Symmetric Channel Research Articles

A study of cold roll forming technology and peak strain behavior of asymmetric corrugated channels

The peak strain (PS) of sheet metal highly affects the process design and the quality of roll formed product. Different from the traditional roll forming technology (RFT) that all the cross section contours of the product are rolled simultaneously, a symmetric RFT is developed with respect to the corrugated channels to avoid defects like tearing, twist, and redundant deformations. The behaviors of their peak strains are subsequently simulated with finite element (FE), and the effects of three factors of the rolling speed, friction coefficient, and the bending angle of roll are analyzed, respectively. Finally, both the rationality of RFT and the accuracy of final rolled product are verified by experiments. Results show that the maximum peak strains are also distinguished for their different channel width, with respect to two symmetrical channels forming simultaneously even under the same bending angle and the pressure of roll. The maximum PS of the narrow channel is significantly larger than that of the wide, and the closer to the middle channel, the greater the PS of the narrow channel, which is on the right of bending angle of the trough. Moreover, the maximum PS is mainly influenced by the friction coefficient and bending angle of the first forming pass. This can provide a reference for other design of RFT and rolled forming quality improvement of the corrugated channels.

Two-dimensional diffusion biased by a transverse gravitational force in an asymmetric channel: Reduction to an effective one-dimensional description.

We focus on the derivation of a general position-dependent effective diffusion coefficient to describe two-dimensional (2D) diffusion in a narrow and smoothly asymmetric channel of varying width under a transverse gravitational external field, a generalization of the symmetric channel case using the projection method introduced earlier by Kalinay and Percus [P. Kalinay and J. K. Percus, J. Chem. Phys. 122, 204701 (2005)10.1063/1.1899150]. To this end, we project the 2D Smoluchowski equation into an effective one-dimensional generalized Fick-Jacobs equation in the presence of constant force in the transverse direction. The expression for the diffusion coefficient given in Eq.(34) is our main result. This expression is a more general effective diffusion coefficient for narrow 2D channels in the presence of constant transverse force, which contains the well-known previous results for a symmetric channel obtained by Kalinay, as well as the limiting cases when the transverse gravitational external field goes to zero and infinity. Finally, we show that diffusivity can be described by the interpolation formula proposed by Kalinay, D_{0}/[1+(1/4)w^{'2}(x)]^{-η}, where spatial confinement, asymmetry, and the presence of a constant transverse force can be encoded in η, which is a function of channel width (w), channel centerline, and transverse force. The interpolation formula also reduces to well-known previous results, namely, those obtained by Reguera and Rubi [D. Reguera and J. M. Rubi, Phys. Rev. E 64, 061106 (2001)10.1103/PhysRevE.64.061106] and by Kalinay [P. Kalinay, Phys. Rev. E 84, 011118 (2011)10.1103/PhysRevE.84.011118].

A novel mathematical modeling with solution for movement of fluid through ciliary caused metachronal waves in a channel

In the present research, a novel mathematical model for the motion of cilia using non-linear rheological fluid in a symmetric channel is developed. The strength of analytical perturbation technique is employed for the solution of proposed physical process using mectachoronal rhythm based on Cilia induced flow for pseudo plastic nano fluid model by considering the low Reynolds number and long wave length approximation phenomena. The role of ciliary motion for the fluid transport in various animals is explained. Analytical expressions are gathered for stream function, concentration, temperature profiles, axial velocity, and pressure gradient. Whereas, transverse velocity, pressure rise per wave length, and frictional force on the wall of the tubule are investigated with aid of numerical computations and their outcomes are demonstrated graphically. A comprehensive analysis for comparison of Perturb and numerical solution is done. This analysis validates the analytical solution.

The integrated MHD thermal performance with slip conditions on metachronal propulsion: the engineering material for biomedical applications

PurposeParticular attention is given to the viscous damping force parameter, stiffness parameter, rigidity parameter, and Brinkman number and plotted their graph for thermal distribution, momentum profile and concentration profile.Design/methodology/approachIn the field of engineering, biologically inspired propulsion systems are getting the utmost importance. Keeping in view their developmental progress, the present study was made. The theoretical analysis explores the effect of heat and mass transfer on non-Newtonian Sisko fluid with slip effects and transverse magnetic field in symmetric compliant channel. Using low Reynolds number, so that the authors neglect inertial forces and for keeping the pressure constant during the flow, channel height is used largely as compared to the ratio of wavelength. The governing equations of fluid flow problem are solved using the perturbation analysis.FindingsResults are considered for thickening, thinning and viscous nature of fluid models. It is found that the velocity distribution profile is boosted for increasing values of the Sisko fluid parameter and porous effect, while thermal profile is reducing for Brinkman number (viscous dissipation effects) for all cases. Moreover, shear-thicken and shear-thinning behavior of non-Newtonian Sisko fluid is also explained through the graphs.Originality/valueHear-thicken and shear-thinning behavior of non-Newtonian Sisko fluid is also explained through the graphs.

