Large-eddy simulation of turbulent flows and pollutant transport inside and above idealized urban street canyons under different unstable thermal stratification

Large-eddy simulation (LES) is employed to study the behaviours of flows and pollutant transport inside and over idealized urban street canyons under different unstable thermal stratification. Three configurations of idealized street canyon, consisting of building-height-to-street-width (aspect) ratios, 0.5, 1 and 2, are considered. Under unstable stratification, the vertical profiles of streamwise velocity and temperature over the bottom rough surface are more uniform and the turbulent transport of momentum and heat are enhanced. Inside the street canyons, the ventilation performance, which are characterized by the air exchange rate (ACH), pollutant exchange rate (PCH), pollutant retention time and average pollutant concentration, is found improved in unstable stratification.postprin

Development of the vestibular system

This review mainly focuses on the development of the vestibular system in humans and other mammals, but reference is made to anurans and other species where applicable. In the first section, the steps involved in the development of undifferentiated cells into mature vestibular receptors are analysed. Available data indicate that in humans, maturation of the vestibular receptor and its afferent innervations involves a similar sequence of events as in other mammalian species. In the second section, morphological and physiological aspects of the maturation of the central vestibular system are presented. Undifferentiated neuron precursors have been identified in specific segregrated domains of the hindbrain neural tube, and these can develop into secondary vestibular neurons with unique properties. Several neuronal populations in the vestibulospinal and vestibulo-ocular pathways have been found to correlate with rhombomeric domains at early embryonic stages. In rodents, the vestibular system continues to develop postnatally in terms of morphology and function until it achieves its final form. The postnatal changes in the properties of vestibular nuclear neurons are chronologically matched with structural changes and serve to prime the development of vestibular-induced reflexes. Copyright © 2002 S. Karger AG, Basel.published_or_final_versio

Fabric defect detection by Fourier analysis

Many fabric defects are very small and undistinguishable, which are very difficult to detect by only monitoring the intensity change. Faultless fabric is a repetitive and regular global texture and Fourier transform can be applied to monitor the spatial frequency spectrum of a fabric. When a defect occurs in fabric, its regular structure is changed so that the corresponding intensity at some specific positions of the frequency spectrum would change. However, the three-dimensional frequency spectrum is very difficult to analyze. In this paper, a simulated fabric model is used to understand the relationship between the fabric structure in the image space and in the frequency space. Based on the three-dimensional frequency spectrum, two significant spectrum diagrams are defined and used for analyzing the fabric defect. These two diagrams are called the central spatial frequency spectrums. The defects are broadly classified into four classes: (1) double yarn; (2) missing yarn; (3) webs or broken fabric; and (4) yarn densities variation. After evaluating these four classes of defects using some simulated models and real samples, seven characteristic parameters for central spatial frequency spectrum are extracted for defect classification.published_or_final_versio

DSP controlled power converter

A digital controller is designed and implemented by a Digital Signal Processor (DSP) to replace the Pulse Width Modulator (PWM) and error amplifier compensation network in a two wheeler forward converter. The DSP controller is designed in three approaches: a) Discretization of analog controller - the design is based on the transfer function of the error amplifier compensation network. b) Digital PID controller design - the design is based on the general form of the pulse transfer function of PID controller. c) Deadbeat controller design - the design is based on the open-loop pulse transfer function of the power converter. The controller design is optimised by running computer simulation with the MATLAB numerical calculation package and the experimental results agree with the simulated analysis.published_or_final_versio

A Study of the Impact of Thirteen Celebrity Suicides on Subsequent Suicide Rates in South Korea from 2005 to 2009

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