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THE UNUSUAL STELLAR MASS FUNCTION OF STARBURST CLUSTERS
Dib, Sami The Korean Astronomical Society 2007 Journal of The Korean Astronomical Society Vol.40 No.4
I present a model to explain the mass segregation and shallow mass functions observed in the central parts of starburst stellar clusters. The model assumes that the initial pre-stellar cores mass function resulting from the turbulent fragmentation of the proto-cluster cloud is significantly altered by the cores coalescence before they collapse to form stars. With appropriate, yet realistic parameters, this model based on the competition between cores coalescence and collapse reproduces the mass spectra of the well studied Arches cluster. Namely, the slopes at the intermediate and high mass ends, as well as the peculiar bump observed at $6M_{\bigodot}$. This coalescence-collapse process occurs on a short timescale of the order of the free fall time of the proto-cluster cloud (i.e., a few $10^4$ years), suggesting that mass segregation in Arches and similar clusters is primordial. The best fitting model implies the total mass of the Arches cluster is $1.45{\times}10^5M_{\bigodot}$, which is slightly higher than the often quoted, but completeness affected, observational value of a few $10^4M_{\bigodot}$. The model implies a star formation efficiency of ${\sim}30$ percent which implies that the Arches cluster is likely to a gravitationally bound system.
Signatures of Dirac and Majorana sterile neutrinos in trilepton events at the LHC
Dib, Claudio O.,Kim, C. S.,Wang, Kechen American Physical Society 2017 Physical Review D Vol.95 No.11
<P>Heavy sterile neutrinos with masses below MW can induce trilepton events at the 14 TeV LHC through purely leptonic W decays of W-+/--> e(+/-) e(+/-) mu(+/-)nu. and mu(+/-)mu(+/-)e(+/-)nu. where the heavy neutrino will be in an intermediate state on its mass shell. Discovery and exclusion limits for the heavy neutrinos are found using both cut-and-count (CC) and multivariate analysis (MVA) methods in this study. We also show that it is possible to discriminate between a Dirac and a Majorana heavy neutrino, even when lepton number conservation cannot be directly tested due to unobservability of the final state neutrino. This discrimination is done by exploiting a combined set of kinematic observables that differ between the Majorana and Dirac cases. We find that the MVA method can greatly enhance the discovery and discrimination limits in comparison with the CC method. For a 14-TeV pp collider with integrated luminosity of 3000 fb(-1), sterile neutrinos can be found with 5s significance if heavy-to-light neutrino mixings vertical bar U-Ne broken vertical bar(2)similar to vertical bar U-N mu vertical bar(2) similar to 10(-6), while the Majorana vs Dirac type can be distinguished if vertical bar U-Ne broken vertical bar(2)similar to vertical bar U-N mu vertical bar(2) similar to 10(-5) or even U-N mu vertical bar(2) similar to 10(-6) if one of the mixing elements is at least an order of magnitude smaller than the other.</P>
Gerges Dib,Surajit Roy,Pradeep Ramuhalli,채장범 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.3
Second harmonic generation using nonlinear ultrasonic waves have been shown to be an early indicatorof possible fatigue damage in nuclear power plant components. This technique relies on measuringamplitudes, making it highly susceptible to variations in transducer coupling and instrumentation. Thispaper proposes an experimental procedure for in-situ surface wave nonlinear ultrasound measurementson specimen with permanently mounted transducers under high cycle fatigue loading without interruptingthe experiment. It allows continuous monitoring and minimizes variation due to transducercoupling. Moreover, relations describing the effects of the measurement system nonlinearity includingthe effects of the material transfer function on the measured nonlinearity parameter are derived. An insituhigh cycle fatigue test was conducted using two 304 stainless steel specimens with two differentexcitation frequencies. A comprehensive analysis of the nonlinear sources, which result in variations inthe measured nonlinearity parameters, was performed and the effects of the system nonlinearities areexplained and identified. In both specimens, monotonic trend was observed in nonlinear parameterwhen the value of fundamental amplitude was not changing.
On induced $L$−fuzzy uniformities
K. A. DiB,G. A. Kamel,H. M. Rezk 원광대학교 기초자연과학연구소 2017 ANNALS OF FUZZY MATHEMATICS AND INFORMATICS Vol.14 No.2
The extension of the uniformity on the family of fuzzy subsets $L^Y$ to a uniformity on the family of fuzzy subsets $L^X : Y \subseteq X$ and the restriction of the uniformity on $L^Y$ to a uniformity on $L^Y$ are defined and studied. The induced (fuzzy) quasi-uniformity on $P^∗(L)^X$ for each given (fuzzy) quasi-uniformity on $L^X$ is defined. Moreover, the induced $(P^∗(L), M)$−fuzzy quasi-uniformity on $P^∗(L)^X$, for each $(L, M)$−fuzzy quasi-uniformity on $L^X$ is studied. In each case, the relation between their interior operators is obtained. Finally, the relation between the category $\bf Qunif(L,M)$ of all $(L, M)$−fuzzy quasi uniformity spaces and all quasiuniformly continuous functions, and the category $\bf FQunif(P^∗(L),M)$ of all $(P^∗ (L), M)$−fuzzy quasi uniformity spaces and quasi-uniformly continuous fuzzy functions is outlined. It is remarked that all kinds of categories of quasi-uniform spaces and quasi-uniformly continuous functions can be derived from the category $\bf FQunif(P^∗(L),M)$.
Carla de Amorim Lana Dib,Guilherme Henrique dos Santos Ramos,Gregório Sandro Vieira 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.5
Cold-formed steel (CFS) members stand out among steel structures notably due to their lightness, structural efficiency (high strength-to-weight ratio) and versatility, however, given their high width-to-thickness ratio, are highly susceptible to instability phenomena (buckling). The objective of this research is to analyze the structural behavior of cold-formed steel hat-section beams under non-uniform bending about the major and minor-axis, regarding the risks of distortional failure. Through the Generalized Beam Theory, using the computational program GBTUL, the geometries where the distortional failure is predominant were selected and through the computational program ABAQUS, a shell finite element model was developed to perform the buckling and post-buckling analysis on the selected elements. The results obtained from the developed model—which include critical buckling moments, failure moments, equilibrium paths, deformed configurations and collapse mechanisms—show that the developed model adequately simulates the distortional buckling and post-buckling behavior of the considered CFS beams and demonstrate how loading affects such behaviors.