Search results for: boundary layer instability

Authors: Puneet Chawla, Balwinder Singh

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Recently, increased attention has been devoted to the voltage instability phenomenon in power systems. Many techniques have been proposed in the literature for evaluating and predicting voltage stability using steady state analysis methods. In this paper, P-V and Q-V curves have been generated for a 57 bus Patiala Rajpura circle of India. The power-flow program is developed in MATLAB using Newton-Raphson method. Using Q-V curves, the weakest bus of the power system and the maximum reactive power change permissible on that bus is calculated. STATCOMs are placed on the weakest bus to improve the voltage and hence voltage stability and also the power transmission capability of the line.

Keywords: voltage stability, reactive power, power flow, weakest bus, STATCOM

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Authors: A. Khosravi, S. Ghadirian, J. S. McCartney

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Evaluation of the seismic-induced settlement of an unsaturated soil layer depends on several variables, among which the small strain shear modulus, Gmax, and soil’s state of stress have been demonstrated to be of particular significance. Recent interpretation of trends in Gmax revealed considerable effects of the degree of saturation and hydraulic hysteresis on the shear stiffness of soils in unsaturated states. Accordingly, the soil layer is expected to experience different settlement behaviors depending on the soil saturation and seasonal weathering conditions. In this study, a semi-empirical formulation was adapted to extend an existing Gmax model to infer hysteretic effects along different paths of the SWRC including scanning curves. The suitability of the proposed approach is validated against experimental results from a suction-controlled resonant column test and from data reported in literature. The model was observed to follow the experimental data along different paths of the SWRC, and showed a slight hysteresis in shear modulus along the scanning curves.

Keywords: hydraulic hysteresis, scanning path, small strain shear modulus, unsaturated soil

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Authors: Wei Jun, Liao Hualin, Wang Huajian, Chen Jingkai, Liang Hongjun, Liu Chuanfu

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Kuqa Piedmont is rich in oil and gas resources and has great development potential in Tarim Basin, China. However, there is a huge thick gravel layer developed with high content, wide distribution and variation in size of gravel, leading to the condition of strong heterogeneity. So that, the drill string is in a state of severe vibration and the drill bit is worn seriously while drilling, which greatly reduces the rock-breaking efficiency, and there is a complex load state of impact and three-dimensional in-situ stress acting on the rock in the bottom hole. The dynamic mechanical properties and the influencing factors of conglomerate, the main component of gravel layer, are the basis of engineering design and efficient rock breaking method and theoretical research. Limited by the previously experimental technique, there are few works published yet about conglomerate, especially rare in dynamic load. Based on this, a kind of 3D SHPB system, three-dimensional prestress, can be applied to simulate the in-situ stress characteristics, is adopted for the dynamic test of the conglomerate. The results show that the dynamic strength is higher than its static strength obviously, and while the three-dimensional prestress is 0 and the loading strain rate is 81.25~228.42 s-1, the true triaxial equivalent strength is 167.17~199.87 MPa, and the strong growth factor of dynamic and static is 1.61~1.92. And the higher the impact velocity, the greater the loading strain rate, the higher the dynamic strength and the greater the failure strain, which all increase linearly. There is a critical prestress in the impact direction and its vertical direction. In the impact direction, while the prestress is less than the critical one, the dynamic strength and the loading strain rate increase linearly; otherwise, the strength decreases slightly and the strain rate decreases rapidly. In the vertical direction of impact load, the strength increases and the strain rate decreases linearly before the critical prestress, after that, oppositely. The dynamic strength of the conglomerate can be reduced properly by reducing the amplitude of impact load so that the service life of rock-breaking tools can be prolonged while drilling in the stratum rich in gravel. The research has important reference significance for the speed-increasing technology and theoretical research while drilling in gravel layer.

Keywords: huge thick gravel layer, conglomerate, 3D SHPB, dynamic strength, the deformation characteristics, prestress

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Authors: Ritesh Kumar, Gitanjali Chhetri, Mandira Bhatia, Mohit Mishra, Abhijith Bailur, Abhinav

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The prevalence of the internet and technology in our day to day lives is creating more security issues than ever. The need for protecting and providing a secure access to private and business data has led to the development of many security systems. One of the potential solutions is to employ the bio-metric authentication technique. In this paper we present an innovative biometric authentication method that utilizes a person’s EEG signal, which is acquired in response to an auditory stimulus,and transferred wirelessly to a computer that has the necessary ANN algorithm-Multi layer perceptrol neural network because of is its ability to differentiate between information which is not linearly separable.In order to determine the weights of the hidden layer we use Gaussian random weight initialization. MLP utilizes a supervised learning technique called Back propagation for training the network. The complex algorithm used for EEG classification reduces the chances of intrusion into the protected public or private data.

Keywords: EEG signal, auditory evoked potential, biometrics, multilayer perceptron neural network, back propagation rule, Gaussian random weight initialization

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Authors: A. Chellil, A. Nour, S. Lecheb, H.Mechakra, A. Bouderba, H. Kebir

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In this paper, the numerical study for the instability of a composite rotor is presented, under dynamic loading response in the harmonic analysis condition. The analysis of the stress which operates the rotor is done. Calculations of different energies and the virtual work of the aerodynamic loads from the rotor is developed. The use of the composite material for the rotor, offers a good Stability. Numerical calculations on the model develop of three dimensions prove that the damage effect has a negative effect on the stability of the rotor. The study of the composite rotor in transient system allowed to determine the vibratory responses due to various excitations.

