Search results for: crystal size

Authors: V. Pérez-Herranz, C. González-Buch, E. M. Ortega, S. Mestre

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In this work new macroporous Ni electrodes modified with Au nanoparticles for hydrogen production have been developed. The supporting macroporous Ni electrodes have been obtained by means of the electrodeposition at high current densities. Then, the Au nanoparticles were synthesized and added to the electrode surface. The electrocatalytic behaviour of the developed electrocatalysts was studied by means of pseudo-steady-state polarization curves, electrochemical impedance spectroscopy (EIS) and hydrogen discharge curves. The size of the Au synthetized nanoparticles shows a monomodal distribution, with a very sharp band between 10 and 50 nm. The characteristic parameters d10, d50 and d90 were 14, 20 and 31 nm respectively. From Tafel polarization data has been concluded that the Au nanoparticles improve the catalytic activity of the developed electrodes towards the HER respect to the macroporous Ni electrodes. EIS permits to obtain the electrochemically active area by means of the roughness factor value. All the developed electrodes show roughness factor values in the same order of magnitude. From the activation energy results it can be concluded that the Au nanoparticles improve the intrinsic catalytic activity of the macroporous Ni electrodes.

Keywords: Au nano particles, hydrogen evolution reaction, porous Ni electrodes, electrochemical impedance spectroscopy

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Authors: Mohammad Azam

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The purpose of this study is to investigate risk and real excess portfolio returns using inflation adjusted risk-free rates, a measuring technique that focuses on the momentum augmented Fama-French six-factor model and use monthly data from 1994 to 2022. With the exception of profitability, the data show that market, size, value, momentum, and investment factors are all strongly associated to excess portfolio stock returns using ordinary lease square regression technique. According to the Gibbons, Ross, and Shanken test, the momentum augmented Fama-French six-factor model outperforms the market. This technique discovery may be utilised by academics and professionals to acquire an in-depth knowledge of the Pakistan Stock Exchange across a broad stock pattern for investing decisions and portfolio construction.

Keywords: real excess portfolio returns, momentum augmented fama & french five-factor model, GRS-test, pakistan stock exchange

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Authors: Kuan Lun Pan, Moo Been Chang

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Volatile organic compounds (VOCs) are one of major air contaminants, and they can react with nitrogen oxides (NOx) in atmosphere to form ozone (O3) and peroxyacetyl nitrate (PAN) with solar irradiation, leading to environmental hazards. In addition, some VOCs are toxic at low concentration levels and cause adverse effects on human health. How to effectively reduce VOCs emission has become an important issue. Thermal catalysis is regarded as an effective way for VOCs removal because it provides oxidation route to successfully convert VOCs into carbon dioxide (CO2) and water (H2O(g)). Single perovskite-type catalysts are promising for VOC removal, and they are of good potential to replace noble metals due to good activity and high thermal stability. Single perovskites can be generally described as ABO3 or A2BO4, where A-site is often a rare earth element or an alkaline. Typically, the B-site is transition metal cation (Fe, Cu, Ni, Co, or Mn). Catalytic properties of perovskites mainly rely on nature, oxidation states and arrangement of B-site cation. Interestingly, single perovskites could be further synthesized to form double perovskite-type catalysts which can simply be represented by A2B’B”O6. Likewise, A-site stands for an alkaline metal or rare earth element, and the B′ and B′′ are transition metals. Double perovskites possess unique surface properties. In structure, three-dimensional of B-site with ordered arrangement of B’O6 and B”O6 is presented alternately, and they corner-share octahedral along three directions of the crystal lattice, while cations of A-site position between the void of octahedral. It has attracted considerable attention due to specific arrangement of alternating B-site structure. Therefore, double perovskites may have more variations than single perovskites, and this greater variation may promote catalytic performance. It is expected that activity of double perovskites is higher than that of single perovskites toward VOC removal. In this study, double perovskite-type catalyst (La2CoMnO6) is prepared and evaluated for VOC removal. Also, single perovskites including LaCoO3 and LaMnO3 are tested for the comparison purpose. Toluene (C7H8) is one of the important VOCs which are commonly applied in chemical processes. In addition to its wide application, C7H8 has high toxicity at a low concentration. Therefore, C7H8 is selected as the target compound in this study. Experimental results indicate that double perovskite (La2CoMnO6) has better activity if compared with single perovskites. Especially, C7H8 can be completely oxidized to CO2 at 300oC as La2CoMnO6 is applied. Characterization of catalysts indicates that double perovskite has unique surface properties and is of higher amounts of lattice oxygen, leading to higher activity. For durability test, La2CoMnO6 maintains high C7H8 removal efficiency of 100% at 300oC and 30,000 h-1, and it also shows good resistance to CO2 (5%) and H2O(g) (5%) of gas streams tested. For various VOCs including isopropyl alcohol (C3H8O), ethanal (C2H4O), and ethylene (C2H4) tested, as high as 100% efficiency could be achieved with double perovskite-type catalyst operated at 300℃, indicating that double perovskites are promising catalysts for VOCs removal, and possible mechanisms will be elucidated in this paper.

