75,906 research outputs found
Management system, organizational climate and performance relationships
Seven aerospace firms were investigated to determine if a relationship existed among management systems, organizational climate, and organization performance. Positive relationships were found between each of these variables, but a statistically significant relationship existed only between the management system and organizational climate. The direction and amount of communication and the degree of decentralized decision-making, elements of the management system, also had a statistically significant realtionship with organization performance
Thermodynamic energy exchange in a moving plate capacitor
In this paper we describe an apparent paradox concerning a moving plate capacitor driven by thermal noise from a resistor. The plates are attracted together, but a demon restores the plates of the capacitor to their original position when the voltage across the capacitor is small-hence only small forces are present for the demon to work against. The demon has to work harder than this to avoid the situation of perpetual motion, but the open question is how? This is unsolved, however we explore the concept of a moving plate capacitor by examining the case where it is still excited by thermal noise, but where the restoring force on the capacitor plates is provided by a simple spring rather than some unknown demon. We display simulation results with interesting behavior, particularly where the capacitor plates collide with each other. (c) 2001 American Institute of Physics.B. R. Davis, D. Abbott, and J. M. R. Parrond
Configurations of Handles and the Classification of Divergences in the String Partition Function
The divergences that arise in the regularized partition function for closed
bosonic string theory in flat space lead to three types of perturbation series
expansions, distinguished by their genus dependence. This classification of
infinities can be traced to geometrical characteristics of the string
worldsheet. Some categories of divergences may be eliminated in string theories
formulated on compact manifolds.Comment: 24 pages, DAMTP-R/94/1
Limits of sympathetic cooling of fermions: The role of the heat capacity of the coolant
The sympathetic cooling of an initially degenerate Fermi gas by either an
ideal Bose gas below or an ideal Boltzmann gas is investigated. It is
shown that the efficiency of cooling by a Bose gas below is by no means
reduced when its heat capacity becomes much less than that of the Fermi gas,
where efficiency is measured by the decrease in the temperature of the Fermi
gas per number of particles evaporated from the coolant. This contradicts the
intuitive idea that an efficient coolant must have a large heat capacity. In
contrast, for a Boltzmann gas a minimal value of the ratio of the heat
capacities is indeed necessary to achieve T=0 and all of the particles must be
evaporated.Comment: 5 pages, 3 figure
Searching for jet rotation in Class 0/I sources observed with GEMINI/GNIRS.
Original article can be found at: http://www.aanda.org/
Copyright The European Southern ObservatoryContext: In recent years, there has been a number of detections of gradients in the radial velocity profile across jets from young stars. The significance of these results is considerable. They may be interpreted as a signature of jet rotation about its symmetry axis, thereby representing the only existing observational indications supporting the theory that jets extract angular momentum from star-disk systems. However, the possibility that we are indeed observing jet rotation in pre-main sequence systems is undergoing active debate.
Aims: To test the validity of a rotation argument, we must extend the survey to a larger sample, including younger sources.
Methods: We present the latest results of a radial velocity analysis on jets from Class 0 and I sources, using high resolution data from the infrared spectrograph GNIRS on GEMINI South. We obtained infrared spectra of protostellar jets HH 34, HH 111-H, HH 212 NK1 and SK1.
Results: The [Fe II] emission was unresolved in all cases and so Doppler shifts across the jet width could not be accessed. The H2 emission was resolved in all cases except HH 34. Doppler profiles across the molecular emission were obtained, and gradients in radial velocity of typically 3 km s-1 identified.
Conclusions: Agreement with previous studies implies they may be interpreted as jet rotation, leading to toroidal velocity and angular momentum flux estimates of 1.5 km s-1 and 1 × 10-5 yr-1 AU km s-1 respectively. However, caution is needed. For example, emission is asymmetric across the jets from HH 212 suggesting a more complex interpretation is warranted. Furthermore, observations for HH 212 and HH 111-H are conducted far from the source implying external influences are more likely to confuse the intrinsic flow kinematics. These observations demonstrate the difficulty of conducting this study from the ground, and highlight the necessity for high angular resolution via adaptive optics or space-based facilities
Uniaxial-stress induced phase transitions in [001]c-poled 0.955Pb(Zn1/3Nb2/3)O3-0.045PbTiO3
First-order, rhombohedral to orthorhombic, stress-induced phase transitions
have been evidenced by bulk charge-stress measurements and X-ray diffraction
derived lattice strain measurements in [001]c-poled PZN-4.5PT. The transitions
are induced by uniaxial, compressive loads applied either along or
perpendicular to the poling direction. In each case, they occur via rotation of
the polar vector in the Cm monoclinic plane and the induced lattice strain is
hysteretic yet reversible. Although no depoling is observed in the transverse
mode, net depolarization is observed under longitudinal stress which is
important for the use of [001]c-poled PZN-PT and PMN-PT single crystals in
Tonpilz-type underwater projectors.Comment: To be published in Applied Physics Letters, 16 pages, 3 figure
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