Publication Date: 2018
Scientia Iranica (23453605)25(3C)pp. 1395-1411
The sol-gel method was used for the synthesis of zero-valent iron/titanium dioxide supported on activated carbon (Fe0/TiO2/AC) adsorbents, and the adsorbents were comprehensively characterized by XRF, XRD, FT-IR, BET, FE-SEM, and EDX analyses. The batch experiments were performed to evaluate the effect of adsorbent type, pH of solution, pollutant initial concentration, and contact time on the 2,4-dichlorophenoxyacetic acid (2,4-D) adsorption efficiency. The equilibrium experiments revealed that the Langmuir isotherm was in good agreement with the adsorption equilibrium data, whereas the adsorption kinetic experiments indicated that the adsorption procedure was described perfectly through a pseudo-first-order kinetic model. The obtained maximum adsorption capacities from Langmuir isotherms of 86.5, 87.5, 86,57, and 88.76 mg/g were achieved for Activated Carbon (AC), zero-valent iron/activated carbon (Fe0/AC), titanium dioxide/activated carbon (TiO2/AC), and Fe0/TiO2/AC at the 2,4-D initial concentration of 90 mg/L, pH = 4 and 25°C, respectively. © 2018 Sharif University of Technology.All rights reserved.
Publication Date: 2018
Environmental Nanotechnology, Monitoring and Management (22151532)10pp. 212-222
The sol-gel procedure is applied to prepare zero-valent iron/dioxide titanium nanocomposite based on activated carbon and the nanocomposite is characterized by XRF, XRD, FT-IR, BET, FE-SEM and EDX analysis. The response surface methodology (RSM) of experimental design is adopted to evaluate the effects of five operational factors, including 2,4-D initial concentration, nanocomposite concentration, irradiation time, pH, and the ratio of hydrogen peroxide concentration to the 2,4-D initial concentration on the performance of photocatalytic degradation of 2,4-D. An increase in the 2,4-D initial concentration, nanocomposite concentration, and pH, reduces the 2,4-D degradation. The performance of degradation is increased and then slightly decreased by increasing the irradiation time and the ratio of hydrogen peroxide concentration to the 2,4-D initial concentration. The optimum conditions are determined at the maximum 2,4-D initial concentration, the minimum concentrations of nanocomposite and hydrogen peroxide, and neutral pH. © 2018
Publication Date: 2012
Marine Pollution Bulletin (0025326X)64(9)pp. 1956-1961
The natural radioactivity levels in sediment samples of the northern coast of Oman Sea, covering the coastal strip from Hormoz canyon to Goatr seaport, as the first time has been determined. The results of measurements will serve as background reference level for Oman Sea coastlines. Sediments from 36 coastal and near shore locations were collected for analysis. Analysis on the collected samples were carried out to determine 235U, 238U, 232Th, 40K and 137Cs using two high purity germanium detectors with 38.5% and 55% relative efficiencies. The concentration of 235U, 238U, 232Th, 40K and 137Cs in sediment samples ranged between 1.01 and 2.87Bq/kg, 11.83 and 22.68Bq/kg, 10.7 and 25.02Bq/kg, 222.89 and 535.07Bq/kg and 0.14 and 2.8Bq/kg, respectively. The radium equivalent activity was well below the defined limit of 370Bq/kg. The external hazard indices were found to be less than 1, indicating a low dose. © 2012 Elsevier Ltd.
Publication Date: 2009
Marine Pollution Bulletin (0025326X)58(5)pp. 658-662
The determination of activity concentrations of the radioactive elements 238U, 232Th, 40K and 137Cs was performed on grab samples taken from a polluted environment. The samples were sliced into strata from 5 cm depth, dried and ground to sieved through a 170 mesh size prior to the analysis. Activity concentration was quantified using gamma spectroscopy. The results showed that the concentrations of activity in the sediment samples are 177 ± 12.4, 117 ± 11.5, 1085 ± 101.6 and 131 ± 4.8 Bq kg-1 for 238U, 232Th, 40K and 137Cs, respectively. In general, the distribution of activity concentrations along the southern coast of the Caspian Sea area exceeded international limits. The hazard index of the samples was 0.19-0.88, with an average of 0.49. The mean values of radium equivalent activity and dose rate are 176 Bq kg-1 and 63 nGy h-1, respectively. © 2009 Elsevier Ltd. All rights reserved.