Keywords: volatile organic compounds, Toluene (C7H8), double perovskite-type catalyst, catalysis

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Authors: Giulia Fredi, Andrea Dorigato, Luca Fambri, Alessandro Pegoretti

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Thermal energy storage (TES) is the storage of heat for later use, thus filling the gap between energy request and supply. The most widely used materials for TES are the organic solid-liquid phase change materials (PCMs), such as paraffin. These materials store/release a high amount of latent heat thanks to their high specific melting enthalpy, operate in a narrow temperature range and have a tunable working temperature. However, they suffer from a low thermal conductivity and need to be confined to prevent leakage. These two issues can be tackled by confining PCMs with carbon nanotubes (CNTs). TES applications include the buildings industry, solar thermal energy collection and thermal management of electronics. In most cases, TES systems are an additional component to be added to the main structure, but if weight and volume savings are key issues, it would be advantageous to embed the TES functionality directly in the structure. Such multifunctional materials could be employed in the automotive industry, where the diffusion of lightweight structures could complicate the thermal management of the cockpit environment or of other temperature sensitive components. This work aims to produce epoxy/carbon structural laminates containing CNT-stabilized paraffin. CNTs were added to molten paraffin in a fraction of 10 wt%, as this was the minimum amount at which no leakage was detected above the melting temperature (45°C). The paraffin/CNT blend was cryogenically milled to obtain particles with an average size of 50 µm. They were added in various percentages (20, 30 and 40 wt%) to an epoxy/hardener formulation, which was used as a matrix to produce laminates through a wet layup technique, by stacking five plies of a plain carbon fiber fabric. The samples were characterized microstructurally, thermally and mechanically. Differential scanning calorimetry (DSC) tests showed that the paraffin kept its ability to melt and crystallize also in the laminates, and the melting enthalpy was almost proportional to the paraffin weight fraction. These thermal properties were retained after fifty heating/cooling cycles. Laser flash analysis showed that the thermal conductivity through the thickness increased with an increase of the PCM, due to the presence of CNTs. The ability of the developed laminates to contribute to the thermal management was also assessed by monitoring their cooling rates through a thermal camera. Three-point bending tests showed that the flexural modulus was only slightly impaired by the presence of the paraffin/CNT particles, while a more sensible decrease of the stress and strain at break and the interlaminar shear strength was detected. Optical and scanning electron microscope images revealed that these could be attributed to the preferential location of the PCM in the interlaminar region. These results demonstrated the feasibility of multifunctional structural TES composites and highlighted that the PCM size and distribution affect the mechanical properties. In this perspective, this group is working on the encapsulation of paraffin in a sol-gel derived organosilica shell. Submicron spheres have been produced, and the current activity focuses on the optimization of the synthesis parameters to increase the emulsion efficiency.

Keywords: carbon fibers, carbon nanotubes, lightweight materials, multifunctional composites, thermal energy storage

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Authors: Elif Kalkanli, Constantinos Soutis

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The use of textile preform in the advanced fields including aerospace, automotive and marine has exponentially grown in recent years. These preforms offer excellent advantages such as being lightweight and low-cost, and also, their suitability for creating different fiber architectures with different materials whilst improved mechanical properties in certain aspects. In this study, a novel honeycomb core is developed by a 3Dweaving process. The assembly of the layers is achieved thanks to innovative weaving design. Polyester yarn is selected for the 3D woven honeycomb core (3DWHC). The core is used to manufacture a sandwich panel with 2x2 twill glass fiber composite face sheets. These 3DWHC sandwich panels will be tested in three-point bending. The in-plane and out-of-plane (through-the-thickness) mechanical response of the core will be examined as a function of cell size in addition to the flexural response of the sandwich panel. The failure mechanisms of the core and the sandwich skins will be reported in addition to flexural strength and stiffness. Possible engineering applications will be identified.

Keywords: 3D woven, assembly, failure modes, honeycomb sandwich panel

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Authors: Junichiro Kawaguchi

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Space debris problems have emerged and threatened the use of low earth orbit around the Earth owing to a large number of spacecraft. In debris removal, a number of research and patents have been proposed and published so far. They assume servicing spacecraft, robots to be built for accessing the target debris objects. The robots should be sophisticated enough automatically to access the debris articulating the attitude and the translation motion with respect to the debris. This paper presents the idea of using the torpedo-like third unsophisticated and disposable body, in addition to the first body of the servicing robot and the second body of the target debris. The third body is launched from the first body from a distance farer than the size of the second body. This paper presents the method and the system, so that the third body is launched from the first body. The third body carries both a net and an inflatable or extendible drag deceleration device and is built small and light. This method enables even a micro to nano satellite to perform contactless and multiple debris removal even via a single flight.

