflicts and resulting collisions between vehicles. In developing countries like India, drivers at such intersections do not yield to higher priority movements which cause more crashes between vehicles. The objective of this study is to analyze and model the gap acceptance behavior of minor street drivers at uncontrolled T-intersections considering their aggressive nature. Three intersections in the northeast region of India have been selected as the case study area. Preliminary analysis of the data revealed that drivers behave aggressively, not because they have to wait for a long time at the stop line, but because of their lack of respect for traffic rules. Binary logit models are developed for minor road right turning vehicles which show that gap acceptance behavior is influenced by gap duration, clearing time and aggressive nature of drivers. The equations obtained were used to estimate the critical gaps for aggressive and non-aggressive drivers. Critical gaps are also calculated using an existing method called clearing behavior approach. It is also shown that the estimation of critical gap is more realistic if clearing time and aggressive behavior of drivers are considered.

最佳材料选择的决策工具:综述

本文回顾了考虑不同参数的用于选择最佳材料的决策工具(材料比较和选择工具)。主要解决了以下重要问题:1)不同材料选择和排序方法所涉及的工程应用;2)解决工程应用最佳材料选择使用的主要决策工具;3)所使用的决策工具的优缺点;4)在选择合适的替代材料时考虑的主要使用标准或目标;5)关于材料选择领域的DEA概述。本文研究了全球不同地区1988年以来的文献,不仅强调了材料选择在产品开发早期设计阶段的重要性,而且还有助于设计和材料工程师系统地应用不同的决策工具。

A new four-dimensional hyperjerk system with stable equilibrium point, circuit implementation, and its synchronization by using an adaptive integrator backstepping control

This paper reports a new simple four-dimensional（4 D） hyperjerk chaotic system. The proposed system has only one stable equilibrium point. Hence, its strange attractor belongs to the category of hidden attractors. The proposed system exhibits various dynamical behaviors including chaotic, periodic, stable nature, and coexistence of various attractors. Numerous theoretical and numerical methods are used for the analyses of this system. The chaotic behavior of the new system is validated using circuit implementation. Further, the synchronization of the proposed systems is shown by designing an adaptive integrator backstepping controller. Numerical simulation validates the synchronization strategy.

采用基于灰度的混合方法优化Al6061/空心微珠复合材料电火花切割工艺参数（英文）

粉煤灰作为铝基复合材料的增强剂已得到越来越多的关注,其可以增强特定的性能,还可以减少制备成本。然而,铝基复合材料的加工性能较差限制了其发展。本研究采用复合铸造方法制备粉煤灰增强Al6061合金。X射线衍射分析表明铝基复合材料中只含有粉煤灰颗粒,不含其他金属间化合物。采用电火花切割评价所制备金属基复合材料的加工性能。采用不同的电火花切割工艺参数组合对材料去除率、电极磨损率、表面粗糙度等性能参数进行评价。采用响应曲面方法的中心复合设计对所需实验的数量进行优化,获得基于灰度的响应曲面方法,并用以预测电火花切割最佳工艺组合。采用基于灰度响应曲面方法预测得到的最佳工艺参数组合时,所得性能参数得到明显提高,电火花切割表面的3D轮廓图表明材料的表面质量和织构都得到提升。

Electrical Tracking,Erosion and Fire Retardancy Performance of Silicone Rubber Insulation Containing Aluminum Trihydrate,Graphene and Glass Fiber Additives

Silicone rubber composite is a priority electrical insulating material used in high-voltage outdoor insulation applications.Low electrical tracking/erosion and poor flame resistance performance of silicone rubber once ignited,substantially reduce its working life.This paper attempts to investigate tracking/erosion performance of room temperature vulcanized(RTV)silicone rubber along with flame retardant parameters using aluminum trihydrate(ATH),graphene nanosheets(GN)and milled glass fiber(GF)additives.The inclined plane test(IPT)was performed in line with criteria defined in IEC 60587 using step-up tracking voltage method while flame retardancy is evaluated according to ASTM E 1354.0 using a cone calorimeter.Results suggest 30% of ATH assists in improving physical tracking/erosion resistance of pristine silicone elastomer rubber by impeding development of leakage current and a great reduction in maximum average temperatures on the surface of RTV2.Further improvement in performance of RTV2 is achieved through introduction of 1%of GN and 5% of GF as seen in RTV4.Moreover,30% of ATH reduces heat release rate and smoke production rate,and this trend is improved with the introduction of GN/GF.RTV4 has pop up as the most promising silicone rubber composite with excellent electrical tracking,erosion,and flame resistance performance relative to its counterparts in this study.

