Publication Date: 2012
International Journal of Advanced Manufacturing Technology (14333015)(5-8)
Data envelopment analysis (DEA) is an important managerial tool for evaluating and improving the performance of decision making units. The existing DEA models are mostly limited to static environment using crisp data and are time-consuming and also have weak discriminating power. The aim of this work is to introduce a new fuzzy dynamic DEA model with missing values, which benefits from strengths of multi-objective modeling to overcome weakness and drawbacks of the classic DEA models. To check for quality and accuracy of the proposed model, this paper offers a comparative study to compare the discriminating power and computational efforts of the model with two problems in the literature taken as benchmarks. Also, this paper presents a real application of the fuzzy dynamic DEA model for assessing and ranking the level of performance for 56 railways around the globe using real data gathered from credible sources. The numerical case illustrates the model and the result may be used by railways to improve their performance efficiency compared to the best in the sample. Results for the comparative study and the real case reveal significant improvement in computational time and discriminating power. © Springer-Verlag London Limited 2011.
Unbalanced line currents cause unbalanced voltage drops on the three phases of the supply system. Consequently, the voltage system within the supply network will become unbalanced. Voltage unbalance has different detrimental effects in electrical power systems, such as the growth of losses in drive systems and adjustable speed drives, supplementary heating, line-current unbalance, derating, torque pulsation, mechanical stresses, etc. This paper makes an effort to have a comprehensive analysis of the effects of different connection types of three phase transformers on voltage unbalance propagation in distribution networks. The indices of voltage unbalance factor (VUF) and current unbalance factor (IUF) are used in this paper to evaluate the unbalance propagation. These indices are acquired utilizing symmetrical component theory on three phase voltages and currents earned through the system impedance matrix. © 2012 IEEE.
Precise speed control of a Linear Induction Motor (LIM) drive becomes a complex issue due to the end effect phenomena which results in the weakening of the airgap flux and thrust. The end effect becomes severe when the LIM drive operates at higher speeds. The main purpose of this paper is to present an accurate qd dynamic model of linear induction motor suitable for vector control and drive applications considering the end effects. In this model not only the magnetizing inductance is modified but also the series resistance reflecting the eddy current is considered in the series with the magnetizing branch in both q and d axes. Moreover, a corresponding indirect field oriented control (IFOC) scheme is suggested. The effectiveness of the proposed IFOC scheme based LIM drive is verified by simulation results at different operating conditions. In addition, a five-level Cascaded H-bridge (CHB) inverter with multiband hysteresis modulation has been successfully applied for drive performance improvements. The results prove that the proposed LIM model and its related IFOC scheme show more accurate and comprehensive resultants and are therefore closer to the reality. Furthermore, utilization of the multilevel CHB inverter guarantees high drive performance and perfect control characteristics. ©2013 IEEE.
Publication Date: 2014
Transport (16484142)29(1)pp. 28-35
The evaluation of railway line capacity is an important problem, which effects majority of problems in rail transportation planning. The railway capacity is dependent on infrastructure, traffic, and operating parameters. A key factor affecting railway line capacity is the impact of different train types. As the combination of different train types increases, more interference is generated. In this paper, for evaluation of train type interactions on railway line capacity, an integer-programming model for both line and line section is presented. The problem is formulated as a multicommodity network design model on a space-discrete time network. The railway capacity is calculated using data typically available to planners. The inputs of the model are the characteristic of each train type and railway line attributes. The model determines railway capacity based on train type mixes. In addition, this model considers impact of train types on capacity and waiting time. In order to show the features of the model, a case study is implemented in Iran Railways. The capacity tends to increase non-linearly with small incremental changes in parameters. The mixture of train types reduces the railway line capacity. The proposed model can help railway managers for long-term planning. © 2014 Copyright © 2014 Vilnius Gediminas Technical University (VGTU) Press.
