This paper numerically investigates the radio wave scattering by the artificial acoustic disturbance in the atmospheric boundary layer. The numerical model is based on the finitedifference time-domain（FDTD） method f...This paper numerically investigates the radio wave scattering by the artificial acoustic disturbance in the atmospheric boundary layer. The numerical model is based on the finitedifference time-domain（FDTD） method for radio wave propagation and fluid simulation for atmospheric disturbance by acoustics waves. The characteristics of radio wave scattering propagation in the artificial acoustic perturbations are investigated by this numerical model. The numerical simulation results demonstrate that the radio wave propagation scattered by acoustic scatterer has the characteristic of forward tropospheric scatter. When the radio waves are scattered, they distribute in all directions; a majority of radio waves continues to propagate along the original direction, and only a small part of the energy is scattered. For the same acoustic scatterer, if we merely change the radio wave emission elevation, the horizontal spans of forward scattering radio wave packets centers gradually decrease with the increasing of emission elevations; and the energy of wave packets increases firstly and then decreases with launching elevation, reaching the maximum at a certain angle. If we merely change the wave emitting position, the horizontal spans decrease with the increasing of emission positions, and the energy of wave packets also increases firstly and then decreases with launch position, reaching the maximum at a certain position. This approach can be very promising for atmospheric scatter communications.展开更多
Electron density profiles of Venus＇ ionosphere are inverted from the Venus Express （VEX） one-way open-loop radio occultation experiments carried out by the Shanghai 25 m antenna from November 2011 to January 2012 a...Electron density profiles of Venus＇ ionosphere are inverted from the Venus Express （VEX） one-way open-loop radio occultation experiments carried out by the Shanghai 25 m antenna from November 2011 to January 2012 at solar maximum conditions and by the New Norcia 35 m antenna from August 2006 to June 2008 at solar intermediate conditions. The electron density profile （from 110 km to 400 km）, retrieved from the X-band egress observation at the Shanghai station, shows a single peak near 147 km with a peak density of about 2 × 10^4 cm-3 at a solar zenith angle of 94° As a comparison, the VEX radio science （VeRa） observations at the New Norcia station were also examined, including S- and X-band and dual-frequency data in the ingress mode. The results show that the electron density profiles retrieved from the S-band data are more analogous to the dual-frequency data in terms of the profile shape, compared with the X-band data. Generally, the S-band results slightly underestimate the magnitude of the peak density, while the X-band results overestimate it. The discrepancy in the X-band profile is probably due to the relatively larger unmod- eled orbital errors. It is also expected that the ionopause height is sensitive to the solar wind dynamical pressure in high and intermediate solar activities, usually in the range of 200-1000 km on the dayside and much higher on the nightside. Structural variations （＂bulges＂ and fluctuations） can be found in the electron density profiles during intermediate solar activity, which may be caused by the interaction of the solar wind with the ionosphere. Considerable ionizations can be observed in Venus＇ nightside ionosphere, which are unexpected for the Martian nightside ionosphere in most cases.展开更多
The study of the relationship of climate and indoor thermal environments in architecture is essential to understand the inhabitants＇ sensory perception. This is even more relevant when working in the existing housing...The study of the relationship of climate and indoor thermal environments in architecture is essential to understand the inhabitants＇ sensory perception. This is even more relevant when working in the existing housing stock in view of the new challenges posed by the conservation of the 20th century architectural heritage and the adaption of these buildings to our current comfort and environmental criteria. This article aims to develop a balanced understanding of the approach of Modernist architecture to climate, indoor atmospheres and inhabitants＇ thermal comfort. To do so, we complement the quantitative approach of environmental assessment methods with the qualitative angle of the history of sensory and architecture. The goal is to understand the environmental performance of architecture for dealing nowadays with thermal comfort issues while respecting its cultural and historical values. Two modernist houses have been selected as case studies： the Villa Curutchet of the master Le Corbusier and the Villa Chupin of his discipte Andr Wogenscky. As a result, the article reveals potentialities and constraints in terms of thermal comfort when working with Modern Architecture.展开更多
