Search results for: high entropy alloy

Authors: R. Kiš, M. Malcho, M. Janovcová

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This work aims to present a numerical analysis of the natural gas which flows through a high-pressure pipeline and an orifice plate, through the use of CFD methods. The paper contains CFD calculations for the flow of natural gas in a pipe with different geometry used for the orifice plates. One of them has a standard geometry and a shape without any deformation and the other is deformed by the action of the pressure differential. It shows the behaviour of natural gas in a pipeline using the velocity profiles and pressure fields of the gas in both models with their differences. The entire research is based on the elimination of any inaccuracy which should appear in the flow of the natural gas measured in the high-pressure pipelines of the gas industry and which is currently not given in the relevant standard.

Keywords: orifice plate, high-pressure pipeline, natural gas, CFD analysis

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Authors: R. M. Chandler, A. J. Stringer

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In adults, short bursts of high-intensity exercise (intensities between 80-95% of maximum heart rates) increase cardiovascular and metabolic function without the time investment of traditional aerobic training. Similar improvements in various health indices are also becoming increasingly evident in children in countries other than the United States. In the United States, physical education programs have become shorter in length and fewer in frequency. With this in the background, it is imperative that health and physical educators delivered well-organized and focused fitness programs that can be tolerated across many different somatotypes. Perhaps the least effective lag-time in a US physical education (PE) class is the first 10 minutes, a time during which children warm up. Replacing a traditional PE warmup with a 10 min high-intensity excise protocol is a time-efficient method to impact health, leaving as much time for other PE material such as skill development, motor behavior development as possible. This supplemented 10 min high-intensity exercise increases cardiovascular function as well as induces favorable body composition changes in as little as six weeks with further enhancement throughout a semester of activity. The supplemental high-intensity exercise did not detract from the PE lesson outcomes.

Keywords: cardiovascular fitness, high intensity interval training, high intensity exercise, pediatric

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Authors: Johannes Atug, Stefan Braunreuther, Gunther Reinhart

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Volatile markets, as well as increasing global competition in manufacturing, lead to a high demand of flexible and agile production systems. These advanced production systems in turn conduct to high capital expenditure along with high investment risks. Developments in production regarding digitalization and cyber-physical systems result to a merger of informational- and operational technology. The approach of this paper is to benefit from this merger and present a framework of a production network with scalable production capacity and low capital expenditure by adaptation of the IT concept 'everything as a service' into the production environment.

Keywords: digital manufacturing system, everything as a service, reconfigurable production, value network

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Authors: Elizabeth Hoyos, Hernán Alvarez, Diana Lopez, Yesid Montoya

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The main goal of this research relates to the modeling of FSW from a different or unusual perspective coming from mechanical engineering, particularly looking for a way to establish process windows by assessing soundness of the joints as a priority and with the added advantage of lower computational time. This paper presents the use of a previously developed model applied to specific aspects of soundness evaluation of AA7075 FSW welds. EMSO software (Environment for Modeling, Simulation, and Optimization) was used for simulation and an adapted CNC machine was used for actual welding. This model based approach showed good agreement with the experimental data, from which it is possible to set a window of operation for commercial aluminum alloy AA7075, all with low computational costs and employing simple quality indicators that can be used by non-specialized users in process modeling.

Keywords: aluminum AA7075, friction stir welding, phenomenological based semiphysical model, processing map

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Authors: Arjun, Gautam, Sanjeev Naval

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Concrete technology has been changing rapidly and constantly since its discovery. Concrete is the most widely used man-made construction material, versatility of making concrete is the 2nd largest consumed material on earth. In this paper an effort has been made to use metal aggregates in concrete has been discussed, the metal aggregates has been named as “BAUT” which had outstandingly qualities to resist shear, tension and compression forces. In this paper, COARSE BAUT AGGREGATES (C.B.A.) 10mm & 20mm and FINE BAUT AGGREGATES (F.B.A.) 3mm were divided and used for making high performance concrete (H.P.C). This “BAUT” had cutting edge technology through draft and design by the use of Auto CAD, ANSYS software can be used effectively In this research paper we study high performance concrete (H.P.C) with “BAUT” and consider the grade of M65 and finally we achieved the result of 90-95 Mpa (high compressive strength) for mega structures and irregular structures where center of gravity (CG) is not balanced. High Performance BAUT Concrete is the extraordinary qualities like long-term performance, no sorptivity by BAUT AGGREGATES, better rheological, mechanical and durability proportion that conventional concrete. This high strength BAUT concrete using “BAUT” is applied in the construction of mega structure like skyscrapers, dam, marine/offshore structures, nuclear power plants, bridges, blats and impact resistance structures. High Performance BAUT Concrete which is a controlled concrete possesses invariable high strength, reasonable workability and negligibly permeability as compare to conventional concrete by the mix of Super Plasticizers (SMF), silica fume and fly ash.

