The Experts below are selected from a list of 13173 Experts worldwide ranked by ideXlab platform
Weijia Yang - One of the best experts on this subject based on the ideXlab platform.
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Linear synthetic inertia for improved frequency quality and reduced hydropower Wear and Tear
International Journal of Electrical Power & Energy Systems, 2018Co-Authors: Linn Saarinen, Per Norrlund, Weijia Yang, Urban LundinAbstract:Abstract The power system inertia is decreasing in many electrical grids as the share of production from directly connected synchronous generators decreases. Lower inertia increases the frequency deviations in normal operation, which leads to increased Wear and Tear in hydropower turbines and other units providing frequency control to the system. The predominant concepts for synthetic inertia from for example wind power does not address the frequency quality in normal operation, only the acute problem of frequency stability during large disturbances. This paper investigates how the frequency quality and frequency controlling hydropower units are affected by decreasing inertia and damping, using the Nordic power system as a case study. A new type of synthetic inertia (SI), which is linear and continuously active, is suggested as a means to mitigate the impacts on these units. It is shown that the suggested linear SI controller can effectively replace synchronous inertia and damping, improving frequency quality and reducing hydropower Wear and Tear. The controller includes an energy recovery feedback loop, to avoid depletion of the energy source behind the controller. The power and energy needed to provide linear SI is quantified, and the impact of the SI energy recovery integration time constant is investigated.
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Linear Synthetic Inertia for Improved Frequency Quality and Reduced Hydropower Wear and Tear
IEEE Transactions on Sustainable Energy, 2016Co-Authors: Linn Saarinen, Per Norrlund, Weijia YangAbstract:Linear Synthetic Inertia for Improved Frequency Quality and Reduced Hydropower Wear and Tear
Linn Saarinen - One of the best experts on this subject based on the ideXlab platform.
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Linear synthetic inertia for improved frequency quality and reduced hydropower Wear and Tear
International Journal of Electrical Power & Energy Systems, 2018Co-Authors: Linn Saarinen, Per Norrlund, Weijia Yang, Urban LundinAbstract:Abstract The power system inertia is decreasing in many electrical grids as the share of production from directly connected synchronous generators decreases. Lower inertia increases the frequency deviations in normal operation, which leads to increased Wear and Tear in hydropower turbines and other units providing frequency control to the system. The predominant concepts for synthetic inertia from for example wind power does not address the frequency quality in normal operation, only the acute problem of frequency stability during large disturbances. This paper investigates how the frequency quality and frequency controlling hydropower units are affected by decreasing inertia and damping, using the Nordic power system as a case study. A new type of synthetic inertia (SI), which is linear and continuously active, is suggested as a means to mitigate the impacts on these units. It is shown that the suggested linear SI controller can effectively replace synchronous inertia and damping, improving frequency quality and reducing hydropower Wear and Tear. The controller includes an energy recovery feedback loop, to avoid depletion of the energy source behind the controller. The power and energy needed to provide linear SI is quantified, and the impact of the SI energy recovery integration time constant is investigated.
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Linear Synthetic Inertia for Improved Frequency Quality and Reduced Hydropower Wear and Tear
IEEE Transactions on Sustainable Energy, 2016Co-Authors: Linn Saarinen, Per Norrlund, Weijia YangAbstract:Linear Synthetic Inertia for Improved Frequency Quality and Reduced Hydropower Wear and Tear
R W Gracy - One of the best experts on this subject based on the ideXlab platform.
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Molecular Wear and Tear leads to terminal marking and the unstable isoforms of aging
Journal of Experimental Zoology, 1998Co-Authors: R W Gracy, J M Talent, A I ZvaigzneAbstract:Our studies focus on the mechanisms of molecular Wear and Tear, terminal marking, protein degradation, and how these processes are altered with age. Molecular Wear and Tear directly links catalysis with postsynthetic terminal marking. For example, the binding of ligands and catalysis cause conformational changes that are transmitted from the catalytic center to the site of terminal marking and enhance the rates of specific covalent modifications, such as deamidation or oxidation. These oxidations or deamidations can introduce “KFERQ motifs” into proteins, which may permit them to be recognized and transported to the site(s) of complete degradation. Terminally marked proteins accumulate in aging cells and tissues and account for many of the health problems of the elderly. Two-dimensional protein fingerprinting coupled with immunostaining permits identification and characterization of these proteins. Free-radical traps or caloric restriction, which may prevent the formation or enhance the degradation of terminally marked proteins, may be useful in the prevention or treatment of age- associated health problems, including dementia. J. Exp. Zool. 282:18–27, 1998. © 1998 Wiley-Liss, Inc.
