Channel Transfer Research Articles

Dynamic Power Splitting for SWIPT With Nonlinear Energy Harvesting in Ergodic Fading Channel

We study the dynamic power splitting for simultaneous wireless information and power transfer (SWIPT) in the ergodic fading channel. Considering the nonlinearity of practical energy harvesting circuits, we adopt the realistic nonlinear energy harvesting (EH) model rather than the idealistic linear EH model. To characterize the optimal rate-energy (RE) tradeoff, we consider the problem of maximizing the R-E region, which is nonconvex. We solve this challenging problem for two different cases of the channel state information (CSI): (i) when the CSI is known only at the receiver (the CSIR case) and (ii) when the CSI is known at both the transmitter and the receiver (the CSI case). For these two cases, we develop the corresponding optimal dynamic power splitting schemes. To address the complexity issue, we also propose the suboptimal schemes with low complexities. Comparing the proposed schemes to the existing schemes, we provide various useful and interesting insights into the dynamic power splitting for the nonlinear EH. Furthermore, we extend the analysis to the scenarios of the partial CSI at the transmitter and the harvested energy maximization. Numerical results demonstrate that the proposed schemes significantly outperform the existing schemes and the proposed suboptimal scheme works very close to the optimal scheme at a much lower complexity.

Evaluation of Human Body Characteristics for Electric Signal Transmission Based on Measured Body Impulse Response

Human body communications (HBCs) have recently emerged as an innovative alternative to the current radio frequency communications for realizing wireless body area networks (WBANs) using the human body as a transmission channel without wired or wireless connections. This article addresses the provision of reliable modeling of the human body as a passage of the electric signal delivery based on the impulse response measurement through the proposal of a measurement setup and signal processing techniques applicable to wearable devices for healthcare and biosignal acquisition. In the experiments, customized impulse signals were applied to the body using battery-powered devices isolated to the earth ground for the operating environments of wearable devices. The impulse responses passed through the body were measured by considering 52 measurement conditions determined by the device locations from the head to ankle and the body postures. Body channel transfer functions (BCTFs) for the respective conditions were derived by an adaptive filter approach using an iterative algorithm to minimize the mean squared error between the measured and modeled impulse responses. The channel analysis parameters, such as mean path loss, root-mean-square delay spread, and mean and maximum excess delays, were analyzed based on the measured body impulse responses. In addition, the practical bit-error-rate performance for HBC based on the BCTFs reproducing intersymbol interference effects caused by the delay spreads of the body channels was explored to verify communication reliability in terms of the transmitter structures adopting digital transmission, sorts of human body channels, data rates, and operating frequencies.

Experimental study of single-phase flow and heat transfer in rectangular channels under uniform and non-uniform heating

Characteristics of single-phase convective heat transfer in a rectangular channel are reported for heated and non-heated conditions. Results indicated that the friction factors were basically the same in the laminar region. However, in the transition and quasi-turbulent region, the heated friction factor was slightly lower than the non-heated values, and the value of non-uniform heating was slightly higher than that of uniform heating. The transition started critical Reynolds number increased from 2700 without heating to about 3000 with heating only due to the viscosity decreased with increasing temperatures. Due to the transition started and ended Reynolds number increased simultaneously under heating, the width of flow transition was almost the same as that without heating. The transverse power distribution influenced the average Nusselt number of the channel, although measured differences were small for uniform and non-uniform heating conditions. For the heat transfer data under uniform heating conditions obtained in this study, 15 correlations were evaluated. It is found that the existing correlations underestimated the experimental data for Re < 3000 and overestimated the data for 3000 < Re < 6000. A large database of heat transfer in rectangular channels including the experimental data obtained from this study and other researchers' work was established, and new heat transfer correlations for laminar (Re < 3000) and transition (3000 < Re < 10000) flows were developed. The Dittus-Boelter correlation was confirmed to provide a good prediction for the heat transfer for Re > 10000, with almost all data being within ±20% errors.

A Brief History of Pacemaking.

