Avalanche dynamics by Newton. Reply to comments on avalanche flow models based on the concept of random kinetic energy

ABSTRACTThe critique by Issler and other (2017) of our avalanche dynamics model maintains that we disregard well-established results of particulate gravity flows. Here we show that the arguments of Issler and others (1) violate Newton's laws of motion in the avalanche core and (2) ignore size-dependent drag forces on snow particles (Stokes law) that lead to the formation of avalanche suspension layers. We explain why we cannot amend our model equations to accommodate their suggestions. The goal of our approach is to describe highly non-stationary processes in the avalanche core that lead to a wide range of avalanche flow types and therefore different flow behavior. This is important for practical applications.

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Fully Developed Flow of a Nanofluid through a Circular Micropipe in the Presence of Electroosmotic Effects

Mathematical Problems in Engineering ◽

10.1155/2020/1723256 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15 ◽

Cited By ~ 2

Author(s):

Muhammad D. K. Niazi ◽

Hang Xu

Keyword(s):

Double Layer ◽

Electrical Double Layer ◽

Microelectromechanical Systems ◽

Flow Behavior ◽

Fluid Viscosity ◽

Buongiorno’S Model ◽

Flow Models ◽

Similarity Transformations ◽

Modern Engineering ◽

Wide Range

Microscale heat sinks based on channels or pipes are designed to restrict the temperatures of microelectromechanical systems, which have a wide range of applications in the modern engineering and mechanics. In this context, this work aims to study heat convection and entropy generation of a fully developed nanofluid flow in a circular micropipe in the presence of an electrical double layer. Buongiorno’s model is employed to exhibit the nanofluid behavior. The governing equations are reduced to a system of nonlinear ordinary differential equations through appropriate similarity transformations. Particularly, we rectify the pressure term as an unknown constant, which makes our flow model compatible with those well-known fluid flow models in macrosize. Highly accurate solutions are obtained and verified. Analysis for physical properties of electric field, velocity field, temperature, and nanoparticle distributions is discussed followed by an investigation of the entropy evolution in the flow. The results show that flow behavior and total entropy of the system depend on the electroosmosis, thermophoresis, and fluid viscosity. However, the influence of the electrical double layer on the flow and system entropy is negligible when the electroosmotic parameter exceeds a maximum value.

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Perspectives on Snow Avalanche Dynamics Research

Geosciences ◽

10.3390/geosciences11020057 ◽

2021 ◽

Vol 11 (2) ◽

pp. 57

Author(s):

Kouichi Nishimura ◽

Fabrizio Barpi ◽

Dieter Issler

Keyword(s):

Experimental Studies ◽

Snow Avalanche ◽

Particle Interactions ◽

Snow Avalanches ◽

Special Issue ◽

Erosion And Deposition ◽

Field Surveys ◽

Wide Range ◽

Avalanche Dynamics ◽

Avalanche Flow

As an introduction for non-specialists to the Special Issue on snow avalanche dynamics, this paper first outlines how understanding the dynamics of snow avalanches can contribute to reducing risk for settlements and infrastructure. The main knowledge gaps in this field of research concern (i) the properties of the flow regimes and the transitions between them, and (ii) the dynamics of mass change due to erosion and deposition. These two aspects are intertwined and determine not only the reach of an avalanche, but also its velocity, course and impact pressure. Experimental studies described in this Special Issue comprise a wide range of scales from small rotating drums to real snow avalanches. In addition, several papers describe post-event field surveys of specific avalanches and analyze them using different methods and techniques, demonstrating how valuable qualitative insight can be gained in this way. The theoretical developments range from exploratory studies of fluid–particle interactions to a comprehensive review of half a century of avalanche flow modeling in Russia.

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A New Detector System For The HB5 Stem Instrument

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117674 ◽

1985 ◽

Vol 43 ◽

pp. 134-135

Author(s):

J.M. Cowley

Keyword(s):

Dark Field ◽

Detector System ◽

Electron Holography ◽

Small Specimen ◽

Bright Field ◽

Multiple Images ◽

Practical Applications ◽

Wide Range ◽

Diffraction Patterns ◽

Operational Modes

The HB5 STEM instrument at ASU has been modified previously to include an efficient two-dimensional detector incorporating an optical analyser device and also a digital system for the recording of multiple images. The detector system was built to explore a wide range of possibilities including in-line electron holography, the observation and recording of diffraction patterns from very small specimen regions (having diameters as small as 3Å) and the formation of both bright field and dark field images by detection of various portions of the diffraction pattern. Experience in the use of this system has shown that sane of its capabilities are unique and valuable. For other purposes it appears that, while the principles of the operational modes may be verified, the practical applications are limited by the details of the initial design.

