Kangaroos, Monopoly and Discrete Logarithms

The kangaroo method computes a discrete logarithm in an arbitrary cyclic group, given that the value is known to lie in a certain interval. A parallel version has been given by van Oorschot and Wiener with ``linear speed-up'. We improve the analysis of the running time, both for serial and parallel computers. We explore the variation of the running time with the set of ``jumps' of the kangaroos, and confirm that powers of two are a good choice (we do not claim they are the best choice). We illustrate the theory with some calculations of interest to Monopoly players, and the method itself with a card trick due to Kruskal. Received 23 January 1998 and revised 27 September 1999 Online publication 18 August 2000     

Technology education challenges and solutions in Latin America

The world has become dependent on information, technology, and telecommunications, better known as information technology and telecommunications (IT&T), a term that encompasses the fields of electrical and computer engineering, and computer science. Increasingly, IT&T is an effective indicator of the difference between developed and developing nations. The competitiveness of a nation is directly related to its incorporation of IT&T which requires a substantial restructuring of the forms and procedures in attempting to generate a base for development of science and technology. To achieve this, it is important to revise the education of human technical and scientific resources. This paper summarizes the experience of the Ibero-American Science and Technology Education (ISTEC) consortium in IT education in Latin America     

Building cameras for capturing documents

This paper explores those aspects of document capture that are specific to cameras. Each of them must be addressed in order to close the gap between taking a photograph of a document and capturing the document itself. We present results in five areas: (1) framing documents using structured light, (2) robustly dealing with ambient illumination when capturing glossy documents, (3) improving text quality when using mosaiced color sensors, (4) robustly and passively recovering perspective and image plane skew using text flow, and (5) measuring and undoing page curl using structured light and an applicable surface model. The ultimate success of subsequent document recognition will be heavily dependent on the successful completion of these tasks.Received: 8 December 2003, Revised: 6 April 2004, Published online: 11 March 2005     

Surface Plasmon Measurement of the Bonding Potential between an Organic Fluid and a Gold Film

Abstract

The optical excitation of a surface plasmon-polariton (SPP) at a gold/air interface has been used to monitor the thickness of an organic fluid layer condensed on the gold. By passing a current through the gold film its temperature (as monitored directly by its resistance) is elevated above that of the organic fluid reservoir. Measurement of the SPP resonance position as a function of the difference in temperature between the gold film and the fluid reservoir gives a direct determination of the equilibrium film thickness for a known thermal energy. From the degrees of freedom available to the molecules the variation of the bonding potential with distance from the gold surface is established. For methanol and monochlorobenzene the extra contribution to the free energy μ_Au-organic takes the forms of a power law in distance: μ_Au-methanol ∝thickness^?0·53 and μ_{Au-chlorobenzene} ∝thickness^?1·25.     

Fine co-location of pre-corrected ATSR images

A fast and automatic algorithm is presented in this paper for co-locating nadir and forward views of the Along Track Scanning Radiometer (ATSR) images by using a binary cross-correlation matching technique. The proposed algorithm does not require any auxiliary information, a priori knowledge, or any human operation. Singlechannel thermal infrared (IR) data (11 μm) are used for this algorithm, giving faster processing and avoiding the imperfect coregistration problem observed with multiple channels. Coastlines in images are detected by a region segmentation and an automatic thresholding technique. The matching procedure is carried out with binary coastline images (nadir and forward), and it gives comparable accuracy and faster processing than a patch based matching technique. This technique reduces geometric errors between two views to ±0·7 pixel.     

Financial Variables in Mental Housing

Urban activities surveys are workable bases for continuing planner-citizen dialogues. Seeking both to inform and to involve citizens, these exchanges also provide the planner with an avenue of collaboration with his client community. Findings from the surveys may be maintained in an activities base, which includes both quantitative and qualitative data on activities. Policy and planning decisions benefit from activities base data on the concerns and potentials of subcommunities. A pilot study of household activities demonstrates the usefulness and feasibility of the collaborative approach. This approach seems particularly appropriate in light of the wider definition of the planning realm now being recognized.     

