High power broadband millimeter wave TWTs

NASA Astrophysics Data System (ADS)

James, Bill G.

1999-05-01

In the early 1980's the requirement for high power broadband millimeter wave sources encouraged the development of microwave vacuum device amplifiers for radar and communication systems. Many government funded programs were implemented for the development of high power broadband millimeter wave amplifiers that would meet the needs of the high power community. The tube design capable of meeting these goals was the slow wave coupled cavity traveling wave device, which had a proven technology base at the lower frequencies (X Band). However scaling this technology to the millimeter frequencies had severe shortcomings in both thermal and manufacturing design. These shortcomings were overcome with the development of the Ladder Circuit technology. In conjunction with the circuit development high power electron beam systems had to be developed for the generation of high rf powers. These beam systems had to be capable of many megawatts of beam power density and high current densities. The cathode technology required to be capable of operating at current densities of 10 amperes per square centimeter at long pulse lengths and high duty cycle. Since the introduction of the Ladder Circuit technology a number of high power broadband millimeter wave amplifiers have been developed using this technology, and have been deployed in operating radar and communication systems. Broadband millimeter wave sources have been manufactured in the frequency range from 27 GHz to 100 GHz with power levels ranging from 100 watts to 50 kilowatts. Today the power levels achieved by these devices are nearing the limits of this technology; therefore to gain a significant increase in power at the millimeter wave frequencies other technologies will have to be considered particularly fast wave devices. This paper will briefly review the ladder circuit technology and present the designs of a number of broadband high power devices developed at Ka and W band. The discussion will include the beam systems employed in these devices which are the highest power density linear beams generated to date. In conclusion the limits of the power generating capability of this technology will be presented.

High Power Broadband Millimeter Wave TWTs

NASA Astrophysics Data System (ADS)

James, Bill G.

1998-04-01

In the early 1980's the requirement for high power broadband millimeter wave sources encouraged the development of microwave vacuum device amplifiers for radar and communication systems. Many government funded programs were implemented for the development of high power broadband millimeter wave amplifiers that would meet the needs of the high power community. The tube design capable of meeting these goals was the slow wave coupled cavity traveling wave device, which had a proven technology base at the lower frequencies (X Band). However scaling this technology to the millimeter frequencies had severe shortcomings in both thermal and manufacturing design. These shortcomings were overcome with the development of the Ladder Circuit technology. In conjunction with the circuit development high power electron beam systems had to be developed for the generation of high rf powers. These beam systems had to be capable of many megawatts of beam power density and high current densities. The cathode technology required to be capable of operating at current densities of 10 amperes per square centimeter at long pulse lengths and high duty cycle. Since the introduction of the Ladder Circuit technology a number of high power broadband millimeter wave amplifiers have been developed and deployed in operating radar and communication systems. Broadband millimeter wave sources have been manufactured in the frequency range from 27 GHz to 100 GHz with power levels ranging from 100 watts CW to 10 kilowatts Peak at W band over a 2 GHz bandwidth. Also a 50 kW peak power and 10 kW average power device at Ka band with 2 GHz bandwidth has been developed. Today the power levels achieved by these devices are nearing the limits of this technology; therefore to gain a significant increase in power at the millimeter wave frequencies, other technologies will have to be considered, particularly fast wave devices. This paper will briefly review the ladder circuit technology and present the designs of a number of broadband high power devices developed at Ka and W band. The discussion will include the beam systems employed in these devices which are the highest power density linear beams generated to date. In conclusion the limits of the power generating capability of this technology will be presented.

Frequency domain laser velocimeter signal processor

NASA Technical Reports Server (NTRS)

Meyers, James F.; Murphy, R. Jay

1991-01-01

A new scheme for processing signals from laser velocimeter systems is described. The technique utilizes the capabilities of advanced digital electronics to yield a signal processor capable of operating in the frequency domain maximizing the information obtainable from each signal burst. This allows a sophisticated approach to signal detection and processing, with a more accurate measurement of the chirp frequency resulting in an eight-fold increase in measurable signals over the present high-speed burst counter technology. Further, the required signal-to-noise ratio is reduced by a factor of 32, allowing measurements within boundary layers of wind tunnel models. Measurement accuracy is also increased up to a factor of five.

Towards coherent combining of X-band high power microwaves: phase-locked long pulse radiations by a relativistic triaxial klystron amplifier

PubMed Central

Ju, Jinchuan; Zhang, Jun; Qi, Zumin; Yang, Jianhua; Shu, Ting; Zhang, Jiande; Zhong, Huihuang

2016-01-01

The radio-frequency breakdown due to ultrahigh electric field strength essentially limits power handling capability of an individual high power microwave (HPM) generator, and this issue becomes more challenging for high frequency bands. Coherent power combining therefore provides an alternative approach to achieve an equivalent peak power of the order of ∼100 GW, which consequently provides opportunities to explore microwave related physics at extremes. The triaxial klystron amplifier (TKA) is a promising candidate for coherent power combing in high frequency bands owing to its intrinsic merit of high power capacity, nevertheless phase-locked long pulse radiation from TKA has not yet been obtained experimentally as the coaxial structure of TKA can easily lead to self-excitation of parasitic modes. In this paper, we present investigations into an X-band TKA capable of producing 1.1 GW HPMs with pulse duration of about 103 ns at the frequency of 9.375 GHz in experiment. Furthermore, the shot-to-shot fluctuation standard deviation of the phase shifts between the input and output microwaves is demonstrated to be less than 10°. The reported achievements open up prospects for accomplishing coherent power combining of X-band HPMs in the near future, and might also excite new development interests concerning high frequency TKAs. PMID:27481661

Towards coherent combining of X-band high power microwaves: phase-locked long pulse radiations by a relativistic triaxial klystron amplifier.

PubMed

Ju, Jinchuan; Zhang, Jun; Qi, Zumin; Yang, Jianhua; Shu, Ting; Zhang, Jiande; Zhong, Huihuang

2016-08-02

The radio-frequency breakdown due to ultrahigh electric field strength essentially limits power handling capability of an individual high power microwave (HPM) generator, and this issue becomes more challenging for high frequency bands. Coherent power combining therefore provides an alternative approach to achieve an equivalent peak power of the order of ∼100 GW, which consequently provides opportunities to explore microwave related physics at extremes. The triaxial klystron amplifier (TKA) is a promising candidate for coherent power combing in high frequency bands owing to its intrinsic merit of high power capacity, nevertheless phase-locked long pulse radiation from TKA has not yet been obtained experimentally as the coaxial structure of TKA can easily lead to self-excitation of parasitic modes. In this paper, we present investigations into an X-band TKA capable of producing 1.1 GW HPMs with pulse duration of about 103 ns at the frequency of 9.375 GHz in experiment. Furthermore, the shot-to-shot fluctuation standard deviation of the phase shifts between the input and output microwaves is demonstrated to be less than 10°. The reported achievements open up prospects for accomplishing coherent power combining of X-band HPMs in the near future, and might also excite new development interests concerning high frequency TKAs.

Note: A kinematic shaker system for high amplitude, low frequency vibration testing

NASA Astrophysics Data System (ADS)

Swaminathan, Anand; Poese, Matthew E.; Smith, Robert W. M.; Garrett, Steven L.

2015-11-01

This note describes a shaker system capable of high peak-velocity, large amplitude, low frequency, near-sinusoidal excitation that has been constructed and employed in experiments on the inhibition of Rayleigh-Bénard convection using acceleration modulation. The production of high peak-velocity vibration is of interest in parametric excitation problems of this type and reaches beyond the capabilities of standard electromagnetic shakers. The shaker system described employs a kinematic linkage to two counter-rotating flywheels, driven by a variable-speed electrical motor, producing peak-to-peak displacements of 15.24 cm to a platform mounted on two guide rails. In operation, this shaker has been demonstrated to produce peak speeds of up to 3.7 m/s without failure.

Coherent Frequency Reference System for the NASA Deep Space Network

NASA Technical Reports Server (NTRS)

Tucker, Blake C.; Lauf, John E.; Hamell, Robert L.; Gonzaler, Jorge, Jr.; Diener, William A.; Tjoelker, Robert L.

2010-01-01

The NASA Deep Space Network (DSN) requires state-of-the-art frequency references that are derived and distributed from very stable atomic frequency standards. A new Frequency Reference System (FRS) and Frequency Reference Distribution System (FRD) have been developed, which together replace the previous Coherent Reference Generator System (CRG). The FRS and FRD each provide new capabilities that significantly improve operability and reliability. The FRS allows for selection and switching between frequency standards, a flywheel capability (to avoid interruptions when switching frequency standards), and a frequency synthesis system (to generate standardized 5-, 10-, and 100-MHz reference signals). The FRS is powered by redundant, specially filtered, and sustainable power systems and includes a monitor and control capability for station operations to interact and control the frequency-standard selection process. The FRD receives the standardized 5-, 10-, and 100-MHz reference signals and distributes signals to distribution amplifiers in a fan out fashion to dozens of DSN users that require the highly stable reference signals. The FRD is also powered by redundant, specially filtered, and sustainable power systems. The new DSN Frequency Distribution System, which consists of the FRS and FRD systems described here, is central to all operational activities of the NASA DSN. The frequency generation and distribution system provides ultra-stable, coherent, and very low phase-noise references at 5, l0, and 100 MHz to between 60 and 100 separate users at each Deep Space Communications Complex.

Bipolar-power-transistor-based limiter for high frequency ultrasound imaging systems.

PubMed

Choi, Hojong; Yang, Hao-Chung; Shung, K Kirk

2014-03-01

High performance limiters are described in this paper for applications in high frequency ultrasound imaging systems. Limiters protect the ultrasound receiver from the high voltage (HV) spikes produced by the transmitter. We present a new bipolar power transistor (BPT) configuration and compare its design and performance to a diode limiter used in traditional ultrasound research and one commercially available limiter. Limiter performance depends greatly on the insertion loss (IL), total harmonic distortion (THD) and response time (RT), each of which will be evaluated in all the limiters. The results indicated that, compared with commercial limiter, BPT-based limiter had less IL (-7.7 dB), THD (-74.6 dB) and lower RT (43 ns) at 100 MHz. To evaluate the capability of these limiters, they were connected to a 100 MHz single element transducer and a two-way pulse-echo test was performed. It was found that the -6 dB bandwidth and sensitivity of the transducer using BPT-based limiter were better than those of the commercial limiter by 22% and 140%, respectively. Compared to the commercial limiter, BPT-based limiter is shown to be capable of minimizing signal attenuation, RT and THD at high frequencies and is thus suited for high frequency ultrasound applications. Copyright © 2013 Elsevier B.V. All rights reserved.

Performances of OsO(4) stabilized CO(2) lasers as optical frequency standards near 29 THz.

PubMed

Daussy, C; Ducos, F; Rovera, G D; Acef, O

2000-01-01

In this paper, we report on the metrological capabilities of CO (2)/OsO(4) optical frequency standards operating around 29 THz. Those frequency standards are currently involved in various fields, such as frequency metrology, high resolution spectroscopy, and Rydberg constant measurements. The most impressive features of the standards lies in the 10(-15) level frequency stability allied to a long-term reproducibility (1 yr) of 1.3x10 (-13).

Global Broadcast Service (GBS)

DTIC Science & Technology

2013-12-01

as to be unusable by smaller and more mobile units. To this end, GBS currently uses broadcast payloads on two Ultra-High Frequency Follow-On ( UFO ...operational on UFO satellites 8, 9, 10. - Full Satellite Broadcast Manager capability. - Field 20% of JPO Receive Suites (19 units). - Personnel training...capabilities. - Augment UFO GBS with leased commercial satellite services to cover gaps over CONUS. - Demonstrate smart push and user pull capability

Development of a high-frequency and large-stroke fatigue testing system for rubber

NASA Astrophysics Data System (ADS)

Chen, Gang; Wu, Hao; Gao, Jianwen; Lin, Qiang

2017-04-01

The limited capabilities of current fatigue testing machines have resulted in studies on the fatigue behavior of rubber under large-displacement amplitude and high frequency being very sparse. In this study, a fatigue testing system that can carry out large-displacement amplitude and high-frequency fatigue tests on rubber was developed using a moving magnet voice coil motor (MMVCM) actuator, with finite element analysis applied to analyze the thrust of the MMVCM actuator. The results of a series of cyclic tension tests conducted on vulcanized natural rubber specimens using the developed fatigue testing system verify that it has high precision, low noise, large-stroke, and high-frequency characteristics. Further, the load frame with the developed MMVCM actuator is feasible for material testing, especially for large-stroke and high-frequency fatigue tests.

Mechanical design and fabrication of the VHF-gun, the Berkeley normal-conducting continuous-wave high-brightness electron source

NASA Astrophysics Data System (ADS)

Wells, R. P.; Ghiorso, W.; Staples, J.; Huang, T. M.; Sannibale, F.; Kramasz, T. D.

2016-02-01

A high repetition rate, MHz-class, high-brightness electron source is a key element in future high-repetition-rate x-ray free electron laser-based light sources. The VHF-gun, a novel low frequency radio-frequency gun, is the Lawrence Berkeley National Laboratory (LBNL) response to that need. The gun design is based on a normal conducting, single cell cavity resonating at 186 MHz in the VHF band and capable of continuous wave operation while still delivering the high accelerating fields at the cathode required for the high brightness performance. The VHF-gun was fabricated and successfully commissioned in the framework of the Advanced Photo-injector EXperiment, an injector built at LBNL to demonstrate the capability of the gun to deliver the required beam quality. The basis for the selection of the VHF-gun technology, novel design features, and fabrication techniques are described.

Mechanical design and fabrication of the VHF-gun, the Berkeley normal-conducting continuous-wave high-brightness electron source.

PubMed

Wells, R P; Ghiorso, W; Staples, J; Huang, T M; Sannibale, F; Kramasz, T D

2016-02-01

A high repetition rate, MHz-class, high-brightness electron source is a key element in future high-repetition-rate x-ray free electron laser-based light sources. The VHF-gun, a novel low frequency radio-frequency gun, is the Lawrence Berkeley National Laboratory (LBNL) response to that need. The gun design is based on a normal conducting, single cell cavity resonating at 186 MHz in the VHF band and capable of continuous wave operation while still delivering the high accelerating fields at the cathode required for the high brightness performance. The VHF-gun was fabricated and successfully commissioned in the framework of the Advanced Photo-injector EXperiment, an injector built at LBNL to demonstrate the capability of the gun to deliver the required beam quality. The basis for the selection of the VHF-gun technology, novel design features, and fabrication techniques are described.

Characteristics of a four element gyromagnetic nonlinear transmission line array high power microwave source.

PubMed

Johnson, J M; Reale, D V; Krile, J T; Garcia, R S; Cravey, W H; Neuber, A A; Dickens, J C; Mankowski, J J

2016-05-01

In this paper, a solid-state four element array gyromagnetic nonlinear transmission line high power microwave system is presented as well as a detailed description of its subsystems and general output capabilities. This frequency agile S-band source is easily adjusted from 2-4 GHz by way of a DC driven biasing magnetic field and is capable of generating electric fields of 7.8 kV/m at 10 m correlating to 4.2 MW of RF power with pulse repetition frequencies up to 1 kHz. Beam steering of the array at angles of ±16.7° is also demonstrated, and the associated general radiation pattern is detailed.

Characteristics of a four element gyromagnetic nonlinear transmission line array high power microwave source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, J. M., E-mail: jared.johnson@ttu.edu; Reale, D. V.; Garcia, R. S.

2016-05-15

In this paper, a solid-state four element array gyromagnetic nonlinear transmission line high power microwave system is presented as well as a detailed description of its subsystems and general output capabilities. This frequency agile S-band source is easily adjusted from 2-4 GHz by way of a DC driven biasing magnetic field and is capable of generating electric fields of 7.8 kV/m at 10 m correlating to 4.2 MW of RF power with pulse repetition frequencies up to 1 kHz. Beam steering of the array at angles of ±16.7° is also demonstrated, and the associated general radiation pattern is detailed.

Power Supply for Variable Frequency Induction Heating Using MERS Soft-Switching High Frequency Inverter

NASA Astrophysics Data System (ADS)

Isobe, Takanori; Kitahara, Tadayuki; Fukutani, Kazuhiko; Shimada, Ryuichi

Variable frequency induction heating has great potential for industrial heating applications due to the possibility of achieving heating distribution control; however, large-scale induction heating with variable frequency has not yet been introduced for practical use. This paper proposes a high frequency soft-switching inverter for induction heating that can achieve variable frequency operation. One challenge of variable frequency induction heating is increasing power electronics ratings. This paper indicates that its current source type dc-link configuration and soft-switching characteristics can make it possible to build a large-scale system with variable frequency capability. A 90-kVA 150-1000Hz variable frequency experimental power supply for steel strip induction heating was developed. Experiments confirmed the feasibility of variable frequency induction heating with proposed converter and the advantages of variable frequency operation.

An adjustable multi-scale single beam acoustic tweezers based on ultrahigh frequency ultrasonic transducer.

PubMed

Chen, Xiaoyang; Lam, Kwok Ho; Chen, Ruimin; Chen, Zeyu; Yu, Ping; Chen, Zhongping; Shung, K Kirk; Zhou, Qifa

2017-11-01

This paper reports the fabrication, characterization, and microparticle manipulation capability of an adjustable multi-scale single beam acoustic tweezers (SBAT) that is capable of flexibly changing the size of "tweezers" like ordinary metal tweezers with a single-element ultrahigh frequency (UHF) ultrasonic transducer. The measured resonant frequency of the developed transducer at 526 MHz is the highest frequency of piezoelectric single crystal based ultrasonic transducers ever reported. This focused UHF ultrasonic transducer exhibits a wide bandwidth (95.5% at -10 dB) due to high attenuation of high-frequency ultrasound wave, which allows the SBAT effectively excite with a wide range of excitation frequency from 150 to 400 MHz by using the "piezoelectric actuator" model. Through controlling the excitation frequency, the wavelength of ultrasound emitted from the SBAT can be changed to selectively manipulate a single microparticle of different sizes (3-100 μm) by using only one transducer. This concept of flexibly changing "tweezers" size is firstly introduced into the study of SBAT. At the same time, it was found that this incident ultrasound wavelength play an important role in lateral trapping and manipulation for microparticle of different sizes. Biotechnol. Bioeng. 2017;114: 2637-2647. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Extreme-Environment Silicon-Carbide (SiC) Wireless Sensor Suite

NASA Technical Reports Server (NTRS)

Yang, Jie

2015-01-01

Phase II objectives: Develop an integrated silicon-carbide wireless sensor suite capable of in situ measurements of critical characteristics of NTP engine; Compose silicon-carbide wireless sensor suite of: Extreme-environment sensors center, Dedicated high-temperature (450 deg C) silicon-carbide electronics that provide power and signal conditioning capabilities as well as radio frequency modulation and wireless data transmission capabilities center, An onboard energy harvesting system as a power source.

77 FR 70945 - Revisions to the Export Administration Regulations (EAR): Control of Military Electronic...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-28

... subparagraphs ranging from the lowest to the highest operating frequency ranges, with a gap for MMIC power... control high frequency (HF) surface wave radar capable of ``tracking'' surface targets on oceans... surreptitious interception of wire, oral, or electronic communications.'') Paragraph .c would control microwave...

Dual frequency comb metrology with one fiber laser

NASA Astrophysics Data System (ADS)

Zhao, Xin; Takeshi, Yasui; Zheng, Zheng

2016-11-01

Optical metrology techniques based on dual optical frequency combs have emerged as a hotly studied area targeting a wide range of applications from optical spectroscopy to microwave and terahertz frequency measurement. Generating two sets of high-quality comb lines with slightly different comb-tooth spacings with high mutual coherence and stability is the key to most of the dual-comb schemes. The complexity and costs of such laser sources and the associated control systems to lock the two frequency combs hinder the wider adoption of such techniques. Here we demonstrate a very simple and rather different approach to tackle such a challenge. By employing novel laser cavity designs in a mode-locked fiber laser, a simple fiber laser setup could emit dual-comb pulse output with high stability and good coherence between the pulse trains. Based on such lasers, comb-tooth-resolved dual-comb optical spectroscopy is demonstrated. Picometer spectral resolving capability could be realized with a fiber-optic setup and a low-cost data acquisition system and standard algorithms. Besides, the frequency of microwave signals over a large range can be determined based on a simple setup. Our results show the capability of such single-fiber-laser-based dual-comb scheme to reduce the complexity and cost of dual-comb systems with excellent quality for different dual-comb applications.

Wide-field high spatial frequency domain imaging of tissue microstructure

NASA Astrophysics Data System (ADS)

Lin, Weihao; Zeng, Bixin; Cao, Zili; Zhu, Danfeng; Xu, M.

2018-02-01

Wide-field tissue imaging is usually not capable of resolving tissue microstructure. We present High Spatial Frequency Domain Imaging (HSFDI) - a noncontact imaging modality that spatially maps the tissue microscopic scattering structures over a large field of view. Based on an analytical reflectance model of sub-diffusive light from forward-peaked highly scattering media, HSFDI quantifies the spatially-resolved parameters of the light scattering phase function from the reflectance of structured light modulated at high spatial frequencies. We have demonstrated with ex vivo cancerous tissue to validate the robustness of HSFDI in significant contrast and differentiation of the microstructutral parameters between different types and disease states of tissue.

Dual-Polarization, Sideband-Separating, Balanced Receiver for 1.5 THz

NASA Technical Reports Server (NTRS)

Chattopadhyay, Goutman; Ward, John; Manohara, Harish; Siegel, Peter

2009-01-01

A proposed heterodyne receiver would be capable of detecting electromagnetic radiation in both of two orthogonal linear polarizations, separating sidebands, and providing balanced outputs in a frequency band centered at 1.5 THz with a fractional bandwidth greater than 40 percent. Dual polarization, sideband-separating, and balanced-output receivers are well-known and have been used extensively at frequencies up to about 100 GHz; and there was an earlier proposal for such a receiver for frequencies up to 900 GHz. However, the present proposal represents the first realistic design concept for such a receiver capable of operating above 1 THz. The proposed receiver is intended to be a prototype of mass-producible receiver units, operating at frequencies up to 6 THz, that would be incorporated into highly sensitive heterodyne array instruments to be used in astronomical spectroscopic and imaging studies.

Organic Diode Rectifiers Based on a High-Performance Conjugated Polymer for a Near-Field Energy-Harvesting Circuit.

PubMed

Higgins, Stuart G; Agostinelli, Tiziano; Markham, Steve; Whiteman, Robert; Sirringhaus, Henning

2017-12-01

Organic diodes manufactured on a plastic substrate capable of rectifying a high-frequency radio-frequency identification signal (13.56 MHz), with sufficient power to operate an interactive smart tag, are reported. A high-performance conjugated semiconductor (an indacenodithiophene-benzothiadiazole copolymer) is combined with a carefully optimized architecture to satisfy the electrical requirements for an organic-semiconductor-based logic chip. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Diamond Technology Study.

DTIC Science & Technology

1979-06-11

has been conducted into the use of diamond as a TWT helix support material to increase the average output power capability of broadband high frequency...unifilar helix is the one TWT circuit capable of broadband operation with good efficiency, methods to increase jT its power dissipation capability are of...BIBLIOGRAPHY IRa D> AE .,L,-,# ACot .,i n iv 4 I IPT-5413 LIST OF ILLUSTRATIONS Figure No. Title 1 Temperature Differences in a PPM Focused Helix TWT

Optimizing the Navy’s Investment in Space Professionals

DTIC Science & Technology

2011-09-01

UFO Ultra High Frequency Follow-On UHF Ultra High Frequency URL Unrestricted Line USA United States Army USAF United States Air Force USCYBERCOM...LEASAT), and eight UHF Follow-On ( UFO ) satellites all flying in geostationary orbit (GEO). NAVSOC is the principle Navy command that operates, manages...and maintains the DoD’s narrowband UHF capability from five different ground stations. The replacement satellite for the aging UFO system is the

The Next Generation of High-Speed Dynamic Stability Wind Tunnel Testing (Invited)

NASA Technical Reports Server (NTRS)

Tomek, Deborah M.; Sewall, William G.; Mason, Stan E.; Szchur, Bill W. A.

2006-01-01

Throughout industry, accurate measurement and modeling of dynamic derivative data at high-speed conditions has been an ongoing challenge. The expansion of flight envelopes and non-conventional vehicle design has greatly increased the demand for accurate prediction and modeling of vehicle dynamic behavior. With these issues in mind, NASA Langley Research Center (LaRC) embarked on the development and shakedown of a high-speed dynamic stability test technique that addresses the longstanding problem of accurately measuring dynamic derivatives outside the low-speed regime. The new test technique was built upon legacy technology, replacing an antiquated forced oscillation system, and greatly expanding the capabilities beyond classic forced oscillation testing at both low and high speeds. The modern system is capable of providing a snapshot of dynamic behavior over a periodic cycle for varying frequencies, not just a damping derivative term at a single frequency.

High spatial resolution distributed optical fiber dynamic strain sensor with enhanced frequency and strain resolution.

PubMed

Masoudi, Ali; Newson, Trevor P

2017-01-15

A distributed optical fiber dynamic strain sensor with high spatial and frequency resolution is demonstrated. The sensor, which uses the ϕ-OTDR interrogation technique, exhibited a higher sensitivity thanks to an improved optical arrangement and a new signal processing procedure. The proposed sensing system is capable of fully quantifying multiple dynamic perturbations along a 5 km long sensing fiber with a frequency and spatial resolution of 5 Hz and 50 cm, respectively. The strain resolution of the sensor was measured to be 40 nε.

Sensing Surveillance & Navigation

DTIC Science & Technology

2012-03-07

Removing Atmospheric Turbulence Goal: to restore a single high quality image from the observed sequence Prof. Peyman...Computer Sciences – Higher wavelet studies , time-scale, time-frequency transformations, Reduced Signature Targets, Low Probability of Intercept...Range Dependent Beam -patterns •Electronic Steering with Frequency Offsets •Inherent Countermeasure Capability Why? W1(t) W2(t) W3

Small-scale rotor test rig capabilities for testing vibration alleviation algorithms

NASA Technical Reports Server (NTRS)

Jacklin, Stephen A.; Leyland, Jane Anne

1987-01-01

A test was conducted to assess the capabilities of a small scale rotor test rig for implementing higher harmonic control and stability augmentation algorithms. The test rig uses three high speed actuators to excite the swashplate over a range of frequencies. The actuator position signals were monitored to measure the response amplitudes at several frequencies. The ratio of response amplitude to excitation amplitude was plotted as a function of frequency. In addition to actuator performance, acceleration from six accelerometers placed on the test rig was monitored to determine whether a linear relationship exists between the harmonics of N/Rev control input and the least square error (LSE) identification technique was used to identify local and global transfer matrices for two rotor speeds at two batch sizes each. It was determined that the multicyclic control computer system interfaced very well with the rotor system and kept track of the input accelerometer signals and their phase angles. However, the current high speed actuators were found to be incapable of providing sufficient control authority at the higher excitation frequencies.

Investigations of a bearing fault detector for railroad bearings

NASA Technical Reports Server (NTRS)

Wilson, D. S.; Frarey, J. L.

1975-01-01

The laboratory tests are described which were conducted on new and damaged bearings to determine the feasibility of using high-frequency vibration as a diagnostic tool. A high-frequency band pass filter and demodulator was assembled to permit field measurements of the high-frequency vibrations. Field tests were conducted on an actual truck and on an axle assembly run in a grease test rig. These field tests were directed toward demonstration of the suitability and capabilities of the high-frequency technique for field application. Two specific areas of field application were identified as being cost effective for railroad use. One area is the examination of railroad roller bearings at a derailment site, and the second is as a wayside detector to supplement present hot box detectors for defective roller bearings.

The resonant body transistor.

PubMed

Weinstein, Dana; Bhave, Sunil A

2010-04-14

This paper introduces the resonant body transistor (RBT), a silicon-based dielectrically transduced nanoelectromechanical (NEM) resonator embedding a sense transistor directly into the resonator body. Combining the benefits of FET sensing with the frequency scaling capabilities and high quality factors (Q) of internal dielectrically transduced bar resonators, the resonant body transistor achieves >10 GHz frequencies and can be integrated into a standard CMOS process for on-chip clock generation, high-Q microwave circuits, fundamental quantum-state preparation and observation, and high-sensitivity measurements. An 11.7 GHz bulk-mode RBT is demonstrated with a quality factor Q of 1830, marking the highest frequency acoustic resonance measured to date on a silicon wafer.

High-efficiency piezoelectric micro harvester for collecting low-frequency mechanical energy.

PubMed

Li, Xin; Song, Jinhui; Feng, Shuanglong; Xie, Xiong; Li, Zhenhu; Wang, Liang; Pu, Yayun; Soh, Ai Kah; Shen, Jun; Lu, Wenqiang; Liu, Shuangyi

2016-12-02

A single-layer zinc oxide (ZnO) nanorod array-based micro energy harvester was designed and integrated with a piezoelectric metacapacitor. The device presents outstanding low-frequency (1-10 Hz) mechanical energy harvesting capabilities. When compared with conventional pristine ZnO nanostructured piezoelectric harvesters or generators, both open-circuit potential and short-circuit current are significantly enhanced (up to 3.1 V and 124 nA cm -2 ) for a single mechanical knock (∼34 kPa). Higher electromechanical conversion efficiency (1.3 pC/Pa) is also observed. The results indicate that the integration of the piezoelectric metacapacitor is a crucial factor for improving the low-frequency energy harvesting performance. A double piezoelectric-driven mechanism is proposed to explain current higher output power, in which the metacapacitor plays the multiple roles of charge pumping, storing and transferring. An as-fabricated prototype device for lighting an LED demonstrates high power transference capability, with over 95% transference efficiency to the external load.

Non-planar pad-printed thick-film focused high-frequency ultrasonic transducers for imaging and therapeutic applications.

PubMed

Lethiecq, Marc; Lou-Moeller, Rasmus; Ketterling, Jeffrey; Levassort, Franck; Tran-Huu-Hue, Louis Pascal; Filoux, Erwan; Silverman, Ronald H; Wolny, Wanda W

2012-09-01

Pad-printed thick-film transducers have been shown to be an interesting alternative to lapped bulk piezoceramics, because the film is deposited with the required thickness, size, and geometry, thus avoiding any subsequent machining to achieve geometrical focusing. Their electromechanical properties are close to those of bulk ceramics with similar composition despite having a higher porosity. In this paper, padprinted high-frequency transducers based on a low-loss piezoceramic composition are designed and fabricated. High-porosity ceramic cylinders with a spherical top surface are used as the backing substrate. The transducers are characterized in view of imaging applications and their imaging capabilities are evaluated with phantoms containing spherical inclusions and in different biological tissues. In addition, the transducers are evaluated for their capability to produce high-acoustic intensities at frequencies around 20 MHz. High-intensity measurements, obtained with a calibrated hydrophone, show that transducer performance is promising for applications that would require the same device to be used for imaging and for therapy. Nevertheless, the transducer design can be improved, and simulation studies are performed to find a better compromise between low-power and high-power performance. The size, geometry, and constitutive materials of optimized configurations are proposed and their feasibility is discussed.

High-frequency modulation of the four states of polarization of light with a single phase modulator

NASA Astrophysics Data System (ADS)

Compain, Eric; Drevillon, Bernard

1998-04-01

A method for light polarization modulation is described. It allows us to independently modulate, at a high frequency, the four components of the Stokes vector of light using a single phase modulator. It works in a double-pass configuration: the polarization of light is modulated a first time by the phase modulator, and is then modified by a coupling object before being modulated a second time by the same modulator. The coupling object consists of multiple glass plates, oriented at the Brewster angle, acting as a partial polarizer and in a right angle prism acting as a phase shifter and back reflector. Its polarimetric properties are obtained from refractive index contrast effects, which provides optimized and constant properties over a wide spectral range. The phase modulator can be either an electro-optic modulator providing a very high-frequency capability (up to 100 MHz) or a photoelastic modulator providing a wide spectral range capability. It is robust because there is no moving part and simple to implement because of the presence of one modulation. It displays a high level of sensitivity because all the components are high-frequency modulated. Two applications using this modulator in a polarimeter or in a polarization states generator are described. The four modulations, having the same fundamental frequency, are easily demodulated by numerical data processing. Optimized demodulation processing, adapted to the different kind of phase modulator is described. Its adaptation taking into account the bandwidth limitation and the variation of the sampling phase, are finally presented in the case of a photoelastic modulator.

Microwave soft x-ray microscopy for nanoscale magnetization dynamics in the 5–10 GHz frequency range

DOE PAGES

Bonetti, Stefano; Kukreja, Roopali; Chen, Zhao; ...

2015-09-10

In this study, we present a scanning transmission x-ray microscopy setup combined with a novel microwave synchronization scheme in order to study high frequency magnetization dynamics at synchrotron light sources. The sensitivity necessary to detect small changes of the magnetization on short time scales and nanometer spatial dimensions is achieved by combination of the developed excitation mechanism with a single photon counting electronics that is locked to the synchrotron operation frequency. The required mechanical stability is achieved by a compact design of the microscope. Our instrument is capable of creating direct images of dynamical phenomena in the 5-10 GHz range,more » with 35 nm resolution. When used together with circularly polarized x-rays, the above capabilities can be combined to study magnetic phenomena at microwave frequencies, such as ferromagnetic resonance (FMR) and spin waves. We demonstrate the capabilities of our technique by presenting phase resolved images of a –6 GHz nanoscale spin wave generated by a spin torque oscillator, as well as the uniform ferromagnetic precession with ~0.1° amplitude at –9 GHz in a micrometer-sized cobalt strip.« less

The role of superconductivity in the Space Program: An assessment of present capabilities and future potential

NASA Technical Reports Server (NTRS)

Sullivan, D. B. (Editor)

1978-01-01

Technical subject areas discussed include: (1) high field magnets; (2) magnetometers; (3) digital electronics; (4) high frequency detectors; (5) instruments related to gravitational studies; and (6) ultra high Q cavities. Applications of superconductivity which are of potential interest to NASA were identified.

Low-frequency noise reduction of lightweight airframe structures

NASA Technical Reports Server (NTRS)

Getline, G. L.

1976-01-01

The results of an experimental study to determine the noise attenuation characteristics of aircraft type fuselage structural panels were presented. Of particular interest was noise attenuation at low frequencies, below the fundamental resonances of the panels. All panels were flightweight structures for transport type aircraft in the 34,050 to 45,400 kg (75,000 to 100,000 pounds) gross weight range. Test data include the results of vibration and acoustic transmission loss tests on seven types of isotropic and orthotropically stiffened, flat and curved panels. The results show that stiffness controlled acoustically integrated structures can provide very high noise reductions at low frequencies without significantly affecting their high frequency noise reduction capabilities.

Systematic study of high-frequency ultrasonic transducer design for laser-scanning photoacoustic ophthalmoscopy

PubMed Central

Ma, Teng; Zhang, Xiangyang; Chiu, Chi Tat; Chen, Ruimin; Kirk Shung, K.; Zhou, Qifa; Jiao, Shuliang

2014-01-01

Abstract. Photoacoustic ophthalmoscopy (PAOM) is a high-resolution in vivo imaging modality that is capable of providing specific optical absorption information for the retina. A high-frequency ultrasonic transducer is one of the key components in PAOM, which is in contact with the eyelid through coupling gel during imaging. The ultrasonic transducer plays a crucial role in determining the image quality affected by parameters such as spatial resolution, signal-to-noise ratio, and field of view. In this paper, we present the results of a systematic study on a high-frequency ultrasonic transducer design for PAOM. The design includes piezoelectric material selection, frequency selection, and the fabrication process. Transducers of various designs were successfully applied for capturing images of biological samples in vivo. The performances of these designs are compared and evaluated. PMID:24441942

Systematic study of high-frequency ultrasonic transducer design for laser-scanning photoacoustic ophthalmoscopy.

PubMed

Ma, Teng; Zhang, Xiangyang; Chiu, Chi Tat; Chen, Ruimin; Kirk Shung, K; Zhou, Qifa; Jiao, Shuliang

2014-01-01

Photoacoustic ophthalmoscopy (PAOM) is a high-resolution in vivo imaging modality that is capable of providing specific optical absorption information for the retina. A high-frequency ultrasonic transducer is one of the key components in PAOM, which is in contact with the eyelid through coupling gel during imaging. The ultrasonic transducer plays a crucial role in determining the image quality affected by parameters such as spatial resolution, signal-to-noise ratio, and field of view. In this paper, we present the results of a systematic study on a high-frequency ultrasonic transducer design for PAOM. The design includes piezoelectric material selection, frequency selection, and the fabrication process. Transducers of various designs were successfully applied for capturing images of biological samples in vivo. The performances of these designs are compared and evaluated.

Induction motor control

NASA Technical Reports Server (NTRS)

Hansen, Irving G.

1990-01-01

Electromechanical actuators developed to date have commonly utilized permanent magnet (PM) synchronous motors. More recently switched reluctance (SR) motors have been advocated due to their robust characteristics. Implications of work which utilizes induction motors and advanced control techniques are discussed. When induction motors are operated from an energy source capable of controlling voltages and frequencies independently, drive characteristics are obtained which are superior to either PM or SR motors. By synthesizing the machine frequency from a high frequency carrier (nominally 20 kHz), high efficiencies, low distortion, and rapid torque response are available. At this time multiple horsepower machine drives were demonstrated, and work is on-going to develop a 20 hp average, 40 hp peak class of aerospace actuators. This effort is based upon high frequency power distribution and management techniques developed by NASA for Space Station Freedom.

Induction motor control

NASA Technical Reports Server (NTRS)

Hansen, Irving G.

1990-01-01

Electromechanical actuators developed to date have commonly ultilized permanent magnet (PM) synchronous motors. More recently switched reluctance (SR) motors have been advocated due to their robust characteristics. Implications of work which utilized induction motors and advanced control techniques are discussed. When induction motors are operated from an energy source capable of controlling voltages and frequencies independently, drive characteristics are obtained which are superior to either PM or SR motors. By synthesizing the machine frequency from a high-frequency carrier (nominally 20 kHz), high efficiencies, low distortion, and rapid torque response are available. At this time multiple horsepower machine drives were demonstrated, and work is on-going to develop a 20 hp average, 40 hp peak class of aerospace actuators. This effort is based upon high-frequency power distribution and management techniques developed by NASA for Space Station Freedom.

High-Frequency Axial Fatigue Test Procedures for Spectrum Loading

DTIC Science & Technology

2016-07-20

histories can be performed at frequencies much higher than standard servo-hydraulic test frames by using a test frame that is optimized to run at higher...by using a test frame that is optimized to run at higher frequencies. AIR 4.3 has conducted a research program to develop a test capability for...Applied Research (BAR) program (219BAR-10-008) was initiated in 2010. The program investigated the influence of a generic rotorcraft main rotor blade root

Advanced systems requirements for ocean observations via microwave radiometers

NASA Technical Reports Server (NTRS)

Blume, H.-J. C.; Swift, C. T.; Kendall, B. M.

1978-01-01

A future microwave spectroradiometer operating in several frequency bands will have the capability to step or sweep frequencies on an adaptable or programmable basis. The on-board adaptable frequency shifting can make the systems immune from radio interference. Programmable frequency sweeping with on-board data inversion by high speed computers would provide for instantaneous synoptic measurements or sea surface temperature and salinity, water surface and volume pollution, ice thickness, ocean surface winds, snow depth, and soil moisture. Large structure satellites will allow an order of magnitude improvement in the present radiometric measurement spacial resolution.

Resonant-tunneling oscillators and multipliers for submillimeter receivers

NASA Technical Reports Server (NTRS)

Sollner, T. C. L. Gerhard

1988-01-01

Resonant tunneling through double-barrier heterostructures has attracted increasing interest recently, largely because of the fast charge transport it provides. In addition, the negative differential resistance regions that exist in the current-voltage (I-V) curve (peak-to-valley ratios of 3.5:1 at room temperature, and nearly 10:1 at 77 K, were measured) suggest that high-speed devices based on the character of the I-V curve should be possible. For example, the negative differential resistance region is capable of providing the gain necessary for high-frequency oscillations. In the laboratory attempts were made to increase the frequency and power of these oscillators and to demonstrate several different high-frequency devices.

Design and Measurement of a Digital Phase Locked BWO for Accurately Extracting the Quality Factors in a Biconcave Resonator System

NASA Astrophysics Data System (ADS)

Gao, Yuanci; Charles, Jones R.; Yu, Guofen; Jyotsna, Dutta M.

2012-03-01

A long loop phase locked backward-wave oscillator (BWO) for a high quality factor resonator system operating at D-band frequencies (130-170GHz) was described, the phase noise of the phased locked BWO was analyzed and measured at typical frequencies. When it used with a high quality factor open resonator for measuring the quality factor of simple harmonic resonators based on the magnitude transfer characteristic, this system has proven to be capable of accurate measuring the quality factor as high as 0.8 million with an uncertainty of less than 1.3% (Lorentzian fitting) at typical frequencies in the range of 130GHz-170GHz.

ASAP progress and expenditure report for the month of December 1--31, 1995. Joint UK/US radar program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Twogood, R.E.; Brase, J.M.; Chambers, D.H.

1996-01-19

The RAR/SAR is a high-priority radar system for the joint US/UK Program. Based on previous experiment results and coordination with the UK, specifications needed for future radar experiments were identified as follows: dual polarimetric (HH and VV) with medium to high resolution in SAR mode. Secondary airborne installation requirements included; high power (circa 10kw) and SLIER capability to emulate Tupelev-134 type system; initially x-band but easily extendible to other frequencies. In FY96 we intended to enhance the radar system`s capabilities by providing a second polarization (VV), spotlight imaging mode, extended frequency of operation to include S- band, increase power, andmore » interface to an existing infrared sensor. Short term objectives are: continue to evaluate and characterize the radar system; upgrade navigation and real-time processing capability to refine motion compensation; upgrade to dual polarimetry (add VV); and develop a ``spotlight`` mode capability. Accomplishments this reporting period: design specifications for the SAR system polarimetric upgrade are complete. The upgrade is ready to begin the procurement cycle when funds become available. System characterization is one of the highest priority tasks for the SAR. Although the radar is dedicated for our use, Hughes is waiting for contract funding before allowing us access to the hardware« less

Weighted network analysis of high-frequency cross-correlation measures

NASA Astrophysics Data System (ADS)

Iori, Giulia; Precup, Ovidiu V.

2007-03-01

In this paper we implement a Fourier method to estimate high-frequency correlation matrices from small data sets. The Fourier estimates are shown to be considerably less noisy than the standard Pearson correlation measures and thus capable of detecting subtle changes in correlation matrices with just a month of data. The evolution of correlation at different time scales is analyzed from the full correlation matrix and its minimum spanning tree representation. The analysis is performed by implementing measures from the theory of random weighted networks.

Silicon Technologies Adjust to RF Applications

NASA Technical Reports Server (NTRS)

Reinecke Taub, Susan; Alterovitz, Samuel A.

1994-01-01

Silicon (Si), although not traditionally the material of choice for RF and microwave applications, has become a serious challenger to other semiconductor technologies for high-frequency applications. Fine-line electron- beam and photolithographic techniques are now capable of fabricating silicon gate sizes as small as 0.1 micron while commonly-available high-resistivity silicon wafers support low-loss microwave transmission lines. These advances, coupled with the recent development of silicon-germanium (SiGe), arm silicon integrated circuits (ICs) with the speed required for increasingly higher-frequency applications.

Variometric approach for real-time GNSS navigation: First demonstration of Kin-VADASE capabilities

NASA Astrophysics Data System (ADS)

Branzanti, Mara; Colosimo, Gabriele; Mazzoni, Augusto

2017-06-01

The use of Global Navigation Satellite Systems (GNSS) kinematic positioning for navigational applications dramatically increased over the last decade. Real-time high performance navigation (positioning accuracy from one to few centimeters) can be achieved with established techniques such as Real Time Kinematic (RTK), and Precise Point Positioning (PPP). Despite their potential, the application of these techniques is limited mainly by their high cost. This work proposes the Kinematic implementation of the Variometric Approach for Displacement Analysis Standalone Engine (Kin-VADASE) and gives a demonstration of its performances in the field of GNSS navigation. VADASE is a methodology for the real-time detection of a standalone GNSS receiver displacements. It was originally designed for seismology and monitoring applications, where the receiver is supposed to move for few minutes, in the range of few meters, around a predefined position. Kin-VADASE overcomes the aforementioned limitations and aims to be a complete methodology with fully kinematic capabilities. Here, for the first time, we present its application to two test cases in order to estimate high rate (i.e., 10 Hz) kinematic parameters of moving vehicles. In this demonstration, data are collected and processed in the office, but the same results can be obtained in real-time through the implementation of Kin-VADASE in the firmware of a GNSS receiver. All the Kin-VADASE processing were carried out using double and single frequency observations in order to investigate the potentialities of the software with geodetic class and low-cost single frequency receivers. Root Mean Square Errors in 3D with respect to differential positioning are at the level of 50 cm for dual frequency and better than 1 meter for single frequency data. This reveals how Kin-VADASE features the main advantage of the standalone approach and the single frequency capability and, although with slightly lower accuracy with respect to the established techniques, can be a valid alternative to estimate kinematic parameters of vehicle in motions.

Robust control of dielectric elastomer diaphragm actuator for human pulse signal tracking

NASA Astrophysics Data System (ADS)

Ye, Zhihang; Chen, Zheng; Asmatulu, Ramazan; Chan, Hoyin

2017-08-01

Human pulse signal tracking is an emerging technology that is needed in traditional Chinese medicine. However, soft actuation with multi-frequency tracking capability is needed for tracking human pulse signal. Dielectric elastomer (DE) is one type of soft actuating that has great potential in human pulse signal tracking. In this paper, a DE diaphragm actuator was designed and fabricated to track human pulse pressure signal. A physics-based and control-oriented model has been developed to capture the dynamic behavior of DE diaphragm actuator. Using the physical model, an H-infinity robust control was designed for the actuator to reject high-frequency sensing noises and disturbances. The robust control was then implemented in real-time to track a multi-frequency signal, which verified the tracking capability and robustness of the control system. In the human pulse signal tracking test, a human pulse signal was measured at the City University of Hong Kong and then was tracked using DE actuator at Wichita State University in the US. Experimental results have verified that the DE actuator with its robust control is capable of tracking human pulse signal.

Visualization of the microcirculatory network in skin by high frequency optoacoustic mesoscopy

NASA Astrophysics Data System (ADS)

Schwarz, Mathias; Aguirre, Juan; Buehler, Andreas; Omar, Murad; Ntziachristos, Vasilis

2015-07-01

Optoacoustic (photoacoustic) imaging has a high potential for imaging melanin-rich structures in skin and the microvasculature of the dermis due to the natural chromophores (de)oxyhemoglobin, and melanin. The vascular network in human dermis comprises a large network of arterioles, capillaries, and venules, ranging from 5 μm to more than 100 μm in diameter. The frequency spectrum of the microcirculatory network in human skin is intrinsically broadband, due to the large variety in size of absorbers. In our group we have developed raster-scan optoacoustic mesoscopy (RSOM) that applies a 100 MHz transducer with ultra-wide bandwidth in raster-scan mode achieving lateral resolution of 18 μm. In this study, we applied high frequency RSOM to imaging human skin in a healthy volunteer. We analyzed the frequency spectrum of anatomical structures with respect to depth and show that frequencies >60 MHz contain valuable information of structures in the epidermis and the microvasculature of the papillary dermis. We illustrate that RSOM is capable of visualizing the fine vascular network at and beneath the epidermal-dermal junction, revealing the vascular fingerprint of glabrous skin, as well as the larger venules deeper inside the dermis. We evaluate the ability of the RSOM system in measuring epidermal thickness in both hairy and glabrous skin. Finally, we showcase the capability of RSOM in visualizing benign nevi that will potentially help in imaging the penetration depth of melanoma.

Slip-pulse rupture behavior on a 2 meter granite fault

USGS Publications Warehouse

McLaskey, Gregory C.; Kilgore, Brian D.; Beeler, Nicholas M.

2015-01-01

We describe observations of dynamic rupture events that spontaneously arise on meter-scale laboratory earthquake experiments. While low-frequency slip of the granite sample occurs in a relatively uniform and crack-like manner, instruments capable of detecting high frequency motions show that some parts of the fault slip abruptly (velocity >100 mm∙s-1, acceleration >20 km∙s-2) while the majority of the fault slips more slowly. Abruptly slipping regions propagate along the fault at nearly the shear wave speed. We propose that the dramatic reduction in frictional strength implied by this pulse-like rupture behavior has a common mechanism to the weakening reported in high velocity friction experiments performed on rotary machines. The slip pulses can also be identified as migrating sources of high frequency seismic waves. As observations from large earthquakes show similar propagating high frequency sources, the pulses described here may have relevance to the mechanics of larger earthquakes.

Review of GaN-based devices for terahertz operation

NASA Astrophysics Data System (ADS)

Ahi, Kiarash

2017-09-01

GaN provides the highest electron saturation velocity, breakdown voltage, operation temperature, and thus the highest combined frequency-power performance among commonly used semiconductors. The industrial need for compact, economical, high-resolution, and high-power terahertz (THz) imaging and spectroscopy systems are promoting the utilization of GaN for implementing the next generation of THz systems. As it is reviewed, the mentioned characteristics of GaN together with its capabilities of providing high two-dimensional election densities and large longitudinal optical phonon of ˜90 meV make it one of the most promising semiconductor materials for the future of the THz emitters, detectors, mixers, and frequency multiplicators. GaN-based devices have shown capabilities of operation in the upper THz frequency band of 5 to 12 THz with relatively high photon densities in room temperature. As a result, THz imaging and spectroscopy systems with high resolution and deep depth of penetration can be realized through utilizing GaN-based devices. A comprehensive review of the history and the state of the art of GaN-based electronic devices, including plasma heterostructure field-effect transistors, negative differential resistances, hetero-dimensional Schottky diodes, impact avalanche transit times, quantum-cascade lasers, high electron mobility transistors, Gunn diodes, and tera field-effect transistors together with their impact on the future of THz imaging and spectroscopy systems is provided.

Optical Processing of Microwave Signals - Part B

DTIC Science & Technology

2003-04-01

Gay Lussac ,78851 Elancourt Cedex Daniel Dolfi, Sylvie Tonda-Goldstein, Jean-Pierre Huignard, Thales Research & Technology 91401 Orsay Cedex, France...each microwave frequency component fk (phase and amplitude) by the control of the transmission law of the SLMs’. When attributing one frequency to a...a high speed photodiode. Considering the capability offered by 2D SLMs to provide reconfigurable complex phase law , sophisticated programmable

The INSU and DMN network of ST radars

NASA Technical Reports Server (NTRS)

Petitdidier, M.; Klaus, V.; Baudin, F.; Crochet, M.; Penazzi, G.; Quinty, P.

1986-01-01

Due to their capabilities of measuring wind profiles with good time and height resolution, Stratosphere-Troposphere (ST) are well adapted to carry out atmospheric research. In France, a Very High Frequency (VHF) and an Ultrahigh Frequency (UHF) ST radar are working for research purposes. The INSU (Institut National des Sciences de l'Univers) and the DMN (Direction de la Meteorologie Nationale) networks are discussed.

Global high-frequency source imaging accounting for complexity in Green's functions

NASA Astrophysics Data System (ADS)

Lambert, V.; Zhan, Z.

2017-12-01

The general characterization of earthquake source processes at long periods has seen great success via seismic finite fault inversion/modeling. Complementary techniques, such as seismic back-projection, extend the capabilities of source imaging to higher frequencies and reveal finer details of the rupture process. However, such high frequency methods are limited by the implicit assumption of simple Green's functions, which restricts the use of global arrays and introduces artifacts (e.g., sweeping effects, depth/water phases) that require careful attention. This motivates the implementation of an imaging technique that considers the potential complexity of Green's functions at high frequencies. We propose an alternative inversion approach based on the modest assumption that the path effects contributing to signals within high-coherency subarrays share a similar form. Under this assumption, we develop a method that can combine multiple high-coherency subarrays to invert for a sparse set of subevents. By accounting for potential variability in the Green's functions among subarrays, our method allows for the utilization of heterogeneous global networks for robust high resolution imaging of the complex rupture process. The approach also provides a consistent framework for examining frequency-dependent radiation across a broad frequency spectrum.

Realtime photoacoustic microscopy in vivo with a 30-MHz ultrasound array transducer.

PubMed

Zemp, Roger J; Song, Liang; Bitton, Rachel; Shung, K Kirk; Wang, Lihong V

2008-05-26

We present a novel high-frequency photoacoustic microscopy system capable of imaging the microvasculature of living subjects in realtime to depths of a few mm. The system consists of a high-repetition-rate Q-switched pump laser, a tunable dye laser, a 30-MHz linear ultrasound array transducer, a multichannel high-frequency data acquisition system, and a shared-RAM multi-core-processor computer. Data acquisition, beamforming, scan conversion, and display are implemented in realtime at 50 frames per second. Clearly resolvable images of 6-microm-diameter carbon fibers are experimentally demonstrated at 80 microm separation distances. Realtime imaging performance is demonstrated on phantoms and in vivo with absorbing structures identified to depths of 2.5-3 mm. This work represents the first high-frequency realtime photoacoustic imaging system to our knowledge.

Defense Acquisitions: Assessments of Selected Weapon Programs

DTIC Science & Technology

2010-03-01

improved availability for small terminals. It is to replace the Ultra High Frequency (UHF) Follow-On ( UFO ) satellite system currently in operation...of MUOS capabilities is time-critical due to the operational failures of two UFO satellites. The MUOS program has taken several steps to address...failures of two UFO satellites. Based on the current health of on-orbit satellites, UHF communication capabilities are predicted to fall below the

Frequency-agile wireless sensor networks

NASA Astrophysics Data System (ADS)

Arms, Steven W.; Townsend, Christopher P.; Churchill, David L.; Hamel, Michael J.; Galbreath, Jacob H.; Mundell, Steven W.

2004-07-01

Our goal was to demonstrate a wireless communications system capable of simultaneous, high speed data communications from a variety of sensors. We have previously reported on the design and application of 2 KHz data logging transceiver nodes, however, only one node may stream data at a time, since all nodes on the network use the same communications frequency. To overcome these limitations, second generation data logging transceivers were developed with software programmable radio frequency (RF) communications. Each node contains on-board memory (2 Mbytes), sensor excitation, instrumentation amplifiers with programmable gains & offsets, multiplexer, 16 bit A/D converter, microcontroller, and frequency agile, bi-directional, frequency shift keyed (FSK) RF serial data link. These systems are capable of continuous data transmission from 26 distinct nodes (902-928 MHz band, 75 kbaud). The system was demonstrated in a compelling structural monitoring application. The National Parks Service requested a means for continual monitoring and recording of sensor data from the Liberty Bell during a move to a new location (Philadelphia, October 2003). Three distinct, frequency agile, wireless sensing nodes were used to detect visible crack shear/opening micromotions, triaxial accelerations, and hairline crack tip strains. The wireless sensors proved to be useful in protecting the Liberty Bell.

Selective and Catalyst-free Oxidation of D-Glucose to D-Glucuronic acid induced by High-Frequency Ultrasound

NASA Astrophysics Data System (ADS)

Amaniampong, Prince N.; Karam, Ayman; Trinh, Quang Thang; Xu, Kai; Hirao, Hajime; Jérôme, François; Chatel, Gregory

2017-01-01

This systematic experimental investigation reveals that high-frequency ultrasound irradiation (550 kHz) induced oxidation of D-glucose to glucuronic acid in excellent yield without assistance of any (bio)catalyst. Oxidation is induced thanks to the in situ production of radical species in water. Experiments show that the dissolved gases play an important role in governing the nature of generated radical species and thus the selectivity for glucuronic acid. Importantly, this process yields glucuronic acid instead of glucuronate salt typically obtained via conventional (bio)catalyst routes, which is of huge interest in respect of downstream processing. Investigations using disaccharides revealed that radicals generated by high frequency ultrasound were also capable of promoting tandem hydrolysis/oxidation reactions.

On-Chip Power-Combining for High-Power Schottky Diode-Based Frequency Multipliers

NASA Technical Reports Server (NTRS)

Chattopadhyay, Goutam; Mehdi, Imran; Schlecht, Erich T.; Lee, Choonsup; Siles, Jose V.; Maestrini, Alain E.; Thomas, Bertrand; Jung, Cecile D.

2013-01-01

A 1.6-THz power-combined Schottky frequency tripler was designed to handle approximately 30 mW input power. The design of Schottky-based triplers at this frequency range is mainly constrained by the shrinkage of the waveguide dimensions with frequency and the minimum diode mesa sizes, which limits the maximum number of diodes that can be placed on the chip to no more than two. Hence, multiple-chip power-combined schemes become necessary to increase the power-handling capabilities of high-frequency multipliers. The design presented here overcomes difficulties by performing the power-combining directly on-chip. Four E-probes are located at a single input waveguide in order to equally pump four multiplying structures (featuring two diodes each). The produced output power is then recombined at the output using the same concept.

Experimental investigation on the dissipative and elastic characteristics of a yaw colloidal damper destined to carbody suspension of a bullet train

NASA Astrophysics Data System (ADS)

Suciu, B.; Tomioka, T.

2016-09-01

Yaw damper represents a major source of excitation for flexural vibration of the railway carbody. In order to reduce transmissibility of such undesired excitation, yaw damper should allow for large force transmission at low working frequencies, but should behave as vibration isolator at high working frequencies. Unfortunately, the yaw oil damper (OD), which is nowadays in service, has poor intrinsic elastic capabilities and provides damping forces varying as a power function versus the piston speed. Since colloidal damper (CD) has intrinsic elastic capabilities and larger damping forces at lower excitation frequencies, it occurs as an attractive alternative solution to traditional yaw dampers. In this work, a yaw CD destined to carbody suspension of a bullet train was designed and manufactured; then, its dynamic characteristics, produced by both the frictional and colloidal effects, were evaluated from the experimental results, obtained during horizontal vibration tests, performed on a ball-screw shaker. Compared to the corresponding classical yaw OD, the trial yaw CD allowed for: weight reduction of 31.6%; large damping force, dissipated energy and spring constant at long piston stroke under low excitation frequency; low damping force, dissipated energy and spring constant at short piston stroke under high excitation frequency. Elastic properties were justified by introducing a model for the spring constant that included the effect of pore size distribution.

Prospects for detecting decreasing exoplanet frequency with main-sequence age using PLATO

NASA Astrophysics Data System (ADS)

Veras, Dimitri; Brown, David J. A.; Mustill, Alexander J.; Pollacco, Don

2015-10-01

The space mission PLATO will usher in a new era of exoplanetary science by expanding our current inventory of transiting systems and constraining host star ages, which are currently highly uncertain. This capability might allow PLATO to detect changes in planetary system architecture with time, particularly because planetary scattering due to Lagrange instability may be triggered long after the system was formed. Here, we utilize previously published instability time-scale prescriptions to determine PLATO's capability to detect a trend of decreasing planet frequency with age for systems with equal-mass planets. For two-planet systems, our results demonstrate that PLATO may detect a trend for planet masses which are at least as massive as super-Earths. For systems with three or more planets, we link their initial compactness to potentially detectable frequency trends in order to aid future investigations when these populations will be better characterized.

Prospects for detecting decreasing exoplanet frequency with main-sequence age using PLATO

NASA Astrophysics Data System (ADS)

Veras, D.; Brown, D. J. A.; Mustill, A. J.; Pollacco, D.

2017-09-01

The space mission PLATO will usher in a new era of exoplanetary science by expanding our current inventory of transiting systems and constraining host star ages, which are currently highly uncertain. This capability might allow PLATO to detect changes in planetary system architecture with time, particularly because planetary scattering due to Lagrange instability may be triggered long after the system was formed. Here, we utilize previously published instability time-scale prescriptions to determine PLATO's capability to detect a trend of decreasing planet frequency with age for systems with equal- mass planets. For two-planet systems, our results demonstrate that PLATO may detect a trend for planet masses which are at least as massive as super-Earths. For systems with three or more planets, we link their initial compactness to potentially detectable frequency trends in order to aid future investigations when these populations will be better characterized.

Noncritical generation of nonclassical frequency combs via spontaneous rotational symmetry breaking

NASA Astrophysics Data System (ADS)

Navarrete-Benlloch, Carlos; Patera, Giuseppe; de Valcárcel, Germán J.

2017-10-01

Synchronously pumped optical parametric oscillators (SPOPOs) are optical cavities driven by mode-locked lasers, and containing a nonlinear crystal capable of down-converting a frequency comb to lower frequencies. SPOPOs have received a lot of attention lately because their intrinsic multimode nature makes them compact sources of quantum correlated light with promising applications in modern quantum information technologies. In this work we show that SPOPOs are also capable of accessing the challenging and interesting regime where spontaneous symmetry breaking confers strong nonclassical properties to the emitted light, which has eluded experimental observation so far. Apart from opening the possibility of studying experimentally this elusive regime of dissipative phase transitions, our predictions will have a practical impact, since we show that spontaneous symmetry breaking provides a specific spatiotemporal mode with large quadrature squeezing for any value of the system parameters, turning SPOPOs into robust sources of highly nonclassical light above threshold.

Analog Ranging Modem Code Processor and Generator

DOT National Transportation Integrated Search

1974-05-01

The report details technical development efforts to implement an analog ranging modem using recently developed linear integrated circuits where possible. The breadboard hardware is capable of acquiring frequency and phase of a weak signal in a high n...

Superresolved digital in-line holographic microscopy for high-resolution lensless biological imaging

NASA Astrophysics Data System (ADS)

Micó, Vicente; Zalevsky, Zeev

2010-07-01

Digital in-line holographic microscopy (DIHM) is a modern approach capable of achieving micron-range lateral and depth resolutions in three-dimensional imaging. DIHM in combination with numerical imaging reconstruction uses an extremely simplified setup while retaining the advantages provided by holography with enhanced capabilities derived from algorithmic digital processing. We introduce superresolved DIHM incoming from time and angular multiplexing of the sample spatial frequency information and yielding in the generation of a synthetic aperture (SA). The SA expands the cutoff frequency of the imaging system, allowing submicron resolutions in both transversal and axial directions. The proposed approach can be applied when imaging essentially transparent (low-concentration dilutions) and static (slow dynamics) samples. Validation of the method for both a synthetic object (U.S. Air Force resolution test) to quantify the resolution improvement and a biological specimen (sperm cells biosample) are reported showing the generation of high synthetic numerical aperture values working without lenses.

