The Diffraction of Rayleigh Waves by Twin Circular Cavities in a Poroelastic Half-Space

The diffraction of Rayleigh waves by twin circular cavities in a poroelastic half-space is investigated using the indirect boundary integral equation method (IBIEM). To satisfy the boundary conditions on the free surface, Green’s functions of compressional and shear wave sources in a poroelastic half-space are derived based on Biot’s theory. It is verified that the IBIEM has great accuracy and numerical stability. Then, the influences of the drainage boundary condition, incident wave frequency, porosity, and cavity spacing on the dynamic responses are investigated by numerical examples. The results show that the amplification effect of the twin cavities is greater in the case of undrained boundary conditions, lower frequencies, and smaller cavity spacings. The porosity of the saturated medium also influences the dynamic responses because the velocity of the Rayleigh wave will change with the porosity of the saturated medium.     

Dynamic Analysis and Seismic Response of Planar Circular Arches with Variable Cross-Section

The aim of this paper is to investigate the dynamic response of planar circular arches with variable cross-section subjected to seismic ground motions. Arches have a wide range of application (e.g. bridges, roofs) thanks to their capacity to span large areas by resolving vertical actions into compressive stresses and confining tensile stresses. The full understanding of their dynamic response is a challenging technical and computational problem, especially when seismic loading is considered. For example, the assumption of axial inextensibility simplifies the differential equations but overestimates the vibration frequencies, especially those of shallow arches since axial forces are of paramount importance (as opposed to beams). In lieu of the above, our formulation incorporates the effect of axial extension, and the arches are modeled using a new generic curved beam model that includes both axial (tangential) and transverse (normal) to the arch centerline deformations, and is able to account for variable mass and stiffness properties, as well as elastic support or restraint. The resulting dynamic governing equations of the circular arch are formulated in terms of the displacements, and solved using an efficient integral equation method. Three circular arches with variable rectangular cross-section are analyzed in order to investigate their dynamic properties and seismic performance. Using both time history and modal analysis useful conclusions are drawn with regard to the contribution of each mode on the calculation of different response quantities.     

Evaluation of 2D Seismic Site Response due to Hill-Cavity Interaction Using Boundary Element Technique

This paper deals with the evaluation of two-dimensional site-effects due to the seismic interaction between hills with various configurations and underground cavities. The time-domain boundary element method is used to evaluate the site-effects of hill-cavity interaction subjected to vertically propagating in-plane SV and P waves. The presence of an underground cavity and the hill topography are expected to induce significant effects on the surface ground motion. To further examine the contribution of the amplification ratio of the hill-cavity system, a fairly simple approach, which can compute the response spectra of the hill’s surface motion above a cavity based on the real input motions, is also used to input motions.     

A numerical model of the ionospheric dynamo—I. Formulation and numerical technique

A new method of numerically solving a suitably formulated ionospheric wind dynamo equation for electrostatic potential and field is developed. Unlike in many other dynamo models, the upper boundary does not exist and the formulation asymptotically approaches the equatorial boundary condition. Therefore, it naturally incorporates the symmetric, asymmetric E- and F-region dynamo actions in any given ionosphere and any given global or local wind field. It also enables the equation to be posed as an initial value problem and solved numerically using an efficient, accurate, stable and fast integration method of ordinary differential equations. The numerical technique can be extended to compute three dimensional dynamo-generated electric currents in the ionosphere.     

A Raman spectroscopic study of glass trade beads excavated at Mapungubwe hill and K2, two archaeological sites in southern Africa,raises questions about the last occupation date of the hill

Thousands of glass trade beads were excavated over a 75 year period on Mapungubwe Hill and at K2, two archaeological sites in the Limpopo valley, South Africa. An assemblage of 175 beads that appeared to be different in shape, size and colour (red, yellow, green, blue, white, black, pink, plum) was studied with Raman scattering. At least seven different chromophores or pigments (lazurite, lead tin yellow type II, Ca/Pb arsenate, chromate, calcium antimonate, Fe–S “amber” and a spinel) have been identified. Pigment identification allows the recognition of specific productions and indicated that many of the pigments colouring the beads excavated on Mapungubwe hill were manufactured after the 13th century, confirming the presence of modern beads in the archaeological record, some dating from the 19th century. This date is in agreement with the last occupation date for the hill suggested by the earlier excavators and raises questions about the revision of this date to 1290 AD by archaeologists in the 1970’s.     