Publication Date: 2009
Optics InfoBase Conference Papers (21622701)
Using cis-trans isomerization of azo polymers we can fabricate waveguides, gratings and other periodic structures. Here we have fabricated a two dimensional photonic crystal which acts as an active Add/Drop WDM switch. © 2009 OSA.
Publication Date: 2025
Journal of Chromatography A (00219673)1757
Microfluidic lab-on-a-chip technologies are revolutionizing diagnostic processes by enabling High-purity particle separation in heterogeneous mixtures, like blood, crucial for swift and accurate diagnoses, particularly in common diseases like cancer or infections where effective pathogen isolation is required. Passive deterministic lateral displacement (DLD) and active acoustophoresis are prominent microfluidic separation methods, each with distinct advantages and limitations. A hybrid approach, combining both, allows simultaneous utilization of their benefits, and enhances separation efficiency and purity through optimal design. A groundbreaking versatile 3D finite element (FE) model of an innovative-designed hybrid microfluidic device, featuring I-shaped DLD arrays and acoustofluidic module based on tilted-angle standing surface acoustic wave (TaSSAW) with focused interdigital transducers (FIDTs), has been presented, accurately predicting particles' behavior and separation dynamics. Simulations of individual devices were also conducted to optimize hybrid device performance, revealing high-efficiency and high-purity separation of polystyrene particles and bioparticles, including circulating tumor cells (MCF-7 CTCs), RBCs, and Escherichia coli bacteria. In the optimized acoustofluidic device, 15 µm polystyrene particles were separated with 100 % purity and 94 % efficiency, while MCF-7 CTCs were separated with 100 % purity and 98 % efficiency. The optimized DLD device achieved 100 % purity and efficiency for 2 µm and 8 µm polystyrene particles, RBCs, and bacteria. In the hybrid device, due to unpredictable factors, MCF-7 CTCs were isolated with 100 % purity but 40 % efficiency, while RBCs and bacteria maintained 100 % purity and efficiency. The results highlight the potential for further geometrical and fluidic optimizations to improve performance, with the 3D model providing a superior predictive tool compared to 2D models, facilitating cost-effective modeling of complex lab-on-a-chip structures. © 2025 Elsevier B.V.
Publication Date: 2024
ARABIAN JOURNAL OF CHEMISTRY (18785352)17(9)
This research aimed to fabricate and evaluate Poly(lactic acid)/poly(epsilon-caprolactone)/graphene (PLA/PCL/G) nanocomposite scaffolds for peripheral nerve tissue engineering. To achieve this goal, scaffolds were fabricated using the fused deposition modeling (FDM) 3D printing method with the following compositions: 50 wt% PLA50 wt% PCL (PLA-PCL), 98.5 wt% PLA-1.5 wt% G (PLA-G), 98.5 wt% PCL-1.5 wt% G (PCL-G), and 50 wt% PLA48.5 wt% PCL-1.5 wt% G (PLA-PCL-G). The microstructure and chemical composition of the scaffolds were characterized using SEM, XRD, and FTIR. SEM images revealed that the PLA-PCL-G scaffold exhibited a more regular and uniform morphology compared to the others, with the PLA-PCL scaffold displaying the least regularity. The porosity percentage and pore size of the scaffolds ranged from 50 % to 86 % and 300 to 500 mu m, respectively. Mechanical properties were assessed via compression testing, indicating that the elastic modulus of the PLA-PCL-G scaffold was approximately 22.36 MPa, suitable for peripheral nerve tissue applications. Electrical conductivity testing showed that PLA-PCL-G had a conductivity of about 8.2E-5S/cm, similar to PLA-G. Biodegradability was evaluated by immersing samples in phosphate-buffered saline (PBS), revealing that PLAPCL-G exhibited a weight loss of approximately 1.3 % and a degradation rate of 0.14 mm/day over four weeks, closely matching peripheral nerve tissue regeneration rates. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide) assay results confirmed that PLA-PCL-G scaffolds were non-cytotoxic to PC12 cells. Overall, these findings suggest that the 50 wt% PLA-48.5 wt% PCL-1.5 wt% G scaffold holds promise for peripheral nerve tissue engineering applications.
