The determination of virtual constraints is always one of the key and difficult problems in traditional mobility calculation. To make mobility calculation simple, considering avoiding virtual constraints, some new for...The determination of virtual constraints is always one of the key and difficult problems in traditional mobility calculation. To make mobility calculation simple, considering avoiding virtual constraints, some new formulae have been presented, however these formulae can hardly intuitively reflect general link group's restrictions on output member and its influences on independence of output parameters, which is premise to the judgment of the properties of mobility. Towards the problem to reveal the intrinsic relationship between the degree of freedom(DOF) of a mechanism, the link group, and the dimension of output parameters, also to avoid determination of virtual constraint, based on the new concepts of the "DOF of general link group" and "node parameters", a new formula in the calculation of the mobility of mechanisms is presented that is expressed with DOFs of the general link groups and rank of motion parameters of base point of the output link. It is named GOM(mobility of groups and output parameter) formula. On the basis of new concepts of"effective parameters" and "invalid parameters", a rule is put forward for solving the DOF of mechanisms with invalid parameters by GOM formula, that is, the base point parameters are the subset of effective parameters of link group. Thereafter, several examples are enumerated and the results coincide with the prototype data, which proves the validity of the proposed formula. Meanwhile, it is obtained that the necessary and sufficient condition for the judgment of output parameters independence is that each of the DOF of the link group is not less than zero. The proposed formula which is simple in calculation provides theoretical basis for the judgment of independence of output parameters and provides references for type synthesis of novel parallel mechanisms with independence requirements of their output parameters.展开更多
In this paper, the Lie symmetry algebra of the coupled Kadomtsev-Petviashvili (cKP) equation is obtained by the classical Lie group method and this algebra is shown to have a Kac-Moody-Virasoro loop algebra structur...In this paper, the Lie symmetry algebra of the coupled Kadomtsev-Petviashvili (cKP) equation is obtained by the classical Lie group method and this algebra is shown to have a Kac-Moody-Virasoro loop algebra structure. Then the general symmetry groups of the cKP equation is also obtained by the symmetry group direct method which is proposed by Lou et alo From the general symmetry groups, the Lie symmetry group can be recovered and a group of discrete transformations can be derived simultaneously. Lastly, from a known simple solution of the cKP equation, we can easily obtain two new solutions by the general symmetry groups.展开更多
A typical example for the algebraic groups is the general linear groups G=GL(n,F), we have studied the structure of such groups and paid special attention to its important substructures, namely the Parabolic subgroups...A typical example for the algebraic groups is the general linear groups G=GL(n,F), we have studied the structure of such groups and paid special attention to its important substructures, namely the Parabolic subgroups. For a given G we computed all the Parabolic subgroups and determined their number, depending on the fact that any finite group has a composition series and the composition factors of a composition series are simple groups which are completely classified, we report here some investigations on the computed Parabolic subgroups. This has been done with the utility of GAP.展开更多
The tyre industry is one of the industries with the longest history in modern industry. It embodies a country’s economic and technical power. The United States, Germany, Italy and France are not rubber producers. How...The tyre industry is one of the industries with the longest history in modern industry. It embodies a country’s economic and technical power. The United States, Germany, Italy and France are not rubber producers. However, they had their vehicles equipped with air tyres展开更多
The Shandong Xinye Garment Group General Co. is located in Jining City of southern Shandong Province. It is one of Shandong’s largest export garment production bases, with an annual output of 1.5 million suits and a ...The Shandong Xinye Garment Group General Co. is located in Jining City of southern Shandong Province. It is one of Shandong’s largest export garment production bases, with an annual output of 1.5 million suits and a total sales volume of RMB60 million. Under the group, there are the Xinye Children’s Garment Factory, Xinye Garment Factory, Huahe Garment Co. Ltd, Sino-Japanese Joint-invested Taihe Hotel, Taihe Brewery, Taibe Musical Instrument Co. Ltd and Taihe Garment Bazaar. It has 1,400 staff and workers and covers an area of 20,000 sq.m. Since its establishment in the 1980s,展开更多