Yaghini, M.,
Sarmadi, M.,
Nikoo, N.,
Momeni, M. Publication Date: 2014
Networks and Spatial Economics (1566113X)14(3-4)pp. 317-333
In this paper, a compressed timetable is generated to calculate capacity consumption for under construction railway routes using an optimization approach. Since the detailed timetable for under construction routes does not exist, the timetable is not required in the applied model. The model generates a compressed timetable based on UIC 406 method. The capacity consumption problem is formulated as a multicommodity network design model on a space-discrete time network. A local branching heuristic algorithm is proposed to solve the model. The main idea underlining the local branching algorithm is the utilization of a general mixed integer programming solver to explore neighborhoods and locally search around the best-known solution by employing tree search. The parameters of the algorithm are tuned by using design of experiments. The proposed method is implemented in Iran Railways and the results are reported. © 2014, Springer Science+Business Media New York.
Ziari, H.,
Farahani h., H.Z.,
Goli, A.,
Galooyak, S.S. Publication Date: 2014
Petroleum Science and Technology (15322459)32(17)pp. 2102-2108
With the increase of traffic and consequently, and the loads applied on the roads, the need for a more durable pavement has a special significance. Therefore, the researchers have been seeking to improve the functional properties of bitumen and asphalt. For this reason, different materials have been used to modify these properties. In this study, the carbon nano tube (CNT) has been used as the modifier of bitumen performance. The use of this additive has improved both the classic (softening point, penetration degree, and so on) and performance (complex modulus, phase angle, fatigue parameter, rutting factor) properties of bitumen in comparison to the standard bitumen. © Taylor & Francis Group, LLC.
Galooyak, S.S.,
Palassi, M.,
Farahani h., H.Z.,
Goli, A. Publication Date: 2015
Petroleum and Coal (13377027)57(5)pp. 556-564
Carbon nanotubes are one of the most widely used Nanomaterial that have two main features of light-weight and high strength material for tensile, compressive, impact and thermal stresses. In this study, different contents of carbon nanotube are used for the modification of the conventional bitumen. For the samples prepared by the ultrasonic mixer, it is observed that the agglomerated Nano-materials are peeled off and uniformly dispersed in bitumen. Then classical experiments of bitumen, x ray analysis, and rheological tests using Dynamic Shear Rheometer, were conducted on the modified bitumen. Master curves are plotted, and the results depicted that addition of 1.2 wt% of carbon nanotubes to the bitu-men have improved rheological properties of bitumen at high and low temperature service, significantly. Also addition of Nanotube was increased the stiffness and reduced the phase angle of base bitumen.
Zalnezhad, H.,
Galooyak, S.S.,
Farahani h., H.Z.,
Goli, A. Publication Date: 2015
Petroleum and Coal (13377027)57(5)pp. 509-515
In this investigation, Nano-silica has been added in three percentages of 2%, 4% and 6% to improve the physical, rheological and mechanical properties of warm mix asphalt (WMA) containing 2% Sasobit. Several experiments have been conducted to evaluate and characterize the prepared samples. The results of investigations indicated that by increasing the percentage of Nano-silica, the qualification and functionality of the warm mix asphalt has been improved. Resilient modulus of WMA was slightly increased by increasing the Nano-silica content. So, the response of pavement to traffic loading at 25oC has been improved. Depth of cracking at a specified load cycles was decreased dramatically by adding the Nano-silica to the Sasobit WMA. At the same time, the stiffness of modified samples was much lower than control WMA. As a result, the Nano-silica extends the fatigue life of asphalt concrete. In addition, the wheel tracking test results depicted that the rutting depth have been reduced by increasing the Nano-silica content. Regarding the results of qualification tests, 4 wt% of Nano-silica was selected as the optimum content.
