Information about soil nitric oxide （NO） emissions from subtropical forests is quite limited, and even less is known about the pulse emission of NO when wetting soils after a long period of dryness. In this study, w...Information about soil nitric oxide （NO） emissions from subtropical forests is quite limited, and even less is known about the pulse emission of NO when wetting soils after a long period of dryness. In this study, we measured NO fluxes following wetting of dry soft in a broadleaf forest and a pine forest in subtropical China. Large pulses of NO fluxes were observed after soil wetting in both forests. NO fluxes increased significantly within 0.5 h following wetting in both forests and reached peak 1 and 4 h after soil wetting in the pine forest and the broadleaf forest, respectively. In the broadleaf forest, averaged peak flux of NO pulses was 157 ng N m^-2 s^-1, which was 8 times the flux value before wetting, and in the pine forest, the averaged peak flux was 135 ng N m-2 s 1, which was 15.5 times the flux value before wetting. The total pulses-induced NO emissions during the dry season were roughly estimated to be 29.4 mg N m^-2 in the broadleaf forest and 22.2 mg N m^-2 in the pine forest or made up a proportion of 4.6% of the annual NO emission in the broadleaf forest and 5.3% in the pine forest.展开更多
In November 2011, the Australian government approved the legislation （Clean Energy Act 2011） to introduce a reduction plan of carbon emissions in Australia. This plan will be implemented from July 2012. This is one ...In November 2011, the Australian government approved the legislation （Clean Energy Act 2011） to introduce a reduction plan of carbon emissions in Australia. This plan will be implemented from July 2012. This is one of the first accounting studies to investigate the potential impacts of this plan on long-lived asset values and operating cash flows for Australian listed companies. A sample of Australian Securities Exchange （ASX） 200 indexed companies from 2＇006 to 2010 is used. Hypotheses are tested based on Heckman＇s （1979） two-stage approach. Three regression models are developed to examine the association between carbon emissions and asset values/operating cash flows. This study finds that asset values and operating cash flows will be adversely affected, if the reduction plan is implemented. Specifically, this study finds that the book value of long-lived assets will decrease, if listed companies are considered to be emissions-liable. The book value of long-lived assets is further found to be negatively associated with listed companies＇ carbon emission levels. This study also demonstrates that operating cash flows of emissions-liable companies will be adversely affected. However, this study does not find a relationship between operating cash flows and companies＇ emission levels. The empirical findings from Australian listed companies provide the evidence that the reduction plan of carbon emissions will adversely affect corporate entities＇ asset values and operating cash flows. The results further indicate that the magnitude of the impact will be proportional to the companies＇ emission levels. The implications of these empirical findings for listed companies, for the accounting profession, and for carbon emission regulators are also discussed.展开更多
For centrifugal compressors used in automotive turbochargers, the extension of the surge margin is demanded because of lower engine speed. In order to estimate the surge line exactly, it is required to acquire the com...For centrifugal compressors used in automotive turbochargers, the extension of the surge margin is demanded because of lower engine speed. In order to estimate the surge line exactly, it is required to acquire the compressor characteristics at small or negative flow rate. In this paper, measurement and numerical simulation of the characteristics at small or negative flow rate are carried out. In the measurement, an experimental facility with a valve immediately downstream of the compressor is used to suppress the surge. In the numerical work, a new boundary condition that specifies mass flow rate at the outlet boundary is used to simulate the characteristics around the zero flow rate region. Furthermore, flow field analyses at small or negative flow rate are performed with the numerical results. The separated and re-circulated flow fields are investigated by visualization to identify the origin of losses.展开更多
