变分原理和大气运动的稳定性     

罗德海 《成都信息工程学院学报》1993,(4)

本文通过引入守恒的伪动量(Pseudo-Momentum),并利用Hamilton函数,Casimir泛函,建立了一个新的Lyapunov泛函,在此基础上使用变分原理得到了大气运动所满足的广义稳定性判据。当基本气流仅存在经向切变时,所得到的广义稳定性判据与用经典标准模方法所得到的稳定性判据是一致的。  相似文献   

CLASS B 1359 + 154: Modelling lensing by a group of galaxies     

Sunita Nair 《Journal of Astrophysics and Astronomy》2002,23(1-2):115-118

The recently discovered gravitationally lensed system CLASS B1359 +154 appears to have six detectable images of a single background source at a redshift of 3.235. A group of galaxies acts as the lens, at a redshift of ∼ 1. The present work identifies two distinct, physically plausible image configurations, a 7-image one and a 9-image one. Mass models are constructed corresponding to realizations of these two configurations. Both models call for, in addition to non-singular galaxy-type lenses, a larger scale mass component that resembles the extended dark matter distributions seen in relatively low-redshift galaxy groups. It is presently observationally impossible to study the extended X-ray emission from a group at such a high redshift, hence lensing studies are of some interest. A lensed system with a high image multiplicity does not necessarily admit of a unique lensing interpretation; discrimination is possible with additional observable details (e.g., the image parities, which are uncommon among even the simpler systems).  相似文献   

The Fundamental Plane of E Galaxies in Compact Groups     

R. de Carvalho  I. de La Rosa  Steve Zepf 《Astrophysics and Space Science》2003,285(1):79-84

We present a study focusing on the nature of compact groups through the study of their elliptical galaxies. We determine central velocity dispersions (σ_o) for 18 bright elliptical galaxies located in the core of Hickson compact groups and a control sample of 12 brightbona fide ellipticals located in the field or very loose groups. Several tests are carried out to avoid systematic effects in σ measurements. We use these velocity dispersions to compare the position of 11 compact group galaxies in the Fundamental Plane to that of a large and homogeneous sample of elliptical galaxies (Burstein et al., 1987).We find that little or no significant difference exists, as far as the Fundamental Plane is concerned, between ellipticals in compact groups and their counterparts in other environments. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

D—子群及超限下Abel群     

张志让 《成都信息工程学院学报》1988,(2)

本文通过对D-子群(Perfect Subgroup)的研究,证明群G为超限下Abe1群的充分必要条件是G无非平凡的D-子群。  相似文献   

Study on Optical Properties of Unpigmented Suspended Particles,Yellow Substance and Phytoplankton Algae in Taihu Lake   总被引：1，自引：0，他引：1  

俞宏蔡启铭  吴敬禄 《中国海洋湖沼学报》2004,22(1):24-33

The optical properties of a waterbody are subjects of research on limnological hydrooptics. The optical properties of, and parameterization methods for, three impurities in Taihu Lake, namely unpigmented suspensions, yellow substance and phytoplankton algae, are analyzed in detail in this paper dealing with the optical types of Taihu Lake waters both in winter and in summer. The results showed that : 1 ) The optical parameters of suspended particles can be calculated by the application of Mie Theory; 2) The absorption of yellow substance decreases exponentially with increasing wavelength, with the mean value of decreasing rate being about 0.014 nm^-1 ; 3) Taihu Lake waters appeared to be of type PY in winter, with suspended particles and yellow substance being the dominant light absorbers, and type CPY in summer, with suspended particles, yellow substance and phytoplankton algae being the dominant light absorbers; 4) In winter or summer, unpigmented suspension has the main effect on the scattering property of Taihu Lake waters.  相似文献   

Annual Primary Production in Narragansett Bay with no Bay-Wide Winter–Spring Phytoplankton Bloom     

C. Oviatt  A. Keller  L. Reed 《Estuarine, Coastal and Shelf Science》2002,54(6):1013

Primary production was estimated over the annual cycle from ¹⁴C incubations conducted in 5 m deep enclosures and modeled for 16 stations in Narragansett Bay with data from biweekly surveys in which light, chlorophyll, attenuation coefficients and other parameters were measured. Annual values ranged from 160 g C m⁻² y⁻¹ in the lower West Passage to 619 g C m⁻² y⁻¹ at the mouth of the Providence River. The annual bay-wide, area mean fell near the middle of this range at 323 g C m⁻² y⁻¹ and was not apparently different from previous surveys. In the 1998 warm, El Niño winter, no bay-wide winter–spring phytoplankton flowered. Bloom limitation was correlated with warm temperatures which may have stimulated grazing rates. The lack of a bloom did not change annual levels of primary production but this alteration in carbon flow may impact macrofauna in the benthic infauna community.  相似文献   

