| 1. |
- Ahmad, Shakeel, 1977-
(författare)
-
Stimuli Generation Techniques for On-Chip Mixed-Signal Test
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With increased complexity of the contemporary very large integrated circuits the need for onchip test addressing not only the digital but also analog and mixed-signal RF blocks has emerged. The standard production test has become more costly and the instrumentation is pushed to its limits by the leading edge integrated circuit technologies. Also the chip performance for high frequency operation and the area overhead appear a hindrance in terms of the test access points needed for the instrumentation-based test. To overcome these problems, test implemented on a chip can be used by sharing the available resources such as digital signal processing (DSP) and A/D, D/A converters to constitute a built-in-self-test. In this case, the DSP can serve both as a stimuli generator and response analyzer.Arbitrary test signals can be achieved using DSP. Specifically, the ΣΔ modulation technique implemented in software is useful to encode a single- or two-tone stimulus as a onebit sequence to generate a spectrally pure signal with a high dynamic range. The sequence can be stored in a cyclic memory on a chip and applied to the circuit under test using a buffer and a simple reconstruction filter. In this way ADC dynamic test for harmonic and intermodulation distortion is carried out in a simple setup. The FFT artifacts are avoided by careful frequency planning for low-pass and band-pass ΣΔ encoding technique. A noise shaping based on a combination of low- and band-pass ΣΔ modulation is also useful providing a high dynamic range for measurements at high frequencies that is a new approach. However, a possible asymmetry between rise and fall time due to CMOS process variations in the driving buffer results in nonlinear distortion and increased noise at low frequencies. A simple iterative predistortion technique is used to reduce the low frequency distortion components by making use of an on-chip DC calibrated ADC that is another contribution of the author.Some tests, however, like the two-tone RF test that targets linearity performance of a radio receiver, require test stimuli based on a dedicated hardware. For the measurement of the thirdor second-intercept point (IP3/IP2) a spectrally clean stimulus is essential. Specifically, the second- or third-order harmonic or intermodulation products of the stimulus generator should be avoided as they can obscure the test measurement. A challenge in this design is the phase noise performance and spurious tones of the oscillators, and also the distortion-free addition of the two tones. The mutual pulling effect can be minimized by layout isolation techniques.A new two-tone RF generator based on a specialized phase-locked loop (PLL) architecture is presented as a viable solution for IP3/IP2 on-chip test. The PLL provides control over the frequency spacing of two voltage controlled oscillators. For the two-tone stimulus a highly linear analog adder is designed to limit distortion which could obscure the IP3 test. A specialized feedback circuit in the PLL is proposed to overcome interference by the reference spurs. The circuit is designed using 65 nm CMOS process. By using a fine spectral resolution the observed noise floor can be reduced to enable the measurement of second- or third-order intermodulation product tones. This also reflects a tradeoff between the test time and the test performance. While the test time to collect the required number of samples can be of milliseconds the number of samples need not be excessive, since the measurements are carried out at the receiver baseband, where the required sampling frequency is relatively low.
|
|
| 2. |
- Ahmad, Shafqat, et al.
(författare)
-
Telomere length in blood and skeletal muscle in relation to measures of glycaemia and insulinaemia.
- 2012
-
Ingår i: Diabetic Medicine: A journal of the British Diabetic Association. - : Wiley. - 1464-5491 .- 0742-3071. ; 29:10, s. 377-381
-
Tidskriftsartikel (refereegranskat)abstract
- Aims: Skeletal muscle is a major metabolic organ and plays important roles in glucose metabolism, insulin sensitivity and insulin action. Muscle telomere length reflects the myocyte's exposure to harmful environmental factors. Leukocyte telomere length is considered a marker of muscle telomere length and is used in epidemiologic studies to assess associations with ageing-related diseases where muscle physiology is important. However, the extent to which leucocyte and muscle telomere length are correlated is unknown, as are their relative correlations with glucose and insulin concentrations. The purpose of this study was to determine the extent of these relationships. Methods: Leucocyte and muscle telomere length were measured by quantitative real-time polymerase chain reaction in participants from the Malmö Exercise Intervention (n = 27) and the Prevalence, Prediction and Prevention of Diabetes-Botnia studies (n = 31). Participants in both studies were free from Type 2 diabetes. We assessed the association between leucocyte telomere length, muscle telomere length and metabolic traits using Spearmen correlations and multivariate linear regression. Bland-Altman analysis was used to assess agreement between leucocyte and muscle telomere length. Results: In age-, study-, diabetes family history- and sex-adjusted models, leucocyte and muscle telomere length were positively correlated (r = 0.39, 95% CI 0.15-0.59). Leucocyte telomere length was inversely associated with 2-h glucose concentrations (r = -0.58, 95% CI -1.0 to -0.16), but there was no correlation between muscle telomere length and 2-h glucose concentrations (r = 0.05, 95% CI -0.35 to 0.46) or between leucocyte or muscle telomere length with other metabolic traits. Conclusions: In summary, the current study supports the use of leucocyte telomere length as a proxy for muscle telomere length in epidemiological studies of Type 2 diabetes aetiology.
