Seals were a major dietary item for coastal hunter-gatherers and herders in South Africa. At Nelson Bay Cave (NBC), more than half of the Holocene mammal bones are from Cape Fur seals (Arctocephalus pusillus). Previous analyses of the seal assemblage from this site have studied only selected skeletal elements. This study is the first comprehensive analysis of seal remains from selected archaeological levels at Nelson Bay Cave and from the 2007/2008 excavations at nearby Hoffmans/Robberg Cave (HRC). Body part representation and frequency, age distribution and bone modification have been documented to determine the role of seals in the lifeways of hunter-gatherers and pastoralists at Robberg throughout the Holocene. The age profiles indicate that seals were obtained directly from a breeding colony throughout the Holocene. A breeding colony at Robberg would have been a rich and reliable resource for coastal foragers throughout the year. There were differences in skeletal element representation in the Early and Middle Holocene, compared with the Late Holocene. Axial skeletal elements are under-represented in earlier time periods, probably due to field butchery and the return of only parts of the seals to the living sites. In the Late Holocene, entire animals were taken back to site. Within each time period, the skeletal profiles of juveniles and adults indicate that both were processed similarly suggesting that aspects such as carcass size, weight and foraging distance were less important factors in transport decisions than the terrain of the Robberg Peninsula and the size of the hunting party. A large proportion of the bones were complete, or almost complete. There was little evidence of canid gnawing. The skeletal element representation, frequency and cut mark patterns suggest that the heads and flippers were highly sought after throughout the Holocene, as recorded in Arctic ethnography. Seals were also of spiritual significance, possibly in aiding transitions from the material into the spirit world.

By defined structuring of sliding surfaces at dynamic contact seals friction and leakage can be reduced. Compared to macro-structures, micro-structures have the advantage of a quasi-homogeneous influence on the fluid behavior in the sealing gap. The development of suitable microstructures based on prototypes, whose properties are studied on the test bench, is very expensive and time-consuming due to the challenging manufacturing process and measuring technologies, which are necessary to investigate the complex rheological behavior within the sealing gap. A simulation-based development of microstructured sealing surfaces offers a cost- and time-saving alternative. This paper presents a method for simulative design and optimization of microstructured sealing surfaces at the example of a microstructured mechanical face seal.

No description available.

Thesis (MA (Ancient Studies)--University of Stellenbosch, 1992. / In the course of this M.A. thesis, 65 stamp seals (conoids, scaraboids, signet rings and scarabs) have been collected, described, and analyzed. They stem from legal archaeological excavations in Syro-Palestine, and have been found in strata and contexts which can clearly be ascribed to the Persian period. Methodological questions were addressed, including the following: historical outline of the Persian period, geographical limitations of the study, archaeological considerations, and the iconographic and epigraphic aspects of the study. For the description process, a computerized system was developed, by means of which the seals could be described on three levels: general description, element description, modification description. In this way, a uniform way of handling the data was achieved. The description procedure is reflected in the fonn of a catalogue. In order to facilitate the analysis, the seal corpus was organized in three, at times overlapping, classes: iconographic seals, epigraphic seals, and hieroglyphic seals. The different classes were then analyzed according to their peculiarities, e.g. geographical distribution, iconographic motif groups, palaeography, onomastica, etc. It was shown that the corpus of stamp seals from the Persian period consists of a wide variety of objects in tenns of form and content, and could by no means be characterized as being homogenous. A certain relationship between geographical origin, fonn, and content of the seal could be established.

Cylinder seal impressions occur in many contexts in the ancient Near East. This disssertation focuses specifically on the function of sealing in the manipulation of state resources (land, labor, and goods) in second millennium B.C. Syria. The sources of information utilized in this study include textual references to sealing practices, sealed documents, bullae, and the seals themselves. The archives of Mari, Alalah, and Ugarit are particularly important as they provide textual and archaeological information on seals and sealing within the physical and institutional context of the palace, the center of state administration. Chapter 1 surveys the previous research on seals and sealing and briefly outlines Syrian geography and political history in the second millennium B.C. Chapter 2 examines the physical qualities of the seals--materials, methods of production, distribution and style. Chapter 3 addresses the problem of the physical and institutional context of seal use. A functional division between legal and administrative texts is reflected in the use of seals on them. On both types of documents, however, the use of a seal acknowledges the obligation of the sealer. The nature of that obligation varies with the contents of the text itself. Chapter 4 evaluates the use of seals on legal texts in palace archives. Most of these sealed documents record land grants. The historical trend in second millennium Syria is to an increasing involvement of heads-of-state in granting state land. Other sealed legal documents were kept in palace archives because the participants were in some way associated with the palace. Chapter 5 details the administrative use of seals at Mari. Receipts and expenditures are the most common sealed documents. The use of seals on these texts signals the acceptance by the sealer of responsibility for the goods or actions described therein. The conclusions (Chapter 6) summarize the differences in sealing practices in Mari, Alalah and Ugarit in light of the different historical circumstances and political needs of each state.

