The South Dakota School of Mines and Technology is a public institution of higher learning in Rapid City, South Dakota governed by the South Dakota Board of Regents. Founded in 1885 as the Dakota School of Mines, Tech offers degree programs in engineering and science fields. 2,311 students were enrolled in fall 2011. The school athletic teams are called the Hardrockers. Wikipedia.
Korde U.A.,South Dakota School of Mines and Technology |
Ertekin R.C.,University of Hawaii at Manoa
This paper investigates wave energy conversion in open water where the goal is to utilize the wave-field focusing effect of a stationary disc submerged a short depth beneath the water surface. Dynamic interaction of the disc with additional coupled, submerged inertias is used to minimize its oscillation. The method used to enable and extend this favorable dynamic coupling is discussed here. An oscillating water column in a submerged duct attached under a small circular opening in the disc and driven by the wave-field over the disc is used for wave energy conversion. Non-real-time reactive control of the water column response to enhance energy absorption is examined. Added mass, radiation damping, and exciting force values for the submerged disc are computed, and the focusing effect of a submerged stationary disc is confirmed with numerical calculations of surface elevation over the disc. Calculations of hydrodynamic performance suggest that energy absorption from the oscillating water column is significantly greater under control holding the disc stationary, and can be improved further by applying reactive loads tuned to the optimal susceptance and conductance associated with the oscillating water column. Although the control forces involved in holding the disc stationary may be large at lower wave numbers, the maximum deflection amplitudes of the compensation system are found to be within reasonable limits. © 2013 Elsevier Ltd. Source
Korde U.A.,South Dakota School of Mines and Technology
Applied Ocean Research
Real-time smooth reactive control and optimal damping of wave energy converters in irregular waves is difficult in part because the radiation impulse response function is real and causal, which constrains the frequency-dependent added mass and radiation damping according to the Kramers-Kronig relations. Optimal control for maximum energy conversion requires independent synthesis of the impulse response functions corresponding to these two quantities. Since both are non-causal (one being odd and other even), full cancellation of reactive forces and matching of radiation damping requires knowledge or estimation of device velocity into the future. To address this difficulty and the non-causality of the exciting force impulse response function, this paper investigates the use of propagating-wave surface elevation up-wave of the device to synthesize the necessary forces. Long-crested waves are assumed, and the approach is based on the formulations of Naito and Nakamura  and Falnes . A predominantly heaving submerged device comprised of three vertically stacked discs driving a linear power take-off is studied. The overall formulation leads to smooth control that is near-optimal, given the approximations involved in the time-shifting of the non-causal impulse response functions and the consequent up-wave distances at which wave surface elevation is required. Absorbed power performance with the near-optimal approach is compared with two other cases, (i) when single-frequency tuning is used based on non-real time adjustment of the reactive and resistive loads to maximize conversion at the spectral peak frequency, and (ii) when no control is applied with damping set to a constant value. Simulation results for wave spectra over a range of energy periods and significant wave heights are compared for the three situations studied. While practical implementation presents engineering challenges, in terms of time-averaged absorbed power, unconstrained near-optimal control is found to perform significantly better than single-frequency tuning in the spectra with longer energy periods (>10. s for the present device), and somewhat better in the spectra with shorter energy periods (here ≤10. s). © 2014 Elsevier Ltd. Source
Warner T.A.,South Dakota School of Mines and Technology
We present high-speed camera observations (up to 7200 images per second) and correlated electric field measurements of upward lightning leaders initiated simultaneously from multiple tall towers. Four towers spanning a horizontal distance of 2.9. km and ranging in height from 121 to 191. m, developed upward leaders following a nearby positive cloud-to-ground (+. CG) flash on 7/16/09 UT in Rapid City, South Dakota, USA during the summer thunderstorm season. The optical and electric field observations suggest that all four upward propagating leaders were positive polarity (i.e., upward negative lightning) and initiated simultaneously approximately 2. ms following the + CG return stroke. There was significant intracloud flash activity prior to the return stroke, and upward leader initiation coincided with the passage of horizontally extensive in-cloud negative breakdown following the + CG return stroke. This observation supports the idea that downward positive cloud-to-ground lightning can trigger upward negative lightning from multiple tall objects. Specifically, the triggering component is an area of horizontally propagating negative breakdown following the + CG return stroke that influences a broad area resulting in simultaneous or near-simultaneous, positive polarity upward leader initiation from multiple tall objects. © 2011 Elsevier B.V. Source
South Dakota School of Mines and Technology | Date: 2010-04-30
A method and apparatus for determining standardized carbon emission reduction credits is disclosed. General regional data and site-specific data, if available, are input into a carbon sequestration model to determine the approximate change in the level of carbon compounds stored in a media, such as soil, over a specified period of time. An uncertainty analysis is conducted on the results to quantify and normalize carbon emission reduction credits. Standardized carbon emission reduction credits may be compiled for trade and other carbon emission reduction credits are placed in reserve.
South Dakota School of Mines and Technology | Date: 2014-03-14
An optically scannable code antenna is provided. Encoded matrix codes are printed with electrically conductive material on a substrate. An antenna pattern is generated on the substrate from the electrically conductive material. Enclosed information in the matrix code and accessible via the antenna pattern is provided. At least a portion of the antenna pattern is also a portion of the matrix code. Signals are transmitted and received from the antenna pattern made up of a portion of the matrix code formed on the substrate by electrically conductive materials. Authentication and security measures using the matrix code and signal from the antenna pattern are also provided.