Additive manufacturing (AM) technology of thermoset polymer composites has great potential to address the disadvantages of widely used thermoplastic resins in terms of processing, cost, modification of compound formulation, dimensional stability, and stress crack resistance. Whilst there are other AM processes for thermoset polymer composites, the two most common techniques; VAT photopolymerization and extrusion-based methods are discussed. This chapter deals with the basics of these two technologies and attempts to describe the limitations and advantages of each. In particular, the key features and challenges regarding both techniques are presented. Furthermore, common materials available for thermosetting AM systems are described in combination with the 3D printing of fiber-reinforced polymer composites. A description of the important parameters that enhance the performance of printed parts is provided. © 2024 Elsevier Inc. All rights are reserved including those for text and data mining AI training and similar technologies.
Active gate driving is a technique that aims to enhance the switching performance of power semiconductors via the gate signal. Utilizing a simplified gate profile can help avoid the complexities associated with advanced gate driver designs. Employing models and simulations derisk the experimental trial-and-errors for optimizing gate signal profiles. This paper demonstrates open-loop 3-step gate control of a 400 A SiC power module, to reduce turn-off voltage overshoot and ringing, coupled with an LTSpice model that is adapted from the commercially available device model, to identify safe gate current profiles. The device model adaptations are presented, including an experimental validation. A model of a gate driver with 3 parallel outputs and 3 gate resistors is used to find turn-off gate current profiles that could be implemented with commercially available components. This gate current profile is programmed into a previously reported custom active gate driver IC, and validated experimentally. This profile results in safe experimental switching waveforms, with visible improvements over gate driving with a single-step driver and a single gate resistor, that is lower voltage overshoot, no ringing, and no reduction in dv/dt. This method is designed to be implemented using available low-cost components and closed-loop optimisation of a single-parameter. © 2025 IEEE.
Publication Date: 2021
AEU - International Journal of Electronics and Communications (16180399)140
Sensor nodes and IoT systems require blocks that not only consume low power but also have good accuracy. Voltage reference generators are also considered important building blocks in sensor interface circuits. This paper presents a solution to increase the accuracy of low power subthreshold voltage generators by lowering the circuit sensitivity to temperature and supply voltage variations. The enhancement is achieved by using two separate stages for temperature coefficient (TC) and line sensitivity (LS) correction. A 0.18 µm standard CMOS process has been used for the proposed structure. The effects of parameter variations in the fabrication process are investigated using post-layout simulation and Monte Carlo analysis. In the supply voltage of 0.4–2 V, an LS of 143.8 ppm/V is obtained. In typical corner conditions, the achieved TC is 7.45 ppm/°C over the temperature range of 0–80 °C. Due to process changes, and mainly affected by threshold voltage variations, the average TC can change to 39.2 ppm/°C. The minimum power consumption at 0 °C and at a supply voltage of 0.4 V is 3.25 pW while the power consumption increases to 2.84 nW in 80 °C and at the maximum supply voltage of 2 V. © 2021 Elsevier GmbH
Habibi, M.,
Shahpari n., N.,
Habibi M.,
Malcovati p., ,
De La Rosa J.M. Publication Date: 2023
IEEE Access (21693536)11pp. 67113-67125
The input capacitance of the SAR ADC is considered a drawback in many applications. In this paper, a 12-bit low-power SAR ADC with low-input capacitance is proposed. The ADC is based on a separated DAC and sample-and-hold blocks (SB) structure. The SB structure suffers from variation in the input common-mode voltage of the comparator, leading to nonlinear input-referred offset and kickback noise. Here, a closed-loop low-power rail-to-rail offset cancellation technique for the comparator, based on body voltage tuning, is proposed. In order to stabilize the closed loop structure, the open loop gain is controlled by adapting the gain of the preamplifier. Using this structure, the rail-to-rail offset is kept lower than 110 mu V and the overall power of the comparator is 1 pJ/Conv. Complementary-clocked dynamic branches are exploited at the input of the comparator to decrease the common-mode dependent kickback