1,175 research outputs found

### Theory of the spatial structure of non-linear lasing modes

A self-consistent integral equation is formulated and solved iteratively
which determines the steady-state lasing modes of open multi-mode lasers. These
modes are naturally decomposed in terms of frequency dependent biorthogonal
modes of a linear wave equation and not in terms of resonances of the cold
cavity. A one-dimensional cavity laser is analyzed and the lasing mode is found
to have non-trivial spatial structure even in the single-mode limit. In the
multi-mode regime spatial hole-burning and mode competition is treated exactly.
The formalism generalizes to complex, chaotic and random laser media.Comment: 4 pages, 3 figure

### Three-Dimensional Computed Tomography of the Pulmonary Veins

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73906/1/j.1540-8167.2002.00521.x.pd

### Tachycardia and Bradycardia Coexisting in the Same Pulmonary Vein

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73709/1/j.1540-8167.2002.00186.x.pd

### On the Low-Frequency Behavior of Vector Potential Integral Equations for Perfect Electrically Conducting Scatterers

Low-frequency behavior of vector potential integral equations (VPIEs) for perfect electrically conducting scatterers is investigated. Two equation sets are considered: The first set (VPIE-1) enforces the tangential component of the vector potential on the scatterer surface to be zero and uses the fundamental field relation on its normal component. The second set (VPIE-2) uses the same condition as VPIE-1 for the tangential component of the vector potential but enforces its divergence to be zero. In both sets, unknowns are the electric current and the normal component of the vector potential on the scatterer surface and are expanded using Rao-Wilton-Glisson (RWG) and pulse basis functions, respectively. To achieve a conforming discretization, RWG, scalar Buffa-Christiansen, and pulse testing functions are used. Theoretical and numerical analyses of the resulting matrix systems show that the electric current obtained by solving VPIE-1 has the wrong frequency scaling and is inaccurate at low frequencies

### Physical applications of second-order linear differential equations that admit polynomial solutions

Conditions are given for the second-order linear differential equation P3 y"
+ P2 y'- P1 y = 0 to have polynomial solutions, where Pn is a polynomial of
degree n. Several application of these results to Schroedinger's equation are
discussed. Conditions under which the confluent, biconfluent, and the general
Heun equation yield polynomial solutions are explicitly given. Some new classes
of exactly solvable differential equation are also discussed. The results of
this work are expressed in such way as to allow direct use, without preliminary
analysis.Comment: 13 pages, no figure

### A calderon multiplicative preconditioner for coupled surface-volume electric field integral equations

A well-conditioned coupled set of surface (S) and volume (V) electric field integral equations (S-EFIE and V-EFIE) for analyzing wave interactions with densely discretized composite structures is presented. Whereas the V-EFIE operator is well-posed even when applied to densely discretized volumes, a classically formulated S-EFIE operator is ill-posed when applied to densely discretized surfaces. This renders the discretized coupled S-EFIE and V-EFIE system ill-conditioned, and its iterative solution inefficient or even impossible. The proposed scheme regularizes the coupled set of S-EFIE and V-EFIE using a Calderon multiplicative preconditioner (CMP)-based technique. The resulting scheme enables the efficient analysis of electromagnetic interactions with composite structures containing fine/subwave-length geometric features. Numerical examples demonstrate the efficiency of the proposed scheme

### Solutions for certain classes of Riccati differential equation

We derive some analytic closed-form solutions for a class of Riccati equation
y'(x)-\lambda_0(x)y(x)\pm y^2(x)=\pm s_0(x), where \lambda_0(x), s_0(x) are
C^{\infty}-functions. We show that if \delta_n=\lambda_n
s_{n-1}-\lambda_{n-1}s_n=0, where \lambda_{n}=
\lambda_{n-1}^\prime+s_{n-1}+\lambda_0\lambda_{n-1} and
s_{n}=s_{n-1}^\prime+s_0\lambda_{k-1}, n=1,2,..., then The Riccati equation has
a solution given by y(x)=\mp s_{n-1}(x)/\lambda_{n-1}(x). Extension to the
generalized Riccati equation y'(x)+P(x)y(x)+Q(x)y^2(x)=R(x) is also
investigated.Comment: 10 page

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