14,765 research outputs found
Building on CHASM: A Study of Using Counts for the Analysis of Static Models of Processes
Process modelling is gaining increasing acceptance by software engineers as a useful discipline to facilitate both process understanding and improvement activities. This position paper builds upon previous work reported at the 1997 ICSE workshop on process models and empirical studies of software engineering (Phalp and Counsell 1997). In the previous paper, we argued that simple counts could be used to support analysis of static process models. We also illustrated the idea with a coupling measure for Role Activity Diagrams, a graphical process modelling notation adapted from Petri Nets. At that time only limited empirical work had been carried out, based upon a single industrial study, where we found high levels of coupling in an inefficient process (a more thorough description may be found in (Phalp and Shepperd 1999)). We now summarise a more recent study, which uses a similar analysis of process coupling again based on simple counts. In the study, we compared ten software prototyping processes drawn from eight different organisations. We found that this approach does yield insights into process problems, which could potentially be missed by qualitative analysis alone. This is particularly so when analysing real world processes, which are frequently more complex than their text book counterparts. One notable finding was that despite differences in size and domain, role types across the organisations exhibited similar levels of coupling. Furthermore, where there were deviations in one particular role type, this led the authors to discover a relationship between project size and the coupling levels within that type of role. Given the simplicity of our approach and the complexity of many real world processes we argue that quantitative analysis of process models should be considered as a process analysis technique
Analysing Process Models Quantitatively
Over the years, there has been much interest in modelling processes. Processes include those associated with the development of software and those business processes that make use of software systems. Recent research in Systems Engineering for Business Process Change highlights the importance of modelling business processes in order to evolve and maintain the legacy systems that support those processes. Business processes are typically described with static (diagrammatic) models. This paper illustrates how quantitative techniques can facilitate analysis of such models. This is illustrated with reference to the process modelling notation Role Activity Diagrams (RADs). An example process, taken from an investigation of the bidding process of a large telecommunications systems supplier, is used to show how a quantitative approach can be used to highlight features in RADs that are useful to the process modeller. We show how simple measures reveal high levels of role coupling and discrepancies between different perspectives. Since the models are non-trivial — there are 101 roles and almost 300 activities — we argue that quantitative analysis can be a useful adjunct for the modeller
Chebyshev constants for the unit circle
It is proven that for any system of n points z_1, ..., z_n on the (complex)
unit circle, there exists another point z of norm 1, such that
Equality holds iff the point system is a
rotated copy of the nth unit roots.
Two proofs are presented: one uses a characterisation of equioscillating
rational functions, while the other is based on Bernstein's inequality.Comment: 11 page
Ferroelectric Materials for Solar Energy Conversion: Photoferroics Revisited
The application of ferroelectric materials (i.e. solids that exhibit
spontaneous electric polarisation) in solar cells has a long and controversial
history. This includes the first observations of the anomalous photovoltaic
effect (APE) and the bulk photovoltaic effect (BPE). The recent successful
application of inorganic and hybrid perovskite structured materials (e.g.
BiFeO3, CsSnI3, CH3NH3PbI3) in solar cells emphasises that polar semiconductors
can be used in conventional photovoltaic architectures. We review developments
in this field, with a particular emphasis on the materials known to display the
APE/BPE (e.g. ZnS, CdTe, SbSI), and the theoretical explanation. Critical
analysis is complemented with first-principles calculation of the underlying
electronic structure. In addition to discussing the implications of a
ferroelectric absorber layer, and the solid state theory of polarisation (Berry
phase analysis), design principles and opportunities for high-efficiency
ferroelectric photovoltaics are presented
Using Counts as Heuristics for the Analysis of Static Models
The upstream activities of software development are often viewed as both the most
important, in terms of cost, and the yet the least understood, and most problematic, particularly in terms of satisfying customer requirements. Business process modelling is
one solution that is being increasingly used in conjunction with traditional software
development, often feeding in to requirements and analysis activities. In addition,
research in Systems Engineering for Business Process Change, highlights the importance
of modelling business processes in evolving and maintaining the legacy systems that
support those processes. However, the major use of business process modelling, is to
attempt to restructure the business process, in order to improve some given aspect, e.g.,
cost or time. This restructuring may be seen either as separate activity or as a pre-cursor
to the development of systems to support the new or improved process. Hence, the
analysis of these business models is vital to the improvement of the process, and as a
consequence to the development of supporting software systems. Supporting this analysis
is the focus of this paper.
Business processes are typically described with static (diagrammatic) models. This paper
proposes the use of measures (counts) to aid analysis and comparison of these static
process descriptions. The proposition is illustrated by showing how measures can be
applied to a commonly used process-modelling notation, Role Activity Diagrams (RADs).
Heuristics for RADs are described and measures suggested which support those
heuristics. An example process is used to show how a coupling measure can be used to
highlight features in RADs useful to the process modeller.
