8,879 research outputs found
The influence of convective activity on the vorticity budget
The influence of convective activity on the vorticity budget was determined during the AVE VII and AVE-SESAME I periods. This was accomplished by evaluating each term in the expanded vorticity equation with twisting and tilting and friction representing the residual of all other terms. Convective areas were delineated by use of radar summary charts. The influence of convective activity was established by analyzing contoured fields of each term as well as numerical values and profiles of the various terms in convective and nonconvective areas. Vertical motion was computed by the kinematic method, and all computations were performed over the central United States using a grid spacing of 158 km. The results show that, in convective areas in particular, the residual is of comparable magnitude to the horizontal advection and divergence terms, and therefore, cannot be neglected. In convective areas, the residual term represents a sink of vorticity below 500 mb and a strong source near 300 mb. In nonconvective areas, the residual was small in magnitude at all levels, but tended to be negative (vorticity sink) at 300 mb. The local change term, over convective areas, tended to be balanced by the residual term, and appeared to be a good indicator of development (vorticity becoming more cyclonic). Finally, the shape of the vertical profiles of the term in the budget equation agreed with those found by other investigators for easterly waves, but the terms were one order of magnitude larger than those for easterly waves
Higher-dimensional resolution of dilatonic black hole singularities
We show that the four-dimensional extreme dilaton black hole with dilaton
coupling constant can be interpreted as a {\it completely
non-singular}, non-dilatonic, black -brane in dimensions provided
that is {\it odd}. Similar results are obtained for multi-black holes and
dilatonic extended objects in higher spacetime dimensions. The non-singular
black -brane solutions include the self-dual three brane of ten-dimensional
N=2B supergravity and a multi-fivebrane solution of eleven-dimensional
supergravity. In the case of a supersymmetric non-dilatonic -brane solution
of a supergravity theory, we show that it saturates a bound on the energy per
unit -volume.Comment: 27 pages, R/94/28, UCSBTH-94-35 (Comments added to the discussion
section
Force reflecting hand controller
A universal input device for interfacing a human operator with a slave machine such as a robot or the like includes a plurality of serially connected mechanical links extending from a base. A handgrip is connected to the mechanical links distal from the base such that a human operator may grasp the handgrip and control the position thereof relative to the base through the mechanical links. A plurality of rotary joints is arranged to connect the mechanical links together to provide at least three translational degrees of freedom and at least three rotational degrees of freedom of motion of the handgrip relative to the base. A cable and pulley assembly for each joint is connected to a corresponding motor for transmitting forces from the slave machine to the handgrip to provide kinesthetic feedback to the operator and for producing control signals that may be transmitted from the handgrip to the slave machine. The device gives excellent kinesthetic feedback, high-fidelity force/torque feedback, a kinematically simple structure, mechanically decoupled motion in all six degrees of freedom, and zero backlash. The device also has a much larger work envelope, greater stiffness and responsiveness, smaller stowage volume, and better overlap of the human operator's range of motion than previous designs
Centrifugal Breakout of Magnetically Confined Line-Driven Stellar Winds
We present 2D MHD simulations of the radiatively driven outflow from a
rotating hot star with a dipole magnetic field aligned with the star's rotation
axis. We focus primarily on a model with moderately rapid rotation (half the
critical value), and also a large magnetic confinement parameter, . The magnetic field
channels and torques the wind outflow into an equatorial, rigidly rotating disk
extending from near the Kepler corotation radius outwards. Even with
fine-tuning at lower magnetic confinement, none of the MHD models produce a
stable Keplerian disk. Instead, material below the Kepler radius falls back on
to the stellar surface, while the strong centrifugal force on material beyond
the corotation escape radius stretches the magnetic loops outwards, leading to
episodic breakout of mass when the field reconnects. The associated dissipation
of magnetic energy heats material to temperatures of nearly K, high
enough to emit hard (several keV) X-rays. Such \emph{centrifugal mass ejection}
represents a novel mechanism for driving magnetic reconnection, and seems a
very promising basis for modeling X-ray flares recently observed in rotating
magnetic Bp stars like Ori E.Comment: 5 pages, 3 figures, accepted by ApJ
The most rapidly rotating He-strong emission line star: HR7355
Using archival spectroscopic and photometric data, we searched for massive
stars with Balmer-emission consistent with magnetically confined circumstellar
material. HR 7355 is a formerly unknown He-strong star showing Balmer emission.
At V=6.02 mag, it is one of the brightest objects simultaneously showing
anomalous helium absorption and hydrogen emission. Among similar objects, only
sigma Ori E has so far been subjected to any systematic analysis of the
circumstellar material responsible for the emission. We argue that the
double-wave photometric period of 0.52d corresponds to the rotation period. In
tandem with the high projected equatorial velocity, v sin i=320 km/s, this
short period suggests that HR 7355 is the most rapidly rotating He-strong star
known to date; a class that was hitherto expected to host stars with slow to
moderate rotation only.Comment: 4 pages with 2 figures. Accepted for publication as Research Note by
Astronomy and Astrophysic
On a self-sustained process at large scale in the turbulent channel flow
Large-scale motions, important in turbulent shear flows, are frequently
attributed to the interaction of structures at smaller scale. Here we show
that, in a turbulent channel at Re_{\tau} \approx 550, large-scale motions can
self-sustain even when smaller-scale structures populating the near-wall and
logarithmic regions are artificially quenched. This large-scale self-sustained
mechanism is not active in periodic boxes of width smaller than Lz ~ 1.5h or
length shorter than Lx ~ 3h which correspond well to the most energetic large
scales observed in the turbulent channel
Sexist Comments & Responses: Study Introduction and Overview
Sexism takes many forms, from blatant and aggressive to unintentional and subtle. Gender-related societal attitudes, social norms, unconscious biases, and microaggressions all contribute to sexist behaviors and attitudes that are partially responsible for much of the inequity women face every day. Researchers have noted that “in both private and public spaces, women encounter messages that reinforce gender roles and stereotypes, demean women as a gender group, and sexually objectify women.” Sexist comments and remarks are prevalent and normalized in everyday conversation, public discourse, and virtually every other social setting. Though not the only form of sexism, sexist comments often take people by surprise, leaving women wishing they were better prepared to respond and refute this form of sexist expression. Further, face-to-face confrontation of sexism can be extremely difficult, so in an attempt to avoid backlash or retaliation, women often choose to ignore or minimize the sexism they experience
Strategies that Male Allies use to Advance Women in the Workplace
The purpose of this research study was to identify and examine, from both men’s and women’s perspectives, the specific behaviors and strategies male allies use to successfully support the advancement of women in workplace settings. From a survey of 243 men and women, the team gathered qualitative survey data that were analyzed to identify the strategies and behaviors used by male allies. Top responses included developmental relationships, human resource (HR) processes, leadership development, recognition (both public and private), treating women as equals, and challenging sexist behavior. Some differences existed between perceptions of men and women in terms of the most critical ally behaviors. These research findings have scholarly and practical implications in future efforts to work toward greater gender parity
Representations of p-brane topological charge algebras
The known extended algebras associated with p-branes are shown to be
generated as topological charge algebras of the standard p-brane actions. A
representation of the charges in terms of superspace forms is constructed. The
charges are shown to be the same in standard/extended superspace formulations
of the action.Comment: 22 pages. Typos fixed, refs added. Minor additions to comments
sectio
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