This paper presents a study on the effects of phase transitions on the mantle convection of Venus in a three-dimensional （3D） spherical shell domain. Our model includes strong depth- and temperature-dependent viscos...This paper presents a study on the effects of phase transitions on the mantle convection of Venus in a three-dimensional （3D） spherical shell domain. Our model includes strong depth- and temperature-dependent viscosity and exothermic phase change from olivine to spinel as well as endothermic phase change from spinel to perovskite. From extensive numerical simulations of the effects of Rayleigh number （Ra）, and the Clapeyron slopes and depths of phase changes, we found the following： （1） The endothermic phase change prevents mass flow through the interface. Increasing the absolute value of the Clapeyron slopes decreases radial mass flux and normalized radial mass flux at the endotbermic phase boundary, and decreases the number of mantle plumes. In other words, mass flow through the phase boundary decreases. The inhibition influence of phase changes increases, as do convective wavelengths. （2） Increasing Ra also increases the convective wavelength and decreases the number of mantle plumes, but it has less influence on the mass exchange. As Ra increases, the convective vigor increases along with the radial mass flux and the mass flow through the phase boundary; however, the normalized mass flux through the phase boundary varies little with Ra, which is different from the conclusion that increasing Ra will greatly increase the inhibition of mass flow through the phase boundary based on two-dimensional （2D） modeling. （3） Increasing the depth of endothermic phase change will slightly decrease the number of mantle plumes, but has little effect on the mass flow through the phase boundary. Consistent with previous studies, our results show that the phase change from spinel to perovskite could inhibit the mass flow through the phase boundary, but they also show that the buildup of hot materials under the endothermic phase boundary in the 3D model could not be so large as to cause strong episodic overturns of mantle materials, which is quite different from previous 2D studies. Our results suggest that it is difficult for phase changes to cause significant magmatism on Venus; in other words, phase changes may not be the primary cause of catastrophic resurfacing on Venus.展开更多
The connectivity and tunability of superconducting quantum devices provide a rich platform to build quantum simulators and study novel many-body physics. Here we study quantum phase transition in a detuned multi-conne...The connectivity and tunability of superconducting quantum devices provide a rich platform to build quantum simulators and study novel many-body physics. Here we study quantum phase transition in a detuned multi-connected Jaynes-Cummings lattice, which can be constructed with superconducting circuits. This model is composed of alternatively connected qubits and cavity modes.Using a numerical method, we show that by varying the detuning between the qubits and the cavities, a phase transition from the superfluid phase to the Mott insulator phase occurs at commensurate fillings in a one-dimensional array. We study the phase transition in lattices with symmetric and asymmetric couplings, respectively.展开更多
With the rapid development of the computational fluid dynamics(CFD),a parameter-free upwind scheme capable of simulating all speeds accurately and efficiently is in high demand.To achieve this goal,we present a new up...With the rapid development of the computational fluid dynamics(CFD),a parameter-free upwind scheme capable of simulating all speeds accurately and efficiently is in high demand.To achieve this goal,we present a new upwind scheme called AUSMPWM in this paper.This scheme computes the numerical mass flux as the AUSMPW+and computes the interfacial sound speed in a different way.Also,it computes the pressure flux by limiting the dissipation if the Mach number is less than 1.Series of numerical experiments show that AUSMPWM can satisfy the following attractive properties independent of any tuning coefficient:(1)Robustness against the shock anomaly and high discontinuity’s resolution;(2)high accuracy on hypersonic heating prediction and capability to give smooth reproductions of heating profiles;(3)low dissipation at low speeds;and(4)strong grid,reconstruction scheme,and Mach number independence in low speeds’simulations.These properties suggest that AUSMPWM is promising to be widely used to accurately and efficiently simulate flows of all speeds.展开更多
