Short Bar Research Articles

Development of a HTS Squirrel Cage Induction Motor With HTS Rotor Bars

Efficiency at full load and starting torque at starting are basic performance criteria of the induction motor. Conventionally deep bar or double cage bar have been used to increase the efficiency and starting torque of the induction motor. Effective resistance of the deep bar and double cage differs from starting to full load operation. To increase the efficiency and starting torque, HTS tapes can be used as the rotor bars. The resistance of HTS tapes develops at starting because of large starting current which exceeds the critical current of the HTS tape and it vanishes as the speed builds up. This paper presents the construction and test results of a HTS induction motor. End rings and short bars were made of HTS tapes. Stator of the conventional induction motor was used as the stator of the HTS motor. Rated capacity of the conventional motor was 0.75 kW. Performances of the HTS induction motor were compared with those of the conventional motor with same volume and specification. Test result showed that the speeds of the HTS induction motor were the same with synchronous speed up to 2.6 Nm and 1788 rpm at 9.7 Nm. It guarantees the high efficiency of the HTS motor. Starting torque of the HTS motor was more than twice of the conventional motor.

Anaphase-promoting complex in Caenorhabditis elegans.

Anaphase-promoting complex in Caenorhabditis elegans.

Bars and the connection between dark and visible matter

Isolated barred galaxies evolve by redistributing their internal angular momentum, which is emitted mainly at the inner disc resonances and absorbed mainly at the resonances in the outer disc and the halo. This causes the bar to grow stronger and its pattern speed to decrease with time. A massive, responsive halo enhances this process. I show correlations and trends between the angular momentum absorbed by the halo and the bar strength, pattern speed and morphology. It is thus possible to explain why some disc galaxies are strongly barred, while others have no bar, or only a short bar or an oval. in some cases, a bar is found also in the halo component. This “halo bar” is triaxial, but more prolate-like, is shorter than the disc bar and rotates with roughly the same pattern speed. I finally discuss whether bars can modify the density cusps found in cosmological CDM simulations of dark matter haloes.

Test of an induction motor with HTS wire at end ring and bars

Motors with HTS wires or bulks have been developed recently. These are a large synchronous motor with HTS wires at the field winding in the rotor, hysteresis and reluctance motors with HTS bulk in the rotor. This paper presents the fabrication and test results of an HTS induction motor. Conventional end rings and short bars were replaced with HTS wires in the motor. Stator of the conventional induction motor was used as the stator of the HTS motor. Rated capacity and rpm at full rotor of the conventional motor were 0.75 kW and 1710 rpm. Two HTS wires are used in parallel to make the end rings and bars. The critical current of the BSCCO-2223 HTS wire which was used in the bars and end rings were 115 A. An electrodynamometer was coupled directly to the shaft of the rotor with HTS wires.

Bars and Dark Matter Halo Cores

Self-consistent bars that form in galaxies embedded within cuspy halos are unable to flatten the cusp. Short bars form in models with quasi-flat rotation curves. They lose angular momentum to the halo through dynamical friction, but the continuous concentration of mass within the disk as the bar grows actually compresses the halo further, overwhelming any density reduction due to the modest angular momentum transfer to the halo. Thus, the Weinberg-Katz proposed solution to the nonexistence of the predicted cuspy halos from cold dark matter simulations would seem to be unworkable. I also find that the concerns over the performance of N-body codes raised by these authors do not apply to the methods used here.

