Nonlinear mechanics of fluidization of beds of spherical particles

1987 ◽  
Vol 177 ◽  
pp. 467-483 ◽  
Author(s):  
A. F. Fortes ◽  
D. D. Joseph ◽  
T. S. Lundgren
Keyword(s):  
Cross Section ◽  
Rectangular Cross Section ◽  
Two Dimensions ◽  
The Other ◽  
Three Dimensions ◽  
Spherical Particles ◽  
Inertial Effects ◽  
Nonlinear Mechanics ◽  
Clear Water ◽  
Cooperative Motion

Experiments on fluidization with water of spherical particles falling against gravity in columns of rectangular cross-section are described. All of them are dominated by inertial effects associated with wakes. Two local mechanisms are involved: drafting and kissing and tumbling into stable cross-stream arrays. Drafting, kissing and tumbling are rearrangement mechanisms in which one sphere is captured in the wake of the other. The kissing spheres are aligned with the stream. The streamwise alignment is massively unstable and the kissing spheres tumble into more stable cross-stream pairs of doublets which can aggregate into larger relatively stable horizontal arrays. Cross-stream arrays in beds of spheres constrained to move in two dimensions are remarkable. These arrays may even coalesce into aggregations of close-packed spheres separated by regions of clear water. A somewhat weaker form of cooperative motion of cross-stream arrays of rising spheres is found in beds of square cross-section where the spheres may move freely in three dimensions. Horizontal arrays rise where drafting spheres fall because of greater drag. Aggregation of spheres seems to be associated with relatively stable cooperative motions of horizontal arrays of spheres rising in their own wakes.

scholarly journals Behavior of reinforced concrete columns strenghtened by partial jacketing

2016 ◽  
Vol 9 (1) ◽  
pp. 1-21 ◽  
Author(s):  
D. B. FERREIRA ◽  
R. B. GOMES ◽  
A. L. CARVALHO ◽  
G. N. GUIMARÃES
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Concrete Columns ◽  
The Other ◽  
Self Compacting Concrete ◽  
Reinforced Concrete Columns ◽  
Compressive Stresses ◽  
Concrete Layer ◽  
Ultimate Resistance

This article presents the study of reinforced concrete columns strengthened using a partial jacket consisting of a 35mm self-compacting concrete layer added to its most compressed face and tested in combined compression and uniaxial bending until rupture. Wedge bolt connectors were used to increase bond at the interface between the two concrete layers of different ages. Seven 2000 mm long columns were tested. Two columns were cast monolithically and named PO (original column) e PR (reference column). The other five columns were strengthened using a new 35 mm thick self-compacting concrete layer attached to the column face subjected to highest compressive stresses. Column PO had a 120mm by 250 mm rectangular cross section and other columns had a 155 mm by 250mm cross section after the strengthening procedure. Results show that the ultimate resistance of the strengthened columns was more than three times the ultimate resistance of the original column PO, indicating the effectiveness of the strengthening procedure. Detachment of the new concrete layer with concrete crushing and steel yielding occurred in the strengthened columns.

Assessing the Validity of SWAT as a Workload Measurement Instrument

1983 ◽  
Vol 27 (2) ◽  
pp. 124-128 ◽  
Author(s):  
Stephen P. Boyd
Keyword(s):  
Mental Workload ◽  
Measurement Instrument ◽  
Two Dimensions ◽  
The Other ◽  
Three Dimensions ◽  
One Dimension ◽  
Implicit Assumption ◽  
Workload Measurement ◽  
Positive Correlations ◽  
High Level

The Subjective Workload Asssessment Technique (SWAT) carries with it the implicit assumption that people can accurately predict the amount of mental workload they would experience under various levels of three component dimensions. Research suggests that the perceptions of these dimensions may not be independent. This study was designed to measure the subjective interactions between the dimensions used in SKAT. Mental workload was generated using a text editing task in which the dimensions were manipulated independently. Results revealed significant positive correlations between the subjective levels of the three dimensions. That is, when a subject experienced a high level of one dimension, s/he also tended to rate the other two dimensions high. It may be unreasonable to assume that people can accurately predict the magnitude of these interactions when performing the ranking process which is used to derive the workload scale.

scholarly journals On an approximate solution for the bending of a beam of rectangular cross-section under any system of load, with special reference to points of concentrated or discontinuous loading

1902 ◽  
Vol 70 (459-466) ◽  
pp. 491-496
Keyword(s):  
Approximate Solution ◽  
Special Reference ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Elastic Equilibrium ◽  
Elastic Solid ◽  
Two Dimensions ◽  
Two Dimensional ◽  
Applied Stresses

The paper investigates the elastic equilibrium of a long bar of rectangular cross-section in those cases where the problem may be treated as one of two dimensions, namely:— ( a .) When the strain being in the plane of xy , the elastic solid extends indefinitely in the direction of the applied stresses over the bounding planes y = ± b , x = ± a being the same for any two sections parallel to the plane of xy . We then have a strictly two-dimensional strain.

