Towards a pipelined Prolog processor

This paper describes the design of a Prolog machine architecture and organization. Our objective was to determine the maximum performance attainable by a sequential Prolog machine for “reasonable” cost. The paper compares the organization to both general purpose micro-coded machines and reduced instruction set machines. Hand timings indicate a peak performance rate of 450 K LIPS (logical inferences per second) is well within current technology limitations and 1 M LIPS is potentially feasible.     

A GPS/GIS method for travel mode detection in New York City

Handheld GPS provides a new technology to trace people’s daily travels and has been increasingly used for household travel surveys in major cities worldwide. However, methodologies have not been developed to successfully manage the enormous amount of data generated by GPS, especially in a complex urban environment such as New York City where urban canyon effects are significant and transportation networks are complicated. We develop a GIS algorithm that automatically processes the data from GPS-based travel surveys and detects five travel modes (walk, car, bus, subway, and commuter rail) from a multimodal transportation network in New York City. The mode detection results from the GIS algorithm are checked against the travel diaries from two small handheld GPS surveys. The combined success rate is a promising 82.6% (78.9% for one survey and 86.0% for another). Challenges we encountered in the mode detection process, ways we developed to meet these challenges, as well as possible future improvement to the GPS/GIS method are discussed in the paper, in order to provide a much-needed methodology to process GPS-based travel data for other cities.     

Impossible spaces: maximizing natural walking in virtual environments with self-overlapping architecture

Walking is only possible within immersive virtual environments that fit inside the boundaries of the user's physical workspace. To reduce the severity of the restrictions imposed by limited physical area, we introduce "impossible spaces," a new design mechanic for virtual environments that wish to maximize the size of the virtual environment that can be explored with natural locomotion. Such environments make use of self-overlapping architectural layouts, effectively compressing comparatively large interior environments into smaller physical areas. We conducted two formal user studies to explore the perception and experience of impossible spaces. In the first experiment, we showed that reasonably small virtual rooms may overlap by as much as 56% before users begin to detect that they are in an impossible space, and that the larger virtual rooms that expanded to maximally fill our available 9.14 m x 9.14 m workspace may overlap by up to 31%. Our results also demonstrate that users perceive distances to objects in adjacent overlapping rooms as if the overall space was uncompressed, even at overlap levels that were overtly noticeable. In our second experiment, we combined several well-known redirection techniques to string together a chain of impossible spaces in an expansive outdoor scene. We then conducted an exploratory analysis of users' verbal feedback during exploration, which indicated that impossible spaces provide an even more powerful illusion when users are naive to the manipulation.     

REED: Flexible rule based programming of wireless sensor networks at runtime

Wireless Sensor Networks (WSNs) have emerged as an enabling technology for a variety of distributed applications. WSN middleware eases the development of these applications by providing a uniform programming environment. In this paper we present a rule based approach called REED (Rule Execution and Event Distribution) and describe how it supports flexible programming of WSNs at runtime. Indeed REED is required by the nature of its project setting to allow runtime programming. We demonstrate that by combining this runtime programmability with rules in an event, condition, action format we can support a range of paradigms, including Publish-subscribe and data aggregation algorithms. Current WSN middleware solutions have limited on-line programmability support so the applications cannot re-configure their WSNs while operational. Yet the runtime nature of the prototype requires both the distribution of rules and the events that trigger them so we also describe the rule management approach used to support the rule distribution; in particular a novel rule merging and filtering algorithm is described. The paper reports on the results gained from a REED prototype system constructed in our laboratory using Gumstix.     

Viscoplastic flows in ducts

Axial flows in generalized ducts are analyzed for viscoplastic materials behaving as Bingham plastics with a yield stress. A constitutive equation proposed by Papanastasiou is used, which applies everywhere in the flow field in both yielded and practically unyielded regions. Numerical simulations are presented in several two-dimensional cross-sectional geometries, such as square and rectangular ducts (straight and concave), and eccentric annular conduits, for different flow rate and pressure drop ranges. The extent and shape of yielded/unyielded regions are shown as the dimensionless yield stress or Bingham number increases. Master curves are given for the dimensionless flow rate vs dimensionless pressure drop or vs Bingham number for quick engineering calculations useful in practical applications of materials processing.     

Epistemic Mediation: Aligning Expertise across Boundaries within an Endangered Species Habitat Conservation Plan

This paper uses videotaping and discourse analysis to study participants' dialogue and conduct during preparation of the Coachella Valley habitat conservation plan in southern California. The research uses social worlds analysis to reveal that the plan's technical advisors did not find facts through the collective discovery of scientific truths with unitary meanings, but instead constructed facts by aligning professional visions of space, time, and agency. The validity of the resulting plan relied on its ability to be a “boundary object”, meaning different things to different groups, while simultaneously laying claim to universality and objectivity. However, its subsequent failure to satisfy an unexpected scientific peer review demonstrates the importance of anticipating downstream reception and use when developing such documents. This case study shows that planners can be epistemic mediators, creating and stabilizing technical knowledge claims that project authority by showing a responsive face to many audiences.     