One day in April,our reporters visitedthis national super-large enterprise.Mr Huang Xiaoping,the generalmanager,briefed us on the company’s brilliantpast and bright future. The Yuejin Auto Group Company isfamed all o...One day in April,our reporters visitedthis national super-large enterprise.Mr Huang Xiaoping,the generalmanager,briefed us on the company’s brilliantpast and bright future. The Yuejin Auto Group Company isfamed all over the world for producing YuejinBrand automobiles.In 1958,the firstgeneration of Yuejin Brand automobiles cameout,and China has since had its first展开更多
After series of reforms including the introduction of the shareholding system, re-organization of capital, expansion of business fields and scale through cooperation or merge with other enterprises,Zhongda Group has n...After series of reforms including the introduction of the shareholding system, re-organization of capital, expansion of business fields and scale through cooperation or merge with other enterprises,Zhongda Group has now become a comprehensive enterprise group integrating import and export, foreign and domestic trade, ?and industry and serviceS.In the past five years stan-展开更多
The group velocity used in meteorology in the last 30 years was derived in terms of conservation of wave energy or crests in wave propagation. The conservation principle is a necessary but not a sufficient condition f...The group velocity used in meteorology in the last 30 years was derived in terms of conservation of wave energy or crests in wave propagation. The conservation principle is a necessary but not a sufficient condition for deriving the mathematical form of group velocity, because it cannot specify a unique direction in which wave energy or crests propagate. The derived mathematical expression is available only for isotropic waves. But for anisotropic waves, the traditional group velocity may have no a definite direction, because it varies with rotation of coordinates. For these reasons, it cannot be considered as a general expression of group velocity. A ray defined by using this group velocity may not be the trajectory of a reference point in an anisotropic wave train. The more general and precise expression of group velocity which is applicable for both isotropic and anisotropic waves and is independent of coordinates will be derived following the displacement of not only a wave envelope phase but also a wave reference point on the phase.展开更多
For the holonomic nonconservative system, by using the Noether symmetry, a non-Noether conserved quantity is obtained directly under general infinitesimal transformations of groups in which time is variable. At first,...For the holonomic nonconservative system, by using the Noether symmetry, a non-Noether conserved quantity is obtained directly under general infinitesimal transformations of groups in which time is variable. At first,the Noether symmetry, Lie symmetry, and Noether conserved quantity are given. Secondly, the condition under which the Noether symmetry is a Lie symmetry under general infinitesimal transformations is obtained. Finally, a set of nonNoether conserved quantities of the system are given by the Noether symmetry, and an example is given to illustrate the application of the results.展开更多
Structures of two classes of solvable subgroups in SL(3, C) are given in this paper, and the integrability of the 3-order Fuchsian equation which is integrable in the sense that its monodromy group is solvable is di...Structures of two classes of solvable subgroups in SL(3, C) are given in this paper, and the integrability of the 3-order Fuchsian equation which is integrable in the sense that its monodromy group is solvable is discussed.展开更多
In this paper,the automorphism group of G is determined,where G is a 4 × 4 upper unitriangular matrix group over Z.Let K be the subgroup of AutG consisting of all elements of AutG which act trivially on G/G,G /ζ...In this paper,the automorphism group of G is determined,where G is a 4 × 4 upper unitriangular matrix group over Z.Let K be the subgroup of AutG consisting of all elements of AutG which act trivially on G/G,G /ζG and ζG,then (i) InnG ■ K ■ AutG;(ii) AutG/K≌=G_1×D_8×Z_2,where G_1=(a,b,c|a^4=b^2=c^2=1,a^b=a^(-1),[a,c]= [b,c]=1 ;(iii) K/Inn G≌=Z×Z×Z.展开更多
This paper presents data from a 21 cm H I emission drift scan observation of a field partially covering the NGC 4636 galaxy group with the Five-hundred meter Aperture Radio Telescope(FAST). We construct a pipeline to ...This paper presents data from a 21 cm H I emission drift scan observation of a field partially covering the NGC 4636 galaxy group with the Five-hundred meter Aperture Radio Telescope(FAST). We construct a pipeline to reduce the data, and use So Fi A for source finding. When not contaminated by Radio Frequency Interference(RFI), the FAST observations are capable of detecting all of the galaxies previously detected by the Arecibo Legacy Fast ALFA(ALFALFA) survey in the same region. Comparing to ALFALFA for the detections in common, the FAST data show consistent integrated spectra