Low‐order moment‐based estimation of shape parameter of CGIG clutter model

2016 ◽  
Vol 52 (18) ◽  
pp. 1561-1563 ◽  
Author(s):  
Han Yu ◽  
Peng‐Lang Shui ◽  
Yu‐Ting Huang
Keyword(s):  
Shape Parameter ◽  
Order Moment ◽  
Low Order

On the geometry of d-orbitals: W (001) surface

1988 ◽  
Vol 53 (4) ◽  
pp. 661-664 ◽  
Author(s):  
Štěpán Pick
Keyword(s):  
Surface Reconstruction ◽  
Moment Analysis ◽  
Order Moment ◽  
Additional Mechanism ◽  
D Orbitals ◽  
Surface Coupling ◽  
Low Order

Low-order moment analysis of the W (001) surface reconstruction leads to the following conclusions: 1) The d-orbitals participate in the reconstruction-induced surface-surface coupling, the effect being most pronounced for the x2 - y2 orbital. 2) A non-negligible surface-bulk coupling exists and it is due to the (x - y) z orbital. An additional mechanism favouring the zig-zag mode is suggested.

A High-precision and Fast Solution Method of Gamma Raindrop Size Distribution based on 0-Moment and 3-Moment in South China

2021 ◽  
Author(s):  
XIANTONG LIU ◽  
HUIQI LI ◽  
SHENG Hu ◽  
QILIN WAN ◽  
HUI XIAO ◽  
...  
Keyword(s):  
Size Distribution ◽  
High Precision ◽  
South China ◽  
Solution Method ◽  
Shape Parameter ◽  
Weather Prediction ◽  
Order Moment ◽  
Raindrop Size Distribution ◽  
Fast Solution ◽  
Raindrop Size

AbstractAccording to the high accuracy linear shape-slope (μ-Λ) relationship observed by several 2-Dimensional-Video-Distrometers (2DVD) in South China, a high-precision and fast solution method of gamma (Γ) raindrop size distribution (RSD) function based on the zeroth order moment (M0) and the third order moment (M3) of RSD has been proposed. The 0-moment (M0) and 3-moment (M3) of RSD can be easily calculated from rain mass mixing ratio (Qr) and total number concentration (Ntr) simulated by the two-moment (2M) microphysical scheme, respectively. Three typical heavy rainfall processes and all RSD samples observed during 2019 in South China were selected to verify the accuracy of the method. Compared to the current widely used exponential RSD with a fixed shape parameter of zero in 2M microphysical scheme, the Γ RSD function using the linear constrained gamma (C-G) method agreed better with the Γ fit RSD from 2DVD observations. The characteristic precipitation parameters (e.g., rain rate, M2, M6 and M9) obtained by the proposed method are generally consistent with the parameters calculated by Γ fit RSD from 2DVD observations. The proposed method has effectively solved the problem that the shape parameter in the 2M microphysical scheme set to a constant, so that the Γ RSD functions are closer to the observations and have obviously smaller errors. This method has a good potential to be applied to the 2M microphysical schemes to improve the simulation of heavy precipitation in South China, but also paves the way for in-depth applications of radar data in numerical weather prediction models.

the effects of resonance with Jupiter in the system of short-period comets

1974 ◽  
Vol 22 ◽  
pp. 193-203
Author(s):  
L̆ubor Kresák
Keyword(s):  
Structural Effects ◽  
Order Resonance ◽  
Mean Motion ◽  
Short Period ◽  
The Mean ◽  
Compound Effect ◽  
Low Order

AbstractStructural effects of the resonance with the mean motion of Jupiter on the system of short-period comets are discussed. The distribution of mean motions, determined from sets of consecutive perihelion passages of all known periodic comets, reveals a number of gaps associated with low-order resonance; most pronounced are those corresponding to the simplest commensurabilities of 5/2, 2/1, 5/3, 3/2, 1/1 and 1/2. The formation of the gaps is explained by a compound effect of five possible types of behaviour of the comets set into an approximate resonance, ranging from quick passages through the gap to temporary librations avoiding closer approaches to Jupiter. In addition to the comets of almost asteroidal appearance, librating with small amplitudes around the lower resonance ratios (Marsden, 1970b), there is an interesting group of faint diffuse comets librating in characteristic periods of about 200 years, with large amplitudes of about±8% in μ and almost±180° in σ, around the 2/1 resonance gap. This transient type of motion appears to be nearly as frequent as a circulating motion with period of revolution of less than one half that of Jupiter. The temporary members of this group are characteristic not only by their appearance but also by rather peculiar discovery conditions.

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