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Molecular Wear and Tear leads to terminal marking and the unstable isoforms of aging.
The Journal of experimental zoology, 1998Co-Authors: R W Gracy, J M Talent, A I ZvaigzneAbstract:Our studies focus on the mechanisms of molecular Wear and Tear, terminal marking, protein degradation, and how these processes are altered with age. Molecular Wear and Tear directly links catalysis with postsynthetic terminal marking. For example, the binding of ligands and catalysis cause conformational changes that are transmitted from the catalytic center to the site of terminal marking and enhance the rates of specific covalent modifications, such as deamidation or oxidation. These oxidations or deamidations can introduce "KFERQ motifs" into proteins, which may permit them to be recognized and transported to the site(s) of complete degradation. Terminally marked proteins accumulate in aging cells and tissues and account for many of the health problems of the elderly. Two-dimensional protein fingerprinting coupled with immunostaining permits identification and characterization of these proteins. Free-radical traps or caloric restriction, which may prevent the formation or enhance the degradation of terminally marked proteins, may be useful in the prevention or treatment of age-associated health problems, including dementia.
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Deamidation of triosephosphate isomerase in reverse micelles: effects of water on catalysis and molecular Wear and Tear.
Biochemistry, 1994Co-Authors: Georgina Garza-ramos, M. Tuena De Gómez-puyou, Armando Gómez-puyou, K. U. Yuksel, R W GracyAbstract:The specific deamidation of asparagine-71 of triosephosphate isomerase increases upon substrate binding and catalysis. This deamidation at the dimer interface initiates subunit dissociation, unfolding, and protein degradation. The apparent connection between catalysis and terminal marking supports the concept of "molecular Wear and Tear", and raises questions related to the molecular events that lead to deamidation. In order to explore this interaction, triosephosphate isomerase was entrapped in reverse micelles with different water contents that support different catalytic rates. Deamidation was quantified for the free enzyme, the enzyme in the presence of substrates, and the enzyme which had been covalently modified at the catalytic center with the substrate analogue 3-chloroacetol phosphate (CAP). Both in water and in reverse micelles of cetyltrimethylammonium with 3% and 6% water, substrate binding enhanced deamidation. Studies of the extent of deamidation at various water concentrations showed that deamidation per catalytic turnover was about 6 and 17 times higher in 6% and 3% water than in 100% water, respectively. The enzyme was also entrapped in micelles formed with toluene, phospholipids, and Triton X-100 to explore the process at much lower water concentrations (e.g., 0.3%). Under these conditions, catalysis was very low, and hardly any deamidation took place. Deamidation of the CAP-labeled enzyme was also markedly diminished. At these low-water conditions, the enzyme exhibited markedly increased thermostability and resistance to hydrolysis of the amide bonds. The data suggest that the rate of deamidation not only is dependent on the number of catalytic events but also is related to the time that asparagine-71 exists in a conformation or solvent environment more favorable for deamidation.
Michalis Polychronakis - One of the best experts on this subject based on the ideXlab platform.
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spotless sandboxes evading malware analysis systems using Wear and Tear artifacts
IEEE Symposium on Security and Privacy, 2017Co-Authors: Najmeh Miramirkhani, Mahathi Priya Appini, Nick Nikiforakis, Michalis PolychronakisAbstract:Malware sandboxes, widely used by antivirus companies, mobile application marketplaces, threat detection appliances, and security researchers, face the challenge of environment-aware malware that alters its behavior once it detects that it is being executed on an analysis environment. Recent efforts attempt to deal with this problem mostly by ensuring that well-known properties of analysis environments are replaced with realistic values, and that any instrumentation artifacts remain hidden. For sandboxes implemented using virtual machines, this can be achieved by scrubbing vendor-specific drivers, processes, BIOS versions, and other VM-revealing indicators, while more sophisticated sandboxes move away from emulation-based and virtualization-based systems towards bare-metal hosts. We observe that as the fidelity and transparency of dynamic malware analysis systems improves, malware authors can resort to other system characteristics that are indicative of artificial environments. We present a novel class of sandbox evasion techniques that exploit the "Wear and Tear" that inevitably occurs on real systems as a result of normal use. By moving beyond how realistic a system looks like, to how realistic its past use looks like, malware can effectively evade even sandboxes that do not expose any instrumentation indicators, including bare-metal systems. We investigate the feasibility of this evasion strategy by conducting a large-scale study of Wear-and-Tear artifacts collected from real user devices and publicly available malware analysis services. The results of our evaluation are alarming: using simple decision trees derived from the analyzed data, malware can determine that a system is an artificial environment and not a real user device with an accuracy of 92.86%. As a step towards defending against Wear-and-Tear malware evasion, we develop statistical models that capture a system's age and degree of use, which can be used to aid sandbox operators in creating system images that exhibit a realistic Wear-and-Tear state.
