Water-induced disasters in long-distance pipelines are prevalent geological hazards,characterized by their frequency and widespread distribution.The complexity of factors contributing to pipeline damage in practical e...Water-induced disasters in long-distance pipelines are prevalent geological hazards,characterized by their frequency and widespread distribution.The complexity of factors contributing to pipeline damage in practical engineering poses a significant challenge for analysis using solely theoretical models.This study systematically reveals the cross-scale failure mechanism of long-distance pipelines under hydrodynamic impact through the combination of multi-scale experimental representation and theoretical modeling.Employing a combination of macroscopic measurements,advanced material testing of residual samples from failed pipelines,and consideration of operational conditions and environmental factors,the failure modes is systematically analyzed.The findings reveal that under the vibrations induced by water impulses,the pipe material exhibits a pronounced ratchet effect,leading to an 8.92%reduction in elongation at break.Furthermore,the Bauschinger effect is observed,resulting in a 2.95%decrease in yield strength.Cyclic hardening significantly diminishes the impact toughness of the weld by 22.2%.Notably,at high vibration frequencies of approximately 18.98 Hz,the stress concentration in the girth weld near the axial midpoint of the pipe section initiates cracking,ultimately leading to failure under the alternating load generated by the oscillation.This study provides valuable insights into the scientific understanding of pipeline failure mechanisms under water impact,contributing to the development ofmore robust and resilient pipeline systems.展开更多
We evaluate the impact of temperature on the output behavior of a carbon nanotube field effect transistor （CNFET） based chaotic generator. The sources cause the variations in both current-voltage characteristics of ...We evaluate the impact of temperature on the output behavior of a carbon nanotube field effect transistor （CNFET） based chaotic generator. The sources cause the variations in both current-voltage characteristics of the CNFET device and an overall chaotic circuit is pointed out. To verify the effect of temperature variation on the output dynamics of the chaotic circuit, a simulation is performed by employing the CNFET compact model of Wong et al. in HSPICE with a temperature range from -100℃ to 100℃. The obtained results with time series, frequency spectra, and bifurcation diagram from the simulation demonstrate that temperature plays a significant role in the output dynamics of the CNFET-based chaotic circuit. Thus, temperature-related issues should be taken into account while designing a high-quality chaotic generator with high stability.展开更多
Chronotype is determined by circadian rhythms,influenced by polygenic variations and environmental factors. Typically, chronotypes are categorized into morning-, intermediate-, and evening-types^([1]). Most cognitive ...Chronotype is determined by circadian rhythms,influenced by polygenic variations and environmental factors. Typically, chronotypes are categorized into morning-, intermediate-, and evening-types^([1]). Most cognitive functions follow daily and circadian rhythms, with the “synchronization effect” reflecting performance variations between optimal and non-optimal times based on an individual's chronotype.展开更多
In a variable nozzle turbine(VNT),the nozzle vane and rotor clearance can generate complicated tip leakage flow,which produces a large flow loss and results in a noticeable reduction in the VNT performance.Therefore,i...In a variable nozzle turbine(VNT),the nozzle vane and rotor clearance can generate complicated tip leakage flow,which produces a large flow loss and results in a noticeable reduction in the VNT performance.Therefore,it is necessary to study the influence of the nozzle vane and rotor clearance on the VNT performance to reveal the underlying mechanisms.In this study,the variation of VNT performance resulting from the nozzle vane and rotor clearance was studied numerically using the commercial CFD code.The numerical results were in good agreement with the experimental data.VNT performance under three varied clearance conditions under different clearance sizes,rotating speeds,and expansion ratios was analyzed.Clearance conditions included the individual effect of nozzle vane clearance,the individual effect of rotor clearance,and the combined effect of nozzle vane and rotor clearance.The results showed that the rotor clearance(clearance size equal to 0.4 mm)resulted in a certain reduction in thermal efficiency(–3.98%)and torque(–4.48%).Meanwhile,the nozzle vane hub and shroud clearance also affected the thermal efficiency(–3.66%and–13.37%,respectively)and torque(12.54%and–0.05%,respectively).Compared with the rotor clearance,the nozzle vane clearance dominated the variation in the VNT performance,and the values of the mass flow ratio,thermal efficiency,and torque increased by 12.15%,5.43%,and 8.01%,respectively(The clearance on both sides of the vane was equal to 0.2 mm.).Under the combined effect of the nozzle vane and rotor clearance,the deviation of the thermal efficiency and mass flow ratio was smaller than the sum of the values of their individual effects;when the clearance on both sides of the vane was equal to 0.2 mm and the rotor clearance was equal to 0.6 mm,the value was reduced by 2.77%and 1.71%,respectively.This study also explains the influence mechanisms of clearance at both ends of the nozzle vane and the vane/rotor clearance interaction on the VNT performance in detail.展开更多