noise error to less than 1 LSB. The bootstrapped switch's controlling signal is also modified to achieve less than 1 LSB error and 18.9% lower power consumption. The proposed ADC is designed in standard 180 nm CMOS technology with a 1.8 V supply voltage and the input capacitance is reduced to 2 pF, which leads to power consumption of 41 nW in the input voltage supply. Electrical simulations including PVT, MonteCarlo, and post-layout parasitic extraction were conducted to ensure the effectiveness of the approach. The ADC features an ENOB of 11.1-bit and a sampling rate of 1 MHz with a power consumption of 117.9 mu W including the input power supply which are competitive with the state-of-the-art, and demonstrate the virtue of the proposed approach.
Publication Date: 2025
IET Power Electronics (17554543)18(1)
This paper presents a novel high-performance and dependable step-up multi-level inverter topology designed specifically for photovoltaic applications. A gain factor of nine is attained, coupled with automatic self-voltage balancing of capacitors and the intrinsic capability to generate both positive and negative voltage levels. All power switches withstand voltages lower than the peak of the output voltage. The quantity of power switches, DC input sources, and the blocking voltage on the switches are reduced. Also, the proposed inverter demonstrates a minimal cost function in comparison to similar topologies. The performance of the 19-level step-up inverter has been confirmed through simulation as well as laboratory results obtained from a constructed prototype. © 2025 The Author(s). IET Power Electronics published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.
Publication Date: 2024
Engineering Failure Analysis (13506307)
Accurate prediction of ductile damage is a critical challenge for the safe design of sheet metal structures. The Lemaitre's ductile damage model has been widely used for prediction of ductile damage, however its accuracy fully depends on loading conditions and calibration range. This paper eliminates this limitation by proposing a 2D Lode improved model (LIM) of the original Lemaitre (OL) for sheet metals. The modification incorporates the Lode parameter, a crucial, often-neglected factor influencing damage evolution. First, the LIM's theoretical framework and constitutive equations for the plane stress conditions in sheet metals including the Lode parameter is completely presented. Then, numerical approaches such as counting search and Taguchi methods are employed and validated for identification of the model parameters. Finally, to evaluate the LIM's performance, a user-defined VUMAT subroutine is developed for numerically simulation of numerous specimens under diverse loading conditions as well as to assess the model's effectiveness and reliability. The numerical simulation results are compared with experimental data and the comparison demonstrates a significant improvement in accuracy of the LIM rather than the OL ductile damage model. © 2024 Elsevier Ltd
Abdollahzadeh jamalabadi, M.Y.,
Ghasemi, M.,
Alamian, R.,
Afshari, E.,
Wongwises, S.,
Rashidi, M.M.,
Shadloo m.s., M.S. Publication Date: 2019
Applied Sciences (Switzerland) (20763417)9(17)
The fuel cell is an electrochemical energy converter that directly converts the chemical energy of the fuel into electrical current and heat. The fuel cell has been able to identify itself as a source of clean energy over the past few decades. In order to achieve the durability and stability of fuel cells, many parameters should be considered and evaluated Therefore, in this study, a single-channel high-temperature polymer exchange membrane fuel cell (HT-PEMFC) has been numerically simulated in three-dimensional, isothermal and single-phase approach. The distribution of the hydrogen and oxygen concentrations, as well as water in the anode and cathode, are shown; then the effect of different parameters of the operating pressure, the gas diffusion layer porosity, the electrical conductivity of the gas diffusion layer, the ionic conductivity of the membrane and the membrane thickness are investigated and evaluated on the fuel cell performance. The results showed that the pressure drop in the cathode channel was higher than the anode channel, so that the pressure drop in the cathode channel was higher than 9 bars but, in the anode channel was equal to 2 bars. By examining the species concentration, it was observed that their concentration at the entrance was higher and at the output was reduced due to participation in the reaction and consumption. Also, with increasing the operating pressure, the electrical conductivity of the gas diffusion layer and ionic conduction of the membrane, the performance of the fuel cell is improved. © 2019 by the authors.