Keywords: ballute, debris removal, echo satellite, gossamer, gun-net, inflatable space structure, small satellite, un-cooperated target

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Authors: Lacramioara Ochiuz, Manuela Hortolomei, Aurelia Vasile, Iulian Stoleriu, Marcel Popa, Cristian Peptu

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Local antibiotherapy is one of the most effective acne therapies. Erythromycin (ER) is a macrolide antibiotic topically administered for over 30 years in the form of gel, ointment or hydroalcoholic solution for the acne therapy. The use of ER as a base for topical dosage forms raises some technological challenges due to the physicochemical properties of this substance. The main disadvantage of ER is the poor water solubility (2 mg/mL) that limits both formulation using hydrophilic bases and skin permeability. Cyclodextrins (CDs) are biocompatible cyclic oligomers of glucose, with hydrophobic core and hydrophilic exterior. CDs are used to improve the bioavailability of drugs by increasing their solubility and/or their rate of dissolution after including the poorly water soluble substances (such as ER) in the hydrophobic cavity of CDs. Adding CDs leads to the increase of solubility and improved stability of the drug substance, increased permeability of substances of low water solubility, decreased toxicity and even to active dose reduction as a result of increased bioavailability. CDs increase skin tolerability by reducing the irritant effect of certain substances. We have included ER to lactide modified β-cyclodextrin, in order to improve the therapeutic effect of topically administered ER. The aims of the present study were to synthesise and describe a new complex with prolonged release of ER with lactide modified β-cyclodextrin (CD-LA_E), to investigate the CD-LA_E complex by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), to analyse the effect of semisolid base on the in vitro and ex vivo release characteristics of ER in the CD-LA_E complex by assessing the permeability coefficient and the release kinetics by fitting on mathematical models. SEM showed that, by complexation, ER changes its crystal structure and enters the amorphous phase. FTIR analysis has shown that certain specific bands of some groups in the ER structure move during the incapsulation process. The structure of the CD-LA_E complex has a molar ratio of 2.12 to 1 between lactide modified β-cyclodextrin and ER. The three semisolid bases (2% Carbopol, 13% Lutrol 127 and organogel based on Lutrol and isopropyl myristate) show a good capacity for incorporating the CD-LA_E complex, having a content of active ingredient ranging from 98.3% to 101.5% as compared to the declared value of 2% ER. The results of the in vitro dissolution test showed that the ER solubility was significantly increased by CDs incapsulation. The amount of ER released from the CD-LA_E gels was in the range of 76.23% to 89.01%, whereas gels based on ER released a maximum percentage of 26.01% ER. The ex vivo dissolution test confirms the increased ER solubility achieved by complexation, and supports the assumption that the use of this process might increase ER permeability. The highest permeability coefficient was obtained in ER released from gel based on 2% Carbopol: in vitro 33.33 μg/cm2/h, and ex vivo 26.82 μg/cm2/h, respectively. The release kinetics of complexed ER is performed by Fickian diffusion, according to the results obtained by fitting the data in the Korsmeyer-Peppas model.

Keywords: erythromycin, acne, lactide, cyclodextrin

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Authors: Yoshinori Kitsutaka, Fumiya Ikedo

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In this study, the mechanical model of various anchors embedded in gypsum board subjected cyclic shear loading were investigated. Shear tests for anchors embedded in 200 mm square size gypsum board were conducted to measure the load - load displacement curves. The strength of the gypsum board was changed for three conditions and 12 kinds of anchors were selected which were ordinary used for gypsum board anchoring. The loading conditions were a monotonous loading and a cyclic loading controlled by a servo-controlled hydraulic loading system to achieve accurate measurement. The fracture energy for each of the anchors was estimated by the analysis of consumed energy calculated by the load - load displacement curve. The effect of the strength of gypsum board and the types of anchors on the shear properties of gypsum board anchors was cleared. A numerical model to predict the load-unload curve of shear deformation of gypsum board anchors caused by such as the earthquake load was proposed and the validity on the model was proved.

Keywords: gypsum board, anchor, shear test, cyclic loading, load-unload curve

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Authors: Ateeq Ur Rehman

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This article deals with the promotional effects of CeO2 on PtPd/CeO2-OMC electrocatalysts. The synthesized catalysts are characterized using different physicochemical techniques and evaluated in a formic acid oxidation fuel cell. N2 adsorption/desorption analysis shows that CeO2 modification increases the surface area of OMC from 1005 m2/g to 1119 m2/g. SEM, XRD and TEM analysis reveal that the presence of CeO2 enhances the active metal(s) dispersion on the CeO2-OMC surface. The average particle size of the dispersed metal decreases with the increase of Pt/Pd ratio on CeO2-OMC support. Cyclic voltametry measurement of Pd/CeO2-OMC gives 12 % higher anodic current activity with 83 mV negative shift of the peak potential as compared to unmodified Pd/OMC. In bimetallic catalysts, the addition of Pt improves the activity and stability of the catalysts significantly. Among the bimetallic samples, Pd3Pt1/CeO2-OMC displays superior current density (74.6 mA/cm2), which is 28.3 times higher than that of Pt/CeO2-OMC. It also shows higher stability in extended period of runs with least indication of CO poisoning effects.

Keywords: CeO2, ordered mesoporous carbon (OMC), nano particles, formic acid fuel cell

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Authors: Rejab Hajlaoui, Tarek Moulahi, Hervé Guyennet

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In a highway scenario, the vehicle speed can exceed 120 kmph. Therefore, any vehicle can enter or leave the network within a very short time. This mobility adversely affects the network connectivity and decreases the life time of all established links. To ensure an effective stability in vehicular ad hoc networks with minimum broadcasting storm, we have developed a weighted algorithm based on the k-medoids clustering algorithm (WKCA). Indeed, the number of clusters and the initial cluster heads will not be selected randomly as usual, but considering the available transmission range and the environment size. Then, to ensure optimal assignment of nodes to clusters in both k-medoids phases, the combined weight of any node will be computed according to additional metrics including direction, relative speed and proximity. Empirical results prove that in addition to the convergence speed that characterizes the k-medoids algorithm, our proposed model performs well both AODV-Clustering and OLSR-Clustering protocols under different densities and velocities in term of end-to-end delay, packet delivery ratio, and throughput.

