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Number of results: 150
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Abstract

This paper presents the design methodology of a small guided bomb for Unmanned Aerial Vehicles. This kind of next-generation munition has recently gained a lot of attention in the military market. The bomb is planned to be equipped with inertial measurement unit and infrared seeker. The nose shape and fin optimization procedure was described shortly. Aerodynamic characteristics were calculated by means of theoretical and engineering-level methods. The flight dynamics model of the bomb was obtained and implemented in Simulink software. The numerical simulations of uncontrolled and controlled trajectories were compared. The results indicate that the usage of such a guided small munition, like the designed bomb, might improve significantly the offensive capabilities of Unmanned Aerial Vehicles.
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Abstract

The small number of available complete modern pump characteristics makes the safety analysis of nuclear and conventional power plants based on the characteristics made over half a century ago of specific speeds n_q=24.6, 147.1 and 261.4. The aim of the paper is to check sensitivity of the power plant system response for different complete pump characteristics - modern and available from older tests for n_q=24.6, 147.1 and 261.4. It has been shown that Suter's characteristics for modern pumps give a different response to the pumping system of a power plant in breakdown than those used so far.
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Abstract

In thermosfluid dynamics, free convection flows external to different geometries, such as cylinders, ellipses, spheres, curved walls, wavy plates, cones, etc., play major role in various industrial and process engineering systems. The thermal buoyancy force associated with natural convection flows can play a critical role in determining skin friction and heat transfer rates at the boundary. In thermal engineering, natural convection flows from cylindrical bodies has gained exceptional interest. In this article, we mathematically evaluate an entropy analysis of magnetohydrodynamic third-grade convection flows from permeable cylinder considering velocity and thermal slip effects. The resulting non-linear coupled partial differential conservation equations with associated boundary conditions are solved with an efficient unconditionally stable implicit finite difference Keller-Box technique. The impacts of momentum and heat transport coefficients, entropy generation and Bejan number are computed for several values of non-dimensional parameters arising in the flow equations. Streamlines are plotted to analyze the heat transport process in a two-dimensional domain. Furthermore, the deviations of the flow variables are compared with those computed for a Newtonian fluid and this has important implications in industrial thermal material processing operations, aviation technology, different enterprises, energy systems and thermal enhancement of industrial flow processes.
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Abstract

An important phenomenon of delta wing is the mechanism of vortex core, which indicates the increase in lifting force until the occurrence of the vortex breakdown. The computational fluid dynamics (CFD) is very helpful in visualizing and providing analysis of the detailed data. The use of turbulent models will affect the quality of results in obtaining the vortex breakdown phenomenon. This study used several models of turbulence to capture the occurrence of vortex breakdown and compare it with experiments using water tunnel test facility. The results show that all turbulence models give good results at a low angle of attack (AoA), but at a high AoA the DES model gives the results closest to experimental ones with Cl error value of about 1%. Taking into account the time required and the acceptable level of accuracy, the use of SST and k-omega models is an alternative option for use in the detection of vortex breakdown.
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Abstract

The functionality of a prosthesis is determined by clinical procedures, the manufacturing technology applied, the material used and its strength parameters. The aim of the paper is to evaluate the static strength and fatigue strength of acrylic construction materials directly after the process of polymerisation and for aged materials. It has been confirmed that the deformation speed of the tested materials has an evident impact on their mechanical characteristics. With greater deformation speed, a consistent increase in the material elasticity was observed in static compression tests, which was accompanied by a reduction in engineering stresses at the final stage of deformation. The greatest fatigue strength was observed for Vertex. It was by about 33% greater than the strength of Villacryl – the material that has the lowest fatigue properties. The resistance of acrylic polymers to cyclic loading applied with the frequency of 1 Hz may become an indication for the selection of the material to be used in the clinical procedures in which a patient is provided with full dentures.
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Abstract

Recent developments in automation and technology have revolutionized the way products are made. It is directly seen in the evolution of part miniaturization in the sectors such as aerospace, electronics, biomedicine and medical implants. Micromachining is a promising technology to fulfill the need of miniaturization. A review has been done on the micromachining processes such as micro electric discharge machining (micro-EDM) and wire EDM (WEDM), micro electrochemical machining (micro-ECM). Recent literature were studied and categorized in terms of materials, process parameters, performances, product manufactured, and miniature product generation. Starting with brief introduction to micromachining, classifications and applications, technical aspects of discussions from the literature have been presented on key factors such as parameters and the response variables. Important aspects of recast layer, heat effected zone, micro-hardness, micro cracks, residual stress, etc., have been given. A special focus is given to the status of the research on microgear manufacturing. Comparison has been made between other conventional process suitable for micro-gear manufacturing and WEDM. The miniature gear machined by WEDM shows the defect-free microstructure, better surface finish, thin recast layer and improved gear quality parameters such as profile and pitch. Finally, the research gaps and future research directions have been presented.
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Abstract