Implants provide better health-related quality of life than conventional treatment for edentulous patients

Question: Does use of dental implants in edentulous patients result in better quality of life compared with conventional treatment? Objective To compare the effect on health-related quality of life of two treatments for edentulism, conventional mandibular dentures and implant-supported prostheses. Design A randomised controlled trial in a hospital setting. Intervention A total of 102 people were assigned randomly into either implant or conventional treatment groups. The implant group received two implants in the lower canine region connected by a short bar. Either a conventional denture or over denture was provided in the lower jaw with conventional upper denture. Patients were analysed using the intent-to-treat principle, with patients who withdrew being allocated their pretreatment OHIP scores Outcome measures An oral health impact profile (OHIP) was conducted at the initial appointment and 2 months after the fitting of the prosthesis. Results See Table 1. Conclusions Using a validated standard assessment tool, this trial suggests that patients who had implant treatment experienced more improvements in perceived oral health than patients having conventional treatment. Acknowledgements Nobel Biocare Canada, Laboratoire Dentachrome, Dentsply Canada, the Canadian MRC, Health and Welfare Canada (NHRDP) and Fonds de Recherché en Santé du Québec.

Discovery and Implications of a New Large-Scale Stellar Bar in NGC 5248

For decades, the grand-design SAB spiral galaxy NGC 5248 has been postulated to host a short bar of semimajor axis 22'' (1.6 kpc). From dynamical and morphological arguments, however, we argue that its spiral structure is being driven by a large-scale bar whose corotation radius lies at ~115'' (8.6 kpc). Our estimate is based partially on a deep R-band image, which reveals that the feature previously thought to be an inclined disk is in fact an extended stellar bar. The bar is embedded within a fainter outer disk visible out to a radius of 230'' (17.2 kpc). The bar has a deprojected ellipticity of 0.44 and a semimajor axis of 95'' (7.1 kpc). The classical grand-design spirals of NGC 5248, prominent in B, R, and K light, lie on the leading edge of the large-scale stellar bar and are accompanied by concave dust lanes out to at least 70''. The offset between the dust and young stars is consistent with our understanding of gas flows in barred galaxies, where shocks along the leading edges of a moderately strong bar compress the gas to form massive young stars. While in many strongly barred galaxies, optical spiral arms are prominent outside the bar but not within it, NGC 5248 illustrates how intense star formation along a moderately strong bar can lead to conspicuous open spiral arms within the bar itself. NGC 5248 also provides a clear example of how a large-scale stellar bar embedded within a faint outer optical disk can be misidentified as an inclined disk when imaging studies lack the sensitivity to detect the actual outer disk. We discuss the implications for the estimated bar fraction at higher redshifts.

Remarks on some species of tardigrades from South America with the description of two new species

Six species of Tardigrada are reported from South America, two of which, Isohypsibius sabellai and Hypsibius septulatus, are new to science. Isohypsibius sabellai has a cuticle with about 20 undulations and reticular sculpture, a pharyngeal bulb with apophyses and two macroplacoids. It differs from Isohypsibius undulatus Thulin, 1928 in some characters of the cuticular sculpture, the shape and size of the claws (in I. sabellai they are longer and more slender), and by having the stylet supports inserted on the buccal tube in a more caudal position. Hypsibius septulatus has an unsculptured cuticle with about 22 dorsal undulations, two macroplacoids and the septulum, a cuticular bar near the internal claws on the first three pairs of legs and near the anterior claw of the hind legs, and a short cuticular bar between the claw bases on all legs. Other species reported are: Macrobiotus coronatus De Barros, 1942; Macrobiotus danielae Pilato, Binda, Napolitano and Moncada, 2001; Hypsibius dujardini (Doyère, 1840); and Diphascon (Adropion) onorei Pilato, Binda, Napolitano and Moncada, 2002.

A landscape perspective of surface-subsurface hydrological exchanges in river corridors