Keywords: BAUT, High Strength Concrete, High Performance Concrete, Fine BAUT Aggregate, Coarse BAUT Aggregate, metal aggregates, cutting edge technology

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Authors: Elena Kalcheva, Ahmad Taki, Yuri Hadi

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Urban regeneration often includes residential high-rises as a way of optimum use of land. However, high-rises are in many cases connected to placelessness, this is not due to some intrinsic characteristic of the typology, but more to a failure to provide meaningful places in connection to them. The reason to study the Isle of the Dogs regeneration is the successful process that led to vibrant area with strong identity and social sustainability. Therefore, the purpose of this research is to identify the gaps into the sound strategy for the development of the area and in its implementation which will make the place more sustainable. The paper addresses four research questions: are the residential high-rises supporting a proper physical form; is there deployed properly scaled mix of land uses and functions in connection with residential high-rises; are there possible quality activities in quality places near the residential high-rises; and is there a strong sense of place created with the residential high-rise buildings and their surroundings. The methodology relies on observational survey of the researched area together with structured questions, to evaluate the external qualities of the residential high-rises and their surroundings. Visual information can help identify the mistakes and the omissions of the provided project examples. It can provide insight on how can be improved imageability, legibility and human scale. In this connection, the paper argues that although the quality of the architecture of the high-rises is superb, there is a failure to create meaningful, high quality public realm in connection with them. As such, it does not function as well as the designers intended to do: the functional quality of the public realm is quite low. The implications of the study suggest that actions need to take place in order to improve and foster further regeneration of the area.

Keywords: high-rises, isle of the dogs, public realm, regeneration

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Authors: Mst Nazmunnahar, Juan del Val, Alena Vimmrova, Blanca Hernando, Julian González

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We report the microstructural and magnetic properties of Ni50Mn39Sn11 and Ni50Mn36Sn14 ribbon Heusler alloys. Experimental results were obtained by differential scanning calorymetry, X-ray diffraction and vibrating sample magnetometry techniques. The Ni-Mn-Sn system undergoes a martensitic structural transformation in a wide temperature range. For example, for Ni50Mn39Sn11 the start and finish temperatures of the martensitic and austenite phase transformation for ribbon alloy were Ms = 336K , Mf = 328K, As = 335K and Af = 343K whereas no structural transformation is observed for Ni50Mn36Sn14 alloys. Magnetic measurements show the typical ferromagnetic behavior with Curie temperature 207K at low applied field of 50 Oe. The complex behavior exhibited by these Heusler alloys should be ascribed to the strong coupling between magnetism and structure, being their magnetic behavior determined by the distance between Mn atoms.

Keywords: as-cast ribbon, Heusler alloys, magnetic properties, structural transformation

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Authors: Samson Ehindero, Oluwole Akinola

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Substantial evidence has shown an association between type 2 diabetes (T2D) and cognitive decline, Trans Cinnamaldehyde (TCA) has been shown to have many potent pharmacological properties. In this present study, we are currently investigating the effects of TCA on type II diabetes-induced neurodegeneration. Neurodegeneration was induced in forty (40) adult wistar rats using high fat diet (HFD) for 4 months followed by low dose of streptozotocin (STZ) (40 mg/kg, i.p.) administration. TCA was administered orally for 30 days at the doses of 40mg/kg and 60mg/kg body weight. Animals were randomized and divided into following groups; A- control group, B- diabetic group, C- TCA (high dose), D- diabetic + TCA (high dose), E- diabetic + TCA (high dose) with high fat diet, F- TCA Low dose, G- diabetic + TCA (low dose) and H- diabetic + TCA (low dose) with high fat diet. Animals were subjected to behavioral tests followed by histological studies of the hippocampus. Demented rats showed impaired behavior in Y- Maze test compared to treated and control groups. Trans Cinnamaldehyde restores the histo architecture of the hippocampus of demented rats. This present study demonstrates that treatment with trans- cinnamaldehyde improves behavioral deficits, restores cellular histo architecture in rat models of neurodegeneration.