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IEEE Symposium on Security and Privacy - Spotless Sandboxes: Evading Malware Analysis Systems Using Wear-and-Tear Artifacts
2017 IEEE Symposium on Security and Privacy (SP), 2017Co-Authors: Najmeh Miramirkhani, Mahathi Priya Appini, Nick Nikiforakis, Michalis PolychronakisAbstract:Malware sandboxes, widely used by antivirus companies, mobile application marketplaces, threat detection appliances, and security researchers, face the challenge of environment-aware malware that alters its behavior once it detects that it is being executed on an analysis environment. Recent efforts attempt to deal with this problem mostly by ensuring that well-known properties of analysis environments are replaced with realistic values, and that any instrumentation artifacts remain hidden. For sandboxes implemented using virtual machines, this can be achieved by scrubbing vendor-specific drivers, processes, BIOS versions, and other VM-revealing indicators, while more sophisticated sandboxes move away from emulation-based and virtualization-based systems towards bare-metal hosts. We observe that as the fidelity and transparency of dynamic malware analysis systems improves, malware authors can resort to other system characteristics that are indicative of artificial environments. We present a novel class of sandbox evasion techniques that exploit the "Wear and Tear" that inevitably occurs on real systems as a result of normal use. By moving beyond how realistic a system looks like, to how realistic its past use looks like, malware can effectively evade even sandboxes that do not expose any instrumentation indicators, including bare-metal systems. We investigate the feasibility of this evasion strategy by conducting a large-scale study of Wear-and-Tear artifacts collected from real user devices and publicly available malware analysis services. The results of our evaluation are alarming: using simple decision trees derived from the analyzed data, malware can determine that a system is an artificial environment and not a real user device with an accuracy of 92.86%. As a step towards defending against Wear-and-Tear malware evasion, we develop statistical models that capture a system's age and degree of use, which can be used to aid sandbox operators in creating system images that exhibit a realistic Wear-and-Tear state.
Per Norrlund - One of the best experts on this subject based on the ideXlab platform.
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Linear synthetic inertia for improved frequency quality and reduced hydropower Wear and Tear
International Journal of Electrical Power & Energy Systems, 2018Co-Authors: Linn Saarinen, Per Norrlund, Weijia Yang, Urban LundinAbstract:Abstract The power system inertia is decreasing in many electrical grids as the share of production from directly connected synchronous generators decreases. Lower inertia increases the frequency deviations in normal operation, which leads to increased Wear and Tear in hydropower turbines and other units providing frequency control to the system. The predominant concepts for synthetic inertia from for example wind power does not address the frequency quality in normal operation, only the acute problem of frequency stability during large disturbances. This paper investigates how the frequency quality and frequency controlling hydropower units are affected by decreasing inertia and damping, using the Nordic power system as a case study. A new type of synthetic inertia (SI), which is linear and continuously active, is suggested as a means to mitigate the impacts on these units. It is shown that the suggested linear SI controller can effectively replace synchronous inertia and damping, improving frequency quality and reducing hydropower Wear and Tear. The controller includes an energy recovery feedback loop, to avoid depletion of the energy source behind the controller. The power and energy needed to provide linear SI is quantified, and the impact of the SI energy recovery integration time constant is investigated.
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Linear Synthetic Inertia for Improved Frequency Quality and Reduced Hydropower Wear and Tear
IEEE Transactions on Sustainable Energy, 2016Co-Authors: Linn Saarinen, Per Norrlund, Weijia YangAbstract:Linear Synthetic Inertia for Improved Frequency Quality and Reduced Hydropower Wear and Tear
