Anatomy of Hillfort Enclosure

2012 ◽  
Author(s):  
Dennis Harding
Keyword(s):  
Cross Section ◽  
A Priori ◽  
Apparent Absence ◽  
Notable Feature ◽  
Building Activity ◽  
Complex Structural

The most conspicuous element of a hillfort is generally its perimeter works, whether rubble wall or degraded bank and ditch. Their excavation in cross-section is a means of disclosing the structural sequence, which need not correspond to the occupational sequence of the site. The next most notable feature of the enclosure is its entrance, marked by a gap or inturn in the wall or bank, and a natural causeway across the ditch. Many hillforts are the product of a complex structural sequence, reflecting successive periods of occupation and building activity. Their perimeter works may range from relatively simple palisaded enclosures to more elaborate double or multiple earthworks that may occupy as great an area as that enclosed. Though a succession of occupational phases may result in progressive enhancement of the enclosing earthworks in both scale and complexity, it would be facile to assume a progression through time from the simplest form of construction to the most elaborate. There is no a priori reason why any given configuration, univallate rampart, bivallate, or multivallate, or method of construction, palisade, wall rampart, dump rampart, could not have been chosen at any given stage of a site's use. Though there are instances where a palisaded enclosure has been superseded by a timber-framed box rampart fronted by a ditch and subsequently by a dump rampart created by enlarging and deepening the ditch, in principle there is no reason why simple dump or glacis ramparts should not have been as early as or earlier than more elaborately constructed timber-framed ramparts, being less demanding of resources and requiring no greater manpower or effort to build. In practice, however, it would be difficult to replace a dump rampart, or a timber-framed rampart that had fallen into disrepair, with a timber-framed structure without labour-intensive clearance, because of the problems presented by the horizontal ties. This doubtless accounts for the apparent absence of horizontals from rampart B at Cadbury Castle (Alcock 1972), as a result of which the structure was fatally weakened. The only practical option would be to clear out and enlarge the ditch to create a heightened dump over the debris of the earlier wall.

scholarly journals A benchmarking procedure for PIGE related differential cross-sections

2019 ◽  
Vol 24 ◽  
pp. 36
Author(s):  
M. Axiotis ◽  
A. Lagoyannis ◽  
S. Fazinić ◽  
S. Harrisopulos ◽  
M. Kokkoris ◽  
...  
Keyword(s):  
Differential Cross Section ◽  
Cross Section ◽  
Cross Sections ◽  
Differential Cross ◽  
A Priori ◽  
Light Element ◽  
Thick Target ◽  
A Priori Knowledge ◽  
Differential Cross Sections ◽  
The World

The application of standard-less PIGE requires the a priori knowledge of the differential cross section of the reaction used for the quantification of each detected light element. Towards this end, a lot of datasets have been published the last few years from several laboratories around the world. The discrepancies found can be resolved by applying a rigorous benchmarking procedure through the measurement of thick target yields. Such a procedure is proposed in the present paper and is applied in the case of the 19F(p,p’γ)19F reaction.

Finite element modeling of guyed back spars in cable logging

2004 ◽  
Vol 34 (4) ◽  
pp. 817-828 ◽  
Author(s):  
Albert Saravi ◽  
C Kevin Lyons
Keyword(s):  
Finite Element ◽  
Normal Stress ◽  
Cross Section ◽  
A Priori ◽  
Element Model ◽  
Transverse Cross Section ◽  
Stress Fields ◽  
Stress Concentrations ◽  
Maximum Normal Stress ◽  
Tree Method

In this study a finite element model of a back spar system was developed with three guylines opposing the skyline strap tension. In this paper the allowable skyline strap tension is the tension in the skyline strap that results in the maximum normal stress on a transverse cross section of the tree being equal to an assumed allowable stress. An iterative routine was developed to find the allowable skyline strap tension, and this routine was found to converge rapidly from initial values that were below and above the allowable skyline strap tension. Two algorithms were developed for finding the maximum normal stress on a transverse cross section of a tree, method 1 and method 2. If the plane that the tree displaced in was known a priori, then method 2 could be used, and it was found to be less sensitive to mesh coarseness. If the plane that the tree displaced in was not known a priori, then method 1 had to be used with a less coarse mesh. It was found that the stress concentrations due to simplified cable connections were not significant for rigging configurations that allowed a larger rigging point displacement. The rigging configurations that allowed larger rigging point displacements have stress fields that are dominated by bending, while for rigging configurations that allow only small rigging point displacements, the stress fields are dominated by axial compression.

scholarly journals Study of information completeness of radar data for air target classification.

