Vibration suppression and slewing control of a flexible structure

Examined here are the effects of motor dynamics and secondary piezoceramic actuators on vibration suppression during the slewing of flexible structures. The approach focuses on the interaction between the structure, the actuators, and the choice of control law. The results presented here are all simulated, but are based on experimentally determined parameters for the motor, structure, piezoceramic actuators, and piezofilm sensors. The simulation results clearly illustrate that the choice of motor inertia relative to beam inertia makes a critical difference in the performance of the system. In addition, the use of secondary piezoelectric actuators reduces the load requirements on the motor and also reduces the overshoot of the tip deflection. The structures considered here are a beam and a frame. The majority of results are based on a Euler Bernoulli beam model. The slewing frame introduces substantial torsional modes and a more realistic model. The slewing frame results are incomplete and represent work in progress

Static and dynamic characteristics of a piezoceramic strut

The experimental study of a piezoceramic active truss is presented. This active strut is unique in that the piezoceramic configurations allow the stroke length of the strut not to be dependent on the piezoceramic material's expansion range but on the deflection range of the piezoceramic bender segment. A finite element model of a piezoceramic strut segment was constructed. Piezoceramic actuation was simulated using thermally induced strains. This model yielded information on the stiffness and force range of a bender element. The static and dynamic properties of the strut were identified experimentally. Feedback control was used to vary the stiffness of the strut. The experimentally verified model was used to explore implementation possibilities of the strut

Concept verification of three dimensional free motion simulator for space robot

In the development of automatic assembling technologies for space structures, it is an indispensable matter to investigate and simulate the movements of robot satellites concerned with mission operation. The movement investigation and simulation on the ground will be effectively realized by a free motion simulator. Various types of ground systems for simulating free motion have been proposed and utilized. Some of these methods are a neutral buoyancy system, an air or magnetic suspension system, a passive suspension balance system, and a free flying aircraft or drop tower system. In addition, systems can be simulated by computers using an analytical model. Each free motion simulation method has limitations and well known problems, specifically, disturbance by water viscosity, limited number of degrees-of-freedom, complex dynamics induced by the attachment of the simulation system, short experiment time, and the lack of high speed super-computer simulation systems, respectively. The basic idea presented here is to realize 3-dimensional free motion. This is achieved by combining a spherical air bearing, a cylindrical air bearing, and a flat air bearing. A conventional air bearing system has difficulty realizing free vertical motion suspension. The idea of free vertical suspension is that a cylindrical air bearing and counter balance weight realize vertical free motion. This paper presents a design concept, configuration, and basic performance characteristics of an innovative free motion simulator. A prototype simulator verifies the feasibility of 3-dimensional free motion simulation

The avian remains from El Juyo, Lower Magdalenian Cantabrian Spain

El Juyo is one of the Cantabrian sites of Iberia known from long ago for its important Lower Magdalenian sequence. The present study reports the results of the zooarchaeological and taphonomic analysis of the avian remains recovered at the site, which complements the archaeological and palaeoecological data already avail-able. The remains recovered are limited, but they seem to indicate that humans were the main accumulating agent in the site, with sporadic presence of owls' activity. Additionally, humans could have used birds for other purposes than as a dietary resource, as suggested by cut marks observed on two wing bones.info:eu-repo/semantics/publishedVersio

Особенности художественного отображения агрессии, направленной против Азербайджана

[EN]: The micromammals remains from the Late Pleistocene site of the cave of El Castillo studied here in detail, came from the Aurignacian levels 18b and 18c (dated in 40.000-45.000 BP), level 19, and the Musterian levels 20b, 20c, 20d, 20e (dated in 41.000-49.000 BP), 21a and 21b. The micromammal association is the following: Erinaceus europaeus, Crocidura russula, Sorex coronatus, Sorex minutus, Neomys fodiens, Talpa europaea, Galemys pyrenaicus, cf. Miniopterus schreibersii, Chiroptera indet., Pliomys lenki, Microtus arvalis – Microtus agrestis, Microtus lusitanicus, Microtus oeconomus, Chionomys nivalis, Arvicola terrestris, Apodemus sylvaticus – Apodemus flavicollis and Lepus sp. Most of these species are in the present fauna of Cantabria, except Pliomys lenki that got extinct in the last third of the Upper Pleistocene, and Microtus oeconomus that disappeared from the Iberian Peninsula during the Holocene, in historical times, and is nowadays present in northern Euroasiatic regions. There is a great continuity of most of the taxa in all the levels. The faunal association seems to indicate a mainly open environment, in general with wet meadows (and few dry meadows), with good vegetation cover in the soil, with perhaps also some tree-covered areas, and some watercourses. The thermophiles indicators are very scarce, which could indicate that the climate could be a lesser temperate than other Upper Pleistocene periods and the present-day climate in the area.[ES]: El material de micromamíferos del yacimiento del Pleistoceno Superior de la cueva de El Castillo, objeto de estudio detallado en este trabajo, proviene de los niveles auriñacienses 18b y 18c (datados en 40.000-45.000 BP), nivel 19, y niveles musterienses 20b, 20c, 20d, 20e (datados en 41.000-49.000 BP), 21a y 21b. La asociación de micromamíferos es la siguiente: Erinaceus europaeus, Crocidura russula, Sorex coronatus, Sorex minutus, Neomys fodiens, Talpa europaea, Galemys pyrenaicus, cf. Miniopterus schreibersii, Chiroptera indet., Pliomys lenki, Microtus arvalis – Microtus agrestis, Microtus lusitanicus, Microtus oeconomus, Chionomys nivalis, Arvicola terrestris, Apodemus sylvaticus – Apodemus flavicollis y Lepus sp. La mayoría de estas especies están presentes en la fauna actual de Cantabria, excepto Pliomys lenki que se extinguió en el último tercio del Pleistoceno Superior, y Microtus oeconomus, que persistió en la península ibérica durante el Holoceno bien avanzado hasta su desaparición en tiempos históricos, y que actualmente está en regiones euroasiáticas más septentrionales. Hay una gran continuidad de la gran mayoría de los taxones en todos los niveles. La fauna en su conjunto parece indicar un medio predominantemente abierto, por lo general de praderas húmedas (y en mucha menor medida praderas secas) con una buena cobertura vegetal a nivel del suelo, en el que habría también algunas zonas arboladas o boscosas, y algún curso de agua. Los indicadores termófilos son escasos y poco abundantes, lo que podría indicar que el clima podría ser algo menos templado que en otros periodos del Pleistoceno Superior y quizás también que actualmente en la zona.Peer Reviewe