scholarly journals The effect of collar width ratio on the flow pattern around oblong pier in bend

2021 ◽  
Author(s):  
Danesh Dehghan ◽  
Mohammad Vaghefi ◽  
Masoud Ghodsian
Keyword(s):  
Flow Pattern ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Width Ratio ◽  
Curvature Radius ◽  
Reynolds Stresses ◽  
Clear Water ◽  
Flow Conditions ◽  
Channel Bend ◽  
Oblong Pier

Abstract In this paper, the effect of collar width ratio on the flow pattern around an oblong pier in a 180-degree channel bend was experimentally studied. This channel has a rectangular cross section. It is 1 m in width and 0.7 m in height. The upstream and downstream paths are respectively 6.5 and 5 m long. The ratio of the bend's central curvature radius to the channel width is 2; hence, it qualifies as a sharp bend. Experiments were carried out under clear water approach flow conditions. The results showed that the presence of collars around an oblong pier creates vortices in the opposite direction of the longitudinal flow, causes the distortion and disturbance of the streamlines toward the pier downstream, and decreases downflow strength in front of the pier nose. Furthermore, doubling the collar width results in 0.68 and 0.93 times the vorticity and the power of the secondary flow on the pier upstream, respectively. It also reduced the maximum values of the Reynolds stresses perpendicular to the y-plane in x direction and perpendicular to the z-plane in y direction by respectively 45 and 60%, and increased the Reynolds stress perpendicular to the z-plane in x direction by 25%.

Trust in E-Commerce

2008 ◽  
pp. 771-788
Author(s):  
Ye Diana Wang ◽  
Henry H. Emurian
Keyword(s):  
Factor Analysis ◽  
Confirmatory Factor Analysis ◽  
Interface Design ◽  
Two Dimensions ◽  
The Other ◽  
Three Dimensions ◽  
Design Features ◽  
Social Cue ◽  
The Social ◽  
Confirmatory Factor

The design of the interface for e-commerce transactions is one source of influence that can affect an online shopper’s trust in the merchant. This paper undertook a confirmatory factor analysis involving 14 trust-inducing interface design features that populated a conceptual framework proposed in our previous study. The factor analysis of self-reported ratings of the features, which were illustrated on a synthetic e-commerce interface by 181 survey respondents, revealed the following three underlying dimensions: (1) visual, (2) content, and (3) social-cue design dimensions. All 14 features were found to contribute to the composition of the three dimensions. The social-cue dimension was rated as less important than the other two dimensions, and shoppers who had been cheated by an online merchant showed lower overall trust ratings in comparison to the remaining shoppers. Qualitative reports by the survey respondents yielded additional insights about the importance of the interface. The results of this study may contribute to an appreciation of interface design features that may influence a user’s perception of the trustworthiness of an online merchant’s Web site.

Mechanics of magnetic robots akin to soft beams supported at unanchored contacts

2021 ◽  
pp. 1-39
Author(s):  
Amanda De Oliveira Barros ◽  
Sukalyan Bhattacharya ◽  
James Yang
Keyword(s):  
Cross Section ◽  
Mathematical Theory ◽  
Numerical Scheme ◽  
Rectangular Cross Section ◽  
The Other ◽  
Theoretical Simulation ◽  
Multiple Contacts ◽  
Dimensional Parameters ◽  
Novel Algorithm ◽  
Single Contact

Abstract This article presents a novel algorithm to predict the shape and the support configurations of a magnetic robot acting like a supple beam which deforms due to an imposed magnetic field. The soft magnet loosely rests on a flat horizontal surface which provides the pivoting supports to the robot to attain its deformed shape. The key difficulty in analysis of the mechanics is the lack of any prior knowledge about the location of the contacts where the distorted beam finds support from the ground. This paper outlines an algorithm in which different possibilities referred to as modes are checked systematically to locate the placement and the nature of such supports. Consequently, the 2D shape of the soft beam can be determined without any heuristic assumption about where the magnetic robot is touching the solid surface. This work focuses on single contact sections although the algorithm idea is valid for multiple contacts as well. The mathematical theory and the numerical scheme are validated by comparing the simulated results with existing experimentally obtained configurations. Also, the parametric space of system-defining non-dimensional parameters is explored to determine when a transition happens from one mode to another, and which magnetization methods are desirable for higher stability. Through theoretical simulation the results show that a thin rectangular cross-section provides higher deformation when compared to the other two tested shapes (circular and equilateral triangle cross-section).

