Effects Of Changes In Parameters Research Articles

Prediction Of Solidification Behaviour Of Alloy Steel Ingot Casting

This paper focuses on the mathematical modeling of solidification of 4 ton steel ingot casting using ANSYS simulation software. The model includes the phenomenon associated with fluid flow, temperature distribution, liquid fraction and solidification time at various instances of solidification was examined. The numerical simulation was done for parametric analysis of solidification process in casting based on boundary conditions, grid independency test and code validation test. The solidification process is analyzed by studying the effect of change in parameters of steel ingot on solidification with respect to time and the effect of pouring temperature. The pouring temperature and velocity defines the uniformity and soundness in the casting and accordingly the solidification takes place. The inlet velocity has an important effect on solidification process. The inlet velocity should neither be too high nor too low for proper grains formation and decreasing the turbulence and formation of defects.

An Inventory Model for Deteriorating Items with Generalised Exponential Decreasing Demand, Constant Holding Cost and Time-Varying Deterioration Rate

In this present paper, an inventory model with a generalised exponential decreasing demand is considered. A numerical example is used to illustrate the application of the model. Sensitivity analysis of the optimal solution with respect to various parameters is carried out to see the effect of parameter changes on the solution.

Least-squares finite element analysis of flow of a generalized Newtonian fluid past a circular cylinder

ABSTRACTA mixed least-squares finite element model (LSFEM) with spectral/hp approximations is developed for the analysis of steady, two-dimensional flows of generalized Newtonian fluids obeying the Carreau–Yasuda constitutive model. The finite element model (FEM) is composed of velocity, pressure, and stress fields as independent variables (therefore, called a mixed model). FEMs based on least-squares formulations are considered an alternative variational setting to the conventional weak-form Galerkin models for the Navier–Stokes equations, and no compatibility conditions on the approximation spaces are needed for the velocity, pressure, and stress fields if the polynomial order (p) is sufficiently high (say, p > 3, as determined numerically). In addition, applying high-order spectral/hp approximation functions to the least-squares formulation avoids various forms of locking that often occur in low-order LSFEMs for incompressible viscous fluids, and accurate results can be obtained with exponential convergence. The benchmark problem of the flow past a circular cylinder is solved to verify and validate the model. Then, a parametric study is performed to examine the effect of change in parameters of the Carreau–Yasuda model on the flow past a circular cylinder.

An EOQ model for weibull distribution deterioration with time-dependent cubic demand and backlogging

In this article we introduce an economic order quantity model with weibull deterioration and time dependent cubic demand rate where holding costs as a linear function of time. Shortages are allowed in the inventory system are partially and fully backlogging. The objective of this model is to minimize the total inventory cost by using the optimal order quantity and the cycle length. The proposed model is illustrated by numerical examples and the sensitivity analysis is performed to study the effect of changes in parameters on the optimum solutions.

Investigation on thermophysical properties of Tio2–Cu/H2O hybrid nanofluid transport dependent on shape factor in MHD stagnation point flow

An analysis on the subject of “induced magnetic field effect on stagnation flow of a TiO2-Cu/water hybrid nanofluid over a stretching sheet” has been carried out in this paper. It should be noted that hybrid nanofluid consists of two or more types of nanoparticles along with a base fluid and it is used to increase the heat transfer. Furthermore, the non-linear differential equations modeling this issue are included in this article. In order to solve these equations numerically, Runge-Kutta Fehlberg method is used as a numerical method in this problem. The main objective of this paper is to investigate the effects of change in parameters of stretching ratio parameter (A∗), nanoparticles volumetric fractions (∅2), magnetic parameter (β) and reciprocal magnetic Prandtl number (λ) on the functions including velocity, induced magnetic field and temperature for both Cu-water nanofluid and TiO2-Cu/water hybrid nanofluid. Also Lorentz force which is derived from magnetic field is mentioned in this section. In addition, the impacts of (∅2), (β) and (λ) on the profiles of nanofluid and hybrid nanofluid temperature for three categories of nanoparticle shapes named brick, cylinders, and platelets are analyzed. At the end, the influences of (∅2), (β) and (λ) on skin friction coefficient (Cf) and Nusselt number (Nux) for Cu-water nanofluid and TiO2-Cu/water hybrid fluid for different nanoparticles shapes are discussed. In all of these studies it can be seen that applying platelets shaped nanoparticles is more effective.