Cardiac pacemaking is a most fundamental cardiac function, thoroughly investigated for decades with a multiscale approach at organ, tissue, cell and molecular levels, to clarify the basic mechanisms underlying generation and control of cardiac rhythm. Understanding the processes involved in pacemaker activity is of paramount importance for a basic physiological knowledge, but also as a way to reveal details of pathological dysfunctions useful in the perspective of a therapeutic approach. Among the mechanisms involved in pacemaking, the “funny” (If) current has properties most specifically fitting the requirements for generation and control of repetitive activity, and has consequently received the most attention in studies of the pacemaker function. Present knowledge of the basic mechanisms of pacemaking and the properties of funny channels has led to important developments of clinical relevance. These include: (1) the successful development of heart rate-reducing agents, such as ivabradine, able to control cardiac rhythm and useful in the treatment of diseases such as coronary artery disease, heart failure and tachyarrhythmias; (2) the understanding of the genetic basis of disorders of cardiac rhythm caused by HCN channelopathies; (3) the design of strategies to implement biological pacemakers based on transfer of HCN channels or of stem cell-derived pacemaker cells expressing If, with the ultimate goal to replace electronic devices. In this review, I will give a brief historical account of the discovery of the funny current and the development of the concept of If-based pacemaking, in the context of a wider, more complex model of cardiac rhythmic function.

Analysis and application of a convergent difference scheme to nonlinear transport in a Brinkman flow

Purpose The purpose of this paper is to formulate and analyse a convergent numerical scheme and apply it to investigate the coupled problem of fluid flow with heat and mass transfer in a porous channel with variable transport properties. Design/methodology/approach This paper derives the model by assuming a fully developed Brinkman flow with temperature-dependent viscosity and incorporating viscous dissipation, variable transport properties and nonlinear heat and mass sources. For the numerical formulation, the nonlinear sources are treated in semi-implicit manner, whereas the non-constant transport properties are treated by lagging in time leading to decoupled diagonally dominant systems. The consistency, stability and convergence results are derived. The method of manufactured solutions is adopted to numerically verify the theoretical results. The scheme is then applied to investigate the impact of relevant parameters, such as the viscosity parameter, on the flow. Findings Based on the numerical findings, the proposed scheme was found to be unconditionally stable and convergent with first- and second-order accuracy in time and space, respectively. Physical results showed that the flow parameters have influence on the flow fields, particularly, the flow is enhanced by increasing porosity and viscosity parameters and the concentration decreases with increasing diffusivity, whereas both the temperature and Nusselt number decrease with increasing thermal conductivity. Practical implications Numerically, the proposed numerical scheme can be applied without concerns on time steps size restrictions. Non-physical solutions cannot be computed. Physically, the flow can be increased by increasing the viscosity parameters. Pollutants with higher diffusivity will have their concentration decreased faster than those of lower diffusivity. The fluid temperature would decrease faster if its thermal conductivity is higher. Originality/value A fully coupled fluid flow with heat and mass transfer problem having nonlinear properties and nonlinear fractional sources and sink terms, presumably, has not been investigated in a general form as done in this study. The detailed numerical analysis of this particular scheme for the identified general model has also not been considered in the past, to the best of the author’s knowledge.

Heat transfer in an unsteady vertical porous channel with injection/suction in the presence of heat generation

This paper studies convective heat transfer in an unsteady vertical porous channel with suction/injection in the presence of heat generation. A semi-implicit finite difference method was employed to solve the Cartesian coordinate forms of the governing equations. Subsequently, the entropy generation number for varying values of intrinsic parameters, as well as the temperature and velocity profile, Bejan number and irreversibility of the system were successfully calculated. We observed that the convective cooling by suction is more effective on thermal properties than injection convective cooling. Hence, the process of entropy can be enhanced by convective heat transfer and viscous dissipation.