Evidence of fatal skeletal injuries on Malapa Hominins 1 and 2

Malapa is one of the richest early hominin sites in Africa and the discovery site of the hominin species, Australopithecus sediba. The holotype and paratype (Malapa Hominin 1 and 2, or MH1 and MH2, respectively) skeletons are among the most complete in the early hominin record. Dating to approximately two million years BP, MH1 and MH2 are hypothesized to have fallen into a natural pit trap. All fractures evident on MH1 and MH2 skeletons were evaluated and separated based on wet and dry bone fracture morphology/characteristics. Most observed fractures are post-depositional, but those in the right upper limb of the adult hominin strongly indicate active resistance to an impact, while those in the juvenile hominin mandible are consistent with a blow to the face. The presence of skeletal trauma independently supports the falling hypothesis and supplies the first evidence for the manner of death of an australopith in the fossil record that is not attributed to predation or natural death.The National Research Foundation of South Africa (NRF)http://www.nature.com/scientificreportsam201

Geological and taphonomic context for the new hominin species Homo naledi from the Dinaledi Chamber, South Africa

We describe the physical context of the Dinaledi Chamber within the Rising Star cave, South Africa, which contains the fossils of Homo naledi. Approximately 1550 specimens of hominin remains have been recovered from at least 15 individuals, representing a small portion of the total fossil content. Macro-vertebrate fossils are exclusively H. naledi, and occur within clay-rich sediments derived from in situ weathering, and exogenous clay and silt, which entered the chamber through fractures that prevented passage of coarser-grained material. The chamber was always in the dark zone, and not accessible to non-hominins. Bone taphonomy indicates that hominin individuals reached the chamber complete, with disarticulation occurring during/after deposition. Hominins accumulated over time as older laminated mudstone units and sediment along the cave floor were eroded. Preliminary evidence is consistent with deliberate body disposal in a single location, by a hominin species other than Homo sapiens, at an as-yet unknown date

Evidence of fatal skeletal injuries on Malapa Hominins 1 and 2

Malapa is one of the richest early hominin sites in Africa and the discovery site of the hominin species, Australopithecus sediba. The holotype and paratype (Malapa Hominin 1 and 2, or MH1 and MH2, respectively) skeletons are among the most complete in the early hominin record. Dating to approximately two million years BP, MH1 and MH2 are hypothesized to have fallen into a natural pit trap. All fractures evident on MH1 and MH2 skeletons were evaluated and separated based on wet and dry bone fracture morphology/characteristics. Most observed fractures are post-depositional, but those in the right upper limb of the adult hominin strongly indicate active resistance to an impact, while those in the juvenile hominin mandible are consistent with a blow to the face. The presence of skeletal trauma independently supports the falling hypothesis and supplies the first evidence for the manner of death of an australopith in the fossil record that is not attributed to predation or natural death

New fossil remains of Homo naledi from the Lesedi Chamber, South Africa

The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Chamber, representing a minimum of 15 individuals attributed to Homo naledi. Further exploration led to the discovery of hominin material, now comprising 131 hominin specimens, within a second chamber, the Lesedi Chamber. The Lesedi Chamber is far separated from the Dinaledi Chamber within the Rising Star cave system, and represents a second depositional context for hominin remains. In each of three collection areas within the Lesedi Chamber, diagnostic skeletal material allows a clear attribution to H. naledi. Both adult and immature material is present. The hominin remains represent at least three individuals based upon duplication of elements, but more individuals are likely present based upon the spatial context. The most significant specimen is the near-complete cranium of a large individual, designated LES1, with an endocranial volume of approximately 610 ml and associated postcranial remains. The Lesedi Chamber skeletal sample extends our knowledge of the morphology and variation of H. naledi, and evidence of H. naledi from both recovery localities shows a consistent pattern of differentiation from other hominin species

Health and safety issues in the Victorian workplace: an example of mandibular phosphorus necrosis from Gloucester, UK

Working conditions in factories during the Industrial Era in Great Britain have been linked to numerous occupational diseases. In this paper, the authors present a case study from Victorian Gloucester, where skeletal remains of a young male recovered from the Southgate Street 3/89 excavation exhibit osteonecrosis on the left mandibular ramus, a condition known as “phossy jaw”. The case is examined in terms of macroscopic characteristics, distribution and severity of lesions and differential diagnosis. The lesions consist of extensive bone necrosis with periosteal reaction and subperiosteal new bone formation that affects the left side of the mandible. Conditions that may have produced similar changes were considered and include various forms of neoplasms, actinomycosis and taphonomic alterations. However, these are rejected as they are not supported by the lesion characteristics. Additional supportive evidence for the case of phosphorus necrosis is offered by the historical context: in the 19th century, Gloucester was one of the main centres for match manufacture and it is well known that individuals who were directly exposed to phosphorus fumes developed a condition known as “phossy jaw”. The potential contribution of the current analysis in our understanding of working conditions in Victorian Gloucester is evaluated