A Comparison of Homogenization and Averaging Techniques for the Treatment of Roughness in Slip-Flow-Modified Reynolds Equation

2001 ◽  
Vol 124 (2) ◽  
pp. 327-335 ◽  
Author(s):  
M. Jai ◽  
B. Bou-Saı¨d
Keyword(s):  
Slip Flow ◽  
Rotating Disk ◽  
Homogenization Theory ◽  
Storage Device ◽  
Magnetic Storage ◽  
Roughness Effects ◽  
Small Surface ◽  
Air Gaps ◽  
Practical Applications ◽  
Recent Developments

This article is concerned with the simulation of a magnetic storage device consisting of a flying head above a rigid rotating disk. The need to improve the transfer rate has led, at present, to very small surface-to-surface distances (air gaps). In this situation it is compulsory to take into account roughness effects. A popular method consists in averaging film-thickness from Mitsuya et al. (1989), with good reported results compared with experimental data. To overcome some limitations that become apparent at very small air gaps, notably when the roughness is two-dimensional, Jai in 1995 introduced a new technique based on a rigorous homogenization theory. Recent developments from Buscaglia and Jai (2000) have greatly reduced the computational complexity of the homogenization-based method, rendering it suitable for practical applications. We propose in this paper an original approach based on strength and rigorous mathematical model to avoid numerical problems which are usually encountered in classical approaches. The validation of the homogenization-based method is in some sense, a generalization of the film-averaging technique suitable for configurations in which some parameters of the latter (such as the Boltzmann correction factor) are not unambiguously defined.

A Study of Roughness and Non-Newtonian Effects in Lubricated Contacts

2005 ◽  
Vol 127 (3) ◽  
pp. 575-581 ◽  
Author(s):  
Malal Kane ◽  
Benyebka Bou-Said
Keyword(s):  
Film Thickness ◽  
Numerical Solutions ◽  
Operating Conditions ◽  
Homogenization Theory ◽  
Roughness Effects ◽  
Small Surface ◽  
Lubricated Contacts ◽  
Lubricated Contact ◽  
A New Technique ◽  
Numer Anal

This article is concerned with the simulation of a lubricated contact considering the fluid to be non-Newtonian of the Maxwell type. Severe operating conditions lead to very small surface-to-surface distances. In this situation it is necessary to take roughness effects into account. A popular method consists in averaging the film thickness following Patir and Cheng (ASME J. Lubr. Technol., 100, pp. 12–17, 1978), or more recently Wang et al. (Tribol. Trans., 45(1), pp. 1–10, 2000), with good reported results compared with experimental data. To overcome certain limitations that become apparent at very small film thickness, notably when the roughness is two-dimensional, in 1995 Jai (Math. Modell. Numer. Anal., 29(2), pp. 199–233, 1995) introduced a new technique based on a rigorous homogenization theory in the case of compressible fluid flow. This procedure was further mathematically developed by Buscaglia and Jai (Math. Probl. Eng., 7(4), pp. 355–377, 2001) and applied to tribological problems by Jai and Bou-Saı¨d (ASME J. Tribol., 124, pp. 327–355, 2002). In this paper, we propose a similar homogenized approach in the case of non-Newtonian fluids to avoid numerical problems which are often encountered in other approaches. Results in the homogenized roughness case are obtained and compared with direct numerical solutions.

Models for Gaseous Slip Flow in Non-Circular Microchannels

2007 ◽  
Author(s):  
Zhipeng Duan ◽  
Y. S. Muzychka
Keyword(s):  
Friction Factor ◽  
Cross Sections ◽  
Slip Flow ◽  
Analytical Models ◽  
Roughness Effects ◽  
Practical Applications ◽  
Micro Channels ◽  
Mems Technology ◽  
Compressibility Effects ◽  
Circular Microchannels

Micro-scale fluid dynamics has received intensive interest due to the emergence of Micro-Electro-Mechanical Systems (MEMS) technology. Non-circular cross sections are common channel shapes that can be produced through a variety of micro-fabrication techniques. Non-circular microchannels have extensive practical applications in MEMS. Slip flow in noncircular microchannels has been examined by the authors and a review of several new models obtained by the authors is presented. These models are general and robust, and can be used by the research community for practical engineering design of microchannel flow systems. The reviewed models address: (i) fully developed slip flow in non-circular microchannels, (ii) hydrodynamically developing slip flow in non-circular microchannels, (iii) compressibility effects, and (iv) roughness effects. A model is proposed to predict the friction factor and Reynolds product fRe for fully developed and developing slip flow in most non-circular micro-channels. Compressibility effects on slip flow in non-circular microchannels have been examined and simple models are proposed to predict the pressure distribution and mass flow rate for slip flow in most non-circular microchannels. Finally, the effect of corrugated surface roughness on fully developed laminar flow in microtubes is examined. Simple analytical models are developed to predict friction factor and pressure drop in corrugated rough microtubes for continuum flow and slip flow.

