Low frequency acoustic and electromagnetic scattering

This paper deals with two classes of problems arising from acoustics and electromagnetics scattering in the low frequency stations. The first class of problem is solving Helmholtz equation with Dirichlet boundary conditions on an arbitrary two dimensional body while the second one is an interior-exterior interface problem with Helmholtz equation in the exterior. Low frequency analysis show that there are two intermediate problems which solve the above problems accurate to 0(k(2) log k) where k is the frequency. These solutions greatly differ from the zero frequency approximations. For the Dirichlet problem numerical examples are shown to verify the theoretical estimates

On the accurate long-time solution of the wave equation in exterior domains: Asymptotic expansions and corrected boundary conditions

We consider the solution of scattering problems for the wave equation using approximate boundary conditions at artificial boundaries. These conditions are explicitly viewed as approximations to an exact boundary condition satisfied by the solution on the unbounded domain. We study the short and long term behavior of the error. It is provided that, in two space dimensions, no local in time, constant coefficient boundary operator can lead to accurate results uniformly in time for the class of problems we consider. A variable coefficient operator is developed which attains better accuracy (uniformly in time) than is possible with constant coefficient approximations. The theory is illustrated by numerical examples. We also analyze the proposed boundary conditions using energy methods, leading to asymptotically correct error bounds

Time domain numerical calculations of unsteady vortical flows about a flat plate airfoil

A time domain numerical scheme is developed to solve for the unsteady flow about a flat plate airfoil due to imposed upstream, small amplitude, transverse velocity perturbations. The governing equation for the resulting unsteady potential is a homogeneous, constant coefficient, convective wave equation. Accurate solution of the problem requires the development of approximate boundary conditions which correctly model the physics of the unsteady flow in the far field. A uniformly valid far field boundary condition is developed, and numerical results are presented using this condition. The stability of the scheme is discussed, and the stability restriction for the scheme is established as a function of the Mach number. Finally, comparisons are made with the frequency domain calculation by Scott and Atassi, and the relative strengths and weaknesses of each approach are assessed

Blockchain: An EOM approach to reconciliation in banking

Purpose: The aim of this study is to evaluate the contribution of Blockchain technology (Cryptobanking) using the expected operating model (EOM) to address the pain points in reconciliation at middle and back-office operational levels in assessing the significance of this technology on return on investment.Design/Methodology: A structured questionnaire was designed to collect primary data using a stratified sampling method from 120 respondents working in leading Investment banks operating in the geographical locality of urban Bangalore. Demographic variables, accounting variables, data reporting variables, approach variables, and variables of EOM were considered to validate the hypothesis with the help of statistical tools, namely ANOVA, and Multiple Stepwise Regression Analysis.Findings: The results obtained confirm that there is a significant difference in reconciliation with the implementation of an innovative business process. Financial analysis is the highest predictor of ROI when integrated with technology as the adapted Blockchain innovation in reconciliation is the most influencing factor in enhancing, improving ROI playing a pivotal role in the Investment banks. Originality/Value: Blockchain Technology (Crypto banking) facilitates transforming the reconciliation process of these banks with improved operational efficiency. Blockchain and settlement platforms offer inter-organization solutions facilitating the reconciliation of various transactions in real-time through a trust-based network in the form of digital settlements with better consortiums