Compact high voltage, high peak power, high frequency transformer for converter type modulator applications.

PubMed

Reghu, T; Mandloi, V; Shrivastava, Purushottam

2016-04-01

The design and development of a compact high voltage, high peak power, high frequency transformer for a converter type modulator of klystron amplifiers is presented. The transformer has been designed to operate at a frequency of 20 kHz and at a flux swing of ±0.6 T. Iron (Fe) based nanocrystalline material has been selected as a core for the construction of the transformer. The transformer employs a specially designed solid Teflon bobbin having 120 kV insulation for winding the high voltage secondary windings. The flux swing of the core has been experimentally found by plotting the hysteresis loop at actual operating conditions. Based on the design, a prototype transformer has been built which is per se a unique combination of high voltage, high frequency, and peak power specifications. The transformer was able to provide 58 kV (pk-pk) at the secondary with a peak power handling capability of 700 kVA. The transformation ratio was 1:17. The performance of the transformer is also presented and discussed.

Gender Identification Using High-Frequency Speech Energy: Effects of Increasing the Low-Frequency Limit.

PubMed

Donai, Jeremy J; Halbritter, Rachel M

The purpose of this study was to investigate the ability of normal-hearing listeners to use high-frequency energy for gender identification from naturally produced speech signals. Two experiments were conducted using a repeated-measures design. Experiment 1 investigated the effects of increasing high-pass filter cutoff (i.e., increasing the low-frequency spectral limit) on gender identification from naturally produced vowel segments. Experiment 2 studied the effects of increasing high-pass filter cutoff on gender identification from naturally produced sentences. Confidence ratings for the gender identification task were also obtained for both experiments. Listeners in experiment 1 were capable of extracting talker gender information at levels significantly above chance from vowel segments high-pass filtered up to 8.5 kHz. Listeners in experiment 2 also performed above chance on the gender identification task from sentences high-pass filtered up to 12 kHz. Cumulatively, the results of both experiments provide evidence that normal-hearing listeners can utilize information from the very high-frequency region (above 4 to 5 kHz) of the speech signal for talker gender identification. These findings are at variance with current assumptions regarding the perceptual information regarding talker gender within this frequency region. The current results also corroborate and extend previous studies of the use of high-frequency speech energy for perceptual tasks. These findings have potential implications for the study of information contained within the high-frequency region of the speech spectrum and the role this region may play in navigating the auditory scene, particularly when the low-frequency portion of the spectrum is masked by environmental noise sources or for listeners with substantial hearing loss in the low-frequency region and better hearing sensitivity in the high-frequency region (i.e., reverse slope hearing loss).

Partial null astigmatism-compensated interferometry for a concave freeform Zernike mirror

NASA Astrophysics Data System (ADS)

Dou, Yimeng; Yuan, Qun; Gao, Zhishan; Yin, Huimin; Chen, Lu; Yao, Yanxia; Cheng, Jinlong

2018-06-01

Partial null interferometry without using any null optics is proposed to measure a concave freeform Zernike mirror. Oblique incidence on the freeform mirror is used to compensate for astigmatism as the main component in its figure, and to constrain the divergence of the test beam as well. The phase demodulated from the partial nulled interferograms is divided into low-frequency phase and high-frequency phase by Zernike polynomial fitting. The low-frequency surface figure error of the freeform mirror represented by the coefficients of Zernike polynomials is reconstructed from the low-frequency phase, applying the reverse optimization reconstruction technology in the accurate model of the interferometric system. The high-frequency surface figure error of the freeform mirror is retrieved from the high-frequency phase adopting back propagating technology, according to the updated model in which the low-frequency surface figure error has been superimposed on the sag of the freeform mirror. Simulations verified that this method is capable of testing a wide variety of astigmatism-dominated freeform mirrors due to the high dynamic range. The experimental result using our proposed method for a concave freeform Zernike mirror is consistent with the null test result employing the computer-generated hologram.

Exploiting NiTi shape memory alloy films in design of tunable high frequency microcantilever resonators

NASA Astrophysics Data System (ADS)

Stachiv, I.; Sittner, P.; Olejnicek, J.; Landa, M.; Heller, L.

2017-11-01

Shape memory alloy (SMA) films are very attractive materials for microactuators because of their high energy density. However, all currently developed SMA actuators utilize martensitic transformation activated by periodically generated heating and cooling; therefore, they have a slow actuation speed, just a few Hz, which restricts their use in most of the nanotechnology applications such as high frequency microcantilever based physical and chemical sensors, atomic force microscopes, or RF filters. Here, we design tunable high frequency SMA microcantilevers for nanotechnology applications. They consist of a phase transforming NiTi SMA film sputtered on the common elastic substrate material; in our case, it is a single-crystal silicon. The reversible tuning of microcantilever resonant frequencies is then realized by intentionally changing the Young's modulus and the interlayer stress of the NiTi film by temperature, while the elastic substrate guarantees the high frequency actuation (up to hundreds of kHz) of the microcantilever. The experimental results qualitatively agree with predictions obtained from the dedicated model based on the continuum mechanics theory and a phase characteristic of NiTi. The present design of SMA microcantilevers expands the capability of current micro-/nanomechanical resonators by enabling tunability of several consecutive resonant frequencies.

Half-Watt average power femtosecond source spanning 3-8 µm based on subharmonic generation in GaAs

NASA Astrophysics Data System (ADS)

Smolski, Viktor; Vasilyev, Sergey; Moskalev, Igor; Mirov, Mike; Ru, Qitian; Muraviev, Andrey; Schunemann, Peter; Mirov, Sergey; Gapontsev, Valentin; Vodopyanov, Konstantin

2018-06-01

Frequency combs with a wide instantaneous spectral span covering the 3-20 µm molecular fingerprint region are highly desirable for broadband and high-resolution frequency comb spectroscopy, trace molecular detection, and remote sensing. We demonstrate a novel approach for generating high-average-power middle-infrared (MIR) output suitable for producing frequency combs with an instantaneous spectral coverage close to 1.5 octaves. Our method is based on utilizing a highly-efficient and compact Kerr-lens mode-locked Cr2+:ZnS laser operating at 2.35-µm central wavelength with 6-W average power, 77-fs pulse duration, and high 0.9-GHz repetition rate; to pump a degenerate (subharmonic) optical parametric oscillator (OPO) based on a quasi-phase-matched GaAs crystal. Such subharmonic OPO is a nearly ideal frequency converter capable of extending the benefits of frequency combs based on well-established mode-locked pump lasers to the MIR region through rigorous, phase- and frequency-locked down conversion. We report a 0.5-W output in the form of an ultra-broadband spectrum spanning 3-8 µm measured at 50-dB level.

Bias-field controlled phasing and power combination of gyromagnetic nonlinear transmission lines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reale, D. V., E-mail: david.reale@ttu.edu; Bragg, J.-W. B.; Gonsalves, N. R.

2014-05-15

Gyromagnetic Nonlinear Transmission Lines (NLTLs) generate microwaves through the damped gyromagnetic precession of the magnetic moments in ferrimagnetic material, and are thus utilized as compact, solid-state, frequency agile, high power microwave (HPM) sources. The output frequency of a NLTL can be adjusted by control of the externally applied bias field and incident voltage pulse without physical alteration to the structure of the device. This property provides a frequency tuning capability not seen in many conventional e-beam based HPM sources. The NLTLs developed and tested are mesoband sources capable of generating MW power levels in the L, S, and C bandsmore » of the microwave spectrum. For an individual NLTL the output power at a given frequency is determined by several factors including the intrinsic properties of the ferrimagnetic material and the transmission line structure. Hence, if higher power levels are to be achieved, it is necessary to combine the outputs of multiple NLTLs. This can be accomplished in free space using antennas or in a transmission line via a power combiner. Using a bias-field controlled delay, a transient, high voltage, coaxial, three port, power combiner was designed and tested. Experimental results are compared with the results of a transient COMSOL simulation to evaluate combiner performance.« less

Bias-field controlled phasing and power combination of gyromagnetic nonlinear transmission lines.

PubMed

Reale, D V; Bragg, J-W B; Gonsalves, N R; Johnson, J M; Neuber, A A; Dickens, J C; Mankowski, J J

2014-05-01

Gyromagnetic Nonlinear Transmission Lines (NLTLs) generate microwaves through the damped gyromagnetic precession of the magnetic moments in ferrimagnetic material, and are thus utilized as compact, solid-state, frequency agile, high power microwave (HPM) sources. The output frequency of a NLTL can be adjusted by control of the externally applied bias field and incident voltage pulse without physical alteration to the structure of the device. This property provides a frequency tuning capability not seen in many conventional e-beam based HPM sources. The NLTLs developed and tested are mesoband sources capable of generating MW power levels in the L, S, and C bands of the microwave spectrum. For an individual NLTL the output power at a given frequency is determined by several factors including the intrinsic properties of the ferrimagnetic material and the transmission line structure. Hence, if higher power levels are to be achieved, it is necessary to combine the outputs of multiple NLTLs. This can be accomplished in free space using antennas or in a transmission line via a power combiner. Using a bias-field controlled delay, a transient, high voltage, coaxial, three port, power combiner was designed and tested. Experimental results are compared with the results of a transient COMSOL simulation to evaluate combiner performance.

High-resolution high-sensitivity and truly distributed optical frequency domain reflectometry for structural crack detection

NASA Astrophysics Data System (ADS)

Li, Wenhai; Bao, Xiaoyi; Chen, Liang

2014-05-01

Optical Frequency Domain Reflectometry (OFDR) with the use of polarization maintaining fiber (PMF) is capable of distinguishing strain and temperature, which is critical for successful field applications such as structural health monitoring (SHM) and smart material. Location-dependent measurement sensitivities along PMF are compensated by cross- and auto-correlations measurements of the spectra form a distributed parameter matrix. Simultaneous temperature and strain measurement accuracy of 1μstrain and 0.1°C is achieved with 2.5mm spatial resolution in over 180m range.

High-power VCSELs for smart munitions

NASA Astrophysics Data System (ADS)

Geske, Jon; MacDougal, Michael; Cole, Garrett; Snyder, Donald

2006-08-01

The next generation of low-cost smart munitions will be capable of autonomously detecting and identifying targets aided partly by the ability to image targets with compact and robust scanning rangefinder and LADAR capabilities. These imaging systems will utilize arrays of high performance, low-cost semiconductor diode lasers capable of achieving high peak powers in pulses ranging from 5 to 25 nanoseconds in duration. Aerius Photonics is developing high-power Vertical-Cavity Surface-Emitting Lasers (VCSELs) to meet the needs of these smart munitions applications. The authors will report the results of Aerius' development program in which peak pulsed powers exceeding 60 Watts were demonstrated from single VCSEL emitters. These compact packaged emitters achieved pulse energies in excess of 1.5 micro-joules with multi kilo-hertz pulse repetition frequencies. The progress of the ongoing effort toward extending this performance to arrays of VCSEL emitters and toward further improving laser slope efficiency will be reported.

Tomography and Purification of the Temporal-Mode Structure of Quantum Light

NASA Astrophysics Data System (ADS)

Ansari, Vahid; Donohue, John M.; Allgaier, Markus; Sansoni, Linda; Brecht, Benjamin; Roslund, Jonathan; Treps, Nicolas; Harder, Georg; Silberhorn, Christine

2018-05-01

High-dimensional quantum information processing promises capabilities beyond the current state of the art, but addressing individual information-carrying modes presents a significant experimental challenge. Here we demonstrate effective high-dimensional operations in the time-frequency domain of nonclassical light. We generate heralded photons with tailored temporal-mode structures through the pulse shaping of a broadband parametric down-conversion pump. We then implement a quantum pulse gate, enabled by dispersion-engineered sum-frequency generation, to project onto programmable temporal modes, reconstructing the quantum state in seven dimensions. We also manipulate the time-frequency structure by selectively removing temporal modes, explicitly demonstrating the effectiveness of engineered nonlinear processes for the mode-selective manipulation of quantum states.

Demonstration of transmission high energy electron microscopy

DOE PAGES

Merrill, F. E.; Goett, J.; Gibbs, J. W.; ...

2018-04-06

High energy electrons have been used to investigate an extension of transmission electron microscopy. This technique, transmission high energy electron microscopy (THEEM), provides two additional capabilities to electron microscopy. First, high energy electrons are more penetrating than low energy electrons, and thus, they are able to image through thicker samples. Second, the accelerating mode of a radio-frequency linear accelerator provides fast exposures, down to 1 ps, which are ideal for flash radiography, making THEEM well suited to study the evolution of fast material processes under dynamic conditions. Lastly, initial investigations with static objects and during material processing have been performedmore » to investigate the capabilities of this technique.« less

Recent progress in synchrotron-based frequency-domain Fourier-transform THz-EPR.

PubMed

Nehrkorn, Joscha; Holldack, Karsten; Bittl, Robert; Schnegg, Alexander

2017-07-01

We describe frequency-domain Fourier-transform THz-EPR as a method to assign spin-coupling parameters of high-spin (S>1/2) systems with very large zero-field splittings. The instrumental foundations of synchrotron-based FD-FT THz-EPR are presented, alongside with a discussion of frequency-domain EPR simulation routines. The capabilities of this approach is demonstrated for selected mono- and multinuclear HS systems. Finally, we discuss remaining challenges and give an outlook on the future prospects of the technique. Copyright © 2017 Elsevier Inc. All rights reserved.

Improvement of Space Shuttle Main Engine Low Frequency Acceleration Measurements

NASA Technical Reports Server (NTRS)

Stec, Robert C.

1999-01-01

The noise floor of low frequency acceleration data acquired on the Space Shuttle Main Engines is higher than desirable. Difficulties of acquiring high quality acceleration data on this engine are discussed. The approach presented in this paper for reducing the acceleration noise floor focuses on a search for an accelerometer more capable of measuring low frequency accelerations. An overview is given of the current measurement system used to acquire engine vibratory data. The severity of vibration, temperature, and moisture environments are considered. Vibratory measurements from both laboratory and rocket engine tests are presented.

Flexibility of space structures makes design shaky

NASA Technical Reports Server (NTRS)

Hearth, D. P.; Boyer, W. J.

1985-01-01

An evaluation is made of the development status of high stiffness space structures suitable for orbital construction or deployment of large diameter reflector antennas, with attention to the control system capabilities required by prospective space structure system types. The very low structural frequencies typical of very large, radio frequency antenna structures would be especially difficult for a control system to counteract. Vibration control difficulties extend across the frequency spectrum, even to optical and IR reflector systems. Current research and development efforts are characterized with respect to goals and prospects for success.

Compact, Lightweight Servo-Controllable Brakes

NASA Technical Reports Server (NTRS)

Lovchik, Christopher S.; Townsend, William; Guertin, Jeffrey; Matsuoka, Yoky

2010-01-01

Compact, lightweight servo-controllable brakes capable of high torques are being developed for incorporation into robot joints. A brake of this type is based partly on the capstan effect of tension elements. In a brake of the type under development, a controllable intermediate state of torque is reached through on/off switching at a high frequency.

Sub-micron materials characterization using near-field optics

NASA Astrophysics Data System (ADS)

Blodgett, David Wesley

1998-12-01

High-resolution sub-surface materials characterization and inspection are critical in the microelectronics and thin films industries. To this end, a technique is described that couples the bulk property measurement capabilities of high-frequency ultrasound with the high-resolution surface imaging capabilities of the near-field optical microscope. Sensing bulk microstructure variations in the material, such as grain boundaries, requires a detection footprint smaller than the variation itself. The near-field optical microscope, with the ability to exceed the diffraction limit in optical resolution, meets this requirement. Two apertureless near-field optical microscopes, on-axis and off-axis illumination, have been designed and built. Near-field and far-field approach curves for both microscopes are presented. The sensitivity of the near-field approach curve was 8.3 muV/nm. Resolution studies for the near-field microscope indicate optical resolutions on the order of 50 nm, which exceeds the diffraction limit. The near-field microscope has been adapted to detect both contact-transducer-generated and laser-generated ultrasound. The successful detection of high-frequency ultrasound with the near-field optical microscope demonstrates the potential of this technique.

Extremely high frequency sensitivity in a 'simple' ear.

PubMed

Moir, Hannah M; Jackson, Joseph C; Windmill, James F C

2013-08-23

An evolutionary war is being played out between the bat, which uses ultrasonic calls to locate insect prey, and the moth, which uses microscale ears to listen for the approaching bat. While the highest known frequency of bat echolocation calls is 212 kHz, the upper limit of moth hearing is considered much lower. Here, we show that the greater wax moth, Galleria mellonella, is capable of hearing ultrasonic frequencies approaching 300 kHz; the highest frequency sensitivity of any animal. With auditory frequency sensitivity that is unprecedented in the animal kingdom, the greater wax moth is ready and armed for any echolocation call adaptations made by the bat in the on-going bat-moth evolutionary war.

Optical injection locking-based amplification in phase-coherent transfer of optical frequencies.

PubMed

Kim, Joonyoung; Schnatz, Harald; Wu, David S; Marra, Giuseppe; Richardson, David J; Slavík, Radan

2015-09-15

We demonstrate the use of an optical injection phase locked loop (OIPLL) as a regenerative amplifier for optical frequency transfer applications. The optical injection locking provides high gain within a narrow bandwidth (<100  MHz) and is capable of preserving the fractional frequency stability of the incoming carrier to better than 10(-18) at 1000 s. The OIPLL was tested in the field as a mid-span amplifier for the transfer of an ultrastable optical carrier, stabilized to an optical frequency standard, over a 292 km long installed dark fiber link. The transferred frequency at the remote end reached a fractional frequency instability of less than 1×10(-19) at averaging time of 3200 s.

Wafer scale millimeter-wave integrated circuits based on epitaxial graphene in high data rate communication.

PubMed

Habibpour, Omid; He, Zhongxia Simon; Strupinski, Wlodek; Rorsman, Niklas; Zirath, Herbert

2017-02-01

In recent years, the demand for high data rate wireless communications has increased dramatically, which requires larger bandwidth to sustain multi-user accessibility and quality of services. This can be achieved at millimeter wave frequencies. Graphene is a promising material for the development of millimeter-wave electronics because of its outstanding electron transport properties. Up to now, due to the lack of high quality material and process technology, the operating frequency of demonstrated circuits has been far below the potential of graphene. Here, we present monolithic integrated circuits based on epitaxial graphene operating at unprecedented high frequencies (80-100 GHz). The demonstrated circuits are capable of encoding/decoding of multi-gigabit-per-second information into/from the amplitude or phase of the carrier signal. The developed fabrication process is scalable to large wafer sizes.

Realtime photoacoustic microscopy in vivo with a 30-MHz ultrasound array transducer

PubMed Central

Zemp, Roger J.; Song, Liang; Bitton, Rachel; Shung, K. Kirk; Wang, Lihong V.

2009-01-01

We present a novel high-frequency photoacoustic microscopy system capable of imaging the microvasculature of living subjects in realtime to depths of a few mm. The system consists of a high-repetition-rate Q-switched pump laser, a tunable dye laser, a 30-MHz linear ultrasound array transducer, a multichannel high-frequency data acquisition system, and a shared-RAM multi-core-processor computer. Data acquisition, beamforming, scan conversion, and display are implemented in realtime at 50 frames per second. Clearly resolvable images of 6-µm-diameter carbon fibers are experimentally demonstrated at 80 µm separation distances. Realtime imaging performance is demonstrated on phantoms and in vivo with absorbing structures identified to depths of 2.5–3 mm. This work represents the first high-frequency realtime photoacoustic imaging system to our knowledge. PMID:18545502

Spectral analysis and filtering techniques in digital spatial data processing

USGS Publications Warehouse

Pan, Jeng-Jong

1989-01-01

A filter toolbox has been developed at the EROS Data Center, US Geological Survey, for retrieving or removing specified frequency information from two-dimensional digital spatial data. This filter toolbox provides capabilities to compute the power spectrum of a given data and to design various filters in the frequency domain. Three types of filters are available in the toolbox: point filter, line filter, and area filter. Both the point and line filters employ Gaussian-type notch filters, and the area filter includes the capabilities to perform high-pass, band-pass, low-pass, and wedge filtering techniques. These filters are applied for analyzing satellite multispectral scanner data, airborne visible and infrared imaging spectrometer (AVIRIS) data, gravity data, and the digital elevation models (DEM) data. -from Author

A stepped-plate bi-frequency source for generating a difference frequency sound with a parametric array.

PubMed

Je, Yub; Lee, Haksue; Park, Jongkyu; Moon, Wonkyu

2010-06-01

An ultrasonic radiator is developed to generate a difference frequency sound from two frequencies of ultrasound in air with a parametric array. A design method is proposed for an ultrasonic radiator capable of generating highly directive, high-amplitude ultrasonic sound beams at two different frequencies in air based on a modification of the stepped-plate ultrasonic radiator. The stepped-plate ultrasonic radiator was introduced by Gallego-Juarez et al. [Ultrasonics 16, 267-271 (1978)] in their previous study and can effectively generate highly directive, large-amplitude ultrasonic sounds in air, but only at a single frequency. Because parametric array sources must be able to generate sounds at more than one frequency, a design modification is crucial to the application of a stepped-plate ultrasonic radiator as a parametric array source in air. The aforementioned method was employed to design a parametric radiator for use in air. A prototype of this design was constructed and tested to determine whether it could successfully generate a difference frequency sound with a parametric array. The results confirmed that the proposed single small-area transducer was suitable as a parametric radiator in air.

Selective and Catalyst-free Oxidation of D-Glucose to D-Glucuronic acid induced by High-Frequency Ultrasound

PubMed Central

Amaniampong, Prince N.; Karam, Ayman; Trinh, Quang Thang; Xu, Kai; Hirao, Hajime; Jérôme, François; Chatel, Gregory

2017-01-01

This systematic experimental investigation reveals that high-frequency ultrasound irradiation (550 kHz) induced oxidation of D-glucose to glucuronic acid in excellent yield without assistance of any (bio)catalyst. Oxidation is induced thanks to the in situ production of radical species in water. Experiments show that the dissolved gases play an important role in governing the nature of generated radical species and thus the selectivity for glucuronic acid. Importantly, this process yields glucuronic acid instead of glucuronate salt typically obtained via conventional (bio)catalyst routes, which is of huge interest in respect of downstream processing. Investigations using disaccharides revealed that radicals generated by high frequency ultrasound were also capable of promoting tandem hydrolysis/oxidation reactions. PMID:28084448

Deterministic ion beam material adding technology for high-precision optical surfaces.

PubMed

Liao, Wenlin; Dai, Yifan; Xie, Xuhui; Zhou, Lin

2013-02-20

Although ion beam figuring (IBF) provides a highly deterministic method for the precision figuring of optical components, several problems still need to be addressed, such as the limited correcting capability for mid-to-high spatial frequency surface errors and low machining efficiency for pit defects on surfaces. We propose a figuring method named deterministic ion beam material adding (IBA) technology to solve those problems in IBF. The current deterministic optical figuring mechanism, which is dedicated to removing local protuberances on optical surfaces, is enriched and developed by the IBA technology. Compared with IBF, this method can realize the uniform convergence of surface errors, where the particle transferring effect generated in the IBA process can effectively correct the mid-to-high spatial frequency errors. In addition, IBA can rapidly correct the pit defects on the surface and greatly improve the machining efficiency of the figuring process. The verification experiments are accomplished on our experimental installation to validate the feasibility of the IBA method. First, a fused silica sample with a rectangular pit defect is figured by using IBA. Through two iterations within only 47.5 min, this highly steep pit is effectively corrected, and the surface error is improved from the original 24.69 nm root mean square (RMS) to the final 3.68 nm RMS. Then another experiment is carried out to demonstrate the correcting capability of IBA for mid-to-high spatial frequency surface errors, and the final results indicate that the surface accuracy and surface quality can be simultaneously improved.

40 HP Electro-Mechanical Actuator

NASA Technical Reports Server (NTRS)

Fulmer, Chris

1996-01-01

This report summarizes the work performed on the 40 BP electro-mechanical actuator (EMA) system developed on NASA contract NAS3-25799 for the NASA National Launch System and Electrical Actuation (ELA) Technology Bridging Programs. The system was designed to demonstrate the capability of large, high power linear ELA's for applications such as Thrust Vector Control (TVC) on rocket engines. It consists of a motor controller, high frequency power source, drive electronics and a linear actuator. The power source is a 25kVA 20 kHz Mapham inverter. The drive electronics are based on the pulse population modulation concept and operate at a nominal frequency of 40 kHz. The induction motor is a specially designed high speed, low inertia motor capable of a 68 peak HP. The actuator was originally designed by MOOG Aerospace under an internal R & D program to meet Space Shuttle Main Engine (SSME) TVC requirements. The design was modified to meet this programs linear rate specification of 7.4 inches/second. The motor and driver were tested on a dynamometer at the Martin Marietta Space Systems facility. System frequency response and step response tests were conducted at the Marshall Space Flight Center facility. A complete description of the system and all test results can be found in the body of the report.

The Polar Plasma Wave Instrument

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Persoon, A. M.; Randall, R. F.; Odem, D. L.; Remington, S. L.; Averkamp, T. F.; Debower, M. M.; Hospodarsky, G. B.; Huff, R. L.; Kirchner, D. L.

1995-01-01

The Plasma Wave Instrument on the Polar spacecraft is designed to provide measurements of plasma waves in the Earth's polar regions over the frequency range from 0.1 Hz to 800 kHz. Three orthogonal electric dipole antennas are used to detect electric fields, two in the spin plane and one aligned along the spacecraft spin axis. A magnetic loop antenna and a triaxial magnetic search coil antenna are used to detect magnetic fields. Signals from these antennas are processed by five receiver systems: a wideband receiver, a high-frequency waveform receiver, a low-frequency waveform receiver, two multichannel analyzers; and a pair of sweep frequency receivers. Compared to previous plasma wave instruments, the Polar plasma wave instrument has several new capabilities. These include (1) an expanded frequency range to improve coverage of both low- and high-frequency wave phenomena, (2) the ability to simultaneously capture signals from six orthogonal electric and magnetic field sensors, and (3) a digital wideband receiver with up to 8-bit resolution and sample rates as high as 249k samples s(exp -1).

170-MHz electrodeless quartz crystal microbalance biosensor: capability and limitation of higher frequency measurement.

PubMed

Ogi, Hirotsugu; Nagai, Hironao; Naga, Hironao; Fukunishi, Yuji; Hirao, Masahiko; Nishiyama, Masayoshi

2009-10-01

We develop a highly sensitive quartz crystal microbalance (QCM) biosensor with a fundamental resonance frequency of 170 MHz. A naked AT-cut quartz plate of 9.7 microm thick is set in a sensor cell. Its shear vibration is excited by the line wire, and the vibration signals are detected by the other line wire, achieving the noncontacting measurement of the resonance frequency. The mass sensitivity of the 170 MHz QCM biosensor is 15 pg/(cm2 Hz), which is better than that of a conventional 5 MHz QCM by 3 orders of magnitude. Its high sensitivity is confirmed by detecting human immunoglobulin G (hIgG) via Staphylococcus protein A immobilized nonspecifically on both surfaces of the quartz plate. The detection limit is 0.5 pM. Limitation of the high-frequency QCM measurement is then theoretically discussed with a continuum mechanics model for a plate with point masses connected by elastic springs. The result indicates that a QCM measurement will break down at frequencies one-order-of-magnitude higher than the local resonance frequency at specific binding cites.

Applications Technology Satellite 6 - Upgrading the life style of millions of people. [health and educational TV broadcasting

NASA Technical Reports Server (NTRS)

Thole, J. M.; Dornbrand, H.

1974-01-01

The primary objective of the ATS-6 is to demonstrate the feasibility of operating a high-powered geosynchronous communications satellite capable of relaying color TV and other high-quality signals on multiple frequencies to relatively simple and inexpensive ground receivers. Other capabilities include providing a link between ships, aircraft, or other earth satellites (e.g., low-orbit meteorological satellites) and the ground. The ATS-6 flight-objective accomplishments and subsystem performance for its first 30 days in orbit are summarized. Success is predicted for most of the experiments carried.

Electro-Mechanical Actuator. DC Resonant Link Controller

NASA Technical Reports Server (NTRS)

Schreiner, Kenneth E.

1996-01-01

This report summarizes the work performed on the 68 HP electro-mechanical actuator (EMA) system developed on NASA contract for the Electrical Actuation (ELA) Technology Bridging Program. The system was designed to demonstrate the capability of large, high power linear ELAs for applications such as Thrust Vector Control (TVC) on rocket engines. It consists of a motor controller, drive electronics and a linear actuator capable of up to 32,00 lbs loading at 7.4 inches/second. The drive electronics are based on the Resonant DC link concept and operate at a nominal frequency of 55 kHz. The induction motor is a specially designed high speed, low inertia motor capable of a 68 peak HP. The actuator was originally designed by MOOG Aerospace under an internal R & D program to meet Space Shuttle Main Engine (SSME) TVC requirements. The design was modified to meet this programs linear rate specification of 7.4 inches/second. The motor and driver were tested on a dynamometer at the Martin Marietta Space Systems facility. System frequency response, step response and force-velocity tests were conducted at the MOOG Aerospace facility. A complete description of the system and all test results can be found in the body of the report.

Missileer: The Dawn, Decline, and Reinvigoration of America’s Intercontinental Ballistic Missile Operators

DTIC Science & Technology

2017-06-01

Group, resulting in all missiles entering ‘ radio mode’ and making them air-launch accessible.1 This loss of communications was an anomaly caused by an...MEECN) Program (MMP) Part of MEECN program that replaced legacy Survivable Low Frequency Communications System (SLFCS) with integrated extremely high...very low/low frequency (EHF/VLF/LF) communications capability. Began in 2003 and finished in 2005. Security Modernization (Three phases: Fast

Ultrahigh Frequency Lensless Ultrasonic Transducers for Acoustic Tweezers Application

PubMed Central

Hsu, Hsiu-Sheng; Li, Ying; Lee, Changyang; Lin, Anderson; Zhou, Qifa; Kim, Eun Sok; Shung, Kirk Koping

2014-01-01

Similar to optical tweezers, a tightly focused ultrasound microbeam is needed to manipulate microparticles in acoustic tweezers. The development of highly sensitive ultrahigh frequency ultrasonic transducers is crucial for trapping particles or cells with a size of a few microns. As an extra lens would cause excessive attenuation at ultrahigh frequencies, two types of 200-MHz lensless transducer design were developed as an ultrasound microbeam device for acoustic tweezers application. Lithium niobate single crystal press-focused (PF) transducer and zinc oxide self-focused transducer were designed, fabricated and characterized. Tightly focused acoustic beams produced by these transducers were shown to be capable of manipulating single microspheres as small as 5 μm two-dimensionally within a range of hundreds of micrometers in distilled water. The size of the trapped microspheres is the smallest ever reported in the literature of acoustic PF devices. These results suggest that these lensless ultrahigh frequency ultrasonic transducers are capable of manipulating particles at the cellular level and that acoustic tweezers may be a useful tool to manipulate a single cell or molecule for a wide range of biomedical applications. PMID:23042219

Visible-Frequency Dielectric Metasurfaces for Multiwavelength Achromatic and Highly Dispersive Holograms.

PubMed

Wang, Bo; Dong, Fengliang; Li, Qi-Tong; Yang, Dong; Sun, Chengwei; Chen, Jianjun; Song, Zhiwei; Xu, Lihua; Chu, Weiguo; Xiao, Yun-Feng; Gong, Qihuang; Li, Yan

2016-08-10

Dielectric metasurfaces built up with nanostructures of high refractive index represent a powerful platform for highly efficient flat optical devices due to their easy-tuning electromagnetic scattering properties and relatively high transmission efficiencies. Here we show visible-frequency silicon metasurfaces formed by three kinds of nanoblocks multiplexed in a subwavelength unit to constitute a metamolecule, which are capable of wavefront manipulation for red, green, and blue light simultaneously. Full phase control is achieved for each wavelength by independently changing the in-plane orientations of the corresponding nanoblocks to induce the required geometric phases. Achromatic and highly dispersive meta-holograms are fabricated to demonstrate the wavefront manipulation with high resolution. This technique could be viable for various practical holographic applications and flat achromatic devices.

TerraHertz Free Electron Laser Applications for Satellite Remote Sensing

NASA Technical Reports Server (NTRS)

Heaps, William S.

2003-01-01

The development of a Free Electron Laser (EL) operating in the terahertz frequency regime by the group at the University of Hawaii (Elias et al.) represents a significant new opportunity in the area of atmospheric remote sensing. The FEL has 2 salient features that create a unique opportunity. First of all it represents the only source in this frequency range with sufficient power to enable lidar instrumentation. Secondly its very high electrical efficiency (several times more efficient than any currently employed spaceborne laser) renders it a strong candidate for use in satellite remote sensing. On the negative side the atmosphere is rather strongly absorbing throughout this frequency range due primarily to the water vapor continuum absorption. This means that the instruments using this laser will not be able to access the lower troposphere because of its very high water concentration.. However the instrument will be very capable of measurements in the upper troposphere and stratosphere. A passive instrument, the Microwave Limb Sounder on the UARS satellite operated by Jet Propulsion Laboratory, has already demonstrated that this wavelength region can be used for chemical species with strong emission lines. A lidar would complement the capabilities of this instrument by providing the capability to measure absorbing species in the upper atmosphere. I will discuss the design of such an instrument in greater detail and estimate its performance in measuring a number of chemical species of interest to the Earth Science community.

Controlling Wind Turbines for Secondary Frequency Regulation: An Analysis of AGC Capabilities Under New Performance Based Compensation Policy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aho, Jacob; Pao, Lucy Y.; Fleming, Paul

2014-11-13

As wind energy becomes a larger portion of the world's energy portfolio there has been an increased interest for wind turbines to control their active power output to provide ancillary services which support grid reliability. One of these ancillary services is the provision of frequency regulation, also referred to as secondary frequency control or automatic generation control (AGC), which is often procured through markets which recently adopted performance-based compensation. A wind turbine with a control system developed to provide active power ancillary services can be used to provide frequency regulation services. Simulations have been performed to determine the AGC trackingmore » performance at various power schedule set-points, participation levels, and wind conditions. The performance metrics used in this study are based on those used by several system operators in the US. Another metric that is analyzed is the damage equivalent loads (DELs) on turbine structural components, though the impacts on the turbine electrical components are not considered. The results of these single-turbine simulations show that high performance scores can be achieved when there are insufficient wind resources available. The capability of a wind turbine to rapidly and accurately follow power commands allows for high performance even when tracking rapidly changing AGC signals. As the turbine de-rates to meet decreased power schedule set-points there is a reduction in the DELs, and the participation in frequency regulation has a negligible impact on these loads.« less

A dual frequency microstrip antenna for Ka band

NASA Technical Reports Server (NTRS)

Lee, R. Q.; Baddour, M. F.

1985-01-01

For fixed satellite communication systems at Ka band with downlink at 17.7 to 20.2 GHz and uplink at 27.5 to 30.0 GHz, the focused optics and the unfocused optics configurations with monolithic phased array feeds have often been used to provide multiple fixed and multiple scanning spot beam coverages. It appears that a dual frequency microstrip antenna capable of transmitting and receiving simultaneously is highly desirable as an array feed element. This paper describes some early efforts on the development and experimental testing of a dual frequency annular microstrip antenna. The antenna has potential application for use in conjunction with a monolithic microwave integrated circuit device as an active radiating element in a phased array of phased array feeds. The antenna is designed to resonate at TM sub 12 and TM sub 13 modes and tuned with a circumferential microstrip ring to vary the frequency ratio. Radiation characteristics at both the high and low frequencies are examined. Experimental results including radiating patterns and swept frequency measurements are presented.

Laser source for dimensional metrology: investigation of an iodine stabilized system based on narrow linewidth 633 nm DBR diode

NASA Astrophysics Data System (ADS)

Rerucha, Simon; Yacoot, Andrew; Pham, Tuan M.; Cizek, Martin; Hucl, Vaclav; Lazar, Josef; Cip, Ondrej

2017-04-01

We demonstrated that an iodine stabilized distributed Bragg reflector (DBR) diode based laser system lasing at a wavelength in close proximity to λ =633 nm could be used as an alternative laser source to the helium-neon lasers in both scientific and industrial metrology. This yields additional advantages besides the optical frequency stability and coherence: inherent traceability, wider optical frequency tuning range, higher output power and high frequency modulation capability. We experimentally investigated the characteristics of the laser source in two major steps: first using a wavelength meter referenced to a frequency comb controlled with a hydrogen maser and then on an interferometric optical bench testbed where we compared the performance of the laser system with that of a traditional frequency stabilized He-Ne laser. The results indicate that DBR diode laser system provides a good laser source for applications in dimensional (nano)metrology, especially in conjunction with novel interferometric detection methods exploiting high frequency modulation or multiaxis measurement systems.

ALDO: A radiation-tolerant, low-noise, adjustable low drop-out linear regulator in 0.35 μm CMOS technology

NASA Astrophysics Data System (ADS)

Carniti, P.; Cassina, L.; Gotti, C.; Maino, M.; Pessina, G.

2016-07-01

In this work we present ALDO, an adjustable low drop-out linear regulator designed in AMS 0.35 μm CMOS technology. It is specifically tailored for use in the upgraded LHCb RICH detector in order to improve the power supply noise for the front end readout chip (CLARO). ALDO is designed with radiation-tolerant solutions such as an all-MOS band-gap voltage reference and layout techniques aiming to make it able to operate in harsh environments like High Energy Physics accelerators. It is capable of driving up to 200 mA while keeping an adequate power supply filtering capability in a very wide frequency range from 10 Hz up to 100 MHz. This property allows us to suppress the noise and high frequency spikes that could be generated by a DC/DC regulator, for example. ALDO also shows a very low noise of 11.6 μV RMS in the same frequency range. Its output is protected with over-current and short detection circuits for a safe integration in tightly packed environments. Design solutions and measurements of the first prototype are presented.

Easily disassembled electrical connector for high voltage, high frequency connections

DOEpatents

Milner, Joseph R.

1994-01-01

An easily accessible electrical connector capable of rapid assembly and disassembly wherein a wide metal conductor sheet may be evenly contacted over the entire width of the conductor sheet by opposing surfaces on the connector which provide an even clamping pressure against opposite surfaces of the metal conductor sheet using a single threaded actuating screw.

High-Speed, high-power, switching transistor

NASA Technical Reports Server (NTRS)

Carnahan, D.; Ohu, C. K.; Hower, P. L.

1979-01-01

Silicon transistor rate for 200 angstroms at 400 to 600 volts combines switching speed of transistors with ruggedness, power capacity of thyristor. Transistor introduces unique combination of increased power-handling capability, unusally low saturation and switching losses, and submicrosecond switching speeds. Potential applications include high power switching regulators, linear amplifiers, chopper controls for high frequency electrical vehicle drives, VLF transmitters, RF induction heaters, kitchen cooking ranges, and electronic scalpels for medical surgery.

Wafer scale millimeter-wave integrated circuits based on epitaxial graphene in high data rate communication

PubMed Central

Habibpour, Omid; He, Zhongxia Simon; Strupinski, Wlodek; Rorsman, Niklas; Zirath, Herbert

2017-01-01

In recent years, the demand for high data rate wireless communications has increased dramatically, which requires larger bandwidth to sustain multi-user accessibility and quality of services. This can be achieved at millimeter wave frequencies. Graphene is a promising material for the development of millimeter-wave electronics because of its outstanding electron transport properties. Up to now, due to the lack of high quality material and process technology, the operating frequency of demonstrated circuits has been far below the potential of graphene. Here, we present monolithic integrated circuits based on epitaxial graphene operating at unprecedented high frequencies (80–100 GHz). The demonstrated circuits are capable of encoding/decoding of multi-gigabit-per-second information into/from the amplitude or phase of the carrier signal. The developed fabrication process is scalable to large wafer sizes. PMID:28145513

Static FBG strain sensor with high resolution and large dynamic range by dual-comb spectroscopy.

PubMed

Kuse, Naoya; Ozawa, Akira; Kobayashi, Yohei

2013-05-06

We demonstrate a fiber Bragg grating (FBG) strain sensor with optical frequency combs. To precisely characterize the optical response of the FBG when strain is applied, dual-comb spectroscopy is used. Highly sensitive dual-comb spectroscopy of the FBG enabled strain measurements with a resolution of 34 nε. The optical spectral bandwidth of the measurement exceeds 1 THz. Compared with conventional FBG strain sensor using a continuous-wave laser that requires rather slow frequency scanning with a limited range, the dynamic range and multiplexing capability are significantly improved by using broadband dual-comb spectroscopy.

200 Deg C Demonstration Transformer Operates Efficiently at 50 kHz

NASA Technical Reports Server (NTRS)

Niedra, Janis M.; Schwarze, Gene E. (Technical Monitor)

2003-01-01

A compact, high temperature demonstration transformer was constructed, using a moly permalloy powder core and Teflon -insulated copper wire. At 50 kHz and 200 C, this 1:2 ratio transformer is capable of 98 percent efficiency when operating at a specific power of 6.1 kW/kg at 4 kW. This roughly 7 cm diameter transformer has a mass of 0.65 kg. Although Teflon is unstable above 200 C, about the same electrical performance was seen at 250 C. A plot of winding loss versus frequency illustrates the need to control these losses at high frequency.

Extremely high frequency sensitivity in a ‘simple’ ear

PubMed Central

Moir, Hannah M.; Jackson, Joseph C.; Windmill, James F. C.

2013-01-01

An evolutionary war is being played out between the bat, which uses ultrasonic calls to locate insect prey, and the moth, which uses microscale ears to listen for the approaching bat. While the highest known frequency of bat echolocation calls is 212 kHz, the upper limit of moth hearing is considered much lower. Here, we show that the greater wax moth, Galleria mellonella, is capable of hearing ultrasonic frequencies approaching 300 kHz; the highest frequency sensitivity of any animal. With auditory frequency sensitivity that is unprecedented in the animal kingdom, the greater wax moth is ready and armed for any echolocation call adaptations made by the bat in the on-going bat–moth evolutionary war. PMID:23658005

Method for high resolution magnetic resonance analysis using magic angle technique

DOEpatents

Wind, Robert A.; Hu, Jian Zhi

2003-11-25

A method of performing a magnetic resonance analysis of a biological object that includes placing the biological object in a main magnetic field and in a radio frequency field, the main magnetic field having a static field direction; rotating the biological object at a rotational frequency of less than about 100 Hz around an axis positioned at an angle of about 54.degree.44' relative to the main magnetic static field direction; pulsing the radio frequency to provide a sequence that includes a magic angle turning pulse segment; and collecting data generated by the pulsed radio frequency. According to another embodiment, the radio frequency is pulsed to provide a sequence capable of producing a spectrum that is substantially free of spinning sideband peaks.

THE HYPERFINE STRUCTURE OF THE ROTATIONAL SPECTRUM OF HDO AND ITS EXTENSION TO THE THz REGION: ACCURATE REST FREQUENCIES AND SPECTROSCOPIC PARAMETERS FOR ASTROPHYSICAL OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cazzoli, Gabriele; Lattanzi, Valerio; Puzzarini, Cristina

2015-06-10

The rotational spectrum of the mono-deuterated isotopologue of water, HD{sup 16}O, has been investigated in the millimeter- and submillimeter-wave frequency regions, up to 1.6 THz. The Lamb-dip technique has been exploited to obtain sub-Doppler resolution and to resolve the hyperfine (hf) structure due to the deuterium and hydrogen nuclei, thus enabling the accurate determination of the corresponding hf parameters. Their experimental determination has been supported by high-level quantum-chemical calculations. The Lamb-dip measurements have been supplemented by Doppler-limited measurements (weak high-J and high-frequency transitions) in order to extend the predictive capability of the available spectroscopic constants. The possibility of resolving hfmore » splittings in astronomical spectra has been discussed.« less

On the use of high-frequency SCADA data for improved wind turbine performance monitoring

NASA Astrophysics Data System (ADS)

Gonzalez, E.; Stephen, B.; Infield, D.; Melero, J. J.

2017-11-01

SCADA-based condition monitoring of wind turbines facilitates the move from costly corrective repairs towards more proactive maintenance strategies. In this work, we advocate the use of high-frequency SCADA data and quantile regression to build a cost effective performance monitoring tool. The benefits of the approach are demonstrated through the comparison between state-of-the-art deterministic power curve modelling techniques and the suggested probabilistic model. Detection capabilities are compared for low and high-frequency SCADA data, providing evidence for monitoring at higher resolutions. Operational data from healthy and faulty turbines are used to provide a practical example of usage with the proposed tool, effectively achieving the detection of an incipient gearbox malfunction at a time horizon of more than one month prior to the actual occurrence of the failure.

Examination of the high-frequency capability of carbon nanotube FETs

NASA Astrophysics Data System (ADS)

Pulfrey, David L.; Chen, Li

2008-09-01

New results are added to a recent critique of the high-frequency performance of carbon nanotube field-effect transistors (CNFETs). On the practical side, reduction of the number of metallic tubes in CNFETs fashioned from multiple nanotubes has allowed the measured fT to be increased to 30 GHz. On the theoretical side, the opinion that the band-structure-determined velocity limits the high-frequency performance has been reinforced by corrections to recent simulation results for doped-contact CNFETs, and by the ruling out of the possibility of favourable image-charge effects. Inclusion in the simulations of the features of finite gate-metal thickness and source/drain contact resistance has given an indication of likely practical values for fT. A meaningful comparison between CNFETs with doped-contacts and metallic contacts has been made.

Command and Service Module Communications

NASA Technical Reports Server (NTRS)

Interbartolo, Michael

2009-01-01

This viewgraph presentation examines Command and Service Module (CSM) Communications. The communication system's capabilities are defined, including CSM-Earth, CSM-Lunar Module and CSM-Extravehicular crewman communications. An overview is provided for S-band communications, including data transmission and receiving rates, operating frequencies and major system components (pre-modulation processors, unified S-band electronics, S-band power amplifier and S-band antennas). Additionally, data transmission rates, operating frequencies and the capabilities of VHF communications are described. Major VHF components, including transmitters and receivers, and the VHF multiplexer and antennas are also highlighted. Finally, communications during pre-launch, ascent, in-flight and entry are discussed. Overall, the CSM communication system was rated highly by flight controllers and crew. The system was mostly autonomous for both crew and flight controllers and no major issues were encountered during flight.

Adhesion, friction, and wear of plasma-deposited thin silicon nitride films at temperatures to 700 C

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Pouch, J. J.; Alterovitz, S. A.; Pantic, D. M.; Johnson, G. A.

1988-01-01

The adhesion, friction, and wear behavior of silicon nitride films deposited by low- and high-frequency plasmas (30 kHz and 13.56 MHz) at various temperatures to 700 C in vacuum were examined. The results of the investigation indicated that the Si/N ratios were much greater for the films deposited at 13.56 MHz than for those deposited at 30 kHz. Amorphous silicon was present in both low- and high-frequency plasma-deposited silicon nitride films. However, more amorphous silicon occurred in the films deposited at 13.56 MHz than in those deposited at 30 kHz. Temperature significantly influenced adhesion, friction, and wear of the silicon nitride films. Wear occurred in the contact area at high temperature. The wear correlated with the increase in adhesion and friction for the low- and high-frequency plasma-deposited films above 600 and 500 C, respectively. The low- and high-frequency plasma-deposited thin silicon nitride films exhibited a capability for lubrication (low adhesion and friction) in vacuum at temperatures to 500 and 400 C, respectively.

Comparing the Capabilities and Performance of the Ultra High Frequency Follow-On System With the Mobile User Objective System

DTIC Science & Technology

2011-06-01

designed to augment and eventually replace the currently oversubscribed UHF Follow- On ( UFO ) System. MUOS adapts a commercial third generation (3G...towers) with the goal of providing a more capable UHF SATCOM system. This research aims at investigating the differences between the legacy UFO and...improvements. The study finds that MUOS can tolerate a traffic demand rate of about 83 calls/messages per second whereas UFO saturates at roughly 4 calls

Nested neural networks

NASA Technical Reports Server (NTRS)

Baram, Yoram

1988-01-01

Nested neural networks, consisting of small interconnected subnetworks, allow for the storage and retrieval of neural state patterns of different sizes. The subnetworks are naturally categorized by layers of corresponding to spatial frequencies in the pattern field. The storage capacity and the error correction capability of the subnetworks generally increase with the degree of connectivity between layers (the nesting degree). Storage of only few subpatterns in each subnetworks results in a vast storage capacity of patterns and subpatterns in the nested network, maintaining high stability and error correction capability.

Advanced Wavefront Control Techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olivier, S S; Brase, J M; Avicola, K

2001-02-21

Programs at LLNL that involve large laser systems--ranging from the National Ignition Facility to new tactical laser weapons--depend on the maintenance of laser beam quality through precise control of the optical wavefront. This can be accomplished using adaptive optics, which compensate for time-varying aberrations that are often caused by heating in a high-power laser system. Over the past two decades, LLNL has developed a broad capability in adaptive optics technology for both laser beam control and high-resolution imaging. This adaptive optics capability has been based on thin deformable glass mirrors with individual ceramic actuators bonded to the back. In themore » case of high-power lasers, these adaptive optics systems have successfully improved beam quality. However, as we continue to extend our applications requirements, the existing technology base for wavefront control cannot satisfy them. To address this issue, this project studied improved modeling tools to increase our detailed understanding of the performance of these systems, and evaluated novel approaches to low-order wavefront control that offer the possibility of reduced cost and complexity. We also investigated improved beam control technology for high-resolution wavefront control. Many high-power laser systems suffer from high-spatial-frequency aberrations that require control of hundreds or thousands of phase points to provide adequate correction. However, the cost and size of current deformable mirrors can become prohibitive for applications requiring more than a few tens of phase control points. New phase control technologies are becoming available which offer control of many phase points with small low-cost devices. The goal of this project was to expand our wavefront control capabilities with improved modeling tools, new devices that reduce system cost and complexity, and extensions to high spatial and temporal frequencies using new adaptive optics technologies. In FY 99, the second year of this project, work was performed in four areas (1) advanced modeling tools for deformable mirrors (2) low-order wavefront correctors with Alvarez lenses, (3) a direct phase measuring heterdyne wavefront sensor, and (4) high-spatial-frequency wavefront control using spatial light modulators.« less

High Frequency Direction Finding Using Structurally Integrated Antennas on a Large Airborne Platform

DTIC Science & Technology

2011-03-24

signal processing techniques, including superresolution techniques, as a possible way to extend the airborne DF capability to the HF band. Structurally...electrically or mechan- ically scanned beams has been diminished by array processing techniques [4]. The implementation of superresolution algorithms

Combined electromechanical impedance and fiber optic diagnosis of aerospace structures

NASA Astrophysics Data System (ADS)

Schlavin, Jon; Zagrai, Andrei; Clemens, Rebecca; Black, Richard J.; Costa, Joey; Moslehi, Behzad; Patel, Ronak; Sotoudeh, Vahid; Faridian, Fereydoun

2014-03-01

Electromechanical impedance is a popular diagnostic method for assessing structural conditions at high frequencies. It has been utilized, and shown utility, in aeronautic, space, naval, civil, mechanical, and other types of structures. By contrast, fiber optic sensing initially found its niche in static strain measurement and low frequency structural dynamic testing. Any low frequency limitations of the fiber optic sensing, however, are mainly governed by its hardware elements. As hardware improves, so does the bandwidth (frequency range * number of sensors) provided by the appropriate enabling fiber optic sensor interrogation system. In this contribution we demonstrate simultaneous high frequency measurements using fiber optic and electromechanical impedance structural health monitoring technologies. A laboratory specimen imitating an aircraft wing structure, incorporating surfaces with adjustable boundary conditions, was instrumented with piezoelectric and fiber optic sensors. Experiments were conducted at different structural boundary conditions associated with deterioration of structural health. High frequency dynamic responses were collected at multiple locations on a laboratory wing specimen and conclusions were drawn about correspondence between structural damage and dynamic signatures as well as correlation between electromechanical impedance and fiber optic sensors spectra. Theoretical investigation of the effect of boundary conditions on electromechanical impedance spectra is presented and connection to low frequency structural dynamics is suggested. It is envisioned that acquisition of high frequency structural dynamic responses with multiple fiber optic sensors may open new diagnostic capabilities for fiber optic sensing technologies.

High-resolution time-frequency representation of EEG data using multi-scale wavelets

NASA Astrophysics Data System (ADS)

Li, Yang; Cui, Wei-Gang; Luo, Mei-Lin; Li, Ke; Wang, Lina

2017-09-01

An efficient time-varying autoregressive (TVAR) modelling scheme that expands the time-varying parameters onto the multi-scale wavelet basis functions is presented for modelling nonstationary signals and with applications to time-frequency analysis (TFA) of electroencephalogram (EEG) signals. In the new parametric modelling framework, the time-dependent parameters of the TVAR model are locally represented by using a novel multi-scale wavelet decomposition scheme, which can allow the capability to capture the smooth trends as well as track the abrupt changes of time-varying parameters simultaneously. A forward orthogonal least square (FOLS) algorithm aided by mutual information criteria are then applied for sparse model term selection and parameter estimation. Two simulation examples illustrate that the performance of the proposed multi-scale wavelet basis functions outperforms the only single-scale wavelet basis functions or Kalman filter algorithm for many nonstationary processes. Furthermore, an application of the proposed method to a real EEG signal demonstrates the new approach can provide highly time-dependent spectral resolution capability.

Investigation of a compact coaxially fed switched oscillator.

PubMed

Wang, Yuwei; Chen, Dongqun; Zhang, Jiande; Cao, Shengguang; Li, Da; Liu, Chebo

2013-09-01

To generate a relative high frequency mesoband microwave, a compact coaxially fed transmission line switched oscillator with high voltage capability is investigated. The characteristic impedance and voltage capability of the low impedance transmission line (LITL) have been analyzed. It is shown that the working voltage of the oscillator can reach up to 200 kV when it is filled by pressurized nitrogen and charged by a nanosecond driving source. By utilizing a commercial electromagnetic simulation code, the transient performance of the switched oscillator with a lumped resistance load is simulated. It is illustrated that the center frequency of the output signal reaches up to ~0.6 GHz when the spark gap practically closes with a single channel. Besides, the influence of the closing mode and rapidity of the spark gap, the permittivity of the insulator at the output end of the LITL, and the load impedance on the transient performance of the designed oscillator has been analyzed in quantification. Finally, the good transient performance of the switched oscillator has been preliminarily proved by the experiment.

Spinning Reserve From Hotel Load Response: Initial Progress

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kueck, John D; Kirby, Brendan J

2008-11-01

This project was motivated by the fundamental match between hotel space conditioning load response capability and power system contingency response needs. As power system costs rise and capacity is strained demand response can provide a significant system reliability benefit at a potentially attractive cost. At ORNL s suggestion, Digital Solutions Inc. adapted its hotel air conditioning control technology to supply power system spinning reserve. This energy saving technology is primarily designed to provide the hotel operator with the ability to control individual room temperature set-points based upon occupancy (25% to 50% energy savings based on an earlier study [Kirby andmore » Ally, 2002]). DSI added instantaneous local load shedding capability in response to power system frequency and centrally dispatched load shedding capability in response to power system operator command. The 162 room Music Road Hotel in Pigeon Forge Tennessee agreed to host the spinning reserve test. The Tennessee Valley Authority supplied real-time metering equipment in the form of an internet connected Dranetz-BMI power quality meter and monitoring expertise to record total hotel load during both normal operations and test results. The Sevier County Electric System installed the metering. Preliminary testing showed that hotel load can be curtailed by 22% to 37% depending on the outdoor temperature and the time of day. These results are prior to implementing control over the common area air conditioning loads. Testing was also not at times of highest system or hotel loading. Full response occurred in 12 to 60 seconds from when the system operator s command to shed load was issued. The load drop was very rapid, essentially as fast as the 2 second metering could detect, with all units responding essentially simultaneously. Load restoration was ramped back in over several minutes. The restoration ramp can be adjusted to the power system needs. Frequency response testing was not completed. Initial testing showed that the units respond very quickly. Problems with local power quality generated false low frequency signals which required testing to be stopped. This should not be a problem in actual operation since the frequency trip points will be staggered to generate a droop curve which mimics generator governor response. The actual trip frequencies will also be low enough to avoid power quality problems. The actual trip frequencies are too low to generate test events with sufficient regularity to complete testing in a reasonable amount of time. Frequency response testing will resume once the local power quality problem is fully understood and reasonable test frequency settings can be determined. Overall the preliminary testing was extremely successful. The hotel response capability matches the power system reliability need, being faster than generation response and inherently available when the power system is under the most stress (times of high system and hotel load). Periodic testing is scheduled throughout the winter and spring to characterize hotel response capability under a full range of conditions. More extensive testing will resume when summer outdoor temperatures are again high enough to fully test hotel response.« less

Clusters of α-LiFeO2 nanoparticles incorporated into multi-walled carbon nanotubes: a lithium-ion battery cathode with enhanced lithium storage properties.

PubMed

Rahman, Md Mokhlesur; Glushenkov, Alexey M; Chen, Zhiqiang; Dai, Xiujuan J; Ramireddy, Thrinathreddy; Chen, Ying

2013-12-14

We report the preparation of a novel nanocomposite architecture of α-LiFeO2-MWCNT based on clusters of α-LiFeO2 nanoparticles incorporated into multiwalled carbon nanotubes (MWCNTs). The composite represents a promising cathode material for lithium-ion batteries. The preparation of the nanocomposite is achieved by combining a molten salt precipitation process and a radio frequency oxygen plasma for the first time. We demonstrate that clusters of α-LiFeO2 nanoparticles incorporated into MWCNTs are capable of delivering a stable and high reversible capacity of 147 mA h g(-1) at 1 C after 100 cycles with the first cycle Coulombic efficiency of ~95%. The rate capability of the composite is significantly improved and its reversible capacity is measured to be 101 mA h g(-1) at a high current rate of 10 C. Both rate capability and cycling stability are not simply a result of introduction of functionalized MWCNTs but most likely originate from the unique composite structure of clusters of α-LiFeO2 nanoparticles integrated into a network of MWCNTs. The excellent electrochemical performance of this new nanocomposite opens up new opportunities in the development of high-performance electrode materials for energy storage application using the radio frequency oxygen plasma technique.

Direct frequency comb optical frequency standard based on two-photon transitions of thermal atoms

PubMed Central

Zhang, S. Y.; Wu, J. T.; Zhang, Y. L.; Leng, J. X.; Yang, W. P.; Zhang, Z. G.; Zhao, J. Y.

2015-01-01

Optical clocks have been the focus of science and technology research areas due to their capability to provide highest frequency accuracy and stability to date. Their superior frequency performance promises significant advances in the fields of fundamental research as well as practical applications including satellite-based navigation and ranging. In traditional optical clocks, ultrastable optical cavities, laser cooling and particle (atoms or a single ion) trapping techniques are employed to guarantee high stability and accuracy. However, on the other hand, they make optical clocks an entire optical tableful of equipment, and cannot work continuously for a long time; as a result, they restrict optical clocks used as very convenient and compact time-keeping clocks. In this article, we proposed, and experimentally demonstrated, a novel scheme of optical frequency standard based on comb-directly-excited atomic two-photon transitions. By taking advantage of the natural properties of the comb and two-photon transitions, this frequency standard achieves a simplified structure, high robustness as well as decent frequency stability, which promise widespread applications in various scenarios. PMID:26459877

Association of physical capacity with heart rate variability based on a short-duration measurement of resting pulse rate in older adults with obesity

PubMed Central

Liao, Chun-De; Tsauo, Jau-Yih; Hsiao, Dun-Jen; Liou, Tsan-Hon

2017-01-01

Background Obesity can limit physical capacity and lower physical activity levels in elderly people. Low physical activity levels may be mediated by autonomic dysfunction with decreased heart rate variability (HRV). However, the relationship between autonomic dysfunction and low physical capability remains unclear. This cross-sectional study investigated the association of low physical capability with HRV in older adults with obesity. Materials and methods We recruited 231 old man and 210 old women with a mean (range) age of 65.5 (51−78) and 62.9 (52−76) years, respectively. Physical capability was measured using mobility tasks, including functional reach, single-leg stance (SLS), gait speed (GS), timed up and go, and timed chair rise (TCR), and the scores on these tasks were merged and transformed into a global physical capability score (GPCS). HRV was measured using a 7-min resting pulse-based technique, and the time- and frequency-domain indices of HRV were obtained including standard deviation of normal-to-normal intervals (SDNN), root mean square of successive differences at rest (rMSSD), and high-frequency (HF) power. All HRV indices were natural log (ln) transformed for analysis. Participants were divided into high, moderate, and low physical-capability groups according to their physical performance. Multivariate analysis of covariance was performed to test differences in HRV indices among physical-capability groups with participants’ characteristics serving as covariates. A stepwise regression model was established to identify the determinants of HRV indices. We used hierarchical regression analysis to identify the association of the GPCS with HRV indices. Results In both men and women, the low physical-capability group exhibited significantly increased heart rate (P <0.05) and decreased HRV in terms of a decreased ln[SDNN] (P <0.001), ln[rMSSD] (P <0.05) and ln[HF] (P <0.05), compared with the high physical-capability group. GS positively predicted ln[SDNN], whereas SLS, GS, and TCR were determinants of ln[HF], regardless of gender. The GPCS in older men and women independently accounted for 29.9% (P <0.001) and 23.7% (P <0.001), respectively, in variance in ln[SDNN]. Conclusions A low physical-capability level is an independent determinant of decreased HRV in older adults with obesity. PMID:29267296

Improved near-field characteristics of phased arrays for assessing concrete and cementitious materials

NASA Astrophysics Data System (ADS)

Wooh, Shi-Chang; Azar, Lawrence

1999-01-01

The degradation of civil infrastructure has placed a focus on effective nondestructive evaluation techniques to correctly assess the condition of existing concrete structures. Conventional high frequency ultrasonic response are severely affected by scattering and material attenuation, resulting in weak and confusing signal returns. Therefore, low frequency ultrasonic transducers, which avoid this problem of wave attenuation, are commonly used for concrete with limited capabilities. The focus of this research is to ascertain some benefits and limitations of a low frequency ultrasonic phased array transducer. In this paper, we investigate a novel low-frequency ultrasonic phased array and the results of experimental feasibility test for practical condition assessment of concrete structures are reported.

