Search results for: Samira Saleh

Authors: Kelaiaia Mounia Samira, Labar Hocine, Mesbah Tarek, Kelaiaia samia

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The photovoltaic panel produces green power, and because of its availability across the globe, it can supply isolated loads (site away of the electrical network or difficult of access). Unfortunately this energy remains very expensive. The most application of these types of power needs storage devices, the Lithium batteries are commonly used because of its powerful storage capability. Using a solar panel or an array of panels without a controller that can perform MPPT will often result in wasted power, which results in the need to install more panels for the same power requirement. For devices that have the battery connected directly to the panel, this will also result in premature battery failure or capacity loss. In this paper it is proposed a modified P&O algorithm for the MPPT which takes in account the battery’s internal resistance vs temperature and stage of charging. Of course the temperature variation and irradiation of the PV panel are also introduced.

Keywords: modeling, battery, MPPT, charging, PV Panel

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Authors: Othman Saleh Al-Razgan

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Obesity establishes an epidemic along with an array of comorbidities and this call for careful clinical assessment, to identify causal factors and comprehensive management. In Kuwait, this epidemic reflects the progressive, socio-economic and age-related issues, along with the shift of nutrition from traditional to modern-style. The current research attempts to narrate the obesity and related health issues in Kuwait, with a special emphasis on the magnitude of the issue in Kuwait, nutrition transition over the past three decades, change in life-style, and possible solution for this issue.

Keywords: clinical assessment, comorbidities, obesity, socio-economic

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Authors: El Hadi Zouaoui, Djamel Nibou, Mohamed Haddouche, Wan Azlina Wan Ab Karim Ghani, Samira Amokrane

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In this study, CH₄ adsorption isotherms on NaX or Faujasite X and exchanged zeolites with Li⁺(LiX), and K⁺(KX) at different temperatures (298, 308, 323 and 353 K) has been investigated, using high pressure (3 MPa (30 bar)) thermo-gravimetric analyser. The experimental results were then validated using several isothermal kinetics models, namely Langmuir, Toth, and Marczewski-Jaroniec, followed by a calculation of the error coefficients between the experimental and theoretical results. It was found that the CH₄ adsorption isotherms are characterized by a strong increase in adsorption at low pressure and a tendency towards a high pressure limit value Qₘₐₓ. The size and position of the exchanged cations, the spherical shape of methane, the specific surface, and the volume of the pores revealed the most important influence parameters for this study. These results revealed that the experimentation and the modeling, well correlated with Marczewski-Jaroniec, Toth, and gave the best results whatever the temperature and the material used.

Keywords: CH₄ adsorption, exchange cations, exchanged zeolite, isotherm study, NaX zeolite

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Authors: Samira Mohabbatdar, Abbas Ahmadi, Mohsen S. Sajadieh

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This paper deals with a two-level supply chain consisted of one manufacturer and one retailer for single-type product. The demand function of the customers depends on price. We consider an integrated production inventory system where the manufacturer processes raw materials in order to deliver finished product with imperfect quality to the retailer. Then retailer inspects the products and after that delivers perfect products to customers. The proposed model is based on the joint total profit of both the manufacturer and the retailer, and it determines the optimal ordering lot-size, number of shipment and selling price of the retailer. A numerical example is provided to analyse and illustrate the behaviour and application of the model. Finally, sensitivity analysis of the key parameters are presented to test feasibility of the model.

Keywords: supply chain, pricing policy, defective quality, joint economic lot sizing

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Authors: Samira-Sadat JamaliDinan, Haidar Almohri, Mohammad-Reza Nazem-Zadeh

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Lateralization of temporal lobe epilepsy (TLE) is very important for positive surgical outcomes. We propose a machine learning framework to ultimately identify the epileptogenic hemisphere for temporal lobe epilepsy (TLE) cases using magnetoencephalography (MEG) coherence source imaging (CSI) and diffusion tensor imaging (DTI). Unlike most studies that use classification algorithms, we propose an effective clustering approach to distinguish between normal and TLE cases. We apply the famous Minkowski weighted K-Means (MWK-Means) technique as the clustering framework. To overcome the problem of poor initialization of K-Means, we use particle swarm optimization (PSO) to effectively select the initial centroids of clusters prior to applying MWK-Means. We demonstrate that compared to K-means and MWK-means independently, this approach is able to improve the result of a benchmark data set.

