714,431 research outputs found
Quench characteristics of a Cu-Stabilized 2G HTS conductor
No full textThe prospect of medium/high field superconducting magnets using 2G HTS tapes is approaching to reality with continued enhancement in the performance of these conductors. Direct measurements of 1d adiabatic quench initiation and propagation of a Cu-stabilized 2G conductor have been carried out with spatial-temporal recording of temperature and voltage following the deposition of various local heat pulses to the conductor at different temperatures between 40K and 64K carrying different transport currents. It was found that the stabilizer-free 2G tape maintains the unique characteristics previously measured in non-stabilized tape of increasing MPZ with transport current and higher quench energy at lower temperatures. The minimum quench energy, minimum propagation zone (MPZ) length are determined as a function of temperature and transport current. The change in MPZ size is investigated with measured temperature dependent E-J characteristics. The results add more detail to help understand the unique characteristics of increasing MPZ with transport current and lower temperatures
Evolutionary computation in dynamic and uncertain environments
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Abstraction Refinement Guided by a Learnt Probabilistic Model
Get PDFThe core challenge in designing an effective static program analysis is to find a good program abstraction -- one that retains only details relevant to a given query. In this paper, we present a new approach for automatically finding such an abstraction. Our approach uses a pessimistic strategy, which can optionally use guidance from a probabilistic model. Our approach applies to parametric static analyses implemented in Datalog, and is based on counterexample-guided abstraction refinement. For each untried abstraction, our probabilistic model provides a probability of success, while the size of the abstraction provides an estimate of its cost in terms of analysis time. Combining these two metrics, probability and cost, our refinement algorithm picks an optimal abstraction. Our probabilistic model is a variant of the Erdos-Renyi random graph model, and it is tunable by what we call hyperparameters. We present a method to learn good values for these hyperparameters, by observing past runs of the analysis on an existing codebase. We evaluate our approach on an object sensitive pointer analysis for Java programs, with two client analyses (PolySite and Downcast)
Structural performance of flexibly formed concrete T beams with wound FRP reinforcement
No full textFlexible formwork has been used in the casting of structural concrete since the 1980s. Research has shown that it is potentially unconservative to design fabric formed concrete beams in shear using existing codes and standards. In addition, with traditional steel reinforcement, it is time and labour consuming to fabricate the cage of beam with variable depth and the difficulty of bending steel leads to inaccurate locating of the cages. Moreover, corrosion of steel will increase the life-cycle cost of concrete structures. In this work, Wound Fibre Reinforced Polymer (W-FRP) was introduced to flexibly formed concrete. Eight T-beams with W-FRP reinforcement were designed and tested. Different codes and a revised Modified Compression Field Theory (MCFT) model were compared with the test results. The flexural and shear performances of the specimens were analysed. Key conclusions are that 1) W-FRP reinforcement is capable of supplying sufficient shear capacity; 2) arranging W-FRP in an optimal pattern can increase the shear capacity of the specimens and avoid shear failure; 3) debonding failures demonstrate the importance of longitudinal bars in carrying shear and the anchorage strength in design; and 4) the MCFT model gave better predictions than the two codified predictions
Preparation and characterisation of Tl<sub>2</sub>Ba<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>y</sub> Superconducting Tapes
No full textA Novel 4x4 Optical Switch Using An Anisotropically-etched Micro-mirror Array and A Bi-stable Mini-actuator Array
No full textIntersystem soft handover for converged DVB-H and UMTS networks
Get PDFDigital video broadcasting for handhelds (DVB-H) is the standard for broadcasting Internet Protocol (IP) data services to mobile portable devices. To provide interactive services for DVB-H, the Universal Mobile Telecommunications System (UMTS) can be used as a terrestrial interaction channel for the unidirectional DVB-H network. The converged DVB-H and UMTS network can be used to address the congestion problems due to the limited multimedia channel accesses of the UMTS network. In the converged network, intersystem soft handover between DVB-H and UMTS is needed for an optimum radio resource allocation, which reduces network operation cost while providing the required quality of service. This paper deals with the intersystem soft handover between DVB-H and UMTS in such a converged network. The converged network structure is presented. A novel soft handover scheme is proposed and evaluated. After considering the network operation cost, the performance tradeoff between the network quality of service and the network operation cost for the intersystem soft handover in the converged network is modeled using a stochastic tree and analyzed using a numerical simulation. The results show that the proposed algorithm is feasible and has the potential to be used for implementation in the real environment
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