scholarly journals Pre-solar grains from supernovae and novae

2006 ◽  
Vol 2 (14) ◽  
pp. 349-352
Author(s):  
Sachiko Amari ◽  
Katharina Lodders
Keyword(s):  
Silicon Carbide ◽  
Fine Tuning ◽  
Isotopic Ratios ◽  
Low Density ◽  
Density Graphite ◽  
Neutron Burst ◽  
Isotopic Anomalies

AbstractPre-solar grains from supernova ejecta – silicon carbide of type X, Si3N4 and low-density graphite – are characterized by Si isotopic anomalies (mainly 28Si excesses), low 14N/15N, high 26Al/27 Al ratios, and occasionally by excesses in 44Ca (from 44Ti decay). Overall isotopic features of these SiC and graphite grains can be explained by mixing of inner Si-rich zones and the outer C-and He-rich zones, but supernova models require fine tuning to account for 14N/15N and 29Si/28Si ratios of the grains. Isotopic ratios of Zr, Mo and Ba in SiC X grains may be explained by a neutron burst model. Some of the pre-solar nanodiamonds require a supernova origin to explain measured xenon isotopic ratios. Only a few nova grain candidates, with low 12C/13C, 14N/15N, and high 26Al/27 Al ratios, have been identified.

Low‐Density Graphite Grains and Mixing in Type II Supernovae

1999 ◽  
Vol 510 (1) ◽  
pp. 325-354 ◽  
Author(s):  
Claudia Travaglio ◽  
Roberto Gallino ◽  
Sachiko Amari ◽  
Ernst Zinner ◽  
Stan Woosley ◽  
...  
Keyword(s):  
Low Density ◽  
Type Ii ◽  
Density Graphite

scholarly journals Mask R-CNN Refitting Strategy for Plant Counting and Sizing in UAV Imagery

2020 ◽  
Vol 12 (18) ◽  
pp. 3015 ◽  
Author(s):  
Mélissande Machefer ◽  
François Lemarchand ◽  
Virginie Bonnefond ◽  
Alasdair Hitchins ◽  
Panagiotis Sidiropoulos
Keyword(s):  
Deep Learning ◽  
Fine Tuning ◽  
Aerial Images ◽  
Individual Plant ◽  
Low Density ◽  
Tracking Accuracy ◽  
Potato Plants ◽  
The Individual ◽  
Segmentation Task ◽  
Vision Algorithm

This work introduces a method that combines remote sensing and deep learning into a framework that is tailored for accurate, reliable and efficient counting and sizing of plants in aerial images. The investigated task focuses on two low-density crops, potato and lettuce. This double objective of counting and sizing is achieved through the detection and segmentation of individual plants by fine-tuning an existing deep learning architecture called Mask R-CNN. This paper includes a thorough discussion on the optimal parametrisation to adapt the Mask R-CNN architecture to this novel task. As we examine the correlation of the Mask R-CNN performance to the annotation volume and granularity (coarse or refined) of remotely sensed images of plants, we conclude that transfer learning can be effectively used to reduce the required amount of labelled data. Indeed, a previously trained Mask R-CNN on a low-density crop can improve performances after training on new crops. Once trained for a given crop, the Mask R-CNN solution is shown to outperform a manually-tuned computer vision algorithm. Model performances are assessed using intuitive metrics such as Mean Average Precision (mAP) from Intersection over Union (IoU) of the masks for individual plant segmentation and Multiple Object Tracking Accuracy (MOTA) for detection. The presented model reaches an mAP of 0.418 for potato plants and 0.660 for lettuces for the individual plant segmentation task. In detection, we obtain a MOTA of 0.781 for potato plants and 0.918 for lettuces.