Keywords: neurodegeneration, trans cinnamaldehyde, high fat diet, streptozotocin

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Authors: Kang Hyun Yi

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This paper presents a new parallel output LLC DC/DC converter for electric vehicle. The electric vehicle has two batteries. One is a high voltage battery for the powertrain of the vehicle and the other is a low voltage battery for the vehicle electric system. The low voltage is charged from the high voltage battery and the high voltage input and the high current output DC/DC converter is needed. Therefore, the new LLC converter with the input voltage compensation is proposed for the high voltage input and the low voltage output DC/DC converter. The proposed circuit has two LLC converters with the series input voltage from the battery for the powertrain and the parallel output low battery voltage for the vehicle electric system because the battery voltage for the powertrain and the electric power for the vehicle become high. Also, the input series voltage compensation capacitor is used for balancing the input current in the two LLC converters. The proposed converter has an equal electric stress of the semiconductor parts and the reactive components, high efficiency and good heat dissipation.

Keywords: electric vehicle, LLC DC/DC converter, input voltage balancing, parallel output

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Authors: Ana M. Korol, Bibiana Riquelme, Osvaldo A. Rosso

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Since erythrocyte deformability analysis is mostly qualitative, the development of quantitative nonlinear methods is crucial for restricting subjectivity in the study of cell behaviour. An electro-optic mechanic system called erythrodeformeter has been developed and constructed in our laboratory in order to evaluate the erythrocytes' viscoelasticity. A numerical method formulated on the basis of fractal approximation for ordinary (OBM) and fractionary Brownian motion (FBM), as well as wavelet transform analysis, are proposed to distinguish chaos from noise based on the assumption that diffractometric data involves both deterministic and stochastic components, so it could be modelled as a system of bounded correlated random walk. Here we report studies on 25 donors: 4 alpha thalassaemic patients, 11 beta thalassaemic patients, and 10 healthy controls non-alcoholic and non-smoker individuals. The Correlation Coefficient, a nonlinear parameter, showed evidence of the changes in the erythrocyte deformability; the Wavelet Entropy could quantify those differences which are detected by the light diffraction patterns. Such quantifiers allow a good deal of promise and the possibility of a better understanding of the rheological erythrocytes aspects and also could help in clinical diagnosis.

Keywords: red blood cells, deformability, nonlinear dynamics, chaos theory, wavelet trannsform

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Authors: S. Yun, M. Kwak

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This study is about an aerodynamic brake device for a high-speed train. In order to apply an aerodynamic brake device, an influence of the aerodynamic brake device on a high-speed train was studied aerodynamically, acoustically and dynamically. Wind tunnel test was conducted to predict an effect of braking distance reduction with a scale model of 1/30. Aerodynamic drag increases by 244% with a brake panel of a 90 degree angle. Braking distance for an emergency state was predicted to decrease by 13%.

Keywords: aerodynamic brake, braking distance, drag coefficient, high-speed train, wind-tunnel test

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Authors: P. Abachi, S. Karami, K. Purazrang

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The amorphous reinforcements (metallic glasses) can be considered as promising options for reinforcing light-weight aluminum and its alloys. By using the proper type of reinforcement, one can overcome to drawbacks such as interfacial de-cohesion and undesirable reactions which can be created at ceramic particle and metallic matrix interface. In this work, the Zr-based amorphous phase was produced via mechanical milling of elemental powders. Based on Miedema semi-empirical Model and diagrams for formation enthalpies and/or Gibbs free energies of Zr-Cu amorphous phase in comparison with the crystalline phase, the glass formability range was predicted. The composite was produced using the powder mixture of the aluminum and metallic glass and spark plasma sintering (SPS) at the temperature slightly above the glass transition Tg of the metallic glass particles. The selected temperature and rapid sintering route were suitable for consolidation of an aluminum matrix without crystallization of amorphous phase. To characterize amorphous phase formation, X-ray diffraction (XRD) phase analyses were performed on powder mixture after specified intervals of milling. The microstructure of the composite was studied by optical and scanning electron microscope (SEM). Uniaxial compression tests were carried out on composite specimens with the dimension of 4 mm long and a cross-section of 2 ˟ 2mm2. The micrographs indicated an appropriate reinforcement distribution in the metallic matrix. The comparison of stress–strain curves of the consolidated composite and the non-reinforced Al matrix alloy in compression showed that the enhancement of yield strength and mechanical strength are combined with an appreciable plastic strain at fracture. It can be concluded that metallic glasses (amorphous phases) are alternative reinforcement material for lightweight metal matrix composites capable of producing high strength and adequate ductility. However, this is in the expense of minor density increase.

