冻融循环作用下路基土回弹模量试验研究

为研究季节冻土地区冻融循环作用对路基土回弹模量的影响,以2种路基土作为研究对象,通过风干和加湿的方法,使高50mm、直径为50mm无侧限圆柱体试件达到5种预期含水率;采用承载板法进行回弹模量试验,分析了路基土在0～12次冻融循环作用下,回弹模量随冻融循环次数变化的规律.结果表明:随着冻融循环次数的增加,土体的回弹模量减小,到第6次冻融循环后土体回弹模量衰减基本稳定.在进行季节冻土地区路面设计时,应考虑冻融循环作用对路基土的影响,建议选取第6次冻融循环后的土体回弹模量作为路基强度设计值.     

Moho depth variation beneath southwestern Japan revealed from the velocity structure based on receiver function inversion

The Philippine Sea plate is subducting under the Eurasian plate beneath the Chugoku-Shikoku region, southwestern Japan. We have constructed depth contours for the continental and oceanic Mohos derived from the velocity structure based on receiver function inversion. Receiver functions were calculated using teleseismic waveforms recorded by the high-density seismograph network in southwestern Japan. In order to determine crustal velocity structure, we first improved the linearized time-domain receiver function inversion method. The continental Moho is relatively shallow ( 30 km) at the coastline of the Sea of Japan and at the Seto Inland Sea, and becomes deeper–greater than 40 km–around 35°N and 133.8°E. Near the Seto Inland Sea, a low-velocity layer of thickness 10 km lies under the continental Moho. This low-velocity layer corresponds to the subducting oceanic crust of the Philippine Sea plate. The oceanic Moho continues to descend from south to northwest and exhibits complicated ridge and valley features. The oceanic Moho runs around 25 km beneath the Pacific coast and 45 km beneath the Seto Inland Sea, and it extends to at least to 34.5°N. The depth variation of the Moho discontinuities is in good qualitative agreement with the concept of isostasy. From the configurations of both the continental and oceanic Mohos, we demonstrate that the continental lower crust and the subducting oceanic crust overlap beneath the southern and central part of Shikoku and that a mantle wedge may exist beneath the western and eastern part of Shikoku. The southern edge of the overlapping region coincides with the downdip limit of the slip area of a megathrust earthquake.     

The Hubble Flow: Why Does the Cosmological Expansion Preserve Its Kinematical Identity from a Few Mpc Distance to the Observation Horizon?

The problem of the physical nature of the Hubble flow in the Local Volume (D < 10 Mpc) stated by Sandage is studied. New observational data on galaxy motions and matter distribution around the Local Group and nearby similar systems are described. Dynamical models are discussed on the basis of the recent data on cosmic vacuum or dark energy.     

Peculiar velocities of 3000 spiral galaxies from the 2MFGC catalog

The 2MFGC catalog we have used contains 18020 galaxies selected from the extended objects in the 2MASS infrared sky survey as having apparent ratios of the axes b/a<0.3. Most of them are spiral galaxies of later morphological types whose disks are seen almost edge-on. The individual distances to the 2724 2MFGC galaxies with known rotation velocities and radial velocities are determined using a multiparameter infrared Tully-Fisher relation. A list of the distances and peculiar velocities of these galaxies is presented. The collective motion of the 2MFGC galaxies relative to the cosmic microwave background is characterized by a velocity V = 199 ± 37 km/s in the direction l = 304° ±11°, b = −8°±8°. Our list is currently the most representative and uniform sample for analyzing non-Hubble motions of galaxies on a scale of ∼100 Mpc. __________ Translated from Astrofizika, Vol. 49, No. 4, pp. 527–540 (November 2006).     

空间大地测量测定板块运动的新进展及其与地质学成果的比较

阐述利用空间大地测量测定和研究板块运动的基本方法、研究成果及最新进展 ,并和地质学方法进行了比较。结果表明 ,用地质学方法与用大地测量方法建立的板块运动模型参数在整体上具有很好的一致性 ,但对某些板块而言两者相差甚大 ,超出了模型误差的范围 ,其中 ,所有大地测量得到的太平洋板块速率都大于地质模型 ,极位置经度都偏小。不同作者利用空间大地测量建立的板块运动模型参数也存在着一定的差异 ,这种差异与所利用的数据类型、板块及其边界划分方案、测站的数量与分布状态及测站取舍的原则有关 ,尤其是与测站的分布及强变形 (非刚性板块运动 )测站的取舍有关。在研究区域性地壳运动时 ,采用不同的板块运动模型将会得到不同的背景场 ,从而会得到不同的区域运动图像 ,因此选择合适的背景场模型是至关重要的。     

