Hollow Ground Research Articles

Transparent and flexible fish-tail shaped antenna for ultra-wideband MIMO systems

Abstract The article presents an innovative transparent, flexible antenna design tailored specifically for ultra-wideband multiple-input multiple-output (MIMO) systems. Using polyethylene terephthalate substrates as the base material, we enhance the antenna’s radiation performance, transparency, and flexibility. Broadband impedance matching is achieved through a hollow ground plane fed by a fish-tail radiator and coplanar waveguide. Additionally, significant MIMO antenna isolation in ultra-wideband scenarios is achieved through the vertical arrangement of units and neutral lines. The MIMO antennas we manufactured exhibit minimum transparencies of 71.1% and 85.9% with and without reflectors, respectively. Measurement results demonstrate that the antenna operates within the 3–20 GHz frequency range, with over 24 dB of isolation, 2 ± 2 dBi of peak gain, and 45% ± 5% of radiation efficiency, suitable for applications in wearable devices, vehicle intelligence, and other fields.

Integral Seismic Deformation Method: A Pseudo-static Method for Seismic Design of Underground Structures

The traditional seismic deformation method is among the most popular pseudo-static methods for seismic design of underground structures by considering soil-structure interaction through the layout of foundation springs. It can be mechanically proved that the traditional method has a relatively rigorous theory except the discrete foundation springs. A new kind of pseudo-static method, called the integral seismic deformation method, is proposed in this paper by establishing the finite element models of hollow ground and integral soil-and-structure. Equivalent seismic loads of the proposed method are composed of three parts: shear stress of free field, inertia force of underground structure and equivalent nodal forces acquired by the static analysis of the hollow ground model. In order to verify the efficiency of the proposed method, a series of numerical calculations of Daikai subway station are conducted by the two pseudo-static methods and the dynamic time-history analysis, respectively. Comparison of the calculation results shows that the proposed method achieves high precision and extensive applicability. It is also convenient and time-saving to operate. Therefore, the integral seismic deformation method can be widely used for seismic design of underground structures.

Palaeo-earthquake and palaeo-mudflow events at the Machangyuan Ruins in the Huangshui River valley, northeastern margin of the Tibetan Plateau

Palaeo-earthquake event recorded by loess rapture fissures (N30°–40°W and N40°–50°E trending) and palaeo-mudflow event recorded by red clay deposits were identified at the Machangyuan Ruins in the Huangshui River valley, at the foot of the northeastern Tibetan Plateau. Comparative analysis of grain-size distributions and geochemical elements of local outcrops indicates that the red mudflows were sourced from the gullies on the valley side where unconsolidated Neogene red clay formation was exposed The palaeo-earthquake was associated with regional tectonic structures including a NNW-trending left-lateral strike-slip fault (Lajishan fault) and a NE-trending local fault (Bazhougou fault). Analysis combining optically stimulated luminescence ages and radiocarbon ages of archaeological record dates the palaeo-earthquake and palaeo-mudflow events to ca. 4.80 ka BP. During that stage, many Neolithic settlements distributed around the Machangyuan Ruins. Enhanced human activities of the Majiayao Culture disturbed the landscape of the Minhe Basin causing widespread soil erosion. Contemporaneous storm rain and earthquake mobilized the loosened sediments in the upper stream gullies forming mudflows. The hollow ground around the Machangyuan Ruins was covered by mudflow and the earthquake fissures were filled in by the mudflow at the same time. This study provides important insights into early human impact during climatic and tectonic events in the environmentally vulnerable zones over the world.