Publication Date: 2015
Advances in Electrical and Computer Engineering (18447600)15(3)pp. 3-12
Accurate vector control of a linear induction motor (LIM) drive is a complicated subject because of the end effect phenomenon especially in the field-weakening region. This paper concentrates on a novel field-weakening speed control strategy for LIM drive in which the end effect is taken into account. Considering the end effect, new voltage and current limits have been calculated using the Duncan's model. Accordingly, control strategies such as constant force region, partial field-weakening region, and full field-weakening region have been analytically calculated for the first time in this work. In order to improve the control characteristics of the LIM drive, Fuzzy Logic Controller (FLC) has been also implemented. Simulation results manifest the satisfactory resultants of the proposed FLC based LIM in the fieldweakening region including fast response, no overshoot, negligible steady-state error, and adaptability to load changes. In addition, a new constant force pattern is introduced in this paper by which the reductions of the LIM thrust due to the end effect will be compensated and thus, the current and voltage amplitudes in steady state will remarkably decrease.
Publication Date: 2015
Wireless Networks (10220038)(8)
A vehicular ad hoc network (VANET) is a network in which vehicles acting as dynamic nodes communicate with each other. A VANET is a suitable piece of infrastructure for developing intelligent transportation systems. Stable communication within a VANET leads to enhanced driver safety and better traffic management. The clustering technique, which organizes similar vehicles into similar groups, is a possible method for improving the stability of connectivity within a VANET. In this paper, two new clustering algorithms suited to the dynamic environment of a VANET are proposed. The multi-objective data envelopment analysis clustering algorithm as a mathematical clustering model and the ant system-based clustering algorithm as a meta-heuristic clustering model are introduced as algorithms for VANETs. A comparative simulation study in a highway environment is presented as well to evaluate the introduced methods and compare them with the most commonly used VANET clustering algorithms. The results show that the proposed algorithms offer improved stability and runtime along with relatively better performance than existing algorithms. Furthermore, the results show that in the VANET environment, the mathematical clustering model proposed herein yields better results than the meta-heuristic algorithm. © 2015, Springer Science+Business Media New York.
Publication Date: 2015
Wireless Personal Communications (09296212)(1)
In vehicular ad-hoc network (VANET), vehicles are dynamic nodes communicating with each other by wireless technology in their own transmission range. Consequently, with regard to larger communication due to the greater number of vehicles and high mobility of nodes, communication management and creation of a stable network in VANET are most challenging subjects. Hence, clustering as a possible solution to address this challenge, should take into consideration to produce stable clustering structure. Clustering technique is for organizing nodes into groups, making the network more robust and scalable. This paper introduces two new Improved Ant System-based Clustering algorithm (IASC1 and IASC2) suitable for dynamic environment of the VANET. Simulation is run to evaluate the introduced methods and compare them with the most commonly VANET clustering algorithms as found in the literature review. Results reveal the proposed algorithms have improved the stability and the runtime of VANET clustering algorithm and have a relatively good performance compared with other algorithms. © 2015, Springer Science+Business Media New York.
Publication Date: 2016
Advances in Electrical and Computer Engineering (18447600)16(3)pp. 15-24
Multicarrier based PWM switching patterns are commonly utilized to control Cascaded H-bridge (CHB) inverters. The main contribution of this paper is to comprehensively investigate the effect of various multicarrier based PWM techniques on harmonic content of the CHB multilevel inverter. In order to achieve this, both of the CHB output voltage and the input current at power grid side have been taken into account. In this work, various PWM modulations such as level shifted (LS), phase shifted (PS), hybrid, and rotative-LS (R-LS) have been studied through both simulation and implementation of an experimental setup. By extracting the frequency spectrum and calculation of THD and WTHD indices, a quantitative comparative study of various multicarrier PWM techniques has been carried out. According to the results, the R-LS-PWM methods (i.e. R-PD, and two new proposed R-POD and R-APOD) reduce the harmonic distortion of the input current while keeping the obvious advantage of LS-PWM modulation such as lower harmonic distortion of the output voltage. Specially, the proposed R-APOD-PWM modulation offers these preferable privileges at odd frequency ratio values. © 2016 AECE.
