scholarly journals Addressing Spatial Variability of Surface-Layer Wind with Long-Range WindScanners

2015 ◽  
Vol 32 (3) ◽  
pp. 518-527 ◽  
Author(s):  
Jacob Berg ◽  
Nikola Vasiljevíc ◽  
Mark Kelly ◽  
Guillaume Lea ◽  
Michael Courtney
Keyword(s):  
Spatial Variability ◽  
Long Range ◽  
Three Dimensional ◽  
Proof Of Concept ◽  
Large Area ◽  
Vertical Velocity Component ◽  
Sonic Anemometers ◽  
Wind Measurements ◽  
The Mean

AbstractThis paper presents an analysis of mean wind measurements from a coordinated system of long-range WindScanners. From individual scan patterns the mean wind field was reconstructed over a large area, and hence it highlights the spatial variability. From comparison with sonic anemometers, the quality of the WindScanner data is high, although the fidelity of the estimated vertical velocity component is significantly limited by the elevation angles of the scanner heads. The system of long-range WindScanners presented in this paper is close to being fully operational, with the pilot study herein serving not only as a proof of concept but also verifying expectations of reliable wind measurements over arbitrary three-dimensional volumes, in future sustained meteorological campaigns.

scholarly journals Experimental and Numerical Investigations of a Novel Laser Impact Liquid Flexible Microforming Process

Metals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 599 ◽  
Author(s):  
Fei Liu ◽  
Huixia Liu ◽  
Chenkun Jiang ◽  
Youjuan Ma ◽  
Xiao Wang
Keyword(s):  
Numerical Simulation ◽  
Laser Energy ◽  
Pure Copper ◽  
Three Dimensional ◽  
Element Model ◽  
Force Transmission ◽  
Large Area ◽  
Laser Impact ◽  
Metallic Foils

A novel high strain rate microforming technique, laser impact liquid flexible embossing (LILFE), which uses laser induced shock waves as an energy source, and liquid as a force transmission medium, is proposed by this paper in order to emboss three-dimensional large area micro arrays on metallic foils and to overcome some of the defects of laser direct shock microembossing technology. The influences of laser energy and workpiece thickness on the deformation characteristics of the pure copper foils with the LILFE process were investigated through experiments and numerical simulation. A finite element model was built to further understand the typical stages of deformation, and the results of the numerical simulation are consistent with those achieved from the experiments. The experimental and simulation results show that the forming accuracy and depth of the embossed parts increases with the increase in laser energy and decrease in workpiece thickness. The thickness thinning rate of the embossed parts increases with the decrease of the workpiece thickness, and the severest thickness thinning occurs at the bar corner region. The experimental results also show that the LILFE process can protect the workpiece surface from being ablated and damaged, and can ensure the surface quality of the formed parts. Besides, the numerical simulation studies reveal the plastic strain distribution of embossed microfeatures under different laser energy.

An analysis of  flow distortion in a multipath sonic anemometer

2021 ◽  
Author(s):  
Ebba Dellwik ◽  
Poul Hummelshøj ◽  
Gerhard Peters
Keyword(s):  
Vertical Velocity ◽  
Velocity Component ◽  
Sonic Anemometer ◽  
Three Dimensional ◽  
Turbulence Theory ◽  
Flow Distortion ◽  
Vertical Velocity Component ◽  
Ongoing Research ◽  
Sonic Anemometers

