The Experts below are selected from a list of 607203 Experts worldwide ranked by ideXlab platform
Erich J. Plate - One of the best experts on this subject based on the ideXlab platform.
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Methods of investigating urban wind fields—Physical Models
Atmospheric Environment, 1999Co-Authors: Erich J. PlateAbstract:For evaluation of environmental problems in urban areas, Models are needed. Physical Models and mathematical Models are the tools of the trade. Both types of Models have advantages and limitations. The emphasis here is on boundary layer wind tunnels, which are well suited for the study of many urban climate situations. The boundary layer flow along the floor of a meteorological wind tunnel is a real flow which approximately represents a scaled down version of the atmospheric boundary layer under conditions of neutral stratification. Therefore, important practical problems involving urban atmospheric conditions can be studied in such wind tunnels by means of geometrically similar Models of the urban area. Such problems involve wind forces on structures, pedestrian comfort, and diffusion processes from point sources, such as chimneys, tunnel exhausts and gaseous spills, or from line sources, such as traffic lines. The investigation of these processes in a wind tunnel must be seen, however, as one link only in a chain of actions.
Ahmed Elbeih - One of the best experts on this subject based on the ideXlab platform.
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the mitigation effect of synthetic polymers on initiation reactivity of cl 20 Physical Models and chemical pathways of thermolysis
Journal of Physical Chemistry C, 2014Co-Authors: Qi-long Yan, Svatopluk Zeman, Tong-lai Zhang, P Sanchez E Jimenez, Luis A Perezmaqueda, Ahmed ElbeihAbstract:In this paper, the thermal decomposition Physical Models of different CL-20 polymorph crystals and their polymer bonded explosives (PBXs) bonded by polymeric matrices using polyisobutylene (PIB), acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), Viton A, and Fluorel binders are obtained and used to predict the temperature profiles of constant rate decomposition. The Physical Models are further supported by the detailed decomposition pathways simulated by a reactive molecular dynamics (ReaxFF-lg) code. It has been shown that both e-CL-20 and α-CL-20 decompose in the form of γ-CL-20, resulting in close activation energy (169 kJ mol–1) and Physical model (first-order autoaccelerated model, AC1). Fluoropolymers could change the decomposition mechanism of e-CL-20 from the “first-order autocatalytic” model to a “three-dimensional nucleation and growth” model (A3), while the polymer matrices of Formex P1, Semtex, and C4 could change e-CL-20 decomposition from a single-step process to a multis...
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The Mitigation Effect of Synthetic Polymers on Initiation Reactivity of CL-20: Physical Models and Chemical Pathways of Thermolysis
2014Co-Authors: Qi-long Yan, Svatopluk Zeman, P. Sánchez E. Jiménez, Tong-lai Zhang, L. A. Pérez-maqueda, Ahmed ElbeihAbstract:In this paper, the thermal decomposition Physical Models of different CL-20 polymorph crystals and their polymer bonded explosives (PBXs) bonded by polymeric matrices using polyisobutylene (PIB), acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), Viton A, and Fluorel binders are obtained and used to predict the temperature profiles of constant rate decomposition. The Physical Models are further supported by the detailed decomposition pathways simulated by a reactive molecular dynamics (ReaxFF-lg) code. It has been shown that both ε-CL-20 and α-CL-20 decompose in the form of γ-CL-20, resulting in close activation energy (169 kJ mol–1) and Physical model (first-order autoaccelerated model, AC1). Fluoropolymers could change the decomposition mechanism of ε-CL-20 from the “first-order autocatalytic” model to a “three-dimensional nucleation and growth” model (A3), while the polymer matrices of Formex P1, Semtex, and C4 could change ε-CL-20 decomposition from a single-step process to a multistep one with different activation energies and Physical Models. Compared to fluoropolymers, PIB, SBR and NBR may make ε-CL-20 undergo more complete N–NO2 scission before collapse of the cage structure. This is likely the main reason why those polymer bases could greatly mitigate the decomposition process of ε-CL-20 from a single step to a multistep, resulting in lower impact sensitivity, whereas fluoropolymers have only a little effect on that. For ε-CL-20 and its PBXs, the impact sensitivity depends not only on the heat built-up period of their decomposition, but also on the probability of hotspot generation (defects in solid crystals and interfaces) especially when it decomposes in a solid state
Takayuki Arai - One of the best experts on this subject based on the ideXlab platform.
