Design of a WCET-Aware C Compiler

This paper presents techniques to tightly integrate worst-case execution time information into a compiler framework. Currently, a tight integration of WCET information into the compilation process is strongly desired, but only some ad-hoc approaches have been reported currently. Previous publications mainly used self-written WCET estimators with very limited functionality and preciseness during compilation. A very tight integration of a high quality industry-relevant WCET analyzer into a compiler was not yet achieved up to now. This work is the first to present techniques capable of achieving such a tight coupling between a compiler and the WCET analyzer aiT. This is done by automatically translating the assembly-like contents of the compiler\u27s low-level intermediate representation (LLIR) to aiT\u27s exchange format CRL2. Additionally, the results produced by the WCET analyzer are automatically collected and re-imported into the compiler infrastructure. The work described in this paper is smoothly integrated into a C compiler environment for the Infineon TriCore processor. It opens up new possibilities for the design of WCET-aware optimizations in the future. The concepts for extending the compiler infrastructure are kept very general so that they are not limited to WCET information. Rather, it is possible to use our structures also for multi-objective optimization of e.g. best-case execution time (BCET) or energy dissipation

Multi-core Interference-Sensitive WCET Analysis Leveraging Runtime Resource Capacity Enforcement

The performance and power efficiency of multi-core processors are attractive features for safety-critical applications, as in avionics. But increased integration and average-case performance optimizations pose challenges when deploying them for such domains. In this paper we propose a novel approach to compute a interference-sensitive Worst-Case Execution Time (isWCET) considering variable accesses delays due to the concurrent use of shared resources in multi-core processors. Thereby we tackle the problem of temporal partitioning as it is required by safety-critical applications. In particular, we introduce additional phases to state-of-the-art timing analysis techniques to analyse an applications resource usage and compute an interference delay. We further complement the offline analysis with a runtime monitoring concept to enforce resource usage guarantees. The concepts are evaluated on Freescale's P4080 multi-core processor in combination with SYSGO's commercial real-time operating system PikeOS and AbsInt's timing analysis framework aiT. We abstract real applications' behavior using a representative task set of the EEMBC Autobench benchmark suite. Our results show a reduction of up to 75% of the multi-core Worst-Case Execution Time (WCET), while implementing full transparency to the temporal and functional behavior of applications, enabling the seamless integration of legacy applications

Kinetics of rapid covalent bond formation of aniline with humic acid: ESR investigations with nitroxide spin labels

ABSTRACT The bioavailability of many soil contaminants depends on their interaction with the soil organic matter. The paper presents a new approach of using stable paramagnetic spin labels for investigating the kinetics of covalent binding of specific xenobiotic functional groups with humic acids, a major organic matter fraction. Leonardite humic acid (LHA) was incubated with the nitroxide spin labels amino-TEMPO (4-amino-2,2,6,6-Tetramethylpiperidin-1-oxyl) and anilino-NO (2,5,5-Trimethyl-2-(3-aminophenyl)pyrrolidin-1-oxyl), respectively, which contain an aliphatic or aromatic functionality susceptible to interaction with LHA. Electron spin resonance (ESR) spectra of LHA samples without and with the enzyme laccase were recorded at X-band frequency (9.43 GHz) at room temperature and neutral pH. Binding was detected by a pronounced broadening of the spectral lines after incubation of LHA for both spin labels. The development of a broad signal component in the spectrum of anilino-NO indicated the immobilization due to strong binding of the aniline group. The reorientational correlation time of bound anilino-NO is more than two orders of magnitude greater than that of the free label. The ratio of the amount of bound to the unbound species was used to determine the kinetics of the covalent bond formation. Reaction rate constants of 0.16 min-1 and 0.01 min-1 were determined corresponding to half-times of 4.3 min and 69.3 min, respectively. Treatment of LHA with laccase enhanced the amount of the reacting anilino-NO species by a factor of 7.6, but left the reaction rate unaltered. Oxidative radical coupling was excluded by using the spin trap agent n-tert-butyl-alpha-phenylnitrone

Observations of Very High Energy Gamma-Ray Emission from Supernova Remnants with VERITAS