On a Casson Fluid Motion: Nonuniform Width Symmetric Channel and Peristaltic Flows

Widely used for modeling biological fluids flows—in particular, blood vessel flows—a Casson flow is studied in a symmetric channel for which the aspect ratio enables one to use the lubrication approximation. Two flow driving conditions are prescribed: inlet–outlet pressure difference and peristaltic oscillations of the vessel walls. In both cases, starting from mass and momentum balance and using lubrication approximation, we investigate the conditions to be imposed on the driving mechanisms so that the inner plug does not come in touch with the walls. The study of the peristaltic flow is of great importance in view of its applications in physiology (including microcirculation applications).

Effect of Asymmetry of Channels on Flows in Parallel Plates with a Sudden Expansion

In order to quantitatively grasp the influence of asymmetry of a channel, flow in an eccentric sudden expansion channel, in which the channel centers are different on the upstream and downstream sides, was calculated to be less than the Reynolds number of 400, where the expansion rate was 2. The asymmetry of a channel is expressed by an eccentricity S, where a symmetric expansion channel is S = 0 and a channel with one side step is S = 1. Both flows firstly reattached on the wall located on the short and long side of a sudden expansion and were observed in the range of S ≤ 0.2, although only the former was seen in the range of S > 0.2. The critical Reynolds number of the multiple solutions increases parabolically to S. At least two separation vortices occur, and the third separation vortex is generated in both solutions above the critical Reynolds number of the third vortex. The length of an entrance region increases linearly to the Reynolds number and slightly with the increase in S. The pressure drop coefficient is proportional to the power of the Reynolds number and increases with S.

Error Exponents in the Bee Identification Problem

The bee identification problem is a problem of properly recognizing a massive amount of data (a numerous amount of bees in a beehive, for example) which have been mixed and corrupted by noise. We derive various error exponents in the bee identification problem under two different decoding rules. Under naïve decoding, which decodes each bee independently of the others, we analyze a general discrete memoryless channel and a relatively wide family of stochastic decoders. Upper and lower bounds to the random coding error exponent are derived and proved to be equal at relatively high coding rates. Then, we propose a lower bound on the error exponent of the typical random code, which improves upon the random coding exponent at low coding rates. We also derive a third bound, which is related to expurgated codes, which turns out to be strictly higher than the other bounds, also at relatively low rates. We show that the universal maximum mutual information decoder is optimal with respect to the typical random code and the expurgated code. Moving further, we derive error exponents under optimal decoding, the relatively wide family of symmetric channels, and the maximum likelihood decoder. We first propose a random coding lower bound, and then, an improved bound which stems from an expurgation process. We show numerically that our second bound strictly improves upon the random coding bound at an intermediate range of coding rates, where a bound derived in a previous work no longer holds.

New insights on manipulating the material removal characteristics of Jet-Electrochemical machining through nozzle design

Jet-Electrochemical machining (Jet-ECM) is a novel variation of traditional electrochemical machining in which electrically conductive material is removed through anodic dissolution by means of a fine jet of electrolyte. In this study, the effect of nozzle geometry on material removal characteristics are investigated through physical experiments performed on a Jet-ECM system under development at the university of Manchester. A total of 8 nozzles with holes encompassing converging, diverging and rounded features are studied at flow rates between 0.125 and 0.225 l/min. The results show that the nozzle hole geometry has a significant effect on the machined profile produced due to variations in flow velocity, pressure, and electric current distribution with converging hole nozzles providing an increased depth of cut than the symmetrical cylindrical channel by up to 9.7%. A 2D Star CCM+ simulation is also proposed, and numerical results developed and compared with experimental ones to investigate the feasibility of using simulation to develop future nozzle designs. The simulated results show good profile comparison to the experimental results, however, the model needs developing to improve the process repeatability for future use in nozzle design.