Keywords: aluminum matrix composite, amorphous phase, mechanical alloying, spark plasma sintering

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Authors: Han Run-Sheng, Li Wen-Yao, Wang Feng, Liu Fei, Qiu Wen-Long, Lei Li

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Accurately positioning detection of concealed deposits or ore-bodies is one of the difficult problems in mineral exploration field. Theory calculation and exploration practices for tunnel gravity indicate that 3D high-precision Tunnel Gravity Exploration Method (TGEM) can find concealed high-density three-dimensional ore-bodies in the depth. The ore-finding breakthroughs at the depth of the Zhaotong Maoping carbonate-hosted Zn–Pb–(Ag–Ge) deposit in Northeastern Yunnan have proved that the exploration method in combination with MEAHFZ method is effective to detect concealed high-density ore-bodies. TGEM may overcome anomalous ambiguity of other geophysical methods for 3D positioning of concealed ore-bodies.

Keywords: 3D tunnel gravity exploration method, concealed high-density Ore-bodies, Zn–Pb–(Ag–Ge) deposit, Zaotong mapping, Northeastern Yunnan

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Authors: J.-Y. Lee, H.-S. Lim, S.-E. Kim

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Recently, the use of high-strength materials is increasing as the construction of large structures and high-rise structures increases. This paper presents an analysis of the shear behavior of prestressed concrete members with various types of materials by simulating a finite element (FE) analysis. The analytical results indicated that the shear strength and shear failure mode were strongly influenced by not only the shear reinforcement ratio but also the yield strength of shear reinforcement and the compressive strength of concrete. Though the yield strength of shear reinforcement increased the shear strength of prestressed concrete members, there was a limit to the increase in strength because of the change of shear failure modes. According to the results of FE analysis on various parameters, the maximum yield strength of the steel stirrup that can be applied to prestressed concrete members was about 860 MPa.

Keywords: prestressed concrete members, high strength reinforcing bars, high strength concrete, shear behavior

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Authors: Loretta Baryeh

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Unprecedented disruptions to world economies unfolded consequently to the pandemic that hit the globe in 2020. The severe sickness with no cure at the time led to record deaths, and this affected everyday life for most people, stifling production, hospitality, entertainment, and most sectors of the economy. This paper was an extension of Baryeh 2021, that studied the pandemic effect on economic growth and if that was exacerbated by corruption. It was found that there was a positively high significant correlation between countries that reported high cases of the virus and countries that reported more deaths due to the virus. Furthermore, it was shown that countries with high COVID-19 cases were highly corrupt. Additionally, there was a negative association between high COVID-19 cases and economic development.

Keywords: COVID-19, corruption, economic, performance

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Authors: Bing-Wen Chen, Alvin W. Y. Su, Yu-Lin Wang

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Electromyography (EMG) is one of the important indicators during exercise, as it is closely related to the level of muscle activations. This work quantifies the muscle conditions of the lower limbs in a constant workload exercise. Surface EMG signals of the vastus laterals (VL), vastus medialis (VM), rectus femoris (RF), gastrocnemius medianus (GM), gastrocnemius lateral (GL) and Soleus (SOL) were recorded from fourteen healthy males. The EMG signals were segmented in two phases: activation segment (AS) and relaxation segment (RS). Period entropy (PE), peak count (PC), zero crossing (ZC), wave length (WL), mean power frequency (MPF), median frequency (MDF) and root mean square (RMS) are calculated to provide the quantitative information of the measured EMG segments. The outcomes reveal that the PE, PC, ZC and RMS have significantly changed (p<.001); WL presents moderately changed (p<.01); MPF and MDF show no changed (p>.05) during exercise. The results also suggest that the RS is also preferred for performance evaluation, while the results of the extracted features in AS are usually affected directly by the amplitudes. It is further found that the VL exhibits the most significant changes within six muscles during pedaling exercise. The proposed work could be applied to quantify the stamina analysis and to predict the instant muscle status in athletes.

