Search results for: Hatem Ben Maad

Authors: Miled Amel, Ben Maad Hatem, Askri Faouzi, Ben Nasrallah Sassi

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Metal hydride water pumping system uses hydrogen as working fluid to pump water for low head and high discharge. The principal operation of this pump is based on the desorption of hydrogen at high pressure and its absorption at low pressure by a metal hydride. This work is devoted to study a concept of the dynamic behavior of a metal hydride pump using unsteady model and LaNi5 as hydriding alloy. This study shows that with MHP, it is possible to pump 340l/kg-cycle of water in 15 000s using 1 Kg of LaNi5 at a desorption temperature of 360 K, a pumping head equal to 5 m and a desorption gear ratio equal to 33. This study reveals also that the error given by the steady model, using LaNi5 is about 2%.A dimensional mathematical model and the governing equations of the pump were presented to predict the coupled heat and mass transfer within the MHP. Then, a numerical simulation is carried out to present the time evolution of the specific water discharge and to test the effect of different parameters (desorption temperature, absorption temperature, desorption gear ratio) on the performance of the water pumping system (specific water discharge, pumping efficiency and pumping time). In addition, a comparison between results obtained with steady and unsteady model is performed with different hydride mass. Finally, a geometric configuration of the reactor is simulated to optimize the pumping time.

Keywords: dynamic behavior, LaNi5, performance of water pumping system, unsteady model

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Authors: Damien Gondre, Hatem Ben Maad, Abdelkrim Trabelsi, Frédéric Kuznik, Joseph Virgone

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The use of a radiant cooling solution would enable to lower cooling needs which is of great interest when the demand is initially high (hot climate). But, radiant systems are not naturally compatibles with humid climates since a low-temperature surface leads to condensation risks as soon as the surface temperature is close to or lower than the dew point temperature. A radiant cooling system combined to a dehumidification system would enable to remove humidity for the space, thereby lowering the dew point temperature. The humidity removal needs to be especially effective near the cooled surface. This requirement could be fulfilled by a system using a single desiccant fluid for the removal of both excessive heat and moisture. This task aims at providing an estimation of the specification requirements of such system in terms of cooling power and dehumidification rate required to fulfill comfort issues and to prevent any condensation risk on the cool panel surface. The present paper develops a preliminary study on the specification requirements, performances and behavior of a combined dehumidifier/cooling ceiling panel for different operating conditions. This study has been carried using the TRNSYS software which allows nodal calculations of thermal systems. It consists of the dynamic modeling of heat and vapor balances of a 5m x 3m x 2.7m office space. In a first design estimation, this room is equipped with an ideal heating, cooling, humidification and dehumidification system so that the room temperature is always maintained in between 21^◦C and 25^◦C with a relative humidity in between 40% and 60%. The room is also equipped with a ventilation system that includes a heat recovery heat exchanger and another heat exchanger connected to a heat sink. Main results show that the system should be designed to meet a cooling power of 42W.m⁻² and a desiccant rate of 45 g_H2O.h⁻¹. In a second time, a parametric study of comfort issues and system performances has been achieved on a more realistic system (that includes a chilled ceiling) under different operating conditions. It enables an estimation of an acceptable range of operating conditions. This preliminary study is intended to provide useful information for the system design.

Keywords: dehumidification, nodal calculation, radiant cooling panel, system sizing

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Authors: Aicha Rima Cheniti, Hatem Besbes, Joseph Haggege, Christophe Sintes

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In this paper, we consider a drift flux mixture model of the blood flow. The mixture consists of gas phase which is carbon dioxide and liquid phase which is an aqueous carbon dioxide solution. This model was used to determine the distributions of the mixture velocity, the mixture pressure, and the carbon dioxide pressure. These theoretical data are used to determine a measurement method of mean gas pressure through the determination of radial velocity distribution. This method can be applicable in experimental domain.

