Search results for: density approximation

Authors: T. S. Almutairi, Paul May, Neil Allan

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The geometrical, electronic and magnetic properties of the neutral Mg center and MgN₃ cluster in diamond have been studied theoretically in detail by means of an HSE06 Hamiltonian that includes a fraction of the exact exchange term; this is important for a satisfactory picture of the electronic states of open-shell systems. Another batch of the calculations by GGA functionals have also been included for comparison, and these support the results from HSE06. The local perturbations in the lattice by introduced Mg defect are restricted in the first and second shell of atoms before eliminated. The formation energy calculated with HSE06 and GGA of single Mg agrees with the previous result. We found the triplet state with C₃ᵥ is the ground state of Mg center with energy lower than the singlet with C₂ᵥ by ~ 0.1 eV. The recent experimental ZPL (557.4 nm) of Mg center in diamond has been discussed in the view of present work. The analysis of the band-structure of the MgN₃ cluster confirms that the MgN₃ defect introduces a shallow donor level in the gap lying within the conduction band edge. This observation is supported by the EMM that produces n-type levels shallower than the P donor level. The formation energy of MgN₂ calculated from a 2NV defect (~ 3.6 eV) is a promising value from which to engineer MgN₃ defects inside the diamond. Ion-implantation followed by heating to about 1200-1600°C might induce migration of N related defects to the localized Mg center. Temperature control is needed for this process to restore the damage and ensure the mobilities of V and N, which demands a more precise experimental study.

Keywords: empirical marker method, generalised gradient approximation, Heyd–Scuseria–Ernzerhof screened hybrid functional, zero phono line

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Authors: M. Maciejewska, F. Walkiewicz

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The aim of this work was to study the activity of several novel benzalkonium and alkylammonium and alkylimidazolium ionic liquids with 2-mercaptobenzothiazolate for use as accelerators in the sulphur vulcanisation of butadiene-styrene elastomer (SBR). The application of novel ionic liquids allowed for the elimination of N-cyclohexyl-2-benzothiazolesulfenamide from SBR compounds and for the considerable reduction of the amount of 2-mercaptobenzothiazole present in rubber products, which is favourable because, it is an allergenic agent. Synthesised salts could be used alternatively to standard accelerators in the vulcanisation of SBR, without any detrimental effects on the vulcanisation process, the physical properties or the thermal stability of the obtained vulcanisates. Ionic liquids increased the crosslink density of the vulcanisates and improved their thermal stability.

Keywords: ionic liquids, mechanical properties, styrene-butadiene rubber, vulcanisation

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Authors: Abel S. Huaynacho, Yoni D. Huaynacho

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The improvement of procedure test ASTM D1556, plays an important role in the developing of testing in field to obtain a higher quality of data QA/QC. The traditional process takes a considerable amount of time for only one test. Even making various testing are tasks repeating and it takes a long time to obtain better results. Moreover, if the adequate tools the help these testing are not properly managed, the improvement in the development for various testing could be stooped. This paper presents an optimized process for various testing ASTM D1556 which uses an initial standard process to another one the uses a simpler and improved management tools.

Keywords: cone sand test, density bulk, ASTM D1556, QA/QC

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Authors: Aleksandras Velykis, Antanas Satkus

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Clay loam and clay soils are typical for northern Lithuania. These soils are susceptible to physical degradation in the case of intensive use of heavy machinery for field operations. However, clayey soils having poor physical properties by origin require more intensive tillage to maintain proper physical condition for grown crops. Therefore not only choice of suitable tillage system is very important for these soils in the region, but also additional search of other measures is essential for good soil physical state maintenance. Research objective: To evaluate the long-term effects of different intensity tillage as well as its combinations with supplementary agronomic practices on improvement of soil physical conditions and environmental sustainability. The experiment examined the influence of deep and shallow ploughing, ploughless tillage, combinations of ploughless tillage with incorporation of lime sludge and cover crop for green manure and application of the same cover crop for mulch without autumn tillage under spring and winter crop growing conditions on clay loam (27% clay, 50% silt, 23% sand) Endocalcaric Endogleyic Cambisol. Methods: The indicators characterizing the impact of investigated measures were determined using the following methods and devices: Soil dry bulk density – by Eijkelkamp cylinder (100 cm3), soil water content – by weighing, soil structure – by Retsch sieve shaker, aggregate stability – by Eijkelkamp wet sieving apparatus, soil mineral nitrogen – in 1 N KCL extract using colorimetric method. Results: Clay loam soil physical state (dry bulk density, structure, aggregate stability, water content) depends on tillage system and its combination with additional practices used. Application of cover crop winter mulch without tillage in autumn, ploughless tillage and shallow ploughing causes the compaction of bottom (15-25 cm) topsoil layer. However, due to ploughless tillage the soil dry bulk density in subsoil (25-35 cm) layer is less compared to deep ploughing. Soil structure in the upper (0-15 cm) topsoil layer and in the seedbed (0-5 cm), prepared for spring crops is usually worse when applying the ploughless tillage or cover crop mulch without autumn tillage. Application of lime sludge under ploughless tillage conditions helped to avoid the compaction and structure worsening in upper topsoil layer, as well as increase aggregate stability. Application of reduced tillage increased soil water content at upper topsoil layer directly after spring crop sowing. However, due to reduced tillage the water content in all topsoil markedly decreased when droughty periods lasted for a long time. Combination of reduced tillage with cover crop for green manure and winter mulch is significant for preserving the environment. Such application of cover crops reduces the leaching of mineral nitrogen into the deeper soil layers and environmental pollution. This work was supported by the National Science Program ‘The effect of long-term, different-intensity management of resources on the soils of different genesis and on other components of the agro-ecosystems’ [grant number SIT-9/2015] funded by the Research Council of Lithuania.

