Sharif Digital Repository

In this paper, the conventional 2D H-filter is modified to 3D multi-layer structures fabricated by low-cost xurography. The extraction efficiency was studied experimentally for different 3D structures and then compared with conventional 2D H-filter. Numerical simulations were performed to model the diffusion flow in the proposed H-filters, showing a good agreement with the experimental observations. Results show that 3D H-filters have higher extraction efficiency at the same Reynolds number. Moreover, these structures could benefit low-cost and commercial applications due to their higher efficiency at smaller sizes. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH... 

This paper proposes a novel design of the variable reluctance permanent magnet (VRPM) resolvers. It utilizes a slotless stator to reduce the resolver volume. The proposed design overcomes the complex structure of windings by replacing them with magnetic flux measurement units (MFMU). The new design eliminates the computationally-expensive demodulation process of output signals by relying on none-modulated signals. An analytical model based on the nonlinear magnetic equivalent circuit (MEC) method is used to extract the output signals of the proposed resolver design. The accuracy of applied analytical model is verified against the time-stepping finite-element method (TSFEM). An optimization... 

This article proposes a novel design of the variable reluctance permanent magnet (VRPM) resolvers. It utilizes a slotless stator to reduce the resolver volume. The proposed design overcomes the complex structure of windings by replacing them with magnetic flux measurement units. The new design eliminates the computationally-expensive demodulation process of output signals by relying on none-modulated signals. An analytical model based on the nonlinear magnetic equivalent circuit method is used to extract the output signals of the proposed resolver design. The accuracy of applied analytical model is verified against the time-stepping finite-element method (TSFEM). An optimization is... 

Electrodeposition of long and well-defined gold nanotubes in polycarbonate (PC) templates is still a major concern due to pore blockage problems. In the present study, we introduce a novel method for electrodeposition of long gold nanotubes within the pores of PC templates for the first time. In order to deposit gold atoms onto the pore walls preferentially, pore walls were functionalized with a coupling agent. Short and thin Ni nanotubes were then electrodeposited at the bottom of the pores. Gold nanotubes were subsequently electrodeposited at constant potentials and low solution concentrations. The morphology of nanotubes was characterized by electron microscopy and their formation... 

Phosphatidylcholine (PC) possesses amphiphilic characteristics to form vesicles or liposome nanoparticles and can be utilized to deliver essential nutrients such as proteins, peptide antigens, and essential fatty acids. In this study, an attempt has been made to obtain purified PC and evaluate its potential in nanoliposome synthesis and its corresponding drug release profile. In this regard, four physical separation techniques comprising extraction, precipitation, static, and dynamic adsorption were assessed and applied to purify PC from soybean lecithin. Different solvents and the ratio of lecithin to solvent were used to achieve the highest PC percentage. The results of an HPLC test showed... 

Phosphatidylcholine (PC) possesses amphiphilic characteristics to form vesicles or liposome nanoparticles and can be utilized to deliver essential nutrients such as proteins, peptide antigens, and essential fatty acids. In this study, an attempt has been made to obtain purified PC and evaluate its potential in nanoliposome synthesis and its corresponding drug release profile. In this regard, four physical separation techniques comprising extraction, precipitation, static, and dynamic adsorption were assessed and applied to purify PC from soybean lecithin. Different solvents and the ratio of lecithin to solvent were used to achieve the highest PC percentage. The results of an HPLC test showed... 

Polycaprolactone-polylactide block copolymers (PCL-block-PLA) were grafted onto filled multi-wall carbon nanotubes (MWCNT) successfully. In this synthesis, MWCNTs were opened and functionalized, and then they were filled by silver nanoparticles. The filled MWCNT were used as macroinitiator for ring opening polymerization of ε-caprolactone and L-lactide. Then the end hydroxyl functional groups of MWCNT-graft-PCL or MWCNT-graft-PLA were used as initiator for ring opening polymerization of lactide and ε-caprolactone and MWCNT-graft-PCL-block-PLA or MWCNT-graft-PLA-block-PCL were obtained, respectively. Length of grafted copolymer chains onto the MWCNT was controlled using CNT/monomer ratio.... 

In this work, the synthesis and characterization of a new nanocomposite from carbon nanotubes-graft-polymer (CNTs-g-P) is reported. The products were obtained by the filling of multi-walled carbon nanotubes (MWCNTs) (inner diameter 2040 nm) with CoFe2O4 magnetic nanoparticles, been grafted with poly (caprolactone). The filling process was carried out by using acid treatment through wet chemistry. The structure and the properties of the new nanocomposite were studied with TEM, VSM, TGA, and spectroscopic techniques. © 2009 World Scientific Publishing Company  

Transparent electrowetting is a branch of Electrowetting on Dielectric (EWOD) devices that use transparent electrodes. These devices are often utilized for optical applications like liquid lenses and reflective displays. In this paper, for the first time, a transparent EWOD with permanent liquid electrodes is introduced. A conductive solution was used as electrodes instead of conventional solid-state ones. We study the speed of droplets in both the proposed design and a similar conventional Printed Circuit Board (PCB) EWOD. The concept of Liquid Electrode EWOD (LEWOD) is successfully implemented on both rigid and flexible substrates. Our results generally show a promising performance similar... 