1. River corridors can be visualised as a three-dimensional mosaic of surface–subsurface exchange patches over multiple spatial scales. Along major flow paths, surface water downwells into the sediment, travels for some distance beneath or along the stream, eventually mixes with ground water, and then returns to the stream. 2. Spatial variations in bed topography and sediment permeability result in a mosaic of patch types (e.g. gravel versus sandy patches) that differ in their hydrological exchange rate with the surface stream. Biogeochemical processes and invertebrate assemblages vary among patch types as a function of the flux of advected channel water that determines the supply of organic matter and terminal electron acceptors. 3. The overall effect of surface–subsurface hydrological exchanges on nutrient cycling and biodiversity in streams not only depends on the proportion of the different patch types, but also on the frequency distribution of patch size and shape. 4. Because nutrients are essentially produced or depleted at the downwelling end of hyporheic flow paths, reach-scale processing rates of nutrients should be greater in stretches with many small patches (e.g. short compact gravel bars) than in stretches with only a few large patches (e.g. large gravel bars). 5. Based on data from the Rhone River, we predict that a reach with many small bars should offer more hyporheic refugia for epigean fauna than a reach containing only a few large gravel bars because benthic organisms accumulate preferentially in sediments located at the upstream and downwelling edge of bars during floods. However, large bars are more stable and may provide the only refugia during severe flood events. 6. In river floodplain systems exhibiting pronounced expansion/contraction cycles, hyporheic assemblages within newly created patches not only depend on the intrinsic characteristics of these patches but also on their life span, hydrological connection with neighbouring patches, and movement patterns of organisms. 7. Empirical and theoretical evidence illustrate how the spatial arrangement of surface–subsurface exchange patches affects heterogeneity in stream nutrient concentration, surface water temperature, and colonisation of dry reaches by invertebrates. 8. Interactions between fluvial action and geomorphic features, resulting from seasonal and episodic flow pulses, alter surface–subsurface exchange pathways and repeatedly modify the configuration of the mosaic, thereby altering the contribution of the hyporheic zone to nutrient transformation and biodiversity in river corridors.

Nested Bars in Disk Galaxies: No Offset Dust Lanes in Secondary Nuclear Bars

Under certain conditions, subkiloparsec nuclear bars form inside large-scale stellar bars of disk galaxies. These secondary bars spend a fraction of their lifetime in a dynamically decoupled state, tumbling in the gravitational field of the outer bars. We analyze the flow pattern in such nested-bar systems under the conditions of negligible self-gravity and find that secondary bars differ fundamentally from their large-scale counterparts in gas flow pattern and other dynamical properties. In particular, the gas flow across the bar-bar interface in these systems can be more chaotic or more regular in nature and, contrary to predictions, has no difficulty in penetrating the secondary bars along the primary large-scale shocks. The outer parts of both short and long nuclear bars (with respect to their corotation) appear to be depopulated of gas, while deep inside them the flow exhibits low Mach numbers and follows oval-shaped orbits with little dissipation. Long nuclear bars remain gas-rich longer and for this relatively short period of time are largely of a rectangular shape, again with a small dissipation. We find that gas-dominated and star-dominated nuclear bars avoid the bar-bar interface, making both types of bars short relative to their corotation. Furthermore, our earlier work has shown that dynamically coupled secondary bars exhibit a similarly relaxed low-dissipation flow as well. Therefore, no large-scale shocks form in the nuclear bars, and consequently, no offset dust lanes are expected there. We find that offset dust lanes cannot be used in the search for secondary (nuclear) bars. Finally, we discuss the importance of gas self-gravity in the further evolution of these systems.

MTOC formation during mitotic exit in fission yeast.

Microtubules polymerise from nucleation templates containing gamma tubulin. These templates are generally concentrated in discrete structures called microtubule organising centres (MTOCs). In Schizosaccharomyces pombe, an equatorial MTOC (EMTOC) forms mid-way through anaphase B and then disassembles during the final stages of cell separation. We show that the EMTOC was generated by recruiting gamma tubulin to the equatorial F-actin ring before it constricted to cleave the cell in two during cytokinesis. The EMTOC was not a continuous ring. It had a variable structure ranging from a horseshoe to a number of short bars. EMTOC integrity depended upon the integrity of the F-actin but not the microtubule cytoskeleton. EMTOC assembly required the activity of both the septation-inducing network (SIN) that regulates the onset of cytokinesis and the anaphase-promoting complex. Activation of the SIN in interphase cells induced F-actin ring formation and contraction and the synthesis of the primary septum but did not promote EMTOC assembly. In contrast, overproduction of the polo-like kinase, Plo1, which also induced multiple rounds of septation in interphase cells, induced EMTOC formation. Thus, the network governing EMTOC formation shared many of the regulatory elements that control cytokinesis but was more complex and revealed an additional function for Plo1 during mitotic exit.