Keywords: clay loam, endocalcaric endogleyic cambisol, mineral nitrogen, physical state

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Authors: Liu Li, Kim Seng Lee, Li Lu

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The high-energy-density Li-rich layered materials are promising cathode materials for the next-generation high-performance lithium-ion batteries. They have attracted a lot of attentions due mainly to their high reversible capacity of more than 250 mAh•g-1 at low charge-discharge current. However several drawbacks still hinder their applications, such as voltage decay caused by an undesired phase transformation during cycling and poor rate capability. To conquer these issues, the authors applied F modification methods on the pristine Li1.2Mn0.54Ni0.13Co0.13O2 to enhance its electrochemical performance.

Keywords: Li-ion battery, Li-rich layered cathode material, phase transformation, cycling stability, rate capability

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Authors: Sangwoo Han, Saeed Khaleghi Rahimian, Ying Liu

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Vehicle electrification is gaining momentum, and many car manufacturers promise to deliver more electric vehicle (EV) models to consumers in the coming years. In controlling the battery pack, the battery management system (BMS) must maintain optimal battery performance while ensuring the safety of a battery pack. Tasks related to battery performance include determining state-of-charge (SOC), state-of-power (SOP), state-of-health (SOH), cell balancing, and battery charging. Safety related functions include making sure cells operate within specified, static and dynamic voltage window and temperature range, derating power, detecting faulty cells, and warning the user if necessary. The BMS often utilizes an RC circuit model to model a Li-ion cell because of its robustness and low computation cost among other benefits. Because an equivalent circuit model such as the RC model is not a physics-based model, it can never be a prognostic model to predict battery state-of-health and avoid any safety risk even before it occurs. A physics-based Li-ion cell model, on the other hand, is more capable at the expense of computation cost. To avoid the high computation cost associated with a full-order model, many researchers have demonstrated the use of a single particle model (SPM) for BMS applications. One drawback associated with the single particle modeling approach is that it forces to use the average current density in the calculation. The SPM would be appropriate for simulating drive cycles where there is insufficient time to develop a significant current distribution within an electrode. However, under a continuous or high-pulse electrical load, the model may fail to predict cell voltage or Li⁺ plating potential. To overcome this issue, a multi-particle reduced-order model is proposed here. The use of multiple particles combined with either linear or nonlinear charge-transfer reaction kinetics enables to capture current density distribution within an electrode under any type of electrical load. To maintain computational complexity like that of an SPM, governing equations are solved sequentially to minimize iterative solving processes. Furthermore, the model is validated against a full-order model implemented in COMSOL Multiphysics.

Keywords: battery management system, physics-based li-ion cell model, reduced-order model, single-particle and multi-particle model

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Authors: Bing Zhang, Jingyi Zhang, Mudan Chen

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Fibre-reinforced polymer (FRP) composites have been extensively utilised in various industries due to their high specific strength, e.g., aerospace, renewable energy, automotive, and marine. However, they have relatively low electrical conductivity than metals, especially in the out-of-plane direction. Conductive metal strips or meshes are typically employed to protect composites when designing lightweight structures that may be subjected to lightning strikes, such as composite wings. Unfortunately, this approach downplays the lightweight advantages of FRP composites, thereby limiting their potential applications. Extensive studies have been undertaken to improve the electrical conductivity of FRP composites. The authors are amongst the pioneers who use through-thickness reinforcement (TTR) to tailor the electrical conductivity of composites. Compared to the conventional approaches using conductive fillers, the through-thickness reinforcement approach has been proven to be able to offer a much larger improvement to the through-thickness conductivity of composites. In this study, an advanced high-fidelity numerical modelling strategy is presented to investigate the effects of through-thickness reinforcement on both the in-plane and out-of-plane electrical conductivities of FRP composites. The critical micro-structural features of through-thickness reinforced composites incorporated in the modelling framework are 1) the fibre waviness formed due to TTR insertion; 2) the resin-rich pockets formed due to resin flow in the curing process following TTR insertion; 3) the fibre crimp, i.e., fibre distortion in the thickness direction of composites caused by TTR insertion forces. In addition, each interlaminar interface is described separately. An IMA/M21 composite laminate with a quasi-isotropic stacking sequence is employed to calibrate and verify the modelling framework. The modelling results agree well with experimental measurements for bothering in-plane and out-plane conductivities. It has been found that the presence of conductive TTR can increase the out-of-plane conductivity by around one order, but there is less improvement in the in-plane conductivity, even at the TTR areal density of 0.1%. This numerical tool provides valuable references as a design tool for through-thickness reinforced composites when exploring their electrical applications. Parametric studies are undertaken using the numerical tool to investigate critical parameters that affect the electrical conductivities of composites, including TTR material, TTR areal density, stacking sequence, and interlaminar conductivity. Suggestions regarding the design of electrical through-thickness reinforced composites are derived from the numerical modelling campaign.

Keywords: composite structures, design, electrical conductivity, numerical modelling, through-thickness reinforcement

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Authors: M. Atef Gabr, M. H. Abdel Latif, Ramadan El Gamsy

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Sandwich panels comprise a thick, light-weight plastic foam such as polyurethane (PU) sandwiched between two relatively thin faces. One or both faces may be flat, lightly profiled or fully profiled. Until recently sandwich panel construction in Egypt has been widely used in cold-storage buildings, cold trucks, prefabricated buildings and insulation in construction. Recently new techniques are used in mass production of Sandwich Materials such as Reaction Injection Molding (RIM) and Vacuum bagging technique. However, in recent times their use has increased significantly due to their widespread structural applications in building systems. Structural sandwich panels generally used in Egypt comprise polyurethane foam core and thinner (0.42 mm) and high strength about 550 MPa (yield strength) flat steel faces bonded together using separate adhesives and By RIM technique. In this paper, we will use a new technique in sandwich panel preparation by using different face sheet materials in combination with polyurethane foam to form sandwich panel structures. Previously, PU Foam core with same thin 2 faces material was used, but in this work, we use different face materials and thicknesses for the upper face sheet such as Galvanized steel sheets (G.S),Aluminum sheets (Al),Fiberglass sheets (F.G) and Aluminum-Rubber composite sheets (Al/R) with polyurethane foam core 10 mm thickness and 45 Kg/m3 Density and Galvanized steel as lower face sheet. Using Aluminum-Rubber composite sheets as face sheet is considered a hybrid composite sandwich panel which is built by Hand-Layup technique by using PU glue as adhesive. This modification increases the benefits of the face sheet that will withstand different working environments with relatively small increase in its weight and will be useful in several applications. In this work, a 3-point bending test is used assistant professor to measure the most important factor in sandwich materials that is strength to weight ratio(STW) for different combinations of sandwich structures and make a comparison to study the effect of changing the face sheet material on the mechanical behavior of PU sandwich material. Also, the density of the different prepared sandwich materials will be measured to obtain the specific bending strength.