Keywords: temporal lobe epilepsy, machine learning, clustering, magnetoencephalography

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Authors: Mohammad ASadian, Samira RajiAsadabadi

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Osteoporosis is very common, particularly in post-menopausal women and is characterized by a decrease in bone mass and strength. Osteoporosis also affects the jawbone and it is considered a potential contraindication to the placement of dental implants. The present paper reviews the literature regarding the effect of osteoporosis on the osseointegration of implants. Experimental models have shown that osteoporosis affects the process of osseointegration, which can be reversed by treatment. However, studies in subjects with osteoporosis have shown no differences in the survival of the implants compared to healthy individuals. Therefore, osteoporosis cannot be considered a contraindication for implant placement. Oral bisphosphonates are the most commonly used pharmacological agents in the treatment of osteoporosis. Although there have been cases of osteonecrosis of the jaw in patients treated with bisphosphonates, they are very rare and it is more usually associated with intravenous bisphosphonates in patients with neoplasms or other serious diseases. Nevertheless, patients treated with bisphosphonates must be informed in writing about the possibility of this complication and must give informed consent. Ceasing to use of bisphosphonates before implant placement does not seem to be necessary.

Keywords: Osteoporosis, dental implant, bisphosphonates, survival

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Authors: Saleh Elawgali

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Current spectrums of a four pole-pair, 400 kW induction machine were calculated for the cases of full symmetry and static eccentricity. The calculations involve integration of 93 electrical plus four mechanical ordinary differential equations. Electrical equations account for variable inductances affected by slotting and eccentricities. The calculations were followed by Fourier analysis of the stator currents in steady state operation. Zooms of the current spectrums, around the 50 Hz fundamental harmonic as well as of the main slot harmonic zone, were included. The spectrums included refer to both calculated and measured currents.

Keywords: diagnostic, harmonic, induction machine, spectrum

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Authors: Samira Ghizellaoui, Manel Boumagoura, Rayane Menzri

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The ground water Hamma rich in calcium and bicarbonate likely to deposit the tartar and subsequently lead to the obstruction of the pipes and the seizing of the stopping devices in addition to the financial losses resulting there from. It is therefore necessary to optimise an antiscaling treatment in order to avoid the risk of formation of tartar deposits in the various installations and to protect the equipment in contact with this water. MgCl2 is the chemical inhibitor which was tested. To optimise the effective concentration of this product, we used two electrochemical methods (chronoamperometry and impedancemetry) to identify the best method for optimizing antiscaling treatment. IR, RX, Raman spectroscopy and SEM indicate that the raw waters of Hamma give precipitates in the form of calcite (the most stable form), with the presence of a small amount of magnesian calcite and aragonite. In the presence of the inhibitor (MgCl2), calcium carbonate changes morphology to other forms that do not exist in the deposit obtained from the raw water (vaterite and calcium carbonate monohydrate).

Keywords: calcium carbonate, MgCl2, chronoamperometry, Impedancemetry

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Authors: Asma Aid, Samira Amokrane, Djamel Nibou, Hadj Mekatel

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The marine Enteromorpha Compressa (L.) (ECL) biomass was used as a low-cost biological adsorbent for the removal of Cr⁶⁺, Co²⁺ and Ni²⁺ ions from artificially contaminated aqueous solutions. The operating variables pH, the initial concentration C₀, the solid/liquid ratio R and the temperature T were studied. A full factorial experimental design technique enabled us to obtain a mathematical model describing the adsorption of Cr⁶⁺, Co²⁺ and Ni²⁺ ions and to study the main effects and interactions among operational parameters. The equilibrium isotherm has been analyzed by Langmuir, Freundlich, and Dubinin-Radushkevich models; it has been found that the adsorption process follows the Langmuir model for the used ions. Kinetic studies showed that the pseudo-second-order model correlates our experimental data. Thermodynamic parameters showed the endothermic heat of adsorption and the spontaneity of the adsorption process for Cr⁶⁺ ions and exothermic heat of adsorption for Co²⁺ and Ni²⁺ ions.

Keywords: enteromorpha Compressa, adsorption process, Cr⁶⁺, Co²⁺ and Ni²⁺, equilibrium isotherm

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Authors: Ali Hamad, Ibrahim Al-Drous, Saleh Al-Jufout

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This paper presents a case study of using STATCOM to enhance the performance of Al-Qatraneh 33-kV transmission line. The location of the STATCOM was identified maintaining minimum voltage drops at the 110 load nodes. The transmission line and the 110 load nodes have been modeled by MATLAB/Simulink. The suggested STATCOM and its location will increase the transmission capability of this transmission line and overcome the overload expected in the year 2020. The annual percentage loading rise has been considered as 14%. A graphical representation of the line voltages and the voltage drops at different load nodes has been illustrated.