Inertial Response of Wind Power Plants: A Comparison of Frequency-Based Inertial Control and Stepwise Inertial Control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xiao; Gao, Wenzhong; Wang, Jianhui

The frequency regulation capability of a wind power plant plays an important role in enhancing frequency reliability especially in an isolated power system with high wind power penetration levels. A comparison of two types of inertial control methods, namely frequency-based inertial control (FBIC) and stepwise inertial control (SIC), is presented in this paper. Comprehensive case studies are carried out to reveal features of the different inertial control methods, simulated in a modified Western System Coordination Council (WSCC) nine-bus power grid using real-time digital simulator (RTDS) platform. The simulation results provide an insight into the inertial control methods under various scenarios.

Multiple layer optical memory system using second-harmonic-generation readout

DOEpatents

Boyd, Gary T.; Shen, Yuen-Ron

1989-01-01

A novel optical read and write information storage system is described which comprises a radiation source such as a laser for writing and illumination, the radiation source being capable of radiating a preselected first frequency; a storage medium including at least one layer of material for receiving radiation from the radiation source and capable of being surface modified in response to said radiation source when operated in a writing mode and capable of generating a pattern of radiation of the second harmonic of the preselected frequency when illuminated by the radiation source at the preselected frequency corresponding to the surface modifications on the storage medium; and a detector to receive the pattern of second harmonic frequency generated.

High frequency two-stage pulse tube cryocooler with base temperature below 20 K

NASA Astrophysics Data System (ADS)

Yang, L. W.; Thummes, G.

2005-02-01

High frequency (30-50 Hz) multi-stage pulse tube coolers that are capable of reaching temperatures close to 20 K or even lower are a subject of recent research and development activities. This paper reports on the design and test of a two-stage pulse tube cooler which is driven by a linear compressor with nominal input power of 200 W at an operating frequency of 30-45 Hz. A parallel configuration of the two pulse tubes is used with the warm ends of the pulse tubes located at ambient temperature. For both stages, the regenerator matrix consists of a stack of stainless steel screen. At an operating frequency of 35 Hz and with the first stage at 73 K a lowest stationary temperature of 19.6 K has been achieved at the second stage. The effects of input power, frequency, average pressure, and cold head orientation on the cooling performance are also reported. An even lower no-load temperature can be expected from the use of lead or other regenerator materials of high heat capacity in the second stage.

Decreased echolocation performance following high-frequency hearing loss in the false killer whale (Pseudorca crassidens).

PubMed

Kloepper, L N; Nachtigall, P E; Gisiner, R; Breese, M

2010-11-01

Toothed whales and dolphins possess a hypertrophied auditory system that allows for the production and hearing of ultrasonic signals. Although the fossil record provides information on the evolution of the auditory structures found in extant odontocetes, it cannot provide information on the evolutionary pressures leading to the hypertrophied auditory system. Investigating the effect of hearing loss may provide evidence for the reason for the development of high-frequency hearing in echolocating animals by demonstrating how high-frequency hearing assists in the functioning echolocation system. The discrimination abilities of a false killer whale (Pseudorca crassidens) were measured prior to and after documented high-frequency hearing loss. In 1992, the subject had good hearing and could hear at frequencies up to 100 kHz. In 2008, the subject had lost hearing at frequencies above 40 kHz. First in 1992, and then again in 2008, the subject performed an identical echolocation task, discriminating between machined hollow aluminum cylinder targets of differing wall thickness. Performances were recorded for individual target differences and compared between both experimental years. Performances on individual targets dropped between 1992 and 2008, with a maximum performance reduction of 36.1%. These data indicate that, with a loss in high-frequency hearing, there was a concomitant reduction in echolocation discrimination ability, and suggest that the development of a hypertrophied auditory system capable of hearing at ultrasonic frequencies evolved in response to pressures for fine-scale echolocation discrimination.

49 CFR 180.407 - Requirements for test and inspection of specification cargo tanks.

Code of Federal Regulations, 2014 CFR

2014-10-01

... constructed of mild steel or high-strength, low-alloy steel, that create air cavities adjacent to the tank...) Equipment must consist of: (A) A high frequency spark tester capable of producing sufficient voltage to...; and (C) A steel calibration coupon 30.5 cm × 30.5 cm (12 inches × 12 inches) covered with the same...

49 CFR 180.407 - Requirements for test and inspection of specification cargo tanks.

Code of Federal Regulations, 2012 CFR

2012-10-01

... constructed of mild steel or high-strength, low-alloy steel, that create air cavities adjacent to the tank...) Equipment must consist of: (A) A high frequency spark tester capable of producing sufficient voltage to...; and (C) A steel calibration coupon 30.5 cm × 30.5 cm (12 inches × 12 inches) covered with the same...

49 CFR 180.407 - Requirements for test and inspection of specification cargo tanks.

Code of Federal Regulations, 2011 CFR

2011-10-01

... constructed of mild steel or high-strength, low-alloy steel, that create air cavities adjacent to the tank...) Equipment must consist of: (A) A high frequency spark tester capable of producing sufficient voltage to...; and (C) A steel calibration coupon 30.5 cm × 30.5 cm (12 inches × 12 inches) covered with the same...

Easily disassembled electrical connector for high voltage, high frequency connections

DOEpatents

Milner, J.R.

1994-05-10

An easily accessible electrical connector capable of rapid assembly and disassembly is described wherein a wide metal conductor sheet may be evenly contacted over the entire width of the conductor sheet by opposing surfaces on the connector which provide an even clamping pressure against opposite surfaces of the metal conductor sheet using a single threaded actuating screw. 13 figures.

H. F. Frequency management by frequency sharing as assisted by models updated in real-time

NASA Astrophysics Data System (ADS)

Uffelman, D. R.; Harnish, L. O.; Goodman, J. M.

1984-03-01

Frequency management systems for the high frequencies (HF) currently in use by the U.S. Department of Defense (DoD) rely heavily on manual selection of frequencies which have been allocated on a circuit by circuit basis. There is no capability to anticipate frequency changes (QSY's) in advance in a manner such that a frequency being released by one user can be utilized effectively and immediately by a second user. NRL has been examining a scheme by which a small computer of the HF channel can be made to perform very accurately to anticipate channel characteristics in a short term prediction mode. It is proposed that this model be utilized to provide automated frequency management which would allow one to anticipate frequency availability and thereby allow sharing of frequencies between several users (frequency pooling). Utilizing data obtained from an oblique sounder net on the East Coast of the United States, this report suggests a method by which this may be accomplished.

High-frequency graphene voltage amplifier.

PubMed

Han, Shu-Jen; Jenkins, Keith A; Valdes Garcia, Alberto; Franklin, Aaron D; Bol, Ageeth A; Haensch, Wilfried

2011-09-14

While graphene transistors have proven capable of delivering gigahertz-range cutoff frequencies, applying the devices to RF circuits has been largely hindered by the lack of current saturation in the zero band gap graphene. Herein, the first high-frequency voltage amplifier is demonstrated using large-area chemical vapor deposition grown graphene. The graphene field-effect transistor (GFET) has a 6-finger gate design with gate length of 500 nm. The graphene common-source amplifier exhibits ∼5 dB low frequency gain with the 3 dB bandwidth greater than 6 GHz. This first AC voltage gain demonstration of a GFET is attributed to the clear current saturation in the device, which is enabled by an ultrathin gate dielectric (4 nm HfO(2)) of the embedded gate structures. The device also shows extrinsic transconductance of 1.2 mS/μm at 1 V drain bias, the highest for graphene FETs using large-scale graphene reported to date.

DSP/FPGA Design for a High-Speed Programmable S-Band Space Transceiver

NASA Technical Reports Server (NTRS)

Janicik, Jeffrey; Friedman, Assi

2013-01-01

Traditional command uplink receivers are very limited in performance capability, take a long time to acquire, cannot operate on both uplink bands (NASA & AFSCN), and only support low-rate communications. As a result, transceivers end up on many programs critical paths, even though they should be a standard purchased spacecraft subsystem. Also, many missions are impacted by the low effective uplink throughput. In order to tackle these challenges, a transceiver was developed that will provide on-site frequency agility, support of high uplink rates, and operation on both NASA and AFSCN frequency bands. The device is a low-power, high-reliability, and high-performance digital signal processing (DSP) demodulator for an on-orbit programmable command receiver.

Silicon-Carbide Power MOSFET Performance in High Efficiency Boost Power Processing Unit for Extreme Environments

NASA Technical Reports Server (NTRS)

Ikpe, Stanley A.; Lauenstein, Jean-Marie; Carr, Gregory A.; Hunter, Don; Ludwig, Lawrence L.; Wood, William; Del Castillo, Linda Y.; Fitzpatrick, Fred; Chen, Yuan

2016-01-01

Silicon-Carbide device technology has generated much interest in recent years. With superior thermal performance, power ratings and potential switching frequencies over its Silicon counterpart, Silicon-Carbide offers a greater possibility for high powered switching applications in extreme environment. In particular, Silicon-Carbide Metal-Oxide- Semiconductor Field-Effect Transistors' (MOSFETs) maturing process technology has produced a plethora of commercially available power dense, low on-state resistance devices capable of switching at high frequencies. A novel hard-switched power processing unit (PPU) is implemented utilizing Silicon-Carbide power devices. Accelerated life data is captured and assessed in conjunction with a damage accumulation model of gate oxide and drain-source junction lifetime to evaluate potential system performance at high temperature environments.

High-speed AFM and the reduction of tip-sample forces

NASA Astrophysics Data System (ADS)

Miles, Mervyn; Sharma, Ravi; Picco, Loren

High-speed DC-mode AFM has been shown to be routinely capable of imaging at video rate, and, if required, at over 1000 frames per second. At sufficiently high tip-sample velocities in ambient conditions, the tip lifts off the sample surface in a superlubricity process which reduces the level of shear forces imposed on the sample by the tip and therefore reduces the potential damage and distortion of the sample being imaged. High-frequency mechanical oscillations, both lateral and vertical, have been reported to reduced the tip-sample frictional forces. We have investigated the effect of combining linear high-speed scanning with these small amplitude high-frequency oscillations with the aim of reducing further the force interaction in high-speed imaging. Examples of this new version of high-speed AFM imaging will be presented for biological samples.

High frequency inductive lamp and power oscillator

DOEpatents

MacLennan, Donald A.; Dymond, Jr., Lauren E.; Gitsevich, Aleksandr; Grimm, William G.; Kipling, Kent; Kirkpatrick, Douglas A.; Ola, Samuel A.; Simpson, James E.; Trimble, William C.; Tsai, Peter; Turner, Brian P.

2001-01-01

A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and I or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency. Various control circuits may be employed to adjust the driving frequency of the oscillator.

Genomic Physics. Multiple Laser Beam Treatment of Alzheimer's Disease

NASA Astrophysics Data System (ADS)

Stefan, V. Alexander

2014-03-01

The synapses affected by Alzheimer's disease can be rejuvenated by the multiple ultrashort wavelength laser beams.[2] The guiding lasers scan the whole area to detect the amyloid plaques based on the laser scattering technique. The scanning lasers pinpoint the areas with plaques and eliminate them. Laser interaction is highly efficient, because of the focusing capabilities and possibility for the identification of the damaging proteins by matching the protein oscillation eigen-frequency with laser frequency.[3] Supported by Nikola Tesla Labs, La Jolla, California, USA.

A High Temperature Silicon Carbide mosfet Power Module With Integrated Silicon-On-Insulator-Based Gate Drive

DOE PAGES

Wang, Zhiqiang; Shi, Xiaojie; Tolbert, Leon M.; ...

2014-04-30

Here we present a board-level integrated silicon carbide (SiC) MOSFET power module for high temperature and high power density application. Specifically, a silicon-on-insulator (SOI)-based gate driver capable of operating at 200°C ambient temperature is designed and fabricated. The sourcing and sinking current capability of the gate driver are tested under various ambient temperatures. Also, a 1200 V/100 A SiC MOSFET phase-leg power module is developed utilizing high temperature packaging technologies. The static characteristics, switching performance, and short-circuit behavior of the fabricated power module are fully evaluated at different temperatures. Moreover, a buck converter prototype composed of the SOI gate drivermore » and SiC power module is built for high temperature continuous operation. The converter is operated at different switching frequencies up to 100 kHz, with its junction temperature monitored by a thermosensitive electrical parameter and compared with thermal simulation results. The experimental results from the continuous operation demonstrate the high temperature capability of the power module at a junction temperature greater than 225°C.« less

Single-frequency 3D synthetic aperture imaging with dynamic metasurface antennas.

PubMed

Boyarsky, Michael; Sleasman, Timothy; Pulido-Mancera, Laura; Diebold, Aaron V; Imani, Mohammadreza F; Smith, David R

2018-05-20

Through aperture synthesis, an electrically small antenna can be used to form a high-resolution imaging system capable of reconstructing three-dimensional (3D) scenes. However, the large spectral bandwidth typically required in synthetic aperture radar systems to resolve objects in range often requires costly and complex RF components. We present here an alternative approach based on a hybrid imaging system that combines a dynamically reconfigurable aperture with synthetic aperture techniques, demonstrating the capability to resolve objects in three dimensions (3D), with measurements taken at a single frequency. At the core of our imaging system are two metasurface apertures, both of which consist of a linear array of metamaterial irises that couple to a common waveguide feed. Each metamaterial iris has integrated within it a diode that can be biased so as to switch the element on (radiating) or off (non-radiating), such that the metasurface antenna can produce distinct radiation profiles corresponding to different on/off patterns of the metamaterial element array. The electrically large size of the metasurface apertures enables resolution in range and one cross-range dimension, while aperture synthesis provides resolution in the other cross-range dimension. The demonstrated imaging capabilities of this system represent a step forward in the development of low-cost, high-performance 3D microwave imaging systems.

Adjustable, High Voltage Pulse Generator with Isolated Output for Plasma Processing

NASA Astrophysics Data System (ADS)

Ziemba, Timothy; Miller, Kenneth E.; Prager, James; Slobodov, Ilia

2015-09-01

Eagle Harbor Technologies (EHT), Inc. has developed a high voltage pulse generator with isolated output for etch, sputtering, and ion implantation applications within the materials science and semiconductor processing communities. The output parameters are independently user adjustable: output voltage (0 - 2.5 kV), pulse repetition frequency (0 - 100 kHz), and duty cycle (0 - 100%). The pulser can drive loads down to 200 Ω. Higher voltage pulsers have also been tested. The isolated output allows the pulse generator to be connected to loads that need to be biased. These pulser generators take advantage modern silicon carbide (SiC) MOSFETs. These new solid-state switches decrease the switching and conduction losses while allowing for higher switching frequency capabilities. This pulse generator has applications for RF plasma heating; inductive and arc plasma sources; magnetron driving; and generation of arbitrary pulses at high voltage, high current, and high pulse repetition frequency. This work was supported in part by a DOE SBIR.

Frequency domain laser velocimeter signal processor: A new signal processing scheme

NASA Technical Reports Server (NTRS)

Meyers, James F.; Clemmons, James I., Jr.

1987-01-01

A new scheme for processing signals from laser velocimeter systems is described. The technique utilizes the capabilities of advanced digital electronics to yield a smart instrument that is able to configure itself, based on the characteristics of the input signals, for optimum measurement accuracy. The signal processor is composed of a high-speed 2-bit transient recorder for signal capture and a combination of adaptive digital filters with energy and/or zero crossing detection signal processing. The system is designed to accept signals with frequencies up to 100 MHz with standard deviations up to 20 percent of the average signal frequency. Results from comparative simulation studies indicate measurement accuracies 2.5 times better than with a high-speed burst counter, from signals with as few as 150 photons per burst.

The Microfluidic Jukebox

NASA Astrophysics Data System (ADS)

Tan, Say Hwa; Maes, Florine; Semin, Benoît; Vrignon, Jérémy; Baret, Jean-Christophe

2014-04-01

Music is a form of art interweaving people of all walks of life. Through subtle changes in frequencies, a succession of musical notes forms a melody which is capable of mesmerizing the minds of people. With the advances in technology, we are now able to generate music electronically without relying solely on physical instruments. Here, we demonstrate a musical interpretation of droplet-based microfluidics as a form of novel electronic musical instruments. Using the interplay of electric field and hydrodynamics in microfluidic devices, well controlled frequency patterns corresponding to musical tracks are generated in real time. This high-speed modulation of droplet frequency (and therefore of droplet sizes) may also provide solutions that reconciles high-throughput droplet production and the control of individual droplet at production which is needed for many biochemical or material synthesis applications.

On-chip microfluid induced by oscillation of microrobot for noncontact cell transportation

NASA Astrophysics Data System (ADS)

Feng, Lin; Liang, Shuzhang; Zhou, Xiangcong; Yang, Jianlei; Jiang, Yonggang; Zhang, Deyuan; Arai, Fumihito

2017-11-01

The importance of cell manipulation and cultivation is increasing rapidly in various fields, such as drug discovery, regenerative medicine, and investigation of new energy sources. This paper presents a method to transport cells in a microfluidic chip without contact. A local vortex was generated when high-frequency oscillation of a microtool was induced in a microfluidic chip. The vortex was controlled by tuning the tool's oscillation parameters, such as the oscillation amplitude and frequency. The cells were then transported in the chip based on the direction of the tool's movement, and their position, posture, and trajectories were controlled. Bovine oocyte manipulations, that is, transportation and rotation, were conducted to demonstrate the capability of the proposed method, without any contact by the microrobot with high-frequency oscillation.

Stroboscopic versus nonstroboscopic dynamics in the Floquet realization of the Harper-Hofstadter Hamiltonian

NASA Astrophysics Data System (ADS)

Bukov, Marin; Polkovnikov, Anatoli

2014-10-01

We study the stroboscopic and nonstroboscopic dynamics in the Floquet realization of the Harper-Hofstadter Hamiltonian. We show that the former produces the evolution expected in the high-frequency limit only for observables, which commute with the operator to which the driving protocol couples. On the contrary, nonstroboscopic dynamics is capable of capturing the evolution governed by the Floquet Hamiltonian of any observable associated with the effective high-frequency model. We provide exact numerical simulations for the dynamics of the number operator following a quantum cyclotron orbit on a 2×2 plaquette, as well as the chiral current operator flowing along the legs of a 2×20 ladder. The exact evolution is compared with its stroboscopic and nonstroboscopic counterparts, including finite-frequency corrections.

The application of real-time model update by oblique ionospheric sounders to frequency sharing

NASA Astrophysics Data System (ADS)

Uffelman, D. R.; Harnish, L. O.; Goodman, J. M.

1983-03-01

Frequency management systems for the high frequencies (HF) currently in use by the US Department of Defense (DoD) rely heavily on manual selection of frequencies which were allocated on a circuit by circuit basis. There is no capability to anticipate frequency changes (QSY's) in advance in a manner such that a frequency being released by one user is utilized effectively and immediately by a second user. A scheme by which a small computer model of the maximum usage frequency (MUF) of the HF channel (MINIMUF 3.5) is made to perform very accurately to anticipate channel characteristics in a short term prediction mode was examined. It is proposed that this model be utilized to provide automated frequency management which would allow one to anticipate frequency availability and thereby sharing of frequencies between several users. Utilizing data obtained from an oblique sounder net on the East Coast of the United States, the manner in which this might be accomplished is demonstrated.

Active locking and entanglement in type II optical parametric oscillators

NASA Astrophysics Data System (ADS)

Ruiz-Rivas, Joaquín; de Valcárcel, Germán J.; Navarrete-Benlloch, Carlos

2018-02-01

Type II optical parametric oscillators are amongst the highest-quality sources of quantum-correlated light. In particular, when pumped above threshold, such devices generate a pair of bright orthogonally-polarized beams with strong continuous-variable entanglement. However, these sources are of limited practical use, because the entangled beams emerge with different frequencies and a diffusing phase difference. It has been proven that the use of an internal wave-plate coupling the modes with orthogonal polarization is capable of locking the frequencies of the emerging beams to half the pump frequency, as well as reducing the phase-difference diffusion, at the expense of reducing the entanglement levels. In this work we characterize theoretically an alternative locking mechanism: the injection of a laser at half the pump frequency. Apart from being less invasive, this method should allow for an easier real-time experimental control. We show that such an injection is capable of generating the desired phase locking between the emerging beams, while still allowing for large levels of entanglement. Moreover, we find an additional region of the parameter space (at relatively large injections) where a mode with well defined polarization is in a highly amplitude-squeezed state.

Experimental demonstration of subwavelength domino plasmon devices for compact high-frequency circuit.

PubMed

Ma, Y G; Lan, L; Zhong, S M; Ong, C K

2011-10-24

In optical frequency, surface plasmons of metal provide us a prominent way to build compact photonic devices or circuits with non-diffraction limit. It is attributed by their extraordinary electromagnetic confining effect. But in the counterpart of lower frequencies, plasmonics behavior of metal is screened by eddy current induced in a certain skin depth. To amend this, spoof plasmons engineered by artificial structures have been introduced to mimic surface plasmons in these frequencies. But it is less useful for practical application due to their weak field confinement as manifested by large field decaying length in the upper dielectric space. Recently, a new type of engineered plasmons, domino plasmon was theoretically proposed to produce unusual field confinement and waveguiding capabilities that make them very attractive for ultra-compact device applications [Opt. Exp. 18, 754-764 (2010)]. In this work, we implemented these ideas and built three waveguiding devices based on domino plasmons. Their strong capabilities to produce versatile and ultra-compact devices with multiple electromagnetic functions have been experimentally verified in microwaves. And that can be extended to THz regime to pave the way for a new class of integrated wave circuits. © 2011 Optical Society of America

Tunable Microcavity-Stabilized Quantum Cascade Laser for Mid-IR High-Resolution Spectroscopy and Sensing.

PubMed

Borri, Simone; Siciliani de Cumis, Mario; Insero, Giacomo; Bartalini, Saverio; Cancio Pastor, Pablo; Mazzotti, Davide; Galli, Iacopo; Giusfredi, Giovanni; Santambrogio, Gabriele; Savchenkov, Anatoliy; Eliyahu, Danny; Ilchenko, Vladimir; Akikusa, Naota; Matsko, Andrey; Maleki, Lute; De Natale, Paolo

2016-02-17

The need for highly performing and stable methods for mid-IR molecular sensing and metrology pushes towards the development of more and more compact and robust systems. Among the innovative solutions aimed at answering the need for stable mid-IR references are crystalline microresonators, which have recently shown excellent capabilities for frequency stabilization and linewidth narrowing of quantum cascade lasers with compact setups. In this work, we report on the first system for mid-IR high-resolution spectroscopy based on a quantum cascade laser locked to a CaF₂ microresonator. Electronic locking narrows the laser linewidth by one order of magnitude and guarantees good stability over long timescales, allowing, at the same time, an easy way for finely tuning the laser frequency over the molecular absorption line. Improvements in terms of resolution and frequency stability of the source are demonstrated by direct sub-Doppler recording of a molecular line.

Tunable Microcavity-Stabilized Quantum Cascade Laser for Mid-IR High-Resolution Spectroscopy and Sensing

PubMed Central

Borri, Simone; Siciliani de Cumis, Mario; Insero, Giacomo; Bartalini, Saverio; Cancio Pastor, Pablo; Mazzotti, Davide; Galli, Iacopo; Giusfredi, Giovanni; Santambrogio, Gabriele; Savchenkov, Anatoliy; Eliyahu, Danny; Ilchenko, Vladimir; Akikusa, Naota; Matsko, Andrey; Maleki, Lute; De Natale, Paolo

2016-01-01

The need for highly performing and stable methods for mid-IR molecular sensing and metrology pushes towards the development of more and more compact and robust systems. Among the innovative solutions aimed at answering the need for stable mid-IR references are crystalline microresonators, which have recently shown excellent capabilities for frequency stabilization and linewidth narrowing of quantum cascade lasers with compact setups. In this work, we report on the first system for mid-IR high-resolution spectroscopy based on a quantum cascade laser locked to a CaF2 microresonator. Electronic locking narrows the laser linewidth by one order of magnitude and guarantees good stability over long timescales, allowing, at the same time, an easy way for finely tuning the laser frequency over the molecular absorption line. Improvements in terms of resolution and frequency stability of the source are demonstrated by direct sub-Doppler recording of a molecular line. PMID:26901199

Power-Smoothing Scheme of a DFIG Using the Adaptive Gain Depending on the Rotor Speed and Frequency Deviation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Hyewon; Hwang, Min; Muljadi, Eduard

In an electric power grid that has a high penetration level of wind, the power fluctuation of a large-scale wind power plant (WPP) caused by varying wind speeds deteriorates the system frequency regulation. This paper proposes a power-smoothing scheme of a doubly-fed induction generator (DFIG) that significantly mitigates the system frequency fluctuation while preventing over-deceleration of the rotor speed. The proposed scheme employs an additional control loop relying on the system frequency deviation that operates in combination with the maximum power point tracking control loop. To improve the power-smoothing capability while preventing over-deceleration of the rotor speed, the gain ofmore » the additional loop is modified with the rotor speed and frequency deviation. The gain is set to be high if the rotor speed and/or frequency deviation is large. In conclusion, the simulation results based on the IEEE 14-bus system clearly demonstrate that the proposed scheme significantly lessens the output power fluctuation of a WPP under various scenarios by modifying the gain with the rotor speed and frequency deviation, and thereby it can regulate the frequency deviation within a narrow range.« less

Power-Smoothing Scheme of a DFIG Using the Adaptive Gain Depending on the Rotor Speed and Frequency Deviation

DOE PAGES

Lee, Hyewon; Hwang, Min; Muljadi, Eduard; ...

2017-04-18

In an electric power grid that has a high penetration level of wind, the power fluctuation of a large-scale wind power plant (WPP) caused by varying wind speeds deteriorates the system frequency regulation. This paper proposes a power-smoothing scheme of a doubly-fed induction generator (DFIG) that significantly mitigates the system frequency fluctuation while preventing over-deceleration of the rotor speed. The proposed scheme employs an additional control loop relying on the system frequency deviation that operates in combination with the maximum power point tracking control loop. To improve the power-smoothing capability while preventing over-deceleration of the rotor speed, the gain ofmore » the additional loop is modified with the rotor speed and frequency deviation. The gain is set to be high if the rotor speed and/or frequency deviation is large. In conclusion, the simulation results based on the IEEE 14-bus system clearly demonstrate that the proposed scheme significantly lessens the output power fluctuation of a WPP under various scenarios by modifying the gain with the rotor speed and frequency deviation, and thereby it can regulate the frequency deviation within a narrow range.« less

Adaptive Gain-based Stable Power Smoothing of a DFIG

DOE PAGES

Muljadi, Eduard; Lee, Hyewon; Hwang, Min; ...

2017-11-01

In a power system that has a high wind penetration, the output power fluctuation of a large-scale wind turbine generator (WTG) caused by the varying wind speed increases the maximum frequency deviation, which is an important metric to assess the quality of electricity, because of the reduced system inertia. This paper proposes a stable power-smoothing scheme of a doubly-fed induction generator (DFIG) that can suppress the maximum frequency deviation, particularly for a power system with a high wind penetration. To do this, the proposed scheme employs an additional control loop relying on the system frequency deviation that operates in combinationmore » with the maximum power point tracking control loop. To improve the power-smoothing capability while guaranteeing the stable operation of a DFIG, the gain of the additional loop is modified with the rotor speed and frequency deviation. The gain is set to be high if the rotor speed and/or frequency deviation is large. Here, the simulation results based on the IEEE 14-bus system demonstrate that the proposed scheme significantly lessens the output power fluctuation of a WTG under various scenarios by modifying the gain with the rotor speed and frequency deviation, and thereby it can regulate the frequency deviation within a narrow range.« less

A novel power-efficient high-speed clock management unit using quantum-dot cellular automata

NASA Astrophysics Data System (ADS)

Abutaleb, M. M.

2017-04-01

Quantum-dot cellular automata (QCA) is one of the most attractive alternatives for complementary metal-oxide semiconductor technology. The QCA widely supports a new paradigm in the field of nanotechnology that has the potential for high density, low power, and high speed. The clock manager is an essential building block in the new microwave and radio frequency integrated circuits. This paper describes a novel QCA-based clock management unit (CMU) that provides innovative clocking capabilities. The proposed CMU is achieved by utilizing edge-triggered D-type flip-flops (D-FFs) in the design of frequency synthesizer and phase splitter. Edge-triggered D-FF structures proposed in this paper have the successful QCA implementation and simulation with the least complexity and power dissipation as compared to earlier structures. The frequency synthesizer is used to generate new clock frequencies from the reference clock frequency based on a combination of power-of-two frequency dividers. The phase splitter is integrated with the frequency synthesizer to generate four clock signals that are 90o out of phase with each other. This paper demonstrates that the proposed QCA CMU structure has a superior performance. Furthermore, the proposed CMU is straightforwardly scalable due to the use of modular component architecture.

Adaptive Gain-based Stable Power Smoothing of a DFIG

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muljadi, Eduard; Lee, Hyewon; Hwang, Min

In a power system that has a high wind penetration, the output power fluctuation of a large-scale wind turbine generator (WTG) caused by the varying wind speed increases the maximum frequency deviation, which is an important metric to assess the quality of electricity, because of the reduced system inertia. This paper proposes a stable power-smoothing scheme of a doubly-fed induction generator (DFIG) that can suppress the maximum frequency deviation, particularly for a power system with a high wind penetration. To do this, the proposed scheme employs an additional control loop relying on the system frequency deviation that operates in combinationmore » with the maximum power point tracking control loop. To improve the power-smoothing capability while guaranteeing the stable operation of a DFIG, the gain of the additional loop is modified with the rotor speed and frequency deviation. The gain is set to be high if the rotor speed and/or frequency deviation is large. Here, the simulation results based on the IEEE 14-bus system demonstrate that the proposed scheme significantly lessens the output power fluctuation of a WTG under various scenarios by modifying the gain with the rotor speed and frequency deviation, and thereby it can regulate the frequency deviation within a narrow range.« less

Passive UHF RFID Tag with Multiple Sensing Capabilities

PubMed Central

Fernández-Salmerón, José; Rivadeneyra, Almudena; Martínez-Martí, Fernando; Capitán-Vallvey, Luis Fermín; Palma, Alberto J.; Carvajal, Miguel A.

2015-01-01

This work presents the design, fabrication, and characterization of a printed radio frequency identification tag in the ultra-high frequency band with multiple sensing capabilities. This passive tag is directly screen printed on a cardboard box with the aim of monitoring the packaging conditions during the different stages of the supply chain. This tag includes a commercial force sensor and a printed opening detector. Hence, the force applied to the package can be measured as well as the opening of the box can be detected. The architecture presented is a passive single-chip RFID tag. An electronic switch has been implemented to be able to measure both sensor magnitudes in the same access without including a microcontroller or battery. Moreover, the chip used here integrates a temperature sensor and, therefore, this tag provides three different parameters in every reading. PMID:26506353

Precision spectral manipulation of optical pulses using a coherent photon echo memory.

PubMed

Buchler, B C; Hosseini, M; Hétet, G; Sparkes, B M; Lam, P K

2010-04-01

Photon echo schemes are excellent candidates for high efficiency coherent optical memory. They are capable of high-bandwidth multipulse storage, pulse resequencing and have been shown theoretically to be compatible with quantum information applications. One particular photon echo scheme is the gradient echo memory (GEM). In this system, an atomic frequency gradient is induced in the direction of light propagation leading to a Fourier decomposition of the optical spectrum along the length of the storage medium. This Fourier encoding allows precision spectral manipulation of the stored light. In this Letter, we show frequency shifting, spectral compression, spectral splitting, and fine dispersion control of optical pulses using GEM.

Thin-thick quadrature frequency conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eimerl, D.

1985-02-07

The quadrature conversion scheme is a method of generating the second harmonic. The scheme, which uses two crystals in series, has several advantages over single-crystal or other two crystal schemes. The most important is that it is capable of high conversion efficiency over a large dynamic range of drive intensity and detuning angle.

THE VERTICAL PLANAR MOTION MECHANISM; A DYNAMIC TEST APPARATUS FOR EVALUATING CURRENT METERS AND OTHER MARINE INSTRUMENTATION

EPA Science Inventory

The overall objective was to provide a dynamic test apparatus that can produce known, controlled high frequency dynamics for the evaluation of current meters and other marine instrumentation. Of primary interest is the establishment of flow sensor measurement capabilities, and he...

47 CFR 80.913 - Radiotelephone receivers.

Code of Federal Regulations, 2011 CFR

2011-10-01

... pursuant to § 80.909 of this part. (c) If a very high frequency radiotelephone installation is provided... radiotelephone installation must have a sensitivity of at least 50 microvolts in the case of MF equipment, and 1... be capable of efficient operation when energized by the reserve source of energy. (g) The sensitivity...

47 CFR 80.913 - Radiotelephone receivers.

Code of Federal Regulations, 2012 CFR

2012-10-01

... pursuant to § 80.909 of this part. (c) If a very high frequency radiotelephone installation is provided... radiotelephone installation must have a sensitivity of at least 50 microvolts in the case of MF equipment, and 1... be capable of efficient operation when energized by the reserve source of energy. (g) The sensitivity...

47 CFR 80.913 - Radiotelephone receivers.

Code of Federal Regulations, 2010 CFR

2010-10-01

... pursuant to § 80.909 of this part. (c) If a very high frequency radiotelephone installation is provided... radiotelephone installation must have a sensitivity of at least 50 microvolts in the case of MF equipment, and 1... be capable of efficient operation when energized by the reserve source of energy. (g) The sensitivity...

47 CFR 80.913 - Radiotelephone receivers.

Code of Federal Regulations, 2013 CFR

2013-10-01

... pursuant to § 80.909 of this part. (c) If a very high frequency radiotelephone installation is provided... radiotelephone installation must have a sensitivity of at least 50 microvolts in the case of MF equipment, and 1... be capable of efficient operation when energized by the reserve source of energy. (g) The sensitivity...

47 CFR 80.913 - Radiotelephone receivers.

Code of Federal Regulations, 2014 CFR

2014-10-01

... pursuant to § 80.909 of this part. (c) If a very high frequency radiotelephone installation is provided... radiotelephone installation must have a sensitivity of at least 50 microvolts in the case of MF equipment, and 1... be capable of efficient operation when energized by the reserve source of energy. (g) The sensitivity...

Department of the Navy Fiscal Year 2011 Annual Financial Report. Mission Ready: Managing Risk and Meeting Objectives

DTIC Science & Technology

2011-01-01

Earthquake Relief Effort Haiti Migrant Operational Support Deepwater Horizon Oil Spill Tennessee Flooding Pakistan Flooding Typhoon Megi (Philippines) Natural...provide relevant capabilities and to enable Operationally Responsive Space. TacSat-4 provides ten Ultra High Frequency (UHF) channels, which can be used

Disturbance-Adaptive Short-Term Frequency Support of a DFIG Associated With the Variable Gain Based on the ROCOF and Rotor Speed

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hwang, Min; Muljadi, Eduard; Jang, Gilsoo

This paper proposes a disturbance-adaptive short-term frequency support scheme of a doubly fed induction generator (DFIG) that can improve the frequency-supporting capability while ensuring stable operation. In the proposed scheme, the output of the additional control loop is determined as the product of the frequency deviation and adaptive gain, which is modified depending on the rate of change of frequency (ROCOF) and rotor speed. To achieve these objectives, the adaptive gain is set to be high during the early stage of a disturbance, when the ROCOF and rotor speed are high. Until the frequency nadir (FN), the gain decreases withmore » the ROCOF and rotor speed. After the FN, the gain decreases only with the rotor speed. The simulation results demonstrate that the proposed scheme improves the FN and maximum ROCOF while ensuring the stable operation of a DFIG under various wind conditions irrespective of the disturbance conditions by adaptively changing the control gain with the ROCOF and rotor speed, even if the wind speed decreases and a consecutive disturbance occurs.« less

Edge technique lidar for high accuracy, high spatial resolution wind measurement in the Planetary Boundary Layer

NASA Technical Reports Server (NTRS)

Korb, C. L.; Gentry, Bruce M.

1995-01-01

The goal of the Army Research Office (ARO) Geosciences Program is to measure the three dimensional wind field in the planetary boundary layer (PBL) over a measurement volume with a 50 meter spatial resolution and with measurement accuracies of the order of 20 cm/sec. The objective of this work is to develop and evaluate a high vertical resolution lidar experiment using the edge technique for high accuracy measurement of the atmospheric wind field to meet the ARO requirements. This experiment allows the powerful capabilities of the edge technique to be quantitatively evaluated. In the edge technique, a laser is located on the steep slope of a high resolution spectral filter. This produces large changes in measured signal for small Doppler shifts. A differential frequency technique renders the Doppler shift measurement insensitive to both laser and filter frequency jitter and drift. The measurement is also relatively insensitive to the laser spectral width for widths less than the width of the edge filter. Thus, the goal is to develop a system which will yield a substantial improvement in the state of the art of wind profile measurement in terms of both vertical resolution and accuracy and which will provide a unique capability for atmospheric wind studies.

Capture, acceleration and bunching rf systems for the MEIC booster and storage rings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Shaoheng; Guo, Jiquan; Lin, Fanglei

2015-09-01

The Medium-energy Electron Ion Collider (MEIC), proposed by Jefferson Lab, consists of a series of accelerators. The electron collider ring accepts electrons from CEBAF at energies from 3 to 12 GeV. Protons and ions are delivered to a booster and captured in a long bunch before being ramped and transferred to the ion collider ring. The ion collider ring accelerates a small number of long ion bunches to colliding energy before they are re-bunched into a high frequency train of very short bunches for colliding. Two sets of low frequency RF systems are needed for the long ion bunch energymore » ramping in the booster and ion collider ring. Another two sets of high frequency RF cavities are needed for re-bunching in the ion collider ring and compensating synchrotron radiation energy loss in the electron collider ring. The requirements from energy ramping, ion beam bunching, electron beam energy compensation, collective effects, beam loading and feedback capability, RF power capability, etc. are presented. The preliminary designs of these RF systems are presented. Concepts for the baseline cavity and RF station configurations are described, as well as some options that may allow more flexible injection and acceleration schemes.« less

Applications of a nanocomposite-inspired in-situ broadband ultrasonic sensor to acousto-ultrasonics-based passive and active structural health monitoring.

PubMed

Liu, Menglong; Zeng, Zhihui; Xu, Hao; Liao, Yaozhong; Zhou, Limin; Zhang, Zhong; Su, Zhongqing

2017-07-01

A novel nanocomposite-inspired in-situ broadband ultrasonic sensor previously developed, with carbon black as the nanofiller and polyvinylidene fluoride as the matrix, was networked for acousto-ultrasonic wave-based passive and active structural health monitoring (SHM). Being lightweight and small, this kind of sensor was proven to be capable of perceiving strain perturbation in virtue of the tunneling effect in the formed nanofiller conductive network when acousto-ultrasonic waves traverse the sensor. Proof-of-concept validation was implemented, to examine the sensor performance in responding to acousto-ultrasonic waves in a broad frequency regime: from acoustic emission (AE) of lower frequencies to guided ultrasonic waves (GUWs) of higher frequencies. Results have demonstrated the high fidelity, ultrafast response and high sensitivity of the sensor to acousto-ultrasonic waves up to 400kHz yet with an ultra-low magnitude (of the order of micro-strain). The sensor is proven to possess sensitivity and accuracy comparable with commercial piezoelectric ultrasonic transducers, whereas with greater flexibility in accommodating curved structural surfaces. Application paradigms of using the sensor for damage evaluation have spotlighted the capability of the sensor in compromising "sensing cost" with "sensing effectiveness" for passive AE- or active GUW-based SHM. Copyright © 2017 Elsevier B.V. All rights reserved.

Scattering from Rock and Rock Outcrops

DTIC Science & Technology

2018-01-23

scattering and rough areas as seen on the rock outcrop in Fig. 1, display high variability which could pose difficulty for target detection and...classification systems. The primary long-term goal of this research project is to increase understanding and modeling capabilities for high -frequency acoustic...Arlington, VA 22203-1995 10. SPONSOR/MONITOR’S ACRONYM(S) BD025 11. SPONSORING/MONITORING AGENCY REPORT NUMBER 12. DISTRIBUTION AVAILABILITY

Arctic Planning: DOD Expects to Play a Supporting Role to Other Federal Agencies and Has Efforts Under Way to Address Capability Needs and Update Plans

DTIC Science & Technology

2015-06-01

example, in 2014 DOD tested a new communication system— the Mobile User Objective System—that is intended to provide a secure, ultra -high-frequency...national security needs, stating that DOD does not anticipate a need to begin construction of additional bases or a deepwater port in Alaska before 2020.b...in Nome, Alaska, to support a deepwater port. Page 21 GAO-15-566 Arctic Planning Capability need Actions taken by the Department of

Adaptive and mobile ground sensor array.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holzrichter, Michael Warren; O'Rourke, William T.; Zenner, Jennifer

The goal of this LDRD was to demonstrate the use of robotic vehicles for deploying and autonomously reconfiguring seismic and acoustic sensor arrays with high (centimeter) accuracy to obtain enhancement of our capability to locate and characterize remote targets. The capability to accurately place sensors and then retrieve and reconfigure them allows sensors to be placed in phased arrays in an initial monitoring configuration and then to be reconfigured in an array tuned to the specific frequencies and directions of the selected target. This report reviews the findings and accomplishments achieved during this three-year project. This project successfully demonstrated autonomousmore » deployment and retrieval of a payload package with an accuracy of a few centimeters using differential global positioning system (GPS) signals. It developed an autonomous, multisensor, temporally aligned, radio-frequency communication and signal processing capability, and an array optimization algorithm, which was implemented on a digital signal processor (DSP). Additionally, the project converted the existing single-threaded, monolithic robotic vehicle control code into a multi-threaded, modular control architecture that enhances the reuse of control code in future projects.« less

An open-loop system design for deep space signal processing applications

NASA Astrophysics Data System (ADS)

Tang, Jifei; Xia, Lanhua; Mahapatra, Rabi

2018-06-01

A novel open-loop system design with high performance is proposed for space positioning and navigation signal processing. Divided by functions, the system has four modules, bandwidth selectable data recorder, narrowband signal analyzer, time-delay difference of arrival estimator and ANFIS supplement processor. A hardware-software co-design approach is made to accelerate computing capability and improve system efficiency. Embedded with the proposed signal processing algorithms, the designed system is capable of handling tasks with high accuracy over long period of continuous measurements. The experiment results show the Doppler frequency tracking root mean square error during 3 h observation is 0.0128 Hz, while the TDOA residue analysis in correlation power spectrum is 0.1166 rad.

Hydrothermal synthesis of poly(3,4-ethylenedioxythiophene) for high-rate performance supercapacitor

NASA Astrophysics Data System (ADS)

Ahmed, Sultan; Parvaz, M.; Johari, Rahul; Bilal, M.; Ahmad, Sultan; Zaid, M.; Hussain, S.; Islamuddin, Khan, Zishan H.; Rafat, M.

2018-05-01

This work reports the successful preparation of Poly (3,4-ethylenedioxythiophene) (PEDOT) from monomer ethylenedioxythiophene (EDOT), employing hydrothermal method. The structure of the prepared sample was characterized by Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) and the results indicates the successful polymerization of EDOT to the formation of polymer PEDOT. The capacitive performance of the prepared sample were investigated in two-electrode assembly using aqueous solution of 6 M KOH. The assembled capacitor cell shows high rate capability which is evident from both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) studies. The observed CV patterns are almost rectangular even for high scan rates (˜30 V s-1), confirming the high rate performance, while high knee frequency (˜1 kHz), and low response time (˜5.8 ms) observed by impedance analysis confirms the high rate capability of supercapacitor.

Evaluation of components, subsystems, and networks for high rate, high frequency space communications

NASA Technical Reports Server (NTRS)

Kerczewski, Robert J.; Ivancic, William D.; Zuzek, John E.

1991-01-01

The development of new space communications technologies by NASA has included both commercial applications and space science requirements. NASA's Systems Integration, Test and Evaluation (SITE) Space Communication System Simulator is a hardware based laboratory simulator for evaluating space communications technologies at the component, subsystem, system, and network level, geared toward high frequency, high data rate systems. The SITE facility is well-suited for evaluation of the new technologies required for the Space Exploration Initiative (SEI) and advanced commercial systems. Described here are the technology developments and evaluation requirements for current and planned commercial and space science programs. Also examined are the capabilities of SITE, the past, present and planned future configurations of the SITE facility, and applications of SITE to evaluation of SEI technology.

Optimization of a lensless digital holographic otoscope system for transient measurements of the human tympanic membrane

PubMed Central

Dobrev, I.; Furlong, C.; Cheng, J. T.; Rosowski, J. J.

2014-01-01

In this paper, we propose a multi-pulsed double exposure (MPDE) acquisition method to quantify in full-field-of-view the transient (i.e., >10 kHz) acoustically induced nanometer scale displacements of the human tympanic membrane (TM or eardrum). The method takes advantage of the geometrical linearity and repeatability of the TM displacements to enable high-speed measurements with a conventional camera (i.e., <20 fps). The MPDE is implemented on a previously developed digital holographic system (DHS) to enhance its measurement capabilities, at a minimum cost, while avoiding constraints imposed by the spatial resolutions and dimensions of high-speed (i.e., >50 kfps) cameras. To our knowledge, there is currently no existing system to provide such capabilities for the study of the human TM. The combination of high temporal (i.e., >50 kHz) and spatial (i.e., >500k data points) resolutions enables measurements of the temporal and frequency response of all points across the surface of the TM simultaneously. The repeatability and accuracy of the MPDE method are verified against a Laser Doppler Vibrometer (LDV) on both artificial membranes and ex-vivo human TMs that are acoustically excited with a sharp (i.e., <100 μs duration) click. The measuring capabilities of the DHS, enhanced by the MPDE acquisition method, allow for quantification of spatially dependent motion parameters of the TM, such as modal frequencies, time constants, as well as inferring local material properties. PMID:25780271

Digital EPR with an arbitrary waveform generator and direct detection at the carrier frequency

PubMed Central

Tseitlin, Mark; Quine, Richard W.; Rinard, George A.; Eaton, Sandra S.; Eaton, Gareth R.

2011-01-01

A digital EPR spectrometer was constructed by replacing the traditional bridge with an arbitrary waveform generator (AWG) to produce excitation patterns and a high-speed digitizer for direct detection of the spin system response at the carrier frequency. Digital down-conversion produced baseband signals in quadrature with very precise orthogonality. Real-time resonator tuning was performed by monitoring the Fourier transforms of signals reflected from the resonator during frequency sweeps generated by the AWG. The capabilities of the system were demonstrated by rapid magnetic field scans at 256 MHz carrier frequency, and FID and spin echo experiments at 1 and 10 GHz carrier frequencies. For the rapid scan experiments the leakage through a cross-loop resonator was compensated by adjusting the amplitude and phase of a sinusoid at the carrier frequency that was generated with another AWG channel. PMID:21968420

High-speed duplex optical wireless communication system for indoor personal area networks.

PubMed

Wang, Ke; Nirmalathas, Ampalavanapillai; Lim, Christina; Skafidas, Efstratios

2010-11-22

In this paper a new hybrid wireless access system incorporating high bandwidth line-of-sight free space optical wireless and radio frequency localization is proposed and demonstrated. This system is capable of supporting several gigabits/second up-stream and down-stream data transmission and ideally suited for high bandwidth indoor applications such as personal area networks. A radio frequency signal is used to achieve localization of subscribers, offering limited mobility to subscribers within a practical office scenario. Even with the modest transmitted power of 5 dBm, we demonstrate satisfactory performance of bit error rates better than 10(-9) over the entire room in the presence of strong background light. Using simulations, the effectiveness of the proposed system architecture is investigated and the key performance trade-offs identified. Proof-of-concept experiments have also been carried out to validate simulation model, and initial experimental results successfully demonstrate the feasibility of the system capable of supporting 2.5 Gbps over a 1-2 m optical wireless link (limited by the length of the sliding rail used in the experiment) with a 45 degrees diffused beam in an indoor environment for the first time.

Highly linear dual ring resonator modulator for wide bandwidth microwave photonic links.

PubMed

Hosseinzadeh, Arash; Middlebrook, Christopher T

2016-11-28

A highly linear dual ring resonator modulator (DRRM) design is demonstrated to provide high spur-free dynamic range (SFDR) in a wide operational bandwidth. Harmonic and intermodulation distortions are theoretically analyzed in a single ring resonator modulator (RRM) with Lorentzian-shape transfer function and a strategy is proposed to enhance modulator linearity for wide bandwidth applications by utilizing DRRM. Third order intermodulation distortion is suppressed in a frequency independent process with proper splitting ratio of optical and RF power and proper dc biasing of the ring resonators. Operational bandwidth limits of the DRRM are compared to the RRM showing the capability of the DRRM in providing higher SFDR in an unlimited operational bandwidth. DRRM bandwidth limitations are a result of the modulation index from each RRM and their resonance characteristics that limit the gain and noise figure of the microwave photonic link. The impact of the modulator on microwave photonic link figure of merits is analyzed and compared to RRM and Mach-Zehnder Interference (MZI) modulators. Considering ± 5 GHz operational bandwidth around the resonance frequency imposed by the modulation index requirement the DRRM is capable of a ~15 dB SFDR improvement (1 Hz instantaneous bandwidth) versus RRM and MZI.

Dual-frequency transducer with a wideband PVDF receiver for contrast-enhanced, adjustable harmonic imaging

NASA Astrophysics Data System (ADS)

Kim, Jinwook; Lindsey, Brooks D.; Li, Sibo; Dayton, Paul A.; Jiang, Xiaoning

2017-04-01

Acoustic angiography is a contrast-enhanced, superharmonic microvascular imaging method. It has shown the capability of high-resolution and high-contrast-to-tissue-ratio (CTR) imaging for vascular structure near tumor. Dual-frequency ultrasound transducers and arrays are usually used for this new imaging technique. Stacked-type dual-frequency transducers have been developed for this vascular imaging method by exciting injected microbubble contrast agent (MCA) in the vessels with low-frequency (1-5 MHz), moderate power ultrasound burst waves and receiving the superharmonic responses from MCA by a high-frequency receiver (>10 MHz). The main challenge of the conventional dual-frequency transducers is a limited penetration depth (<25 mm) due to the insufficient receiving sensitivity for highfrequency harmonic signal detection. A receiver with a high receiving sensitivity spanning a wide superharmonic frequency range (3rd to 6th) enables selectable bubble harmonic detection considering the required penetration depth. Here, we develop a new dual-frequency transducer composed of a 2 MHz 1-3 composite transmitter and a polyvinylidene fluoride (PVDF) receiver with a receiving frequency range of 4-12 MHz for adjustable harmonic imaging. The developed transducer was tested for harmonic responses from a microbubble-injected vessel-mimicking tube positioned 45 mm away. Despite the long imaging distance (45 mm), the prototype transducer detected clear harmonic response with the contrast-to-noise ratio of 6-20 dB and the -6 dB axial resolution of 200-350 μm for imaging a 200 um-diameter cellulose tube filled with microbubbles.

Fluorescence lifetime as a new parameter in analytical cytology measurements

NASA Astrophysics Data System (ADS)

Steinkamp, John A.; Deka, Chiranjit; Lehnert, Bruce E.; Crissman, Harry A.

1996-05-01

A phase-sensitive flow cytometer has been developed to quantify fluorescence decay lifetimes on fluorochrome-labeled cells/particles. This instrument combines flow cytometry (FCM) and frequency-domain fluorescence spectroscopy measurement principles to provide unique capabilities for making phase-resolved lifetime measurements, while preserving conventional FCM capabilities. Cells are analyzed as they intersect a high-frequency, intensity-modulated (sine wave) laser excitation beam. Fluorescence signals are processed by conventional and phase-sensitive signal detection electronics and displayed as frequency distribution histograms. In this study we describe results of fluorescence intensity and lifetime measurements on fluorescently labeled particles, cells, and chromosomes. Examples of measurements on intrinsic cellular autofluorescence, cells labeled with immunofluorescence markers for cell- surface antigens, mitochondria stains, and on cellular DNA and protein binding fluorochromes will be presented to illustrate unique differences in measured lifetimes and changes caused by fluorescence quenching. This innovative technology will be used to probe fluorochrome/molecular interactions in the microenvironment of cells/chromosomes as a new parameter and thus expand the researchers' understanding of biochemical processes and structural features at the cellular and molecular level.

Oversampling in virtual visual sensors as a means to recover higher modes of vibration

NASA Astrophysics Data System (ADS)

Shariati, Ali; Schumacher, Thomas

2015-03-01

Vibration-based structural health monitoring (SHM) techniques require modal information from the monitored structure in order to estimate the location and severity of damage. Natural frequencies also provide useful information to calibrate finite element models. There are several types of physical sensors that can measure the response over a range of frequencies. For most of those sensors however, accessibility, limitation of measurement points, wiring, and high system cost represent major challenges. Recent optical sensing approaches offer advantages such as easy access to visible areas, distributed sensing capabilities, and comparatively inexpensive data recording while having no wiring issues. In this research we propose a novel methodology to measure natural frequencies of structures using digital video cameras based on virtual visual sensors (VVS). In our initial study where we worked with commercially available inexpensive digital video cameras we found that for multiple degrees of freedom systems it is difficult to detect all of the natural frequencies simultaneously due to low quantization resolution. In this study we show how oversampling enabled by the use of high-end high-frame-rate video cameras enable recovering all of the three natural frequencies from a three story lab-scale structure.

Rolling ball sifting algorithm for the augmented visual inspection of carotid bruit auscultation

NASA Astrophysics Data System (ADS)

Huang, Adam; Lee, Chung-Wei; Liu, Hon-Man

2016-07-01

Carotid bruits are systolic sounds associated with turbulent blood flow through atherosclerotic stenosis in the neck. They are audible intermittent high-frequency (above 200 Hz) sounds mixed with background noise and transmitted low-frequency (below 100 Hz) heart sounds that wax and wane periodically. It is a nontrivial task to extract both bruits and heart sounds with high fidelity for further computer-aided auscultation and diagnosis. In this paper we propose a rolling ball sifting algorithm that is capable to filter signals with a sharper frequency selectivity mechanism in the time domain. By rolling two balls (one above and one below the signal) of a suitable radius, the balls are large enough to roll over bruits and yet small enough to ride on heart sound waveforms. The high-frequency bruits can then be extracted according to a tangibility criterion by using the local extrema touched by the balls. Similarly, the low-frequency heart sounds can be acquired by a larger radius. By visualizing the periodicity information of both the extracted heart sounds and bruits, the proposed visual inspection method can potentially improve carotid bruit diagnosis accuracy.

Frequency-tuned microwave photon counter based on a superconductive quantum interferometer

NASA Astrophysics Data System (ADS)

Shnyrkov, V. I.; Yangcao, Wu; Soroka, A. A.; Turutanov, O. G.; Lyakhno, V. Yu.

2018-03-01

Various types of single-photon counters operating in infrared, ultraviolet, and optical wavelength ranges are successfully used to study electromagnetic fields, analyze radiation sources, and solve problems in quantum informatics. However, their operating principles become ineffective at millimeter band, S-band, and ultra-high frequency bands of wavelengths due to the decrease in quantum energy by 4-5 orders of magnitude. Josephson circuits with discrete Hamiltonians and qubits are a good foundation for the construction of single-photon counters at these frequencies. This paper presents a frequency-tuned microwave photon counter based on a single-junction superconducting quantum interferometer and flux qutrit. The control pulse converts the interferometer into a two-level system for resonance absorption of photons. Decay of the photon-induced excited state changes the magnetic flux in the interferometer, which is measured by a SQUID magnetometer. Schemes for recording the magnetic flux using a DC SQUID or ideal parametric detector, based on a qutrit with high-frequency excitation, are discussed. It is shown that the counter consisting of an interferometer with a Josephson junction and a parametric detector demonstrates high performance and is capable of detecting single photons in a microwave band.

LOX/hydrocarbon rocket engine analytical design methodology development and validation. Volume 2: Appendices

NASA Technical Reports Server (NTRS)

Niiya, Karen E.; Walker, Richard E.; Pieper, Jerry L.; Nguyen, Thong V.

1993-01-01

This final report includes a discussion of the work accomplished during the period from Dec. 1988 through Nov. 1991. The objective of the program was to assemble existing performance and combustion stability models into a usable design methodology capable of designing and analyzing high-performance and stable LOX/hydrocarbon booster engines. The methodology was then used to design a validation engine. The capabilities and validity of the methodology were demonstrated using this engine in an extensive hot fire test program. The engine used LOX/RP-1 propellants and was tested over a range of mixture ratios, chamber pressures, and acoustic damping device configurations. This volume contains time domain and frequency domain stability plots which indicate the pressure perturbation amplitudes and frequencies from approximately 30 tests of a 50K thrust rocket engine using LOX/RP-1 propellants over a range of chamber pressures from 240 to 1750 psia with mixture ratios of from 1.2 to 7.5. The data is from test configurations which used both bitune and monotune acoustic cavities and from tests with no acoustic cavities. The engine had a length of 14 inches and a contraction ratio of 2.0 using a 7.68 inch diameter injector. The data was taken from both stable and unstable tests. All combustion instabilities were spontaneous in the first tangential mode. Although stability bombs were used and generated overpressures of approximately 20 percent, no tests were driven unstable by the bombs. The stability instrumentation included six high-frequency Kistler transducers in the combustion chamber, a high-frequency Kistler transducer in each propellant manifold, and tri-axial accelerometers. Performance data is presented, both characteristic velocity efficiencies and energy release efficiencies, for those tests of sufficient duration to record steady state values.

Defense Science and Technology Success Stories

DTIC Science & Technology

2007-01-01

Active Auroral Research Project ( HAARP ) ........................................................................136 Weapons Strategic Illuminator Laser...drawing 136 Service/Agency Background: The High Frequency Active Auroral Research Project ( HAARP ) developed new experimental research capabilities and...Appropriation Act provided funds for the creation of HAARP , jointly managed by the Air Force Research Laboratory and the Office of Naval Research to exploit

Fighting in a Contested Space Environment: Training Marines for Operations with Degraded or Denied Space-Enabled Capabilities

DTIC Science & Technology

2015-06-01

System UFG Ulchi Freedom Guardian UFO UHF Follow-On System UHF Ultra-High Frequency URE User Range Error VTC Video Teleconference WGS Wideband...in the UHF band; two legacy systems, Fleet Satellite Communication System (FLTSATCOM) and UHF Follow-on ( UFO ), and the new constellation being

Somatic embryogenesis and polyamines in woody plants

Treesearch

Rakesh Minocha; Subhash C. Minocha; Liisa Kaarina Simola

1995-01-01

The formation of whole plants from cultured cells is interesting not only because of its applications for mass propagation but also as a prime example of the process of controlled development and differentiation in plants. Cultures capable of producing somatic embryos with high frequency provide ideal experimental systems to study and understand the biochemical basis...

Building and Operating Weather Satellite Ground Stations for High School Science. Teachers Guide.

ERIC Educational Resources Information Center

Summers, R. Joe; Gotwald, Timothy

Automatic Picture Transmission (APT) images are real-time weather pictures transmitted from satellites on a radio frequency in a video format. Amateur radio enthusiasts and electronic experimenters have for a number of years designed, built, and operated direct readout stations capable of receiving APT photographs. The equipment to receive weather…

MMIC Amplifier Produces Gain of 10 dB at 235 GHz

NASA Technical Reports Server (NTRS)

Dawson, Douglas; Fung, King Man; Lee, Karen; Samoska, Lorene; Wells, Mary; Gaier, Todd; Kangaslahti, Pekka; Grundbacher, Ronald; Lai, Richard; Raja, Rohit;

High-temperature, gas-filled ceramic rectifiers, thyratrons, and voltage-reference tubes

NASA Technical Reports Server (NTRS)

Baum, E. A.

1969-01-01

Thyratron, capable of being operated as a rectifier and a voltage-reference tube, was constructed and tested for 1000 hours at temperatures to 800 degrees C. With current levels at 15 amps and peak voltages of 2000 volts and frequencies at 6000 cps, tube efficiency was greater than 97 percent.

Investigation of a compact coaxially fed switched oscillator

NASA Astrophysics Data System (ADS)

Wang, Yuwei; Chen, Dongqun; Zhang, Jiande; Cao, Shengguang; Li, Da; Liu, Chebo

2013-09-01

To generate a relative high frequency mesoband microwave, a compact coaxially fed transmission line switched oscillator with high voltage capability is investigated. The characteristic impedance and voltage capability of the low impedance transmission line (LITL) have been analyzed. It is shown that the working voltage of the oscillator can reach up to 200 kV when it is filled by pressurized nitrogen and charged by a nanosecond driving source. By utilizing a commercial electromagnetic simulation code, the transient performance of the switched oscillator with a lumped resistance load is simulated. It is illustrated that the center frequency of the output signal reaches up to ˜0.6 GHz when the spark gap practically closes with a single channel. Besides, the influence of the closing mode and rapidity of the spark gap, the permittivity of the insulator at the output end of the LITL, and the load impedance on the transient performance of the designed oscillator has been analyzed in quantification. Finally, the good transient performance of the switched oscillator has been preliminarily proved by the experiment.

An analog integrated circuit beamformer for high-frequency medical ultrasound imaging.

PubMed

Gurun, Gokce; Zahorian, Jaime S; Sisman, Alper; Karaman, Mustafa; Hasler, Paul E; Degertekin, F Levent

2012-10-01

We designed and fabricated a dynamic receive beamformer integrated circuit (IC) in 0.35-μm CMOS technology. This beamformer IC is suitable for integration with an annular array transducer for high-frequency (30-50 MHz) intravascular ultrasound (IVUS) imaging. The beamformer IC consists of receive preamplifiers, an analog dynamic delay-and-sum beamformer, and buffers for 8 receive channels. To form an analog dynamic delay line we designed an analog delay cell based on the current-mode first-order all-pass filter topology, as the basic building block. To increase the bandwidth of the delay cell, we explored an enhancement technique on the current mirrors. This technique improved the overall bandwidth of the delay line by a factor of 6. Each delay cell consumes 2.1-mW of power and is capable of generating a tunable time delay between 1.75 ns to 2.5 ns. We successfully integrated the fabricated beamformer IC with an 8-element annular array. Experimental test results demonstrated the desired buffering, preamplification and delaying capabilities of the beamformer.

