Glottal inverse filtering (GIF) refers to methods of estimating the source of voiced speech, the glottal volume velocity waveform. GIF is based on the idea of inversion, in which the effects of the vocal tract and lip radiation are cancelled from the output of the voice production mechanism, the speech signal. This article provides a review on GIF research by examining an era spanning five decades during which this topic has been under development. The topic is handled from three main perspectives: the estimation methods of the glottal source, the parameterization techniques that have been developed to express the estimated glottal excitations in numerical forms, and the application areas of GIF. Finally, the strengths and limitations of the GIF approach are discussed.
In this paper, the effect of surface radiation in a square cavity containing an absorbing, emitting and scattering medium with four heated boundaries is investigated, numerically. Lattice Boltzmann method (LBM) is used to solve the energy equation of a transient conduction-radiation heat transfer problem and the radiative heat transfer equation is solved using finite-volume method (FVM). In this work, two different heat flux boundary conditions are considered for the east wall: a uniform and a sinusoidally varying heat flux profile. The results show that as the value of conduction-radiation decreases, the dimensionless temperature in the medium increases. Also, it is clarified that, for an arbitrary value of the conduction-radiation parameter, the temperature decreases with decreasing scattering albedo. It is observed that when the boundaries reflect more, a higher temperature is achieved in the medium and on boundaries.
A low-frequency approximation of the discrete Sommerfeld diffraction problems, involving the scattering of a time harmonic lattice wave incident on square lattice by a discrete Dirichlet or a discrete Neumann half-plane, is investigated. It is established that the exact solution of the discrete model converges to the solution of the continuum model, i.e., the continuous Sommerfeld problem, in the discrete Sobolev space defined by Hackbusch. A proof of convergence has been provided for both types of boundary conditions when the imaginary part of incident wavenumber is positive.
Aluminium matrix composites (AMCs) refer to the class of light weight high performance aluminium centric material systems. The reinforcement in AMCs could be in the form of continuous/discontinuous fibres, whisker or particulates, in volume fractions ranging from a few percent to 70%. Properties of AMCs can be tailored to the demands of different industrial applications by suitable combinations of matrix, reinforcement and processing route. Presently several grades of AMCs are manufactured by different routes. Three decades of intensive research have provided a wealth of new scientific knowledge on the intrinsic and extrinsic effects of ceramic reinforcement vis-a-vis physical, mechanical, thermo-mechanical and tribological properties of AMCs. In the last few years, AMCs have been utilised in high-tech structural and functional applications including aerospace, defence, automotive, and thermal management areas, as well as in sports and recreation. It is interesting to note that research on particle-reinforced cast AMCs took root in India during the 70’s, attained industrial maturity in the developed world and is currently in the process of joining the mainstream of materials. This paper presents an overview of AMC material systems on aspects relating to processing, microstructure, properties and applications.
This study mainly focused on the comparison of the effect of single and simultaneous suction and blowing jets on the aerodynamic performance of an airfoil with/without flap to evaluate the most effective flow control configuration using computational fluid dynamics (CFD) method. Moreover, the effect of applying single and simultaneous jets have been conducted on delaying and controlling the flow separation. The results were obtained using two-dimensional incompressible Unsteady Reynolds-Averaged Navier–Stokes (URANS), and the turbulence was simulated with SST k-ω turbulence model. Also, different parameters including two jet locations (Ljet), three jet velocity ratios (Rjet), three jet angles (θjet) and three flap deflections (δf) were analyzed to find the most effective case of applying flow control jets to delay the boundary layer separation. It was concluded that applying a single suction jet and simultaneous suction and blowing jets on the flapped airfoil was more effective to improve the lift-to-drag ratio (CL/CD) than applying these jets to the without flap case. The maximum value of CL/CD was achieved by single suction jet for the without flap case which was equal to 73.7. The maximum increment of stall angle over the without flap airfoil and flapped airfoil was obtained by applying single suction jet, which increased the stall angle from 14° to 20° and 14° to 16° for the suction angle of −90° and suction velocity ratio of 0.15, respectively.