when the H I disks are spatially unresolved, and capture more flux when the H I disks are resolved. The FAST data further reveal 10 new detections in the region mutually covered with ALFALFA, and 18 new detections beyond the footprint of ALFALFA. All of the new detections have the matching optical counterparts. For the member galaxies of the NGC 4636 group, the detection limit of FAST is deeper by 0.4 dex in H I mass than that of the ALFALFA data. After correcting for the incompleteness caused by RFI contamination, we show that the H I detection rate of galaxies rises steeply with radius out to the virial radius of the group, and flattens beyond that. We also examine four spatially resolved galaxy systems with potential tidal interaction features in detail. Considering that the data have been taken during the“shared-risk” period before a major source of local RFI was eliminated, the results highlight the power of FAST in detecting extragalactic H I.展开更多
We create mock X-ray observations of hot gas in galaxy clusters with a new extension of the L-Galaxies semianalytic model of galaxy formation,which includes the radial distribution of hot gas in each halo.Based on the...We create mock X-ray observations of hot gas in galaxy clusters with a new extension of the L-Galaxies semianalytic model of galaxy formation,which includes the radial distribution of hot gas in each halo.Based on the model outputs,we first build some mock light cones,then generate mock spectra with the SOXS package and derive the mock images in the light cones.Using the mock data,we simulate mock X-ray spectra for the ROSAT all-sky survey,and compare the mock spectra with the observational results.Then,we consider the design parameters of the HUBS mission and simulate the observation of the halo hot gas for HUBS as an important application of our mock work.We find:(1)our mock data match the observations by current X-ray telescopes.(2)The survey of hot baryons in resolved clusters by HUBS is effective below redshift 0.5,and the observations of the emission lines in point-like sources at z>0.5 by HUBS help us understand the hot baryons in the early universe.(3)By taking advantage of the large simulation box and flexibility in semi-analytic models,our mock X-ray observations provide the opportunity to select targets and observation strategies for forthcoming X-ray facilities.展开更多
A presentation of hyperbolic unitary group is an important part in the unitary group. The group KG 2,n (R) plays an elementary role in presentation of unitary group. It is proved that KG 2,n(R)=1 for n≥2 over a...A presentation of hyperbolic unitary group is an important part in the unitary group. The group KG 2,n (R) plays an elementary role in presentation of unitary group. It is proved that KG 2,n(R)=1 for n≥2 over a ring R with division ring of quotients, using a new method, and a presentation of GE n(R) is given.展开更多
A presentation of hyperbolic unitary group is an important part in the unitary group. The group KG 2,n (R) plays an elementary role in presentation of unitary group. It is proved that KG 2,n(R)=1 for n≥2 over a...A presentation of hyperbolic unitary group is an important part in the unitary group. The group KG 2,n (R) plays an elementary role in presentation of unitary group. It is proved that KG 2,n(R)=1 for n≥2 over a ring R with division ring of quotients, using a new method, and a presentation of GE n(R) is given.展开更多
A small fraction (〈 10%) of the SDSS main galaxy (MG) sample has not been targeted with spectroscopy due to the effect of fiber collisions. These galaxies have been compiled into the input catalog of the LAMOST E...A small fraction (〈 10%) of the SDSS main galaxy (MG) sample has not been targeted with spectroscopy due to the effect of fiber collisions. These galaxies have been compiled into the input catalog of the LAMOST ExtraGAlactic Surveys and named the complementary galaxy sample. In this paper, we introduce this project and status of the spectroscopies associated with the complementary galaxies in the first two years of the LAMOST spectral survey (till Sep. of 2014). Moreover, we present a sample of 1102 galaxy pairs identified from the LAMOST complementary galaxies and SDSS MGs, which are defined as two members that have a projected distance smaller than 100 h^-01kpc and a recessional velocity difference smaller than 500 km s-1. Compared with galaxy pairs that are only selected from SDSS, the LAMOST- SDSS pairs have the advantages of not being biased toward large separations and therefore act as a useful supplement in statistical studies of galaxy interaction and galaxy merging.展开更多