Keywords: electromyographic feature extraction, muscle status, pedaling exercise, relaxation segment

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Authors: Sul-Ah Ahn, Youngim Jung

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The research activities of the computational scientists using high-performance computing are analyzed using bibliometric approaches. This study aims at providing computational scientists using high-performance computing and relevant policy planners with useful bibliometric results for an assessment of research activities. In order to achieve this purpose, we carried out a co-authorship network analysis of journal articles to assess the research activities of computational scientists using high-performance computing as a case study. For this study, we used journal articles of the Scopus database from Elsevier covering the time period of 2006-2015. We extracted the author rank in the computational science field using high-performance computing by the number of papers published during ten years from 2006. Finally, we drew the co-authorship network for 50 top-authors and their coauthors and described some features of the co-authorship network in relation to the author rank. Suggestions for further studies are discussed.

Keywords: co-authorship network analysis, computational science, high performance computing, research activity

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Authors: Mounir Gaci, Salim Meziani, Atmane Fouathia

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The purpose of the present paper is to model the behavior of metal alloy, type TRIP steel (Transformation Induced Plasticity), during solid/solid phase transition. A two-dimensional micromechanical model is implemented in finite element software (ZEBULON) to simulate the martensitic transformation in Fe-Ni-C steel grain under mechanical tensile stress of 250 MPa. The effects of non-uniform grain boundary and the criterion of mechanical shear load on the transformation and on the TRIP value during martensitic transformation are studied. The suggested mechanical criterion is favourable to the influence of the shear phenomenon on the progression of the martensitic transformation (Magee’s mechanism). The obtained results are in satisfactory agreement with experimental ones and show the influence of the grain boundary shape and the chosen mechanical criterion (SMF) on the transformation parameters.

Keywords: martensitic transformation, non-uniform Grain Boundary, TRIP, shear Mechanical force (SMF)

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Authors: Shady Sayed, Samer Wagdy, Ahmed Badawy, Moutaz M. Hegaze

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A symmetrical single mass resonant gyroscope is discussed in this paper. The symmetrical design allows matched resonant frequencies for driving and sensing vibration modes, which leads to amplifying the sensitivity of the gyroscope by the mechanical quality factor of the sense mode. It also achieves decoupled vibration modes for getting a low zero-rate output shift and more stable operation environment. A new suspension beams design is developed to get a symmetrical gyroscope with matched and decoupled modes at the same time. Finite element simulations are performed using ANSYS software package to verify the theoretical calculations. The gyroscope is fabricated from aluminum alloy 2024 substrate, the measured drive and sense resonant frequencies of the fabricated model are matched and equal 81.4 Hz with 5.7% error from the simulation results.

Keywords: decoupled mode shapes, resonant sensor, symmetrical gyroscope, finite element simulation

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Authors: Sahil Kumar, Surinder Pal, Rahul Kapoor

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This paper is focused on to define the basic difference between hot and cold chamber high pressure die casting process which is not fully defined in a research before paper which we have studied. The pressure die casting is basically defined into two types (1) Hot chamber Die Casting (2) Cold chamber Die Casting. Cold chamber die casting is used for casting alloys that require high pressure and have a high melting temperature, such as brass, aluminum, magnesium, copper based alloys and other high melting point nonferrous alloys. Hot chamber die casting is suitable for casting zinc, tin, lead, and low melting point alloys. In hot chamber die casting machine, the molten metal is an integral pan of the machine. It mainly consists of hot chamber and gooseneck type metal container made of cast iron. This machine is mainly used for low melting alloys and alloys of metals like zinc, lead etc. Metals and alloys having a high melting point and those which are having an affinity for iron cannot be cast by this machine, which could otherwise attack the shot sleeve and damage the machine.

Keywords: hot chamber die casting, cold chamber die casting, metals and alloys, casting technology

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Authors: Atasi Dan, Kamanio Chattopadhyay, Bikramjit Basu

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A cost-effective titanium diboride (TiB2) paint coating has been developed on stainless steel substrate using commercially available polyvinylpyrrolidone as a binder by convenient dip-coating technique. The emittance of the coating has been explored by tailoring various process parameters to obtain highest thermal radiation. The optimized coating has achieved a high thermal emittance of 0.85. In addition, the coating exhibited an excellent thermal stability while heat-treated at 500 °C in air. Along with the emittance, the structural and physical properties of the As-deposited and heat-treated coatings have been investigated systematically. The high temperature annealing has not affected the emittance, chemical composition and morphology of the coating significantly. Hence, the fabricated paint coating is expected to open up new possibilities for using it as a low-cost, thermally stable emitter in high temperature applications.