Loaches of the genus Lepidocephalichthys, from Manipur, with description of a new species

A new species Lepidocephalichthys manipurensis is described, confined to the Chandel district of Manipur near the adjoining borderland areas of Manipur, India and Burma (Myanmar). It is distinguished by the following combination of characters: a sharp small black dot just above the upper base of the caudal fin; 8-9 dorsal short dark ashy brown bars from occiput to the base of the caudal fin; absence of scales on the vertex of head; caudal fin fork, pectoral, ventral and anal fins are non-immaculate; least depth of caudal peduncle 50.00-60.24% (mean 54.09) of its length and 7.69-8.11% L s (mean 8.22); caudal fin with 4-5 W-shaped bands: a single dark black stripe from tip of snout to eye; 8-11 spots on the mid lateral line; and 30-31 vertebrae. A key to the identification of lepidocephalid loaches of Manipur is provided.

Secular evolution of late-type disc galaxies: formation of bulges and the origin of bar dichotomy

Origins of galactic bulges and bars remain elusive, although they constitute fundamental components of disc galaxies. This paper proposes that the secular evolution process driven by the interstellar gas in galactic discs is closely associated with the formation of bulges and bars, and tries to explain the observed variation of these components along the Hubble morphological sequence. The ample interstellar medium serves as a coolant which makes the galactic disc gravitationally unstable and induces fragmentation of the disc. The resulting clumps spiral in to the disc centre because of dynamical friction. Efficiency of this process is governed by the gas-richness of the galactic disc, which is in turn controlled by two parameters: (i) the rapidity of the infall of the halo primordial gas to the disc plane and (ii) the amount of total accreted matter. When these two parameters are appropriately related to the mass and density of the galaxy and the effect of a star formation threshold in the disc is introduced, the gas-driven evolution through disc clumping leads to the appearance of two evolution regimes along the Hubble sequence, separated by the intermediate Hubble type for which the gas-driven mass concentration is minimal. Spiral galaxies of relatively early Hubble type (characterized by large mass and density) experience a rapid clump accumulation to the disc centre in their early evolution phase, which is identified with the formation of a bulge. On the other hand, the evolution of late-type spirals having small mass and density is strongly influenced by the existence of the star formation threshold. The disc in these galaxies becomes gas-rich in a relatively late epoch and experiences a prolonged clump-driven mass accumulation. I argue that this process leads to the formation of not a bulge but a short bar embedded in the galactic disc. The present scenario provides a natural explanation for the well-known bar dichotomy, namely that galactic bars are divided into two major groups on morphological grounds and each group is associated with different Hubble types.

The Shape and Figure Rotation of the Dark Halo of NGC 2915

NGC 2915 is a blue compact dwarf galaxy with a very extended H I disk. This disk shows a short central bar and extended spiral arms, both reaching far beyond the optical component. We use Tremaine & Weinberg's method to measure the pattern speed of the bar and spiral arms from H I radio synthesis data. Our measurements yield a pattern speed Ωp = 0.21 ± 0.06 km s-1 arcsec-1 (8.0 ± 2.4 km s-1 kpc-1 for D = 5.3 kpc), in disagreement with the general view that corotation in barred disks lies just outside the end of the bar, but consistent with recent models of barred galaxies with dense dark matter halos. Our adopted bar semilength, rb ≈ 180'', puts corotation at more than 1.7rb. The existence of the pattern is also problematic. Because NGC 2915 is isolated, gravitational interactions cannot account for the structure observed in the H I disk. We also demonstrate that the low surface density observed in the disk and the location of the pseudorings make it unlikely that swing amplification or bar-driven spiral arms could explain the bar and spiral pattern. Based on the similarity of the dark matter and H I surface density profiles, we discuss the possibility of dark matter distributed in a disk and following closely the H I distribution. This disk then becomes gravitationally unstable and can naturally form a bar and spiral pattern. However, this explanation is difficult to reconcile with some properties of NGC 2915. We also consider the effect of a massive and extended triaxial dark matter halo with a rotating figure. The existence of such halos is supported by cold dark matter simulations showing strongly triaxial dark halos with slow figure rotation. The observed structure of the H I disk can then arise through forcing by the rotating triaxial figure. We associate the measured pattern speed in NGC 2915 with the figure rotation of its dark halo.

