281 research outputs found
Construction of GCM hypersurfaces in perturbations of Kerr
No full textThis is a follow-up of \cite{KS:Kerr1} on the general covariant modulated
(GCM) procedure in perturbations of Kerr. In this paper, we construct GCM
hypersurfaces, which play a central role in extending GCM admissible spacetimes
in \cite{KS:main} where decay estimates are derived in the context of nonlinear
stability of Kerr family for . As in \cite{KS}, the central idea of
the construction of GCM hypersurfaces is to concatenate a --parameter family
of GCM spheres of \cite{KS:Kerr1} by solving an ODE system. The goal of this
paper is to get rid of the symmetry restrictions in the GCM procedure
introduced in \cite{KS} and thus remove an essential obstruction in extending
the results to a full stability proof of the Kerr family.Comment: 113 pages, 2 figures, minor improvements, accepted in Annals of PDE.
arXiv admin note: substantial text overlap with arXiv:1911.00697 by other
author
An Architecture for the AES-GCM Security Standard
No full textI hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii The forth recommendation of symmetric block cipher mode of operation SP800-38D, Galois/Counter Mode of Operation (GCM) was developed by David A McGrew and John Viega. GCM uses an approved symmetric key block cipher with a block size of 128 bits and a universal hashing over a binary Galois field to provide confidentiality and authentication. It is built specifically to support very high data rates as it can take advantage of pipelining and parallel processing techniques. Before GCM, SP800-38A only provided confidentiality and SP800-38B provided authentication. SP800-38C provided confidentiality using the counter mode and authentication. However the authentication technique in SP800-38C was not parallelizable and slowed down the throughput of the cipher. Hence, none of these three recommendations were suitable for high speed network and computer system applications. With the advent of GCM, authenticated encryption at data rates of several Gbps is now practical, permitting high grade encryption and authentication on systems which previously could not be fully protected. However there have not yet been any published results on actual architectures for this standard based on FPGA technology. This thesis presents a fully pipelined and parallelized hardware architecture for AES-GCM which is GCM running under symmetric block cipher AES on a FPGA multi-core platform corresponding to the IPsec ESP data flow. The results from this thesis show that the round transformations of confidentiality and hash operations of authentication in AES-GCM can cooperate very efficiently within this pipelined architecture. Furthermore, this AES-GCM hardware architecture never unnecessarily stalls data pipelines. For the first time this thesis provides a complete FPGAbased high speed architecture for the AES-GCM standard, suitable for high speed embedded applications. ii
Geophysical methods for forensic investigations: detection and characterization of simulated clandestine burials using GPR and GCM
No full textIn this thesis I conducted ground penetrating radar (GPR) and ground conductivity meter (GCM) surveys to detect the presence of simulated clandestine burials at the Amsterdam Research Initiative for Subsurface Taphonomy and Anthropology (ARISTA) test facility, and determine their characteristic response in this environment; providing valuable insights and recommendations for forensic investigations. I performed four days of GPR and GCM surveys over three simulated clandestine burials at ARISTA. I collected common-offset GPR data to investigate changes to burial detectability due to different central antenna frequencies (250 MHz and 500 MHz), different GPR instruments (NOGGIN or pulseEKKO), changes to survey grid orientation relative to burials, and increased soil moisture content in the survey area. Additionally, I acquired common-source GPR data to examine the efficacy of electromagnetic interferometry (EI) and adaptive subtraction (AS) methods in improving burial detectability. I conducted GCM surveys with two coil configurations, (horizontal co-planar (HCP) and vertical co-planar (VCP)), three intercoil spacings (0.32 m, 0.71 m, 1.18 m), two different line spacings (0.5 m, 0.25 m) and in the presence of variable soil moisture content. I also performed low induction number (LIN) correction and elevation correction procedures on GCM data to determine the extent to which these influence the detectability of clandestine burials in this environment.In common-offset radargrams characteristic burial anomalies take on many forms, appearing as disruptions to existing features (direct-wave arrivals and soil horizons) and as isolated reflection events (hyperbolic events and burial length horizontal anomalies). In timeslices, burials are characterized by high or low amplitude rectangular anomalies. When used in conjunction, radargrams and timeslices produced characteristic responses regardless of survey grid orientation, consistent with the locations of the burials. Increased soil moisture at the site improved the detectability of burials and the 250 MHz antenna was found to be superior to the 500 MHz antenna in obtaining a characteristic burial response, though both were successful to a large extent. EI and AS processing techniques were successful in removing direct-wave contributions in radargrams, though detectability was not significantly improved when compared to raw data. Overall, the three burials were detected using GPR to various extents, and in future work thorough historical data in addition to zero-measurements should be obtained for all burials in order to investigate the source of these differences. GCM surveys conducted in this work were largely unsuccessful in detecting simulated clandestine burials due to significant conductive noise sources (metal fence, sensors, etc.) and the limited conductivity contrast in the soil. Low conductivity zones were detected over some burials using HCP at an intercoil spacing of 1.18 m, however, confidence in the validity of these responses is low due to the dominating noise sources.Applied Geophysics | IDEA Leagu
Growth curve modeling (GCM) and possible application in fish stock assessment.
