Sharif Digital Repository

Resistive pulse sensing (RPS) has proved to be a viable method for the detection and characterization of micro and nano particles. Modern fabrication methods have introduced different nanopore geometries for resistive pulse sensors. In this paper, we have numerically studied the effects of membrane thickness and the pore's cone angle, as the main geometrical parameters, on the sensing performance of the nanopores used for nanoparticle detection in the resistive pulse sensing method. To compare the sensing performance, three resistive pulse quality parameters were investigated-sensitivity, pulse duration and pulse amplitude. The thorough investigation on the relations between the geometrical... 

Achieving dense off-chip interconnection with satisfactory electrical performance is emerging as a major challenge in advanced system engineering. Graphene nanoribbons (GNRs) have been recently proposed as one of the potential candidate materials for both transistors and interconnect. In addition, development is still underway for alternative materials and processes for high aspect ratio (AR) contacts. Studding the effect of varying aspect ratio on relative stability of graphene nanoribbon interconnects is an important viewpoint in performance evaluation of system. In this paper, Nyquist stability analysis based on transmission line modeling (TLM) for GNR interconnects is investigated. In... 

In this study, turbulent natural convection in a square enclosure including one or four hot and cold bodies is numerically investigated in the range of Rayleigh numbers of 1010 < Ra < 1012. The shape of the internal bodies is square or rectangular with the same surface areas and different aspect ratios. In all cases, the horizontal walls of the enclosure are adiabatic, and the vertical ones are isothermal. It is desired to investigate the influence of different shapes and arrangements of internal bodies on the heat transfer rate inside the enclosure with wide-ranging applications such as ventilation of buildings, electronic cooling, and industrial cold box packages. Governing equations,... 

In this study, turbulent natural convection in a square enclosure including one or four hot and cold bodies is numerically investigated in the range of Rayleigh numbers of 1010 < Ra < 1012. The shape of the internal bodies is square or rectangular with the same surface areas and different aspect ratios. In all cases, the horizontal walls of the enclosure are adiabatic, and the vertical ones are isothermal. It is desired to investigate the influence of different shapes and arrangements of internal bodies on the heat transfer rate inside the enclosure with wide-ranging applications such as ventilation of buildings, electronic cooling, and industrial cold box packages. Governing equations,... 

The network structure of styrene-butadiene rubber (SBR) in the presence of carbon black (CB) with two different structures and multi-walled carbon nanotubes (MWCNTs) was investigated. Swelling behaviour, tensile properties at various strain rates and cure kinetics were characterized. Experimental data were analysed using the Flory-Rehner model as well as the tube model theory. It is found that the network structure of CB-filled SBR follows a three-phase composite model including rigid particles, semi-rigid bound rubber and matrix rubber. This bound rubber is postulated to be critical for the mechanical and deformational properties, development of crosslinking density in matrix rubber and... 

We investigate the effects of anisotropy on the finite-size scaling of connectivity and conductivity of continuum percolation in three dimensions. We consider a system of size X×Y×Z in which cubic bodies of size a×b×c are placed randomly. We define two aspect ratios to request anisotropy then we expect that the displacement of average connected fraction P (averaged over the realizations), about the isotropic universal curves will be a function of the two aspect ratios. This is accounted by considering an apparent percolation threshold in each direction which leads to 50% of realizations connecting in that direction. We find the aspect ratios' dependency of the apparent threshold and... 

Accurate estimation of the in-plane shear modulus of solids reinforced by nano-/micro-size elliptical multi-coated fibers is the focus of this paper. It is well-known that at the scales comparable to the nanoscopic length scales of the material, traditional theory of elasticity ceases to hold and, moreover, due to lack of consideration of such length scales has an innate weakness of sensing the size effect. Therefore, it is proposed to formulate and calculate the effective shear modulus of the nano-/micro-composite within micropolar theory which introduces two material characteristic lengths into the field equations. For this purpose, Mori-Tanaka theory is extended to treat nested... 

The theoretical need to recognize the link between the basic microstructure of nonlinear porous materials and their macroscopic mechanical behavior is continuously rising owing to the existing engineering applications. In this regard, a semi-analytical homogenization model is proposed to establish an overall, continuum-level constitutive law for nonlinear elastic materials containing prolate/oblate spheroidal voids undergoing finite axisymmetric deformations. The microgeometry of the porous materials is taken to be voided spheroid assemblage consisting of confocally voided spheroids of all sizes having the same orientation. Following a kinematically admissible deformation field for a... 

Prediction of the anti-plane moduli of solids consisting of a given distribution of unidirectionally aligned elliptic multi-coated fibers with interfacial damage is the focus of this paper. The fibers and their coating layers may be in the order of nano or micro scales. All the constituent phases of the composite are supposed to be described in terms of couple stress elasticity. Accordingly, the bounds for the overall shear moduli of the aforementioned composites are provided by employing the principles of minimum potential and complementary energies. Certain subtleties associated with the elliptic multi-coated fibers for three cases of pure sliding (completely damaged), imperfect (partially... 

In this paper, the instability of cantilevered horizontal composite pipes is investigated. To this aim, the lateral flow forces are modelled as a distributed lateral force and the nozzle effect is modelled as a compressive axial follower force and a concentrated end mass. The coupled bending-torsional equations of motion are derived using Hamilton's principal and Galerkin method. In order to obtain the stability margin of the pipe, the standard Eigen value problem is solved. Finally, effects of elastic coupling parameter and nozzle aspect ratio are considered on the stability margin of the pipe and some conclusions are drawn  

The end diaphragm of bridges are normally designed to resist lateral seismic forces imposed on the superstructure in earthquake prone regions. Using ductile diaphragms with high deformation capacity could reduce the seismic demands on the substructure and prevent costly damage under strong ground motions. The end diaphragms of steel tub girder bridges with high lateral stiffness and dominant shear behavior have a potential to be used as ductile fuse elements. In this study, a steel plate shear diaphragm (SPSD) is introduced as an external end diaphragm of tub girder steel bridges to reduce the seismic demands imposed on the substructure. Quasi static nonlinear analyses were conducted to... 

