390,306 research outputs found

    Vulnerabilities, Cybersecurity, and the Role of Law and Regulation herein

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    Nowadays, it is not difficult to conjure up images of hacked power plants, remote-hijacked public transportation systems, etc. By exploiting hidden vulnerabilities, hackers are plundering business secrets, stealing digital consumers’ records, and trying to reshape the world inconspicuously. Most of society lacks awareness of software vulnerabilities. Software vendors seem unlikely to discuss flaws in their products publicly, and the related markets of vulnerabilities are often opaque. This thesis tries to introduce its readers to a structured discussion and analysis of software vulnerabilities vis-à-vis the challenges of cyberattacks. This thesis focuses on an analysis of software vulnerabilities and their relevance to cybersecurity from an economic perspective, and it discusses the role of law and regulation designed to address problems of vulnerabilities and cybersecurity utilizing the law and economics approach. A software vulnerability has its intrinsic value and a life cycle. There are people who search for these vulnerabilities - the bug hunters, and there are three markets for vulnerabilities - white, grey, and black. The assumption of profit maximization in traditional economics also applies to bug hunters. Moreover, this thesis finds that the nature of the white market vis-à-vis the grey or black market is much more competitive. Among the factors that influence the price level of a software vulnerability in the black market, the bounty price (white market price) is particularly worthy of attention. This thesis finds that the practice of governments to retain vulnerabilities is acceptable in the short run for the purpose of legal enforcement or intelligence, given the advanced encryption and anonymization technologies used by criminals. However, in the long run, government agencies should avoid vulnerability transactions. Furthermore, government agencies should give the utmost attention to how to protect their vulnerability stockpiles from being stolen. The empirical results of this thesis prove that a market failure exists at least to some extent in relation to vulnerabilities. There was no significant market pressure upon the software vendor even when the software had been proved seriously risky by a severe cyberattack. Possible avenues to correct this market failure could be found in private law, administrative law, or 2 other means of central intervention. This thesis advocates a solution of jointly using liability rules and safety regulation backed by a public fine (regulation backed by an administrative fine) for the harm caused by a vulnerability. More details are provided by means of an economic model. It is a combination of torts and regulation (ex-ante and ex-post), which is in line with the suggestions made in Shavell (1984), and Faure, Visscher & Weber (2016)

    A four-level dual active bridge converter for data center applications

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    The Dual Active Bridge (DAB) bi-directional DC/DC converter is a popular topology originally designed for energy storage applications. It has high efficiency, galvanic isolation, and, most importantly, controllable power flow. However, for high voltage conversion ratio applications, there are challenges on switch stress and component size. In this work, we are replacing the half bridges on the primary side of the original DAB with Flying-Capacitor Multi-Level (FCML) topology using Phase-Shifted Pulse Width Modulation (PS-PWM) control scheme. While the original benefits are still available, the voltage stress across each switch is reduced, enabling the use of faster GaN switches that also have smaller drain-to-source turn-on resistance. The increased switching frequency at the AC node also decreases the size of the auxiliary inductor. The theory of operation and the simulation result of the new topology will be discussed. Then, the initial measurements from an experimental prototype are presented. The hardware prototype demonstrates the converter topology's ability to maintain a steady voltage output for a varying load at a high voltage conversion ratio and a large voltage input.LimitedAuthor requested closed access (OA after 2yrs) in Vireo ETD syste

    Diastereoselective Synthesis of Dihydroisoindolo[2,1‚ÄĎa]quinolin-11- ones by Solvent-Free AMCell-SO3H‚ÄĎCatalyzed Imino Diels‚ąíAlder/Intramolecular Amide Cyclization Cascade Reactions

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    Nineteen bioactive highly functionalized 6,6a-dihydroisoindolo[2,1-a]quinolin-11(5H)-one derivatives were easily prepared in good yield without solvent using catalytic amorphous milled cellulose sulfonic acid (AMCell-SO3H), substituted anilines, propenyl-phenols, and phthaldehydic acid. The cascade reaction gave high regioselectivity and diastereoselectivity.Departamento Administrativo de Ciencia, Tecnología e Innovación [CO] Colciencias5507-543-31904Programa: Bioprospección y desarrollo de ingredientes naturales para las industrias cosmética, farmacéutica y de productos de aseo con base en la biodiversidad colombianan

    Advanced thermal management system driven by phase change materials for power lithium-ion batteries: A review

