Sharif Digital Repository

A miniaturized patch antenna is proposed and its radiation properties are experimentally investigated. A new metamaterial configuration based on circular spiral inclusion is used as the patch antenna substrate. The proposed antenna has not only a lighter profile but also a higher gain in comparison with its previously reported counterparts. It is shown that by using this new configuration a miniaturization factor of 3.1 can be realized. © 2017 Wiley Periodicals, Inc  

Untethered small-scale robots can accomplish tasks which are not feasible by conventional macro robots. In the current research, we have designed and fabricated a miniature magnetic robot actuated by an external magnetic field. The proposed robot has two coaxial wheels and one magnetic dipole which is capable of rolling and moving on the surface by variation in the direction of magnetic field. To generate the desired magnetic field, a Helmholtz electromagnetic coil is manufactured. To steer the robot to the desired position, at first the robot dynamics is investigated, and subsequently a controller based on a neuro-fuzzy network has been designed. Finally, the proposed controller is... 

In this study, a novel prototype high-efficiency miniature pump that uses magnetic properties of a ferrofluid in both pumping and valving mechanisms is presented. The minichannel consisting of a cylindrical pumping chamber, a check valve, an inlet and an outlet, comprises six bonded layers of PMMA. A cylindrical permanent magnet that is placed inside the chamber and is externally actuated by a motorized off-center permanent magnet, functions as a revolving piston which sweeps the perimeter of the cylinder. Ferrofluid is used to cover the gaps between the magnetic piston and the channel walls, also serves as a separating plug between the inlet and the outlet of the chamber preventing... 

Desktop and miniaturized machine tools are a new trend in small scale and customized manufacturing. The performance of these machines in terms of their energy consumption, machining fluid consumption and their precision have been investigated in the literature, but the effect of miniaturization on static deflection, stability against chatter and the resulting surface error has not been studied. In this paper, the performance of the desktop milling machine tool in terms of their static and dynamic form errors is studied. The performance of a miniature milling machine used for end milling of a typical workpiece is compared with a similar machine of conventional size through dimensional... 

This paper introduces a new array architecture, in which antenna elements are arranged in a spiral curve. The spiral array enhances ultra-wideband (UWB) pattern characteristics compared to alternative array geometries of similar elements, without requiring a complex feed network for frequency change compensation. A number of examples are illustrated to demonstrate the array capability in broadband array designs. It is revealed that for the same number of elements and curvature lengths, a spiral array has a wider radiation bandwidth than the corresponding circular and linear array antennas. In addition, it is also demonstrated that the spiral architecture discussed here can be best suited for... 

Micro actuators are an irreplaceable part of motion control in miniaturized systems and are intended to have a high range of deformation, high accuracy, large force, and quick response. In this article, an analytical model for a hybrid thermopiezoelectric micro actuator is developed in which a double lead-zirconnate-titanate piezoceramic (PZT) beam structure consisting of two arms with different lengths are used. Governing differential equation of motion and electrical field are derived and solved. Out of parametric studies it was observed that, under application of temperature and voltage gradients, the deflection of the actuator shows different trends depending on the geometry of the micro... 

In proton exchange membrane fuel cell (PEMFC) operations, the electrochemical reactions produce a rise in temperature. A fuel cell stack therefore requires an effective cooling system for optimum performance. In this study, miniature heat pipes were applied for cooling in PEMFC. Three alternatives were considered in tests: free convection, forced convection cooling with air, and also water. An analytical model was developed to show the possibility of evoking heat from inside a fuel cell stack with different numbers of miniature heat pipes. An experiment setup was designed and then used for further analysis. The proposed experiment setup consisted of a simulated fuel cell that produced heat... 

Demand increasing for next generation portable and miniaturized electronics has aroused much interest to explore microscale and lightweight energy storage devices. Herein, we demonstrate successful development of flexible wire-shaped micro-supercapacitors (micro-SCs) based on novel CoNi2S4/E-NZP film@Cu wire electrode. The etched Ni-Zn-P (E-NZP) film was synthesized by directly deposition of NZP film on Cu wire, followed by a chemical etching process. Alkaline etching treatment provides a micro- and mesoporous structure with high surface area and facilitates the penetration of electrolyte ions into the electrode matrix. Then, CoNi2S4 nanosheets as electroactive material are electrochemically... 