Effects of Hall Current and Ohmic Heating on Non-Newtonian Fluid Flow in a Channel due to Peristaltic Wave

In this paper, the study of non-Newtonian fluid flow with heat transfer in a porous asymmetric channel due to peristaltic wave was taken out. Hall current and Ohmic heating effects were introduced in the present study. A Casson non-Newtonian constitutive model was employed for the transport of fluid. Analytical solutions were obtained for stream function, temperature and heat transfer coefficient. The coupled nonlinear equations have also been solved numerically using MATLAB software (by bvp4c function). The influences of many evolving parameters on the flow characteristic have been explained with the help of 2D and 3D plots. Again the obtained results were compared with the results available in the literature and were found in good agreement.

Optimal Transceiver Design for SWIPT in Interference Alignment Network

This paper studies simultaneous wireless information and power transfer in a K-user multiple-input multiple-output interference channel. A new scheme jointly designing interference ali ...

Biologically inspired transport of solid spherical nanoparticles in an electrically-conducting viscoelastic fluid with heat transfer

Bio-inspired pumping systems exploit a variety of mechanisms including peristalsis to achieve more efficient propulsion. Non-conducting, uniformly dispersed, spherical nanosized solid particles suspended in viscoelastic medium forms a complex working matrix. Electromagnetic pumping systems often employ complex working fluids. A simulation of combined electromagnetic bio-inspired propulsion is observed in the present article. Currents formation has increasingly more applications in mechanical and medical industry. A mathematical study is conducted for MHD pumping of a bi-phase nanofluid coupled with heat transfer in a planar channel. Two-phase model is employed to separately identity the effects of solid nanoparticles. Base fluid employs Jeffery?s model to address viscoelastic characteristics. The model is simplified using long wavelength and creeping flow approximations. The formulation is taken to wave frame and non-dimensionalise the equations. The resulting boundary value problem is solved analytically, and exact expressions are derived for the fluid velocity, particulate velocity, fluid-particle temperature, fluid and particulate volumetric flow rates, axial pressure gradient and pressure rise. The influence of volume fraction density, Prandtl number, Hartmann number, Eckert number, and relaxation time on flow and thermal characteristics is evaluated in detail. The axial flow is accelerated with increasing relaxation time and greater volume fraction whereas it is decelerated with greater Hartmann number. Both fluid and particulate temperature are increased with increment in Eckert and Prandtl numbers, whereas it is reduced when the volume fraction density increases. With increasing Hartmann number pressure rise is reduced

Mathematical Model of Electromembrane Separation of Copper-Electroplating Production Solutions

This study is devoted to the development of a mathematical model of electromembrane separation of copper-containing solutions in copper plating industry based on the solution of the Nernst–Planck and Poisson–Boltzmann equations. The model tracks the dependence of the volumetric permeate flows and solution concentration on the time of the electromembrane process. The mathematical model allows us to calculate the concentration at the outlet of the electromembrane apparatus, specific outlet flow of the solvent, and energy consumption for membrane separation of solutions. The equations of the model allow for mass transfer and solution flow hydrodynamics in the intermembrane channel. The adequacy of the mathematical model was verified by comparing the calculated and experimental data on the change in the concentration of the desired substance in the retentate relative to pressure at a constant current density.

Effect of optically thick radiation heat transfer in a horizontal channel

Effect of optically thick radiation heat transfer in a horizontal channel

Impact of Velocity Second Slip and Inclined Magnetic Field on Peristaltic Flow Coating with Jeffrey Fluid in Tapered Channel

The peristaltic flow of velocity second slip boundary conditions and inclined magnetic field of Jeffrey fluid by means of heat and mass transfer in asymmetric channel was inspected in the present study. Leading equations described the existing flow were then simplified under lubrication approach. Therefore, exact solutions of stream function, concentration and temperature were deduced. Further, the numerical solutions of pressure rise and pressure gradient were computed using Mathematica software. Furthermore, the effect of the second slip parameter was argued via graphs. It has been depicted that this kind of slip is mandatory and very imperative to foresee the physical model. On the other hand, false results will be obtained.

