The Experts below are selected from a list of 354 Experts worldwide ranked by ideXlab platform

Luís A. Alexandre - One of the best experts on this subject based on the ideXlab platform.

  • Text Pre-processing for Lossless ComPression
    Data Compression Conference (dcc 2008), 2008
    Co-Authors: Luís Batista, Luís A. Alexandre
    Abstract:

    Textual data holds a number of properties that can be taken into account in order to improve ComPression. Pre-processing deals with these properties by applying a number of transformations that make the redundancy "more visible" to the comPressor. One of the most commonly used concepts in text Pre-processing is called capital conversion. Words with capital letters are converted to their lowercase versions while signaling the change with a flag. This way not only context similarities are increased but also dictionaries used for word replacement only need to contain words in their lowercase versions. Word replacement consists of replacing words with shorter codes which are references to their location in a dictionary.

  • DCC - Text Pre-processing for Lossless ComPression
    Data Compression Conference (dcc 2008), 2008
    Co-Authors: Luís Batista, Luís A. Alexandre
    Abstract:

    Textual data holds a number of properties that can be taken into account in order to improve ComPression. Pre-processing deals with these properties by applying a number of transformations that make the redundancy "more visible" to the comPressor. One of the most commonly used concepts in text Pre-processing is called capital conversion. Words with capital letters are converted to their lowercase versions while signaling the change with a flag. This way not only context similarities are increased but also dictionaries used for word replacement only need to contain words in their lowercase versions. Word replacement consists of replacing words with shorter codes which are references to their location in a dictionary.

D Regazzi - One of the best experts on this subject based on the ideXlab platform.

  • 20th European Conference on Fracture (ECF20) Load interaction effects in medium and high strength steels for railway axles
    2020
    Co-Authors: D Regazzi, Stefano Beretta, M Carboni
    Abstract:

    It is well-known from the literature that an interaction effect on crack propagation arises when a specimen or a component is subjected to variable amplitude loading. In dependence of the applied load sequence, a certain amount of retardation or acceleration onto fatigue crack growth rate can then be observed if compared to the constant amplitude case. In the case of structural ductile materials, the interaction phenomenon is mainly addressed by the local plasticity at the crack tip and can be explained, from a global point of view, by adopting the crack closure concept. Considering the applicative case of railway axles, a good correlation between crack growth interaction effects under variable amplitude loading and the amount of plasticity-induced crack closure has been Previously derived by the authors, relatively to the standardized EA1N steel. The other standardized European steel for railway axles, a 25CrMo4 grade named EA4T, is instead considered in the Present research, as well as an high strenght steel grade. An experimental campaign was carried on this material, using SE(T) specimens, in order to understand and quantify the interaction effects arising from relevant load sequences derived from service. Firstly, tests were performed directly applying the acquired load time history. Eventually, the load history was transformed into an equivalent block loading sequence and applied to different specimens varying the number of cycles of each single block. Finally, the experimental outcomes were modeled adopting both a strip yield model and a simple no-interaction approach, in order to quantify the possible interaction effects. The modeling was carried out considering different experimental techniques for deriving the crack growth and threshold behaviors of the material, i.e. the traditionalK-decreasing technique and the ComPression Pre-cracking one. c

  • Load Interaction Effects in a Medium Strength Steel for Railway Axles
    Materials Performance and Characterization, 2014
    Co-Authors: Stefano Beretta, Michele Carboni, D Regazzi
    Abstract:

    As is well known, an interaction effect arises on crack propagation when a specimen or a component is subjected to variable amplitude fatigue loading. Depending on the applied load sequence, a certain amount of retardation or acceleration can then be observed, on the fatigue crack growth rate, with respect to the constant amplitude case. In the case of structural ductile materials, the interaction phenomenon is mainly addressed by the local plasticity at the crack tip and can be explained, from a global point of view, by adopting the crack closure concept. From this point of view, in the Present research, load interaction effects in a medium strength steel for railway axles are analyzed. An experimental campaign was carried on this material, using SE(T) specimens, in order to understand and quantify the interaction effects arising from relevant load sequences derived from service. The experimental outcomes were then modeled adopting both a simple no-interaction approach and a more sophisticated strip-yield model in order to quantify the possible interaction effects. The modeling was carried out considering different experimental techniques for deriving the crack growth and threshold behaviors of the material, i.e., the traditional △K-decreasing technique and the ComPression Pre-cracking one.