Keywords: mean carbon dioxide pressure, mean mixture pressure, mixture velocity, radial velocity

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Authors: Osama Terra, Mariesa Nel, Hatem Hussein

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Calibration of Optical Time Domain Reflectometer (OTDR) has a crucial role for the accurate determination of fault locations and the accurate calculation of loss budget of long-haul optical fibre links during installation and repair. A comparison has been made between the Egyptian National Institute for Standards (NIS-Egypt) and the National Metrology institute of South Africa (NMISA-South Africa) for the calibration of an OTDR. The distance and the attenuation scales of a transfer OTDR have been calibrated by both institutes using their standards according to the standard IEC 61746-1 (2009). The results of this comparison have been compiled in this report.

Keywords: OTDR calibration, recirculating loop, concatenated method, standard fiber

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Authors: Ahmed Khalil, Hatem M. El-Desoky

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The present paper deals with the petrography and geochemistry of the Basic Dokhan Volcanics, Eastern Desert, Egypt. The basalts from Gabal Wassif, Atalla volcanics and Gabal Esh Mellaha were tested for use as aggregates in concrete mixes. The representative twelve samples were collected from areas. These samples were examined by using a petrographic microscope to evaluate sample texture, degree of alteration and the presence of volcanic glass in the matrix. The results obtained indicate that basalt can be used successfully for preparing concrete, but some attention should be paid to the choice of the suitable types of basalt. A general improvement in concrete mix properties has been found by using basalt aggregates in the mix.

Keywords: basic Dokhan volcanics, petrography, geochemistry, petrogenesis and concrete aggregates

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Authors: Ridha Zgolli, Hatem Kanfoudi

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Cavitating flows inside a diesel injection nozzle hole were simulated using a mixture model. A 2D numerical model is proposed in this paper to simulate steady cavitating flows. The Reynolds-averaged Navier-Stokes equations are solved for the liquid and vapor mixture, which is considered as a single fluid with variable density which is expressed as function of the vapor volume fraction. The closure of this variable is provided by the transport equation with a source term TEM. The processes of evaporation and condensation are governed by changes in pressure within the flow. The source term is implanted in the CFD code ANSYS CFX. The influence of numerical and physical parameters is presented in details. The numerical simulations are in good agreement with the experimental data for steady flow.

Keywords: cavitation, injection nozzle, numerical simulation, k–ω

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Authors: Osama Terra, Hatem Hussein, Adriaan Van Brakel

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Dense wavelength division multiplexing (DWDM) technology requires tight specification and therefore measurement of wavelength accuracy and stability of the telecommunication lasers. Thus, calibration of the used Optical Spectrum Analyzers (OSAs) that are used to measure wavelength is of a great importance. Proficiency testing must be performed on such measuring activity to insure the accuracy of the measurement results. In this paper, a new comparison scheme is introduced to test the performance of such calibrations. This comparison scheme is implemented between NIS-Egypt and NMISA-South Africa for the calibration of the wavelength scale of an OSA. Both institutes employ reference gas cell to calibrate OSA according to the standard IEC/ BS EN 62129 (2006). The result of this comparison is compiled in this paper.

Keywords: OSA calibration, HCN gas cell, DWDM technology, wavelength measurement

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Authors: Hatem Hamdy Ghieth

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In the recent time many fires happened in many skeleton buildings. The fire may be continues for a long time. This fire may cause a collapse of the building. This collapse may be happened due to the time of exposure to fire as well as the rate of the loading to the carrying elements. In this research a laboratory study for reinforced concrete columns under effect of fire with temperature reaches (650 ْ C) on the behavior of columns which loaded with axial load and with exposing to fire temperature only from all sides of columns. the main parameters of this study are level of load applying to the column, and the temperature applied to the fire, this temperatures was 500oC and 650oc. Nine concrete columns with dimensions 20x20x100 cms were casted one of these columns was tested to determine the ultimate load while the least were fired according to the experimental schedule.

