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Acoustic Scattering Performance for Sources in Arbitrary Motion
Get PDFIn this paper, an analytical time domain formulation based on Ffowcs Williams-Hawkings (FW-H) equation is derived for the prediction of the acoustic velocity field generated by moving bodies. This provides the imposition of the Neumann boundary condition on a rigid scattering surface. In order to calculate the scattering sound pressure of the duct, a thin-body boundary element method (BEM) has been proposed. The radiate sound pressure is calculated using the acoustic analogy FW-H equation. The scattering effect of the duct wall on the propagation of the sound wave is presented using the thin-body BEM. Computational results for a pulsating sphere, dipole source, and a tail rotor verify the method. The sound pressure directivity and scattering effect are shown to demonstrate the applicability and validity of the approach
Modeling of Canonical Switching Cell Converter Using Genetic Algorithm
Get PDFThe working of Canonical switching cell (CSC) converter was studied and its equivalent circuit during ON and OFF states were obtained. State space model of CSC converter in ON and OFF states were developed using the Kirchhoff laws. The state space matrices were used to construct the transfer functions of ON & OFF states. The step response of the converter was simulated using MATLAB. The step response curve was obtained using different values of circuit components (L, C1, C2 and RL)and optimized. The characteristic parameters such as rise time, overshoot, settling time, steady state error and stability were determined using the step response curve. The response curve shows that there is no overshoot; the rise time and settling time are very low as expected for a converter and its stability is very high but the amplitude is very. The circuit was tuned to attain the expected amplitude using PID controller with the help of Genetic algorithm. The excellent results of circuits’ characteristic parameters are very useful guideline for constructing such CSC converters for DC-DC conversions. The circuit characteristic parameters are useful in constructing such CSC converters for DC- DC conversions in driving solar energy using solar panel
Glass Fibre Reinforced Concrete Rebound Optimization
Get PDFGlass fibre reinforced concrete placement technique generates losses due to rebound effects of the already sprayed concrete particles. Rebounded concrete amount cause a significant difference between the initial mix design and emplaced mix compositions. Apart from the structural differences, it comes with a cost increase which was resulted by the splashed concrete amount. Many factors such as viscosity and quantity of mixes dominate this rebound amount in sprayed glass fibre reinforced concrete applications depending on production technologies and processes; however, this research focuses on the spray distance and the angle of the spray gun which mainly effects the rebound amount in glass fibre reinforced concrete production. This paper aims to understand the required angle and distance for glass fibre reinforced concrete mixes having on-site plastic viscosity values. Glass fibre reinforced mixtures were also modelled with a finite element method based software and, the analysis results were compared with production line results. Results of the analysis and on-site studies showed a decisive correlation between, discharge distance, discharge angle and the viscosity of the concrete
Shear Stress-mediated Angiogenesis Through Id1 Relevant to Atherosclerosis
Get PDFAbnormal shear stress in the blood vessel is an important stimulating factor for the formation of angiogenesis and vulnerable plaques. This paper intended to explore the role of shear stress-regulated Id1 in angiogenesis. First, we applied a carotid artery ring ligation to create local stenosis in ApoE-/- mice. Then, 3D geometry of the vessel network was reconstructed based on MRI, and our analysis of computational fluid dynamics revealed that wall shear stress of the proximal region was much higher than that of the distal region. In addition, results from histological staining of the proximal region found more vulnerable-probe plaques with new capillary formation, the presence of macrophages and collagen fibers degradation. Our in vitro and in vivo experiments further indicated high shear stress can induce endothelial cell-mediated angiogenesis and high expression of Id1. Id1-overexpression promoted endothelial cells migration and angiogenesis through collagen degradation mediated by MT-MMPs. Together, our results support a biomechanical role for Id1 in angiogenesis, suggesting manipulation of the Id1 activity may offer a novel anti-angiogenic therapeutic strategy in vulnerable plaques
A Fuzzy Approach for an IoT-based Automated Employee Performance Appraisal
Get PDFThe ubiquitous Internet of Things (IoT) through RFIDs, GPS, NFC and other wireless devices is capable of sensing the activities being carried around Industrial environment so as to automate industrial processes. In almost every industry, employee performance appraisal is done manually which may lead to favoritisms. This paper proposes a framework to perform automatic employee performance appraisal based on data sensed from IoT. The framework classifies raw IoT data into three activities (Positive, Negative, Neutral), co-locates employee and activity in order to calculate employee implication and then performs cognitive decision making using fuzzy logic. From the experiments carried out it is observed that automatic system has improved performance of employees. Also the impact of the proposed system leads to motivation among employees. The simulation results show how fuzzy approach can be exploited to reward or penalize employees based on their performance
