121 research outputs found
Comparing clusterings and numbers of clusters by aggregation of calibrated clustering validity indexes
No full textAkhanli, Serhat Emre/0000-0001-7173-3277WOS: 000543319300001A key issue in cluster analysis is the choice of an appropriate clustering method and the determination of the best number of clusters. Different clusterings are optimal on the same data set according to different criteria, and the choice of such criteria depends on the context and aim of clustering. Therefore, researchers need to consider what data analytic characteristics the clusters they are aiming at are supposed to have, among others within-cluster homogeneity, between-clusters separation, and stability. Here, a set of internal clustering validity indexes measuring different aspects of clustering quality is proposed, including some indexes from the literature. Users can choose the indexes that are relevant in the application at hand. In order to measure the overall quality of a clustering (for comparing clusterings from different methods and/or different numbers of clusters), the index values are calibrated for aggregation. Calibration is relative to a set of random clusterings on the same data. Two specific aggregated indexes are proposed and compared with existing indexes on simulated and real data.EPSRCEngineering & Physical Sciences Research Council (EPSRC) [EP/K033972/1]The work of the second author was supported by EPSRC grant EP/K033972/1
Focal waveform of a prolate-spheroidal impulse radiating antenna (IRA)
No full textImpulse Radiating Antennas (IRAs) are designed to radiate very fast pulses in a narrow beam with low dispersion and high field amplitude. For this reason they have been used in a variety of applications.
IRAs have been developed for the transient far-field region using paraboloidal reflectors. However, in this dissertation we focus on the near field region and develop the field waveform at the second focus of a prolate-spheroidal IRA. Recent research has shown that it is possible to kill certain skin cancers by the application of fast, high-amplitude electric-field pulses. This has been accomplished by the insertion of electrodes near the tumor, with direct contact from a high-voltage pulse generator. It has been suggested that it would be desirable to be able to apply fast, high-electric-field pulses without direct contact for this biological application, i.e., to irradiate them using an antenna from a distance.
Analytical, numerical and experimental behaviors for the focal waveforms of two and four-feed arm prolate-spheroidal IRAs are explored. With appropriate choice of the driving waveform we maximize the impulse field at the second focus. The focal waveform of a prolate-spheroidal IRA has been explained theoretically, verified experimentally and simulated using the CST-MWS (Microwave Studio) software. Finally, different lens design procedures are discussed for a prolate-spheroidal IRA for better concentrating the energy from an impulse.Air Force Office of Scientific ResearchDoctor of Computer EngineeringDoctoralUniversity of New Mexico. Dept. of Electrical and Computer EngineeringSchamiloglu, EdlChristodoulou, Chrostos G.Baum, Carl E.Stone, Ale
Focal waveform of a prolate-spheroidal impulse radiating antenna (IRA)
No full textImpulse Radiating Antennas (IRAs) are designed to radiate very fast pulses in a narrow beam with low dispersion and high field amplitude. For this reason they have been used in a variety of applications. IRAs have been developed for the transient far-field region using paraboloidal reflectors. However, in this dissertation we focus on the near field region and develop the field waveform at the second focus of a prolate-spheroidal IRA. Recent research has shown that it is possible to kill certain skin cancers by the application of fast, high-amplitude electric-field pulses. This has been accomplished by the insertion of electrodes near the tumor, with direct contact from a high-voltage pulse generator. It has been suggested that it would be desirable to be able to apply fast, high-electric-field pulses without direct contact for this biological application, i.e., to irradiate them using an antenna from a distance. Analytical, numerical and experimental behaviors for the focal waveforms of two and four-feed arm prolate-spheroidal IRAs are explored. With appropriate choice of the driving waveform we maximize the impulse field at the second focus. The focal waveform of a prolate-spheroidal IRA has been explained theoretically, verified experimentally and simulated using the CST-MWS (Microwave Studio) software. Finally, different lens design procedures are discussed for a prolate-spheroidal IRA for better concentrating the energy from an impulse
