There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

비만아 부모의 돌봄 경험: q 방법론

Finite element methods for Maxwell's equations.

An elastic-plastic finite element model for the frictionless contact of a deformable sphere pressed by a rigid flat is presented. The evolution of the elastic-plastic contact with increasing interference is analyzed revealing three distinct stages that range from fully elastic through elastic-plastic to fully plastic contact interface. The model provides dimensionless expressions for the contact load, contact area, and mean contact pressure, covering a large range of interference values from yielding inception to fully plastic regime of the spherical contact zone. Comparison with previous elastic-plastic models that were based on some arbitrary assumptions is made showing large differences. ©2002 ASME

Elastic-Plastic Contact Analysis of a Sphere and a Rigid Flat

Traditionally electromagnetic leakage fields have largely been of interest to the designers of electrical machinery and magnetic tape heads. An increasingly important application of such leakage fields, however, relates to their use as a mechanism for the detection of defects in ferromagnetic materials. The finite element simulation of three-dimensional active leakage fields is described, and the theoretical predictions are compared with experimentally obtained leakage field profiles for a rectangular slot in a carbon steel bar. Particular emphasis is placed on techniques for determining boundary conditions and the appropriate excitation current distribution in the bar.

3-D finite element predictions of magnetostatic leakage fields

A dual/triple redundant computer system having in one of the preferred embodiments triple redundant I/O modules and dual redundant central processor modules (CPM) that operate in parallel executing the same application program. Each input module includes three input circuits operating in parallel. The first CPM receives input data from first and third input circuits and transmits input data of the first input circuit to the second CPM. The second CPM receives input data from second and third input circuits and transmits input data of the second input circuit to the first CPM. Each CPM then performs a two-out-of-two vote among input data produced by first, second, and third input circuits and utilizes an outvoted data as input to the application program to provide output data by execution of the application program. Each output module includes three microcontrollers operating in parallel. First and second microcontroller receives output data respectively from first and second CPM, while a third microcontroller receives at the same time output data from both first and second CPM. First microcontroller transmits output data to a first and a second output circuit. Second microcontroller transmits output data to second and third output circuit. The third microcontroller performs a selected logic operation among output data produced by first and second CPM and then transmits a result of this operation to third and first output circuits. Each output circuit generates a logical product of output data received from two associated microcontrollers. Outputs of first, second, and third output circuit are connected to each other for providing a two-out-of-three voting among output data produced by first, second, and third microcontroller, and for allowing the system to generate a system output as a result of a two-out-of-two voting of output data generated by first and second central processor modules.

Dual/triple redundant computer system

The conventional node-based finite-element method frequently yields nonphysical solutions to the vector eigenvalue problem in electromagnetic (EM) cavities. The nonphysical modes are mainly due to inadequacy in enforcing the divergence free condition and boundary (as well as interface) conditions. The edge-based finite element method with divergence free shape functions can delete the resulting spurious solutions. This method has been used to solve various eigenvalue problems in both lossless and lossy cavities. No spurious modes are observed in the frequency range of interest. Good predictions of the lower modes are obtained in all examples. In addition to being a reliable tool for cavity mode analysis, the method also finds application in the characterization of materials when loaded in an EM cavity. >

Eigenvalue analysis in electromagnetic cavities using divergence free finite elements

This paper aims at detecting and characterizing inclusions in concrete structures by inverting ground-penetrating radar (GPR) data. First, the signal is preprocessed using the principal component analysis (PCA) and then used to train an artificial neural network (ANN). The GPR data consists of 1200 time steps. Using PCA, the data can be compressed to 286 dimensions without losing any information. Moreover, with 99.99% of the original variance the data needs only 139 dimensions. This dimensional reduction makes the ANN training easier and faster. The ANN were trained to find the buried inclusions characteristics-and-considering a nonhomogenous host medium by inverting the preprocessed data. The results show that the expected maximum error was kept under 1%, which is a remarkable result, since the host medium is nonhomogenous.

/pdf/characterization-of-inclusions-in-a-nonhomogeneous-gpr-3jz4dbhvdo.pdf

Characterization of Inclusions in a Nonhomogeneous GPR Problem by Artificial Neural Networks

Pump apparatus (10; 110) for the controlled ingress and egress of a fluid comprising, a generally cylindrical housing (11; 111), flexible septum (55; 155) disposed within the housing and attached to the housing substantially axially medially thereof, an electromagnet assembly (65; 165, 165') affixed to the septum, a pair of inlet ports (25, 25; 125, 125) in the housing with one disposed to either side of the septum, valves (35; 135) in the inlet ports permitting only ingress of fluid to said housing, a pair of outlet ports (26, 26; 126, 126) in the housing with one disposed to either side of the septum, valves (35; 135) in the outlet ports permitting only the egress of fluid from the housing, permanent magnets (45, 46; 145, 146) disposed proximate the axial extremities of the housing, and a controller (70; 170) for selectively energizing the electromagnet assembly for the controlled displacement of the septum axially of the housing to alternately effect the ingress and egress of fluid from the inlet and outlet ports to either side of the septum.

Nathan Ida

Papers

3-D finite element predictions of magnetostatic leakage fields

Dual/triple redundant computer system

Eigenvalue analysis in electromagnetic cavities using divergence free finite elements

Characterization of Inclusions in a Nonhomogeneous GPR Problem by Artificial Neural Networks

Pumping apparatus with an electromagnet affixed to the septum