Silicon Carbide MOSFET-Based Switching Power Amplifier for Precision Magnet Control

NASA Astrophysics Data System (ADS)

Miller, Kenneth; Ziemba, Timothy; Prager, James; Picard, Julian

2016-10-01

Eagle Harbor Technologies, Inc. (EHT) is using the latest in solid-state switching technologies to advance the state-of-the-art in magnet control for fusion science. Silicon carbide (SiC) MOSFETs offer advantages over IGBTs including lower drive energy requirements, lower conduction and switching losses, and higher switching frequency capabilities. When comparing SiC and traditional silicon-based MOSFETs, SiC MOSFETs provide higher current carrying capability allowing for smaller package weights and sizes and lower operating temperature. To validate the design, EHT has developed a low-power switching power amplifier (SPA), which has been used for precision control of magnetic fields, including rapidly changing the fields in coils. This design has been incorporated in to a high power SPA, which has been bench tested. This high power SPA will be tested at the Helicity Injected Torus (HIT) at the University of Washington. Following successful testing, EHT will produce enough SiC MOSFET-based SPAs to replace all of the units at HIT, which allows for higher frequency operation and an overall increase in pulsed current levels.

High frequency inductive lamp and power oscillator

DOEpatents

MacLennan, Donald A.; Turner, Brian P.; Dolan, James T.; Kirkpatrick, Douglas A.; Leng, Yongzhang

2000-01-01

A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and/or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency. Various control circuits may be employed to match the driving frequency of the oscillator to a plurality of tuning states of the lamp.

Active Control of High Frequency Combustion Instability in Aircraft Gas-Turbine Engines

NASA Technical Reports Server (NTRS)

Corrigan, Bob (Technical Monitor); DeLaat, John C.; Chang, Clarence T.

2003-01-01

Active control of high-frequency (greater than 500 Hz) combustion instability has been demonstrated in the NASA single-nozzle combustor rig at United Technologies Research Center. The combustor rig emulates an actual engine instability and has many of the complexities of a real engine combustor (i.e. actual fuel nozzle and swirler, dilution cooling, etc.) In order to demonstrate control, a high-frequency fuel valve capable of modulating the fuel flow at up to 1kHz was developed. Characterization of the fuel delivery system was accomplished in a custom dynamic flow rig developed for that purpose. Two instability control methods, one model-based and one based on adaptive phase-shifting, were developed and evaluated against reduced order models and a Sectored-1-dimensional model of the combustor rig. Open-loop fuel modulation testing in the rig demonstrated sufficient fuel modulation authority to proceed with closed-loop testing. During closed-loop testing, both control methods were able to identify the instability from the background noise and were shown to reduce the pressure oscillations at the instability frequency by 30%. This is the first known successful demonstration of high-frequency combustion instability suppression in a realistic aero-engine environment. Future plans are to carry these technologies forward to demonstration on an advanced low-emission combustor.

Feasibility of Rotational Scan Ultrasound Imaging by an Angled High Frequency Transducer for the Posterior Segment of the Eye

PubMed Central

Paeng, Dong-Guk; Chang, Jin Ho; Chen, Ruimin; Humayun, Mark S.; Shung, K. Kirk

2009-01-01

High frequency ultrasound over 40 MHz has been used to image the anterior segment of the eye, but it is not suitable for the posterior segment due to the frequency-dependent attenuation of ultrasound and thus the limitation of penetration depth. This paper proposes a novel scan method to image the posterior segment of the eye with an angled high frequency (beyond 40 MHz) ultrasound needle transducer. In this method, the needle transducer is inserted into the eye through a small incision hole (∼1 mm in diameter) and rotated around the axial direction to form a cone-shaped imaging plane, allowing the spatial information of retinal vessels and diagnosis of their occlusion to be displayed. The feasibility of this novel technique was tested with images of a wire phantom, a polyimide tube, and an excised pig eye obtained by manually rotating a 40-MHz PMN-PT needle transducer with a beveled tip of 45°. From the results, we believe that rotational scan imaging will help expand the minimally invasive applications of high frequency ultrasound to other areas due to the capability of increased closeness of an angled needle transducer to structures of interest buried in other tissues. PMID:19411226

Feasibility of rotational scan ultrasound imaging by an angled high frequency transducer for the posterior segment of the eye.

PubMed

Paeng, Dong-Guk; Chang, Jin Ho; Chen, Ruimin; Humayun, Mark S; Shung, K Kirk

2009-03-01

High frequency ultrasound over 40 MHz has been used to image the anterior segment of the eye, but it is not suitable for the posterior segment due to the frequency dependent attenuation of ultrasound and thus the limitation of penetration depth. This paper proposes a novel scan method to image the posterior segment of the eye with an angled high frequency (beyond 40 MHz) ultrasound needle transducer. In this method, the needle transducer is inserted into the eye through a small incision hole (approximately 1 mm in diameter) and rotated around the axial direction to form a cone-shaped imaging plane, allowing the spatial information of retinal vessels and diagnosis of their occlusion to be displayed. The feasibility of this novel technique was tested with images of a wire phantom, a polyimide tube, and an excised pig eye obtained by manually rotating a 40-MHz PMN-PT needle transducer with a beveled tip of 45 degrees . From the results, we believe that rotational scan imaging will help expand the minimally invasive applications of high frequency ultrasound to other areas due to the capability of increased closeness of an angled needle transducer to structures of interest buried in other tissues.

Frequency tunable electronic sources working at room temperature in the 1 to 3 THz band

NASA Astrophysics Data System (ADS)

Maestrini, Alain; Mehdi, Imran; Siles, José V.; Lin, Robert; Lee, Choonsup; Chattopadhyay, Goutam; Pearson, John; Siegel, Peter

2012-10-01

Compact, room temperature terahertz sources are much needed in the 1 to 3 THz band for developing multi-pixel heterodyne receivers for astrophysics and planetary science or for building short-range high spatial resolution THz imaging systems able to see through low water content and non metallic materials, smoke or dust for a variety of applications ranging from the inspection of art artifacts to the detection of masked or concealed objects. All solid-sate electronic sources based on a W-band synthesizer followed by a high-power W-band amplifier and a cascade of Schottky diode based THz frequency multipliers are now capable of producing more than 1 mW at 0.9THz, 50 μW at 2 THz and 18 μW at 2.6 THz without the need of any cryogenic system. These sources are frequency agile and have a relative bandwidth of 10 to 15%, limited by the high power W-band amplifiers. The paper will present the latest developments of this technology and its perspective in terms of frequency range, bandwidth and power.

33 CFR 26.03 - Radiotelephone required.

Code of Federal Regulations, 2011 CFR

2011-07-01

... on board capable of operation from its navigational bridge, or in the case of a dredge, from its main control station, and capable of transmitting and receiving on the frequency or frequencies within the 156... section must be carried on board the described vessels, dredges, and floating plants upon the navigable...

33 CFR 26.03 - Radiotelephone required.

Code of Federal Regulations, 2010 CFR

2010-07-01

... on board capable of operation from its navigational bridge, or in the case of a dredge, from its main control station, and capable of transmitting and receiving on the frequency or frequencies within the 156... section must be carried on board the described vessels, dredges, and floating plants upon the navigable...

Operation ranges and dynamic capabilities of variable-speed pumped-storage hydropower

NASA Astrophysics Data System (ADS)

Mercier, Thomas; Olivier, Mathieu; Dejaeger, Emmanuel

2017-04-01

The development of renewable and intermittent power generation creates incentives for the development of both energy storage solutions and more flexible power generation assets. Pumped-storage hydropower (PSH) is the most established and mature energy storage technology, but recent developments in power electronics have created a renewed interest by providing PSH units with a variable-speed feature, thereby increasing their flexibility. This paper reviews technical considerations related to variable-speed PSH in link with the provision of primary frequency control, also referred to as frequency containment reserves (FCRs). Based on the detailed characteristics of a scale model pump-turbine, the variable-speed operation ranges in pump and turbine modes are precisely assessed and the implications for the provision of FCRs are highlighted. Modelling and control for power system studies are discussed, both for fixed- and variable-speed machines and simulation results are provided to illustrate the high dynamic capabilities of variable-speed PSH.

Hybrid GMR Sensor Detecting 950 pT/sqrt(Hz) at 1 Hz and Room Temperature

PubMed Central

Guedes, André; Macedo, Rita; Jaramillo, Gerardo; Freitas, Paulo P.; Horsley, David A.

2018-01-01

Advances in the magnetic sensing technology have been driven by the increasing demand for the capability of measuring ultrasensitive magnetic fields. Among other emerging applications, the detection of magnetic fields in the picotesla range is crucial for biomedical applications. In this work Picosense reports a millimeter-scale, low-power hybrid magnetoresistive-piezoelectric magnetometer with subnanotesla sensitivity at low frequency. Through an innovative noise-cancelation mechanism, the 1/f noise in the MR sensors is surpassed by the mechanical modulation of the external magnetic fields in the high frequency regime. A modulation efficiency of 13% was obtained enabling a final device’s sensitivity of ~950 pT/Hz1/2 at 1 Hz. This hybrid device proved to be capable of measuring biomagnetic signals generated in the heart in an unshielded environment. This result paves the way for the development of a portable, contactless, low-cost and low-power magnetocardiography device. PMID:29509677

Evaluation of Q-band instrumentation requirements for Strategic Satellite System (SSS) program

NASA Astrophysics Data System (ADS)

Raponi, D. J.

1981-12-01

Q-band instrumentation appropriate for testing the Strategic Satellite System (SSS) satellite terminal is evaluated in terms of current and projected availability; desired and practical measurement capabilities; required development; and schedule/cost impacts to the program. The Air Force is considering several approaches to increasing the strategic communications capability now provided by the recently deployed ultra high frequency (UHF) Air Force Satellite Communications (AFSATCOM) system. The Strategic Satellite System (SSS) was proposed to improve antijam (AJ) characteristics through the use of advanced modulation techniques and higher frequencies (8 and 44 GHz) on links between ground and airborne terminals and the satellites. This report is an assessment of Q-band (44 GHz) test instrumentation requirements, availability, and accuracy as these factors affect cost and schedule for the SSS satellite terminal development program. Though the SSS program has been cancelled, information presented in the report has applicability to the EHF MILSTAR program.

Frequency stabilization of diode-laser-pumped solid state lasers

NASA Technical Reports Server (NTRS)

Byer, Robert L.

1988-01-01

The goal of the NASA Sunlite program is to fly two diode-laser-pumped solid-state lasers on the space shuttle and while doing so to perform a measurement of their frequency stability and temporal coherence. These measurements will be made by combining the outputs of the two lasers on an optical radiation detector and spectrally analyzing the beat note. Diode-laser-pumped solid-state lasers have several characteristics that will make them useful in space borne experiments. First, this laser has high electrical efficiency. Second, it is of a technology that enables scaling to higher powers in the future. Third, the laser can be made extremely reliable, which is crucial for many space based applications. Fourth, they are frequency and amplitude stable and have high temporal coherence. Diode-laser-pumped solid-state lasers are inherently efficient. Recent results have shown 59 percent slope efficiency for a diode-laser-pumped solid-state laser. As for reliability, the laser proposed should be capable of continuous operation. This is possible because the diode lasers can be remote from the solid state gain medium by coupling through optical fibers. Diode lasers are constructed with optical detectors for monitoring their output power built into their mounting case. A computer can actively monitor the output of each diode laser. If it sees any variation in the output power that might indicate a problem, the computer can turn off that diode laser and turn on a backup diode laser. As for stability requirements, it is now generally believed that any laser can be stabilized if the laser has a frequency actuator capable of tuning the laser frequency as far as it is likely to drift in a measurement time.

Experimental research of high frequency standing wave thermoacoustic refrigerator driven by loudspeaker

NASA Astrophysics Data System (ADS)

Chunping, Zhang; Wei, Liu; Zhichun, Yang; Zhengyu, Li; Xiaoqing, Zhang; Feng, Wu

2012-05-01

A small size standing wave thermoacoustic refrigerator driven by a high frequency loudspeaker has been experimentally studied. Instead of water cooling, the cold heat exchanger of the refrigerator was cooled by air through fins on it. By working at 600-700 Hz and adjusting the position of the thermoacoustic core components including the stack and adjacent exchangers, the influences of it on the capability of refrigeration were experimentally investigated. The lowest temperature of 4.1 °C in the cold heat exchanger with the highest temperature difference of 21.5 °C between two heat exchangers were obtained. And the maximum cooling power of 9.7 W has been achieved.

Ultraminiaturized photovoltaic and radio frequency powered optoelectronic systems for wireless optogenetics.

PubMed

Park, Sung Il; Shin, Gunchul; Banks, Anthony; McCall, Jordan G; Siuda, Edward R; Schmidt, Martin J; Chung, Ha Uk; Noh, Kyung Nim; Mun, Jonathan Guo-Han; Rhodes, Justin; Bruchas, Michael R; Rogers, John A

2015-10-01

Wireless control and power harvesting systems that operate injectable, cellular-scale optoelectronic components provide important demonstrated capabilities in neuromodulatory techniques such as optogenetics. Here, we report a radio frequency (RF) control/harvesting device that offers dramatically reduced size, decreased weight and improved efficiency compared to previously reported technologies. Combined use of this platform with ultrathin, multijunction, high efficiency solar cells allows for hundred-fold reduction of transmitted RF power, which greatly enhances the wireless coverage. Fabrication involves separate construction of the harvester and the injectable µ-ILEDs. To test whether the presence of the implantable device alters behavior, we implanted one group of wild type mice and compared sociability behavior to unaltered controls. Social interaction experiments followed protocols defined by Silverman et al. with minor modifications. The results presented here demonstrate that miniaturized RF harvesters, and RF control strategies with photovoltaic harvesters can, when combined with injectable µ-ILEDs, offer versatile capabilities in optogenetics. Experimental and modeling studies establish a range of effective operating conditions for these two approaches. Optogenetics studies with social groups of mice demonstrate the utility of these systems. The addition of miniaturized, high performance photovoltaic cells significantly expands the operating range and reduces the required RF power. The platform can offer capabilities to modulate signaling path in the brain region of freely-behaving animals. These suggest its potential for widespread use in neuroscience.

In Vivo Demonstration of Addressable Microstimulators Powered by Rectification of Epidermically Applied Currents for Miniaturized Neuroprostheses

PubMed Central

2015-01-01

Electrical stimulation is used in order to restore nerve mediated functions in patients with neurological disorders, but its applicability is constrained by the invasiveness of the systems required to perform it. As an alternative to implantable systems consisting of central stimulation units wired to the stimulation electrodes, networks of wireless microstimulators have been devised for fine movement restoration. Miniaturization of these microstimulators is currently hampered by the available methods for powering them. Previously, we have proposed and demonstrated a heterodox electrical stimulation method based on electronic rectification of high frequency current bursts. These bursts can be delivered through textile electrodes on the skin. This approach has the potential to result in an unprecedented level of miniaturization as no bulky parts such as coils or batteries are included in the implant. We envision microstimulators designs based on application-specific integrated circuits (ASICs) that will be flexible, thread-like (diameters < 0.5 mm) and not only with controlled stimulation capabilities but also with sensing capabilities for artificial proprioception. We in vivo demonstrate that neuroprostheses composed of addressable microstimulators based on this electrical stimulation method are feasible and can perform controlled charge-balanced electrical stimulation of muscles. We developed miniature external circuit prototypes connected to two bipolar probes that were percutaneously implanted in agonist and antagonist muscles of the hindlimb of an anesthetized rabbit. The electronic implant architecture was able to decode commands that were amplitude modulated on the high frequency (1 MHz) auxiliary current bursts. The devices were capable of independently stimulating the target tissues, accomplishing controlled dorsiflexion and plantarflexion joint movements. In addition, we numerically show that the high frequency current bursts comply with safety standards both in terms of tissue heating and unwanted electro-stimulation. We demonstrate that addressable microstimulators powered by rectification of epidermically applied currents are feasible. PMID:26147771

In Vivo Demonstration of Addressable Microstimulators Powered by Rectification of Epidermically Applied Currents for Miniaturized Neuroprostheses.

PubMed

Becerra-Fajardo, Laura; Ivorra, Antoni

2015-01-01

Electrical stimulation is used in order to restore nerve mediated functions in patients with neurological disorders, but its applicability is constrained by the invasiveness of the systems required to perform it. As an alternative to implantable systems consisting of central stimulation units wired to the stimulation electrodes, networks of wireless microstimulators have been devised for fine movement restoration. Miniaturization of these microstimulators is currently hampered by the available methods for powering them. Previously, we have proposed and demonstrated a heterodox electrical stimulation method based on electronic rectification of high frequency current bursts. These bursts can be delivered through textile electrodes on the skin. This approach has the potential to result in an unprecedented level of miniaturization as no bulky parts such as coils or batteries are included in the implant. We envision microstimulators designs based on application-specific integrated circuits (ASICs) that will be flexible, thread-like (diameters < 0.5 mm) and not only with controlled stimulation capabilities but also with sensing capabilities for artificial proprioception. We in vivo demonstrate that neuroprostheses composed of addressable microstimulators based on this electrical stimulation method are feasible and can perform controlled charge-balanced electrical stimulation of muscles. We developed miniature external circuit prototypes connected to two bipolar probes that were percutaneously implanted in agonist and antagonist muscles of the hindlimb of an anesthetized rabbit. The electronic implant architecture was able to decode commands that were amplitude modulated on the high frequency (1 MHz) auxiliary current bursts. The devices were capable of independently stimulating the target tissues, accomplishing controlled dorsiflexion and plantarflexion joint movements. In addition, we numerically show that the high frequency current bursts comply with safety standards both in terms of tissue heating and unwanted electro-stimulation. We demonstrate that addressable microstimulators powered by rectification of epidermically applied currents are feasible.

Modal Analysis with the Mobile Modal Testing Unit

NASA Technical Reports Server (NTRS)

Wilder, Andrew J.

2013-01-01

Recently, National Aeronautics and Space Administration's (NASA's) White Sands Test Facility (WSTF) has tested rocket engines with high pulse frequencies. This has resulted in the use of some of WSTF's existing thrust stands, which were designed for static loading, in tests with large dynamic forces. In order to ensure that the thrust stands can withstand the dynamic loading of high pulse frequency engines while still accurately reporting the test data, their vibrational modes must be characterized. If it is found that they have vibrational modes with frequencies near the pulsing frequency of the test, then they must be modified to withstand the dynamic forces from the pulsing rocket engines. To make this determination the Mobile Modal Testing Unit (MMTU), a system capable of determining the resonant frequencies and mode shapes of a structure, was used on the test stands at WSTF. Once the resonant frequency has been determined for a test stand, it can be compared to the pulse frequency of a test engine to determine whether or not that stand can avoid resonance and reliably test that engine. After analysis of test stand 406 at White Sands Test Facility, it was determined that natural frequencies for the structure are located around 75, 125, and 240 Hz, and thus should be avoided during testing.

Multi-frequency Electromagnetic Induction Survey for Archaeological Prospection: Approach and Results in Han Hangu Pass and Xishan Yang in China

NASA Astrophysics Data System (ADS)

Tang, Panpan; Chen, Fulong; Jiang, Aihui; Zhou, Wei; Wang, Hongchao; Leucci, Giovanni; de Giorgi, Lara; Sileo, Maria; Luo, Rupeng; Lasaponara, Rosa; Masini, Nicola

2018-04-01

This study presents the potential of multi-frequency electromagnetic induction (EMI) in archaeology. EMI is currently less employed for archaeological prospection with respect to other geophysical techniques. It is capable of identifying shallow subsurface relics by simultaneously measuring the apparent electrical conductivity (ECa) and apparent magnetic susceptibility (MSa). Moreover, frequency sounding is able to quantify the depths and vertical shapes of buried structures. In this study, EMI surveys with five frequencies were performed at two heritage sites with different geological conditions: Han Hangu Pass characterized by cinnamon soil and Xishan Yang by sandy loams. In the first site, high ECa values were observed with variations in depth correlated to archaeological remains. Moreover, electromagnetic anomalies related to an ancient road and five kiln caves were identified. In the second site, an ancient tomb, indicating extremely low ECa and high MSa, was discovered. Its electromagnetic properties are attributed to the cavity and ferroferric oxides.

Vibro-Acoustic Modulation Based Damage Identification in a Composite Skin-Stiffener Structure

NASA Technical Reports Server (NTRS)

Ooijevaar, T. H.; Loendersloot, R.; Rogge, M. D.; Akkerman, R.; Tinga, T.

2014-01-01

The vibro-acoustic modulation method is applied to a composite skin-stiffener structure to investigate the possibilities to utilize this method for damage identification in terms of detection, localisation and damage quantification. The research comprises a theoretical part and an experimental part. An impact load is applied to the skin-stiffener structure, resulting in a delamination underneath the stiffener. The structure is interrogated with a low frequency pump excitation and a high frequency carrier excitation. The analysis of the response in a frequency band around the carrier frequency is employed to assess the damage identification capabilities and to gain a better understanding of the modulations occurring and the underlying physical phenomena. Though vibro-acoustic is shown to be a sensitive method for damage identification, the complexity of the damage, combined with a high modal density, complicate the understanding of the relation between the physical phenomena and the modulations occurring. more research is recommended to reveal the physics behind the observations.

Numerical study of low-frequency discharge oscillations in a 5 kW Hall thruster

NASA Astrophysics Data System (ADS)

Le, YANG; Tianping, ZHANG; Juanjuan, CHEN; Yanhui, JIA

2018-07-01

A two-dimensional particle-in-cell plasma model is built in the R–Z plane to investigate the low-frequency plasma oscillations in the discharge channel of a 5 kW LHT-140 Hall thruster. In addition to the elastic, excitation, and ionization collisions between neutral atoms and electrons, the Coulomb collisions between electrons and electrons and between electrons and ions are analyzed. The sheath characteristic distortion is also corrected. Simulation results indicate the capability of the built model to reproduce the low-frequency oscillation with high accuracy. The oscillations of the discharge current and ion density produced by the model are consistent with the existing conclusions. The model predicts a frequency that is consistent with that calculated by the zero-dimensional theoretical model.

Use of the SAR (Synthetic Aperture Radar) P band for detection of the Moche and Lambayeque canal networks in the Apurlec region, Perù

NASA Astrophysics Data System (ADS)

Ilaria Pannaccione Apa, Maria; Santovito, Maria Rosaria; Pica, Giulia; Catapano, Ilaria; Fornaro, Gianfranco; Lanari, Riccardo; Soldovieri, Francesco; Wester La Torre, Carlos; Fernandez Manayalle, Marco Antonio; Longo, Francesco; Facchinetti, Claudia; Formaro, Roberto

2016-04-01

In recent years, research attention has been devoted to the development of a new class of airborne radar systems using low frequency bands ranging from VHF/UHF to P and L ones. In this frame, the Italian Space Agency (ASI) has promoted the development of a new multi-mode and multi-band airborne radar system, which can be considered even a "proof-of-concept" for the next space-borne missions. In particular, in agreement with the ASI, the research consortium CO.RI.S.T.A. has in charge the design, development and flight validation of such a kind of system, which is the first airborne radar entirely built in Italy. The aim was to design and realize a radar system able to work in different modalities as: nadir-looking sounder at VHF band (163 MHz); side-looking imager (SAR) at P band with two channels at 450 MHz and 900 MHz. The P-band is a penetration radar. Exploiting penetration features of low frequency electromagnetic waves, dielectric discontinuities of observed scene due to inhomogeneous materials rise up and can be detected on the resulting image. Therefore buried objects or targets placed under vegetation may be detected. Penetration capabilities essentially depend on microwave frequency. Typically, penetration distance is inversely proportional to microwave frequency. The higher the frequency, the lower the penetration depth. Terrain characteristics affect penetration capabilities. Humidity acts as a shield to microwave penetration. Hence terrain with high water content are not good targets for P-band applicability. Science community, governments and space agencies have increased their interest about low frequency radar for their useful applicability in climatology, ecosystem monitoring, glaciology, archaeology. The combination of low frequency and high relative bandwidth of such a systems has a large applicability in both military and civilian applications, ranging from forestry applications, biomass measuring, archaeological and geological exploration, glaciers investigation, biomass monitoring, detection of buried targets. Its extension to non-civil application concerns sub-surface target detection and foliage penetration (FOPEN). In order to achieve the flexibility to face all the above mentioned fields of application, the CORISTA system has been designed as a multi-mode and multi-frequency radar. Multimode stands for the functionality of the system both as Sounder and Imager. In addition, P-band radar is a multi-frequency instrument, since it is designed to work in three different frequency bands, as mentioned above: lower frequency band is used in sounder operative mode, higher frequency in imager operative mode. In the Imager operative mode, low resolution and high resolution capabilities are implemented. The data collected by the radar system have been processed using a model-based microwave tomographic approach, recently developed by IREA-CNR, with the aim to enhance the interpretability of the raw-data radar images. Currently, the non-invasive SAR P band application is under evaluation for testing in the Northern Coast of Perù, in collaboration with the Museo Arqueológico Nacional Brüning. The project will aim to recognize the subsurface ancient Moche (100-700 d.C.) and Lambayeque (700-1375 d.C.) canal networks, whose water supply comes from the Canal Taymi, started to be dug by the Mochicas, still in use by local communities.

Using time-frequency analysis to determine time-resolved detonation velocity with microwave interferometry.

PubMed

Kittell, David E; Mares, Jesus O; Son, Steven F

2015-04-01

Two time-frequency analysis methods based on the short-time Fourier transform (STFT) and continuous wavelet transform (CWT) were used to determine time-resolved detonation velocities with microwave interferometry (MI). The results were directly compared to well-established analysis techniques consisting of a peak-picking routine as well as a phase unwrapping method (i.e., quadrature analysis). The comparison is conducted on experimental data consisting of transient detonation phenomena observed in triaminotrinitrobenzene and ammonium nitrate-urea explosives, representing high and low quality MI signals, respectively. Time-frequency analysis proved much more capable of extracting useful and highly resolved velocity information from low quality signals than the phase unwrapping and peak-picking methods. Additionally, control of the time-frequency methods is mainly constrained to a single parameter which allows for a highly unbiased analysis method to extract velocity information. In contrast, the phase unwrapping technique introduces user based variability while the peak-picking technique does not achieve a highly resolved velocity result. Both STFT and CWT methods are proposed as improved additions to the analysis methods applied to MI detonation experiments, and may be useful in similar applications.

Design and development of ultra-wideband 3 dB hybrid coupler for Ion cyclotron resonance frequency heating in tokamak.

PubMed

Yadav, Rana Pratap; Kumar, Sunil; Kulkarni, S V

2014-04-01

Design and development of a high power ultra-wideband, 3 dB tandem hybrid coupler is presented and its application in ICRF heating of the tokamak is discussed. In order to achieve the desired frequency band of 38-112 MHz and 200 kW power handling capability, the 3 dB hybrid coupler is developed using two 3-element 8.34 ± 0.2 dB coupled lines sections in tandem. In multi-element coupled lines, junctions are employed for the joining of coupled elements that produce the undesirable reactance called junction discontinuity effect. The effect becomes prominent in the high power multi-element coupled lines for high frequency (HF) and very high frequency(VHF) applications because of larger structural dimensions. Junction discontinuity effect significantly deteriorates coupling and output performance from the theoretical predictions. For the analysis of junction discontinuity effect and its compensation, a theoretical approach has been developed and generalized for n-element coupled lines section. The theory has been applied in the development of the 3 dB hybrid coupler. The fabricated hybrid coupler has been experimentally characterized using vector network analyzer and obtained results are found in good agreement with developed theory.

SiGe:C Heterojunction Bipolar Transistors: From Materials Research to Chip Fabrication

NASA Astrophysics Data System (ADS)

Ruecker, H.; Heinemann, B.; Knoll, D.; Ehwald, K.-E.

Incorporation of substitutional carbon ( ~10^20 cm^-3) into the SiGe region of a heterojunction bipolar transistor (HBT) strongly reduces boron diffusion during device processing. We describe the physical mechanism behind the suppression of B diffusion in C-rich Si and SiGe, and explain how the increased thermal stability of doping profiles in SiGe:C HBTs can be used to improve device performance. Manufacturability of SiGe:C HBTs with transit frequencies of 100 GHz and maximum oscillation frequencies of 130 GHz is demonstrated in a BiCMOS technology capable of fabricating integrated circuits for radio frequencies with high yield.

Spike train generation and current-to-frequency conversion in silicon diodes

NASA Technical Reports Server (NTRS)

Coon, D. D.; Perera, A. G. U.

1989-01-01

A device physics model is developed to analyze spontaneous neuron-like spike train generation in current driven silicon p(+)-n-n(+) devices in cryogenic environments. The model is shown to explain the very high dynamic range (0 to the 7th) current-to-frequency conversion and experimental features of the spike train frequency as a function of input current. The devices are interesting components for implementation of parallel asynchronous processing adjacent to cryogenically cooled focal planes because of their extremely low current and power requirements, their electronic simplicity, and their pulse coding capability, and could be used to form the hardware basis for neural networks which employ biologically plausible means of information coding.

HISCAT: A proposed new scatter facility in Northern Scandinavia

NASA Technical Reports Server (NTRS)

Bostrom, R.; Thide, B.

1986-01-01

It is proposed that a new versatile ionospheric and atmospheric scatter radar be constructed in northern Scandavia through a multinational collaborative effort. The new facility tentatively named HISCAT (High frequency, High power, High latitude, Heating and Ionospheric Scatter facility), should be used for scientific investigations of: the physics of the neutral (middle) atmosphere; fundamental plasma phenomena, natural or artificially induced in the ionosphere; electrodynamic conditions at high altitudes above the auroral region and in the polar cap ionosphere; plasma waves in the solar atmosphere. The system should thus be able to operate as a mesosphere-stratosphere-troposphere (MST) radar, a so-called ionospheric modification facility, incoherent-scatter radar, coherent-scatter radar, and solar radar. Basically, the new facility should be a device that can operate simultaneously on several frequencies in the frequency range 5 to 50 MHz not covered by other instruments. It should comprise: powerful transmitters, capable of delivering a total average power of several megawatts; an advanced phased antenna array of high gain forming one or two steerable and well collimated beams; and an advanced data collection and analysis system.

Development of a frequency-modulated ultrasonic sensor inspired by bat echolocation

NASA Astrophysics Data System (ADS)

Kepa, Krzysztof; Abaid, Nicole

2015-03-01

Bats have evolved to sense using ultrasonic signals with a variety of different frequency signatures which interact with their environment. Among these signals, those with time-varying frequencies may enable the animals to gather more complex information for obstacle avoidance and target tracking. Taking inspiration from this system, we present the development of a sonar sensor capable of generating frequency-modulated ultrasonic signals. The device is based on a miniature mobile computer, with on board data capture and processing capabilities, which is designed for eventual autonomous operation in a robotic swarm. The hardware and software components of the sensor are detailed, as well their integration. Preliminary results for target detection using both frequency-modulated and constant frequency signals are discussed.

47 CFR 2.815 - External radio frequency power amplifiers.

Code of Federal Regulations, 2014 CFR

2014-10-01

... amplifier is any device which, (1) when used in conjunction with a radio transmitter as a signal source is capable of amplification of that signal, and (2) is not an integral part of a radio transmitter as... following: (1) The external radio frequency power amplifier shall not be capable of amplification in the...

47 CFR 2.815 - External radio frequency power amplifiers.

Code of Federal Regulations, 2013 CFR

2013-10-01

... amplifier is any device which, (1) when used in conjunction with a radio transmitter as a signal source is capable of amplification of that signal, and (2) is not an integral part of a radio transmitter as... following: (1) The external radio frequency power amplifier shall not be capable of amplification in the...

47 CFR 2.815 - External radio frequency power amplifiers.

Code of Federal Regulations, 2012 CFR

2012-10-01

... amplifier is any device which, (1) when used in conjunction with a radio transmitter as a signal source is capable of amplification of that signal, and (2) is not an integral part of a radio transmitter as... following: (1) The external radio frequency power amplifier shall not be capable of amplification in the...

A high and low noise model for strong motion accelerometers

NASA Astrophysics Data System (ADS)

Clinton, J. F.; Cauzzi, C.; Olivieri, M.

2010-12-01

We present reference noise models for high-quality strong motion accelerometer installations. We use continuous accelerometer data acquired by the Swiss Seismological Service (SED) since 2006 and other international high-quality accelerometer network data to derive very broadband (50Hz-100s) high and low noise models. The proposed noise models are compared to the Peterson (1993) low and high noise models designed for broadband seismometers; the datalogger self-noise; background noise levels at existing Swiss strong motion stations; and typical earthquake signals recorded in Switzerland and worldwide. The standard strong motion station operated by the SED consists of a Kinemetrics Episensor (2g clip level; flat acceleration response from 200 Hz to DC; <155dB dynamic range) coupled with a 24-bit Nanometrics Taurus datalogger. The proposed noise models are based on power spectral density (PSD) noise levels for each strong motion station computed via PQLX (McNamara and Buland, 2004) from several years of continuous recording. The 'Accelerometer Low Noise Model', ALNM, is dominated by instrument noise from the sensor and datalogger. The 'Accelerometer High Noise Model', AHNM, reflects 1) at high frequencies the acceptable site noise in urban areas, 2) at mid-periods the peak microseismal energy, as determined by the Peterson High Noise Model and 3) at long periods the maximum noise observed from well insulated sensor / datalogger systems placed in vault quality sites. At all frequencies, there is at least one order of magnitude between the ALNM and the AHNM; at high frequencies (> 1Hz) this extends to 2 orders of magnitude. This study provides remarkable confirmation of the capability of modern strong motion accelerometers to record low-amplitude ground motions with seismic observation quality. In particular, an accelerometric station operating at the ALNM is capable of recording the full spectrum of near source earthquakes, out to 100 km, down to M2. Of particular interest for the SED, this study provides acceptable noise limits for candidate sites for the on-going Strong Motion Network modernisation.

Development of a Pulsed Combustion Actuator For High-Speed Flow Control

NASA Technical Reports Server (NTRS)

Cutler, Andrew D.; Beck, B. Terry; Wilkes, Jennifer A.; Drummond, J. Philip; Alderfer, David W.; Danehy, Paul M.

2005-01-01

This paper describes the flow within a prototype actuator, energized by pulsed combustion or detonations, that provides a pulsed jet suitable for flow control in high-speed applications. A high-speed valve, capable of delivering a pulsed stream of reactants a mixture of H2 and air at rates of up to 1500 pulses per second, has been constructed. The reactants burn in a resonant chamber, and the products exit the device as a pulsed jet. High frequency pressure transducers have been used to monitor the pressure fluctuations in the device at various reactant injection frequencies, including both resonant and off-resonant conditions. The combustion chamber has been constructed with windows, and the flow inside it has been visualized using Planar Laser-Induced Fluorescence (PLIF). The pulsed jet at the exit of the device has been observed using schlieren.

Accurate step-FMCW ultrasound ranging and comparison with pulse-echo signaling methods

NASA Astrophysics Data System (ADS)

Natarajan, Shyam; Singh, Rahul S.; Lee, Michael; Cox, Brian P.; Culjat, Martin O.; Grundfest, Warren S.; Lee, Hua

2010-03-01

This paper presents a method setup for high-frequency ultrasound ranging based on stepped frequency-modulated continuous waves (FMCW), potentially capable of producing a higher signal-to-noise ratio (SNR) compared to traditional pulse-echo signaling. In current ultrasound systems, the use of higher frequencies (10-20 MHz) to enhance resolution lowers signal quality due to frequency-dependent attenuation. The proposed ultrasound signaling format, step-FMCW, is well-known in the radar community, and features lower peak power, wider dynamic range, lower noise figure and simpler electronics in comparison to pulse-echo systems. In pulse-echo ultrasound ranging, distances are calculated using the transmit times between a pulse and its subsequent echoes. In step-FMCW ultrasonic ranging, the phase and magnitude differences at stepped frequencies are used to sample the frequency domain. Thus, by taking the inverse Fourier transform, a comprehensive range profile is recovered that has increased immunity to noise over conventional ranging methods. Step-FMCW and pulse-echo waveforms were created using custom-built hardware consisting of an arbitrary waveform generator and dual-channel super heterodyne receiver, providing high SNR and in turn, accuracy in detection.

Flicker in a twisted nematic spatial light modulator

NASA Astrophysics Data System (ADS)

Calderón-Hermosillo, Yuliana; García-Márquez, Jorge; Espinosa-Luna, Rafael; Ochoa, Noé Alcalá; López, Víctor; Aguilar, Alberto; Noé-Arias, Enrique; Alayli, Yasser

2013-06-01

Liquid Crystal on Silicon (LCoS) Spatial Light Modulators (SLM) are widely used for their capability to control beams howbeit fluctuations in phase and amplitude. It is then necessary to understand the negative effects of these fluctuations, also known as flicker, and the means to mitigate them. The flicker is observed either as high frequency variations of polarization, attenuation or high phase fluctuations on the wave front modulated by the LCoS device. Here, we compare the flicker behavior in a twisted nematic (TN) LCoS-SLM for different polarization schemes and temperatures. The quantitative evaluation shows that flicker is effectively reduced only by chilling the LCoS panel to temperatures just below 0 °C but, the LCoS modulation capability is also affected.

High-frequency health data and spline functions.

PubMed

Martín-Rodríguez, Gloria; Murillo-Fort, Carlos

2005-03-30

Seasonal variations are highly relevant for health service organization. In general, short run movements of medical magnitudes are important features for managers in this field to make adequate decisions. Thus, the analysis of the seasonal pattern in high-frequency health data is an appealing task. The aim of this paper is to propose procedures that allow the analysis of the seasonal component in this kind of data by means of spline functions embedded into a structural model. In the proposed method, useful adaptions of the traditional spline formulation are developed, and the resulting procedures are capable of capturing periodic variations, whether deterministic or stochastic, in a parsimonious way. Finally, these methodological tools are applied to a series of daily emergency service demand in order to capture simultaneous seasonal variations in which periods are different.

Three-layered radio frequency coil arrangement for sodium MRI of the human brain at 9.4 Tesla.

PubMed

Shajan, G; Mirkes, Christian; Buckenmaier, Kai; Hoffmann, Jens; Pohmann, Rolf; Scheffler, Klaus

2016-02-01

A multinuclei imaging setup with the capability to acquire both sodium ((23) Na) and proton ((1) H) signals at 9.4 Tesla is presented. The main objective was to optimize coil performance at the (23) Na frequency while still having the ability to acquire satisfactory (1) H images. The setup consisted of a combination of three radio frequency (RF) coils arranged in three layers: the innermost layer was a 27-channel (23) Na receive helmet which was surrounded by a four-channel (23) Na transceiver array. The outer layer consisted of a four-channel (1) H dipole array for B0 shimming and anatomical localization. Transmit and receive performance of the (23) Na arrays was compared to a single-tuned (23) Na birdcage resonator. While the transmit efficiency of the (23) Na transceiver array was comparable to the birdcage, the (23) Na receive array provided substantial signal-to-noise ratio (SNR) gain near the surface and comparable SNR in the center. The utility of this customized setup was demonstrated by (23) Na images of excellent quality. High SNR, efficient transmit excitation and B0 shimming capability can be achieved for (23) Na MRI at 9.4T using novel coil combination. This RF configuration is easily adaptable to other multinuclei applications at ultra high field (≥ 7T). © 2015 Wiley Periodicals, Inc.

A sophisticated, multi-channel data acquisition and processing system for high frequency noise research

NASA Technical Reports Server (NTRS)

Hall, David G.; Bridges, James

1992-01-01

A sophisticated, multi-channel computerized data acquisition and processing system was developed at the NASA LeRC for use in noise experiments. This technology, which is available for transfer to industry, provides a convenient, cost-effective alternative to analog tape recording for high frequency acoustic measurements. This system provides 32-channel acquisition of microphone signals with an analysis bandwidth up to 100 kHz per channel. Cost was minimized through the use of off-the-shelf components. Requirements to allow for future expansion were met by choosing equipment which adheres to established industry standards for hardware and software. Data processing capabilities include narrow band and 1/3 octave spectral analysis, compensation for microphone frequency response/directivity, and correction of acoustic data to standard day conditions. The system was used successfully in a major wind tunnel test program at NASA LeRC to acquire and analyze jet noise data in support of the High Speed Civil Transport (HSCT) program.

High-frequency Oscillations in the Atmosphere above a Sunspot Umbra

NASA Astrophysics Data System (ADS)

Wang, Feng; Deng, Hui; Li, Bo; Feng, Song; Bai, Xianyong; Deng, Linhua; Yang, Yunfei; Xue, Zhike; Wang, Rui

2018-03-01

We use high spatial and temporal resolution observations, simultaneously obtained with the New Vacuum Solar Telescope and Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, to investigate the high-frequency oscillations above a sunspot umbra. A novel time–frequency analysis method, namely, the synchrosqueezing transform (SST), is employed to represent their power spectra and to reconstruct the high-frequency signals at different solar atmospheric layers. A validation study with synthetic signals demonstrates that SST is capable of resolving weak signals even when their strength is comparable to the high-frequency noise. The power spectra, obtained from both SST and the Fourier transform, of the entire umbral region indicate that there are significant enhancements between 10 and 14 mHz (labeled as 12 mHz) at different atmospheric layers. Analyzing the spectrum of a photospheric region far away from the umbra demonstrates that this 12 mHz component exists only inside the umbra. The animation based on the reconstructed 12 mHz component in AIA 171 Å illustrates that an intermittently propagating wave first emerges near the footpoints of coronal fan structures, and then propagates outward along the structures. A time–distance diagram, coupled with a subsonic wave speed (∼49 km s‑1), highlights the fact that these coronal perturbations are best described as upwardly propagating magnetoacoustic slow waves. Thus, we first reveal the high-frequency oscillations with a period around one minute in imaging observations at different height above an umbra, and these oscillations seem to be related to the umbral perturbations in the photosphere.

Modulating the Neutron Flux from a Mirror Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryutov, D D

2011-09-01

A 14-MeV neutron source based on a Gas-Dynamic Trap will provide a high flux of 14 MeV neutrons for fusion materials and sub-component testing. In addition to its main goal, the source has potential applications in condensed matter physics and biophysics. In this report, the author considers adding one more capability to the GDT-based neutron source, the modulation of the neutron flux with a desired frequency. The modulation may be an enabling tool for the assessment of the role of non-steady-state effects in fusion devices as well as for high-precision, low-signal basic science experiments favoring the use of the synchronousmore » detection technique. A conclusion is drawn that modulation frequency of up to 1 kHz and modulation amplitude of a few percent is achievable. Limitations on the amplitude of modulations at higher frequencies are discussed.« less

Stable, low cost SAW microwave transmitter

NASA Astrophysics Data System (ADS)

Lau, K. F.; Yen, K. H.

1986-06-01

The design flexibility and application possibilities of surface acoustic wave (SAW) technology is discussed. When a highly stable, AM-modulated transmitter is required, a SAW resonator can provide an oscillator Q of up to 20,000 at 1 GHz. When FM modulation is required, the SAW delay line can provide a lower oscillator Q, which represents the optimum tradeoff between frequency stability and FM modulability. The capabilities of SAW oscillators are reviewed, and two example transmitters are presented. One transmitter operates at 1680 MHz and provides an AM-modulated signal. The second operates at the 400 to 406 MHz range and provides an FM-modulated output at one of six frequencies. SAW transmitters are suitable for applications where moderately high stability and low cost are key factors. With direct generation of signals at microwave frequencies and the flexibility of SAW oscillator design, a wide range of performance characteristics can be achieved.

Radio frequency analog electronics based on carbon nanotube transistors

PubMed Central

Kocabas, Coskun; Kim, Hoon-sik; Banks, Tony; Rogers, John A.; Pesetski, Aaron A.; Baumgardner, James E.; Krishnaswamy, S. V.; Zhang, Hong

2008-01-01

The potential to exploit single-walled carbon nanotubes (SWNTs) in advanced electronics represents a continuing, major source of interest in these materials. However, scalable integration of SWNTs into circuits is challenging because of difficulties in controlling the geometries, spatial positions, and electronic properties of individual tubes. We have implemented solutions to some of these challenges to yield radio frequency (RF) SWNT analog electronic devices, such as narrow band amplifiers operating in the VHF frequency band with power gains as high as 14 dB. As a demonstration, we fabricated nanotube transistor radios, in which SWNT devices provide all of the key functions, including resonant antennas, fixed RF amplifiers, RF mixers, and audio amplifiers. These results represent important first steps to practical implementation of SWNTs in high-speed analog circuits. Comparison studies indicate certain performance advantages over silicon and capabilities that complement those in existing compound semiconductor technologies. PMID:18227509

Bilateral preictal signature of phase-amplitude coupling in canine epilepsy.

PubMed

Gagliano, Laura; Bou Assi, Elie; Nguyen, Dang K; Rihana, Sandy; Sawan, Mohamad

2018-01-01

Seizure forecasting would improve the quality of life of patients with refractory epilepsy. Although early findings were optimistic, no single feature has been found capable of individually characterizing brain dynamics during transition to seizure. Cross-frequency phase amplitude coupling has been recently proposed as a precursor of seizure activity. This work evaluates the existence of a statistically significant difference in mean phase amplitude coupling distribution between the preictal and interictal states of seizures in dogs with bilaterally implanted intracranial electrodes. Results show a statistically significant change (p<0.05) of phase amplitude coupling during the preictal phase. This change is correlated with the position of implanted electrodes and is more significant within high-gamma frequency bands. These findings highlight the potential benefit of bilateral iEEG analysis and the feasibility of seizure forecasting based on slow modulation of high frequency amplitude. Copyright © 2017 Elsevier B.V. All rights reserved.

Radio Frequency Electromagnetic Radiation From Streamer Collisions

NASA Astrophysics Data System (ADS)

Luque, Alejandro

2017-10-01

We present a full electromagnetic model of streamer propagation where the Maxwell equations are solved self-consistently together with electron transport and reactions including photoionization. We apply this model to the collision of counter-propagating streamers in gaps tens of centimeters wide and with large potential differences of hundreds of kilovolts. Our results show that streamer collisions emit electromagnetic pulses that, at atmospheric pressure, dominate the radio frequency spectrum of an extended corona in the range from about 100 MHz to a few gigahertz. We also investigate the fast penetration, after a collision, of electromagnetic fields into the streamer heads and show that these fields are capable of accelerating electrons up to about 100 keV. By substantiating the link between X-rays and high-frequency radio emissions and by describing a mechanism for the early acceleration of runaway electrons, our results support the hypothesis that streamer collisions are essential precursors of high-energy processes in electric discharges.

Precise and fast spatial-frequency analysis using the iterative local Fourier transform.

PubMed

Lee, Sukmock; Choi, Heejoo; Kim, Dae Wook

2016-09-19

The use of the discrete Fourier transform has decreased since the introduction of the fast Fourier transform (fFT), which is a numerically efficient computing process. This paper presents the iterative local Fourier transform (ilFT), a set of new processing algorithms that iteratively apply the discrete Fourier transform within a local and optimal frequency domain. The new technique achieves 2¹⁰ times higher frequency resolution than the fFT within a comparable computation time. The method's superb computing efficiency, high resolution, spectrum zoom-in capability, and overall performance are evaluated and compared to other advanced high-resolution Fourier transform techniques, such as the fFT combined with several fitting methods. The effectiveness of the ilFT is demonstrated through the data analysis of a set of Talbot self-images (1280 × 1024 pixels) obtained with an experimental setup using grating in a diverging beam produced by a coherent point source.

Radio Frequency Electromagnetic Radiation From Streamer Collisions.

PubMed

Luque, Alejandro

2017-10-16

We present a full electromagnetic model of streamer propagation where the Maxwell equations are solved self-consistently together with electron transport and reactions including photoionization. We apply this model to the collision of counter-propagating streamers in gaps tens of centimeters wide and with large potential differences of hundreds of kilovolts. Our results show that streamer collisions emit electromagnetic pulses that, at atmospheric pressure, dominate the radio frequency spectrum of an extended corona in the range from about 100 MHz to a few gigahertz. We also investigate the fast penetration, after a collision, of electromagnetic fields into the streamer heads and show that these fields are capable of accelerating electrons up to about 100 keV. By substantiating the link between X-rays and high-frequency radio emissions and by describing a mechanism for the early acceleration of runaway electrons, our results support the hypothesis that streamer collisions are essential precursors of high-energy processes in electric discharges.

Pyrotechnic shock measurement and data analysis requirements

NASA Technical Reports Server (NTRS)

Albers, L.

1975-01-01

A study of laboratory measurement and analysis of pyrotechnic shock prompted by a discrepancy in preliminary Mariner Jupiter/Saturn shock test data is reported. It is shown that before generating shock response plots from any recorded pyrotechnic event, a complete review of each instrumentation and analysis system must be made. In addition, the frequency response capability of the tape recorder used should be as high as possible; the discrepancies in the above data were due to inadequate frequency response in the FM tape recorders. The slew rate of all conditioning amplifiers and input converters must be high enough to prevent signal distortion at maximum input voltage; amplifier ranges should be selected so that the input pulse is approximately 50% of full scale; the Bessel response type should be chosen for digital shock analysis if antialiasing filters are employed; and transducer selection must consider maximum acceleration limit, mounted resonance frequency, flat clean mounting surfaces, base bending sensitivity, and proper torque.

Proposal of a gigawatt-class L/Ku dual-band magnetically insulated transmission line oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ju, J.-C., E-mail: jujinchuan@126.com; Fan, Y.-W.; Shu, T.

2014-10-15

We present a gigawatt (GW)-class magnetically insulated transmission line oscillator (MILO) which is capable of generating dual-band high power microwaves (HPMs). The proposed device, deriving from previously studied complex MILO and dual-frequency MILO, is designed to produce two HPMs in L-band and Ku-band, respectively. It is found in particle-in-cell (PIC) simulation that when the diode voltage is 610 kV, HPMs with frequencies of 1.72 GHz and 14.6 GHz can be achieved with powers of 3.3 GW and 2.4 GW, respectively. The corresponding total power conversion efficiency is approximately 12.8%. Power difference of the two generated HPMs is approximately 1.4 dB, and frequency difference of themmore » reaches a level as high as ∼10 dB.« less

Low and High Frequency Models of Response Statistics of a Cylindrical Orthogrid Vehicle Panel to Acoustic Excitation

NASA Technical Reports Server (NTRS)

Smith, Andrew; LaVerde, Bruce; Teague, David; Gardner, Bryce; Cotoni, Vincent

2010-01-01

This presentation further develops the orthogrid vehicle panel work. Employed Hybrid Module capabilities to assess both low/mid frequency and high frequency models in the VA One simulation environment. The response estimates from three modeling approaches are compared to ground test measurements. Detailed Finite Element Model of the Test Article -Expect to capture both the global panel modes and the local pocket mode response, but at a considerable analysis expense (time & resources). A Composite Layered Construction equivalent global stiffness approximation using SEA -Expect to capture response of the global panel modes only. An SEA approximation using the Periodic Subsystem Formulation. A finite element model of a single periodic cell is used to derive the vibroacoustic properties of the entire periodic structure (modal density, radiation efficiency, etc. Expect to capture response at various locations on the panel (on the skin and on the ribs) with less analysis expense

A high-throughput flow cytometry-on-a-CMOS platform for single-cell dielectric spectroscopy at microwave frequencies.

PubMed

Chien, Jun-Chau; Ameri, Ali; Yeh, Erh-Chia; Killilea, Alison N; Anwar, Mekhail; Niknejad, Ali M

2018-06-06

This work presents a microfluidics-integrated label-free flow cytometry-on-a-CMOS platform for the characterization of the cytoplasm dielectric properties at microwave frequencies. Compared with MHz impedance cytometers, operating at GHz frequencies offers direct intracellular permittivity probing due to electric fields penetrating through the cellular membrane. To overcome the detection challenges at high frequencies, the spectrometer employs on-chip oscillator-based sensors, which embeds simultaneous frequency generation, electrode excitation, and signal detection capabilities. By employing an injection-locking phase-detection technique, the spectrometer offers state-of-the-art sensitivity, achieving a less than 1 aFrms capacitance detection limit (or 5 ppm in frequency-shift) at a 100 kHz noise filtering bandwidth, enabling high throughput (>1k cells per s), with a measured cellular SNR of more than 28 dB. With CMOS/microfluidics co-design, we distribute four sensing channels at 6.5, 11, 17.5, and 30 GHz in an arrayed format whereas the frequencies are selected to center around the water relaxation frequency at 18 GHz. An issue in the integration of CMOS and microfluidics due to size mismatch is also addressed through introducing a cost-efficient epoxy-molding technique. With 3-D hydrodynamic focusing microfluidics, we perform characterization on four different cell lines including two breast cell lines (MCF-10A and MDA-MB-231) and two leukocyte cell lines (K-562 and THP-1). After normalizing the higher frequency signals to the 6.5 GHz ones, the size-independent dielectric opacity shows a differentiable distribution at 17.5 GHz between normal (0.905 ± 0.160, mean ± std.) and highly metastatic (1.033 ± 0.107) breast cells with p ≪ 0.001.

Solving Component Structural Dynamic Failures Due to Extremely High Frequency Structural Response on the Space Shuttle Program

NASA Technical Reports Server (NTRS)

Frady, Greg; Nesman, Thomas; Zoladz, Thomas; Szabo, Roland

2010-01-01

For many years, the capabilities to determine the root-cause failure of component failures have been limited to the analytical tools and the state of the art data acquisition systems. With this limited capability, many anomalies have been resolved by adding material to the design to increase robustness without the ability to determine if the design solution was satisfactory until after a series of expensive test programs were complete. The risk of failure and multiple design, test, and redesign cycles were high. During the Space Shuttle Program, many crack investigations in high energy density turbomachines, like the SSME turbopumps and high energy flows in the main propulsion system, have led to the discovery of numerous root-cause failures and anomalies due to the coexistences of acoustic forcing functions, structural natural modes, and a high energy excitation, such as an edge tone or shedding flow, leading the technical community to understand many of the primary contributors to extremely high frequency high cycle fatique fluid-structure interaction anomalies. These contributors have been identified using advanced analysis tools and verified using component and system tests during component ground tests, systems tests, and flight. The structural dynamics and fluid dynamics communities have developed a special sensitivity to the fluid-structure interaction problems and have been able to adjust and solve these problems in a time effective manner to meet budget and schedule deadlines of operational vehicle programs, such as the Space Shuttle Program over the years.

Helicity multiplexed broadband metasurface holograms.

PubMed

Wen, Dandan; Yue, Fuyong; Li, Guixin; Zheng, Guoxing; Chan, Kinlong; Chen, Shumei; Chen, Ming; Li, King Fai; Wong, Polis Wing Han; Cheah, Kok Wai; Pun, Edwin Yue Bun; Zhang, Shuang; Chen, Xianzhong

2015-09-10

Metasurfaces are engineered interfaces that contain a thin layer of plasmonic or dielectric nanostructures capable of manipulating light in a desirable manner. Advances in metasurfaces have led to various practical applications ranging from lensing to holography. Metasurface holograms that can be switched by the polarization state of incident light have been demonstrated for achieving polarization multiplexed functionalities. However, practical application of these devices has been limited by their capability for achieving high efficiency and high image quality. Here we experimentally demonstrate a helicity multiplexed metasurface hologram with high efficiency and good image fidelity over a broad range of frequencies. The metasurface hologram features the combination of two sets of hologram patterns operating with opposite incident helicities. Two symmetrically distributed off-axis images are interchangeable by controlling the helicity of the input light. The demonstrated helicity multiplexed metasurface hologram with its high performance opens avenues for future applications with functionality switchable optical devices.

Helicity multiplexed broadband metasurface holograms

PubMed Central

Wen, Dandan; Yue, Fuyong; Li, Guixin; Zheng, Guoxing; Chan, Kinlong; Chen, Shumei; Chen, Ming; Li, King Fai; Wong, Polis Wing Han; Cheah, Kok Wai; Yue Bun Pun, Edwin; Zhang, Shuang; Chen, Xianzhong

2015-01-01

Metasurfaces are engineered interfaces that contain a thin layer of plasmonic or dielectric nanostructures capable of manipulating light in a desirable manner. Advances in metasurfaces have led to various practical applications ranging from lensing to holography. Metasurface holograms that can be switched by the polarization state of incident light have been demonstrated for achieving polarization multiplexed functionalities. However, practical application of these devices has been limited by their capability for achieving high efficiency and high image quality. Here we experimentally demonstrate a helicity multiplexed metasurface hologram with high efficiency and good image fidelity over a broad range of frequencies. The metasurface hologram features the combination of two sets of hologram patterns operating with opposite incident helicities. Two symmetrically distributed off-axis images are interchangeable by controlling the helicity of the input light. The demonstrated helicity multiplexed metasurface hologram with its high performance opens avenues for future applications with functionality switchable optical devices. PMID:26354497

Synthesis of monopolar ultrasound pulses for therapy: the frequency-compounding transducer.

PubMed

Lin, Kuang-Wei; Hall, Timothy L; McGough, Robert J; Xu, Zhen; Cain, Charles A

2014-07-01

In diagnostic ultrasound, broadband transducers capable of short acoustic pulse emission and reception can improve axial resolution and provide sufficient bandwidth for harmonic imaging and multi-frequency excitation techniques. In histotripsy, a cavitation-based ultrasound therapy, short acoustic pulses (<2 cycles) can produce precise tissue ablation wherein lesion formation only occurs when the applied peak negative pressure exceeds an intrinsic threshold of the medium. This paper investigates a frequency compounding technique to synthesize nearly monopolar (half-cycle) ultrasound pulses. More specifically, these pulses were generated using a custom transducer composed of 23 individual relatively-broadband piezoceramic elements with various resonant frequencies (0.5, 1, 1.5, 2, and 3 MHz). Each frequency component of the transducer was capable of generating 1.5-cycle pulses with only one high-amplitude negative half-cycle using a custom 23-channel high-voltage pulser. By varying time delays of individual frequency components to allow their principal peak negative peaks to arrive at the focus of the transducer constructively, destructive interference occurs elsewhere in time and space, resulting in a monopolar pulse approximation with a dominant negative phase (with measured peak negative pressure [P-]: peak positive pressure [P+] = 4.68: 1). By inverting the excitation pulses to individual elements, monopolar pulses with a dominant positive phase can also be generated (with measured P+: P- = 4.74: 1). Experiments in RBC phantoms indicated that monopolar pulses with a dominant negative phase were able to produce very precise histotripsy-type lesions using the intrinsic threshold mechanism. Monopolar pulses with a dominant negative phase can inhibit shock scattering during histotripsy, leading to more predictable lesion formation using the intrinsic threshold mechanism, while greatly reducing any constructive interference, and potential hot-spots elsewhere. Moreover, these monopolar pulses could have many potential benefits in ultrasound imaging, including axial resolution improvement, speckle reduction, and contrast enhancement in pulse inversion imaging.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Hao, E-mail: hc000211@ohio.edu; Nanoscale and Quantum Phenomena Institute, Physics & Astronomy Department, Ohio University, Athens, Ohio 45701; Cummings, Marvin

High-speed beam choppers are a crucial part of time-resolved x-ray studies as well as a necessary component to enable elemental contrast in synchrotron x-ray scanning tunneling microscopy (SX-STM). However, many chopper systems are not capable of operation in vacuum, which restricts their application to x-ray studies with high photon energies, where air absorption does not present a significant problem. To overcome this limitation, we present a fully ultra-high vacuum (UHV) compatible chopper system capable of operating at variable chopping frequencies up to 4 kHz. The lightweight aluminum chopper disk is coated with Ti and Au films to provide the required beammore » attenuation for soft and hard x-rays with photon energies up to about 12 keV. The chopper is used for lock-in detection of x-ray enhanced signals in SX-STM.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Hao; Cummings, Marvin L.; Shirato, Nozomi

High-speed beam choppers are a crucial part of time-resolved x-ray studies as well as a necessary component to enable elemental contrast in synchrotron x-ray scanning tunneling microscopy (SX-STM). However, many chopper systems are not capable of operation in vacuum, which restricts their application to x-ray studies with high photon energies, where air absorption does not present a significant problem. To overcome this limitation, we present a fully ultra-high vacuum (UHV) compatible chopper system capable of operating at variable chopping frequencies up to 4 kHz. The lightweight aluminum chopper disk is coated with Ti and Au films to provide the requiredmore » beam attenuation for soft and hard x-rays with photon energies up to about 12 keV. The chopper is used for lock-in detection of x-ray enhanced signals in SX-STM.« less

Spectrum Situational Awareness Capability: The Military Need and Potential Implementation Issues

DTIC Science & Technology

2006-10-01

Management Sensor Systems Frequency Management EW Systems Frequency Management Allied Battlespace Spectrum Management Restricted Frequency List Frequency...Management Restricted Frequency List Frequency Allocation Table Civil Frequency Use Data Inputs Negotiation and allocation process © Dstl 2006 26th...Management Restricted Frequency List Data Inputs Negotiation and allocation process Frequency Allocation Table SSA ES INT COP etc WWW Spectrum

Outperforming hummingbirds' load-lifting capability with a lightweight hummingbird-like flapping-wing mechanism.

PubMed

Leys, Frederik; Reynaerts, Dominiek; Vandepitte, Dirk

2016-08-15

The stroke-cam flapping mechanism presented in this paper closely mimics the wing motion of a hovering Rufous hummingbird. It is the only lightweight hummingbird-sized flapping mechanism which generates a harmonic wing stroke with both a high flapping frequency and a large stroke amplitude. Experiments on a lightweight prototype of this stroke-cam mechanism on a 50 mm-long wing demonstrate that a harmonic stroke motion is generated with a peak-to-peak stroke amplitude of 175° at a flapping frequency of 40 Hz. It generated a mass lifting capability of 5.1 g, which is largely sufficient to lift the prototype's mass of 3.39 g and larger than the mass-lifting capability of a Rufous hummingbird. The motor mass of a hummingbird-like robot which drives the stroke-cam mechanism is considerably larger (about five times) than the muscle mass of a hummingbird with comparable load-lifting capability. This paper presents a flapping wing nano aerial vehicle which is designed to possess the same lift- and thrust-generating principles of the Rufous hummingbird. The application is indoor flight. We give an overview of the wing kinematics and some specifications which should be met to develop an artificial wing, and also describe the applications of these in the mechanism which has been developed in this work. © 2016. Published by The Company of Biologists Ltd.