Experimental study on the performance of twin plate breakwater

The wave transmission characteristics and wave induced pressures on twin plate breakwater are investigated experimentally in regular and random waves.A total of twenty pressure transducers are fixed on four surfaces of twin plate to measure the wave induced dynamic pressures.The spatial distribution of dynamic wave pressure is given along the surface of the twin plate.The uplift wave force obtained by integrating the hydrodynamic pressure along the structure is presented.Discussed are the influence of different incident wave parameters including the relative plate width B /L,relative wave height /i H a and relative submergence depth s /a on the non-dimensional dynamic wave pressures and total wave forces.From the investigation,it is found that the optimum transmission coefficient,t K occurs around B /L 0.41 ~ 0.43,and the twin plate breakwater is more effective in different water depths.The maximum of pressure ratio decreases from 1.8 to 1.1 when the relative submergence depth of top plate is increased from 0.8to +0.8.     

Hydrodynamic characteristics of semi-immersed breakwater with an attached porous plate

In the present study, wave interaction with a fixed, partially immersed breakwater of box type with a plate attached (impermeable-permeable) at the front part of the structure is investigated numerically and experimentally. The large scale laboratory experiments on the interaction of regular waves with the special breakwater were conducted in the wave flume of Laboratori d’Enginyeria Marνtima (LIM) at Universitat Politecnica de Catalunya (UPC) in Barcelona. Experimental results are compared with numerical results obtained with the use of the Cornell breaking Wave and Structures (COBRAS) wave model. The effects of an impermeable as well as a permeable plate attached to the bottom of the breakwater on its hydrodynamic characteristics (wave transmission, reflection, dissipation, velocity and turbulence kinetic energy) are investigated. Computed velocities and turbulence kinetic energy in the vicinity of the structure indicate the effects of the breakwater with the attached (impermeable/permeable) plate on the flow pattern and the turbulence structure. The attached impermeable plate at the front part of the breakwater enhances significantly the efficiency of the structure in attenuating the incident waves. The permeable plate reduces the efficiency of the structure since wave energy is transmitted through the porous body of the plate. Based on the hydrodynamic characteristics it is inferred that the breakwater with an impermeable plate attached to its bottom is more efficient. The comparison of horizontal and vertical forces acting on the breakwater for all cases examined reveals that plate porosity influences slightly vertical force and severely horizontal force acting on the structure, reducing maximum values in both cases.     

IDENTITY,BANAL NATIONALISM,CONTESTATION, AND NORTH AMERICAN LICENSE PLATES*

In the early 1900s, U.S. state and Canadian provincial governments began to register automobiles and issue license plates to their owners. Within several decades of the first issuance of license plates, state and provincial governments began to use these plates for advertising purposes, such as promoting local economies and tourism. In recent decades, however, governments have used license plates to promote national identities and nationalist ideals. Using examples from the United States and Canada, I examine how governments have used such banal signifiers of place as license plates to craft and promote these identities and how drivers have contested that usage.     

A Family of Symmetrical Schubart-Like Interplay Orbits and their Stability in the One-Dimensional Four-Body Problem

We locate members of an important category of periodic orbits in the Newtonian four-body problem. These systems perform an interplay motion similar to that of the periodic three-body orbit discovered by Schubart. Such orbits, when stable, have been shown to be a key feature and influence on the dynamics of few-body systems. We consider the restricted case where the masses are collinear and are distributed symmetrically about their centre of mass. A family of orbits is generated from the known (three-dimensionally) unstable equal masses case by varying the mass ratio, whilst maintaining the symmetry. The stability of these orbits to perturbation is studied using linear stability analysis, analytical approximation of limiting cases and nonlinear simulation. We answer the natural question: are there any stable periodic orbits of this kind? Three ranges of the mass ratio are found to have stable orbits and three ranges have unstable orbits for three-dimensional motion. The systems closely resemble their three-body counterparts. Here the family of interplay orbits is simpler requiring just one parameter to characterise the mass ratio. Our results provide a further insight into three-body orbits studied previously.     

Infrared Properties of Late - Type Stars Provided by the First Byurakan Spectral Sky Survey. The Nature of the Red Objects

Using modern astronomical databases, particularly 2MASS All - Sky Data Release Point Source Catalog and USNO-B1.0 catalog, we investigate the properties of about 840 FBS red stars in order to clarifiy their nature. We use and analyse their JHK 2MASS photometry, together with the R-band magnitudes and the proper motions provided by USNO - B1.0. Approximately 70% of all objects appear to be Asymptotic Giant Branch stars, 18% are giants, and close to 12% are objects with detectable proper motions, allowing to consider them as dwarf M-type stars. When plotted in a J - K versus R - K colour-colour diagram, one finds that objects with proper motions are well separated into a narrow belt.__________Published in Astrofizika, Vol. 48, No. 3, pp. 383–392 (August 2005).