Sharif Digital Repository

In this work two phenol biosensors, one based on polyaniline nanofibers (PNFs) and the other based on the newly created and introduced linear-dendritic matrix of poly(citric acid)-block-poly(ethylene glycol) copolymers (PCA-PEG-PCA), were chemically modified with horseradish peroxidase (HRP) enzyme. These phenol biosensors showed an oxidation peak at 0.55 V. The amperometric response for biosensors based on PNFs showed a linear response range from 2.5 × 10-6 to 2.5 × 10-5 mol/L, with a detection limit of 2.5 M phenol. Also, the amperometric response for a biosensor based on PCA-PEG-PCA showed a linear response range from 2.5 × 10-6 to 4 × 10-5 mol/L, with a detection limit of 1.5 M phenol  

Estimating the mechanical properties of metal foams is becoming important in developing new materials and advancing new manufacturing processes. Among various mechanical properties, effective Young’s modulus as one of the key properties may be evaluated through several measurement methods, but because of some limitations, merely a few techniques can be used in each application. Metal foam as a novel conventional material is one of the significant materials with limited methods for effective Young’s modulus measurement. Recently, several empirical relationships have been developed between effective Young’s modulus and metal foam’s porosity to estimate its elasticity based on the material’s... 

The present article aims to investigate the cause-and-effect relationship between the employees’ psychological empowerment (PE) and dimensions of knowledge management (KM) in an oil company, using the fuzzy decision-making trial and evaluation laboratory method. The study population consists of oil company experts. The sample size is determined based on the theoretical saturation limit. The present findings show that PE is the strongest causative factor with significant effects on knowledge creation (KC) and knowledge dissemination (KD). Among the KM dimensions, the most influential factors are the dimensions of KC, knowledge application, and knowledge capture (KCA). Of all KM dimensions,... 

Linear-dendritic triblock copolymers of linear poly(ethylene glycol) and hyperbranched poly(citric acid) (PCA-PEG-PCA) were used as the reducing and capping agents to encapsulate gold and silver nanoparticles (AuNPs and AgNPs). PCA-PEG-PCA copolymers in four different molecular weights were synthesized using 2, 5, 10 and 20 citric acid/PEG molar ratios and were called A 1, A 2, A 3 and A 4, respectively. Nanoparticles were encapsulated simultaneously during the preparation process. AuNPs were simply synthesized and encapsulated by addition a boiling aqueous solution of HAuCl 4 to aqueous solutions of A 1, A 2, A 3 and A 4. In the case of silver, an aqueous solution of AgNO 3 was reduced... 

An economic-statistical design with multiple assignable causes following exponential distribution is presented in this paper for linear profiles. For this purpose, a tri-objective optimization model is proposed to minimize the cost with desired statistical performances. Average Run Length (ARL) as the primary statistical measure is employed for the appraisal of the designed linear profiles. The first objective to be minimized is a cost function that models the implementation cost in different states. The second objective is to maximize ARL or the in-control average run-length of the monitoring scheme. The third objective to be minimized is ARL 1 or the out-of-control average run-length of... 

In this work, the modified Flory-Huggins coupled with the free-volume concept and the artificial neural network models were used to obtain the osmotic pressure of aqueous poly(ethylene glycol) solutions. In the artificial neural network, the osmotic pressure of aqueous poly(ethylene glycol) solutions depends on temperature, molecular weight and the mole fractions of poly(ethylene glycol) in aqueous solution. The network topology is optimized and the (3-1-1) architecture is found using optimization of an objective function with batch back propagation (BBP) method for 134 experimental data points. The results obtained from the neural network in obtaining of the osmotic pressure of aqueous... 

In this paper, high cycle fatigue behavior and thermal properties of blend specimens made of polylactic acid (PLA) and polycaprolactone (PCL) were studied and the influence of crystallization was investigated on the fatigue behavior. In this regard, fused deposition modeling method was employed to manufacture neat-PLA, neat-PCL, PLA/10wt.% PCL (90/10), and PLA/20wt.% PCL (80/20) specimens. The results show that the addition of 10wt.% and 20wt.% of PCL to the neat-PLA increases the elongation of the specimens by 32% and 284%, respectively, compared to that of the neat-PLA. However, Young’s modulus respectively decreases by 22% and 34%. According to the differential scanning calorimetry (DSC)... 

Considering the desirable biodegradable properties and mechanical characteristics of poly lactic acid (PLA) and poly caprolactone (PCL), these polymers are recently widely utilized in medical applications including the fabrication of body-compatible implants. One of the most efficient manufacturing methods to fabricate polymer-based implants is 3D printing, due to its ability to rapidly produce parts with complex geometries. In this study, an effort has been made to study the impact of the dip-coating process on tensile and high cycle fatigue behavior of 3D printed PLA/PCL blends, using PCL/chloroform solution. The results demonstrate that after applying the PCL coating on the surface of the... 

Given the various advantages of electric vehicles compared to conventional gasoline vehicles in terms of energy efficiency and environmental pollution (among others), this paper studies the factors affecting customers’ willingness to purchase electric vehicles. An integrated discrete choice and agent-based approach is applied to model the customers’ choice for the valuation of electric vehicles based on the internal reference price. The agent-based model evaluates customers’ preferences for a number of personal and vehicle attributes, according to which vehicle they chose. Data from 376 respondents are collected to estimate a random-parameter logit model where customers are asked to reveal... 

