15,041 research outputs found
Analysis of MAGSAT and surface data of the Indian region
Techniques and significant results of an analysis of MAGSAT and surface data of the Indian region are described. Specific investigative tasks included: (1) use of the multilevel data at different altitudes to develop a model for variation of magnetic anomaly with altitude; (2) development of the regional model for the description of main geomagnetic field for the Indian sub-continent using MAGSAT and observatory data; (3) development of regional mathematical model of secular variations over the Indian sub-continent; and (4) downward continuation of the anomaly field obtained from MAGSAT and its combination with the existing observatory data to produce a regional anomaly map for elucidating tectonic features of the Indian sub-continent
Analysis of MAGSAT data of the Indian region
Data tapes were decoded and 24 tracks over the Indian region were reduced to common elevation. Profiles of raw scalar and vector field data and the residuals along few passes were prepared. An anomaly data set was created from the Investigator-B tape. Data was sampled on an 0.5 deg by 0.5 deg grid
A quasi-linear control theory analysis of timesharing skills
The compliance of the human ankle joint is measured by applying 0 to 50 Hz band-limited gaussian random torques to the foot of a seated human subject. These torques rotate the foot in a plantar-dorsal direction about a horizontal axis at a medial moleolus of the ankle. The applied torques and the resulting angular rotation of the foot are measured, digitized and recorded for off-line processing. Using such a best-fit, second-order model, the effective moment of inertia of the ankle joint, the angular viscosity and the stiffness are calculated. The ankle joint stiffness is shown to be a linear function of the level of tonic muscle contraction, increasing at a rate of 20 to 40 Nm/rad/Kg.m. of active torque. In terms of the muscle physiology, the more muscle fibers that are active, the greater the muscle stiffness. Joint viscosity also increases with activation. Joint stiffness is also a linear function of the joint angle, increasing at a rate of about 0.7 to 1.1 Nm/rad/deg from plantar flexion to dorsiflexion rotation
Generation of Symmetric Dicke States of Remote Qubits with Linear Optics
We propose a method for generating all symmetric Dicke states, either in the
long-lived internal levels of N massive particles or in the polarization
degrees of freedom of photonic qubits, using linear optical tools only. By
means of a suitable multiphoton detection technique, erasing Welcher-Weg
information, our proposed scheme allows the generation and measurement of an
important class of entangled multiqubit states.Comment: New version, a few modifications and a new figure, accepted in
Physical Review Letter
Off Resonant Pumping for Transition from Continuous to Discrete Spectrum and Quantum Revivals in Systems in Coherent States
We show that in parametrically driven systems and, more generally, in systems
in coherent states, off-resonant pumping can cause a transition from a
continuum energy spectrum of the system to a discrete one, and result in
quantum revivals of the initial state. The mechanism responsible for quantum
revivals in the present case is different from that in the non-linear
wavepacket dynamics of systems such as Rydberg atoms. We interpret the reported
phenomena as an optical analog of Bloch oscillations realized in Fock space and
propose a feasible scheme for inducing Bloch oscillations in trapped ions.Comment: 5 pages, 4 figures, submitted to Jnl. of Optics
Further observations on the relationship of EMG and muscle force
Human skeletal muscle may be regarded as an electro-mechanical transducer. Its physiological input is a neural signal originating at the alpha motoneurons in the spinal cord and its output is force and muscle contraction, these both being dependent on the external load. Some experimental data taken during voluntary efforts around the ankle joint and by direct electrical stimulation of the nerve are described. Some of these experiments are simulated by an analog model, the input of which is recorded physiological soleus muscle EMG. The output is simulated foot torque. Limitations of a linear model and effect of some nonlinearities are discussed
Intensity-intensity correlations as a probe of interferences - under conditions of none in the intensity
The different behaviour of first order interferences and second order
correlations are investigated for the case of two coherently excited atoms. For
intensity measurements this problem is equivalent to Young's double slit
experiment and was investigated in an experiment by Eichmann et al. [Phys. Rev.
Lett. 70, 2359 (1993)] and later analyzed in detail by Itano et al. [Phys. Rev.
A 57, 4176 (1998)]. Our results show that in cases where the intensity
interferences disappear the intensity-intensity correlations can display an
interference pattern with a visibility of up to 100%. The contrast depends on
the polarization selected for the detection and is independent of the strength
of the driving field. The nonclassical nature of the calculated
intensity-intensity correlations is also discussed.Comment: 14 pages, 2 figure
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