Keywords: titanium diboride, emittance, paint coating, thermal stability

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Authors: Gerald Abdesaken, Thomas O. Miller

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This paper analyzes the performance of gold as a safe-haven investment. Assuming high market volatility as an impetus to seek a safe haven in gold, the return of gold relative to the stock market, as measured by the S&P 500, is tracked. Using the Chicago Board Options Exchange (CBOE) volatility index (VIX) as a measure of stock market volatility, various criteria are established for when an investor would seek a safe haven to avoid high levels of risk. The results show that in a vast majority of cases, the S&P 500 outperforms gold during these periods of high volatility and suggests investors who seek safe haven are underperforming the market.

Keywords: gold, portfolio management, safe haven, VIX

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Authors: S. Ghorbani, N. I. Polushin

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The machinability of workpieces (AISI 1045 Steel, AA2024 aluminum alloy, A48-class30 gray cast iron) in turning operation has been carried out using different types of cutting tool (conventional, cutting tool with holes in toolholder and cutting tool filled up with composite material) under dry conditions on a turning machine at different stages of spindle speed (630-1000 rpm), feed rate (0.05-0.075 mm/rev), depth of cut (0.05-0.15 mm) and tool overhang (41-65 mm). Experimentation was performed as per Taguchi’s orthogonal array. To evaluate the relative importance of factors affecting surface roughness the single decision tree (SDT), Decision tree forest (DTF) and Group method of data handling (GMDH) were applied.

Keywords: decision tree forest, GMDH, surface roughness, Taguchi method, turning process

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Authors: Yue-Tzu Yang, Hsiang-Wen Tang, Jian-Zhang Yin, Chao-Han Wu

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Three-dimensional incompressible turbulent fluid flow and heat transfer of pin fin heat sinks using air as a cooling fluid are numerically studied in this study. Two different kinds of pin fins are compared in the thermal performance, including circular and square cross sections, both are in-line and staggered arrangements. The turbulent governing equations are solved using a control-volume- based finite-difference method. Subsequently, numerical computations are performed with the realizable k - ԑ turbulence for the parameters studied, the fin height H, fin diameter D, and Reynolds number (Re) in the range of 7 ≤ H ≤ 10, 0.75 ≤ D ≤ 2, 2000 ≤ Re ≤ 126000 respectively. The numerical results are validated with available experimental data in the literature and good agreement has been found. It indicates that circular pin fins are streamlined in comparing with the square pin fins, the pressure drop is small than that of square pin fins, and heat transfer is not as good as the square pin fins. The thermal performance of the staggered pin fins is better than that of in-line pin fins because the staggered arrangements produce large disturbance. Both in-line and staggered arrangements show the same behavior for thermal resistance, pressure drop, and the entropy generation.

Keywords: pin-fin, heat sinks, simulations, turbulent flow

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Authors: Mohammad Lutfur Rahman

Abstract:

School students of Dhaka are in extreme risk of natural disasters. However, the study on assessment of the real scenario of high school students about perceptions of earthquake is very little. The purpose of this cross-sectional study is to assess the seismic risk perception and preparedness levels about earthquake among high school students in Shavar, Dhaka. A questionnaire was developed, and data collection was done about a group of high school students in seven classrooms. The author uses a method of surveying high school students to identify and describe the factors that influence their knowledge and perceptions about earthquake. This study examines gender and grade differences in perceived risk and communication behavior in response to the earthquake. Female students’ preparation, participation, and communication with family are more frequent than that of male students. Female students have been found to be more likely to learn about a disaster than male students. Higher grade students have more awareness but less preparedness about earthquake than that of the younger one. This research concludes that irrespective of grades, high school students are vulnerable to earthquake due to the lack of a seismic education program.