Understanding the demographic drivers of realized population growth rates.

Identifying the demographic parameters (e.g., reproduction, survival, dispersal) that most influence population dynamics can increase conservation effectiveness and enhance ecological understanding. Life table response experiments (LTRE) aim to decompose the effects of change in parameters on past demographic outcomes (e.g., population growth rates). But the vast majority of LTREs and other retrospective population analyses have focused on decomposing asymptotic population growth rates, which do not account for the dynamic interplay between population structure and vital rates that shape realized population growth rates (λt=Nt+1/Nt) in time-varying environments. We provide an empirical means to overcome these shortcomings by merging recently developed "transient life-table response experiments" with integrated population models (IPMs). IPMs allow for the estimation of latent population structure and other demographic parameters that are required for transient LTRE analysis, and Bayesian versions additionally allow for complete error propagation from the estimation of demographic parameters to derivations of realized population growth rates and perturbation analyses of growth rates. By integrating available monitoring data for Lesser Scaup over 60yr, and conducting transient LTREs on IPM estimates, we found that the contribution of juvenile female survival to long-term variation in realized population growth rates was 1.6 and 3.7 times larger than that of adult female survival and fecundity, respectively. But a persistent long-term decline in fecundity explained 92% of the decline in abundance between 1983 and 2006. In contrast, an improvement in adult female survival drove the modest recovery in Lesser Scaup abundance since 2006, indicating that the most important demographic drivers of Lesser Scaup population dynamics are temporally dynamic. In addition to resolving uncertainty about Lesser Scaup population dynamics, the merger of IPMs with transient LTREs will strengthen our understanding of demography for many species as we aim to conserve biodiversity during an era of non-stationary global change.

Evaluation of the ocean ecosystem: Climate change modelling with backstop technologies

This paper discusses the economic impacts of climate change, including those on ecosystems, and whether a new backstop technology should be used under conditions of strict temperature targets. Using the dynamic integrated climate-economy (DICE) model, we developed a new model to calculate the optimal path by considering new backstop technologies, such as CO2 capture and storage (CCS). We identify the effects of parameter changes based on the resulting differences in CO2 leakage and sites, and we analyse the feasibility of CCS. In addition, we focus on ocean acidification and consider the impact on economic activity. As a result, when CCS is assumed to carry a risk of CO2 leakage and acidification is considered to result in a decrease in utility, we find that CCS can only delay the effects of climate change, but its use is necessary to achieve strict targets, such as a 1.5°C limit. This observation suggests that if the target temperature is too tight, we might end up employing a technology that sacrifices the ecosystem too greatly.

Facile preparation of defective black TiO2 through the solution plasma process: Effect of parametric changes for plasma discharge on its structural and optical properties

Defective TiO2 or black TiO2 nanoparticles (NPs) are remarkably attractive for photocatalytic applications, since the defect-disordered structure crucially affects the optical properties. In this work, high visible light-active black TiO2 NPs were synthesized by an innovative solution plasma process (SPP) with a titanium (Ti) electrode in HNO3 solution. The effects of the plasma operating parameters, in terms of the pulse frequency (20–80 kHz) and pulse width (0.5–2.0 μs) under two different HNO3 concentrations (0.3 mM and 3.0 mM) on the morphology, structural and optical properties of the obtained black TiO2 NPs were explored. Increasing the pulse frequency, pulse width and concentration of HNO3 all increased the input energy per pulse and energy per second, which induced an increased volume-based particle size, synthesis rate and Ti3+/Ti4+ ratio, but decreased the rutile mass fraction, the Ti-OH/TiO ratio and the band gap energy of the obtained black TiO2 NPs. Among all the prepared black TiO2 NP samples, those prepared at a pulse frequency of 20 kHz, pulse width of 2 μs (energy input per second of 17.3 J) in 3.0 mM HNO3 exhibited the highest visible-light absorption capability (the lowest band gap energy of ∼2.44 eV). The variation in the band gap energy was more strongly dependent on the Ti3+/Ti4+ ratio than the Ti-OH/TiO ratio in the structure of black TiO2 NPs.

