183 research outputs found
協調的エッジクラウドコンピューティングのためのマルチエージェント強化学習
No full text京都大学新制・課程博士博士(情報学)甲第24261号情博第805号新制||情||136(附属図書館)京都大学大学院情報学研究科社会情報学専攻(主査)教授 伊藤 孝行, 教授 吉川 正俊, 教授 神田 崇行, 特定准教授 LIN Donghui学位規則第4条第1項該当Doctor of InformaticsKyoto UniversityDFA
Experimental and Computational Studies of the Low Velocity Impact and Compression After Impact of Carbon Fiber Reinforced Polymer Composites
No full textCarbon fiber reinforced polymer (CFRP) composites have been widely used in many industrial sectors because of their high strength-to-weight ratio, cost advantages, and the possibility of tailoring the design. During the lifetime of a composite structure, low velocity impact (LVI) tends to happen in many scenarios, including manufacturing, service, and maintenance operations. A small event such as a tool drop may cause barely visible impact damage (BVID) with extensive internal cracking while without any noticeable marks on the outer surface of a composite structure. LVI-induced damage can lead to a significant reduction in post-impact compressive strength. Therefore, the LVI and compression after impact (CAI) problems have received continued attention for decades. Considerable effort on experimental and numerical investigations persists. Generations of accurate, efficient, versatile, and robust numerical tools have been developed to tackle the LVI and CAI problems virtually to save experimental costs and accelerate the verification and validation (V&V) process. Experimental and computational studies on the LVI and CAI damage of CFRP laminated composites are presented in this dissertation. Effects of laminate stacking sequence, impact energy, and panel size on the LVI and CAI are investigated.
In the experimental part, LVI test results are reported. Non-destructive inspection (NDI) techniques, including ultrasound C-scanning and micro computed tomography (µCT), are conducted to characterize the impact damage. With the high-resolution µCT scanning, damage mechanisms are analyzed. Following the LVI tests and NDI characterization, CAI tests are done to relate the impact energy to the degradation of compressive strength. CAI fixtures for standard-size composite panels are modified to customize to panels with increased sizes. Post-buckling responses during the CAI of panels with increased sizes are presented.
Parallel with the experimental results, computational results are obtained with the enhanced Schapery Theory (EST) model, which is a seamless combination of the Schapery theory (ST) and the crack band (CB) method. EST based on 2D plane stress is extended to a 3D stress state. A novel mixed-mode cohesive law is integrated to model the degradation of stress components progressively and simultaneously. The capability of EST to capture matrix inelasticity is implemented. 2D and 3D EST applied to LVI and CAI modeling are verified against the experimental results. A high-fidelity and high-efficiency LVI-CAI computational framework is established based on 2D EST to accurately predict the LVI damage and CAI strength with significantly improved efficiency. The computational results agree well with the experimental results in terms of the load responses, damage morphology, and CAI strength.
This dissertation provides detailed LVI and CAI results concerning the effects of stacking sequence, impact energy, and panel size. The EST model developed is validated and will be useful in the V&V process of aeronautical composite structures. Furthermore, the high-fidelity and high-efficiency LVI-CAI computational framework enables obtaining the CAI strength with significantly reduced computational time, which will help enlarge the design space of CFRP laminated composites with increased impact resistance.PhDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/171345/1/sylinae_1.pd
A Flexible Multiprocessor Resource Sharing Framework for Ada
No full textLock-based resource sharing protocols for single processor systems are well understood and supported in programming languages such as Ada and the Real-Time Specification for Java, and in Real-Time Operating Systems, and those that conform to the Real-Time POSIX
standard. In contrast, multiprocessor resource sharing protocols are still in their infancy with no agreed best practices, and yet current real-time programming languages and operating systems claim to be suitable for supporting multiprocessor applications.
This thesis argues that, instead of supporting a single resource sharing protocol, a resource sharing framework should be provided that allows application-defined resource sharing protocols to be implemented. The framework should be flexible and adaptive so that a wide range of protocols with different design characteristics can be integrated and implemented effectively with minimum runtime overheads. The thesis reviews the currently available multiprocessor resource allocation policies and analyzes their applicability to the main industry standard real-time programming languages. It then proposes a framework that allows programmers to define and implement their own locking policy for monitor based concurrent control mechanisms. Instantiation of the framework is illustrated for the Real-Time Specification for Java and POSIX. A prototype implementation of the full framework for Ada is developed and evaluated
Redox-responsive F127-folate/F127-disulfide bond-D-α-tocopheryl polyethylene glycol 1000 succinate/P123 mixed micelles loaded with paclitaxel for the reversal of multidrug resistance in tumors
No full textJing Lin,* Chaoyue Zhao,* Cuijuan Liu, Shiyao Fu, Luying Han, Xinping Lu, Chunrong Yang College of Pharmacy, Jiamusi University, Jiamusi, Heilongjiang, China *These authors contributed equally to this work Introduction: The development of nanodrug carriers utilizing tumor microenvironment has become a hotspot in reversing multidrug resistance (MDR). Materials and methods: This study synthesized a redox-sensitive copolymer, Pluronic F127-disulfide bond-D-α-tocopheryl polyethylene glycol 1000 succinate (FSST), through the connection of the reduction-sensitive disulfide bond between F127 and D-α-tocopheryl polyethylene glycol 1000 succinate. This polymer could induce the elevation of reactive oxygen species (ROS) levels, ultimately resulting in cytotoxicity. Moreover, the redox-responsive mixed micelles, F127-folate (FA)/FSST/P123 (FFSSTP), based on FSST, Pluronic F127-FA, and Pluronic P123, were prepared to load paclitaxel (PTX). Results: The in vitro release study demonstrated that FFSSTP/PTX accelerated the PTX release through the breakage of disulfide bond in reductive environment. In cellular experiment, FFSSTP/PTX induced significant apoptosis in PTX-resistant MCF-7/PTX cells through inhibiting adenosine triphosphate (ATP)-binding cassette proteins from pumping out PTX by interfering with the mitochondrial function and ATP synthesis. Furthermore, FFSSTP/PTX induced apoptosis through elevating the intracellular levels of ROS. Conclusion: FFSSTP could become a potential carrier for the treatment of MDR tumors. Keywords: redox responsive, mixed micelles, multidrug resistance, paclitaxel, tumor microenvironmen
Micromechanical Progressive Failure Analyses of Composite Materials Using Continuum Decohesive Finite Element
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Experimental and Numerical Investigation on the Low Velocity Impact Response of a Highly Anisotropic Composite Panel
No full textHigh-fidelity Numerical Prediction of the Compressive Strength of Laminated Composites after Low Velocity Impact
No full textExperimental and Numerical Study on Low Velocity Impact Damage of a Shear Dominated Composite Laminate
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