We use recent X-ray observations of the intracluster medium (ICM) of the galaxy group NGC 5813 to confront theoretical studies of ICM thermal evolution with the newly derived ICM prop- erties. We argue that the ICM ...We use recent X-ray observations of the intracluster medium (ICM) of the galaxy group NGC 5813 to confront theoretical studies of ICM thermal evolution with the newly derived ICM prop- erties. We argue that the ICM of the cooling flow in the galaxy group NGC 5813 is more likely to be heated by mixing of post-shock gas from jets residing in hot bubbles with the ICM, than by shocks or turbulent- heating. Shocks thermalize only a small fraction of their energy in the inner regions of the cooling flow; in order to adequately heat the inner part of the ICM, they would overheat the outer regions by a large factor, leading to its ejection from the group. Heating by mixing, which was found to be much more efficient than turbulent-heating and shocks-heating, hence, rescues the outer ICM of NGC 5813 from its predestined fate according to cooling flow feedback scenarios that are based on heating by shocks.展开更多
In this paper,we present a very simple explicit description of Langlands Eisenstein series for SL(n,Z).The functional equations of these Eisenstein series are heuristically derived from the functional equations of cer...In this paper,we present a very simple explicit description of Langlands Eisenstein series for SL(n,Z).The functional equations of these Eisenstein series are heuristically derived from the functional equations of certain divisor sums and certain Whittaker functions that appear in the Fourier coefficients of the Eisenstein series.We conjecture that the functional equations are unique up to a real affine transformation of the s variables defining the Eisenstein series and prove the uniqueness conjecture in certain cases.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.51275438,51005195)Hebei Provincial Natural Science Foundation of(Grant No.E2011203214)Development Program of Qinhuangdao City,China(Grant No.201101A069)
文摘The determination of virtual constraints is always one of the key and difficult problems in traditional mobility calculation. To make mobility calculation simple, considering avoiding virtual constraints, some new formulae have been presented, however these formulae can hardly intuitively reflect general link group's restrictions on output member and its influences on independence of output parameters, which is premise to the judgment of the properties of mobility. Towards the problem to reveal the intrinsic relationship between the degree of freedom(DOF) of a mechanism, the link group, and the dimension of output parameters, also to avoid determination of virtual constraint, based on the new concepts of the "DOF of general link group" and "node parameters", a new formula in the calculation of the mobility of mechanisms is presented that is expressed with DOFs of the general link groups and rank of motion parameters of base point of the output link. It is named GOM(mobility of groups and output parameter) formula. On the basis of new concepts of"effective parameters" and "invalid parameters", a rule is put forward for solving the DOF of mechanisms with invalid parameters by GOM formula, that is, the base point parameters are the subset of effective parameters of link group. Thereafter, several examples are enumerated and the results coincide with the prototype data, which proves the validity of the proposed formula. Meanwhile, it is obtained that the necessary and sufficient condition for the judgment of output parameters independence is that each of the DOF of the link group is not less than zero. The proposed formula which is simple in calculation provides theoretical basis for the judgment of independence of output parameters and provides references for type synthesis of novel parallel mechanisms with independence requirements of their output parameters.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10747141 and 10735030)National Basic Research Program of China (Grant No 2007CB814800)+2 种基金Natural Science Foundations of Zhejiang Province of China (Grant No605408)Ningbo Natural Science Foundation (Grant Nos 2007A610049 and 2008A610017)K. C.Wong Magna Fund in Ningbo University
文摘In this paper, the Lie symmetry algebra of the coupled Kadomtsev-Petviashvili (cKP) equation is obtained by the classical Lie group method and this algebra is shown to have a Kac-Moody-Virasoro loop algebra structure. Then the general symmetry groups of the cKP equation is also obtained by the symmetry group direct method which is proposed by Lou et alo From the general symmetry groups, the Lie symmetry group can be recovered and a group of discrete transformations can be derived simultaneously. Lastly, from a known simple solution of the cKP equation, we can easily obtain two new solutions by the general symmetry groups.
文摘A typical example for the algebraic groups is the general linear groups G=GL(n,F), we have studied the structure of such groups and paid special attention to its important substructures, namely the Parabolic subgroups. For a given G we computed all the Parabolic subgroups and determined their number, depending on the fact that any finite group has a composition series and the composition factors of a composition series are simple groups which are completely classified, we report here some investigations on the computed Parabolic subgroups. This has been done with the utility of GAP.