Biomechanical Optimization of a Novel Circular External Fixator (Optimization of Circular External Fixator)

The purpose of this study was to investigate biomechanical optimization of the newly designed circular external fixator (CEF) system, used in the orthopaedics surgery, that is capable of continuous compression at the fracture line. External fixators are devices applied from outside the body to treat bone and joint injuries as well as to correct skeletal deformities. In this study, the effects of parametric changes on CEF mounted for the fracture were investigated with using response surface optimization (RSO) module in ANSYS software using the finite element method. The pressure acting on fracture line is an essential factor on fracture healing. The RSO module showed that the contribution of the parameters on this essential factor was as follows in the descending order; pre-load, spring coefficient, wire diameter and angle between the wires. According to the results of the numerical study; (a) there was a positive correlation between the wire diameter and the normal stress at the fracture line. The increase in wire diameter and pre-loading caused an increase in the normal stress at the fracture line. (b) The angle between the wires has a relatively little effect on the whole system. (c) The most effective parameters on the system were determined as the pre-loading and spring coefficient.

Development of slag based Shirasu geopolymer

Shirasu, a pyroclastic flow deposit, showed considerable performance as aluminosilicate source in geopolymer, based on past research. However, the polymerization reactivity was somewhat lower compared to the traditional fly ash based geopolymer even though the long-term strength was fairly good. The present study concentrates on the development of higher initial strength performance of Shirasu based geopolymer by utilizing ground granulated blast furnace slag as an admixture. Mortars with various mix proportions were adopted to study the effect of parametric changes on strength development along with the addition of slag in different percentages. A combination of sodium hydroxide and sodium silicate was used as alkaline activators considering parameters like molar ratios of alkali to geopolymer water and silica to alkali molar ratio. The mortars were cured at elevated temperatures under different curing conditions to analyze the effect on strength development. Compressive strength test, mercury intrusion porosimetry and X-ray powder diffraction were carried out to assess the strength performance and microstructure of slag-Shirasu based geopolymer. Based on the experimental study, it was observed that the initial and long-term strength development of Slag-Shirasu geopolymer were improved by the addition of slag.

The effects of parametric changes in electropolishing process on surface properties of 316L stainless steel

Corrosion resistance and biocompatibility of 316L stainless steel implants depend on the surface features and the nature of the passive film. The influence of electropolishing on the surface topography, surface free energy and surface chemistry was determined by atomic force microscopy, contact angle meter and X-ray photoelectron spectroscopy, respectively. The electropolishing of 316L stainless steel was conducted at the oxygen evolution potential (EPO) and below the oxygen evolution potential (EPBO). Compared to mechanically polished (MP) and EPO, the EPBO sample depicted lower surface roughness (Ra=6.07nm) and smaller surface free energy (44.21mJ/m2). The relatively lower corrosion rate (0.484mpy) and smaller passive current density (0.619μA/cm2) as determined from cyclic polarization scans was found to be related with the presence of OH, Cr(III), Fe(0), Fe(II) and Fe(III) species at the surface. These species assured the existence of relatively uniform passive oxide film over EPBO surface. Moreover, the relatively large charge transfer (Rct) and passive film resistance (Rf) registered by EPBO sample from impedance spectroscopy analysis confirmed its better electrochemical performance. The in vitro response of these polished samples toward MC3T3 pre-osteoblast cell proliferation was determined to be directly related with their surface and electrochemical properties.

A systematic approach to calibrate a transferable polarizable force field parameter set for primary alcohols.

In this work, parameters are optimized for a charge-on-spring based polarizable force field for linear alcohols. We show that parameter transferability can be obtained using a systematic approach in which the effects of parameter changes on physico-chemical properties calculated from simulation are predicted. Our previously described QM/MM calculations are used to attribute condensed-phase polarizabilities, and starting from the non-polarizable GROMOS 53A5/53A6 parameter set, van der Waals and Coulomb interaction parameters are optimized to reproduce pure-liquid (thermodynamic, dielectric, and transport) properties, as well as hydration free energies. For a large set of models, which were obtained by combining small perturbations of 10 distinct parameters, values for pure-liquid properties of the series methanol to butanol were close to experiment. From this large set of models, we selected 34 models without special repulsive van der Waals parameters to distinguish between hydrogen-bonding and non-hydrogen-bonding atom pairs, to make the force field simple and transparent. © 2017 Wiley Periodicals, Inc.