Outperforming hummingbirds’ load-lifting capability with a lightweight hummingbird-like flapping-wing mechanism

PubMed Central

Reynaerts, Dominiek; Vandepitte, Dirk

2016-01-01

ABSTRACT The stroke-cam flapping mechanism presented in this paper closely mimics the wing motion of a hovering Rufous hummingbird. It is the only lightweight hummingbird-sized flapping mechanism which generates a harmonic wing stroke with both a high flapping frequency and a large stroke amplitude. Experiments on a lightweight prototype of this stroke-cam mechanism on a 50 mm-long wing demonstrate that a harmonic stroke motion is generated with a peak-to-peak stroke amplitude of 175° at a flapping frequency of 40 Hz. It generated a mass lifting capability of 5.1 g, which is largely sufficient to lift the prototype's mass of 3.39 g and larger than the mass-lifting capability of a Rufous hummingbird. The motor mass of a hummingbird-like robot which drives the stroke-cam mechanism is considerably larger (about five times) than the muscle mass of a hummingbird with comparable load-lifting capability. This paper presents a flapping wing nano aerial vehicle which is designed to possess the same lift- and thrust-generating principles of the Rufous hummingbird. The application is indoor flight. We give an overview of the wing kinematics and some specifications which should be met to develop an artificial wing, and also describe the applications of these in the mechanism which has been developed in this work. PMID:27444790

Excitation of high frequency pressure driven modes in non-axisymmetric equilibrium at high βpol in PBX-M

NASA Astrophysics Data System (ADS)

Sesnic, S.; Holland, A.; Kaita, R.; Kaye, S. M.; Okabayashi, M.; Takahashi, H.; Asakura, N.; Bell, R. E.; Bernabei, S.; Chance, M. S.; Duperrex, P.-A.; Fonck, R. J.; Gammel, G. M.; Greene, G. J.; Hatcher, R. E.; Jardin, S. C.; Jiang, T.; Kessel, C. E.; Kugel, H. W.; Leblanc, B.; Levinton, F. M.; Manickam, J.; Ono, M.; Paul, S. F.; Powell, E. T.; Qin, Y.; Roberts, D. W.; Sauthoff, N. R.

1993-12-01

High frequency pressure driven modes have been observed in high poloidal beta discharges in the Princeton Beta Experiment Modification (PBX-M). These modes are excited in a non-axisymmetric equilibrium characterized by a large, low frequency mt = 1/nt = 1 island, and they are capable of expelling fast ions. The modes reside on or very close to the q = 1 surface and have mode numbers with either mh = nh or (less probably) mh/nh = mh/(mh-1), with mh varying between 3 and 10. Occasionally these modes are simultaneously localized in the vicinity of the ml = 2/nl = 1 island. The high frequency modes near the q = 1 surface also exhibit a ballooning character, being significantly stronger on the large major radius side of the plasma. When a large mt = 1/nt = 1 island is present, the mode is poloidally localized in the immediate vicinity of the X point of the island. The modes occur exclusively in high beta beam heated discharges and are likely to be driven by the beam ions. They can thus be a manifestation of either a toroidicity induced shear Alfven eigenmode (TAE) at q = (2mh+1)/2nh, a kinetic ballooning mode, or some other type of pressure driven (high β) mode. Most of the data are consistent with the theoretical predictions for the TAE gap mode. Since the high frequency modes in PBX-M, however, are found exclusively on or in the immediate neighbourhood of magnetic surfaces with low rational numbers (q = 1, 2,...), other possibilities are not excluded

A compact nanosecond pulse generator for DBD tube characterization.

PubMed

Rai, S K; Dhakar, A K; Pal, U N

2018-03-01

High voltage pulses of very short duration and fast rise time are required for generating uniform and diffuse plasma under various operating conditions. Dielectric Barrier Discharge (DBD) has been generated by high voltage pulses of short duration and fast rise time to produce diffuse plasma in the discharge gap. The high voltage pulse power generators have been chosen according to the requirement for the DBD applications. In this paper, a compact solid-state unipolar pulse generator has been constructed for characterization of DBD plasma. This pulsar is designed to provide repetitive pulses of 315 ns pulse width, pulse amplitude up to 5 kV, and frequency variation up to 10 kHz. The amplitude of the output pulse depends on the dc input voltage. The output frequency has been varied by changing the trigger pulse frequency. The pulsar is capable of generating pulses of positive or negative polarity by changing the polarity of pulse transformer's secondary. Uniform and stable homogeneous dielectric barrier discharge plasma has been produced successfully in a xenon DBD tube at 400-mbar pressure using the developed high voltage pulse generator.

A compact nanosecond pulse generator for DBD tube characterization

NASA Astrophysics Data System (ADS)

Rai, S. K.; Dhakar, A. K.; Pal, U. N.

2018-03-01

High voltage pulses of very short duration and fast rise time are required for generating uniform and diffuse plasma under various operating conditions. Dielectric Barrier Discharge (DBD) has been generated by high voltage pulses of short duration and fast rise time to produce diffuse plasma in the discharge gap. The high voltage pulse power generators have been chosen according to the requirement for the DBD applications. In this paper, a compact solid-state unipolar pulse generator has been constructed for characterization of DBD plasma. This pulsar is designed to provide repetitive pulses of 315 ns pulse width, pulse amplitude up to 5 kV, and frequency variation up to 10 kHz. The amplitude of the output pulse depends on the dc input voltage. The output frequency has been varied by changing the trigger pulse frequency. The pulsar is capable of generating pulses of positive or negative polarity by changing the polarity of pulse transformer's secondary. Uniform and stable homogeneous dielectric barrier discharge plasma has been produced successfully in a xenon DBD tube at 400-mbar pressure using the developed high voltage pulse generator.

Thermal-distortion analysis of an antenna strongback for geostationary high-frequency microwave applications

NASA Technical Reports Server (NTRS)

Farmer, Jeffrey T.; Wahls, Deborah M.; Wright, Robert L.

1990-01-01

The global change technology initiative calls for a geostationary platform for Earth science monitoring. One of the major science instruments is the high frequency microwave sounder (HFMS) which uses a large diameter, high resolution, high frequency microwave antenna. This antenna's size and required accuracy dictates the need for a segmented reflector. On-orbit disturbances may be a significant factor in its design. A study was performed to examine the effects of the geosynchronous thermal environment on the performance of the strongback structure for a proposed antenna concept for this application. The study included definition of the strongback and a corresponding numerical model to be used in the thermal and structural analyses definition of the thermal environment, determination of structural element temperature throughout potential orbits, estimation of resulting thermal distortions, and assessment of the structure's capability to meet surface accuracy requirements. Analyses show that shadows produced by the antenna reflector surface play a major role in increasing thermal distortions. Through customization of surface coating and element expansion characteristics, the segmented reflector concept can meet the tight surface accuracy requirements.

A multi-frequency impedance analysing instrument for eddy current testing

NASA Astrophysics Data System (ADS)

Yin, W.; Dickinson, S. J.; Peyton, A. J.

2006-02-01

This paper presents the design of a high-performance multi-frequency impedance analysing instrument (MFIA) for eddy current testing which has been developed primarily for monitoring a steel production process using an inductive sensor. The system consists of a flexible multi-frequency waveform generator and a voltage/current measurement unit. The impedance of the sensor is obtained by cross-spectral analysis of the current and voltage signals. The system contains high-speed digital-to-analogue, analogue-to-digital converters and dual DSPs with one for control and interface and one dedicated to frequency-spectra analysis using fast Fourier transformation (FFT). The frequency span of the signal that can be analysed ranges from 1 kHz to 8 MHz. The system also employs a high-speed serial port interface (USB) to communicate with a personal computer (PC) and to allow for fast transmission of data and control commands. Overall, the system is capable of delivering over 250 impedance spectra per second. Although the instrument has been developed mainly for use with an inductive sensor, the system is not restricted to inductive measurement. The flexibility of the design architecture is demonstrated with capacitive and resistive measurements by using appropriate input circuitry. Issues relating to optimizing the phase of the spectra components in the excitation waveform are also discussed.

Photonic generation of low phase noise arbitrary chirped microwave waveforms with large time-bandwidth product.

PubMed

Xie, Weilin; Xia, Zongyang; Zhou, Qian; Shi, Hongxiao; Dong, Yi; Hu, Weisheng

2015-07-13

We present a photonic approach for generating low phase noise, arbitrary chirped microwave waveforms based on heterodyne beating between high order correlated comb lines extracted from frequency-agile optical frequency comb. Using the dual heterodyne phase transfer scheme, extrinsic phase noises induced by the separate optical paths are efficiently suppressed by 42-dB at 1-Hz offset frequency. Linearly chirped microwave waveforms are achieved within 30-ms temporal duration, contributing to a large time-bandwidth product. The linearity measurement leads to less than 90 kHz RMS frequency error during the entire chirp duration, exhibiting excellent linearity for the microwave and sub-THz waveforms. The capability of generating arbitrary waveforms up to sub-THz band with flexible temporal duration, long repetition period, broad bandwidth, and large time-bandwidth product is investigated and discussed.

Rare-earth-doped materials with application to optical signal processing, quantum information science, and medical imaging technology

NASA Astrophysics Data System (ADS)

Cone, R. L.; Thiel, C. W.; Sun, Y.; Böttger, Thomas; Macfarlane, R. M.

2012-02-01

Unique spectroscopic properties of isolated rare earth ions in solids offer optical linewidths rivaling those of trapped single atoms and enable a variety of recent applications. We design rare-earth-doped crystals, ceramics, and fibers with persistent or transient "spectral hole" recording properties for applications including high-bandwidth optical signal processing where light and our solids replace the high-bandwidth portion of the electronics; quantum cryptography and information science including the goal of storage and recall of single photons; and medical imaging technology for the 700-900 nm therapeutic window. Ease of optically manipulating rare-earth ions in solids enables capturing complex spectral information in 105 to 108 frequency bins. Combining spatial holography and spectral hole burning provides a capability for processing high-bandwidth RF and optical signals with sub-MHz spectral resolution and bandwidths of tens to hundreds of GHz for applications including range-Doppler radar and high bandwidth RF spectral analysis. Simply stated, one can think of these crystals as holographic recording media capable of distinguishing up to 108 different colors. Ultra-narrow spectral holes also serve as a vibration-insensitive sub-kHz frequency reference for laser frequency stabilization to a part in 1013 over tens of milliseconds. The unusual properties and applications of spectral hole burning of rare earth ions in optical materials are reviewed. Experimental results on the promising Tm3+:LiNbO3 material system are presented and discussed for medical imaging applications. Finally, a new application of these materials as dynamic optical filters for laser noise suppression is discussed along with experimental demonstrations and theoretical modeling of the process.

SCINTILLATION ARCS IN LOW-FREQUENCY OBSERVATIONS OF THE TIMING-ARRAY MILLISECOND PULSAR PSR J0437–4715

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhat, N. D. R.; Ord, S. M.; Tremblay, S. E.

2016-02-10

Low-frequency observations of pulsars provide a powerful means for probing the microstructure in the turbulent interstellar medium (ISM). Here we report on high-resolution dynamic spectral analysis of our observations of the timing-array millisecond pulsar PSR J0437–4715 with the Murchison Widefield Array (MWA), enabled by our recently commissioned tied-array beam processing pipeline for voltage data recorded from the high time resolution mode of the MWA. A secondary spectral analysis reveals faint parabolic arcs akin to those seen in high-frequency observations of pulsars with the Green Bank and Arecibo telescopes. Data from Parkes observations at a higher frequency of 732 MHz revealmore » a similar parabolic feature with a curvature that scales approximately as the square of the observing wavelength (λ{sup 2}) to the MWA's frequency of 192 MHz. Our analysis suggests that scattering toward PSR J0437–4715 predominantly arises from a compact region about 115 pc from the Earth, which matches well with the expected location of the edge of the Local Bubble that envelopes the local Solar neighborhood. As well as demonstrating new and improved pulsar science capabilities of the MWA, our analysis underscores the potential of low-frequency pulsar observations for gaining valuable insights into the local ISM and for characterizing the ISM toward timing-array pulsars.« less

Silicon Carbide Emitter Turn-Off Thyristor

DOE PAGES

Wang, Jun; Wang, Gangyao; Li, Jun; ...

2008-01-01

A novel MOS-conmore » trolled SiC thyristor device, the SiC emitter turn-off thyristor (ETO) is a promising technology for future high-voltage switching applications because it integrates the excellent current conduction capability of a SiC thyristor with a simple MOS-control interface. Through unity-gain turn-off, the SiC ETO also achieves excellent Safe Operation Area (SOA) and faster switching speeds than silicon ETOs. The world's first 4.5-kV SiC ETO prototype shows a forward voltage drop of 4.26 V at 26.5  A / cm 2 current density at room and elevated temperatures. Tested in an inductive circuit with a 2.5 kV DC link voltage and a 9.56-A load current, the SiC ETO shows a fast turn-off time of 1.63 microseconds and a low 9.88 mJ turn-off energy. The low switching loss indicates that the SiC ETO could operate at about 4 kHz if 100  W / cm 2 conduction and the 100  W / cm 2 turn-off losses can be removed by the thermal management system. This frequency capability is about 4 times higher than 4.5-kV-class silicon power devices. The preliminary demonstration shows that the SiC ETO is a promising candidate for high-frequency, high-voltage power conversion applications, and additional developments to optimize the device for higher voltage (>5 kV) and higher frequency (10 kHz) are needed.« less

Nuclear quadrupole resonance studies project. [spectrometer design and spectrum analysis

NASA Technical Reports Server (NTRS)

Murty, A. N.

1978-01-01

The participation of undergraduates in nuclear quadrupole resonance research at Grambling University was made possible by NASA grants. Expanded laboratory capabilities include (1) facilities for high and low temperature generation and measurement; (2) facilities for radio frequency generation and measurement with the modern spectrum analyzers, precision frequency counters and standard signal generators; (3) vacuum and glass blowing facilities; and (4) miscellaneous electronic and machine shop facilities. Experiments carried out over a five year period are described and their results analyzed. Theoretical studies on solid state crystalline electrostatic fields, field gradients, and antishielding factors are included.

Waveguide Multimode Directional Coupler for Harvesting Harmonic Power from the Output of Traveling-Wave Tube Amplifiers

NASA Technical Reports Server (NTRS)

Simons, Rainee N.; Wintucky, Edwin G.

2017-01-01

The paper presents the design, fabrication, and test results for a novel waveguide multimode directional coupler (MDC). The coupler fabricated from dissimilar frequency band waveguides, is capable of isolating power at the 2nd harmonic frequency from the fundamental power at the output port of a high power traveling-wave tube amplifier. The major advantage of the MDC is significantly lower insertion loss compared to a diplexer. The presentation slides for the paper that was approved is attached. The tracking number for the paper that was approved is TN 37015.

High-Speed Printing Process Characterization using the Lissajous Trajectory Method

NASA Astrophysics Data System (ADS)

Lee, Sangwon; Kim, Daekeun

2018-04-01

We present a novel stereolithographic three-dimensional (3D) printing process that uses Lissajous trajectories. By using Lissajous trajectories, this 3D printing process allows two laser-scanning mirrors to operate at similar high-speed frequencies simultaneously, and the printing speed can be faster than that of raster scanning used in conventional stereolithography. In this paper, we first propose the basic theoretical background for this printing process based on Lissajous trajectories. We also characterize its printing conditions, such as printing size, laser spot size, and minimum printing resolution, with respect to the operating frequencies of the scanning mirrors and the capability of the laser modulation. Finally, we demonstrate simulation results for printing basic 2D shapes by using a noble printing process algorithm.

Far-Infrared Heterodyne Spectrometer for Sofia

NASA Technical Reports Server (NTRS)

Betz, A. L.

1998-01-01

The project goal was to evaluate the scientific capabilities and technical requirements for a far-infrared heterodyne spectrometer suitable for the SOFIA Airborne Observatory, which is now being developed by NASA under contract to the Universities Space Research Association (USRA). The conclusions detailed below include our specific recommendations for astronomical observations, as well as our intended technical approach for reaching these scientific goals. These conclusions were presented to USRA in the form of a proposal to build this instrument. USRA subsequently awarded the University of Colorado a 3-year grant to develop the proposed Hot-Electron micro-Bolometer (HEB) mixer concept for high frequencies above 3 THz, as well as other semiconductor mixer technologies suitable for high sensitivity receivers in the 2-6 THz frequency band.

Overview of laser systems for the Orion facility at the AWE.

PubMed

Hopps, Nicholas; Danson, Colin; Duffield, Stuart; Egan, David; Elsmere, Stephen; Girling, Mark; Harvey, Ewan; Hillier, David; Norman, Michael; Parker, Stefan; Treadwell, Paul; Winter, David; Bett, Thomas

2013-05-20

The commissioning of the Orion laser facility at the Atomic Weapons Establishment (AWE) in the UK has recently been completed. The facility is a twelve beam Nd:glass-based system for studying high energy density physics. It consists of ten frequency-tripled beam-lines operating with nanosecond pulses, synchronized with two beam-lines with subpicosecond pulses, each capable of delivering 500 J to target. One of the short pulse beams has the option of frequency doubling, at reduced aperture, to yield up to 100 J at 527 nm in a subpicosecond pulse with high temporal contrast. An extensive array of target diagnostics is provided. This article describes the laser design and commissioning and presents key performance data of the facility's laser systems.

Polarimetry of 600 pulsars from observations at 1.4 GHz with the Parkes radio telescope

NASA Astrophysics Data System (ADS)

Johnston, Simon; Kerr, Matthew

2018-03-01

Over the past 13 yr, the Parkes radio telescope has observed a large number of pulsars using digital filter bank backends with high time and frequency resolution and the capability for Stokes recording. Here, we use archival data to present polarimetry data at an observing frequency of 1.4 GHz for 600 pulsars with spin-periods ranging from 0.036 to 8.5 s. We comment briefly on some of the statistical implications from the data and highlight the differences between pulsars with high and low spin-down energy. The data set, images and table of properties for all 600 pulsars are made available in a public data archive maintained by the CSIRO.

Biomimetic Beetle-Inspired Flapping Air Vehicle Actuated by Ionic Polymer-Metal Composite Actuator.

PubMed

Zhao, Yang; Xu, Di; Sheng, Jiazheng; Meng, Qinglong; Wu, Dezhi; Wang, Lingyun; Xiao, Jingjing; Lv, Wenlong; Chen, Qinnan; Sun, Daoheng

2018-01-01

During the last decades, the ionic polymer-metal composite (IPMC) received much attention because of its potential capabilities, such as large displacement and flexible bending actuation. In this paper, a biomimetic flapping air vehicle was proposed by combining the superiority of ionic polymer metal composite with the bionic beetle flapping principle. The blocking force was compared between casted IPMC and IPMC. The flapping state of the wing was investigated and the maximum displacement and flapping angle were measured. The flapping displacement under different voltage and frequency was tested. The flapping displacement of the wing and the support reaction force were measured under different frequency by experiments. The experimental results indicate that the high voltage and low frequency would get large flapping displacement.

Electronic stethoscope with frequency shaping and infrasonic recording capabilities.

PubMed

Gordon, E S; Lagerwerff, J M

1976-03-01

A small electronic stethoscope with variable frequency response characteristics has been developed for aerospace and research applications. The system includes a specially designed piezoelectric pickup and amplifier with an overall frequency response from 0.7 to 5,000 HZ (-3 dB points) and selective bass and treble boost or cut of up to 15 dB. A steep slope, high pass filter can be switched in for ordinary clinical auscultation without overload distortion from strong infrasonic signal inputs. A commercial stethoscope-type headset, selected for best overall response, is used which can adequately handle up to 100 mW of audio power delivered from the amplifier. The active components of the amplifier consist of only four opamp-type integrated circuits.

A study of the high frequency limitations of series resonant converters

NASA Technical Reports Server (NTRS)

Stuart, T. A.; King, R. J.

1982-01-01

A transformer induced oscillation in series resonant (SR) converters is studied. It may occur in the discontinuous current mode. The source of the oscillation is an unexpected resonant circuit formed by normal resonance components in series with the magnetizing inductance of the output transformers. The methods for achieving cyclic stability are: to use a half bridge SR converter where q0.5. Q should be as close to 1.0 as possible. If 0.5q1.0, the instability will be avoided if psi2/3q-1/3. The second objective was to investigate a power field effect transistor (FET) version of the SR converter capable of operating at frequencies above 100 KHz, to study component stress and losses at various frequencies.

Seamless Modeling for Research & Predictability of Severe Tropical Storms from Weather-to-Climate Timescales

NASA Astrophysics Data System (ADS)

Ramaswamy, V.; Chen, J. H.; Delworth, T. L.; Knutson, T. R.; Lin, S. J.; Murakami, H.; Vecchi, G. A.

2017-12-01

Damages from catastrophic tropical storms such as the 2017 destructive hurricanes compel an acceleration of scientific advancements to understand the genesis, underlying mechanisms, frequency, track, intensity, and landfall of these storms. The advances are crucial to provide improved early information for planners and responders. We discuss the development and utilization of a global modeling capability based on a novel atmospheric dynamical core ("Finite-Volume Cubed Sphere or FV3") which captures the realism of the recent tropical storms and is a part of the NOAA Next-Generation Global Prediction System. This capability is also part of an emerging seamless modeling system at NOAA/ Geophysical Fluid Dynamics Laboratory for simulating the frequency of storms on seasonal and longer timescales with high fidelity e.g., Atlantic hurricane frequency over the past decades. In addition, the same modeling system has also been employed to evaluate the nature of projected storms on the multi-decadal scales under the influence of anthropogenic factors such as greenhouse gases and aerosols. The seamless modeling system thus facilitates research into and the predictability of severe tropical storms across diverse timescales of practical interest to several societal sectors.

Rapid Solidification of a New Generation Aluminum-Lithium Alloy via Electrospark Deposition

NASA Astrophysics Data System (ADS)

Heard, David W.; Boselli, Julien; Gauvin, Raynald; Brochu, Mathieu

Electrospark deposition (ESD) is a rapid solidification processing technique capable of depositing a metal onto a conductive substrate. The short pulse duration and high pulse frequency, combined with the small amount of material transferred during each pulse, results in high cooling rates being realized, on the order of 105-106 C/sec. This study investigates the ability to induce solute trapping behavior, for a new generation aluminum-lithium alloy, AA2199, using ESD.

Coil design considerations for a high-frequency electromagnetic induction sensing instrument

NASA Astrophysics Data System (ADS)

Sigman, John B.; Barrowes, Benjamin E.; Wang, Yinlin; Bennett, Hollis J.; Simms, Janet E.; Yule, Donald E.; O'Neill, Kevin; Shubitidze, Fridon

2016-05-01

Intermediate electrical conductivity (IEC) materials (101S/m < σ < 104S/m), such as carbon fiber (CF), have recently been used to make smart bombs. In addition, homemade improvised explosive devices (IED) can be produced with low conducting materials (10-4S/m < σ < 1S/m), such as Ammonium Nitrate (AN). To collect unexploded ordnance (UXO) from military training ranges and thwart deadly IEDs, the US military has urgent need for technology capable of detection and identification of subsurface IEC objects. Recent analytical and numerical studies have showed that these targets exhibit characteristic quadrature response peaks at high induction frequencies (100kHz - 15MHz, the High Frequency Electromagnetic Induction (HFEMI) band), and they are not detectable with traditional ultra wideband (UWB) electromagnetic induction (EMI) metal detectors operating between 100Hz - 100kHz. Using the HFEMI band for induction sensing is not so simple as driving existing instruments at higher frequencies, though. At low frequency, EMI systems use more wire turns in transmit and receive coils to boost signal-to-noise ratios (SNR), but at higher frequencies, the transmitter current has non-uniform distribution along the coil length. These non-uniform currents change the spatial distribution of the primary magnetic field and disturb axial symmetry and thwart established approaches for inferring subsurface metallic object properties. This paper discusses engineering tradeoffs for sensing with a broader band of frequencies ever used for EMI sensing, with particular focus on coil geometries.

Fully Integrated, Miniature, High-Frequency Flow Probe Utilizing MEMS Leadless SOI Technology

NASA Technical Reports Server (NTRS)

Ned, Alex; Kurtz, Anthony; Shang, Tonghuo; Goodman, Scott; Giemette. Gera (d)

2013-01-01

This work focused on developing, fabricating, and fully calibrating a flowangle probe for aeronautics research by utilizing the latest microelectromechanical systems (MEMS), leadless silicon on insulator (SOI) sensor technology. While the concept of angle probes is not new, traditional devices had been relatively large due to fabrication constraints; often too large to resolve flow structures necessary for modern aeropropulsion measurements such as inlet flow distortions and vortices, secondary flows, etc. Mea surements of this kind demanded a new approach to probe design to achieve sizes on the order of 0.1 in. (.3 mm) diameter or smaller, and capable of meeting demanding requirements for accuracy and ruggedness. This approach invoked the use of stateof- the-art processing techniques to install SOI sensor chips directly onto the probe body, thus eliminating redundancy in sensor packaging and probe installation that have historically forced larger probe size. This also facilitated a better thermal match between the chip and its mount, improving stability and accuracy. Further, the leadless sensor technology with which the SOI sensing element is fabricated allows direct mounting and electrical interconnecting of the sensor to the probe body. This leadless technology allowed a rugged wire-out approach that is performed at the sensor length scale, thus achieving substantial sensor size reductions. The technology is inherently capable of high-frequency and high-accuracy performance in high temperatures and harsh environments.

Three-dimensional laser microvision.

PubMed

Shimotahira, H; Iizuka, K; Chu, S C; Wah, C; Costen, F; Yoshikuni, Y

2001-04-10

A three-dimensional (3-D) optical imaging system offering high resolution in all three dimensions, requiring minimum manipulation and capable of real-time operation, is presented. The system derives its capabilities from use of the superstructure grating laser source in the implementation of a laser step frequency radar for depth information acquisition. A synthetic aperture radar technique was also used to further enhance its lateral resolution as well as extend the depth of focus. High-speed operation was made possible by a dual computer system consisting of a host and a remote microcomputer supported by a dual-channel Small Computer System Interface parallel data transfer system. The system is capable of operating near real time. The 3-D display of a tunneling diode, a microwave integrated circuit, and a see-through image taken by the system operating near real time are included. The depth resolution is 40 mum; lateral resolution with a synthetic aperture approach is a fraction of a micrometer and that without it is approximately 10 mum.

Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

NASA Astrophysics Data System (ADS)

Fu, H. Y.; Scales, W. A.; Bernhardt, P. A.; Briczinski, S. J.; Kosch, M. J.; Senior, A.; Rietveld, M. T.; Yeoman, T. K.; Ruohoniemi, J. M.

2015-08-01

Observations of secondary radiation, stimulated electromagnetic emission (SEE), produced during ionospheric modification experiments using ground-based, high-power, high-frequency (HF) radio waves are considered. The High Frequency Active Auroral Research Program (HAARP) facility is capable of generating narrowband SEE in the form of stimulated Brillouin scatter (SBS) and stimulated ion Bernstein scatter (SIBS) in the SEE spectrum. Such narrowband SEE spectral lines have not been reported using the European Incoherent Scatter (EISCAT) heater facility before. This work reports the first EISCAT results of narrowband SEE spectra and compares them to SEE previously observed at HAARP during electron gyro-harmonic heating. An analysis of experimental SEE data shows observations of emission lines within 100 Hz of the pump frequency, interpreted as SBS, during the 2012 July EISCAT campaign. Experimental results indicate that SBS strengthens as the pump frequency approaches the third electron gyro-harmonic. Also, for different heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics, whereas electron temperature enhancement weakens as measured by EISCAT/UHF radar. The main features of these new narrowband EISCAT observations are generally consistent with previous SBS measurements at HAARP.

Applications of Cavity-Enhanced Direct Frequency Comb Spectroscopy

NASA Astrophysics Data System (ADS)

Cossel, Kevin C.; Adler, Florian; Maslowski, Piotr; Ye, Jun

2010-06-01

Cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) is a unique technique that provides broad bandwidth, high resolution, and ultra-high detection sensitivities. This is accomplished by combining a femtosecond laser based optical frequency comb with an enhancement cavity and a broadband, multichannel imaging system. These systems are capable of simultaneously recording many terahertz of spectral bandwidth with sub-gigahertz resolution and absorption sensitivities of 1×10-7 cm-1 Hz-1/2. In addition, the ultrashort pulses enable efficient nonlinear processes, which makes it possible to reach spectral regions that are difficult to access with conventional laser sources. We will present an application of CE-DFCS for trace impurity detection in the semiconductor processing gas arsine near 1.8 μm and the development of a high-power, mid-infrared frequency comb for breath analysis in the 2.8-4.8 μm region. M. J. Thorpe, K. D. Moll, R. J. Jones, B. Safdi, and J. Ye. Science 311, 1595-1599 (2006) F. Adler, M. J. Thorpe, K. C. Cossel, and J. Ye. Annu. Rev. Anal. Chem. 3, 175-205 (2010) F. Adler, K. C. Cossel, M. J. Thorpe, I. Hartl, M. E. Fermann, and J. Ye. Opt. Lett. 34, 1330-1332 (2009)

Nonlinear model predictive control of a vortex-induced vibrations bladeless wind turbine

NASA Astrophysics Data System (ADS)

Azadi Yazdi, E.

2018-07-01

In this paper, a nonlinear model predictive controller (NMPC) is proposed for a vortex-induced vibrations bladeless wind turbine (BWT). The BWT consists of a long rigid cylinder mounted on a flexible beam. The nonlinear dynamic model of the transverse vibrations of the BWT is obtained under the fluctuating lift force due to periodically shedding vortices. The NMPC method is used to design a controller that achieves maximum energy production rate. It is observed that the power generation of the NMPC drops in high wind speeds due to a mismatch between the vortex shedding frequency and the structural natural frequency. Therefore, a secondary gain-scheduling (GS) controller is proposed to virtually increase the natural frequency of the structure to match the vortex shedding frequency for high winds. Although previous studies predicted the output power of the studied BWT to be less than 100 W, with the proposed GS-NMPC scheme the output power reaches the value of 1 kW. Therefore, the capability of the BWT as a renewable energy generation device was highly underestimated in the literature. The computed values of the aero-mechanical efficiency suggest the BWT as a major competitor to the conventional wind turbines.

Wedding ring shaped excitation coil

DOEpatents

MacLennan, Donald A.; Tsai, Peter

2001-01-01

A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and/or a flanged face to aid in thermal management. The lamp head is preferably an integrated lamp head comprising a metal matrix composite surrounding an insulating ceramic with the excitation integrally formed on the ceramic. A novel solid-state oscillator preferably provides RF power to the lamp. The oscillator is a single active element device capable of providing over 70 watts of power at over 70% efficiency.

Evaluation of components, subsystems, and networks for high rate, high frequency space communications

NASA Technical Reports Server (NTRS)

Kerczewski, Robert J.; Ivancic, William D.; Zuzek, John E.

1991-01-01

The development of new space communications technologies by NASA has included both commercial applications and space science requirements. At NASA's Lewis Research Center, methods and facilities have been developed for evaluating these new technologies in the laboratory. NASA's Systems Integration, Test and Evaluation (SITE) Space Communication System Simulator is a hardware-based laboratory simulator for evaluating space communications technologies at the component, subsystem, system, and network level, geared toward high frequency, high data rate systems. The SITE facility is well-suited for evaluation of the new technologies required for the Space Exploration Initiative (SEI) and advanced commercial systems. This paper describes the technology developments and evaluation requirements for current and planned commercial and space science programs. Also examined are the capabilities of SITE, the past, present, and planned future configurations of the SITE facility, and applications of SITE to evaluation of SEI technology.

High-Frequency, High-Temperature Fretting Experiments

NASA Technical Reports Server (NTRS)

Matlik, J. F.; Farris, T. N.; Haake, F. K.; Swanson, G. R.; Duke, G. C.

2005-01-01

Fretting is a structural damage mechanism observed when two nominally clamped surfaces are subjected to an oscillatory loading. A critical location for fretting induced damage has been identified at the blade/disk and blade/damper interfaces of gas turbine engine turbomachinery and space propulsion components. The high-temperature, high-frequency loading environment seen by these components lead to severe stress gradients at the edge-of-contact. These contact stresses drive crack nucleation and propagation in fretting and are very sensitive to the geometry of the contacting bodies, the contact loads, materials, temperature, and contact surface tribology (friction). To diagnose the threat that small and relatively undetectable fretting cracks pose to damage tolerance and structural integrity of in-service components, the objective of this work is to develop a well-characterized experimental fretting rig capable of investigating fretting behavior of advanced aerospace alloys subjected to load and temperature conditions representative of such turbomachinery components.

A High Frequency Response Relaxed Eddy Accumulation Flux Measurement System for Sampling Short-Lived Biogenic Volatile Organic Compounds

EPA Science Inventory

A second-generation relaxed eddy accumulation system was built and tested with the capability to measure vertical biogenic volatile organic compound (VOC) fluxes at levels as low as 10 µg C m⁻² hr⁻¹. The system features a continuous, integrated gas-phase ozo...

Design and testing of an annular array for very-high-frequency imaging

NASA Astrophysics Data System (ADS)

Ketterling, Jeffrey A.; Ramachandran, Sarayu; Lizzi, Frederic L.; Aristizábal, Orlando; Turnbull, Daniel H.

2004-05-01

Very-high-frequency ultrasound (VHFU) transducer technology is currently experiencing a great deal of interest. Traditionally, researchers have used single-element transducers which achieve exceptional lateral image resolution although at a very limited depth of field. A 5-ring focused annular array, a transducer geometry that permits an increased depth of field via electronic focusing, has been constructed. The transducer is fabricated with a PVDF membrane and a copper-clad Kapton film with an annular array pattern. The PVDF is bonded to the Kapton film and pressed into a spherically curved shape. The back side of the transducer is then filled with epoxy. One side of the PVDF is metallized with gold, forming the ground plane of the transducer. The array elements are accessed electrically via copper traces formed on the Kapton film. The annular array consists of 5 equal-area rings with an outer diameter of 1 cm and a radius of curvature of 9 mm. A wire reflector target was used to test the imaging capability of the transducer by acquiring B-scan data for each transmit/receive pair. A synthetic aperture approach was then used to reconstruct the image and demonstrate the enhanced depth of field capabilities of the transducer.

Atomic force microscopy capable of vibration isolation with low-stiffness Z-axis actuation.

PubMed

Ito, Shingo; Schitter, Georg

2018-03-01

For high-resolution imaging without bulky external vibration isolation, this paper presents an atomic force microscope (AFM) capable of vibration isolation with its internal Z-axis (vertical) actuators moving the AFM probe. Lorentz actuators (voice coil actuators) are used for the Z-axis actuation, and flexures guiding the motion are designed to have a low stiffness between the mover and the base. The low stiffness enables a large Z-axis actuation of more than 700 µm and mechanically isolates the probe from floor vibrations at high frequencies. To reject the residual vibrations, the probe tracks the sample by using a displacement sensor for feedback control. Unlike conventional AFMs, the Z-axis actuation attains a closed-loop control bandwidth that is 35 times higher than the first mechanical resonant frequency. The closed-loop AFM system has robustness against the flexures' nonlinearity and uses the first resonance for better sample tracking. For further improvement, feedforward control with a vibration sensor is combined, and the resulting system rejects 98.4% of vibrations by turning on the controllers. The AFM system is demonstrated by successful AFM imaging in a vibrational environment. Copyright © 2017 Elsevier B.V. All rights reserved.

Raytheon advanced pulse-tube cryocoolers

NASA Astrophysics Data System (ADS)

Conrad, Ted; Yates, Ryan; Kuo, Daniel; Schaefer, Brian; Arnoult, Matt

2016-05-01

Since the 1970s, Raytheon has developed, built, tested and integrated high performance cryocoolers. Our versatile designs for single and multi-stage cryocoolers provide reliable operation for temperatures from 10 to 200 Kelvin with power levels ranging from 50 W to nearly 600 W. These cryocoolers incorporate clearance seals, flexure suspensions, hermetic housings and dynamic balancing to provide long service life and reliable operation in all relevant environments. Recently, Raytheon has developed an advanced regenerator technology capable of operating efficiently at high frequencies and outperforming traditional screen regenerators. The Raytheon Advanced Miniature (RAM-100) cryocooler, a flight packaged, high frequency, single stage pulse tube cooler with an integrated surge volume and inertance tube, has been designed for use with this regenerator. Design details and experimentally measured performance of two iterations of the RAM cryocooler are presented in this paper.

Time-Spectral Rotorcraft Simulations on Overset Grids

NASA Technical Reports Server (NTRS)

Leffell, Joshua I.; Murman, Scott M.; Pulliam, Thomas H.

2014-01-01

The Time-Spectral method is derived as a Fourier collocation scheme and applied to NASA's overset Reynolds-averaged Navier-Stokes (RANS) solver OVERFLOW. The paper outlines the Time-Spectral OVERFLOWimplementation. Successful low-speed laminar plunging NACA 0012 airfoil simulations demonstrate the capability of the Time-Spectral method to resolve the highly-vortical wakes typical of more expensive three-dimensional rotorcraft configurations. Dealiasing, in the form of spectral vanishing viscosity (SVV), facilitates the convergence of Time-Spectral calculations of high-frequency flows. Finally, simulations of the isolated V-22 Osprey tiltrotor for both hover and forward (edgewise) flight validate the three-dimensional Time-Spectral OVERFLOW implementation. The Time-Spectral hover simulation matches the time-accurate calculation using a single harmonic. Significantly more temporal modes and SVV are required to accurately compute the forward flight case because of its more active, high-frequency wake.

Galaxies and cosmology with ALMA

NASA Astrophysics Data System (ADS)

Planesas, P.

2011-12-01

Intensive work is being carried out at the Joint ALMA Observatory in order to bring four bands of a 16-antenna mm/submm interferometer into scientific operation. Specific tests of the advertised capabilities for Early Science are being carried out as well as further tests in order to bring ALMA into full operation as planned. Some of the measurements were taken towards extragalactic objects. In fact, the high sensitivity, high angular resolution, high image fidelity, and high mapping speed, together with a large frequency coverage, will make ALMA the right instrument for high redshift studies, and detailed dynamical and chemical studies of nearby galaxies.

Development of an Atmospheric Pressure Ionization Mass Spectrometer

NASA Technical Reports Server (NTRS)

1998-01-01

A commercial atmospheric pressure ionization mass spectrometer (APIMS) was purchased from EXTREL Mass Spectrometry, Inc. (Pittsburgh, PA). Our research objectives were to adapt this instrument and develop techniques for real-time determinations of the concentrations of trace species in the atmosphere. The prototype instrument is capable of making high frequency measurements with no sample preconcentrations. Isotopically labeled standards are used as an internal standard to obtain high precision and to compensate for changes in instrument sensitivity and analyte losses in the sampling manifold as described by Bandy and coworkers. The prototype instrument is capable of being deployed on NASA C130, Electra, P3, and DC8 aircraft. After purchasing and taking delivery by June 1994, we assembled the mass spectrometer, data acquisition, and manifold flow control instrumentation in electronic racks and performed tests.

Microstrip Antenna for Remote Sensing of Soil Moisture and Sea Surface Salinity

NASA Technical Reports Server (NTRS)

Ramhat-Samii, Yahya; Kona, Keerti; Manteghi, Majid; Dinardo, Steven; Hunter, Don; Njoku, Eni; Wilson, Wiliam; Yueh, Simon

2009-01-01

This compact, lightweight, dual-frequency antenna feed developed for future soil moisture and sea surface salinity (SSS) missions can benefit future soil and ocean studies by lowering mass, volume, and cost of the antenna system. It also allows for airborne soil moisture and salinity remote sensors operating on small aircraft. While microstrip antenna technology has been developed for radio communications, it has yet to be applied to combined radar and radiometer for Earth remote sensing. The antenna feed provides a key instrument element enabling high-resolution radiometric observations with large, deployable antennas. The design is based on the microstrip stacked-patch array (MSPA) used to feed a large, lightweight, deployable, rotating mesh antenna for spaceborne L-band (approximately equal to 1 GHz) passive and active sensing systems. The array consists of stacked patches to provide dual-frequency capability and suitable radiation patterns. The stacked-patch microstrip element was designed to cover the required L-band center frequencies at 1.26 GHz (lower patch) and 1.413 GHz (upper patch), with dual-linear polarization capabilities. The dimension of patches produces the required frequencies. To achieve excellent polarization isolation and control of antenna sidelobes for the MSPA, the orientation of each stacked-patch element within the array is optimized to reduce the cross-polarization. A specialized feed-distribution network was designed to achieve the required excitation amplitude and phase for each stacked-patch element.

Effects of vocal training on singing and speaking voice characteristics in vocally healthy adults and children based on choral and nonchoral data.

PubMed

Siupsinskiene, Nora; Lycke, Hugo

2011-07-01

This prospective cross-sectional study examines the effects of voice training on vocal capabilities in vocally healthy age and gender differentiated groups measured by voice range profile (VRP) and speech range profile (SRP). Frequency and intensity measurements of the VRP and SRP using standard singing and speaking voice protocols were derived from 161 trained choir singers (21 males, 59 females, and 81 prepubescent children) and from 188 nonsingers (38 males, 89 females, and 61 children). When compared with nonsingers, both genders of trained adult and child singers exhibited increased mean pitch range, highest frequency, and VRP area in high frequencies (P<0.05). Female singers and child singers also showed significantly increased mean maximum voice intensity, intensity range, and total VRP area. The logistic regression analysis showed that VRP pitch range, highest frequency, maximum voice intensity, and maximum-minimum intensity range, and SRP slope of speaking curve were the key predictors of voice training. Age, gender, and voice training differentiated norms of VRP and SRP parameters are presented. Significant positive effect of voice training on vocal capabilities, mostly singing voice, was confirmed. The presented norms for trained singers, with key parameters differentiated by gender and age, are suggested for clinical practice of otolaryngologists and speech-language pathologists. Copyright © 2011 The Voice Foundation. Published by Mosby, Inc. All rights reserved.

An Exploration of Software-Based GNSS Signal Processing at Multiple Frequencies

NASA Astrophysics Data System (ADS)

Pasqual Paul, Manuel; Elosegui, Pedro; Lind, Frank; Vazquez, Antonio; Pankratius, Victor

2017-01-01

The Global Navigation Satellite System (GNSS; i.e., GPS, GLONASS, Galileo, and other constellations) has recently grown into numerous areas that go far beyond the traditional scope in navigation. In the geosciences, for example, high-precision GPS has become a powerful tool for a myriad of geophysical applications such as in geodynamics, seismology, paleoclimate, cryosphere, and remote sensing of the atmosphere. Positioning with millimeter-level accuracy can be achieved through carrier-phase-based, multi-frequency signal processing, which mitigates various biases and error sources such as those arising from ionospheric effects. Today, however, most receivers with multi-frequency capabilities are highly specialized hardware receiving systems with proprietary and closed designs, limited interfaces, and significant acquisition costs. This work explores alternatives that are entirely software-based, using Software-Defined Radio (SDR) receivers as a way to digitize the entire spectrum of interest. It presents an overview of existing open-source frameworks and outlines the next steps towards converting GPS software receivers from single-frequency to dual-frequency, geodetic-quality systems. In the future, this development will lead to a more flexible multi-constellation GNSS processing architecture that can be easily reused in different contexts, as well as to further miniaturization of receivers.

Cryogenic probe station for on-wafer characterization of electrical devices

NASA Astrophysics Data System (ADS)

Russell, Damon; Cleary, Kieran; Reeves, Rodrigo

2012-04-01

A probe station, suitable for the electrical characterization of integrated circuits at cryogenic temperatures is presented. The unique design incorporates all moving components inside the cryostat at room temperature, greatly simplifying the design and allowing automated step and repeat testing. The system can characterize wafers up to 100 mm in diameter, at temperatures <20 K. It is capable of highly repeatable measurements at millimeter-wave frequencies, even though it utilizes a Gifford McMahon cryocooler which typically imposes limits due to vibration. Its capabilities are illustrated by noise temperature and S-parameter measurements on low noise amplifiers for radio astronomy, operating at 75-116 GHz.

Technical overview of the millimeter-wave imaging reflectometer on the DIII-D tokamak (invited)

DOE PAGES

Muscatello, Christopher M.; Domier, Calvin W.; Hu, Xing; ...

2014-07-22

The two-dimensional mm-wave imaging reflectometer (MIR) on DIII-D is a multi-faceted device for diagnosing electron density fluctuations in fusion plasmas. Its multi-channel, multi-frequency capabilities and high sensitivity permit visualization and quantitative diagnosis of density perturbations, including correlation length, wavenumber, mode propagation velocity, and dispersion. The two-dimensional capabilities of MIR are made possible with twelve vertically separated sightlines and four-frequency operation (corresponding to four radial channels). The 48-channel DIII-D MIR system has a tunable source that can be stepped in 500 µs increments over a range of 56 to 74 GHz. An innovative optical design keeps both on-axis and off-axis channelsmore » focused at the cutoff surface, permitting imaging over an extended poloidal region. As a result, the integrity of the MIR optical design is confirmed by comparing Gaussian beam calculations to laboratory measurements of the transmitter beam pattern and receiver antenna patterns.« less

Microwave and Millimeter Wave Imaging of the Space Shuttle External Fuel Tank Spray on Foam Insulation (SOFI) using Synthetic Aperture Focusing Techniques (SAFT}

NASA Technical Reports Server (NTRS)

Case, J. T.; Robbins, J.; Kharkivskiy, S.; Hepburn, F.; Zoughi, R.

2005-01-01

The Space Shuttle Columbia s catastrophic failure is thought to have been caused by a dislodged piece of external tank spray on foam insulation (SOFI) striking the left wing of the orbiter causing significant damage to some of the reinforced carbodcarbon leading edge wing panels. Microwave and millimeter wave nondestructive evaluation methods have shown great potential for inspecting SOFI for the purpose of detecting anomalies such as small air voids that may cause separation of the SOFI from the external tank during a launch. These methods are capable of producing relatively high-resolution images of the interior of SOFI particularly when advanced imaging algorithms are incorporated into the overall system. To this end, synthetic aperture focusing techniques (SAFT) are being developed. This paper presents some of the preliminary results of this investigation using SAFT-based methods and microwave holography at relatively low frequencies illustrating their potential capabilities for operation at millimeter wave frequencies.

Diamond Heat-Spreader for Submillimeter-Wave Frequency Multipliers

NASA Technical Reports Server (NTRS)

Lin, Robert H.; Schlecht, Erich T.; Chattopadhyay, Goutam; Gill, John J.; Mehdi, Imran; Siegel, Peter H.; Ward, John S.; Lee, Choonsup; Thomas, Bertrand C.; Maestrini, Alain

2010-01-01

The planar GaAs Shottky diode frequency multiplier is a critical technology for the local oscillator (LO) for submillimeter- wave heterodyne receivers due to low mass, tenability, long lifetime, and room-temperature operation. The use of a W-band (75-100 GHz) power amplifier followed by a frequency multiplier is the most common for submillimeter-wave sources. Its greatest challenge is to provide enough input power to the LO for instruments onboard future planetary missions. Recently, JPL produced 800 mW at 92.5 GHz by combining four MMICs in parallel in a balanced configuration. As more power at W-band is available to the multipliers, their power-handling capability be comes more important. High operating temperatures can lead to degradation of conversion efficiency or catastrophic failure. The goal of this innovation is to reduce the thermal resistance by attaching diamond film as a heat-spreader on the backside of multipliers to improve their power-handling capability. Polycrystalline diamond is deposited by hot-filament chemical vapor deposition (CVD). This diamond film acts as a heat-spreader to both the existing 250- and 300-GHz triplers, and has a high thermal conductivity (1,000-1,200 W/mK). It is approximately 2.5 times greater than copper (401 W/mK) and 20 times greater than GaAs (46 W/mK). It is an electrical insulator (resistivity approx. equals 10(exp 15) Ohms-cm), and has a low relative dielectric constant of 5.7. Diamond heat-spreaders reduce by at least 200 C at 250 mW of input power, compared to the tripler without diamond, according to thermal simulation. This superior thermal management provides a 100-percent increase in power-handling capability. For example, with this innovation, 40-mW output power has been achieved from a 250-GHz tripler at 350-mW input power, while the previous triplers, without diamond, suffered catastrophic failures. This breakthrough provides a stepping-stone for frequency multipliers-based LO up to 3 THz. The future work for this design is to apply the high output power from both the 250 and 300 GHz to multiple chains in order to generate milliwatts at 2.3 THz. Using the first generation of results for this innovation, 40 mW of output power were produced from a 240-GHz tripler at 350-mW input power, and 27- mW output power was produced from a 300-GHz tripler at 408-mW input power. This is two times higher than the current state-of-the-art output power capability. A finite-element thermal simulation also shows that 30-microns thick diamond dropped the temperature of the anodes by at least 200 C.

High-speed polarization sensitive optical frequency domain imaging with frequency multiplexing

PubMed Central

Yun, S.H.; Vakoc, B.J.; Shishkov, M.; Desjardins, A.E.; Park, B.H.; de Boer, J.F.; Tearney, G.J.; Bouma, B.E.

2009-01-01

Polarization sensitive optical coherence tomography (PS-OCT) provides a cross-sectional image of birefringence in biological samples that is complementary in many applications to the standard reflectance-based image. Recent ex vivo studies have demonstrated that birefringence mapping enables the characterization of collagen and smooth muscle concentration and distribution in vascular tissues. Instruments capable of applying these measurements percutaneously in vivo may provide new insights into coronary atherosclerosis and acute myocardial infarction. We have developed a polarization sensitive optical frequency domain imaging (PS-OFDI) system that enables high-speed intravascular birefringence imaging through a fiber-optic catheter. The novel design of this system utilizes frequency multiplexing to simultaneously measure reflectance of two incident polarization states, overcoming concerns regarding temporal variations of the catheter fiber birefringence and spatial variations in the birefringence of the sample. We demonstrate circular cross-sectional birefringence imaging of a human coronary artery ex vivo through a flexible fiber-optic catheter with an A-line rate of 62 kHz and a ranging depth of 6.2 mm. PMID:18542183

Frequency accurate coherent electro-optic dual-comb spectroscopy in real-time.

PubMed

Martín-Mateos, Pedro; Jerez, Borja; Largo-Izquierdo, Pedro; Acedo, Pablo

2018-04-16

Electro-optic dual-comb spectrometers have proved to be a promising technology for sensitive, high-resolution and rapid spectral measurements. Electro-optic combs possess very attractive features like simplicity, reliability, bright optical teeth, and typically moderate but quickly tunable optical spans. Furthermore, in a dual-comb arrangement, narrowband electro-optic combs are generated with a level of mutual coherence that is sufficiently high to enable optical multiheterodyning without inter-comb stabilization or signal processing systems. However, this valuable tool still presents several limitations; for instance, on most systems, absolute frequency accuracy and long-term stability cannot be guaranteed; likewise, interferometer-induced phase noise restricts coherence time and limits the attainable signal-to-noise ratio. In this paper, we address these drawbacks and demonstrate a cost-efficient absolute electro-optic dual-comb instrument based on a frequency stabilization mechanism and a novel adaptive interferogram acquisition approach devised for electro-optic dual-combs capable of operating in real-time. The spectrometer, completely built from commercial components, provides sub-ppm frequency uncertainties and enables a signal-to-noise ratio of 10000 (intensity noise) in 30 seconds of integration time.

Real time recognition of explosophorous group and explosive material using laser induced photoacoustic spectroscopy associated with novel algorithm for time and frequency domain analysis.

PubMed

El-Sharkawy, Yasser H; Elbasuney, Sherif

2018-06-07

Energy-rich bonds such as nitrates (NO 3 - ) and percholorates (ClO 4 - ) have an explosive nature; they are frequently encountered in high energy materials. These bonds encompass two highly electronegative atoms competing for electrons. Common explosive materials including urea nitrate, ammonium nitrate, and ammonium percholorates were subjected to photoacoustic spectroscopy. The captured signal was processed using novel digital algorithm designed for time and frequency domain analysis. Frequency domain analysis offered not only characteristic frequencies for NO 3 - and ClO 4 - groups; but also characteristic fingerprint spectra (based on thermal, acoustical, and optical properties) for different materials. The main outcome of this study is that phase-shift domain analysis offered an outstanding signature for each explosive material, with novel discrimination between explosive and similar non-explosive material. Photoacoustic spectroscopy offered different characteristic signatures that can be employed for real time detection with stand-off capabilities. There is no two materials could have the same optical, thermal, and acoustical properties. Copyright © 2018 Elsevier B.V. All rights reserved.

Submillimeter sources for radiometry using high power Indium Phosphide Gunn diode oscillators

NASA Technical Reports Server (NTRS)

Deo, Naresh C.

1990-01-01

A study aimed at developing high frequency millimeter wave and submillimeter wave local oscillator sources in the 60-600 GHz range was conducted. Sources involved both fundamental and harmonic-extraction type Indium Phosphide Gunn diode oscillators as well as varactor multipliers. In particular, a high power balanced-doubler using varactor diodes was developed for 166 GHz. It is capable of handling 100 mW input power, and typically produced 25 mW output power. A high frequency tripler operating at 500 GHz output frequency was also developed and cascaded with the balanced-doubler. A dual-diode InP Gunn diode combiner was used to pump this cascaded multiplier to produce on the order of 0.5 mW at 500 GHz. In addition, considerable development and characterization work on InP Gunn diode oscillators was carried out. Design data and operating characteristics were documented for a very wide range of oscillators. The reliability of InP devices was examined, and packaging techniques to enhance the performance were analyzed. A theoretical study of a new class of high power multipliers was conducted for future applications. The sources developed here find many commercial applications for radio astronomy and remote sensing.

GaN-on-Silicon - Present capabilities and future directions

NASA Astrophysics Data System (ADS)

Boles, Timothy

2018-02-01

Gallium Nitride, in the form of epitaxial HEMT transistors on various substrate materials, is the newest and most promising semiconductor technology for high performance devices in the RF, microwave, and mmW arenas. This is particularly true for GaN-on-Silicon based devices and MMIC's which enable both state-of-the-art high frequency functionality and the ability to scale production into large wafer diameter CMOS foundries. The design and development of GaN-on-Silicon structures and devices will be presented beginning with the basic material parameters, growth of the required epitaxial construction, and leading to the fundamental operational theory of high frequency, high power HEMTs. In this discussion comparisons will be made with alternative substrate materials with emphasis on contrasting the inherent advantages of a silicon based system. Theory of operation of microwave and mmW high power HEMT devices will be presented with special emphasis on fundamental limitations of device performance including inherent frequency limiting transit time analysis, required impedance transformations, internal and external parasitic reactance, thermal impedance optimization, and challenges improved by full integration into monolithic MMICs. Lastly, future directions for implementing GaN-on-Silicon into mainstream CMOS silicon semiconductor technologies will be discussed.

Demonstration of Space Optical Transmitter Development for Multiple High Frequency Bands

NASA Technical Reports Server (NTRS)

Nguyen, Hung; Simons, Rainee; Wintucky, Edwin; Freeman, Jon

2013-01-01

As the demand for multiple radio frequency carrier bands continues to grow in space communication systems, the design of a cost-effective compact optical transmitter that is capable of transmitting selective multiple RF bands is of great interest, particularly for NASA Space Communications Network Programs. This paper presents experimental results that demonstrate the feasibility of a concept based on an optical wavelength division multiplexing (WDM) technique that enables multiple microwave bands with different modulation formats and bandwidths to be combined and transmitted all in one unit, resulting in many benefits to space communication systems including reduced size, weight and complexity with corresponding savings in cost. Experimental results will be presented including the individual received RF signal power spectra for the L, C, X, Ku, Ka, and Q frequency bands, and measurements of the phase noise associated with each RF frequency. Also to be presented is a swept RF frequency power spectrum showing simultaneous multiple RF frequency bands transmission. The RF frequency bands in this experiment are among those most commonly used in NASA space environment communications.

Nonlinear channelizer.

PubMed

In, Visarath; Longhini, Patrick; Kho, Andy; Neff, Joseph D; Leung, Daniel; Liu, Norman; Meadows, Brian K; Gordon, Frank; Bulsara, Adi R; Palacios, Antonio

2012-12-01

The nonlinear channelizer is an integrated circuit made up of large parallel arrays of analog nonlinear oscillators, which, collectively, serve as a broad-spectrum analyzer with the ability to receive complex signals containing multiple frequencies and instantaneously lock-on or respond to a received signal in a few oscillation cycles. The concept is based on the generation of internal oscillations in coupled nonlinear systems that do not normally oscillate in the absence of coupling. In particular, the system consists of unidirectionally coupled bistable nonlinear elements, where the frequency and other dynamical characteristics of the emergent oscillations depend on the system's internal parameters and the received signal. These properties and characteristics are being employed to develop a system capable of locking onto any arbitrary input radio frequency signal. The system is efficient by eliminating the need for high-speed, high-accuracy analog-to-digital converters, and compact by making use of nonlinear coupled systems to act as a channelizer (frequency binning and channeling), a low noise amplifier, and a frequency down-converter in a single step which, in turn, will reduce the size, weight, power, and cost of the entire communication system. This paper covers the theory, numerical simulations, and some engineering details that validate the concept at the frequency band of 1-4 GHz.

Electronic Warfare in Operations

DTIC Science & Technology

2009-02-25

intelligence-related portion of the EW running estimate. Provides input to the restricted frequency list by recommending guarded frequencies. Provides...preparation of the restricted frequency list and issuance of emissions control guidance. Coordinates frequency allotment, assignment, and use... frequency list . Validating and approving or denying cease-jamming requests. Maintaining situational awareness of all jamming-capable systems in the area

Flexible and wearable 3D graphene sensor with 141 KHz frequency signal response capability

NASA Astrophysics Data System (ADS)

Xu, R.; Zhang, H.; Cai, Y.; Ruan, J.; Qu, K.; Liu, E.; Ni, X.; Lu, M.; Dong, X.

2017-09-01

We developed a flexible force sensor consisting of 3D graphene foam (GF) encapsulated in flexible polydimethylsiloxane (PDMS). Because the 3D GF/PDMS sensor is based on the transformation of an electronic band structure aroused by static mechanical strain or KHz vibration, it can detect frequency signals by both tuning fork tests and piezoelectric ceramic transducer tests, which showed a clear linear response from audio frequencies, including frequencies up to 141 KHz in the ultrasound range. Because of their excellent response with a wide bandwidth, the 3D GF/PDMS sensors are attractive for interactive wearable devices or artificial prosthetics capable of perceiving seismic waves, ultrasonic waves, shock waves, and transient pressures.

Numerical investigation of the inertial cavitation threshold by dual-frequency excitation in the fluid and tissue.

PubMed

Wang, Mingjun; Zhou, Yufeng

2018-04-01

Inertial cavitation thresholds, which are defined as bubble growth by 2-fold from the equilibrium radius, by two types of ultrasonic excitation (at the classical single-frequency mode and dual-frequency mode) were calculated. The effect of the dual-frequency excitation on the inertial cavitation threshold in the different surrounding media (fluid and tissue) was studied, and the paramount parameters (driving frequency, amplitude ratio, phase difference, and frequency ratio) were also optimized to maximize the inertial cavitation. The numerical prediction confirms the previous experimental results that the dual-frequency excitation is capable of reducing the inertial cavitation threshold in comparison to the single-frequency one at the same output power. The dual-frequency excitation at the high frequency (i.e., 3.1 + 3.5 MHz vs. 1.1 + 1.3 MHz) is preferred in this study. The simulation results suggest that the same amplitudes of individual components, zero phase difference, and large frequency difference are beneficial for enhancing the bubble cavitation. Overall, this work may provide a theoretical model for further investigation of dual-frequency excitation and guidance of its applications for a better outcome. Copyright © 2017 Elsevier B.V. All rights reserved.

Exploring the Birth and Evolution of the Universe: How Detectors Have Revolutionized Space Astronomy

NASA Technical Reports Server (NTRS)

Moseley, Samuel H.

2012-01-01

The past century has seen tremendous advances in the capability of instruments used for astronomical imaging and spectroscopy. Capabilities of instruments have expanded in many dimensions; the scale of telescopes has grown tremendously, the wavelengths used for astronomy have grown from visible light to the full electromagnetic spectrum, extending from gamma rays to low frequency radio waves. Additional advances have been enabled by the availability of space facilities, which eliminate the effects of the earths atmosphere and magnetosphere, and allow cooling of instruments to avoid instrumental thermal radiation. Even with all these advances, the increase in capability of detection systems has produced truly revolutionary improvements in capability. Today, I will describe the advances in astronomical detection from the photographic plates of the early 20th century to the giant high efficiency focal planes being developed for modern space and ground based astronomical instrument. I will review the demanding performance requirements set by space astronomy, and show how the detector community has risen to the challenge in producing high performance detectors for the Hubble Space Telescope, the Spitzer Space Telescope, and the James Webb Space Telescope, now under development.

Plasma wave observations during ion gun experiments

NASA Astrophysics Data System (ADS)

Olsen, R. C.; Weddle, L. E.; Roeder, J. L.

1990-06-01

Experiments in charge control on the AF/NASA P78-2 (SCATHA) satellite were conducted with a plasma/ion source in the inner magnetosphere. These experiments were monitored with plasma wave instruments capable of high temporal and frequency resolution in the 0-6 kHz frequency range. Ion gun experiments revealed two distinct classes of behavior. Nonneutralized ion beam operation at 1 mA, 1kV resulted in arcing signatures (spiky in time, broad frequency range), coincident with induced satellite potentials of -600 to -900 V. This signature disappeared when the accelerating voltage was switched off or the beam was neutralized. The signal is attributed to arcing between differentially charged surfaces. An additional feature was noted in the 100-kHz channel of the wave receiver. During emission of dense, low-energy plasma, a signal is generated which may be at the upper hybrid, or plasma frequency for the local plasma.

High stability lasers for lidar and remote sensing

NASA Astrophysics Data System (ADS)

Heine, Frank; Lange, Robert; Seel, Stefan; Smutny, Berry

2017-11-01

Tesat-Spacecom is currently building a set flight models of frequency stabilized lasers for the ESA Missions AEOLUS and LTP. Lasers with low intensity noise in the kHz region and analogue tuning capabilities for frequency and output power are developed for the on board metrology of the LTP project, the precursor mission for LISA. This type of laser is internally stabilized by precise temperature control, approaching an ALLAN variance of 10-9 for 100 sec. It can be easily locked to external frequency references with <50kHz bandwidth. The Seed laser for the AEOLUS mission (wind LIDAR) is used as the master frequency reference and is stabilized internally by a optical cavity. It shows a 3* 10-11 Allan variance from time intervals 1 sec - 1000 sec. Furthermore it is step-tunable for calibration of the receiver instrument with a speed of GHz / sec by a digital command interface. Performance and environmental test results will be presented.