Keywords: FACTS, MATLAB, STATCOM, transmission line, voltage drop

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Authors: Samira Gharehkhani, Seyed Farid Seyed Shirazi, Abdolreza Gharehkhani, Hooman Yarmand, Ahmad Badarudin, Rushdan Ibrahim, Salim Newaz Kazi

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Nanocrystalline cellulose (NCC) were prepared by acid hydrolysis and ultrasound treatment of bleached Acacia mangium fibers. The obtained rod-shaped nanocrystals showed a uniform size. The results showed that NCC with high crystallinity can be obtained using 64 wt% sulfuric acid. The effect of synthesis condition was investigated. Different reaction times were examined to produce the NCC and the results revealed that an optimum reaction time has to be used for preparing the NCC. Morphological investigation was performed using the transmission electron microscopy (TEM). Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) were performed. X-ray diffraction (XRD) analysis revealed that the crystallinity increased with successive treatments. The NCC suspension was homogeneous and stable and no sedimentation was observed for a long time.

Keywords: acid hydrolysis, nanocrystalline cellulose, nano material, reaction time

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Authors: Brahim Ferdi, Samira Dib

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The unified power quality conditioner (UPQC), a combination of shunt and series active power filter, is one of the best solutions towards the mitigation of voltage and current harmonics problems in distribution power system. PI controller is very common in the control of UPQC. However, one disadvantage of this conventional controller is the difficulty in tuning its gains (Kp and Ki). To overcome this problem, an adaptive fuzzy logic PI controller is proposed. The controller is composed of fuzzy controller and PI controller. According to the error and error rate of the control system and fuzzy control rules, the fuzzy controller can online adjust the two gains of the PI controller to get better performance of UPQC. Simulations using MATLAB/SIMULINK are carried out to verify the performance of the proposed controller. The results show that the proposed controller has fast dynamic response and high accuracy of tracking the current and voltage references.

Keywords: adaptive fuzzy PI controller, current harmonics, PI controller, voltage harmonics, UPQC

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Authors: Alouaoui Redha, Ferhat Samira, Bouaziz Mohamed Najib

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In this work, we examine the thermal radiation effect on heat and mass transfer in steady laminar boundary layer flow of an incompressible viscous micropolar fluid over a vertical plate, with the presence of a magnetic field. Rosseland approximation is applied to describe the radiative heat flux in the energy equation. The resulting similarity equations are solved numerically. Many results are obtained and representative set is displayed graphically to illustrate the influence of the various parameters on different profiles. The conclusion is drawn that the flow field, temperature, concentration and microrotation as well as the skin friction coefficient and the both local Nusselt and local Sherwood numbers are significantly influenced by Magnetic parameter, material parameter and thermal radiation parameter.

Keywords: MHD, micropolar fluid, thermal radiation, heat and mass transfer, boundary layer

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Authors: S. Alireza Mirghasemi, Shervin Rashidinia, Mohammad Saleh Sadeghi, Mohsen Talebizadeh, Narges Rahimi Gabaran, Seyed Shahin Eftekhari, Sara Shahmoradi

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Avascular necrosis of femoral head is a pathologic condition that the main cause is decreased blood supply of femoral head. Among predisposing risk factors, chronic use of corticosteroids, alcoholism, smocking and hip traumas have more important role. Also we can mention OCP consumption as a risk factor among less common predisposing factors that lead to AVNF, in this study we introduce another cause of AVNF with a period of treatment with moderate dose of corticosteroids accompanied by OCP as a probable facilitating factor that leads to AVNF.

Keywords: AVN, corticosteroids consumption, femoral head osteonecrosis, OCP

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Authors: Ahmed Saleh Summan

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This article presents the results of a technical report on the evaluation of occupational noise exposures among a musical conductor in a musical rehearsal hall (party–center). A calibrated noise dosimeter was used to measure the personal exposure of a music teacher/conductor for 8 hours in two days of rehearsal involving 90 players. Results showed that noise exposure levels were much higher than the permissible levels regulated 85dBA/8hr by NIOSH. In fact, the first day of measurements recorded the highest exposure levels (91 dBA). A number of factors contributed to these results, such as players number, types of instruments used, and activities. Noise control measures were recommended to solve this situation.