Simulation of Spatially Variable Seismic Underground Motions in U-Shaped Canyons

This paper focuses on the study of simulations for spatially variable seismic underground motions in U-shaped canyons. First, a canyon ground cross-coherence function based on commonly used coherence function models of flat terrain, is deduced and presented. To further obtain the underground cross-coherence function, a mathematical expression, including its specific deduction process for describing the relationship between coherence functions of multi-support ground and underground motions, is also given in detail and adopted. Then, the key factors (i.e. canyon underground power spectrum density and canyon underground coherence function) for simulating the spatially variable seismic underground motions are obtained by a two-step transferring method from flat-ground to underground soil. Furthermore, a program is coded for generating the spatially variable seismic underground motions. The effectiveness of the generated seismic motions is further verified. Finally, two numerical examples are taken to validate the proposed simulation approach, illustrating the specific characteristics of canyon coherence function. The analysis results show the apparent differences of the simulated seismic motions using the canyon coherence function from those using conventional coherence function models of flat terrain. The proposed approach provides some insights for anti-earthquake analysis of soil-structure interaction or underground structures in canyon topography.     

Assemblage,Structure and Meaning in Bronze Metalwork Studies: an Analysis of the British Penard Assemblage

Multi‐object metalwork deposits provide the foundation block for many branches of enquiry, yet surprisingly little attention has been paid to the methodological issues that underlie their analysis and interpretation. The framework outlined here aims to circumvent some of the dangers of circular argument inherent in the concepts of metalwork ‘stages’, ‘phases’ or ‘traditions’, as well as in assumptions of pan‐regional synchronizations in metalwork developments. The term ‘Assemblage’ is defined to provide a carefully circumscribed but interpretatively neutral framework for the study of metalwork groups linked by association. Assemblage subdivisions allow significant internal variations to be explored for temporal, social and cultural meanings. These analytical devices used in conjunction with ‘bubble chronologies’ allow flexibility in detailed interpretation whilst holding on to a consensually agreed near‐empirical structure. Consideration is also given to the problem of regional phase groups of metalwork that lack associations and thus preclude Assemblage definition. The case of the Penard Assemblage is salient owing to the debate about whether the ‘Wallington complex’ should be considered an integral part of it. Although the ‘Assemblage/Aspect/Group’ structure applied here can accommodate some divergence in views, available evidence supports typo‐chronological coherence between Penard and Wallington material. Occasional associations used recently to justify a ‘Limehouse phase’ between Penard to Wilburton metalwork are just as easily understood as representing a transition towards 1100 bc . The lack of associations for the Limehouse family of swords, largely contemporary with late Penard, is argued to be an accentuation of the already rare occurrence of swords in earlier associations. The depositional phenomena of the Penard Assemblage are instead centred on an array of palstaves, rapiers, spearheads, shields and gold ornaments.     

Triassic nautiloid Sibyllonautilus from Gua Bama,Peninsular Malaysia and its regional stratigraphic implications

Coiled nautiloid Shells referred to Sibyllonautilus bamaensis Sone sp. nov. are reported from the top of the Gua Bama limestone hill in Pahang, Peninsular Malaysia. This is the first record of the genus in Southeast Asia; a pre-Ladinian, Triassic age is indicated for the occurrence. Based on the presence of Sibyllonautilus and previously reported Late Permian (Lopingian) foraminifers and algae, the Gua Bama limestones are interpreted to range from the Late Permian to the Triassic. It further seems plausible that some parts of Gua Bama are stratigraphically correlated to those of the nearby Gua Sei limestone hill, which has yielded basal Triassic conodonts, and that either or both the Gua Bama and Gua Sei hills may contain yet unconfirmed successions of the Permian-Triassic boundary.     

Compensation-theorem analyses of ground wave propagation over irregular,inhomogeneous terrains

Work during the last 40 years on various aspects of ground wave propagation is surveyed, including dipole propagation over flat homogeneous and inhomogeneous terrains, smooth homogeneous earth, and irregular homogeneous and inhomogeneous terrains. The Ott-Volterra integral equation for TM_p ground wave field over irregular homogeneous paths is discussed and an occasional troublesome behavior of the modified Sommerfeld attenuation function explained. Several representations of spatially distributed transmitter current are presented. A Compensation-theorem Volterra for the ground wave over inhomogeneous terrain is derived, in the parabolic wave equation approximation. A recent Compensation-theorem integral equation for general terrain satisfying the hyperbolic wave equation is reviewed. Computations for several very rough terrains indicate the ‘parabolic’ integral equations may often be more accurate.     

