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Institution

National Physical Laboratory

FacilityLondon, United Kingdom
About: National Physical Laboratory is a facility organization based out in London, United Kingdom. It is known for research contribution in the topics: Dielectric & Thin film. The organization has 7615 authors who have published 13327 publications receiving 319381 citations.


Papers
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Journal ArticleDOI
TL;DR: Grain-boundary grooving at the interface between solid platinum and solid alumina has been studied and its relevance to spheroidisation and particle coarsening noted.
Abstract: Grain-boundary grooving at the interface between solid platinum and solid alumina has been studied and its relevance to spheroidisation and particle coarsening noted. Analysis of the equilibrium shape of the grooves in conjunction with zero creep studies on platinum shows that the platinum/alumina interfacial energy is 1050 ergs/cm2 at 1400° C. The rate of growth of the grooves shows that volume diffusion is the operative mass transport mechanism at all temperatures considered (1240 to 1540° C); however, there are indications that diffusion through the metal is rate-determining at lower temperatures (< 1410° C) while diffusion through the ceramic phase predominates at higher temperatures.

76 citations

Journal ArticleDOI
TL;DR: In this paper, the method is based on the following theorem: if A is a positive definite matrix of band form such that A = 0, then there exists a real non-singular lower triangular matrix L such that L{L^T} = A,
Abstract: The method is based on the following theorem. If A is a positive definite matrix of band form such that $${a_{ij}} = 0{\rm{ (|}}i - j| >m{\rm{)}}$$ (1) then there exists a real non-singular lower triangular matrix L such that $$L{L^T} = A,{\rm{ where }}{l_{ij}} = 0{\rm{ (}}i - j >m{\rm{)}}{\rm{.}}$$ (2)

76 citations

Journal ArticleDOI
TL;DR: An overview is given of recent breakthroughs in characterization and understanding of the pit-to-crack transition using advanced three-dimensional imaging techniques, which inspired a new concept for the role of pitting in stress corrosion cracking based on the growing pit inducing local dynamic plastic strain.
Abstract: In many applications, corrosion pits act as precursors to cracking, but qualitative and quantitative prediction of damage evolution has been hampered by lack of insights into the process by which a crack develops from a pit. An overview is given of recent breakthroughs in characterization and understanding of the pit-to-crack transition using advanced three-dimensional imaging techniques such as X-ray computed tomography and focused ion beam machining with scanning electron microscopy. These techniques provided novel insights with respect to the location of crack development from a pit, supported by finite-element analysis. This inspired a new concept for the role of pitting in stress corrosion cracking based on the growing pit inducing local dynamic plastic strain, a critical factor in the development of stress corrosion cracks. Challenges in quantifying the subsequent growth rate of the emerging small cracks are then outlined with the potential drop technique being the most viable. A comparison is made with the growth rate for short cracks (through-thickness crack in fracture mechanics specimen) and long cracks and an electrochemical crack size effect invoked to rationalize the data.

76 citations

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed ionosonde data for some 31 stations to study the long term trends in hmF2 and foF2, and concluded that the present data do not provide definitive evidence of any global long term trend in the ionosphere.
Abstract: Theoretical calculations predict that CO2 doubling would produce a 50 K decrease in the thermospheric temperature which can result in about 20 km decrease in the F2 peak height (hmF2) and a minor decrease in the F2 layer critical frequency (foF2) [Rishbeth and Roble 1992]. In this paper we analyze ionosonde data for some 31 stations to study the long term trends in hmF2 and foF2. Regression coefficients for hmF2 and foF2 as a function of solar activity, are obtained for each station and departures (anomalies) from expected values derived for both these parameters. An analysis of hmF2 and foF2 anomalies indicates negative trends for some stations and positive trends for others. These varied between +29 to −20 km for hmF2 and +0.7 to −0.6 MHz for foF2 in the 34 year period since 1957, the International Geophysical Year (IGY). We conclude that the present data do not provide a definitive evidence of any global long term trend in the ionosphere.

76 citations

Journal ArticleDOI
TL;DR: The tests included in G4-Med are described and the results derived from the benchmarking of Geant4 10.5 against reference data will aid users in tailoring physics lists to their particular application.
Abstract: Background: Geant4 is a Monte Carlo code extensively used in medical physics for a wide range of applications, such as dosimetry, micro- and nanodosimetry, imaging, radiation protection, and nuclear medicine. Geant4 is continuously evolving, so it is crucial to have a system that benchmarks this Monte Carlo code for medical physics against reference data and to perform regression testing. Aims: To respond to these needs, we developed G4-Med, a benchmarking and regression testing system of Geant4 for medical physics. Materials and Methods: G4-Med currently includes 18 tests. They range from the benchmarking of fundamental physics quantities to the testing of Monte Carlo simulation setups typical of medical physics applications. Both electromagnetic and hadronic physics processes and models within the prebuilt Geant4 physics lists are tested. The tests included in G4-Med are executed on the CERN computing infrastructure via the use of the geant-val web application, developed at CERN for Geant4 testing. The physical observables can be compared to reference data for benchmarking and to results of previous Geant4 versions for regression testing purposes. Results: This paper describes the tests included in G4-Med and shows the results derived from the benchmarking of Geant4 10.5 against reference data. Discussion: Our results indicate that the Geant4 electromagnetic physics constructor G4EmStandardPhysics_option4 gives a good agreement with the reference data for all the tests. The QGSP_BIC_HP physics list provided an overall adequate description of the physics involved in hadron therapy, including proton and carbon ion therapy. New tests should be included in the next stage of the project to extend the benchmarking to other physical quantities and application scenarios of interest for medical physics. Conclusion: The results presented and discussed in this paper will aid users in tailoring physics lists to their particular application. (Less)

76 citations


Authors

Showing all 7655 results

NameH-indexPapersCitations
Rajesh Kumar1494439140830
Akhilesh Pandey10052953741
A. S. Bell9030561177
David R. Clarke9055336039
Praveen Kumar88133935718
Richard C. Thompson8738045702
Xin-She Yang8544461136
Andrew J. Pollard7967326295
Krishnendu Chakrabarty7999627583
Vinod Kumar7781526882
Bansi D. Malhotra7537519419
Matthew Hall7582724352
Sanjay K. Srivastava7336615587
Michael Jones7233118889
Sanjay Singh71113322099
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202315
202242
2021356
2020438
2019434
2018406