Evaluation of Yttria Coated High Density Graphite with Silicon Carbide Interlayer for Uranium Melting Applications

2019 ◽  
Vol 45 (9) ◽  
pp. 11694-11702 ◽  
Author(s):  
B. Madhura ◽  
E. Vetrivendan ◽  
Ch. Jagadeeswara Rao ◽  
P. Venkatesh ◽  
S. Ningshen
Keyword(s):  
Silicon Carbide ◽  
High Density ◽  
Density Graphite

scholarly journals Generation of periodic structures on SiC upon laser plasma XUV/NIR radiations

2013 ◽  
Vol 31 (3) ◽  
pp. 547-550 ◽  
Author(s):  
L. Gemini ◽  
D. Margarone ◽  
S. Trusso ◽  
L. Juha ◽  
J. Limpouch ◽  
...  
Keyword(s):  
Thin Film ◽  
Silicon Carbide ◽  
Laser Pulse ◽  
Extreme Ultraviolet ◽  
Periodic Structures ◽  
Laser Pulses ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Efficient Coupling ◽  
Sic Film

AbstractSurface periodic structures are generated upon irradiation of a silicon carbide (SiC) thin film by the plasma produced by 40 fs pulses from a Ti:Sapphire laser focused onto a thick low density polyethylene (LDPE) foil facing the SiC film. Independently of the number of laser pulses applied, these structures, with average regular periodicity of 710 nm, are evident throughout all irradiated areas. We attribute their formation to the efficient coupling of the unfocused femtosecond laser pulse with the incoherent extreme ultraviolet component of the laser-generated LDPE plasma.

Low density biomorphic silicon carbide: microstructure and mechanical properties

2002 ◽  
Vol 22 (14-15) ◽  
pp. 2719-2725 ◽  
Author(s):  
F.M Varela-Feria ◽  
J Martı́nez-Fernández ◽  
A.R de Arellano-López ◽  
M Singh
Keyword(s):  
Mechanical Properties ◽  
Silicon Carbide ◽  
Low Density ◽  
Microstructure And Mechanical Properties

Synthesis, Characterization and Mechanical Properties of Silicon Carbide Nanowires

2010 ◽  
Author(s):  
Huan Zhang ◽  
Weiqiang Ding ◽  
Daryush Aidun
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Silicon Carbide ◽  
Physical And Mechanical Properties ◽  
High Hardness ◽  
High Strength ◽  
Harsh Environments ◽  
Low Density ◽  
Low Thermal Expansion ◽  
Oxidation And Corrosion

Silicon carbide (SiC) material has many outstanding physical and mechanical properties such as high strength, high hardness, low density, high thermal conductivity, low thermal expansion coefficient, large band-gap, and excellent oxidation and corrosion resistances [1–3]. It is a leading material for components and devices operating at high temperature, high power and under harsh environments [4–5]. Micro-sized SiC particles and whiskers are commonly used as reinforcement materials for ceramics, metals and alloys in various structural and tribological applications [6–7].

scholarly journals Erratum: Large isotopic anomalies of Si, C, N and noble gases in interstellar silicon carbide from the Murray meteorite

Nature ◽  
1988 ◽  
Vol 331 (6156) ◽  
pp. 548-548 ◽  
Author(s):  
Ernst Zinner ◽  
Tang Ming ◽  
Edward Anders
Keyword(s):  
Silicon Carbide ◽  
Noble Gases ◽  
Isotopic Anomalies

New Advanced SiC Ceramics Based on Natural Biomaterials

2012 ◽  
Vol 729 ◽  
pp. 350-355 ◽  
Author(s):  
László A. Gömze ◽  
Dóra Lipusz ◽  
Ludmila N. Gömze
Keyword(s):  
Silicon Carbide ◽  
High Purity ◽  
Raw Materials ◽  
Xrd Analysis ◽  
Ceramic Composites ◽  
Low Density ◽  
High Porosity ◽  
X Ray Diffraction ◽  
Trade Name ◽  
Sic Ceramic

On the basis of several years experiments in investigation of hetero-modulus material structures and using natural biomaterials and high purity quartz powders the authors successfully developed new high porosity low density SiC ceramic cellulars and foams. For the development of new silicon-carbide and carbon-silicon-carbide (C/SiC) cellular ceramic composites and foams the author used high purity SiO2 powders mined in Fehervarcsurgo (Hungary) and a biomaterial reagents made from renewable vegetable under trade-name IG-R1. These low density high porosity silicon-carbides probably can be successfully applied in development of light weight ceramic reinforced metal alloy composites in the future. The structure and X-ray diffraction (XRD) analysis of used raw materials and the achieved by authors new SiC and C/SiC ceramic composites and foams are described and shown in present work.

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