Keywords: communication, clustering algorithm, k-medoids, sensor, vehicular ad hoc network

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Authors: H. Kazemi Esfeh, V. Akbari, M. Ehdaei, T. N. G. Borhani, A. Shamiri, M. Najafi

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In an industrial fluidized bed polymerization reactor, particle size distribution (PSD) plays a significant role in the reactor efficiency evaluation. The computational fluid dynamic (CFD) models coupled with population balance equation (CFD-PBM) have been extensively employed to investigate the flow behavior in the poly-disperse multiphase fluidized bed reactors (FBRs) utilizing ANSYS Fluent code. In this study, an existing CFD-PBM/ DQMOM coupled modeling framework has been used to highlight its potential to analyze the industrial-scale gas phase polymerization reactor. The predicted results reveal an acceptable agreement with the observed industrial data in terms of pressure drop and bed height. The simulated results also indicate that the higher particle growth rate can be achieved for bigger particles. Hence, the 2D CFD-PBM/DQMOM coupled model can be used as a reliable tool for analyzing and improving the design and operation of the gas phase polymerization FBRs.

Keywords: computational fluid dynamics, population balance equation, fluidized bed polymerization reactor, direct quadrature method of moments

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Authors: Tim Bolle, Franziska Kreimendahl, Thomas Gries, Stefan Jockenhoevel

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The therapeutic treatment of extensive, deep wounds is limited. Autologous split-skin grafts are used as a so-called ‘gold standard’. Most common deficits are the defects at the donor site, the risk of scarring as well as the limited availability and quality of the autologous grafts. The aim of this project is a tissue engineered dermal-epidermal skin replacement to overcome the limitations of the gold standard. A key requirement for the development of such a three-dimensional implant is the formation of a functional capillary-like network inside the implant to ensure a sufficient nutrient and gas supply. Tailored three-dimensional warp knitted spacer fabrics are used to reinforce the mechanically week fibrin gel-based scaffold and further to create a directed in vitro pre-vascularization along the parallel-oriented pile yarns within a co-culture. In this study various three-dimensional warp knitted spacer fabrics were developed in a factorial design to analyze the influence of the machine parameters such as the stitch density and the pattern of the fabric on the scaffold performance and further to determine suitable parameters for a successful fibrin gel-incorporation and a physiological performance of the scaffold. The fabrics were manufactured on a Karl Mayer double-bar raschel machine DR 16 EEC/EAC. A fine machine gauge of E30 was used to ensure a high pile yarn density for sufficient nutrient, gas and waste exchange. In order to ensure a high mechanical stability of the graft, the fabrics were made of biocompatible PVDF yarns. Key parameters such as the pore size, porosity and stress/strain behavior were investigated under standardized, controlled climate conditions. The influence of the input parameters on the mechanical and morphological properties as well as the ability of fibrin gel incorporation into the spacer fabric was analyzed. Subsequently, the pile yarns of the spacer fabrics were colonized with Human Umbilical Vein Endothelial Cells (HUVEC) to analyze the ability of the fabric to further function as a guiding structure for a directed vascularization. The cells were stained with DAPI and investigated using fluorescence microscopy. The analysis revealed that the stitch density and the binding pattern have a strong influence on both the mechanical and morphological properties of the fabric. As expected, the incorporation of the fibrin gel was significantly improved with higher pore sizes and porosities, whereas the mechanical strength decreases. Furthermore, the colonization trials revealed a high cell distribution and density on the pile yarns of the spacer fabrics. For a tailored reinforcing structure, the minimum porosity and pore size needs to be evaluated which still ensures a complete incorporation of the reinforcing structure into the fibrin gel matrix. That will enable a mechanically stable dermal graft with a dense vascular network for a sufficient nutrient and oxygen supply of the cells. The results are promising for subsequent research in the field of reinforcing mechanically weak biological scaffolds and develop functional three-dimensional scaffolds with an oriented pre-vascularization.

Keywords: fibrin-gel, skin replacement, spacer fabric, pre-vascularization

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Authors: Ali A. Al-Jazaairry, Tahsin T. Sabbagh

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The stability of a single model pile located adjacent to a continuous cavity was studied. This paper is an attempt to understand the behaviour of axially loaded single pile embedded in clayey soil with the presences of cavities. The performance of piles located in such soils was studied analytically. A verification analysis was carried out on available studies to assess the ability of analytical model to correctly interpret the system behaviour. The study was adopted by finite element program (PLAXIS). The study included many cases; in each case, there is a critical value in which the presence of cavities has shown minimum effect on the pile performance. Figures including the load carrying capacity of pile with the affecting factors are presented. These figures provide beneficial information for pile design constructed close to underground cavities. It was concluded that the load carrying capacity of the pile is reduced by the presence of the cavity within the soil mass. This reduction varies according to the size and location of cavity.