Keywords: hybrid sandwich panel, mechanical behavior, PU foam, sandwich panel, 3-point bending, flexural strength

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Authors: Mohamed Abdelkareem

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Remote sensing data contributed on predicting the prospective areas of water resources. Integration of microwave and multispectral data along with climatic, hydrologic, and geological data has been used here. In this article, Sentinel-2, Landsat-8 Operational Land Imager (OLI), Shuttle Radar Topography Mission (SRTM), Tropical Rainfall Measuring Mission (TRMM), and Advanced Land Observing Satellite (ALOS) Phased Array Type L‐band Synthetic Aperture Radar (PALSAR) data were utilized to identify the geological, hydrologic and structural features of Wadi Asyuti which represents a defunct tributary of the Nile basin, in the eastern Sahara. The image transformation of Sentinel-2 and Landsat-8 data allowed characterizing the different varieties of rock units. Integration of microwave remotely-sensed data and GIS techniques provided information on physical characteristics of catchments and rainfall zones that are of a crucial role for mapping groundwater prospective zones. A fused Landsat-8 OLI and ALOS/PALSAR data improved the structural elements that difficult to reveal using optical data. Lineament extraction and interpretation indicated that the area is clearly shaped by the NE-SW graben that is cut by NW-SE trend. Such structures allowed the accumulation of thick sediments in the downstream area. Processing of recent OLI data acquired on March 15, 2014, verified the flood potential maps and offered the opportunity to extract the extent of the flooding zone of the recent flash flood event (March 9, 2014), as well as revealed infiltration characteristics. Several layers including geology, slope, topography, drainage density, lineament density, soil characteristics, rainfall, and morphometric characteristics were combined after assigning a weight for each using a GIS-based knowledge-driven approach. The results revealed that the predicted groundwater potential zones (GPZs) can be arranged into six distinctive groups, depending on their probability for groundwater, namely very low, low, moderate, high very, high, and excellent. Field and well data validated the delineated zones.

Keywords: GIS, remote sensing, groundwater, Egypt

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Authors: Wasan Ismail Khalil, Hisham Khalid Ahmed, Zainab Ali

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Structural Lightweight Aggregate Concrete (SLWAC) has been developed in recent years because it reduces the dead load, cost, thermal conductivity and coefficient of thermal expansion of the structure. So SLWAC has the advantage of being a relatively green building material. Lightweight Aggregate (LWA) is either occurs as natural material such as pumice, scoria, etc. or as artificial material produced from different raw materials such as expanded shale, clay, slate, etc. The use of SLWAC in Iraq is limited due to the lack in natural LWA. The existence of Iraqi clay deposit with different types and characteristics leads to the idea of producing artificial expanded clay aggregate. The main aim in this work is to present of the properties of artificial LWA produced in the laboratory. Available local bentonite clay which occurs in the Western region of Iraq was used as raw material to produce the LWA. Sodium silicate as liquid industrial waste material from glass plant was mixed with bentonite clay in mix proportion 1:1 by weight. The manufacturing method of the lightweight aggregate including, preparation and mixing of clay and sodium silicate, burning of the mixture in the furnace at the temperature between 750-800˚C for two hours, and finally gradually cooling process. The produced LWA was then crushed to small pieces then screened on standard sieve series and prepared with grading which conforms to the specifications of LWA. The maximum aggregate size used in this investigation is 10 mm. The chemical composition and the physical properties of the produced LWA are investigated. The results indicate that the specific gravity of the produced LWA is 1.5 with the density of 543kg/m3 and water absorption of 20.7% which is in conformity with the international standard of LWA. Many trail mixes were carried out in order to produce LWAC containing the artificial LWA produced in this research. The selected mix proportion is 1:1.5:2 (cement: sand: aggregate) by weight with water to cement ratio of 0.45. The experimental results show that LWAC has oven dry density of 1720 kg/m3, water absorption of 8.5%, the thermal conductivity of 0.723 W/m.K and compressive strength of 23 N/mm2. The SLWAC produced in this research can be used in the construction of different thermal insulated buildings and masonry units. It can be concluded that the SLWA produced in this study contributes to sustainable development by, using industrial waste materials, conserving energy, enhancing the thermal and structural efficiency of concrete.

Keywords: expanded clay, lightweight aggregate, structural lightweight aggregate concrete, sustainable

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Authors: Della Saddam Housseyn

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Gold, the quintessential noble metal, is one of the most popular metals today, given its ever-increasing cost in the international market. The Amesmessa gold deposit is one of the gold-producing deposits. The first step in our job is to analyze the ore (considered rich ore). Mineralogical and chemical analysis has shown that the general constitution of the ore is quartz in addition to other phases such as Al2O3, Fe2O3, CaO, dolomite. The second step consists of all the leaching tests carried out in rolling bottles. These tests were carried out on 14 samples to determine the maximum recovery rate and the optimum consumption of reagent (NaCN and CaO). Tests carried out on a pulp density at 50% solid, 500 ppm cyanide concentration and particle size less than 0.6 mm at alkaline pH gave a recovery rate of 94.37%.