The nature and source of cosmic rays has been at the core of particle astrophysics since their discovery almost a century ago. The cosmic ray spectrum is best described by a broken power law, and can be better understood as three distinct parts. Theory holds that cosmic rays up to ∼1015 eV – those below the “knee” or steepening in the spectrum – are produced in the shocks of supernova remnants. Direct detection of cosmic rays produced in supernova remnant shocks is impossible, however, as cosmic rays below ∼1018 eV are deflected by the Galactic magnetic field and cannot be traced back to their origins. If high energy hadrons are produced within the immediate environment of a supernova remnant, collisions will occur within the surrounding medium. As a result, pion production and subsequent decay will give rise to very high energy gamma rays (E\u3e100 GeV). Since these gamma rays will not interact with any magnetic field, they can be traced back to their point of origin. Thus, Atmospheric Cherenkov Detectors like VERITAS, which have the capability to detect very high energy gamma rays via their interaction with our atmosphere, provide us the means of directly testing the theory of the origin of cosmic rays in supernova remnants. Observations of 13 supernovae made with the VERITAS instrument are presented herein, including 5 individually targeted remnants and 8 remnants within the VERITAS Cygnus region Sky Survey. The observations provide detections of two known VHE remnants (Cassiopeia A and the Crab Nebula), and meaningful flux limits on the remainder. Comparison of these results to both hadronic- and leptonic-origin emission models is carried out

Orbital-scale fluctuations in continental weathering flux and continental ice-volume during greenhouse and icehouse climate intervals : evidence from oxygen and neodymium isotopes

Rapid changes in global and local climate and weather, noticeable over our lifetimes, have spurred heated public and political debate over the cause of these climatic changes, whether or not we can reverse, stop or slow down this process, and how to create adequate models that can predict Earth\u27s changing climate. To create the most accurate models of future climate, many researchers look to past greenhouse intervals for insight; intervals of time identified by high modeled atmospheric CO2, a lack of glacial deposits, and geologic evidence of globally high sea-levels--all of which suggest little to no glacial ice and a relatively monotonous climate. However, recent stratigraphic and geochemical evidence from the Cretaceous \u27supergreenhouse\u27 interval document compelling evidence to support dynamic greenhouse climates. The goals of the studies hereafter described are to document and describe orbital-scale (104-105 yr) climate fluctuations recorded by δ18O as a proxy for glacio-eustasy and sea surface temperature and µNd as a proxy for continental weathering and wet/warm or dry/cool climate during two global greenhouse intervals: the Late Silurian and Late Devonian. The first study (Chapter 1) explores whether glacio-eustasy was the driver for orbital-scale shallowing-upward cycles developed in Late Silurian and early Late Devonian tropical and subtropical greenhouse climates. Two intra-cycle δ18O conodont apatite trends were observed: asymmetric trends demonstrating progressive δ18O increases coincident with facies shallowing, or symmetric trends demonstrating initially decreasing, then increasing δ18O values. These isotopic trends and intra-cycle magnitudes support the hypothesis that these cycles developed in response to glacio-eustasy during glacial stages, implying that Late Silurian and Late Devonian greenhouse climates were more dynamic than traditionally assumed. Relationships between orbital-scale continental weathering flux and glacial-interglacial marine cycles was first assessed comparing intra-cycle µNd and δ18O values from Middle Pennsylvanian icehouse cycles (Chapter 2). Observed conodont δ18O trends support previous interpretations that sampled cycles were generated by glacio-eustasy (30-50 m magnitudes) combined with \u3c1° sea surface temperature changes. µNd trends typically demonstrate lower µNd values during interglacial intervals and higher µNd during glacial intervals, supporting claims that increases in precipitation and/or air temperatures during interglacial intervals result in increased continental weathering rates and/or increased flux to marine basins. Using this initial continental weathering flux study and Pleistocene Nd-isotope studies as a model, we tested the phase-relationships of continental weathering flux and sea-level change in Upper Silurian and Upper Devonian greenhouse cycles (Chapter 3). Upper Silurian µNd demonstrates relatively uniform intra-cycle values, due to averaging out of far-field source variations in continental weathering flux, relatively uniform Late Silurian sub-tropical climate, and/or subdued continental weathering and flux due to the absence of upland and inland vascular land plants. Upper Devonian µNd demonstrate greater intra-cycle variation in µNd, which may be due to enhanced chemical weathering as a result of upland and inland colonization of land plants with large root systems and an intensified hydrologic cycle due to evapotranspiration. Observed µNd trends support the hypothesis that these greenhouse cycles record increases and decreases in continental weathering due to increases and decreases in precipitation and/or air temperature. µNd and 147Sm/144Nd values for Upper Silurian and Upper Devonian cycles support previous claims of far-field transport of Caledonian Mountain Belt material via trans-Laurentian fluvial systems

The role of neuropsychological profiles in adult ADHD and ischemic stroke : Implications for clinical practice