Effect of Vortex Generator on Flow and Heat Transfer in Rectangular Channel

Effect of Vortex Generator on Flow and Heat Transfer in Rectangular Channel

Matched-Phase Weighting Beamformer to Improve the Gain of a Long Linear Array in the Range-Dependent Ocean Waveguide

The array gain degrades significantly suffering from a decrease of signal spatial coherence caused by imperfectly correlated acoustic channels with spatial and temporal fluctuations. For a long linear array collecting signals in the range-dependent ocean waveguide, the amplitude and phase of the received signals show more viriation over the elements, which causes the signal coherence to attenuate seriously. The gain of traditional beamformers, such as the conventional beamformer (CBF), minimum variance distortionless response beamformer (MVDR-BF), and eigenvalue beamformer (EBF), will deviate from their ideal values. In this paper, a matched-phase weighting beamformer (MPBF) is proposed to obtain high gain in an ocean waveguide. The variational phase of acoustic channel transfer functions over the elements can be compensated for by matched-phase weighting, and then, the acoustic channel spatial coherence can be restored to achieve a high gain. The weighting-matrix of MPBF is obtained by the received signals; hence, environmental parameters or channel transfer functions do not have to be estimated. Simulations and experiments considering a long horizontal uniform linear array (HLA) in the slope region receiving a narrow-band signal from a deep-water source (upslope waveguide) are performed. The results demonstrate that MPBF can achieve a higher gain than CBF, MVDR-BF and EBF in a complex ocean waveguide.

Machine Learning Detectors for MU-MIMO Systems With One-Bit ADCs

We consider an uplink multiuser multiple-input multiple-output (MU-MIMO) system with one-bit analog-to-digital converters (ADCs). In this system, the construction of a low-complexity detector is quite challenging due to the non-linearity of an end-to-end channel transfer function. Recently, a supervised-learning (SL) detector was proposed by modeling the complex non-linear function as a tractable Bernoulli-mixture model. It achieves an optimal maximum-likelihood (ML) performance, provided the channel state information (CSI) is perfectly known at a receiver. However, when a system-size is large, SL detector is not practical because of requiring a large amount of labeled data (i.e., pilot signals) to estimate the model parameters. We address this problem by proposing a semi-supervised learning (SSL) detector in which both pilot signals (i.e., labeled data) and some part of data signals (i.e., unlabeled data) are used to estimate them via expectation-maximization (EM) algorithm. We further extend the proposed detector for time-varying channels, by leveraging the idea of online learning, which is called online-learning (OL) detector. Simulation results demonstrate that the proposed SSL detector can achieve the almost same performance of the corresponding SL detector with significantly lower pilot overhead. In addition, it is shown that the proposed OL detector is more robust to channel variations compared with the existing detectors.

Convolutional-Type Neural Networks for Fading Channel Forecasting

In this article, a series of convolutional-type predictive neural networks are proposed for the issue of fading channel forecasting for orthogonal frequency-division multiplexing (OFDM) transmission systems in a multiple-input and multiple-output (MIMO) mode via a noisy channel. The proposed neural networks all employ convolutional connections that operate in a translation-invariant manner in the frequency domain of the time-varying channel transfer function, which effectively tackles the essential challenges of high dimensionality and denoising. Each of the proposed convolutional-type neural networks is built on a specific overall network architecture and functions as an independent predictor that offers advantages regarding a specific aspect such as accuracy over a certain prediction span or computational effort. Comparative evaluations against common prediction methods such as the Kalman filtering scheme and the standard long-short term memory units (LSTMs) are provided on the basis of transmission simulations over dispersive fading channels with Rayleigh components according to the well-established 3GPP Long Term Evolution (LTE) standards.

Improved RMS Delay Spread Estimation for mmWave Channels Using Savitzky–Golay Filters

In this paper, a novel method for improving the estimation accuracy of the root mean square (RMS) delay spread from the magnitude of the Channel Transfer Function (CTF) is presented. We utilize the level crossing rate metric in the frequency domain, which is based on scalar power measurement. The Savitzky–Golay (S-G) filtering method is used to improve the fidelity of the channel delay spread estimator. The presented concept is simple to implement and inexpensive. The proposed method is tested on the CTF magnitude data measured in the mmWave frequency band at low Signal-to-Noise Ratio (SNR).

