Production of superconductor/carbon bicomponent fibers

Certain materials are unable to be drawn or spun into fiber form due to their improper melting characteristics or brittleness. However, fibrous samples of such materials are often necessary for the fabrication of intricate shapes and composites. In response to this problem, a unique process, referred to as the piggyback process, was developed to prepare fibrous samples of a variety of nonspinnable ceramics. In this technique, specially produced C shaped carbon fibers serve as micromolds to hold the desired materials prior to sintering. Depending on the sintering atmosphere used, bicomponent or single component fibers result. While much has been shown worldwide concerning the YBa2Cu3O(7-x) superconductor, fabrication into unique forms has proven quite difficult. However, a variety of intricate shapes are necessary for rapid commercialization of the superconducting materials. The potential for producing fibrous samples of the YBa2Cu3O(7-x) compound by the piggyback process is being studied. Various organic and acrylic materials were studied to determine suspending ability, reactivity with the YBa2Cu3O(7-x) compound during long term storage, and burn out characteristics. While many questions were answered with respect to the interfacial reactions between YBa2Cu3O(7-x) and carbon, much work is still necessary to improve the quality of the sintered material if the fibers produced are to be incorporated into useful composite or cables

Production of superconductor/carbon bicomponent fibers

Certain materials are unable to be drawn or spun into fiber form due to their improper melting characteristics or brittleness. However, fibrous samples of such materials are often necessary for the fabrication of intricate shapes and composites. In response to this problem, a unique process, referred to as the piggyback process, was developed to prepare fibrous samples of a variety of nonspinnable ceramics. In this technique, specially produced C-shaped carbon fibers serve as micromolds to hold the desired materials prior to sintering. Depending on the sintering atmosphere used, bicomponent or single component fibers result. While much has been demonstrated worldwide concerning the YBa2Cu3O(7-x) superconductor, fabrication into unique forms has proven quite difficult. However, a variety of intricate shapes are necessary for rapid commercialization of the superconducting materials. The potential for producing fibrous samples of the YBa2Cu3O(7-x) compound by the piggyback process is being investigated. Various organic and acrylic materials were investigated to determine suspending ability, reactivity with the YBa2Cu3O(7-x) compound during long term storage, and burn out characteristics. While many questions were answered with respect to the interfacial reactions between YBa2Cu3O(7-x) and carbon, much work is still necessary to improve the quality of the sintered material if the fibers produced are to be incorporated into useful composites or cables. Additional research is necessary to evaluate quality of the barrier layer during long soakings at the peak temperature; adjust the firing schedule to avoid microcracking and improve densification; and increase the solids loading in the superconductive suspension to decrease porosity

ASSOCIATIONS BETWEEN JAVELIN THROWING TECHNIQUE AND AERODYNAMIC DISTANCE

The javelin is the most aerodynamic of the four track and field throwing implements. It is twenty times more aerodynamic than the discus (Hubbard, 1984). The official distance of a throw is measured by the meet officials. The vacuum flight distance is determined by the release parameters and the range equation. The aerodynamic distance is the distance gained (where official distance is greater than vacuum flight distance) or lost (where official distance is smaller than vacuum flight distance) due to aerodynamic factors that affect the flight (Hay & Yu, 1995). The ability to gain aerodynamic distance may be the differentiating factor between athletes with near-maximal release speeds and vacuum flight distances. It may be possible for a javelin thrower to increase their aerodynamic distance independently of other performance variables, such as release speed. A javelin throwers technique determines the release parameters of the javelin, which determines the aerodynamic distance. The purpose of this study was to determine which technique variables are associated with greater aerodynamic distances

INDIVIDUALIZED OPTIMAL RELEASE ANGLE IN DISCUS THROWING

Release angle is a parameter that significantly influences the official distance through its effects on the vacuum flight distance and the aerodynamic distance (distance gain or lose due to aerodynamic effect) in discus throwing. Significant efforts have been made to determine the optimal release angle for discus throwing. Previous studies on the optimal release angle in discus throwing were based on two critical assumptions: (1) the release angles and the release speeds were independent of each other, and (2) the optimal release angle was the same for all discus throwers. These two assumptions may have been violated in previous studies on the optimal release angle (Hubbard et al., 2001; Linthorne, 2001; Viitasalo et al., 2007). The violation of these two assumptions may have resulted in significant errors in the optimal release angles for discus throwers reported in the current literature. The purposes of this study were: (1) to determine the relationships between the release speed and the release angle for individual discus throwers, (2) to determine the relationships between the aerodynamic distance and the release angle for individual discus throwers, and (3) to determine the optimal release angles for individual discus throwers; using data collected in competitio

ASSOCIATIONS BETWEEN JAVELIN THROWING TECHNIQUE AND RELEASE SPEED

In javelin throwing, as with other throwing events, the release speed is the single most important factor contributing to long throws (Best et al., 1993; Hay & Yu, 1995; Hubbard et al., 2001). A greater release speed will increase the vacuum flight distance approximately in proportion to the square of the release speed (Hubbard, 1984). The vacuum flight distance is the major partial distance of official distance (Hay & Yu, 1995), and the official distance determines javelin throwing performance. Increasing release speed, therefore, will improve javelin throwing performance. The purpose of this study was to determine which technique variables are associated with greater release speeds

