Determination of cross over effects in lattice models from the local height difference distribution

2006 ◽  
Vol 52 (4) ◽  
pp. 557-562
Author(s):  
S. V. Ghaisas
Keyword(s):  
Lattice Models ◽  
Height Difference

scholarly journals On the determination of step energies. Theoretical considerations and application to an anisotropic Kossel model

2006 ◽  
Vol 39 (4) ◽  
pp. 563-570 ◽  
Author(s):  
M. A. Deij ◽  
J. H. Los ◽  
H. Meekes ◽  
E. Vlieg
Keyword(s):  
Lattice Models ◽  
Single Step ◽  
Spiral Growth ◽  
Growth Theory ◽  
Two Dimensional ◽  
Island Growth ◽  
Growth Step ◽  
Step Flow ◽  
Theoretical Considerations

Steps on surfaces are important in crystal growth theory, as the step free energy determines the two-dimensional nucleation rate, island growth, step flow and spiral growth. In this paper, it is illustrated that in general in lattice models the step energy of a single step cannot be determined directly by counting broken bonds. A new method is proposed that uses the geometry of a step together with the bonding topology, allowing for a straightforward determination of single-step energies for any case. The method is applied to an anisotropic Kossel model.

Experimental Method of Determination of Structural Correlations in Surface Layers of Oxide Glass

1990 ◽  
Vol 216 ◽  
Author(s):  
Zenon BochyŃski
Keyword(s):  
Structural Changes ◽  
Lattice Models ◽  
Molecular Size ◽  
Oxide Glass ◽  
X Ray Diffraction ◽  
Surface Layers ◽  
X Ray ◽  
The Real ◽  
Inorganic Glasses

ABSTRACTA new method of X-ray diffraction analysis of structural inhomogeneities in the quartz/Si02/n based inorganic glasses is presented. The method enables the determination of structural changes occuring in the real nodal lattice in the regions of 10…20 Å or more as well as substructural changes in the regions 5…15 Å comparable to the molecular size of SiO2…SiO4. In consequence these changes can be correlated with approximate nodal lattice models of different degree of ordering. The applied method provided the possibility of constructing structural models of nodal lattices describing the surface and inner layers of the real glasses, changes in the local inhomogeneities as well as boundaries in water-gel associates.

scholarly journals Determination of the orthometric height difference based on optical fiber frequency transfer technique

2021 ◽  
Author(s):  
Anh The Hoang ◽  
Ziyu Shen ◽  
WenBin Shen ◽  
Chenghui Cai ◽  
Wei Xu ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Orthometric Height ◽  
Height Difference ◽  
Frequency Transfer

scholarly journals Comparative Analysis of Change between Ellipsoidal Height Differences and Equivalent Orthometric Height Difference

2020 ◽  
Vol 12 (1) ◽  
pp. 132-144
Author(s):  
Tata Herbert ◽  
Raufu Ibrahim Olatunji
Keyword(s):  
Comparative Analysis ◽  
Global Positioning System ◽  
Orthometric Height ◽  
Ellipsoidal Height ◽  
Height Difference ◽  
Significant Difference ◽  
Global Positioning ◽  
Analysis Of Change ◽  
Automatic Level

Height is an important component in the determination of the position of a point. The study aimed at performing a comparative analysis of change between ellipsoidal height differences and the equivalent orthometric height difference of points. A hi-target Differential Global Positioning System (DGPS) was used to acquire GPS data with an occupation period of thirty (30) minutes on each point, which were processed using Hi-target Geomatics Office (HGO) software to obtain the ellipsoidal heights. An automatic level instrument was used to acquire leveling data, which were processed using the height of collimation method to obtain the orthometric heights. A total of fifty (50) points were occupied as common points for both the GPS and levelling observations at 20-meter intervals. The accuracy of the height difference was determined using standard deviation with the ellipsoidal height difference as 53.59cm and the orthometric height as 53.07cm respectively. A Root Mean Square Error value of 0.0621m was obtained as the accuracy of the change between the two height differences. Statistical analysis using the independent-sample Z test was used to analyze the data at a 5% significant level. The result shows no significant difference in the performance of the two height systems. It is worthy to note that GPS and spirit levelling height differences can be used interchangeably for any heighting in short distances for surveying and engineering applications.

scholarly journals A Comparative Study of Precise Point Positioning (PPP) Accuracy Using Online Services