Keywords: rotor, composite, damage, finite element, numerical

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Authors: Alicia Muñoz, Pedro Oyola, Cristian Henriquez

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Pollution in Santiago de Chile has a spatial variability due to different factors, including meteorological parameters and emission sources. Socioenvironmental aspects are also significant for pollution in the canopy layer since it influences the type of edification, vegetal mass proportion and other environmental conditions. This study analyzes spatially urban pollution in Santiago, specifically, from the bike path perspective. Bike paths are located in high traffic zones, as consequence, users are constantly exposed to urban pollution. Measurements were made at the higher polluted hour, three days a week, including three transit regimes, on the most polluted month of the year. The environmental parameters are fine particulate matter (Model 8520, DustTrak Aerosol Monitor, TSI), temperature and relative humidity; it was also considerate urban parameters as sky view factor and vegetal mass. Identification of an environmental injustice will be achieved with a spatial modeling, including all urban factors and environmental mediations with an economic index of population.

Keywords: canopy layer, environmental injustice, spatial modeling, urban pollution

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Authors: Radka Králová, Libor Kvítek, Václav Ranc, Aleš Panáček, Radek Zbořil

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Surface–Enhanced Raman Scattering (SERS) is an optical spectroscopic technique with very good potential for sensitive detection of substances. In this research, active substrates with high enhancement were provided. Novel silver particles (nanostructures) with high roughened, flower–like morphology were prepared by reduction of cation complex [Ag(NH3)2]+ in presence of sodium borohydride as reducing agent and stabilized polyacrylic acid. The products were characterized by UV/VIS absorption spectrophotometry. Special shapes of silver particles were determined by scanning electron microscopy (SEM) and transmission electron spectroscopy (TEM). Dispersions of this particle were put on fixed substrate to producing suitable layer for SERS. Adenine was applied as basic substance whose effect of enhancement on the layer of silver nanostructures was studied. By comparison with our work, the important influence of stabilizers, polyacrylic acid with various molecular weight and concentration, on the transfer of particles and formation of new structure was confirmed.

Keywords: metals, nanostructures, chemical reduction, Raman spectroscopy, optical properties

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Authors: Rasha Sharaf, Nehal Sharaf

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Pulpectomy of primary teeth aims to remove the necrotic pulp tissue from the infected root canal and clean the root canal walls from any remnant of pulp tissue. Different irrigant activation systems have been recently used, and one of these devices is the Eddy which helps in removal of smear layer and improves the intimate contact between the filling material and the root canal wall. Aim: To evaluate the efficacy of Eddy in cleanliness of the root canal during pulpectomy of primary teeth. Materials and methods: 45 freshly extracted primary anterior teeth were divided into 3 equal groups, in the 1st group sodium hypochlorite only was used during pulpectomy, in the 2nd group irrigation using sodium hypochlorite with file agitation was performed and in the 3rd group sodium hypochlorite was used with Eddy for irrigant activation. All samples were sectioned longitudinally and scanned using scanning electron microscope to evaluate the cleanliness of the root canals. Results: It was found that Eddy showed high efficacy in removal of smear layer during pulpectomy of primary teeth.

Keywords: Eddy, irrigant activation, irrigation, pulpectomy

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Authors: Foyewa R. A.

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This paper examined the role of English language and the quest for a national language in Nigeria. Various hindrances to the choice of a national language in Nigeria were observed. These include: The dominant role of English language, political instability and multilingual nature of the country. The writer suggested that ’’the three big’’ that is, Hausa, Igbo and Yoruba should be selected as the national languages. It was also suggested that a credit pass in a student’s mother tongue and one of “the three big” (Hausa, Igbo and Yoruba) should constitute the prerequisite for admission into Nigerian higher institutions.

Keywords: English, roles of English, national language, Nigerian languages, Hausa, Igbo, Yoruba

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Authors: Alemayehu Mengesha, Solomon Belay

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We determine the general dispersion relation for the propagation of magnetohydrodynamic (MHD) waves in an astrophysical plasma by considering the effect of viscosity with an anisotropic pressure tensor. Basic MHD equations have been derived and linearized by the method of perturbation to develop the general form of the dispersion relation equation. Our result indicates that an astrophysical plasma with an anisotropic pressure tensor is stable in the presence of viscosity and a strong magnetic field at considerable wavelength. Currently, we are doing the numerical analysis of this work.

Keywords: astrophysical, magnetic field, instability, MHD, wavelength, viscosity

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Authors: Hanene Akrout, Ines Elaissaoui, Sabrina Grassini, Daniele Fulginiti, Latifa Bousselmi

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The main objective of this work is to investigate the efficiency of depollution power related to PbO₂ layer deposited onto a stainless steel (SS) substrate with SiOx as interlayer. The elaborated electrode was used as anode for anodic oxidation of wastewater containing Amaranth dye, as recalcitrant organic pollutant model. SiOx interlayer was performed using Plasma Enhanced Chemical Vapor Deposition ‘PECVD’ in plasma fed with argon, oxygen, and tetraethoxysilane (TEOS, Si precursor) in different ratios, onto the SS substrate. PbO₂ layer was produced by pulsed electrodeposition on SS/SiOx. The morphological of different surfaces are depicted with Field Emission Scanning Electron Microscope (FESEM) and the composition of the lead oxide layer was investigated by X-Ray Diffractometry (XRD). The results showed that the SiOx interlayer with more rich oxygen content improved better the nucleation of β-PbO₂ form. Electrochemical Impedance Spectroscopy (EIS) measurements undertaken on different interfaces (at optimized conditions) revealed a decrease of Rfilm while CPE film increases for SiOx interlayer, characterized by a more inorganic nature and deposited in a plasma fed by higher O2-to-TEOS ratios. Quantitative determinations of the Amaranth dye degradation rate were performed in terms of colour and COD removals, reaching a 95% and an 80% respectively removal at pH = 2 in 300 min. Results proved the improvement of the degradation wastewater containing the amaranth dye. During the electrolysis, the Amaranth dye solution was sampled at 30 min intervals and analyzed by ‘High-performance Liquid Chromatography’ HPLC. The gradual degradation of the Amaranth dye confirmed by the decrease in UV absorption using the SS/SiOx(20:20:1)/PbO₂ anode, the reaction exhibited an apparent first-order kinetic for electrolysis time of 5 hours, with an initial rate constant of about 0.02 min⁻¹.