Keywords: columns, fire duration, concrete strength, level of loading

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Authors: Fairouz Fakhfakh, Hatem Hadj Kacem, Ahmed Hadj Kacem

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Cloud computing offers a new model of service provisioning for workflow applications, thanks to its elasticity and its paying model. However, it presents various challenges that need to be addressed in order to be efficiently utilized. The resources provisioning problem for workflow applications has been widely studied. Nevertheless, the existing works did not consider the change in workflow instances while they are being executed. This functionality has become a major requirement to deal with unusual situations and evolution. This paper presents a first step towards the resources provisioning for a dynamic workflow. In fact, we propose a provisioning algorithm which minimizes the overall workflow execution cost, while meeting a deadline constraint. Then, we extend it to support the dynamic adding of tasks. Experimental results show that our proposed heuristic demonstrates a significant reduction in resources cost by using a consolidation process.

Keywords: cloud computing, resources provisioning, dynamic workflow, workflow applications

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Authors: Meryem Kanzari, Rabah Boukhanouf, Hatem G. Ibrahim

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Indirect Evaporative Cooling process has the advantage of supplying cool air at constant moisture content. However, such system can only supply air at temperatures above wet bulb temperature. This paper presents a mathematical model for a sub-wet bulb temperature indirect evaporative cooling arrangement that can overcome this limitation and supply cool air at temperatures approaching dew point and without increasing its moisture content. In addition, the use of porous ceramics as wet media materials offers the advantage of integration into building elements. Results of the computer show that the proposed design is capable of cooling air to temperatures lower than the ambient wet bulb temperature and achieving wet bulb effectiveness of about 1.17.

Keywords: indirect evaporative cooling, porous ceramic, sub-wet bulb temperature, mathematical modeling

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Authors: J. V. Thanikal, M. Torrijos, Philipe Sousbie, S. M. Rizwan, R. Senthil Kumar, Hatem Yezdi

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Co-digestion is one of the advantages of anaerobic digestion process because; several wastes having complimentary characteristics can be treated in a single process. The anaerobic co-digestion process, which can be defined as the simultaneous treatment of two –or more – organic biodegradable waste streams by anaerobic digestion offers great potential for the proper disposal of the organic fraction of solid waste coming from source or separate collection systems. The results of biogas production for sewage sludge, when used as a single substrate, were low (350ml/d), and also the biodegradation rate was slow. Sewage sludge as a co-substrate did not show much effect on biogas yield. The vegetable substrates (Potato, Carrot, Spinach) with a total charge of 27–36 g VS, with a HRT starting from 3 days and ending with 1 day, shown a considerable increase in biogas yield 3.5-5 l/d.

Keywords: anaerobic digestion, co-digestion, vegetable substrate, sewage sludge

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Authors: Maad Kamal Al-Anni

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This study is about an algorithmic dependence of Artificial Neural Network on Multilayer Perceptron (MPL) pertaining to the classification and clustering presentations for Mobile Adhoc Network vulnerabilities. Moreover, mobile ad hoc network (MANET) is ubiquitous intelligent internetworking devices in which it has the ability to detect their environment using an autonomous system of mobile nodes that are connected via wireless links. Security affairs are the most important subject in MANET due to the easy penetrative scenarios occurred in such an auto configuration network. One of the powerful techniques used for inspecting the network packets is Intrusion Detection System (IDS); in this article, we are going to show the effectiveness of artificial neural networks used as a machine learning along with stochastic approach (information gain) to classify the malicious behaviors in simulated network with respect to different IDS techniques. The monitoring agent is responsible for detection inference engine, the audit data is collected from collecting agent by simulating the node attack and contrasted outputs with normal behaviors of the framework, whenever. In the event that there is any deviation from the ordinary behaviors then the monitoring agent is considered this event as an attack , in this article we are going to demonstrate the  signature-based IDS approach in a MANET by implementing the back propagation algorithm over ensemble-based Traffic Table (TT), thus the signature of malicious behaviors or undesirable activities are often significantly prognosticated and efficiently figured out, by increasing the parametric set-up of Back propagation algorithm during the experimental results which empirically shown its effectiveness  for the ratio of detection index up to 98.6 percentage. Consequently it is proved in empirical results in this article, the performance matrices are also being included in this article with Xgraph screen show by different through puts like Packet Delivery Ratio (PDR), Through Put(TP), and Average Delay(AD).