Fiber optic sensors have emerged as a promising technology for precise measurements in various applications. In this study, we propose an integrated all-fiber Cascade Fabry–Perot (CFP) sensor that uses the harmonic Vernier effect to enhance its sensitivity. The sensor consists of a Silica Capillary Tube (SCT) fusion spliced to a Single-Mode Fiber (SMF), and its cavity length is optimized to locate Vernier's internal envelopes for three different Vernier harmonic orders within the spectral range of 1500 nm–1600 nm. Three CFPs were fabricated and utilized as strain and temperature sensors. By analyzing and tracing Vernier's internal envelopes, we experimentally demonstrated that sensitivity... 

The thermal behavior of Fe3Si2O5(OH)4·Sb3O6(OH)·Sb2O3 (a sample of antimony from Sefidabe mine in Zahedan) was investigated by the technique of thermogravimetry under air atmosphere from 25 to 1200 °C. The obtained results from TGA were reported. This study reports comprehensive information about these minerals. XRD and XRF techniques, UV/visible and elemental analysis such as ICP are used to identify the products at different decomposition steps. The acidic leaching of this mineral Fe3Si2O5(OH)4·Sb3O6(OH)·Sb2O3 is carried out, and the obtained results are reported. In total, the recovery was achieved by leaching with hydrochloric acid was 85% at D80 granulation below 45 microns. In leaching... 

This paper presents a new solution framework to locate the workstations in the tandem automated guided vehicle (AGV) systems. So far, the research has focused on minimizing the total flow or minimizing the total AGV transitions in each zone. In this paper, we focus on minimizing total cumulative flow among workstations. This objective allocates workstations to an AGV route such that total waiting time of workstations to be supplied by the AGV is minimized. We develop a property which simplifies the available mathematical formulation of the problem. We also develop a heuristic algorithm for the problem. Computational results show that our heuristic could yield very high-quality solutions and... 

Linear-dendritic ABA triblock copolymers containing poly(ethylene glycol) (PEG) as B block and hyperbranched poly(citric acid) (PCA) as A blocks were synthesized through polycondensation. The molecular self-assembly of synthesized PCA-PEG-PCA copolymers in water led to formation of nanoparticles and fibers in different sizes and shapes depending on the time and size of PCA blocks. Ten days after dissolving PCA-PEG-PCA copolymers in water, the size of fibers had reached several millimeters. Mixing a water solution of fluorescein as a small guest molecule and PCA-PEG-PCA copolymers led to the encapsulation of fluorescein by products of molecular self-assembly. To investigate their potential... 

Linear-dendritic copolymers containing hyperbranched poly(citric acid) and linear poly(ethylene glycol) blocks (PCA-PEG-PCA) were used as reducing and capping agents to synthesize and support gold nanoparticles (AuNPs). PCA-PEG-PCA copolymers with 1758, 1889 and 3446 molecular weights, called A1, A2 and A3 through this work, respectively, were synthesized using 2, 5, and 10 citric acid/PEG molar ratios. The diameter of A1, A2 and A3 in a fresh water solution was investigated using dynamic light scattering (DLS) and it was between 1.8 and 2.8 nm. AuNPs were simply synthesized and supported by addition a boiling aqueous solution of HAuCl4 to aqueous solutions of A1, A2 and A3. Supported AuNPs... 

In this paper, a novel travelling-wave printed Frequency Scanning Antenna (FSA), which can be used for imaging purposes, is proposed. All sample designs scan the space symmetrically about the broadside direction. For different scanning ranges, two low profile antennas are designed on a 6.6 mils thick Rogers 4350 board substrate layer. Impedance bandwidth of the first one covers 6.5GHz, from 29.5GHz to 36GHz, and this antenna scans 56° in angular space. The second antenna has 5.6GHz bandwidth from 30.6GHz to 36.2GHz, and scans 98° in angular space by means of switching the input port. The average gain and the Side-lobe level (SLL) of the first and the second antennas are 11.46dBi, 12.8dB, and... 

In this study, biocompatible ceramic layers containing TiO2 and hydroxyapatite (HA) nanoparticles (TiO2/HA) were deposited on pure commercial titanium (Grade 2) by using plasma electrolytic oxidation and AC power supply. The coating process was carried out in five different solutions for various times at a current density of 500 mA cm−2. To achieve the optimum conditions for thickness and microstructure, the coating process was conducted in solutions with a 3 g L−1 concentration of HA nanoparticles. FESEM, XRD, and FTIR results showed that HA nanoparticles were successfully incorporated into the pores of the layer. Furthermore, the corrosion behavior of the coating layers in the simulated... 

In this paper, methods for reduction of coupling between receiving and transmitting antenna arrays are proposed and tested. Coupling between RX and TX causes saturation and a higher noise level in IF. So, coupling reduction improves image quality of system. Antenna element of arrays are printed antipodal Yagi-Uda antenna with greater than 8 dBi gain and higher than 4 GHz bandwidth. Frequency bandwidth of this imaging system is 27 to 30.5 GHz. Half power beamwidth of this antenna element is larger than 90 dB. Front to back ratio of this antenna is improved in this paper to 30 dB at 29 GHz. © 2019 IEEE