There are five Species of swan in the world. Three of them were recorded in China. They are whooper swan(Cygnus cygnus ). whistling swan (Cygnus columbianus ) and mute swan (Cygnus olor). Among them. whooper swan is t...There are five Species of swan in the world. Three of them were recorded in China. They are whooper swan(Cygnus cygnus ). whistling swan (Cygnus columbianus ) and mute swan (Cygnus olor). Among them. whooper swan is themost famous in China. Whooper swan is a resident bird in China. They breed in Xinjiang Ugyur Autonomous Region. InnerMongol Autonomous Region, Hcilongiiang Province. etc.. and winter in Qinghai. Shandong. Henan Provincc. etc.. and thelower reaches of the Changjiang River. The total number in China is about 5.000 in breeding grounds and 15.000 in winter-ing grounds. Higher number Were found in 1960s. Because of the changes in environment and hunting, of picking up eggsand of catching nestlings. their population is being reduced rapidly. They are in danger now. In order to protect the whooperswans. some protection measuresmust be taken. such as strcngthening public education and scientitic research- establishinga base of raising and breeding; deieloping intcrnational cooperation. strengthening the construction of natural reserves in thebreeding and wintering grounds. Up to the cnd of 1993. 34 natural reserves have been established in China.展开更多
Quantities characterizing temporal property, e.g., power density, coherence, and time lag, can be defined and calculated directly in the time domain without using the Fourier transformation. Spectral hardness, variab...Quantities characterizing temporal property, e.g., power density, coherence, and time lag, can be defined and calculated directly in the time domain without using the Fourier transformation. Spectral hardness, variability duration, and correlation between different characteristic quamtities on different time scale can be studied in the time domain as well. The temporal analysis technique in the time domain is a powerful tool, particularly in studying rapid variability on short time scales (or in high frequencies). Results of studying variabilities of X-rays from Cyg X-1 with the analysis technique in the time domain and RXTE data reveal valuable clues to understanding production and propagation processes of X-rays and structure of accretion disk in the black hole system.展开更多
Calculating the time lags over different timescales using the cross-correlation technique may lead to a biased estimate of small timescales.Given a timescale for lightcurve binning,we propose to subtract the local ave...Calculating the time lags over different timescales using the cross-correlation technique may lead to a biased estimate of small timescales.Given a timescale for lightcurve binning,we propose to subtract the local average instead of the global average during the cross-correlation,in order to filter variations on timescales larger than the bin size.The new method allows us to make an unbiased estimate of the time lags using RXTE/PCA data on timescales as small as-5 ms,where the Fourier technique becomes invalid.We calculate the time lag spectra of Cygnus X-1 at different spectral states with the new method,and find that the source appears to have similar X-ray lags on small timescales independent of its spectral states.展开更多
Già da vari anni è rilevabile la presenza di individui semiselvatici di Cigno reale sulLago d’Iseo.Nel gennaio 1991,durante il censimento annuale degli Anatidi,sono staticontati 4 individui nella zona del b...Già da vari anni è rilevabile la presenza di individui semiselvatici di Cigno reale sulLago d’Iseo.Nel gennaio 1991,durante il censimento annuale degli Anatidi,sono staticontati 4 individui nella zona del basso lago (Clusane) di cui almeno 2 perfettamentevolanti.Durante successive visite il 13 aprile nella Riserva Naturale delle Torbiere (località《Lamette》) abbiamo constatato la prima nidificazione certa per l’intero bacino lacustre.展开更多
The thin layer approximation applied to the expansion of a supernova remnant assumes that all the swept mass resides in a thin shell. The law of motion in the thin layer approximation is therefore found using the cons...The thin layer approximation applied to the expansion of a supernova remnant assumes that all the swept mass resides in a thin shell. The law of motion in the thin layer approximation is therefore found using the conservation of momentum. Here we instead introduce the conservation of energy in the framework of the thin layer approximation. The first case to be analysed is that of an interstellar medium with constant density and the second case is that of 7 profiles of decreasing density with respect to the centre of the explosion. The analytical and numerical results are applied to 4 supernova remnants: Tycho, Cas A, Cygnus loop, and SN 1006. The back reaction due to the radiative losses for the law of motion is evaluated in the case of constant density of the interstellar medium.展开更多