Final Technical Report for ELF/VLF Electromagnetic Detection and Characterization of Deeply Buried Targets

DTIC Science & Technology

1998-06-22

remote (e.g. HAARP /HIPAS), and natural sources (e.g. external noise); b) model the perturbed fields due to the specified underground structures...examined in this study are of three types • Remote man-made sources, e.g. HAARP /HIPAS • Local sources, e.g. metal-detector loop • Natural sources, e.g...The High Power Auroral Stimulation Observatory (HIPAS) and the High Frequency Active Auroral Research Program ( HAARP ) are capable of exciting plasma

Combinatorial FSK modulation for power-efficient high-rate communications

NASA Technical Reports Server (NTRS)

Wagner, Paul K.; Budinger, James M.; Vanderaar, Mark J.

1991-01-01

Deep-space and satellite communications systems must be capable of conveying high-rate data accurately with low transmitter power, often through dispersive channels. A class of noncoherent Combinatorial Frequency Shift Keying (CFSK) modulation schemes is investigated which address these needs. The bit error rate performance of this class of modulation formats is analyzed and compared to the more traditional modulation types. Candidate modulator, demodulator, and digital signal processing (DSP) hardware structures are examined in detail. System-level issues are also discussed.

Computational and Mathematical Modeling of Coupled Superconducting Quantum Interference Devices

NASA Astrophysics Data System (ADS)

Berggren, Susan Anne Elizabeth

This research focuses on conducting an extensive computational investigation and mathematical analysis into the average voltage response of arrays of Superconducting Quantum Interference Devices (SQUIDs). These arrays will serve as the basis for the development of a sensitive, low noise, significantly lower Size, Weight and Power (SWaP) antenna integrated with Low-Noise Amplifier (LNA) using the SQUID technology. The goal for this antenna is to be capable of meeting all requirements for Guided Missile Destroyers (DDG) 1000 class ships for Information Operations/Signals Intelligence (IO/SIGINT) applications in Very High Frequency/Ultra High Frequency (V/UHF) bands. The device will increase the listening capability of receivers by moving technology into a new regime of energy detection allowing wider band, smaller size, more sensitive, stealthier systems. The smaller size and greater sensitivity will allow for ships to be “de-cluttered” of their current large dishes and devices, replacing everything with fewer and smaller SQUID antenna devices. The fewer devices present on the deck of a ship, the more invisible the ship will be to enemy forces. We invent new arrays of SQUIDs, optimized for signal detection with very high dynamic range and excellent spur-free dynamic range, while maintaining extreme small size (and low radar cross section), wide bandwidth, and environmentally noise limited sensitivity, effectively shifting the bottle neck of receiver systems forever away from the antenna itself deeper into the receiver chain. To accomplish these goals we develop and validate mathematical models for different designs of SQUID arrays and use them to invent a new device and systems design. This design is capable of significantly exceeding, per size weight and power, state-of-the-art receiver system measures of performance, such as bandwidth, sensitivity, dynamic range, and spurious-free dynamic range.

High-Frequency Observation of Water Spectrum and Its Application in Monitoring of Dynamic Variation of Suspended Materials in the Hangzhou Bay.

PubMed

Dai, Qian; Pan, De-lu; He, Xian-qiang; Zhu, Qian-kun; Gong, Fang; Huang, Hai-qing

2015-11-01

In situ measurement of water spectrum is the basis of the validation of the ocean color remote sensing. The traditional method to obtain the water spectrum is based on the shipboard measurement at limited stations, which is difficult to meet the requirement of validation of ocean color remote sensing in the highly dynamic coastal waters. To overcome this shortage, continuously observing systems of water spectrum have been developed in the world. However, so far, there are still few high-frequency observation systems of the water spectrum in coastal waters, especially in the highly turbid and high-dynamic waters. Here, we established a high-frequency water-spectrum observing system based on tower in the Hangzhou Bay. The system measures the water spectrum at a step of 3 minutes, which can fully match the satellite observation. In this paper, we primarily developed a data processing method for the tower-based high-frequency water spectrum data, to realize automatic judgment of clear sky, sun glint, platform shadow, and weak illumination, etc. , and verified the processing results. The results show that the normalized water-leaving radiance spectra obtained through tower observation have relatively high consistency with the shipboard measurement results, with correlation coefficient of more than 0. 99, and average relative error of 9.96%. In addition, the long-term observation capability of the tower-based high-frequency water-spectrum observing system was evaluated, and the results show that although the system has run for one year, the normalized water-leaving radiance obtained by this system have good consistency with the synchronously measurement by Portable spectrometer ASD in respect of spectral shape and value, with correlation coefficient of more than 0.90 and average relative error of 6.48%. Moreover, the water spectra from high-frequency observation by the system can be used to effectively monitor the rapid dynamic variation in concentration of suspended materials with tide. The tower-based high-frequency water-spectrum observing system provided rich in situ spectral data for the validation of ocean color remote sensing in turbid waters, especially for validation of the high temporal-resolution geostationary satellite ocean color remote sensing.

Gear fault diagnosis based on the structured sparsity time-frequency analysis

NASA Astrophysics Data System (ADS)

Sun, Ruobin; Yang, Zhibo; Chen, Xuefeng; Tian, Shaohua; Xie, Yong

2018-03-01

Over the last decade, sparse representation has become a powerful paradigm in mechanical fault diagnosis due to its excellent capability and the high flexibility for complex signal description. The structured sparsity time-frequency analysis (SSTFA) is a novel signal processing method, which utilizes mixed-norm priors on time-frequency coefficients to obtain a fine match for the structure of signals. In order to extract the transient feature from gear vibration signals, a gear fault diagnosis method based on SSTFA is proposed in this work. The steady modulation components and impulsive components of the defective gear vibration signals can be extracted simultaneously by choosing different time-frequency neighborhood and generalized thresholding operators. Besides, the time-frequency distribution with high resolution is obtained by piling different components in the same diagram. The diagnostic conclusion can be made according to the envelope spectrum of the impulsive components or by the periodicity of impulses. The effectiveness of the method is verified by numerical simulations, and the vibration signals registered from a gearbox fault simulator and a wind turbine. To validate the efficiency of the presented methodology, comparisons are made among some state-of-the-art vibration separation methods and the traditional time-frequency analysis methods. The comparisons show that the proposed method possesses advantages in separating feature signals under strong noise and accounting for the inner time-frequency structure of the gear vibration signals.

Commissioning of two RF operation modes for RF negative ion source experimental setup at HUST

NASA Astrophysics Data System (ADS)

Li, D.; Chen, D.; Liu, K.; Zhao, P.; Zuo, C.; Wang, X.; Wang, H.; Zhang, L.

2017-08-01

An RF-driven negative ion source experimental setup, without a cesium oven and an extraction system, has been built at Huazhong University of Science and Technology (HUST). The working gas is hydrogen, and the typical operational gas pressure is 0.3 Pa. The RF generator is capable of delivering up to 20 kW at 0.9 - 1.1 MHz, and has two operation modes, the fixed-frequency mode and auto-tuning mode. In the fixed-frequency mode, it outputs a steady RF forward power (Pf) at a fixed frequency. In the auto-tuning mode, it adjusts the operating frequency to seek and track the minimum standing wave ratio (SWR) during plasma discharge. To achieve fast frequency tuning, the RF signal source adopts a direct digital synthesizer (DDS). To withstand high SWR during the discharge, a tetrode amplifier is chosen as the final stage amplifier. The trend of maximum power reflection coefficient |ρ|2 at plasma ignition is presented at the fixed frequency of 1.02 MHz with the Pf increasing from 5 kW to 20 kW, which shows the maximum |ρ|2 tends to be "steady" under high RF power. The experiments in auto-tuning mode fail due to over-current protection of screen grid. The possible reason is the relatively large equivalent anode impedance caused by the frequency tuning. The corresponding analysis and possible solution are presented.

Individual differences and specificity of prefrontal gamma frequency-tACS on fluid intelligence capabilities.

PubMed

Santarnecchi, E; Muller, T; Rossi, S; Sarkar, A; Polizzotto, N R; Rossi, A; Cohen Kadosh, R

2016-02-01

Emerging evidence suggests that transcranial alternating current stimulation (tACS) is an effective, frequency-specific modulator of endogenous brain oscillations, with the potential to alter cognitive performance. Here, we show that reduction in response latencies to solve complex logic problem indexing fluid intelligence is obtained through 40 Hz-tACS (gamma band) applied to the prefrontal cortex. This improvement in human performance depends on individual ability, with slower performers at baseline receiving greater benefits. The effect could have not being explained by regression to the mean, and showed task and frequency specificity: it was not observed for trials not involving logical reasoning, as well as with the application of low frequency 5 Hz-tACS (theta band) or non-periodic high frequency random noise stimulation (101-640 Hz). Moreover, performance in a spatial working memory task was not affected by brain stimulation, excluding possible effects on fluid intelligence enhancement through an increase in memory performance. We suggest that such high-level cognitive functions are dissociable by frequency-specific neuromodulatory effects, possibly related to entrainment of specific brain rhythms. We conclude that individual differences in cognitive abilities, due to acquired or developmental origins, could be reduced during frequency-specific tACS, a finding that should be taken into account for future individual cognitive rehabilitation studies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Energy-Based Tetrahedron Sensor for High-Temperature, High-Pressure Environments

NASA Technical Reports Server (NTRS)

Gee, Kent L.; Sommerfeldt, Scott D.; Blotter, Jonathan D.

2012-01-01

An acoustic energy-based probe has been developed that incorporates multiple acoustic sensing elements in order to obtain the acoustic pressure and three-dimensional acoustic particle velocity. With these quantities, the user can obtain various energy-based quantities, including acoustic energy density, acoustic intensity, and acoustic impedance. In this specific development, the probe has been designed to operate in an environment characterized by high temperatures and high pressures as is found in the close vicinity of rocket plumes. Given these capabilities, the probe is designed to be used to investigate the acoustic conditions within the plume of a rocket engine or jet engine to facilitate greater understanding of the noise generation mechanisms in those plumes. The probe features sensors mounted inside a solid sphere. The associated electronics for the probe are contained within the sphere and the associated handle for the probe. More importantly, the design of the probe has desirable properties that reduce the bias errors associated with determining the acoustic pressure and velocity using finite sum and difference techniques. The diameter of the probe dictates the lower and upper operating frequencies for the probe, where accurate measurements can be acquired. The current probe design implements a sphere diameter of 1 in. (2.5 cm), which limits the upper operating frequency to about 4.5 kHz. The sensors are operational up to much higher frequencies, and could be used to acquire pressure data at higher frequencies, but the energy-based measurements are limited to that upper frequency. Larger or smaller spherical probes could be designed to go to lower or higher frequency range

High-frequency ground motion amplification during the 2011 Tohoku earthquake explained by soil dilatancy

NASA Astrophysics Data System (ADS)

Roten, D.; Fäh, D.; Bonilla, L. F.

2013-05-01

Ground motions of the 2011 Tohoku earthquake recorded at Onahama port (Iwaki, Fukushima prefecture) rank among the highest accelerations ever observed, with the peak amplitude of the 3-D acceleration vector approaching 2g. The response of the site was distinctively non-linear, as indicated by the presence of horizontal acceleration spikes which have been linked to cyclic mobility during similar observations. Compared to records of weak ground motions, the response of the site during the Mw 9.1 earthquake was characterized by increased amplification at frequencies above 10 Hz and in peak ground acceleration. This behaviour contrasts with the more common non-linear response encountered at non-liquefiable sites, which results in deamplification at higher frequencies. We simulate propagation of SH waves through the dense sand deposit using a non-linear finite difference code that is capable of modelling the development of excess pore water pressure. Dynamic soil parameters are calibrated using a direct search method that minimizes the difference between observed and simulated acceleration envelopes and response spectra. The finite difference simulations yield surface acceleration time-series that are consistent with the observations in shape and amplitude, pointing towards soil dilatancy as a likely explanation for the high-frequency pulses recorded at Onahama port. The simulations also suggest that the occurrence of high-frequency spikes coincided with a rapid increase in pore water pressure in the upper part of the sand deposit between 145 and 170 s. This sudden increase is possibly linked to a burst of high-frequency energy from a large slip patch below the Iwaki region.

The Jansky VLA: Rebuilt for 21st Century Astronomy

NASA Astrophysics Data System (ADS)

Hallinan, Gregg

2016-01-01

At the start of this decade, the Very Large Array underwent a transformative upgrade. While retaining its original 27 antennas, the signal transmission and processing systems, originally developed and built in the 1970s, have been replaced with state of the art wideband receivers and a new data transmission system, as well as one of the most powerful correlators yet built. With a ten-fold increase in continuum sensitivity, up to 4 million frequency channels and complete frequency coverage from 1-50 GHz, the resulting increase in capability and versatility is analogous to the transition from photographic plate to CCD technology that revolutionized optical astronomy in the 1980s. Post upgrade, the Jansky VLA will be the most sensitive radio interferometer in the world for this decade, probing the sub-uJy radio sky for the first time, and will remain the most versatile, frequency-agile radio telescope for the foreseeable future. Underscoring this versatility, is the VLA's capability to trace both thermal and non-thermal emission over a wide range of spatial, time and velocity resolution. At the highest frequencies, this includes imaging cool gas in high redshift galaxies and dusty disks in nearby protoplanetary systems, while at the lowest frequencies tracing AGN activity and star formation back to the epoch of reionization. In the time domain, the VLA can respond to external triggers within 15 minutes to provide an instantaneous broadband radio spectrum of explosive events. I will review some of the exciting science emerging from the Jansky VLA as well as the range of science-ready data products that will make the VLA increasingly accessible to the wider astronomical community. Finally, I will briefly introduce the new VLA Sky Survey (VLASS), a community-driven project to image 80% of the sky over multiple epochs with the VLA, reaching a depth of ~70 uJy and detecting ~10 million radio sources at high spatial and spectral resolution with full polarization information.

Micromachined PIN-PMN-PT crystal composite transducer for high-frequency intravascular ultrasound (IVUS) imaging.

PubMed

Li, Xiang; Ma, Teng; Tian, Jian; Han, Pengdi; Zhou, Qifa; Shung, K Kirk

2014-07-01

In this paper, we report the use of micromachined PbIn1/2Nb1/2O3-PbMg1/3Nb2/3O3-PbTiO 3 (PIN-PMNPT) single crystal 1-3 composite material for intravascular ultrasound (IVUS) imaging application. The effective electromechanical coupling coefficient kt(eff) of the composite was measured to be 0.75 to 0.78. Acoustic impedance was estimated to be 20 MRayl. Based on the composite, needle-type and flexible-type IVUS transducers were fabricated. The composite transducer achieved an 86% bandwidth at the center frequency of 41 MHz, which resulted in a 43 μm axial resolution. Ex vivo IVUS imaging was conducted to demonstrate the improvement of axial resolution. The composite transducer was capable of identifying the three layers of a cadaver coronary artery specimen with high resolution. The PIN-PMN-PT-based composite has superior piezoelectric properties comparable to PMN-PT-based composite and its thermal stability is higher than PMN-PT. PIN-PMN-PT crystal can be an alternative approach for fabricating high-frequency composite, instead of using PMN-PT.

Singular value decomposition based impulsive noise reduction in multi-frequency phase-sensitive demodulation of electrical impedance tomography

NASA Astrophysics Data System (ADS)

Hao, Zhenhua; Cui, Ziqiang; Yue, Shihong; Wang, Huaxiang

2018-06-01

As an important means in electrical impedance tomography (EIT), multi-frequency phase-sensitive demodulation (PSD) can be viewed as a matched filter for measurement signals and as an optimal linear filter in the case of Gaussian-type noise. However, the additive noise usually possesses impulsive noise characteristics, so it is a challenging task to reduce the impulsive noise in multi-frequency PSD effectively. In this paper, an approach for impulsive noise reduction in multi-frequency PSD of EIT is presented. Instead of linear filters, a singular value decomposition filter is employed as the pre-stage filtering module prior to PSD, which has advantages of zero phase shift, little distortion, and a high signal-to-noise ratio (SNR) in digital signal processing. Simulation and experimental results demonstrated that the proposed method can effectively eliminate the influence of impulsive noise in multi-frequency PSD, and it was capable of achieving a higher SNR and smaller demodulation error.

Development and Performance of an Ultrawideband Stepped-Frequency Radar for Landmine and Improvised Explosive Device (IED) Detection

NASA Astrophysics Data System (ADS)

Phelan, Brian R.; Gallagher, Kyle A.; Sherbondy, Kelly D.; Ranney, Kenneth I.; Narayanan, Ram M.

2014-11-01

Under support from the Army Research Laboratory's Partnerships in Research Transition program, a stepped-frequency radar (SFR) is currently under development, which allows for manipulation of the radiated spectrum while still maintaining an effective ultra-wide bandwidth. The SFR is a vehicle-mounted forward-looking ground-penetrating radar designed for high-resolution detection of buried landmines and improvised explosive devices. The SFR can be configured to precisely excise prohibited or interfering frequency bands and also possesses frequency-hopping capabilities. This paper discusses the expected performance features of the SFR as derived from laboratory testing and characterization. Ghosts and artifacts appearing in the range profile arise from gaps in the operating band when the system is configured to omit specific frequencies. An analysis of these effects is discussed and our current solution is presented. Future prospects for the SFR are also discussed, including data collection campaigns at the Army's Adelphi Laboratory Center and the Countermine Test Site.

Frequency-agile dual-frequency lidar for integrated coherent radar-lidar architectures.

PubMed

Vercesi, Valeria; Onori, Daniel; Laghezza, Francesco; Scotti, Filippo; Bogoni, Antonella; Scaffardi, Mirco

2015-04-01

We propose a novel architecture for implementing a dual-frequency lidar (DFL) exploiting differential Doppler shift measurement. The two frequency tones, needed for target velocity measurements, are selected from the spectrum of a mode-locked laser operating in the C-band. The tones' separation is easily controlled by using a programmable wavelength selective switch, thus allowing for a dynamic trade-off among robustness to atmospheric turbulence and sensitivity. Speed measurements for different tone separations equal to 10, 40, 80, and 160 GHz are demonstrated, proving the system's capability of working in different configurations. Thanks to the acquisition system based on an analog-to-digital converter and digital-signal processing, real-time velocity measurements are demonstrated. The MLL-based proposed architecture enables the integration of the DFL with a photonic-based radar that exploits the same laser for generating and receiving radio-frequency signal with high performance, thus allowing for simultaneous or complementary target observations by exploiting the advantages of both radar and lidar.

Handheld microwave bomb-detecting imaging system

NASA Astrophysics Data System (ADS)

Gorwara, Ashok; Molchanov, Pavlo

2017-05-01

Proposed novel imaging technique will provide all weather high-resolution imaging and recognition capability for RF/Microwave signals with good penetration through highly scattered media: fog, snow, dust, smoke, even foliage, camouflage, walls and ground. Image resolution in proposed imaging system is not limited by diffraction and will be determined by processor and sampling frequency. Proposed imaging system can simultaneously cover wide field of view, detect multiple targets and can be multi-frequency, multi-function. Directional antennas in imaging system can be close positioned and installed in cell phone size handheld device, on small aircraft or distributed around protected border or object. Non-scanning monopulse system allows dramatically decrease in transmitting power and at the same time provides increased imaging range by integrating 2-3 orders more signals than regular scanning imaging systems.

Advanced Global Atmospheric Gases Experiment (AGAGE)

NASA Technical Reports Server (NTRS)

Prinn, Ronald G.; Kurylo, Michael (Technical Monitor)

2004-01-01

We seek funding from NASA for the third year (2005) of the four-year period January 1, 2003 - December 31, 2006 for continued support of the MIT contributions to the multi-national global atmospheric trace species measurement program entitled Advanced Global Atmospheric Gases Experiment (AGAGE). The case for real-time high-frequency measurement networks like AGAGE is very strong and the observations and their interpretation are widely recognized for their importance to ozone depletion and climate change studies and to verification issues arising from the Montreal Protocol (ozone) and Kyoto Protocol (climate). The proposed AGAGE program is distinguished by its capability to measure over the globe at high frequency almost all of the important species in the Montreal Protocol and almost all of the significant non-CO2 gases in the Kyoto Protocol.

Injection locking of a low cost high power laser diode at 461 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pagett, C. J. H.; Moriya, P. H., E-mail: paulohisao@ifsc.usp.br; Celistrino Teixeira, R.

2016-05-15

Stable laser sources at 461 nm are important for optical cooling of strontium atoms. In most existing experiments, this wavelength is obtained by frequency doubling infrared lasers, since blue laser diodes either have low power or large emission bandwidths. Here, we show that injecting less than 10 mW of monomode laser radiation into a blue multimode 500 mW high power laser diode is capable of slaving at least 50% of the power to the desired frequency. We verify the emission bandwidth reduction by saturation spectroscopy on a strontium gas cell and by direct beating of the slave with the mastermore » laser. We also demonstrate that the laser can efficiently be used within the Zeeman slower for optical cooling of a strontium atomic beam.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verbiest, G. J., E-mail: Verbiest@physik.rwth-aachen.de; Zalm, D. J. van der; Oosterkamp, T. H.

The application of ultrasound in an Atomic Force Microscope (AFM) gives access to subsurface information. However, no commercially AFM exists that is equipped with this technique. The main problems are the electronic crosstalk in the AFM setup and the insufficiently strong excitation of the cantilever at ultrasonic (MHz) frequencies. In this paper, we describe the development of an add-on that provides a solution to these problems by using a special piezo element with a lowest resonance frequency of 2.5 MHz and by separating the electronic connection for this high frequency piezo element from all other connections. In this sense, wemore » support researches with the possibility to perform subsurface measurements with their existing AFMs and hopefully pave also the way for the development of a commercial AFM that is capable of imaging subsurface features with nanometer resolution.« less

Biomimetic Beetle-Inspired Flapping Air Vehicle Actuated by Ionic Polymer-Metal Composite Actuator

PubMed Central

Zhao, Yang; Xu, Di; Sheng, Jiazheng; Meng, Qinglong; Wu, Dezhi; Wang, Lingyun; Xiao, Jingjing; Lv, Wenlong; Sun, Daoheng

2018-01-01

During the last decades, the ionic polymer-metal composite (IPMC) received much attention because of its potential capabilities, such as large displacement and flexible bending actuation. In this paper, a biomimetic flapping air vehicle was proposed by combining the superiority of ionic polymer metal composite with the bionic beetle flapping principle. The blocking force was compared between casted IPMC and IPMC. The flapping state of the wing was investigated and the maximum displacement and flapping angle were measured. The flapping displacement under different voltage and frequency was tested. The flapping displacement of the wing and the support reaction force were measured under different frequency by experiments. The experimental results indicate that the high voltage and low frequency would get large flapping displacement. PMID:29682006

Statement Testimony of The Honorable Zachary J. Lemnios Director, Defense Research and Engineering Before the United States House of Representatives Committee on Armed Services Subcommittee on Terrorism, Unconventional Threats and Capabilities

DTIC Science & Technology

2010-03-23

nationwide virtual science libary adapted for Afghanistan’s needs. Prepare for an Uncertain Future In preparing for an uncertain future, a...to assess the military implications of the ubiquitous availability of high performance analog, digital , electro-optical, radio frequency and signal

CREE: Making the Switch

ScienceCinema

Grider, David; Palmer, John

2018-05-11

CREE, with the help of ARPA-E funding, has developed a Silicon Carbide (SIC) transistor which can be used to create solid state transformers capable of meeting the unique needs of the emerging smart grid. SIC transistors are different from common silicon computer chips in that they handle grid scale voltages with ease and their high frequency switching is well suited to the intermittent nature of renewable energy generation.

Advanced Pumped Storage Hydropower and Ancillary Services Provision

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muljadi, Eduard; Gevorgian, Vahan; Mohanpurkar, Manish

This paper presents a high-level overview of the capability of advanced pumped storage hydropower to provide ancillary services including frequency regulation and oscillation damping. Type 3 and Type 4 generators are discussed. The examples given are for a small power system that uses a diesel generator as the main generator and a very large system that uses a gas turbine as the main generator.

Sound Modeling Simplifies Vehicle Noise Management

NASA Technical Reports Server (NTRS)

2015-01-01

Under two SBIR contracts with Langley Research Center, Ann Arbor, Michigan-based Comet Technology Corporation developed Comet EnFlow, a software program capable of predicting both high- and low-frequency noise and vibration behavior in plane fuselages and other structures. The company now markets the software to airplane, automobile, and ship manufacturers, and Langley has found an unexpected use for it in leak detection on the International Space Station.

Wideband monolithically integrated front-end subsystems and components

NASA Astrophysics Data System (ADS)

Mruk, Joseph Rene

This thesis presents the analysis, design, and measurements of passive, monolithically integrated, wideband recta-coax and printed circuit board front-end components. Monolithic fabrication of antennas, impedance transformers, filters, and transitions lowers manufacturing costs by reducing assembly time and enhances performance by removing connectors and cabling between the devices. Computational design, fabrication, and measurements are used to demonstrate the capabilities of these front-end assemblies. Two-arm wideband planar log-periodic antennas fed using a horizontal feed that allows for filters and impedance transformers to be readily fabricated within the radiating region of the antenna are demonstrated. At microwave frequencies, low-cost printed circuit board processes are typically used to produce planar devices. A 1.8 to 11 GHz two-arm planar log-periodic antenna is designed with a monolithically integrated impedance transformer. Band rejection methods based on modifying the antenna aperture, use of an integrated filter, and the application of both methods are investigated with realized gain suppressions of over 25 dB achieved. The ability of standard circuit board technology to fabricate millimeter-wave devices up to 110 GHz is severely limited. Thin dielectrics are required to prevent the excitation of higher order modes in the microstrip substrate. Fabricating the thin line widths required for the antenna aperture also becomes prohibitively challenging. Surface micro-machining typically used in the fabrication of MEMS devices is capable of producing the extremely small features that can be used to fabricate antennas extending through W-band. A directly RF fed 18 to 110 GHz planar log-periodic antenna is developed. The antenna is fabricated with an integrated impedance transformer and additional transitions for measurement characterization. Singly terminated low-loss wideband millimeter-wave filters operating over V- and W- band are developed. High quality performance of an 18 to 100 GHz front-end is realized by dividing the single instantaneous antenna into two apertures operating from 18 to 50 and 50 to 100 GHz. Each channel features an impedance transformer, low-pass (low-frequency) or band-pass (high-frequency) filter, and grounded CPW launch. This dual-aperture front-end demonstrates that micromachining technology is now capable of fabricating broadband millimeter-wave components with a high degree of integration.

GPR Imaging for Deeply Buried Objects: A Comparative Study Based on FDTD Models and Field Experiments

NASA Technical Reports Server (NTRS)

Tilley, roger; Dowla, Farid; Nekoogar, Faranak; Sadjadpour, Hamid

2012-01-01

Conventional use of Ground Penetrating Radar (GPR) is hampered by variations in background environmental conditions, such as water content in soil, resulting in poor repeatability of results over long periods of time when the radar pulse characteristics are kept the same. Target objects types might include voids, tunnels, unexploded ordinance, etc. The long-term objective of this work is to develop methods that would extend the use of GPR under various environmental and soil conditions provided an optimal set of radar parameters (such as frequency, bandwidth, and sensor configuration) are adaptively employed based on the ground conditions. Towards that objective, developing Finite Difference Time Domain (FDTD) GPR models, verified by experimental results, would allow us to develop analytical and experimental techniques to control radar parameters to obtain consistent GPR images with changing ground conditions. Reported here is an attempt at developing 20 and 3D FDTD models of buried targets verified by two different radar systems capable of operating over different soil conditions. Experimental radar data employed were from a custom designed high-frequency (200 MHz) multi-static sensor platform capable of producing 3-D images, and longer wavelength (25 MHz) COTS radar (Pulse EKKO 100) capable of producing 2-D images. Our results indicate different types of radar can produce consistent images.

Towards thermal noise free optomechanics

NASA Astrophysics Data System (ADS)

Page, Michael A.; Zhao, Chunnong; Blair, David G.; Ju, Li; Ma, Yiqiu; Pan, Huang-Wei; Chao, Shiuh; Mitrofanov, Valery P.; Sadeghian, Hamed

2016-11-01

Thermal noise generally greatly exceeds quantum noise in optomechanical devices unless the mechanical frequency is very high or the thermodynamic temperature is very low. This paper addresses the design concept for a novel optomechanical device capable of ultrahigh quality factors in the audio frequency band with negligible thermal noise. The proposed system consists of a minimally supported millimeter scale pendulum mounted in a double end-mirror sloshing cavity that is topologically equivalent to a membrane-in-the-middle cavity. The radiation pressure inside the high-finesse cavity allows for high optical stiffness, cancellation of terms which lead to unwanted negative damping and suppression of quantum radiation pressure noise. We solve the optical spring dynamics of the system using the Hamiltonian, find the noise spectral density and show that stable optical trapping is possible. We also assess various loss mechanisms, one of the most important being the acceleration loss due to the optical spring. We show that practical devices, starting from a centre-of-mass pendulum frequency of 0.1 Hz, could achieve a maximum quality factor of (1014) with optical spring stiffened frequency 1-10 kHz. Small resonators of mass 1 ≤ft(μ \\right) g or less could achieve a Q-factor of (1011) at a frequency of 100 kHz. Applications for such devices include white light cavities for improvement of gravitational wave detectors, or sensors able to operate near the quantum limit.

Highly chirped single-bandpass microwave photonic filter with reconfiguration capabilities.

PubMed

Bolea, Mario; Mora, José; Ortega, Beatriz; Capmany, José

2011-02-28

We propose a novel photonic structure to implement a chirped single-bandpass microwave photonic filter based on the amplitude modulation of a broadband optical signal transmitted by a non-linear dispersive element and an interferometric system prior to balanced photodetection. A full reconfigurability of the filter is achieved since amplitude and phase responses can be independently controlled. We have experimentally demonstrated chirp values up to tens of ns/GHz, which is, as far as we know, one order of magnitude better than others achieved by electrical approaches and furthermore, without restrictions in terms of frequency tuning since a frequency operation range up to 40 GHz has been experimentally demonstrated.

Characterisation of human thyroid epithelial cells immortalised in vitro by simian virus 40 DNA transfection.

PubMed Central

Lemoine, N. R.; Mayall, E. S.; Jones, T.; Sheer, D.; McDermid, S.; Kendall-Taylor, P.; Wynford-Thomas, D.

1989-01-01

Human primary thyroid follicular epithelial cells were transfected with a plasmid containing an origin-defective SV40 genome (SVori-) to produce several immortal cell lines. Two of the 10 cell lines analysed expressed specific features of thyroid epithelial function (iodide-trapping and thyroglobulin production). These two lines were characterised in detail and found to be growth factor-independent, capable of anchorage-independent growth at low frequency but non-tumorigenic in nude mice. These differentiated, These differentiated, partially transformed cell lines were shown to be suitable for gene transfer at high frequency using simple coprecipitation techniques. Images Figure 2 Figure 3 Figure 4 PMID:2557880

Spectroscopic thermoacoustic imaging of water and fat composition

NASA Astrophysics Data System (ADS)

Bauer, Daniel R.; Wang, Xiong; Vollin, Jeff; Xin, Hao; Witte, Russell S.

2012-07-01

During clinical studies, thermoacoustic imaging (TAI) failed to reliably identify malignant breast tissue. To increase detection capability, we propose spectroscopic TAI to differentiate samples based on the slope of their dielectric absorption. Phantoms composed of different ratios of water and fat were imaged using excitation frequencies between 2.7 and 3.1 GHz. The frequency-dependent slope of the TA signal was highly correlated with that of its absorption coefficient (R2 = 0.98 and p < 0.01), indicating spectroscopic TAI can distinguish materials based on their intrinsic dielectric properties. This approach potentially enhances cancer detection due to the increased water content of many tumors.

Direct magnetocaloric characterization and simulation of thermomagnetic cycles

NASA Astrophysics Data System (ADS)

Porcari, G.; Buzzi, M.; Cugini, F.; Pellicelli, R.; Pernechele, C.; Caron, L.; Brück, E.; Solzi, M.

2013-07-01

An experimental setup for the direct measurement of the magnetocaloric effect capable of simulating high frequency magnetothermal cycles on laboratory-scale samples is described. The study of the magnetocaloric properties of working materials under operative conditions is fundamental for the development of innovative devices. Frequency and time dependent characterization can provide essential information on intrinsic features such as magnetic field induced fatigue in materials undergoing first order magnetic phase transitions. A full characterization of the adiabatic temperature change performed for a sample of Gadolinium across its Curie transition shows the good agreement between our results and literature data and in-field differential scanning calorimetry.

6.2-GHz modulated terahertz light detection using fast terahertz quantum well photodetectors.

PubMed

Li, Hua; Wan, Wen-Jian; Tan, Zhi-Yong; Fu, Zhang-Long; Wang, Hai-Xia; Zhou, Tao; Li, Zi-Ping; Wang, Chang; Guo, Xu-Guang; Cao, Jun-Cheng

2017-06-14

The fast detection of terahertz radiation is of great importance for various applications such as fast imaging, high speed communications, and spectroscopy. Most commercial products capable of sensitively responding the terahertz radiation are thermal detectors, i.e., pyroelectric sensors and bolometers. This class of terahertz detectors is normally characterized by low modulation frequency (dozens or hundreds of Hz). Here we demonstrate the first fast semiconductor-based terahertz quantum well photodetectors by carefully designing the device structure and microwave transmission line for high frequency signal extraction. Modulation response bandwidth of gigahertz level is obtained. As an example, the 6.2-GHz modulated terahertz light emitted from a Fabry-Pérot terahertz quantum cascade laser is successfully detected using the fast terahertz quantum well photodetector. In addition to the fast terahertz detection, the technique presented in this work can also be used for optically characterizing the frequency stability of terahertz quantum cascade lasers, heterodyne detections and photomixing applications.

Damage detection and locating using tone burst and continuous excitation modulation method

NASA Astrophysics Data System (ADS)

Li, Zheng; Wang, Zhi; Xiao, Li; Qu, Wenzhong

2014-03-01

Among structural health monitoring techniques, nonlinear ultrasonic spectroscopy methods are found to be effective diagnostic approach to detecting nonlinear damage such as fatigue crack, due to their sensitivity to incipient structural changes. In this paper, a nonlinear ultrasonic modulation method was developed to detect and locate a fatigue crack on an aluminum plate. The method is different with nonlinear wave modulation method which recognizes the modulation of low-frequency vibration and high-frequency ultrasonic wave; it recognizes the modulation of tone burst and high-frequency ultrasonic wave. In the experiment, a Hanning window modulated sinusoidal tone burst and a continuous sinusoidal excitation were simultaneously imposed on the PZT array which was bonded on the surface of an aluminum plate. The modulations of tone burst and continuous sinusoidal excitation was observed in different actuator-sensor paths, indicating the presence and location of fatigue crack. The results of experiments show that the proposed method is capable of detecting and locating the fatigue crack successfully.

Theoretical Evaluation of Electroactive Polymer Based Micropump Diaphragm for Air Flow Control

NASA Technical Reports Server (NTRS)

Xu, Tian-Bing; Su, Ji; Zhang, Qiming

2004-01-01

An electroactive polymer (EAP), high energy electron irradiated poly(vinylidene fluoride-trifluoroethylene) [P(VDFTrFE)] copolymer, based actuation micropump diaphragm (PAMPD) have been developed for air flow control. The displacement strokes and profiles as a function of amplifier and frequency of electric field have been characterized. The volume stroke rates (volume rate) as function of electric field, driving frequency have been theoretically evaluated, too. The PAMPD exhibits high volume rate. It is easily tuned with varying of either amplitude or frequency of the applied electric field. In addition, the performance of the diaphragms were modeled and the agreement between the modeling results and experimental data confirms that the response of the diaphragms follow the design parameters. The results demonstrated that the diaphragm can fit some future aerospace applications to replace the traditional complex mechanical systems, increase the control capability and reduce the weight of the future air dynamic control systems. KEYWORDS: Electroactive polymer (EAP), micropump, diaphragm, actuation, displacement, volume rate, pumping speed, clamping ratio.

Broadband focusing ultrasonic transducers based on dimpled LiNbO3 plate with inversion layer.

PubMed

Chen, Jin; Dai, Ji-Yan; Zhang, Chao; Zhang, Zhitian; Feng, Guanping

2012-12-01

A high-frequency broadband focusing transducer based on dimpled LiNbO(3) inversion layer plate has been fabricated and characterized. A spherical surface with a curvature radius of 6 mm is formed on the half-thickness LiNbO(3) inversion layer plate of Y36° cut orientation. The domain structure in the cross section is observed after a hydrofluoric acid etching process. For transducer fabrication, conductive epoxy is used as the backing material and polymer is deposited on the front face as the matching layer. The center frequency, bandwidth, and insertion loss of the focused transducer are measured to be 72 MHz, 136%, and -32 dB, respectively. The focused transducer has been successfully used for rabbit eyeball imaging and a better imaging capability compared with the planar transducer has been demonstrated. These promising results prove that the dimpled LiNbO(3) inversion layer plate has great potential for fabrication of high-frequency broadband focusing ultrasonic transducers.

Ultra High-Speed Radio Frequency Switch Based on Photonics.

PubMed

Ge, Jia; Fok, Mable P

2015-11-26

Microwave switches, or Radio Frequency (RF) switches have been intensively used in microwave systems for signal routing. Compared with the fast development of microwave and wireless systems, RF switches have been underdeveloped particularly in terms of switching speed and operating bandwidth. In this paper, we propose a photonics based RF switch that is capable of switching at tens of picoseconds speed, which is hundreds of times faster than any existing RF switch technologies. The high-speed switching property is achieved with the use of a rapidly tunable microwave photonic filter with tens of gigahertz frequency tuning speed, where the tuning mechanism is based on the ultra-fast electro-optics Pockels effect. The RF switch has a wide operation bandwidth of 12 GHz and can go up to 40 GHz, depending on the bandwidth of the modulator used in the scheme. The proposed RF switch can either work as an ON/OFF switch or a two-channel switch, tens of picoseconds switching speed is experimentally observed for both type of switches.

Bright squeezed vacuum in a nonlinear interferometer: Frequency and temporal Schmidt-mode description

NASA Astrophysics Data System (ADS)

Sharapova, P. R.; Tikhonova, O. V.; Lemieux, S.; Boyd, R. W.; Chekhova, M. V.

2018-05-01

Control over the spectral properties of the bright squeezed vacuum (BSV), a highly multimode nonclassical macroscopic state of light that can be generated through high-gain parametric down conversion, is crucial for many applications. In particular, in several recent experiments BSV is generated in a strongly pumped SU(1,1) interferometer to achieve phase supersensitivity, perform broadband homodyne detection, or tailor the frequency spectrum of squeezed light. In this work, we present an analytical approach to the theoretical description of BSV in the frequency domain based on the Bloch-Messiah reduction and the Schmidt-mode formalism. As a special case we consider a strongly pumped SU(1,1) interferometer. We show that different moments of the radiation at its output depend on the phase, dispersion, and the parametric gain in a nontrivial way, thereby providing additional insights on the capabilities of nonlinear interferometers. In particular, a dramatic change in the spectrum occurs as the parametric gain increases.

Note: High-speed Z tip scanner with screw cantilever holding mechanism for atomic-resolution atomic force microscopy in liquid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reza Akrami, Seyed Mohammad; Miyata, Kazuki; Asakawa, Hitoshi

High-speed atomic force microscopy has attracted much attention due to its unique capability of visualizing nanoscale dynamic processes at a solid/liquid interface. However, its usability and resolution have yet to be improved. As one of the solutions for this issue, here we present a design of a high-speed Z-tip scanner with screw holding mechanism. We perform detailed comparison between designs with different actuator size and screw arrangement by finite element analysis. Based on the design giving the best performance, we have developed a Z tip scanner and measured its performance. The measured frequency response of the scanner shows a flatmore » response up to ∼10 kHz. This high frequency response allows us to achieve wideband tip-sample distance regulation. We demonstrate the applicability of the scanner to high-speed atomic-resolution imaging by visualizing atomic-scale calcite crystal dissolution process in water at 2 s/frame.« less

Evaluation of a miniature magnetostrictive actuator using Galfenol under tensile stress

NASA Astrophysics Data System (ADS)

Ueno, Toshiyuki; Miura, Hidemitsu; Yamada, Sotoshi

2011-02-01

We are, at present, developing miniature actuators using an iron-gallium alloy (Galfenol). Galfenol is an iron-based magnetostrictive material with magnetostriction exceeding 200 ppm, Young's modulus of 70 GPa and a high relative permeability (>100). The advantages of an actuator using this material are capability of miniaturization, stability against external force, low voltage driving and high power. In this study, a miniature vibrator using an E core of Galfenol under tensile stress up to 20 MPa was investigated. The vibrator did not fracture and maintained the magnetostriction even under a high tensile stress. In addition, the resonance frequency, unchanged under the tensile stress, was lower than the cutoff frequency, hence the vibrator can be driven with a low voltage even in resonance driving. The temperature rise in resonance driving was low and creep was not observed in resonance driving under tensile stress. The vibrator will be applicable in flat panel or bone conductive speakers.

Effect of Surface Impulsive Thermal Loads on Fatigue Behavior of Constant Volume Propulsion Engine Combustor Materials

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Fox, Dennis S.; Miller, Robert A.; Ghosn, Louis J.; Kalluri, Sreeramesh

2004-01-01

The development of advanced high performance constant-volume-combustion-cycle engines (CVCCE) requires robust design of the engine components that are capable of enduring harsh combustion environments under high frequency thermal and mechanical fatigue conditions. In this study, a simulated engine test rig has been established to evaluate thermal fatigue behavior of a candidate engine combustor material, Haynes 188, under superimposed CO2 laser surface impulsive thermal loads (30 to 100 Hz) in conjunction with the mechanical fatigue loads (10 Hz). The mechanical high cycle fatigue (HCF) testing of some laser pre-exposed specimens has also been conducted under a frequency of 100 Hz to determine the laser surface damage effect. The test results have indicated that material surface oxidation and creep-enhanced fatigue is an important mechanism for the surface crack initiation and propagation under the simulated CVCCE engine conditions.

Spectral and angular characteristics of dielectric resonator metasurface at optical frequencies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zou, Longfang; Department of Electrical and Electronic Engineering, The University of Bristol, Bristol, BS8 1TH; López-García, Martin

2014-11-10

The capability of manipulating light at subwavelength scale has fostered the applications of flat metasurfaces in various fields. Compared to metallic structure, metasurfaces made of high permittivity low-loss dielectric resonators hold the promise of high efficiency by avoiding high conductive losses of metals at optical frequencies. This letter investigates the spectral and angular characteristics of a dielectric resonator metasurface composed of periodic sub-arrays of resonators with a linearly varying phase response. The far-field response of the metasurface can be decomposed into the response of a single grating element (sub-array) and the grating arrangement response. The analysis also reveals that couplingmore » between resonators has a non-negligible impact on the angular response. Over a wide wavelength range, the simulated and measured angular characteristics of the metasurface provide a definite illustration of how different grating diffraction orders can be selectively suppressed or enhanced through antenna sub-array design.« less

Predicting Risk for Suicide: A Preliminary Examination of Non-Suicidal Self-Injury and the Acquired Capability Construct in a College Sample.

PubMed

Brackman, Emily H; Morris, Blair W; Andover, Margaret S

2016-01-01

The interpersonal psychological theory of suicide provides a useful framework for considering the relationship between non-suicidal self-injury and suicide. Researchers propose that NSSI increases acquired capability for suicide. We predicted that both NSSI frequency and the IPTS acquired capability construct (decreased fear of death and increased pain tolerance) would separately interact with suicidal ideation to predict suicide attempts. Undergraduate students (N = 113) completed self-report questionnaires, and a subsample (n = 66) also completed a pain sensitivity task. NSSI frequency significantly moderated the association between suicidal ideation and suicide attempts. However, in a separate model, acquired capability did not moderate this relationship. Our understanding of the relationship between suicidal ideation and suicidal behavior can be enhanced by factors associated with NSSI that are distinct from the acquired capability construct.

High-gain dipole antenna using polydimethylsiloxane-glass microsphere (PDMS-GM) substrate for 5G applications

NASA Astrophysics Data System (ADS)

Muhamad, Wan Asilah Wan; Ngah, Razali; Jamlos, Mohd Faizal; Soh, Ping Jack; Ali, Mohd Tarmizi

2017-01-01

A new dipole antenna designed using polydimethylsiloxane-glass microsphere (PDMS-GM) substrate is presented. The PDMS-GM substrate offered a lower permittivity of 1.85 compared to pure PDMS of 2.7. This resulted in a wide operating frequency range from 19 GHz up to more than 45 GHz, indicating a bandwidth of more than 28 GHz. The proposed PDMS-GM antenna featured a gain of up to 13.3 dB compared to pure PDMS which only produced 13 GHz of bandwidth and 5.5 dB gain. Instead of wide bandwidth and high gain, the proposed antenna is capable of becoming water resistant by covering its radiator and SMA connector. Such capabilities of the new PDMS-GM antenna indicated suitability for the fifth-generation (5G) wireless communication systems.

Improved high-resolution ultrasonic imaging of the eye.

PubMed

Silverman, Ronald H; Ketterling, Jeffrey A; Mamou, Jonathan; Coleman, D Jackson

2008-01-01

Currently, virtually all clinical diagnostic ultrasound systems used in ophthalmology are based on fixed-focus, single-element transducers. High-frequency (> or = 20-MHz) transducers introduced to ophthalmology during the last decade have led to improved resolution and diagnostic capabilities for assessment of the anterior segment and the retina. However, single-element transducers are restricted to a small depth of field, limiting their capacity to image the eye as a whole. We fabricated a 20-MHz annular array probe prototype consisting of 5 concentric transducer elements and scanned an ex vivo human eye. Synthetically focused images of the bank eye showed improved depth of field and sensitivity, allowing simultaneous display of the anterior and posterior segments and the full lens contour. This capability may be useful in assessment of vitreoretinal pathologies and investigation of the accommodative mechanism.

High sensitivity field asymmetric ion mobility spectrometer

NASA Astrophysics Data System (ADS)

Chavarria, Mario A.; Matheoud, Alessandro V.; Marmillod, Philippe; Liu, Youjiang; Kong, Deyi; Brugger, Jürgen; Boero, Giovanni

2017-03-01

A high sensitivity field asymmetric ion mobility spectrometer (FAIMS) was designed, fabricated, and tested. The main components of the system are a 10.6 eV UV photoionization source, an ion filter driven by a high voltage/high frequency n-MOS inverter circuit, and a low noise ion detector. The ion filter electronics are capable to generate square waveforms with peak-to-peak voltages up to 1000 V at frequencies up to 1 MHz with adjustable duty cycles. The ion detector current amplifier has a gain up to 1012 V/A with an effective equivalent input noise level down to about 1 fA/Hz1/2 during operation with the ion filter at the maximum voltage and frequency. The FAIMS system was characterized by detecting different standard chemical compounds. Additionally, we investigated the use of a synchronous modulation/demodulation technique to improve the signal-to-noise ratio in FAIMS measurements. In particular, we implemented the modulation of the compensation voltage with the synchronous demodulation of the ion current. The analysis of the measurements at low concentration levels led to an extrapolated limit of detection for acetone of 10 ppt with an averaging time of 1 s.

An improved dual-frequency technique for the remote sensing of ocean currents and wave spectra

NASA Technical Reports Server (NTRS)

Schuler, D. L.; Eng, W. P.

1984-01-01

A two frequency microwave radar technique for the remote sensing of directional ocean wave spectra and surface currents is investigated. This technique is conceptually attractive because its operational physical principle involves a spatial electromagnetic scattering resonance with a single, but selectable, long gravity wave. Multiplexing of signals having different spacing of the two transmitted frequencies allows measurements of the entire long wave ocean spectrum to be carried out. A new scatterometer is developed and experimentally tested which is capable of making measurements having much larger signal/background values than previously possible. This instrument couples the resonance technique with coherent, frequency agility radar capabilities. This scatterometer is presently configured for supporting a program of surface current measurements.

All-optical central-frequency-programmable and bandwidth-tailorable radar

PubMed Central

Zou, Weiwen; Zhang, Hao; Long, Xin; Zhang, Siteng; Cui, Yuanjun; Chen, Jianping

2016-01-01

Radar has been widely used for military, security, and rescue purposes, and modern radar should be reconfigurable at multi-bands and have programmable central frequencies and considerable bandwidth agility. Microwave photonics or photonics-assisted radio-frequency technology is a unique solution to providing such capabilities. Here, we demonstrate an all-optical central-frequency-programmable and bandwidth-tailorable radar architecture that provides a coherent system and utilizes one mode-locked laser for both signal generation and reception. Heterodyning of two individually filtered optical pulses that are pre-chirped via wavelength-to-time mapping generates a wideband linearly chirped radar signal. The working bands can be flexibly tailored with the desired bandwidth at a user-preferred carrier frequency. Radar echoes are first modulated onto the pre-chirped optical pulse, which is also used for signal generation, and then stretched in time or compressed in frequency several fold based on the time-stretch principle. Thus, digitization is facilitated without loss of detection ability. We believe that our results demonstrate an innovative radar architecture with an ultra-high-range resolution. PMID:26795596

A digital, constant-frequency pulsed phase-locked-loop instrument for real-time, absolute ultrasonic phase measurements

NASA Astrophysics Data System (ADS)

Haldren, H. A.; Perey, D. F.; Yost, W. T.; Cramer, K. E.; Gupta, M. C.

2018-05-01

A digitally controlled instrument for conducting single-frequency and swept-frequency ultrasonic phase measurements has been developed based on a constant-frequency pulsed phase-locked-loop (CFPPLL) design. This instrument uses a pair of direct digital synthesizers to generate an ultrasonically transceived tone-burst and an internal reference wave for phase comparison. Real-time, constant-frequency phase tracking in an interrogated specimen is possible with a resolution of 0.000 38 rad (0.022°), and swept-frequency phase measurements can be obtained. Using phase measurements, an absolute thickness in borosilicate glass is presented to show the instrument's efficacy, and these results are compared to conventional ultrasonic pulse-echo time-of-flight (ToF) measurements. The newly developed instrument predicted the thickness with a mean error of -0.04 μm and a standard deviation of error of 1.35 μm. Additionally, the CFPPLL instrument shows a lower measured phase error in the absence of changing temperature and couplant thickness than high-resolution cross-correlation ToF measurements at a similar signal-to-noise ratio. By showing higher accuracy and precision than conventional pulse-echo ToF measurements and lower phase errors than cross-correlation ToF measurements, the new digitally controlled CFPPLL instrument provides high-resolution absolute ultrasonic velocity or path-length measurements in solids or liquids, as well as tracking of material property changes with high sensitivity. The ability to obtain absolute phase measurements allows for many new applications than possible with previous ultrasonic pulsed phase-locked loop instruments. In addition to improved resolution, swept-frequency phase measurements add useful capability in measuring properties of layered structures, such as bonded joints, or materials which exhibit non-linear frequency-dependent behavior, such as dispersive media.

A Novel Photonic Clock and Carrier Recovery Device

NASA Technical Reports Server (NTRS)

Yao, X. Steve; Lutes, George; Maleki, Lute

1996-01-01

As data communication rates climb toward ten Gb/s, clock recovery and synchronization become more difficult, if not impossible, using conventional electronic circuits. We present in this article experimental results of a high speed clock and carrier recovery using a novel device called a photonic oscillator that we recently developed in our laboratory. This device is capable of recovering clock signals up to 70 GHz. To recover the clock, the incoming data is injected into the photonic oscillator either through the optical injection port or the electrical injection port. The free running photonic oscillator is tuned to oscillate at a nominal frequency equal to the clock frequency of the incoming data. With the injection of the data, the photonic oscillator will be quickly locked to clock frequency of the data stream while rejecting other frequency components associated with the data. Consequently, the output of the locked photonic oscillator is a continuous periodical wave synchronized with the incoming data or simply the recovered clock. We have demonstrated a clock to spur ratio of more than 60 dB of the recovered clock using this technique. Similar to the clock recovery, the photonic oscillator can be used to recover a high frequency carrier degraded by noise and an improvement of about 50 dB in signal-to-noise ratio was demonstrated. The photonic oscillator has both electrical and optical inputs and outputs and can be directly interfaced with a photonic system without signal conversion. In addition to clock and carrier recovery, the photonic oscillator can also be used for (1) stable high frequency clock signal generation, (2) frequency multiplication, (3) square wave and comb frequency generation, and (4) photonic phase locked loop.

Ultrabroadband phased-array radio frequency (RF) receivers based on optical techniques

NASA Astrophysics Data System (ADS)

Overmiller, Brock M.; Schuetz, Christopher A.; Schneider, Garrett; Murakowski, Janusz; Prather, Dennis W.

2014-03-01

Military operations require the ability to locate and identify electronic emissions in the battlefield environment. However, recent developments in radio detection and ranging (RADAR) and communications technology are making it harder to effectively identify such emissions. Phased array systems aid in discriminating emitters in the scene by virtue of their relatively high-gain beam steering and nulling capabilities. For the purpose of locating emitters, we present an approach realize a broadband receiver based on optical processing techniques applied to the response of detectors in conformal antenna arrays. This approach utilizes photonic techniques that enable us to capture, route, and process the incoming signals. Optical modulators convert the incoming signals up to and exceeding 110 GHz with appreciable conversion efficiency and route these signals via fiber optics to a central processing location. This central processor consists of a closed loop phase control system which compensates for phase fluctuations induced on the fibers due to thermal or acoustic vibrations as well as an optical heterodyne approach for signal conversion down to baseband. Our optical heterodyne approach uses injection-locked paired optical sources to perform heterodyne downconversion/frequency identification of the detected emission. Preliminary geolocation and frequency identification testing of electronic emissions has been performed demonstrating the capabilities of our RF receiver.

Three-Dimensional Nacelle Aeroacoustics Code With Application to Impedance Education

NASA Technical Reports Server (NTRS)

Watson, Willie R.

2000-01-01

A three-dimensional nacelle acoustics code that accounts for uniform mean flow and variable surface impedance liners is developed. The code is linked to a commercial version of the NASA-developed General Purpose Solver (for solution of linear systems of equations) in order to obtain the capability to study high frequency waves that may require millions of grid points for resolution. Detailed, single-processor statistics for the performance of the solver in rigid and soft-wall ducts are presented. Over the range of frequencies of current interest in nacelle liner research, noise attenuation levels predicted from the code were in excellent agreement with those predicted from mode theory. The equation solver is memory efficient, requiring only a small fraction of the memory available on modern computers. As an application, the code is combined with an optimization algorithm and used to reduce the impedance spectrum of a ceramic liner. The primary problem with using the code to perform optimization studies at frequencies above I1kHz is the excessive CPU time (a major portion of which is matrix assembly). The research recommends that research be directed toward development of a rapid sparse assembler and exploitation of the multiprocessor capability of the solver to further reduce CPU time.

DFL, Canada's Space AIT Facilities - Current and Planned Capabilities

NASA Astrophysics Data System (ADS)

Singhal, R.; Mishra, S.; Choueiry, E.; Dumoulin, J.; Ahmed, S.

2004-08-01

The David Florida Laboratory (DFL) of the Canadian Space Agency is the Canadian national ISO 9001:2000 registered facility for the assembly, integration, and (environmental) testing of space hardware. This paper briefly describes the three main qualification facilities: Structural Qualification Facilities (SQF); Radio Frequency Qualification Facilities (RFQF); and Thermal Qualification Facilities (TQF). The paper also describes the planned/new upgrades/improvements to the DFL's existing capabilities. These include: cylindrical near-field antenna measurement system, current capabilities in multi-frequency multi-band passive intermodulation (PIM) measurement; combined thermal/vibration test facility, improvement in efficiency and performance of the photogrammetry capability, acquisition of an additional mass properties measurement system for small and micro-satellites; combined control and data acquisition system for all existing thermal vacuum facilities, plus a new automatic thermal control system and hypobaric chamber.

On-line evaluation of multiloop digital controller performance

NASA Technical Reports Server (NTRS)

Wieseman, Carol D.

1993-01-01

The purpose of this presentation is to inform the Guidance and Control community of capabilities which were developed by the Aeroservoelasticity Branch to evaluate the performance of multivariable control laws, on-line, during wind-tunnel testing. The capabilities are generic enough to be useful for all kinds of on-line analyses involving multivariable control in experimental testing. Consequently, it was decided to present this material at this workshop even though it has been presented elsewhere. Topics covered include: essential on-line analysis requirements; on-line analysis capabilities; on-line analysis software; frequency domain procedures; controller performance evaluation frequency-domain flutter suppression; and plant determination.

High-Frequency Nanocapacitor Arrays: Concept, Recent Developments, and Outlook.

PubMed

Lemay, Serge G; Laborde, Cecilia; Renault, Christophe; Cossettini, Andrea; Selmi, Luca; Widdershoven, Frans P

2016-10-18

We have developed a measurement platform for performing high-frequency AC detection at nanoelectrodes. The system consists of 65 536 electrodes (diameter 180 nm) arranged in a sub-micrometer rectangular array. The electrodes are actuated at frequencies up to 50 MHz, and the resulting AC current response at each separately addressable electrode is measured in real time. These capabilities are made possible by fabricating the electrodes on a complementary metal-oxide-semiconductor (CMOS) chip together with the associated control and readout electronics, thus minimizing parasitic capacitance and maximizing the signal-to-noise ratio. This combination of features offers several advantages for a broad range of experiments. First, in contrast to alternative CMOS-based electrical systems based on field-effect detection, high-frequency operation is sensitive beyond the electrical double layer and can probe entities at a range of micrometers in electrolytes with high ionic strength such as water at physiological salt concentrations. Far from being limited to single- or few-channel recordings like conventional electrochemical impedance spectroscopy, the massively parallel design of the array permits electrically imaging micrometer-scale entities with each electrode serving as a separate pixel. This allows observation of complex kinetics in heterogeneous environments, for example, the motion of living cells on the surface of the array. This imaging aspect is further strengthened by the ability to distinguish between analyte species based on the sign and magnitude of their AC response. Finally, we show here that sensitivity down to the attofarad level combined with the small electrode size permits detection of individual 28 nm diameter particles as they land on the sensor surface. Interestingly, using finite-element methods, it is also possible to calculate accurately the full three-dimensional electric field and current distributions during operation at the level of the Poisson-Nernst-Planck formalism. This makes it possible to validate the interpretation of measurements and to optimize the design of future experiments. Indeed, the complex frequency and spatial dependence of the data suggests that experiments to date have only scratched the surface of the method's capabilities. Future iterations of the hardware will take advantage of the higher frequencies, higher electrode packing densities and smaller electrode sizes made available by continuing advances in CMOS manufacturing. Combined with targeted immobilization of targets at the electrodes, we anticipate that it will soon be possible to realize complex biosensors based on spatial- and time-resolved nanoscale impedance detection.

Preliminary design approach for large high precision segmented reflectors

NASA Technical Reports Server (NTRS)

Mikulas, Martin M., Jr.; Collins, Timothy J.; Hedgepeth, John M.

1990-01-01

A simplified preliminary design capability for erectable precision segmented reflectors is presented. This design capability permits a rapid assessment of a wide range of reflector parameters as well as new structural concepts and materials. The preliminary design approach was applied to a range of precision reflectors from 10 meters to 100 meters in diameter while considering standard design drivers. The design drivers considered were: weight, fundamental frequency, launch packaging volume, part count, and on-orbit assembly time. For the range of parameters considered, on-orbit assembly time was identified as the major design driver. A family of modular panels is introduced which can significantly reduce the number of reflector parts and the on-orbit assembly time.

Developing High-Frequency Quantitative Ultrasound Techniques to Characterize Three-Dimensional Engineered Tissues

NASA Astrophysics Data System (ADS)

Mercado, Karla Patricia E.

Tissue engineering holds great promise for the repair or replacement of native tissues and organs. Further advancements in the fabrication of functional engineered tissues are partly dependent on developing new and improved technologies to monitor the properties of engineered tissues volumetrically, quantitatively, noninvasively, and nondestructively over time. Currently, engineered tissues are evaluated during fabrication using histology, biochemical assays, and direct mechanical tests. However, these techniques destroy tissue samples and, therefore, lack the capability for real-time, longitudinal monitoring. The research reported in this thesis developed nondestructive, noninvasive approaches to characterize the structural, biological, and mechanical properties of 3-D engineered tissues using high-frequency quantitative ultrasound and elastography technologies. A quantitative ultrasound technique, using a system-independent parameter known as the integrated backscatter coefficient (IBC), was employed to visualize and quantify structural properties of engineered tissues. Specifically, the IBC was demonstrated to estimate cell concentration and quantitatively detect differences in the microstructure of 3-D collagen hydrogels. Additionally, the feasibility of an ultrasound elastography technique called Single Tracking Location Acoustic Radiation Force Impulse (STL-ARFI) imaging was demonstrated for estimating the shear moduli of 3-D engineered tissues. High-frequency ultrasound techniques can be easily integrated into sterile environments necessary for tissue engineering. Furthermore, these high-frequency quantitative ultrasound techniques can enable noninvasive, volumetric characterization of the structural, biological, and mechanical properties of engineered tissues during fabrication and post-implantation.

Advanced radiometric and interferometric milimeter-wave scene simulations

NASA Technical Reports Server (NTRS)

Hauss, B. I.; Moffa, P. J.; Steele, W. G.; Agravante, H.; Davidheiser, R.; Samec, T.; Young, S. K.

1993-01-01

Smart munitions and weapons utilize various imaging sensors (including passive IR, active and passive millimeter-wave, and visible wavebands) to detect/identify targets at short standoff ranges and in varied terrain backgrounds. In order to design and evaluate these sensors under a variety of conditions, a high-fidelity scene simulation capability is necessary. Such a capability for passive millimeter-wave scene simulation exists at TRW. TRW's Advanced Radiometric Millimeter-Wave Scene Simulation (ARMSS) code is a rigorous, benchmarked, end-to-end passive millimeter-wave scene simulation code for interpreting millimeter-wave data, establishing scene signatures and evaluating sensor performance. In passive millimeter-wave imaging, resolution is limited due to wavelength and aperture size. Where high resolution is required, the utility of passive millimeter-wave imaging is confined to short ranges. Recent developments in interferometry have made possible high resolution applications on military platforms. Interferometry or synthetic aperture radiometry allows the creation of a high resolution image with a sparsely filled aperture. Borrowing from research work in radio astronomy, we have developed and tested at TRW scene reconstruction algorithms that allow the recovery of the scene from a relatively small number of spatial frequency components. In this paper, the TRW modeling capability is described and numerical results are presented.