It is essential to provide responses to queries within time deadlines,even if not exact and complete.To reduce the query latency,systems usually partition large-scale data computations as a series of tasks over many p...It is essential to provide responses to queries within time deadlines,even if not exact and complete.To reduce the query latency,systems usually partition large-scale data computations as a series of tasks over many processes and aggregate them to reduce the response time by using aggregation trees.An obstacle is that the involved processes of a query usually differ in their speeds,thus not all processes can complete their tasks in time.This would directly degrade the response quality(the number of outputs received by the root of an aggregation tree).In this paper,we propose a general aggregation tree model,Tarot,to maximize the response quality by systematically addressing the following challenging issues:(1)fine-grained partition of the query deadline along the multi-level aggregation tree;(2)learning the distribution of durations at each level in the aggregation tree to optimize the wait durations at aggregators;(3)adaptively reassigning tasks over processes according to their status;(4)performing periodic aggregation of received outputs from the low level to avoid missing the deadline.The prior model does not consider the four aspects simultaneously.Extensive evaluations indicate that Tarot can adapt to multi-level trees and considerably improve the response quality compared to prior work while guaranteeing the query deadline.展开更多
基金supported by the Youth Science and Technology New Star Project of Shaanxi Province(grants Nos.2024ZC-KjXX-002,2021KJXX65 and 2023KJXX-092)the Natural Science Foundation of Shaanxi Province(grant No.2021JQ-947)the Basic Research and Strategic Reserve Technology Research Fund of the China National Petroleum Corporation(projects Nos.2022DQ03-05 and 2023DQ03-07).
文摘Water-induced disasters in long-distance pipelines are prevalent geological hazards,characterized by their frequency and widespread distribution.The complexity of factors contributing to pipeline damage in practical engineering poses a significant challenge for analysis using solely theoretical models.This study systematically reveals the cross-scale failure mechanism of long-distance pipelines under hydrodynamic impact through the combination of multi-scale experimental representation and theoretical modeling.Employing a combination of macroscopic measurements,advanced material testing of residual samples from failed pipelines,and consideration of operational conditions and environmental factors,the failure modes is systematically analyzed.The findings reveal that under the vibrations induced by water impulses,the pipe material exhibits a pronounced ratchet effect,leading to an 8.92%reduction in elongation at break.Furthermore,the Bauschinger effect is observed,resulting in a 2.95%decrease in yield strength.Cyclic hardening significantly diminishes the impact toughness of the weld by 22.2%.Notably,at high vibration frequencies of approximately 18.98 Hz,the stress concentration in the girth weld near the axial midpoint of the pipe section initiates cracking,ultimately leading to failure under the alternating load generated by the oscillation.This study provides valuable insights into the scientific understanding of pipeline failure mechanisms under water impact,contributing to the development ofmore robust and resilient pipeline systems.
基金Supported by the Basic Science Research Program through the National Research Foundation of Korea Funded by the Ministry of Education,Science and Technology under Grant No 2012-0002777
文摘We evaluate the impact of temperature on the output behavior of a carbon nanotube field effect transistor （CNFET） based chaotic generator. The sources cause the variations in both current-voltage characteristics of the CNFET device and an overall chaotic circuit is pointed out. To verify the effect of temperature variation on the output dynamics of the chaotic circuit, a simulation is performed by employing the CNFET compact model of Wong et al. in HSPICE with a temperature range from -100℃ to 100℃. The obtained results with time series, frequency spectra, and bifurcation diagram from the simulation demonstrate that temperature plays a significant role in the output dynamics of the CNFET-based chaotic circuit. Thus, temperature-related issues should be taken into account while designing a high-quality chaotic generator with high stability.