Keywords: axial load, cavity, clay, pile, ultimate capacity

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Authors: Wilmer Osvaldo Martinez, Manuel Dario Hernandez, Juan Manuel Julio

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We propose to assess the performance of k forecast procedures by exploring the distributions of forecast errors and error losses. We argue that non systematic forecast errors minimize when their distributions are symmetric and unimodal, and that forecast accuracy should be assessed through stochastic loss order rather than expected loss order, which is the way it is customarily performed in previous work. Moreover, since forecast performance evaluation can be understood as a one way analysis of variance, we propose to explore loss distributions under two circumstances; when a strict (but unknown) joint stochastic order exists among the losses of all forecast alternatives, and when such order happens among subsets of alternative procedures. In spite of the fact that loss stochastic order is stronger than loss moment order, our proposals are at least as powerful as competing tests, and are robust to the correlation, autocorrelation and heteroskedasticity settings they consider. In addition, since our proposals do not require samples of the same size, their scope is also wider, and provided that they test the whole loss distribution instead of just loss moments, they can also be used to study forecast distributions as well. We illustrate the usefulness of our proposals by evaluating a set of real world forecasts.

Keywords: forecast evaluation, stochastic order, multiple comparison, non parametric test

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Authors: Ebrahim Asadi-Gangraj

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Hybrid flow shop scheduling problem (HFS) contains sequencing in a flow shop where, at any stage, there exist one or more related or unrelated parallel machines. This production system is a common manufacturing environment in many real industries, such as the steel manufacturing, ceramic tile manufacturing, and car assembly industries. In this research, a mixed integer linear programming (MILP) model is presented for the hybrid flow shop scheduling problem, in which, the objective consists of minimizing the maximum completion time (makespan). For this purpose, a Benders Decomposition (BD) method is developed to solve the research problem. The proposed approach is tested on some test problems, small to moderate scale. The experimental results show that the Benders decomposition approach can solve the hybrid flow shop scheduling problem in a reasonable time, especially for small and moderate-size test problems.

Keywords: hybrid flow shop, mixed integer linear programming, Benders decomposition, makespan

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Authors: Cinna Soltanpur, Mohammad Ghamari, Behzad Momahed Heravi, Fatemeh Zare

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Low-density parity-check (LDPC) codes have been shown to deliver capacity approaching performance; however, problematic graphical structures (e.g. trapping sets) in the Tanner graph of some LDPC codes can cause high error floors in bit-error-ratio (BER) performance under conventional sum-product algorithm (SPA). This paper presents a serial concatenation scheme to avoid the trapping sets and to lower the error floors of LDPC code. The outer code in the proposed concatenation is the LDPC, and the inner code is a high rate array code. This approach applies an interactive hybrid process between the BCJR decoding for the array code and the SPA for the LDPC code together with bit-pinning and bit-flipping techniques. Margulis code of size (2640, 1320) has been used for the simulation and it has been shown that the proposed concatenation and decoding scheme can considerably improve the error floor performance with minimal rate loss.

Keywords: concatenated coding, low–density parity–check codes, array code, error floors

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Authors: M. Reni Sagayaraj, S. Anand Gnana Selvam, R. Reynald Susainathan

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This study analyzed a queueing system with blocking and no waiting line. The customers arrive according to a Poisson process and the service times follow exponential distribution. There are two non-identical servers in the system. The queue discipline is FCFS, and the customers select the servers on fastest server first (FSF) basis. The service times are exponentially distributed with parameters μ1 and μ2 at servers I and II, respectively. Besides, the catastrophes occur in a Poisson manner with rate γ in the system. When server I is busy or blocked, the customer who arrives in the system leaves the system without being served. Such customers are called lost customers. The probability of losing a customer was computed for the system. The explicit time dependent probabilities of system size are obtained and a numerical example is presented in order to show the managerial insights of the model. Finally, the probability that arriving customer finds system busy and average number of server busy in steady state are obtained numerically.

Keywords: queueing system, blocking, poisson process, heterogeneous servers, queue discipline FCFS, busy period

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Authors: Mahmoud Rabh

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Garnet has been used for decades as an abrasive in water jet cutting and sand blasting because of its superior physical properties. When added to use in water-cutting process of marble. A standard commercial sample of the mineral was tested in terms of the hardness and abrasiveness properties. The sample was sized to 4 fractions having the size of < 60 um, > 60 < 100 um, > 100 < 180 um > 1280 < 250 and 250 um designated the symbols, FF, MF, MC and C respectively. Each sample was separately heated in controlled conditions at temperatures up to 1000 °C at a heating rate of 10°C/min in an electrically heated chamber furnace. Soaking time at the maximum temperature was up to 6 h. Hardness and abrasiveness properties of the heat treated samples were tested to cut marble having a thickness of 25 mm. Results revealed that H/A of the natural garnet mineral increased by heating at temperatures up to 600°C and exhibited pronounced decrease with higher temperatures up to 1000 °C. Results were explained in the light of a structural irreversible dislocation (SD) of the crystals of garnet almandine Fe2+3Al2Si3O12 and pyrope Mg3Al2Si3O12. Characterization of the mineral was carried out with the help of XRD, SEM and FT-IR measurements.