Improvement of isolation and envelop correlation coefficient using C‐loaded λ/4 loop antenna on hollow ground

ABSTRACTA C‐loaded λ/4 loop antenna on a hollow ground is presented to improve the isolation and envelop correlation coefficient (ECC) in the mobile terminals. The designed antenna is composed of a straight type of C‐loaded λ/4 loop on hollow ground and a monopole branch operating for LTE800 and LTE1900 bands, respectively. The proper value of a loaded capacitor of the loop makes λ/4 resonance, resulting in the parallel current flow on the ground plane while a conventional planar inverted‐F antenna (PIFA) generates a vertical current flow in the ground. Thus, the combination of two antennas will give rise to high isolation and low ECC. The isolation and ECC of both cases of PIFA (primary) versus PIFA (secondary) and PIFA (primary) versus C‐loaded λ/4 loop antenna with a monopole branch (secondary) are compared when they are diagonally placed in a mobile handset. The isolations in the former and latter cases are measured to be lower than −5.3 and −22 dB in the LTE800 band, respectively. Also, the ECC values in the former and latter cases are measured to be 0.81 and 0.29 from far‐field radiation patterns in the LTE800 band, respectively. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2189–2194, 2016

Hollow ground: a novel

Hollow ground: a novel

Hollow Ground by Stephen Marion (review)

Hollow Ground by Stephen Marion (review)

Performing Feeling Without Fear

Performing Feeling Without Fear

Holocene landscape development and human impact in the Connemara Uplands, Western Ireland

AimAim Investigate: (1) the role of human impact in shaping the landscape and particularly the initiation of blanket bog; (2) the short‐lived abrupt changes and their causation; (3) the phenomenon of large‐scale upland peat erosion to answer the question of when and why erosion of upland blanket peat commenced in the Connemara uplands.LocationLough Maumeen in the Maumeen Gap, Connemara, Western Ireland.MethodsPollen, sedimentary analysis and 14C dating on the lake sediment cores.ResultsPollen diagrams, charcoal fragments, bulk and dry densities, mineral content (or loss‐on‐ignition), whole core magnetic susceptibility, specific magnetic susceptibility for the core profile.Main conclusionsPine‐dominated woodland developed from 9250 BP. Human activities effected the deforestation between 5050–4000 BP. Peat bog initiated on the wet hollow ground in the gap during the elm decline. The major expansion of blanket bog landscape in the upland commenced at 4000 BP following immediately the Taxus decline. Human impact was the dynamic force responsible for the destruction of the woodland and the formation of blanket bog in the upland. Three episodes of short‐lived erosion events were identified between 8650–8400 BP, 5450–5250 BP, and 600–200 cal. BP, respectively. They are very different from each other in their causation. Large‐scale peat erosion is a recent phenomenon. It has been caused by intensive sheep grazing, which has been extended to the upland blanket bogs since the late eighteen century.