Keywords: cyanide, DRX, FX, gold, leaching, rate of recovery, SAA

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Authors: Yawen Dai, Ping Cheng, Jian Ru Gong

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Photoelctrochemical (PEC) water splitting using semiconductors (SCs) provides a convenient way to convert sustainable but intermittent solar energy into clean hydrogen energy, and it has been regarded as one of most promising technology to solve the energy crisis and environmental pollution in modern society. However, the record energy conversion efficiency of a PEC cell (~3%) is still far lower than the commercialization requirement (~10%). The sluggish kinetics of oxygen evolution reaction (OER) half reaction on photoanodes is a significant limiting factor of the PEC device efficiency, and electrocatalysts (ECs) are always deposited on SCs to accelerate the hole injection for OER. However, an active EC cannot guarantee enhanced PEC performance, since the newly emerged SC-EC interface complicates the interfacial charge behavior. Herein, α-Fe2O3 photoanodes coated with Co3O4 and CoO ECs are taken as the model system to glean fundamental understanding on the EC-dependent interfacial charge behavior. Intensity modulated photocurrent spectroscopy and electrochemical impedance spectroscopy were used to investigate the competition between interfacial charge transfer and recombination, which was found to be dominated by the charge storage capacities of ECs. The combined results indicate that both ECs can store holes and increase the hole density on photoanode surface. It is like a double-edged sword that benefit the multi-hole participated OER, as well as aggravate the SC-EC interfacial charge recombination due to the Coulomb attraction, thus leading to a nonmonotonic PEC performance variation trend with the increasing surface hole density. Co3O4 has low hole storage capacity which brings limited interfacial charge recombination, and thus the increased surface holes can be efficiently utilized for OER to generate enhanced photocurrent. In contrast, CoO has overlarge hole storage capacity that causes severe interfacial charge recombination, which hinders hole transfer to electrolyte for OER. Therefore, the PEC performance of α-Fe2O3 is improved by Co3O4 but decreased by CoO despite the similar electrocatalytic activity of the two ECs. First-principle calculation was conducted to further reveal how the charge storage capacity depends on the EC’s intrinsic property, demonstrating that the larger hole storage capacity of CoO than that of Co3O4 is determined by their Co valence states and original Fermi levels. This study raises up a new strategy to manipulate interfacial charge behavior and the resultant PEC performance by the charge storage capacity of ECs, providing insightful guidance for the interface design in PEC devices.

Keywords: charge storage capacity, electrocatalyst, interfacial charge behavior, photoelectrochemistry, water-splitting

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Authors: Hyeuk Ju Ko, Eui Ju Lee

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Many electronic devices are powered by various rechargeable batteries such as lithium-ion today, but occasionally the batteries undergo thermal runaway and cause fire, explosion, and other hazards. If a battery fire should occur in an electronic device of vehicle and aircraft cabin, it is important to quickly extinguish the fire and cool the batteries to minimize safety risks. Attempts to minimize these risks have been carried out by many researchers but the number of study on the successful extinguishment is limited. Because most rechargeable batteries are operated on the ion state with electron during charge and discharge of electricity, and the reaction of this electrolyte has a big difference with normal combustion. Here, we focused on the effect of ions on reaction stability and pollutant emissions during combustion process. The other importance for understanding ionized fuel combustion could be found in high efficient and environment-friendly combustion technologies, which are used to be operated an extreme condition and hence results in unintended flame instability such as extinction and oscillation. The use of electromagnetic energy and non-equilibrium plasma is one of the way to solve the problems, but the application has been still limited because of lack of excited ion effects in the combustion process. Therefore, the understanding of ion role during combustion might be promised to the energy safety society including the battery safety. In this study, the effects of an ionized fuel on the flame stability and pollutant emissions were experimentally investigated in the hydrocarbon jet diffusion flames. The burner used in this experiment consisted of 7.5 mm diameter tube for fuel and the gaseous fuels were ionized with the ionizer (SUNJE, SPN-11). Methane (99.9% purity) and propane (commercial grade) were used as a fuel and open ambient air was used as an oxidizer. As the performance of ionizer used in the experiment was evaluated at first, ion densities of both propane and methane increased linearly with volume flow rate but the ion density of propane is slightly higher than that of methane. The results show that the overall flame stability and shape such as flame length has no significant difference even in the higher ion concentration. However, the fuel ionization affects to the pollutant emissions such as NOx and soot. NOx and CO emissions measured in post flame region decreased with increasing fuel ionization, especially at high fuel velocity, i.e. high ion density. TGA analysis and morphology of soot by TEM indicates that the fuel ionization makes soot to be matured.

Keywords: battery fires, ionization, jet flames, stability, NOx and soot

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Authors: Md. S. Ansari, S. S. Motsa

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In this paper, an analysis has been made on the flow of non-Newtonian viscoelastic nanofluid over a linearly stretching sheet under the influence of uniform magnetic field. Heat transfer characteristics is analyzed taking into the effect of nonlinear radiation and non-uniform heat source/sink. Transport equations contain the simultaneous effects of Brownian motion and thermophoretic diffusion of nanoparticles. The relevant partial differential equations are non-dimensionalized and transformed into ordinary differential equations by using appropriate similarity transformations. The transformed, highly nonlinear, ordinary differential equations are solved by spectral local linearisation method. The numerical convergence, error and stability analysis of iteration schemes are presented. The effects of different controlling parameters, namely, radiation, space and temperature-dependent heat source/sink, Brownian motion, thermophoresis, viscoelastic, Lewis number and the magnetic force parameter on the flow field, heat transfer characteristics and nanoparticles concentration are examined. The present investigation has many industrial and engineering applications in the fields of coatings and suspensions, cooling of metallic plates, oils and grease, paper production, coal water or coal–oil slurries, heat exchangers’ technology, and materials’ processing and exploiting.