2016 ◽  
Vol 102 (1) ◽  
pp. 15-31 ◽  
Author(s):  
Marcin Malinowski ◽  
Janusz Kwiecień
Keyword(s):  
Precise Point Positioning ◽  
Reference Station ◽  
Horizontal Distance ◽  
Relative Height ◽  
Height Difference ◽  
Spatial Reference ◽  
Point Positioning ◽  
The Difference ◽  
The Impact

Abstract Precise Point Positioning (PPP) is a technique used to determine the position of receiver antenna without communication with the reference station. It may be an alternative solution to differential measurements, where maintaining a connection with a single RTK station or a regional network of reference stations RTN is necessary. This situation is especially common in areas with poorly developed infrastructure of ground stations. A lot of research conducted so far on the use of the PPP technique has been concerned about the development of entire day observation sessions. However, this paper presents the results of a comparative analysis of accuracy of absolute determination of position from observations which last between 1 to 7 hours with the use of four permanent services which execute calculations with PPP technique such as: Automatic Precise Positioning Service (APPS), Canadian Spatial Reference System Precise Point Positioning (CSRS-PPP), GNSS Analysis and Positioning Software (GAPS) and magicPPP - Precise Point Positioning Solution (magicGNSS). On the basis of acquired results of measurements, it can be concluded that at least two-hour long measurements allow acquiring an absolute position with an accuracy of 2-4 cm. An evaluation of the impact on the accuracy of simultaneous positioning of three points test network on the change of the horizontal distance and the relative height difference between measured triangle vertices was also conducted. Distances and relative height differences between points of the triangular test network measured with a laser station Leica TDRA6000 were adopted as references. The analyses of results show that at least two hours long measurement sessions can be used to determine the horizontal distance or the difference in height with an accuracy of 1-2 cm. Rapid products employed in calculations conducted with PPP technique reached the accuracy of determining coordinates on a close level as in elaborations which employ Final products.

scholarly journals Determination of interaction potentials of amino acids from native protein structures: Tests on simple lattice models

1999 ◽  
Vol 110 (20) ◽  
pp. 10123-10133 ◽  
Author(s):  
Jort van Mourik ◽  
Cecilia Clementi ◽  
Amos Maritan ◽  
Flavio Seno ◽  
Jayanth R. Banavar
Keyword(s):  
Amino Acids ◽  
Protein Structures ◽  
Lattice Models ◽  
Native Protein ◽  
Interaction Potentials ◽  
Simple Lattice

Optical clocks for gravity field observation and further geodetic applications

2020 ◽  
Author(s):  
Hu Wu ◽  
Jürgen Müller ◽  
Annike Knabe
Keyword(s):  
Gravity Field ◽  
Rapid Development ◽  
Satellite Orbit ◽  
Equipotential Surface ◽  
Gravity Potential ◽  
Height Difference ◽  
The Earth ◽  
Temporal Gravity ◽  
Reference Clock

<p>In the past three decades, optical clocks and frequency transfer techniques have experienced a rapid development. They are approaching a fractional frequency uncertainty of 1.0x10<sup>-18</sup>, corresponding to about 1.0 cm in height. This makes them promising to realize “relativistic geodesy”, and it opens a new door to directly obtain gravity potential values by the comparison of clock frequencies. Clocks are thus considered as a novel candidate for determining the Earth’s gravity field. We propose to use a spaceborne clock to obtain gravity potential values along a satellite orbit through its comparison with reference clocks on ground or with a co-orbital clock. The sensitivity of clock measurements is mapped to gravity field coefficients through closed-loop simulations.</p><p>In addition, clocks are investigated for other geodetic applications. Since they are powerful in providing the height difference between distant sites, clocks can be applied for the unification of local/regional height systems, by estimating the offsets between different height datums and the systematic errors within levelling networks. In some regions like Greenland, clocks might be a complementary tool to GRACE(-FO) for detecting temporal gravity signals. They can be operated at locations of interest and continuously track changes w.r.t. reference clock stations. The resulting time-series of gravity potential values reveal the temporal gravity signals at these points. Moreover, as the equipotential surface at a high satellite altitude is more regular than that on the Earth’s surface, a couple of clocks in geostationary orbits can realize a space-based reference for the determination of physical heights at any point on the Earth through clock comparisons.</p><p>We gratefully acknowledge the financial support by the Deutsche Forschungsgemeinschaft (DFG) under Germany’s Excellence Strategy EXC-2123/1 (Project-ID: 390837967).</p>

Sign in / Sign up

Export Citation Format

Share Document