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
A.V. Kvasnov ◽  
Keyword(s):  
Remote Sensing ◽  
Cross Section ◽  
A Priori ◽  
Feature Space ◽  
Radar Data ◽  
Maximum Deviation ◽  
Target Classification ◽  
Transport Aircraft ◽  
Reference Information ◽  
Reflected Signal

In the article considers the estimation of completeness of radar data that obtained by the reflected signal from air spot targets as result of remote sensing. The feature space analyses based on information theory therefore evaluates maximum deviation data, which can be used for automatic target classification. The article demonstrates the study of trajectory (velocity, climb and height of flight) and signal (radar cross section and radar existing) features in respect of potential detected accuracy. As a priori data, reference information is used on various types and classes of air objects - aircraft (large transport aircraft, medium-haul aircraft, business jets, light motor aircraft, etc.). Modeling shows the most efficiency and completeness features are height of flight (Hh ≈ 5.17)  and velocity  (Hv ≈ 4.17)  of air object systems.

scholarly journals ASYMPTOTIC BEHAVIOR OF STRUCTURES MADE OF CURVED RODS

2008 ◽  
Vol 06 (01) ◽  
pp. 11-22 ◽  
Author(s):  
GEORGES GRISO
Keyword(s):  
Asymptotic Behavior ◽  
Variational Problem ◽  
Cross Section ◽  
A Priori Estimates ◽  
A Priori ◽  
The Other ◽  
Linearized Elasticity ◽  
Curved Rods ◽  
The Cross ◽  
Linearized Elasticity System

In this paper, we study the asymptotic behavior of a structure made of curved rods of thickness 2δ when δ tends to 0. This study is carried on within the frame of linear elasticity by using the unfolding method. It is based on several decompositions of the structure displacements and on the passing to the limit in fixed domains. We show that any displacement of a structure is the sum of an elementary rods-structure displacement (e.r.s.d.) concerning the rods' cross sections and a residual one related to the deformation of the cross section. The e.r.s.d. coincides with rigid body displacements in the junctions. Any e.r.s.d. is given by two functions belonging to [Formula: see text] where [Formula: see text] is the skeleton structure (i.e. the set of rods with middle lines). One of this function [Formula: see text] is the skeleton displacement, the other [Formula: see text] gives the cross section rotation. We show that [Formula: see text] is the sum of an extensional displacement and an inextensional one. We establish a priori estimates and then, we characterize the unfolded limits of the rods-structure displacements. Eventually, we pass to the limit in the linearized elasticity system and using all results in [6], where on one hand, we obtain a variational problem that is satisfied by the limit extensional displacement, and on the other hand, a variational problem coupling the limit of inextensional displacement and the limit of the rod torsion angles.

scholarly journals Effect of Complex Structural Material Coated the Flight Body to Measure the Absorption of Radar Radiation at Different Elevations of Flight Latitude

2018 ◽  
Vol 7 (2.23) ◽  
pp. 205
Author(s):  
Abbas Ali Mhmood Karwi
Keyword(s):  
Composite Materials ◽  
Cross Section ◽  
Maximum Rate ◽  
Erosion Resistance ◽  
Polymeric Materials ◽  
Low Density ◽  
High Tensile Strength ◽  
Rate Of Absorption ◽  
Coating Layers ◽  
Complex Structural

Avoiding radar detection is a prime importance in several fields. We design multi reinforced polymeric materials to absorb radar waves, these materials have low density, high elastic modulus, high tensile strength good erosion resistance and good fatigue strength. Composite materials are made by three principle techniques, injection, spraying and compression. Jet technique was used to measure materials resistance for erosion. We find that  polytetrafluroethylene with multi mixtures  has the best specification than other polymeric materials. We manufacture twenty-one alloys (A, B, C, D, E, F…..W) used in this work. Composite materials (A-W) are making by adding fillers to matrices. Absorption coefficient of fillers and matrices was evaluated and measured alone or as a composite. Dynamic and static radar cross section shapes (eight shapes)were studied in this work. The better shapes for absorption waves are (spherical, conical, cylindrical, and parabolic). All parameters controlled reflectivity and absorption were studied. We found that the maximum rate of absorption is more than (70%), this percent observed in certain coating layers. Metallurgical and mechanical work on composite materials have been investigated. Model designed to compute multi variables affecting on absorption and reflection.    

scholarly journals Consequences of viscous anisotropy in a deforming, two-phase aggregate. Why is porosity-band angle lowered by viscous anisotropy?

