Search results for "axial"

Chapter 1 The Resolution Challenge in 3D Optical Microscopy

2009

Publisher Summary This chapter discusses the theoretical principles of 3D microscopy with the widespread realizations of 3D microscopy.Based on the paraxial diffraction equations, it has been shown that conventional microscopes, when dealing with 3D fluorescent samples, provide sets of 2D images. These images of the different transverse sections of the 3D object contain, in addition to the sharp image of the in focus section, the blurred images of the rest of the specimen. The paraxial formalism has been generalized in a very simple way to a non-paraxial context, showing that the equations that govern non-paraxial imaging are similar to those that govern paraxial imaging. The only differenc…

A Unified Phenomenological Description of Quadrupole Excitations in Even-Even Nuclei

1976

A phenomenological model is developed for the collective quadrupole properties of all even-even nuclei. Rotational. vibrational and transitional nuclei are included in the model on an equal footing. A Bohr-type intrinsic Hamiltonian for harmonic quadrupole vibrations about an axially deformed shape is solved exactly. States of good angular momentum are projected out of the intrinsic states, and they are made orthogonal by a Schmidt scheme. The angular-momentum and phonon-number composition of the states is analyzed at various stages; states with K = 1 are found spurious. Excitation energies for the ground, β, and γ bands are calculated as expectation values of a radically simplified nuclear…

Quantum effects in the capture of charged particles by dipolar polarizable symmetric top molecules. I. General axially nonadiabatic channel treatment

2013

The rate coefficients for capture of charged particles by dipolar polarizable symmetric top molecules in the quantum collision regime are calculated within an axially nonadiabatic channel approach. It uses the adiabatic approximation with respect to rotational transitions of the target within first-order charge-dipole interaction and takes into account the gyroscopic effect that decouples the intrinsic angular momentum from the collision axis. The results are valid for a wide range of collision energies (from single-wave capture to the classical limit) and dipole moments (from the Vogt-Wannier and fly-wheel to the adiabatic channel limit).

Analytical and Semi-Analytical Solutions for the Force Between Circular Loops in Parallel Planes

2013

Closed-form solutions are presented for the force between noncoaxial coplanar circular current loops. A semi-analytical solution is given for the case where the loops lie in parallel planes. Numerical results are given which cross check these solutions against each other and against an independently developed method. The closed form solution for the force between a circular loop and a coaxial circular arc segment is also given.

Calculation of Population Densities of Excited CI and CII Levels in Helium and Argon Plasmas Containing Small Admixtures of CO2- Importance to Analys…

1997

Simulations with Smoothed Particles Confirm Stationary Shocks in Accretion Flows onto Black Holes

1994

We present the results of time dependent numerical simulations of the accretion of gas onto Schartzschild black holes. We find that stable shocks are a common feature for flows of inviscid gas accreting with small angular momentum per unit mass. We used the Smoothed Particles Hydrodynamics tecnique, expressed into cylindrical coordinates to exploit the axial symmetry of the problem. For the case of 1-Dimensional axis-symmetric simulations we find that the shock location is exactly at the position predicted by the stationary analysis developed by Chakrabarti. We solve also the ambiguity related to the two possible shock positions: only the outer shock is stable. The case of 2-Dimensional axi…

Efficient CAD of Generalized Coaxial Probes in Rectangular Waveguide using the 3D BI-RME Method

2006

An efficient full-wave method based on the 3D BI-RME (boundary integral-resonant mode expansion) technique for the accurate design of generalized probe-excited rectangular waveguides is presented. The flexibility of the developed CAD tool allows to analyze two common configurations frequently used in modern coaxial-fed microwave devices: conventional and disc-ended coaxial probe excitation. This last configuration is used to drastically improve the electrical response of the classical coaxial probe excitation. Moreover, the influence of the distance from the probe to the waveguide shortcircuit is also discussed, and it is shown that it plays a very important role in the design of probe-exci…

Gyrotron interaction simulations with tapered magnetostatic field

2010

We investigate the interaction of the electron beam with the RF wave in a gyrotron, in the presence of an axially tapered magnetic field. The simulation results of three interaction codes are compared and the different modelings are discussed.

Positron Annihilation in Steel Samples Deformed by Uniaxial Tension

2008

Angular distributions of the positron annihilation quanta were measured for steel ST2 SAL samples deformed by uniaxial tension up to difierent deformation degrees. The dependences of the S parameter on the relative elongation of the samples are presented. The positron annihilation data for steel are compared with the results obtained previously for polycrystalline iron samples deformed by uniaxial tension up to difierent deformation degrees in the proportionality and limited proportionality regions.

Paraxial waves in the far-field region

2002

Summary By investigating the changes suffered by a paraxial beam propagating in the near-field and in the far-field regions, it has been found a set of wave equations valid for points gradually closer to the near field. A relevant expression for the validity of the far-field approximation is given from the paraxial Helmholtz equation. It is pointed out that the well-known Fresnel number associated with every transverse diffraction pattern can be interpreted as a magnitude that measures the relative standard deviation of the Fraunhofer pattern and a first-order field, thus reporting on an integral expression suitable for a general case. Finally, the Rayleigh range of the optical beam is dedu…