Stereotyping Older Workers and Retirement: The Managers' Point of View

2005 ◽  
Vol 24 (4) ◽  
pp. 353-366 ◽  
Author(s):  
Kène Henkens
Keyword(s):  
Older Workers ◽  
Organizational Factors ◽  
Two Dimensions ◽  
Point Of View ◽  
The Other ◽  
Three Dimensions ◽  
Older Employees ◽  
Psychological Mechanisms ◽  
Frequent Contact ◽  
Components Analysis

ABSTRACTThis article presents the results of a study into stereotyping by managers of their older workers and the influence of these stereotypes on the inclination of managers to keep their older workers in employment. The data for the study were gathered among 796 managers. Through principal components analysis, 15 opinions about older workers were reduced to three dimensions of stereotypes. The first dimension deals with the productivity of older staff; the other two dimensions have to do with their reliability and their adaptability. These stereotypical ideas about older workers influence managers' attitudes toward the retirement of their employees. The analyses show that, besides organizational factors, psychological mechanisms also explain why people view older workers through stereotypes. Managers who are older and in more frequent contact with older employees tend to hold more positive views.

Numerical Computation of Flow in Rotating Ducts

1977 ◽  
Vol 99 (1) ◽  
pp. 148-153 ◽  
Author(s):  
A. K. Majumdar ◽  
V. S. Pratap ◽  
D. B. Spalding
Keyword(s):  
Experimental Data ◽  
Kinetic Energy ◽  
Finite Difference ◽  
Numerical Computation ◽  
Cross Section ◽  
Dissipation Rate ◽  
Rectangular Cross Section ◽  
Longitudinal Direction ◽  
The Other ◽  
Constant Area

A finite-difference procedure is employed to predict the turbulent flow in ducts of rectangular cross-section, rotating about an axis normal to the longitudinal direction. The flows were treated as “parabolic” and the turbulence model used involved the solution of two differential equations, one for the kinetic energy of the turbulence and the other for its dissipation rate. Agreement with experimental data is good for a constant-area duct at low rotation, but less satisfactory for a divergent duct at larger rotation. It is argued that a “partially-parabolic” procedure will be needed to predict the latter flow correctly.

scholarly journals Transport of Non-Spherical Particles in Square Microchannel Flows: A Review

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 277
Author(s):  
Tohme Tohme ◽  
Pascale Magaud ◽  
Lucien Baldas
Keyword(s):  
Cross Section ◽  
Microfluidic Devices ◽  
Rotational Behavior ◽  
Spherical Particles ◽  
Inertial Effects ◽  
Lateral Migration ◽  
Streamwise Direction ◽  
Particle Rotation ◽  
Inertial Migration ◽  
Square Microchannel

Understanding the behavior of a single particle flowing in a microchannel is a necessary step in designing and optimizing efficient microfluidic devices for the separation, concentration, counting, detecting, sorting, or mixing of particles in suspension. Although the inertial migration of spherical particles has been deeply investigated in the last two decades, most of the targeted applications involve shaped particles whose behavior in microflows is still far from being completely understood. While traveling in a channel, a particle both rotates and translates: it translates in the streamwise direction driven by the fluid flow but also in the cross-section perpendicular to the streamwise direction due to inertial effects. In addition, particles’ rotation and translation motions are coupled. Most of the existing works investigating the transport of particles in microchannels decouple their rotational and lateral migration behaviors: particle rotation is mainly studied in simple shear flows, whereas lateral migration is neglected, and studies on lateral migration mostly focus on spherical particles whose rotational behavior is simple. The aim of this review is to provide a summary of the different works existing in the literature on the inertial migration and the rotational behavior of non-spherical particles with a focus and discussion on the remaining scientific challenges in this field.

Modified Building Shapes for Reducing Vibrations of Tall Building

2013 ◽  
Vol 871 ◽  
pp. 3-8
Author(s):  
Ki Pyo You ◽  
Young Moon Kim ◽  
Jang Youl You
Keyword(s):  
Wind Tunnel ◽  
Aspect Ratio ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Damping Ratio ◽  
Tall Building ◽  
The Other ◽  
Torsional Vibrations ◽  
Side Ratio ◽  
Building Models

To investigate the aerodynamic method for reducing motion induced vortex excitation as well as the galloping and torsional flutter of a tall building, We conducted wind tunnel tests on a tall building having a rectangular cross-section with a side ratio, D/B of 4.0 and aspect ratio of 10.0. Three aeroelastic building models were constructed to assess the effect of modified building shapes on the reduction of these vibrations. One is a plain model and the others are the shape-modified versions of the plain model, in which one has chamfered corners and the other has two openings at the top level. Experimental results showed that the chamfered model was more effective than model with the opening in reducing the above-mentioned types of vibrations, especially in motion induced vortex excitation, but not in reducing torsional vibration when the reduced velocity is high. Increasing the damping ratio might not be effective in reducing the bending and torsional vibrations of both the chamfered model and the model with openings when the reduced velocity is high.

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