Keywords: garnet abrasive, heat treatment, water jet cutting, hardness abrasiveness

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Authors: Jyoti Bharj, Sarabjit Singh, Subhash Chander, Rabinder Singh

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The outstanding mechanical properties of Carbon Nanotubes (CNTs) have generated great interest for their potential as reinforcements in high performance cementitious composites. The main challenge in research is the proper dispersion of carbon nanotubes in the cement matrix. The present work discusses the role of dispersion of Multiwall Carbon Nanotubes (MWCNTs) on the compressive strength characteristics of hydrated Portland IS 1489 cement paste. Cement-MWCNT composites with different mixing techniques were prepared by adding 0.2% (by weight) of MWCNTs to Portland IS 1489 cement. Rectangle specimens of size approximately 40mm × 40mm ×160mm were prepared and curing of samples was done for 7, 14, 28, and 35 days. An appreciable increase in compressive strength with both techniques; mixture of MWCNTs with cement in powder form and mixture of MWCNTs with cement in hydrated form 7 to 28 days of curing time for all the samples was observed.

Keywords: carbon nanotubes, Portland cement, composite, compressive strength

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Authors: Mohammad Reza Ghaani, Michele Catti

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The reduction of CoO/Fe₂O₃ oxides supported on carbon xerogels was studied to elucidate the effect of nano-size distribution of the catalyst in carbon matrices. Resorcinol formaldehyde xerogels were synthesized, impregnated with iron and cobalt nitrates, and subsequently heated to obtain the oxides. The mechanism of oxide reduction to metal was investigated by in-situ synchrotron X-ray diffraction in dynamic, non-isothermal conditions. Kinetic profiles of the reactions were obtained by plotting the diffraction intensities of selected Bragg peaks vs. temperature. The extracted Temperature-Programmed-Reduction (TPR) diagrams were analyzed by appropriate kinetic models, leading to best results with the Avrami-Erofeev model for all reduction reactions considered. The activation energies for the two-step reduction of iron oxide were 65 and 37 kJmol⁻¹, respectively. The average value for the reduction of CoO to Co was found to be around 21 kJ mol⁻¹. Such results may contribute to develop efficient and inexpensive non-noble metal-based catalysts in element form, e.g., Fe, Co, via heterogenization of metal complexes on mesoporous supports.

Keywords: non-isothermal kinetics, carbon aerogel, in-situ synchrotron X-ray diffraction, reduction mechanisms

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Authors: Maryam Mohammad Hadi, Heather Nesbitt, Hamzah Masood, Hashim Ahmed, Mark Emberton, John Callan, Alexander MacRobert, Anthony McHale, Nikolitsa Nomikou

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Sonodynamic therapy (SDT) utilises ultrasound in combination with sensitizers, such as porphyrins, for the production of cytotoxic reactive oxygen species (ROS) and the confined ablation of tumours. Ultrasound can be applied locally, and the acoustic waves, at frequencies between 0.5-2 MHz, are transmitted efficiently through tissue. SDT does not require highly toxic agents, and the cytotoxic effect only occurs upon ultrasound exposure at the site of the lesion. Therefore, this approach is not associated with adverse side effects. Further highlighting the benefits of SDT, no cancer cell population has shown resistance to therapy-triggered ROS production or their cytotoxic effects. This is particularly important, given the as yet unresolved issues of radiation and chemo-resistance, to the authors’ best knowledge. Another potential future benefit of this approach – considering its non-thermal mechanism of action – is its possible role as an adjuvant to immunotherapy. Substantial pre-clinical studies have demonstrated the efficacy and targeting capability of this therapeutic approach. However, SDT has yet to be fully characterised and appropriately exploited for the treatment of cancer. In this study, a formulation based on multistimulus-responsive sensitizer-containing nanoparticles that can accumulate in advanced prostate tumours and increase the therapeutic efficacy of SDT has been developed. The formulation is based on a polyglutamate-tyrosine (PGATyr) co-polymer carrying hematoporphyrin. The efficacy of SDT in this study was demonstrated using prostate cancer as the translational exemplar. The formulation was designed to respond to the microenvironment of advanced prostate tumours, such as the overexpression of the proteolytic enzymes, cathepsin-B and prostate-specific membrane antigen (PSMA), that can degrade the nanoparticles, reduce their size, improving both diffusions throughout the tumour mass and cellular uptake. The therapeutic modality was initially tested in vitro using LNCaP and PC3 cells as target cell lines. The SDT efficacy was also examined in vivo, using male SCID mice bearing LNCaP subcutaneous tumours. We have demonstrated that the PGATyr co-polymer is digested by cathepsin B and that digestion of the formulation by cathepsin-B, at tumour-mimicking conditions (acidic pH), leads to decreased nanoparticle size and subsequent increased cellular uptake. Sonodynamic treatment, at both normoxic and hypoxic conditions, demonstrated ultrasound-induced cytotoxic effects only for the nanoparticle-treated prostate cancer cells, while the toxicity of the formulation in the absence of ultrasound was minimal. Our in vivo studies in immunodeficient mice, using the hematoporphyrin-containing PGATyr nanoparticles for SDT, showed a 50% decrease in LNCaP tumour volumes within 24h, following IV administration of a single dose. No adverse effects were recorded, and body weight was stable. The results described in this study clearly demonstrate the promise of SDT to revolutionize cancer treatment. It emphasizes the potential of this therapeutic modality as a fist line treatment or in combination treatment for the elimination or downstaging of difficult to treat cancers, such as prostate, pancreatic, and advanced colorectal cancer.