The Velocity Dispersion in the X-Ray Scaling Laws     

M.E. Zimer  A.I. Zabludoff  J.S. Mulchaey 《Astrophysics and Space Science》2003,285(1):37-42

We used a sample of 20 poor groups of galaxies to study the low mass tail of the relationships among the X-ray temperature T, the X-ray luminosity L_x and the optical velocity dispersion σ. We obtained redshifts for the fainter members of these groups. We find that X-ray bright groups have more members and higher velocity dispersions on average. Using the fainter group members and MonteCarlo tests, we define the number of group members required to calculate a robust velocity dispersion. There is a tendency to underestimate the group velocity dispersion for samples of fewer than∼ 10 members that introduces systematic errors in the slope of the relationships among L_x, T, and σ. A comparison with the data of Ponman and Mahdavi shows that our improved velocity dispersions provide better constraints on the relationship between the kinematics of the hot gas and galaxies in these common environments. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

New evidence of the azimuthal alignment of quasars spin vector in the LQG U1.28, U1.27, U1.11, cosmologically explained     

《New Astronomy》2022

There has been observational evidence about spin axes of quasars in large quasar groups correlated over hundreds of Mpc. This is seen in the radio spectrum as well as in the optical range. There is not yet a satisfactory explanation of this “spooky” alignment. This alignment cannot be explained by mutual interaction at the time that quasars manifest themselves optically. A cosmological explanation could be possible in the formation of superconducting vortices (cosmic strings) in the early universe, just after the symmetry-breaking phase of the universe. We gathered from the NASA/IPAC and SIMBAD extragalactic databases the right ascension, declination, inclination, position angle and eccentricity of the host galaxies of three large quasar groups to obtain the azimuthal and polar angle of the spin vectors. The alignment of the azimuthal angle of the spin vectors of quasars in their host galaxy is confirmed in the large quasar group U1.27 and compared with two other groups in the vicinity, i.e., U1.11 and U1.28, investigated by Clowes (2013). It is well possible that the azimuthal angle alignment fits the predicted azimuthal angle dependency in the theoretical model of the formation of general relativistic superconducting vortices, where the initial axial symmetry is broken just after the symmetry breaking of the scalar-gauge field.  相似文献   

功能区视角下城市夜光与夜间“两抢一盗”犯罪的空间相关性——以H市市辖区为例     

王灿祥  朱萌  滕茹洁  姚宇超  何佳琦  余帆 《热带地理》2022,42(10):1739-1751

以H市市辖区为例,基于POI数据识别城市功能区,并结合NPP-VIIRS夜光遥感数据与夜间“两抢一盗”犯罪数据,构建双变量空间自相关分析模型,从整体及不同功能区角度探讨城市夜光与夜间“两抢一盗”犯罪的空间关系。结果表明：1）整体上,H市夜间“两抢一盗”犯罪形成“一主一副”的犯罪热点,且夜光与夜间“两抢一盗”犯罪存在空间异质性关系。2）大部分功能区在全局Moran's Ι上表现为正相关。在局部LISA聚类上,只有居住用地、商业服务业用地和道路与交通设施用地呈现显著的空间异质性。商业用地的高-高聚类多数分布在一环及二环以内,低-低聚类多数分布在城市外围及边缘地带,高-低聚类与低-高聚类则零散分布在二者之间的区域;居住用地的聚类情况呈现南北区域差异;道路与交通设施用地则由于报警地点与实际案发地点可能有所出入,因而结果可信度降低。  相似文献   

Perception of pleasure in the urban running environment with street view images and running routes     

ZHANG An  SONG Liuyi  ZHANG Fan 《地理学报(英文版)》2022,32(12):2624-2640

The urban environment affects human behavior and health. Most studies on the feelings of street spaces have not considered a specific kind of realistic scene, such as running. To overcome this limitation, we explored the relationship between the urban environment and the pleasure of running. We collected 8260 street view images from 153 running routes in Beijing and invited more than 400 volunteers of different genders and ages to rate their sense of pleasure in street view images of the urban running environment through an online survey. Then, the proportion of visual elements in street images was extracted based on semantic segmentation, and the landscape was divided. Finally, a linear mixed model was used to predict the pleasure scores of different gender and age groups for different landscapes. The results show significant differences in the pleasure scores for different landscapes and age groups. Middle-aged people's sense of pleasure was lower than that of the young and the elderly. More greenery was associated with a higher pleasure score, while the proportion of urban elements such as buildings was negatively correlated with the pleasure score. The results indicate that running in a natural landscape is pleasurable and beneficial for mental health.  相似文献