文摘The tyre industry is one of the industries with the longest history in modern industry. It embodies a country’s economic and technical power. The United States, Germany, Italy and France are not rubber producers. However, they had their vehicles equipped with air tyres
文摘The Shandong Xinye Garment Group General Co. is located in Jining City of southern Shandong Province. It is one of Shandong’s largest export garment production bases, with an annual output of 1.5 million suits and a total sales volume of RMB60 million. Under the group, there are the Xinye Children’s Garment Factory, Xinye Garment Factory, Huahe Garment Co. Ltd, Sino-Japanese Joint-invested Taihe Hotel, Taihe Brewery, Taibe Musical Instrument Co. Ltd and Taihe Garment Bazaar. It has 1,400 staff and workers and covers an area of 20,000 sq.m. Since its establishment in the 1980s,
文摘One day in April,our reporters visitedthis national super-large enterprise.Mr Huang Xiaoping,the generalmanager,briefed us on the company’s brilliantpast and bright future. The Yuejin Auto Group Company isfamed all over the world for producing YuejinBrand automobiles.In 1958,the firstgeneration of Yuejin Brand automobiles cameout,and China has since had its first
文摘After series of reforms including the introduction of the shareholding system, re-organization of capital, expansion of business fields and scale through cooperation or merge with other enterprises,Zhongda Group has now become a comprehensive enterprise group integrating import and export, foreign and domestic trade, ?and industry and serviceS.In the past five years stan-
文摘The group velocity used in meteorology in the last 30 years was derived in terms of conservation of wave energy or crests in wave propagation. The conservation principle is a necessary but not a sufficient condition for deriving the mathematical form of group velocity, because it cannot specify a unique direction in which wave energy or crests propagate. The derived mathematical expression is available only for isotropic waves. But for anisotropic waves, the traditional group velocity may have no a definite direction, because it varies with rotation of coordinates. For these reasons, it cannot be considered as a general expression of group velocity. A ray defined by using this group velocity may not be the trajectory of a reference point in an anisotropic wave train. The more general and precise expression of group velocity which is applicable for both isotropic and anisotropic waves and is independent of coordinates will be derived following the displacement of not only a wave envelope phase but also a wave reference point on the phase.
基金国家自然科学基金,湖南省自然科学基金,the Scientific Research Foundation of Education Burean of Hunan Province
文摘For the holonomic nonconservative system, by using the Noether symmetry, a non-Noether conserved quantity is obtained directly under general infinitesimal transformations of groups in which time is variable. At first,the Noether symmetry, Lie symmetry, and Noether conserved quantity are given. Secondly, the condition under which the Noether symmetry is a Lie symmetry under general infinitesimal transformations is obtained. Finally, a set of nonNoether conserved quantities of the system are given by the Noether symmetry, and an example is given to illustrate the application of the results.
文摘Structures of two classes of solvable subgroups in SL(3, C) are given in this paper, and the integrability of the 3-order Fuchsian equation which is integrable in the sense that its monodromy group is solvable is discussed.
基金Supported by the Tianyuan Fund for Mathematics of NSFC(11126273)Supported by the NSF of Henan Educational Committee(2011B110011)Supported by the Doctor Foundation of Henan University of Technology(2009BS029)
文摘In this paper,the automorphism group of G is determined,where G is a 4 × 4 upper unitriangular matrix group over Z.Let K be the subgroup of AutG consisting of all elements of AutG which act trivially on G/G,G /ζG and ζG,then (i) InnG ■ K ■ AutG;(ii) AutG/K≌=G_1×D_8×Z_2,where G_1=(a,b,c|a^4=b^2=c^2=1,a^b=a^(-1),[a,c]= [b,c]=1 ;(iii) K/Inn G≌=Z×Z×Z.
基金supported by the National Natural Science Foundation of China (11988101,11721303,11991052,12011540375,12073002,11903003)the China Manned Space Project (CMS-CSST-2021-A04+3 种基金CMS-CSST-2021-A06)support from the science research grants from the China Manned Space Project with No.CMS-CS ST-2021-B02the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D),through project No.CE170100013support from the Natural Sciences and Engineering Research Council of Canada (NSERC)。
文摘This paper presents data from a 21 cm H I emission drift scan observation of a field partially covering the NGC 4636 galaxy group with the Five-hundred meter Aperture Radio Telescope(FAST). We construct a pipeline to reduce the data, and use So Fi A for source finding. When not contaminated by Radio Frequency Interference(RFI), the FAST observations are capable of detecting all of the galaxies previously detected by the Arecibo Legacy Fast ALFA(ALFALFA) survey in the same region. Comparing to ALFALFA for the detections in common, the FAST data show consistent integrated spectra when the H I disks are spatially unresolved, and capture more flux when the H I disks are resolved. The FAST data further reveal 10 new detections in the region mutually covered with ALFALFA, and 18 new detections beyond the footprint of ALFALFA. All of the new detections have the matching optical counterparts. For the member galaxies of the NGC 4636 group, the detection limit of FAST is deeper by 0.4 dex in H I mass than that of the ALFALFA data. After correcting for the incompleteness caused by RFI contamination, we show that the H I detection rate of galaxies rises steeply with radius out to the virial radius of the group, and flattens beyond that. We also examine four spatially resolved galaxy systems with potential tidal interaction features in detail. Considering that the data have been taken during the“shared-risk” period before a major source of local RFI was eliminated, the results highlight the power of FAST in detecting extragalactic H I.