The dynamics and control of satellite have been widely studied, because of their technological significance. There are many tools to observe or examine spacecraft control laws and one of the most common of them is simulation. Simulation has been used for educating students and users, too. Many solutions exist to the problem of simulating the functional space environment, for example: underwater test tanks, magnetic suspension systems and also air-bearings. Spherical air-bearings have been used for spacecraft attitude determination and control hardware verification and software development for nearly 50 years, because they provide frictionless environment and unrestricted motion. In spherical air bearings, pressurized air passes through holes in the grounded section of bearing (cup) and establishes a thin film that supports the weight of sphere. The purpose of this article is to describe a laboratory-based test-bed that will be used to explore various issues and concepts in spacecraft dynamics and control. The main components of this facility are spherical air-bearing, three-axial sensor, battery, on-board processor and three reaction wheels. All of these subsystems have been designed and manufactured by our team in Space Research Lab., because of some limitations in preparing them from foreign companies.
Previous methods for narrowband interference suppression in spread spectrum systems require training sequences. In practical overlay systems, transmission of the training sequences is impossible, because narrowband system and spread spectrum system are two separate entities, and presently the narrowband systems are in use and standardized and any changes may not be allowed. Hence, the narrowband systems cannot transmit training sequences for the spread spectrum system. In this paper we present a blind method for narrowband interference suppression in direct sequence Code Division Multiple Access (CDMA) systems. The proposed scheme is a nonlinear predictor consisting of a non-linear device and two random walk tracking algorithms. The main feature of this approach is that it does not require training sequences for tracking and suppressing narrowband interference. Simulation results show that in multiuser case, the performance of the proposed approach is better than Kalman filter. © 2004 IEEE.
Publication Date: 2012
Computers and Operations Research (03050548)39(12)pp. 2978-2990
This paper considers the problem of scheduling a single machine, in which the objective function is to minimize the weighted quadratic earliness and tardiness penalties and no machine idle time is allowed. We develop a branch and bound algorithm involving the implementation of lower and upper bounding procedures as well as some dominance rules. The lower bound is designed based on a lagrangian relaxation method and the upper bound includes two phases, one for constructing initial schedules and the other for improving them. Computational experiments on a set of randomly generated instances show that one of the proposed heuristics, used as an upper bound, has an average gap less than 1.3% for instances optimally solved. The results indicate that both the lower and upper bounds are very tight and the branch-and-bound algorithm is the first algorithm that is able to optimally solve problems with up to 30 jobs in a reasonable amount of time. © 2012 Elsevier Ltd. All rights reserved.
