25,400 research outputs found
Supernovae Shedding Light on Gamma-Ray Bursts
We review the observational status of the Supernova (SN)/Gamma-Ray Burst
(GRB) connection. In section 2 we provide a short summary of the observational
properties of core-collapse SNe. In sections 3-6 we review the circumstantial
evidences and the direct observations that support the existence of a deep
connection between the death of massive stars and GRBs. Present data suggest
that SNe associated with GRBs form a heterogeneous class of objects including
both bright and faint Hypernovae and perhaps also `standard' Ib/c events. In
section 7, we provide an empirical estimate of the rate of Hypernovae, for a
``MilkyWay-like'' galaxy, of about yr that may
imply the ratio GRB/Hypernovae to be in the range . In the same
framework we find the ratio GRB/SNe-Ibc to be . In section
8 we discuss the possible existence of a lag between the SN explosion and the
associated gamma-ray event. In the few SN/GRB associations so far discovered
the SN explosions and GRB events appear to go off simultaneously. In section 9
we present the conclusions and highlight the open problems that Swift hopefully
will allow us to solve.Comment: 20 pages, 13 figures, invited review at the 4th Workshop Gamma-Ray
Bursts in the Afterglow Era, Rome,18-22 October 2004. Editors: L. Piro, L.
Amati, S. Covino, and B. Gendre. Il Nuovo Cimento, in pres
How to improve business process performance using process mining
Due to the increased use of information systems by organizations to support process execution, detailed information on the implementation of business processes is being recorded. This fact enables using process mining projects as a powerful tool for improving performance. Process Mining is a relative young research discipline that sits between data science on the one hand and process modelling and analysis on the other hand. Process mining allows gaining knowledge of the organization’s actual business processes by extracting data from existing information systems mediums such as event logs, transaction logs etc.
The purpose of this presentation is to demonstrate how a process for conducting process mining projects was designed, developed and applied in some organizational units.
The process was implemented through nine research steps, inspired by the V-model, where elements on the right-hand side aim to answer questions presented in steps on the left-hand side. In the first two steps, the research problem and the research objectives were defined. A literature review was performed in step 3. In the fourth step, requirements for the process were identified and implemented. In step 5, a running example was carried out to test the process. Verification and validation of the process were performed in step 6 and step 7. Step 8 covered the discussion of results. The last step concludes the research, including checking if the research problem was solved.
Organizations seeking for performance improvement can now benefit of a process that explicitly states which process mining tools, techniques and algorithms to be used in process mining projects
Incoherent Mollow triplet
A counterpart of the Mollow triplet (luminescence lineshape of a two-level
system under coherent excitation) is obtained for the case of incoherent
excitation in a cavity. Its analytical expression, in excellent agreement with
numerical results, pinpoints analogies and differences between the conventional
resonance fluorescence spectrum and its cavity QED analogue under incoherent
excitation.Comment: 4 pages, 3 figure
Three-Loop Calculation of the Anyonic Full Cluster Expansion
We calculate the perturbative correction to every cluster coefficient of a
gas of anyons through second order in the anyon coupling constant, as described
by Chern-Simons field theory.Comment: 10 pages, PlainTex with macro 'manumac', include
Comprehensive learning incorporating Ako – a tertiary education approach at Wintec
This article outlines the design and implementation of a scenario-based approach to teaching and learning in tertiary education, inspired from Ako, adopted at the Waikato Institute of Technology (Wintec). This learning approach, titled ‘Comprehensive Learning (CL)’, aligns with the holistic objective of enabling students with an active, flexible, personalised, authentic and practical approach to learning that builds upon students’ interests and experiences. The article explains the motivation and the process used in creating and applying this approach to teach some of the IT and Business modules. The main reason to implement this approach is to encourage/enable critical thinking while learning in a continuous and personalised manner. CL allows students to specialize in a context of their choice, which in turn induces learning. In addition, students are less motivated to plagiarize due to the unique nature of their scenarios, and inherent safeguards present within the approach
Comprehensive learning incorporating Ako: A tertiary education approach at Wintec
This article outlines the design and implementation of a scenario-based approach to teaching and learning in tertiary education, inspired from Ako, adopted at the Waikato Institute of Technology (Wintec). This learning approach, titled ‘Comprehensive Learning (CL)’, aligns with the holistic objective of enabling students with an active, flexible, personalised, authentic and practical approach to learning that builds upon students’ interests and experiences. The article explains the motivation and the process used in creating and applying this approach to teach some of the IT and Business modules. The main reason to implement this approach is to encourage/enable critical thinking while learning in a continuous and personalised manner. CL allows students to specialize in a context of their choice, which in turn induces learning. In addition, students are less motivated to plagiarize due to the unique nature of their scenarios, and inherent safeguards present within the approach
Two populations of progenitors for type Ia SNe?
We use recent observations of type Ia Supernova (SN Ia) rates to derive, on
robust empirical grounds, the distribution of the delay time (DTD) between the
formation of the progenitor star and its explosion as a SN. Our analysis finds:
i) delay times as long as 3-4 Gyr, derived from observations of SNe Ia at high
redshift, cannot reproduce the dependence of the SN Ia rate on the colors and
on the radio-luminosity of the parent galaxies, as observed in the local
Universe; ii) the comparison between observed SN rates and a grid of
theoretical "single-population" DTDs shows that only a few of them are possibly
consistent with observations. The most successful models are all predicting a
peak of SN explosions soon after star formation and an extended tail in the
DTD, and can reproduce the data but only at a modest statistical confidence
level; iii) present data are best matched by a bimodal DTD, in which about 50%
of type Ia SNe (dubbed "prompt" SN Ia) explode soon after their stellar birth,
in a time of the order of 10^8 years, while the remaining 50% ("tardy" SN Ia)
have a much wider distribution, well described by an exponential function with
a decay time of about 3 Gyr. This fact, coupled with the well established
bimodal distribution of the decay rate, suggests the existence of two classes
of progenitors. We discuss the cosmological implications of this result and
make simple predictions. [Abridged]Comment: 11 pages, MNRAS, in press, modified after referee's comment
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