Tuning of frictional properties in torsional contact by means of disk grading

AbstractThe contact of two surfaces in relative rotating motion occurs in many practical applications, from mechanical devices to human joints, displaying an intriguing interplay of effects at the onset of sliding due to the axisymmetric stress distribution. Theoretical and numerical models have been developed for some typical configurations, but work remains to be done to understand how to modify the emergent friction properties in this configuration. In this paper, we extend the two-dimensional (2D) spring-block model to investigate friction between surfaces in torsional contact. We investigate how the model describes the behavior of an elastic surface slowly rotating over a rigid substrate, comparing results with analytical calculations based on energy conservation. We show that an appropriate grading of the tribological properties of the surface can be used to avoid a non-uniform transition to sliding due to the axisymmetric configuration.

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Analytical Evaluation of MCE Collapse Performance of Seismically Base Isolated Buildings Located at Low-to-Moderate Seismicity Regions

Applied Sciences ◽

10.3390/app10249150 ◽

2020 ◽

Vol 10 (24) ◽

pp. 9150

Author(s):

Hyung-Joon Kim ◽

Dong-Hyeon Shin

Keyword(s):

Base Isolation ◽

Numerical Models ◽

Influential Factors ◽

Collapse Mechanism ◽

Total System ◽

Practical Applications ◽

Seismic Design Code ◽

Moderate Seismicity ◽

Design Requirements ◽

Isolation Systems

The promising seismic response emerged by the concept of base isolation leads to increasing practical applications into buildings located at low-to-moderate seismicity regions. However, it is questionable that their collapse capacities can be ensured with reasonable reliability, although they would be designed according to a current seismic design code. This paper aims to investigate the collapse capacities of isolated buildings governed by the prescribed design criteria on the displacement and strength capacities of the employed isolation systems. In order to evaluate their collapse capacity under maximum considered earthquakes (MCEs), simplified numerical models are constructed for a larger number of nonlinear incremental dynamic analyses. The influential factors on the collapse probabilities of the prototype buildings are found out to specifically suggest the potential modifications of the design requirements. Although the MCE collapse probabilities of all isolated buildings are smaller than those expected for typical non-isolated buildings, these values are significantly different according to the degree of seismicity. The MCE collapse probabilities are dependent upon the governing collapse mechanism and the total system uncertainty. For the prototype buildings located at low-to-moderate seismicity regions, this study proposed the acceptable uncertainty to achieve a similar collapse performance to the corresponding buildings built at high seismicity regions.

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Two-dimensional metal carbides and nitrides (MXenes): preparation, property, and applications in cancer therapy

Nanophotonics ◽

10.1515/nanoph-2019-0550 ◽

2020 ◽

Vol 9 (8) ◽

pp. 2125-2145 ◽

Cited By ~ 1

Author(s):

Lu Ming Dong ◽

Cui Ye ◽

Lin Lin Zheng ◽

Zhong Feng Gao ◽

Fan Xia

Keyword(s):

Cancer Therapy ◽

Scientific Community ◽

Critical Role ◽

High Specific Surface Area ◽

Future Perspective ◽

Two Dimensional ◽

Metal Carbides ◽

Practical Applications ◽

Two Dimensional Materials ◽

Size And Morphology

AbstractTransition metal carbides and nitrides (MXenes), which comprise a rapidly growing family of two-dimensional materials, have attracted extensive attention of the scientific community, owing to its unique characteristics of high specific surface area, remarkable biocompatibility, and versatile applications. Exploring different methods to tune the size and morphology of MXenes plays a critical role in their practical applications. In recent years, MXenes have been demonstrated as promising nanomaterials for cancer therapy with substantial performances, which not only are helpful to clarify the mechanism between properties and morphologies but also bridge the gap between MXene nanotechnology and forward-looking applications. In this review, recent progress on the preparation and properties of MXenes are summarized. Further applications in cancer therapy are also discussed. Finally, the current opportunities and future perspective of MXenes are described.