Near-surface imaging of a buried foundation in the Western Desert,Egypt, using space-borne and ground penetrating radar

ALOS/PALSAR L-band full polarimetric data have been used to detect and characterize a well-defined geometric target hidden under sand deposits in the Western Desert of Egypt. This buried object is rectangular in shape with very straight boundaries and encloses an area of 500 m². Inside the rectangular area there is a perfectly circular feature of approximately 53 m² area. High and medium resolution optical satellite images (WorldView-2, ALOS/AVNIR-2) and field investigation confirm that the topography of the study area is relatively flat and completely covered by dry sand. The electromagnetic wave scattering behavior of the detected buried object was measured by decomposing the scattering matrix of ALOS/PALSAR full polarimetric data into Entropy-Alpha (H/α) and Freeman and Durden decompositions. Furthermore, a combination of unsupervised classification algorithms and Constant False-Alarm Rate (CFAR) edge detection was performed on the polarimetric data which revealed a well-defined geometric shape with straight borders. These borders have high α angles with low entropy, which physically means double bounce scattering mechanism with low randomness and is very similar to that of an urban scatterer, indicating that the detected target might be a buried wall-like foundation of a man-made structure. Moreover, 28 ground penetrating radar (GPR) profiles were acquired using a 270 MHz shielded antenna to validate the satellite radar remote sensing results. The GPR profiles reveal very clear hyperbolic shapes at 1.5 m depth with one of them showing a large hyperbolic shape-like structure, which might indicate the presence of a buried foundation. Thus the site might have significance to archaeological studies of the Western Desert, particularly previous human occupation and the sources of water for such habitation.     

Shock Response from Pseudodynamic Test Using Momentum Equations of Motion

The feasibility of using pseudodynamic techniques to yield shock responses from impulses is studied herein. A direct integration method is often used to solve the force equation of motion in performing a conventional pseudodynamic test. However, this technique might not be applicable to obtain an accurate shock response from an impulse as a load discontinuity occurs at the end of the impulse. This is because this discontinuity will lead to an extra amplitude distortion and the amount of this amplitude distortion is increased with the increase of time step. Hence, a small time step is needed to reduce the extra amplitude distortion and thus the displacement increment for each time step might be smaller than or as small as the resolution of the displacement transducer. As a result, the displacement increment cannot be accurately imposed upon the specimen and the responses will be contaminated by the noise. In addition, the test duration is drastically increased. Alternatively, this difficulty might be overcome if the momentum equation of motion instead of the force equation of motion is solved pseudodynamically. Hence, an external momentum is used in the solution of the momentum equation of motion. Since the external momentum is a resultant of the time integration of the external force the discontinuity problem will automatically disappear. Consequently, reliable shock responses can be obtained from pseudodynamic tests.     

3. THE NOSTALGIAS FOR EMPIRE

The aim of this article is to explore the theoretical and practical differences between colonial and imperial nostalgia. It opens with a substantial theoretical discussion of the relevant scholarship followed by an analysis of the nostalgias of empire. Nostalgia, in relation to empire, is usually analyzed as a longing for a period of former imperial and colonial glory, thus blurring the various hegemonic practices associated with empire. This elision arises out of the fact colonialism was integral to European imperialism. Yet there is a significant distinction between imperial and colonial nostalgia. With its main focus on postcolonial society in France and Britain, the article will theorize the differences between them, arguing that one is connected to the loss of global power and the other to the loss of a socioeconomic lifestyle. It will explore the way in which these two types of nostalgia are constructed and historicized, examining their differences from historical memory through the responses of both former colonizing and colonized individuals or groups. It will demonstrate that collective nostalgia is not merely a “feel‐good” sentiment about an idealized political or socioeconomic past, but can be readily connected to coming to terms with past trauma(s) thus being a mechanism to elide violence experienced and violence perpetrated by highlighting one to the detriment of the other.     