<p>Sonic anemometers provide point observations of the three-dimensional velocity field at high sampling rates and are crucial instruments for understanding and quantifying the fluxes of momentum, energy and scalars between the atmosphere and Earth’s surface. Since the beginning of sonic anemometry 50 years ago, the characterization of flow distortion, i.e. how the instrument structure alters the flow, has been an ongoing research topic. Multi-path sonic anemometry provides a new opportunity to research and understand flow distortion on the vertical velocity component, since several positions in the small measurement volume can be measured simultaneously. In this work, we use data from a flat terrain measurement campaign in 2020, in which several sonic anemometers were mounted on 4m towers placed 4m apart. The analysis is focused on the Multipath Class-A sonic anemometer (Metek GmbH, Germany), which provides vertical velocity observations from three vertical paths 120 degrees and 0.1m apart. Vertical velocities are also calculated from several combinations of the tilted paths. We investigate how the vertical velocity component is altered depending on wind direction relative to different parts of the instrument structure. We demonstrate that by an optimal combination of the different paths, the vertical velocity variance and fluxes can be significantly enhanced. We also show spectra, and especially look at the high frequency end of the spectrum, where the relative behaviour of the velocity components is known from fundamental turbulence theory. Further, the relative importance of transducer shadowing and pressure-induced blockage effects is discussed.</p>

A Numerical Method for the Calculation of Image Aberrations of Inhomogeneous Magnetic Sector Fields Between Conical Pole Faces

1966 ◽  
Vol 21 (1-2) ◽  
pp. 2-8 ◽  
Author(s):  
F. Rüdenauer ◽  
F. P. Viehböck
Keyword(s):  
Numerical Method ◽  
Isotope Separation ◽  
Three Dimensional ◽  
Nuclear Spectroscopy ◽  
Isotope Separator ◽  
Analytical Treatment ◽  
Magnetic Sector ◽  
Know How ◽  
The Mean

Owing to their increased dispersion magnetic analysers with inhomogeneous magnetic fields may be useful for various applications e. g. nuclear spectroscopy, mass spectroscopy, and isotope separation. This inhomogeneity may be aquired by conically shaped pole faces. Boerboom and Tasman gave an analytical treatment of these fields, which allows the calculation of aberrations for particles along the medium radius. For some applications e. g. simultaneous collection of more isotopes in an isotope separator it would be important to know how the quality of focus varies with increasing distance from the mean radius. In this paper a numerical method is described which allows a three dimensional ray-tracing throughout inhomogeneous magnetic sector fields. Some of the results have been published elsewhere 1.

An Active Micromixer Enhances Mixing by Rotating Shuttlecock Rotor

2008 ◽  
Author(s):  
Thien Xuan Dinh ◽  
Yoshifumi Ogami
Keyword(s):  
Strouhal Number ◽  
Three Dimensional ◽  
Exit Channel ◽  
Mean Velocity ◽  
Mixing Performance ◽  
Two Fluids ◽  
Active Mixer ◽  
The Mean ◽  
Downstream Flow

Mixing performance of an active mixer which mixes two fluids by three-dimensional flow surrounding a rotating shuttlecock rotor in continuous flow is numerically investigated. The mixer consists of a step contraction-expansion microchannel and a shuttlecock micro-rotor placed in the step. The obtained results show that mixing quality of solution does not depend on neither rotation speed nor mean velocity in the mixer, but rather on the ratio of tip paddle velocity of the rotor to the mean velocity (i.e. Strouhal number). Streaklines demonstrate that two fluids from the inlet can penetrate into the space between the paddles of the rotor, and then are mixed here before flowing to the exit channel. In small Strouhal number (∼10) cases, two fluids are twisted 90 degrees after passing the rotor region. In the other words, mixing in downstream flow behind the rotor takes place in the height instead of the width of the exit channel, which makes the mixer applicable for channels with high aspect ratio of the cross section. It is observed that mixing is dominantly enhanced in the rotor region and increasing Strouhal number results in faster mixing in the mixer.

scholarly journals Fabrication Methods of the Polygonal Masonry of Large Tightly Fitted Stone Blocks with Curved Surface Interfaces in Megalithic Structures of Peru

2021 ◽  
Author(s):  
Rostislav Lapshin
Keyword(s):  
Small Area ◽  
18Th Century ◽  
Three Dimensional ◽  
Curved Surfaces ◽  
Large Area ◽  
High Quality ◽  
Three Dimensional Objects ◽  
Large Stone ◽  
Clay Model