An improved halo for fixing facial fractures

TRAUMATIC maxillary displacement in most cases is posterior and downwards in direction. The maxillary block slides under the curving base of the skull and comes to lie in the open bite position with varying degrees of posterior shift and impacfion. This position is often forcibly maintained by the spastic contraction of the injured pterygoid muscles, the externus pulling the block towards the temporomandibular joint and the internus aided by the masseter muscle pulling the back of the block closer to the descending ramus of the mandible. In the majority of cases this displacement is easily corrected by manipulation under general anaesthesia and the maxilla can be held in the corrected position by a light halo apparatus in the usual way. There are, however, cases that do not respond so readily ; some early ones and nearly all late ones. After a few days an unreduced fracture becomes daily more firmly fixed and continuous traction rather than forcible disimpaction becomes the only way to effect reduction. This has led to the development of a halo which can exert pressure on the displaced maxilla in any direction through the medium of two self tapping screws inserted in the premaxilla (Grocott and Wilson, I972). A number of different frame types were tried ; that finally selected is an adjustable but rigid structure which gives access to the vault of the skull and is comfortable to the patient in bed. Necessarily this means a heavier structure than the standard halo but the weight has been progressively reduced to about 350 gm. by the use of light alloy. The frame (Fig. I) consists of a horizontal metal platform conforming in contour to the forehead and adjustable side arms pivoted at the outer ends of the platform. The platform itself carries 2 insulating blocks or bushes which in turn carry the stainless steel frontal screw pins (Fig. 2). In the centre of the platform is a ball or universal joint which forms the pivot for a vertical extensible beam dropping down to the maxillary attachment. The joint is fully adjustable by screws so that the beam may rotate and swing in an antero-posterior or lateral direction in any combination. The pivoted side arms are adjustable by screws and can be locked in final adjustment by nut and bolt. They are drilled and can carry vertical arms if desired. The posterior ends are slotted to carry the nylon insulated bushes which hold the mastoid screw pins. It is very advantageous to have as short a length of screw pin as possible between the frame and the skull. This ensures greater rigidity and obviates movement of the pin carriers or bending of the pins under stresses tangential to thc ~t'ull The skull strong points selected for insertion of the pins are on each temporal ridge area and each mastoid area at the level of the floor of the anterior fossa. The pin holders are first adjusted for position and then the angles are set for radial contact with the bone. The clamp is applied so that the mastoid pins register just in front of the mastoid suture line with the occipital bone; there is a depression here which is easily felt behind the ear. The lateral arms are tightened until the pins register against the bone in the depression. The pins, which are hollow ground, are screwed in a few turns until the whole clamp can be hinged up and down with the frontal pins just clearing the forehead. The frontal pins are now screwed home to register just above the superciliary ridges and just medial to the temporal ridges of the frontal bone. When these and the mastoid pins are tightened the platform is solidly fixed to the base of the skull.

Low Speed Microtomy for the Electron Microscope

The beam of a 50-kv electron microscope does not penetrate specimens that are thicker than 0.1 μ. Thus, in order to study biological specimens with this type of microscope we have further developed the technic described by Pease and Baker, who altered a Spencer Rotary Microtome (model 820) by adding a wedge to the mechanism for forward movement. We reduced the angle of the inclined plane surface by a factor of 10 to 1 so that each step is 0.1 μ rather than 1.0 μ. Since forward movement results from a pin in sliding contact with an inclined plane surface, it is important that the surface of the plane be as nearly perfectly flat as possible. The accompanying photograph, Fig. 1, illustrates the means by which the problem of a flat surface for even forward movement was solved. At the left of the picture (A) the original plane can be seen. The reduced angle is shown by D. The light gray triangular area (B) is an angle-reducing block of steel, to which is fastened an optical flat (C). A brass disc (E) instead of a pin is used for the feed screw tip. Horizontal movement of the disc is responsible for forward movement of the specimen. Vertical movement of the flat and the mechanism to which it is attached causes the slicing action of the microtome. Since the disc and flat are held firmly in contact by a spring, any irregularities in the surface of the plane will be evident on the sliced section. Since the ordinary microtome knife cannot be used to cut sections as thin as 0.1μ, ours was especially made, hollow ground on both sides, with a long bevel.

Further Studies on the Effects of Irradiation on Proliferation and Metabolic Processes of Normal and Malignant Tissues

THE time-intensity factor related to the effectiveness of irradiation upon living processes remains to-day an unsettled problem among the investigators in this specialized field. The question as to whether high dosage rates for a short time or low dosage rates for a long period of exposure produce more marked effects of radiation has not yet been definitely answered. The present series of experiments was undertaken in an attempt to throw some light upon this question. Before presenting the results obtained from these experiments, reference will be made to our previous investigation (1). The determination of the lethal and sublethal doses produced by different types of radiation for various tissues grown in vitro was chosen as a basis for that investigation. The following technic and criteria were used: Freshly excised tissue fragments embedded in a nutritive medium on a No. 1 coverslip and covered with a mica sheet were inverted over a hollow ground slide, sealed with paraffin wax, and irradiated. The irr...