Control Mechanism of Surface Subsidence and Overburden Movement in Backfilling Mining based on Laminated Plate Theory
Get PDFThe backfilling mining technology is a type of high-efficiency coal mining technology that is used to address the environmental issues caused by the caving mining technology. In this paper, the mechanical model of symmetrical laminated plate representing the overburden movement caused by the backfilling mining technology is established, and the governing differential equation of the motion of the overburden is derived. The boundary conditions of the mechanical model are put forward, and the analytical solution of the overburden movement and surface subsidence is obtained. The numerical model of the overburden movement and surface subsidence, under mining with backfilling, is established by means of the FLAC3D numerical software, which aims to systematically study the influence of backfilling compactness, mining thickness, and mining depth on the overburden movement and surface subsidence in backfilling mining. When the compactness η is less than 70%, the overburden movement and surface subsidence is greater, while when η is greater than 70%, the overburden movement and surface subsidence is reduced significantly. On this basis, the control mechanism of surface subsidence and overburden movement in backfilling mining is obtained. The suitable backfilling compactness is the key to controlling surface subsidence and overburden movement in backfilling mining
Investigation of the Melting Coupled Natural Convection of Nano Phase Change Material: A Fan Less Cooling of Heat Sources
Get PDFA two-dimensional numerical model that accounts for heat transfer by conduction and natural convection in the molten region of nano enhanced Phase Change Material (PCM) is performed. Numerical investigations were conducted using an enthalpy- porosity method in order to examine the impact of the dispersion of copper (CuO) nanoparticles on the heat source temperature and the effect on the heat sink secured working time and the melting rate. Results show that heat spreads more easily along the conducting plate and to the PCM and, consequently, the PCM melts rapidly and the heat source is efficiency cooled by the addition of nanopartices. In contrast, the heat source secured working time decreases for high nanoparticles fraction
Analytical and Numerical Study of the Evaporation on Mixed Convection in aVertical Rectangular Cavity
Get PDFWe consider an ascending laminar air flow in a vertical channel formed by two parallel flat plates wetted by a thin water film and under different temperature and concentration conditions. The study includes a numerical finite volume method for the treatment of the double diffusion problem, where the analytical solution is given to the thermal diffusion. The analytical study showed that the reversed flow is observed only under some wall temperature conditions and also for certain values of Re/Gr. The reversed flow is also strongly dependent on the aspect ratio A2, which is based on the cross section of the channel.
Indeed, the results show than this dependence is very strong for values less than a certain critical one equal to 2.22. In the absence of the mass transfer the results showed that the evaporation rate remains null along the channel, decreases when the mass gradient is favorable and it finally vanishes at x=15. However, the evaporation rate increases in the case of an unfavorable mass gradient, to cancel at position x=20, then merges with the curve representing the forced convection. In the absence of heat transfer the evaporation rate is less important and amounts to fifty percent of the double diffusion. The results obtained by the analytical and numerical methods are compared each other and with those of a similar works and a good agreement was found
A Note on the Transient Electrohydrodynamics of a Liquid Drop
Get PDFThe evolution of the flow field in and around a liquid drop in a unifor-m electric field for fluid systems corresponding to region (II) of the circulation-deformation map is fundamentally different than that for the rest of the map and has not been explored before. This is examined here and justified mathematical-ly. Furthermore a methodology is developed to predict the flow pattern, which is likely to be helpful in predicting the evolution of the flow field in more complex circumstances
Reliability Analysis for Complex Systems based on Dynamic Evidential Network Considering Epistemic Uncertainty
Get PDFFault tolerant technology has greatly improved the reliability of modern systems on one hand and makes their failure mechanisms more complex on the other. The characteristics of dynamics of failure, diversity of distribution and epistemic uncertainty always exist in these systems, which increase the challenges in the reliability assessment of these systems significantly. This paper presents a novel reliability analysis framework for complex systems within which the failure rates of components are expressed in interval numbers. Specifically, it uses a dynamic fault tree (DFT) to model the dynamic fault behaviors and copes with the epistemic uncertainty using Dempster- Shafer (D-S) theory and interval numbers. Furthermore, an approach is presented to convert a DFT into a dynamic evidential network (DEN) to calculate the reliability parameters. Additionally, a sorting method based on the possibility degree is proposed to rank the importance of components represented by interval numbers in order to obtain the most critical components, which can be used to provide the guidance for system design, maintenance planning and fault diagnosis. Finally, a numerical example is provided to illustrate the availability and efficiency of the proposed method