Teaching Hydraulic Design Using Equation Solvers

Civil engineering graduates need to be competent in hydraulic theory, as well as in the application of that theory to the solution of practical problems. Teachers of hydraulic design are faced with the dilemma that most realistic hydraulics problems are too complex to solve by hand, while most commercially available software packages obscure the theoretical background for program algorithms. Equation solvers provide a valuable tool for bridging these gaps. Students can develop an appropriate linear or nonlinear mathematical model to depict a realistic system, then use an equation solver package to solve that model for any combination of input data desired. Computer-based studio classrooms further enhance the learning experience by allowing students to solve problems under the instructor's supervision during class periods. This paper will describe how effective equation solvers and the studio classroom can be in teaching hydraulic design for water distribution systems and open-channel flow. The theory is developed in class through the use of printed notes. Students then develop the nonlinear mathematical model for a simple example, solve the model using an equation solver, and check the correctness of the solution. Students are able to investigate the dynamic response and the sensitivity of the model by varying the equation solver input variable values. Next they apply the theory and solution methods to a practical applications exercise. The final step is to complete a comprehensive, realistic design problem. Students are required to present their results to the class at all stages of the process. Course-end evaluation scores have risen significantly since the class has been converted to the studio format. Student comments indicate that they think equation solvers are a valuable engineering design tool, not only for learning, but in professional practice as well. The instructor has observed that students learn and retain the theory much better when they can apply it immediately to realistic problems. Much more realistic and sophisticated quizzes can be given when the students have computers available to assist with the analysis.     

1.2-μm GaAsP/InGaAs strain compensated single-quantum-well diodelaser on GaAs using metal-organic chemical vapor deposition

We demonstrate here 1.2-μm laser emission from a GaAsP-InGaAs strain compensated single-quantum-well (SQW) diode. This development enables the fabrication of vertical-cavity surface-emitting lasers for optical interconnection through Si wafers. Strain compensation and low temperature growth were used to extend the wavelength of emission to the longest yet achieved on a GaAs substrate in this materials system. The minimum threshold density achieved was 273.4 A/cm² at a cavity length of 610 μm. We have also demonstrated an 1.144-μm lasing wavelength in a 820-μm-long cavity on a GaAs substrate with a strained InGaAs-GaAs SQW laser for comparison using a low-temperature metal-organic chemical vapor deposition growth technique. The threshold current density for a 590-μm-long cavity under CW operation was 149.7 A/cm²     

ESTIMATING ANNUAL RIVERBANK EROSION RATES—A DENDROGEOMORPHIC METHOD

An accurate estimation of riverbank erosion rates is critical for the evaluation of the past, present, and future sediment regime of river systems. Understanding these relationships allows watershed managers and regulators to prioritize river restoration and contaminated site remediation projects. In this dendrogeomorphic study, changes in the anatomy of tree roots exposed between 1 and 31 years were used to estimate the average annual erosion rates of riverbank sediments on a large river in Michigan, USA. Exposed root samples from diffuse and ring‐porous hardwoods, together with buried ones as controls, were analyzed. Differences in the arrangement, size and frequency of vessels, fiber diameter, cell wall thickness, growth ring width, and scarring between the exposed and the buried samples were used to identify the first year of root exposure. Results of the regression analysis between the average annual erosion rate and the Bank Erosion Hazard Index (BEHI) indicated that the more recently exposed roots (less than 7 years in this study) explained more of the variance (R² = 0.67) than when all samples were included (R² = 0.38). Although the average erosion rates for long periods can be accurately determined from the dating of exposed tree roots, attempts to relate these rates using the BEHI for longer periods are less successful, as BEHI values can vary considerably over time as the riverbank erodes. Consequently, when using exposed tree roots to develop regression equations and erosion rate curves for the estimation of erosion rates based on BEHI scores, it is necessary to use roots that were recently exposed. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of Axial Segmentation of Permanent Magnets on Rotor Loss in Modular Permanent-Magnet Brushless Machines

This paper presents a computationally efficient technique in determining the influence of the finite axial length of the permanent magnets on the rotor eddy-current loss in modular brushless ac machines. The technique is employed to quantify the effectiveness of axially segmenting the permanent magnets of four-phase, eight-slot, ten-pole and five-phase, ten-slot, 12-pole brushless machines, which have been designed to meet the performance requirements of an electromechanical flight control surface actuator for a "more-electric" aircraft.     