Modeling and simulation of enhancement mode p-GaN Gate AlGaN/GaN HEMT for RF circuit switch applications

An enhancement mode p-GaN gate AlGaN/GaN HEMT is proposed and a physics based virtual source charge model with Landauer approach for electron transport has been developed using Verilog-A and simulated using Cadence Spectre,in order to predict device characteristics such as threshold voltage,drain current and gate capacitance.The drain current model incorporates important physical effects such as velocity saturation,short channel effects like DIBL（drain induced barrier lowering）,channel length modulation（CLM）,and mobility degradation due to self-heating.The predicted Id–V（ds）,Id–V（gs）,and C–V characteristics show an excellent agreement with the experimental data for both drain current and capacitance which validate the model.The developed model was then utilized to design and simulate a single-pole single-throw（SPST）RF switch.

DTM Simulation of Peristaltic Viscoelastic Biofluid Flow in Asymmetric Porous Media： A Digestive Transport Model

A biofluid dynamics mathematical model is developed to study peristaltic flow of non-Newtonian physiological liquid in a two-dimensional asymmetric channel containing porous media as a simulation of obstructed digestive （intestinal） transport. The fractional Oldroyd-B viscoelastic rheological model is utilized. The biophysical flow regime is constructed as a wave-like motion and porous medium is simulated with a modified Darcy-Brinkman model. This model is aimed at describing the diges- tive transport in intestinal tract containing deposits which induce impedance. A low Reynolds number approximation is em- ployed to eliminate inertial effects and the wavelength to diameter ratio is assumed to be large. The differential transform method （DTM）, a semi-computational technique is employed to obtain approximate analytical solutions to the boundary value problem. The influences of fractional （rheological material） parameters, relaxation time, retardation time, amplitude of the wave, and permeability parameter on peristaltic flow characteristics such as volumetric flow rate, pressure difference and wall friction force are computed. The present model is relevant to flow in diseased intestines.

Impact of barrier thickness on gate capacitance—modeling and comparative analysis of GaN based MOSHEMTs

A mathematical model is developed predicting the behavior of gate capacitance with the nanoscale variation of barrier thickness in AlN/GaN MOSHEMT and its effect on gate capacitances of AIInN/GaN and AlGaN/GaN MOSHEMTs through TCAD simulations is compared analytically. AlN/GaN and AIInN/GaN MOSHEMTs have an advantage of a significant decrease in gate capacitance up to 108 fF/μm^2 with an increase in barrier thickness up to 10 nm as compared to conventional AlGaN/GaN MOSHEMT. This decrease in gate capacitance leads to improved RF performance and hence reduced propagation delay.

VO(acac)_2 catalyzed condensation of o-phenylenediamine with aromatic carboxylic acids/aldehydes under microwave radiation affording benzimidazoles

Vanadyl acetylacetonate， VO (acac ) 2，被发现了是为在没有溶剂的状况下面的许多 benzimidazoles 的合成的很有效的催化剂。没有任何溶剂或支持的代理人的使用，方法论包含 o-phenylenediamine 和选择芳香的羧基的酸 / 醛的混合物的暴露到微波放射。benzimidazoles 与高收益在快时间被获得。

Small-signal model parameter extraction of E-mode N-polar GaN MOS-HEMT using optimization algorithms and its comparison

An improved small-signal parameter extraction technique for short channel enhancement-mode N-polar GaN MOS-HEMT is proposed, which is a combination of a conventional analytical method and optimization techniques. The extrinsic parameters such as parasitic capacitance, inductance and resistance are extracted under the pinch-off condition. The intrinsic parameters of the small-signal equivalent circuit（SSEC） have been extracted including gate forward and backward conductance. Different optimization algorithms such as PSO, Quasi Newton and Firefly optimization algorithm is applied to the extracted parameters to minimize the error between modeled and measured S-parameters. The different optimized SSEC models have been validated by comparing the S-parameters and unity current-gain with TCAD simulations and available experimental data from the literature. It is observed that the Firefly algorithm based optimization approach accurately extracts the small-signal model parameters as compared to other optimization algorithm techniques with a minimum error percentage of 1.3%.