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simple Physical Models of the vocal tract for education in speech science
Conference of the International Speech Communication Association, 2009Co-Authors: Takayuki AraiAbstract:In the speech-related field, Physical Models of the vocal tract are effective tools for education in acoustics. Arai’s cylindertype Models are based on Chiba and Kajiyama’s measurement of vocal-tract shapes. The Models quickly and effectively demonstrate vowel production. In this study, we developed Physical Models with simplified shapes as educational tools to illustrate how vocal-tract shape accounts for differences among vowels. As a result, the five Japanese vowels were produced by tube-connected Models, where several uniform tubes with different cross-sectional areas and lengths are connected as Fant’s and Arai’s three-tube Models. Index Terms: speech science, vocal-tract model, education in acoustics, vowel production, acoustic tube
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INTERSPEECH - Simple Physical Models of the Vocal Tract for Education in Speech Science
2009Co-Authors: Takayuki AraiAbstract:In the speech-related field, Physical Models of the vocal tract are effective tools for education in acoustics. Arai’s cylindertype Models are based on Chiba and Kajiyama’s measurement of vocal-tract shapes. The Models quickly and effectively demonstrate vowel production. In this study, we developed Physical Models with simplified shapes as educational tools to illustrate how vocal-tract shape accounts for differences among vowels. As a result, the five Japanese vowels were produced by tube-connected Models, where several uniform tubes with different cross-sectional areas and lengths are connected as Fant’s and Arai’s three-tube Models. Index Terms: speech science, vocal-tract model, education in acoustics, vowel production, acoustic tube
X X Zhu - One of the best experts on this subject based on the ideXlab platform.
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Physical Models of diffusion for polymer solutions gels and solids
Progress in Polymer Science, 1999Co-Authors: L Masaro, X X ZhuAbstract:Diffusion in polymer solutions and gels has been studied by various techniques such as gravimetry, membrane permeation, fluorescence and radioactive labeling. These studies have led to a better knowledge on polymer morphology, transport phenomena, polymer melt and controlled release of drugs from polymer carriers. Various theoretical descriptions of the diffusion processes have been proposed. The theoretical Models are based on different Physical concepts such as obstruction effects, free volume effects and hydrodynamic interactions. With the availability of pulsed field gradient NMR techniques and other modern experimental methods, the study of diffusion has become much easier and data on diffusion in polymers have become more available. This review article summarizes the different Physical Models and theories of diffusion and their uses in describing the diffusion in polymer solutions, gels and even solids. Comparisons of the Models and theories are made in an attempt to illustrate the applicability of the Physical concepts. Examples in the literature are used to illustrate the application and applicability of the Models in the treatment of diffusion data in various systems. q 1999 Elsevier Science Ltd. All rights reserved.
Changxi Yang - One of the best experts on this subject based on the ideXlab platform.
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ultrasonic imaging of seismic Physical Models using a phase shifted fiber bragg grating
Optics Express, 2014Co-Authors: Qun Zhao, Changxi YangAbstract:We report what is to our knowledge the first ultrasonic imaging of seismic Physical Models by using a phase-shifted fiber Bragg grating (PS-FBG). Seismic Models, which consist of multiple layer structures, were immersed in water. Piezoelectric (PZT) transducer was used to generate ultrasonic waves and a PS-FBG as a receiver. Two-dimensional (2D) ultrasonic images were reconstructed by scanning the PS-FBG with a high-precision position scanning device. In order to suppress the low-frequency drift of the Bragg wavelength during scanning, a tight wavelength tracking method was employed to lock the laser to the PS-FBG resonance in its reflection bandgap. The ultrasonic images captured by the PS-FBG have been compared with the images obtained by the geoPhysical imaging system, Sinopec, demonstrating the feasibility of our PS-FBG based imaging system in seismic modeling studies.