Keywords: Intrusion Detection System (IDS), Mobile Adhoc Networks (MANET), Back Propagation Algorithm (BPA), Neural Networks (NN)

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Authors: Shatha A. Yousif, Hatem Jasim, Ali R. Abas, Dheya P. Yousef

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To study the effect of the cross direction in bead wheat, three hybrid combinations (Babyle 113 , Iratome), (Sawa , Tamose2) and (Al Hashymya Al Iraq) were tested for plant height, number of tillers/m, number of grains per spike, weight of grains per spike, 1000-grain weight and grain yield. The results revealed that the direction of the cross had significant effect the number of grain/spike, tillers/m and grain yields. Grain yield was positively and significantly correlated with 1000-grain weight, number of grains per spike and tillers. Depend on the result of heritability and genetic advance it was suggested that 1000-grain weight number of grains per spike and tillers should be given emphasis for future wheat yield improvement programs.

Keywords: correlation, genetic advance, heritability, wheat, yield traits

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Authors: Osama Terra, Hatem Hussein

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Calibration of Optical Time Domain Reflectometer (OTDR) is crucial for the accurate determination of loss budget for long optical fiber links. In this paper, the calibration of the attenuation scale of an OTDR using two different techniques is discussed and implemented. The first technique is the external modulation method (EM). A setup is proposed to calibrate an OTDR over a dynamic range of around 15 dB based on the EM method. Afterwards, the OTDR is calibrated using two standard reference fibers (SRF). Both SRF are calibrated using cut-back technique; one of them is calibrated at our home institute (the National Institute of Standards – NIS) while the other at the National Physical Laboratory (NPL) of the United Kingdom to confirm our results. In addition, the parameters contributing the calibration uncertainty are thoroughly investigated. Although the EM method has several advantages over the SRF method, the uncertainties in the SRF method is found to surpass that of the EM method.

Keywords: optical time domain reflectometer, fiber attenuation measurement, OTDR calibration, external source method

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Authors: Hatem Abdel Moniem Ahmed, Ragaa Mohamed Abdel Maaboud, Heba A. Mubarak

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A commercially available Stone Hair Dye (SHD) was spread in Upper Egypt and used for dying woman's hair. Paraphenyl-diamine (PPD) is the main component of SHD and reported as a toxic substance. This work aims to study the systemic effects induced in experimental animals as a result of dermal application of SHD. 21 rats were divided into three groups, and doses of SHD and PPD were applied according to body weight (25 mg/100 g body weight) for 90 days. The results revealed that insignificant decrease in RBC count and Hb level, but there were significant increases in the WBC count, AST, ALT, GPT, and total protein while creatinine level was insignificantly increased. Hepatocytes showed a lot of degenerative changes in the form of vacuolated cytoplasm and irregular deeply stained nuclei with vascular congestion and lymphocytic infiltration, while renal affection indicated the occurrence of atrophy of glomerular capillaries, hyperplasia, and widening of bowman space.

Keywords: PPD, SHD, rats and histology, biochemistry and hematology

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Authors: Aicha Rima Cheniti, Hatem Besbes, Joseph Haggege, Christophe Sintes

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In this paper, we are interested to determine the carbon dioxide pressure in the arterial blood through radial velocity difference. The blood was modeled as a two phase mixture (an aqueous carbon dioxide solution with carbon dioxide gas) by Drift flux model and the Young-Laplace equation. The distributions of mixture velocities determined from the considered model permitted the calculation of the radial velocity distributions with different values of mean mixture pressure and the calculation of the mean carbon dioxide pressure knowing the mean mixture pressure. The radial velocity distributions are used to deduce a calculation method of the mean mixture pressure through the radial velocity difference between two positions which is measured by ultrasound. The mean carbon dioxide pressure is then deduced from the mean mixture pressure.