Keywords: electrochemical treatment, PbO₂ anodes, COD removal, plasma

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Authors: Hua Li, Hongwu Deng

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The turbine blade's leading edge is usually cooled by jet impingement cooling technology due to the heaviest heat load. For a rotating turbine blade, however, the channel orientation (β, the angle between the jet direction and the rotating plane) could play an important role in influencing the flow field and heat transfer. Therefore, in this work, the effects of channel orientation (from 90° to 180°) on heat transfer in a jet impingement cooling channel are experimentally investigated. Furthermore, the investigations are conducted under an isothermal boundary condition. Both the jet-to-target surface distance and jet-to-jet spacing are three times the jet hole diameter. The jet Reynolds number is 5,000, and the maximum jet rotation number reaches 0.24. The results show that the rotation-induced variations of heat transfer are different in each channel orientation. In the cases of 90°≤β≤135°, a vortex generated in the low-radius region of the supply channel changes the mass-flowrate distribution in each jet hole. Therefore, the heat transfer in the low-radius region decreases with the rotation number, whereas the heat transfer in the high-radius region increases, indicating that a larger temperature gradient in the radial direction could appear in the turbine blade's leading edge. When 135°<β≤180°; however, the heat transfer of the entire stagnant zone decreases with the rotation number. The rotation-induced jet deflection is the primary factor that weakens the heat transfer, and jets cannot reach the target surface at high rotation numbers. For the downstream regions, however, the heat transfer is enhanced by 50%-80% in every channel orientation because the dead zone is broken by the rotation-induced secondary flow in the impingement channel.

Keywords: heat transfer, jet impingement cooling, channel orientation, high rotation number, isothermal boundary

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Authors: Amaechi O. Azi, Uche D. Aluge, Lim H. San, Godwin A. Agbo

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This paper is centered on the investigation of mineral deposits in selected locations in Oshiri province in Ebonyi State. Mineral deposits contribute immensely to the economic growth of a society. In researching lead and zinc oxide-bearing sites at Oshiri, geological and geophysical research technique was employed. Petrozenith, Earth Resistivity Meter, and Schlumberger setup were selected to examine the electrical characteristics of the subsurface. To determine the apparent resistivity of the subsurface, five soundings were taken, and the field data were processed using WinResist software. The mudstone, lead-shale, shale-granite, and lateritic topsoil were the four geoelectric strata that were found. The third layer, which corresponds to the shale-lead lithology, has a resistivity value between 211.9 m to 807.7 m at a depth of 25 m. Due to its resistivity levels and geological trend, this layer makes an excellent signature for lead-zinc occurrence. This zone is expected to house deposits of lead and zinc oxide in commercial quantity.

Keywords: Schlumberger, current, resistivity, lithology

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Authors: Vaso K. Kapnopoulou, Piero Caridis

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The fatigue of ship structural details is of major concern in the maritime industry as it can generate fracture issues that may compromise structural integrity. In the present study, a fatigue analysis of the lower hopper knuckle connection of a bulk carrier was conducted using the Finite Element Method by means of ABAQUS/CAE software. The fatigue life was calculated using Miner’s Rule and the long-term distribution of stress range by the use of the two-parameter Weibull distribution. The cumulative damage ratio was estimated using the fatigue damage resulting from the stress range occurring at each load condition. For this purpose, a cargo hold model was first generated, which extends over the length of two holds (the mid-hold and half of each of the adjacent holds) and transversely over the full breadth of the hull girder. Following that, a submodel of the area of interest was extracted in order to calculate the hot spot stress of the connection and to estimate the fatigue life of the structural detail. Two hot spot locations were identified; one at the top layer of the inner bottom plate and one at the top layer of the hopper plate. The IACS Common Structural Rules (CSR) require that specific dynamic load cases for each loading condition are assessed. Following this, the dynamic load case that causes the highest stress range at each loading condition should be used in the fatigue analysis for the calculation of the cumulative fatigue damage ratio. Each load case has a different effect on ship hull response. Of main concern, when assessing the fatigue strength of the lower hopper knuckle connection, was the determination of the maximum, i.e. the critical value of the stress range, which acts in a direction normal to the weld toe line. This acts in the transverse direction, that is, perpendicularly to the ship's centerline axis. The load cases were explored both theoretically and numerically in order to establish the one that causes the highest damage to the location examined. The most severe one was identified to be the load case induced by beam sea condition where the encountered wave comes from the starboard. At the level of the cargo hold model, the model was assumed to be simply supported at its ends. A coarse mesh was generated in order to represent the overall stiffness of the structure. The elements employed were quadrilateral shell elements, each having four integration points. A linear elastic analysis was performed because linear elastic material behavior can be presumed, since only localized yielding is allowed by most design codes. At the submodel level, the displacements of the analysis of the cargo hold model to the outer region nodes of the submodel acted as boundary conditions and applied loading for the submodel. In order to calculate the hot spot stress at the hot spot locations, a very fine mesh zone was generated and used. The fatigue life of the detail was found to be 16.4 years which is lower than the design fatigue life of the structure (25 years), making this location vulnerable to fatigue fracture issues. Moreover, the loading conditions that induce the most damage to the location were found to be the various ballasting conditions.