  • Load Interaction Effects in Medium and High Strength Steels for Railway Axles
    Procedia Materials Science, 2014
    Co-Authors: D Regazzi, Stefano Beretta, Michele Carboni
    Abstract:

    It is well-known from the literature that an interaction effect on crack propagation arises when a specimen or a component is subjected to variable amplitude loading. In dependence of the applied load sequence, a certain amount of retardation or acceleration onto fatigue crack growth rate can then be observed if compared to the constant amplitude case. In the case of structural ductile materials, the interaction phenomenon is mainly addressed by the local plasticity at the crack tip and can be explained, from a global point of view, by adopting the crack closure concept. Considering the applicative case of railway axles, a good correlation between crack growth interaction effects under variable amplitude loading and the amount of plasticity-induced crack closure has been Previously derived by the authors, relatively to the standardized EA1N steel. The other standardized European steel for railway axles, a 25CrMo4 grade named EA4T, is instead considered in the Present research, as well as an high strenght steel grade. An experimental campaign was carried on this material, using SE(T) specimens, in order to understand and quantify the interaction effects arising from relevant load sequences derived from service. Firstly, tests were performed directly applying the acquired load time history. Eventually, the load history was transformed into an equivalent block loading sequence and applied to different specimens varying the number of cycles of each single block. Finally, the experimental outcomes were modeled adopting both a strip yield model and a simple no-interaction approach, in order to quantify the possible interaction effects. The modeling was carried out considering different experimental techniques for deriving the crack growth and threshold behaviors of the material, i.e. the traditional ΔK-decreasing technique and the ComPression Pre-cracking one.

  • Effect of the experimental technique onto R dependence of ΔKth
    Procedia Engineering, 2011
    Co-Authors: Michele Carboni, D Regazzi
    Abstract:

    Abstract An experimental study on two structural steels (normalized C45 and 25CrMo4 grades) was conducted to determine the influence of the adopted technique onto the threshold SIF value. For both the tested materials, the standard approach used to Pre-crack the specimens showed to have an influence on determining the thresholds, generating SIF higher than the ones estimated adopting ComPression Pre-cracking techniques. This observation can have a huge effect on both life Prediction and inspection intervals for a real structure. An example of life Prediction was carried out applying the Nasgro equations, with the experimentally estimated parameters, to the propagation of a crack located at the T-transition of a generic railway axle, assumed to be built using the two tested steel grades.

  • determination of δ k th by ComPression Pre cracking in a structural steel
    Journal of Astm International, 2009
    Co-Authors: M Carboni, L Patriarca, D Regazzi
    Abstract:

    The traditional experimental procedures used to generate thresholds (known as “ΔK-decreasing” and “constant Kmax”) have been challenged because it seems they affect the experimental results, sometimes in a non conservative way. In order to fix this problem, different experimental procedures (“ComPression Pre-cracking constant amplitude” and “ComPression Pre-cracking load reduction” (CPLR)) based on a ComPression-ComPression Pre-cracking of fracture mechanics specimens have been proposed. Up till now, such procedures are not yet wide-sPread between fracture mechanics experimentalists. In particular, due to the recent introduction, CPLR has been applied only to few cases: Al alloys, Ti alloys, and high strength steels (ultimate tensile strength>1300 MPa), all in the shape of M(T) or C(T) specimens subjected to positive stress ratios. The Present paper deals with the application of these novel “ComPression Pre-cracking” procedures, with particular attention to CPLR, to the unexplored and technically very important case of the structurally mild A1N steel grade (very commonly used to produce European railway axles) in the shape of SE(B) specimens subjected to stress ratios varying between −2 and 0.85.

Niels Henrik Holländer - One of the best experts on this subject based on the ideXlab platform.

  • High-Precision radiotherapy of motor deficits due to metastatic spinal cord ComPression (Pre-MODE): a multicenter phase 2 study
    BMC Cancer, 2017
    Co-Authors: Dirk Rades, Jon Cacicedo, Antonio J. Conde-moreno, Claudia Doemer, Jürgen Dunst, Darejan Lomidze, Barbara Segedin, Denise Olbrich, Niels Henrik Holländer
    Abstract:

    Background For metastatic spinal cord ComPression (MSCC), conventional radiotherapy with 10 × 3 Gy in 2 weeks results in better local progression-free survival (LPFS) than 5 × 4 Gy in 1 week. Since patients with MSCC are often significantly impaired, an overall treatment time of 1 week would be Preferable if resulting in similar outcomes as longer programs. This may be achieved with 5 × 5 Gy in 1 week, since the biologically effective dose is similar to 10 × 3 Gy. It can be expected that 5 × 5 Gy (like 10 × 3) Gy results in better LPFS than 5 × 4 Gy in 1 week. Methods/Design This phase 2 study investigates LPFS after high-Precision RT with 5 × 5 Gy in 1 week. LPFS is defined as freedom from both progression of motor deficits during RT and new or progressive motor deficits dur to an in-field recurrence of MSCC following RT. Considering the tolerance dose of the spinal cord, 5 × 5 Gy can be safely administered with high-Precision radiotherapy such as volumetric modulated arc therapy (VMAT) or stereotactic body radiotherapy (SBRT). Maximum dose to the spinal cord should not exceed 101.5% of the Prescribed dose to keep the risk of radiation myelopathy below 0.03%. Primary endpoint is LPFS at 6 months following radiotherapy; secondary endpoints include motor function/ability to walk, sensory function, sphincter dysfunction, LPFS directly and 1 and 3 months following radiotherapy, overall survival, pain relief, quality of life and toxicity. Follow-up visits will be performed directly and at 1, 3 and 6 months following radiotherapy. After completion of this phase 2 study, patients will be compared to a historical control group receiving conventional radiotherapy with 5 × 4 Gy in 1 week. Forty-four patients will be included assuming 5 × 5 Gy will provide the same benefit in LPFS when compared to 5 × 4 Gy as reported for 10 × 3 Gy. Discussion If superiority regarding LPFS is shown for high-Precision radiotherapy with 5 × 5 Gy when compared to conventional radiotherapy with 5 × 4 Gy, patients with MSCC would benefit from 5 × 5 Gy, since high LPFS rates could be achieved with 1 week of radiotherapy instead of 2 weeks (10 × 3 Gy). Trial registration clinicaltrials.gov NCT03070431 . Registered 27 February 2017.

  • High-Precision radiotherapy of motor deficits due to metastatic spinal cord ComPression (Pre-MODE): a multicenter phase 2 study.
    BMC Cancer, 2017
    Co-Authors: Dirk Rades, Jon Cacicedo, Antonio J. Conde-moreno, Claudia Doemer, Jürgen Dunst, Darejan Lomidze, Barbara Segedin, Denise Olbrich, Niels Henrik Holländer
    Abstract:

    For metastatic spinal cord ComPression (MSCC), conventional radiotherapy with 10 × 3 Gy in 2 weeks results in better local progression-free survival (LPFS) than 5 × 4 Gy in 1 week. Since patients with MSCC are often significantly impaired, an overall treatment time of 1 week would be Preferable if resulting in similar outcomes as longer programs. This may be achieved with 5 × 5 Gy in 1 week, since the biologically effective dose is similar to 10 × 3 Gy. It can be expected that 5 × 5 Gy (like 10 × 3) Gy results in better LPFS than 5 × 4 Gy in 1 week. This phase 2 study investigates LPFS after high-Precision RT with 5 × 5 Gy in 1 week. LPFS is defined as freedom from both progression of motor deficits during RT and new or progressive motor deficits dur to an in-field recurrence of MSCC following RT. Considering the tolerance dose of the spinal cord, 5 × 5 Gy can be safely administered with high-Precision radiotherapy such as volumetric modulated arc therapy (VMAT) or stereotactic body radiotherapy (SBRT). Maximum dose to the spinal cord should not exceed 101.5% of the Prescribed dose to keep the risk of radiation myelopathy below 0.03%. Primary endpoint is LPFS at 6 months following radiotherapy; secondary endpoints include motor function/ability to walk, sensory function, sphincter dysfunction, LPFS directly and 1 and 3 months following radiotherapy, overall survival, pain relief, quality of life and toxicity. Follow-up visits will be performed directly and at 1, 3 and 6 months following radiotherapy. After completion of this phase 2 study, patients will be compared to a historical control group receiving conventional radiotherapy with 5 × 4 Gy in 1 week. Forty-four patients will be included assuming 5 × 5 Gy will provide the same benefit in LPFS when compared to 5 × 4 Gy as reported for 10 × 3 Gy. If superiority regarding LPFS is shown for high-Precision radiotherapy with 5 × 5 Gy when compared to conventional radiotherapy with 5 × 4 Gy, patients with MSCC would benefit from 5 × 5 Gy, since high LPFS rates could be achieved with 1 week of radiotherapy instead of 2 weeks (10 × 3 Gy). clinicaltrials.gov NCT03070431 . Registered 27 February 2017.