The article suggests methods that allow creating the most complicated type of polygonal masonry found in Peru. This masonry consists of large stone blocks weighing from several hundred kilograms to several tons fitted close to each other almost without a gap between complicated curved surfaces of large area. The work provides a description of techniques, which apparently were used by builders who arrived from Europe. The techniques under discussion are based on the use of a reduced clay model, 3D-pantograph and replicas. The use of a reduced clay model and a pantograph provides not only the unique appearance and high quality of masonry with large blocks, but also allows to significantly increase the productivity of the builders. As machines copying three-dimensional objects are known since the 18th century, the stone structures under consideration should be dated by that and later time. The remaining simpler types of polygonal masonry with smaller stones or fitted surfaces are almost flat, or stones contact with each other by a small area, or there are significant gaps between stones, are quite consistent with the well-known methods of stone processing of those and earlier years, and, therefore, they do not require any additional explanations.

scholarly journals Formation of Three Dimensional Ni Nanostructures for Large Area Catalysts

2004 ◽  
Vol 820 ◽  
Author(s):  
J. D. Carey ◽  
S. J. Henley ◽  
E. Mendoza ◽  
C. E. Giusca ◽  
A. A. D. T. Adikaari ◽  
...  
Keyword(s):  
Thin Films ◽  
Surface Morphology ◽  
Laser Annealing ◽  
Ostwald Ripening ◽  
Three Dimensional ◽  
Small Island ◽  
Large Area ◽  
Weakly Bound ◽  
Mean Diameter ◽  
The Mean

AbstractThe formation of Ni nanostructures to act as catalysts in the growth of carbon nanotubes is reported. The changes in the surface morphology of Ni produced by three methods - thermal evaporation and annealing of thin films, pulsed laser ablation and annealing of Ni, and the use of metal containing macromolecules - have been investigated by atomic force microscopy and scanning electron microscopy. In the case of thermal annealing of thin metal films in the temperature range 300-500°C we observe an increase in the mean diameter of the islands formed, accompanied by a reduction in the mean island density with increasing temperature. We attribute this effect to mass transport of weakly bound individual Ni atoms and/or small island clusters across the surface to form larger isolated islands, in a process similar to Ostwald ripening. Using a pulsed KrF excimer laser for ablation of a Ni target we show that nanometre smooth Ni thin films can be produced provided a sufficient number of laser shots is used. The surface morphology of these smooth films can then be altered by laser annealing to form Ni droplets. It is found that the mean diameter of the Ni droplets depends not only on the initial Ni thickness but also the laser fluence. It is also found that the nanostructuring of the film depends on the presence of an oxide under layer, with a higher fluence required on thinner oxides and no nanostructuring observed on bare Si. Finally, we show that Ni nanostructuring can be formed by suitable annealing of a Ni containing aqueous dendrimer solutions.

scholarly journals Fabrication Methods of the Polygonal Masonry of Large Tightly Fitted Stone Blocks with Curved Surface Interfaces in Megalithic Structures of Peru

2021 ◽  
Author(s):  
Rostislav Lapshin
Keyword(s):  
Small Area ◽  
18Th Century ◽  
Three Dimensional ◽  
Curved Surfaces ◽  
Large Area ◽  
High Quality ◽  
Three Dimensional Objects ◽  
Large Stone ◽  
Clay Model

The article suggests methods that allow creating the most complicated type of polygonal masonry found in Peru. This masonry consists of large stone blocks weighing from several hundred kilograms to several tons fitted close to each other almost without a gap between complicated curved surfaces of large area. The work provides a description of techniques, which apparently were used by builders who arrived from Europe. The techniques under discussion are based on the use of a reduced clay model, 3D-pantograph and replicas. The use of a reduced clay model and a pantograph provides not only the unique appearance and high quality of masonry with large blocks, but also allows to significantly increase the productivity of the builders. As machines scaling three-dimensional objects are known since the beginning of the 18th century, the stone structures under consideration should be dated by that and later time. The remaining simpler types of polygonal masonry with smaller stones or fitted surfaces are almost flat, or stones contact with each other by a small area, or there are significant gaps between stones, are quite consistent with the well-known methods of stone processing of those and earlier years, and, therefore, they do not require any additional explanations.