Keywords: dynamic load cases, finite element method, high cycle fatigue, lower hopper knuckle

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Authors: Debamitra Chakravorty, Pratap K. Parida

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Cold-adapted proteases enhance wash performance in low-temperature laundry resulting in a reduction in energy consumption and wear of textiles and are also used in the dehairing process in leather industries. Unfortunately, the possible drawbacks of using cold-adapted proteases are their instability at higher temperatures. Therefore, proteases with broad temperature stability are required. Unfortunately, wild-type cold-adapted proteases exhibit instability at higher temperatures and thus have low shelf lives. Therefore, attempts to engineer cold-adapted proteases by protein engineering were made previously by directed evolution and random mutagenesis. The lacuna is the time, capital, and labour involved to obtain these variants are very demanding and challenging. Therefore, rational engineering for cold stability without compromising an enzyme's optimum pH and temperature for activity is the current requirement. In this work, mutations were rationally designed with the aid of high throughput computational methodology of network analysis, evolutionary conservation scores, and molecular dynamics simulations for Savinase from Bacillus lentus with the intention of rendering the mutants cold stable without affecting their temperature and pH optimum for activity. Further, an attempt was made to incorporate a mutation in the most stable mutant rationally obtained by this method to introduce oxidative stability in the mutant. Such enzymes are desired in detergents with bleaching agents. In silico analysis by performing 300 ns molecular dynamics simulations at 5 different temperatures revealed that these three mutants were found to be better in cold stability compared to the wild type Savinase from Bacillus lentus. Conclusively, this work shows that cold adaptation without losing optimum temperature and pH stability and additionally stability from oxidative damage can be rationally designed by in silico enzyme engineering. The key findings of this work were first, the in silico data of H5 (cold stable savinase) used as a control in this work, corroborated with its reported wet lab temperature stability data. Secondly, three cold stable mutants of Savinase from Bacillus lentus were rationally identified. Lastly, a mutation which will stabilize savinase against oxidative damage was additionally identified.

Keywords: cold stability, molecular dynamics simulations, protein engineering, rational design

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Authors: Meftah O. Bashir, Fatma A. Karkory

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Rapid prototyping is a new group of manufacturing processes, which allows fabrication of physical of any complexity using a layer by layer deposition technique directly from a computer system. The rapid prototyping process greatly reduces the time and cost necessary to bring a new product to market. The prototypes made by these systems are used in a range of industrial application including design evaluation, verification, testing, and as patterns for casting processes. These processes employ a variety of materials and mechanisms to build up the layers to build the part. The present work was to build a FDM prototyping machine that could control the X-Y motion and material deposition, to generate two-dimensional and three-dimensional complex shapes. This study focused on the deposition of wax material. This work was to find out the properties of the wax materials used in this work in order to enable better control of the FDM process. This study will look at the integration of a computer controlled electro-mechanical system with the traditional FDM additive prototyping process. The characteristics of the wax were also analysed in order to optimize the model production process. These included wax phase change temperature, wax viscosity and wax droplet shape during processing.

Keywords: rapid prototyping, wax, manufacturing processes, shape

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Authors: Yuchen Yang, Zhenming Wang, Jun Zhu, Ning Zhao

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An easy-to-implement and robust finite volume multi-resolution Weighted Essentially Non-Oscillatory (WENO) scheme is proposed on adaptive cartesian grids in this paper. Such a multi-resolution WENO scheme is combined with the ghost cell immersed boundary method (IBM) and wall-function technique to solve Navier-Stokes equations. Unlike the k-exact finite volume WENO schemes which involve large amounts of extra storage, repeatedly solving the matrix generated in a least-square method or the process of calculating optimal linear weights on adaptive cartesian grids, the present methodology only adds very small overhead and can be easily implemented in existing edge-based computational fluid dynamics (CFD) codes with minor modifications. Also, the linear weights of this adaptive finite volume multi-resolution WENO scheme can be any positive numbers on condition that their sum is one. It is a way of bypassing the calculation of the optimal linear weights and such a multi-resolution WENO scheme avoids dealing with the negative linear weights on adaptive cartesian grids. Some benchmark viscous problems are numerical solved to show the efficiency and good performance of this adaptive multi-resolution WENO scheme. Compared with a second-order edge-based method, the presented method can be implemented into an adaptive cartesian grid with slight modification for big Reynolds number problems.

Keywords: adaptive mesh refinement method, finite volume multi-resolution WENO scheme, immersed boundary method, wall-function technique.