Validation of a finite element model of the cold roll forming process on the basis of 3D geometric accuracy

Cold roll forming is an incremental sheet metal forming process used to supply products to numerous industries such as automotive, architecture and construction, etc. In recent years there has been an increase in the demand by customers for high value products, through the forming of high strength materials, or complex profiles. Such demands increase the challenges faced by the tooling designer to bring a successful product through from design to manufacture, on time and within specification. Finite element (FE) simulations are increasingly applied in industry due to the desired advantage of reducing design iterations by allowing the designer to investigate the effects of parameter changes, without the risk of expensive tooling costs. Some successful validation of the numerical modelling of the cold roll forming process can be found in literature, in particular when analysing the strain distribution across the material or comparing the final rolled profile geometry. However, cold roll forming is a continuous process and no one has published work on the measurement of the profile on a pass to pass basis, in particular, the three dimensional geometry of the profile. Experimental trials were carried out to obtain a 3D point cloud model of the top surface of a roll formed section. This investigation aimed to quantify how accurate FE simulation may be in relation to physical data.

Mathematical model for integrated coal fired thermal boiler using physical laws

The boiler of coal-fired thermal power plant consists of integrating process units such as the furnace, economizer, drum, and superheater. There is a lack of proper dynamic model derived from mass and energy balances of individual units integrated together where dynamics of material and energy flow are not understood properly supporting the larger footprints and environmental impact of the specific industry. This paper considers formulation of simple mathematical models for integrated boiler units based on first principle laws (excluding furnace). The derived equations are validated with the real-time plant data from 210 MW coal-fired thermal power plant. Though temperature and pressures are convertible at equilibrium through Clausius-Clapeyron equation, the model supports for level, temperature and pressure measurements and predictions. The effects of change in parameters of the boiler are studied and discussed in detail. The model can be used for further process control studies.

Virtuous Circles and the Case for Aid

It is sometimes argued that foreign aid leads to a virtuous circle in which growth becomes self-reinforcing. We study two versions of this argument, using a modified neoclassical growth model in which the effects of parameter changes and capital accumulation are amplified. Simulations are used to quantify the welfare benefits from aid transfers. We find that, contrary to expectations, amplification makes only a modest difference to the welfare benefits from aid. This is true even when aid allows a faster exit from a vicious circle or poverty trap.

Computational Modeling of Lipid Metabolism in Yeast.

Lipid metabolism is essential for all major cell functions and has recently gained increasing attention in research and health studies. However, mathematical modeling by means of classical approaches such as stoichiometric networks and ordinary differential equation systems has not yet provided satisfactory insights, due to the complexity of lipid metabolism characterized by many different species with only slight differences and by promiscuous multifunctional enzymes. Here, we present an object-oriented stochastic model approach as a way to cope with the complex lipid metabolic network. While all lipid species are treated objects in the model, they can be modified by the respective converting reactions based on reaction rules, a hybrid method that integrates benefits of agent-based and classical stochastic simulation. This approach allows to follow the dynamics of all lipid species with different fatty acids, different degrees of saturation and different headgroups over time and to analyze the effect of parameter changes, potential mutations in the catalyzing enzymes or provision of different precursors. Applied to yeast metabolism during one cell cycle period, we could analyze the distribution of all lipids to the various membranes in time-dependent manner. The presented approach allows to efficiently treat the complexity of cellular lipid metabolism and to derive conclusions on the time- and location-dependent distributions of lipid species and their properties such as saturation. It is widely applicable, easily extendable and will provide further insights in healthy and diseased states of cell metabolism.

Research into rheological transformations in a piezoceramic ultrasonic sensor of fluid level control