Publication Date: 2016
Petroleum Science and Technology (15322459)34(6)pp. 505-511
Fatigue is defined as a fracture phenomenon due to a repetitive load or a variable dynamic load that occurs at a lower load than the ultimate static load. Fatigue stability of an asphalt mixture is its ability of enduring the repetitive flexural loads. In this study, the carbon nanotubes are used as the bitumen modifier in the way that the prepared samples contain 0%, 0.3%, 0.6%, 0.9%, 1.2%, and 1.5% carbon nanotubes. Then, the classic and rheological experiments are conducted on these samples. This additive improves the classical properties of bitumen (softening point, penetration degree, and so on) and also the fatigue parameter of bitumen (i.e., G*Sinδ) in comparison to the standard bitumen. Using the rheological graphs, it can be predicted that adding the carbon nanotubes to bitumen might improve the fatigue life of the asphalt mixtures. To evaluate the accuracy of this prediction, the fatigue experiment are performed on the prepared beam samples using a four-point loading in the case of constant strain (600 microstrain) with a semi-sinusoidal wave at 20°C. The end of the samples’ fatigue life is 50% reduction in their initial rigidity. It is observed that with an increase in the percentage of carbon nanotube in fatigue samples, the fatigue life of asphalt mixtures remarkably increases. © 2016 Taylor & Francis Group, LLC.
Zeinoddin, H.S.,
Abtahi, S.M.,
Hejazi, S.M.,
Babamohammadi, S.,
Goli, A.,
Amuchi, M. Publication Date: 2016
Transportation Infrastructure Geotechnology (21967202)3(3-4)pp. 91-108
In traditional method of hot mix asphalt (HMA) production, large energy consumption and increased environmental awareness have resulted in the innovation of a production technology named warm mix asphalt (WMA). In this technology, various methods are used to reduce the temperature of production and paving. On the other hand, steel slag is the by-product of iron and steel factories, and many researches have been done around the world to use these materials in several fields, such as HMA industry. Various studies show steel slag to be considerably effective in improving the performance of asphalt concrete. One of the properties of steel slag is having high heat capacity value which leads to higher energy consumption during the production of HMA compared to conventional aggregates. The main aim of this study is therefore using WMA technology to reduce the energy consumption and to produce steel slag warm mix asphalt (SSWMA). In order to fabricate SSWMA in lab, an amino-based resin was used as an additive to decrease the viscosity of the bitumen. The amount of resin was ranged from 5 to 15 % by the weight of bitumen. The performance of SSWMA samples was evaluated by several tests, including dynamic shear rheometer, bending beam rheometer, Marshall test, moisture sensitivity, indirect tensile strength, and resilient modulus. Experimental results revealed that amino-based resin additive can decrease the viscosity of the bitumen by producing foam particles. This reduction of viscosity leads to reduction of asphalt production temperature as much as 25 °C in application of 10 % resin by the total weight of the bitumen. It can be also concluded that SSWMA proposed acceptable moisture resistance, and modified bitumen showed a superior performance rather than the neat bitumen in the case of rutting resistance. © 2016, Springer Science+Business Media New York.
Publication Date: 2016
Journal of Materials in Civil Engineering (19435533)28(12)
Bitumen as a main and efficient material in the behavior of hot mix asphalt (HMA) already has attracted the attention of various researchers. Bitumen modification with polymeric and nonpolymeric materials was considered one of the main research subjects relevant to increasing road life cycles. Crumb rubber is one of the appropriate bitumen modifiers due to its desired properties, and it also helps to reduce environmental pollution. In the current research, two types of mesh, crumb rubber (mesh of Nos. 14 and 50), with three different percentages (10, 15, and 20%), have been mixed with three types of bitumen, and the obtained results have been investigated on high-temperature (HT), intermediate-temperature (IT), low-temperature (LT), and viscosity properties. Also, in order to investigate the impact of aging on stated parameters, test results on bitumen samples modified by crumb rubber, before and after aging, have been studied. © 2016 American Society of Civil Engineers.