2015 ◽  
Vol 784 ◽  
pp. 199-224 ◽  
Author(s):  
Yasuko Takei ◽  
Richard F. Katz
Keyword(s):  
Cross Section ◽  
Laboratory Experiments ◽  
A Priori ◽  
Shear Plane ◽  
High Porosity ◽  
Anisotropic Model ◽  
Maximum Compressive Stress ◽  
Two Phase ◽  
The Difference ◽  
Do So

In laboratory experiments that impose shear deformation on partially molten aggregates of initially uniform porosity, melt segregates into high-porosity sheets (bands in cross-section). The bands emerge at $15^{\circ }$–$20^{\circ }$ to the shear plane. A model of viscous anisotropy can explain these low angles whereas previous simpler models have failed to do so. The anisotropic model is complex, however, and the reason that it produces low-angle bands has not been understood. Here we show that there are two mechanisms: (i) suppression of the well-known tensile instability, and (ii) creation of a new shear-driven instability. We elucidate these mechanisms using linearised stability analysis in a coordinate system that is aligned with the perturbations. We consider the general case of anisotropy that varies dynamically with deviatoric stress, but approach it by first considering uniform anisotropy that is imposed a priori and showing the difference between static and dynamic cases. We extend the model of viscous anisotropy to include a strengthening in the direction of maximum compressive stress. Our results support the hypothesis that viscous anisotropy is the cause of low band angles in experiments.

On the bifurcation of steady vortex rings from a Green function

1994 ◽  
Vol 116 (3) ◽  
pp. 555-568 ◽  
Author(s):  
Tadie
Keyword(s):  
Green Function ◽  
Free Boundary ◽  
Cross Section ◽  
Free Boundary Problems ◽  
A Priori ◽  
Elliptic Partial Differential Equation ◽  
Vortex Rings ◽  
Boundary Problems ◽  
Bounded Set ◽  
The Green Function

This paper is a supplement to [2]. There, solutions ψ., (μ) of certain free-boundary problems, depending on a small parameter μ, are related to the Green function G., (a(μ)) of a second-order, elliptic, partial differential equation defined on a bounded set Ω ⊂ ℝ2. The free boundary is the boundary of a set A(μ) ⊂ Ω that is unknown a priori and corresponds to the cross-section of a steady vortex ring or of a confined plasma in equilibrium, for example.

Nuclear Spin Relaxation in Dilute Gas Mixtures

1971 ◽  
Vol 49 (8) ◽  
pp. 1018-1028 ◽  
Author(s):  
Krovvidi Lalita ◽  
Myer Bloom
Keyword(s):  
Cross Section ◽  
Spin Relaxation ◽  
Room Temperature ◽  
A Priori ◽  
Rotational Quantum Number ◽  
Gas Mixtures ◽  
Proton Spin ◽  
Molecular Reorientation ◽  
Hydrogen Molecules ◽  
Dilute Gas

Measurements of the proton spin relaxation time T1 have been carried out in hydrogen–helium dilute gas mixtures between room temperature and 730 K and in hydrogen–carbon dioxide mixtures between room temperature and 500 K as a function of density and concentration. When the measurements on H2–He are combined with those previously made at lower temperatures, a pronounced minimum in the dependence of T1 on temperature is obtained in the vicinity of 70 K for the limit of 100% helium. The data are analyzed on the assumption that collisions between hydrogen molecules and helium atoms which change the rotational quantum number J of the H2 are much less frequent than those which cause molecular reorientation with no change in J. Under this assumption, the data over the entire temperature range are fitted remarkably well by the theory of Kinsey, Riehl, and Waugh for the velocity dependence of the cross section for molecular reorientation in H2–He collisions using an exponential–6,H2–He potential based on "a priori considerations". The high temperature data are consistent with a reorientation cross section behaving approximately as σ α ν2.4 in the limit of high velocities. The H2–CO2 data below 400 K are consistent with a CO2 quadrupole moment of 4.1 × 10−26 e.s.u. but the behavior of the proton spin relaxation above 400 K is not yet understood.

Optimal Tax and Expenditure Policy with Aggregate Uncertainty

2014 ◽  
Vol 6 (1) ◽  
pp. 205-257 ◽  
Author(s):  
Felix J. Bierbrauer
Keyword(s):  
Public Goods ◽  
Cross Section ◽  
A Priori ◽  
Income Taxation ◽  
Public Goods Provision ◽  
Optimal Income Taxation ◽  
Tax System ◽  
Aggregate Uncertainty ◽  
Optimal Tax ◽  
The Cross

We study optimal income taxation and public-goods provision under the assumption that the cross-section distributions of productive abilities or public-goods preferences are not known a priori. A conventional Mirrleesian treatment is shown to provoke manipulations of the policy mechanism by individuals with similar interests. The analysis therefore incorporates a requirement of coalition-proofness. The main result is that increased public-goods provision is associated with a more distortionary and a more redistributive tax system. With a conventional Mirrleesian treatment, the level of public-goods provision is not related to how distortionary or redistributive the tax system is. (JEL D82, H21, H23, H41)

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