Charismatic species are often reported by the media,providing information for detecting population status and public perception.To identify the number and distribution of free-living Black Swan(Cygnus atratus),a chari...Charismatic species are often reported by the media,providing information for detecting population status and public perception.To identify the number and distribution of free-living Black Swan(Cygnus atratus),a charismatic alien species in Chinese mainland and to detect the public and the media attitudes to the species,we analyzed the reports and emotional tendency from media coverage in 2000-2022 using manual reading,crawler extraction and latent Dirichlet allocation.A total of 6654 Black Swans were reported at 711 sites,including 147 individuals at 30 nature reserves.Successful breeding was reported at one-fourth of the total sites,including five nature reserves.The proportion of positive emotional tendency to Black Swans was overwhelming in the reports and was higher than that to alien species in general,suggesting that the public and the media are unaware of the risk of biological invasion.Effective management of invasive species requires the media clarifies the invasion risk of charismatic alien species.Promoting the unity between the harmfulness of abstract concept of alien species and the charisma of a specific alien species among the public help effective management.展开更多
In this paper we derive three equations of motion for a supernova remnant (SNR) in the framework of the thin layer approximation using the Padé approximant. The circumstellar medium is assumed to follow a density...In this paper we derive three equations of motion for a supernova remnant (SNR) in the framework of the thin layer approximation using the Padé approximant. The circumstellar medium is assumed to follow a density profile of either an exponential type, a Gaussian type, or a Lane-Emden (n = 5) type. The three equations of motion are applied to four SNRs: Tycho, Cas A, Cygnus loop, and SN 1006. The percentage error of the Padé approximated solution is always less than 10%. The theoretical decrease of the velocity over ten years for SNRs is evaluated.展开更多
We have investigated the relation between the root mean square(rms)variability and the X-ray flux(rms-flux relation)of the Z source Cyg X-2,and as well the energy dependence based on the Rossi X-ray Timing Explorer(RX...We have investigated the relation between the root mean square(rms)variability and the X-ray flux(rms-flux relation)of the Z source Cyg X-2,and as well the energy dependence based on the Rossi X-ray Timing Explorer(RXTE)observations.We currently focus on the horizontal branch(HB),due to the negative correlation in flux of the soft and the hard X-rays.The rms-flux correlation has energy dependence as follows:positive at hard X-rays(above 10 keV)but negative at soft X-rays(below 10 keV).This provides a feature different from the previous one,and may be suggestive of different origins of X-rays below and above 10 keV.Nevertheless,the overall spectrum can be well fitted with a model consisting of a blackbody and Comptonization components,but the fitting results do not reveal any features around 10 keV that could account for such a change in the rms-flux relation.展开更多
文摘There are five Species of swan in the world. Three of them were recorded in China. They are whooper swan(Cygnus cygnus ). whistling swan (Cygnus columbianus ) and mute swan (Cygnus olor). Among them. whooper swan is themost famous in China. Whooper swan is a resident bird in China. They breed in Xinjiang Ugyur Autonomous Region. InnerMongol Autonomous Region, Hcilongiiang Province. etc.. and winter in Qinghai. Shandong. Henan Provincc. etc.. and thelower reaches of the Changjiang River. The total number in China is about 5.000 in breeding grounds and 15.000 in winter-ing grounds. Higher number Were found in 1960s. Because of the changes in environment and hunting, of picking up eggsand of catching nestlings. their population is being reduced rapidly. They are in danger now. In order to protect the whooperswans. some protection measuresmust be taken. such as strcngthening public education and scientitic research- establishinga base of raising and breeding; deieloping intcrnational cooperation. strengthening the construction of natural reserves in thebreeding and wintering grounds. Up to the cnd of 1993. 34 natural reserves have been established in China.
基金the Special Funds for Major State Basic Research Projects and by the National Natural Science Foundation of China
文摘Quantities characterizing temporal property, e.g., power density, coherence, and time lag, can be defined and calculated directly in the time domain without using the Fourier transformation. Spectral hardness, variability duration, and correlation between different characteristic quamtities on different time scale can be studied in the time domain as well. The temporal analysis technique in the time domain is a powerful tool, particularly in studying rapid variability on short time scales (or in high frequencies). Results of studying variabilities of X-rays from Cyg X-1 with the analysis technique in the time domain and RXTE data reveal valuable clues to understanding production and propagation processes of X-rays and structure of accretion disk in the black hole system.
