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Sample records for frequency system development

  1. Development and approach to low-frequency microgravity isolation systems

    NASA Technical Reports Server (NTRS)

    Grodsinsky, Carlos M.

    1990-01-01

    The low-gravity environment provided by space flight has afforded the science community a unique arena for the study of fundamental and technological sciences. However, the dynamic environment observed on space shuttle flights and predicted for Space Station Freedom has complicated the analysis of prior microgravity experiments and prompted concern for the viability of proposed space experiments requiring long-term, low-gravity environments. Thus, isolation systems capable of providing significant improvements to this random environment are being developed. The design constraints imposed by acceleration-sensitive, microgravity experiment payloads in the unique environment of space and a theoretical background for active isolation are discussed. A design is presented for a six-degree-of-freedom, active, inertial isolation system based on the baseline relative and inertial isolation techniques described.

  2. A theory of the visual system biology underlying development of spatial frequency lateralization.

    PubMed

    Howard, Mary F; Reggia, James A

    2007-07-01

    The spatial frequency hypothesis contends that performance differences between the hemispheres on various visuospatial tasks are attributable to lateralized processing of the spatial frequency content of visual stimuli. Hellige has proposed that such lateralization could arise during infant development from the earlier maturation of the right hemisphere combined with the increasing sensitivity of the visual system to high spatial frequencies. This proposal is intuitively appealing but lacks an explicit theory with respect to the underlying visual system biology. In this paper, we develop such a theory based on knowledge of visual system processing and development. We then translate our theory into a computational model that serves as the basis for a series of development simulations. We find that the simulations produce spatial frequency lateralization effects consistent with those observed empirically. We relate the nature of the neural asymmetry implied by our theory to empirical findings on visual pathway bias and the relative spatial frequency lateralization effect.

  3. 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.

  4. Development of the circuit system in high frequency satellite laser ranging equipment based on FPGA

    NASA Astrophysics Data System (ADS)

    Chen, Chong; Fan, Chunbo; Li, Zhenwei; Zhao, You

    2008-12-01

    High frequency, as well as automation and day light ranging, is a signify feature of new generation Satellite Laser Ranging (SLR) systems. In spite of increase the quantity of observation data, the high frequency SLR can also significantly improve the SP and NP precision. These trends of SLR technology lead to new requirement of control circuit. In this paper, an implementation of control circuit in single FPGA chip was present. SOPC (system on programmable chip) system was proposed to solve these problems. To realize the system, a control circuit custom component was designed and simulated by us. Then, the component was integrated into a SOPC system. Cooperated with software, the circuit has the ability to control the SLR system running at high frequency. Finally, the system was simulated in the Quartus software and NIOS IDE provided by Altera and implemented in an Altera EP1S10 development kit.

  5. The Development of Nuclear Frequency Standard with the Use of Ion Crystals Manipulation System

    NASA Astrophysics Data System (ADS)

    Troyan, V. I.; Pal'chikov, V. G.; Yakovlev, Y. P.; Krasavin, A. V.; Borisyuk, P. V.; Chernyshev, D. M.; Poteshin, S. S.; Sysoev, Alexey A.

    The perspectives for the increase in the accuracy of optical frequency standards by means of the development of "nuclear clocks" - a novel frequency standard based on the nuclear transition to the long-living isomer nuclear state of thorium-229 with energy ∼7.6 eV are discussed. Theoretical estimations give a possible accuracy Δν/ν ∼1×10-20, that allows wide scope of applications for a frequency standard, from satellite navigation systems to experimental verification of the principles of the general theory of relativity. The results are presented and the future prospects for research are discussed on the measurement of the isomeric transition in the nucleus of thorium-229 and creation on its basis the frequency standard of the new generation.

