Speech enhancement via Mel-scale Wiener filtering with a frequency-wise voice activity detector

This paper presents a speech enhancement system that enables a comfortable communication inside an automobile. A couple of novel concepts are proposed in an effort to improve two major building blocks in the existing speech enhancement systems: a voice activity detector (VAD) and a noise filtering algorithm. The proposed VAD classifies a given data frame as speech or noise at each frequency, enabling the frequency-wise updates of noise statistics and thereby improving the effectiveness of the noise filtering algorithms by providing more up-to-date noise statistics. The celebrated Wiener filter is adopted in this paper as the accompanying noise filtering algorithm, which results in significant noise suppression. Yet, the musical noise present in most Wiener filter-based systems prompts the idea of applying the Wiener filter in the Mel-scale in which the human auditory system responds to the external stimulation. It turns out that the Mel-scale Wiener filter creates some masking effects and thereby reduces musical noise significantly, leading to smooth transition between data frames.     

Statistical energy analysis of non-resonant response of isotropic and orthotropic plates

The conventional SEA model considers only the resonant part of the structural response to an acoustic excitation. Therefore, this study investigates non-resonant responses of isotropic and orthotropic plates to acoustically induced vibrations in a reverberation chamber. A modified SEA model is introduced to predict the non-resonant plate response. The estimated non-resonant and resonant responses are then compared with those obtained experimentally, and good agreement is observed for isotropic and orthotropic plates. For an isotropic plate with a small dissipation loss factor, when the non-resonant part is ignored, the estimated response can lead to significant errors at frequencies near and above the critical frequency, while large errors may occur at frequencies below the critical frequency for an orthotropic plate with a high dissipation loss factor. The experimental study indicates that the non-resonant response component should be included in the estimated responses to enhance predictive accuracy.     

Particle deposition in random fibrous porous materials: effect of acoustic fields,fibres distribution and porosity

Porous filters are widely used to control air pollution and have different industrial applications since they constitute a reliable and low cost solution to separate particulate matter from an air stream.In this study, the particle deposition within 3D porous filters subjected to low-frequency acoustic fields is studied following a numerical approach. Findings demonstrate that the application of acoustic waves enhançes the deposition of particles, which in turn improves filter performance. It is shown that frequencies ranging from 200 to 1000 Hz (intensity 120 dB) increase particle deposition up to 2.5 times. Besides, the manner in which fibres are distributed in the porous material and the filter porosity affect considerably the number of particles deposited, for filters subjected to the same filtration velocity.     

Design,fabrication and experimental investigation of a planar pump using electro-conjugate fluid

This paper presents the design, fabrication, and experimental investigation of a novel planar pump using electro-conjugate fluid. The electro-conjugate fluid (ECF) is a kind of dielectric functional fluid which generates a powerful jet flow (ECF-jet) when a static electric field is applied via a pair of rod-like electrodes. This phenomenon that ECF can generate jet flows from the positive electrode to the ground electrode in an applied electric field is called the ECF effect, and converts electric energy directly into kinetic energy of the fluid. The ECF-jet acts directly on the working fluids; therefore, the proposed planar ECF pump requires no moving parts and produces no vibration or noise. The fabricated planar ECF pump consists of three parts: a pump base, a top cover, and an electrode substrate with dimensions of 280 mm × 190 mm × 1 mm. In this paper, five different electrode patterns and three different flow channel heights were investigated for the realization of a high-performance planar ECF pump. Each array of electrodes was patterned on the glass epoxy substrates using a wet-etching process, and the flow channel heights were either 200 μm, 300 μm, or 500 μm. The pumping experiments used FF-1_EHA2 as the working fluid. Experimentation showed that a no-load flow rate of 5.5 cm³/s, maximum output pressure of 7.2 kPa, and maximum output power of 11.6 mW were achieved at an applied voltage of 2.0 kV.     