Keywords: magnetic field, nonlinear radiation, non-uniform heat source/sink, similar solution, spectral local linearisation method, Rosseland diffusion approximation

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Authors: S. Murr, S. Phillips

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One of the biggest challenges entering a market with a carsharing or any other shared mobility (SM) service is sound investment decision-making. To support this process, the authors think that a city index evaluating different criteria is necessary. The goal of such an index is to benchmark cities along a set of external measures to answer the main two challenges: financially viability and the understanding of its specific requirements. The authors have consulted several shared mobility projects and industry experts to create such a Shared Mobility City Index (SMCI). The current proposal of the SMCI consists of 11 individual index measures: general data (demographics, geography, climate and city culture), shared mobility landscape (current SM providers, public transit options, commuting patterns and driving culture) and political vision and goals (vision of the Mayor, sustainability plan, bylaws/tenders supporting SM). To evaluate the suitability of the index, 16 cities on the East Coast of North America were selected and secondary research was conducted. The main sources of this study were census data, organisational records, independent press releases and informational websites. Only non-academic sources where used because the relevant data for the chosen cities is not published in academia. Applying the index measures to the selected cities resulted in three major findings. Firstly, density (city area divided by number of inhabitants) is not an indicator for the number of SM services offered: the city with the lowest density has five bike and carsharing options. Secondly, there is a direct correlation between commuting patterns and how many shared mobility services are offered. New York, Toronto and Washington DC have the highest public transit ridership and the most shared mobility providers. Lastly, except one, all surveyed cities support shared mobility with their sustainability plan. The current version of the shared mobility index is proving a practical tool to evaluate cities, and to understand functional, political, social and environmental considerations. More cities will have to be evaluated to refine the criteria further. However, the current version of the index can be used to assess cities on their suitability for shared mobility services and will assist investors deciding which city is a financially viable market.

Keywords: carsharing, transportation, urban planning, shared mobility city index

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Authors: Ali Moafi, Kourosh Kalantarzadeh, Richard Kaner, Parviz Parvin, Ebrahim Asl Soleimani, Dougal McCulloch

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In-situ Raman spectroscopy of flexible graphene-oxide films examined upon exposure to hydrogen gas, air, and synthetic air. The changes in D and G peaks are attributed to defects responding to atomic hydrogen spilled over from the catalytic behavior of Pt nanoparticles distributed all over the film. High-resolution transmission electron microscopy images (HRTEM) as well as electron energy loss spectroscopy (EELS) were carried out to define the density of the samples.

Keywords: in situ Raman Spectroscopy, EELS, TEM, graphene oxide, graphene, atomic hydrogen

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Authors: Javad Saeidaskari, Mohammad Hassan Baziar

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Soil structures have been frequently damaged during piping, earthquake and other types of failures. As far as adverse circumstances were developed subsequent to piping or other similar failure types, hydraulic parameters of soil such as hydraulic conductivity should be considered. As a result, acquiring an approach to diminish soil permeability is inevitable. There are many ground improvement methods to reduce seepage, which are classified under soil treatment and stabilization methods. Recently, one of the soil improvement methods is known as nanogeotechnology. This study aims to investigate the influence of Cloisite 30B nanoclay on permeability of compacted clayey sand soils. The samples are prepared by mixing two soil types, including Kaolin clay and Firouzkooh sand, in 1:9 and 1:5 clay:sand (by mass) proportions. In experimental procedure, initially, the optimum water content and maximum dry unit weight of each samples were obtained for compaction. Then, series of permeability tests were conducted by triaxial apparatus on prepared specimens with identical relative density of 95% of maximum dry density and water content of 1% wet of optimum for different weight percentages of nanoclay (1% to 4%). Therefore, in this paper, the effect of time on treated specimen was appraised, as well as two approaches of manual mixing and ball milling were compared to reveal the importance of dispersion issue. The results show that adding nanoclay up to 3%, as its optimum content, causes notable reduction in permeability (1.60e-03 to 5.51e-05 cm/s and 3.32e-04 to 8.44e-07 cm/s in samples with 1:9 and 1:5 mixture proportions, respectively). The hydraulic conductivity of treated clayey sand (1:5 mixture proportion with 3% nanoclay) decreases gradually from 8.44e-07 to 3.00e-07 cm/s within 90 days and then tends to be consistent. The influence of mixing method on permeability results shows that the utilization of ball mill mixing effectively leads to lower values than those of manual mixing, in other words, by adding 3% nanoclay, hydraulic conductivity of specimen declines from 8.44e-07 to 2.00e-07 cm/s. In order to evaluate the interaction between soil particles and, to ensure proper dispersion of nanoparticles through clayey sand mixture, they were magnified by means of scanning electron microscope (SEM). In conclusion, the nanoclay particles in vicinity of moisture can cause soil stabilization to prevent water penetration, which eventually result in lower usage of clay and operation costs.

Keywords: nanoclay, cloisite 30b, clayey sand, hydraulic conductivity

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Authors: Orkide Donma, Mustafa M. Donma

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Morbid obesity is a health threatening condition particularly in children. Generally, it leads to the development of metabolic syndrome (MetS) characterized by central obesity, elevated fasting blood glucose (FBG), triglyceride (TRG), blood pressure values and suppressed high density lipoprotein cholesterol (HDL-C) levels. However, some ambiguities exist during the diagnosis of MetS in children below 10 years of age. Therefore, clinicians are in the need of some surrogate markers for the laboratory assessment of pediatric MetS. In this study, the aim is to develop an index, which will be more helpful during the evaluation of further risks detected in morbid obese (MO) children. A total of 235 children with normal body mass index (N-BMI), with varying degrees of obesity; overweight (OW), obese (OB), MO as well as MetS participated in this study. The study was approved by the Institutional Ethical Committee. Informed consent forms were obtained from the parents of the children. Obesity states of the children were classified using BMI percentiles adjusted for age and sex. For the purpose, tabulated data prepared by WHO were used. MetS criteria were defined. Systolic and diastolic blood pressure values were measured. Parameters related to glucose and lipid metabolisms were determined. FBG, insulin (INS), HDL-C, TRG concentrations were determined. Diagnostic Obesity Notation Model Assessment Laboratory (DONMA_LAB) Index [ln TRG/HDL-C*INS] was introduced. Commonly used insulin resistance (IR) indices such as Homeostatic Model Assessment for IR (HOMA-IR) as well as ratios such as TRG/HDL-C, TRG/HDL-C*INS, HDL-C/TRG*INS, TRG/HDL-C*INS/FBG, log, and ln versions of these ratios were calculated. Results were interpreted using statistical package program (SPSS Version 16.0) for Windows. The data were evaluated using appropriate statistical tests. The degree for statistical significance was defined as 0.05. 35 N, 20 OW, 47 OB, 97 MO children and 36 with MetS were investigated. Mean ± SD values of TRG/HDL-C were 1.27 ± 0.69, 1.86 ± 1.08, 2.15 ± 1.22, 2.48 ± 2.35 and 4.61 ± 3.92 for N, OW, OB, MO and MetS children, respectively. Corresponding values for the DONMA_LAB index were 2.17 ± 1.07, 3.01 ± 0.94, 3.41 ± 0.93, 3.43 ± 1.08 and 4.32 ± 1.00. TRG/HDL-C ratio significantly differed between N and MetS groups. On the other hand, DONMA_LAB index exhibited statistically significant differences between N and all the other groups except the OW group. This index was capable of discriminating MO children from those with MetS. Statistically significant elevations were detected in MO children with MetS (p < 0.05). Multiple parameters are commonly used during the assessment of MetS. Upon evaluation of the values obtained for N, OW, OB, MO groups and for MO children with MetS, the [ln TRG/HDL-C*INS] value was unique in discriminating children with MetS.