This paper proposes a structural design and multi-objective optimization of a two-degree-of-freedom (DOF) monolithic mechanism. The mechanism is designed based on compliant mechanism with flexure hinge and is compact in size (126 mm by 107 mm). Unlike traditional one-lever mechanisms, a new double-lever mechanism is developed to increase the working travel amplification ratio of the monolithic mechanism. The ideal amplification ratio, the working travel, the statics and the dynamics of the mechanism are taken into consideration. The effects of design variables on the output responses such as the displacement and first natural frequency are investigated via finite-element analysis based on response surface methodology. The fuzzy-logic-based Taguchi method is then used to simultaneously optimize the displacement and the first natural frequency. Experimental validations are conducted to verify the optimal results, which are compared to those of the original design. On using a finite-element method, the validation results indicated that the displacement and frequency are enhanced by up to 12.47% and 33.27%, respectively, over those of the original design. The experiment results are in a good agreement with the simulations. It also revealed that the developed fuzzy-logic-based Taguchi method is an effectively systematic reasoning approach for optimizing the multiple quality characteristics of compliant mechanisms. It was noted that the working travel/displacement of the double-lever mechanism is much larger than that of the traditional one-lever mechanism. It leads to the conclusion that the proposed mechanism has good performances for manipulations and positioning systems.
Integrated vibration in electrical discharge machining (EDM) plays a key role in achieving high efficiency. High levels of variables can be employed in this approach due to integration. However, simultaneous optimization of the EDM parameters to achieve multi-objectives is still very complex and challenging. Studies on integrated vibration are still in a preliminary stage. This report addresses multi-objective optimization in EDM for SKD61 die steel using low-frequency vibration. MOORA (Multi-objective optimization based on ratio analysis) was chosen to resolve this multi-objective optimization problem. The material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR) were selected as performance measures in the EDM process. An analytical hierarchical process (AHP) was used to determine the weight value of the quality indicators. The results indicate that low-frequency vibrations significantly improve machining efficiency. When the frequency of the vibrations increased, MRR increased significantly such that MRRMAX = 64.48%. TWR and SR are smaller and their increase are given as TWRMAX = 20.3% and SRMAX = 18.47%. MOORA has been identified as a suitable alternative to multi-objective optimization in an EDM process using low-frequency vibrations for an assigned workpiece. The optimum parameters required to achieve the multi-objective were Ton = 25 μs, I = 8 A, Tof = 5.5 μs and F = 512 Hz, at the resultant quality criteria of MRR = 9.564 mm3/min, TWR = 1.944 mm3/min and SR = 3.24 µm with a maximum error of 8.24%.
In this paper, the effectiveness of airfoil-shaped pier with and without a collar on local scour depth reduction is numerically investigated utilizing FLOW-3D model. The results show that on a constant T* = VT/D (V: velocity, T: time, D: pier width), increasing the width of the ballet of pier would result on the reduction of maximum scour depth and it would mitigate the scouring depth behind the piers. Also, because of lack of uplift vortices in using airfoil-shaped pier, there would be no scouring behind the piers. Utilizing collar on the airfoil-shaped pier would result in a reduction of maximum scouring depth in front of the pier as well and the uplift vortices behind the pier would reduce. Investigation of orientation discipline of the airfoil-shaped pier on flow route shows that the pier which is reversely placed in the flow direction (the keen part in front), will cause the horseshoe vortex to weaken and make the scouring to start from downstream. However, scouring caused by horseshoe vortex in front of the airfoil-shaped pier is strongly more than scouring caused by wake vortex in the rear of the pier.