  6. Development of Low-Frequency AC Voltage Measurement System Using Single-Junction Thermal Converter

    NASA Astrophysics Data System (ADS)

    Amagai, Yasutaka; Nakamura, Yasuhiro

    Accurate measurement of low-frequency AC voltage using a digital multimeter at frequencies of 4-200Hz is a challenge in the mechanical engineering industry. At the National Metrology Institute of Japan, we developed a low-frequency AC voltage measurement system for calibrating digital multimeters operating at frequencies down to 1 Hz. The system uses a single-junction thermal converter and employs a theoretical model and a three-parameter sine wave fitting algorithm based on the least-square (LS) method. We calibrated the AC voltage down to 1Hz using our measurement system and reduced the measurement time compared with that using thin-film thermal converters. Our measurement results are verified by comparison with those of a digital sampling method using a high-resolution analog-to-digital converter; our data are in agreement to within a few parts in 105. Our proposed method enables us to measure AC voltage with an uncertainty of 25 μV/V (k = 1) at frequencies down to 4 Hz and a voltage of 10 V.

  7. Effect of amplitude-modulated radio frequency radiation on cholinergic system of developing rats.

    PubMed

    Kunjilwar, K K; Behari, J

    1993-01-22

    We examined the effect of long-term exposure to radio frequency radiation 147 MHz and its sub-harmonics 73.5 and 36.75 MHz amplitude modulated at 16 and 76 Hz (30-35 days, 3 h per day) on cholinergic systems in developing rat brain. A significant decrease in acetylcholine esterase activity was found in exposed rats as compared to the control. Decrease in acetylcholine esterase (AChE) activity was independent of carrier wave frequencies. A short-term exposure did not have any significant effect on AChE activity.

  8. Development of multichannel intermediate frequency system for electron cyclotron emission radiometer on KSTAR Tokamak

    SciTech Connect

    Kogi, Yuichiro; Sakoda, Takuya; Mase, Atsushi; Ito, Naoki; Yokota, Yuya; Yamaguchi, Soichiro; Nagayama, Yoshio; Kawahata, Kazuo; Jeong, Seung H.; Kwon, Myeun

    2008-10-15

    Plasma experiments on KSTAR are scheduled to start up this year (2008). We have developed an electron cyclotron emission (ECE) radiometer to measure the radial electron temperature profiles in KSTAR experiments. The radiometer system consists, briefly, of two downconversion stages, amplifiers, bandpass filter banks, and video detectors. These components are made commercially or developed in house. The system detects ECE power in the frequency range from 110 to 196 GHz, the detected signal being resolved by means of 48 frequency windows. Before installation of this system on KSTAR, we installed a part of this system on large helical device (LHD) to study the system under similar plasma conditions. In this experiment, the signal amplitude, considered to be proportional to the electron temperature, is measured. The time-dependent traces of the electron temperature measured by this radiometer are in good agreement with those provided by the LHD Michelson spectrometer. The system noise level which limits the minimum measurable temperature (converted to the electron temperature) is about 30 eV.

  9. [High-frequency ventilation. Development of new ventilation systems--experimental and clinical results].

    PubMed

    Mutz, N

    1984-01-01

    Based on the well known High Frequency Jet Ventilation (HFJV) two modified types of High Frequency Ventilation, Forced Diffusion Ventilation (FDV) and High Frequency Pulsation (HFP) have been developed. Both systems are designed to allow ventilation with very small volume portions in the upper range of HFV frequencies. In dog experiments sufficient gas exchange could be maintained during FDV up to frequencies 3000 per minute and even with an uninterrupted "continuous" jet entering the lungs on carina level. With this mode of ventilation lung could be kept in a resting position. Due to particular configuration of a pair of nozzles at the tip of a modified endotracheal catheter fresh gas is forced down the airways along the inner edges of bifurcations towards the lung periphery. At the same time stale gas leaves the lung via the remaining cross section of the airways. Thus a continuous scavanging process can be established without significant lung inflation. This mechanisms are not met during HFP. Therefore the range of frequencies achievable with this type of ventilation is significantly lower (250 to 500/min.) and "tidal volumes" are much higher. However, they are still beyond the anatomical dead space which suggest again a contribution of alternative mechanisms to gas transport. The impact of both types of HFV on gas exchange and pressure-flow conditions were studied in lung models as well as in animal experiments. FDV and HFP were also applied successfully to a group of 23 patients undergoing major lung surgery. In all patients it was possible to maintain excellent gas exchange throughout the whole surgical procedure. The exposure of the surgical field was much more quiet as compared to IPPV. Due to the small tidal volumes lung pressures can be kept much lower and gas losses via the open bronchi and lung surface are reduced dramatically.