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Authors: Mayoorika Shukla, Pramila Jakhar, Tejendra Dixit, I. A. Palani, Vipul Singh

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Biosensors are analytical devices with wide range of applications in biological, chemical, environmental and clinical analysis. It comprises of bio-recognition layer which has biomolecules (enzymes, antibodies, DNA, etc.) immobilized over it for detection of analyte and transducer which converts the biological signal into the electrical signal. The performance of biosensor primarily the depends on the bio-recognition layer and therefore it has to be chosen wisely. In this regard, nanostructures of metal oxides such as ZnO, SnO2, V2O5, and TiO2, etc. have been explored extensively as bio-recognition layer. Recently, ZnO has the attracted attention of researchers due to its unique properties like high iso-electric point, biocompatibility, stability, high electron mobility and high electron binding energy, etc. Although there have been many reports on usage of ZnO as bio-recognition layer but to the authors’ knowledge, none has ever observed correlation between optical properties like defect suppression and biosensing capability of the sensor. Here, ZnO nanorods (ZNR) have been synthesized by a low cost, simple and low-temperature hydrothermal growth process, over Platinum (Pt) coated glass substrate. The ZNR have been synthesized in two steps viz. initially a seed layer was coated over substrate (Pt coated glass) followed by immersion of it into nutrient solution of Zinc nitrate and Hexamethylenetetramine (HMTA) with in situ addition of KMnO4. The addition of KMnO4 was observed to have a profound effect over the growth rate anisotropy of ZnO nanostructures. Clustered and powdery growth of ZnO was observed without addition of KMnO4, although by addition of it during the growth, uniform and crystalline ZNR were found to be grown over the substrate. Moreover, the same has resulted in suppression of defects as observed by Normalized Photoluminescence (PL) spectra since KMnO4 is a strong oxidizing agent which provides an oxygen rich growth environment. Further, to explore the correlation between defect suppression and biosensing capability of the ZNR Glucose oxidase (Gox) was immobilized over it, using physical adsorption technique followed by drop casting of nafion. Here the main objective of the work was to analyze effect of defect suppression over biosensing capability, and therefore Gox has been chosen as model enzyme, and electrochemical amperometric glucose detection was performed. The incorporation of KMnO4 during growth has resulted in variation of optical and charge transfer properties of ZNR which in turn were observed to have deep impact on biosensor figure of merits. The sensitivity of biosensor was found to increase by 12-18 times, due to variations introduced by addition of KMnO4 during growth. The amperometric detection of glucose in continuously stirred buffer solution was performed. Interestingly, defect suppression has been observed to contribute towards the improvement of biosensor performance. The detailed mechanism of growth of ZNR along with the overall influence of defect suppression on the sensing capabilities of the resulting enzymatic electrochemical biosensor and different figure of merits of the biosensor (Glass/Pt/ZNR/Gox/Nafion) will be discussed during the conference.

Keywords: biosensors, defects, KMnO4, ZnO nanorods

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Authors: Shoujia Fang, Guoqing Ding, Xin Chen

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The quality of press-fit assembly is closely related to reliability and safety of product. The paper proposed a keypoint detection method based on convolutional neural network to improve the accuracy of keypoint detection in press-fit curve. It would provide an auxiliary basis for judging quality of press-fit assembly. The press-fit curve is a curve of press-fit force and displacement. Both force data and distance data are time-series data. Therefore, one-dimensional convolutional neural network is used to process the press-fit curve. After the obtained press-fit data is filtered, the multi-layer one-dimensional convolutional neural network is used to perform the automatic learning of press-fit curve features, and then sent to the multi-layer perceptron to finally output keypoint of the curve. We used the data of press-fit assembly equipment in the actual production process to train CNN model, and we used different data from the same equipment to evaluate the performance of detection. Compared with the existing research result, the performance of detection was significantly improved. This method can provide a reliable basis for the judgment of press-fit quality.

Keywords: keypoint detection, curve feature, convolutional neural network, press-fit assembly

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Authors: Huu Hue Van

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The Mekong Delta is the region in southwestern Vietnam where the Mekong River approaches and flow into the sea through a network of distributaries. The Climate Change Research Institute at University of Can Tho, in studying the possible consequences of climate change, has predicted that, many provinces in the Mekong Delta will be flooded by the year 2030. The Mekong Delta lacks fresh water in the dry season. Being served for daily life, industry and agriculture in the dry season, the water is mainly taken from layers of soil contained water under the ground (aquifers) depleted water; the water level in aquifers have decreased. Previously, the Mekong Delta can withstand two bad scenarios in the future: 1) The Mekong Delta will be submerged into the sea again: Due to subsidence of the ground (over-exploitation of groundwater), subsidence of constructions because of the low groundwater level (10 years ago, some of constructions were built on the foundation of Melaleuca poles planted in Mekong Delta, Melaleuca poles have to stay in saturated soil layer fully, if not, they decay easyly; due to the top of Melaleuca poles are higher than the groundwater level, the top of Melaleuca poles will decay and cause subsidence); erosion the river banks (because of the hydroelectric dams in the upstream of the Mekong River is blocking the flow, reducing the concentration of suspended substances in the flow caused erosion the river banks) and the delta will be flooded because of sea level rise (climate change). 2) The Mekong Delta will be deserted: People will migrate to other places to make a living because of no planting due to alum capillary (In Mekong Delta, there is a layer of alum soil under the ground, the elevation of groundwater level is lower than the the elevation of layer of alum soil, alum will be capillary to the arable soil layer); there is no fresh water for cultivation and daily life (because of saline intrusion and groundwater depletion in the aquifers below). Mekong Delta currently has about seven aquifers below with a total depth about 500 m. The water mainly has exploited in the middle - upper Pleistocene aquifer (qp2-3). The major cause of two bad scenarios in the future is over-exploitation of water in aquifers. Therefore, studying and building water reservoirs in seven aquifers will solve many pressing problems such as preventing subsidence, providing water for the whole delta, especially in coastal provinces, favorable to nature, saving land ( if we build the water lake on the surface of the delta, we will need a lot of land), pollution limitation (because when building some hydraulic structures for preventing the salt instrutions and for storing water in the lake on the surface, we cause polluted in the lake)..., It is necessary to build a reservoir under the ground in aquifers in the Mekong Delta. The super-sized reservoir will contribute to the existence and development of the Mekong Delta.