In the present study, the estimation of suspended sediment load is computed by four Artificial Neural Networks (ANNs) algorithms, Cascade Forward Back Propagation (CFBP), Feed Forward Back Propagation (FFBP), Radial Basis Function (RBF), and Recurrent Neural Network (RNN). Five cases of model input are calibrated to establish the relationship among precipitation, discharge and suspended sediment load. While discharge and rainfall up to four previous days as employed for input, model gives pre-eminent performance. Sensitivity of all models is appraised concerning Nash-Sutcliffe coefficient (ENS) and coefficient of determination (R2) for predicting sediment load. Among all ANNs, MMF (Morgan-Morgan-Finney) model when trained with stream flow as the input in RNN, gives best result with coefficient of determination, R2 as 0.9474, while the values for FFBP, CFBP and RBF are 0.9115, 0.8766 and 0.8511, respectively. Performance of all results show that an MMF model is superior to conventional SRC (Sediment Rating Curve) and MLR (Multiple Linear Regression) models in determining the complex relationship between discharge and suspended sediment load.
The whole world understands about the crisis of harmful electronic waste as it is increasing the usage and its disposal. The Government of India asked researchers to come out with innovative alternative solutions, apart from existing conventional methods for safe reuse, recycling and proper disposal particularly for electronic solid waste system. The solution is found which consists of microwave heat treatment followed by acid leaching. The e-waste was first crushed and then the sample was melted in microwave heat treatment to recover the valuable metal in the form of metallic mixture. This mixture was further subjected to acid leaching process in the presence of hydrogen peroxide to form leached liquor. The analysis with X-ray diffraction, image mapping and energy-dispersive X-ray spectroscopy shows that the leached liquor sample mainly contain iron, aluminum and copper, mostly in the form of alloys. The results with field-emission scanning electron microscope analysis, also shows that approximately ninety percent leaching efficiency is observed for nickel, cobalt and copper with hydrochloric acid as solvent, whereas iron and aluminum produced less than forty percent. Further, these results are also compared with the existing methods based on the response surface method through thermal plasma process.
The present work was aimed at analysing the oxidation behaviour of three nickel-based superalloys-Superni 718, Superni 75 and Superni 750, by conducting in-situ study in the secondary chamber of a medical waste incinerator at 800–850°C for 1000 h. It was observed that among the three superalloys, Superni 75 is best suited for such an environment. This was concluded by comparing the weight change after 100 h for total 1000 h, constituting 10 thermal cycles. The morphology of the oxide scale formed on the substrate was analysed using FE-SEM. The elemental composition was obtained by EDS. The depth profiling of the scale was done using the XPS technique. The chemical composition was also examined by the XRD analysis. The superior oxidation property of Superni 75 is due to the higher Ni-Cr content. The oxidation resistance of the nickel-based superalloys in the aggressive environment of medical waste incinerator is attributed to the presence of chromia oxide-Cr2O3 and spinel NiCr2O4.
The number of cloud users and their aspiration for completion of tasks at less energy consumption and operating cost are rapidly increasing. Hence, the authors of this paper aim to minimize the makespan and operating cost by optimally scheduling the tasks and allocating the resources of cloud service. The optimum task scheduling and resource allocation are obtained for each objective function using the simple genetic algorithm. Further, the non-dominated solutions of the dual objectives are obtained using the non-dominated sorting genetic algorithm-II, the most successful multi-objective optimization technique. A complex cloud service problem consisting of ten tasks, fifteen subtasks and fifteen heterogeneous resources is considered to investigate the proposed method. The numerical results obtained in the single objective and multi objective optimization problems show that the makespan and the operating cost are significantly reduced using the simple genetic algorithm and a wide range of non-dominated solutions are obtained in the multi-objective optimization problem, by which the cloud users shall be benefitted to choose the most appropriate solution based on the other design constraints they have.