Keywords: sonodynamic therapy, nanoparticles, tumour ablation, ultrasound

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Authors: Khon Natalya, Kim Alla, Mukhitdinova Tansulu

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The aim of the research was to reveal the link between mental variables, such as spatial abilities, memory, intellect and professional experience of drivers. Participants were allocated within 4 groups: no experience, inexperienced, skilled and professionals (total 85 participants). Level of ability for spatial navigation and indicator of nonverbal memory grow along the process of accumulation of driving experience. At high levels of driving experience this tendency is especially noticeable. The professionals having personal achievements in driving (racing) differ from skilled drivers in better feeling of direction which is specific for them not just in a short-term situation of an experimental task, but in life-size perspective. The level of ability of mental rotation does not grow with growth of driving experience which confirms the multiple intelligence theory according to which spatial abilities represent specific, other than logical intelligence type of intellect. The link between spatial abilities, memory, intellect, and professional experience of drivers seems to be different relating spatial navigation or mental rotation as different kinds of spatial abilities.

Keywords: memory, spatial ability, intellect, drivers

Procedia PDF Downloads 597

Authors: Reginald Umunakwe, Obinna Chibuzor Okoye, Uzoma Samuel Nwigwe, Damilare John Olaleye, Akinlabi Oyetunji

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The potential for the development of PPS-AlMMCs as light weight material for industrial applications was investigated. Periwinkle shells were milled and the density of the particles determined. Particulate periwinkle shell of particle size 75µm was used to reinforce aluminium 6063 alloy at 10wt% filler loading using two-step stir casting technique. The composite materials were stirred for five minutes in a semi-solid state and the stirring time varied as 3, 6 and 9 minutes at above the liquidus temperature. A specimen was also produced with pre-heated filler. The effect of variation in stirring time and reinforcement pre-heating on the porosity of the composite materials was investigated. The results of the analysis show that a composition of reinforcement pre-heating and stirring for 3 minutes produced a composite material with the lowest porosity of 1.05%.

Keywords: composites, periwinkle shell, two-step casting, porosity

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Authors: Lin Chang

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Birmingham, England was a town in the late-eighteenth century and became the nation’s second largest city in the late nineteenth century. The city expanded rapidly in terms of its population and size. Three generations of artists from a local family, the Lines, made a large number of drawings and paintings depicting the growth and changes of their city. At first sight, the meaning of the pictures seems straight-forward: providing records of what were torn down and newly-built. However, except for being read as maps, the pictures reveal a struggle in vision as to whether unsightly manufactories and their smoking chimneys should be visualized and how far the borders of the town should have been positioned and understood as they continued to grow and encroached upon its immediate countryside. This art-historic paper examines some topographic views by the Lines family and explores how they, through unusual depiction of rural and urban scenery, manage to give form to the borderlands between the country and the city. This paper argues that while the idea of the country and the city seems to be common sense, the two realms actually pose difficulty for visual representation as to where exactly their borders are and the idea itself has dichotomized the way people consider landscape imageries to be.

Keywords: Birmingham, suburb, urban fringes, landscape

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Authors: Vrinda Hari Ankolekar

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Introduction: The advancement of various audio-visual aids in the present era has led to progressive changes in education. Use of powerpoint presentations play a key role in anatomy to learn and understand a particular topic. As the subject of anatomy involves more of illustrations and demonstrations, powerpoint presentations become essential in conveying the necessary information. Objectives: To assess the students’ perspective about the use of powerpoint presentations in teaching anatomy.Method: A questionnaire was constructed and 55 students were asked to put forth their preferences for the powerpoint presentations or blackboard that would help them to understand the subject better. Results and conclusion: 30 voted PPT as better and effective tool to explain the subject efficiently. 35 chose PPT as more creative than Blackboard to create interest in the subject. 20 wanted to retain chalk and talk for teaching their subject instead of replacing it with PowerPoint. 36 felt chalk and talk as more useful and appropriate tool for teaching than PowerPoint. Only 25 felt chalk and talk relatively more boring than PowerPoint. 23 experienced more involvement and active participation in the class when chalk and talk is used as the teaching tool. 26 stated that chalk and talk has most of the features needed for teaching.One of the limitations of this study is that the sample size is drawn from one institution only and deals with the experience of one particular group of individuals.

Keywords: chalk and board, powerpoint presentation, presentation skills, teaching technologies

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Authors: Satya Srii, V., Nethra, N.

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An image analyzer system is described to study the process of imbibition in Melia dubia seeds. The experimental system consisted of control C (seeds with intact pericarp) with two treatments, namely T1 (seeds with pericarp punctured) and T2 (naked seeds without pericarp). The measurement software in the image analyzer can determine the area and perimeter as descriptors of changes in seed size during swelling resulting from imbibition. Using the area and perimeter parameter, the imbibition process in C, T1, and T2 was described by a series of curves similar to the triphasic pattern of water uptake, with the extent and rate depending upon the treatment. Naked seeds without pericarp (T2) took lesser time to reach phase III during imbition followed by seeds with pericarp punctured (T1) while the seeds with intact pericarp (C) were the slowest to attain phase III. This shows the effect of pericarp in acting as a potential inhibitor to imbibition inducing a large delay in germination. The sensitivity and feasibility of the method to investigate individual seeds within a population imply that the image analyzer has high potential in seed biology studies.

