Michigan Technological University

About: Michigan Technological University is a education organization based out in Houghton, Michigan, United States. It is known for research contribution in the topics: Population & Volcano. The organization has 8023 authors who have published 17422 publications receiving 481780 citations. The organization is also known as: MTU & Michigan Tech.

Channel Convection in Partly Solidified Systems

Abstract: Channel plume flow arising from thermosolutal convection has been examined in metallic, aqueous and organic systems, covering a range of Prandtl numbers over three orders of magnitude. Observations were made directly in the transparent aqueous and organic systems and after the event in fully solidified metallic alloys. Plume dimensions and those of the concomitant channels are remarkably similar in all three materials, as are the composition differences between plumes or channels and the matrices. Detailed measurements and observations of these dimensions and of flow rates in the transparent materials are described and discussed. Analysis of plume flow rates in the transparent systems, if extrapolated to metals, would predict convective flow rates between 0.1 m s -1 and 0.2 m s -1 . The validity of this extrapolation is qualified by the way in which posthumous solute channels develop in the fully solidified metallic samples.

Development of an additive equation for predicting the electrical conductivity of carbon‐filled composites

Abstract: The electrical conductivity of polymeric materials can be increased by the addition of carbon fillers. The resulting composites can be used in applications such as electrostatic dissipation and interference shielding. Electrical conductivity models are often proposed to predict the conductivity behavior of these materials. The electrical conductivity of carbon-filled polymers was studied here by the addition of three single fillers to nylon 6,6 and polycarbonate in increasing concentrations. The fillers used in this project were carbon black, synthetic-graphite particles, and milled pitch-based carbon fibers. Materials were extruded and injection-molded into test specimens, and then the electrical conductivity was measured. Additional material characterization tests included optical microscopy for determining the filler aspect ratio and orientation. The filler and matrix surface energies were also determined. An updated model developed by Mamunya and others and a new additive model (including the constituent conductivities, filler volume fraction, percolation threshold, constituent surface energies, filler aspect ratio, and filler orientation) fit the electrical conductivity results well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2280–2299, 2003

Optical-chemical-microphysical relationships and closure studies for mixed carbonaceous aerosols observed at Jeju Island; 3-laser photoacoustic spectrometer, particle sizing, and filter analysis

Abstract: . Transport of aerosols in pollution plumes from the mainland Asian continent was observed in situ at Jeju, South Korea during the Cheju Asian Brown Cloud Plume-Asian Monsoon Experiment (CAPMEX) field campaign throughout August and September 2008 using a 3-laser photoacoustic spectrometer (PASS-3), chemical filter analysis, and size distributions. The PASS-3 directly measures the effects of morphology (e.g. coatings) on light absorption that traditional filter-based instruments are unable to address. Transport of mixed sulfate, carbonaceous, and nitrate aerosols from various Asian pollution plumes to Jeju accounted for 74% of the deployment days, showing large variations in their measured chemical and optical properties. Analysis of eight distinct episodes, spanning wide ranges of chemical composition, optical properties, and source regions, reveals that episodes with higher organic carbon (OC)/sulfate (SO42−) and nitrate (NO3−)/SO42− composition ratios exhibit lower single scatter albedo at shorter wavelengths (ω405). We infer complex refractive indices (n–ik) as a function of wavelength for the high, intermediate, and low OC/SO42− pollution episodes by using the observed particle size distributions and the measured optical properties. The smallest mean particle diameter corresponds to the high OC/SO42− aerosol episode. The imaginary part of the refractive index (k) is greater for the high OC/SO42− episode at all wavelengths. A distinct, sharp increase in k at short wavelength implies enhanced light absorption by OC, which accounts for 50% of the light absorption at 405 nm, in the high OC/SO42− episode. Idealized analysis indicates increased absorption at 781 nm by factors greater than 3 relative to denuded black carbon in the laboratory. We hypothesize that coatings of black carbon cores are the mechanism of this enhancement. This implies that climate warming and atmospheric heating rates from black carbon particles can be significantly larger than have been estimated previously. The results of this study demonstrate ways in which atmospheric processing and mixing can amplify particle light absorption for carbonaceous aerosol, significantly at short wavelength, underscoring the need to understand and predict chemical composition effects on optical properties to accurately estimate the climate radiative forcing by mixed carbonaceous aerosols.

Analysis of Combustion Knock Metrics in Spark-Ignition Engines

Abstract: Combustion knock detection and control in internal combustion engines continues to be an important feature in engine management systems. In spark-ignition engine applications, the frequency of occurrence of combustion knock and its intensity are controlled through a closedlooped feedback system to maintain knock at levels that do not cause engine damage or objectionable audible noise. Many methods for determination of the feedback signal for combustion knock in spark-ignition internal combustion engines have been employed with the most common technique being measurement of engine vibration using an accelerometer. With this technique single or multiple piezoelectric accelerometers are mounted on the engine and vibrations resulting from combustion knock and other sources are converted to electrical signals. These signals are input to the engine control unit and are processed to determine the signal strength during a period of crank angle when combustion knock is expected. As the accelerometer detects a number of sources of vibrations in addition to the desired vibration from knock, the signal quality varies significantly from engine to engine, cylinder to cylinder, and over the operating conditions of the engine. To evaluate the effectiveness and accuracy of knock detection via accelerometers, a reference system is commonly employed. One of the most common reference metrics is the signal strength of the combustion pressure over the appropriate frequency range as measured with in-cylinder pressure transducers. This analysis examines both cylinder pressure and accelerometer-based knock intensity metrics, where the pressure-based knock intensity metric is used as the reference measure. Distributions of the knock metrics over a number of engine cycles for various engine speeds, loads, cam timings, and knock levels are measured and fit to a log-normal model distribution. The lognormal model is shown to provide a good fit to the measured distribution and also captures the characteristics of the distribution to include skewness and peakness. In addition the accelerometer intensity metric is correlated to the reference pressure intensity metric. The result of this correlation provides the coefficient of determination, which is used as a measure of the accelerometer intensity metric's ability to indicate knock. The effects of the distribution of the pressure intensity metric on the coefficient of determination are examined by analyzing subsets of the distribution