Synthesis and Electrochemical Properties of NiFe-Se/rGO Nanocomposites

2020 ◽  
Vol 13 ◽  
Author(s):  
Rouwei Yan ◽  
Biao Xu ◽  
K. P. Annamalai ◽  
Tianlu Chen ◽  
Zhiming Nie ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Graphene Oxide ◽  
Energy Storage ◽  
Synergistic Effects ◽  
Nitrogen Adsorption ◽  
Storage Device ◽  
Energy Storage And Conversion ◽  
Step Method ◽  
Practical Applications ◽  
Device Applications

Background : Renewable energies are in great demand because of the shortage of traditional fossil energy and the associated environmental problems. Ni and Se-based materials are recently studied for energy storage and conversion owing to their reasonable conductivities and enriched redox activities as well as abundance. However, their electrochemical performance is still unsatisfactory for practical applications. Objective: To enhance the capacitance storage of Ni-Se materials via modification of their physiochemical properties with Fe. Methods: A two-step method was carried out to prepare FeNi-Se loaded reduced graphene oxide (FeNi-Se/rGO). In the first step, metal salts and graphene oxide (GO) were mixed under basic condition and autoclaved to obtain hydroxide intermediates. As a second step, selenization process was carried out to acquire FeNi-Se/rGO composites. Results: X-ray diffraction measurements (XRD), nitrogen adsorption at 77K, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were carried out to study the structures, porosities and the morphologies of the composites. Electrochemical measurements revealed that FeNi-Se/rGO notably enhanced capacitance than the NiSe/G composite. This enhanced performance was mainly attributed to the positive synergistic effects of Fe and Ni in the composites, which not only had influence on the conductivity of the composite but also enhanced redox reactions at different current densities. Conclusion: NiFe-Se/rGO nanocomposites were synthesized in a facile way. The samples were characterized physicochemically and electrochemically. NiFeSe/rGO giving much higher capacitance storage than the NiSe/rGO explained that the nanocomposites could be an electrode material for energy storage device applications.

Assessment and Orff Schulwerk Pedagogy

2019 ◽  
pp. 538-560
Author(s):  
Daniel Johnson
Keyword(s):  
Teacher Educators ◽  
Authentic Assessment ◽  
Research Literature ◽  
National Standards ◽  
International Adoptions ◽  
Practical Applications ◽  
Orff Schulwerk ◽  
Recent Developments ◽  
Based Instruction ◽  
Assessment Strategies

This chapter on assessing student learning and Orff Schulwerk examines the foundations of this approach, its focus on creativity, and practical applications of this pedagogy. By reviewing current research literature and international adoptions of the Schulwerk, the chapter focuses on three assessment-related challenges: a lack of clearly defined teaching practices, a de-emphasis of evaluation in the Orff process, and inherent challenges related to assessing creativity. An examination of professional resource documents and recent developments in national standards provides ways to address each of these assessment challenges in Orff-based instruction. A discussion of curricular levels offers more possibilities for enhancing authentic assessment strategies. Practical recommendations for Orff Schulwerk teachers to improve their assessment protocols and implications for teacher-educators conclude this chapter.

scholarly journals Latest Developments in Insect Sex Pheromone Research and Its Application in Agricultural Pest Management

Insects ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 484
Author(s):  
Syed Arif Hussain Rizvi ◽  
Justin George ◽  
Gadi V. P. Reddy ◽  
Xinnian Zeng ◽  
Angel Guerrero
Keyword(s):  
Sex Pheromone ◽  
Pest Management ◽  
Interdisciplinary Approach ◽  
Pheromone Biosynthesis ◽  
Insect Pheromones ◽  
Agricultural Pest ◽  
Practical Applications ◽  
The Past ◽  
Significant Research ◽  
Recent Developments