CENTER POINTS, EQUILIBRIUM POSITIONS, AND THE OBNOXIOUS LOCATION PROBLEM

ABSTRACT. Real variable analysis has een used to great benefit in a variety of classical problems in location theory. In this paper we explore basic complex variable techniques in one formulation of the obnoxious location problem. A general definition of center points is first given and used to formulate several alternate versions of the obnoxious location problem. A logarithmic transformation is then used to demonstrate some equivalences between these families of distinct location problems (defined via center points). A prototype logarithmic potential function which results from this formulation is then investigated, and it is demonstrated that the extremal solutions with this objective reside on the boundary of its domain of definition. An application using zero- and one-dimensional centers is discussed, and a generalization to the spatial obnoxious problem is also briefly examined. We define a zero-dimensional center as a critical point of the logarithmic potential function, and it is shown that these centers are equivalent to the solutions of the Complex Moment Problem.     

ELF fields for an inhomogeneous ionosphere with diffusive lower boundary

An ELF field equation is derived for an inhomogeneous ionosphere with diffusive lower boundary. Numerical results are presented to show that consistent ELF fields independent of the stratification of the ionosphere can be obtained by using this field equation.     

New observational techniques for studying the dynamics of the middle atmosphere using the Chung Li VHF radar

Taking advantage of the newly developed volume scattering model for MST radar and the unique features of the Chung Li VHF radar, several novel observational techniques have been developed and implemented. Techniques such as oblique spaced antenna (OSA), the frequency domain analysis of spaced antenna data, the full spectrum analysis (FSA) and the multifrequency frequency domain interferometer (FDI) will be discussed and experimental results will be presented. Potential applications of the new techniques to study the dynamics of the middle atmosphere will be discussed.     

Water,Geopolitics, and Economic Development in the Conceptualization of a Region

Two U.S.-based geographers outline three dimensions (geopolitical, economical, and biophysical) used to define the basin of the Mekong River as a region, which reveal multi-scalar water governance policies and discourses that lie at the core of current challenges and tensions within the basin. Drawing on their extensive knowledge and fieldwork, the authors demonstrate that processes integral to the framing of the Mekong as a region of economic integration and international cooperation (water resource development through construction of large dams) conflict sharply with the functioning of the Mekong as a region of highly connected biophysical processes. The approach utilized in the paper can be applied to the study of other transboundary river-basin regions in Eurasia and elsewhere facing similar contradictions among the geopolitical, economic, and biophysical dimensions used to define them. By focusing on a region as constructed simultaneously through multiple social and biophysical processes, the authors contribute to current debates within geography and related fields on the nature of regions.     

Relief and Neotectonics of the Foredelta of the Ganges and Brahmaputra Rivers

The techniques of geomorphic analysis, map measurements and field observations are used to trace the formation of the Bengal delta with particular reference to recent and present crustal movements. The oldest channel appears to be the Ganges submarine canyon, formed during a period of significant uplifting. Later the Hooghly appears to have become the main channel. Against a background of general subsidence, relative uplifting of the Barisal section (in the center of the delta) then led to the confluence of the Ganges and the Brahmaputra and a shift of the principal outlet to the Meghna River in the eastern part of the delta. The annual discharge of sediment (1.4 million tons) seems to be roughly compensated by downfolding of the estuary of the Meghna at the rate of 4 to 5 centimeters a year.     

Surface Rotations on and Around a Semi-Parabolic Canyon in an Elastic Half-Space Induced by Out-of-Plane SH-Waves,I: Torsion

The surface displacement amplitudes excited by out-of-plane SH waves on and around a semi-parabolic canyon had solution that was introduced over twenty years ago. In 2015, such solution was updated to much (5 times) higher frequencies, using a transformation involving the Wronskian. The same excitations also introduce rotations on and around the parabolic canyon. This article is the first of two that discuss the torsional component of rotations, with the rocking components discussed in the subsequent article. The rotational amplitudes of motions, as much as the displacement amplitudes, play an important role in studying the surface responses of structures, and can lead to a better understanding of the behavior of surface topographies in the event of seismic excitation.     

《论语》雌雉节新解

《论语》雌雉节汉代以来无定解。朱熹在《四书集注》中判此节两处有阙文,此说遂成定论。此节与《乡党》篇旨通意连,决无阙文。两千年来先贤大师释不通此节,关键在于离开“雌雉”之“雌”而去释解“时哉时哉”,结果变成离“礼’’释义。只要从“雌”字着眼,以“雌”释“时”,“山梁雌雉,时哉时哉”就与“礼”连接起来。雌雉节是子路惊飞孵卵雌雉,孔子强调此时正是雌雉孵卵之时,责备子路不应违反“不唐不卵”的时令之“礼”。子路打拱认错,雌雉终又惊飞。此解不见于《论语》讲读各家释义。