Conformal Symmetry on the Instanton Moduli Space

The conformal symmetry on the instanton moduli space is discussed using the ADHM construction, where a viewpoint of "homogeneous coordinates" for both the spacetime and the moduli space turns out to be useful. It is shown that the conformal algebra closes only up to global gauge transformations, which generalizes the earlier discussion by Jackiw et al. An interesting 5-dimensional interpretation of the SU(2) single-instanton is also mentioned.Comment: 7 pages, LaTeX, version to appear in J. Phys. A: Math. Ge

Using porous metals to enhance heat transfer in phase change materials (PCMs)

Heat transfer enhancement mechanism of Phase Change Materials (PCMs) by high-porosity metal foams was investigated in this study. The Darcy-Brinkman-Forchheimer modified flow model was employed in the numerical simulations to consider the non-Darcy effects in metal foams: viscous flow resistance and inertia flow resistance. Local Non-Thermal Equilibrium (LNTE) model was used to consider the temperature difference between PCM and metal foam. The results showed that in the solid and two-phase zone the heat transfer rate in PCMs was significantly increased by metal foams, whilst in the liquid zone, natural convection was found to be weakened by the large flow resistance of metal foams, despite which the overall heat transfer rate was still higher than the case where metal foams were not used. Metal foams of low porosity and high pore density were found to perform better than the ones of high porosity and low pore density

Universal Quantum Degeneracy Point for Superconducting Qubits

The quantum degeneracy point approach [D. Vion et al., Science 296, 886 (2002)] effectively protects superconducting qubits from low-frequency noise that couples with the qubits as transverse noise. However, low-frequency noise in superconducting qubits can originate from various mechanisms and can couple with the qubits either as transverse or as longitudinal noise. Here, we present a quantum circuit containing a universal quantum degeneracy point that protects an encoded qubit from arbitrary low-frequency noise. We further show that universal quantum logic gates can be performed on the encoded qubit with high gate fidelity. The proposed scheme is robust against small parameter spreads due to fabrication errors in the superconducting qubits.Comment: 7 pages, 4 figure

Importance of mutual benefits in online knowledge sharing communities

The sustainability of knowledge sharing e-communities is a major issue at present. A hypothesis was proposed at the outset in the paper that the provision of mutual benefits among participants will lead to positive participation. Drawing from the economic and social theories, a framework for analysis was developed and tested in an empirical study. The preliminary results demonstrated a direct relationship between mutual benefits and the level of participation, and hence supported the hypothesis

R134a flow boiling heat transfer in small diameter tubes

Copyright @ 2007 RT Edwards Inc.Boiling heat transfer in small diameter tubes has been experimentally investigated using R134a as the working fluid. The heat transfer periments were conducted with two stainless steel tubes of internal diameter 4.26 mm and 2.01 mm respectively. Other parameters were varied in the range: mass flux 100 – 500 kg/m2s; pressure 8 – 14 bar; quality up to 0.9; heat flux 13 - 150 kW/m2. The heat transfer coefficient was found to be independent of vapour quality when the quality was less than about 40% to 50% for the 4.26 mm tube and 20% to 30 % for the 2.01 mm tube. Above these quality values, the heat transfer coefficient decreases with vapour quality. Furthermore, at high heat flux values this decrease occurs for the entire quality range. The heat transfer rates were compared with existing correlations.

Infrared imaging investigation of temperature fluctuation and spatial distribution for a large laminated lithium ion power battery

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The present study investigates the thermal behaviors of a naturally cooled NCM-type LIB (LiNi1−x−yCoxMnyO2 as cathode) from an experimental and systematic approach. The temperature distribution was acquired for different discharge rates and Depth of Discharge (DOD) by the infrared imaging (IR) technology. Two new factors, the temperature variance ( ) and local overheating index (LOH index), were proposed to assess the temperature fluctuation and distribution. Results showed that the heat generation rate was higher on the cathode side than that on the anode side due to the different resistivity of current collectors. For a low-power discharge, the eventual stable high-temperature zone occurred in the center of the battery, while with a high-power discharge, the upper part of the battery was the high temperature region from the very beginning of discharge. It was found that the temperature variance ( ) and local overheating index (LOH index) were capable of holistically exhibiting the temperature non-uniformity both on numerical fluctuation and spatial distribution with varying discharge rates and DOD. With increasing the discharge rate and DOD, temperature distribution showed an increasingly non-uniform trend, especially at the initial and final stage of high-power discharge, the heat accumulation and concentration area increased rapidly

How to select combination operators for fuzzy expert systems using CRI

A method to select combination operators for fuzzy expert systems using the Compositional Rule of Inference (CRI) is proposed. First, fuzzy inference processes based on CRI are classified into three categories in terms of their inference results: the Expansion Type Inference, the Reduction Type Inference, and Other Type Inferences. Further, implication operators under Sup-T composition are classified as the Expansion Type Operator, the Reduction Type Operator, and the Other Type Operators. Finally, the combination of rules or their consequences is investigated for inference processes based on CRI

The Implementation of Flipped Classroom in Efl Class: a Taiwan Case Study

This article reports on a case study designed to examine the implementation of flipped classroom in the EFL classroom in Taiwan.  In addition, students' perception of flipped classroom was also investigated. Sixty-one senior high school students participated in this study; data were gathered from students' English midterm exam score and questionnaire. The data then were quantitatively analyzed by using T-test and descriptive statistics. The results show that students' English proficiency in flipped classroom was not significantly different with students in traditional classroom. However, the results reveal that students' perception of flipped classroom were generally favorable. Students' contended that flipped classroom enhanced their motivation in learning English, as they liked the self-pace through the course and they stated that flipped classroom gave them more class time to practice English. The results presented here may facilitate improvements in the implementation of flipped classroom in EFL class. Furthermore, suggestions for further research are also presented