This thesis assesses cognitive functions by means of the WAIS-IV in adults with ADHD and in patients with a first-ever unilateral, ischemic stroke in comparison to a control group. In addition, the contribution of self-reports for predicting cognitive functioning in adults with ADHD is evaluated. The results on adults with ADHD reveal deficits in cognitive functions when compared to a control group. Lower performances appear to be robust with respect to comorbidity and medication. No relationship between self-reported symptoms and cognitive performance can be found. With respect to patients with a stroke, it is demonstrated that both right hemisphere stroke (RHS) and left hemisphere stroke (LHS) patients are likely to have significant impairments in all domains of cognitive functions compared to a control group. RHS patients are particularly deficient in measures requiring visuo-spatial abilities and LHS patients in those with language and processing speed demands

Her Journey. Her Way. Understanding the Development of Career Self-efficacy through the Connect Mentoring Program for Women Faculty in STEM: A Case Study

The Connect STEM Mentoring Program aims to provide professional and career connections to women in STEM. As a product of an ADVANCE grant funded by the National Science Foundation, this program strives to promote advancement for women in STEM. As a male- dominated field, women in STEM commonly face barriers to advancement opportunities which can negatively impact a woman’s career self-efficacy. This single-embedded case study seeks to understand how and why, if at all, the Connect STEM Mentoring Program develops career self- efficacy in career advancement for mid-level and senior-level female faculty members. The study investigates faculty members’ participation in a three-component mentoring program including online mentoring training, mentoring relationships between mentees and mentors, and networking luncheons. The findings of the study provided an extension of the literature and discovered the Connect STEM Mentoring Program provides a personal and professional experience that continued to develop participants\u27 self-efficacy for career advancement even after the program concluded. The study is grounded in Social Cognitive Career Theory, an extension of Self-efficacy Theory, as the foundation for inquiry and analysis

Constraints on the kinematics of the 44Ti ejecta of Cassiopeia A from INTEGRAL/SPI

The medium-lived 44Ti isotope is synthesised by explosive Si-burning in core-collapse supernovae. It is extremely sensitive to the dynamics of the explosion and therefore can be used to indirectly probe the explosion scenario. The young supernova remnant Cassiopeia A is to date the only source of gamma-ray lines from 44Ti decay. The emission flux has been measured by CGRO/COMPTEL, BeppoSAX/PDS and INTEGRAL/IBIS. The high-resolution spectrometer SPI on-board the INTEGRAL satellite can provide spectrometric information about the emission. The line profiles reflect the kinematics of the 44Ti in Cassiopeia A and can thus place constraints on its nucleosynthesis and potentially on the associated explosion process. Using 4 years of data from INTEGRAL/SPI, we have searched for the gamma-ray signatures from the decay of the 44Ti isotope. The overwhelming instrumental background noise required an accurate modelling and a solid assessment of the systematic errors in the analysis. Due to the strong variability of the instrumental background noise, it has not been possible to extract the two lines at 67.9 and 78.4keV. Regarding the high-energy line at 1157.0keV, no significant signal is seen in the 1140-1170keV band, thereby suggesting that the line signal from Cassiopeia A is broadened by the Doppler effect. From our spectrum, we derive a ~ 500km/s lower limit at 2sigma on the expansion velocity of the 44Ti ejecta. Our result does not allow us to constrain the location of 44Ti since the velocities involved throughout the remnant, derived from optical and X-ray studies, are all far above our lower limit.Comment: 7 pages, 8 figures, published in A&

Detection of Extended VHE Gamma Ray Emission from G106.3+2.7 with VERITAS

We report the detection of very-high-energy (VHE) gamma-ray emission from supernova remnant (SNR) G106.3+2.7. Observations performed in 2008 with the VERITAS atmospheric Cherenkov gamma-ray telescope resolve extended emission overlapping the elongated radio SNR. The 7.3 sigma (pre-trials) detection has a full angular extent of roughly 0.6deg by 0.4deg. Most notably, the centroid of the VHE emission is centered near the peak of the coincident 12CO (J = 1-0) emission, 0.4deg away from the pulsar PSR J2229+6114, situated at the northern end of the SNR. Evidently the current-epoch particles from the pulsar wind nebula are not participating in the gamma-ray production. The VHE energy spectrum measured with VERITAS is well characterized by a power law dN/dE = N_0(E/3 TeV)^{-G} with a differential index of G = 2.29 +/- 0.33stat +/- 0.30sys and a flux of N_0 = (1.15 +/- 0.27stat +/- 0.35sys)x 10^{-13} cm^{-2} s^{-1} TeV^{-1}. The integral flux above 1 TeV corresponds to ~5 percent of the steady Crab Nebula emission above the same energy. We describe the observations and analysis of the object and briefly discuss the implications of the detection in a multiwavelength context.Comment: 5 pages, 2 figure