Luís Batista - One of the best experts on this subject based on the ideXlab platform.

  • Text Pre-processing for Lossless ComPression
    Data Compression Conference (dcc 2008), 2008
    Co-Authors: Luís Batista, Luís A. Alexandre
    Abstract:

    Textual data holds a number of properties that can be taken into account in order to improve ComPression. Pre-processing deals with these properties by applying a number of transformations that make the redundancy "more visible" to the comPressor. One of the most commonly used concepts in text Pre-processing is called capital conversion. Words with capital letters are converted to their lowercase versions while signaling the change with a flag. This way not only context similarities are increased but also dictionaries used for word replacement only need to contain words in their lowercase versions. Word replacement consists of replacing words with shorter codes which are references to their location in a dictionary.

  • DCC - Text Pre-processing for Lossless ComPression
    Data Compression Conference (dcc 2008), 2008
    Co-Authors: Luís Batista, Luís A. Alexandre
    Abstract:

    Textual data holds a number of properties that can be taken into account in order to improve ComPression. Pre-processing deals with these properties by applying a number of transformations that make the redundancy "more visible" to the comPressor. One of the most commonly used concepts in text Pre-processing is called capital conversion. Words with capital letters are converted to their lowercase versions while signaling the change with a flag. This way not only context similarities are increased but also dictionaries used for word replacement only need to contain words in their lowercase versions. Word replacement consists of replacing words with shorter codes which are references to their location in a dictionary.

C. P. Rajendran - One of the best experts on this subject based on the ideXlab platform.

  • Short Note The June 2010 Nicobar Earthquake: Fault Reactivation on the Subducting Oceanic Plate
    2020
    Co-Authors: Kusala Rajendran, Vanessa Andrade, C. P. Rajendran
    Abstract:

    The ∼1300-km-long rupture zone of the 2004 Andaman-Sumatra mega- thrust earthquake continues to generate a mix of thrust, normal, and strike-slip faulting events. The 12 June 2010 Mw 7.5 event on the subducting plate is the most recent large earthquake on the Nicobar segment. The left-lateral faulting mechanism of this event is unusual for the outer-rise region, considering the stress transfer processes that follow great underthrusting earthquakes. Another earthquake (Mw 7.2) with a similar mechanism occurred very close to this event on 24 July 2005. These earthquakes and most of their aftershocks on the subducting plate were generated by left-lateral strike- slip faulting on north-northeast-south-southwest oriented near-vertical faults, in response to north-northwest-south-southeast directed ComPression. Pre-2004 earth- quake faulting mechanisms on the subducting oceanic plate are consistent with this pattern. Post-2004, left-lateral faulting on the subducting oceanic plate clusters between 5° N and 9° N, where the 90° E ridge impinges the trench axis. Our study observes that the subducting plate off the Sumatra and Nicobar segments behaves similarly to a chip of the India-Australia plate, deforming in response to a generally northwest-southeast oriented ComPression, an aspect that must be factored into the plate deformation models.

  • The June 2010 Nicobar Earthquake: Fault Reactivation on the Subducting Oceanic Plate
    Bulletin of the Seismological Society of America, 2011
    Co-Authors: Kusala Rajendran, Vanessa Andrade, C. P. Rajendran
    Abstract:

    The similar to 1300-km-long rupture zone of the 2004 Andaman-Sumatra megathrust earthquake continues to generate a mix of thrust, normal, and strike-slip faulting events. The 12 June 2010 M(w) 7.5 event on the subducting plate is the most recent large earthquake on the Nicobar segment. The left-lateral faulting mechanism of this event is unusual for the outer-rise region, considering the stress transfer processes that follow great underthrusting earthquakes. Another earthquake (M(w) 7.2) with a similar mechanism occurred very close to this event on 24 July 2005. These earthquakes and most of their aftershocks on the subducting plate were generated by left-lateral strike-slip faulting on north-northeast-south-southwest oriented near-vertical faults, in response to north-northwest-south-southeast directed ComPression. Pre-2004 earthquake faulting mechanisms on the subducting oceanic plate are consistent with this pattern. Post-2004, left-lateral faulting on the subducting oceanic plate clusters between 5 degrees N and 9 degrees N, where the 90 degrees E ridge impinges the trench axis. Our study observes that the subducting plate off the Sumatra and Nicobar segments behaves similarly to a chip of the India-Australia plate, deforming in response to a generally northwest-southeast oriented ComPression, an aspect that must be factored into the plate deformation models.