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URBAN FACADE GEOMETRY ON OUTDOOR COMFORT CONDITIONS: A REVIEW

INDONESIAN JOURNAL OF URBAN AND ENVIRONMENTAL TECHNOLOGY ◽

10.25105/urbanenvirotech.v4i1.7151 ◽

2020 ◽

Vol 4 (1) ◽

pp. 45

Author(s):

Elahe Mirabi ◽

Nasrollahi Nazanin

Keyword(s):

Thermal Comfort ◽

Urban Areas ◽

Natural Ventilation ◽

Flow Behavior ◽

Air Flow ◽

Urban Geometry ◽

Wide Range ◽

Low Energy Buildings ◽

Outdoor Comfort ◽

Solar Access

Designing urban facades is considered as a major factor influencing issues such as natural ventilation of buildings and urban areas, radiations in the urban canyon for designing low-energy buildings, cooling demand for buildings in urban area, and thermal comfort in urban streets. However, so far, most studies on urban topics have been focused on flat facades without details of urban layouts. Hence, the effect of urban facades with details such as the balcony and corbelling on thermal comfort conditions and air flow behavior are discussed in this literature review. Aim: This study was carried out to investigate the effective factors of urban facades, including the effects of building configuration, geometry and urban canyon’s orientation. Methodology and Results: According to the results, the air flow behavior is affected by a wide range of factors such as wind conditions, urban geometry and wind direction. Urban façade geometry can change outdoor air flow pattern, thermal comfort and solar access. Conclusion, significance and impact study: In particular, the geometry of the facade, such as indentation and protrusion, has a significant effect on the air flow and thermal behavior in urban facades and can enhance outdoor comfort conditions. Also, Alternation in façade geometry can affect pedestrians' comfort and buildings energy demands.

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Solvent-Ligand Interactions in Colloidal Nanocrystals

10.26434/chemrxiv.6447884 ◽

2018 ◽

Author(s):

Jonathan De Roo ◽

Nuri Yazdani ◽

Emile Drijvers ◽

Alessandro Lauria ◽

Jorick Maes ◽

...

Keyword(s):

Direct Method ◽

Line Broadening ◽

H Nmr ◽

Size Dependent ◽

Line Shape Analysis ◽

Wide Range ◽

Nanocrystal Synthesis ◽

Ligand Interactions ◽

Indispensable Tool ◽

Theoretical Evidence

Although solvent-ligand interactions play a major role in nanocrystal synthesis, dispersion formulation and assembly, there is currently no direct method to study this. Here we examine the broadening of 1H NMR resonances associated with bound ligands, and turn this poorly understood descriptor into a tool to assess solvent-ligand interactions. We show that the line broadening has both a homogeneous and a heterogeneous component. The former is nanocrystal-size dependent and the latter results from solvent-ligand interactions. Our model is supported by experimental and theoretical evidence that correlates broad NMR lines with poor ligand solvation. This correlation is found across a wide range of solvents, extending from water to hexane, for both hydrophobic and hydrophilic ligand types, and for a multitude of oxide, sulfide and selenide nanocrystals. Our findings thus put forward NMR line shape analysis as an indispensable tool to form, investigate and manipulate nanocolloids.

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Thin structure of heterogeneous and multiphase fluid flows

Proceedings of the Mavlyutov Institute of Mechanics ◽

10.21662/uim2012.1.036 ◽

2012 ◽

Vol 9 (1) ◽

pp. 175-180

Author(s):

Yu.D. Chashechkin

Keyword(s):

Large Scale ◽

Fundamental System ◽

Fluid Flows ◽

Regular Solutions ◽

Flow Models ◽

Group Methods ◽

Wide Range ◽

Thin Structure ◽

Multiphase Fluid ◽

Complete Solutions

According to the results of visualization of streams, the existence of structures in a wide range of scales is noted: from galactic to micron. The use of a fundamental system of equations is substantiated based on the results of comparing symmetries of various flow models with the usage of theoretical group methods. Complete solutions of the system are found by the methods of the singular perturbations theory with a condition of compatibility, which determines the characteristic equation. A comparison of complete solutions with experimental data shows that regular solutions characterize large-scale components of the flow, a rich family of singular solutions describes formation of the thin media structure. Examples of calculations and observations of stratified, rotating and multiphase media are given. The requirements for the technique of an adequate experiment are discussed.

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Ring-Forming Polymerization toward Perfluorocyclobutyl and Ortho-Diynylarene-Derived Materials: From Synthesis to Practical Applications

Materials ◽

10.3390/ma14061486 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1486

Author(s):

Eugene B. Caldona ◽

Ernesto I. Borrego ◽

Ketki E. Shelar ◽

Karl M. Mukeba ◽

Dennis W. Smith

Keyword(s):

Chemical Resistance ◽

Structural Features ◽

Review Article ◽

Aryl Ether ◽

Aromatic Rings ◽

Practical Applications ◽

Repeat Units ◽

Wide Range ◽

Synthetic Routes ◽

The Cost

Many desirable characteristics of polymers arise from the method of polymerization and structural features of their repeat units, which typically are responsible for the polymer’s performance at the cost of processability. While linear alternatives are popular, polymers composed of cyclic repeat units across their backbones have generally been shown to exhibit higher optical transparency, lower water absorption, and higher glass transition temperatures. These specifically include polymers built with either substituted alicyclic structures or aromatic rings, or both. In this review article, we highlight two useful ring-forming polymer groups, perfluorocyclobutyl (PFCB) aryl ether polymers and ortho-diynylarene- (ODA) based thermosets, both demonstrating outstanding thermal stability, chemical resistance, mechanical integrity, and improved processability. Different synthetic routes (with emphasis on ring-forming polymerization) and properties for these polymers are discussed, followed by their relevant applications in a wide range of aspects.