Publication Date: 2019
Iranian Polymer Journal (10261265)28(3)pp. 203-211
A conductive polymer composite (CPC) was designed as a gas sensor for the detection of lung cancer biomarkers. A poly(ether-imide) with aromatic bulky pendant groups was synthesized and used as a CPC transducer by introducing multi-walled carbon nanotubes for the detection of acetone, toluene, methanol, ethanol and water vapor as lung cancer biomarkers. The following trend in CPC response was observed for different vapors: AR (acetone) > AR (toluene) > AR (ethanol) > AR (methanol) > AR (water). The sensing ability of the conductive polymer composite towards the above biomarkers was evaluated based on Hansen solubility parameters of the analytes. The prepared sensitive layer showed a good sensitivity against a wide range of analytes with various polarities. The good sensitivity of designed sensitive layer was attributed to the non-polar –CH3 groups besides the bulky aromatic pendant groups of the as-synthesized polymer. The aromatic pendant groups have established relatively strong attractions with the carbon nanotube (CNT) surfaces leading to the creation of significant active sites in the CNTs’ junctions. As a result of adsorption of the analyte molecules on those active sites, especially at low concentrations, the bulky aromatic groups were found much to improve the sensitivity of the prepared gas detector by affecting the electron tunneling of 3-D nano-conductive filler architecture. The experimental results illustrated that the synthesized CPC has a promising potential as a lung cancer biomarker detector. © 2019, Iran Polymer and Petrochemical Institute.
Marateb, H.R.,
Roohafza, H.,
Noohi, F.,
Hosseini S.G.,
Alemzadeh-Ansari M.,
Bagherieh, S.,
Mansourian, M.,
Mousavi, A.F.,
Seyedhosseini S.M.,
Farshidi H.,
Ahmadi N.,
Yazdani A.,
Sadeghi, M. Publication Date: 2023
Current Problems in Cardiology (1462806)(7)
This study aims to provide a comprehensive risk-assessment model including lifestyle, psychological parameters, and traditional risk factors to determine the risk of major adverse cardiovascular events (MACE) in patients with the first acute ST-segment elevation myocardial infarction episode. Patients were recruited from new hospital admissions of acute ST-segment elevation myocardial infarction and will be followed up to 3 years. Clinical and paraclinical characteristics, lifestyle, psychological, and MACE information are collected and will be used in the risk-assessment model. Totally, 1707 patients were recruited (male: 81.4%, mean age: 56.60 ± 10.34). Primary percutaneous coronary intervention was the most prevalent type of coronary revascularization (81.9%). In case of baseline psychological characteristics, mean depression score was 5.40 ± 4.88, and mean distress score was 7.64 ± 5.08. A comprehensive approach, focusing on medical, lifestyle, and psychological factors, will lead to better identification of cardiovascular disease patients at risk of developing MACE through comprehensive risk-assessment models. © 2022 Elsevier Inc.
Publication Date: 2009
Chaos, Solitons and Fractals (09600779)42(3)pp. 1755-1765
In this paper, a chattering-free sliding mode controller design for uncertain chaotic systems is presented. Since the implementation of the sliding mode control may cause a significant problem of chattering, many modified methodologies have been developed to overcome this drawback. However, each of them has own problems such as lack of robustness against disturbance variations, steady-state error, large convergence time and effect on transient performance. This paper proposes an improved sliding mode control strategy in which a modified sliding condition in a continuous function in control signal is taken into account instead of discontinuous part and also it adds an auxiliary continuous control to the control input. Then, the stability of controlled system is proved by using Lyapunov's direct method. The usefulness of this proposed method for eliminating the chattering phenomenon in transient and steady states, in the face of uncertain chaotic systems with disturbances, is well appeared. For this purpose, the Lorenz system is studied and its simulation results are presented to demonstrate the effectiveness of the proposed control scheme. © 2009 Elsevier Ltd. All rights reserved.
Shahsavani, I.,
Goli, A.,
Hajiaghaei-keshteli, M. Publication Date: 2024
Annals of Operations Research (02545330)
In the past decade, the implementation of the circular economy has emerged as a compelling alternative to the linear model, proving effective in addressing critical global challenges such as climate change, population growth, and the depletion of non-renewable resources. Integrating the circular economy into supply chain networks results in the formation of a circular supply chain. Regrettably, many industries, including agriculture, have not fully embraced this valuable approach within their supply chain networks. This study addresses this gap by presenting an integrated circular supply chain network designed specifically for citrus fruits. The proposed model is grounded in the fundamental principles of the circular economy, leveraging both closed and open loops simultaneously. To address the complexities, a set of exact and metaheuristic methods is employed. In contrast to previous works, a comprehensive comparison of circular, closed-loop, and linear supply network structures is undertaken. Moreover, a sensitivity analysis is performed on key parameters. The model achieves significant milestones: firstly, a zero-waste outcome by eliminating waste in plastic crate usage and fruit residuals; secondly, an impressive 42% reduction in water consumption compared to traditional linear models. Environmental sustainability is further demonstrated by a 3% reduction in carbon emissions within the circular model. Importantly, these achievements do not compromise economic efficiency, as the circular supply chain showcases a nearly 1% decrease in total costs compared to its linear counterparts. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.