基金supported by the National Natural Science Foundation of China(412041114157414641774162)
文摘This paper numerically investigates the radio wave scattering by the artificial acoustic disturbance in the atmospheric boundary layer. The numerical model is based on the finitedifference time-domain（FDTD） method for radio wave propagation and fluid simulation for atmospheric disturbance by acoustics waves. The characteristics of radio wave scattering propagation in the artificial acoustic perturbations are investigated by this numerical model. The numerical simulation results demonstrate that the radio wave propagation scattered by acoustic scatterer has the characteristic of forward tropospheric scatter. When the radio waves are scattered, they distribute in all directions; a majority of radio waves continues to propagate along the original direction, and only a small part of the energy is scattered. For the same acoustic scatterer, if we merely change the radio wave emission elevation, the horizontal spans of forward scattering radio wave packets centers gradually decrease with the increasing of emission elevations; and the energy of wave packets increases firstly and then decreases with launching elevation, reaching the maximum at a certain angle. If we merely change the wave emitting position, the horizontal spans decrease with the increasing of emission positions, and the energy of wave packets also increases firstly and then decreases with launch position, reaching the maximum at a certain position. This approach can be very promising for atmospheric scatter communications.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11103063 and 11178008)the National Key Basic Research Program of China (Grant No. 2015CB857101)partly supported by the Key Laboratory of Planetary Sciences, Chinese Academy of Sciences (Grant No. PSL15 04)
文摘Electron density profiles of Venus＇ ionosphere are inverted from the Venus Express （VEX） one-way open-loop radio occultation experiments carried out by the Shanghai 25 m antenna from November 2011 to January 2012 at solar maximum conditions and by the New Norcia 35 m antenna from August 2006 to June 2008 at solar intermediate conditions. The electron density profile （from 110 km to 400 km）, retrieved from the X-band egress observation at the Shanghai station, shows a single peak near 147 km with a peak density of about 2 × 10^4 cm-3 at a solar zenith angle of 94° As a comparison, the VEX radio science （VeRa） observations at the New Norcia station were also examined, including S- and X-band and dual-frequency data in the ingress mode. The results show that the electron density profiles retrieved from the S-band data are more analogous to the dual-frequency data in terms of the profile shape, compared with the X-band data. Generally, the S-band results slightly underestimate the magnitude of the peak density, while the X-band results overestimate it. The discrepancy in the X-band profile is probably due to the relatively larger unmod- eled orbital errors. It is also expected that the ionopause height is sensitive to the solar wind dynamical pressure in high and intermediate solar activities, usually in the range of 200-1000 km on the dayside and much higher on the nightside. Structural variations （＂bulges＂ and fluctuations） can be found in the electron density profiles during intermediate solar activity, which may be caused by the interaction of the solar wind with the ionosphere. Considerable ionizations can be observed in Venus＇ nightside ionosphere, which are unexpected for the Martian nightside ionosphere in most cases.
文摘The study of the relationship of climate and indoor thermal environments in architecture is essential to understand the inhabitants＇ sensory perception. This is even more relevant when working in the existing housing stock in view of the new challenges posed by the conservation of the 20th century architectural heritage and the adaption of these buildings to our current comfort and environmental criteria. This article aims to develop a balanced understanding of the approach of Modernist architecture to climate, indoor atmospheres and inhabitants＇ thermal comfort. To do so, we complement the quantitative approach of environmental assessment methods with the qualitative angle of the history of sensory and architecture. The goal is to understand the environmental performance of architecture for dealing nowadays with thermal comfort issues while respecting its cultural and historical values. Two modernist houses have been selected as case studies： the Villa Curutchet of the master Le Corbusier and the Villa Chupin of his discipte Andr Wogenscky. As a result, the article reveals potentialities and constraints in terms of thermal comfort when working with Modern Architecture.