Publication Date: 2016
Wireless Personal Communications (09296212)(4)
Publication Date: 2016
Wireless Personal Communications (09296212)(2)
Mirabimoghadam m.h., ,
Goli, A.,
Molayem m., ,
Ameri, M. Publication Date: 2016
Petroleum Science and Technology (15322459)34(11-12)pp. 971-975
ABSTRACT: The present research study investigates the fatigue resistance of asphalt binders modified with carbon nanoparticles. Three different modified bitumens containing three different dosages of carbon nanoparticles were tested to capture fatigue properties under the concept of viscoelastic continuum damage mechanics through frequency sweep and linear amplitude sweep tests. Results show that adding carbon nanoparticles can enhance the fatigue life of neat asphalt binders. © 2016 Taylor & Francis Group, LLC.
Ziari, H.,
Akbari t., ,
Farahani h., H.Z.,
Goli, A. Publication Date: 2016
Petroleum Science and Technology (15322459)34(6)pp. 512-516
Asphalt has a short life cycle, failing mainly due to temperature changes, traffic load, and UV solar radiation. Therefore, the researchers have been seeking to improve the functional properties of bitumen and asphalt. For this reason, different materials have been used to modify these properties. One common way of increasing the performance of the bitumen is blending the asphalt with polymer modifiers (PMA). PMA has better mechanical properties and higher durability than the nonmodified asphalt. Polymers are divided into three general groups including elastomers, plastomers, and elastoplastomers. Styrene-butadiene-styrene is one of the most applicable polymers. In this study, Lucobit polymer, a polyolefin, has been used as the modifier of bitumen performance. The use of this polymer has improved both the classic (softening point, penetration, and so on) and performance properties of bitumen in comparison to the standard bitumen. © 2016 Taylor & Francis Group, LLC.
This paper presents a modeling and simulation of two different vehicles topologies (parallel hybrid electric vehicle and series hybrid electric vehicle) using the ADVISOR (ADvanced Vehicle SimulatOR). An accurate analysis of the performance of a hybrid electric vehicle, as well as of its consumption and pollution level, requires a dynamic analysis of its behavior. Two kinds of simulation tools for electric and hybrid electric vehicles exist: steady state and dynamic tools. An accurate analysis of the vehicle performance requires a dynamic model that includes many components such as its electric motor, its batteries and its motor controller. The central controller of this sedan consists of I/O Board, Adapter and Microcontroller of motor drive. In a first step, the vehicle components are sized, using a power flow analysis, to meet the requirements of energy and power of a typical 'Sedan vehicle'. In a second step, simulation results are presented and discussed to analysis complexity and performance. © 2017 IEEE.
Publication Date: 2017
Gradevinar (03502465)69(11)pp. 1017-1029
Bridge response to predefined loading schemes is described and recorded by instrumenting the structure with deflectometers and accelerometers. Test results suggest that although vertical deflections of mid-spans are almost constant for all crossing speeds, the root mean square of acceleration values are positively correlated with the crossing speed. Field test results are then used to calibrate and verify the 3D finite element model of the bridge, and the latter is employed to assess behaviour of the structure at the serviceability limit state.
Publication Date: 2017
International Journal of Architectural Heritage (15583066)11(8)pp. 1086-1100
Health monitoring of masonry railway bridges is vital due to their long life in service, an increasing demand for higher axle loads, and the recent trends in sustainability that requires the preservation of aged masonry bridges. Safety assessment of a 70-year-old masonry arch bridge is presented. The bridge is situated in a S-shaped curved section of the track and has long spans of 36 m. Added the deterioration of masonry due to old age of the bridge and complex behavior of masonry arch bridges, dynamic load tests are employed and global structural responses to allowable loading schemes of the bridge are determined. Dynamic amplification factors are determined and compared to those proposed by standards and it is concluded that experimental values are higher than those proposed by standards. Model calibration is carried out using deflection signatures. Experimental and analytical natural frequencies are compared for model verification. Having the model calibrated and verified, safety of bridge in serviceability and ultimate limit states due to application of operational loading schemes and higher axle loads are assessed. It is concluded that the bridge is safe regarding operational loading patterns, and could withstand an increased axle load of 25 tons. © 2017 Taylor & Francis.