This paper performs a numerical simulation of three-dimensional flow field in a centrifugal compressor with long inlet and outlet pipes using CFX software.By arranging virtual probes at different positions in both inl...This paper performs a numerical simulation of three-dimensional flow field in a centrifugal compressor with long inlet and outlet pipes using CFX software.By arranging virtual probes at different positions in both inlet and outlet planes,the aerodynamic performance of the centrifugal compressor is measured and compared with each other.Then effects of measuring positions on measurement results are discussed.The results show that it will generate notable measuring errors of the pressure ratio and efficiency if the inlet total pressure is measured using a single-point probe.The inlet total pressure data can be accurate when they are measured using a 3-point rake.The outlet total pressure and total temperature data can not be accurate if they are respectively measured at one circumferential position even using a multi-point rake.Increasing tangential measuring positions at the outlet is effective to improve the test accuracy.When the outlet total pressure and total temperature are respectively measured at 3 tangential positions,the data can be almost accurate.展开更多
基金Project supported by the National Key Basic Research and Development Program of China (No. 2002CB410803)
文摘Information about soil nitric oxide （NO） emissions from subtropical forests is quite limited, and even less is known about the pulse emission of NO when wetting soils after a long period of dryness. In this study, we measured NO fluxes following wetting of dry soft in a broadleaf forest and a pine forest in subtropical China. Large pulses of NO fluxes were observed after soil wetting in both forests. NO fluxes increased significantly within 0.5 h following wetting in both forests and reached peak 1 and 4 h after soil wetting in the pine forest and the broadleaf forest, respectively. In the broadleaf forest, averaged peak flux of NO pulses was 157 ng N m^-2 s^-1, which was 8 times the flux value before wetting, and in the pine forest, the averaged peak flux was 135 ng N m-2 s 1, which was 15.5 times the flux value before wetting. The total pulses-induced NO emissions during the dry season were roughly estimated to be 29.4 mg N m^-2 in the broadleaf forest and 22.2 mg N m^-2 in the pine forest or made up a proportion of 4.6% of the annual NO emission in the broadleaf forest and 5.3% in the pine forest.
文摘In November 2011, the Australian government approved the legislation （Clean Energy Act 2011） to introduce a reduction plan of carbon emissions in Australia. This plan will be implemented from July 2012. This is one of the first accounting studies to investigate the potential impacts of this plan on long-lived asset values and operating cash flows for Australian listed companies. A sample of Australian Securities Exchange （ASX） 200 indexed companies from 2＇006 to 2010 is used. Hypotheses are tested based on Heckman＇s （1979） two-stage approach. Three regression models are developed to examine the association between carbon emissions and asset values/operating cash flows. This study finds that asset values and operating cash flows will be adversely affected, if the reduction plan is implemented. Specifically, this study finds that the book value of long-lived assets will decrease, if listed companies are considered to be emissions-liable. The book value of long-lived assets is further found to be negatively associated with listed companies＇ carbon emission levels. This study also demonstrates that operating cash flows of emissions-liable companies will be adversely affected. However, this study does not find a relationship between operating cash flows and companies＇ emission levels. The empirical findings from Australian listed companies provide the evidence that the reduction plan of carbon emissions will adversely affect corporate entities＇ asset values and operating cash flows. The results further indicate that the magnitude of the impact will be proportional to the companies＇ emission levels. The implications of these empirical findings for listed companies, for the accounting profession, and for carbon emission regulators are also discussed.
文摘For centrifugal compressors used in automotive turbochargers, the extension of the surge margin is demanded because of lower engine speed. In order to estimate the surge line exactly, it is required to acquire the compressor characteristics at small or negative flow rate. In this paper, measurement and numerical simulation of the characteristics at small or negative flow rate are carried out. In the measurement, an experimental facility with a valve immediately downstream of the compressor is used to suppress the surge. In the numerical work, a new boundary condition that specifies mass flow rate at the outlet boundary is used to simulate the characteristics around the zero flow rate region. Furthermore, flow field analyses at small or negative flow rate are performed with the numerical results. The separated and re-circulated flow fields are investigated by visualization to identify the origin of losses.