No full textNo abstracts are to be cited without prior reference to the author. A new analytical approach to fish growth dynamics (Growth curve modeling, GCM), has been developed at the Aquaculture Laboratory of the MRI in Iceland. GCM-modeling is based on the analysis of growth trajectory and links larval- to long term growth performance. The method was initially developed for Atlantic cod (Gadus morhua) but can arguably be applied to all fish species, creating a new perspective on the underlying growth dynamics of fishes. GCM-modeling shows how the long-term growth potential can be traced back to the initial larval growth performance and how the early larval benchmark sizes are systematically reflected throughout the later juvenile- and adult life stages. GCM-modeling further shows how the life-span is divided into consecutive stages with fixed growth potential and how the potential maximum size of the fish is already fixed at the larval stage. When applied to historical data from the Icelandic cod stock, GCM-modeling reveals a previously overlooked fluctuation pattern in cohort growth rates
From GCM energy kernels to Weyl-Wigner Hamiltonians: A particular mapping
No full textA particular mapping is established which directly connects GCM energy kernels to Weyl-Wigner Hamiltonians under the assumption of a gaussian overlap kernel. As an application of this mapping scheme the author derives the collective Hamiltonians for some giant resonances.Instituto de Fisica Teorica Rua Pamplona 145, Caixa Postal 5659, 01405 Sao Paul
Geophysical indices input file for TIE-GCM
No full textA GPI_NCFILE input for the thermosphere-ionosphere-electrodynamics general circulation model (TIE-GCM; Richmond et al., 1992; doi: 10.1029/92GL00401).
This file provides Daily F10.7, 81-day centered mean of F10.7, and Kp for the time period 1950-01-01 – 2023-01-10.
Netcdf file description
netcdf gpi_1950001_2023010 {
dimensions:
ndays = 26673 ;
nkp = 8 ;
variables:
int year_day(ndays) ;
year_day:long_name = "4-digit year followed by 3-digit day" ;
double f107d(ndays) ;
f107d:long_name = "Penticton observed daily 10.7 cm solar flux (sfu)" ;
double f107a(ndays) ;
f107a:long_name = "Penticton 81-day average 10.7 cm solar flux (sfu)" ;
double kp(ndays, nkp) ;
kp:long_name = "GFZ 3-hourly Kp index" ;
// global attributes:
:title = "Geophysical indices input file for TIE-GCM" ;
:history = "Created: Tue Feb 21 09:56:36 2023" ;
:yearday_beg = 1950003 ;
:yearday_end = 2023008 ;
:author = "Timothy Kodikara (DLR.de)" ;
:write_source = "make_tiegcm_gpincfile.py, write_gpi_ncfile.py" ;
:Kp_source = "Geomagnetic Observatory Niemegk, GFZ German Research Centre for Geosciences [doi.org/10.5880/Kp.0001]" ;
:F107_source = "Observed solar flux provided by the Dominion Radio Astrophysical Observatory and Natural Resources Canada [ftp://ftp.seismo.nrcan.gc.ca/spaceweather/solar_flux/daily_flux_values/fluxtable.txt]" ;
:info = "When using this file, please cite the source as https://doi.org/10.5281/zenodo.7660253" ;
}When using this file, please cite the source as https://doi.org/10.5281/zenodo.766025
Stochastic convection parameterization with Markov Chains in an intermediate-complexity GCM
No full textConditional Markov chain (CMC) models have proven to be promising building blocks for stochastic convection parameterizations. In this paper, it is demonstrated how two different CMC models can be used as mass flux closures in convection parameterizations. More specifically, the CMC models provide a stochastic estimate of the convective area fraction that is directly proportional to the cloud-base mass flux. Since, in one of the models, the number of CMCs decreases with increasing resolution, this approach makes convection parameterizations scale aware and introduces stochastic fluctuations that increase with