Low accuracy, requirement of expensive instruments, derivatization and multi-step sample preparation, inconsistencies during the fabrication process, time-consuming procedures and utilization of eco-unfriendly chemicals are some limitations of various developed methods for detection of 4-methylimidazol (4-MeI). Herein, a rapid and miniaturized fluorescent probe based on the ultrasound‒assisted formation of carbon dots (CDs) in a metallic deep eutectic solvent (MDES) was developed and conveniently implemented to detect 4-MeI in commercial dark soft drinks. In-situ synthesis of CDs-chelated metals in the presence of the target analyte facilitates a kinetically fluorescence emission with no... 

In this study, new method for NAA purposes at 30 kW Isfahan MNSR is suggested. An algorithm based on ANN is proposed to quantitatively predict the unknown elements with no need standard sample. A three-layer feed-forward ANN with back-propagation algorithm has been used to determine concentration of selenium and fluorine in Multiple Sclerosis patients and healthy people blood samples. Predicted concentration of elements show good agreement between new method and experiment results. The correlation coefficient between the experimentally determined and predicted values are 0.99104 and 0.99364, respectively. This method is a rapid and precise approach for elemental analysis. © 2022, Akadémiai... 

In salting-out liquid-liquid extraction (SALLE) technique, water-miscible organic solvents are used for extraction of polar analytes from saline solutions. In this study, for the first time, a coupled 1-mL syringes system was utilized to perform a miniaturized SALLE method. Sulfanilamide antibiotic was extracted and determined via the developed method followed by high performance liquid chromatography-ultraviolet detection (HPLC-UV). The extraction process was carried out by rapid shooting of acetonitrile as extraction solvent (syringe B) into saline aqueous sample solution (syringe A), and then the shooting was repeated several times at a rate of 1 cycle s-1. Thereby, an extremely large... 

Microfluidics based systems could be useful for drug discovery as they allow for miniaturization and could potentially be run as multiple parallel cell based assays. Such miniaturization allows assays at single cell level and reduces the amount of test material needed, which, in the case of natural product extracts, simplifies the preparation. Thyme species extracts have been reported to show some promising anti-cancer effects. In the present work, we used a microfluidics based system to study the effects of Thymus kotschyanusm Boiss plant extract on two human breast cancer cells lines which are MDA-MB-231 and MCF-7. For better understanding a single cancer cell death mechanism and a flow... 

The increasing energy demand for next-generation portable and miniaturized electronics has drawn tremendous attention to develop microscale energy storage and conversion devices with light weight and flexible characteristics. Herein, we report the preparation of flower-like cobalt vanadium selenide/nickel copper selenide (CoVSe/NiCuSe) microspheres with three-dimensional hierarchical structure of micropore growth on copper wire for a flexible fiber microsupercapacitor (microSC) and overall water splitting. The CoV-LDH microspheres are anchored on the dendrite-like NiCu nanostructured Cu wire using a hydrothermal method (CoV-LDH/NiCu@CW). The sulfidation and selenization of CoV-LDH/NiCu was... 

The aim of this study was to use finite element analysis (FEA) to assess the influence of microthread design at the implant neck on stress distribution in the surrounding bone. A commercially available implant with 3.5 mm diameter and 10.5 mm length was selected and used as a model. For the purpose of designing the microthread implant model, microthreads were added to the implant neck in a computerized model. A force measuring 100 N was then applied to the entire surface of the abutment in the vertical direction. The results showed that in both models, stress was mainly concentrated at the cortical bone adjacent to the neck of the implant. Maximum stress values in the cortical bone... 

Miniaturized systems based on the principles of microfluidics are widely used in various fields, such as biochemical and biomedical applications. Systematic design processes are demanded the proper use of these microfluidic devices based on mathematical simulations. Aggregated proteins (e.g., inclusion bodies) in solution with chaotropic agents (such as urea) at high concentration in combination with reducing agents are denatured. Refolding methods to achieve the native proteins from inclusion bodies of recombinant protein relying on denaturant dilution or dialysis approaches for suppressing protein aggregation is very important in the industrial field. In this paper, a modeling approach is...