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A New Troughlike Nonimaging Solar Concentrator

Journal of Solar Energy Engineering ◽

10.1115/1.1435650 ◽

2001 ◽

Vol 124 (1) ◽

pp. 51-54 ◽

Cited By ~ 3

Author(s):

Eduardo A. Rinco´n ◽

Fidel A. Osorio

Keyword(s):

Concentration Ratio ◽

Glass Tube ◽

Two Dimensional ◽

Solar Concentrator ◽

Steam Generation ◽

Acceptance Angle ◽

Practical Applications ◽

Optimal Shapes ◽

Heating Steam ◽

East West

A new two-dimensional concentrator for solar energy collection has been developed. The concentrator has the following advantages, when compared with the classic Compound Parabolic Concentrators invented by Roland Winston, W. T. Welford, A. Rabl, Baranov, and other researchers: 1) It allows the use of parabolic mirrors, which have a reflecting area much smaller for a given concentration ratio and acceptance angle. 2) Between the mirror and the absorber, there is a large gap so that conduction losses are reduced. Convection losses can be reduced, too, if the absorber is enclosed within a glass tube. 3) It can be easily manufactured. Instead of seeking the shape of the mirrors for a given shape of the absorber, we have made the inverse statement of the problem, and we have obtained the optimal shapes of the absorbers with a prescribed acceptance angle, for parabolic mirrors, assuming that the intercept factor is unity, the mirrors are perfect, and the absorber surfaces are convex. The concentrator should be east-west oriented, and could be seasonal or monthly tilt adjusted. This concentrator could have many practical applications, such as fluid heating, steam generation, etc.

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CFD Analysis of Urban Canopy Flows Employing the V2F Model: Impact of Different Aspect Ratios and Relative Heights

Advances in Meteorology ◽

10.1155/2018/2189234 ◽

2018 ◽

Vol 2018 ◽

pp. 1-16 ◽

Cited By ~ 2

Author(s):

Fabio Nardecchia ◽

Annalisa Di Bernardino ◽

Francesca Pagliaro ◽

Paolo Monti ◽

Giovanni Leuzzi ◽

...

Keyword(s):

Flow Field ◽

Water Channel ◽

Flow Regimes ◽

Two Dimensional ◽

Mean Flow ◽

Ansys Fluent ◽

Practical Applications ◽

Aspect Ratios ◽

Starting Point ◽

Step Down

Computational fluid dynamics (CFD) is currently used in the environmental field to simulate flow and dispersion of pollutants around buildings. However, the closure assumptions of the turbulence usually employed in CFD codes are not always physically based and adequate for all the flow regimes relating to practical applications. The starting point of this work is the performance assessment of the V2F (i.e., v2¯ − f) model implemented in Ansys Fluent for simulating the flow field in an idealized array of two-dimensional canyons. The V2F model has been used in the past to predict low-speed and wall-bounded flows, but it has never been used to simulate airflows in urban street canyons. The numerical results are validated against experimental data collected in the water channel and compared with other turbulence models incorporated in Ansys Fluent (i.e., variations of both k-ε and k-ω models and the Reynolds stress model). The results show that the V2F model provides the best prediction of the flow field for two flow regimes commonly found in urban canopies. The V2F model is also employed to quantify the air-exchange rate (ACH) for a series of two-dimensional building arrangements, such as step-up and step-down configurations, having different aspect ratios and relative heights of the buildings. The results show a clear dependence of the ACH on the latter two parameters and highlight the role played by the turbulence in the exchange of air mass, particularly important for the step-down configurations, when the ventilation associated with the mean flow is generally poor.

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Nonlinear processes in the bunched electron beams of high-power klystrons and the limits of analytical and one-dimensional numerical models applicability for their analysis.

