1,409 research outputs found
LF : a language for reliable embedded systems
Thesis (MSc)--University of Stellenbosch, 2001.ENGLISH ABSTRACT: Computer-aided verification techniques, such as model checking, are often considered essential
to produce highly reliable software systems. Modern model checkers generally require models to
be written in eSP-like notations. Unfortunately, such systems are usually implemented using
conventional imperative programming languages. Translating the one paradigm into the other is
a difficult and error prone process.
If one were to program in a process-oriented language from the outset, the chasm between implementation
and model could be bridged more readily. This would lead to more accurate models
and ultimately more reliable software.
This thesis covers the definition of a process-oriented language targeted specifically towards embedded
systems and the implementation of a suitable compiler and run-time system.
The language, LF, is for the most part an extension of the language Joyce, which was defined by
Brinch Hansen. Both LF and Joyce have features which I believe make them easier to use than
other esp based languages such as occam. An example of this is a selective communication
primitive which allows for both input and output guards which is not supported in occam.
The efficiency of the implementation is important. The language was therefore designed to be
expressive, but constructs which are expensive to implement were avoided. Security, however, was
the overriding consideration in the design of the language and runtime system.
The compiler produces native code. Most other esp derived languages are either interpreted or
execute as tasks on host operating systems. Arguably this is because most implementations of
esp and derivations thereof are for academic purposes only. LF is intended to be an implementation
language.
The performance of the implementation is evaluated in terms of practical metries such as the
time needed to complete communication operations and the average time needed to service an
interrupt.AFRIKAANSE OPSOMMING: Rekenaar ondersteunde verifikasietegnieke soos programmodellering, is onontbeerlik in die ontwikkeling
van hoogs betroubare programmatuur. In die algemeen, aanvaar programme wat modelle
toets eSP-agtige notasie as toevoer. Die meeste programme word egter in meer konvensionele
imperatiewe programmeertale ontwikkel. Die vertaling vanuit die een paradigma na die ander is
'n moelike proses, wat baie ruimte laat vir foute.
Indien daar uit die staanspoor in 'n proses gebaseerde taal geprogrammeer word, sou die verwydering
tussen model en program makliker oorbrug kon word. Dit lei tot akkurater modelle en
uiteindelik tot betroubaarder programmatuur.
Die tesis ondersoek die definisie van 'n proses gebaseerde taal, wat gemik is op ingebedde programmatuur.
Verder word die implementasie van 'n toepaslike vertaler en looptyd omgewing ook
bespreek.
Die taal, LF, is grotendeels gebaseer op Joyce, wat deur Brinch Hansen ontwikkel is. Joyce en op
sy beurt LF, is verbeterings op ander esp verwante tale soos occam. 'n Voorbeeld hiervan is 'n
selektiewe kommunikasieprimitief wat die gebruik van beide toevoer- en afvoerwagte ondersteun.
Omdat 'n effektiewe implementasie nagestreef word, is die taalontwerp om so nadruklik moontlik
te wees, sonder om strukture in te sluit wat oneffektief is om te implementeer. Sekuriteit was egter
die oorheersende oorweging in die ontwerp van die taal en looptyd omgewing.
Die vertaler lewer masjienkode, terwyl die meeste ander implementasies van eSP-agtige tale
geinterpreteer word of ondersteun word as prosesse op 'n geskikte bedryfstelsel- die meeste
eSP-agtige tale word slegs vir akademiese doeleindes aangewend. LF is by uitstek ontwerp
as implementasie taal.
Die evaluasie van die stelsel se werkverrigting is gedoen aan die hand van praktiese maatstawwe
soos die tyd wat benodig word vir kommunikasie, sowel as die gemiddelde tyd benodig vir die
hantering van onderbrekings
Consumer & Behaviour Group on track? Food choice research at the LEI Consumer & Behaviour group benchmarked against international literature
Intraoperative arthroscopic classification tool for posterolateral elbow instability
Background: Introducing and implementing an arthroscopic classification tool for posterolateral elbow instability. Methods: Thirty arthroscopies were performed on 30 patients, and all recordings were collected, blinded, and labeled. Three orthopedic surgeons reviewed and scored all 30 recordings three times with a period of at least seven days in between to analyze the intraobserver and interobserver reliability. The classification consisted of five different grades. Results: Indications for elbow arthroscopy included impingement (n = 7), osteochondritis dissecans (n = 5), pain (n = 7), osteoarthritis (n = 6), and other (n = 5). The kappa value for intrarater reliability was 0.71, indicating good reliability, while the kappa value for inter-rater reliability was 0.38 indicating fair reliability. Conclusion: This new classification is a tool for an arthroscopic assessment of PLRI and can be used as a standardized grading system for further research and communication between orthopedic surgeons. We demonstrated good intrarater reliability (k = 0.71) with fair inter-rater reliability (k = 0.38). However, further research is necessary to study the clinical significance.</p
The incidence of associated fractures of the upper limb in fractures of the radial head
Radial head fractures are common injuries. In American publications, one-third of the patients with these fractures have been shown to have associated injuries. The aim of this retrospective study is to describe the epidemiology of radial head fractures and associated fractures of the ipsilateral upper extremity in a European population. This study describes the epidemiology of radial head and associated fractures of the upper extremity in a Dutch population by a retrospective radiographic review of all patients with a radial head fracture between 1 January 2006 and 1 July 2007. A total of 147 radial head fractures were diagnosed in 145 patients. The incidence in the general population was 2.5 per 10.000 per year. The average age was 45.9 (SD 17.3) years and male–female ratio was 2:3. The mean age of males was significantly lower (37.1, SD 14.2 years) than of women (53.9, SD 16.4 years). Associated fracture of the upper extremity was found in 10.2%. Coronoid fractures were most common (4.1%). Associated upper limb fractures in patients with a radial head fracture are common in the European population. It is of clinical importance to suspect associated lesions and to perform a thorough physical examination and additional radiological examination on demand
Dynamics of Generalized Assisted Inflation
We study the dynamics of multiple scalar fields and a barotropic fluid in an
FLRW-universe. The scalar potential is a sum of exponentials. All critical
points are constructed and these include scaling and de Sitter solutions. A
stability analysis of the critical points is performed for generalized assisted
inflation, which is an extension of assisted inflation where the fields
mutually interact. Effects in generalized assisted inflation which differ from
assisted inflation are emphasized. One such a difference is that an
(inflationary) attractor can exist if some of the exponential terms in the
potential are negative.Comment: 27 page
Influence of morphology on photoluminescence properties of methylammonium lead tribromide films
The morphology of hybrid perovskite thin films plays a crucial role for their photophysical properties. However, the underlying mechanisms are still unclear. To gain further insight into this phenomenon, methylammonium lead tribromide films of different morphology were investigated using photoluminescence spectroscopy. Photostability measurements demonstrate three mechanisms: (A) reversible degradation of the photoluminescence, depending positively on the grain-boundary density, which is presumably caused by photo-induced bromide vacancies, (B) enhancement of the photoluminescence intensity in the presence of oxygen and moisture and (C) destruction of the perovskite after several minutes of ultraviolet illumination with excitation power above 100 W/cm(2). Both the intensity and the lifetime of the photoluminescence were significantly smaller in films with micrometer-sized crystallites compared to granular films. This is ascribed to crystals being partially isolated in the former, causing smaller diffusion lengths, whereas the carriers in the granular films can diffuse from grain to grain resulting in higher photoluminescence lifetime and intensity
Precision, comfort and mechanical performance of the Quadriso-tester, a quadriceps force measuring device
Precision, comfort and mechanical performance of the Quadriso-tester, a quadriceps force measuring device
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