Publication Date: 2024
Applied Thermal Engineering (13594311)257
Green vehicles, particularly Fuel Cell Vehicles (FCVs), offer a promising solution to environmental challenges. One of the major obstacles for FCVs is starting the Polymer Electrolyte Membrane (PEM) fuel cell stacks in subfreezing temperatures, where the water produced by chemical reactions can freeze and hinder the cold-start process. Preheating the inlet air to the stack up to 80 °C is an effective approach to overcome this issue. However, conventional heating systems, such as electric heaters, are unable to heat the air quickly enough. This paper introduces a novel heating method to enhance the cold-start capability of FCVs. The proposed solution involves integrating vortex tubes, which are simple and cost-effective, with the vehicle's existing compressor. This system not only preheats the inlet air to the stacks but also provides warm air for the passengers simultaneously. By developing a 3D-CFD model of the vortex tube, the results demonstrate that the system can preheat the inlet air to the stacks from −30 °C to 80 °C and the air entering the passenger compartment from −30 °C to nearly 37 °C in just about 5 s. In comparison, conventional heating systems require over 600 s (10 min) to achieve the same temperature rise. © 2024
Hosseini-motlagh, S.,
Nematollahi, M.,
Johari, M.,
Sarker, B.R. Publication Date: 2018
International Journal of Production Economics (0925-5273)204pp. 108-122
In recent years, competition among enterprises has been significantly increased. Trade credit and promotional effort are two important tools that have been extensively used for increasing competitive advantage. In today's business environment, retailers compete each other on new factors such as the length of credit period offered to end customers. In this paper, the performance of a supply chain (SC) consisting of a monopolistic manufacturer and two competing retailers has been analyzed under a promotional-effort credit-period dependent demand. The promotional efforts made by the manufacturer and the trade credits offered by competing retailers stimulate the market demand. The investigated SC is modeled under the decentralized, centralized and coordinated decision-making structures. In the decentralized model, three game structures are proposed to reflect the retailers' behaviors according to their market dominance: (1) retailers' Cournot behavior, (2) retailers' Collusion behavior, and (3) retailers' Stackelberg behavior. In the centralized model, the optimal decisions on promotional efforts and credit periods are determined to maximize the profits of the entire channel. However, the results indicate that the centralized solution will not necessarily be acceptable to all members as it does not consider the individual profit of each SC member. To remedy shortcomings of the centralized model and coordinate the channel, a novel collaborative model is proposed in order to not only increase the whole SC profits, but also guarantee participation of all SC members. Finally, a numerical example along with a comprehensive sensitivity analysis is carried out to compare the performance of the proposed models. © 2018 Elsevier B.V.
Publication Date: 2011
Structural Engineering and Mechanics (12254568)37(2)pp. 149-162
The aim of this research is a comprehensive review and evaluation of beam theories resting on elastic foundations that used to model mode-I delamination in multidirectional laminated composite by DCB specimen. A compliance based approach is used to calculate critical strain energy release rate (SERR). Two well-known beam theories, i.e. Euler-Bernoulli (EB) and Timoshenko beams (TB), on Winkler and Pasternak elastic foundations (WEF and PEF) are considered. In each case, a closed-form solution is presented for compliance versus crack length, effective material properties and geometrical dimensions. Effective flexural modulus (Efx) and out-of-plane extensional stiffness (E z) are used in all models instead of transversely isotropic assumption in composite laminates. Eventually, the analytical solutions are compared with experimental results available in the literature for unidirectional ([0°]6) and antisymmetric angle-ply ([±30°]5, and [±45°]5) lay-ups. TB on WEF is a simple model that predicts more accurate results for compliance and SERR in unidirectional laminates in comparison to other models. TB on PEF, in accordance with Williams (1989) assumptions, is too stiff for unidirectional DCB specimens, whereas in angle-ply DCB specimens it gives more reliable results. That it shows the effects of transverse shear deformation and root rotation on SERR value in composite DCB specimens.
