scholarly journals Early results from the Whisper instrument on Cluster: an overview

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1241-1258 ◽  
Author(s):  
P. M. E. Décréau ◽  
P. Fergeau ◽  
V. Krasnoselskikh ◽  
E. Le Guirriec ◽  
M. Lévêque ◽  
...  
Keyword(s):  
Electron Density ◽  
Small Scale ◽  
Data Sets ◽  
Total Density ◽  
Total Electron Density ◽  
Data Set ◽  
Total Electron ◽  
Density Data ◽  
Early Results ◽  
Natural Emissions

Abstract. The Whisper instrument yields two data sets: (i) the electron density determined via the relaxation sounder, and (ii) the spectrum of natural plasma emissions in the frequency band 2–80 kHz. Both data sets allow for the three-dimensional exploration of the magnetosphere by the Cluster mission. The total electron density can be derived unambiguously by the sounder in most magnetospheric regions, provided it is in the range of 0.25 to 80 cm-3 . The natural emissions already observed by earlier spacecraft are fairly well measured by the Whisper instrument, thanks to the digital technology which largely overcomes the limited telemetry allocation. The natural emissions are usually related to the plasma frequency, as identified by the sounder, and the combination of an active sounding operation and a passive survey operation provides a time resolution for the total density determination of 2.2 s in normal telemetry mode and 0.3 s in burst mode telemetry, respectively. Recorded on board the four spacecraft, the Whisper density data set forms a reference for other techniques measuring the electron population. We give examples of Whisper density data used to derive the vector gradient, and estimate the drift velocity of density structures. Wave observations are also of crucial interest for studying small-scale structures, as demonstrated in an example in the fore-shock region. Early results from the Whisper instrument are very encouraging, and demonstrate that the four-point Cluster measurements indeed bring a unique and completely novel view of the regions explored.Key words. Space plasma physics (instruments and techniques; discontinuities, general or miscellaneous)

Revisiting the charge density analysis of 2,5-dichloro-1,4-benzoquinone at 20 K

2017 ◽  
Vol 73 (4) ◽  
pp. 654-659 ◽  
Author(s):  
Zhijie Chua ◽  
Bartosz Zarychta ◽  
Christopher G. Gianopoulos ◽  
Vladimir V. Zhurov ◽  
A. Alan Pinkerton
Keyword(s):  
Charge Density ◽  
Electron Density ◽  
Topological Analysis ◽  
Diffraction Measurement ◽  
X Ray Diffraction ◽  
Total Electron Density ◽  
Total Electron ◽  
Structure Factors ◽  
Density Analysis ◽  
Experimental Charge Density

A high-resolution X-ray diffraction measurement of 2,5-dichloro-1,4-benzoquinone (DCBQ) at 20 K was carried out. The experimental charge density was modeled using the Hansen–Coppens multipolar expansion and the topology of the electron density was analyzed in terms of the quantum theory of atoms in molecules (QTAIM). Two different multipole models, predominantly differentiated by the treatment of the chlorine atom, were obtained. The experimental results have been compared to theoretical results in the form of a multipolar refinement against theoretical structure factors and through direct topological analysis of the electron density obtained from the optimized periodic wavefunction. The similarity of the properties of the total electron density in all cases demonstrates the robustness of the Hansen–Coppens formalism. All intra- and intermolecular interactions have been characterized.

scholarly journals Seasonal and intra-diurnal variability of small-scale gravity waves in OH airglow at two Alpine stations

2019 ◽  
Vol 12 (1) ◽  
pp. 457-469 ◽  
Author(s):  
Patrick Hannawald ◽  
Carsten Schmidt ◽  
René Sedlak ◽  
Sabine Wüst ◽  
Michael Bittner
Keyword(s):  
Gravity Waves ◽  
High Frequency ◽  
Phase Speed ◽  
Propagation Direction ◽  
Field Of View ◽  
Small Scale ◽  
Data Sets ◽  
Data Set ◽  
Diurnal Variability ◽  
Fully Automatic

Abstract. Between December 2013 and August 2017 the instrument FAIM (Fast Airglow IMager) observed the OH airglow emission at two Alpine stations. A year of measurements was performed at Oberpfaffenhofen, Germany (48.09∘ N, 11.28∘ E) and 2 years at Sonnblick, Austria (47.05∘ N, 12.96∘ E). Both stations are part of the network for the detection of mesospheric change (NDMC). The temporal resolution is two frames per second and the field-of-view is 55 km × 60 km and 75 km × 90 km at the OH layer altitude of 87 km with a spatial resolution of 200 and 280 m per pixel, respectively. This resulted in two dense data sets allowing precise derivation of horizontal gravity wave parameters. The analysis is based on a two-dimensional fast Fourier transform with fully automatic peak extraction. By combining the information of consecutive images, time-dependent parameters such as the horizontal phase speed are extracted. The instrument is mainly sensitive to high-frequency small- and medium-scale gravity waves. A clear seasonal dependency concerning the meridional propagation direction is found for these waves in summer in the direction to the summer pole. The zonal direction of propagation is eastwards in summer and westwards in winter. Investigations of the data set revealed an intra-diurnal variability, which may be related to tides. The observed horizontal phase speed and the number of wave events per observation hour are higher in summer than in winter.