Design and control of a novel spherical permanent magnet actuator with three degrees of freedom

The paper describes the design and control of a new version of a spherical permanent magnet actuator, which is capable of three degrees of freedom and a high specific torque. Based on an analytical magnetic field distribution, the torque vector and back-emf are derived in closed forms. An optimal design procedure is proposed to achieve maximum output torque or maximum acceleration for a given payload. The control of the actuator, whose dynamics are similar to those of robotic manipulators, is facilitated by the establishment of a complete actuation system model and the application of the computed torque control law. The validity of the analysis and design techniques, and the effectiveness of the control strategy, are confirmed by measurements.     

A broad-band distributed-star network using subcarrier fibertransmission

The development of British Telecom's distributed-star system through the 1980s is described, with particular reference to the development of the optical transmission of video channels. The latest all-fiber network design is detailed, with an explanation of the thinking behind the transmission parameters for the subcarrier scheme adopted. The future policy on modulation techniques is reviewed in light of likely technology and service developments     

Bayesian data assimilation provides rapid decision support for vector-borne diseases

Predicting the spread of vector-borne diseases in response to incursions requires knowledge of both host and vector demographics in advance of an outbreak. Although host population data are typically available, for novel disease introductions there is a high chance of the pathogen using a vector for which data are unavailable. This presents a barrier to estimating the parameters of dynamical models representing host–vector–pathogen interaction, and hence limits their ability to provide quantitative risk forecasts. The Theileria orientalis (Ikeda) outbreak in New Zealand cattle demonstrates this problem: even though the vector has received extensive laboratory study, a high degree of uncertainty persists over its national demographic distribution. Addressing this, we develop a Bayesian data assimilation approach whereby indirect observations of vector activity inform a seasonal spatio-temporal risk surface within a stochastic epidemic model. We provide quantitative predictions for the future spread of the epidemic, quantifying uncertainty in the model parameters, case infection times and the disease status of undetected infections. Importantly, we demonstrate how our model learns sequentially as the epidemic unfolds and provide evidence for changing epidemic dynamics through time. Our approach therefore provides a significant advance in rapid decision support for novel vector-borne disease outbreaks.     

Innovation in Construction Engineering Education Using Two Applications of Internet-Based Information Technology to Provide Real-Time Project Observations

Improvements in construction engineering education result when innovative information technologies are incorporated into academic curricula. Through the use of internet-based communication technologies, no longer must students physically travel to a construction project site to observe and hear construction operations. This paper discusses two applications of internet-based, audio and video technologies currently being piloted at Iowa State University (ISU) and at the University of Calgary (UC) for the purpose of bringing live construction projects into the university classroom. Virtual Project Tours have been piloted at Iowa State University in which real-time video and audio are delivered from active construction projects to a remote classroom through the internet. The second application discussed in this paper, Virtual Supervision, is being piloted at the University of Calgary and consists of the monitoring and analysis of construction projects by using imagery gathered by web-enabled, digital cameras of fixed location transmitting video through the internet. This paper also presents a vision of a globally networked organization of engineering and construction education institutions each sharing the unique engineering and building techniques of their respective part of the globe with design and construction students located around the world. This exchange of construction project observations among the institutions will be enabled by the internet-based applications of virtual project tours and virtual supervision systems described in this paper.     

Limits on cloud-induced fluctuation in photovoltaic generation

The cost and the effect on utility reliability of rapidly changing PV (photovoltaic) generation on a partly-cloudy day were investigated. When cloud shadows move across a PV array, the array's power output is reduced. It resumes full production when the shadow moves away. The utility must follow these changes with other types of generation. Under certain cloud conditions, these changes can be large and fast. A methodology is presented to assess the cost of such fluctuations in PV generation and their effect on a utility's ability to serve its load. A case study of one large utility in Kansas is performed using this technique