To fully illustrate the proposition the paper describes and applies a framework for the
theoretical validation of the coupling measure. An empirical evaluation follows. This is
illustrated by two case studies; the first based on the bidding process of a large
telecommunications systems supplier, and the second a study of ten prototyping processes
across a number of organisations.
These studies found that roles of the same type exhibited similar levels of coupling across
processes. Where roles did not adhere to tentative threshold values, further investigation
revealed unusual circumstances or hidden behaviour. Notably, study of the prototyping
roles, which exhibited the greatest variation in coupling, found that coupling was highly
correlated with the size of the development team. This suggests that prototyping in large
projects had a different process to that for small projects, using more mechanisms for
communication. Hence, the empirical studies support the view that counts (measures)
may be useful in the analysis of static process models
Reciprocal intronic and exonic histone modification regions in humans.
While much attention has been focused on chromatin at promoters and exons, human genes are mostly composed of intronic sequences. Analyzing published surveys of nucleosomes and 41 chromatin marks in humans, we identified histone modifications specifically associated with 5' intronic sequences, distinguishable from promoter marks and bulk nucleosomes. These intronic marks were spatially reciprocal to trimethylated histone H3 Lys36 (H3K36me3), typically transitioning near internal exons. Several marks transitioned near bona fide exons, but not near nucleosomes at exon-like sequences. Therefore, we examined whether splicing affects histone marking. Even with considerable changes in regulated alternative splicing, histone marks were stable. Notably, these findings are consistent with exon definition influencing histone marks. In summary, we show that the location of many intragenic marks in humans can be distilled into a simple organizing principle: association with 5' intronic or 3' exonic regions
Efficient optimisation of structures using tabu search
This paper presents a novel approach to the optimisation of structures using
a Tabu search (TS) method. TS is a metaheuristic which is used to guide local
search methods towards a globally optimal solution by using flexible memory
cycles of differing time spans. Results are presented for the well established
ten bar truss problem and compared to results published in the literature. In
the first example a truss is optimised to minimise mass and the results
compared to results obtained using an alternative TS implementation. In the
second example, the problem has multiple objectives that are compounded into a
single objective function value using game theory. In general the results
demonstrate that the TS method is capable of solving structural optimisation
problems at least as efficiently as other numerical optimisation approaches
Oxidative Stress Response to Short Duration Bout of Submaximal Aerobic Exercise in Healthy Young Adults
The purpose of this study was to investigate the oxidative stress response to a short duration bout of submaximal exercise in a cohort of healthy young adults. 15 apparently healthy college age males and females completed a modified Bruce-protocol treadmill test to 75–80% of their heart rate reserve. Blood samples collected immediately before (pre-exercise), immediately after, 30, 60 and 120 minutes post-exercise were assayed for total antioxidant capacity (TAC), superoxide disumutase (SOD), thiobarbituric acid-reactive substances (TBARS), and protein carbonyls (PC). SOD activity was significantly increased from pre-exercise levels at 30 minutes (77%), 60 minutes (33%), and 120 minutes (37%) post-exercise. TAC levels were also significantly increased from pre-exercise levels at 60 minutes (30%) and 120 minutes (33%) post-exercise. There were no significant changes in biomarkers for reactive oxygen/nitrogen species (RONS) mediated damage (TBARS and PC) across all post-exercise time points. In a cohort of healthy young adults, a short duration bout of submaximal aerobic exercise elicited increases in antioxidant activity/concentration, but did not evoke changes in oxidative stress-induced damage. These results may suggest that: (1) short duration bouts of submaximal aerobic exercise are sufficient to induce RONS generation; and (2) the antioxidant defense system is capable of protecting against enhanced RONS production induced by a short duration, submaximal exercise bout in healthy young adults
Trispectrum versus Bispectrum in Single-Field Inflation
In the standard slow-roll inflationary cosmology, quantum fluctuations in a
single field, the inflaton, generate approximately Gaussian primordial density
perturbations. At present, the bispectrum and trispectrum of the density
perturbations have not been observed and the probability distribution for these
perturbations is consistent with Gaussianity. However, Planck satellite data
will bring a new level of precision to bear on this issue, and it is possible
that evidence for non-Gaussian effects in the primordial distribution will be
discovered. One possibility is that a trispectrum will be observed without
evidence for a non-zero bispectrum. It is not difficult for this to occur in
inflationary models where quantum fluctuations in a field other than the
inflaton contribute to the density perturbations. A natural question to ask is
whether such an observation would rule out the standard scenarios. We explore
this issue and find that it is possible to construct single-field models in
which inflaton-generated primordial density perturbations have an observable
trispectrum, but a bispectrum that is too small to be observed by the Planck
satellite. However, an awkward fine tuning seems to be unavoidable.Comment: 15 pages, 3 figures; journal versio
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