This study reveals significant and emergent research topics in the field ‘engineering, mechanical’ through bibliometric analysis of articles indexed in Web of Science (WoS) from 1997 to 2016. Publications under consideration (219,191 articles) were examined using quantitative and qualitative methods to evaluate general information about publications; evolution of research topics by keyword analysis; performance of countries, research centers and journals; and international collaborations. There was a threefold increase in number of articles throughout the period. The publications were related to 35 WoS categories; and mechanics and thermodynamics were dominating ones. International Journal of Heat and Mass Transfer was the leading journal in the field. The USA and China were outstanding countries of the field. Collaboration between these countries corresponded to 6.57% of all collaborative publications. Industrialized and developing countries dominated research activities in the field. Indian Institute of Technology was the leading research center due to number of publications. The results showed that heat transfer, finite element method, friction, wear, simulation, and fatigue are important topics of the field. There is an upward trend in research related to nanofluids, microchannel, phase change materials, and carbon nanotubes.
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Abstract

The authors developed a simple and efficient method, called the Coupled Displacement method, to study the linear free vibration behavior of the moderately thick rectangular plates in which a single-term trigonometric/algebraic admissible displacement, such as total rotations, are assumed for one of the variables (in both X,Y directions), and the other displacement field, such as transverse displacement, is derived by making use of the coupling equations. The coupled displacement method makes the energy formulation to contain half the number of unknown independent coefficients in the case of a moderately thick plate, contrary to the conventional Rayleigh-Ritz method. The smaller number of undetermined coefficients significantly simplifies the vibration problem. The closed form expression in the form of fundamental frequency parameter is derived for all edges of simply supported moderately thick rectangular plate resting on Pasternak foundation. The results obtained by the present coupled displacement method are compared with existing open literature values wherever possible for various plate boundary conditions such as all edges simply supported, clamped and two opposite edges simply supported and clamped and the agreement found is good.
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Abstract

Two fundamental challenges in investigation of nonlinear behavior of cantilever beam are the reliability of developed theory in facing with the reality and selecting the proper assumptions for solving the theory-provided equation. In this study, one of the most applicable theory and assumption for analyzing the nonlinear behavior of the cantilever beam is examined analytically and experimentally. The theory is concerned with the slender inextensible cantilever beam with large deformation nonlinearity, and the assumption is using the first-mode discretization in dealing with the partial differential equation provided by the theory. In the analytical study, firstly the equation of motion is derived based on the theory of large deformable inextensible beam. Then, the partial differential equation of motion is discretized using the Galerkin method via the assumption of the first mode. An exact solution to the obtained nonlinear ordinary differential equation is developed, because the available semi analytical and approximated methods, due to their limitations, are not always sufficiently reliable. Finally, an experiment set-up is developed to measure the nonlinear frequency of oscillations of an aluminum beam within a domain of initial displacement. The results show that the proposed analytical method has excellent convergence with experimental data.
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Abstract

This article employs the classical Euler–Bernoulli beam theory in connection with Green–Naghdi’s generalized thermoelasticity theory without energy dissipation to investigate the vibrating microbeam. The microbeam is considered with linearly varying thickness and subjected to various boundary conditions. The heat and motion equations are obtained using the modified couple stress analysis in terms of deflection with only one material length-scale parameter to capture the size-dependent behavior. Various combinations of free, simply-supported, and clamped boundary conditions are presented. The effect of length-to-thickness ratio, as well as the influence of both couple stress parameter and thermoelastic coupling, are all discussed. Furthermore, the effect of reference temperature on the eigenfrequency is also investigated. The vibration frequencies indicate that the tapered microbeam modeled by modified couple stress analysis causes more responses than that modeled by classical continuum beam theory, even the thermoelastic coupled is taken into account.
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Abstract

Modern gas turbine systems operate in temperatures ranging from 1200°C to even 1500°C, which creates bigger problems related to the blade material thermal strength. In order to ensure appropriate protection of the turbine blades, a sophisticated cooling system is used. Current emphasis is placed on the application of non-stationary flow effects to improve cooling conditions, e.g., the unsteady-jet heat transfer or the heat transfer enhancement using high-amplitude oscillatory motion. The presented research follows a similar direction. A new concept is proposed of intensification of the heat transfer in the cooling channels with the use of an acoustic wave generator. The acoustic wave is generated by an appropriately shaped fixed cavity or group of cavities. The phenomenon is related to the coupling mechanism between the vortex shedding generated at the leading edge and the acoustic waves generated within the cavity area. Strong instabilities can be observed within a certain range of the free flow velocities. The presented study includes determination of the relationship between the amplitude of acoustic oscillations and the cooling conditions within the cavity. Different geometries of the acoustic generator are investigated. Calculations are also performed for variable flow conditions. The research presented in this paper is based on a numerical model prepared using the Ansys CFX-17.0 commercial CFD code.
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Abstract