Temporal and spatial analysis of dynamics of hybrid transversely excited atmospheric pressure (TEA)-CO2 lasers is studied using two different models with four and eight energy levels. These models are used for simulation of the laser and computing the output energy. Effects of several parameters such as input energies and gas mixture concentrations (especially presence of CO molecules) are also studied. © 2007 Elsevier Ltd. All rights reserved  

Fabrication of well-defined gold nanowires (GNWs) is of significant importance in many fields such as sensing applications. In this study, the electrodeposition of well-defined GNWs inside polycarbonate (PC) template has been discussed in detail. GNWs were potentiostatically electrodeposited at different filling rates. The growth of GNWs at different stages of pore filling was monitored by electrochemical measurements and field-emission scanning electron microscopy (FE-SEM). It was confirmed that under growth rates between 2.5 and 4 nm/s, GNWs with smooth ends grew uniformly inside the template without any imperfections or corrugations. The length of GNWs was electrochemically controlled to... 

As a novel and highly sensitive sensor, three-dimensional gold nanoelectrode ensembles (3D GNE) prepared by gold deposition inside the parallel pores of a porous template have been successfully applied in electrochemical determination experiments. In this study, we report on the fabrication of 3D gold nanotubes (GNT) and their application in determination of Hg (II) in water. The morphology and crystal structure of the 3D GNT were characterized by field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD), respectively. The sensitivity of the fabricated electrode towards Hg (II) was examined using anodic stripping voltammetry (ASV) as a powerful technique in... 

Organic-inorganic hybrid halide perovskite materials have been most attractive for wide range of optoelectronic applications. Investigating the photo-response in these devices will be very useful to understanding cell performance in different conditions and applications. For understanding non-linearity photo-response we use the Bathocuproine (BCP) as blocking layer in two interfaces of inverted perovskite solar cell (FTO/NiO/BCP/Perovskite/PCBM/Au and FTO/NiO/Perovskite/PCBM/BCP/Au). Employing thick BCP layer (≈15 nm) caused s-shaped JV curve due to charge accumulation at interfaces. The nonlinearity effect was also explored for devices with s-shaped JV and established that device parameters... 

Due to their cost-effective manufacturing and robust structure, an electromagnetic sensor called resolver is being applied in a wide range of applications, especially in those which high reliability is particularly essential. Since resolvers are usually chosen as position detector units in harsh environments, their chronic exposure to high temperature and mechanical shocks is unpreventable and accordingly, performance failure as a result of output signal winding open circuit fault (OCF) is inevitable. In this paper, a new technique is proposed to keep the performance of the resolver within an acceptable range of position error while one of the output signals (SIN/COS) is inaccessible. To... 

Variable reluctance resolver (VR-Resolver) is a robust electromagnetic sensor that provides position information for closed-loop control systems of permanent magnet synchronous motors (PMSMs). For specific motion control applications, an outer rotor structure is presented for the VR-Resolver in this article with a nonoverlapping tooth-coil windings configuration to simplify the manufacturing process. The study on the structure of the proposed position sensor is carried out, followed by the description of the working principle. The presented outer rotor VR-Resolver is simulated and its performance is investigated in detail with the aid of transient finite-element analysis (TFEA). Sensitivity... 

Resolvers as position sensors need a high frequency AC excitation voltage, and the induced voltage in their 2-phase perpendicular windings are amplitude modulated (AM) signals. For calculating the position, it is required to demodulated the output signals and calculate their envelopes. Then, inverse tangent can be used for calculating the position. Despite the advantages of resolvers, there are some drawbacks in their application. Calculating the envelopes is always one of the deep concerns in using resolvers. Furthermore, due to low-amplitude of the excitation flux, the performance of the resolvers is strongly affected by electromagnetic interference by the stray fields of motor and brake.... 

Linear permanent magnet machines are increasingly used in industrial applications where they need position sensors to improve their performance. Variable Reluctance resolvers are one the best position sensors that can be used in unfriendly environment conditions, with high mechanical vibration, wide temperature variation and polluted environments. However, conventional VR resolvers suffer from complicated winding process, undesirable performance under eccentricities, and high position error in two-pole applications. So, in this paper a new linear resolver is proposed based on the sinusoidal variation of common area between the moving and the stationary parts. Then, the influence of... 

During the milling process, one of the most important factors in reducing tool life expectancy and quality of workpiece is the chattering phenomenon due to self-excitation. The milling process is considered as a MIMO strongly coupled nonlinear plant with time delay terms in cutting forces. We stabilize the plant using two independent Emotional Learning-based Intelligent Controller (ELIC) in parallel. Control inputs are considered as forces Ux and Uy in two directions x and y, which are applied by the piezoelectrics. The ELIC consists of three elements; Critic, TSK controller and the learning element. The results of the ELIC have been compared with a Sliding Mode Controller (SMC). The... 

Resolver, as an electromagnetic sensor, is widely used in many industrial applications. It can detect the position of the rotary part of the electric machines precisely. In commercial resolvers, excitation winding is connected to the High-Frequency (HF) AC source. The amplitude-modulated voltages induced in signal windings need to be demodulated in order to calculate the envelope of the output signals and detect the position accordingly. On the other hand, in PM-resolver, signal windings are replaced by Hall-effect sensors to measure the DC magnetic ux, which is produced by permanent magnets. In this study, the performance of both AC and DC ux resolvers is investigated under di erent...