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Full-Text Articles in Physical Sciences and Mathematics
Observations And Analysis Of Uncorrelated Rain, Michael L. Larsen, Alexander Kostinski, Ali Tokay
Observations And Analysis Of Uncorrelated Rain, Michael L. Larsen, Alexander Kostinski, Ali Tokay
Department of Physics Publications
Most microphysical models in precipitation physics and radar meteorology assume (at least implicitly) that raindrops are completely uncorrelated in space and time. Yet, several recent studies have indicated that raindrop arrivals are often temporally and spatially correlated. Resolution of this conflict must begin with observations of perfectly uncorrelated rainfall, should such “perfectly steady rain” exist at all. Indeed, it does. Using data with high temporal precision from a two-dimensional video disdrometer and the pair-correlation function, a scale-localized statistical tool, several ∼10–20-min rain episodes have been uncovered where no clustering among droplet arrival times is found. This implies that (i) rain …
Structural Control Of Vertically Aligned Multiwalled Carbon Nanotubes By Radio-Frequency Plasmas, Jitendra Menda, Benjamin Ulmen, Lakshman Kumar Vanga, Vijaya Kayastha, Yoke Khin Yap, Zhengwei Pan, Ilia Ivanov, Alex Puretzky, David Geohegan
Structural Control Of Vertically Aligned Multiwalled Carbon Nanotubes By Radio-Frequency Plasmas, Jitendra Menda, Benjamin Ulmen, Lakshman Kumar Vanga, Vijaya Kayastha, Yoke Khin Yap, Zhengwei Pan, Ilia Ivanov, Alex Puretzky, David Geohegan
Department of Physics Publications
Plasma-enhanced chemical vapor deposition is the only technique for growing individual vertically aligned multiwalled carbon nanotubes (VA-MWCNTs) at desired locations. Inferior graphitic order has been a long-standing issue that has prevented realistic applications of these VA-MWCNTs. Previously, these VA-MWCNTs were grown by a one-plasma approach. Here, we demonstrate the capability of controlling graphitic order and diameters of VA-MWCNTs by decoupling the functions of the conventional single plasma into a dual-plasma configuration. Our results indicate that the ionic flux and kinetic energy of the growth species are important for improving graphitic order of VA-MWCMTs.
High-Density Vertically Aligned Multiwalled Carbon Nanotubes With Tubular Structures, Vijaya Kayastha, Yoke Khin Yap, Zhengwei Pan, Ilia Ivonov, Alex Puretzky, David Geohegan
High-Density Vertically Aligned Multiwalled Carbon Nanotubes With Tubular Structures, Vijaya Kayastha, Yoke Khin Yap, Zhengwei Pan, Ilia Ivonov, Alex Puretzky, David Geohegan
Department of Physics Publications
Ammonia (NH3) gas was thought to be essential for the growth of vertically aligned multiwalled carbon nanotubes (VA-MWCNTs) and led to the formation of bamboo-like structures. Here, we show that VA-MWCNTs with ideal tubular structures can be grown on substrates by various mixed gases with or without NH3 gas. The growth of these VA-MWCNTs is guided by a growth model that combined the dissociative adsorption of acetylene molecules (C2H2) and the successive vapor-liquid-solid growth mechanism. Results indicate that the key factor for growing these VA-MWCNTs is a balance between the decomposition rate of …
Mechanism For Spatial Organization In Quantum Dot Self-Assembly, Da Gao, Adam Kaczynski, John A. Jaszczak
Mechanism For Spatial Organization In Quantum Dot Self-Assembly, Da Gao, Adam Kaczynski, John A. Jaszczak
Department of Physics Publications
Inspired by experimental observations of spatially ordered growth hillocks on the (001) surfaces of natural graphite crystals, a mechanism for spatial organization in quantum dotself-assembly is proposed. The regular arrangement of steps from a screw dislocation-generated growth spiral provides the overall template for such ordering. An ordered array of quantum dots may be formed or nucleated from impurities driven to the step corners by diffusion and by their interactions with the spiral’s steps and kinks. Kinetic Monte Carlo simulation of a solid-on-solid model supports the feasibility of such a mechanism.
Obtaining The Drop Size Distribution, Alexander Kostinski, Raymond Shaw
Obtaining The Drop Size Distribution, Alexander Kostinski, Raymond Shaw
Department of Physics Publications
his document is a supplement to “Fluctuations and Luck in Droplet Growth by Coalescence,” by Alexander B. Kostinski and RaymondA. Shaw (Bull. Amer. Meteor. Soc.,86, 235–244) • ©2005 American Meteorological Society
Fluctuations And Luck In Droplet Growth By Coalescence, Alexander Kostinski, Raymond Shaw
Fluctuations And Luck In Droplet Growth By Coalescence, Alexander Kostinski, Raymond Shaw
Department of Physics Publications
After the initial rapid growth by condensation, further growth of a cloud droplet is punctuated by coalescence events. Such a growth process is essentially stochastic. Yet, computational approaches to this problem dominate and transparent quantitative theory remains elusive. The stochastic coalescence problem is revisited and it is shown, via simple back-of-the-envelope results, that regardless of the initial size, the fastest one-in-a-million droplets, required for warm rain initiation, grow about 10 times faster than the average droplet. While approximate, the development presented herein is based on a realistic expression for the rate of coalescence. The results place a lower bound on …
Advantageous Goes Ir Results For Ash Mapping At High Latitudes: Cleveland Eruptions 2001, Yingxin Gu, William I. Rose, David J. Schneider, Gregg J. S. Bluth, M. I. Watson
Advantageous Goes Ir Results For Ash Mapping At High Latitudes: Cleveland Eruptions 2001, Yingxin Gu, William I. Rose, David J. Schneider, Gregg J. S. Bluth, M. I. Watson
Department of Geological and Mining Engineering and Sciences Publications
The February 2001 eruption of Cleveland Volcano, Alaska allowed for comparisons of volcanic ash detection using two-band thermal infrared (10–12 μm) remote sensing from MODIS, AVHRR, and GOES 10. Results show that high latitude GOES volcanic cloud sensing the range of about 50 to 65°N is significantly enhanced. For the Cleveland volcanic clouds the MODIS and AVHRR data have zenith angles 6–65 degrees and the GOES has zenith angles that are around 70 degrees. The enhancements are explained by distortion in the satellite view of the cloud's lateral extent because the satellite zenith angles result in a “side-looking” aspect and …