Publication Date: 2017
Structural Engineering and Mechanics (12254568)64(1)pp. 33-44
In this paper, the dynamic responses of train-bridge system under one-way and two-way high-speed train passing are studied. The 3D finite element modeling is used and the bridge and train are modeled considering their details. The created model is validated by the results of the dynamic field test. To study the effect of train speed, different train passing scenarios are analyzed, including one-way passing, two-way passing in different directions at same speeds, and two-way passing in different directions at different speeds. The results show that the locations of maximum acceleration are different in one-way and two-way passing modes, and the maximum values in two-way passing mode are higher than those in one-way passing mode, while the maximum accelerations in both modes are almost identical. The displacement and acceleration values in different scenarios show peaks at speeds of 260 and 120 km/h, due to the proximity of the natural frequencies of the bridge and loading frequencies of the train at these speeds. Copyright © 2017 Techno-Press, Ltd.
Publication Date: 2017
Construction and Building Materials (09500618)135pp. 260-266
Considering the sustainable development principle, it seems necessary to reduce the temperature demands in producing asphalt mixtures and to replace mineral aggregates with secondary materials. In this study, the long-term performance of warm mix asphalt containing electric arc furnace steel slag was investigated. For this, Marshall Stability, resilient modulus at 25 °C and 40 °C, indirect tensile strength and moisture susceptibility tests were conducted. In the last stage, the ratio between the results of long-term and short-term aging of these tests was presented as an aging index. Using warm mix asphalt and replacing mineral aggregates with steel slag aggregate cause Marshall Stability, stiffness, resilient modulus and indirect tensile strength to increase. Although the tests conducted in this study indicate that using steel slag results in increased aging of the asphalt mixtures, warm asphalt mixtures containing steel slag experience less aging compared to control specimens (hot mix asphalt with limestone). Therefore, warm asphalt mixtures containing steel slag exhibit enhanced short-term and long-term performance as well as less aging. Hence, utilizing warm mix asphalt containing steel slag is generally recommended. © 2017 Elsevier Ltd
Publication Date: 2017
Journal of Materials in Civil Engineering (19435533)29(8)
This study investigated the effects of carbon nanotubes (CNT) as a binder modifier on the performance properties of asphalt binders and storage stability of polymer modified binders. Performance characteristics of CNT modified binders were investigated through physical and rheological tests such as penetration index (PI), viscosity temperature susceptibility (VTS), temperature susceptibility (TS), and frequency sweep tests. Furthermore, the influence of CNT on storage stability of styrene-butadiene-styrene (SBS) modified binders was investigated by measuring rheological properties like separation index (SI), separation ratio (Rs), degradation ratio (Rd), and softening point difference (SPD) of the triple nanocomposite. The results indicated that the addition of CNT decreased PI, TS, and VTS and improved physical and rheological properties of the asphalt binder. Also, the results showed a significant relationship between the CNT content and PI, TS, and VTS in CNT modified binders. Regarding storage stability, adding CNT to the SBS modified binder resulted in improved stability, indicating a strong interaction between the asphalt binder and SBS polymer. © 2017 American Society of Civil Engineers.
Publication Date: 2017
Petroleum Science and Technology (15322459)35(2)pp. 175-182
The authors investigated the effect of nanoclay (NC) on the performance properties and moisture susceptibility of rubberized asphalt mixtures. Two percent crumb rubber modifier (CRM) and NC in both combined and separate modes and the effects of each additive on bitumen performance were examined through administering tests of penetration grade, softening point and temperature susceptibility. Also, indirect tensile strength tests in both dry and saturated states were performed to allow for measuring the moisture susceptibility of asphalt mixtures. Moreover, the effect size of both additives on improving the bitumen performance and asphalt mixtures was assessed by running analysis of variance method and sensitivity analysis. The results of the laboratory test and statistical analyses revealed that CRM and NC improved the properties of bitumen and asphalt mixtures. This improvement was associated with the content and type of the additives applied, and also bitumen and asphalt mixtures had the best performance in presence of a combination of CRM and NC. © 2017 Taylor & Francis Group, LLC.
