Linear Delta Modulation Quantizing Noise Characteristics

A formula for signal-to-quantizing noise ratio (SNR) in delta modulation systems is obtained by modifying an existing result for DPCM systems. Computer simulation is used to examine the behavior of the terms in the modified SNR formula.     

Utilizing Instructional Consultations to Enhance the Teaching Performance of Engineering Faculty

Although many kinds of data can be used to guide instructional consultations, research comparing the efficacy of such data is scant, especially in engineering. In this study, multiple modes of assessment were used to evaluate the impact of consultations informed by different kinds of data. This study illuminates two key aspects of instructional consultations: (1) their efficacy varies depending on the kind of data used to guide them, with student feedback from a Small Group Instructional Diagnosis (SGID) having the largest positive impact, and (2) the instructional consultant plays a key role in helping both interpret the available data and identify strategies for improvement. These findings suggest three implications for practice: (1) whenever possible, SGID‐based consultations should be offered systematically and proactively for engineering faculty, (2) data for other kinds of consultations should be tailored to the needs of the individual instructor, and (3) instructional consultants should be available to collaborate with faculty to enhance their teaching, thereby building an engineering culture that actively supports teaching and learning.     

Optimization of finite element codes

A general algorithm for constructing finite element matrices within a multiple input, multiple data stream (MIMD) vector-processing environment is presented. Efficiency of the vectorized code is determined by the number of elements which differs from the more intuitive algorithms based on the number of quadrature points or shape functions. Performance is evaluated analytically and then verified by timings obtained by a series of experimental runs on a Cray Y-MP. A speedup factor of 25 is observed.     

Phosphate recovery using hybrid anion exchange: Applications to source-separated urine and combined wastewater streams

There is increasing interest in recovering phosphorus (P) from various wastewater streams for beneficial use as fertilizer and to minimize environmental impacts of excess P on receiving waters. One such example is P recovery from human urine, which has a high concentration of phosphate (200–800 mg P/L) and accounts for a small volume (∼1%) of total wastewater flow. Accordingly, the goal of this study was to evaluate the potential to recover P from source-separated and combined wastewater streams that included undiluted human urine, urine diluted with tap water, greywater, mixture of urine and greywater, anaerobic digester supernatant, and secondary wastewater effluent. A hybrid anion exchange (HAIX) resin containing hydrous ferric oxide was used to recover P because of its selectivity for phosphate and the option to precipitate P minerals in the waste regeneration solution. The P recovery potential was fresh urine > hydrolyzed urine > greywater > biological wastewater effluent > anaerobic digester supernatant. The maximum loading of P on HAIX resin was fresh urine > hydrolyzed urine > anaerobic digester supernatant ≈ greywater > biological wastewater effluent. Results indicated that the sorption capacity of HAIX resin for phosphate and the total P recovery potential were greater for source-separated urine than the combined wastewater streams of secondary wastewater effluent and anaerobic digester supernatant. Dilution of urine with tap water decreased the phosphate loading on HAIX resin. The results of this work advance the current understanding of nutrient recovery from complex wastewater streams by sorption processes.     

A comparison of critical flow models for estimating two-phase flow of HCFC22 and HFC134a through short tube orifices

An experimental study to investigate the critical flow of refrigerants through short tube orifices has been performed by measuring the mass flowrates and pressure profiles along the short tube orifice. Eight critical flow models have been examined and their results compared with the experimental data for HCFC22 and HFC134a. These models include four homogeneous equilibrium models, two homogeneous frozen models, and two non-homogeneous equilibrium models. The data indicate that the flow was choked when downstream pressures were lower than the saturation pressure corresponding to the upstream temperature. The observed flows through short tube orifices included a lack of equilibrium due to short time of expansion and homogeneous mist flow at the exit plane. These flow trends would be more consistent with the basic assumptions of the homogeneous frozen models. Based on the comparison of the existing critical flow models and experimental data, the homogeneous frozen models showed the best agreement with the measured data except for exit qualities below 0.06.     