Keywords: germination, imbibition, image analyzer, Melia dubia, pericarp

Procedia PDF Downloads 122

Authors: Bhavini Pandya

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This paper considers Hη: T2 → T2 the Perturbed Cerbelli-Giona map. That is a family of 2-dimensional nonlinear area-preserving transformations on the torus T2=[0,1]×[0,1]= ℝ2/ ℤ2. A single parameter η varies between 0 and 1, taking the transformation from a hyperbolic toral automorphism to the “Cerbelli-Giona” map, a system known to exhibit multifractal properties. Here we study the multifractal properties of the family of maps. We apply a box-counting method by defining a grid of boxes Bi(δ), where i is the index and δ is the size of the boxes, to quantify the distribution of stable and unstable manifolds of the map. When the parameter is in the range 0.51< η <0.58 and 0.68< η <1 the map is ergodic; i.e., the unstable and stable manifolds eventually cover the whole torus, although not in a uniform distribution. For accurate numerical results we require correspondingly accurate construction of the stable and unstable manifolds. Here we use the piecewise linearity of the map to achieve this, by computing the endpoints of line segments which define the global stable and unstable manifolds. This allows the generalized fractal dimension Dq, and spectrum of dimensions f(α), to be computed with accuracy. Finally, the intersection of the unstable and stable manifold of the map will be investigated, and compared with the distribution of periodic points of the system.

Keywords: feed forward, gradient descent, neural network, integral equation

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Authors: Lenka Matulova

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Geopolymers are alumosilicate materials that have long been studied. Despite this fact, little is known about the long-term stability of geopolymer mechanical and structural properties, so crucial for their successful industrial application. To improve understanding, we investigated the effect of four different types of environments on the mechanical and structural properties of a metakaolin-based geopolymer (MK GP). The MK GP samples were stored in laboratory conditions (control samples), in water at 20 °C, in water at 80 °C, and outside exposed to the weather. Compressive and tensile strengths were measured after 28, 56, 90, and 360 days. In parallel, structural properties were analyzed using XRD, SEM, and mercury intrusion porosimetry. Whereas the mechanical properties of the samples in laboratory conditions and in 20 °C water were stable, the mechanical properties of the outdoor samples and the samples 80 °C water decreased noticeably after 360 days. Structural analyses were focused on changes in sample microstructure (developing microcrack network, porosity) and identifying zeolites, the presence of which would indicate detrimental processes in the structure that can change it from amorphous to crystalline. No zeolites were found during the 360-day period in MK GP samples, but the reduction in mechanical properties coincided with a developing network of microcracks and changes in pore size distribution.

Keywords: geopolymer, long-term properties, mechanical properties, metakaolin, structural properties

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Authors: Sabri Gabran Mohammed Elkrghli, Salah A. Mohamed Abdulgader

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Given the emergence and the spreading of the Covid-19 pandemic that swept the globe, it was necessary to address the issue of consumer rights in such unprecedented circumstances. Libyan consumers have been targeted in this study with the aim to measure their attitudes towards the extent to which their rights, as consumers of foodstuff, have been secured during the Covid-19 pandemic. The recommended sample size was randomly selected (384) local participants. Out of this number, only a validated number of (267) responses were deemed valid for the analysis phase. The instrument of this research was developed based on the extant published literature on consumer rights. The study concluded with a set of key results; the most important result is that consumer rights of foodstuffs were below the satisfactory level. Theoretical and practical implications have emerged from the study. The most important implication is that customers of foodstuffs need more protection in Libya. This issue should be given greater importance, especially in the light of contemporary environmental challenges such as the outbreak of Covid-19. Designing and conducting global and local awareness campaigns is another significant advice suggested by this study. Finally, the research concluded with limitations and put forward some future avenues.

Keywords: consumers rights, foodstuffs, COVID-19, Libya

Procedia PDF Downloads 134

Authors: Mohamad Farhat, Bal Virdee

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This paper present a compact Microstrip Bandpass filter exhibiting a very wide stop band and high selectivity. The filter comprises of asymmetric resonator structures, which are interconnected by an inter-digital capacitor to enable the realization of a wide bandwidth with high rejection level. High selectivity is obtained by optimizing the parameters of the interdigital capacitor. The filter has high out-of-band rejection (> 30 dB), less than 0.6 dB of insertion-loss, up to 5.5 GHz spurii free, and about 18 dB of return-loss. Full-wave electromagnetic simulator ADSTM (Mom) is used to analyze and optimize the prototype bandpass filter. The proposed technique was verified practically to validate the design methodology. The experimental results of the prototype circuit are presented and a good agreement was obtained comparing with the simulation results. The dimensions of the proposed filter are 32 x 24 mm2.The filter’s characteristics and compact size make it suitable for wireless communication systems.

Keywords: asymmetric resonator, bandpass filter, microstrip, spurious suppression, ultra-wide stop band

Procedia PDF Downloads 171