resolution in a realistic way. Both CMC models are implemented in a GCM of intermediate complexity. It is shown that with the CMC models, trained with observational data, it is possible to improve both the subgrid-scale variability and the autocorrelation function of the cloud-base mass flux as well as the distribution of the daily accumulated precipitation in the tropics. Hovmöller diagrams and wavenumber–frequency diagrams of the equatorial precipitation indicate that, in this specific GCM, convectively coupled equatorial waves are more sensitive to the mean cloud-base mass flux than to stochastic fluctuations. A smaller mean mass flux tends to increase the power of the simulated MJO and to diminish equatorial Kelvin waves.Geoscience and Remote SensingCivil Engineering and Geoscience
On the projected changes in New Zealand's wave climate and its main drivers
No full textWave climatologies from historical and projected simulations of the ACCESS1.0, MIROC5 and CNRM-CM5 Global Circulation Models (GCM) were sourced from the Coordinated Ocean Wave Climate Project (COWCLIP) and downscaled using the SWAN wave model. Biases between GCM's historical simulations and a regional hindcast were assessed, and the two best-performing models (ACCESS1.0, MIROC5) had their projections analysed. A general increase in wave height and period was observed along the south/west, together with a decrease in (Formula presented.) along the north/east coasts. The projected near-term (NEA21C) period shows mostly a (Formula presented.) increase, whilst for the long-term (END21C) period, increased and decreased (Formula presented.) are present. The areas of statistically significant changes are larger in the END21C than in the NEA21C period. The wave direction change is counter-clockwise along the west and clockwise along the east coasts. This study is a first assessment of historical and projected GCM-forced waves along New Zealand and the database we generated can be of great value for renewable energy research, risk assessment and the mitigation of future coastal hazards.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Coastal Engineerin
Geophysical indices input file for TIE-GCM
No full text<p>A GPI_NCFILE input for the thermosphere-ionosphere-electrodynamics general circulation model (TIE-GCM; Richmond et al., 1992; doi: 10.1029/92GL00401).</p>
<p>This file provides Daily F10.7, 81-day centered mean of F10.7, and Kp for the time period 1950-01-01 – 2023-11-07.</p>
<p><strong>Netcdf file description</strong></p>
<p>netcdf gpi_1950001_2023313 {<br>dimensions:<br> ndays = 26976 ;<br> nkp = 8 ;<br>variables:<br> int year_day(ndays) ;<br> year_day:long_name = "4-digit year followed by 3-digit day" ;<br> double f107d(ndays) ;<br> f107d:long_name = "Penticton observed daily 10.7 cm solar flux (sfu)" ;<br> double f107a(ndays) ;<br> f107a:long_name = "Penticton 81-day average 10.7 cm solar flux (sfu)" ;<br> double kp(ndays, nkp) ;<br> kp:long_name = "GFZ 3-hourly Kp index" ;</p>
<p>// global attributes:<br> :title = "Geophysical indices input file for TIE-GCM" ;<br> :history = "Created: Wed Dec 20 14:48:35 2023" ;<br> :yearday_beg = 1950003 ;<br> :yearday_end = 2023311 ;<br> :author = "Timothy Kodikara (DLR.de)" ;<br> :write_source = "make_tiegcm_gpincfile.py, write_gpi_ncfile.py" ;<br> :Kp_source = "Geomagnetic Observatory Niemegk, GFZ German Research Centre for Geosciences [doi.org/10.5880/Kp.0001]" ;<br> :F107_source = "Observed solar flux provided by the Dominion Radio Astrophysical Observatory and Natural Resources Canada [ftp://ftp.seismo.nrcan.gc.ca/spaceweather/solar_flux/daily_flux_values/fluxtable.txt]" ;<br> :info = "When using this file, please cite the source as https://doi.org/10.5281/zenodo.8017410" ;<br>}</p>
<p> </p>
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