Journal of Radio Electronics ◽

10.30898/1684-1719.2020.12.14 ◽

2020 ◽

Vol 2020 (12) ◽

Author(s):

V.Y. Rodyakin ◽

◽

V.M. Pikunov ◽

V.N. Aksenov ◽

◽

...

Keyword(s):

Electron Beam ◽

High Power ◽

Numerical Models ◽

Nonlinear Effects ◽

Analytical Models ◽

Modulation Amplitude ◽

Two Dimensional ◽

One Dimensional ◽

Charge Parameter ◽

Program Data

We present the results of a comparative theoretical analysis of the electron beam bunching in a single-stage klystron amplifier using analytical models, a one-dimensional disk program, and a two-dimensional program. Data on the influence of various one-dimensional and two-dimensional nonlinear effects on the efficiency of electron beam bunching at different values of the space charge parameter and the modulation amplitude are presented. The limits of applicability of analytical and one-dimensional numerical models for electron beam bunching analysis in high-power klystron amplifiers are found.

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A Synthesis Method for Placing Workpieces in RPR Planar Robotic Workcells in Which Large Rotations Are Required at the Workpiece

Volume 2A: 24th Biennial Mechanisms Conference ◽

10.1115/96-detc/mech-1140 ◽

1996 ◽

Author(s):

K. D. Chaney ◽

J. K. Davidson

Keyword(s):

Reference Frame ◽

Synthesis Method ◽

Analytical Representation ◽

New Method ◽

Two Dimensional ◽

End Effector ◽

Radial Location ◽

Practical Applications ◽

Full Turn ◽

Large Rotations

Abstract A new method is developed for determining both a satisfactory location of a workpiece and a suitable mounting-angle of the tool for planar RPR robots that can provide dexterous workspace. The method is an analytical representation of the geometry of the robot and the task, and is particularly well suited to applications in which the task requires large rotations of the end-effector. It is determined that, when the task requires that the end-effector rotate a full turn at just two locations and when the first or third joint in the robot is rotatable by one turn, then the radial location of the workpiece is fixed in the workcell but its angular location is not fixed. When the mounting-angle of the tool is also a variable, the method accommodates tasks in which the tool must rotate a full turn at three locations on the workpiece. The results are presented as coordinates of points in a two-dimensional Cartesian reference frame attached to the workcell. Consequently, a technician or an engineer can determine the location for the workpiece by laying out these coordinates directly in the workcell. Example problems illustrate the method. Practical applications include welding and deposition of adhesives.

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Molecular design and crystallization process control for thin sheet-shaped organic semiconductor crystals with two-dimensional packing

Journal of Materials Chemistry C ◽

10.1039/d1tc03133c ◽

2021 ◽

Author(s):

Yuejuan Wan ◽

Zejian Zhang ◽

Haichao Liu ◽

Jiadong Zhou ◽

Liqun Liu ◽

...

Keyword(s):

Organic Semiconductor ◽

Essential Role ◽

Crystallization Process ◽

Molecular Design ◽

Thin Sheet ◽

Optoelectronic Devices ◽

Two Dimensional ◽

High Property ◽

Practical Applications ◽

Semiconductor Crystals

The sheet-liked organic semiconductor crystals with two-dimensional (2D) packed structures play an essential role in practical applications of high-property optoelectronic devices. Here, we reported a practical example in combination with...

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A New Two-Dimensional Mutual Coupled Logistic Map and Its Application for Pseudorandom Number Generator

Mathematical Problems in Engineering ◽

10.1155/2019/7685359 ◽

2019 ◽

Vol 2019 ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

Xuan Huang ◽

Lingfeng Liu ◽

Xiangjun Li ◽

Minrong Yu ◽

Zijie Wu

Keyword(s):