Keywords: children, index, laboratory, metabolic syndrome, obesity

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Authors: Rim Zgueb, Noureddine Yacoubi

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The objective of this study was to investigate the thermal property of magnesium oxychloride cement (MOC) using glass powder as a substitute. Glass powder by proportion 0%, 5%, 10%, 15% and 20% of cement’s weight was added to specimens. At the end of a drying time of 28 days, thermal properties, compressive strength and bulk density of samples were determined. Thermal property is measured by Photothermal Deflection Technique by comparing the experimental of normalized amplitude and the phase curves of the photothermal signal to the corresponding theoretical ones. The findings indicate that incorporation of glass powder decreases the thermal properties of MOC.

Keywords: magnesium oxychloride cement (MOC), phototharmal deflection technique, thermal properties, Ddensity

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Authors: Yarra Sulina, Nunna Tagore Sai Priya, Ankhi Banerjee

Abstract:

With the rapid growth in tourist arrivals, there has been a huge demand for the growth of infrastructure in the destinations. With the increasing preference of tourists to stay near attractions, there has been a considerable change in the land use around tourist sites. However, with the inclusion of certain regulations and guidelines provided by the authorities based on the nature of tourism activity and geographical constraints, the pattern of growth of built form is different for various tourist sites. Therefore, this study explores the patterns of growth of built-up for a decade from 2009 to 2019 through two-dimensional and three-dimensional analysis. Land use maps are created through supervised classification of satellite images obtained from LANDSAT 4-5 and LANDSAT 8 for 2009 and 2019, respectively. The overall expansion of the built-up area in the region is analyzed in relation to the distance from the city's geographical center and the tourism-related growth regions are identified which are influenced by the proximity of tourist attractions. The primary tourist sites of various destinations with different geographical characteristics and tourism activities, that have undergone a significant increase in built-up area and are occupied with tourism-related infrastructure are selected for further study. Proximity analysis of the tourism-related growth sites is carried out to delineate the influence zone of the tourist site in a destination. Further, a temporal analysis of volumetric growth of built form is carried out to understand the morphology of the tourist precincts over time. The Digital Surface Model (DSM) and Digital Terrain Model (DTM) are used to extract the building footprints along with building height. Factors such as building height, and building density are evaluated to understand the patterns of three-dimensional growth of the built area in the region. The study also explores the underlying reasons for such changes in built form around various tourist sites and predicts the impact of such growth patterns in the region. The building height and building density around tourist site creates a huge impact on the appeal of the destination. The surroundings that are incompatible with the theme of the tourist site have a negative impact on the attractiveness of the destination that leads to negative feedback by the tourists, which is not a sustainable form of development. Therefore, proper spatial measures are necessary in terms of area and volume of the built environment for a healthy and sustainable environment around the tourist sites in the destination.

Keywords: sustainable tourism, growth patterns, land-use changes, 3-dimensional analysis of built-up area

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Authors: Werner Grommes

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Intelligent wearables (illuminated vests or hand and foot-bands, smart watches with a laser diode, Bluetooth smart glasses) overflow the market today. They are integrated with complex electronics and are worn very close to the body. Optical measurements and limitation of the maximum light density are needed. Smart watches are equipped with a laser diode or control different body currents. Special glasses generate readable text information that is received via radio transmission. Small high-performance batteries (lithium-ion/polymer) supply the electronics. All these products have been tested and evaluated for risk. These products must, for example, meet the requirements for electromagnetic compatibility as well as the requirements for electromagnetic fields affecting humans or implant wearers. Extensive analyses and measurements were carried out for this purpose. Many users are not aware of these risks. The result of this study should serve as a suggestion to do it better in the future or simply to point out these risks. Commercial LED warning vests, LED hand and foot-bands, illuminated surfaces with inverter (high voltage), flashlights, smart watches, and Bluetooth smart glasses were checked for risks. The luminance, the electromagnetic emissions in the low-frequency as well as in the high-frequency range, audible noises, and nervous flashing frequencies were checked by measurements and analyzed. Rechargeable lithium-ion or lithium-polymer batteries can burn or explode under special conditions like overheating, overcharging, deep discharge or using out of the temperature specification. Some risk analysis becomes necessary. The result of this study is that many smart wearables are worn very close to the body, and an extensive risk analysis becomes necessary. Wearers of active implants like a pacemaker or implantable cardiac defibrillator must be considered. If the wearable electronics include switching regulators or inverter circuits, active medical implants in the near field can be disturbed. A risk analysis is necessary.

Keywords: safety and hazards, electrical safety, EMC, EMF, active medical implants, optical radiation, illuminated warning vest, electric luminescent, hand and head lamps, LED, e-light, safety batteries, light density, optical glare effects

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Authors: B. Nabil, O. Zahir, R. Abdelaziz

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We present the results of electrical characterizations current-voltage and capacity-voltage implementation of a method of making a Schottky diode on bulk gallium nitride doped n. We made temporary Schottky contact of Mercury (Hg) and an ohmic contact of silver (Ag), the electrical characterizations current-voltage (I-V) and capacitance-voltage (C-V) allows us to determine the difference parameters of our structure (Hg /n-GaN) as the barrier height (ΦB), the ideality factor (n), the series resistor (Rs), the voltage distribution (Vd), the doping of the substrate (Nd) and density of interface states (Nss).

