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Model validation of an open-source framework for post-processing INS/GNSS systems
No full textThe development of new approaches in the GIS research community may require the use of a computational tool to post-process GNSS and inertial sensors data in order to get more accurate position, velocity, and orientation angles (attitude) information. An open-source framework for simulating integrated navigation systems (INS/GNSS) called NaveGo has been developed using MATLAB/GNU Octave and is freely available on-line. Although preliminary tests have shown that NaveGo appears to work properly, a deep examination must be carried out to confirm that this framework is an adequate tool for post-processing INS/GNSS information. The main goal of this work is to produce a validation methodology to show that NaveGo mathematical model works within its specifications. Firstly, static measurements from inertial sensors are processed and analysed by NaveGo applying the Allan variance for profiling typical errors. Some details of Allan variance procedure are exhibited. Then, performances of NaveGo and Inertial Explorer, a closed-source commercial package software for INS/GNSS integration, are compared for a real-world trajectory. It is statistically concluded that NaveGo presents close accuracy to Inertial Explorer for attitude and position. Consequently, it is demonstrated that NaveGo is an useful INS/GNSS post-processing framework that can be used in GIS applications
RT Level vs. Microarchitecture-Level Reliability Assessment: Case Study on ARM(R) Cortex(R)-A9 CPU
No full textReliability1assessment has always been a major concern in the design of computing systems. The results of the assessment highlight and guide enhancements which trigger redesign cycles; thus early and accurate reliability assessment is of profound importance. For the purposes of early reliability analysis, abstract models of the design (which are available in early design stages) are typically used. These models, however, may not be completely accurate compared to the actual final design. Existing literature has not quantified this inaccuracy, through a comparison between Register-Transfer-Level (RTL) and microarchitecture-level reliability assessment on the same commercial microprocessor design. In this paper, we perform reliability assessment using statistical fault-injection on the RTL and Microarchitectural models of the same commercial ARM® Cortex®-A9 processor. The assessment was performed using the same benchmark workloads and equivalent configurations of the hardware structures. The results show that, compared to RTL model, the almost 200x faster microarchitectural model reports an average difference of 0.7 percentile units (10%) on the vulnerability estimation of register file and 3 percentile units (20%) on the vulnerability estimation of L1 data cache
SIFI: AMD southern islands GPU microarchitectural level fault injector
No full textGeneral Purpose computing on Graphics Processing Unit offers a remarkable speedup for data parallel workloads, leveraging GPUs computational power. However, differently from graphic computing, it requires highly reliable operation in several application domains. In this paper we present SIFI a reliability evaluation framework for soft-errors on AMD GPUs built on top of Multi2Sim, a micro-architectural level simulator. SIFI is capable of computing different reliability metrics by means of two different techniques: fault injection and ACE analysis. Experiments performed on a set of 14 GPGPU applications targeting the AMD Southern Islands GPU architecture show the capability of the tool and the potential of its use to support decisions about the best architectural parameters for a given application
Time-Frequency Analysis for GNSSs: From interference mitigation to system monitoring
No full textIn this article, we discuss the important role of time-frequency (TF) signal representations in enhancing global navigation satellite system (GNSS) receiver performance. Both linear transforms and quadratic TF distributions (QTFDs) are considered. We review recent advances of antijam techniques that exploit the distinction in the TF signatures between the desired and undesired signals, enabling effective jammer excision with minimum distortion to the navigation signals. The characterization of jammers by their instantaneous frequencies (IFs) lends itself to sparse structures in the TF domain and, as such, invites compressive sensing (CS) and sparse reconstruction to aid in joint-variable domain jamming localization and suppression. Furthermore, the integration of the spatial domain with the TFDs, through the use of multiantenna receivers, permits the applications of space-time processing for effective jamming mitigation. The article also describes the fundamental role of TFDs in monitoring the performance of new GNSSs, including satellite clocks and ionospheric scintillation data. Real GNSS data collected in the presence of jamming are used to demonstrate the effectiveness of TF-based antijam approaches
GPU-accelerated algorithms for compressed signals recovery with application to astronomical imagery deblurring
No full textCompressive sensing promises to enable bandwidth-efficient onboard compression of astronomical data by lifting the encoding complexity from the source to the receiver. The signal is recovered off-line, exploiting graphical processing unit (GPU)'s parallel computation capabilities to speedup the reconstruction process. However, inherent GPU hardware constraints limit the size of the recoverable signal and the speedup practically achievable. In this work, we design parallel algorithms that exploit the properties of circulant matrices for efficient GPU-accelerated sparse signals recovery. Our approach reduces the memory requirements, allowing us to recover very large signals with limited memory. In addition, it achieves a 10-fold signal recovery speedup, thanks to adhoc parallelization of matrix-vector multiplications and matrix inversions. Finally, we practically demonstrate our algorithms in a typical application of circulant matrices: deblurring a sparse astronomical image in the compressed domai
Aqueous dye-sensitized solar cells: challenges in electrodes and electrolytes design
No full textDye sensitized solar cells (DSSCs) are not yet commercialized on large scale due to their issues concerning safety and long-term stability. In fact, standard high-efficiency DSSCs are prepared mainly with organic solvent-based liquid electrolytes, i.e. acetonitrile and methoxypropionitrile, and are often characterized by high vapor pressure, toxicity and flammability. In recent years, with the idea of creating efficient, safe, and low-cost DSSCs, the research moved the attention towards alternative solvent-based electrolytes. Above all, DSSCs with water-based electrolytes look like one of the best solution providing reduced costs, nonflammability, better stability, and environmental compatibility. Moreover, the possibility of gelling the liquid solvent into a polymeric matrix can reduce the electrolyte leakage outside the device, increasing the long-term stability. In this contribution, the investigation on a series of iodine/cobalt-based 100% aqueous electrolytes is presented. In parallel, photoanode preparation and sensitization is studied to achieve the best electrode/electrolyte interfaces. Finally, the gelation of aqueous electrolytes with bio-derived polymers is presented, leading to lab-scale devices stable for several months
Hydrogel electrolytes based on bio-derived polymers for solar cells
No full textIn recent years, with the idea of creating efficient, safe, stable and low-cost dye-sensitized solar cells (DSSCs), the research moved the attention towards alternative solvent-based electrolytes. In particular, DSSCs with water-based electrolytes have been proposed as one of the possible solution providing reduced costs, non-flammability and environmental compatibility. Recently we demonstrated that stability issues can be properly addressed by choosing the appropriate dye. Moreover, the possibility of gelling the liquid solvent into a polymeric matrix can reduce the electrolyte leakage outside the device, thus increasing the long-term stability. Above all, bio-derived polymers appear promising being renewable and easy available with low cost. In this work, the study on a series of iodine and cobalt-based 100% aqueous electrolytes is presented. Thanks to our previous experience and to a multivariate approach (Design of Experiment), the effects of the photoanode preparation and the electrolyte compositions have been evaluated on DSSCs performances. Finally, the gelation of aqueous electrolytes with bio-derived polymers has been performed and evaluated. Photovoltaic performances and stabilities will be discussed by comparing liquid and gel electrolytes. In lab-scale solar cells interesting photovoltaic performances superior to 4% were achieved