In this article a simple penetration model for the terminal ballistic of long rod penetrators is developed. The model is to predict the crater depth of a projectile penetrating into a semi-infinite target. A principle objective was to take an account of strength properties of colliding materials using erosive phenomena. The entire velocity regime from low to hypervelocity is analysed. The effect of the penetrator aspect ratio is also considered in the model. The model developed here is based on the steady-state penetration process and is used to compare with existing experimental measurements. The results of the comparison show very good agreement with experimental investigations of other... 

In this study, the effects of geometry and operating conditions upon the thermal and hydraulic performance of Finned Microchannel Heat Sink (FMCHS) were investigated. Water and aluminum were considered as fluid and solid for the computational domain (30 mm × 0.8 mm × 0.8 mm). The Microchannel (MC) was supposed to have 0.65 mm height with an aspect ratio of 0.5. CFD analysis was applied for the assessments of four-types of micro-fins (i.e., conical, pyramidal, cylindrical and cubical). In order to evaluate the effects of height, diameter, the spacing of fins and Reynolds number on the overall performance of FMCHS, central composite design at five levels was used to generate design points.... 

In this paper, n-tier methodology is developed to design multilevel interconnect architecture of macrocells using single-wall carbon nanotube (SWCNT) bundles. Upper limit of low-bias voltage of SWCNT bundle interconnects is derived and its dependence on temperature, SWCNTs' diameter, and interconnect length is studied. Possibility of using SWCNT bundles as local interconnects at 7.5-nm technology node is discussed, and it is shown that SWCNT bundles with 1 nm diameter cannot be used at the first interconnect metal level. Using Cu and SWCNT bundles, multilevel interconnect architecture of a 7.5-nm ASIC macrocell is designed which reduces the number of metal levels by 27% and power dissipation... 

In this paper fabrication of a 0-3 ceramic/ceramic composite lead zirconate titanate, Pb(Zr0.52Ti0.48)O3 thin film has been presented and then a pressure sensor based on multilayer thin-film PZT diaphragm contain of Lead Zirconate Titanate nanocrystalline powders was designed, modeled and optimized. This multilayer diaphragm in general acts as sensor or actuator. ANSYS was used for simulation of diaphragm. Dynamics characteristics of this multilayer diaphragm have been investigated. By this simulation the effective parameters of the multilayer PZT diaphragm for improving the performance of a pressure sensor in different ranges of pressure are optimized. The optimized thickness ratio of PZT... 

This paper proposes a damage assessment framework based on the visual features of a damaged reinforced concrete shear wall, such as crack pattern distribution, crushing areal density, aspect ratio, and the presence of the boundary condition. The study contains two parts including: identifying the performance level of the damaged walls (i.e., Immediate Occupancy, Life Safety, and Collapse Prevention) and estimating the residual strength and drift ratio of the walls. The research database contains 236 images of 72 reinforced concrete shear walls tested in the laboratory under the quasi-static cyclic loadings at various drift ratios between 0 and 4%. To identify the performance level of a... 

The finite number of toroidal field coils of a tokamak destroys the perfect axisymmetry of the device. The coils produce a short wavelength ripple in the toroidal magnetic field strength as a field line follows round the torus, which becomes important in transport and confinement properties of plasma. Hence, a quick and accurate estimation of ripple becomes important. We have noticed that a previously reported analytical formulation by Princeton Plasma Physics Laboratory team is not applicable to our large aspect ratio tokamak, and have devised a slightly modified form which has greatly improved the accuracy of the analytical fit  

Cadmium sulfide (CdS) with different morphologies was successfully prepared by solvothermal process by controlling the processing parameters, including nature of precursor and solvent, reaction temperature and process time. X-ray diffraction patterns revealed that, in all cases highly pure and crystallized CdS with hexagonal structure were obtained. In addition, it was found that the processing parameters influence on preferable growth direction of CdS nanostructures. Field emission scanning electron microscope analysis showed that CdS nanowires with different aspect ratios were obtained (depending upon the reaction temperature and process time) in presence of sulfur powder and... 

The properties of metallic nanorods vary due to changes in their composition, size and shape, which all depend on the aspect ratio of the nanorods. This work focuses on the optimization of the aspect ratio of silver nanorods using response surface methodology (RSM). Seed-mediated approach, which is the newest method with less difficulty, has been used for the synthesis of silver nanorods. First, silver ions were reduced with sodium borohydride in the presence of sodium citrate dehydrate, as stabilizer. Then, the prepared seeds were added to a solution containing more metal salts, a weak reducing agent (ascorbic acid) and a rod-like micellar template (cetyltrimethylammonium bromide, CTAB).... 

For the rapid detection of hyperglycemia in human blood, we adopted a facile and two-step electrochemical procedure to prepare nickel/reduced graphene oxide (rGO) hybrid electrodes in the framework of a three-dimensional (3D) nanostructure. High-density and vertically-aligned nickel submicrorods with an average diameter of 155 ± 15 nm and a length of 7 ± 1 μm (an aspect ratio of about 40-50) were prepared by template-mediated electrochemical deposition techniques. Networks of rGO nanosheets between the rod-shaped arrays were formed by the cathodic electrophoretic deposition method. The synergistic effect of nickel morphology (planar and high-density rod-shaped arrays) and graphene oxide...