Keywords: Bulk Gallium nitride, electrical characterization, Schottky diode, series resistance, substrate doping

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Authors: Sumit Roy, A. Uddin

Abstract:

One of the significant reasons that increase the delay time in the intersections at heterogeneous traffic condition is a sudden reduction of the capacity of the roads. In this study, the delay for this sudden capacity reduction is estimated. Two intersections at Dhaka city were brought in to thestudy, i.e., Kakrail intersection, and SAARC Foara intersection. At Kakrail intersection, the sudden reduction of capacity in the roads is seen at three downstream legs of the intersection, which are because of slowing down or stopping of buses for loading and unloading of passengers. At SAARC Foara intersection, sudden reduction of capacity was seen at two downstream legs. At one leg, it was due to loading and unloading of buses, and at another leg, it was for both loading and unloading of buses and reduction of the number of lanes. With these considerations, the delay due to intentional stoppage or slowing down of buses and reduction of the number of lanes for these two intersections are estimated. Here the delay was calculated by two approaches. The first approach came from the concept of shock waves in traffic streams. Here the delay was calculated by determining the flow, density, and speed before and after the sudden capacity reduction. The second approach came from the deterministic analysis of queues. Here the delay is calculated by determining the volume, capacity and reduced capacity of the road. After determining the delay from these two approaches, the results were compared. For this study, the video of each of the two intersections was recorded for one hour at the evening peak. Necessary geometric data were also taken to determine speed, flow, and density, etc. parameters. The delay was calculated for one hour with one-hour data at both intersections. In case of Kakrail intersection, the per hour delay for Kakrail circle leg was 5.79, and 7.15 minutes, for Shantinagar cross intersection leg they were 13.02 and 15.65 minutes, and for Paltan T intersection leg, they were 3 and 1.3 minutes for 1st and 2nd approaches respectively. In the case of SAARC Foara intersection, the delay at Shahbag leg was only due to intentional stopping or slowing down of busses, which were 3.2 and 3 minutes respectively for both approaches. For the Karwan Bazar leg, the delays for buses by both approaches were 5 and 7.5 minutes respectively, and for reduction of the number of lanes, the delays for both approaches were 2 and 1.78 minutes respectively. Measuring the delay per hour for the Kakrail leg at Kakrail circle, it is seen that, with consideration of the first approach of delay estimation, the intentional stoppage and lowering of speed by buses contribute to 26.24% of total delay at Kakrail circle. If the loading and unloading of buses at intersection is made forbidden near intersection, and any other measures for loading and unloading of passengers are established far enough from the intersections, then the delay at intersections can be reduced at significant scale, and the performance of the intersections can be enhanced.

Keywords: delay, deterministic queue analysis, shock wave, passenger loading-unloading

Procedia PDF Downloads 164

Authors: Zhongzhi Hu, Jie Shen, Jiqiang Wang

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A high precision aeroengine model is needed when developing the engine control system. Compared with other main components, the axial compressor is the most challenging component to simulate. In this paper, a compressor map optimizing tool based on the introduction of a modifiable β function is developed for FWorks (FADEC Works). Three parameters (d density, f fitting coefficient, k₀ slope of the line β=0) are introduced to the β function to make it modifiable. The comparison of the traditional β function and the modifiable β function is carried out for a certain type of compressor. The interpolation errors show that both methods meet the modeling requirements, while the modifiable β function can predict compressor performance more accurately for some areas of the compressor map where the users are interested in.

Keywords: beta function, compressor map, interpolation error, map optimization tool

Procedia PDF Downloads 252

Authors: Nasir Iqbal, Khurram Siraj, Rizwan Raza

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Solid oxide fuel cell (SOFC) is the promising technology now days. SOFC can be operated with different types of fuels available. In this work catalytic anode is prepared with metal oxides i.e. Li, Ni, Zn and Sn and tested for catalytic activity with natural gas as a fuel. The operating temperature range is 170-750°C as observed with the help of TGA. Electrical conductivity and fuel cell performance has been observed for four different samples with varying composition of Sn and Zn. It is concluded that the sample having greater concentration of Zn shows better conductivity and power density results. All the results are promising and verified with different characterizations.

Keywords: catalytic activity, solid oxide fuel cell, energy material, natural gas

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Authors: Giorgio Visentin, Alexei A. Buchachenko

Abstract:

Recent proposals to use Yb dimer as an optical clock and as a sensor for non-Newtonian gravity imply the knowledge of its interaction potential. Here, the ground-state Born-Oppenheimer Yb₂ potential energy curve is represented by a semi-analytical function, consisting of short- and long-range contributions. For the former, the systematic ab initio all-electron exact 2-component scalar-relativistic CCSD(T) calculations are carried out. Special care is taken to saturate diffuse basis set component with the atom- and bond-centered primitives and reach the complete basis set limit through n = D, T, Q sequence of the correlation-consistent polarized n-zeta basis sets. Similar approaches are used to the long-range dipole and quadrupole dispersion terms by implementing the CCSD(3) polarization propagator method for dynamic polarizabilities. Dispersion coefficients are then computed through Casimir-Polder integration. The semiclassical constraint on the number of the bound vibrational levels known for the ¹⁷⁴Yb isotope is used to scale the potential function. The scaling, based on the most accurate ab initio results, bounds the interaction energy of two Yb atoms within the narrow 734 ± 4 cm⁻¹ range, in reasonable agreement with the previous ab initio-based estimations. The resulting potentials can be used as the reference for more sophisticated models that go beyond the Born-Oppenheimer approximation and provide the means of their uncertainty estimations. The work is supported by Russian Science Foundation grant # 17-13-01466.