Keywords: aquifers, aquifers storage, groundwater, land subsidence, underground reservoir

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Authors: Fisayo G. Ojo, Shamala K. Subramaniam, Zuriati Ahmad Zukarnain

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As technology is advancing and wireless applications are becoming dependable sources, while the physical layer of the applications are been embedded into tiny layer, so the more the problem on energy efficiency and consumption. This paper reviews works done in recent years in wireless applications and distributed computing, we discovered that applications are becoming dependable, and resource allocation sharing with other applications in distributed computing. Applications embedded in distributed system are suffering from power stability and efficiency. In the reviews, we also prove that discrete event simulation has been left behind untouched and not been adapted into distributed system as a simulation technique in scheduling of each event that took place in the development of distributed computing applications. We shed more lights on some researcher proposed techniques and results in our reviews to prove the unsatisfactory results, and to show that more work still have to be done on issues of energy efficiency in wireless applications, and congestion in distributed computing.

Keywords: discrete event simulation (DES), distributed computing, energy efficiency (EE), internet of things (IOT), quality of service (QOS), user equipment (UE), wireless mesh network (WMN), wireless sensor network (wsn), worldwide interoperability for microwave access x (WiMAX)

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Authors: Anamika Paul, Sudipto Sarkar

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The flow behaviour of non-Newtonian fluid is quite complicated, although both the pseudoplastic (n < 1, n being the power index) and dilatant (n > 1) fluids under this category are used immensely in chemical and process industries. A limited research work is carried out for flow over a bluff body in non-Newtonian flow environment. In the present numerical simulation we control the vortices of a square cylinder by placing an upstream vertical splitter plate for pseudoplastic (n=0.8), Newtonian (n=1) and dilatant (n=1.2) fluids. The position of the upstream plate is also varied to calculate the critical distance between the plate and cylinder, below which the cylinder vortex shedding suppresses. Here the Reynolds number is considered as Re = 150 (Re = U∞a/ν, where U∞ is the free-stream velocity of the flow, a is the side of the cylinder and ν is the maximum value of kinematic viscosity of the fluid), which comes under laminar periodic vortex shedding regime. The vertical plate is having a dimension of 0.5a × 0.05a and it is placed at the cylinder centre-line. Gambit 2.2.30 is used to construct the flow domain and to impose the boundary conditions. In detail, we imposed velocity inlet (u = U∞), pressure outlet (Neumann condition), symmetry (free-slip boundary condition) at upper and lower domain. Wall boundary condition (u = v = 0) is considered both on the cylinder and the splitter plate surfaces. The unsteady 2-D Navier Stokes equations in fully conservative form are then discretized in second-order spatial and first-order temporal form. These discretized equations are then solved by Ansys Fluent 14.5 implementing SIMPLE algorithm written in finite volume method. Here, fine meshing is used surrounding the plate and cylinder. Away from the cylinder, the grids are slowly stretched out in all directions. To get an account of mesh quality, a total of 297 × 208 grid points are used for G/a = 3 (G being the gap between the plate and cylinder) in the streamwise and flow-normal directions respectively after a grid independent study. The computed mean flow quantities obtained from Newtonian flow are agreed well with the available literatures. The results are depicted with the help of instantaneous and time-averaged flow fields. Qualitative and quantitative noteworthy differences are obtained in the flow field with the changes in rheology of fluid. Also, aerodynamic forces and vortex shedding frequencies differ with the gap-ratio and power index of the fluid. We can conclude from the present simulation that fluent is capable to capture the vortex dynamics of unsteady laminar flow regime even in the non-Newtonian flow environment.

Keywords: CFD, critical gap-ratio, splitter plate, wake-wake interactions, dilatant, pseudoplastic

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Authors: Margarita Dufresne

Abstract:

This study devoted to development TPS for small space re-usable launchers. We have used SIRIUS design for S1 prototype. Multiphysics coupling for hypersonic reactive flow and thermos-structural analysis with and without ablation is provided by -CCM+ and COMSOL Multiphysics and FASTRAN and ACE+. Flow around hypersonic flight vehicles is the interaction of multiple shocks and the interaction of shocks with boundary layers. These interactions can have a very strong impact on the aeroheating experienced by the flight vehicle. A real gas implies the existence of a gas in equilibrium, non-equilibrium. Mach number ranged from 5 to 10 for first stage flight.The goals of this effort are to provide validation of the iterative coupling of hypersonic physics models in STAR-CCM+ and FASTRAN with COMSOL Multiphysics and ACE+. COMSOL Multiphysics and ACE+ are used for thermal structure analysis to simulate Conjugate Heat Transfer, with Conduction, Free Convection and Radiation to simulate Heat Flux from hypersonic flow. The reactive simulations involve an air chemical model of five species: N, N2, NO, O and O2. Seventeen chemical reactions, involving dissociation and recombination probabilities calculation include in the Dunn/Kang mechanism. Forward reaction rate coefficients based on a modified Arrhenius equation are computed for each reaction. The algorithms employed to solve the reactive equations used the second-order numerical scheme is obtained by a “MUSCL” (Monotone Upstream-cantered Schemes for Conservation Laws) extrapolation process in the structured case. Coupled inviscid flux: AUSM+ flux-vector splitting The MUSCL third-order scheme in STAR-CCM+ provides third-order spatial accuracy, except in the vicinity of strong shocks, where, due to limiting, the spatial accuracy is reduced to second-order and provides improved (i.e., reduced) dissipation compared to the second-order discretization scheme. initial unstructured mesh is refined made using this initial pressure gradient technique for the shock/shock interaction test case. The suggested by NASA turbulence models are the K-Omega SST with a1 = 0.355 and QCR (quadratic) as the constitutive option. Specified k and omega explicitly in initial conditions and in regions – k = 1E-6 *Uinf^2 and omega = 5*Uinf/ (mean aerodynamic chord or characteristic length). We put into practice modelling tips for hypersonic flow as automatic coupled solver, adaptative mesh refinement to capture and refine shock front, using advancing Layer Mesher and larger prism layer thickness to capture shock front on blunt surfaces. The temperature range from 300K to 30 000 K and pressure between 1e-4 and 100 atm. FASTRAN and ACE+ are coupled to provide high-fidelity solution for hot hypersonic reactive flow and Conjugate Heat Transfer. The results of both approaches meet the CIRCA wind tunnel results.