Keywords: mean carbon dioxide pressure, mean mixture pressure, mixture velocity, radial velocity difference

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Authors: Helen S. Ghali, Haidy S. Ghali, Salma Ibrahim, Ossama Hosny, Hatem S. Elbehairy

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Infrastructure systems are essential assets in any community; accordingly, authorities aim to maximize its life span while minimizing the life cycle cost. This requires studying the asset conditions throughout its operation and forming a cost-efficient maintenance strategy plan. The objective of this study is to develop a highway management system that provides medium-term maintenance plans with the minimum life cycle cost subject to budget constraints. The model is applied to data collected for the highway network in India with the aim to output a 5-year maintenance plan strategy from 2019 till 2023. The main element considered is the surface coarse, either rigid or flexible pavement. The model outputs a 5-year maintenance plan for each segment given the budget constraint while maximizing the new pavement condition rating and minimizing its life cycle cost.

Keywords: infrastructure, asset management, optimization, maintenance plan

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Authors: Faten Hatem

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This paper explores the associated understanding of the role and meaning of art and whether it is perceived to be separate from smart city construction. The paper emphasises the significance of fulfilling the inherent need for discovery and interaction, driving people to explore new places and think of works of art. This is done by exploring the ways of thinking and types of art in Milton Keynes by illustrating a general pattern of misunderstanding that relies on the separation between smart, art, and architecture, promoting a better and deeper understanding of the interconnections between neuroscience, art, and architecture. A reflective approach is used to clarify the potential and impact of using art-based research, methodology, and ways of knowing when approaching global phenomena and knowledge production while examining the process of making and developing smart cities, in particular, asserting that factors can severely impact it in the process of conducting the study itself. It follows a case study as a research strategy. The qualitative methods included data collection and analysis that involved interviews and observations that depended on visuals.

Keywords: smart cities, art and smart, smart cities design, smart cities making, sustainability, city brain and smart cities metrics, smart cities standards, smart cities applications, governance, planning and policy

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Authors: Rabab A. El Wahsh, Hatem M. Marey, Maha Yousif, Asmaa M. Ibrahim

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Background: OSA and COPD are associated with microvascular changes. Retinal microvasculature can be directly and non-invasively examined. Aim: to evaluate retinal vascular tortuosity in patients with COPD, OSA, and overlap syndrome. Subjects and method: Sixty subjects were included; 15 OSA patients, 15 COPD patients, 15 COPD-OSA overlap patients, and 15 matched controls. They underwent digital retinal photography, polysomnography, arterial blood gases, spirometry, ESS, and stop-bang questionnaires. Results: Tortuosity of most retinal vessels was higher in all patient groups compared to the control group; tortuosity was more marked in overlap syndrome. There was a negative correlation between tortuosity of retinal vessels and PO2, O2 saturation, and minimum O2 desaturation, and a positive correlation with PCO2, AHI, O2 desaturation index, BMI and smoking index. Conclusion: Retinal vascular tortuosity occurs in OSA, COPD and overlap syndrome. Retinal vascular tortuosity is correlated with arterial blood gases parameters, polysomnographic findings, smoking index and BMI.

Keywords: OSA, COPD, overlap syndrome, retinal vascular tortuosity

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Authors: Furqan M. Kadhum, Asmaa A. Hussein, Maysaa Ch. Hatem

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Hyaluronidase enzyme was purified from the clinical isolate Staphyloccus aureus in three purification steps, first by precipitation with 90% saturated ammonium sulfate, ion exchange chromatography on DEAE-Cellulose, and gel filtration chromatography throughout Sephacryl S-300. Specific activity of the purified enzyme was reached 930 U/mg protein with 7.4 folds of purification and 46.5% recovery. The enzyme has an average molecular weight of about 69 kDa, with an optimum pH of enzyme activity and stability at pH 7, also the optimum temperature for activity was 37oC. The enzyme was stable with full activity at a temperature ranged between 30-40 oC. Metal ions showed variable inhibitory degree with the strongest effect for Fe+3, however, the chelating and reducing agents had no or little effects. Cytotoxic studies for purified and crude hyaluronidase against cancer cell Hep G2 type at different enzyme concentrations and exposure times showed that the inhibition effect of both crude and purified enzyme increased by increasing the enzyme concentration with no change was observed at 24hr, while at 48 and 72 hrs the same inhibition rate were observed for purified enzyme and differ for the crude filtrate.

