44 research outputs found
Concert recording 2016-09-30
[Track 1]. All over now / Jacob Hertzog -- [Track 2]. In your own sweet way / Dave Brubeck -- [Track 3]. Hands on [Track 4]. Sky [Track 5]. Summer 81 [Track 6]. Star drops [Track 7]. Gently darling [Track 8]. Common ground / Hertzog -- [Track 9]. Equinox / John Coltrane
Innovative Crossed-Field Devices for the Generation of High Power Microwaves
Modern High Power Microwave (HPM) initiatives pursue challenges in fundamental science, such as fusion research and particle accelerators, as well as industrial applications and homeland security. RADAR, telecommunications, and counter-IED (improvised explosive device) measures also rely on HPM. Crossed-field devices, like the magnetron and magnetically insulated line oscillator (MILO), are a subclass of microwave sources capable of delivering HPM. This dissertation describes the theory, simulation, and design processes applied to produce novel contributions in two separate projects, one a relativistic magnetron and the other a MILO.
The magnetron is an inherently narrowband source, which is undesirable for applications such as counter-IED technologies. Past Recirculating Planar Magnetron (RPM) concepts have proven multispectral microwave generation in magnetrons, and the Harmonic-RPM was designed to expand and further understand these capabilities. In the innovative configuration of this dissertation, the HRPM implements a 1 GHz, L-Band Oscillator (LBO) and a 2 GHz, S-Band Oscillator (SBO) on the same side of the planar cathode, both that are made frequency-agile by leveraging the novel phenomenon of harmonic frequency locking. An experimental investigation of harmonic frequency locking between the LBO and SBO demonstrated the LBO can be used to control the SBO frequency and phase through harmonic beam content, and the SBO responds to this excitation at varying degrees depending on its quality factor. In the low quality factor experiment, the HRPM was driven at 255 ± 19 kV, 1.23 ± 0.32 kA, producing microwave bursts up to 40 MW with shot-averaged pulse duration of 77 ± 17 ns at 7.3 ± 2.4% total efficiency. When the HRPM was properly tuned to excite the SBO on resonance in the low quality factor experiment, the shot-averaged SBO power was 28 ± 9 MW at 2.102 GHz ± 1.5 MHz. Harmonic frequency locking enabled tuning of the SBO over a range of 33 MHz in this experiment, corresponding to 1.6% tunability. By reversing electron rotation direction by the magnetic field, it was shown that the SBO was no longer influenced by the harmonic content of the LBO-modulated beam.
The MILO is a variant of the magnetron, differentiating itself in its method of producing the magnetic field for synchronous interaction. The magnetron uses permanent magnets or pulsed solenoidal coils, whereas the MILO magnetic field is established by large, pulsed currents along the central axis of the device. The vast majority of MILO devices in the literature operate at a low impedance (V/I) of roughly 10 Ω and typically 50-60 kA, resulting in efficiencies commonly in the single digits of percent. The MILO investigated in this dissertation was the first to demonstrate oscillations at less than 10 kA currents, at -240 kV for an impedance of 25-30 Ω. Microwave bursts were observed up to 25 MW at 1.5% efficiency with shot-averaged frequency and pulse duration of 993 ± 7 MHz and 118 ± 43 ns, respectively. The shot-averaged output power was highly irreproducible at 10 ± 7 MW, and is significantly lower than simulation estimates. These experiments were compared with a contemporary theoretical treatment of Brillouin flow in the coaxial MILO geometry, which revealed consistent device operation in a unique condition near the Hull cutoff condition.PHDNuclear Engineering & Radiological SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/169812/1/drupac_1.pd
Concert recording 2018-02-21
[Track 1]. Don\u27t bother [Track 2]. Cozy [Track 3]. Cardinal\u27s flight [Track 4]. Planet of the tardigrades [Track 5]. Gently darling and Free improv [Track 6]. Honest man [Track 7]. Devil and a daydream / Jake Hertzog
Concert recording 2016-05-04
[Track 01]. Duo for flute and piano. Flowing ; [Track 02]. Poetic, somewhat mournful ; Lively, with bounce / Aaron Copland -- [Track 03]. Serenade no. 10, op. 79. Larghetto ; [Track 04]. Allegro comodo ; [Track 05]. Andante grazioso ; [Track 06]. Andante cantabile ; [Track 07]. Allegretto ; [Track 08]. Scherzando ; [Track 09]. Adagietto ; [Track 10]. Vivo / Vincent Persichetti -- [Track 11]. Toward the sea. The night ; [Track 12]. Moby Dick ; [Track 13]. Cape Cod / Toru Takemitsu -- [Track 14]. Oshokun (Lady Wang Zhao Jun) / unknown -- [Track 15]. Horai, traditional honkyoku original pieces of the Kokutai-ji school / unknown -- [Track 16]. Flute sonata in D, op. 94. Moderato ; [Track 17]. Scherzo : presto ; [Track 18]. Andante ; [Track 19]. Allegro con brio / Sergei Prokofiev
High Power Amplifier and Power Supply
A document discusses the creation of a high-voltage power supply (HVPS) that is able to contain voltages up to -20 kV, keep electrical field strengths to below 200 V/mil (approximately equal to 7.87 kV/mm), and can provide a 200-nanosecond rise/fall time focus modulator swinging between cathode potential of 16.3 kV and -19.3 kV. This HVPS can protect the 95-GHz, pulsed extended interaction klystron (EIK) from arcs/discharges from all sources, including those from within the EIK fs vacuum envelope. This innovation has a multi-winding pulse transformer design, which uses new winding techniques to provide the same delays and rise/fall times (less than 10 nanoseconds) at different potential levels ranging from -20 kV to -16 kV. Another feature involves a high-voltage printed-wiring board that was corona-free at -20 kV DC with a 3- kV AC swing. The corona-free multilayer high-voltage board is used to simulate fields of less than 200 V/mil (approximately equal to 7.87 kV/mm) at 20 kV DC. Drive techniques for the modulator FETs (field-effect transistors) (four to 10 in a series) were created to change states (3,000-V swing) without abrupt steps, while still maintaining required delays and transition times. The packing scheme includes a potting mold to house a ten-stage modulator in the space that, in the past, only housed a four-stage modulator. Problems keeping heat down were solved using aluminum oxide substrate in the high-voltage section to limit temperature rise to less than 10 while withstanding -20 kV DC voltage and remaining corona-free
Using photo-elicitation to understand reasons for repeated self-harm: a qualitative study
Background: Reasons for self-harm are not well understood. One of the reasons for this is that first-hand accounts are usually elicited using traditional interview and questionnaire methods. This study aims to explore the acceptability of using an approach (photo-elicitation) that does not rely on solely verbal or written techniques, and to make a preliminary assessment of whether people can usefully employ images to support a discussion about the reasons why they self-harm.
Method: Interviews with eight participants using photo elicitation, a method in which photographs produced by the participant are used as a stimulus and guide within the interview.
Results: Participants responded positively to using images to support a discussion about their self-harm and readily incorporated images in the interview. Four main themes were identified representing negative and positive or adaptive purposes of self-harm: self-harm as a response to distress, self-harm to achieve mastery, self-harm as protective and self-harm as a language or form of communication.
Conclusions: Employing this novel approach was useful in broadening our understanding of self-harm
The management of repair in human computer interaction
SIGLEAvailable from British Library Document Supply Centre- DSC:4335.26205(HPL--93-48) / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Remote homeplace communication What is it like and how might we support it
SIGLEAvailable from British Library Document Supply Centre-DSC:4335.26205(97-85) / BLDSC - British Library Document Supply CentreGBUnited Kingdo