Gemfibrozil treatment increases low-density lipoprotein particle size in Type 2 diabetes mellitus but does not alter in vitro oxidizability

The aim of this study was to determine the effect of the lipid modifying agent gemfibrozil on lipid and coagulation risk factors in patients with Type 2 diabetes mellitus (Type 2 DM). Twenty-six subjects with Type 2 DM and dyslipidaemia were treated for 24 weeks with either gemfibrozil 600 mg orally twice daily or placebo in a double-blind randomized trial. Lipid profiles, fibrinogen, Factor VII, and plasminogen activator inhibitor-1 (PAI-1) were measured by routine laboratory methods. Low density lipoprotein (LDL) size was determined by gradient gel electrophoresis and the resistance of LDL to copper-induced oxidation was assessed by measuring absorbance at 234 nm. Gemfibrozil significantly reduced total cholesterol (-0.9 (-0.48, -1.32) mmol l(-1); p < 0.05) and triglycerides (-2.7 (-1.55, -1.35) mmol l(-1); p < 0.001) vs placebo. The fall in triglyceride was reflected by a fall in VLDL cholesterol levels in the gemfibrozil treated group vs placebo (-1.31 mmol l(-1); p < 0.001). LDL-cholesterol level did not change but LDL particle size increased by 0.5 nm (0.01, 0.93); P < 0.02. The increase in particle size was inversely correlated with the change of triglyceride level (r = -0.79, p < 0.0001) but did not result in any reduction of susceptibility to copper-induced oxidation. There were no significant changes in the coagulation parameters studied. Because of its ability to correct the lipid abnormalities associated with Type 2 DM particularly hypertriglyceridaemia, gemfibrozil provides a useful therapeutic option in the management of diabetic dyslipidaemia but it does not alter in vitro oxidizability of LDL.     

The microscopic failure processes and their relation to the structure of amine-cured bisphenol-A-diglycidyl ether epoxies

Electron and optical microscopy are used to study the relation between the structure and the microscopic flow and failure processes of diethylene triamine-cured bisphenol-A-diglycidyl ether epoxies. By straining films directly in the electron microscope, these epoxies are found to consist of 6 to 9 nm diameter particles which remain intact when flow occurs. It is suggested that these particles are intramolecularly crosslinked molecular domains which can interconnect to form larger network morphological entities. Epoxy films, either strained directly in the electron microscope or strained on a metal substrate, deform and fail by a crazing process. The flow processes that occur during deformation are dependent on the network morphology in which regions of either high or low crosslink density are the continuous phase. The fracture topographies of the epoxies are interpreted in terms of a crazing process. The coarse fracture topography initiation regions result from void growth and coalescence through the centre of a simultaneously growing poorly developed craze which consists of coarse fibrils. The surrounding smooth slow-crack growth mirror-like region results from crack propagation either through the centre or along the craze—matrix boundary interface of a thick, well developed craze consisting of fine fibrils.     

Delta Modulation of Data Signals

This paper is an analytical study to determine the performance of single-integration delta-modulation(DeltaM)encoders with inputs which are various voice-band data signals. Signal-to-quantizing noise ratiosS/Nare calculated forDeltaMbit rates from 16 to 96 K bits/s. The input data signals studied are phase modulation at 1200 and 2400 bits/s, partial response at 4800 and 9600 bits/s, and single sideband at 4800 bits/s. Predictions of the performance of these modems, when transmitted over theDeltaMsystems, are based on the calculatedS/Nratios.     

Distribution Line Carrier Sensitivity Analysis Using Bus Impedance Matrix

In a previous paper[1] we described the use of a bus impedance matrix approach for determining the signal strength of distribution line carrier signals. The technique used bus impedance matrices to calculate transimpedances which are the ratios of the voltage at any point on the line to the current injected at any point on the line. In the current paper we apply sensitivity analysis to this bus impedance approach and show how simply new transimpedances can be obtained from the original values when changes in the distribution line are made.