Keywords: hyaluronidase, S. aureus, metal ions, cytotoxicity

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Authors: Ahmed R. Ismail, Hatem A. El Tawil, Nevin G. Rezk

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Historic paths in today's cities are facing the pressure of the urban development due to the rapid urban growth. Every new development is tearing the old urban fabric and the socio-economic character of the historic paths. Furthermore, in some cases historic paths suffer from negligence and decay. Kom El Dekka historic path was one of those deteriorated paths in the city of Alexandria, Egypt, in spite of its high heritage and socio-economic value. Therefore, there was a need to develop urban regeneration strategies as a part of a wider sustainable development vision, to handle the situation and revitalize the path as a livable space in the heart of the city. This study aims to develop a comprehensive assessment methodology to evaluate the different values of the path and to create community-oriented and economic-based analysis methodology for its socio-economic values. These analysis and assessments provide strategies for any regeneration action plan for Kom El Dekka historic path.

Keywords: community-oriented, economic-based, syntactical analysis, urban regeneration

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Authors: Hatem Ghith

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This research paper experimentally investigates the effect of burning by fire flame from one face on the behavior and load carrying capacity for reinforced columns. Residual ultimate load carrying capacity, axial deformation, crack pattern and maximum crack width for column specimens with and without burning were recorded and discussed. Tested six reinforced concrete columns were divided into control specimen and two groups. The first group was exposed to a fire with a different temperature (300, 500, 700 °C) for an hour with reinforcement ratio 0.89% and the second group was exposed to a fire with a temperature 500 °C for an hour with different reinforcement ratio (0.89%, 2.18%, and 3.57%), then all columns were tested under short-term axial loading. From the obtained results, it could be concluded that the fire parameters significantly influence the fire resistance of R.C columns. The fire parameters cause axial deformation and moment on the column due to the eccentricity that generated from the difference in temperature and consequently the compressive stresses of both faces of the columns but the increased reinforcement ratio enhanced the resistance of columns for axial deformation and moment on the column due to the eccentricity.

Keywords: columns, reinforcement ratio, strength, time exposure

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Authors: Hatem Hajri, Mohamed-Cherif Rahal

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Both Lidars and Radars are sensors for obstacle detection. While Lidars are very accurate on obstacles positions and less accurate on their velocities, Radars are more precise on obstacles velocities and less precise on their positions. Sensor fusion between Lidar and Radar aims at improving obstacle detection using advantages of the two sensors. The present paper proposes a real-time Lidar/Radar data fusion algorithm for obstacle detection and tracking based on the global nearest neighbour standard filter (GNN). This algorithm is implemented and embedded in an automative vehicle as a component generated by a real-time multisensor software. The benefits of data fusion comparing with the use of a single sensor are illustrated through several tracking scenarios (on a highway and on a bend) and using real-time kinematic sensors mounted on the ego and tracked vehicles as a ground truth.

Keywords: ground truth, Hungarian algorithm, lidar Radar data fusion, global nearest neighbor filter

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Authors: Moataz Medhat, Essam Khalil, Hatem Haridy

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The present study investigates the flame structure of turbulent diffusion flame of synthesis fuel in a 300 KW swirl-stabilized burner. The three-dimensional model adopts a realizable k-ε turbulent scheme interacting with two-dimensional PDF combustion scheme by applying flamelet concept. The study reveals more characteristics on turbulent diffusion flame of synthesis fuel when changing the inlet air swirl number and the burner quarl angle. Moreover, it concerns with studying the effect of flue gas recirculation and staging with taking radiation effect into consideration. The comparison with natural gas was investigated. The study showed two zones of recirculation, the primary one is at the center of the furnace, and the location of the secondary one varies by changing the quarl angle of the burner. The results revealed an increase in temperature in the external recirculation zone as a result of increasing the swirl number of the inlet air stream. Also, it was found that recirculating part of the combustion products decreases pollutants formation especially nitrogen monoxide. The predicted results showed a great agreement when compared with the experiments.