Enhancement of Solar PV Panel Using Single Integral Sliding Mode MPPT Control

The maximum power extraction using single integral sliding mode control scheme is established from the sliding mode control scheme. The sliding mode control (SMC) scheme extracts the maximum power during the partial shading weather conditions using the effective selection sliding surface duty cycle ratio in combination of dc/dc boost converter. This dynamic operation of sliding surface selection operation in partial shading conditions aids to enhance the solar panel efficiency compared to the other existing MPPT schemes. The effective dynamic operation of sliding surface mode control is designed using feedback loop control scheme to diminish the steady state voltage error of the solar panel, further to obtain the higher sliding duty cycle ratio. The dc-to-dc boost converter is made active using sliding duty cycle ratio as input gate signal boost converter switch. Hence, higher efficiency attains at higher sliding surface duty ration. This sliding surface duty ratio is limited in sliding mode MPPT control scheme and requires the necessary advancements to achieve the maximum duty cycle ratio. The single integral sliding mode control scheme offers the maximum duty cycle ratio compared to sliding mode control scheme. Therefore, this paper discusses the single integral sliding mode MPPT control scheme. The proposed method employs the effective dynamic sliding operation using integrated steady state voltage error signal and allows to nullify the lacuna of maximum sliding duty cycle ratio. Also, the projected SISMC scheme improves the effective dynamic sliding surface switching operations compared to sliding control scheme. This allows the system to be stable and reliable switching operations. To validate the proposed MPPT control scheme the MATLAB / Simulink model was designed and verified. Also, the SMC scheme was designed and compared with the present method

Enhancement of Solar PV Panel Using Single Integral Sliding Mode MPPT Control

The maximum power extraction using single integral sliding mode control scheme is established from the sliding mode control scheme. The sliding mode control (SMC) scheme extracts the maximum power during the partial shading weather conditions using the effective selection sliding surface duty cycle ratio in combination of dc/dc boost converter. This dynamic operation of sliding surface selection operation in partial shading conditions aids to enhance the solar panel efficiency compared to the other existing MPPT schemes. The effective dynamic operation of sliding surface mode control is designed using feedback loop control scheme to diminish the steady state voltage error of the solar panel, further to obtain the higher sliding duty cycle ratio. The dc-to-dc boost converter is made active using sliding duty cycle ratio as input gate signal boost converter switch. Hence, higher efficiency attains at higher sliding surface duty ration. This sliding surface duty ratio is limited in sliding mode MPPT control scheme and requires the necessary advancements to achieve the maximum duty cycle ratio. The single integral sliding mode control scheme offers the maximum duty cycle ratio compared to sliding mode control scheme. Therefore, this paper discusses the single integral sliding mode MPPT control scheme. The proposed method employs the effective dynamic sliding operation using integrated steady state voltage error signal and allows to nullify the lacuna of maximum sliding duty cycle ratio. Also, the projected SISMC scheme improves the effective dynamic sliding surface switching operations compared to sliding control scheme. This allows the system to be stable and reliable switching operations. To validate the proposed MPPT control scheme the MATLAB / Simulink model was designed and verified. Also, the SMC scheme was designed and compared with the present method

Four-photon interference: a realizable experiment to demonstrate violation of EPR postulates for perfect correlations

Bell's theorem reveals contradictions between the predictions of quantum mechanics and the EPR postulates for a pair of particles only in situations involving imperfect statistical correlations. However, with three or more particles, contradictions emerge even for perfect correlations. We describe an experiment which can be realized in the laboratory, using four-photon entangled states generated by parametric down-conversion, to demonstrate this contradiction at the level of perfect correlations.Comment: publishe

Developing a spinal cord injury rehabilitation service in Madagascar

Rehabilitation for people with spinal cord injury in many low- and middle-income countries is not avail-able or is in the early stages of development. However, rehabilitation is recognized as crucial in order to optimize functional recovery and outcomes for patients with spinal cord injury. With an increasing incidence of spinal cord injury, the unmet need for rehabilitation is huge. This report describes the early development of a specialist rehabilitation service for spinal cord injury in Madagascar, one of the poorest countries in the world. The sustained input to an expanding rehabilitation team has led to reductions in avoidable complications. The input of the rehabilitation team has been welcomed by the neurosurgery department, which has recognized fewer delays in patients undergoing surgical treatments. Cost, lack of resources and trained staff, and poor understanding of disability continue to provide challenges. However, the development of the rehabilitation service using low technology, but with a high level of knowledge and systematic management, is a source of considerable pride. This development in Madagascar can be regarded as a model for spinal cord injury rehabilitation in other low-resource settings