Keywords: noise exposure, music conductors, occupational noise, noise in rooms

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Authors: Samira Ferhat, Redha Alouaoui, Leila Trifi, Abdelmalek Badis

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The objective of this work is the use of natural surfactant (biosurfactant) and synthetic (sodium dodecyl sulfate and tween 80) for environmental application. In fact the solubility of the polycyclic hydrocarbon (naphthalene) and the desorption of the heavy metals in the presence of surfactants. The microorganisms selected in this work are bacterial strain (Bacillus licheniformis) for the production of biosurfactant for use in this study. In the first part of this study, we evaluated the effectiveness of surfactants solubilization certain hydrocarbons few soluble in water such as polyaromatic (case naphthalene). Tests have shown that from the critical micelle concentration, decontamination is performed. The second part presents the results on the desorption of heavy metals (for copper) by the three surfactants, using concentrations above the critical micelle concentration. The comparison between the desorption of copper by the three surfactants, it is shown that the biosurfactant is more effective than tween 80 and sodium dodecyl sulfate.

Keywords: surfactants, biosurfactant, naphthalene, copper, critical micelle concentration, solubilization, desorption

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Authors: Samira Naghdi, Kyong Yop Rhee

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Transfer-free synthesis of graphene on dielectric substrates is highly desirable but remains challenging. Here, by using a thin sacrificial platinum layer as a catalyst, graphene was deposited on a silicon substrate through a simple and transfer-free synthesis method. During graphene growth, the platinum layer evaporated, resulting in direct deposition of graphene on the silicon substrate. In this work, different growth conditions of graphene were optimized. Raman spectra of the produced graphene indicated that the obtained graphene was bilayer. The sheet resistance obtained from four-point probe measurements demonstrated that the deposited graphene had high conductivity. Reflectance spectroscopy of graphene-coated silicon showed a decrease in reflectance across the wavelength range of 200-800 nm, indicating that the graphene coating on the silicon surface had antireflection capabilities.

Keywords: antireflection coating, chemical vapor deposition, graphene, the sheet resistance

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Authors: Samira Khalil, Adib Saad, Malek Ali

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The aim of this research is to determine fish species belonging to the order Pleuronectiforme fish found in Syrian marine water confirm or deny the continuity of the previously registered species, and record the unregistered species that appeared during this research for the first time. The research was carried out in the Laboratory of Marine Sciences, Faculty of Agriculture (Tishreen University); fish samples were collected periodically (bi-monthly) from fishermen in landing areas along the Syrian coast caught from depths (3m to 700m), using various mediums. An appropriate hand is available to fishermen on the Syrian coast (cliff bottom, fixed nets, enclosure nets, shelf nest, and manual disposal network; 451 individuals were captured and studied during the research period. During this study, it was found that the Syrian water includes 15 species, including one species recorded for the first time. On the eastern coast of the Mediterranean, it is Pegusa impar.

Keywords: pleuronectiformes, Syrian coast, flatfish, mediterranean

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Authors: Boumediene Hamzi, Turky N. AlOtaiby, Saleh AlShebeili, Arwa AlAnqary

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We introduce a data-driven method for seizure detection drawing on recent progress in Machine Learning. The method is based on embedding probability measures in a high (or infinite) dimensional reproducing kernel Hilbert space (RKHS) where the Maximum Mean Discrepancy (MMD) is computed. The MMD is metric between probability measures that are computed as the difference between the means of probability measures after being embedded in an RKHS. Working in RKHS provides a convenient, general functional-analytical framework for theoretical understanding of data. We apply this approach to the problem of seizure detection.

Keywords: kernel methods, maximum mean discrepancy, seizure detection, machine learning

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Authors: Aid Asma, Dahdouh Nadjib, Amokrane Samira, Ladjali Samir, Nibou Djamel

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The present work has for main objective the elimination of the textile dye Maxilon Red (MR) by two processes, adsorption on activated clay followed by photocatalysis in presence of ZnO as a photocatalyst. The influence of the physical parameters like the initial pH, adsorbent dose of the activated clay, the MR concentration and temperature has been studied. The best adsorption yield occurs at neutral pH ~ 7 within 60 min with an uptake percentage of 97% for a concentration of 25 mg L⁻¹ and a dose of 0.5 g L⁻¹. The adsorption data were suitably fitted by the Langmuir model with a maximum capacity of 176 mg g⁻¹. The MR adsorption is well described by the pseudo second order kinetic. The second part of this work was dedicated to the photocatalytic degradation onto ZnO under solar irradiation of the residual MR concentration, remained after adsorption. The effect of ZnO dose and MR concentration has also been investigated. The parametric study showed that the elimination is very effective by this process, based essentially on the in situ generation of free radicals *OH which are non-selective and very reactive. The photodegradation process follows a first order kinetic model according to the Langmuir-Hinshelwood model.