Keywords: awareness, earthquake, risk perception, seismic

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Authors: Sebastian Oportus, Fabrizio Alvarez

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3D digitalization of heritage objects is widely used nowadays. However, the most advanced 3D scanners in the market that capture topology and texture at the same time, and are specifically made for this purpose, don’t deliver the accuracy that is needed for scientific research. In the last three years, we have developed a method that combines the use of Metrologic grade laser scans, that allows us to work with a high accuracy topology up to 15 times more precise and combine this mesh with a texture obtained from high definition photogrammetry with up to 100 times more pixel concentrations. The result is an accurate digitalization that promotes heritage preservation, scientific study, high detail reproduction, and digital restoration, among others. In Chile, we have already performed 478 digitalizations of high-value heritage pieces and compared the results with up to five different digitalization methods; the results obtained show a considerable better dimensional accuracy and texture resolution. We know the importance of high precision and resolution for academics and museology; that’s why our proposal is to set a worldwide standard using this open source methodology.

Keywords: 3D digitalization, digital heritage, heritage preservation, digital restauration, heritage reproduction

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Authors: Mohamed Zakaulla, A. R. Anwar Khan

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Al6061 alloy base matrix, reinforced with particles of silicon carbide (10 wt %) and Graphite powder (1wt%), known as hybrid composites have been fabricated by liquid metallurgy route (stir casting technique) and optimized at different parameters like applied load, sliding speed and sliding distance by taguchi method. A plan of experiment generated through taguchi technique was used to perform experiments based on L27 orthogonal array. The developed ANOVA and regression equations are used to find the optimum coefficient of friction and wear under the influence of applied load, sliding speed and sliding distance. On the basis of “smaller the best” the dry sliding wear resistance was analysed and finally confirmation tests were carried out to verify the experimental results.

Keywords: analysis of variance, dry sliding wear, hybrid composite, orthogonal array, Taguchi technique

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Authors: N. Hatraf, L. Merabti, Z. Neffah, W. Taane

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The excessive consumption of fossil energies (electrical energy) during summer caused by the technological development involves more and more climate warming. In order to reduce the worst impact of gas emissions produced from classical air conditioning, heat driven solar absorption chiller is pretty promising; it consists on using solar as motive energy which is clean and environmentally friendly to provide cold. Solar absorption machine is composed by four components using Lithium Bromide /water as a refrigerating couple. LiBr- water is the most promising in chiller applications due to high safety, high volatility ratio, high affinity, high stability and its high latent heat. The lithium bromide solution is constitute by the salt lithium bromide which absorbs water under certain conditions of pressure and temperature however if the concentration of the solution is high in the absorption chillers; which exceed 70%, the solution will crystallize. The main aim of this article is to study the phenomena of the crystallization and to evaluate how the dependence between the electric conductivity and the concentration which should be controlled.

Keywords: absorption, crystallization, experimental results, lithium bromide solution

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Authors: Mustafa Jahanara

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The purpose of the research was to study the relationship between self-esteem, self-Efficacy with psychological distress in the high school teachers. A total of 245 teachers (92 male and 153 female) in the high school of Kabul and Mazar-e-Sharif from Afghanistan completed inventories General Self-Efficacy, Rosenberg Self-Esteem Scale, and General Health Questionnaire-12 and that assessed their Self-Efficacy, self-esteem with psychological distress. Correlational analysis showed that self-efficacy and self-esteem were significantly and positively correlated with each other. The results of the study indicated that psychological distress is negatively related to self-esteem, and self-efficacy. However, the findings suggest that self-esteem, and self-efficacy could influence on mental health.

Keywords: high school teachers, self-esteem, self-efficacy, psychological distress

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Authors: S. Ghorbani, N. I. Polushin

Abstract:

In this study, an approach to identify factors affecting on surface roughness in a machining process is presented. This study is based on 81 data about surface roughness over a wide range of cutting tools (conventional, cutting tool with holes, cutting tool with composite material), workpiece materials (AISI 1045 Steel, AA2024 aluminum alloy, A48-class30 gray cast iron), spindle speed (630-1000 rpm), feed rate (0.05-0.075 mm/rev), depth of cut (0.05-0.15 mm) and tool overhang (41-65 mm). A single decision tree (SDT) analysis was done to identify factors for predicting a model of surface roughness, and the CART algorithm was employed for building and evaluating regression tree. Results show that a single decision tree is better than traditional regression models with higher rate and forecast accuracy and strong value.

Keywords: cutting condition, surface roughness, decision tree, CART algorithm

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