Reining in the Functional Verification of Complex Processor Designs with Automation, Prioritization, and Approximation

Our quest for faster and efficient computing devices has led us to processor designs with enormous complexity. As a result, functional verification, which is the process of ascertaining the correctness of a processor design, takes up a lion's share of the time and cost spent on making processors. Unfortunately, functional verification is only a best-effort process that cannot completely guarantee the correctness of a design, often resulting in defective products that may have devastating consequences.Functional verification, as practiced today, is unable to cope with the complexity of current and future processor designs. In this dissertation, we identify extensive automation as the essential step towards scalable functional verification of complex processor designs. Moreover, recognizing that a complete guarantee of design correctness is impossible, we argue for systematic prioritization and prudent approximation to realize fast and far-reaching functional verification solutions. We partition the functional verification effort into three major activities: planning and test generation, test execution and bug detection, and bug diagnosis. Employing a perspective we refer to as the automation, prioritization, and approximation (APA) approach, we develop solutions that tackle challenges across these three major activities. In pursuit of efficient planning and test generation for modern systems-on-chips, we develop an automated process for identifying high-priority design aspects for verification. In addition, we enable the creation of compact test programs, which, in our experiments, were up to 11 times smaller than what would otherwise be available at the beginning of the verification effort. To tackle challenges in test execution and bug detection, we develop a group of solutions that enable the deployment of automatic and robust mechanisms for catching design flaws during high-speed functional verification. By trading accuracy for speed, these solutions allow us to unleash functional verification platforms that are over three orders of magnitude faster than traditional platforms, unearthing design flaws that are otherwise impossible to reach. Finally, we address challenges in bug diagnosis through a solution that fully automates the process of pinpointing flawed design components after detecting an error. Our solution, which identifies flawed design units with over 70% accuracy, eliminates weeks of diagnosis effort for every detected error.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/137057/1/birukw_1.pd

Electronic properties of poly[3-(2”,5”-diheptyloxyphenyl)-2,2'-bithiophene]/Al junctions

Junctions between a single layer of Poly[3-(2”,5”-diheptyloxyphenyl)-2,2'-bithiophene] and aluminium are studied by means of current–voltage and capacitance-voltage characteristics, and complex impedance spectroscopy. The results indicate the formation of a Schottky barrier type at Poly[3-(2”,5”-diheptyloxyphenyl)-2,2'-bithiophene]/Al interface. Parameters such as the reverse saturation current, the barrier height and the ideality factor are extracted from the I-V curves. The Cole–Cole plots of complex impedance spectroscopy reveal part of a single semicircle, which can be modeled as a single parallel RC circuit. This suggests that the device is a metal-semiconductor (M-S) type. Capacitance per unit area as well as the width of the depletion layer are obtained from the complex impedance analysis. The built-in potential and the charge carrier concentration are also calculated from C-V curves. Keywords/phrases: Electronic properties, built-in potential, depletion width, impedance spectroscopy, Schottky barrier SINET: Ethiop. J. Sci Vol.26(1) 2003:11-1

Essential oil and smoke components of Carissa spinarum

ABSTRACT. Carissa spinarum Linn. is an incense plant traditionally used in Ethiopia and other countries for the treatment of numerous diseases. It also exhibits different biological activities, and different classes of natural compounds were previously reported from the plant. In this study, the essential oil from the roots of C. spinarum together with medicinal smoke obtained from burnt roots of C. spinarum were analyzed by GC-MS. The essential oil of C. spinarum roots was predominantly composed of 2-hydroxyacetophenone (82.97%). The dominant components in the n-hexane soluble fraction of the smoke derived from the roots of C. spinarum were 2,6-dimethoxyphenol (14.16%), 2-methoxyphenol (10.34%) and 2-hydroxyacetophenone (9.51%). On the other hand, the major components in the MeOH-soluble fraction were 2,6-dimethoxyphenol (17.51%), 2-methoxyphenol (13.02%) and 2-hydroxyacetophenone (10.98%). The smoke derived from the roots of C.  spinarum showed 92.60 ± 0.34% DPPH inhibition at concentration of 100 µg/mL. At the same concentration, standard ascorbic acid scavenged the DPPH radical by 96.09 ± 0.16%. This result supports the traditional medicinal use of the plant material as a skin-care and wound healing agent most likely due to the presence of simple phenols and other biologically active compounds.   KEY WORDS: Carissa spinarum Linn., Medicinal smoke, Essential oil, Antioxidant activity, Phenolic compounds Bull. Chem. Soc. Ethiop. 2022, 36(3), 641-649.                                                                DOI: https://dx.doi.org/10.4314/bcse.v36i3.1

Effect of side chain length on the stability and structural properties of 3-(2’,5’-dialkoxyphenyl)thiophenes: a theoretical study

We report on the effect of the alkoxy chain length on the thermodynamic properties of neutral and the corresponding radical cations of 3-(2’,5’-dibutyloxyphenyl)thiophene (DBOPT), 3-(2’,5’-diheptyloxyphenyl)thiophene (DHOPT), and 3-(2’,5’-dioctyloxyphenyl)thiophene (DOOPT) and their dimers studied by Hartree-Fock (HF) and Density Functional Theory (DFT) methods. The DFT calculations suggest that dimers of the dialkoxyphenylthiophenes with longer side chains are thermodynamically more stable by about 61.39 kJ/mol than the ones with shorter side chains at the radical cation state. The results correlate well with the experimental observations made during the electrochemical synthesis of these polymers from their monomers.KEY WORDS: Density functional theory, Hartree-Fock, DialkoxyphenylthiophenesBull. Chem. Soc. Ethiop. 2010, 24(1), 93-102

