250 research outputs found
Tele work: dispersed organizational activity and new forms of spatial - temporal coordination and control
This article focuses on a set of new flexible work arrangements commonly referred to as cctelework) or cctelecommuting,). Although it is not possible to give an unambiguous and precise definition of telework,
there is some working consensus on the subject: the belief is held that information technology has made it possible to relocate many types of work involving the
electronic processing of information geographically,
and telework is the term used to describe workers who have been relocated in this way. An attempt is made to develop theoretical framework in which telework cart be studied. For this purpose the changes that take place:
in the environment of organizations have been taken into consideration.
It is suggested that as a result of the redesign process new organizational forms emerge that are characterized by a ((dispersed activity pattern)). Dispersed
Organizations, are designed to overcome time-andplace constraints associated with rigid bureaucratic structuring and can be distinguished from existing
bureaucratic organizations because they are based on it different design philosophy with regard to how, where and when work is done. Dispersed organizations are
being characterized by different time and place constraints with respect to interaction between operational units. Although organizations with dispersed activities
can be found nowadays in almost every institutional
area, little systematic analysis has yet been undertaken. It is assumed that different forms of telework can be studied within this context. The concept of (dispersed
organizations) will be discussed and illustrated with results from a case-study conducted in an energycompany in the Netherlands
Observational Constraints on Disk Heating as a Function of Hubble Type
Current understanding of the secular evolution of galactic disks suggests
that this process is dominated by two or more heating mechanisms, which
increase the random motions of stars in the disk. In particular, the
gravitational influence of giant molecular clouds and irregularities in the
spiral potential have been proposed to explain the observed velocity
dispersions in the solar neighborhood. Each of these mechanisms acts on
different components of the stellar velocities, which affects the ratio of the
vertical and radial components of the stellar velocity dispersion since the
relative strengths of giant molecular clouds and spiral irregularities vary
with Hubble type. A study of this ratio as function of Hubble type has the
potential to provide strong constraints on disk heating mechanisms. We present
major and minor axis stellar kinematics for four spiral galaxies of Hubble type
from Sa to Sbc, and use the data to infer the ratios sigma_z/sigma_R in the
galaxy disks. The results combined with two galaxies studied previously and
with Milky Way data show that the ratio is generally in the range 0.5 - 0.8.
There is a marginally significant trend of decreasing ratio with advancing
Hubble type, consistent with the predictions of disk heating theories. However,
the errors on individual measurements are large, and the absence of any trend
is consistent with the data at the 1-sigma level. As a byproduct of our study,
we find that three of the four galaxies in our sample have a central drop in
their stellar line-of-sight velocity dispersion, a phenomenon that is
increasingly observed in spiral galaxies. [ABRIDGED]Comment: 24 pages, LaTeX, 5 Postscript figures, to appear in AJ (Dec 2003
Integrated 1st and 2nd generation sugarcane bio-refinery for jet fuel production in Brazil: Techno-economic and greenhouse gas emissions assessment
INTEGRATED DESIGN OF A LIGHTWEIGHT POSITIONING SYSTEM
Abstract In this paper a new approach to the design of positioning systems is introduced. The approach aims at the design of fast and accurate systems that are lightweight compared to classical designs. The new design reduces peak power requirements and thermal effects that deteriorate performance of the whole system
Impedance Analysis of an RMU for On-line PD Measurement
Abstract A new system to monitor partial discharges (PD) online in medium-voltage power cables is being developed. On-line measurement implies that the equipment can be applied when the cable is in operation, i.e. without disrupting service. A PD gives a high frequency pulse, propagating through the MV power cable. At the termination cable, the PD pulses partially reflect and partially propagate into the connected Ring Main Unit (RMU) due to the impedance transition. For correct interpretation of PD signals from the cable under test, it is essential to know the involved impedances up to several megahertz. An analysis of the impedances of the RMU elements is performed. A theoretical analysis based on lumped impedances is verified using various measurements. The measurements have been carried out on a test-grid consisting of two RMUs and several cables and show good agreement with predictions. This method of analysis will be used in the on-line PD monitoring system
Scanning tunneling microscopy and spectroscopy at low temperatures of the (110) surface of Te doped GaAs single crystals
We have performed voltage dependent imaging and spatially resolved
spectroscopy on the (110) surface of Te doped GaAs single crystals with a low
temperature scanning tunneling microscope (STM). A large fraction of the