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Sensing of Nickel(II) Ions by Immobilizing Ligands and Using Different SPEs

Engineering Proceedings ◽

10.3390/i3s2021dresden-10106 ◽

2021 ◽

Vol 6 (1) ◽

pp. 2

Author(s):

Liliana Anchidin-Norocel ◽

Sonia Amariei ◽

Gheorghe Gutt

Keyword(s):

Bismuth Oxide ◽

Human Population ◽

Raw Materials ◽

Sensor Technology ◽

Cyclic Voltammogram ◽

Accurate Analysis ◽

Nickel Allergy ◽

Nickel Ions ◽

Practical Applications ◽

Wide Range

The aim of this paper is the development of a sensor for the quantification of nickel ions in food raw materials and foods. It is believed that about 15% of the human population suffers from nickel allergy. In addition to digestive manifestations, food intolerance to nickel may also have systemic manifestations, such as diffuse dermatitis, diffuse itching, fever, rhinitis, headache, altered general condition. Therefore, it is necessary to control this content of nickel ions for the health of the human population by developing a new method that offers the advantages of a fast, not expensive, in situ, and accurate analysis. For this purpose, bismuth oxide-screen-printed electrodes (SPEs) and graphene-modified SPEs were used with a very small amount of dimethylglyoxime and amino acid L-histidine that were deposited. A potentiostat that displays the response in the form of a cyclic voltammogram was used to study the electrochemical properties of nickel standard solution with different concentrations. The results were compared and the most sensitive sensor proved to be bismuth oxide-SPEs with dimethylglyoxime (Bi2O3/C-dmgH2) with a linear response over a wide range (0.1–10 ppm) of nickel concentrations. Furthermore, the sensor shows excellent selectivity in the presence of common interfering species. The Bi2O3/C-dmgH2 sensor showed good viability for nickel analysis in food samples (cocoa, spinach, cabbage, and red wine) and demonstrated significant advancement in sensor technology for practical applications.

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Assessment of Linearization Approaches for Multibody Dynamics Formulations

Journal of Computational and Nonlinear Dynamics ◽

10.1115/1.4035410 ◽

2017 ◽

Vol 12 (4) ◽

Cited By ~ 6

Author(s):

Francisco González ◽

Pierangelo Masarati ◽

Javier Cuadrado ◽

Miguel A. Naya

Keyword(s):

Mechanical System ◽

Multibody Dynamics ◽

Equations Of Motion ◽

Differential Algebraic Equations ◽

Algebraic Equations ◽

Practical Applications ◽

Linearization Methods ◽

Highly Nonlinear ◽

Wide Range ◽

The Way

Formulating the dynamics equations of a mechanical system following a multibody dynamics approach often leads to a set of highly nonlinear differential-algebraic equations (DAEs). While this form of the equations of motion is suitable for a wide range of practical applications, in some cases it is necessary to have access to the linearized system dynamics. This is the case when stability and modal analyses are to be carried out; the definition of plant and system models for certain control algorithms and state estimators also requires a linear expression of the dynamics. A number of methods for the linearization of multibody dynamics can be found in the literature. They differ in both the approach that they follow to handle the equations of motion and the way in which they deliver their results, which in turn are determined by the selection of the generalized coordinates used to describe the mechanical system. This selection is closely related to the way in which the kinematic constraints of the system are treated. Three major approaches can be distinguished and used to categorize most of the linearization methods published so far. In this work, we demonstrate the properties of each approach in the linearization of systems in static equilibrium, illustrating them with the study of two representative examples.

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Periodic wavelet descriptor of plant leaf and its application in botany

International Journal of Wavelets Multiresolution and Information Processing ◽

10.1142/s0219691315500435 ◽

2015 ◽

Vol 13 (06) ◽

pp. 1550043 ◽

Cited By ~ 3

Author(s):

Qing-Mao Zeng ◽

Tong-Lin Zhu ◽

Xue-Ying Zhuang ◽

Ming-Xuan Zheng

Keyword(s):

Species Identification ◽

Plant Species ◽

Shape Descriptor ◽

Plant Leaf ◽

Practical Applications ◽

Wide Range ◽

Periodic Wavelet ◽

Plant Species Identification ◽

Botanical Research ◽

Wavelet Descriptor

Leaf is one of the most important organs of plant. Leaf contour or outline, usually a closed curve, is a fundamental morphological feature of leaf in botanical research. In this paper, a novel shape descriptor based on periodic wavelet series and leaf contour is presented, which we name as Periodic Wavelet Descriptor (PWD). The PWD of a leaf actually expresses the leaf contour in a vector form. Consequently, the PWD of a leaf has a wide range in practical applications, such as leaf modeling, plant species identification and classification, etc. In this work, the plant species identification and the leaf contour reconstruction, as two practical applications, are discussed to elaborate how to employ the PWD of a plant leaf in botanical research.

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