scholarly journals Role of geo-potential models in gravity field determination

2009 ◽  
pp. 34-37
Author(s):  
Niraj Manandhar ◽  
Rene Forsberg
Keyword(s):  
Gravity Field ◽  
Geopotential Model ◽  
Potential Models ◽  
Geopotential Models ◽  
Gravity Field Determination ◽  
Major Emphasis

This paper sets out to describe the developments of geopotential models and its role in gravity field determination. The paper also focuses in different geopotential models those are available and in use from 1980 onwards till at present with major emphasis placed on WGS84 EGM96 geopotential model.

scholarly journals Accuracy assessment of GOCE-based geopotential models and their use for modelling the gravimetric quasigeoid - A case study for Poland

2014 ◽  
Vol 63 (1) ◽  
pp. 3-24 ◽  
Author(s):  
Walyeldeen Godah ◽  
Malgorzata Szelachowska ◽  
Jan Krynski
Keyword(s):  
Gravity Field ◽  
Ocean Circulation ◽  
Accuracy Assessment ◽  
Gravity Anomalies ◽  
Geopotential Model ◽  
Satellite Gravity ◽  
Earth Gravity ◽  
Geopotential Models ◽  
Gravimetric Quasigeoid ◽  
Gravity Signal

Abstract The GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) has significantly upgraded the knowledge on the Earth gravity field. In this contribution the accuracy of height anomalies determined from Global Geopotential Models (GGMs) based on approximately 27 months GOCE satellite gravity gradiometry (SGG) data have been assessed over Poland using three sets of precise GNSS/levelling data. The fits of height anomalies obtained from 4th release GOCE-based GGMs to GNSS/levelling data were discussed and compared with the respective ones of 3rd release GOCE-based GGMs and the EGM08. Furthermore, two highly accurate gravimetric quasigeoid models were developed over the area of Poland using high resolution Faye gravity anomalies. In the first, the GOCE-based GGM was used as a reference geopotential model, and in the second - the EGM08. They were evaluated with GNSS/levelling data and their accuracy performance was assessed. The use of GOCE-based GGMs for recovering the long-wavelength gravity signal in gravimetric quasigeoid modelling was discussed.

scholarly journals An Assessment of the GOCE High-Level Processing Facility (HPF) Released Global Geopotential Models with Regional Test Results in Turkey

2020 ◽  
Vol 12 (3) ◽  
pp. 586 ◽  
Author(s):  
Bihter Erol ◽  
Mustafa Serkan Işık ◽  
Serdar Erol
Keyword(s):  
Gravity Field ◽  
Numerical Test ◽  
Geopotential Model ◽  
Test Results ◽  
Earth Gravity Field ◽  
Earth Gravity ◽  
Geopotential Models ◽  
Processing Facility ◽  
High Level ◽  
Gravity Field Models

The launch of dedicated satellite missions at the beginning of the 2000s led to significant improvement in the determination of Earth gravity field models. As a consequence of this progress, both the accuracies and the spatial resolutions of the global geopotential models increased. However, the spectral behaviors and the accuracies of the released models vary mainly depending on their computation strategies. These strategies are briefly explained in this article. Comprehensive quality assessment of the gravity field models by means of spectral and statistical analyses provides a comparison of the gravity field mapping accuracies of these models, as well as providing an understanding of their progress. The practical benefit of these assessments by means of choosing an optimal model with the highest accuracy and best resolution for a specific application is obvious for a broad range of geoscience applications, including geodesy and geophysics, that employ Earth gravity field parameters in their studies. From this perspective, this study aims to evaluate the GOCE High-Level Processing Facility geopotential models including recently published sixth releases using different validation methods recommended in the literature, and investigate their performances comparatively and in addition to some other models, such as GOCO05S, GOGRA04S and EGM2008. In addition to the validation statistics from various countries, the study specifically emphasizes the numerical test results in Turkey. It is concluded that the performance improves from the first generation RL01 models toward the final RL05 models, which were based on the entire mission data. This outcome was confirmed when the releases of different computation approaches were considered. The accuracies of the RL05 models were found to be similar to GOCO05S, GOGRA04S and even to RL06 versions but better than EGM2008, in their maximum expansion degrees. Regarding the results obtained from these tests using the GPS/leveling observations in Turkey, the contribution of the GOCE data to the models was significant, especially between the expansion degrees of 100 and 250. In the study, the tested geopotential models were also considered for detailed geoid modeling using the remove-compute-restore method. It was found that the best-fitting geopotential model with its optimal expansion degree (please see the definition of optimal degree in the article) improved the high-frequency regional geoid model accuracy by almost 15%.

scholarly journals Accuracy Evaluation of Geoid Heights in the National Control Points of South Korea Using High-Degree Geopotential Model