A Dynamic Clustering Querying Algorithm Based on Grid in Manufacturing System

2011 ◽  
Vol 323 ◽  
pp. 89-93
Author(s):  
Jun Zeng
Keyword(s):  
Processing Speed ◽  
Manufacturing System ◽  
Data Sets ◽  
Dynamic Clustering ◽  
Data Set ◽  
Density Data ◽  
Clustering Center ◽  
And Performance

This article presents a querying algorithm of dynamic clustering based on grid in manufacturing system. The algorithm divides grids based on the location of nodes, and computes clustering center of grids, then queries based on clustering in the station, processing speed of this method are independent of size of data set, processing speed is quick, it can handle massive and multi-density data sets and performance is better in terms of accuracy and efficiency of querying.

Electron densities and the VSEPR model of molecular geometry

1992 ◽  
Vol 70 (3) ◽  
pp. 742-750 ◽  
Author(s):  
R. J. Gillespie
Keyword(s):  
Electron Density ◽  
Present Status ◽  
Electron Pair ◽  
Molecular Geometry ◽  
Physical Basis ◽  
Valence Shell ◽  
Electron Densities ◽  
Total Electron Density ◽  
Total Electron

This paper reviews the present status of the VSEPR model of molecular geometry in relation to electron densities. The discussion is based on the electron pair domain version of this model. The fundamental postulates of the model are summarized and illustrated by a discussion of the structures of some molecules with five and seven electron pair domains in the valence shell, including the recently discovered ions XeF5− and XeOF6−. The total electron density does not provide any obvious support for the model and although electron density deformation maps do provide some support they are not always reliable. The Laplacian of the electron density, however, shows the presence of valence shell charge concentrations that correspond closely in number and properties to the electron pair domains of the VSEPR model. This correspondence between electron pair domains and valence shell charge concentrations provides a physical basis for a better understanding of the VSEPR model. Keywords: VSEPR model, electron densities, molecular geometry, Laplacian of the electron density, electron pair domain.

Total electron density from thes-electron density

1998 ◽  
Vol 57 (5) ◽  
pp. 3458-3461 ◽  
Author(s):  
Á. Nagy ◽  
E. Bene
Keyword(s):  
Electron Density ◽  
Total Electron Density ◽  
Total Electron

Apple Disease Recognition Based on Small-scale Data Sets

2021 ◽  
Vol 37 (3) ◽  
pp. 481-490
Author(s):  
Chenyong Song ◽  
Dongwei Wang ◽  
Haoran Bai ◽  
Weihao Sun
Keyword(s):  
Identification Accuracy ◽  
Model Complexity ◽  
Geometric Transformation ◽  
Small Scale ◽  
Model Parameters ◽  
Data Sets ◽  
List Type ◽  
Data Set ◽  
Disease Identification ◽  
Scale Data

HighlightsThe proposed data enhancement method can be used for small-scale data sets with rich sample image features.The accuracy of the new model reaches 98.5%, which is better than the traditional CNN method.Abstract: GoogLeNet offers far better performance in identifying apple disease compared to traditional methods. However, the complexity of GoogLeNet is relatively high. For small volumes of data, GoogLeNet does not achieve the same performance as it does with large-scale data. We propose a new apple disease identification model using GoogLeNet’s inception module. The model adopts a variety of methods to optimize its generalization ability. First, geometric transformation and image modification of data enhancement methods (including rotation, scaling, noise interference, random elimination, color space enhancement) and random probability and appropriate combination of strategies are used to amplify the data set. Second, we employ a deep convolution generative adversarial network (DCGAN) to enhance the richness of generated images by increasing the diversity of the noise distribution of the generator. Finally, we optimize the GoogLeNet model structure to reduce model complexity and model parameters, making it more suitable for identifying apple tree diseases. The experimental results show that our approach quickly detects and classifies apple diseases including rust, spotted leaf disease, and anthrax. It outperforms the original GoogLeNet in recognition accuracy and model size, with identification accuracy reaching 98.5%, making it a feasible method for apple disease classification. Keywords: Apple disease identification, Data enhancement, DCGAN, GoogLeNet.

Phase perturbation as a means of electron density map quality evaluation

2008 ◽  
Vol 41 (1) ◽  
pp. 31-37 ◽  
Author(s):  
Olga Kirillova
Keyword(s):  
Electron Density ◽  
Data Sets ◽  
Molecular Replacement ◽  
Data Set ◽  
Density Maps ◽  
Phase Perturbation ◽  
Replacement Solution ◽  
Electron Density Map ◽  
Trial Phase

This paper describes a new means for evaluating the quality of crystallographic electron density maps. It has been found that a better data set possesses greater robustness against perturbations applied to the phases. Thus it allows recognition of a more precise phase set and provides a way to select the best or reject the worst from several noisy data sets derived from the same crystal structure. The results indicate that calculation of the correlations by the procedure described here can be useful in ranking electron density maps in this aspect of quality. The method suggested has potential use for selecting a better molecular replacement solution, as well as for evaluating trial phase sets inab initiophasing procedures.

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