The distribution of Ag in Ag-doped YBa2Cu3O7- thin film prepared by dual-beampulsed-laser deposition

<P>The Ag distribution in Ag-doped YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-<IMG SRC="common/delta.gif" ALT="delta" ALIGN="TOP"/></SUB> (YBCO) thin films fabricated by dual-beam pulsed-laser deposition on SrTiO<SUB>3</SUB> (100) substrates has been studied by Auger electron spectroscopy, microproton-induced x-ray emission, atomic force microscopy and scanning electron microscopy. All the results consistently show that Ag aggregated in the bar-like structures observed in the film. These bars are aligned along the <I>a</I>-<I>b</I>-axis or at 45° to the <I>a</I>-<I>b</I>-axis of the YBCO thin film. The main body of the long bars aligned with the <I>a</I>-<I>b</I>-axes of the film was found to be a combination of metallic Ag with other precipitates of YBCO film that may grow from the substrate surface to the YBCO film surface. There were other precipitates aggregating as well at the surface of these bars, such as oxides of Cu and Ba. The short bars that aligned along 45° to the <I>a</I>-<I>b</I>-axes of the film were found to be deficient in Ag but rich in Cu, Ba and O, which could be oxide precipitates of YBCO. The growth mechanisms of the two types of bars seem quite different.</P>

Study of dynamic mechanical behavior of Fe3Al under tensile impact

In recent years, considerable effort has been devoted to the study of ordered intermetallics. Some of these ordered intermetallics, especially those based on aluminides, such as Fe3Al, possess many attractive properties for structural use at elevated temperature in harsh environments [1, 2]. In general, the aluminides contain sufficient amounts of aluminum to form, in oxidizing environments, oxide scales that are often compact and protective. These intermetallics have relatively low density, high melting point, good thermal conductivity, and superb high-temperature strength. As a result, these intermetallics are particularly suited for structural applications at elevated temperatures. However, the aluminides generally exhibit brittle fracture and low ductility at ambient temperatures [3, 4]. Recent studies have shown that Fe3Al aluminides are intrinsically ductile, and the poor ductility commonly observed in air tests is caused mainly by extrinsic effects [5–7]. Moisture-induced hydrogen embrittlement has been recognized as one of the major causes of low ductility. These attempts have led to the development of more ductility and stronger Fe3Al based alloys for structural applications. However, little effort has been devoted to the behavior of this alloy at high strain rate under tensile impact at present. This paper reports a comprehensive study of the dynamic mechanical behavior of Fe3Al under tensile impact and emphasis is placed on understanding the environmental effect on fracture behavior. Fig. 1 is a schematic diagram of the self-designed bar-bar tensile impact apparatus with a rotating disc. The specimen is glued to slots in the ends of the input bar and the output bar using high shear-strength adhesive agent. As the hammer of the high-speed rotating disc impacts the block, the short metal bar, made of aluminum alloy, breaks and an approximately rectangular input stress impulse wave is transmitted through the input bar to the specimen. A partial impulse wave is reflected to the input bar and the survival wave

Seismic Retrofit of Hinged and Fixed Reinforced Concrete Bridge Columns with Short Bar Anchorage in Footings

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Near-Infrared and Optical Morphology of the Dusty Galaxy NGC 972