Passive microwave receive filter networks using low-Q resonators

In this article, it has been shown that under certain circumstances, i.e., in a receiver, it is possible to allow microwave filters to have significant passband insertion loss. Systems analysis of various receiver configurations shows that acceptable noise figures and intercept points may be obtained in receivers containing lossy filters, i.e., ones with low-Q resonators. Thus, the engineering problem is how to develop design techniques for filters that have low-Q resonators, but with acceptable response in terms of selectivity and pass-band flatness. A review of several techniques for bandpass and bandstop filters is presented.     

Analytical behavior of the noise resistance and the noiseconductance for a network with parallel and series feedback

An analysis is presented of the changes of the noise parameters of a two-port network when noisy series and parallel feedback immittances are applied. Exact formulas for the noise parameters R_n, g _n, and ρ_n are given as functions of the feedback for a given network. It is proved that R_n always reaches a minimum when a reactive series feedback is considered. The same results are demonstrated for g_n since a duality principle is pointed out. The results are valid for a wide range of linear microwave two-port networks, either passive or active, and they are used to confirm the data from previously published work     

Performance analysis and impedance spectral signatures of high temperature PBI–phosphoric acid gel membrane fuel cells

Polarization curves, i.e., dc performance, and impedance spectral signatures of polybenzimidazole (PBI)–phosphoric acid (H₃PO₄) membrane fuel cells are obtained in the temperature range of 160–180 °C, in an effort to investigate the effect of temperature, anode humidification, various cathode stoichs, and use of oxygen versus air. Thus, in situ electrochemical impedance spectroscopy (EIS) was used to obtain various resistances, ohmic as well as charge-transfer resistances, under these conditions. The results obtained show that PBI–H₃PO₄ gel membrane fuel cells exhibit very good performance in the temperature range of 160–180 °C with an ohmic resistance similar to Nafion. Mass transfer limitations were determined by comparing performance polarization curves with air and oxygen along with EIS. Further EIS was also used to obtain signatures during fuel starvation, and electrical shorting across the cell.     

Investigation of molecular weight distribution of LBG galactomannan for flours prepared from individual seeds, mixtures, and commercial samples

The molecular weight distribution has been determined for the galactomannan solubilized from three types of locust bean gum (LBG) flours: single carob seeds, mixtures, and a range of commercial products. To prepare crude endosperm flours from carob seeds with minimal galactomannan degradation, a new extraction and milling method was developed. The method consists of applying a brief thermal shock to the seeds, followed by an extended 3-day swelling period, and manual separation of endosperms; particle size reduction to a flour is accomplished on hydrated endosperms using a centrifugal mill. This method was optimized so that redissolved LBG flours produced solutions with the highest possible viscosity and the least amount of galactomannan degradation as determined by SEC. For the three samples types, the molecular weight distribution, w(M), was found to be unimodal, appearing as a sharply defined main peak (M_p≈1.1×10⁶ g/mol) with a small high molecular weight tail (up to 2.0×10⁶ g/mol) and broad low molecular weight tail (down to 0.01×10⁶ g/mol); polydispersities (M_w/M_n) were estimated to be 1.5–1.8. Variations in M_w and [η] for galactomannans extracted from individual seeds originating from the same carob tree were minimal and nearly indistinguishable from a bulk mixture (6 seeds, M_w=0.96–1.1×10⁶ g/mol, [η]=14.2–15.1 dl/g). There was a higher variability in these molecular parameters for galactomannans solubilized from commercial LBG flours, which generally exhibited lower M_w and [η], broader distributions, and reduced solubilities (M_w=0.86–1.0×10⁶ g/mol, [η]=12.4–13.6 dl/g). These side-effects were attributed to damage caused by industrial scale seed processing. The near constancy of M_p for the three sample types suggests that the average molecular size of LBG galactomannan varies only slightly due to natural or biological causes.