Using Dihedral Angles for Edge Extraction in Range Data

The volume of raw range image data that is required to represent just a single scene can be extensive; hence direct interpretation of range images can incur a very high computational cost. Range image feature extraction has been identified as a mechanism to produce a more compact scene representation, in particular using features such as edges and surfaces, and hence enables less costly scene interpretation for applications such as object recognition and robot navigation. We present an approach to edge detection in range images that can be used directly with any range data, regardless of whether the data have regular or irregular spatial distribution. The approach is evaluated with respect to accuracy of both edge location and visual results are also provided.     

Growth of reading vocabulary in diverse elementary schools: Decoding and word meaning.

The authors charted growth of reading vocabulary for first- through fourth-grade students at three dissimilar elementary schools: School A, a suburban school enrolling White students who spoke standard English; School B, an inner-city school enrolling Black, dialect-speaking students; and School C, a semirural school enrolling economically disadvantaged, dialect-speaking Asian/Pacific students. Multiple-choice and interview tests showed rapid growth of reading vocabulary to an impressive size for all students. However, mainstream (School A) students had larger reading vocabularies, decoded more words, and knew more word meanings than the disadvantaged students at Schools B and C. The gap between mainstream and disadvantaged students was largest for infrequent words. The data suggest that direct instruction in decoding and/or individual word meanings could play a limited role in assisting minority students. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lessons from the design of a PC-based private branch exchange

We designed TigerSwitch, a digital private branch exchange (PBX) implemented on an IBM PC-compatible platform, as an experiment in embedded system design. A telephone switching system is an interesting example of embedded system co-design because it combines a rich functionality with deadlines ranging from seconds to tenths of a millisecond. This paper uses design decisions from TigerSwitch to illustrate the difficulties faced in the partitioning and allocation of a system specification into an architecture: the critical performance paths may not be obvious from the initial specification, and it is often difficult to obtain the performance data required to allocate functions in the architecture.     

Pressure drop through a tapered die with optimized flow characteristics

The flow of power-law liquids through tapered dies has been analyzed in an earlier paper.¹ We now consider a taper which is additionally streamlined so as to make the transition from a broad and sluggish flow to a flow which is narrow and fast and as smooth as possible. This involves (1) the rational selection of an appropriate taper function within the relevant flow geometry and (2) the integration, between limits, of that function.     

Imported malaria from Ethiopia--end of an era?

The immigration of Ethiopian Jews to Israel in the 1980s resulted in the importation of over 2,000 cases of malaria, a major challenge to clinicians and public health officials alike. In contrast, in the massive airlift from Ethiopia in May 1991 and in the sporadic immigration that followed it, malaria prevalence was extremely low, reflecting the routing of the more recent immigrants through nonendemic areas. The dramatic fall in the appearance of new imported malaria cases should not lead to complacency, however, as malaria may still appear in Ethiopians and other immigrants as well as in Israelis returning from regions of the world where the disease is still highly prevalent. A corollary of this caveat is that vigilance in finding and eliminating Anopheles breeding places in Israel must not be allowed to falter.     

Uranium extraction using a deep fluidized bed of ion exchange resin

A fluidized bed 51 mm diameter, about 2100 mm deep and containing IRA 400 resin, has been used to extract uranium from sulphate leach liquors. Breakthrough curves were obtained for fixed bed conditions with resin initially in the chloride, sulphate or nitrate form. These curves were analysed to give average diffusion coefficients for extracted species in the resin. The rate data were confirmed by a batch stirred-tank experiment, indicating the value of such batch experiments. A continuous counter-current experiment was then carried out to demonstrate that laboratory data can be used to estimate the performance of such equipment. Further calculations are required to take axial mixing into account on scaling-up the bed diameter.     

The illumination-invariant matching of deterministic localstructure in color images

The availability of multiple spectral measurements at each pixel in an image provides important additional information for recognition. Spectral information is of particular importance for applications where spatial information is limited. Such applications include the recognition of small objects or the recognition of small features on partially occluded objects. We introduce a feature matrix representation for deterministic local structure in color images. Although feature matrices are useful for recognition, this representation depends on the spectral properties of the scene illumination. Using a linear model for surface spectral reflectance with the same number of parameters as the number of color bands, we show that changes in the spectral content of the illumination correspond to linear transformations of the feature matrices, and that image plane rotations correspond to circular shifts of the matrices. From these relationships, we derive an algorithm for the recognition of local surface structure which is invariant to these scene transformations. We demonstrate the algorithm with a series of experiments on images of real objects     

Dynamic Polygon Visibility Ordering for Head-Slaved Viewing in Virtual Environments

This paper presents an approach to visibility called the Viewpoint Movement Space (VpMS) algorithm which supports the concept of dynamic polygon visibility orderings for head-slaved viewing in virtual environments (VE). The central idea of the approach is that the visibility, in terms of back-to-front polygon visibility ordering, does not change dramatically as the viewpoint moves. Moreover, it is possible to construct a partition of the space into cells, where for each cell the ordering is invariant. As the viewpoint moves across a cell boundary typically only a small and predictable change is made to the visibility ordering. The cost to perform this operation represents a notable reduction when compared with the cost of resolving the visibility information from the BSP tree where the classification of the viewpoint with every node plane has to be performed. The paper demonstrates how the subdivision into such cells can represent the basic source for an acceleration of the rendering process. We also discuss how the same supportive data structure can be exploited to solve other tasks in the graphics pipeline.     

Polyester networks based upon epoxidized and maleinated natural oils

Novel families of flexible, semiflexible and rigid crosslinked polyesters were prepared from modified natural oils such as soybean, rape-seed and linseed oil. Maleinated oils were used as anhydride-functional curing agents of epoxy resins such as bisphenol-A-diglycidylether and epoxidized natural oils. A new class of unsaturated polyester resins was based upon maleic anhydride, epoxidized natural oils and styrene. The resulting thermosetting polyesters were reinforced with natural fibers such as hemp and flax fibers. The influence of molecular architectures, curing conditions and formulations on thermal, mechanical and morphological properties were investigated.