Near-infrared (NIR) and optical surface photometric analyses of the dusty galaxy NGC 972 are presented. The photometric profiles in the BVRJHK bands can be fitted with a combination of Gaussian and exponential profiles, corresponding to a starburst nucleus and a stellar disk, respectively. The exponential scale length in the B band is 2.8 times larger than in the K band, which implies a central B-band optical depth as high as 11. A bulge is absent even in the NIR bands, and hence the galaxy must be of a morphological type later than the usually adopted Sb type. Relatively low rotational velocity and high gas content also favor a later type, probably Sd, for the galaxy. Only one arm can be traced in the distribution of old stars; the second arm, however, can be traced in the distribution of dust and H II regions. Data suggest a short NIR bar, which ends inside the nuclear ring. The slowly rising nature of the rotation curve rules out a resonance origin of the nuclear ring. The ring is most likely not in the plane of the galaxy, given its circular appearance, in spite of the moderately high inclination of the galaxy. The off-planar nature of the star-forming ring, the unusually high fraction (30%) of the total mass in molecular form, the presence of a nuclear starburst, and the asymmetry of spiral arms are probably the result of a merger with a gas-rich companion galaxy.

A planar unimorph-based actuator with large vertical displacement capability. I. Experiment

A piezoelectric actuator utilizing a planar arrangement of unimorph elements that produces displacements perpendicular to the plane of the actuator is described. The elements are connected in series mechanically so that the vertical displacement of each element adds to the vertical displacements of the other elements. Two prototype actuators were built and tested. One was stick-built from individual bars of PZT and aluminum, which were epoxied together and connected to each other with short aluminum connector bars. The other was fabricated monolithically from a single plate of PZT by bead-blasting the PZT plate through a steel shadowmask to mill out the desired actuator shape. Copper bars epoxied to the milled-out PZT bars then formed the unimorph elements. The unloaded output displacement of each actuator versus applied voltage was measured as well as the displacement versus applied force with no applied voltage. These measurements were in agreement with the predictions of an electromechanical model of the actuator that has been developed. The model predicted and measurements verified that stiffeners can be added to the basic geometry that will significantly increase the force output without affecting the displacement versus applied voltage characteristic.

Effect of hybrid layer on fracture toughness of adhesively bonded dentin–resin composite joint

Objectives. Micromechanical retention from the hybrid layer is generally believed to be the mechanism of adhesion of current generation dentin bonding agents. The purpose of this investigation is to evaluate the interfacial fracture toughness of a commercial dentin bonding agent with and without this hybrid layer. Methods. Ten extracted molars (AB2) were flattened on the occlusal surface, All-Bond 2 Universal Adhesive System (Bisco) was applied according to manufacturer's directions and a composite resin (Prodigy, Kerr) crown was formed. Another group of ten molars (AB2Cl) was handled identically with the exception of a 1 min gentle scrubbing application of 5.25% sodium hypochlorite after acid etching to remove the acid-exposed collagen. Plane-strain chevron-notch short bar fracture toughness specimens were fabricated from all 20 composite crowns and tested according to ASTM E1304-89. Each group was tested to failure in tensile mode at 0.1 mm min −1 and the maximum load at failure was used to determine plane-strain fracture toughness ( K QvM). Weibull parameters were calculated and fracture probability distributions were tested for significant difference at the 95% confidence level. Scanning electron microscopy was employed on broken specimens (18/20) to describe the failure mode. Results. Weibull distributions were not significantly different with characteristic plane-strain fracture toughness from maximum load ( K o QvM) of 0.97 MPa m 1/2and 0.81 MPa m 1/2 and a Weibull modulus of 4.7 and 3.9, respectively, for AB2 and AB2Cl. All AB2 samples failed within the adhesive joint, while the AB2Cl crack propagated from the interphase of adhesive resin and dentin to 1–2 μm into dentin. Significance. Under the conditions of this study, the presence of collagen did not contribute to a significantly stronger bonded joint. Interfacial fracture toughness evaluation of the dentin–composite resin bimaterial interface shows promise for future investigations.