The current-voltage（I-V） characteristics of cBN crystal sandwiched between two metallic electrodes are measured and found to be nonlinear. Over 20 samples are measured at room temperature with various electrodes, an...The current-voltage（I-V） characteristics of cBN crystal sandwiched between two metallic electrodes are measured and found to be nonlinear. Over 20 samples are measured at room temperature with various electrodes, and the resulting curves are all similar in shape. When a voltage of about 560V is applied to the cBN crystal, the emitted light is visible to the naked eye in a dark room. We explain these phenomena by the space charge limited current and the electronic transition between the X and Г valleys of the conduction band.展开更多
Oil-air two-phase flow measurement was investigated with a Venturi and void fraction meters in this work. This paper proposes a new flow rate measurement correlation in which the effect of the velocity ratio between g...Oil-air two-phase flow measurement was investigated with a Venturi and void fraction meters in this work. This paper proposes a new flow rate measurement correlation in which the effect of the velocity ratio between gas and liquid was considered. With the pressure drop across the Venturi and the void fraction that was measured by electrical capacitance tomography apparatus, both mixture flow rate and oil flow rate could be obtained by the correlation. Experiments included bubble-, slug-, wave and annular flow with the void fraction ranging from 15% to 83%, the oil flow rate ranging from 0.97 kg/s to 1.78 kg/s, the gas flow rate ranging up to 0.018 kg/s and quality ranging nearly up to 2.0%. The root-mean-square errors of mixture mass flow rate and that of oil mass flow rate were less than 5%. Furthermore, coefficients of the correlation were modified based on flow regimes, with the results showing reduced root-mean-square errors.展开更多
A special device was designed to measure temperature difference in this study of heat transfer of water and oil cross flow inside vertical upward tubes. A new heat transfer correlation was obtained for cross flow. The...A special device was designed to measure temperature difference in this study of heat transfer of water and oil cross flow inside vertical upward tubes. A new heat transfer correlation was obtained for cross flow. The experimental results showed that the dependence of heat transfer on Reynolds is much smaller in a narrow space than that in a wide space. It was found that the heat transfer correlation of cross flow in a narrow space is obviously different from that in a wide space, and that the heat transfer correlation obtained in a wide space may not be applicable to the cross-flow heat transfer in a narrow space. Further, the single-phase heat transfer capability of water cross flow was compared with that of oil cross flow. The experimental results showed that the average heat transfer coefficient of water is about 2～3 times that ofoil when they have the same superficial velocity.展开更多
In this paper, an additive dichotomous noise model and a multiplicative dichotomous noise model are investigated for the effect of the asymmetry of the additive and multiplicative dichotomous noises on the transport o...In this paper, an additive dichotomous noise model and a multiplicative dichotomous noise model are investigated for the effect of the asymmetry of the additive and multiplicative dichotomous noises on the transport of the particles, in the presence of spatial symmetry and asymmetry, respectively. It is shown that, in the presence of spatial asymmetry, the asymmetry of the dichotomous noise can weaken or enhance the transport of the particles; while in the absence of spatial asymmetry, the nonzero current induced by the noise＇s asymmetry is ＂symmetric＂ around the zero current. In addition, a current reversal can be produced by controlling the noise＇s asymmetry parameter; and we find that, for some values of the noise＇s asymmetry parameter, the multiplicative dichotomous noise can more easily induce the transport of the particles than the additive dichotomous noise.展开更多
文摘The current-voltage（I-V） characteristics of cBN crystal sandwiched between two metallic electrodes are measured and found to be nonlinear. Over 20 samples are measured at room temperature with various electrodes, and the resulting curves are all similar in shape. When a voltage of about 560V is applied to the cBN crystal, the emitted light is visible to the naked eye in a dark room. We explain these phenomena by the space charge limited current and the electronic transition between the X and Г valleys of the conduction band.
基金Project (No. 2001AA413210) supported by the Hi-Tech Researchand Development Program (863) of China
文摘Oil-air two-phase flow measurement was investigated with a Venturi and void fraction meters in this work. This paper proposes a new flow rate measurement correlation in which the effect of the velocity ratio between gas and liquid was considered. With the pressure drop across the Venturi and the void fraction that was measured by electrical capacitance tomography apparatus, both mixture flow rate and oil flow rate could be obtained by the correlation. Experiments included bubble-, slug-, wave and annular flow with the void fraction ranging from 15% to 83%, the oil flow rate ranging from 0.97 kg/s to 1.78 kg/s, the gas flow rate ranging up to 0.018 kg/s and quality ranging nearly up to 2.0%. The root-mean-square errors of mixture mass flow rate and that of oil mass flow rate were less than 5%. Furthermore, coefficients of the correlation were modified based on flow regimes, with the results showing reduced root-mean-square errors.
文摘A special device was designed to measure temperature difference in this study of heat transfer of water and oil cross flow inside vertical upward tubes. A new heat transfer correlation was obtained for cross flow. The experimental results showed that the dependence of heat transfer on Reynolds is much smaller in a narrow space than that in a wide space. It was found that the heat transfer correlation of cross flow in a narrow space is obviously different from that in a wide space, and that the heat transfer correlation obtained in a wide space may not be applicable to the cross-flow heat transfer in a narrow space. Further, the single-phase heat transfer capability of water cross flow was compared with that of oil cross flow. The experimental results showed that the average heat transfer coefficient of water is about 2～3 times that ofoil when they have the same superficial velocity.
基金Supported by National Natural Science Foundation of China under Grant No. 10975079the Natural Science Foundation of Ningbo under Grant No. 2008A61003K.C. Wong Magna Fund in Ningbo University of China
文摘In this paper, an additive dichotomous noise model and a multiplicative dichotomous noise model are investigated for the effect of the asymmetry of the additive and multiplicative dichotomous noises on the transport of the particles, in the presence of spatial symmetry and asymmetry, respectively. It is shown that, in the presence of spatial asymmetry, the asymmetry of the dichotomous noise can weaken or enhance the transport of the particles; while in the absence of spatial asymmetry, the nonzero current induced by the noise＇s asymmetry is ＂symmetric＂ around the zero current. In addition, a current reversal can be produced by controlling the noise＇s asymmetry parameter; and we find that, for some values of the noise＇s asymmetry parameter, the multiplicative dichotomous noise can more easily induce the transport of the particles than the additive dichotomous noise.