In a nuclear power plant, one of the most important systems for both safety and performance is the reactor cooling system. The cooling system is generally driven by one or more very large centrifugal pumps. Most reactor coolant pumps utilize a multi-stage mechanical face seal system for fluid containment. As a result, these seal systems are critical to safe, continued operation of a nuclear reactor. Without adequate sealing, loss of coolant volume can occur, and a reactor may be forced to shut down, costing the operating utility significantly until it can be brought online again. The main advantage of mechanical face seals is their self-adjusting properties. These seals are tuned so that they automatically adjust to varying fluid conditions to provide adequate leakage control. Because of the enormous pressures, complicated water chemistry, and possible large temperature transients, the mechanical seals inside a reactor coolant pump must be some of the most robust seals available. In addition, their long service life and continuous operation demand durability and the capability to adjust to a wide range of conditions. However, over time, wear, chemical deposition, or changing operating conditions can alter the face gap, which is the critical geometry between the sealing faces of a seal. An altered face gap can lead to undesirable conditions of too much or not enough leakage, which must be maintained within a certain range to provide lubrication and cooling to the seal faces without resulting in uncontrolled coolant volume loss. Nuclear power plants operate within strict leakage ranges, and long-term effects causing undesirable leakage can eventually necessitate a reactor shutdown if the seal cannot self-adjust to control the leakage. This document will examine possible causes of undesirable leakage rates in a commonly-used reactor coolant pump assembly. These causes will be examined to determine the conditions which promote them, the physical explanation for their effect on the operation of a mechanical seal, and possible methods of mitigation of both the cause and its effect. These findings are based on previous publications by utilities and technical and incident reports from reactor stations which detail actual incidents of abnormal seal performance and their root causes as determined by the utilities. Next, a method of increasing the ability of a mechanical seal to adapt to a wider range of conditions will be proposed. This method involves modifying an existing seal face to include a method of active control. This active control focuses on deliberately deforming one face of the mechanical sealing face pair. This deformation alters the face gap in order to make the fluid conditions inside the face gap more preferable, generating more or less leakage as desired. Two methods of actuation, hydraulic pressure and piezoelectric deformation, will be proposed. Finally, a model of the actively controlled seal faces will be introduced. This model includes a method of numerically solving the Reynolds equation to determine the fluid mechanics that drive the lubrication problem in the seal face and coupling the solution with a deformation analysis in a finite element model of a seal face. The model solves iteratively until a converged solution of a sealed pressure distribution, a resulting face deformation, and a calculated leakage rate is reached. The model includes a study of the effects of induced deformation in the seal via both hydraulic and piezoelectric actuation and the ability of this deformation to control the leakage rate.

Thesis (Ph.D.) -- La Trobe University, 2005. / Submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy to the Zoology Dept., School of Life Sciences, Faculty of Science, Technology and Engineering. Research. Includes bibliographical references (leaves 133-152). Also available via the World Wide Web.

Studying the diet of marine top predators is important for understanding the trophic ecology of the predators but also the distribution, abundance and seasonal variation of prey species. Dietary studies on subantarctic fur seals (Arctocephalus tropicalis) and Antarctic fur seals (A. gazella) is important for assessing their role as predators in the Southern Ocean. Seven hundred and sixty four scats were collected from an A. tropicalis colony at Cape Davis while 659 scats were collected from an A. gazella colony at Watertunnel stream from April 2006 to March 2010. Hard remains such as fish otoliths and cephalopod beaks were used for identification and quantification of prey. A. tropicalis diet comprised of three animal groups (fish, cephalopod and crustaceans) while A. gazella diet was made up of four animal groups (fish, cephalopods, crustaceans and seabirds). Fish contributed substantially more than other prey items in the diet of both fur seal species over the study period. Both species fed predominantly on fish of the family Myctophidae which constituted a numerical abundance of 98.9 percent in scats for both species combined. A. tropicalis fed on fish prey species from eight families, namely: Myctophidae, Notosudidae, Paralepididae, Nototheniidae, Bathylagidae, Chlorophthalmidae, Sternoptychidae and Photichthyidae while A. gazella fed on fish from six of these families, with Chlorophthalmidae and Photichthyidae not represented in its diet. Cephalopods and crustaceans were found in low numbers in the diet of both seal species and seabird remains were only found in the diet of A. gazella. Numerically, the most dominant species were from the genus Gymnoscopelus followed by Protomyctophum and then Electrona. In the diet of A. tropicalis, Gymnoscopelus contributed 66 percent, Protomyctophum 18 percent and Electrona 5.9 percent while in the diet of A. gazella Gymnoscopelus, Protomyctophum and Electrona contributed 59.43 percent, 20.24 percent and 14.24 percent respectively. Gymnoscopelus species comprised G. piabilis, G. bolini, G. braueri, G. fraseri, and G. nicholsi; Protomyctophum comprised Protomyctophum bolini, P. choriodon and P. tenisoni while Electrona comprised Electrona antarctica, E. carlsbergi and E. subaspera. Gymnoscopelus piabilis was the most dominant species from this genus while Electrona carlsbergi and Protomyctophum tenisoni dominated the genus Electrona and Protomyctophum respectively. The total number of fish species utilised by A. tropicalis was twenty four while twenty three fish species were identified in A. gazella diet. Bathysauropsis gracilis only featured in the diet of A. tropicalis while Lampanyctus ater and Lepidonotothen larseni were only found in the diet of A. gazella. To compare the diet of the seal species between seasons, a year was divided into three seasons, early summer, late summer and winter. Their diet was also compared between years from 2006 to 2010. Myctophid fish species showed substantial seasonal and annual fluctuations in the diet of the two fur seal species. E. carlsbergi, G. nicholsi and G. piabilis increased in numerical abundance in winter while Melectrona ventralis increased in late summer. The numerical abundance of G. fraseri and P. tenisoni increased in early summer. Generally, the two fur seal species fed on the same prey species. However, there was a significant difference when the diet of both fur seals was compared seasonally. There was no significant difference when the diet of A. gazella was compared annually, although such a difference was apparent for A. tropicalis.

Please read the abstract in the section 00front of this document / Dissertation (MSc (Zoology))--University of Pretoria, 2006. / Zoology and Entomology / unrestricted

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