This paper highlights the machinability of primary recycled thermoplastics as workpiece (WP) material with secondary recycled (reinforced) thermoplastic composites as rapid tooling (RT). Both WP and RT have been 3D printed on commercial fused deposition modelling. For investigating machinability of primary recycled thermoplastics, un-reinforced WP of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) has been selected. The RT materials were secondary reinforced (recycled) LDPE with double particle size Al2O3 particles and HDPE with triple particle size Al2O3. The machinability has been calculated in terms of weight loss of WP, while machining on a vertical milling set-up. This study also reports the surface hardness, porosity, surface roughness (Ra) and photomicrographic observations of WP and RT under controlled machining conditions. Further thermal analysis suggests that primary recycled thermoplastic can be successfully machined with secondary recycled RT, resulting in improved thermal stability and surface properties.
Local scouring around sloped bridge piers in steady currents was studied both experimentally and mathematically. The effects of different inclination angles, flow intensities, flow depths, and pier size on local scouring were investigated. The experimental results show that the scouring depth increases with an increase in the values of discharge and pier width. The scouring depth for the sloped piers is smaller than the vertical piers one and the maximum scouring depth continuously decreases as the pier inclination angle increases. Prediction of the scouring depth around bridge piers using analytical models can be utilized in the feasibility studies of different models, and evaluations of the parametric analytical. Therefore, it was tried to model the scouring depth as a function of Froude number, flow intensity, and relative roughness parameters using non-dimensional analysis. The regression analysis based models were introduced to determine the scouring depth at upstream side of the pier using experimental tests data. Step-wise linear regression showed that the value of relative scouring depth has considerably good correlation only with two non-dimensionless parameters of inclination angle and normalized approaching flow depth. In this regard, some linear and nonlinear regression tools were utilized to establish functional relationships between these variables. Statistical indices and residual analyses of the models revealed the suitability of the models. Comparison of the experimental and predicted value of relative scouring depth illustrates that the suggested models can reasonably predict this parameter.
Voltage profile and real power loss are the criteria in determining performance of Radial Distribution System (RDS). Presence of Distributed Generators in RDS is assessed by ‘Penetration Ratio’. The use of PR fails in the analysis of the implications of the presence of a Microgrid on RDS as it is zero in islanded mode and sometimes in grid-connected mode. An attempt has been made to introduce a new term ‘Relief Factor’ to overcome this lacuna. This Factor is evaluated by developing an algorithm based on power flow analysis using Backward Forward Sweep method. The developed algorithm is tested on a 34 bus RDS by integration of a two-shift industrial Microgrid. The power flow analysis is run for 24 snapshots of the day. Relief Factor is found to be suitable to analyze the impact of a Microgrid on the performance of RDS in both the modes of Microgrid operation viz. grid-connected mode and islanded mode.
In order to explore the initial pH values of activator solution needed for early activation of slag at different temperatures, the effects of curing temperatures (5, 20 and 35°C) and pH (12.10, 12.55, 13.02 and 13.58) on the activation and hydration characteristics of ground granulated blast-furnace slag (GGBFS) were investigated. Sodium hydroxide (NaOH) was used as the alkaline activator. The compressive strength and non-evaporable water content of GGBFS paste cured for 1, 3, 7, 14 days were determined. The hydration characteristics of slag pastes at different temperatures and pH were analyzed by XRD and SEM. The results showed that the pH value required for slag activation decreased with increasing temperature. Based on the 3 days strength of slag paste, the pH values required for activation of slag activity at 5, 20 and 35°C were 13.58, 13.02 and 12.10, respectively. With the high temperature and high pH of solution, a dense calcium-rich product formed on the surface of slag particles, which suppressed the further slag reaction. With the low temperature and high pH of solution, a layer of network product was found on the surface of the slag particles, and the later strength developed rapidly as the further hydration was not prevented. This study provides a reference for the application of alkali-activated slag.