Keywords: hypersonic, first stage, high speed compressible flow, shock wave, aerodynamic heating, conugate heat transfer, conduction, free convection, radiation, fastran, ace+, comsol multiphysics, star-ccm+, thermal protection system (tps), space launcher, wind tunnel

Procedia PDF Downloads 62

Authors: Y. Lacroix, J.-F. Malbranque

Abstract:

We present a chronological evolution for naval telecommunication networks. We distinguish periods: with or without multiplexers, with switch systems, with federative systems, with medium switching, and with medium switching with wireless networks. This highlights the introduction of new layers and technology in the architecture. These architectures are presented using layer models of transmission, in a unified way, which enables us to integrate pre-existing models. A ship of a naval fleet has internal communications (i.e. applications' networks of the edge) and external communications (i.e. the use of the means of transmission between edges). We propose architectures, deduced from the layer model, which are the point of convergence between the networks on board and the HF, UHF radio, and satellite resources. This modelling allows to consider end-to-end naval communications, and in a more global way, that is from the user on board towards the user on shore, including transmission and networks on the shore side. The new architectures need take care of quality of services for end-to-end communications, the more remote control develops a lot and will do so in the future. Naval telecommunications will be more and more complex and will use more and more advanced technologies, it will thus be necessary to establish clear global communication schemes to grant consistency of the architectures. Our latest model has been implemented in a military naval situation, and serves as the basic architecture for the RIFAN2 network.

Keywords: equilibrium beach profile, eastern tombolo of Giens, potential function, erosion

Procedia PDF Downloads 287

Authors: Chukwuka Justus Iwegbu, Monye Christopher Prayer

Abstract:

Propeller aircraft engines, and more generally engines with a large rotating part (turboprops, high bypass ratio turbojets, etc.) are widely used in the industry and are subject to numerous developments in order to reduce their fuel consumption. In this context, unconventional architectures such as open rotors or distributed propulsion appear, and it is necessary to consider the influence of these systems on the aircraft's stability in flight. Indeed, the tendency to lengthen the blades and wings on which these propulsion devices are fixed increases their flexibility and accentuates the risk of whirl flutter. This phenomenon of aeroelastic instability is due to the precession movement of the axis of rotation of the propeller, which changes the angle of attack of the flow on the blades and creates unsteady aerodynamic forces and moments that can amplify the motion and make it unstable. The whirl flutter instability can ultimately lead to the destruction of the engine. We note the existence of a critical speed of the incident flow. If the flow velocity is lower than this value, the motion is damped and the system is stable, whereas beyond this value, the flow provides energy to the system (negative damping) and the motion becomes unstable. A simple model of whirl flutter is based on the work of Houbolt & Reed who proposed an analytical expression of the aerodynamic load on a rigid blade propeller whose axis orientation suffers small perturbations. Their work considered a propeller subjected to pitch and yaw movements, a flow undisturbed by the blades and a propeller not generating any thrust in the absence of precession. The unsteady aerodynamic forces were then obtained using the thin airfoil theory and the strip theory. In the present study, the unsteady aerodynamic loads are expressed for a general movement of the propeller (not only pitch and yaw). The acceleration and rotation of the flow by the propeller are modeled using a Blade Element Momentum Theory (BEMT) approach, which also enable to take into account the thrust generated by the blades. It appears that the thrust has a stabilizing effect. The aerodynamic model is further developed using Theodorsen theory. A reduced order model of the aerodynamic load is finally constructed in order to perform linear stability analysis.

Keywords: advancing, entrepreneurial, knowledge, industralization

Procedia PDF Downloads 90

Authors: M. A. Hasnat, M. Amirul Islam, M. A. Rashed, Jamil. Safwan, M. Mahabubul Alam

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Symmetric (Cu–Pt|Nafion|Pt–Cu) and asymmetric(Pt|Nafion|Pt–Cu) assemblies were fabricated to study the nitrate reduction processes at the cathode. The electrocatalytic nitrate reduction reactions were performed in these assemblies in order to investigate the prerequisite for the enhanced catalytic activity, electrochemical cell durability as well as preferable product selectivity resulting from the reduction of nitrate at the cathode. It has been observed for the symmetric assembly that Cu particles were oxidized on the anode surface under an applied potential and the resulting copper ions migrated to the cathode surface through the Nafion membrane, which deposited as copper oxide on the cathode surface. The formation of this copper oxide covering layer on the Pt–Cu cathode surface is attributed as the reason for the deactivation of the cathode that governed the reduced nitrate reduction along with increasing nitrite selectivity. These problems were addressed and resolved with the asymmetric design of the electrocatalytic reactor, where enhanced hydrogen evolution activates the surface by eroding the CuO over layer as well as speeding up the slow rate determining hydrogenation reactions.

