Conventional Bar Research Articles

Weakly barred early-type ringed galaxies. IV - The double-ringed SO(+) galaxy NGC 7702

view Abstract Citations (32) References (44) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Weakly Barred Early-Type Ringed Galaxies. IV. The Double-ringed S0 + Galaxy NGC 7702 Buta, R. Abstract The southern galaxy NGC 7702 is an interesting example of a late S0 galaxy showing a high-contrast inner ring surrounding a bright bulge, with no conventional bar crossing the ring as in typical SB(r)-type galaxies. It also has a low-contrast outer ring whose peak surface brightness is only ~ 6% of the night sky brightness in blue light. This paper presents UBVRI CCD surface photometry of NGC 7702 as a mean of evaluating its structure and properties with a view toward understanding the origin of the rings and how they relate to problems of internal dynamics. The photometry reveals the typically complex structure of a double-ringed galaxy both in terms of profile properties and color distribution. The inner ring is a subtle blue enhancement compared to its surroundings, and in addition shows azimuthal variations in color and surface brightness, due in part to internal extinction and tilt and also probably to an intrinsically oval shape. Long-exposure spectra taken along the major and minor axes reveal mainly a continuous spectrum in the inner ring region, and average colors are consistent with a feature that may have experienced a burst of star formation less than 2 x 10^9^ yr ago which abruptly cut off after 10^7^ yr. The bulge of the galaxy shows a distinctive oval shape and may be characterized as a nuclear bar ~ 1 kpc in diameter; it is reminiscent of the triaxial bulges observed in some SB galaxies. Fourier analysis also suggests that the inner ring lies near the boundary of an oval distortion or lens. The nonaxisymmetric component (excluding the nuclear oval) contributes about 14% of the total B band luminosity. Although NGC 7702 is not a conventional barred galaxy, the two rings possess many properties in common with barred galaxy rings. It is possible that NGC 7702 once had a stronger, more important bar which lasted long enough to generate the rings but which is now mostly dissolved. The triaxial bulge may be a relic of such a past feature. Publication: The Astrophysical Journal Pub Date: March 1991 DOI: 10.1086/169797 Bibcode: 1991ApJ...370..130B Keywords: Barred Galaxies; Galactic Evolution; Galactic Structure; Ring Galaxies; Astronomical Photometry; Charge Coupled Devices; Galactic Bulge; Southern Sky; Star Formation; Astrophysics; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 7702; GALAXIES: PHOTOMETRY; GALAXIES: STRUCTURE full text sources ADS | data products SIMBAD (19) NED (1) Related Materials (3) Part 1: 1990ApJ...351...62B Part 2: 1990ApJ...354..428B Part 3: 1990ApJ...356...87B

New laser-trimmed film resistor structures for very high stability requirements

The drift with time and/or temperature of laser-trimmed film resistors limits the effective accuracy attainable form laser-trimmed resistor circuits. This accuracy is dependent on the geometries of the film resistors and on the trimming process. Novel film resistor structures that practically and significantly improve the effective ultimate accuracy attainable with laser-trimmed film resistors over both time and temperature are proposed. The structures are evaluated using computer simulations. This technique is substantiated with an example that shows an improvement in resolution of 4 bits when compared to that attainable with conventional bar resistors. >

A placebo-controlled trial of the effect of two preoperative baths or showers with chlorhexidine detergent on postoperative wound infection rates

The effect of preoperative whole-body washing with chlorhexidine detergent on the incidence of postoperative wound infection was assessed in a placebo-controlled trial of 1989 patients. Patients bathed or showered with chlorhexidine, placebo, or conventional bar soap, on two occasions in the 24 h before operation. The overall infection rate for patients treated with chlorhexidine was 9%, against 12·8% in the bar soap and 11·7% in the placebo groups; in the ‘clean’ surgery group infections were 7·2% against 10·2% and 10%, respectively. The Staphylococcus aureus infection rate in the ‘clean’ group was 3% for chlorhexidine against 6% for bar soap.

Structural Optimization of Cantilever Mechanical Elements

Naturally limited stiffness of cantilever elements due to lack of constraint from other structural components, together with low structural damping, causes intensive and slow-decaying transient vibrations as well as low stability margins for self-excited vibrations. In cases of dimensional limitations (e.g., boring bars), such common antivibration means as dynamic vibration absorbers have limited effectiveness due to low mass ratios. This paper describes novel concepts of structural optimization of cantilever components by using combinations of rigid and light materials for their design. Two examples are given: tool holders (boring bars) and robot arms. Optimized boring bars demonstrate substantially increased natural frequencies, together with the possibility of greatly enhanced mass ratios for dynamic vibration absorbers. Machining tests with combination boring bars have been performed in comparison with conventional boring bars showing superior performance of the former. Computer optimization of combination-type robot arms has shown a potential of 10–60 percent reduction in tip-of-arm deflection, together with a commensurate reduction of driving torque for a given acceleration, and a higher natural frequencies (i.e., shorter transients). Optimization has been performed for various ratios of bending and joint compliance and various payloads.