Statistical Tests ◽

Chaotic Map ◽

Logistic Map ◽

Security Analysis ◽

Three Dimensional ◽

Pseudorandom Number ◽

Pseudorandom Number Generator ◽

Number Generator ◽

Two Dimensional ◽

Practical Applications

Given that the sequences generated by logistic map are unsecure with a number of weaknesses, including its relatively small key space, uneven distribution, and vulnerability to attack by phase space reconstruction, this paper proposes a new two-dimensional mutual coupled logistic map, which can overcome these weaknesses. Our two-dimensional chaotic map model is simpler than the recently proposed three-dimensional coupled logistic map, whereas the sequence generated by our system is more complex. Furthermore, a new kind of pseudorandom number generator (PRNG) based on the mutual coupled logistic maps is proposed for application. Both statistical tests and security analysis show that our proposed PRNG has good randomness and that it can resist all kinds of attacks. The algorithm speed analysis indicates that PRNG is valuable to practical applications.

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Metamaterial Lensing Devices

Molecules ◽

10.3390/molecules24132460 ◽

2019 ◽

Vol 24 (13) ◽

pp. 2460 ◽

Cited By ~ 1

Author(s):

Jiangtao Lv ◽

Ming Zhou ◽

Qiongchan Gu ◽

Xiaoxiao Jiang ◽

Yu Ying ◽

...

Keyword(s):

Building Blocks ◽

Biological Imaging ◽

Transmission Mode ◽

Two Dimensional ◽

Optical Components ◽

Practical Applications ◽

Perfect Lens ◽

Significant Potential ◽

Integrated Optical

In recent years, the development of metamaterials and metasurfaces has drawn great attention, enabling many important practical applications. Focusing and lensing components are of extreme importance because of their significant potential practical applications in biological imaging, display, and nanolithography fabrication. Metafocusing devices using ultrathin structures (also known as metasurfaces) with superlensing performance are key building blocks for developing integrated optical components with ultrasmall dimensions. In this article, we review the metamaterial superlensing devices working in transmission mode from the perfect lens to two-dimensional metasurfaces and present their working principles. Then we summarize important practical applications of metasurfaces, such as plasmonic lithography, holography, and imaging. Different typical designs and their focusing performance are also discussed in detail.

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Experience of employment of computational models for water quality modelling

E3S Web of Conferences ◽

10.1051/e3sconf/20199705030 ◽

2019 ◽

Vol 97 ◽

pp. 05030 ◽

Cited By ~ 16

Author(s):

Anatoly Krutov ◽

Dilshod Bazarov ◽

Begzod Norkulov ◽

Bakhtiyar Obidov ◽

Bobur Nazarov

Keyword(s):

Computational Models ◽

Numerical Models ◽

Qualitative Difference ◽

Three Dimensional ◽

Sufficient Conditions ◽

Aral Sea ◽

Two Dimensional ◽

Dimensional Model ◽

Two Dimensional Model ◽

Wind Currents

The purpose of the article is to develop the required and sufficient conditions under which numerical methods can be used for engineering calculations and for scientific research of hydrodynamic processes in solving practical problems related to predicting the spread of pollutants in water bodies and streams. The conducted studies consisted in comparing the results of laboratory experiments and mathematical modelling, in particular the distribution of heat in a stream with different temperature in water layers was studied. To check the adequacy of the proposed numerical models, calculations were performed and comparisons were made with the results of experimental data. The obtained results allowed to determine the boundaries of the qualitative difference in the flow behaviour for different numbers of Froude and Reynolds. The accuracy of the method was also studied. A number of additional requirements for numerical models were proposed in addition to approcsimation and stability, such as requirements of conservativeness (divergence), existence of trivial solutions on grids, possibility to calculate highly unsteady, quasi-stable, pulsating and stationary flows, requirement of invariance of linearized equations, as well as the requirement of a one-dimensional scheme to be a consequence of a two-dimensional scheme. Distribution of velocities of wind currents using a three-dimensional and two-dimensional model was studied for a real object. A shallow-water bay of the Aral Sea was chosen as the object for the research. Comparison of the calculation results for both models showed that the flow velocity fields, as well as the distribution of pollutants in shallow waters, can be performed using a two-dimensional model.

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