This paper presents the construction of adequate 3-D computer models for simulation research and analysis of dynamic aspects of caliper disc brakes, as well as of drum brakes, actuated by a short stroke electromagnet or a hydraulic thruster, when these brake types are used in the hoisting mechanism of cranes. The adequacy of the 3-D models has been confirmed by comparing their simulation results with results from an experiment and from classic computational models. The classic computational models, related to the study of main dynamic features of friction brakes, are layouts that are based on a number of assumptions, such as that the braking force instantly reaches its steady-state value, the clearance between the friction lining and the disc/drum is neglected, etc. These assumptions lead to a limitation of research options. The proposed 3-D computer models improve the research layouts by eliminating a number of the classic model assumptions. The improvements are related to the determination of the braking time, braking torque, normal force and other dynamic aspects of the brakes by performing simulations that take into account: the braking force as a function of time, the presence of clearance between the friction lining and the disc/drum, etc.
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Abstract

The disposal of ash in a thermal plant through the slurry pipe is subjected to some erosion wear due to the abrasive characteristics of the slurry. A simulation study of particle-liquid erosion of mild steel pipe wall based on CFD-FLUENT that considers the solid-liquid, solid-solid and solid-wall interaction is presented in this work. The multi-phase Euler-Lagrange model with standard k-epsilon turbulence modeling is adopted to predict the particulate erosion wear caused by the flow of bottom ash-water suspension. Erosion rate for different particle size and concentration is evaluated at variable flow rate. It is observed that the pressure drop and erosion rate share direct relationships with flow velocity, particle size and concentration. The flow velocity is found to be the most influencing parameter. A model capable of predicting the erosion wear at variable operating conditions is presented. The simulation findings show good agreement with the published findings.
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Abstract

In rotating machineries, misalignment is considered as the second most major cause of failure after unbalance. In this article, model-based multiple fault identification technique is presented to estimate speed-dependent coupling misalignment and bearing dynamic parameters in addition with speed independent residual unbalances. For brevity in analysis, a simple coupled rotor bearing system is considered and analytical approach is used to develop the identification algorithm. Equations of motion in generalized co-ordinates are derived with the help of Lagrange's equation and least squares fitting approach is used to estimate the speed-dependent fault parameters. Present identification algorithm requires independent sets of forced response data which are generated with the help of different sets of trial unbalances. To avoid/suppress the ill-conditioning of regression equation, independent sets of forced response data are obtained by rotating the rotor in clock-wise and counter clock-wise directions, alternatively. Robustness of algorithm is checked for different levels of measurement noise.
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Abstract

This paper presents an elasticity solution of adhesive tubular joints in laminated composites, with axial symmetry. In this model, adherends are orthotropic shells and the stacking sequences can be either symmetric or asymmetric. Adhesive layer is homogenous and made of isotropic material. They are modelled as continuously distributed tension/compression and shear springs. Employing constitutive, kinematics and equilibrium equations, sets of differential equations for each inside and outside of overlap zones are obtained. By solving these equations, shear and peel stresses in adhesive layer(s), as well as deflections, stress resultants and moment resultants in the adherends are determined. It is seen that the magnitude of peel stresses due to transverse shear stress resultant is much greater than that obtained from axial stress resultant. The developed results are compared with those obtained by finite element analysis using ANSYS software. The comparisons demonstrate the accuracy and effectiveness of the aforementioned methods.
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Abstract

In this work, the design of current mode Fractional order filter using VDTAs (Voltage differencing trans-conductance amplifier) as an active element with grounded capacitors has been proposed. The approximate transfer functions of low and high pass filters of fractional order on the basis of the integer order transfer has been shown and the form of those functions of filters is also implemented using VDTA as an active building block. In this work, filters of the different sequence have been realized. The frequency domain simulation results of the proposed filters are obtained on Matlab and PSPICE with TSMC CMOS 180 nm technology parameters. Stability and sensitivity is also verified.
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Abstract