Since the first identification of the silkworm moth sex pheromone in 1959, significant research has been reported on identifying and unravelling the sex pheromone mechanisms of hundreds of insect species. In the past two decades, the number of research studies on new insect pheromones, pheromone biosynthesis, mode of action, peripheral olfactory and neural mechanisms, and their practical applications in Integrated Pest Management has increased dramatically. An interdisciplinary approach that uses the advances and new techniques in analytical chemistry, chemical ecology, neurophysiology, genetics, and evolutionary and molecular biology has helped us to better understand the pheromone perception mechanisms and its practical application in agricultural pest management. In this review, we present the most recent developments in pheromone research and its application in the past two decades.

scholarly journals Chiral Recognition for Chromatography and Membrane-Based Separations: Recent Developments and Future Prospects

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1145
Author(s):  
Yuan Zhao ◽  
Xuecheng Zhu ◽  
Wei Jiang ◽  
Huilin Liu ◽  
Baoguo Sun
Keyword(s):  
Rapid Development ◽  
Chiral Molecules ◽  
Future Prospects ◽  
Chiral Drugs ◽  
Recognition Mechanism ◽  
Practical Applications ◽  
Food Industries ◽  
Global Industry ◽  
Endocrine Disrupting ◽  
Recent Developments

With the rapid development of global industry and increasingly frequent product circulation, the separation and detection of chiral drugs/pesticides are becoming increasingly important. The chiral nature of substances can result in harm to the human body, and the selective endocrine-disrupting effect of drug enantiomers is caused by differential enantiospecific binding to receptors. This review is devoted to the specific recognition and resolution of chiral molecules by chromatography and membrane-based enantioseparation techniques. Chromatographic enantiomer separations with chiral stationary phase (CSP)-based columns and membrane-based enantiomer filtration are detailed. In addition, the unique properties of these chiral resolution methods have been summarized for practical applications in the chemistry, environment, biology, medicine, and food industries. We further discussed the recognition mechanism in analytical enantioseparations and analyzed recent developments and future prospects of chromatographic and membrane-based enantioseparations.

Internal and Consulting Information Flows in the Process of Knowledge Accumulation

2019 ◽  
Vol 15 (1) ◽  
pp. 19-36 ◽  
Author(s):  
Wiliam Acar ◽  
Rami al-Gharaibeh
Keyword(s):  
Knowledge Creation ◽  
Practical Applications ◽  
Seci Model ◽  
Top Managers ◽  
Deductive Synthesis ◽  
Proposed Model ◽  
Control Framework ◽  
Recent Developments ◽  
And Control ◽  
Knowledge Hierarchy

Practical applications of knowledge management are hindered by a lack of linkage between the accepted data-information-knowledge hierarchy with using pragmatic approaches. Specifically, the authors seek to clarify the use of the tacit-explicit dichotomy with a deductive synthesis of complementary concepts. The authors review appropriate segments of the KM/OL literature with an emphasis on the SECI model of Nonaka and Takeuchi. Looking beyond equating the sharing of knowledge with mere socialization, the authors deduce from more recent developments a knowledge creation, nurturing and control framework. Based on a cyclic and upward-spiraling data-information-knowledge structure, the authors' proposed model affords top managers and their consultants opportunities for capturing, debating and storing richer information – as well as monitoring their progress and controlling their learning process.

Pressure, Frictional Resistance, and Flow Characteristics of the Partially Wetted Rotating Disk

1968 ◽  
Vol 90 (2) ◽  
pp. 395-404 ◽  
Author(s):  
H. N. Ketola ◽  
J. M. McGrew
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Pressure Gradient ◽  
Flow Characteristics ◽  
Frictional Resistance ◽  
Rotating Disk ◽  
Practical Applications ◽  
Stationary Wall ◽  
Spacing Ratio ◽  
Analytical Expressions

A theory of the partially wetted rotating disk is described and experimental data presented which verify the application of this theory in practical applications. Four different flow regimes may be identified according to the value of the disk Reynolds number and the spacing ratio between the disk and stationary wall. The analytical expressions for prediction of the pressure gradient developed and the frictional resistance are uniquely determined by the disk Reynolds number, spacing ratio, and the degree of wetting of the disk.

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