Approximate analysis of two-mass–spring systems and buckling of a column

AbstractMax–Min Approach (MMA) is applied to obtain an approximate solution of three practical cases in terms of a nonlinear oscillation system. After finding maximal and minimal solution thresholds of a nonlinear problem, an approximate solution of the nonlinear equation can be easily achieved using He Chengtian’s interpolation. Numerical results indicate the effectiveness of the proposed method both in respect of the whole range of involved parameters as well as the excellent agreement with the approximate frequencies and periodic solutions with the exact ones. It is predicted that MMA can be found widely applicable in engineering

Accuracy of a no-biopsy approach for the diagnosis of coeliac disease across different adult cohorts

Objective We aimed to determine the predictive capacity and diagnostic yield of a 10-fold increase in serum IgA antitissue transglutaminase (tTG) antibody levels for detecting small intestinal injury diagnostic of coeliac disease (CD) in adult patients. Design The study comprised three adult cohorts. Cohort 1: 740 patients assessed in the specialist CD clinic at a UK centre; cohort 2: 532 patients with low suspicion for CD referred for upper GI endoscopy at a UK centre; cohort 3: 145 patients with raised tTG titres from multiple international sites. Marsh 3 histology was used as a reference standard against which we determined the performance characteristics of an IgA tTG titre of ≥10×ULN for a diagnosis of CD. Results Cohort 1: the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for IgA tTG levels of ≥10×ULN at identifying individuals with Marsh 3 lesions were 54.0%, 90.0%, 98.7% and 12.5%, respectively. Cohort 2: the sensitivity, specificity, PPV and NPV for IgA tTG levels of ≥10×ULN at identifying individuals with Marsh 3 lesions were 50.0%, 100.0%, 100.0% and 98.3%, respectively. Cohort 3: the sensitivity, specificity, PPV and NPV for IgA tTG levels of ≥10×ULN at identifying individuals with Marsh 3 lesions were 30.0%, 83.0%, 95.2% and 9.5%, respectively. Conclusion Our results show that IgA tTG titres of ≥10×ULN have a strong predictive value at identifying adults with intestinal changes diagnostic of CD. This study supports the use of a no-biopsy approach for the diagnosis of adult CD

Analysis of unsteady MHD Eyring-Powell squeezing flow in stretching channel with considering thermal radiation and Joule heating effect using AGM

In this paper, has been investigated the heat and mass transfer in an unsteady two- dimensional squeezing flow of magnetohydromagnetic (MHD) radiative non-Newtonian Eyring-Powell fluid between two parallel infinite plates in the presence of heat generation/absorption, thermal radiation and Joule heating effect. The partial differential equations governing the flow problem converted to ordinary differential equations by using suitable similarity transformation. After that the Akbari- Ganji,s Method (AGM) has been used to solve differential equations governing this problem and during comparing happened between AGM and Runge-Kutta Fehlbrg method (RKF) it's observing AGM is a method with high accuracy for solving differential equations. The main goal of this paper is to investigate the effects of changes in the values of several parameters on the velocity and temperature and also on the local skin friction coefficient, local Nusselt and Sherwood numbers. The most important results of analyzes are Lorentz force generated by magnetic field parameter in the fluid flow field which reduces velocity and decrease in fluid temperature by increasing thermal radiation parameter

Investigation of convective-conductive heat transfer in geothermal system

Geothermal energy is one of the well-known types of renewable energies that can be considered as a promising alternative to fossil fuels in order to mitigate the CO2 emission in atmosphere. Geothermal energy has recently been used for heating and cooling systems in many countries of the world. Therefore, studying such kind of energy seems important and necessary. This paper studies the heat transfer processes in a borehole heat exchanger (BHE). The flow of fluid in a BHE has been considered with different geometries and heat transfer processes are modeled numerically and in a finite volume method through convection and conductivity. First, a single U-shaped BHE was modeled and its thermal properties were investigated and then other geometries were studied to obtain the best geometry and heat transfer efficiency. In order to increase the heat transfer in the inner part of the pipes, the fin with the given specifications was used and the modeling was carried out and the thermal parameters were compared for three BHE’s with different geometries. In the final part, optimization results are presented, and the interaction of parameters on the Nusselt number and friction coefficient have been investigated. Also, the desirability of optimization and reliability is given to the results presented in percentage terms. Comparing the results of this article with the results of previous research shows a very good agreement and therefore the applied method is reliable and accurate. Keywords: Borehole heat exchangers, Numerical method, Heat transfer processes, Geothermal energy, Finite volume analysi

Hybrid semi analytical method for geothermal U shaped heat exchanger

In this paper, convective-conductive heat transfer processes between the all components of geothermal borehole heat exchanger (BHE) such as pipe-in, pipe-out and grout have been studied. A set of coupled partial differential equations subjected to general initial and boundary conditions are governed to this problem. Modified Homotopy perturbation method (MHPM) is a hybrid of discrete Fourier Transform, spectral analysis and Homotopy Perturbation Method that is developed in order to solve the partial differential equations of geothermal borehole systems. The results of MHPM are compared with the numerical solution for validation and, furthermore, the effectiveness and accuracy of the applied method have been shown. Keywords: Borehole heat exchanger, Heat conduction-convection, Discrete Fourier transformation, Homotopy perturbation metho

Nonlinear thermal radiation effect on magneto Casson nanofluid flow with Joule heating effect over an inclined porous stretching sheet

In this paper, mixed convection on MHD flow of casson nanofluid over a non-linearly permeable stretching sheet has been investigated and analyzed numerically. The effects of thermal radiation, chemical reaction, heat generation/absorption, viscous dissipation, suction and Joule heating are considered. The Brownian motion and thermophoresis phenomenon are used to model nanoparticles (Buongiorno's model). After converting PDEs governing the problem to ODEs, they have been solved by Runge-Kutta Fehlberg fourth-fifth order method. Obtained results of investigating the effects of different parameters changes on velocity, temperature, and concentration profiles are reported as diagrams. Fluid flow velocity reduction by increase in Hartman number (magnetic field parameter) is due to existence of Lorentz drag force against flow, flow velocity reduction due to increase in casson fluid parameter, increase in temperature profile due to increase in radiation parameter, and nanoparticle concentration profile reduction due to increase in chemical reaction parameter are some of valuable obtained results. Also, in final section of this paper effects of different parameters on skin friction coefficient, local Nusselt and Sherwood numbers are investigated that positive and ascending behavior for all three are reported. Keywords: Magnetohydrodynamic (MHD), Casson nanofluid, Buongiorno's model, Thermal radiation, Chemical reaction, Heat generation/absorption, Suction, Joule heating effec