Keywords: maxilon red, adsorption, photodegradation, ZnO, coupling

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Authors: Abdulali Bashir Ben Saleh

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The powdered beet red roots (PBRR) were used as an adsorbent to remove dyes namely methylene blue dye (as a typical cationic or basic dye) from aqueous solutions. The present study shows that used beet red roots powder exhibit adsorption trend for the dye. The adsorption processes were carried out at various conditions of concentrations, processing time and a wide range of pH between 2.5-11. Adsorption isotherm equations such as Freundlich, and Langmuir were applied to calculate the values of respective constants. Adsorption study was found that the currently introduced adsorbent can be used to remove cationic dyes such as methylene blue from aqueous solutions.

Keywords: beet red root, removal of deys, methylene blue, adsorption

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Authors: Jahanshah Saleh, Hossein Ghasemi, Ali Shahriari, Faezeh Alizadeh, Yaaghoob Hosseini

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Cadmium and chromium are toxic to most organisms and different mechanisms have been developed for overcoming with the toxic effects of these heavy metals. We studied the uptake and distribution of cadmium and chromium in different organs of tomato (Lycopersicon esculentum L.) plants in nine heavy metal polluted soils in western Hormozgan province, Iran. The accumulation of chromium was in increasing pattern of fruit peel

Keywords: cadmium, chromium, phytoextraction, phytostabilization, tomato

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Authors: Seyedsamad Tahani, Samira Ghorbanpour

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The global warming crisis forced humans to consider their place in the world and the earth's future. In this regard, Electric Vehicles (EVs) are a significant step toward protecting the environment. By identifying factors that influence people's behavior intentions toward using Electric Vehicles (EV), we proposed a theoretical model by extending the Technology Acceptance Model (TAM), including three more concepts, Subjective Norm (SN), Self-Efficacy (SE), and Perceived Behavior Control (PBC). The study was conducted in South Korea, and a random sample was taken at a specific time. In order to collect data, a questionnaire was created in a Google Form and sent via Kakao Talk, a popular social media application used in Korea. There were about 220 participants in this survey. However, 201 surveys were completely done. The findings revealed that all factors in the TAM model and the other added concepts such as subjective norms, self-efficacy and perceived behavior control significantly affect the behavioral intention of using EVs.

Keywords: electric vehicles, behavioral intention, perceived trust, perceived enjoyment, self-efficacy

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Authors: Samira Alvandi

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In the context of the circular economy, production planning aims to eliminate waste and emissions and maximize resource efficiency. Historically production planning is challenged through arrays of uncertainty and complexity arising from the interdependence and variability of products, processes, and systems. Manufacturers worldwide are facing new challenges in tackling various environmental issues such as climate change, resource depletion, and land degradation. In managing the inherited complexity and uncertainty and yet maintaining profitability, the manufacturing sector is in need of a holistic framework that supports energy efficiency and carbon emission reduction schemes. The proposed framework addresses the current challenges and integrates simulation modeling with optimization for finding optimal machine-job allocation to maximize throughput and total energy consumption while minimizing lead time. The aluminium refinery facility in western Sydney, Australia, is used as an exemplar to validate the proposed framework.

Keywords: smart production planning, simulation-optimisation, energy aware capacity planning, energy intensive industries

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Authors: Vu Thu Trang, Lam Xuan Thanh, Samira Sarter, Tomoko Shimamura, Hiroaki Takeuchi　　

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Antimicrobial activities of aminoreductone (AR), a product formed in the initial stage of Maillard reaction, were screened against pathogenic bacteria. A significant growth inhibition of AR against all 7 isolates (Staphylococcus aureus ATCC® 25923™, Salmonella Typhimurium ATCC® 14028™, Bacillus cereus ATCC® 13061™, Bacillus subtilis ATCC® 11774™, Escherichia coli ATCC® 25922™, Enterococcus faecalis ATCC® 29212™, Listeria innocua ATCC® 33090™) were observed by the standard disc diffusion methods. The inhibition zone for each isolate by AR (2.5 mg) ranged from 15±0 mm to 28.3±0.4 mm in diameter. The minimum inhibitory concentration (MIC) of AR ranging from 20 mM to 26 mM was proven in the seven isolates tested. AR also showed the similar effect of growth inhibition in comparison with antibiotics frequently used for the treatment of infections bacteria, such as amikacin, ciprofloxacin, meropennem, and levofloxacin. The results indicated that foods containing AR are valuable sources of bioactive compounds towards pathogenic bacteria.

