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Digital Simulation (digital + simulation)
Selected AbstractsKinetic Study of the Oxidation of Catechols in the Presence of Some Aza-crown Ethers by Digital Simulation of Cyclic VoltammogramsELECTROANALYSIS, Issue 9 2009Davood Nematollahi Abstract The electrochemical oxidation of catechols (1) have been studied in the presence of diaza-18-crown-6 (DA18C6) (3a), diaza-15-crown-5 (DA15C5) (3b), and aza-15-crown-5 (A15C5) (3c) as nucleophiles in aqueous solution, by means of cyclic voltammetry and controlled-potential coulometry. The results indicate the participation of electrochemically generated o -benzoquinones (2) in Michael-type reaction with aza-crown ethers (3) to form the corresponding new o -benzoquinone-aza-crown ether adducts (5). Based on ECE mechanism, the observed homogeneous rate constants (kobs) of the reaction of o -bezoquinones (2) with aza-crown ethers (3) were estimated by comparing the experimental cyclic voltammograms with the digital simulated results. The calculated observed homogeneous rate constants (kobs) was found to vary in the order DA18C6>DA15C5>A15C5. [source] Digital simulation of the transformation of plane stressCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 1 2009Wei-Pin Lee Abstract In this study, we developed a computer program to simulate the transformation of plane stress by using Visual Basic.NET. We applied the equations of stress transformation to plane stress problems to calculate the stresses with respect to the 1,2 axes, which are rotated counterclockwise through an angle , about the x,y origin, and showed the visual results on the screen. In addition, we used animation to observe the change of plane stress. This program was then used in teaching courses, such as Mechanics of Materials and Linear Algebra. Use of the software may help students to understand principal stresses, principal axes, Mohr's circle, eigenvalues, eigenvectors, similar matrices, and invariants. © 2008 Wiley Periodicals, Inc. Comput Appl Eng Educ 17: 25,33, 2009; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae20180 [source] Voltammetric Elucidation of Ion Transfer Through an Extremely Thin MembraneELECTROANALYSIS, Issue 9 2004Nobuyuki Ichieda Abstract Digital simulation of the cyclic voltammogram for the ion transfer through a liquid membrane of thickness from 1,mm to 10,nm was performed. The magnitude of current and the shape of the voltammogram simulated for extremely thin membrane (10,nm thick) were similar to those observed experimentally with a bilayer lipid membrane, BLM, of about 10,nm in thick, when the diffusion coefficient of an ion in the BLM was assumed to be extraordinary small (10,13 to 10,14,cm2 s,1). [source] Evaluation of the Chemical Reactions from Two Electrogenerated Species in Picoliter Volumes by Scanning Electrochemical MicroscopyCHEMPHYSCHEM, Issue 13 2010Qian Wang Abstract The volume created by the positioning of two scanning electrochemical microscope (SECM) probes (tip and substrate) at a micrometric distance defines a "picoliter beaker" where homogeneous electron-transfer reactions are studied. The SECM is used to concurrently electrogenerate in situ two reactive species and to evaluate the possibility of detecting their reactivity. Two reaction cases are studied: the first, called the "reversible case", occurs when the electrochemically generated species at the substrate electrode can also react at the tip to yield the same product as the reaction in the gap. The second case, named the "irreversible case", occurs when the electrochemically generated species at the substrate are not able to react at the tip. Digital simulations are performed and compared to experimental studies. These show that an unusual compensation between collection and feedback effects render the analysis inapplicable in the "reversible case". The "irreversible case" is shown experimentally. [source] A digital simulation of the vibration of a two-mass two-spring systemCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 3 2010Wei-Pin Lee Abstract In this study, we developed a computer program to simulate the vibration of a two-mass two-spring system by using Visual BASIC. Users can enter data for the two-mass two-spring system. The software will derive the eigenvalue problem from the input data. Then the software solves the eigenvalue problem and illustrates the results numerically and graphically on the screen. In addition, the program uses animation to demonstrate the motions of the two masses. The displacements, velocities, and accelerations of the two bodies can be shown if the corresponding checkboxes are selected. This program can be used in teaching courses, such as Linear Algebra, Advanced Engineering Mathematics, Vibrations, and Dynamics. Use of the software may help students to understand the applications of eigenvalue problems and related topics such as modes of vibration, natural frequencies, and systems of differential equations. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 18: 563,573, 2010; View this article online at wileyonlinelibrary.com; DOI 10.1002/cae.20241 [source] Effect of surface roughness on the spatial coherence of X-ray beams from third-generation synchrotron radiation sourcesJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2000Yun Wang The effect of the surface roughness of optical elements, such as Be windows and reflection mirrors, in synchrotron radiation beamlines on the spatial coherence of the X-ray beam is investigated systematically by means of digital simulation, in which a new model for X-ray reflection from a rough surface is proposed. A universal factor is employed to evaluate the spatial coherence quantitatively, based on which critical values for surface roughness are reached. The results from simulation are consistent with those from experiments. [source] The Limits of Urban Simulation: An Interview with Manuel DeLandaARCHITECTURAL DESIGN, Issue 4 2009Neil Leach Abstract What is the potential for applying digital simulation for research in urban planning and development? Neil Leach pursues this question with influential ,street philosopher', one-time programmer and professor Manuel DeLanda. Copyright © 2009 John Wiley & Sons, Ltd. [source] Analysis of the Voltammetric Response of Electroactive Guests in the Presence of Non-Electroactive Hosts at Moderate ConcentrationsELECTROANALYSIS, Issue 18 2004Sandra Mendoza Abstract In this work, we present a method to analyze the voltammetric response of reversible redox systems involving molecules that, bearing m non-interactive electroactive sites, can undergo fast complexation equilibria with host molecules present at concentrations of the same order of magnitude as those of the electroactive guest. The approach focuses on systems for which the relative values of the binding constants for the oxidized and reduced forms of the guest result in the displacement of the voltammetric response of the electroactive molecule as the concentration of the host is increased in the electrolytic solution. This behavior is commonly known as "one wave shift behavior". Based on a series of assumptions, the method allows calculation of all the thermodynamic parameters that describe the electrochemical and complexation equilibria of a given host-guest system. The main strength of the suggested method, however, relies on the fact that it only requires cyclic voltammetry data and that it can be used for systems in which large concentrations of the host can not be employed either due to important changes of the ionic strength or to solubility problems. Although the accuracy of the obtained information is limited by the quality of the data provided by the technique, and by the assumptions employed, it certainly represents an excellent starting point for subsequent refinement either using digital simulations or an independent experimental technique. [source] The Sheer Opacity of Contemporary EnclosureJOURNAL OF ARCHITECTURAL EDUCATION, Issue 2 2003CATHRINE VEIKOS Skins & Screens, the graduate-level elective studio offered at the University of Pennsylvania, posits the building surface as a dynamic condition, simultaneously real and illusory, opaque and evanescent. Termed sheer opacity, this quality of enclosure provides an investigative focus for the consideration of surface as a dynamic perceptual field, a site for the mediation of physical and perceptual phenomena. Close analysis of selected work of the West Coast art movement Light and Space and that of contemporary installation artists inspired projects that used sheer opacity to examine the possibility of transforming space through the design of the building surface. Projects were developed through a series of "layers" in which students made installations, material constructs, digital simulations, and large-scale detail studies of their proposals. [source] | |||||||||||||