Nonlinearities in optical fibers deteriorate system performances and become a major performancelimiting issue. This article aims to investigate the compensation of nonlinear distortions in optical communication systems based on different wavelength propagations over few-mode fiber (FMF). The study adopted Space Division Multiplexing (SDM) based on decision feedback equalizer (DFE). Various transmission wavelength of the FMF system is applied to mitigate the attenuation effect on the system. In this paper, different wavelengths (780, 850 and 1550 nm) are used in SDM. Extensive simulation is performed to assess the attenuation and Bit Error Rate (BER) in each case. The results show that the wavelength of 1550 nm produces higher power and less attenuation in the transmission. Furthermore, this wavelength produces the best distance with less BER compared to 780 nm and 850 nm wavelengths. Moreover, the validations show improvement in BER and eye diagram.
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Abstract

This paper presents active inductor based VCO design for wireless applications based on analysis of active inductor models (Weng-Kuo Cascode active inductor & Liang Regular Cascode active inductor) with feedback resistor technique. Embedment of feedback resistor results in the increment of inductance as well as the quality factor whereas the values are 125.6@2.4GHz (Liang) and 98.7@3.4GHz (Weng-Kuo). The Weng-Kuo active inductor based VCO shows a tuning frequency of 1.765GHz ~2.430GHz (31.7%), while consuming a power of 2.60 mW and phase noise of -84.15 dBc/Hz@1MHz offset. On the other hand, Liang active inductor based VCO shows a frequency range of 1.897GHz ~2.522GHz (28.28%), while consuming a power of 1.40 mW and phase noise of -80.79 dBc/Hz@1MHz offset. Comparing Figure-of-Merit (FoM), power consumption, output power and stability in performance, designed active inductor based VCOs outperform with the stateof- the-art.
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Abstract

The paper considers the technique of modeling and formation educational components of the planned training of CDIO Syllabus, realized in the form of the educational adaptive environment of engineering education. The following key concepts of the methodology have been accepted: competence models of the stages of the CDIO initiative, the method of project training, syntax for describing the concepts of the domain, models for mapping support concepts in the form of expressions of knowledge and ontological engineering.
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Abstract

We address one of the weaknesses of the RSA ciphering systems i.e. the existence of the private keys that are relatively easy to compromise by the attacker. The problem can be mitigated by the Internet services providers, but it requires some computational effort. We propose the proof of concept of the GPGPU-accelerated system that can help detect and eliminate users’ weak keys. We have proposed the algorithms and developed the GPU-optimised program code that is now publicly available and substantially outperforms the tested CPU processor. The source code of the OpenSSL library was adapted for GPGPU, and the resulting code can perform both on the GPU and CPU processors. Additionally, we present the solution how to map a triangular grid into the GPU rectangular grid – the basic dilemma in many problems that concern pair-wise analysis for the set of elements. Also, the comparison of two data caching methods on GPGPU leads to the interesting general conclusions. We present the results of the experiments of the performance analysis of the selected algorithms for the various RSA key length, configurations of GPU grid, and size of the tested key set.
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Abstract

A robust and highly imperceptible audio watermarking technique is presented to secure the electronic patient record of Parkinson’s Disease (PD) affected patient. The proposed DCT-SVD based watermarking technique introduces minimal changes in speech such that the accuracy in classification of PD affected person’s speech and healthy person’s speech is retained. To achieve high imperceptibility the voiced part of the speech is considered for embedding the watermark. It is shown that the proposed watermarking technique is robust to common signal processing attacks. The practicability of the proposed technique is tested: by creating an android application to record & watermark the speech signal. The classification of PD affected speech is done using Support Vector Machine (SVM) classifier in cloud server.
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Abstract

The paper presents the use of visual evoked potentials VEP to the objective assessment of visual acuity. Methods of using visual evoked potentials (VEP) rely on the assessment of changes of the electrical action potentials generated within the cortex. To diagnose the degree of weakening eyesight a series of studies on healthy people and visually impaired ones were made. Electrophysiological studies of the eye, using noninvasive VEP examination allow a noninvasive and objective assessment of visual acuity. The use of visual evoked potentials gives the objectivity in assessment of visual acuity what may be very important in ophthalmology. This particularly may concern children examination, people with mental retardation and suspected of simulation.
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Abstract

The paper presents a method for wireless measurement of car wheel air pressure and temperature using the Tire Pressure Monitoring System, or TPMS module - one of the latest safety systems introduced by the automotive industry - with readings taken on a specifically designed test bench. The paper describes the structure and operating principle of the test bench key elements and how they work with the sensors, the TPMS module, and reference instruments, as well as the data format and accuracy of data transmission between TPMS and the host computer. The software designed for an embedded system emulating the real on-board computer allows for observing raw sensor readings and the effect of calibration in two points of the characteristics.
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