Optimized Polar Codes as Forward Error Correction Coding for Digital Video Broadcasting Systems

Polar codes are featured by their low encoding/decoding complexity for symmetric binary input-discrete memoryless channels. Recently, flexible generic Successive Cancellation List (SCL) decoders for polar codes were proposed to provide different throughput, latency, and decoding performances. In this paper, we propose to use polar codes with flexible fast-adaptive SCL decoders in Digital Video Broadcasting (DVB) systems to meet the growing demand for more bitrates. In addition, they can provide more interactive services with less latency and more throughput. First, we start with the construction of polar codes and propose a new mathematical relation to get the optimized design point for the polar code. We prove that our optimized design point is too close to the one that achieves minimum Bit Error Rate (BER). Then, we compare the performance of polar and Low-Density Parity Check (LDPC) codes in terms of BER, encoder/decoder latencies, and throughput. The results show that both channel coding techniques have comparable BER. However, polar codes are superior to LDPC in terms of decoding latency, and system throughput. Finally, we present the possible performance enhancement of DVB systems in terms of decoding latency and complexity when using optimized polar codes as a Forward Error Correction (FEC) technique instead of Bose Chaudhuri Hocquenghem (BCH) and LDPC codes that are currently adopted in DVB standards.

Soft decoding of short/medium length codes using ordered statistics for quantum key distribution

Quantum key distribution (QKD) is a cryptographic communication protocol that utilizes quantum mechanical properties for provable absolute security against an eavesdropper. The communication is carried between two terminals using random photon polarization states represented through quantum states. Both these terminals are interconnected through disjoint quantum and classical channels. Information reconciliation using delay controlled joint decoding is performed at the receiving terminal. Its performance is characterized using data and error rates. Achieving low error rates is particularly challenging for schemes based on error correcting codes with short code lengths. This article addresses the decoding process using ordered statistics decoding for information reconciliation of both short and medium length Bose–Chaudhuri–Hocquenghem codes over a QKD link. The link’s quantum channel is modeled as a binary symmetric quantum depolarization channel, whereas the classical channel is configured with additive white Gaussian noise. Our results demonstrate the achievement of low bit error rates, and reduced decoding complexity when compared to other capacity achieving codes of similar length and configuration.

Covert Communication Over Adversarially Jammed Channels

Suppose that a transmitter Alice potentially wishes to communicate with a receiver Bob over an adversarially jammed binary channel. An active adversary James eavesdrops on their communication over a binary symmetric channel (BSC( q)), and may maliciously flip (up to) a certain fraction p of their transmitted bits based on his observations. We consider a setting where the communication must be simultaneously covert as well as reliable, i.e., James should be unable to accurately distinguish whether or not Alice is communicating, while Bob should be able to correctly recover Alice's message with high probability regardless of the adversarial jamming strategy. We show that, unlike the setting with passive adversaries, covert communication against active adversaries requires Alice and Bob to have a shared key (of length at least Ω(logn)) even when Bob has a better channel than James. We present lower and upper bounds on the information-theoretically optimal throughput as a function of the channel parameters, the desired level of covertness, and the amount of shared key available. These bounds match for a wide range of parameters of interest. We also develop a computationally efficient coding scheme (based on concatenated codes) when the amount of shared key available is Ω(√n logn), and further show that this scheme can be implemented with much less amount of shared key when the adversary is assumed to be computationally bounded.

Intelligent Reflecting Surface Aided Multi-User Communication: Capacity Region and Deployment Strategy

Intelligent reflecting surface (IRS) is a new promising technology that is able to reconfigure the wireless propagation channel via smart and passive signal reflection. In this paper, we investigate the capacity region of a two-user communication network with one access point (AP) aided by M IRS elements for enhancing the user-AP channels, where the IRS incurs negligible delay, thus the user-AP channels via the IRS follow the classic discrete memoryless channel model. In particular, we consider two practical IRS deployment strategies that lead to different effective channels between the users and AP, namely, the distributed deployment where the M elements form two IRSs, each deployed in the vicinity of one user, versus the centralized deployment where all the M elements are deployed in the vicinity of the AP. First, we consider the uplink multiple-access channel (MAC) and derive the capacity/achievable rate regions for both deployment strategies under different multiple access schemes. It is shown that the centralized deployment generally outperforms the distributed deployment under symmetric channel setups in terms of achievable user rates. Next, we extend the results to the downlink broadcast channel (BC) by leveraging the celebrated uplink-downlink (or MAC-BC) duality framework, and show that the superior rate performance of centralized over distributed deployment also holds. Numerical results are presented that validate our analysis, and reveal new and useful insights for optimal IRS deployment in wireless networks.