scholarly journals Fabrication Methods of the Polygonal Masonry of Large Stone Blocks With Fitted Curved Surfaces in Megalithic Structures of Peru

2021 ◽  
Author(s):  
Rostislav Lapshin
Keyword(s):  
Small Area ◽  
18Th Century ◽  
Three Dimensional ◽  
Curved Surfaces ◽  
Large Area ◽  
High Quality ◽  
Three Dimensional Objects ◽  
Large Stone ◽  
Clay Model

The article suggests methods that allow creating the most complicated type of polygonal masonry found in Peru. This masonry consists of large stone blocks weighing from several hundred kilograms to several tons fitted close to each other almost without a gap between complicated curved surfaces of large area. The work provides a brief description of techniques, which apparently were used by builders who arrived from Europe. The techniques under discussion are based on the use of a reduced clay model, 3D-pantograph and replicas. The use of a reduced clay model and a pantograph provides not only the unique appearance and high quality of masonry with large blocks, but also allows to significantly increase the productivity of the builders. As the pantograph designed to work with three-dimensional objects has been known since the 18th century, the constructions under consideration should be dated by that and later time. The remaining simpler types of polygonal masonry with smaller stones or fitted surfaces are almost flat, or stones contact with each other by a small area, or there are significant gaps between stones, are quite consistent with the well-known methods of stone processing of those and earlier years, and, therefore, they do not require any additional explanations.

scholarly journals comparison of different approaches to hierarchical clustering of ordinal data

2004 ◽  
Vol 1 (1) ◽  
pp. 57-73
Author(s):  
Aleš Žiberna ◽  
Nataša Kejžar ◽  
Petra Golob
Keyword(s):  
Hierarchical Clustering ◽  
Ordinal Data ◽  
Clustering Algorithms ◽  
Three Dimensional ◽  
Ordinal Scale ◽  
The Social ◽  
Strongly Connected ◽  
The Mean ◽  
New Variables

The paper tries to answer the following question: "How should we treat ordinal data in hierarchical clustering?" The question is strongly connected to the use of questionnaires with ordinal scales in the social sciences. The results could help to differentiate among answers to the questions from questionnaires that could be considered as scale variables, those it would be better to convert to ranks and those that should be treated as nominal variables. To make the results general several two-dimensional combinations of group sizes, shapes and differences between their centers were used as well as one three-dimensional combination. Each combination was simulated both with and without unessential variables. All datasets consisted of 3 groups, each with its own multivariate distribution (2 or 3 variables) with known means and covariances. From each design several datasets were simulated. Each variable was cut and recoded to achieve an ordinal scale. Different cutting schemes were used (the intervals were of equal size, either increasing/decreasing from the lowest to the highest value or decreasing from the mean to both extremes). These new variables were then treated as interval, converted to ranks and treated as nominal. Then hierarchical clustering algorithms were used. Ward's algorithm with Squared Euclidean distance was used when data were considered interval or converted to ranks, and Ward's algorithm with matching coefficient as dissimilarity measure was used when they were considered nominal. The quality of the results was assessed by comparing the gained partitions with the three original groups. We also compared results from clustering the original (uncut) data with the three original groups for comparison. The comparison was made using Corrected Rand Index. The results indicate that in most cases treating the data as interval or converting them to ranks yields better results than treating them as nominal, but the differences are sometimes diminished when cutting into a smaller number of intervals.

Sign in / Sign up

Export Citation Format

Share Document