This paper gives two versions of elastic screen method The wide angle version has a better accuracy while the small angle approximation is more e cient The accu racy of the re ectivity is discussed by comparing the analytical results from the screen method and those directly from plane wave re ections The accuracy of waveform is checked by comparing synthetic seis mograms from both screen metho...

A novel method is described for surface pro"le extraction based on morphological processing of multiple range sensor data. The approach taken is extremely #exible and robust, in addition to being simple and straightforward. It can deal with arbitrary numbers and con"gurations of sensors as well as synthetic arrays. The method has the intrinsic ability to suppress spurious readings, crosstalk, a...

Re#ecting on Piaget's recently translated collection of sociological studies, we highlight some salient points in his approach to sociological issues. At the same time we attempt to explain the contrast between Piaget's singular in#uence in cognitive and developmental psychology with nothing comparable in empirical sociology. We believe that our own social research is a genuine continuation of ...

We enumerate various families of planar lattice paths consisting of unit steps in directions N, S, E, or W, which do not cross the x-axis or both x-and y-axes. The proofs are purely combinatorial throughout, using either reeections or bijections between these NSEW-paths and linear NS-paths. We also consider other dimension-changing bijections.

Tropical forests do far more than sustain biodiversity; they are homes to indigenous peoples, pharmacopeias of natural products, and provide vital ecosystem services, such as ̄ood amelioration and soil conservation. At regional and global scales, tropical forests also have a major in ̄uence on carbon storage and climate. I highlight these bene®ts, then assess the pattern and pace of tropical for...

We review the eld of result-checking and suggest that it be extended to a methodology for enforcing hardware/software reliability. We thereby formulate a vision for \self-monitoring" hardware/software whose reliability is augmented through embedded suites of run-time correctness checkers. In particular, we suggest that embedded checkers and correctors may be employed to safeguard against arithm...

With the advent of inexpensive oo-the-shelf sonar ranging units sonar has become a common sensor on mobile robotic platforms. Many diierent algorithms have been proposed to obtain environmental layout and other structural information by integrating sonar measurements from multiple positions and/or sensors. Given perfect distance measurements and telemetry, this integration can be fairly simple....

The paper presents a new re ective model, called Channel Rei cation, which can be used to implement communication abstractions. After a brief review of existing re ective models and how re ections can be used in distributed systems, channel rei cation is presented and compared to the widely used meta-object model. An application to protocol implementation, and hints on other channel application...