Високочастотна плазма при атмосферному тиску як засіб осадження тонких плівок

The main units of the industrial high-frequency generator have been modernized. The design and technical coordination of the plasma torch impedance was developed in order to obtain high-frequency plasma with capacitive coupling for the transmission of electrical energy at atmospheric pressure. The data on the main elements of the structures of adapted units are given, their functional purpose is indicated. Special attention is paid to the principles of operation of the modified units of equipment and their functional relationship when controlling the process of synthesis of films for nanotechnology. The reasons why nanotechnology is not widespread on the existing high-frequency capacitive plasmatrons are analyzed. New effects of high-frequency plasma and ways to improve the plasmatron for deposition of thin films were discovered. A theoretical justification for the effect of working substance transfer in a plasma channel (cord) of a high-frequency capacitive discharge is found. The possibility of ignition of a single-electrode high-frequency flare discharge from a plasma of a high-frequency capacitive discharge is experimentally proved. An explanation of the structure of high-frequency flare discharge under these conditions is given. The possibility of using the near-electrode spot of the torch for the vapor concentration of the working substance and the deposition of the film is revealed. The main regularities for the synthesis of nanofilms on the example of zinc and aluminum oxides are investigated. Pyrolysis is chosen among plasma chemical reactions to prepare a pair of working substances. Plasma luminescence of high-frequency capacitive discharge is studied for the purpose of effective plasmochemical reactions in the channel of argon plasma discharge and steam supply of the working substance to the substrate. Thin layers of Al2O3 and ZnO are synthesized by a new method using high-frequency argon plasma at atmospheric pressure.

Heat Transfer and Pressure Drop Measurements in a High Aspect Ratio Channel With Circular Pins and Strip Fins

Abstract This paper focuses on the measurements of heat transfer enhancement and pressure drop of different pin or fin configurations in a high aspect ratio (AR = 9.57/1.2) channel. Two different pin-fin shapes including circular pins and strip fins were studied. Different pin-fin spacings for circular pins (S/D = 2, 4) and strip fins (S/W = 8, 16) were investigated, respectively. In addition, the thickness effect of the strip fin was included in this study. The regionally averaged heat transfer measurement method was used to acquire the heat transfer coefficients on two opposite featured surfaces within the test channel. For each configuration, the tested Reynolds number was ranging from 20,000 to 80,000. The results indicate that the channel with circular pins has better heat transfer enhancement and higher pressure loss than their strip fins counterparts. However, the strip fins are considered better designs in terms of thermal performance. For the gas turbine designers aim at developing an improved internal cooling feature, this work demonstrates the great potential of the strip fins as a novel and effective cooling design compared with the conventional circular pins.

Nanofluid Heat and Mass Transfer in a Deformable and Peristaltic Pump

Flow heat and mass transfer in a deformable channel of peristaltically moving walls is investigated in this paper. Moreover, the channel is filled with nanofluids. The purpose of this study is to examine the combined effects of surface deformation and peristaltic movement of the walls on the nanofluid flow in a channel. We have considered the effects of nanofluid in the peristaltically deformable porous channel whose walls are contracting or expanding in the normal direction. Nanofluids have been used to enhance the thermo-physical properties of fluids such as thermal diffusivity, thermal conductivity and convective heat transfer coefficients on flow and heat transfer. The analytic solution of the problem have been presented. We have analyzed the effects of different involved parameters such as Reynolds number, surface deformation parameter, Prandtl number, wave number, Brownian and thermophoretic diffusion parameters and Schmidt number on the velocity profile, the temperature profile, pressure distribution and the concentration profile with the help of graphs. The results are shown graphically and discussed physically. It is observed that the deformation increases the axial velocity and temperature of the fluid.