observed defects are identified as Te dopant atoms which can be observed down
to the fifth subsurface layer. For negative sample voltages, the dopant atoms
are surrounded by Friedel charge density oscillations. Spatially resolved
spectroscopy above the dopant atoms and above defect free areas of the GaAs
(110) surface reveals the presence of conductance peaks inside the
semiconductor band gap. The appearance of the peaks can be linked to charges
residing on states which are localized within the tunnel junction area. We show
that these localized states can be present on the doped GaAs surface as well as
at the STM tip apex.Comment: 8 pages, 8 figures, accepted for publication in PR
Investigation of Single Boron Acceptors at the Cleaved Si:B (111) Surface
The cleaved and (2 x 1) reconstructed (111) surface of p-type Si is
investigated by scanning tunneling microscopy (STM). Single B acceptors are
identified due to their characteristic voltage-dependent contrast which is
explained by a local energetic shift of the electronic density of states caused
by the Coulomb potential of the negatively charged acceptor. In addition,
detailed analysis of the STM images shows that apparently one orbital is
missing at the B site at sample voltages of 0.4 - 0.6 V, corresponding to the
absence of a localized dangling-bond state. Scanning tunneling spectroscopy
confirms a strongly altered density of states at the B atom due to the
different electronic structure of B compared to Si.Comment: 6 pages, 7 figure
The Planetary Nebula System of M33
We report the results of a photometric and spectroscopic survey for planetary
nebulae (PNe) in the Local Group spiral galaxy M33. We use our sample of 152
PNe to derive an [O III] planetary nebula luminosity function (PNLF) distance
of (m-M)_0 = 24.86^+0.07-0.11 (0.94^+0.03-0.05 Mpc). Although this value is ~
15% larger than the galaxy's Cepheid distance, the discrepancy likely arises
from differing assumptions about the system's internal extinction. Our
photometry (which extends >3 mag down the PNLF), also reveals that the
faint-end of M33's PN luminosity function is non-monotonic, with an inflection
point ~2 mag below the PNLF cutoff. We argue that this feature is due to the
galaxy's large population of high core-mass planetaries, and that its amplitude
may eventually be useful as a diagnostic for studies of stellar populations.
Fiber-coupled spectroscopy of 140 of the PN candidates confirms that M33's PN
population rotates along with the old disk, with a small asymmetric drift of \~
10km/s. Remarkably, the population's line-of-sight velocity dispersion varies
little over ~4 optical disk scale lengths, with sigma_{rad}~20km/s. We show
that this is due to a combination of factors, including a decline in the radial
component of the velocity ellipsoid at small galactocentric radii, and a
gradient in the ratio of the vertical to radial velocity dispersion. We use our
data to show that the mass scale length of M33's disk is ~2.3 times larger than
that of the system's IR luminosity and that the disk's V-band mass-to-light
ratio changes from M/L_V ~0.3 in the galaxy's inner regions to M/L_V ~2.0 at ~9
kpc. Models in which the dark matter is distributed in the plane of the galaxy
are excluded by our data. (abridged)Comment: 45 pages, including 12 figures (some with reduced resolution);
accepted for publication in the Astrophysical Journa
Impact of community-acquired paediatric rotavirus gastroenteritis on family life: data from the REVEAL study
<p>Abstract</p> <p>Background</p> <p>Rotavirus is the leading cause of acute gastroenteritis (AGE) and the most frequent cause of severe diarrhoea in children aged less than 5 years. Although the epidemiology of rotavirus gastroenteritis (RVGE) is well documented, there are few data on the impact of RVGE on the families of affected children.</p> <p>Methods</p> <p>Data associated with the burden of RVGE, including number of working days lost, levels of parental stress, the need for alternative childcare arrangements and additional nappies used, were extracted from questionnaires completed by parents of children participating in a prospective, multicentre, observational study (Rotavirus gastroenteritis Epidemiology and Viral types in Europe Accounting for Losses in public health and society, REVEAL), conducted during 2004-2005 in selected areas of Belgium, France, Germany, Italy, Spain, Sweden, and the United Kingdom to estimate the incidence of RVGE in children aged less than 5 years seeking medical care as a result of AGE.</p> <p>Results</p> <p>1102 children with RVGE were included in the present analysis. The proportion of RVGE cases that required at least one parent or other person to be absent from work was 39%-91% in the hospital setting, 44%-64% in the emergency department, and 20%-64% in primary care. Self-reported levels of parental stress were generally high (mean stress levels, ≥ 5 on a 10-point visual analogue scale). Additional childcare arrangements were required in up to 21% of RVGE episodes. The mean number of nappies used per day during RVGE episodes was approximately double that used when the child was not ill.</p> <p>Conclusions</p> <p>Paediatric RVGE cases cause disruption to families and parental stress. The burden of RVGE on children and their families could be substantially reduced by routine rotavirus vaccination of infants.</p
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