Circular Shield Research Articles

Calculation of the capacitance matrix of a nonperiodical sequence of drift tubes of varying dimensions with roundings in a circular shield

Calculation of the capacitance matrix of a nonperiodical sequence of drift tubes of varying dimensions with roundings in a circular shield

VI. Conclusions

The origins of the Anglo-Saxon shield are to be found in the Roman Iron Age on the Continent. The Early Saxon shield has the same basic form as the shields in Danish and North German bog deposits: a flat circular board of small to medium size, made up of several planks set side by side, and fitted with an iron boss and grip [46, 47]. None of these features had to be borrowed from Roman shields, which in the first three centuries AD were mostly rectangular or oval and included convex and laminated boards, whilst the Late Roman circular shield may actually be of Germanic origin. The types of Early Saxon iron boss and grip were also rooted in Roman Iron Age types, and the main constructions of wooden handles (particularly ones using a lap-joint) were already used on third-/fourth-century shields in Jutland.

AN EXPERIMENTAL STUDY OF MULTI-CIRCULAR FACE SHIELD TUNNELLING

Using an ordinary circular shield for construction of double track railway tunnel, the cross section becomes larger than the net required section. As a result, the construction work takes not only more cost but also longer time. The multi-circular face (MF) shield tunnelling has been developed to mitigate these problems, and can build a tunnel with a special cross section comprising multi-circles partially overlapped.In this study, the experiment is executed to make clear the basic behaviors of double-circular face shields (one with two faces aligned horizontally and the other with faces aligned vertically). The results show that the cutter torque and total thrust force of the MF shield are smaller than those of a circular face shield to construct the same double track railway, and that the MF shield has good characteristics in the stability of a cutting face and in its maneuverability.

Effusive flow conductance of shielded circular channels

A circular shield coaxial with the conductance channel and spaced a small distance from the channel entrance is used to establish a well defined gas density gradient inside the effusion cell. The gradient and the resultant channel conductance are calculated by previously presented methods with the additional approximation that the plane of entrance to the channel is taken to be a partial absorber and a partial diffuse reflector with the absorption coefficient being the conventional Clausing factor of the channel. Transmission coefficients are calculated for a number of reduced geometries, and a practical means of fabricating shielded conductance elements is described.

Symmetrical Four-Port Edge-Guided Wave Circulators

Four-port microwave-integrated-circuit (MIC) edge-guided wave circulators (BGC) have been designed, fabricated, and tested. A mathematical characterization of the strip conductor's shape as well as a precise mechanical control of the bias inhomogeneity are provided. By means of these two techniques the reproducibility of the device is greatly improved with respect to that of the EGC obtained by the traditional cut-and-try methods. X-band performance data are presented and related to the spatial distribution of the effective magnetic permeability mu/sub eff/ in the ferrite substrate. Experimental evidence is reported that an efficient circulator action occurs when mu/sub eff/< 0 at some point under the central circular shield. The spatial distribution of the RF electric field at the circulator's surface is investigated by a mechanical probing technique. It is found that in the lower part of the operation band, RF fields of considerable amplitude extend in the air in the region between the guiding edge and the substrate's edge.

A Shoshonean Origin for the Plains Shield Bearing Warrior Motif

The shield bearing warrior is a distinctive motif characteristic of the rock art of the Northwestern Plains. It also occurs commonly in the eastern Great Basin as an element of Fremont rock art. Detailed similarities between Plains and Great Basin shield figures suggest cultural relationships between the two areas. This has led some authors to propose that the motif originated in the Northwestern Plains and diffused to the Great Basin. Others argue that the motif spread from the Great Basin to the Plains. Relative dates recently obtained for shield figures at Northwestern Plains sites support the latter hypo thesis. A Shoshonean origin for the Northwestern Plains shield figures is suggested by the dates, and the coincidence between the distribution of the motif, the distribution of diagnostic Shoshonean artifacts, and the ethnohistorically known range of the Plains Shoshone. It is suggested that the Shoshone borrowed the motif from the Fremont Culture during a period of interaction between the two groups. The shield bearing warrior, a distinctive motif that depicts a pedestrian warrior whose body is represented by a large circular shield (Fig. 1), is frequently encountered in the rock art of the western United States. It is especially common at sites on the Northwest ern Plains and in the eastern Great Basin (Fig. 2). 4> #~*i> ^ f a Mb tXc I 1 e JIf > / g ji H Fifl. 1. Exampte of the shield bearing warrior motif, a-e from sites on Northwestern Plainsf-h from Fremont sites.1 Scale variable. '

Design of Dipole Magnet with Circular Iron Shield

Complex variable function theory is used to formulate the magnetostatic problem of a rectangular current block of uniform current density located within a circular region bounded by infinite permeability iron. The magnetic field from the superposition of several blocks arranged to exhibit dipole symmetry is calculated using a generalization of Cauchy's integral formula. Subsequent multipole expansion yields expressions for the multipole coefficients which through the use of variable metric minimization permits block arrangements to be found for rather pure dipole fields. Application is made to superconducting dipoles for both a pancake arrangement and a shell arrangement of the individual blocks.

Simplifications in the transformation of net radiometers into hemispherical radiometers

In a recent paper in this journal (Idso, 1971) I described a technique for transforming polyethylene-shielded net radiometers into hemispherical radiometers. It consisted essentially of constructing a second set of domes, sandwiching three fine thermocouples between the bottom pair, applying a spray application of black and then white paint to the outer surface of the double-layered bottom dome, and then utilizing mid-plane and under-radiometer circular shields. The purpose of this short communication is to introduce some recently developed simplifications of this technique.

Monitoring rime accumulation by radioactive attenuation

A simple density gauge was used as an open-path detector of accumulating rime. Although source activity was a low 2-3 ?g of radium, it was found adequate for measurement over the range of 0-7 mm water equivalent. A circular shield prevents falling snow from affecting the reading.

The Shield Motif in Plains Rock Art

AbstractThe representation in the prehistoric and the early historic art of North America of circular shields or human figures whose torsos are depicted in the form of a shield provide a revealing indication of how widespread and complex was the diffusion of objects, ideas, and forms on the continent. Drawings of the shields and of shield figures are found in rock paintings and engravings, on paintings and skins, and on incised bark scattered throughout the continent. The origin of the motif is still in question, although present evidence would seem to point to central Mexico. The earliest examples north of the Rio Grande would appear to be in the rock paintings of the lower Pecos area of Texas. It next appears as an important form in the rock art of Utah which has been attributed to the Fremont Culture. From this latter area in late Prehistoric times, it apparently spread to the northern Plains, and thence into the central and southern Plains where it briefly became an element in the rock art and the mural paintings of the late Pueblo cultures. During this late period it also entered into the art of the region east of the Mississippi and into the rock art of the far western part of the continent.