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    © 2022 Elsevier Ltd. All rights reserved. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1016/j.rser.2022.112207Power lithium-ion batteries are widely utilized in electric vehicles (EVs) and hybrid electric vehicles (HEVs) for their high energy densities and long service-life. However, thermal safety problems mainly resulting from thermal runaway (TR) must be solved. In general, temperature directly influences the performance of lithium-ion batteries. Hence, an efficient thermal management system is very necessary for battery modules/packs. One particular approach, phase change material (PCM)-based cooling, has exhibited promising applicability due to prominent controlling-temperature and stretching-temperature capacities. However, poor thermal conductivity performance, as the main technical bottleneck, is limiting the practical application. Nevertheless, only promoting the thermal conductivity is far from enough considering the practical application in EVs/HEVs. To fix these flaws, firstly, the heat generation/transfer mechanisms of lithium-ion power batteries were macro- and microscopically reviewed. Following that, the thermal conductivity, structural stability, and flame retardancy of PCM are thoroughly discussed, to which solutions to the aforementioned performances are systematically reviewed. In addition, battery thermal management system (BTMS) employing PCM is illustrated and compared. Eventually, the existing challenges and future directions of PCM-based BTMS are discussed. In summary, this review presents effective approaches to upgrade the PCM performances for high-density lithium-ion BTMS. These strategies furtherly accelerate the commercialization process of PCM BTMS.Peer reviewe

    Monitoring land degradation and assessing its drivers in Central Asia

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    Amino-acid-based chiral ionic liquids characterization and application in aqueous biphasic systems

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    By using amino acids as anions, ten chiral ionic liquids (CILs) composed of tetrabutylammonium or cholinium as cations were synthesized by neutralization reactions and further characterized by assessing their optical rotation, thermophysical properties (melting and decomposition temperatures, density, viscosity and refractive index) and ecotoxicity against the marine bacterium Aliivibrio fischeri. The CILs are shown to display, in general, high thermal stability (> 439 K) and low to moderate toxicities (86-217 mg¬∑L‚ąí1). It was found that the cation plays an important role in the density and viscosity of the CILs. Additionally, the effect of CILs optical configuration on these properties was evaluated by comparing the tetrabutylammonium D/L-phenylalaninate ([N4444][D/L-Phe]) and cholinium D/L-phenylalaninate ([N1112(OH)][D/L-Phe]) pairs. Finally, the CILs potential to form aqueous biphasic systems with sodium sulfate, citrate buffer and phosphate buffer was assessed and the ternary phase diagrams were determined. These allowed to infer the impact of the CILs‚Äô cation, anion, and salt on the aqueous biphasic system formation. It was shown that the cation has a more pronounced impact on the aqueous biphasic system formation than the anion. Cholinium-based CILs failed to form aqueous biphasic systems with sodium sulfate under the tested conditions, contrary to the more hydrophobic tetrabutylammonium-based CILs. The ability of the tested salt and buffers to induce liquid-liquid demixing shows that citrate buffer and sodium sulfate represent the weakest and the strongest salting-out agents, respectively.publishe

    High Accuracy Station-Keeping of Geostationary Satellite

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    This thesis analyses the problem of station-keeping (SK) maneuver planning for geostationary satellites, attempting to reach a target accuracy level of 0.001 deg by using electric thrusters. Geostationary satellites are currently allowed to operate within an accuracy range between 0.1 to 0.05 deg, and are controlled with chemical thrusters, with a control frequency of two weeks. Therefore, the main challenges to be handled in this work are due to the extremely high objective accuracy and the substitution of chemical thrusters with electric thrusters, which provide limited and non-modulable thrust levels. In this work, for a given value of nominal longitude, the SK maneuver planning is addressed as a constrained trajectory optimization problem and solved numerically using the GPOPS software on MATLAB. The performance index to be optimized is the fuel consumption, the constraints on the longitudinal and latitudinal position of the satellite are written as path constraints. By assuming firstly that electric thrusters are able to provide any thrust level and operate constantly, a continuous control profile is derived and is secondly turned into an on-off one, by taking into account the technological limitations of actual electric thrusters. This transformation operation is done by appropriately combining the required Delta-v budget and then effectively spreading it about the properly derived "time barycenters". The resulting control strategy, unlike the traditional one, are characterized by frequent maneuvers, requiring the thrusters to be turned on several times a day. Finally, to assess the validity of the proposed method and the influences of different values of nominal longitudes, the developed control algorithm will be applied to some representative values of nominal longitude
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