Keywords: gas turbine, syngas, analysis, recirculation

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Authors: Hatem A. El-Mezayen, Ahmed Abdelmajeed, Fatehya Metwally, Usama Elsaly, Salwa Atef

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Tumor metastasis involves the dissemination of malignant cells into the basement membrane and vascular system contributes to the circulating pool of these markers. In this context our aim has been focused on development of a non-invasive. Circulating tumor cells (CTCs) represent a unique liquid biopsy carrying comprehensive biological information of the primary tumor. Herein, we sought to develop a novel score based on the combination of the most significant CTCs biomarkers with and routine laboratory tests for accurate detection of metastatic breast cancer. Methods: Cytokeratin 18 (CK18), Cytokeratin 19 (CK19), and CA15.3 were assayed in metastatic breast cancer (MBC) patients (75), non-MBC patients (50) and healthy control (20). Results: Areas under receiving operating curve (AUCs) were calculated and used for construction on novel score. A novel score named MBC-CTCs = CA15.3 (U/L) × 0.08 + CK 18 % × 2.9 + CK19 × 3.1– 510. That function correctly classified 87% of metastatic breast cancer at cut-off value = 0.55. (i.e great than 0.55 indicates patients with metastatic breast cancer and less than 0.55 indicates patients with non-metastatic breast cancer). Conclusion: MBC-CTCs is a novel, non-invasive and simple can applied to discriminate patients with metastatic breast cancer.

Keywords: metastatic breast cancer, circulating tumor cells, cytokeratin, EpiCam

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Authors: Hatem Mrad, Alban Notin, Mohamed Bouazara

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Sheet metal forming process has a multiple successive steps starting from sheets fixation to sheets evacuation. Often after forming operation, the sheet has defects requiring additional corrections steps. For example, in the drawing process, the formed sheet may have several defects such as springback, localized thinning and bends. All these defects are directly dependent on process, geometric and material parameters. The prediction and elimination of these defects requires the control of most sensitive parameters. The present study is concerned with a reliable parametric study of deep forming process in order to control the localized thinning. The proposed approach will be based on stochastic finite element method. Especially, the polynomial Chaos development will be used to establish a reliable relationship between input (process, geometric and material parameters) and output variables (sheet thickness). The commercial software Abaqus is used to conduct numerical finite elements simulations. The automatized parametrical modification is provided by coupling a FORTRAN routine, a PYTHON script and input Abaqus files.

Keywords: sheet metal forming, reliability, localized thinning, parametric simulation

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Authors: Hatem Mrad, Mohamed Bouazara, Fouad Erchiqui

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Fatigue, is considered as one of the main cause of mechanical properties degradation of mechanical parts. Probability and reliability methods are appropriate for fatigue analysis using uncertainties that exist in fatigue material or process parameters. Current work deals with the study of the effect of the number and counting Rainflow cycle on fatigue lifetime (cumulative damage) of an upper arm of the vehicle suspension system. The major part of the fatigue damage induced in suspension arm is caused by two main classes of parameters. The first is related to the materials properties and the second is the road excitation or the applied force of the passenger’s number. Therefore, Young's modulus and road excitation are selected as input parameters to conduct repetitive simulations by Monte Carlo (MC) algorithm. Latin hypercube sampling method is used to generate these parameters. Response surface method is established according to fatigue lifetime of each combination of input parameters according to strain-life method. A PYTHON script was developed to automatize finite element simulations of the upper arm according to a design of experiments.

