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

Following the early success of finite element modeling of magnetostatic and eddy current nondestructive testing phenomena, considerable effort has taken place in order to extend these models to full three dimensional geometries [1,2]. More recently, the formulation of the elastic wave equations has been implemented and applied to the solution of ultrasonic testing situations [3,4].

Performance of Large Scale Finite Element Eddy Current and Ultrasonic Models on a Vector Computer

RF-EMF exposure assessment carried out in an observatory open for general public visits, where there are multiple RF sources in the surrounding area. Fields at some points of interest have exceeded the ICNIRP exposure limits for the general public and, to comply with normative limits, relevant stations reduced their radiated power. Nevertheless, the total electric field strength in the vicinity of the observatory’s metallic parapet still exceeds exposure limits due to re-radiation. Thus, the main broadcast stations reduced even more their transmitted power to comply with the regulatory limits throughout the observatory area. A detailed evaluation is carried out close to metallic objects to assess the re-radiation phenomenon. Additionally, laboratory experiments were carried out to confirm the influence of re-radiation from the metallic parapet.

Electromagnetic Field Exposure Assessment in a Multi Source Telecommunication Environment

It is a well known fact that passing objects into functions by reference (in C++) is more efficient than passing by value. Passing objects, created within functions, out of functions by reference could also be more efficient if it wasn't sure to cause memory-leak in the system. Programmers therefore resort to "pass-by-reference, return-by-value". Here we first briefly look at why it is important to be able to return by reference, particularly for large dynamic objects in mathematical applications, and then present a new scheme for doing so. The new method can attain efficiency comparable to that of 'method of reference counting', but without the undesirable side-effects of the latter.

Passing large dynamic objects out of function frame boundaries: the temporary linked list method

The use of low power UHF wireless links is prevalent in a variety of battery operated devices including remote entry systems and control in both industrial and consumer applications. Much effort has been invested in reducing power consumption, especially in receivers for applications in which the receiver must be on at all times. Commercial devices can be obtained that consume only a few mA in continuous operation. In addition, methodologies such as poling and power cycling have been deviced to further reduce power consumption in receivers. Nevertheless, none of these methods is sufficient for truly low power needs such as in inaccessible sensors or embedded active RFID systems. The current work describes a simple method of power reduction that relies on sampling the receiver's output for extremely short periods and turning the receiver on only when data is present. Otherwise the receiver is in an off mode. Power reductions attainable using the methods and circuits described here are far beyond what can be achieved using traditional methods. Circuits and power budgets for some existing UHF receivers are given as examples.

A sampling method for reduction of power in battery operated receivers

The frequencies chosen for ultrasound reflectometry, based on attenuation and resolution constraints, often result in overlapping echo waveforms [1–3]. Phase information [4] can be used to estimate echo contributions in reflectometry using the Maximum Entropy Method [5]. The method of analysis is presented, along with experimental verification for a simple reflecting structure.

Nathan Ida

Papers

Performance of Large Scale Finite Element Eddy Current and Ultrasonic Models on a Vector Computer

Electromagnetic Field Exposure Assessment in a Multi Source Telecommunication Environment

Passing large dynamic objects out of function frame boundaries: the temporary linked list method

A sampling method for reduction of power in battery operated receivers

Delay Estimation using Maximum Entropy Derived Phase Information