EFFECTS OF MOVEMENT SEQUENCE ON THE PERFORMANCE OF JAVELIN THROWING

The sequence of joint and segment movements during delivery phase is believed to significantly affect on the performance of javelin throwing. Literature reported that elite javelin throwers showed a proximal to distal sequence of joint center maximum linear velocities (Whiting et al., 1991; Best et al., 1993; Mero et al., 1994; Bartlett et al., 1996). The sequence of maximum joint center linear velocities, however, does not necessarily represent the sequence of joint or segment movements. The purpose of this study is to determine the effects of the sequence of upper extremity joint and segment angular movements on the performance of javelin throwing

Three-dimensional light-matter interface for collective spin squeezing in atomic ensembles

We study the three-dimensional nature of the quantum interface between an ensemble of cold, trapped atomic spins and a paraxial laser beam, coupled through a dispersive interaction. To achieve strong entanglement between the collective atomic spin and the photons, one must match the spatial mode of the collective radiation of the ensemble with the mode of the laser beam while minimizing the effects of decoherence due to optical pumping. For ensembles coupling to a probe field that varies over the extent of the cloud, the set of atoms that indistinguishably radiates into a desired mode of the field defines an inhomogeneous spin wave. Strong coupling of a spin wave to the probe mode is not characterized by a single parameter, the optical density, but by a collection of different effective atom numbers that characterize the coherence and decoherence of the system. To model the dynamics of the system, we develop a full stochastic master equation, including coherent collective scattering into paraxial modes, decoherence by local inhomogeneous diffuse scattering, and backaction due to continuous measurement of the light entangled with the spin waves. This formalism is used to study the squeezing of a spin wave via continuous quantum nondemolition (QND) measurement. We find that the greatest squeezing occurs in parameter regimes where spatial inhomogeneities are significant, far from the limit in which the interface is well approximated by a one-dimensional, homogeneous model.Comment: 24 pages, 7 figure

Dynamics of the DBI Spike Soliton

We compare oscillations of a fundamental string ending on a D3-brane in two different settings: (1) a test-string radially threading the horizon of an extremal black D3-brane and (2) the spike soliton of the DBI effective action for a D3-brane. Previous work has shown that overall transverse modes of the test-string appear as l=0 modes of the transverse scalar fields of the DBI system. We identify DBI world-volume degrees of freedom that have dynamics matching those of the test-string relative transverse modes. We show that there is a map, resembling T-duality, between relative and overall transverse modes for the test-string that interchanges Neumann and Dirichlet boundary conditions and implies equality of the absorption coefficients for both modes. We give general solutions to the overall and relative transverse parts of the DBI coupled gauge and scalar system and calculate absorption coefficients for the higher angular momentum modes in the low frequency limit. We find that there is a nonzero amplitude for l>0 modes to travel out to infinity along the spike, demonstrating that the spike remains effectively 3+1-dimensional.Comment: 15 pages, 1 figur

Tubular carbonate concretions as hydrocarbon migration pathways? Examples from North Island, New Zealand

Cold seep carbonate deposits are associated with the development on the sea floor of distinctive chemosyn¬thetic animal communities and carbonate minerali¬sation as a consequence of microbially mediated anaerobic oxidation of methane. Several possible sources of the methane exist, identifiable from the carbon isotope values of the carbonate precipitates. In the modern, seep carbonates can occur on the sea floor above petroleum reservoirs where an important origin can be from ascending thermogenic hydrocar¬bons. The character of geological structures marking the ascent pathways from deep in the subsurface to shallow subsurface levels are poorly understood, but one such structure resulting from focused fluid flow may be tubular carbonate concretions. Several mudrock-dominated Cenozoic (especially Miocene) sedimentary formations in the North Island of New Zealand include carbonate concretions having a wide range of tubular morphologies. The concretions are typically oriented at high angles to bedding, and often have a central conduit that is either empty or filled with late stage cements. Stable isotope analyses (δ13C, δ18O) suggest that the carbonate cements in the concretions precipitated mainly from ascending methane, likely sourced from a mixture of deep thermogenic and shallow biogenic sources. A clear link between the tubular concretions and overlying paleo-sea floor seep-carbonate deposits exists at some sites. We suggest that the tubular carbonate concretions mark the subsurface plumbing network of cold seep systems. When exposed and accessible in outcrop, they afford an opportunity to investigate the geochemical evolution of cold seeps, and possibly also the nature of linkages between subsurface and surface portions of such a system. Seep field development has implications for the characterisation of fluid flow in sedimentary basins, for the global carbon cycle, for exerting a biogeochemical influence on the development of marine communities, and for the evaluation of future hydrocarbon resources, recovery, and drilling and production hazards. These matters remain to be fully assessed within a petroleum systems framework for New Zealand’s Cenozoic sedimentary basins