Publication Date: 2023
International Journal of Computational Intelligence Systems (18756891)16(1)
Over the past decades, different classification approaches with different characteristics have been developed to achieve more efficient and accurate results. Although the loss function used in the training procedure is a significant influential factor in the performance of classification models, it has been less considered. In general, in previous research, two main categories of continuous and semi-continuous distance-based loss functions are often applied to estimate the unknown parameters of classification models. Among these, continuous distance-based cost functions are among the most commonly used and most popular loss functions in diverse statistical and intelligent classifiers. In particular, the fundamental of this category of the loss functions is based on the continuous reduction of the distance between the fitted and actual values with the aim of improving the performance of the model. However, since the goal function of classification models belongs to the class of discrete ones, the application of learning procedures based on a continuous distance-based function is not coordinated with the nature of these problems. Consequently, it is theoretically illogical and practically at least inefficient. Accordingly, in order to fill this research gap, the discrete direction-based loss function in the form of mixed-integer programming is proposed in the training procedure of statistical, shallow/deep intelligent classifiers. In this paper, the impact of the loss function type on the classification rate of the classifiers in the energy domain is investigated. For this purpose, the logistic regression (LR), multilayer perceptron (MLP), and deep multilayer perceptron (DMLP), which are respectively among the most widely used statistical, shallow intelligent, and deep learning classifiers, are exemplarily chosen. Numerical outcomes from 13 benchmark energy datasets show that, in all benchmarks, the performances of the discrete direction learning-based classifiers, i.e., discrete learning-based logistic regression (DILR), discrete learning-based multilayer perceptron (DIMLP), and discrete learning-based deep multilayer perceptron (DIDMLP), is higher than its conventional versions. In addition, the proposed DILR, DIMLP, and DIDMLP models can on average yield an 89.88%, 94.53%, and 96.02% classification rate, which indicate a 6.78%, 5.90%, and 4.69% improvement from the classic versions, which only produce an 84.17%, 89.26%, and 91.72% classification rate. Consequently, the discrete direction-based learning methodology can be a more suitable, effective, and valuable alternative for training processes in statistical and shallow/deep intelligent classification models. © 2023, The Author(s).
Publication Date: 2021
Archive of Applied Mechanics (14320681)91(4)pp. 1859-1878
During tandem cold rolling mill process, strip tearing reduces production rate, damages the rollers, and consequently decreases efficiency of production. Predicting and postponing of this phenomenon leads to less expensive trial and errors in rolling industries. In this research first, DIN1623 St12 steel which is frequently applied in metal forming industries and also Bao–Wierzbicki ductile damage criterion is selected. Then, six curve fitting methods are employed to calibrate the material and are presented in 2D space of equivalent plastic strain to fracture and stress triaxiality. Finally, the achieved fracture loci are validated by comparing corresponding simulation results with experimental tests and the best curve fitting method with aims of high accuracy for tracking the strip tearing in a tandem cold rolling mill process and fewer numbers of required tests is revealed. Eventually, due to engaging this innovative approach, it is possible to trace the strip tearing in tandem cold rolling mill process by performing only two simple tensile tests. Therefore, it is concluded that strip tearing phenomenon can be precisely predicted in tandem cold rolling mill processes by a special focus on calibration of the Bao–Wierzbicki damage criterion in the range of low positive stress triaxiality which causes less number of needed tests. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.