基金the support from the National SKA Program of China No.2020SKA0110102the fund for key programs of Shanghai Astronomical Observatory(Grants E195121009 and E297091002)+1 种基金Shanghai Committee of Science and Technology Grant No.19ZR1466700supported in part by the Natural Science Foundation of China(Grants 12133008,12192220,and 12192223)。
文摘We create mock X-ray observations of hot gas in galaxy clusters with a new extension of the L-Galaxies semianalytic model of galaxy formation,which includes the radial distribution of hot gas in each halo.Based on the model outputs,we first build some mock light cones,then generate mock spectra with the SOXS package and derive the mock images in the light cones.Using the mock data,we simulate mock X-ray spectra for the ROSAT all-sky survey,and compare the mock spectra with the observational results.Then,we consider the design parameters of the HUBS mission and simulate the observation of the halo hot gas for HUBS as an important application of our mock work.We find:(1)our mock data match the observations by current X-ray telescopes.(2)The survey of hot baryons in resolved clusters by HUBS is effective below redshift 0.5,and the observations of the emission lines in point-like sources at z>0.5 by HUBS help us understand the hot baryons in the early universe.(3)By taking advantage of the large simulation box and flexibility in semi-analytic models,our mock X-ray observations provide the opportunity to select targets and observation strategies for forthcoming X-ray facilities.
文摘A presentation of hyperbolic unitary group is an important part in the unitary group. The group KG 2,n (R) plays an elementary role in presentation of unitary group. It is proved that KG 2,n(R)=1 for n≥2 over a ring R with division ring of quotients, using a new method, and a presentation of GE n(R) is given.
文摘A presentation of hyperbolic unitary group is an important part in the unitary group. The group KG 2,n (R) plays an elementary role in presentation of unitary group. It is proved that KG 2,n(R)=1 for n≥2 over a ring R with division ring of quotients, using a new method, and a presentation of GE n(R) is given.
基金Funding for the project has been provided by the National Development and Reform Commissionsupported by the National Basic Research Program of China(973 Program,2014 CB845705)+2 种基金Strategic Priority Research Program“The Emergence of Cosmological Structures”of the Chinese Academy of Sciences(CASgrant XDB09030200)the National Natural Science Foundation of China(Nos.11573050 and 11433003)
文摘A small fraction (〈 10%) of the SDSS main galaxy (MG) sample has not been targeted with spectroscopy due to the effect of fiber collisions. These galaxies have been compiled into the input catalog of the LAMOST ExtraGAlactic Surveys and named the complementary galaxy sample. In this paper, we introduce this project and status of the spectroscopies associated with the complementary galaxies in the first two years of the LAMOST spectral survey (till Sep. of 2014). Moreover, we present a sample of 1102 galaxy pairs identified from the LAMOST complementary galaxies and SDSS MGs, which are defined as two members that have a projected distance smaller than 100 h^-01kpc and a recessional velocity difference smaller than 500 km s-1. Compared with galaxy pairs that are only selected from SDSS, the LAMOST- SDSS pairs have the advantages of not being biased toward large separations and therefore act as a useful supplement in statistical studies of galaxy interaction and galaxy merging.
文摘We use recent X-ray observations of the intracluster medium (ICM) of the galaxy group NGC 5813 to confront theoretical studies of ICM thermal evolution with the newly derived ICM prop- erties. We argue that the ICM of the cooling flow in the galaxy group NGC 5813 is more likely to be heated by mixing of post-shock gas from jets residing in hot bubbles with the ICM, than by shocks or turbulent- heating. Shocks thermalize only a small fraction of their energy in the inner regions of the cooling flow; in order to adequately heat the inner part of the ICM, they would overheat the outer regions by a large factor, leading to its ejection from the group. Heating by mixing, which was found to be much more efficient than turbulent-heating and shocks-heating, hence, rescues the outer ICM of NGC 5813 from its predestined fate according to cooling flow feedback scenarios that are based on heating by shocks.
基金supported by Simons Collaboration(Grant No.567168)。
文摘In this paper,we present a very simple explicit description of Langlands Eisenstein series for SL(n,Z).The functional equations of these Eisenstein series are heuristically derived from the functional equations of certain divisor sums and certain Whittaker functions that appear in the Fourier coefficients of the Eisenstein series.We conjecture that the functional equations are unique up to a real affine transformation of the s variables defining the Eisenstein series and prove the uniqueness conjecture in certain cases.