Keywords: pathogenic bacteria, aminoreductone, Maillard reaction, antimicrobial activity

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Authors: Arefeh Lotfi, Mahdi Babaei, Ayda Mashhadizadeh, Samira Nikpour, Morteza Bagheri

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The main objective of this study is to investigate the key factors in accidents’ severity at rail-road level crossings. The data required for this study is obtained from both accident and inventory database of Iran Railways during 2009-2015. The Ordered Probit model is developed using SPSS software to identify the significant factors in the accident severity at rail-road level crossings. The results show that 'train speed', 'vehicle type' and 'weather' are the most important factors affecting the severity of the accident. The results of these studies assist to allocate resources in the right place. This paper suggests mandating the regulations to reduce train speed at rail-road level crossings in bad weather conditions to improve the safety of rail-road level crossings.

Keywords: rail-road level crossing, ordered probit model, accidents’ severity, significant factors

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Authors: Saleh Mobasseri, Mohammad Mobasseri

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The article refers to the history of the rise of brake system and described it’s importance in passenger’s lives. The disc brake system performance and ABS are also compared with each other by the kinetic and kinematic analysis of the braking system,and evaluate the impact of each parameters is checked on the vehicle stopping distance. Anti−lock braking system (ABS) is one of the most important features that affect on vehicle safety and for this reason much efforts have been made to improve this system. The objectives of the anti−lock system (ABS) are as follows: Preventing the wheels from locking, achieving maximum technical momentum in terms of braking,stability,reducing stopping distances. In this paper,we study the comparative of ABS brake and disc brake.

Keywords: anti−lock braking System (ABS), stopping distances, booster, car stability, force exerted on the brake pedal

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Authors: Afif Saleh Abugharsa

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The IEEE 802.15.4 standard is designed for low-rate wireless personal area networks (LR-WPAN) with focus on enabling wireless sensor networks. It aims to give a low data rate, low power consumption, and low cost wireless networking on the device-level communication. The objective of this study is to investigate the performance of IEEE 802.15.4 based networks using simulation tool. In this project the network simulator 2 NS2 was used to several performance measures of wireless sensor networks. Three scenarios were considered, multi hop network with a single coordinator, star topology, and an ad hoc on demand distance vector AODV. Results such as packet delivery ratio, hop delay, and number of collisions are obtained from these scenarios.

Keywords: ZigBee, wireless sensor networks, IEEE 802.15.4, low power, low data rate

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Authors: Mousa Saleh Daoud

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Rickets is a condition that affects the development of bones in children. It causes soft bones, which can become bowed or curved, this bending and curvature is evident in the age of Walking. The most common cause of rickets is dietary deficiency of vitamin D or Lack of exposure to sunlight or both together. The link between vitamin D and rickets has been known for many years and is well understood by doctors and scientists. If a child does not get enough of the vitamin D, the bones cannot form hard outer shells. This is why they become soft and weak. This study was conducted on children who reviewed by our medical clinic between the years 2011-2013. The study included 400 children, aged between one and six years. 11 children had clear clinical manifestations of rickets of varying degrees and all of them due to lack of vitamin D except for one case of rickets resistant to vitamin D. 389 cases ranged between natural and deficiency in vitamin D without clinical manifestations of Rickets.

Keywords: rickts, bone metabolic diseases, vitamin D, child

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Authors: Sara Ali Alokley, Mansour Saleh Albarrak

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This paper investigates the dependency or clustering of extremes in the financial returns data by estimating the extremal index value θ∈[0,1]. The smaller the value of θ the more clustering we have. Here we apply the method of Ferro and Segers (2003) to estimate the extremal index for a range of threshold values. We compare the dependency structure of extremes in the developed and emerging markets. We use the financial returns of the stock market index in the developed markets of US, UK, France, Germany and Japan and the emerging markets of Brazil, Russia, India, China and Saudi Arabia. We expect that more clustering occurs in the emerging markets. This study will help to understand the dependency structure of the financial returns data.

Keywords: clustring, extremes, returns, dependency, extermal index

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