Keywords: fatigue, monte carlo, rainflow cycle, response surface, suspension system

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Authors: Hatem A. El-Mezayen, Hossam Darwesh

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Background/Aim: Hepatocellular carcinoma (HCC) is often diagnosed at advanced stage where effective therapies are lacking. Identification of new scoring system is needed to discriminate HCC patients from those with chronic liver disease. Based on the link between vascular endothelial growth factor (VEGF) and HCC progression, we aimed to develop a novel score based on combination of VEGF and routine laboratory tests for early prediction of HCC. Methods: VEGF was assayed for HCC group (123), liver cirrhosis group (210) and control group (50) by Enzyme Linked Immunosorbent Assay (ELISA). Data from all groups were retrospectively analyzed including α feto protein (AFP), international normalized ratio (INR), albumin and platelet count, transaminases, and age. Areas under ROC curve were used to develop the score. Results: A novel index named hepatocellular carcinoma-vascular endothelial growth factor score (HCC-VEGF score)=1.26 (numerical constant) + 0.05 ×AFP (U L-1)+0.038 × VEGF(ng ml-1)+0.004× INR –1.02 × Albumin (g l-1)–0.002 × Platelet count × 109 l-1 was developed. HCC-VEGF score produce area under ROC curve of 0.98 for discriminating HCC patients from liver cirrhosis with sensitivity of 91% and specificity of 82% at cut-off 4.4 (ie less than 4.4 considered cirrhosis and greater than 4.4 considered HCC). Conclusion: Hepatocellular carcinoma-VEGF score could replace AFP in HCC screening and follow up of cirrhotic patients.

Keywords: Hepatocellular carcinoma, cirrhosis, HCV, diagnosis, tumor markers

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Authors: Ichrak Hamrouni, Tariq Ouahbi, Natalija Lhuissier, Saïd Taibi, Mehrez Jemai, Olivier Crumeyrolle, Hatem Zenzri

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Raw earth is the oldest building technique used for over 11 centuries, thanks to its various benefits. The most known raw earth construction technics are compressed earth blocks, rammed earth, raw earth concrete, and daub. The raw earth can be stabilized with hydraulic binders, mixed by fibers, or hyper-compacted in order to improve its mechanical behaviour. Moreover, raw earth is characterized by a low thermal conductivity what make it a good thermal insulator, and it has a very important capacity to condense and evaporate relative humidity. In this context, many researches have been developed. They have shown that the mechanical characteristics of earth materials increase with the hyper-compaction and adding fibers or hydraulic binders. Besides, other researches have been determined the thermal and hygroscopic properties of raw earth. They have shown that this material able to contribute to moisture and heat control in constructions. Its hygrothermal properties are better than fired earth bricks and concrete. The aim of this study is to evaluate the thermal and hygrometric behavior of raw earth material using experimental tests allows to determine the main Hygrothermal properties such as the water Vapour permeability and thermal conductivity and compare the results with those of other building materials such as fired clay bricks and cement concrete is presented.

Keywords: raw earth material, hygro-thermal, thermal conductivity, water vapour permeability, building materials, building materials

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Authors: Abdelmajid Timoumi, Salah Alamri, Hatem Alamri

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TiO₂ Graphene Oxide (TiO₂-GO) nanocomposite was prepared using the spin coating technique of suspension of Graphene Oxide (GO) nanosheets and Titanium Tetra Isopropoxide (TIP). The prepared nanocomposites samples were characterized by X-ray diffractometer, Scanning Electron Microscope and Atomic Force Microscope to examine their structures and morphologies. UV-vis transmittance and reflectance spectroscopy was employed to estimate band gap energies. From the TiO₂-GO samples, a 0.25 μm thin layer on a piece of glass 2x2 cm was created. The X-ray diffraction analysis revealed that the as-deposited layers are amorphous in nature. The surface morphology images demonstrate that the layers grew in distributed with some spherical/rod-like and partially agglomerated TiGO on the surface of the composite. The Atomic Force Microscopy indicated that the films are smooth with slightly larger surface roughness. The analysis of optical absorption data of the layers showed that the values of band gap energy decreased from 3.46 eV to 1.40 eV, depending on the grams of GO doping. This reduction might be attributed to electron and/or hole trapping at the donor and acceptor levels in the TiO₂ band structure. Observed results have shown that the inclusion of GO in the TiO₂ matrix have exhibited significant and excellent properties, which would be promising for application in the photovoltaic application.

Keywords: titanium dioxide, graphene oxide, thin films, solar cells

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