Keywords: ab initio coupled cluster methods, interaction potential, semi-analytical function, ytterbium dimer

Procedia PDF Downloads 136

Authors: Mouna Ettoumi, Jouini Marouen, Carmen Mihaela Neculita, Salah Bouhlel, Lucie Coudert, Mostafa Benzaazoua, Y. Taha

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In the context of sustainable development and circular economy, waste valorization is considered a promising alternative to overcome issues related to their disposal or elimination. The aim of this study is to evaluate the potential use of phosphate sludges (tailings) from the Kef Shfeir mine site (Gafsa, Tunisia) as an alternative material in the production of fired bricks. To do so, representative samples of raw phosphate treatment sludges were collected and characterized for their physical, chemical, mineralogical and environmental characteristics. Then, the raw materials were baked at different temperatures (900°C, 1000°C, and 1100°C) for bricks making. Afterward, fired bricks were characterized for their physical (particle size distribution, density, and plasticity), chemical (XRF and digestion), mineralogical (XRD) and mechanical (flexural strength) properties as well as for their environmental behavior (TCLP, SPLP, and CTEU-9) to ensure whether they meet the required construction standards. Results showed that the raw materials had low density (2.47g/cm 3), were non-plastic and were mainly composed of fluoroapatite (15.6%), calcite (23.1%) and clays (22.2% - mainly as heulandite, vermiculite and palygorskite). With respect to the environmental behavior, all metals (e.g., Pb, Zn, As, Cr, Ba, Cd) complied with the requirements set by the USEPA. In addition, fired bricks had varying porosity (9-13%), firing shrinking (5.2-7.5%), water absorption (12.5-17.2%) and flexural strength (3.86-13.4 MPa). Noteworthy, an improvement in the properties (porosity, firing shrinking, water absorption, and flexural strength) of manufactured fired bricks was observed with the increase of firing temperature from 900 to 1100°C. All the measured properties complied with the construction norms and requirements. Moreover, regardless of the firing temperature, the environmental behavior of metals obeyed the requirements of the USEPA standards. Finally, fired bricks could be produced at high temperatures (1000°C) based on 100% of phosphate sludge without any substitution or addition of either chemical agents or binders. This sustainable brick-making process could be a promising approach for the Phosphate Company to partially manage these wastes, which are considered “non-profitable” for the moment and preserve soils that are exploited presently.

Keywords: phosphate treatment sludge, mine waste, backed bricks, waste valorization

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Authors: S. Bentata, W. Benstaali, A. Abbad, H. A. Bentounes, B. Bouadjemi

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The full potential linear augmented plane wave (FPLAPW) based on density-functional theory (DFT) is employed to study the electronic, magnetic and optical properties of some transition metals doped ZnSe. Calculations are carried out by varying the doped atoms. Four 3D transition elements were used as a dopant: Cr, Mn, Co and Cu in order to induce spin polarization. Our results show that, Mn and Cu-doped ZnSe could be used in spintronic devices only if additional dopants are introduced, on the contrary, transition elements showing delocalized quality such as Cr, and Co doped ZnSe might be promising candidates for application in spintronic.

Keywords: spin-up, spin-down, magnetic properties, transition metal, composite materials

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Authors: S. Iffat, B. Bose

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Concrete as a construction material is versatile because it displays high degree of fire-resistance. Concrete’s inherent ability to combat one of the most devastating disaster that a structure can endure in its lifetime, can be attributed to its constituent materials which make it inert and have relatively poor thermal conductivity. However, concrete structures must be designed for fire effects. Structural components should be able to withstand dead and live loads without undergoing collapse. The properties of high-strength concrete must be weighed against concerns about its fire resistance and susceptibility to spalling at elevated temperatures. In this paper, the causes, effects and some remedy of deterioration in concrete due to fire hazard will be discussed. Some cost effective solutions to produce a fire resistant concrete will be conversed through this paper.

Keywords: concrete, fire, spalling, temperature, compressive strength, density

Procedia PDF Downloads 426

Authors: Sadam Elayah

Abstract:

Background: One of the most critical competencies in advanced dentistry is alveolar ridge preservation after exodontia. The aim of this clinical trial was to assess the impact of autologous concentrated growth factor (CGF) as a socket-filling material and its ridge preservation properties following the lower third molar extraction. Materials and Methods: A total of 60 sides of 30 participants who had completely symmetrical bilateral impacted lower third molars were enrolled. The short-term outcome variables were wound healing, swelling and pain, clinically assessed at different time intervals (1st, 3rd & 7th days). While the long-term outcome variables were bone height & width, bone density and socket surface area in the coronal section. Cone beam computed tomography images were obtained immediately after surgery and three months after surgery as a temporal measure. Randomization was achieved by opaque, sealed envelopes. Follow-up data were compared to baseline using Paired & Unpaired t-tests. Results: The wound healing index was significantly better in the test sides (P =0.001). Regarding the facial swelling, the test sides had significantly fewer values than the control sides, particularly on the 1st (1.01±.57 vs 1.55 ±.56) and 3rd days (1.42±0.8 vs 2.63±1.2) postoperatively. Nonetheless, the swelling disappeared within the 7th day on both sides. The pain scores of the visual analog scale were not a statistically significant difference between both sides on the 1st day; meanwhile, the pain scores were significantly lower on the test sides compared with the control sides, especially on the 3rd (P=0.001) and 7th days (P˂0.001) postoperatively. Regarding long-term outcomes, CGF sites had higher values in height and width when compared to Control sites (Buccal wall 32.9±3.5 vs 29.4±4.3 mm, Lingual wall 25.4±3.5 vs 23.1±4 mm, and Alveolar bone width 21.07±1.55vs19.53±1.90 mm) respectively. Bone density showed significantly higher values in CGF sites than in control sites (Coronal half 200±127.3 vs -84.1±121.3, Apical half 406.5±103 vs 64.2±158.6) respectively. There was a significant difference between both sites in reducing periodontal pockets. Conclusion: CGF application following surgical extraction provides an easy, low-cost, and efficient option for alveolar ridge preservation. Thus, dentists may encourage using CGF during dental extractions, particularly when alveolar ridge preservation is required.

Keywords: platelet, extraction, impacted teeth, alveolar ridge, regeneration, CGF

Procedia PDF Downloads 50