It was established that in the piezoceramic transducers of electric excitation pulse into ultrasonic signal that are used for measuring control of level of fluids and gas volumetric rate, similar electromagnetic processes occur. The effect of change in parameters of piezoceramic element on the formation of ultrasonic pulse was studied. It was shown that to create the pulse, the electric field intensity of this element is converted to electrodynamic force, which causes elastic deformation of a membrane unit. It was shown that the elastic deformation of a membrane unit causes electromotive force, which creates current in a piezoceramic element. The latter causes a secondary electrodynamic force, which is braking for a mechanical unit that leads to the deformation of mechanical ultrasonic oscillations. Physical models of irreversible rheological transformations are given and it is shown that the following processes occur in the piezoceramic transducers: conversion of electric exciting momentum to mechanical motion of a membrane of transducer, the latter to mechanical ultrasonic oscillations, and these oscillations to electromotive force of a piezoceramic element. The processes of irreversible rheological transformations are presented by the integrated pulse Dirac delta function. It was shown that such transformations are described by nonlinear differential equations, the right part of which characterizes the rate of decrease (flow) of electrical or mechanical energy, and these equations are the core of the integrated pulse Dirac delta function. Analytical solution of nonlinear differential equations of transfer of energy, mass and momentum by a zero gradient was obtained. A mechanism of the effect of temperature of heating of a piezoceramic element on the ultrasonic pulse form was determined. The essence of the impact is the fact that as a result of the heating of this element by electric current of excitation pulse and secondary electromotive force, its linear dimensions, resistance and density of the material change, leading to a phase shift of the ultrasonic pulse.

An extension of Banerjee and Rahim model in economic and economic statistical designs for multivariate quality characteristics under Burr XII distribution

ABSTRACTThe design parameters of the economic and economic statistical designs of control charts depend on the distribution of process failure mechanism or shock model. So far, only a small number of failure distributions, such as exponential, gamma, and Weibull with fixed or increasing hazard rates, have been used as a shock model in the economic and economic statistical designs of the Hotelling T2 control charts. Due to both theoretical and practical aspects, the lifetime of the process under study may not follow a distribution with fixed or increasing hazard rate. A proper alternative for this situation may be the Burr distribution, in which the hazard rate can be fixed, increasing, decreasing, single mode, or even U-shaped. In this research article, economic and economic statistical designs of the Hotelling T2 control charts under the Burr XII shock models under two uniform and non uniform sampling schemes were proposed, constructed, and compared. The obtained design models were implemented by a numerical example, and a sensitivity analysis was conducted to evaluate the effect of changing parameters of shock model distribution on the optimum values of the proposed design models. The results showed that first the proposed designs under non uniform sampling scheme perform better and second the optimum values of the designs are not significantly sensitive to changing of the Burr XII distribution parameters. We showed that the obtained design models are also true for the beta Burr XII shock model.

GEMSe: Visualization‐Guided Exploration of Multi‐channel Segmentation Algorithms

AbstractWe present GEMSe, an interactive tool for exploring and analyzing the parameter space of multi‐channel segmentation algorithms. Our targeted user group are domain experts who are not necessarily segmentation specialists. GEMSe allows the exploration of the space of possible parameter combinations for a segmentation framework and its ensemble of results. Users start with sampling the parameter space and computing the corresponding segmentations. A hierarchically clustered image tree provides an overview of variations in the resulting space of label images. Details are provided through exemplary images from the selected cluster and histograms visualizing the parameters and the derived output in the selected cluster. The correlation between parameters and derived output as well as the effect of parameter changes can be explored through interactive filtering and scatter plots. We evaluate the usefulness of GEMSe through expert reviews and case studies based on three different kinds of datasets: A synthetic dataset emulating the combination of 3D X‐ray computed tomography with data from K‐Edge spectroscopy, a three‐channel scan of a rock crystal acquired by a Talbot‐Lau grating interferometer X‐ray computed tomography device, as well as a hyperspectral image.

Arts and craftiness: an economic analysis of art heists

We study the incentives that museums face in determining how much resources to invest in the protection of their artwork from theft. We present and analyze a game-theoretic model of art heists that accounts for the strategic interactions between museums’ and art thieves’ decisions and that incorporates several key features of the black market for stolen art. We find that the equilibrium level of security museums choose need not be monotonic in the true market value or the black market value of artwork, i.e., increasing the value of an art piece—whether it is the true market value or the black market value—does not necessarily lead museums to invest more in protecting their artwork. The effects of parameter changes in the model that reflect a shift of public policy depend critically on what type of policy change is considered. For instance, an increase in the penalty imposed for committing art theft cannot raise the amount of theft in equilibrium and could in fact lead museums to increase their level of security. On the other hand, investing more resources on law enforcement agencies so that they are better able to solve art crimes can actually increase the amount of theft in equilibrium by causing museums to spend less on security.