2020 ◽  
Vol 10 (4) ◽  
pp. 1466
Author(s):  
Kwang Bae Kim ◽  
Hong Sik Yun ◽  
Ha Jung Choi
Keyword(s):  
South Korea ◽  
Gravity Field ◽  
Gravity Data ◽  
Altimeter Data ◽  
Airborne Gravity ◽  
Geopotential Model ◽  
Control Points ◽  
Gravimetric Geoid ◽  
Geopotential Models ◽  
High Degree

Precise geoid heights are not as important for understanding Earth’s gravity field, but they are important to geodesy itself, since the vertical datum is defined as geoid in a cm-level accuracy. Several high-degree geopotential models have been derived lately by using satellite tracking data such as those from Gravity Recovery and Climate Experiment (GRACE) and Gravity Field and Steady-State Ocean Circulation Explorer (GOCE), satellite altimeter data, and terrestrial and airborne gravity data. The Korean national geoid (KNGeoid) models of the National Geographic Information Institute (NGII) were developed using the latest global geopotential models (GGMs), which are combinations of gravity data from satellites and land gravity data. In this study, geoid heights calculated from the latest high-degree GGMs were used to evaluate the accuracy of the three GGMs (European Improved Gravity model of Earth by New techniques (EIGEN)-6C4, Earth Gravitational Model 2008 (EGM2008), and GOCE-EGM2008 combined model (GECO)) by comparing them with the geoid heights derived from the Global Navigation Satellite System (GNSS)/leveling of the 1182 unified control points (UCPs) that have been installed by NGII in South Korea since 2008. In addition, the geoid heights derived from the KNGeoid models were compared with the geoid heights derived from the GNSS/leveling of the 1182 UCPs to assess the accuracy of the KNGeoid models in terms of relative geoid heights for further gravimetric geoid determination studies in South Korea. As a result, the EGM2008 model could be selected as the suitable GGM from among the three GGMs for determining a gravimetric geoid model for South Korea.

scholarly journals NADPH oxidase-derived ROS and the regulation of pulmonary vessel tone

2012 ◽  
Vol 302 (11) ◽  
pp. H2166-H2177 ◽  
Author(s):  
G. Frazziano ◽  
H. C. Champion ◽  
P. J. Pagano
Keyword(s):  
Oxygen Tension ◽  
Vascular Tone ◽  
Systemic Circulation ◽  
Oxygen Species ◽  
Partial Pressure Of Oxygen ◽  
Low Oxygen ◽  
Key Factors ◽  
Pulmonary Vessel ◽  
Major Emphasis

Pulmonary vessel constriction results from an imbalance between vasodilator and vasoconstrictor factors released by the endothelium including nitric oxide, endothelin, prostanoids, and reactive oxygen species (ROS). ROS, generated by a variety of enzymatic sources (such as mitochondria and NADPH oxidases, a.k.a. Nox), appear to play a pivotal role in vascular homeostasis, whereas elevated levels effect vascular disease. The pulmonary circulation is very sensitive to changes in the partial pressure of oxygen and differs from the systemic circulation in its response to this change. In fact, the pulmonary vessels contract in response to low oxygen tension, whereas systemic vessels dilate. Growing evidence suggests that ROS production and ROS-related pathways may be key factors that underlie this differential response to oxygen tension. A major emphasis of our laboratory is the role of Nox isozymes in cardiovascular disease. In this review, we will focus our attention on the role of Nox-derived ROS in the control of pulmonary vascular tone.

Dynamic Behaviour of Plain Slideways

1966 ◽  
Vol 181 (1) ◽  
pp. 169-184 ◽  
Author(s):  
R. Bell ◽  
M. Burdekin
Keyword(s):  
Machine Tool ◽  
Dynamic Behaviour ◽  
Damping Capacity ◽  
Friction Characteristic ◽  
Stick Slip ◽  
Friction Characteristics ◽  
Physical Systems ◽  
Major Emphasis

The friction characteristics resulting from the motion of one surface over another form a very important facet of the behaviour of many physical systems. This statement is particularly valid when considering the behaviour of machine tool slideways. Most slideway elements consist of two plain surfaces whose friction characteristic is modified by the addition of a lubricant. In many cases the complete slideway consists of many mating surfaces and the choice of slideway material, slideway machining and lubricant is often influenced by the long term problem of wear. The aim of this paper is to present results of experiments on a test rig designed to be representative of machine tool slideway conditions; the experiments were wholly concerned with the behaviour of the bearing under dynamic conditions. The major emphasis is on results obtained with a polar additive lubricant which appears to exclude the possibility of ‘stick-slip’ oscillations. A parallel series of tests are reported where a normal hydraulic oil was used as lubricant. The use of this second lubricant allowed some study of the ‘stick-slip’ process. The dynamic friction characteristics, cyclic friction characteristics and damping capacity of several slideway surface combinations have been obtained and are discussed in the context of earlier work in the field and the role of slideways in machine tool behaviour.