|
|
| 3. |
|
|
| 4. |
- Vilela, Jéssyka Flavyanne Ferreira, et al.
(författare)
-
Safety Practices in Requirements Engineering : The Uni-REPM Safety Module
- 2020
-
Ingår i: IEEE Transactions on Software Engineering. - : Institute of Electrical and Electronics Engineers Inc.. - 0098-5589 .- 1939-3520. ; 46:3, s. 222-250
-
Tidskriftsartikel (refereegranskat)abstract
- Context: Software is an important part in safety- critical system (SCS) development since it is becoming a major source of hazards. Requirements-related hazards have been as- sociated with many accidents and safety incidents. Requirements issues tend to be mitigated in companies with high processes maturity levels since they do their business in a systematic, consistent and proactive approach. However, requirements en- gineers need systematic guidance to consider safety concerns early in the development process. Goal: the paper investigates which safety practices are suitable to be used in the Requirements Engineering (RE) process for SCS and how to design a safety maturity model for this area. Method: we followed the design science methodology to propose Uni-REPM SCS, a safety module for Unified Requirements Engineering Process Maturity Model (Uni-REPM). We also conducted a static validation with two practitioners and nine academic experts to evaluate its coverage, correctness, usefulness and applicability. Results: The module has seven main processes, fourteen sub-processes and 148 practices that form the basis of safety processes maturity. Moreover, we describe its usage through a tool. Conclusions: The validation indicates a good coverage of practices and well receptivity by the experts. Finally, the module can help companies in evaluating their current practices. IEEE
|
|
| 5. |
- Savitski, Dzmitry, et al.
(författare)
-
Advanced Control Functions Of Decoupled Electro-Hydraulic Brake System
- 2016
-
Ingår i: 2016 IEEE 14TH INTERNATIONAL WORKSHOP ON ADVANCED MOTION CONTROL (AMC). - : IEEE. - 9781479984640 ; , s. 310-317
-
Konferensbidrag (refereegranskat)abstract
- The paper presents results of analytical and experimental investigations on advanced control functions of decoupled electro-hydraulic brake system. These functions address continuous wheel slip control, variation of the brake pedal feel, and brake judder compensation. The performed study demonstrates that the electro-hydraulic brake system has improved performance by relevant criteria of safety and driving comfort both for conventional and electric vehicles.
|
|
| 6. |
- Maivorsdotter, Ninitha, 1966-, et al.
(författare)
-
The act of running : a practical epistemology analysis of aesthetic experience in sport
- 2012
-
Ingår i: Qualitative Research in Sport, Exercise and Health. - Oxon, United Kingdom : Routledge. - 2159-676X .- 2159-6778. ; 4:3, s. 362-381
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to explore aesthetic experiences in sport and how people – in this case a marathon runner – are ‘bodying’ the world aesthetically as part of their participation in sport. Aesthetic experiences in sport are mostly lived through the senses of the body, and even if there is a need to focus on people making sense of bodily movements, there is still the problem of transforming bodily movements and aesthetic experiences into words. In order to try to bridge this gap we suggest that a professional author could have tools for fruitfully articulation of non-linguistic aspects of corporeal existence in words. We therefore use a memoir What I talk about when I talk about running, written by the author and marathon runner Haruki Murakami, as empirical data in order to explore aesthetic experiences in sport through narratives of what we term aesthetic events. Using a practical epistemology analysis (PEA), a tool developed for analyzing meaning making and learning, the study shows that aesthetic experiences during the act of running involve different ways of ‘bodying’ the world in transaction. The major theme is moving and the importance of keeping moving and the two minor themes are moving across a race and moving along the continuum of physical capacity. The study shows how aesthetic experiences play a part of meaning-making and in fulfilling the purposes of running. The study accordingly contributes to a discussion about meaning-making in sport in a non-dualistic manner where emotional aspects of experiences can be taken into account.
|
|
| 7. |
|
|
| 8. |
- Vilela de Abreu, Rodrigo, et al.
