Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 32 for “"VLF"”.
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VLF instrumentation for ground-based D-region studies
National Aeronautics and Space Administration Grant NsG-511
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Radiation of VLF/ELF waves from a magnetospheric tether
… as a way to try to solve this problem through VLF/ELF transmissions in the ionosphere, which will create a pitch-angle scattering of these energetic particles with some of them falling into their loss cone, thus reentering the Earth. The aim of this thesis is to develop an analytical model of …
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Nonlinear ionospheric propagation effects on UHF and VLF radio signals
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991.
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Remote measurement of ELF/VLF radio emissions by lightning and ground-based transmitters
… waves in the very low frequency (VLF, 3-30 kHz) and extremely low frequency (ELF, 3-3000 Hz) bands propagate extremely well in the cavity between the earth and the ionosphere with low attenuation. Because of this, radio waves emitted in this frequency range can be measured at …
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An investigation of factors which degrade phase accuracy in a VLF relative navigation system
A VLF relative navigation system makes use of the fact that, at any given point on the earth, phase delay of a received VLF signal is highly stable and predictable. As the receiver is physically moved, phase delay changes linearly with distance from the transmitting station, so that by keeping …
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Design considerations for the implementation of the front end of an optimum VLF receiver
Thesis: Elec. E., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 1976
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Measurement of the conjugate propagation of VLF waves by matched filter and application to ionospheric diagnosis
Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.
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Whistler Waves Detection - Investigation of modern machine learning techniques to detect and characterise whistler waves
… pulses that routinely cause very low frequency (VLF) waves to propagate across hemispheres along geomagnetic field lines. VLF antenna receivers can be used to detect these whistler waves generated by these lightning strokes. The particular time/frequency dependence of the received whistler wave …
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A sudden ionospheric disturbances monitor
… space into a guided wave into the receiver. A VLF receiver was also considered, which would incorporate all the signal processing and finally a data-logging device after the receiver to act as an interface between the analogue natural events and the digital interface to record data to a PC. At …
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New Way of Generating Electromagnetic Waves Using Permanent Magnet
… harsh environment requires very-low-frequency (VLF) or ultra-low-frequency (ULF) signals to penetrate lossy media that block high-frequency signals. Furthermore, recent advances in neuroscience have demonstrated the potential of VLF and ULF electromagnetic (EM) waves for studying brain function …
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Sleep under stress: the complex web of fear, hypervigilance and mental health in a low socioeconomic status community in South Africa
… very low, low and high frequency power measures (VLF, LF and HF power, respectively). VLF and HF power reflect sympathetic withdrawal and parasympathetic input, respectively while LF is understood to reflect a combination of sympathetic and parasympathetic input. Lower HRV has previously been …
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Structure of the polar electrojet antenna
… in the lower ionosphere, resulting in ELF/VLF radiation at the modulation frequency. Measurements of the radiation, along with analytic and numerical models, suggest that a vertical loop with a scale size of 10 km is the dominant current structure excited during the experiments.
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Control and monitoring of Variable- Leakage-Flux IPMSM
… y las máquinas de flujo de dispersión variable (VLF-PMSMs) son diseñadas apra reducir o incluso eliminar la inyección de corriente de debilitamiento de flujo y sus efectos adversos. Las VF-PMSMs son capaces de cambiar el estado de magnetización de sus PMs durante su funcionamiento, pero este …
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Analysis of Heart Rate Variability in Female Patient with Overactive Bladder
… 통계적으로 유의하게 감소하였고, 이외의 다른 지표인 very low frequency (VLF), low frequency (LF)와 LF/HF ratio에서는 통계학적으로 두 군간의 유의한 차이를 보이지 않았다 결론: 과민성 방광 환자에서 심박동수 변이 지표는 TP, HF에서 대조군에 비하여 통계적으로 의미 있는 감소를 보였다. 이러한 결과는 과민성 방광 환자에서 전반적인 자율신경계의 활성도가 감소되어 있음을 의미한다고 할 수 있다. 그러므로 자율신경계의 활성도 감소가 과민성 방광의 하나의 원인이 될 수 있다고 사료된다."
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Excitation of forced ion acoustic waves, large plasma sheets, and magnetic field fluctuations over Gakona, Alaska
… our own optical (ASIS) and radio instruments (VLF receiving system of IRIS) aided by GPS satellites as well as AMISR radar at Poker Flat, Alaska. We suggest that "Forced ion acoustic waves" detected by MUIR radar on Oct. 29 during 6:20-6:30 UT arise from keV electron precipitation associated …
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Psychological Monitoring: Detecting Real-Time Emotional Changes
… Kalman filter (EKF) to extract frequencies (VLF-UHF) and standard heart rate variability metrics (HRV). These features were mapped onto emotional dimensions using supervised partial least squares (PLS) regressions from behavioral validation measures: facial electromyograph (EMG) for valence, …
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Midlatitude D Region Variations Measured from Broadband Radio Atmospherics
<p>The high power, broadband very low frequency (VLF, 3--30 kHz) and extremely low frequency (ELF, 3--3000 Hz) electromagnetic waves generated by lightning discharges and propagating in the Earth-ionosphere waveguide can be used to measure the average electron density profile of the lower …
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Skuldir heimilanna og hagkerfið
Skuldir heimilanna sem hlutfall af VLF hafa verið að aukast hér á landi og undirliggjandi þættir í þeirri þróun eru, hækkun fasteignaverðs, aukið aðgengi að lánsfjármagni og lækkun vaxta. Þessi þróun hefur fyllt heimilin bjartsýni um framtíðina en jafnframt gert þau viðkvæmari fyrir efnahagslegum …
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Penggunaan teknik bio maklumbalas bagi mengukur ciri-ciri disiplin dan tanggungjawab dalam kalangan mahasiswa
… dan skor spektrum kuasa frekuensi sangat rendah (VLF) merupakan individu yang mempunyai pencapaian akademik cemerlang. Kesimpulannya, hasil dapatan kajian ini menunjukkan teknik bio maklumbalas merupakan salah satu kaedah pengukuran integriti yang berkesan dan boleh digunapakai serta boleh menjadi …
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Investigation of the baroreflex of the rat : steady state and dynamic features
… working area of the baroreflex system is in the VLF region of the blood pressure spectra. The estimated system transportation lag was 1.07s, which would cause the baroreflex system to oscillate at frequencies around 0.4 Hz. Analyses demonstrated that it is not likely that the baroreflex is …
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