CRM for Academic Institution and Universities

2013 ◽  
pp. 198-204 ◽  
Author(s):  
Viral Nagori
Keyword(s):  
Graduate Students ◽  
Service Industry ◽  
Relationship Management ◽  
Customer Relationship ◽  
Academic Environment ◽  
Academic Institutions ◽  
Graduate Courses ◽  
Long Run ◽  
Major Emphasis

“Keep your customers happy and satisfied to create value in the long run for the firm.” The statement is the motto of all business organisations to become a successful enterprise. Customer relationship management is mainly used to identify the buying habits of the customers, analyse trends and patterns, and market the product to the targeted customers. Academic institutions and universities are considered as a service industry, so the scope and role of CRM would be drastically different compared to manufacturing industries. In the Indian context, the main customers of the institutions or universities are parents of the students who spend significant amount on their children’s education. The companies that recruit graduate students are also considered as the customer for academic institutions and universities. The chapter discusses the fundamentals of CRM, its uses and application in academic environment, and technology supporting CRM. The major emphasis of the chapter is on how to automate communication among the students, parents, and faculties. The chapter also focuses on streamlining and providing the details of the performance of students for the campus interview and final placements to the companies. The chapter also throws light on the role of technology in CRM implementation in academic institutions and universities. Advantages offered by CRM in academic environment are also discussed. The chapter provides guidelines for successful implementations of CRM in academic environment. To narrow down the scope of the study, it is confined to CRM for academic institutions universities offering higher education (graduate/post graduate courses) in Indian environment.

Peroxovanadates and Its Bio-Mimicking Relation with Vanadium Haloperoxidases

2016 ◽  
pp. 197-219
Author(s):  
Pranjal Saikia ◽  
Saitanya Kumar Bharadwaj ◽  
Abu Taleb Miah
Keyword(s):  
Amino Acids ◽  
Active Site ◽  
High Efficiency ◽  
Recombinant Enzymes ◽  
Vanadium Compounds ◽  
Reaction Conditions ◽  
The Cost ◽  
Major Emphasis ◽  
Protein Active Site

Vanadium Haloperoxidases (VHPOs) have been used in a variety of biotransformations showing remarkable stereoselectivity and regiospecificity. The high efficiency of the enzyme is influenced by the protein active site and the role of certain amino acids in activation of vanadium(V)-bound peroxide for halide oxidation. The use of natural or recombinant enzymes, or biomimetic vanadium compounds brings up issues regarding the cost of production and reaction conditions. In this chapter, the primary intent is to provide a simple and clear picture of functional mimicking nature of peroxovanadium compounds with haloperoxidases enzymes to the readers. Major emphasis would be given to examine the reactivity of the vanadium haloperoxidases with mechanism.

scholarly journals Discrete Spherical Harmonic Transforms of Nearly Equidistributed Global Data

2011 ◽  
Vol 1 (3) ◽  
pp. 251-258 ◽  
Author(s):  
J. Blais
Keyword(s):  
Spherical Harmonic ◽  
Fourier Transforms ◽  
Simulated Data ◽  
Geopotential Model ◽  
Structural Constraints ◽  
Geopotential Models ◽  
Analysis And Synthesis ◽  
Comparative Results ◽  
Efficiency And Reliability ◽  
Global Data

Discrete Spherical Harmonic Transforms of Nearly Equidistributed Global DataDiscrete Spherical Harmonic Transforms (SHTs) are commonly defined for equiangular grids on the sphere. However, when global array data exhibit near equidistributed patterns rather than equiangular grids, discrete SHTs require appropriate adaptations for analysis and synthesis. Computational efficiency and reliability impose structural constraints on possible equidistribution characteristics of data patterns such as for instance with Chebychev quadratures and Fast Fourier Transforms (FFTs). Following some general introduction to discrete SHTs and equidistributions on the sphere, equitriangular (near equiareal) lattices based on the octahedron and the icosahedron are introduced for SHT analysis and synthesis. The developed formulations are described and implemented using simulated data and geopotential models such as the Earth Geopotential Model EGM 2008. Comparative results for analysis and synthesis at different levels of resolution show the potential of the spherical equitriangular approach for geodetic and other applications with nearly equidistributed global data.

scholarly journals GOCE: assessment of GPS-only gravity field determination

2014 ◽  
Vol 89 (1) ◽  
pp. 33-48 ◽  
Author(s):  
Adrian Jäggi ◽  
H. Bock ◽  
U. Meyer ◽  
G. Beutler ◽  
J. van den IJssel
Keyword(s):  
Gravity Field ◽  
Gravity Field Determination
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