CHROMIC TRANSITIONS IN PHENYL-SUBSTITUTED POLYTHIOPHENES

The solvatochromic and thermochromic behaviours of phenyl-substituted polythiophenes were studied. The pristine polymers, upon dissolution in chloroform, exhibited blue-shifted absorption. The solid films of the polymers showed significant blue-shifted as well as red-shifted absorptions when heated. While the addition of methanol to the chloroform solutions of the polymers caused dramatic chromic changes and development of red-shifted spectra for many of the polymers investigated, the symmetrically phenyl-substituted and sterically hindered polymer (polymer 1) does not show significant changes. These chromic behaviours have been examined in terms of substituent effects and attempt has been made to explain these effects by calculating the energy barrier for rotation to a planar structure using the HF SCF method and 3-21G* basis set. KEY WORDS: Chromic transitions, Phenyl-substituted polythiophenes Bull. Chem. Soc. Ethiop. 2005, 19(2), 267-276

Synthesis, optical and electrochemical characterization of anthrancene and benzothiadiazole-containing polyfluorene copolymers

New solution-processable, anthrancene- and benzothiadiazole-containing polyfluorene copolymers (P1-P3) have been synthesized and characterized. The preparation and characterization of the corresponding blue light-emitting devices are also reported. Polymers P2 and P3 show high photoluminescence efficiency while polymer P2 does not show any significant light emission up to 8.0 V. The results show the need for balance of electron and hole transport in polymer light emitting diodes. KEY WORDS: Anthracene, Benzothiadiazole, Polyfluorene copolymers, Photoluminescence, Light emitting diode  Bull. Chem. Soc. Ethiop. 2006, 20(2), 309-317

Variable denticity of a multidentate terthiophene derivative towards Ni(II) and Zn(II) - structural studies

A multidentate ligand, 3,4-bis(2-iminomethylphenol)-2,2’:5,2’’-terthiophene (L), has been synthesized by the condensation of 3,4-diamino-2,2’:5,2’’-terthiophene and salicylaldehyde. The ligand and Ni(II) and Zn(II) complexes were synthesized and characterized by IR, NMR, UV-Vis, AAS, MS, molar conductivity and magnetic susceptibility measurements. The ligand behaves as neutral ONS-ONS bis-chelant towards Ni(II) in [Ni<sub>2</sub>LCl<sub>4</sub>(H<sub>2</sub>O)<sub>2</sub>]×4H<sub>2</sub>O and as dibasic ONNO donor towards Zn(II) in [ZnL(NH<sub>3</sub>)<sub>2</sub>]. The dinuclear Ni(II) complex exhibits subnormal magnetic moment at room temperature due to metal-metal interaction through extended conjugation. The participation of the ring sulfur in bonding towards Ni(II) and the non-participation of the same towards Zn(II) are notable features. Octahedral geometries are proposed for both complexes. Cyclic voltammetric studies revealed electrochemical polymerization of the free ligand (L) but not of the Ni(II) and Zn(II) complexes. KEY WORDS: Variable denticity, 3,4-bis(2-Iminomethylphenol)-2,2’:5,2’’-terthiophene, Octahedral, Ni(II) complex, Zn(II) complex, Voltammetric studies Bull. Chem. Soc. Ethiop. 2011, 25(2), 221-23

Experimental Demonstration of Staggered CAP Modulation for Low Bandwidth Red-Emitting Polymer-LED based Visible Light Communications

In this paper we experimentally demonstrate, for the first time, staggered carrier-less amplitude and phase (sCAP) modulation for visible light communication systems based on polymer light-emitting diodes emitting at ~639 nm. The key advantage offered by sCAP in comparison to conventional multiband CAP is its full use of the available spectrum. In this work, we compare sCAP, which utilises four orthogonal filters to generate the signal, with a conventional 4-band multi-CAP system and on-off keying (OOK). We transmit each modulation format with equal energy and present a record un-coded transmission speed of ~6 Mb/s. This represents gains of 25% and 65% over the achievable rate using 4-CAP and OOK, respectively.Comment: 6 pages, 9 figures, IEEE ICC 2019 conferenc

A Facile Method to Enhance Photovoltaic Performance of Benzodithiophene-Isoindigo Polymers by Inserting Bithiophene Spacer

This study describes the synthesis and characterization of four polymers based on benzo[1,2-b:4,5-b']dithiophene (BDT) and isoindigo with zero, one, two, and three thiophene spacer groups. Results have demonstrated that the use of bithiophene as a spacer unit improves the geometry of the polymer chain, making it planar, and hence, potentially enhanced π- π stacking occurs. Due to favorable interaction of the polymer chains, enhanced absorption coefficient, and optimal morphology, PBDT-BTI, which possesses bithiophene as a spacer, revealed high current and fill factor leading to a power conversion efficiency of 7.3% in devices, making this polymer the best performing isoindigo-based material in polymer solar cells (PSCs). Also, PBDT-BTI could still maintain efficiency of over 6% with the active layer thickness of 270 nm, making it a potential candidate for a material in printed PSCs. These results demonstrate that the use of thiophene spacers in D-A polymers could be an important design strategy to produce high-performance PSCs