Consensusability of discrete-time multi-agent systems under binary encoding with bit errors

This paper is concerned with the consensusability problem for a class of discrete-time multi-agent systems (DT-MASs). A binary encoding scheme (BES) is employed during the data transmission, and only a finite-length binary bit string is transmitted due primarily to the limited network bandwidth in practice. Meanwhile, the binary bit string, transmitted via memoryless binary symmetric channels, might suffer from random bit errors with a certain probability. The purpose of this paper is to derive some consensusability conditions, under which there must exist a distributed controller such that the mean-square bounded consensus is achieved by the considered DT-MASs with BESs subject to random bit errors. To this end, the statistical properties are first revealed for the BES-induced quantization errors and the random bit errors. Then, by resorting to the solvability analysis of a modified Riccati inequality, some sufficient conditions are, respectively, derived to ensure the mean-square bounded consensus under the undirected communication topology in two scenarios: (1) identical bit-error rates (BERs); and (2) non-identical BERs. In particular, a necessary and sufficient condition is established for a single input case with identical BERs. Furthermore, the ultimate upper bound of the consensus errors in the mean-square sense is established to examine the effects of the length of bit string and the BERs. Finally, an illustrative simulation example is provided to validate the effectiveness of the theoretical results.

Noisy persuasion

We study the effect of noise due to exogenous information distortions in the context of Bayesian persuasion. We first characterize the optimal signal in the prosecutor-judge game from Kamenica and Gentzkow (2011) with a noisy and strongly symmetric communication channel and show that the sender's payoff increases in the number of messages. This implies that, with exogenous noise, the sender prefers to complicate communication. Then, we establish necessary and sufficient conditions for the sender's payoff to weakly increase in the Blackwell-informativeness of the noise channel when the message space and the channel are binary. The reason why a sender may benefit from additional noise is that a garbling may alter the noise structure. Subsequently, we provide sufficient conditions that extend this result to channels of arbitrary cardinality. Finally, we introduce a procedure of making a communication channel more complex and prove that increased complexity benefits the sender.

Theoretical study of an unsteady ciliary hemodynamic fluid flow subject to the Newton’s boundary conditions

This article addresses the hemodynamic flow of biological fluid through a symmetric channel. Methachronal waves induced by the ciliary motion of motile structures are the main source of Couple stress nanofluid flow. Darcy’s law is incorporated in Navier-Stokes equations to highlight the influence of the porous medium. Thermal transport by the microscopic collision of particles is governed by Fourier’s law while a separate expression is obtained for net diffusion of nanoparticles by using Fick’s law. A closed-form solution is achieved of nonlinear differential equations subject to Newton’s boundary conditions. Moreover, the current findings are compared with previous outcomes for the limiting case and found a complete coherence. Parametric study reveals that nanoflow is resisted by employing Newton’s boundary conditions. Thermal profile enhancement is contributed by the viscous dissipation parameter. Finally, one infers that hemodynamic flow of non-Newtonian fluid is an effective mode of heat and mass transfer especially, in medical sciences for the rapid transport of medicines in drug therapy.

Entropy generation and curvature effect on peristaltic thrusting of (Cu–Al2O3) hybrid nanofluid in resilient channel: Nonlinear analysis

AbstractThe pharyngeal stage of bolus transport or blood motion in the arteries cannot ignore the effect of curvature and inertial forces in peristaltic channels. Thus, the nonlinear curvature of peristaltic pumping becomes significant when the moving wall induces a curvilinear fluid motion at infinite Reynolds numbers, also the intrauterine fluid flow in the case of curvature nonpregnant uterus is an application of it. Hybrid nanofluids are new types of nanofluids, which can be produced by the suspension of multiple kinds of nanoparticles in base fluids. A hybrid nanomaterial is a substance that contains chemical and physical features of multiple materials together and gives these features in a homogeneous phase. The synthetic hybrid nanomaterial reveals significant physio‐chemical features that do not present in the individual components. In this investigation, the flow of an incompressible viscous fluid driven by sinusoidal waves moves on boundaries of the symmetric channel is studied when inertia and streamline curvature effects are not negligible, where the flow of nanofluid and hybrid nanofluid has been utilized to investigate the axial and normal behavior of velocities and heat transfer. An approximate solution to the second‐order in the wavenumber (giving the curvature effect) is obtained. To transform the variable cross‐section of the channel to a uniform cross‐section, we used a domain transformation, and this facilitates an easy way of getting a closed‐form of solutions to higher orders. Also, the pressure gradient and time flow rate relations are obtained. The influence of various biophysical parameters has been demonstrated through the graphs. All flow properties, temperature profile, and rate of heat transfer at the walls are greatly influenced by the presence of copper nanofluid. Furthermore, we observed that the case of spherical‐shaped nanoparticles provides a better heat transfer ability as compared to the case of cylindrically shaped nanoparticles. The effects of inertia and curvature are discussed and compared with some previous results in the literature.