Keywords: membrane, nitrate, electrocatalysis, voltammetry, electrolysis

Procedia PDF Downloads 262

Authors: M. Naresh, Pratik Chaturvedi, Srishti Yadav, Varun Dutt, K. V. Uday

Abstract:

Changes in the Earth’s climate are likely to increase natural hazards such as drought, floods, earthquakes, landslides, etc. The present study focusing on to early warning systems (EWS) of landslides, major issues in Himalayan region without prominence to deforestation, encroachments and un-engineered cutting of slopes and reforming for infrastructural purposes. EWS can be depicted by conducting a series of flume tests using micro-electro mechanical systems sensors data after reaching threshold values under controlled laboratory conditions. Based on the threshold value database, an alert will be sent via SMS.

Keywords: slope-instability, flume test, sensors, early warning system

Procedia PDF Downloads 259

Authors: T. Yamaguchi, M. Watanabe, M. Sasajima, C. Yuan, S. Maruyama, T. B. Ibrahim, H. Tomita

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This paper deals with nonlinear vibration analysis using finite element method for frame structures consisting of elastic and viscoelastic damping layers supported by multiple nonlinear concentrated springs with hysteresis damping. The frame is supported by four nonlinear concentrated springs near the four corners. The restoring forces of the springs have cubic non-linearity and linear component of the nonlinear springs has complex quantity to represent linear hysteresis damping. The damping layer of the frame structures has complex modulus of elasticity. Further, the discretized equations in physical coordinate are transformed into the nonlinear ordinary coupled differential equations using normal coordinate corresponding to linear natural modes. Comparing shares of strain energy of the elastic frame, the damping layer and the springs, we evaluate the influences of the damping couplings on the linear and nonlinear impact responses. We also investigate influences of damping changed by stiffness of the elastic frame on the nonlinear coupling in the damped impact responses.

Keywords: dynamic response, nonlinear impact response, finite element analysis, numerical analysis

Procedia PDF Downloads 427

Authors: Karlee J. Hall, Mark Laylor, Jessy Varghese, Paula Polastri, Karen Van Ooteghem, William McIlroy

Abstract:

Balance training is a common part of physiotherapy treatment and often involves a set of proprioceptive exercises which the patient carries out in the clinic and as part of their exercise program. Understanding all contributing factors to altered balance is of utmost importance to the clinical success of treatment of balance dysfunctions. A critical role for the autonomic nervous system (ANS) in the control of balance reactions has been proposed previously, with evidence for potential involvement being inferred from the observation of phasic galvanic skin responses (GSR) evoked by external balance perturbations. The current study explored whether the coupling between ANS reactivity and balance reactions would be observed during spontaneously occurring instability while standing, including standard positions typical of physiotherapy balance assessments. It was hypothesized that time-varying changes in GSR (ANS reactivity) would be associated with time-varying changes in the mediolateral center of pressure (ML-COP) (somatomotor reactivity). Nine individuals (5 females, 4 males, aged 19-37 years) were recruited. To induce varying balance demands during standing, the study compared ML-COP and GSR data across different task conditions varying the availability of vision and width of the base of support. Subjects completed 3, 30-second trials for each of the following stance conditions: standard, narrow, and tandem eyes closed, tandem eyes open, tandem eyes open with dome to shield visual input, and restricted peripheral visual field. ANS activity was evaluated by measures of GSR recorded from Ag-AgCl electrodes on the middle phalanges of digits 2 and 4 on the left hand; balance measures include ML-COP excursion frequency and amplitude recorded from two force plates embedded in the floor underneath each foot. Subjects were instructed to stand as still as possible with arms crossed in front of their chest. When comparing mean task differences across subjects, there was an expected increase in postural sway from tasks with a wide stance and no sensory restrictions (least challenging) to those with a narrow stance and no vision (most challenging). The correlation analysis revealed a significant positive relationship between ML-COP variability and GSR variability when comparing across tasks (r=0.94, df=5, p < 0.05). In addition, correlations coincided within each subject and revealed a significant positive correlation in 7 participants (r= 0.47, 0.57, 0.62, 0.62, 0.81, 0.64, 0.69 respectively, df=19, p < 0.05) and no significant relationship in 2 participants (r=0.36, 0.29 respectively, df=19, p > 0.05). The current study revealed a significant relationship between ML-COP and GSR during balance tasks, revealing the ANS reactivity associated with naturally occurring instability when standing still, which is proportional to the degree of instability. Understanding the link between ANS activity and control of COP is an important step forward in the enhancement of assessment of contributing factors to poor balance and treatment of balance dysfunctions. The next steps will explore the temporal association between the time-varying changes in COP and GSR to establish if the ANS reactivity phase leads or lags the evoked motor reactions, as well as exploration of potential biomarkers for use in screening of ANS activity as a contributing factor to altered balance control clinically.

Keywords: autonomic nervous system, balance control, center of pressure, somatic nervous system

Procedia PDF Downloads 164

Authors: Siamak Feizi, Gunvor Baardvik

Abstract:

Soil erosion has special consequences for landfills that are more serious than those found at conventional construction sites. Different potential heads between two sides of a landfill and the subsequent movement of water through pores within the soil body could trigger the soil erosion and construction instability. Such a condition was encountered in a landfill project in the southern part of Norway. To check the risk of internal erosion due to changes in the groundwater level (because of seasonal flooding in the river), a series of numerical simulations by means of Geo-Seep software was conducted. Output of this study provides a total picture of the landfill stability, possibilities of erosions, and necessary measures to prevent or reduce the risk for the landfill operator.

Keywords: erosion, seepage, landfill, stability

Procedia PDF Downloads 131