Agrochemical-based soil and water contamination has been posing serious threats to ecological balance. Current research investigates the sorption and mobility behaviour of a Benzylurea insecticide, Chlorfluazuron (CFZ), by a standard batch equilibrium method. After investigation of soils’ physical and chemical properties, sorption assays have been performed on five soils from agriculturally significant regions where CFZ can probably occur. CFZ expressed poor adsorption on the selected soils with linear adsorption coefficient, i.e. K d(ads), ranging between 6.08 and 9.57 µg/mL and Freundlich adsorption coefficient K f(ads) having a range of 4.18–9.01 µg/mL. Linear and Freundlich models displayed correlation coefficient R 2 value to be >0.84 and 0.83, respectively, reflecting the goodness of fit of the experimental data. Furthermore, the mobility of CFZ was assessed using the McCall classification based on K oc values. CFZ expressed high mobility in soils with less adsorption. The adsorptive and desorptive interactions were highly dependent upon soil physicochemical characteristics. Based on the current investigation, CFZ can be predicted to be a potential threat for soils with a low adsorptive affinity towards it. Future investigations in this regard can consider the use of sustainable materials and procedure for CFZ decontamination in vulnerable soils.
Electrohydrodynamic (EHD) inkjet is a modern non-contact printing approach, which uses a direct writing technology of functional materials to achieve micro/nanoscale of printing resolution. As an alternative to conventional inkjet technology, the goal of the EHD inkjet printing is to generate uniformly minimized droplets on a substrate. In this study, the effects of applied voltage, standoff height and ink flow rate on droplet diameter formation in EHD inkjet printing process were analysed using Taguchi methodology and regression analysis. Several experiments were carried out using an L27 (313) orthogonal array. Based on signal to noise (S/N) ratio and mean response, optimal droplet diameter was achieved. The analysis of variance (ANOVA) was used to find the significance and percentage of contribution of each input parameter along with their interaction on the output droplet diameter. Analysis of the results revealed that the ink flow rate was the dominant factor that affected the droplet diameter mostly. The effect of the applied voltage is significant until regular ejection starts. It helps reduce droplet diameter more than five times compared with its initial droplet diameter in the absence of the electric field. A confirmation test was carried out with a 90% confidence level to illustrate the effectiveness of the Taguchi optimization method. Both linear and quadratic regression analysis were applied to predict the output droplet diameter. The predicted result from the model and actual test results are very close to each other, justifying the significance of the models.
Transport technologies such as Optical Transport Network and Synchronous Digital Hierarchy are widely used in access and core networks to carry different types of traffic. These technologies define a hierarchy for multiplexing lower rate traffic containers onto higher rate traffic containers. Provisioning refers to the process of allocation of resources to meet a given traffic demand. Due to the continued expansion of transport networks, the power consumption increases, becoming a bottleneck for further expansion. Power-aware allocation of resources to traffic demands will enable power-efficient operation and help in minimizing the capital and operational costs of the network. In this paper, the power consumed by a switch matrix having the capability to switch different traffic containers at different amounts is considered. The objective is to minimize the number of network elements deployed in the network by allocating resources to traffic demands in power-efficient ways. A formulation based on Integer Linear Programming is first presented; later, four different heuristic approaches, based on how higher order trails are used and the use of grooming, are proposed. It is found that the grooming-based heuristics perform better in terms of the total power consumption relative to the weighted number of requests accepted. In the grooming heuristics, threshold on link utilization is set to determine when grooming is to be done, and for the same performance evaluation, it is found that the threshold of 80% gives better results.
E-governance or electronic governance is an application of Information and Communication Technology (ICT) for delivering cost-effective government services by any country to its citizens with reliability, transparency and efficiency. Majority of authentication schemes for e-governance in India are based on single-server environment. To access the services, users need to register themselves at the authentication server for every e-governance service. Various e-governance services work through different servers, and therefore users get registered on each server separately. These services and servers require a unified and integrated authentication scheme to overcome the problem of multiple registrations and login processes. This paper proposes a dynamic authentication protocol based on the identity of a user for multi-server architecture without using verification tables. It is also capable of integrating all the existing e-governance projects. The proposed protocol fulfills the security requirements such as mutual authentication, traceability and identity protection along with the facility to share a session key among all the servers for secure communication.