ATLAS LINKS Electronically Steered Aperture Array System
No full textNASA GSFC and ATLAS Space Operations, Inc. are collaborating through the Space Technology Announcement of Collaborative Opportunity (NASA solicitation NNH17ZOA001K) to advance the state of technology of ATLAS LINKS electronically steered aperture array system. ATLAS LINKS system is a state-of-the-art lightweight, high-performance electronically steered aperture array system. This collaboration provides the opportunity to explore the value of ATLAS technology in supporting NASA Near Earth missions
Classification of juvenile myoclonic epilepsy data acquired through scanning electromyography with machine learning algorithms
No full textOsman, Onur (Arel Author), Özekes, Serhat (Arel Author)In this paper, classification of Juvenile Myoclonic Epilepsy (JME) patients and healthy volunteers included into Normal Control (NC) groups was established using Feed-Forward Neural Networks (NN), Support Vector Machines (SVM), Decision Trees (DT), and Na < ve Bayes (NB) methods by utilizing the data obtained through the scanning EMG method used in a clinical study. An experimental setup was built for this purpose. 105 motor units were measured. 44 of them belonged to JME group consisting of 9 patients and 61 of them belonged to NC group comprising ten healthy volunteers. k-fold cross validation was applied to train and test the models. ROC curves were drawn for k values of 4, 6, 8 and 10. 100% of detection sensitivity was obtained for DT, NN, and NB classification methods. The lowest FP number, which was obtained by NN, was 5
Impulsive Field Near the Second Focus Along the Symmetry Axis of a Prolate-Spheroidal IRA
No full textAdvances in Ka-Band Communication System for CubeSats and SmallSats
No full textA study was performed that evaluated the feasibility of Ka-band communication system to provide CubeSat/SmallSat high rate science data downlink with ground antennas ranging from the small portable 1.2m/2.4m to apertures 5.4M, 7.3M, 11M, and 18M, for Low Earth Orbit (LEO) to Lunar CubeSat missions. This study included link analysis to determine the data rate requirement, based on the current TRL of Ka-band flight hardware and ground support infrastructure. Recent advances in Ka-band transceivers and antennas, options of portable ground stations, and various coverage distances were included in the analysis. The link/coverage analysis results show that Cubesat/Smallsat missions communication requirements including frequencies and data rates can be met by utilizing Near Earth Network (NEN) Ka-band support with 2 W and high gain (>6 dBi) antennas
CubeSat Communication Direction and Capabilities at Morehead State University and NASA Goddard Space Flight Center, Wallops Flight Facility
No full textThe Wallops 18-Meter diameter UHF-Band and the Morehead State 21-Meter diameter current S-band and future X-Band and UHF-Band CubeSat Groundstations answer a growing need for high data rate from CubeSats over government licensed frequencies. About ten years ago, when CubeSats began, they were nothing more than simple science experiments, typically consisting of a camera and a low data rate radio. The success and wide community support for the National Science Foundation (NSF) CubeSat Program combined with the increasing number of NASA proposals that utilize CubeSats, and other large government organizations that have started funding CubeSats, demonstrates the maturation of the CubeSat platform. The natural gain provided by the large diameter UHF-, X- and S-Band Groundstations enables high data rates (e.g. 1.5 Mbit, 150 times the typical 9.6 Kbit for CubeSats over UHF). Government funded CubeSats using amateur radio frequencies violate the intent of the amateur radio service and it is a violation of National Telecommunications Information Administration (NTIA) rules for a government funded ground station to use amateur radio frequencies to communicate with CubeSats. The NSF has led the charge in finding a suitable government frequency band for CubeSats. Although amateur frequency licensing is really easy and fast to obtain, it limits downlink data rate capability due to narrow spectrum bandwidth allocation. In addition to limited bandwidth allocation, using unencrypted and published downlink telemetry data, easily accessible by any receiver, has not satisfied the needs of universities, industry and government agencies. After completing a decade mainly operating at the amateur radio frequency and using inexpensive but unreliable amateur commercial off-the-shelf (COTS) space and ground hardware, the CubeSat community is looking for different CubeSat and ground system communication solutions to support their current and future needs
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