Investigating elastic stability of cylindrical shell with an elastic core under axial compression by energy method

In this paper, the elastic axisymmetric buckling of a thin, isotropic and simply supported cylindrical shell with an elastic core under axial compression has been analyzed using energy method. The nonlinear strain-displacement relations in general cylindrical coordinates are simplified using Sanders kinematic relations (Sanders, 1963) for axial compression. Equilibrium equations are obtained by using minimum potential energy together with Euler equations applied for potential energy function in cylindrical shell. To acquire stability equation of cylindrical shell with an elastic core, minimum potential energy theory and Trefftz criteria are implemented. Stability and compatibility equations for an imperfect cylindrical shell with an elastic core are also obtained by the energy method, and the buckling analysis of shell is carried out using Galerkin method. Critical load curves versus the aspect ratio are obtained and analyzed for a cylindrical shell with an elastic core. It is concluded that the application of an elastic core increases elastic stability and significantly reduces the weight of cylindrical shells.     

A new method of controlling cavity-induced pressure oscillations using sub-cavity

A new passive control technique of cavity-induced pressure oscillations has been investigated numerically for a supersonic two-dimensional flow over open rectangular cavities at Mac h number 1.83 at the cavity entrance. A subcavity on the front wall of the cavity covered by a flat plate was evaluated for the effectiveness of controlling cavity-induced acoustic oscillations. The results showed that sub-cavity is very effective in reducing cavity-induced pressure oscillations. The results also showed that the resultant amount of attenuation of cavity-induced pressure oscillations was dependent on the length and thickness of the flat plate, and also on the depth of the sub-cavity used as an oscillation suppressor.     

Numerical and experimental studies of thin liquid film flow between two forward-rollers

Roll coating is a widely used industrial technique to deposit a thin and uniform liquid film on a sheet or solid substrate. In this paper the three dimensional forward roll coating process has been studied by both experiments and numerical simulations. Experiments were conducted on a 2 roll coating system of pick up roll and application roll using two samples of 50% and 70% by weight aqueous glycerin solutions. The gap between the two rollers at nip was maintained at 100 microns. The coating film thickness and the distance of the film splitting point from the nip were measured during the experiments. The coating film thickness was determined for different speed ratios for both samples. 3D Numerical simulations for forward coating process have been carried out and the simulation results were verified were with experiments. They match very well, the error between them being 5% to 10%.     

An analytical study on the thermal characteristics of flat-plate and evacuated solar collectors

In this study, we highlighted differences in the standards used in performance tests of solar collectors. We analyzed testing results for different types of solar collectors to determine the effects of the collector area and mass flow rate, which were not necessarily consistent across all tests. Our analysis showed that the factor,F′ (τα), including collector efficiency factor (F′), could be correlated with the flow rate or area regardless of the collector type. Moreover, the collector loss coefficient (F′U _L ) per flow rate or area for an evacuated collector was less that of a flat-plate collector; this was also correlated with the flow rate or area, regardless of the type of evacuated collector. As a result of this analysis, we propose a modified heat loss coefficient that includes the effects of all parameters that can be considered in a performance test and show that this coefficient could better describe the thermal characteristics of various types of solar collectors.     

Heat and mass transfer enhancement of the bubble absorption for a binary nanofluid

The main objective of this study is to enhance the heat and transfer process of absorption using the nanofluids as the working medium. Carbon nanotubes—ammonia nanofluids (the binary nanofluids) are prepared. The thermal conductivity of the binary nanofluids and the bubble absorption process enhancement are examined experimentally. The results show the thermal conductivity of the carbon nanotubes—ammonia nanofluid is higher 16% than that of NH₃/H₂O solution. And the carbon nanotubes—ammonia nanofluid has a great enhanced effect to the NH₃/H₂O absorption.     

A study on the force balance of an unbalanced globe valve

A pneumatic control valve is a piping element that controls the volumetric flow rate and pressure of a fluid; it is necessary to analyze the characteristics of the forces with respect to the opening of the valve in order to evaluate its operating performance. The forces occurring during operation are: resisting force and actuator force, where the load resistance is mostly affected by the fluid pressure difference of the valve. In this study, a force balance equation derived from the equilibrium relationship between the resisting force and the actuator force of an unbalanced globe valve is proposed, and the force balance equations are used to model the dynamic equations of a pneumatic unbalanced globe valve installed in nuclear power plants. A CFD analysis is also carried out to evaluate the pressure distribution and forces acting on the top and bottom planes of the valve plug. The results of this analysis have been verified through experimentation. This study has shown that the fluid pressure difference between the inlet and outlet of the valve, measured from the force balance equation of an unbalanced valve, should actually be examined with the fluid-pressure difference between the top and bottom side of the valve plug.