15,434 research outputs found
Trends in social capital: Membership of associations in Great Britain, 1991–98
This Note uses the British Household Panel Study (BHPS) to consider the changing volume and distribution of voluntary association membership (and hence social capital) in Great Britain. We aim to supplement Hall's study of trends in social capital published in this Journal with more recent and longitudinal data. This allows us to show that whilst the volume of social capital is not declining, it is becoming increasingly class specific, and that its relative aggregate stability masks considerable turnover at the individual level. These findings are significant for current debates on social capital
Loading atom lasers by collectivity-enhanced optical pumping
The effect of collectivity on the loading of an atom laser via optical
pumping is discussed. In our model, atoms in a beam are laser-excited and
subsequently spontaneously decay into a trapping state. We consider the case of
sufficiently high particle density in the beam such that the spontaneous
emission is modified by the particle interaction. We show that the collective
effects lead to a better population of the trapping state over a wide range of
system parameters, and that the second order correlation function of the atoms
can be controlled by the applied laser field.Comment: 5 pages, 7 figure
Reliability model for planetary gear
A reliability model is presented for planetary gear trains in which the ring gear is fixed, the Sun gear is the input, and the planet arm is the output. The input and output shafts are coaxial and the input and output torques are assumed to be coaxial with these shafts. Thrust and side loading are neglected. This type of gear train is commonly used in main rotor transmissions for helicopters and in other applications which require high reductions in speed. The reliability model is based on the Weibull distribution of the individual reliabilities of the transmission components. The transmission's basic dynamic capacity is defined as the input torque which may be applied for one million input rotations of the Sun gear. Load and life are related by a power law. The load life exponent and basic dynamic capacity are developed as functions of the component capacities
Popular but peripheral: the ambivalent status of sociology education in schools in England
This article reports the largest UK study of sociology school teachers’ views of the discipline. Drawing on the sociology of the professions, we reflect on the ambivalent positioning of sociology in schools.
Despite buoyant uptake, teachers claim that sociology is perceived as dated and has lower status than other elective courses, often described as a ‘soft’ and ‘easy’ subject that anyone can teach. While many students are reported to benefit from the transformative education that sociology affords, the failure to designate the subject as facilitating entry to higher status universities serves to further marginalise the discipline.
We argue that sociology in schools is weakly bounded, poorly supported and lacks strong professional coherence. While this allows sociology to have an open, critical and reflexive character, it comes at the price of not being able to control delivery in schools and make claims for high status
Stability of continuously pumped atom lasers
A multimode model of a continuously pumped atom laser is shown to be unstable
below a critical value of the scattering length. Above the critical scattering
length, the atom laser reaches a steady state, the stability of which increases
with pumping. Below this limit the laser does not reach a steady state. This
instability results from the competition between gain and loss for the excited
states of the lasing mode. It will determine a fundamental limit for the
linewidth of an atom laser beam.Comment: 4 page
Calibration of the LIGO displacement actuators via laser frequency modulation
We present a frequency modulation technique for calibration of the
displacement actuators of the LIGO 4-km-long interferometric gravitational-wave
detectors. With the interferometer locked in a single-arm configuration, we
modulate the frequency of the laser light, creating an effective length
variation that we calibrate by measuring the amplitude of the frequency
modulation. By simultaneously driving the voice coil actuators that control the
length of the arm cavity, we calibrate the voice coil actuation coefficient
with an estimated 1-sigma uncertainty of less than one percent. This technique
enables a force-free, single-step actuator calibration using a displacement
fiducial that is fundamentally different from those employed in other
calibration methods.Comment: 10 pages, 5 figures, submitted to Classical and Quantum Gravit
Heap Formation in Granular Media
Using molecular dynamics (MD) simulations, we find the formation of heaps in
a system of granular particles contained in a box with oscillating bottom and
fixed sidewalls. The simulation includes the effect of static friction, which
is found to be crucial in maintaining a stable heap. We also find another
mechanism for heap formation in systems under constant vertical shear. In both
systems, heaps are formed due to a net downward shear by the sidewalls. We
discuss the origin of net downward shear for the vibration induced heap.Comment: 11 pages, 4 figures available upon request, Plain TeX, HLRZ-101/9
- …