KCF Technologies (United States)

A 24-in. prestressed concrete cylinder pipe (PCCP) between pump stations in north Dover, DE, and downtown Dover, constructed as part of the original network to convey wastewater to the Kent County Resource Recovery Facility had significant point failures in the past ten years, resulting in substantial damage to surrounding roadways and communities. The county identified 15,000 LF of sewer force main that needed immediate rehabilitation and renewal to prevent future failures. Located below Route 13, a key access road to the state capital, universities, businesses, and major tourist destinations, combined with buried utilities that had to be maintained throughout construction, and with work set to begin during the heavy tourist season and continuing into the holiday season, the project faced challenges that could only be overcome using the correct construction methods and materials. This paper will explore the benefits of using the appropriate rehabilitation technique and construction materials, including trenchless technologies such as sliplining, and jack-and-bore, with a combination of some traditional open-cut installations. Use of the appropriate pipe materials and their suitability for the selected renewal methods will also be discussed. Construction-related topics unique to the rehab method and materials will also be a focus of the discussions.

Vibration-based energy harvesting may hold tremendous impact for future applications of continuous machine and structural health monitoring. Here a novel resonant frequency tuning approach is proposed where the application of a bias voltage to a pre-stretched electroactive polymer (EAP) membrane results in changes in membrane tension which can be used to adjust the resonant frequency of the membrane. The effect of the bias voltage on the EAP membrane, which induces an electrostatic pressure and corresponding reduction in membrane thickness, is determined via an analytical model of the activation response of the EAP membrane, with the results confirmed using FEM simulation in ANSYS. Through a mass-loaded circular membrane vibration model, the effective resonant frequency of the membrane can be determined as a function of changes in membrane tension due to the applied bias voltage. In the case of an EAP membrane, pre-stretch contributes to the mechanical stiffness of the system while the applied bias voltage contributes to a change in electrical stiffness of the membrane. Experimental characterization of the EAP material VHB 4910 from 3 M verified the resonant frequencies corresponding to the bias voltages predicted from the appropriate models. Given an effective system stiffness range between 598 N m−1 (when λ = 1.5, U = 0) and 266 N m−1 (when λ = 5, U = 5000), the corresponding resonant frequency tuning range for a particular circular central loaded EAP membrane device is between 31.4 to 21.8 Hz. The proposed bias voltage tuning approach for the EAP membrane may provide a novel strategy to enable resonant frequency tuning of energy harvesting devices in particular application environments.

A core component of informal statistical inference is the recognition that judgments based on sample data are inherently uncertain. This implies that instruction aimed at developing informal inference needs to foster basic probabilistic reasoning. In this article, we analyze and critique the now-common practice of introducing students to both “theoretical” and “experimental” probability, typically with the hope that students will come to see the latter as converging on the former as the number of observations grows. On the surface of it, this approach would seem to fit well with objectives in teaching informal inference. However, our in-depth analysis of one eighth-grader's reasoning about experimental and theoretical probabilities points to various pitfalls in this approach. We offer tentative recommendations about how some of these issues might be addressed.

In this paper, we examine and evaluate several new mathematical representations developed for The Geometer’s Sketchpad v5 (GSP5) from the perspective of their dynamic mathematical and pedagogic utility or expressibility. We claim the primary contributions of Dynamic Geometry’s principle of dynamism to the emerging concept of “Dynamic Mathematics” to be twofold: first, the powerful, temporalized representation of continuity and continuous change (dynamism’s mathematical aspect), and second, the sensory immediacy of direct interaction with mathematical representations (dynamism’s pedagogic aspect). Seen from this perspective, the growth of “Dynamic Mathematics software,” beyond the initial conception of first-generation planar geometry systems, represents a tremendous diversification and expansion of the mathematical domain of the dynamic principle’s applicability (for example, to dynamic statistics, graphing and 3D geometry). But at the same time, this expansion has come at the cost of a decrease in the immediacy of sensory interactions with mathematical representations, as in so-called dynamic graphing, wherein users modify a graph “at a distance” (through slider-based manipulation of the coefficients of its symbolic equation), or in solid geometry tools, in which users’ interactions with represented solids are mediated and distanced by the inevitably-2D communication interfaces of the computer mouse and screen. Thus we focus on this second aspect–sensory interaction with mathematical representations—in evaluating how novel dynamic representations in GSP5 affect mathematical modeling opportunities, student activity and engagement.

In recent piezoelectric actuator development, a new feed-screw motion accumulation concept has demonstrated reversible, robust, and high force actuation. However, the feed-screw actuator's complicated structure and frequency-dependent operation necessitate the use of an efficient method to optimize its performance. Consequently, this study presents the formulation of a dynamic mathematical feed-screw actuator model and its integration in an optimization algorithm. To accurately model the feed-screw actuator, nonlinear contact stiffness and micro-slip is considered, as well as rate-dependent friction behavior. Results from numerical model simulations compare well with experimental data for a range of loads corresponding to the actuator's peak power output. A simulated annealing optimization algorithm is used to determine an actuator design that maximizes specific power (W/kg). For an actuation rate and load of 0.26in./s and 1220lb, a factor of 5 increase in specific power over that of the original experimental hardware is predicted. Expanding the optimization to consider a broad range of loads and speeds indicates that the feed-screw actuator could achieve a 195 W/kg specific power — a level approximately double that of similarly sized electromagnetic actuator. The most significant design improvements contributing to the large gains in specific power involve an increase in the screw pitch angle and a reduction of its diameter.

The demand for educational software is growing exponentially with the surge of interest in educational reform, the Internet, and distance learning. Educational applications must be flexible because curricula and teaching styles vary greatly among institutions, locations, and even among instructors at the same institution. To meet these needs, a wide array of small-scale, casual developers at universities, research labs, and small businesses develop educational software, but no dominant solution or supplier has seemed to emerge. In this market, smaller suppliers often cannot produce full solutions without depending on the capabilities of other vendors. Until now, components have remained largely the province of full-time programmers. However, component technologies are likely to expand toward an audience that comprises considerably less technical and more domain-oriented users whose job descriptions typically don't include software development. Thus, the lessons learned could become increasingly important to developing good software for any application domain. Having component developers collaborate with domain experts to build applications may be the future of software development. This group of component developers discusses what they've learned in collaborating with educators on educational software components.