The Effect of Radiation on Cell Respiration

THE purpose of this experiment was to correlate the effect of various types of radiation on the growth and respiration of mammalian tissues in vitro. The results of the effect of x-rays, radium, and radon upon growth in vitro are recorded in a separate paper. We were able to determine the lethal dose and sublethal dose of these three types of radiation for tissues of various origin grown in vitro. As in the experiments on proliferation, we have also attempted to determine the effective dose of radiation for respiration. Material and Experimental Procedure In a previous communication (1) we reported the values of O2 uptake and the respiratory quotients of normal mouse kidneys which showed the most uniform respiration. This type of tissue was, therefore, selected for the experiment with radiation. The kidneys removed under aseptic precautions from three- to four-month-old mice, immediately after pitting, were placed in hollow ground Maximov's slides, a small strip of moist filter paper was placed beside the kidneys in order to avoid evaporation, then covered with a sheet of mica sealed with paraffin wax and exposed to radiation. The reason for using Maximov's slides was because the same equipment was used here as for radiation of the tissue cultures. Since a marked decrease in respiration of normal kidneys was observed when they were kept at room or body temperature for several hours and a very slight decrease in respiration when they were kept at 4° C., the radiation, therefore, was administered at 4° C. While one kidney was exposed to radiation at about 4° C., the other was kept in the refrigerator as a control. After a certain dose of radiation was administered, the kidneys were immediately prepared for respiration in vitro. A Ringer-phosphate solution containing 0.2 per cent glucose and at ph 7.4 was used as a nutritive medium. The respiratory exchanges of the tissue were determined by the use of the Barcroft-Warburg manometric apparatus. An improvement in this apparatus which we have found increases the precision of the measurements and saves more than one hour will be briefly described here. The Barcroft-Warburg apparatus consists of 14 vessel manometers which are normally used for each experiment. For the determination of respiratory exchanges of tissues, each vessel manometer is saturated for several minutes with a gas (with O2 for ærobic and N2 for anaerobic glycolysis). The improvement consists of cross-shaped glass tubes which are connected to each other and to the manometers with rubber tubing. The flow of gas to each vessel manometer is regulated with a screw clamp. When these clamps are once regulated so that the pressure in all vessel manometers is uniform, they need no further attention in the subsequent experiments. Before each experiment the glass tubes are attached to the vessel manometers, the whole system is connected with a gas-tank, and the saturation with gas takes only a few minutes.

The Use of Hollow Ground Slides Made with the Dental Engine

The Use of Hollow Ground Slides Made with the Dental Engine

The shape of the human red blood corpuscle

In a paper published in 1909 I presented evidence in refutation of the new teaching that the normal shape of the mammalian red blood-corpuscle is cup-form. This evidence included data derived from an examination of the capillaries in the omentum of an anesthetized cat, sections of variously fixed tissues, and hanging drop preparations of fresh blood. The latter, sealed and kept at body temperature, were thought to simulate closely actual conditions in the blood vessels of the living animal. The free central corpuscles of such a drop preparation are almost exclusively of the circular biconcave disc form. In view of all the evidence there seemed to be no escape from the conclusion that the biconcave disc-shape is the normal, the cup-shape the derived, form of the mammalian erythroplastid. But since opinion still remains divided on the point as to what is the original and normal shape—that is, whether cup or disc—additional evidence is demanded. Cogent confirmatory data accrue from observations of the corpuscles in the gelatin solution recently devised by Hogan as a substitute for salt solutions for transfusion purposes in clinical cases calling for relief to a fall in blood pressure. The special point of advantage claimed for Hogan's normal-salt-gelatin mixture is that it has the colloidal constitution of blood plasma, and in consequence is not lost from the blood vessels through secretion and osmotic processes as salt solutions are supposed to escape. The method of procedure in my investigation was to place the Hogan's solution in an incubator at a temperature of 42'C. Hollow ground culture slides, cover slips, a pipette, and a needle were also kept in the same incubator. The excess above the normal body temperature was planned to compensate for the cooling incident to the frequent opening of the incubator and the transfer of the preparation for study to the microscope stage.