Software Reviews : STATGRAPHICS 1.1

Summary: STATGRAPHICS is a powerful graphics-oriented statistical package for the IBM. It supports a variety of univariate, bivariate, and multivariate statistics including regression, time series analysis, and ANOVA. Graphics include three-dimensional line, surface, and histogram charts as well as conventional bar, pie, x-y, time sequence, and regression charts. Also included is a report writer module and an interface to LOTUS 1-2-3 and other commercial programs. It is easy to use and could be an excellent choice as a research and teaching tool.

Effect of lifter shape and configuration on material transport part I: In rotating drums

This paper presents the steady-state transport behavior of rotating drums fitted with (i) conventional bar lifters, and (ii) forward- and reverse-spiralling square lifters, when monosize hematite was fed through these devices. The steady-state hold-up in the drum fitted with the forward-spiralling square lifters was less than that in the drum fitted with reverse-spiralling square lifters. However, the dimensionless RTDs for the drums were independent of the direction of spiralling of the lifters. Overall, the degree of mixing within the drum hold-up, as revealed by the magnitude of the axial dispersion coefficient of the RTDs, was greater for the drums fitted with square lifters than for the drum fitted with conventional bar lifters. Between the forward- and reverse-spiralling configurations, the former showed a relatively greater degree of mixing. RTDs are discussed in this paper in terms of single-parameter models and mechanistic explanations for the experimental observations are offered where appropriate.

Direction- and velocity-specific responses from beyond the classical receptive field in the middle temporal visual area (MT).

The true receptive field of more than 90% of neurons in the middle temporal visual area (MT) extends well beyond the classical receptive field (crf), as mapped with conventional bar or spot stimuli, and includes a surrounding region that is 50 to 100 times the area of the crf. These extensive surrounds are demonstrated by simultaneously stimulating the crf and the surround with moving stimuli. The surrounds commonly have directional and velocity-selective influences that are antagonistic to the response from the crf. The crfs of MT neurons are organized in a topographic representation of the visual field. Thus MT neurons are embedded in an orderly visuotopic array, but are capable of integrating local stimulus conditions within a global context. The extensive surrounds of MT neurons may be involved in figure-ground discrimination, preattentive vision, perceptual constancies, and depth perception through motion cues.

Polarization sensitive laser calorimetry

Techniques used currently to determine bulk and surface laser absorption coefficients of highly transparent materials have drawbacks both inherent and practical that limit their accuracy. Conventional bar calorimetry attempts a two-coefficient characterization of nine separate physical absorption sites. Photoacoustic techniques require in situ calibration sensitive to sample geometry and material. This paper proposes a new technique in which a set of conventional ballistic laser calorimetry measurements are made on a single prismatic sample. Systematic changes in the polarization and direction of propagation of the laser beam can lead to an explicit determination of individual surface and bulk absorption coefficients. An equilateral prism sample provides a set of independent measurements sufficient to establish the bulk absorption in each of three internal paths and two absorption components on each of the three surfaces. This geometry can be used, in principle, for materials with refractive indices less than 2; more practically, for indices less than 1.7. For higher indices, a truncated prism is proposed which allows seven independent measures to deduce eight absorption components. As assumption of constant surface anisotropy is proposed to complete the analysis. Design criteria for the prism shape are presented, along with analytical expressions for all relevant absorption experiments, and for the simplest cases of uniform, isotropic high and low index materials.

Static and Fatigue Tests of Composite T-Beams Containing Prestressed Concrete Tension Elements

This paper describes the static and fatigue behavior of composite T-beams using a combination of prestressed concrete tension elements and reinforcing bars as the tension reinforcement. Static tests indicated similar behavior of two continuous beams, one being designed with moment redistribution at ultimate load and the other without moment redistribution. Repeated load tests were performed on six composite beams. Test results indicated that by augmenting multiple tension elements with steel reinforcing bars, the endurance limit of the composite beams was increased by nearly 43 percent. It was also shown that, under repeated load tests, the maximum crack width of the beam exclusively reinforced with tension elements was approximately one-half of that of the similar beam reinforced with conventional bars only.

On a Method of Prevent Chatter in Boring Operations : (Manufacture and Test of New Anti-Chatter Boring Bar)

Various kinds of boring bars to prevent chatter in boring operations have been developed, but they are not successful enough. This paper deals with a new boring bar which is composed of a body on which a tool is mounted and an internal plate fitted in a slit of the body. Its structure and dimensions are determined, based on the theoretical analysis in order to achieve the highest performance, and the stability limits of the new boring bar are compared experimentally with those of the conventional bar with the circular solid section of the same diameter and length to diameter ratio. The experimental results show that the new bar can perform stable boring operations in a wide range of cutting speeds.