Effects of simulated clinical fabrication heat treatment and artificial weathering on the hardness testing of prosthetics/orthotics polymers

The hardness behavior was compared for five prosthetics/orthotics polymers: Durr-Plex (copolyester), Polypropylene (polypropylene), Subortholen (polythylene), Surlyn (ionomer), and Uvex (and cellulose acetate butyrate). The hardness is related to a number of factors including the composition and condition of the polymers. The polymers were examined in the as-received and simulated clinical fabrication heat-treated conditions. The simulated clinical fabrication heat-treated specimens were subsequently treated to 2 weeks, 4 weeks, and 8 weeks of artificial weathering conditions, consisting of exposure to cycles of ultraviolet light and heated condensation. Five measurements were taken for each treatment condition using a Durometer hardness tester. The hardness ranges and the respective ranking for the polymers were determined. Analysis of variance (ANOVA) and post hoc Scheffé statistical analyses were performed for different polymers of the same treatment condition, and different treatment conditions of the same polymer. The analysis of variance (ANOVA) showed significant hardness differnces for the five polymers. The choice of material significantly influences the mechanical property of hardness for prosthetics/orthotics polymers. The Durr-Plex polymer had the highest hardness and the Surlyn polymer had the lowest hardness. The ranking trend was Durr-Plex>Uvex>polypropylene>Subortholen>Surlyn. © 1996 John Wiley & Sons, Inc.     

Gadolinium-containing copolymeric chelates—a new potential MR contrast agent

Rationale and objectives: To develop and partially characterize a new class of potential blood pool magnetic resonance (MR) contrast agents.Methods: Various copolymeric chelates of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) were prepared with differing molecular weights of polyethylene glycol (PEG) or polypropylene glycol (PPG) as linkers between the monomeric chelate units. Gadolinium content of the polymeric chelates was determined by atomic absorption spectra. Relaxivity of the polymeric chelates was measured at 1.5 Tesla and compared with Gadolinium-DTPA. MR angiography (MRA) was performed in rabbits comparing Gd-DTPA with Gd-copolymers.Results: The gadolinium content of the copolymeric chelates ranged from 2.95 to 22.2% on weight basis. The molecular weight of the PEG linkers in the copolymers ranged from about 150 to about 3400. Ther ₁ (1/T1, mM⁻¹ s⁻¹) for Gd-DTPA=4.1. Ther ₁ values for the different Gd-containing polymers ranged from 3.8 to 5.8, with the lowestr ₁ for the polymer prepared with the lowest-molecular-weight complex. The higher-molecular-weight complexes resulted in moderately higher relaxivity. MRA with Gd-copolymers, in rabbits, showed markedly greater vascular enhancement relative to an equivalent dose of Gd-DTPA. Vascular enhancement was much more sustained with the copolymeric agent and confined to vascular space; i.e. no appreciable background tissue enhancement—a reflection of distribution into extravascular fluid space—was observed.Conclusions: Relative to Gd-DTPA monomers, PEG-containing Gd-DTPA polymeric complexes provided moderate increases in relaxivity but markedly greater efficacy during in vivo MRA. In vitro relaxivity studies of Gd-copolymers showed only an approximately 50% increase inr ₁ relaxivity compared with Gd-DTPA. The PEG-containing complex's lack of rigidity may have diminished the effect of spin diffusion on relaxation, thereby accounting for this modest increase. The greater efficacy of Gd-copolymers during in vivo MRA may reflect compartmentalization within the vascular space and possibly enhanced relaxation of the macromolecular copolymers in the blood. Gd-copolymers are promising agents that merit additional study.     

PML: Toward a High-Level Formal Language for Biological Systems

Documentation of knowledge about biological pathways is often informal and vague, making it difficult to efficiently synthesize the work of others into a holistic understanding of a system. Several researchers have proposed solving this problem by modeling pathways using formal languages, which have a precise and consistent semantics. While precise, many of these languages may be too low-level to model feasibly complex pathways. We have developed the Pathway Modeling Language (PML), a high-level language for modeling pathways. PML is based on a biological metaphor of molecules with binding sites and has special constructs for handling compartment changes in pathways. Our preliminary work has shown that PML's language constructs serve as a promising basis for modeling complex pathways in a readable and composable manner.