Radio Frequency Identification and Motion-sensitive Video Efficiently Automate Recording of Unrewarded Choice Behavior by Bumblebees

PubMed Central

Orbán, Levente L.; Plowright, Catherine M.S.

2014-01-01

We present two methods for observing bumblebee choice behavior in an enclosed testing space. The first method consists of Radio Frequency Identification (RFID) readers built into artificial flowers that display various visual cues, and RFID tags (i.e., passive transponders) glued to the thorax of bumblebee workers. The novelty in our implementation is that RFID readers are built directly into artificial flowers that are capable of displaying several distinct visual properties such as color, pattern type, spatial frequency (i.e., “busyness” of the pattern), and symmetry (spatial frequency and symmetry were not manipulated in this experiment). Additionally, these visual displays in conjunction with the automated systems are capable of recording unrewarded and untrained choice behavior. The second method consists of recording choice behavior at artificial flowers using motion-sensitive high-definition camcorders. Bumblebees have number tags glued to their thoraces for unique identification. The advantage in this implementation over RFID is that in addition to observing landing behavior, alternate measures of preference such as hovering and antennation may also be observed. Both automation methods increase experimental control, and internal validity by allowing larger scale studies that take into account individual differences. External validity is also improved because bees can freely enter and exit the testing environment without constraints such as the availability of a research assistant on-site. Compared to human observation in real time, the automated methods are more cost-effective and possibly less error-prone. PMID:25489677

Radio Frequency Identification and motion-sensitive video efficiently automate recording of unrewarded choice behavior by bumblebees.

PubMed

Orbán, Levente L; Plowright, Catherine M S

2014-11-15

We present two methods for observing bumblebee choice behavior in an enclosed testing space. The first method consists of Radio Frequency Identification (RFID) readers built into artificial flowers that display various visual cues, and RFID tags (i.e., passive transponders) glued to the thorax of bumblebee workers. The novelty in our implementation is that RFID readers are built directly into artificial flowers that are capable of displaying several distinct visual properties such as color, pattern type, spatial frequency (i.e., "busyness" of the pattern), and symmetry (spatial frequency and symmetry were not manipulated in this experiment). Additionally, these visual displays in conjunction with the automated systems are capable of recording unrewarded and untrained choice behavior. The second method consists of recording choice behavior at artificial flowers using motion-sensitive high-definition camcorders. Bumblebees have number tags glued to their thoraces for unique identification. The advantage in this implementation over RFID is that in addition to observing landing behavior, alternate measures of preference such as hovering and antennation may also be observed. Both automation methods increase experimental control, and internal validity by allowing larger scale studies that take into account individual differences. External validity is also improved because bees can freely enter and exit the testing environment without constraints such as the availability of a research assistant on-site. Compared to human observation in real time, the automated methods are more cost-effective and possibly less error-prone.

How well can we measure the vertical wind speed? Implications for fluxes of energy and mass

Treesearch

John Kochendorfer; Tilden P. Meyers; John Frank; William J. Massman; Mark W. Heuer

2012-01-01

Sonic anemometers are capable of measuring the wind speed in all three dimensions at high frequencies (10­50 Hz), and are relied upon to estimate eddy-covariance-based fluxes of mass and energy over a wide variety of surfaces and ecosystems. In this study, wind-velocity measurement errors from a three-dimensional sonic anemometer with a nonorthogonal transducer...

Sensing Challenges for Controls and PHM in the Hostile Operating Conditions of Modern Turbine Engine (Postprint)

DTIC Science & Technology

2008-07-01

SUBJECT TERMS Gas turbine, sensors, Hostile Operating Conditions, FADEC , High Temperature Regimes for Sensors, Sensor Needs, Turbine Engine...Authority Digital Engine Control ( FADEC ). The frequency and bandwidth capability of sensors for engine control are drastically different for each sensor...metering valve assembly is responsive to electrical signals generated by the FADEC in response to sensors that measure turbine speed, pressure

Test Results From a Simulated High-Voltage Lunar Power Transmission Line

NASA Technical Reports Server (NTRS)

Birchenough, Arthur; Hervol, David

2008-01-01

The Alternator Test Unit (ATU) in the Lunar Power System Facility (LPSF) located at the NASA Glenn Research Center (GRC) in Cleveland, Ohio was modified to simulate high-voltage transmission capability. The testbed simulated a 1 km transmission cable length from the ATU to the LPSF using resistors and inductors installed between the distribution transformers. Power factor correction circuitry was used to compensate for the reactance of the distribution system to improve the overall power factor. This test demonstrated that a permanent magnet alternator can successfully provide high-frequency ac power to a lunar facility located at a distance.

Test Results from a Simulated High Voltage Lunar Power Transmission Line

NASA Technical Reports Server (NTRS)

Birchenough, Arthur; Hervol, David

2008-01-01

The Alternator Test Unit (ATU) in the Lunar Power System Facility (LPSF) located at the NASA Glenn Research Center (GRC) in Cleveland, OH was modified to simulate high voltage transmission capability. The testbed simulated a 1 km transmission cable length from the ATU to the LPSF using resistors and inductors installed between the distribution transformers. Power factor correction circuitry was used to compensate for the reactance of the distribution system to improve the overall power factor. This test demonstrated that a permanent magnet alternator can successfully provide high frequency AC power to a lunar facility located at a distance.

Unique capabilities of AC frequency scanning and its implementation on a Mars Organic Molecule Analyzer linear ion trap.

PubMed

Snyder, Dalton T; Kaplan, Desmond A; Danell, Ryan M; van Amerom, Friso H W; Pinnick, Veronica T; Brinckerhoff, William B; Mahaffy, Paul R; Cooks, R Graham

2017-06-21

A limitation of conventional quadrupole ion trap scan modes which use rf amplitude control for mass scanning is that, in order to detect a subset of an ion population, the rest of the ion population must also be interrogated. That is, ions cannot be detected out of order; they must be detected in order of either increasing or decreasing mass-to-charge (m/z). However, an ion trap operated in the ac frequency scan mode, where the rf amplitude is kept constant and instead the ac frequency is used for mass-selective operations, has no such limitation because any variation in the ac frequency affects only the subset of ions whose secular frequencies match the perturbation frequency. Hence, an ion trap operated in the ac frequency scan mode can perform any arbitrary mass scan, as well as a sequence of scans, using a single ion injection; we demonstrate both capabilities here. Combining these two capabilities, we demonstrate the acquisition of a full mass spectrum, a product ion spectrum, and a second generation product ion spectrum using a single ion injection event. We further demonstrate a "segmented scan" in which different mass ranges are interrogated at different rf amplitudes in order to improve resolution over a portion of the mass range, and a "periodic scan" in which ions are continuously introduced into the ion trap to achieve a nearly 100% duty cycle. These unique scan modes, along with other characteristics of ac frequency scanning, are particularly appropriate for miniature ion trap mass spectrometers. Hence, implementation of ac frequency scanning on a prototype of the Mars Organic Molecule Analyzer mass spectrometer is also described.

Coherent X-ray beam metrology using 2D high-resolution Fresnel-diffraction analysis.

PubMed

Ruiz-Lopez, M; Faenov, A; Pikuz, T; Ozaki, N; Mitrofanov, A; Albertazzi, B; Hartley, N; Matsuoka, T; Ochante, Y; Tange, Y; Yabuuchi, T; Habara, T; Tanaka, K A; Inubushi, Y; Yabashi, M; Nishikino, M; Kawachi, T; Pikuz, S; Ishikawa, T; Kodama, R; Bleiner, D

2017-01-01

Direct metrology of coherent short-wavelength beamlines is important for obtaining operational beam characteristics at the experimental site. However, since beam-time limitation imposes fast metrology procedures, a multi-parametric metrology from as low as a single shot is desirable. Here a two-dimensional (2D) procedure based on high-resolution Fresnel diffraction analysis is discussed and applied, which allowed an efficient and detailed beamline characterization at the SACLA XFEL. So far, the potential of Fresnel diffraction for beamline metrology has not been fully exploited because its high-frequency fringes could be only partly resolved with ordinary pixel-limited detectors. Using the high-spatial-frequency imaging capability of an irradiated LiF crystal, 2D information of the coherence degree, beam divergence and beam quality factor M 2 were retrieved from simple diffraction patterns. The developed beam metrology was validated with a laboratory reference laser, and then successfully applied at a beamline facility, in agreement with the source specifications.

Frequency Rectification Applied to Piezoelectric Energy Harvesting and Improving Available Power of Piezoelectric Motors

NASA Astrophysics Data System (ADS)

Kuroda, Kazuaki; LCGT Collaboration

Piezoelectric materials are just now, within the last decade, coming into their own as a commercial material. Capable of converting energy from the mechanical domain to the electrical domain; piezos are ideal sensors, vibration dampers, energy harvesters, and actuators. Frequency rectification, or the conversion of small, high frequency piezoelectric vibrations into useful low frequency actuation, is required to obtain widespread industrial use of piezoelectric devices. This work examines three manifestations of piezoelectric frequency rectification: energy harvesting, a hydraulic motor, and friction based commercial-off-the-shelf motors. An energy harvesting device is developed, manufactured, and tested in this work, resulting in the development of a high Energy Density (J/m 3), high Power Density (W/m3) energy harvester. The device is shown to have an Energy Density nearly twice that of a similar conventional energy harvesting device. The result of this work is the development of an energy harvesting system that generates more energy in a given volume of piezoelectric material, opening the possibility of miniaturization of energy harvesting devices. Also presented is an effort to integrate a high frequency, high flow rate micromachined valve array into a PiezoHydraulic Pump (PHP), enabling resonant operation of the PHP. Currently, the device is limited by the resonant frequency of the proprietary passive check valves. The PHP is fully characterized, and the microvalve array is tested to determine its resonant frequency in a fluid medium. The valve testing resulted in a resonant frequency of 6.9 kHz, slightly lower than the target operating frequency of 10 kHz. Finally, the results of an examination of frequency rectification as applied to COTS piezoelectric motors are presented. Currently, motors are almost universally characterized based upon their available mechanical power. A better comparison is one based upon the actual Energy Density of the piezoelectric material utilized in the motor compared to the theoretical maximum Energy Density under the motor operating conditions (i.e., frequency, applied electric field). The result of this work is a more descriptive metric to evaluate piezoelectric motors that provides information on the effectiveness of the motor drive train; that is, how effectively the motion of the piezoelectric is transferred to the outside world.

Research on fast algorithm of small UAV navigation in non-linear matrix reductionism method

NASA Astrophysics Data System (ADS)

Zhang, Xiao; Fang, Jiancheng; Sheng, Wei; Cao, Juanjuan

2008-10-01

The low Reynolds numbers of small UAV will result in unfavorable aerodynamic conditions to support controlled flight. And as operated near ground, the small UAV will be affected seriously by low-frequency interference caused by atmospheric disturbance. Therefore, the GNC system needs high frequency of attitude estimation and control to realize the steady of the UAV. In company with the dimensional of small UAV dwindling away, its GNC system is more and more taken embedded designing technology to reach the purpose of compactness, light weight and low power consumption. At the same time, the operational capability of GNC system also gets limit in a certain extent. Therefore, a kind of high speed navigation algorithm design becomes the imminence demand of GNC system. Aiming at such requirement, a kind of non-linearity matrix reduction approach is adopted in this paper to create a new high speed navigation algorithm which holds the radius of meridian circle and prime vertical circle as constant and linearizes the position matrix calculation formulae of navigation equation. Compared with normal navigation algorithm, this high speed navigation algorithm decreases 17.3% operand. Within small UAV"s mission radius (20km), the accuracy of position error is less than 0.13m. The results of semi-physical experiments and small UAV's auto pilot testing proved that this algorithm can realize high frequency attitude estimation and control. It will avoid low-frequency interference caused by atmospheric disturbance properly.

Environmental and reliability test of FBG based geophone as geophysical exploration instrument

NASA Astrophysics Data System (ADS)

Zhang, Xiaolei; Min, Li; Li, Ming; Jiang, Shaodong; Zhang, Faxiang; Sun, Zhihui; Ni, Jiasheng; Peng, Gangding; Wang, Chang

2017-10-01

A fiber Bragg grating (FBG) based geophone is designed for low-frequency signal detection has high acceleration response of about 60 dB re pm/g in a low frequency range of 5 Hz 60 Hz. To Guarantee normal operation in field test and practical application, an acceleration amplitude restriction is added in the mechanical design of the FBG geophone. Then a series of environmental and reliability test have been proceeded with online or offline monitoring of its working performance, including high and low temperature test, vibration test, shock test and free drop test. All the tests are planned according to National standard or Oil & Gas Industry Standard. And the experimental results indicate that our FBG geophone meet the criterion of oil and gas industry product and is capable of field application.

Broadband active electrically small superconductor antennas

NASA Astrophysics Data System (ADS)

Kornev, V. K.; Kolotinskiy, N. V.; Sharafiev, A. V.; Soloviev, I. I.; Mukhanov, O. A.

2017-10-01

A new type of broadband active electrically small antenna (ESA) based on superconducting quantum arrays (SQAs) has been proposed and developed. These antennas are capable of providing both sensing and amplification of broadband electromagnetic signals with a very high spurious-free dynamic range (SFDR)—up to 100 dB (and even more)—with high sensitivity. The frequency band can range up to tens of gigahertz, depending on Josephson junction characteristic frequency, set by fabrication. In this paper we review theoretical and experimental studies of SQAs and SQA-based antenna prototypes of both transformer and transformer-less types. The ESA prototypes evaluated were fabricated using a standard Nb process with critical current density 4.5 kA cm-2. Measured device characteristics, design issues and comparative analysis of various ESA types, as well as requirements for interfaces, are reviewed and discussed.

A Low Cost Traveling Wave Tube for Wireless Communications

NASA Technical Reports Server (NTRS)

Vancil, Bernard Kenneth; Wintucky, Edwin G.; Williams, W. D. (Technical Monitor)

2002-01-01

Demand for high data rate wireless communications is pushing up amplifier power, bandwidth and frequency requirements. Some systems are using vacuum electron devices again because solid-state power amplifiers are not able to efficiently meet the new requirements. The traveling wave tube is the VED of choice because of its excellent broadband capability as well as high power efficiency and frequency. But TWTs are very expensive on a per watt basis below about 200 watts of output power. We propose a new traveling wave tube that utilizes cathode ray tube construction technology and electrostatic focusing. We believe the tube can be built in quantity for under $1,000 each. We discuss several traveling wave tube slow wave circuits that lend themselves to the new construction. We will present modeling results and data on prototype devices.

Millimeter wave sensor for monitoring effluents

DOEpatents

Gopalsami, Nachappa; Bakhtiari, Sasan; Raptis, Apostolos C.; Dieckman, Stephen L.

1995-01-01

A millimeter-wave sensor for detecting and measuring effluents from processing plants either remotely or on-site includes a high frequency signal source for transmitting frequency-modulated continuous waves in the millimeter or submillimeter range with a wide sweep capability and a computer-controlled detector for detecting a plurality of species of effluents on a real time basis. A high resolution spectrum of an effluent, or effluents, is generated by a deconvolution of the measured spectra resulting in a narrowing of the line widths by 2 or 3 orders of magnitude as compared with the pressure broadened spectra detected at atmospheric pressure for improved spectral specificity and measurement sensitivity. The sensor is particularly adapted for remote monitoring such as where access is limited or sensor cost restricts multiple sensors as well as for large area monitoring under nearly all weather conditions.

Fast and High Dynamic Range Imaging with Superconducting Tunnel Junction Detectors

NASA Astrophysics Data System (ADS)

Matsuo, Hiroshi

2014-08-01

We have demonstrated a combined test of the submillimeter-wave SIS photon detectors and GaAs-JFET cryogenic integrated circuits. A relatively large background photo-current can be read out by fast-reset integrating amplifiers. An integration time of 1 ms enables fast frame rate readout and large dynamic range imaging, with an expected dynamic range of 8,000 in 1 ms. Ultimate fast and high dynamic range performance of superconducting tunnel junction detectors (STJ) will be obtained when photon counting capabilities are employed. In the terahertz frequencies, when input photon rate of 100 MHz is measured, the photon bunching gives us enough timing resolution to be used as phase information of intensity fluctuation. Application of photon statistics will be a new tool in the terahertz frequency region. The design parameters of STJ terahertz photon counting detectors are discussed.

Non-line-of-sight (NLOS), secure, low-probability of intercept (LPI), antijam (AJ), high frequency (HF), real time video communication system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lupinetti, F.

1988-01-01

This paper outlines a video communication system capable of non-line-of-sight (NLOS), secure, low-probability of intercept (LPI), antijam, real time transmission and reception of video information in a tactical enviroment. An introduction to a class of ternary PN sequences is presented to familiarize the reader with yet another avenue for spreading and despreading baseband information. The use of the high frequency (HF) band (1.5 to 30 MHz) for real time video transmission is suggested to allow NLOS communication. The spreading of the baseband information by means of multiple nontrivially different ternary pseudonoise (PN) sequence is used in order to assure encryptionmore » of the signal, enhanced security, a good degree of LPI, and good antijam features. 18 refs., 3 figs., 1 tab.« less

Fast and low-cost structured light pattern sequence projection.

PubMed

Wissmann, Patrick; Forster, Frank; Schmitt, Robert

2011-11-21

We present a high-speed and low-cost approach for structured light pattern sequence projection. Using a fast rotating binary spatial light modulator, our method is potentially capable of projection frequencies in the kHz domain, while enabling pattern rasterization as low as 2 μm pixel size and inherently linear grayscale reproduction quantized at 12 bits/pixel or better. Due to the circular arrangement of the projected fringe patterns, we extend the widely used ray-plane triangulation method to ray-cone triangulation and provide a detailed description of the optical calibration procedure. Using the proposed projection concept in conjunction with the recently published coded phase shift (CPS) pattern sequence, we demonstrate high accuracy 3-D measurement at 200 Hz projection frequency and 20 Hz 3-D reconstruction rate. © 2011 Optical Society of America

Multi-point measurement using two-channel reflectometer with antenna switching for study of high-frequency fluctuations in GAMMA 10

NASA Astrophysics Data System (ADS)

Ikezoe, R.; Ichimura, M.; Okada, T.; Itagaki, J.; Hirata, M.; Sumida, S.; Jang, S.; Izumi, K.; Tanaka, A.; Yoshikawa, M.; Kohagura, J.; Sakamoto, M.; Nakashima, Y.

2017-03-01

A two-channel microwave reflectometer system with fast microwave antenna switching capability was developed and applied to the GAMMA 10 tandem mirror device to study high-frequency small-amplitude fluctuations in a hot mirror plasma. The fast switching of the antennas is controlled using PIN diode switches, which offers the significant advantage of reducing the number of high-cost microwave components and digitizers with high bandwidths and large memory that are required to measure the spatiotemporal behavior of the high-frequency fluctuations. The use of two channels rather than one adds the important function of a simultaneous two-point measurement in either the radial direction or the direction of the antenna array to measure the phase profile of the fluctuations along with the normal amplitude profile. The density fluctuations measured using this system clearly showed the high-frequency coherent fluctuations that are associated with Alfvén-ion-cyclotron (AIC) waves in GAMMA 10. A correlation analysis applied to simultaneously measured density fluctuations showed that the phase component that was included in a reflected microwave provided both high coherence and a clear phase difference for the AIC waves, while the amplitude component showed neither significant coherence nor clear phase difference. The axial phase differences of the AIC waves measured inside the hot plasma confirmed the formation of a standing wave structure. The axial variation of the radial profiles was evaluated and a clear difference was found among the AIC waves for the first time, which would be a key to clarify the unknown boundary conditions of the AIC waves.

A Technique for Real-Time Ionospheric Ranging Error Correction Based On Radar Dual-Frequency Detection

NASA Astrophysics Data System (ADS)

Lyu, Jiang-Tao; Zhou, Chen

2017-12-01

Ionospheric refraction is one of the principal error sources for limiting the accuracy of radar systems for space target detection. High-accuracy measurement of the ionospheric electron density along the propagation path of radar wave is the most important procedure for the ionospheric refraction correction. Traditionally, the ionospheric model and the ionospheric detection instruments, like ionosonde or GPS receivers, are employed for obtaining the electron density. However, both methods are not capable of satisfying the requirements of correction accuracy for the advanced space target radar system. In this study, we propose a novel technique for ionospheric refraction correction based on radar dual-frequency detection. Radar target range measurements at two adjacent frequencies are utilized for calculating the electron density integral exactly along the propagation path of the radar wave, which can generate accurate ionospheric range correction. The implementation of radar dual-frequency detection is validated by a P band radar located in midlatitude China. The experimental results present that the accuracy of this novel technique is more accurate than the traditional ionospheric model correction. The technique proposed in this study is very promising for the high-accuracy radar detection and tracking of objects in geospace.

A high-power synthesized ultrawideband radiation source

NASA Astrophysics Data System (ADS)

Efremov, A. M.; Koshelev, V. I.; Plisko, V. V.; Sevostyanov, E. A.

2017-09-01

A high-power ultrawideband radiation source has been developed which is capable of synthesizing electromagnetic pulses with different frequency bands in free space. To this end, a new circuit design comprising a four-channel former of bipolar pulses of durations 2 and 3 ns has been elaborated and conditions for the stable operation of gas gaps of independent channels without external control pulses have been determined. Each element of the 2 × 2 array of combined antennas is driven from an individual channel of the pulse former. Antennas excited by pulses of the same duration are arranged diagonally. Two radiation synthesis modes have been examined: one aimed to attain ultimate field strength and the other aimed to attain an ultimate width of the radiation spectrum. The modes were changed by changing the time delay between the 2-ns and 3-ns pulses. For the first mode, radiation pulses with a frequency band of 0.2-0.8 GHz and an effective potential of 500 kV have been obtained. The synthesized radiation pulses produced in the second mode had an extended frequency band (0.1-1 GHz) and an effective potential of 220 kV. The pulse repetition frequency was 100 Hz.

Plasma characteristics of argon glow discharge produced by AC power supply operating at low frequencies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kongpiboolkid, Watcharapon; Mongkolnavin, Rattachat; Plasma Technology and Nuclear Fusion Research Unit, Chulalongkorn University, Bangkok

2015-04-24

Non-thermal properties of Argon glow discharge operating with various operating pressures were measured and presented in this work. The Argon plasma is produced by a parallel conducting electrodes coupling with a high voltage AC power supply. The power supply can generate high AC voltage at various frequencies. The frequencies for the operation are in the range of a few kHz. The system is capable of generating electric field between the two metal electrodes discharge system. The characteristics of plasma produced were measured by optical emission spectroscopy (OES) technique where electron temperature (T{sub e}) and electron number density (n{sub e}) canmore » be determined by line intensity ratio method. The value of electron number density was then determined from the Saha-Eggert equation. Our results show that the electron number density of the discharge obtained is of the order of 10{sup −17} − 10{sup −18} m{sup −3} where the electron temperature is between 1.00−2.00 eV for various operating frequencies used which are in good agreement with similar results published earlier.« less

Quadrature mixture LO suppression via DSW DAC noise dither

DOEpatents

Dubbert, Dale F [Cedar Crest, NM; Dudley, Peter A [Albuquerque, NM

2007-08-21

A Quadrature Error Corrected Digital Waveform Synthesizer (QECDWS) employs frequency dependent phase error corrections to, in effect, pre-distort the phase characteristic of the chirp to compensate for the frequency dependent phase nonlinearity of the RF and microwave subsystem. In addition, the QECDWS can employ frequency dependent correction vectors to the quadrature amplitude and phase of the synthesized output. The quadrature corrections cancel the radars' quadrature upconverter (mixer) errors to null the unwanted spectral image. A result is the direct generation of an RF waveform, which has a theoretical chirp bandwidth equal to the QECDWS clock frequency (1 to 1.2 GHz) with the high Spurious Free Dynamic Range (SFDR) necessary for high dynamic range radar systems such as SAR. To correct for the problematic upconverter local oscillator (LO) leakage, precision DC offsets can be applied over the chirped pulse using a pseudo-random noise dither. The present dither technique can effectively produce a quadrature DC bias which has the precision required to adequately suppress the LO leakage. A calibration technique can be employed to calculate both the quadrature correction vectors and the LO-nulling DC offsets using the radar built-in test capability.

The artificial retina processor for track reconstruction at the LHC crossing rate

DOE PAGES

Abba, A.; Bedeschi, F.; Citterio, M.; ...

2015-03-16

We present results of an R&D study for a specialized processor capable of precisely reconstructing, in pixel detectors, hundreds of charged-particle tracks from high-energy collisions at 40 MHz rate. We apply a highly parallel pattern-recognition algorithm, inspired by studies of the processing of visual images by the brain as it happens in nature, and describe in detail an efficient hardware implementation in high-speed, high-bandwidth FPGA devices. This is the first detailed demonstration of reconstruction of offline-quality tracks at 40 MHz and makes the device suitable for processing Large Hadron Collider events at the full crossing frequency.

Wide Tuning Capability for Spacecraft Transponders

NASA Technical Reports Server (NTRS)

Lux, James; Mysoor, Narayan; Shah, Biren; Cook, Brian; Smith, Scott

2007-01-01

A document presents additional information on the means of implementing a capability for wide tuning of microwave receiver and transmitter frequencies in the development reported in the immediately preceding article, VCO PLL Frequency Synthesizers for Spacecraft Transponders (NPO- 42909). The reference frequency for a PLL-based frequency synthesizer is derived from a numerically controlled oscillator (NCO) implemented in digital logic, such that almost any reference frequency can be derived from a fixed crystal reference oscillator with microhertz precision. The frequency of the NCO is adjusted to track the received signal, then used to create another NCO frequency used to synthesize the transmitted signal coherent with, and at a specified frequency ratio to, the received signal. The frequencies can be changed, even during operation, through suitable digital programming. The NCOs and the related tracking loops and coherent turnaround logic are implemented in a field-programmable gate array (FPGA). The interface between the analog microwave receiver and transmitter circuits and the FPGA includes analog-to-digital and digital-toanalog converters, the sampling rates of which are chosen to minimize spurious signals and otherwise optimize performance. Several mixers and filters are used to properly route various signals.

Multi-frequency electrical impedance tomography as a non-invasive tool to characterize and monitor crop root systems

NASA Astrophysics Data System (ADS)

Weigand, Maximilian; Kemna, Andreas

2017-02-01

A better understanding of root-soil interactions and associated processes is essential in achieving progress in crop breeding and management, prompting the need for high-resolution and non-destructive characterization methods. To date, such methods are still lacking or restricted by technical constraints, in particular the charactization and monitoring of root growth and function in the field. A promising technique in this respect is electrical impedance tomography (EIT), which utilizes low-frequency (< 1 kHz)- electrical conduction- and polarization properties in an imaging framework. It is well established that cells and cell clusters exhibit an electrical polarization response in alternating electric-current fields due to electrical double layers which form at cell membranes. This double layer is directly related to the electrical surface properties of the membrane, which in turn are influenced by nutrient dynamics (fluxes and concentrations on both sides of the membranes). Therefore, it can be assumed that the electrical polarization properties of roots are inherently related to ion uptake and translocation processes in the root systems. We hereby propose broadband (mHz to hundreds of Hz) multi-frequency EIT as a non-invasive methodological approach for the monitoring and physiological, i.e., functional, characterization of crop root systems. The approach combines the spatial-resolution capability of an imaging method with the diagnostic potential of electrical-impedance spectroscopy. The capability of multi-frequency EIT to characterize and monitor crop root systems was investigated in a rhizotron laboratory experiment, in which the root system of oilseed plants was monitored in a water-filled rhizotron, that is, in a nutrient-deprived environment. We found a low-frequency polarization response of the root system, which enabled the successful delineation of its spatial extension. The magnitude of the overall polarization response decreased along with the physiological decay of the root system due to the stress situation. Spectral polarization parameters, as derived from a pixel-based Debye decomposition analysis of the multi-frequency imaging results, reveal systematic changes in the spatial and spectral electrical response of the root system. In particular, quantified mean relaxation times (of the order of 10 ms) indicate changes in the length scales on which the polarization processes took place in the root system, as a response to the prolonged induced stress situation. Our results demonstrate that broadband EIT is a capable, non-invasive method to image root system extension as well as to monitor changes associated with the root physiological processes. Given its applicability on both laboratory and field scales, our results suggest an enormous potential of the method for the structural and functional imaging of root systems for various applications. This particularly holds for the field scale, where corresponding methods are highly desired but to date are lacking.

Modal Ring Method for the Scattering of Electromagnetic Waves

NASA Technical Reports Server (NTRS)

Baumeister, Kenneth J.; Kreider, Kevin L.

1993-01-01

The modal ring method for electromagnetic scattering from perfectly electric conducting (PEC) symmetrical bodies is presented. The scattering body is represented by a line of finite elements (triangular) on its outer surface. The infinite computational region surrounding the body is represented analytically by an eigenfunction expansion. The modal ring method effectively reduces the two dimensional scattering problem to a one-dimensional problem similar to the method of moments. The modal element method is capable of handling very high frequency scattering because it has a highly banded solution matrix.

Hydraulic Actuator System for Rotor Control

NASA Technical Reports Server (NTRS)

Ulbrich, Heinz; Althaus, Josef

1991-01-01

In the last ten years, several different types of actuators were developed and fabricated for active control of rotors. A special hydraulic actuator system capable of generating high forces to rotating shafts via conventional bearings is addressed. The actively controlled hydraulic force actuator features an electrohydraulic servo valve which can produce amplitudes and forces at high frequencies necessary for influencing rotor vibrations. The mathematical description will be given in detail. The experimental results verify the theoretical model. Simulations already indicate the usefulness of this compact device for application to a real rotor system.

An Airborne Conical Scanning Millimeter-Wave Imaging Radiometer (CoSMIR)

NASA Technical Reports Server (NTRS)

Piepmeier, J.; Racette, P.; Wang, J.; Crites, A.; Doiron, T.; Engler, C.; Lecha, J.; Powers, M.; Simon, E.; Triesky, M.;

a Micro-Uav with the Capability of Direct Georeferencing

NASA Astrophysics Data System (ADS)

Rehak, M.; Mabillard, R.; Skaloud, J.

2013-08-01

This paper presents the development of a low cost UAV (Unmanned Aerial Vehicle) with the capability of direct georeferencing. The advantage of such system lies in its high maneuverability, operation flexibility as well as capability to acquire image data without the need of establishing ground control points (GCPs). Moreover, the precise georeferencing offers an improvement in the final mapping accuracy when employing integrated sensor orientation. Such mode of operation limits the number and distribution of GCPs, which in turns save time in their signalization and surveying. Although the UAV systems feature high flexibility and capability of flying into areas that are inhospitable or inaccessible to humans, the lack of precision in positioning and attitude estimation on-board decrease the gained value of the captured imagery and limits their mode of operation to specific configurations and need of groundreference. Within a scope of this study we show the potential of present technologies in the field of position and orientation determination on a small UAV. The hardware implementation and especially the non-trivial synchronization of all components is clarified. Thanks to the implementation of a multi-frequency, low power GNSS receiver and its coupling with redundant MEMSIMU, we can attain the characteristic of a much larger systems flown on large carries while keeping the sensor size and weight suitable for MAV operations.

Modeling tools for the assessment of microbiological risks during floods: a review

NASA Astrophysics Data System (ADS)

Collender, Philip; Yang, Wen; Stieglitz, Marc; Remais, Justin

2015-04-01

Floods are a major, recurring source of harm to global economies and public health. Projected increases in the frequency and intensity of heavy precipitation events under future climate change, coupled with continued urbanization in areas with high risk of floods, may exacerbate future impacts of flooding. Improved flood risk management is essential to support global development, poverty reduction and public health, and is likely to be a crucial aspect of climate change adaptation. Importantly, floods can facilitate the transmission of waterborne pathogens by changing social conditions (overcrowding among displaced populations, interruption of public health services), imposing physical challenges to infrastructure (sewerage overflow, reduced capacity to treat drinking water), and altering fate and transport of pathogens (transport into waterways from overland flow, resuspension of settled contaminants) during and after flood conditions. Hydrological and hydrodynamic models are capable of generating quantitative characterizations of microbiological risks associated with flooding, while accounting for these diverse and at times competing physical and biological processes. Despite a few applications of such models to the quantification of microbiological risks associated with floods, there exists limited guidance as to the relative capabilities, and limitations, of existing modeling platforms when used for this purpose. Here, we review 17 commonly used flood and water quality modeling tools that have demonstrated or implicit capabilities of mechanistically representing and quantifying microbial risk during flood conditions. We compare models with respect to their capabilities of generating outputs that describe physical and microbial conditions during floods, such as concentration or load of non-cohesive sediments or pathogens, and the dynamics of high flow conditions. Recommendations are presented for the application of specific modeling tools for assessing particular flood-related microbial risks, and model improvements are suggested that may better characterize key microbial risks during flood events. The state of current tools are assessed in the context of a changing climate where the frequency, intensity and duration of flooding are shifting in some areas.

Network Mechanisms Generating Abnormal and Normal Hippocampal High-Frequency Oscillations: A Computational Analysis1,2,3

PubMed Central

Catoni, Nicholas

2015-01-01

Abstract High-frequency oscillations (HFOs) are an intriguing potential biomarker for epilepsy, typically categorized according to peak frequency as either ripples (100–250 Hz) or fast ripples (>250 Hz). In the hippocampus, fast ripples were originally thought to be more specific to epileptic tissue, but it is still very difficult to distinguish which HFOs are caused by normal versus pathological brain activity. In this study, we use a computational model of hippocampus to investigate possible network mechanisms underpinning normal ripples, pathological ripples, and fast ripples. Our results unify several prior findings regarding HFO mechanisms, and also make several new predictions regarding abnormal HFOs. We show that HFOs are generic, emergent phenomena whose characteristics reflect a wide range of connectivity and network input. Although produced by different mechanisms, both normal and abnormal HFOs generate similar ripple frequencies, underscoring that peak frequency is unable to distinguish the two. Abnormal ripples are generic phenomena that arise when input to pyramidal cells overcomes network inhibition, resulting in high-frequency, uncoordinated firing. In addition, fast ripples transiently and sporadically arise from the precise conditions that produce abnormal ripples. Lastly, we show that such abnormal conditions do not require any specific network structure to produce coherent HFOs, as even completely asynchronous activity is capable of producing abnormal ripples and fast ripples in this manner. These results provide a generic, network-based explanation for the link between pathological ripples and fast ripples, and a unifying description for the entire spectrum from normal ripples to pathological fast ripples. PMID:26146658

VCO PLL Frequency Synthesizers for Spacecraft Transponders

NASA Technical Reports Server (NTRS)

Smith, Scott; Mysoor, Narayan; Lux, James; Cook, Brian

2007-01-01

Two documents discuss a breadboard version of advanced transponders that, when fully developed, would be installed on future spacecraft to fly in deep space. These transponders will be required to be capable of operation on any deepspace- communications uplink frequency channel between 7,145 and 7,235 MHz, and any downlink frequency channel between 8,400 and 8,500 MHz. The document focuses on the design and operation of frequency synthesizers for the receiver and transmitter. Heretofore, frequency synthesizers in deep-space transponders have been based on dielectric resonator oscillators (DROs), which do not have the wide tuning bandwidth necessary to tune over all channels in the uplink or downlink frequency bands. To satisfy the requirement for tuning bandwidth, the present frequency synthesizers are based on voltage-controlled-oscillator (VCO) phase-locked loops (PLLs) implemented by use of monolithic microwave integrated circuits (MMICs) implemented using inGaP heterojunction bipolar transistor (HBT) technology. MMIC VCO PLL frequency synthesizers similar to the present ones have been used in commercial and military applications but, until now, have exhibited too much phase noise for use in deep-space transponders. The present frequency synthesizers contain advanced MMIC VCOs, which use HBT technology and have lower levels of flicker (1/f) phase noise. When these MMIC VCOs are used with high-speed MMIC frequency dividers, it becomes possible to obtain the required combination of frequency agility and low phase noise.

Scaling of Yb-Fiber Frequency Combs

NASA Astrophysics Data System (ADS)

Ruehl, Axel; Marcinkevicius, Andrius; Fermann, Martin E.; Hartl, Ingmar

2010-06-01

Immediately after their introduction in 1999, femtosecond laser frequency combs revolutionized the field of precision optical frequency metrology and are key elements in many experiments. Frequency combs based on femtosecond Er-fiber lasers based were demonstrated in 2005, allowing additionally rugged, compact set-ups and reliable unattended long-term operation. The introduction of Yb-fiber technology led to an dramatic improvement in fiber-comb performance in various aspects. Low-noise Yb-fiber femtosecond oscillators enabled a reduction of relative comb tooth linewidth to the sub-Hz level as well as scaling of the fundamental comb spacings up to 1 GHz. This is beneficial for any frequency-domain comb application due to the higher power per comb-mode. Many spectroscopic applications require, however, frequency combs way beyond the wavelength range accessible with broad band laser materials, so nonlinear conversion and hence higher peak intensity is required. We demonstrated power scaling of Yb-fiber frequency combs up to 80 W average power in a strictly linear chirped-pulse amplification schemes compatible with low-noise phase control. These high-power Yb-fiber-frequency combs facilitated not only the extension to the mid-IR spectral region. When coupled to a passive enhancement cavity, the average power can be further scaled to the kW-level opening new capabilities for XUV frequency combs via high-harmonic generation. All these advances of fiber-based frequency combs will trigger many novel applications both in fundamental and applied sciences. Schibli et al., Nature Photonics 2 355 (2008). Hartl et al., MF9 in Advanced Solid-State Photonics. 2009, Optical Society of America. Ruehl et al., AWC7 in Advanced Solid-State Photonics. 2010, Optical Society of America. Adler et al., Optics Letters 34 1330 (2009). Yost et al., Nature Physics 5 815 (2009).

Testing and Development of a Percussive Augmenter for Rotary Drills

NASA Technical Reports Server (NTRS)

Donnelly, Christopher; Bar-Cohen, Yoseph; Chang, Zensheu; Badescu, Mircea; Sherrit, Stewart

2011-01-01

Hammering drills are effective in fracturing the drilled medium while rotary drills remove cuttings. The combination provides a highly effective penetration mechanism. Piezoelectric actuators were integrated into an adapter to produce ultrasonic percussion; augmenting rotary drilling. The drill is capable of operating at low power, low applied force and, with proper tuning, low noise. These characteristics are of great interest for future NASA missions and the construction/remodeling industry. The developed augmenter connects a commercially available drill and bit and was tested to demonstrate its capability. Input power to the drill was read using a multimeter and the augmenter received a separate input voltage. The drive frequency of the piezoelectric actuator was controlled by a hill climb algorithm that optimizes and records average power usage to operate the drill at resonating frequency. Testing the rotary drill and augmenter across a range of combinations with total power constant at 160 Watts has shown results in concrete and limestone samples that are as good as or better than the commercial drill. The drill rate was increased 1.5 to over 10 times when compared to rotation alone.

Current Research in Lidar Technology Used for the Remote Sensing of Atmospheric Aerosols

PubMed Central

Comerón, Adolfo; Muñoz-Porcar, Constantino; Rocadenbosch, Francesc; Rodríguez-Gómez, Alejandro; Sicard, Michaël

2017-01-01

Lidars are active optical remote sensing instruments with unique capabilities for atmospheric sounding. A manifold of atmospheric variables can be profiled using different types of lidar: concentration of species, wind speed, temperature, etc. Among them, measurement of the properties of aerosol particles, whose influence in many atmospheric processes is important but is still poorly stated, stands as one of the main fields of application of current lidar systems. This paper presents a review on fundamentals, technology, methodologies and state-of-the art of the lidar systems used to obtain aerosol information. Retrieval of structural (aerosol layers profiling), optical (backscatter and extinction coefficients) and microphysical (size, shape and type) properties requires however different levels of instrumental complexity; this general outlook is structured following a classification that attends these criteria. Thus, elastic systems (detection only of emitted frequencies), Raman systems (detection also of Raman frequency-shifted spectral lines), high spectral resolution lidars, systems with depolarization measurement capabilities and multi-wavelength instruments are described, and the fundamentals in which the retrieval of aerosol parameters is based is in each case detailed. PMID:28632170

Study of Tissue Phantoms, Tissues, and Contrast Agent with the Biophotoacoustic Radar and Comparison to Ultrasound Imaging for Deep Subsurface Imaging

NASA Astrophysics Data System (ADS)

Alwi, R.; Telenkov, S.; Mandelis, A.; Gu, F.

2012-11-01

In this study, the imaging capability of our wide-spectrum frequency-domain photoacoustic (FD-PA) imaging alias "photoacoustic radar" methodology for imaging of soft tissues is explored. A practical application of the mathematical correlation processing method with relatively long (1 ms) frequency-modulated optical excitation is demonstrated for reconstruction of the spatial location of the PA sources. Image comparison with ultrasound (US) modality was investigated to see the complementarity between the two techniques. The obtained results with a phased array probe on tissue phantoms and their comparison to US images demonstrated that the FD-PA technique has strong potential for deep subsurface imaging with excellent contrast and high signal-to-noise ratio. FD-PA images of blood vessels in a human wrist and an in vivo subcutaneous tumor in a rat model are presented. As in other imaging modalities, the employment of contrast agents is desirable to improve the capability of medical diagnostics. Therefore, this study also evaluated and characterized the use of Food and Drug Administration (FDA)-approved superparamagnetic iron oxide nanoparticles (SPION) as PA contrast agents.

Review of the ionospheric model for the long wave prediction capability. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferguson, J.A.

1992-11-01

The Naval Command, Control and Ocean Surveillance Center's Long Wave Prediction Capability (LWPC) has a built-in ionospheric model. The latter was defined after a review of the literature comparing measurements with calculations. Subsequent to this original specification of the ionospheric model in the LWPC, a new collection of data were obtained and analyzed. The new data were collected aboard a merchant ship named the Callaghan during a series of trans-Atlantic trips over a period of a year. This report presents a detailed analysis of the ionospheric model currently in use by the LWPC and the new model suggested by themore » shipboard measurements. We conclude that, although the fits to measurements are almost the same between the two models examined, the current LWPC model should be used because it is better than the new model for nighttime conditions at long ranges. This conclusion supports the primary use of the LWPC model for coverage assessment that requires a valid model at the limits of a transmitter's reception.... Communications, Very low frequency and low frequency, High voltage, Antennas, Measurement.« less

The Galileo plasma wave investigation

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Kurth, W. S.; Shaw, R. R.; Roux, A.; Gendrin, R.; Kennel, C. F.; Scarf, F. L.; Shawhan, S. D.

1992-01-01

The purpose of the Galileo plasma wave investigation is to study plasma waves and radio emissions in the magnetosphere of Jupiter. The plasma wave instrument uses an electric dipole antenna to detect electric fields, and two search coil magnetic antennas to detect magnetic fields. The frequency range covered is 5 Hz to 5.6 MHz for electric fields and 5 Hz to 160 kHz for magnetic fields. Low time-resolution survey spectrums are provided by three on-board spectrum analyzers. In the normal mode of operation the frequency resolution is about 10 percent, and the time resolution for a complete set of electric and magnetic field measurements is 37.33 s. High time-resolution spectrums are provided by a wideband receiver. The wideband receiver provides waveform measurements over bandwidths of 1, 10, and 80 kHz. Compared to previous measurements at Jupiter this instrument has several new capabilities. These new capabilities include (1) both electric and magnetic field measurements to distinguish electrostatic and electromagnetic waves, (2) direction finding measurements to determine source locations, and (3) increased bandwidth for the wideband measurements.

Partial Discharge Spectral Characterization in HF, VHF and UHF Bands Using Particle Swarm Optimization.

PubMed

Robles, Guillermo; Fresno, José Manuel; Martínez-Tarifa, Juan Manuel; Ardila-Rey, Jorge Alfredo; Parrado-Hernández, Emilio

2018-03-01

The measurement of partial discharge (PD) signals in the radio frequency (RF) range has gained popularity among utilities and specialized monitoring companies in recent years. Unfortunately, in most of the occasions the data are hidden by noise and coupled interferences that hinder their interpretation and renders them useless especially in acquisition systems in the ultra high frequency (UHF) band where the signals of interest are weak. This paper is focused on a method that uses a selective spectral signal characterization to feature each signal, type of partial discharge or interferences/noise, with the power contained in the most representative frequency bands. The technique can be considered as a dimensionality reduction problem where all the energy information contained in the frequency components is condensed in a reduced number of UHF or high frequency (HF) and very high frequency (VHF) bands. In general, dimensionality reduction methods make the interpretation of results a difficult task because the inherent physical nature of the signal is lost in the process. The proposed selective spectral characterization is a preprocessing tool that facilitates further main processing. The starting point is a clustering of signals that could form the core of a PD monitoring system. Therefore, the dimensionality reduction technique should discover the best frequency bands to enhance the affinity between signals in the same cluster and the differences between signals in different clusters. This is done maximizing the minimum Mahalanobis distance between clusters using particle swarm optimization (PSO). The tool is tested with three sets of experimental signals to demonstrate its capabilities in separating noise and PDs with low signal-to-noise ratio and separating different types of partial discharges measured in the UHF and HF/VHF bands.

RXTE Observation of Cygnus X-1. Report 2; TIming Analysis

NASA Technical Reports Server (NTRS)

Nowak, Michael A.; Vaughan, Brian A.; Wilms, Joern; Dove, James B.; Begelman, Mitchell C.

1998-01-01

We present timing analysis for a Rossi X-ray Timing Explorer (RXTE) observation of Cygnus X-1 in its hard/low state. This was the first RXTE observation of Cyg X-1 taken after it transited back to this state from its soft/high state. RXTE's large effective area, superior timing capabilities, and ability to obtain long, uninterrupted observations have allowed us to obtain measurements of the power spectral density (PSD), coherence function, and Fourier time lags to a decade lower in frequency and half a decade higher in frequency than typically was achieved with previous instruments. Notable aspects of our observations include a weak 0.005 Hz feature in the PSD coincident with a coherence recovery; a 'hardening' of the high-frequency PSD with increasing energy; a broad frequency range measurement of the coherence function, revealing rollovers from unity coherence at both low and high frequency; and an accurate determination of the Fourier time lags over two and a half decades in frequency. As has been noted in previous similar observations, the time delay is approximately proportional to f(exp -0.7), and at a fixed Fourier frequency the time delay of the hard X-rays compared to the softest energy channel tends to increase logarithmically with energy. Curiously, the 0.01-0.2 Hz coherence between the highest and lowest energy bands is actually slightly greater than the coherence between the second highest and lowest energy bands. We carefully describe all of the analysis techniques used in this paper, and we make comparisons of the data to general theoretical expectations. In a companion paper, we make specific comparisons to a Compton corona model that we have successfully used to describe the energy spectral data from this observation.

Low-frequency acousto-optic backscattering of Bessel light beams

NASA Astrophysics Data System (ADS)

Khilo, Nikolai A.; Belyi, Vladimir N.; Khilo, Petr A.; Kazak, Nikolai S.

2018-05-01

The use of Bessel light beams, as well as Bessel acoustic beams, substantially enhances the capabilities of acousto-optic methods for control of optical field. We present a theoretical study of the process of optical Bessel beams conversion by means of backward acousto-optic scattering on a Bessel acoustic field in a transversely isotropic crystal. It is shown that, with an appropriate choice of Bessel beams parameters, the backscattering in visible spectral range can be realized at relatively low acoustic frequencies less than one gigahertz. Under conditions of phase matching and transverse spatial synchronism, the efficiency of backscattering is sufficiently high, which is interesting, for example, for construction of acousto-optic spectral analyzers.

Effects of the gaseous and liquid water content of the atmosphere on range delay and Doppler frequency

NASA Technical Reports Server (NTRS)

Flock, W. L.

1981-01-01

When high precision is required for range measurement on Earth space paths, it is necessary to correct as accurately as possible for excess range delays due to the dry air, water vapor, and liquid water content of the atmosphere. Calculations based on representative values of atmospheric parameters are useful for illustrating the order of magnitude of the expected delays. Range delay, time delay, and phase delay are simply and directly related. Doppler frequency variations or noise are proportional to the time rate of change of excess range delay. Tropospheric effects were examined as part of an overall consideration of the capability of precision two way ranging and Doppler systems.

Flexible missile autopilot design studies with PC-MATLAB/386

NASA Technical Reports Server (NTRS)

Ruth, Michael J.

1989-01-01

Development of a responsive, high-bandwidth missile autopilot for airframes which have structural modes of unusually low frequency presents a challenging design task. Such systems are viable candidates for modern, state-space control design methods. The PC-MATLAB interactive software package provides an environment well-suited to the development of candidate linear control laws for flexible missile autopilots. The strengths of MATLAB include: (1) exceptionally high speed (MATLAB's version for 80386-based PC's offers benchmarks approaching minicomputer and mainframe performance); (2) ability to handle large design models of several hundred degrees of freedom, if necessary; and (3) broad extensibility through user-defined functions. To characterize MATLAB capabilities, a simplified design example is presented. This involves interactive definition of an observer-based state-space compensator for a flexible missile autopilot design task. MATLAB capabilities and limitations, in the context of this design task, are then summarized.

A Framework for Dimensioning VDL-2 Air-Ground Networks

NASA Technical Reports Server (NTRS)

Ribeiro, Leila Z.; Monticone, Leone C.; Snow, Richard E.; Box, Frank; Apaza, Rafel; Bretmersky, Steven

2014-01-01

This paper describes a framework developed at MITRE for dimensioning a Very High Frequency (VHF) Digital Link Mode 2 (VDL-2) Air-to-Ground network. This framework was developed to support the FAA's Data Communications (Data Comm) program by providing estimates of expected capacity required for the air-ground network services that will support Controller-Pilot-Data-Link Communications (CPDLC), as well as the spectrum needed to operate the system at required levels of performance. The Data Comm program is part of the FAA's NextGen initiative to implement advanced communication capabilities in the National Airspace System (NAS). The first component of the framework is the radio-frequency (RF) coverage design for the network ground stations. Then we proceed to describe the approach used to assess the aircraft geographical distribution and the data traffic demand expected in the network. The next step is the resource allocation utilizing optimization algorithms developed in MITRE's Spectrum ProspectorTM tool to propose frequency assignment solutions, and a NASA-developed VDL-2 tool to perform simulations and determine whether a proposed plan meets the desired performance requirements. The framework presented is capable of providing quantitative estimates of multiple variables related to the air-ground network, in order to satisfy established coverage, capacity and latency performance requirements. Outputs include: coverage provided at different altitudes; data capacity required in the network, aggregated or on a per ground station basis; spectrum (pool of frequencies) needed for the system to meet a target performance; optimized frequency plan for a given scenario; expected performance given spectrum available; and, estimates of throughput distributions for a given scenario. We conclude with a discussion aimed at providing insight into the tradeoffs and challenges identified with respect to radio resource management for VDL-2 air-ground networks.

High efficiency inductive output tubes with intense annular electron beams

NASA Astrophysics Data System (ADS)

Appanam Karakkad, J.; Matthew, D.; Ray, R.; Beaudoin, B. L.; Narayan, A.; Nusinovich, G. S.; Ting, A.; Antonsen, T. M.

2017-10-01

For mobile ionospheric heaters, it is necessary to develop highly efficient RF sources capable of delivering radiation in the frequency range from 3 to 10 MHz with an average power at a megawatt level. A promising source, which is capable of offering these parameters, is a grid-less version of the inductive output tube (IOT), also known as a klystrode. In this paper, studies analyzing the efficiency of grid-less IOTs are described. The basic trade-offs needed to reach high efficiency are investigated. In particular, the trade-off between the peak current and the duration of the current micro-pulse is analyzed. A particle in the cell code is used to self-consistently calculate the distribution in axial and transverse momentum and in total electron energy from the cathode to the collector. The efficiency of IOTs with collectors of various configurations is examined. It is shown that the efficiency of IOTs can be in the 90% range even without using depressed collectors.

Second-order sliding mode control for DFIG-based wind turbines fault ride-through capability enhancement.

PubMed

Benbouzid, Mohamed; Beltran, Brice; Amirat, Yassine; Yao, Gang; Han, Jingang; Mangel, Hervé

2014-05-01

This paper deals with the fault ride-through capability assessment of a doubly fed induction generator-based wind turbine using a high-order sliding mode control. Indeed, it has been recently suggested that sliding mode control is a solution of choice to the fault ride-through problem. In this context, this paper proposes a second-order sliding mode as an improved solution that handle the classical sliding mode chattering problem. Indeed, the main and attractive features of high-order sliding modes are robustness against external disturbances, the grids faults in particular, and chattering-free behavior (no extra mechanical stress on the wind turbine drive train). Simulations using the NREL FAST code on a 1.5-MW wind turbine are carried out to evaluate ride-through performance of the proposed high-order sliding mode control strategy in case of grid frequency variations and unbalanced voltage sags. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Design of a fast computer-based partial discharge diagnostic system

NASA Technical Reports Server (NTRS)

Oliva, Jose R.; Karady, G. G.; Domitz, Stan

1991-01-01

Partial discharges cause progressive deterioration of insulating materials working in high voltage conditions and may lead ultimately to insulator failure. Experimental findings indicate that deterioration increases with the number of discharges and is consequently proportional to the magnitude and frequency of the applied voltage. In order to obtain a better understanding of the mechanisms of deterioration produced by partial discharges, instrumentation capable of individual pulse resolution is required. A new computer-based partial discharge detection system was designed and constructed to conduct long duration tests on sample capacitors. This system is capable of recording large number of pulses without dead time and producing valuable information related to amplitude, polarity, and charge content of the discharges. The operation of the system is automatic and no human supervision is required during the testing stage. Ceramic capacitors were tested at high voltage in long duration tests. The obtained results indicated that the charge content of partial discharges shift towards high levels of charge as the level of deterioration in the capacitor increases.

Capabilities and prospects of the East Asia Very Long Baseline Interferometry Network

NASA Astrophysics Data System (ADS)

An, T.; Sohn, B. W.; Imai, H.

2018-02-01

The very long baseline interferometry (VLBI) technique offers angular resolutions superior to any other instruments at other wavelengths, enabling unique science applications of high-resolution imaging of radio sources and high-precision astrometry. The East Asia VLBI Network (EAVN) is a collaborative effort in the East Asian region. The EAVN currently consists of 21 telescopes with diverse equipment configurations and frequency setups, allowing flexible subarrays for specific science projects. The EAVN provides the highest resolution of 0.5 mas at 22 GHz, allowing the fine imaging of jets in active galactic nuclei, high-accuracy astrometry of masers and pulsars, and precise spacecraft positioning. The soon-to-be-operational Five-hundred-meter Aperture Spherical radio Telescope (FAST) will open a new era for the EAVN. This state-of-the-art VLBI array also provides easy access to and crucial training for the burgeoning Asian astronomical community. This Perspective summarizes the status, capabilities and prospects of the EAVN.

47 CFR 2.1515 - Spectral measurements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... applicable, change the type of modulation of the EPIRB and record the shift in carrier frequency as observed... Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL... radiated signal from the EPIRB. A signal generator and frequency counter capable of operating at 121.5 and...

An optimized method to calculate error correction capability of tool influence function in frequency domain

NASA Astrophysics Data System (ADS)

Wang, Jia; Hou, Xi; Wan, Yongjian; Shi, Chunyan

2017-10-01

An optimized method to calculate error correction capability of tool influence function (TIF) in certain polishing conditions will be proposed based on smoothing spectral function. The basic mathematical model for this method will be established in theory. A set of polishing experimental data with rigid conformal tool is used to validate the optimized method. The calculated results can quantitatively indicate error correction capability of TIF for different spatial frequency errors in certain polishing conditions. The comparative analysis with previous method shows that the optimized method is simpler in form and can get the same accuracy results with less calculating time in contrast to previous method.

Low frequency electric and magnetic fields

NASA Technical Reports Server (NTRS)

Spaniol, Craig

1989-01-01

Following preliminary investigations of the low frequency electric and magnetic fields that may exists in the Earth-ionospheric cavity, measurements were taken with state-of-the art spectrum analyzers. As a follow up to this activity, an investigation was initiated to determine sources and values for possible low frequency signal that would appear in the cavity. The lowest cavity resonance is estimated at about 8 Hz, but lower frequencies may be an important component of our electromagnetic environment. The potential field frequencies produced by the electron were investigated by a classical model that included possible cross coupling of the electric and gravitation fields. During this work, an interesting relationship was found that related the high frequency charge field with the extremely low frequency of the gravitation field. The results of numerical calculations were surprisingly accurate and this area of investigation is continuing. The work toward continued development of a standardized monitoring facility is continuing with the potential of installing the prototype at West Virginia State College early in 1990. This installation would be capable of real time monitoring of ELF signals in the Earth-ionoshpere cavity and would provide some directional information. A high gain, low noise, 1/f frequency corrected preamplifier was designed and tested for the ferrite core magnetic sensor. The potential application of a super conducting sensor for the ELF magnetic field detection is under investigation. It is hoped that a fully operational monitoring network could pinpoint the location of ELF signal sources and provide new information on where these signals originate and what causes them, assuming that they are natural in origin.

The terrestrial gravitational wave environment from known sources

NASA Technical Reports Server (NTRS)

Webbink, Ronald F.

1993-01-01

The objective of this project was to produce a gravitational wave spectral line list of all known binary stars producing expected strain amplitudes at Earth in excess of h = 10 (exp -21), or gravitational wave fluxes in excess of F = 10 (exp -12) erg cm(exp -2) s(exp -1). These strain and flux limits lie above the anticipated detection thresholds for space-borne laser interferometers capable of detecting gravitational radiation in the 10 micron Hz to 1 Hz frequency range. The source list was intended to provide frequency (including each harmonic), amplitude and phase (for each polarization and harmonic), and celestial coordinates for each system, lacking only the orientation of the principal polarization axis with respect to the pole of the coordinate system, and the sign of the source phase and frequency (or, equivalently, of the sense of rotation of the strain tensor with time) from providing a complete source description. Such a spectral line list would lay essential groundwork for high-sensitivity, low-frequency searches for gravitational radiation.

Big data integration shows Australian bush-fire frequency is increasing significantly.

PubMed

Dutta, Ritaban; Das, Aruneema; Aryal, Jagannath

2016-02-01

Increasing Australian bush-fire frequencies over the last decade has indicated a major climatic change in coming future. Understanding such climatic change for Australian bush-fire is limited and there is an urgent need of scientific research, which is capable enough to contribute to Australian society. Frequency of bush-fire carries information on spatial, temporal and climatic aspects of bush-fire events and provides contextual information to model various climate data for accurately predicting future bush-fire hot spots. In this study, we develop an ensemble method based on a two-layered machine learning model to establish relationship between fire incidence and climatic data. In a 336 week data trial, we demonstrate that the model provides highly accurate bush-fire incidence hot-spot estimation (91% global accuracy) from the weekly climatic surfaces. Our analysis also indicates that Australian weekly bush-fire frequencies increased by 40% over the last 5 years, particularly during summer months, implicating a serious climatic shift.

Multiband coherent perfect absorption in a water-based metasurface.

PubMed

Zhu, Weiren; Rukhlenko, Ivan D; Xiao, Fajun; He, Chong; Geng, Junping; Liang, Xianling; Premaratne, Malin; Jin, Ronghong

2017-07-10

We design an ultrathin water-based metasurface capable of coherent perfect absorption (CPA) at radio frequencies. It is demonstrated that such a metasurface can almost completely absorb two symmetrically incident waves within four frequency bands, each having its own modulation depth of metasurface absorptivity. Specifically, the absorptivity at 557.2 MHz can be changed between 0.59% and 99.99% via the adjustment of the phase difference between the waves. The high angular tolerance of our metasurface is shown to enable strong CPA at oblique incidence, with the CPA frequency almost independent of the incident angle for TE waves and varying from 557.2 up to 584.2 MHz for TM waves. One can also reduce this frequency from 712.0 to 493.3 MHz while retaining strong coherent absorption by varying the water layer thickness. It is also show that the coherent absorption performance can be flexibly controlled by adjusting the temperature of water. The proposed metasurface is low-cost, biocompatible, and useful for electromagnetic modulation and switching.

Achieving pattern uniformity in plasmonic lithography by spatial frequency selection

NASA Astrophysics Data System (ADS)

Liang, Gaofeng; Chen, Xi; Zhao, Qing; Guo, L. Jay

2018-01-01

The effects of the surface roughness of thin films and defects on photomasks are investigated in two representative plasmonic lithography systems: thin silver film-based superlens and multilayer-based hyperbolic metamaterial (HMM). Superlens can replicate arbitrary patterns because of its broad evanescent wave passband, which also makes it inherently vulnerable to the roughness of the thin film and imperfections of the mask. On the other hand, the HMM system has spatial frequency filtering characteristics and its pattern formation is based on interference, producing uniform and stable periodic patterns. In this work, we show that the HMM system is more immune to such imperfections due to its function of spatial frequency selection. The analyses are further verified by an interference lithography system incorporating the photoresist layer as an optical waveguide to improve the aspect ratio of the pattern. It is concluded that a system capable of spatial frequency selection is a powerful method to produce deep-subwavelength periodic patterns with high degree of uniformity and fidelity.

Broadband impedance boundary conditions for the simulation of sound propagation in the time domain.

PubMed

Bin, Jonghoon; Yousuff Hussaini, M; Lee, Soogab

2009-02-01

An accurate and practical surface impedance boundary condition in the time domain has been developed for application to broadband-frequency simulation in aeroacoustic problems. To show the capability of this method, two kinds of numerical simulations are performed and compared with the analytical/experimental results: one is acoustic wave reflection by a monopole source over an impedance surface and the other is acoustic wave propagation in a duct with a finite impedance wall. Both single-frequency and broadband-frequency simulations are performed within the framework of linearized Euler equations. A high-order dispersion-relation-preserving finite-difference method and a low-dissipation, low-dispersion Runge-Kutta method are used for spatial discretization and time integration, respectively. The results show excellent agreement with the analytical/experimental results at various frequencies. The method accurately predicts both the amplitude and the phase of acoustic pressure and ensures the well-posedness of the broadband time-domain impedance boundary condition.