Performance analysis of 20 nm gate-length In_(0:2)Al_(0:8)N/GaN HEMT with Cu-gate having a remarkable high I_(ON)/I_(OFF)ratio

We propose a new structure of InxAll-xN/GaN high electron mobility transistor （HEMT） with gate length of 20 nm. The threshold voltage of this HEMT is achieved as -0.472 V. In this device the InA1N barrier layer is intentionally n-doped to boost the ION/IOFF ratio. The InAlN layer acts as donor barrier layer for this HEMT which exhibits an ION = 10-4.3 A and a very low IOFF = 10-14.4 A resulting in an ION/IoFF ratio of 1010.1. We compared our obtained results with the conventional InAlN/GaN HEMT device having undoped barrier and found that the proposed device has almost l0s times better ION/IOFF ratio. Further, the mobility analysis in GaN channel of this proposed HEMT structure along with DC analysis, C-V and conductance characteristics by using small-signal analysis are also presented in this paper. Moreover, the shifts in threshold voltage by DIBL effect and gate leakage current in the proposed HEMT are also discussed. InAlN was chosen as the most preferred barrier layer as a replacement of AlGaN for its excellent thermal conductivity and very good scalability.

α-Fe2O3 immobilized benzimidazolium tribromide as novel magnetically retrievable catalyst for one-pot synthesis of highly functionalized piperidines

Nanostructured ot-Fe2O3 were prepared by precipitation followed by calcination method. Cetyltrimethylammonium bromide （CRAB） was used as surfactant. The nano α-Fe2O3 was then silanized with （3-chloropropyl）-triethoxysilane （CPTES） by room temperature mixing ofα-Fe2O3 and CPTES to produce silane coated ct-Fe2O3 （CIPr-Si@Fe2O3）. As-synthesized CIPr-Si@Fe2O3 was functionalized via covalent grafting of benzimidazole to produce 3-（1-benzimidazole）Pr-Si@Fe2O3. This was further reacted with bromine to afford α-Fe2O3 immobilized benzimidazolium tribromide （α-Fe2O3-BIM tribromide）. This ionic liquid （IL） α-Fe2O3 BIM tribromide was characterized by FT-IR, XRD, TEM, SEM, TGA, VSM, EDX and BET analysis. The as-synthesized IL tribromide was used as catalyst for one-pot synthesis of highly substituted piperidines. The method is greener in terms of solvent selection, recovery of the catalyst and efficiency.

Modeling of cylindrical surrounding gate MOSFETs including the fringing field effects

A physically based analytical model for surface potential and threshold voltage including the fringing gate capacitances in cylindrical surround gate（CSG） MOSFETs has been developed.Based on this a subthreshold drain current model has also been derived.This model first computes the charge induced in the drain/source region due to the fringing capacitances and considers an effective charge distribution in the cylindrically extended source/drain region for the development of a simple and compact model.The fringing gate capacitances taken into account are outer fringe capacitance,inner fringe capacitance,overlap capacitance,and sidewall capacitance.The model has been verified with the data extracted from 3D TCAD simulations of CSG MOSFETs and was found to be working satisfactorily.

Probing the compound effect of spatially varying intrinsic defects and doping on mechanical properties of hybrid graphene monolayers

Doping in pristine 2 D materials brings about the advantage of modulating wide range of mechanical properties simultaneously.However,intrinsic defects(such as Stone-Wales and nanopore) in such hybrid materials are inevitable due to complex manu facturing and synthesis processes.Besides that,de fects and irregularities can be intentionally induced in a pristine nanostructure for multi-synchronous modulation of various multi-functional properties.Whatever the case may be,in order to realistically analyse a doped graphene sheet,it is of utmost importance to investigate the compound effect of doping and defects in such 2 D monolayers.Here we present a molecular dynamics based investigation for probing mechanical properties(such as Young’s modulus,post-elastic behaviour,failure strength and strain)of doped graphene(C14 and Si) coupling the effect of inevitable defects.Spatial sensitivity of defect and doping are systematically analyzed considering different rational instances.The study reveals the effects of individual defects and doping along with their possible compounded influences on the failure stress,failure strain,Young’s modulus and constitutive relations beyond the elastic regime.Such detailed mechanical characterization under the practically relevant compound effects would allow us to access the viability of adopting doped graphene in various multifunctional nanoelectromechanical devices and systems in a realistic situation.