基金supported by the National Basic Research Program of China(Grant No.2009CB824800)the National Natural Science Foundation of China(Grant No.10533020)
文摘Calculating the time lags over different timescales using the cross-correlation technique may lead to a biased estimate of small timescales.Given a timescale for lightcurve binning,we propose to subtract the local average instead of the global average during the cross-correlation,in order to filter variations on timescales larger than the bin size.The new method allows us to make an unbiased estimate of the time lags using RXTE/PCA data on timescales as small as-5 ms,where the Fourier technique becomes invalid.We calculate the time lag spectra of Cygnus X-1 at different spectral states with the new method,and find that the source appears to have similar X-ray lags on small timescales independent of its spectral states.
文摘Già da vari anni è rilevabile la presenza di individui semiselvatici di Cigno reale sulLago d’Iseo.Nel gennaio 1991,durante il censimento annuale degli Anatidi,sono staticontati 4 individui nella zona del basso lago (Clusane) di cui almeno 2 perfettamentevolanti.Durante successive visite il 13 aprile nella Riserva Naturale delle Torbiere (località《Lamette》) abbiamo constatato la prima nidificazione certa per l’intero bacino lacustre.
文摘The thin layer approximation applied to the expansion of a supernova remnant assumes that all the swept mass resides in a thin shell. The law of motion in the thin layer approximation is therefore found using the conservation of momentum. Here we instead introduce the conservation of energy in the framework of the thin layer approximation. The first case to be analysed is that of an interstellar medium with constant density and the second case is that of 7 profiles of decreasing density with respect to the centre of the explosion. The analytical and numerical results are applied to 4 supernova remnants: Tycho, Cas A, Cygnus loop, and SN 1006. The back reaction due to the radiative losses for the law of motion is evaluated in the case of constant density of the interstellar medium.
基金financially supported by the National Key Research and Development Program of China(Number 2022YFC2601100)。
文摘Charismatic species are often reported by the media,providing information for detecting population status and public perception.To identify the number and distribution of free-living Black Swan(Cygnus atratus),a charismatic alien species in Chinese mainland and to detect the public and the media attitudes to the species,we analyzed the reports and emotional tendency from media coverage in 2000-2022 using manual reading,crawler extraction and latent Dirichlet allocation.A total of 6654 Black Swans were reported at 711 sites,including 147 individuals at 30 nature reserves.Successful breeding was reported at one-fourth of the total sites,including five nature reserves.The proportion of positive emotional tendency to Black Swans was overwhelming in the reports and was higher than that to alien species in general,suggesting that the public and the media are unaware of the risk of biological invasion.Effective management of invasive species requires the media clarifies the invasion risk of charismatic alien species.Promoting the unity between the harmfulness of abstract concept of alien species and the charisma of a specific alien species among the public help effective management.
文摘In this paper we derive three equations of motion for a supernova remnant (SNR) in the framework of the thin layer approximation using the Padé approximant. The circumstellar medium is assumed to follow a density profile of either an exponential type, a Gaussian type, or a Lane-Emden (n = 5) type. The three equations of motion are applied to four SNRs: Tycho, Cas A, Cygnus loop, and SN 1006. The percentage error of the Padé approximated solution is always less than 10%. The theoretical decrease of the velocity over ten years for SNRs is evaluated.
基金supported by the National Basic Re-search Program of China(Grant No.2009CB 824800)the CAS Key Project(Grant No.KJCX2-YW-T03)+1 种基金the National Natural Science Foundation of China(Grant No.10773017)the Natural Science Foundation of Xin-jiang Uygur Autonomous Region of China(Grant No.200821164)
文摘We have investigated the relation between the root mean square(rms)variability and the X-ray flux(rms-flux relation)of the Z source Cyg X-2,and as well the energy dependence based on the Rossi X-ray Timing Explorer(RXTE)observations.We currently focus on the horizontal branch(HB),due to the negative correlation in flux of the soft and the hard X-rays.The rms-flux correlation has energy dependence as follows:positive at hard X-rays(above 10 keV)but negative at soft X-rays(below 10 keV).This provides a feature different from the previous one,and may be suggestive of different origins of X-rays below and above 10 keV.Nevertheless,the overall spectrum can be well fitted with a model consisting of a blackbody and Comptonization components,but the fitting results do not reveal any features around 10 keV that could account for such a change in the rms-flux relation.