基金supported by National Natural Science Foundation of China(Grant Nos.41474082,91014005)Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZCX2-YW-QN507)t
文摘This paper presents a study on the effects of phase transitions on the mantle convection of Venus in a three-dimensional （3D） spherical shell domain. Our model includes strong depth- and temperature-dependent viscosity and exothermic phase change from olivine to spinel as well as endothermic phase change from spinel to perovskite. From extensive numerical simulations of the effects of Rayleigh number （Ra）, and the Clapeyron slopes and depths of phase changes, we found the following： （1） The endothermic phase change prevents mass flow through the interface. Increasing the absolute value of the Clapeyron slopes decreases radial mass flux and normalized radial mass flux at the endotbermic phase boundary, and decreases the number of mantle plumes. In other words, mass flow through the phase boundary decreases. The inhibition influence of phase changes increases, as do convective wavelengths. （2） Increasing Ra also increases the convective wavelength and decreases the number of mantle plumes, but it has less influence on the mass exchange. As Ra increases, the convective vigor increases along with the radial mass flux and the mass flow through the phase boundary; however, the normalized mass flux through the phase boundary varies little with Ra, which is different from the conclusion that increasing Ra will greatly increase the inhibition of mass flow through the phase boundary based on two-dimensional （2D） modeling. （3） Increasing the depth of endothermic phase change will slightly decrease the number of mantle plumes, but has little effect on the mass flow through the phase boundary. Consistent with previous studies, our results show that the phase change from spinel to perovskite could inhibit the mass flow through the phase boundary, but they also show that the buildup of hot materials under the endothermic phase boundary in the 3D model could not be so large as to cause strong episodic overturns of mantle materials, which is quite different from previous 2D studies. Our results suggest that it is difficult for phase changes to cause significant magmatism on Venus; in other words, phase changes may not be the primary cause of catastrophic resurfacing on Venus.
基金supported by the National Science Foundation under Award Number(Grant No.0956064)
文摘The connectivity and tunability of superconducting quantum devices provide a rich platform to build quantum simulators and study novel many-body physics. Here we study quantum phase transition in a detuned multi-connected Jaynes-Cummings lattice, which can be constructed with superconducting circuits. This model is composed of alternatively connected qubits and cavity modes.Using a numerical method, we show that by varying the detuning between the qubits and the cavities, a phase transition from the superfluid phase to the Mott insulator phase occurs at commensurate fillings in a one-dimensional array. We study the phase transition in lattices with symmetric and asymmetric couplings, respectively.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2009CB724104)
文摘With the rapid development of the computational fluid dynamics(CFD),a parameter-free upwind scheme capable of simulating all speeds accurately and efficiently is in high demand.To achieve this goal,we present a new upwind scheme called AUSMPWM in this paper.This scheme computes the numerical mass flux as the AUSMPW+and computes the interfacial sound speed in a different way.Also,it computes the pressure flux by limiting the dissipation if the Mach number is less than 1.Series of numerical experiments show that AUSMPWM can satisfy the following attractive properties independent of any tuning coefficient:(1)Robustness against the shock anomaly and high discontinuity’s resolution;(2)high accuracy on hypersonic heating prediction and capability to give smooth reproductions of heating profiles;(3)low dissipation at low speeds;and(4)strong grid,reconstruction scheme,and Mach number independence in low speeds’simulations.These properties suggest that AUSMPWM is promising to be widely used to accurately and efficiently simulate flows of all speeds.
基金funded by Chinese Key Laboratory Fund,Grant No.9140C3310040705the National Natural Science Foundation of China,Grant No.50776004+1 种基金supported by the 111 Project,No.B07009973 Project,No.2007CB210103
文摘This paper performs a numerical simulation of three-dimensional flow field in a centrifugal compressor with long inlet and outlet pipes using CFX software.By arranging virtual probes at different positions in both inlet and outlet planes,the aerodynamic performance of the centrifugal compressor is measured and compared with each other.Then effects of measuring positions on measurement results are discussed.The results show that it will generate notable measuring errors of the pressure ratio and efficiency if the inlet total pressure is measured using a single-point probe.The inlet total pressure data can be accurate when they are measured using a 3-point rake.The outlet total pressure and total temperature data can not be accurate if they are respectively measured at one circumferential position even using a multi-point rake.Increasing tangential measuring positions at the outlet is effective to improve the test accuracy.When the outlet total pressure and total temperature are respectively measured at 3 tangential positions,the data can be almost accurate.