A Multi-Frequency Polarimetric SAR Sensors Analysis over the UNESCO Archaeological Site of Djebel Barkal (Sudan)

NASA Astrophysics Data System (ADS)

Patruno, Jolanda; Dore, Nicole; Pottier, Eric; Crespi, Mattia

2013-08-01

Differences in vegetation growth and in soil moisture content generate ground anomalies which can be linked to subsurface anthropic structures. Such evidences have been studied by means of aerial photographs and of historical II World War acquisitions first, and of very high spatial resolution of optical satellites later. This work aims to exploit the technique of SAR Polarimetry for the detection of surface and subsurface archaeological structures, comparing ALOS P ALSAR L-band (central frequency 1.27 GHz), with RADARSAT-2 C-band sensor (central frequency 5.405 GHz). The great potential of the two polarimetric sensors with different frequency for the detection of archaeological remains has been demonstrated thanks to the sand penetration capability of both C-band and L- band sensors. The choice to analyze radar sensors is based on their 24-hour observations, independent from Sun illumination and meteorological conditions and on the electromagnetic properties of the target they could provide, information not derivable from optical images.

Big data integration shows Australian bush-fire frequency is increasing significantly

PubMed Central

Dutta, Ritaban; Das, Aruneema; Aryal, Jagannath

2016-01-01

Increasing Australian bush-fire frequencies over the last decade has indicated a major climatic change in coming future. Understanding such climatic change for Australian bush-fire is limited and there is an urgent need of scientific research, which is capable enough to contribute to Australian society. Frequency of bush-fire carries information on spatial, temporal and climatic aspects of bush-fire events and provides contextual information to model various climate data for accurately predicting future bush-fire hot spots. In this study, we develop an ensemble method based on a two-layered machine learning model to establish relationship between fire incidence and climatic data. In a 336 week data trial, we demonstrate that the model provides highly accurate bush-fire incidence hot-spot estimation (91% global accuracy) from the weekly climatic surfaces. Our analysis also indicates that Australian weekly bush-fire frequencies increased by 40% over the last 5 years, particularly during summer months, implicating a serious climatic shift. PMID:26998312

Micromachined PIN-PMN-PT Crystal Composite Transducer for High-Frequency Intravascular Ultrasound (IVUS) Imaging

PubMed Central

Li, Xiang; Ma, Teng; Tian, Jian; Han, Pengdi; Zhou, Qifa; Shung, K. Kirk

2015-01-01

In this paper, we report the use of micromachined PbIn1/2Nb1/2O3–PbMg1/3Nb2/3O3–PbTiO3 (PIN-PMN-PT) single crystal 1–3 composite material for intravascular ultrasound (IVUS) imaging application. The effective electromechanical coupling coefficient kt(eff) of the composite was measured to be 0.75 to 0.78. Acoustic impedance was estimated to be 20 MRayl. Based on the composite, needle-type and flexible-type IVUS transducers were fabricated. The composite transducer achieved an 86% bandwidth at the center frequency of 41 MHz, which resulted in a 43 μm axial resolution. Ex vivo IVUS imaging was conducted to demonstrate the improvement of axial resolution. The composite transducer was capable of identifying the three layers of a cadaver coronary artery specimen with high resolution. The PIN-PMN-PT-based composite has superior piezoelectric properties comparable to PMN-PT-based composite and its thermal stability is higher than PMN-PT. PIN-PMN-PT crystal can be an alternative approach for fabricating high-frequency composite, instead of using PMN-PT. PMID:24960706

Single stock dynamics on high-frequency data: from a compressed coding perspective.

PubMed

Fushing, Hsieh; Chen, Shu-Chun; Hwang, Chii-Ruey

2014-01-01

High-frequency return, trading volume and transaction number are digitally coded via a nonparametric computing algorithm, called hierarchical factor segmentation (HFS), and then are coupled together to reveal a single stock dynamics without global state-space structural assumptions. The base-8 digital coding sequence, which is capable of revealing contrasting aggregation against sparsity of extreme events, is further compressed into a shortened sequence of state transitions. This compressed digital code sequence vividly demonstrates that the aggregation of large absolute returns is the primary driving force for stimulating both the aggregations of large trading volumes and transaction numbers. The state of system-wise synchrony is manifested with very frequent recurrence in the stock dynamics. And this data-driven dynamic mechanism is seen to correspondingly vary as the global market transiting in and out of contraction-expansion cycles. These results not only elaborate the stock dynamics of interest to a fuller extent, but also contradict some classical theories in finance. Overall this version of stock dynamics is potentially more coherent and realistic, especially when the current financial market is increasingly powered by high-frequency trading via computer algorithms, rather than by individual investors.

Measurement of Turbulent Pressure and Temperature Fluctuations in a Gas Turbine Combustor

NASA Technical Reports Server (NTRS)

Passaro, Andrea; LaGraff, John E.; Oldfield, Martin L. G.; Biagioni, Leonardo; Moss, Roger W.; Battelle, Ryan T.; Povinelli, Louis A. (Technical Monitor)

2003-01-01

The present research concerns the development of high-frequency pressure and temperature probes and related instrumentation capable of performing spectral characterization of unsteady pressure and temperature fluctuations over the 0.05 20 kHz range, at the exit of a gas turbine combustor operating at conditions close to nominal ones for large power generation turbomachinery. The probes used a transient technique pioneered at Oxford University; in order to withstand exposure to the harsh environment the probes were fitted on a rapid injection and cooling system jointly developed by Centrospazio CPR and Syracuse University. The experimental runs were performed on a large industrial test rig being operated by ENEL Produzione. The achieved results clearly show the satisfactory performance provided by this diagnostic tool, even though the poor location of the injection port prevented the tests from yielding more insight of the core flow turbulence characteristics. The pressure and temperature probes survived several dozen injections in the combustor hot jet, while consistently providing the intended high frequency performance. The apparatus was kept connected to the combustor during long duration firings, operating as an unobtrusive, self contained, piggy-back experiment: high frequency flow samplings were remotely recorded at selected moments corresponding to different combustor operating conditions.

Single Stock Dynamics on High-Frequency Data: From a Compressed Coding Perspective

PubMed Central

Fushing, Hsieh; Chen, Shu-Chun; Hwang, Chii-Ruey

2014-01-01

High-frequency return, trading volume and transaction number are digitally coded via a nonparametric computing algorithm, called hierarchical factor segmentation (HFS), and then are coupled together to reveal a single stock dynamics without global state-space structural assumptions. The base-8 digital coding sequence, which is capable of revealing contrasting aggregation against sparsity of extreme events, is further compressed into a shortened sequence of state transitions. This compressed digital code sequence vividly demonstrates that the aggregation of large absolute returns is the primary driving force for stimulating both the aggregations of large trading volumes and transaction numbers. The state of system-wise synchrony is manifested with very frequent recurrence in the stock dynamics. And this data-driven dynamic mechanism is seen to correspondingly vary as the global market transiting in and out of contraction-expansion cycles. These results not only elaborate the stock dynamics of interest to a fuller extent, but also contradict some classical theories in finance. Overall this version of stock dynamics is potentially more coherent and realistic, especially when the current financial market is increasingly powered by high-frequency trading via computer algorithms, rather than by individual investors. PMID:24586235

Increasing power and amplified spontaneous emission suppression for weak signal amplification in pulsed fiber amplifier

NASA Astrophysics Data System (ADS)

Luo, Yi; Zhang, Hanwei; Wang, Xiaolin; Su, Rongtao; Ma, Pengfei; Zhou, Pu; Jiang, Zongfu

2017-10-01

In the pulsed fiber amplifiers with repetition frequency of several tens kHz, amplified spontaneous emission (ASE) is easy to build up because of the low repetition frequency and weak pulse signal. The ASE rises the difficulty to amplify the weak pulse signal effectively. We have demonstrated an all-fiber preamplifier stage structure to amplify a 40 kHz, 10 ns bandwidth (FWHM) weak pulse signal (299 μW) with center wavelength of 1062 nm. Compared synchronous pulse pump with continuous wave(CW) pump, the results indicate that synchronous pulse pump shows the better capability of increasing the output power than CW pump. In the condition of the same pump power, the output power of synchronous pulse pump is twice as high as CW pump. In order to suppress ASE, a longer gain fiber is utilized to reabsorb the ASE in which the wavelength is shorter than 1062nm. We amplified weak pulse signal via 0.8 m and 2.1 m gain fiber in synchronous pulse pump experiments respectively, and more ASE in the output spectra are observed in the 0.8 m gain fiber system. Due to the weaker ASE and consequent capability of higher pump power, the 2.1 m gain fiber is capable to achieve higher output power than shorter fiber. The output power of 2.1 m gain fiber case is limited by pump power.

Dispersed Sensing Networks in Nano-Engineered Polymer Composites: From Static Strain Measurement to Ultrasonic Wave Acquisition

PubMed Central

Li, Yehai; Wang, Kai

2018-01-01

Self-sensing capability of composite materials has been the core of intensive research over the years and particularly boosted up by the recent quantum leap in nanotechnology. The capacity of most existing self-sensing approaches is restricted to static strains or low-frequency structural vibration. In this study, a new breed of functionalized epoxy-based composites is developed and fabricated, with a graphene nanoparticle-enriched, dispersed sensing network, whereby to self-perceive broadband elastic disturbance from static strains, through low-frequency vibration to guided waves in an ultrasonic regime. Owing to the dispersed and networked sensing capability, signals can be captured at any desired part of the composites. Experimental validation has demonstrated that the functionalized composites can self-sense strains, outperforming conventional metal foil strain sensors with a significantly enhanced gauge factor and a much broader response bandwidth. Precise and fast self-response of the composites to broadband ultrasonic signals (up to 440 kHz) has revealed that the composite structure itself can serve as ultrasound sensors, comparable to piezoceramic sensors in performance, whereas avoiding the use of bulky cables and wires as used in a piezoceramic sensor network. This study has spotlighted promising potentials of the developed approach to functionalize conventional composites with a self-sensing capability of high-sensitivity yet minimized intrusion to original structures. PMID:29724032

Application of a neural network as a potential aid in predicting NTF pump failure

NASA Technical Reports Server (NTRS)

Rogers, James L.; Hill, Jeffrey S.; Lamarsh, William J., II; Bradley, David E.

1993-01-01

The National Transonic Facility has three centrifugal multi-stage pumps to supply liquid nitrogen to the wind tunnel. Pump reliability is critical to facility operation and test capability. A highly desirable goal is to be able to detect a pump rotating component problem as early as possible during normal operation and avoid serious damage to other pump components. If a problem is detected before serious damage occurs, the repair cost and downtime could be reduced significantly. A neural network-based tool was developed for monitoring pump performance and aiding in predicting pump failure. Once trained, neural networks can rapidly process many combinations of input values other than those used for training to approximate previously unknown output values. This neural network was applied to establish relationships among the critical frequencies and aid in predicting failures. Training pairs were developed from frequency scans from typical tunnel operations. After training, various combinations of critical pump frequencies were propagated through the neural network. The approximated output was used to create a contour plot depicting the relationships of the input frequencies to the output pump frequency.

Miniature fiber-optic multiphoton microscopy system using frequency-doubled femtosecond Er-doped fiber laser

PubMed Central

Huang, Lin; Mills, Arthur K.; Zhao, Yuan; Jones, David J.; Tang, Shuo

2016-01-01

We report on a miniature fiber-optic multiphoton microscopy (MPM) system based on a frequency-doubled femtosecond Er-doped fiber laser. The femtosecond pulses from the laser source are delivered to the miniature fiber-optic probe at 1.58 µm wavelength, where a standard single mode fiber is used for delivery without the need of free-space dispersion compensation components. The beam is frequency-doubled inside the probe by a periodically poled MgO:LiNbO3 crystal. Frequency-doubled pulses at 786 nm with a maximum power of 80 mW and a pulsewidth of 150 fs are obtained and applied to excite intrinsic signals from tissues. A MEMS scanner, a miniature objective, and a multimode collection fiber are further used to make the probe compact. The miniature fiber-optic MPM system is highly portable and robust. Ex vivo multiphoton imaging of mammalian skins demonstrates the capability of the system in imaging biological tissues. The results show that the miniature fiber-optic MPM system using frequency-doubled femtosecond fiber laser can potentially bring the MPM imaging for clinical applications. PMID:27231633

Spectral purity and tunability of terahertz quantum cascade laser sources based on intracavity difference-frequency generation.

PubMed

Consolino, Luigi; Jung, Seungyong; Campa, Annamaria; De Regis, Michele; Pal, Shovon; Kim, Jae Hyun; Fujita, Kazuue; Ito, Akio; Hitaka, Masahiro; Bartalini, Saverio; De Natale, Paolo; Belkin, Mikhail A; Vitiello, Miriam Serena

2017-09-01

Terahertz sources based on intracavity difference-frequency generation in mid-infrared quantum cascade lasers (THz DFG-QCLs) have recently emerged as the first monolithic electrically pumped semiconductor sources capable of operating at room temperature across the 1- to 6-THz range. Despite tremendous progress in power output, which now exceeds 1 mW in pulsed and 10 μW in continuous-wave regimes at room temperature, knowledge of the major figure of merits of these devices for high-precision spectroscopy, such as spectral purity and absolute frequency tunability, is still lacking. By exploiting a metrological grade system comprising a terahertz frequency comb synthesizer, we measure, for the first time, the free-running emission linewidth (LW), the tuning characteristics, and the absolute center frequency of individual emission lines of these sources with an uncertainty of 4 × 10 -10 . The unveiled emission LW (400 kHz at 1-ms integration time) indicates that DFG-QCLs are well suited to operate as local oscillators and to be used for a variety of metrological, spectroscopic, communication, and imaging applications that require narrow-LW THz sources.

The Impact of the Type 094 Ballistic Missile Submarine on China’s Nuclear Policy

DTIC Science & Technology

2009-06-01

74 Figure 9. VLF Towers at Greenbury Point in Annapolis, MD........................................75 Figure 10. ELF Communications Source...China’s ability to utilize these systems. Extremely low frequency ( ELF ) communications have the advantage that messages can be received at depths of...capabilities. Even with this increase, it will still be difficult for China to maintain constant two-way communications with ELF or VLF in high sea

Analysis of Unmanned Undersea Vehicle (UUV) Architectures and an Assessment of UUV Integration into Undersea Applications

DTIC Science & Technology

2010-09-01

Synthetic Long Baseline SSS Side Scan Sonar TCS Time Critical Strike TRL Technology Readiness Level U.S. United States UHF Ultra High...Frequency UN United Nation USBL Ultra Short Baseline UUV Unmanned Undersea Vehicle UUVMP Unmanned Undersea Vehicle Master Plan V Volts...Wilmington, “NURC/SEGM Capabilities: Deepwater AUV,” University of North Carolina Wilmington Web site [Online], Available: http://www.uncw.edu/nurc/auv

InP Heterojunction Bipolar Transistor Amplifiers to 255 GHz

NASA Technical Reports Server (NTRS)

Radisic, Vesna; Sawdai, Donald; Scott, Dennis; Deal, William; Dang, Linh; Li, Danny; Cavus, Abdullah; To, Richard; Lai, Richard

2009-01-01

Two single-stage InP heterojunction bipolar transistor (HBT) amplifiers operate at 184 and 255 GHz, using Northrop Grumman Corporation s InP HBT MMIC (monolithic microwave integrated circuit) technology. At the time of this reporting, these are reported to be the highest HBT amplifiers ever created. The purpose of the amplifier design is to evaluate the technology capability for high-frequency designs and verify the model for future development work.

Free-field propagation of high intensity noise

NASA Technical Reports Server (NTRS)

Welz, Joseph P.; Mcdaniel, Oliver H.

1990-01-01

Observed spectral data from supersonic jet aircraft are known to contain much more high frequency energy than can be explained by linear acoustic propagation theory. It is believed that the high frequency energy is an effect of nonlinear distortion due to the extremely high acoustic levels generated by the jet engines. The objective, to measure acoustic waveform distortion for spherically diverging high intensity noise, was reached by using an electropneumatic acoustic source capable of generating sound pressure levels in the range of 140 to 160 decibels (re 20 micro Pa). The noise spectrum was shaped to represent the spectra generated by jet engines. Two microphones were used to capture the acoustic pressure waveform at different points along the propagation path in order to provide a direct measure of the waveform distortion as well as spectral distortion. A secondary objective was to determine that the observed distortion is an acoustic effect. To do this an existing computer prediction code that deals with nonlinear acoustic propagation was used on data representative of the measured data. The results clearly demonstrate that high intensity jet noise does shift the energy in the spectrum to the higher frequencies along the propagation path. In addition, the data from the computer model are in good agreement with the measurements, thus demonstrating that the waveform distortion can be accounted for with nonlinear acoustic theory.

An adaptable multiple power source for mass spectrometry and other scientific instruments.

PubMed

Lin, T-Y; Anderson, G A; Norheim, R V; Prost, S A; LaMarche, B L; Leach, F E; Auberry, K J; Smith, R D; Koppenaal, D W; Robinson, E W; Paša-Tolić, L

2015-09-01

An Adaptable Multiple Power Source (AMPS) system has been designed and constructed. The AMPS system can provide up to 16 direct current (DC) (±400 V; 5 mA), 4 radio frequency (RF) (two 500 VPP sinusoidal signals each, 0.5-5 MHz) channels, 2 high voltage sources (±6 kV), and one ∼40 W, 250 °C temperature-regulated heater. The system is controlled by a microcontroller, capable of communicating with its front panel or a computer. It can assign not only pre-saved fixed DC and RF signals but also profiled DC voltages. The AMPS system is capable of driving many mass spectrometry components and ancillary devices and can be adapted to other instrumentation/engineering projects.

Design and implementation of a wireless (Bluetooth) four channel bio-instrumentation amplifier and digital data acquisition device with user-selectable gain, frequency, and driven reference.

PubMed

Cosmanescu, Alin; Miller, Benjamin; Magno, Terence; Ahmed, Assad; Kremenic, Ian

2006-01-01

A portable, multi-purpose Bio-instrumentation Amplifier and Data AcQuisition device (BADAQ) capable of measuring and transmitting EMG and EKG signals wirelessly via Bluetooth is designed and implemented. Common topologies for instrumentation amplifiers and filters are used and realized with commercially available, low-voltage, high precision operational amplifiers. An 8-bit PIC microcontroller performs 10-bit analog-to-digital conversion of the amplified and filtered signals and controls a Bluetooth transceiver capable of wirelessly transmitting the data to any Bluetooth enabled device. Electrical isolation between patient/subject, circuitry, and ancillary equipment is achieved by optocoupling components. The design focuses on simplicity, portability, and affordability.

Unity power factor converter

NASA Technical Reports Server (NTRS)

Wester, Gene W. (Inventor)

1980-01-01

A unity power factor converter capable of effecting either inversion (dc-to-dc) or rectification (ac-to-dc), and capable of providing bilateral power control from a DC source (or load) through an AC transmission line to a DC load (or source) for power flow in either direction, is comprised of comparators for comparing the AC current i with an AC signal i.sub.ref (or its phase inversion) derived from the AC ports to generate control signals to operate a switch control circuit for high speed switching to shape the AC current waveform to a sine waveform, and synchronize it in phase and frequency with the AC voltage at the AC ports, by selectively switching the connections to a series inductor as required to increase or decrease the current i.

Description of a Portable Wireless Device for High-Frequency Body Temperature Acquisition and Analysis

PubMed Central

Cuesta-Frau, David; Varela, Manuel; Aboy, Mateo; Miró-Martínez, Pau

2009-01-01

We describe a device for dual channel body temperature monitoring. The device can operate as a real time monitor or as a data logger, and has Bluetooth capabilities to enable for wireless data download to the computer used for data analysis. The proposed device is capable of sampling temperature at a rate of 1 sample per minute with a resolution of 0.01 °C . The internal memory allows for stand-alone data logging of up to 10 days. The device has a battery life of 50 hours in continuous real-time mode. In addition to describing the proposed device in detail, we report the results of a statistical analysis conducted to assess its accuracy and reproducibility. PMID:22408473

Description of a portable wireless device for high-frequency body temperature acquisition and analysis.

PubMed

Cuesta-Frau, David; Varela, Manuel; Aboy, Mateo; Miró-Martínez, Pau

2009-01-01

We describe a device for dual channel body temperature monitoring. The device can operate as a real time monitor or as a data logger, and has Bluetooth capabilities to enable for wireless data download to the computer used for data analysis. The proposed device is capable of sampling temperature at a rate of 1 sample per minute with a resolution of 0.01 °C . The internal memory allows for stand-alone data logging of up to 10 days. The device has a battery life of 50 hours in continuous real-time mode. In addition to describing the proposed device in detail, we report the results of a statistical analysis conducted to assess its accuracy and reproducibility.

Pulse compression favourable aperiodic infrared imaging approach for non-destructive testing and evaluation of bio-materials

NASA Astrophysics Data System (ADS)

Mulaveesala, Ravibabu; Dua, Geetika; Arora, Vanita; Siddiqui, Juned A.; Muniyappa, Amarnath

2017-05-01

In recent years, aperiodic, transient pulse compression favourable infrared imaging methodologies demonstrated as reliable, quantitative, remote characterization and evaluation techniques for testing and evaluation of various biomaterials. This present work demonstrates a pulse compression favourable aperiodic thermal wave imaging technique, frequency modulated thermal wave imaging technique for bone diagnostics, especially by considering the bone with tissue, skin and muscle over layers. In order to find the capabilities of the proposed frequency modulated thermal wave imaging technique to detect the density variations in a multi layered skin-fat-muscle-bone structure, finite element modeling and simulation studies have been carried out. Further, frequency and time domain post processing approaches have been adopted on the temporal temperature data in order to improve the detection capabilities of frequency modulated thermal wave imaging.

Dispersive Fourier transformation for megahertz detection of coherent stokes and anti-stokes Raman spectra

NASA Astrophysics Data System (ADS)

Bohlin, Alexis; Patterson, Brian D.; Kliewer, Christopher J.

2017-11-01

In many fields of study, from coherent Raman microscopy on living cells to time-resolved coherent Raman spectroscopy of gas-phase turbulence and combustion reaction dynamics, the need for the capability to time-resolve fast dynamical and nonrepetitive processes has led to the continued development of high-speed coherent Raman methods and new high-repetition rate laser sources, such as pulse-burst laser systems. However, much less emphasis has been placed on our ability to detect shot to shot coherent Raman spectra at equivalently high scan rates, across the kilohertz to megahertz regime. This is beyond the capability of modern scientific charge coupled device (CCD) cameras, for instance, as would be employed with a Czerny-Turner type spectrograph. As an alternative detection strategy with megahertz spectral detection rate, we demonstrate dispersive Fourier transformation detection of pulsed (∼90 ps) coherent Raman signals in the time-domain. Instead of reading the frequency domain signal out using a spectrometer and CCD, the signal is transformed into a time-domain waveform through dispersive Fourier transformation in a long single-mode fiber and read-out with a fast sampling photodiode and oscilloscope. Molecular O- and S-branch rotational sideband spectra from both N2 and H2 were acquired employing this scheme, and the waveform is fitted to show highly quantitative agreement with a molecular model. The total detection time for the rotational spectrum was 20 ns, indicating an upper limit to the detection frequency of ∼50 MHz, significantly faster than any other reported spectrally-resolved coherent anti-Stokes Raman detection strategy to date.

High Power Intermodulation Measurements up to 30 W of High Temperature Superconducting Filters

NASA Technical Reports Server (NTRS)

Wilker, Charles; Carter, Charles F., III; Shen, Zhi-Yuan

1999-01-01

We have demonstrated a high power intermodulation measurement set-up capable of delivering 30 W in each of two fundamental tones. For closely spaced frequencies (less than 35 MHz), the dynamic range of the measurement is limited by the nonlinear performance of the mixer in the front end of the HP71210C spectrum analyzer. A tunable TE(sub 011) mode copper cavity was fabricated in which one of the endwalls could be adjusted shifting its resonant frequency between 5.7 and 6.6 GHz. Since the Q-value of this cavity is high, greater than 10(exp 4), and its bandwidth is small, less than 1 MHz, it can be used to attenuate the two fundamental tones relative to one of the harmonic tones, which greatly enhances the dynamic range of the measurement. This set-up can be used to measure the two-tone intermodulation distortion of any passive microwave device, e.g. a HTS filter, a connector, a cable, etc., over a frequency range of 5.9 to 6.4 GHz and a power range of 0.1 to 30 W. The third order intercept (TOI) of a prototype HTS filter measured at powers up to 30 W was +81.3 dBm.

Frequency Compounded Imaging with a High-Frequency Dual Element Transducer

PubMed Central

Chang, Jin Ho; Kim, Hyung Ham; Lee, Jungwoo; Shung, K. Kirk

2014-01-01

This paper proposes a frequency compounding method to reduce speckle interferences, where a concentric annular type high-frequency dual element transducer is used to broaden the bandwidth of an imaging system. In frequency compounding methods, frequency division is carried out to obtain sub-band images containing uncorrelated speckles, which sacrifices axial resolution. Therefore, frequency compounding often deteriorates the target-detecting capability, quantified by the total signal-to-noise ratio (SNR), when the speckle’s SNR (SSNR) is not improved as much as the degraded axial resolution. However, this could be avoided if the effective bandwidth required for frequency compounding is increased. The primary goal of the proposed approach, hence, is to improve SSNR by a factor of two under the condition where axial resolution is degraded by a factor of less than two, which indicates the total SNR improvement to higher than 40% compared to that of an original image. Since the method here employs a dual element transducer operating at 20 and 40 MHz, the effective bandwidth necessary for frequency compounding becomes broadened. By dividing each spectrum of RF samples from both elements into two sub-bands, this method eventually enables four sets of the sub-band samples to contain uncorrelated speckles. This causes the axial resolution to be reduced by a factor of as low as 1.85, which means that this method would improve total SNR by at least 47 %. An in vitro experiment on an excised pig eye was performed to validate the proposed approach, and the results showed that the SSNR was improved from 2.081±0.365 in the original image to 4.206±0.635 in the final compounding image. PMID:19914674

Frequency compounded imaging with a high-frequency dual element transducer.

PubMed

Chang, Jin Ho; Kim, Hyung Ham; Lee, Jungwoo; Shung, K Kirk

2010-04-01

This paper proposes a frequency compounding method to reduce speckle interferences, where a concentric annular type high-frequency dual element transducer is used to broaden the bandwidth of an imaging system. In frequency compounding methods, frequency division is carried out to obtain sub-band images containing uncorrelated speckles, which sacrifices axial resolution. Therefore, frequency compounding often deteriorates the target-detecting capability, quantified by the total signal-to-noise ratio (SNR), when the speckle's SNR (SSNR) is not improved as much as the degraded axial resolution. However, this could be avoided if the effective bandwidth required for frequency compounding is increased. The primary goal of the proposed approach, hence, is to improve SSNR by a factor of two under the condition where axial resolution is degraded by a factor of less than two, which indicates the total SNR improvement to higher than 40% compared to that of an original image. Since the method here employs a dual element transducer operating at 20 and 40MHz, the effective bandwidth necessary for frequency compounding becomes broadened. By dividing each spectrum of RF samples from both elements into two sub-bands, this method eventually enables four sets of the sub-band samples to contain uncorrelated speckles. This causes the axial resolution to be reduced by a factor of as low as 1.85, which means that this method would improve total SNR by at least 47%. An in vitro experiment on an excised pig eye was performed to validate the proposed approach, and the results showed that the SSNR was improved from 2.081+/-0.365 in the original image to 4.206+/-0.635 in the final compounding image. Copyright 2009 Elsevier B.V. All rights reserved.

Multisource information fusion applied to ship identification for the recognized maritime picture

NASA Astrophysics Data System (ADS)

Simard, Marc-Alain; Lefebvre, Eric; Helleur, Christopher

2000-04-01

The Recognized Maritime Picture (RMP) is defined as a composite picture of activity over a maritime area of interest. In simplistic terms, building an RAMP comes down to finding if an object of interest, a ship in our case, is there or not, determining what it is, determining what it is doing and determining if some type of follow-on action is required. The Canadian Department of National Defence currently has access to or may, in the near future, have access to a number of civilians, military and allied information or sensor systems to accomplish these purposes. These systems include automatic self-reporting positional systems, air patrol surveillance systems, high frequency surface radars, electronic intelligence systems, radar space systems and high frequency direction finding sensors. The ability to make full use of these systems is limited by the existing capability to fuse data from all sources in a timely, accurate and complete manner. This paper presents an information fusion systems under development that correlates and fuses these information and sensor data sources. This fusion system, named Adaptive Fuzzy Logic Correlator, correlates the information in batch but fuses and constructs ship tracks sequentially. It applies standard Kalman filter techniques and fuzzy logic correlation techniques. We propose a set of recommendations that should improve the ship identification process. Particularly it is proposed to utilize as many non-redundant sources of information as possible that address specific vessel attributes. Another important recommendation states that the information fusion and data association techniques should be capable of dealing with incomplete and imprecise information. Some fuzzy logic techniques capable of tolerating imprecise and dissimilar data are proposed.

A novel model of interaction between high frequency electromagnetic non-ionizing fields and microtubules viewed as coupled two-degrees of freedom harmonic oscillators.

PubMed

Caligiuri, Luigi Maxmilian

2015-01-01

The question regarding the potential biological and adverse health effects of non-ionizing electromagnetic fields on living organisms is of primary importance in biophysics and medicine. Despite the several experimental evidences showing such occurrence in a wide frequency range from extremely low frequency to microwaves, a definitive theoretical model able to explain a possible mechanism of interaction between electromagnetic fields and living matter, especially in the case of weak and very weak intensities, is still missing. In this paper it has been suggested a possible mechanism of interaction involving the resonant absorption of electromagnetic radiation by microtubules. To this aim these have been modeled as non-dissipative forced harmonic oscillators characterized by two coupled "macroscopic" degrees of freedom, respectively describing longitudinal and transversal vibrations induced by the electromagnetic field. We have shown that the proposed model, although at a preliminary stage, is able to explain the ability of even weak electromagnetic radiating electromagnetic fields to transfer high quantities of energy to living systems by means of a resonant mechanism, so capable to easily damage microtubules structure.

Reconstructing a plasmonic metasurface for a broadband high-efficiency optical vortex in the visible frequency.

PubMed

Lu, Bing-Rui; Deng, Jianan; Li, Qi; Zhang, Sichao; Zhou, Jing; Zhou, Lei; Chen, Yifang

2018-06-14

Metasurfaces consisting of a two-dimensional metallic nano-antenna array are capable of transferring a Gaussian beam into an optical vortex with a helical phase front and a phase singularity by manipulating the polarization/phase status of light. This miniaturizes a laboratory scaled optical system into a wafer scale component, opening up a new area for broad applications in optics. However, the low conversion efficiency to generate a vortex beam from circularly polarized light hinders further development. This paper reports our recent success in improving the efficiency over a broad waveband at the visible frequency compared with the existing work. The choice of material, the geometry and the spatial organization of meta-atoms, and the fabrication fidelity are theoretically investigated by the Jones matrix method. The theoretical conversion efficiency over 40% in the visible wavelength range is worked out by systematic calculation using the finite difference time domain (FDTD) method. The fabricated metasurface based on the parameters by theoretical optimization demonstrates a high quality vortex in optical frequencies with a significantly enhanced efficiency of over 20% in a broad waveband.

Pyroshock: Bibliography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zimmerman, R.M.

1993-01-01

This paper represents a review copy for text that is to be included in the Shock and Vibration Recommended Practice Document. This section on pyroshock is written an a general introduction to and description of the topic loading to presentation of an extensive bibliography on the subject. Pyroshock is an evolving science that needs continued focus on both achieving improvements in testing and measurement techniques and advancing instrumentation capabilities. When desired in the near future, recommended practices can be presented. Pyroshock phenomena are associated with separation systems of missiles. spacecraft, and in some cases airplanes. During launch, a rocket drivenmore » vehicle may be exposed to 19 to 30 g's of acceleration with predominant frequencies less than 200 Hz. After launch or takeoffs sections or parts of vehicles may be separated rapidly using explosive driven release mechanisms. Separations can involve stage disconnections for spacecraft sections or payload ejections from missiles and airplanes. At separation, localized pyrotechnic induced accelerations may range from 1000 to over 100,000 g's at frequencies much higher than 1000 Hz. These pyroshocks are characterized by high intensity, high frequency transients that decay rapidly. Pyroshock impulses have insignificant velocity changes.« less

TeraSCREEN: multi-frequency multi-mode Terahertz screening for border checks

NASA Astrophysics Data System (ADS)

Alexander, Naomi E.; Alderman, Byron; Allona, Fernando; Frijlink, Peter; Gonzalo, Ramón; Hägelen, Manfred; Ibáñez, Asier; Krozer, Viktor; Langford, Marian L.; Limiti, Ernesto; Platt, Duncan; Schikora, Marek; Wang, Hui; Weber, Marc Andree

2014-06-01

The challenge for any security screening system is to identify potentially harmful objects such as weapons and explosives concealed under clothing. Classical border and security checkpoints are no longer capable of fulfilling the demands of today's ever growing security requirements, especially with respect to the high throughput generally required which entails a high detection rate of threat material and a low false alarm rate. TeraSCREEN proposes to develop an innovative concept of multi-frequency multi-mode Terahertz and millimeter-wave detection with new automatic detection and classification functionalities. The system developed will demonstrate, at a live control point, the safe automatic detection and classification of objects concealed under clothing, whilst respecting privacy and increasing current throughput rates. This innovative screening system will combine multi-frequency, multi-mode images taken by passive and active subsystems which will scan the subjects and obtain complementary spatial and spectral information, thus allowing for automatic threat recognition. The TeraSCREEN project, which will run from 2013 to 2016, has received funding from the European Union's Seventh Framework Programme under the Security Call. This paper will describe the project objectives and approach.

Measurement of absolute frequency of continuous-wave terahertz radiation in real time using a free-running, dual-wavelength mode-locked, erbium-doped fibre laser

PubMed Central

Hu, Guoqing; Mizuguchi, Tatsuya; Zhao, Xin; Minamikawa, Takeo; Mizuno, Takahiko; Yang, Yuli; Li, Cui; Bai, Ming; Zheng, Zheng; Yasui, Takeshi

2017-01-01

A single, free-running, dual-wavelength mode-locked, erbium-doped fibre laser was exploited to measure the absolute frequency of continuous-wave terahertz (CW-THz) radiation in real time using dual THz combs of photo-carriers (dual PC-THz combs). Two independent mode-locked laser beams with different wavelengths and different repetition frequencies were generated from this laser and were used to generate dual PC-THz combs having different frequency spacings in photoconductive antennae. Based on the dual PC-THz combs, the absolute frequency of CW-THz radiation was determined with a relative precision of 1.2 × 10−9 and a relative accuracy of 1.4 × 10−9 at a sampling rate of 100 Hz. Real-time determination of the absolute frequency of CW-THz radiation varying over a few tens of GHz was also demonstrated. Use of a single dual-wavelength mode-locked fibre laser, in place of dual mode-locked lasers, greatly reduced the size, complexity, and cost of the measurement system while maintaining the real-time capability and high measurement precision. PMID:28186148

The frequency range of TMJ sounds.

PubMed

Widmalm, S E; Williams, W J; Djurdjanovic, D; McKay, D C

2003-04-01

There are conflicting opinions about the frequency range of temporomandibular joint (TMJ) sounds. Some authors claim that the upper limit is about 650 Hz. The aim was to test the hypothesis that TMJ sounds may contain frequencies well above 650 Hz but that significant amounts of their energy are lost if the vibrations are recorded using contact sensors and/or travel far through the head tissues. Time-frequency distributions of 172 TMJ clickings (three subjects) were compared between recordings with one microphone in the ear canal and a skin contact transducer above the clicking joint and between recordings from two microphones, one in each ear canal. The energy peaks of the clickings recorded with a microphone in the ear canal on the clicking side were often well above 650 Hz and always in a significantly higher area (range 117-1922 Hz, P < 0.05 or lower) than in recordings obtained with contact sensors (range 47-375 Hz) or in microphone recordings from the opposite ear canal (range 141-703 Hz). Future studies are required to establish normative frequency range values of TMJ sounds but need methods also capable of recording the high frequency vibrations.

Past, Present, and Future Capabilities of the Transonic Dynamics Tunnel from an Aeroelasticity Perspective

NASA Technical Reports Server (NTRS)

Cole, Stanley R.; Garcia, Jerry L.

2000-01-01

The NASA Langley Transonic Dynamics Tunnel (TDT) has provided a unique capability for aeroelastic testing for forty years. The facility has a rich history of significant contributions to the design of many United States commercial transports, military aircraft, launch vehicles, and spacecraft. The facility has many features that contribute to its uniqueness for aeroelasticity testing, perhaps the most important feature being the use of a heavy gas test medium to achieve higher test densities. Higher test medium densities substantially improve model-building requirements and therefore simplify the fabrication process for building aeroelastically scaled wind tunnel models. Aeroelastic scaling for the heavy gas results in lower model structural frequencies. Lower model frequencies tend to a make aeroelastic testing safer. This paper will describe major developments in the testing capabilities at the TDT throughout its history, the current status of the facility, and planned additions and improvements to its capabilities in the near future.

Development of a 33 kV, 20 A long pulse converter modulator for high average power klystron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reghu, T.; Mandloi, V.; Shrivastava, Purushottam

Research, design, and development of high average power, long pulse modulators for the proposed Indian Spallation Neutron Source are underway at Raja Ramanna Centre for Advanced Technology. With this objective, a prototype of long pulse modulator capable of delivering 33 kV, 20 A at 5 Hz repetition rate has been designed and developed. Three Insulated Gate Bipolar Transistors (IGBT) based switching modules driving high frequency, high voltage transformers have been used to generate high voltage output. The IGBT based switching modules are shifted in phase by 120° with respect to each other. The switching frequency is 25 kHz. Pulses ofmore » 1.6 ms pulse width, 80 μs rise time, and 70 μs fall time have been achieved at the modulator output. A droop of ±0.6% is achieved using a simple segmented digital droop correction technique. The total fault energy transferred to the load during fault has been measured by conducting wire burn tests and is found to be within 3.5 J.« less

Development of a 33 kV, 20 A long pulse converter modulator for high average power klystron

NASA Astrophysics Data System (ADS)

Reghu, T.; Mandloi, V.; Shrivastava, Purushottam

2014-05-01

Research, design, and development of high average power, long pulse modulators for the proposed Indian Spallation Neutron Source are underway at Raja Ramanna Centre for Advanced Technology. With this objective, a prototype of long pulse modulator capable of delivering 33 kV, 20 A at 5 Hz repetition rate has been designed and developed. Three Insulated Gate Bipolar Transistors (IGBT) based switching modules driving high frequency, high voltage transformers have been used to generate high voltage output. The IGBT based switching modules are shifted in phase by 120° with respect to each other. The switching frequency is 25 kHz. Pulses of 1.6 ms pulse width, 80 μs rise time, and 70 μs fall time have been achieved at the modulator output. A droop of ±0.6% is achieved using a simple segmented digital droop correction technique. The total fault energy transferred to the load during fault has been measured by conducting wire burn tests and is found to be within 3.5 J.

Optical see-through head-mounted display with occlusion capability

NASA Astrophysics Data System (ADS)

Gao, Chunyu; Lin, Yuxiang; Hua, Hong

2013-05-01

Lack of mutual occlusion capability between computer-rendered and real objects is one of fundamental problems for most existing optical see-through head-mounted displays (OST-HMD). Without the proper occlusion management, the virtual view through an OST-HMD appears "ghost-like", floating in the real world. To address this challenge, we have developed an innovative optical scheme that uniquely combines the eyepiece and see-through relay optics to achieve an occlusion-capable OST-HMD system with a very compelling form factor and high optical performances. The proposed display system was based on emerging freeform optical design technologies and was designed for highly efficient liquid crystal on silicon (LCoS) type spatial light modulator (SLM) and bright Organic LED (OLED) microdisplay. The proposed display technology was capable of working in both indoor and outdoor environments. Our current design offered a 1280x1024 color resolution based on 0.8" microdisplay and SLM. The MTF values for the majority of the fields at the cutoff frequency of 40lps/mm, which is determined by the pixel size of the microdisplay, are better than 15%. The design achieved a diagonal FOV of 40 degrees, 31.7 degrees horizontally and 25.6 degrees vertically, an exit pupil diameter of 8mm (non-vignetted), and an eye clearance of 18mm. The optics weights about 20 grams per eye. Our proposed occlusion capable OST-HMD system can easily find myriads of applications in various military and commercial sectors such as military training, gaming and entertainment.

Reducing the ingress of urban noise through natural ventilation openings.

PubMed

Oldham, D J; de Salis, M H; Sharples, S

2004-01-01

For buildings in busy urban areas affected by high levels of road traffic noise the potential to use natural ventilation can be limited by excessive noise entering through ventilation openings. This paper is concerned with techniques to reduce noise ingress into naturally ventilated buildings while minimizing airflow path resistance. A combined experimental and theoretical approach to the interaction of airflow and sound transmission through ventilators for natural ventilation applications is described. A key element of the investigation has been the development of testing facilities capable of measuring the airflow and sound transmission losses for a range of ventilation noise control strategies. It is demonstrated that a combination of sound reduction mechanisms -- one covering low frequency sound and another covering high frequency sound -- is required to attenuate effectively noise from typical urban sources. A method is proposed for quantifying the acoustic performance of different strategies to enable comparisons and informed decisions to be made leading to the possibility of a design methodology for optimizing the ventilation and acoustic performance of different strategies. The need for employing techniques for combating low frequency sound in tandem with techniques for reducing high frequency sound in reducing the ingress of noise from urban sources such as road traffic to acceptable levels is demonstrated. A technique is proposed for enabling the acoustic and airflow performance of apertures for natural ventilation systems to be designed simultaneously.

Science highlights from high-sensitivity pulsar observations with the MWA

NASA Astrophysics Data System (ADS)

McSweeney, Samuel; Bhat, Ramesh; Tremblay, Steven; Ord, Stephen

2016-01-01

Pulsars are exquisite probes of the turbulent interstellar medium (ISM), capable of resolving structures down to tens of thousands of kilometres. Understanding the ISM is important for many areas of astrophysics, such as galactic dynamics, the chemical evolution of the galaxy, and the identification of timing noise in the search for gravitational waves using pulsar timing arrays. Low frequency observations of pulsars are key, because the strength of propagation effects scales strongly with frequency.We present the Murchison Widefield Array (MWA) as a key science tool for making high quality observations of pulsars at low frequencies (~80-300 MHz). Recently commissioned software for making tied-array beams and the MWA's high time resolution voltage capture system (VCS) allow an order of magnitude increase in sensitivity, vital for pulsar and other time-domain science. A pipeline has now been developed for observing the scintillation patterns of important pulsars at low frequencies, including a new computational technique for measuring the curvature of parabolic arcs in noisy secondary spectra. A program of MWA observations is being undertaken to sample a large number of millisecond pulsars. We present recent highlights including PSR J0437-4715, which yielded a new measurement of scattering screen distance of ~120 pc from Earth, consistent with a Parkes observation at ~730 MHz, and matching the predicted perimeter of the Local Bubble.

Ultrasensitive, self-calibrated cavity ring-down spectrometer for quantitative trace gas analysis.

PubMed

Chen, Bing; Sun, Yu R; Zhou, Ze-Yi; Chen, Jian; Liu, An-Wen; Hu, Shui-Ming

2014-11-10

A cavity ring-down spectrometer is built for trace gas detection using telecom distributed feedback (DFB) diode lasers. The longitudinal modes of the ring-down cavity are used as frequency markers without active-locking either the laser or the high-finesse cavity. A control scheme is applied to scan the DFB laser frequency, matching the cavity modes one by one in sequence and resulting in a correct index at each recorded spectral data point, which allows us to calibrate the spectrum with a relative frequency precision of 0.06 MHz. Besides the frequency precision of the spectrometer, a sensitivity (noise-equivalent absorption) of 4×10^-11  cm^-1  Hz^-1/2 has also been demonstrated. A minimum detectable absorption coefficient of 5×10^-12  cm^-1 has been obtained by averaging about 100 spectra recorded in 2  h. The quantitative accuracy is tested by measuring the CO₂ concentrations in N₂ samples prepared by the gravimetric method, and the relative deviation is less than 0.3%. The trace detection capability is demonstrated by detecting CO₂ of ppbv-level concentrations in a high-purity nitrogen gas sample. Simple structure, high sensitivity, and good accuracy make the instrument very suitable for quantitative trace gas analysis.

Realizing one-dimensional quantum and high-frequency transport features in aligned single-walled carbon nanotube ropes

NASA Astrophysics Data System (ADS)

Ncube, Siphephile; Chimowa, George; Chiguvare, Zivayi; Bhattacharyya, Somnath

2014-07-01

The superiority of the electronic transport properties of single-walled carbon nanotube (SWNT) ropes over SWNT mats is verified from low temperature and frequency-dependent transport. The overall change of resistance versus in nanotube mats shows that 3D variable range hopping is the dominant conduction mechanism within the 2-300 K range. The magneto-resistance (MR) is found to be predominantly negative with a parabolic nature, which can also be described by the hopping model. Although the positive upturn of the MR at low temperatures establishes the contribution from quantum interference, the inherent quantum transport in individual tubes is suppressed at elevated temperatures. Therefore, to minimize multi-channel effects from inter-tube interactions and other defects, two-terminal devices were fabricated from aligned SWNT (extracted from a mat) for low temperature transport as well as high-frequency measurements. In contrast to the mat, the aligned ropes exhibit step-like features in the differential conductance within the 80-300 K temperature range. The effects of plasmon propagation, unique to one dimension, were identified in electronic transport as a non-universal power-law dependence of the differential conductance on temperature and source-drain voltage. The complex impedance showed high power transmission capabilities up to 65 GHz as well as oscillations in the frequency range up to 30 GHz. The measurements suggest that aligned SWNT ropes have a realistic potential for high-speed device applications.

The ALMA Phasing System: A Beamforming Capability for Ultra-high-resolution Science at (Sub)Millimeter Wavelengths

NASA Astrophysics Data System (ADS)

Matthews, L. D.; Crew, G. B.; Doeleman, S. S.; Lacasse, R.; Saez, A. F.; Alef, W.; Akiyama, K.; Amestica, R.; Anderson, J. M.; Barkats, D. A.; Baudry, A.; Broguière, D.; Escoffier, R.; Fish, V. L.; Greenberg, J.; Hecht, M. H.; Hiriart, R.; Hirota, A.; Honma, M.; Ho, P. T. P.; Impellizzeri, C. M. V.; Inoue, M.; Kohno, Y.; Lopez, B.; Martí-Vidal, I.; Messias, H.; Meyer-Zhao, Z.; Mora-Klein, M.; Nagar, N. M.; Nishioka, H.; Oyama, T.; Pankratius, V.; Perez, J.; Phillips, N.; Pradel, N.; Rottmann, H.; Roy, A. L.; Ruszczyk, C. A.; Shillue, B.; Suzuki, S.; Treacy, R.

2018-01-01

The Atacama Millimeter/submillimeter Array (ALMA) Phasing Project (APP) has developed and deployed the hardware and software necessary to coherently sum the signals of individual ALMA antennas and record the aggregate sum in Very Long Baseline Interferometry (VLBI) Data Exchange Format. These beamforming capabilities allow the ALMA array to collectively function as the equivalent of a single large aperture and participate in global VLBI arrays. The inclusion of phased ALMA in current VLBI networks operating at (sub)millimeter wavelengths provides an order of magnitude improvement in sensitivity, as well as enhancements in u–v coverage and north–south angular resolution. The availability of a phased ALMA enables a wide range of new ultra-high angular resolution science applications, including the resolution of supermassive black holes on event horizon scales and studies of the launch and collimation of astrophysical jets. It also provides a high-sensitivity aperture that may be used for investigations such as pulsar searches at high frequencies. This paper provides an overview of the ALMA Phasing System design, implementation, and performance characteristics.

Quad-channel beam switching WR3-band transmitter MMIC

NASA Astrophysics Data System (ADS)

Müller, Daniel; Eren, Gülesin; Wagner, Sandrine; Tessmann, Axel; Leuther, Arnulf; Zwick, Thomas; Kallfass, Ingmar

2017-05-01

Millimeter wave radar systems offer several advantages such as the combination of high resolution and the penetration of adverse atmosphere like smoke, dust or rain. This paper presents a monolithic millimeter wave integrated circuit (MMIC) transmitter which offers four channel beam steering capabilities and can be used as a radar or communication system transmitter. At the local oscillator input, in order to simplify packaging, a frequency tripler is used to multiply the 76.6 - 83.3 GHz input signal to the intended 230 - 250 GHz output frequency range. A resistive mixer is used for the conversion of the intermediate frequency signal into the RF domain. The actual beam steering network is realized using an active single pole quadruple throw (SP4T) switch, which is connected to a integrated Butler matrix. The MMIC was fabricated in a 35 nm InGaAs mHEMT process and has a size of 4.0 mm × 1.5 mm

A nonlinear multi-mode wideband piezoelectric vibration-based energy harvester using compliant orthoplanar spring

NASA Astrophysics Data System (ADS)

Dhote, Sharvari; Zu, Jean; Zhu, Yang

2015-04-01

In this paper, a nonlinear wideband multi-mode piezoelectric vibration-based energy harvester (PVEH) is proposed based on a compliant orthoplanar spring (COPS), which has an advantage of providing multiple vibration modes at relatively low frequencies. The PVEH is made of a tri-leg COPS flexible structure, where three fixed-guided beams are capable of generating strong nonlinear oscillations under certain base excitation. A prototype harvester was fabricated and investigated through both finite-element analysis and experiments. The frequency response shows multiple resonance which corresponds to a hardening type of nonlinear resonance. By adding masses at different locations on the COPS structure, the first three vibration modes are brought close to each other, where the three hardening nonlinear resonances provide a wide bandwidth for the PVEH. The proposed PVEH has enhanced performance of the energy harvester in terms of a wide frequency bandwidth and a high-voltage output under base excitations.

Critique of a Hughes shuttle Ku-band data sampler/bit synchronizer

NASA Technical Reports Server (NTRS)

Holmes, J. K.

1980-01-01

An alternative bit synchronizer proposed for shuttle was analyzed in a noise-free environment by considering the basic operation of the loop via timing diagrams and by linearizing the bit synchronizer as an equivalent, continuous, phased-lock loop (PLL). The loop is composed of a high-frequency phase-frequency detector which is capable of detecting both phase and frequency errors and is used to track the clock, and a bit transition detector which attempts to track the transitions of the data bits. It was determined that the basic approach was a good design which, with proper implementation of the accumulator, up/down counter and logic should provide accurate mid-bit sampling with symmetric bits. However, when bit asymmetry occurs, the bit synchronizer can lock up with a large timing error, yet be quasi-stable (timing will not change unless the clock and bit sequence drift). This will result in incorrectly detecting some bits.

Foundry fabricated photonic integrated circuit optical phase lock loop.

PubMed

Bałakier, Katarzyna; Fice, Martyn J; Ponnampalam, Lalitha; Graham, Chris S; Wonfor, Adrian; Seeds, Alwyn J; Renaud, Cyril C

2017-07-24

This paper describes the first foundry-based InP photonic integrated circuit (PIC) designed to work within a heterodyne optical phase locked loop (OPLL). The PIC and an external electronic circuit were used to phase-lock a single-line semiconductor laser diode to an incoming reference laser, with tuneable frequency offset from 4 GHz to 12 GHz. The PIC contains 33 active and passive components monolithically integrated on a single chip, fully demonstrating the capability of a generic foundry PIC fabrication model. The electronic part of the OPLL consists of commercially available RF components. This semi-packaged system stabilizes the phase and frequency of the integrated laser so that an absolute frequency, high-purity heterodyne signal can be generated when the OPLL is in operation, with phase noise lower than -100 dBc/Hz at 10 kHz offset from the carrier. This is the lowest phase noise level ever demonstrated by monolithically integrated OPLLs.

[Effects of simulated hypoxia on dielectric properties of mouse erythrocytes].

PubMed

Ma, Qing; Tang, Zhi-Yuan; Wang, Qin-Wen; Zhao, Xin

2008-02-01

To explore the influence of simulated altitude hypoxia on dielectric properties of mouse erythrocytes. Experimental animals were divided into the plain control group(control) and simulated altitude hypoxia group (altitude). The AC impedance of mouse erythrocytes was measured with the Agilent 4294A impedance analyzer, the influence of simulated altitude hypoxia on dielectric properties of mouse erythrocytes was observed by cell dielectric spectroscopy, Cole-Cole plots, loss factor spectrum, loss tangent spectrum, and curve fitting analysis of Cole-Cole equation. After mice were exposed to hypoxia at simulated 5000 m altitude for 4 weeks, permittivity at low frequency (epsilonl) and dielectric increment (deltaepsilon) increased 57% and 59% than that of control group respectively, conductivity at low frequency (kappal) and conductivity at high frequency (kappah) reduced 49% and 11% than that of control group respectively. The simulated altitude hypoxia could arise to increase dielectric capability and depress conductive performance on mouse erythrocytes.

A Model of High-Frequency Self-Mixing in Double-Barrier Rectifier

NASA Astrophysics Data System (ADS)

Palma, Fabrizio; Rao, R.

2018-03-01

In this paper, a new model of the frequency dependence of the double-barrier THz rectifier is presented. The new structure is of interest because it can be realized by CMOS image sensor technology. Its application in a complex field such as that of THz receivers requires the availability of an analytical model, which is reliable and able to highlight the dependence on the parameters of the physical structure. The model is based on the hydrodynamic semiconductor equations, solved in the small signal approximation. The model depicts the mechanisms of the THz modulation of the charge in the depleted regions of the double-barrier device and explains the self-mixing process, the frequency dependence, and the detection capability of the structure. The model thus substantially improves the analytical models of the THz rectification available in literature, mainly based on lamped equivalent circuits.

Stable fiber-optic time transfer by active radio frequency phase locking.

PubMed

Yin, Feifei; Wu, Zhongle; Dai, Yitang; Ren, Tianpeng; Xu, Kun; Lin, Jintong; Tang, Geshi

2014-05-15

In this Letter we demonstrate a fiber link capable of stable time signal transfer utilizing our active long-distance radio frequency (RF) stabilization technology. Taking advantage of the chromatic dispersion in optical fiber, our scheme compensates dynamically the link delay variation by tuning the optical carrier wavelength to phase lock a round-trip RF reference. Since the time signal and the RF reference are carried by the same optical carrier, a highly stable time transfer is achieved at the same time. Experimentally, we demonstrate a stability of the time signal transfer over 50-km fiber with a time deviation of 40 ps at 1-s average and 2.3 ps at 1000-s average. The performance of the RF reference delivery is also tested, with an Allan deviation of 2×10(-15) at 1000-s average. According to our proposal, a simultaneous stable time and frequency transfer is expected.

Optomechanical proposal for monitoring microtubule mechanical vibrations

NASA Astrophysics Data System (ADS)

Barzanjeh, Sh.; Salari, V.; Tuszynski, J. A.; Cifra, M.; Simon, C.

2017-07-01

Microtubules provide the mechanical force required for chromosome separation during mitosis. However, little is known about the dynamic (high-frequency) mechanical properties of microtubules. Here, we theoretically propose to control the vibrations of a doubly clamped microtubule by tip electrodes and to detect its motion via the optomechanical coupling between the vibrational modes of the microtubule and an optical cavity. In the presence of a red-detuned strong pump laser, this coupling leads to optomechanical-induced transparency of an optical probe field, which can be detected with state-of-the art technology. The center frequency and line width of the transparency peak give the resonance frequency and damping rate of the microtubule, respectively, while the height of the peak reveals information about the microtubule-cavity field coupling. Our method opens the new possibilities to gain information about the physical properties of microtubules, which will enhance our capability to design physical cancer treatment protocols as alternatives to chemotherapeutic drugs.

Direct measurement of the pulse duration and frequency chirp of seeded XUV free electron laser pulses

NASA Astrophysics Data System (ADS)

Azima, Armin; Bödewadt, Jörn; Becker, Oliver; Düsterer, Stefan; Ekanayake, Nagitha; Ivanov, Rosen; Kazemi, Mehdi M.; Lamberto Lazzarino, Leslie; Lechner, Christoph; Maltezopoulos, Theophilos; Manschwetus, Bastian; Miltchev, Velizar; Müller, Jost; Plath, Tim; Przystawik, Andreas; Wieland, Marek; Assmann, Ralph; Hartl, Ingmar; Laarmann, Tim; Rossbach, Jörg; Wurth, Wilfried; Drescher, Markus

2018-01-01

We report on a direct time-domain measurement of the temporal properties of a seeded free-electron laser pulse in the extreme ultraviolet spectral range. Utilizing the oscillating electromagnetic field of terahertz radiation, a single-shot THz streak-camera was applied for measuring the duration as well as spectral phase of the generated intense XUV pulses. The experiment was conducted at FLASH, the free electron laser user facility at DESY in Hamburg, Germany. In contrast to indirect methods, this approach directly resolves and visualizes the frequency chirp of a seeded free-electron laser (FEL) pulse. The reported diagnostic capability is a prerequisite to tailor amplitude, phase and frequency distributions of FEL beams on demand. In particular, it opens up a new window of opportunities for advanced coherent spectroscopic studies making use of the high degree of temporal coherence expected from a seeded FEL pulse.

Experimental evaluation of low-pass shock isolation performance of elastomers using frequency-based Kolsky bar analyses

DOE PAGES

Knight, Marlene E.; Sanborn, Brett; Song, Bo; ...

2017-01-26

Elastomeric materials are used as shock isolation materials in a variety of environments to dampen vibrations and/or absorb energy from external impact to minimize energy transfer between two objects or bodies. Some applications require the shock isolation materials to behave as a low-pass mechanical filter to mitigate the shock/impact at high frequencies but transmit the energy at low frequencies with minimal attenuation. To fulfill this requirement, a shock isolation material needs to be carefully evaluated and selected with proper experimental design, procedures, and analyses. In this study, a Kolsky bar was modified with precompression (up to 15.5 kN) and confinementmore » capabilities to evaluate low-pass shock isolation performance in terms of acceleration attenuation through a variety of elastomers. Also investigated were the effects of preload and specimen geometry on the low-pass shock isolation response.« less

Wide bandwidth phase-locked loop circuit

NASA Technical Reports Server (NTRS)

Koudelka, Robert David (Inventor)

2005-01-01

A PLL circuit uses a multiple frequency range PLL in order to phase lock input signals having a wide range of frequencies. The PLL includes a VCO capable of operating in multiple different frequency ranges and a divider bank independently configurable to divide the output of the VCO. A frequency detector detects a frequency of the input signal and a frequency selector selects an appropriate frequency range for the PLL. The frequency selector automatically switches the PLL to a different frequency range as needed in response to a change in the input signal frequency. Frequency range hysteresis is implemented to avoid operating the PLL near a frequency range boundary.

Potential damage to DC superconducting magnets due to the high frequency electromagnetic waves

NASA Technical Reports Server (NTRS)

Gabriel, G. J.

1977-01-01

Experimental data are presented in support of the hypothesis that a dc superconducting magnet coil does not behave strictly as an inductor, but as a complicated electrodynamic device capable of supporting electromagnetic waves. Travel times of nanosecond pulses and evidence of sinusoidal standing waves were observed on a prototype four-layer solenoidal coil at room temperature. Ringing observed during switching transients appears as a sequence of multiple reflected square pulses whose durations are related to the layer lengths. With sinusoidal excitation of the coil, the voltage amplitude between a pair of points on the coil exhibits maxima at those frequencies such that the distance between these points is an odd multiple of half wavelength in free space. Evidence indicates that any disturbance, such as that resulting from switching or sudden fault, initiates multiple reflections between layers, thus raising the possibility for sufficiently high voltages to cause breakdown.

Energy output of a single outer hair cell: Effect of resonance

NASA Astrophysics Data System (ADS)

Iwasa, Kuni H.

2018-05-01

The ability of the mammalian ear in processing high frequency sounds, up to ˜100 kHz, is based on the capability of outer hair cells (OHCs) in responding to stimulation at high frequencies. These cells show a unique motility in their cell body coupled with charge movement. With this motile element, voltage changes generated by stimuli at their hair bundles drive the cell body and that, in turn, amplifies the signal. In vitro experiments show that the movement of these charges significantly increases the membrane capacitance, limiting the motile activity by an additional attenuation of voltage changes. It was found, however, that such an effect is due to the absence of mechanical load. In the presence of mechanical load, particularly inertial load, such as under in vivo conditions, the movement of motile charges should reduce the membrane capacitance, enhancing the mechanical power output.

Performance testing of a high frequency link converter for Space Station power distribution system

NASA Technical Reports Server (NTRS)

Sul, S. K.; Alan, I.; Lipo, T. A.

1989-01-01

The testing of a brassboard version of a 20-kHz high-frequency ac voltage link prototype converter dynamics for Space Station application is presented. The converter is based on a three-phase six-pulse bridge concept. The testing includes details of the operation of the converter when it is driving an induction machine source/load. By adapting a field orientation controller (FOC) to the converter, four-quadrant operation of the induction machine from the converter has been achieved. Circuit modifications carried out to improve the performance of the converter are described. The performance of two 400-Hz induction machines powered by the converter with simple V/f regulation mode is reported. The testing and performance results for the converter utilizing the FOC, which provides the capability for rapid torque changes, speed reversal, and four-quadrant operation, are reported.

Dynamically variable negative stiffness structures.

PubMed

Churchill, Christopher B; Shahan, David W; Smith, Sloan P; Keefe, Andrew C; McKnight, Geoffrey P

2016-02-01

Variable stiffness structures that enable a wide range of efficient load-bearing and dexterous activity are ubiquitous in mammalian musculoskeletal systems but are rare in engineered systems because of their complexity, power, and cost. We present a new negative stiffness-based load-bearing structure with dynamically tunable stiffness. Negative stiffness, traditionally used to achieve novel response from passive structures, is a powerful tool to achieve dynamic stiffness changes when configured with an active component. Using relatively simple hardware and low-power, low-frequency actuation, we show an assembly capable of fast (<10 ms) and useful (>100×) dynamic stiffness control. This approach mitigates limitations of conventional tunable stiffness structures that exhibit either small (<30%) stiffness change, high friction, poor load/torque transmission at low stiffness, or high power active control at the frequencies of interest. We experimentally demonstrate actively tunable vibration isolation and stiffness tuning independent of supported loads, enhancing applications such as humanoid robotic limbs and lightweight adaptive vibration isolators.