(författare)
-
Computation of Aeroacoustic Sources for a Gulfstream G550 Nose Landing Gear Model Using Adaptive FEM
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This work is a direct comparison of our unsteady, turbulent flow simulations with measurements performed using a Gulfstream G550 Nose Landing Gear Model. The experimental campaign, which was carried out by researchers from the NASA Langley Research Center, provided a series of detailed, well documented wind-tunnel measurements for comparison and validation of computational fluid dynamics (CFD) and computational aeroacoustics (CAA) methodologies. Several computational efforts were collected and presented at the Benchmark for Airframe Noise Computation workshops, BANC-I and II. For our simulations, we used a General Galerkin finite element method (G2), where no explicit subgrid model is used, and where the computational mesh is adaptively refined with respect to a posteriori error estimates for a quantity of interest. The mesh is fully unstructured and the solutions are time-resolved, which are key ingredients for solving relevant, industrial applications in the field of aeroacoustics. The comparisons presented here are an attempt to quantify the accuracy of our models, methods and assumptions, and the results, although not perfect, are of relevant quantitative quality. We present several results containing both time-averaged and unsteady flow quantities, always side by side with its corresponding experimental values. The main finding is that we are able to simulate such a complex, unsteady flow problem as the flow past a nose landing gear using a parameter-free methodology for high Reynolds numbers (Re), external aerodynamics and aeroacoustics applications.
|
|
| 9. |
- Botta, Nicola, 1961, et al.
(författare)
-
Extensional equality preservation and verified generic programming
- 2021
-
Ingår i: Journal of Functional Programming. - 1469-7653 .- 0956-7968. ; 31
-
Tidskriftsartikel (refereegranskat)abstract
- In verified generic programming, one cannot exploit the structure of concrete data types but has to rely on well chosen sets of specifications or abstract data types (ADTs). Functors and monads are at the core of many applications of functional programming. This raises the question of what useful ADTs for verified functors and monads could look like. The functorial map of many important monads preserves extensional equality. For instance, if f, g : A → B are extensionally equal, that is, ∀x ∈ A, f x = g x , then map f : List A → List B and map g are also extensionally equal. This suggests that preservation of extensional equality could be a useful principle in verified generic programming. We explore this possibility with a minimalist approach: we deal with (the lack of) extensional equality in Martin-Löf’s intensional type theories without extending the theories or using full-fledged setoids. Perhaps surprisingly, this minimal approach turns out to be extremely useful. It allows one to derive simple generic proofs of monadic laws but also verified, generic results in dynamical systems and control theory. In turn, these results avoid tedious code duplication and ad-hoc proofs. Thus, our work is a contribution towards pragmatic, verified generic programming.
|
|
| 10. |
- Brown, C.L, et al.
(författare)
-
Social Activity and Cognitive Functioning Over Time
- 2012
-
Ingår i: Journal of Aging Research. - : Hindawi Limited. - 2090-2204 .- 2090-2212.
-
Tidskriftsartikel (refereegranskat)abstract
- Social activity is typically viewed as part of an engaged lifestyle that may help mitigate the deleterious effects of advanced age on cognitive function. As such, social activity has been examined in relation to cognitive abilities later in life. However, longitudinal evidence for this hypothesis thus far remains inconclusive. The current study sought to clarify the relationship between social activity and cognitive function over time using a coordinated data analysis approach across four longitudinal studies. A series of multilevel growth models with social activity included as a covariate is presented. Four domains of cognitive function were assessed: reasoning, memory, fluency, and semantic knowledge. Results suggest that baseline social activity is related to some, but not all, cognitive functions. Baseline social activity levels failed to predict rate of decline in most cognitive abilities. Changes in social activity were not consistently associated with cognitive functioning. Our findings do not provide consistent evidence that changes in social activity correspond to immediate benefits in cognitive functioning, except perhaps for verbal fluency.
|
|