基金supported by Zhongda Hospital Affiliated to Southeast University,Jiangsu Province High-Level Hospital Construction Funds(Grant No.GSP-LCYJFH07)。
文摘Chronotype is determined by circadian rhythms,influenced by polygenic variations and environmental factors. Typically, chronotypes are categorized into morning-, intermediate-, and evening-types^([1]). Most cognitive functions follow daily and circadian rhythms, with the “synchronization effect” reflecting performance variations between optimal and non-optimal times based on an individual's chronotype.
文摘In a variable nozzle turbine(VNT),the nozzle vane and rotor clearance can generate complicated tip leakage flow,which produces a large flow loss and results in a noticeable reduction in the VNT performance.Therefore,it is necessary to study the influence of the nozzle vane and rotor clearance on the VNT performance to reveal the underlying mechanisms.In this study,the variation of VNT performance resulting from the nozzle vane and rotor clearance was studied numerically using the commercial CFD code.The numerical results were in good agreement with the experimental data.VNT performance under three varied clearance conditions under different clearance sizes,rotating speeds,and expansion ratios was analyzed.Clearance conditions included the individual effect of nozzle vane clearance,the individual effect of rotor clearance,and the combined effect of nozzle vane and rotor clearance.The results showed that the rotor clearance(clearance size equal to 0.4 mm)resulted in a certain reduction in thermal efficiency(–3.98%)and torque(–4.48%).Meanwhile,the nozzle vane hub and shroud clearance also affected the thermal efficiency(–3.66%and–13.37%,respectively)and torque(12.54%and–0.05%,respectively).Compared with the rotor clearance,the nozzle vane clearance dominated the variation in the VNT performance,and the values of the mass flow ratio,thermal efficiency,and torque increased by 12.15%,5.43%,and 8.01%,respectively(The clearance on both sides of the vane was equal to 0.2 mm.).Under the combined effect of the nozzle vane and rotor clearance,the deviation of the thermal efficiency and mass flow ratio was smaller than the sum of the values of their individual effects;when the clearance on both sides of the vane was equal to 0.2 mm and the rotor clearance was equal to 0.6 mm,the value was reduced by 2.77%and 1.71%,respectively.This study also explains the influence mechanisms of clearance at both ends of the nozzle vane and the vane/rotor clearance interaction on the VNT performance in detail.
基金supported by the National Natural Science Foundation of China(Grant No.61772544)National Basic Research Program(973 program)(2014CB347800)+1 种基金the Hunan Provincial Natural Science Fund for Distinguished Young Scholars(2016JJ1002)the Guangxi Cooperative Innovation Center of Cloud Computing and Big Data(YD16507 and YD17X11).
文摘It is essential to provide responses to queries within time deadlines,even if not exact and complete.To reduce the query latency,systems usually partition large-scale data computations as a series of tasks over many processes and aggregate them to reduce the response time by using aggregation trees.An obstacle is that the involved processes of a query usually differ in their speeds,thus not all processes can complete their tasks in time.This would directly degrade the response quality(the number of outputs received by the root of an aggregation tree).In this paper,we propose a general aggregation tree model,Tarot,to maximize the response quality by systematically addressing the following challenging issues:(1)fine-grained partition of the query deadline along the multi-level aggregation tree;(2)learning the distribution of durations at each level in the aggregation tree to optimize the wait durations at aggregators;(3)adaptively reassigning tasks over processes according to their status;(4)performing periodic aggregation of received outputs from the low level to avoid missing the deadline.The prior model does not consider the four aspects simultaneously.Extensive evaluations indicate that Tarot can adapt to multi-level trees and considerably improve the response quality compared to prior work while guaranteeing the query deadline.