Mixed convection peristalsis of hybrid nanomaterial flow in thermally active symmetric channel

We aim to investigate hybrid nanofluid effects on peristaltic motion of MHD nanofluid. Symmetric channel with slip boundary constraints is taken. Mixed convection, Hall parameter and variable viscosity are also taken into account. Energy equation includes dissipation, Ohmic heating and thermal radiation. Dimensionless equations are simplified under the observation of long wavelength approximation. Final forms of equations are solved via numerical approach. Pressure gradient and flow pattern are graphically observed. The comparative analysis of velocity, temperature and heat transport process are evaluated numerically through tabulated values. Temperature field enhances for higher Hartman number while opposite trend is observed for Hall effects. The inclusion of silver nanomaterial in copper nanofluid can more facilitate heat transport characteristics.

A semi‐staggered finite volume approach applied to two‐ and three‐dimensional flow in channels with gradual expansions

AbstractTwo‐ and three‐dimensional computations have been performed to study incompressible laminar flow of viscous fluids in symmetric channels with gradual expansions. The divergent form advective and viscous terms of Navier–Stokes equations are discretized by means of the UNIFAES scheme, which has been showing unpaired accuracy. Explicit time‐wise integration allows continuity to be imposed via the Poisson equation for the pressure, solved iteratively with several iterations per velocity step in order to ensure mass conservation throughout the transient regime. The proposed finite volume approach uses the semi‐staggered mesh structure, in which pressure is put at the center of the continuity cell and the velocity components at the cell vertexes. Comparative studies have shown this mesh to be highlighted by accuracy, in relation to the traditional, staggered and collocated meshes. Furthermore, it was observed that the semi‐staggered mesh allowed to treat a plane diverging channel in entirely regular fashion without losing accuracy, by appropriate choice of the aspect ratio of the numerical cell, providing geometrical flexibility that does not exist in more common meshes, such as staggered and collocated structures. The present proposal explored the geometric flexibility of the semi‐staggered mesh to solve with simplicity a relevant problem of a channel with gradual expansion. Overall, good agreement was observed against experimental and numerical results in the literature, therefore, it illustrates the capability of the semi‐staggered approach to easily handle flat surfaces nonparallel to the coordinates axes.

Effect of relaxation and retardation times on dusty Jeffrey fluid in a curved channel with peristalsis

In recent work, the Jeffrey liquid with uniform dust particles in a symmetric channel is studied. Moving sinusoidal wave is executed on the walls of the channel, which generates peristaltic transport in the fluid. The governing equations for fluid and dust particles have been formulated using stream function. Perturbation method is used to get analytical solution of the problem by using small wave number. Graphical analysis has been carried out for stream function and velocity of fluid and dust particles. Effects of different parameters such as curvature k, relaxation time [Formula: see text], wave number [Formula: see text] and retardation time [Formula: see text] are debated through graphs for both dust particles and fluid. The noteworthy outcomes are fluid velocity, pressure gradient in the region [Formula: see text] and bolus size increases by increasing [Formula: see text]

Analytical drain current and performance evaluation for inversion type InGaAs gate-all-around MOSFET

This paper presents an analytical investigation of the drain current model for symmetric short channel InGaAs gate-all-around (GAA) MOSFETs valid from depletion to strong inversion using a continuous expression. The development of the core model is facilitated by the solution of the quasi-2D Poisson equation in the doped channel, accounting for interface trap defects and fixed oxide charges. Correction to short channel effects such as threshold voltage roll-off, drain induced barrier lowering, and subthreshold slope degradation is later introduced, complemented with channel length modulation, velocity saturation, and mobility degradation from surface roughness, leading to accurate mobile charge density for electrostatic capacitance–voltage and transport characterization. The effect of physical process parameters such as fin width, oxide thickness, and channel length scaling is thoroughly investigated in both on and off states of the transistor. The robustness of the model is reflected by the precise match with published experimental reports in the literature. An Ron of 1160 Ω μm is obtained from output characteristics and a switching efficiency improvement of 2.5 times is estimated by incorporating a high-κ dielectric into the GAA transistor. Numerical 3D simulations from TCAD corroborate the validity of the proposed model in all regions of operation.