  10. Development of high time resolution measurement system of frequency characteristics in bioelectrical impedance for biodynamic analysis

    NASA Astrophysics Data System (ADS)

    Nakamura, Takao; Kusuhara, Toshimasa; Yamamoto, Yoshitake

    2006-11-01

    We have proposed biodynamic analysis using bioelectrical impedance at 50 kHz, which is measured with synchronous rectification method. In order to analyze impedance parameters in biodynamics, the measurement of frequency characteristics in bioelectrical impedance with a high time resolution are required. Therefore we have developed a high time resolution measurement system for bioelectrical impedance with 10 frequency points and time resolution of 1 ms. A voltage E A, which consisted of fundamental wave and 9 kinds of harmonic wave from 1 kHz to 1MHz, were converted to current. The current flowed through human body and a potential voltage, EV was detected in the measured part. After A/D conversion of EV and E A in the sampling frequency 2 MHz, data number 2048 points, the impedance were calculated using Fast Fourier Transform. The measured time 1.024 ms was the period of the fundamental wave and time resolution of this system. The specification is enough accuracy for measurement of bioelectrical impedance for biodynamic analysis.

  11. Development and Testing of a Single Frequency Terahertz Imaging System for Breast Cancer Detection

    PubMed Central

    St. Peter, Benjamin; Yngvesson, Sigfrid; Siqueira, Paul; Kelly, Patrick; Khan, Ashraf; Glick, Stephen; Karellas, Andrew

    2013-01-01

    The ability to discern malignant from benign tissue in excised human breast specimens in Breast Conservation Surgery (BCS) was evaluated using single frequency terahertz radiation. Terahertz (THz) images of the specimens in reflection mode were obtained by employing a gas laser source and mechanical scanning. The images were correlated with optical histological micrographs of the same specimens, and a mean discrimination of 73% was found for five out of six samples using Receiver Operating Characteristic (ROC) analysis. The system design and characterization is discussed in detail. The initial results are encouraging but further development of the technology and clinical evaluation is needed to evaluate its feasibility in the clinical environment. PMID:25055306

  12. Development of a Hydrogen Energy System as a Grid Frequency Management Tool

    SciTech Connect

    Ewan, Mitch; Rocheleau, Richard; Swider-Lyons, Karen; Virji, Meheboob; Randolph, Guenter

    2016-07-15

    The Hawai‘i Natural Energy Institute (HNEI) is conducting research to assess the technical potential of using an electrolyzer-based hydrogen (H2) production and storage system as a grid demand response tool using battery data from a 200 MW grid to show the kind of response required. The hydrogen produced by the electrolyzer is used for transportation. A 65 kg/day hydrogen energy system (HES) consisting of a PEM electrolyzer, 35 bar buffer tank, 450 bar compressor, and associated chiller systems was purchased and installed at the Hawaii Natural Energy Laboratory Hawaii Authority (NELHA) to demonstrate long-term durability of the electrolyzer under cyclic operation required for frequency regulation on an island grid system. The excess hydrogen was stored for use by three fuel-cell buses to be operated at Hawai‘i Volcanoes National Park (HAVO) and by the County of Hawai‘i Mass Transit Agency (MTA). This paper describes the site selection and equipment commissioning, plus a comprehensive test plan that was developed to characterize the performance and durability of the electrolyzer under dynamic load conditions. The controls were modified for the operating envelope and dynamic limits of the electrolyzer. While the data showed these modifications significantly improved the system response time, it is not fast enough to match a BESS response time for grid frequency management. The electrolyzer can only be used for slower acting changes (1 to 0.5 Hz). A potential solution is to design an electrolyzer/BESS hybrid system and develop a modeling program to find the optimum mix of battery and electrolyzer to provide the maximum grid regulation services at minimum cost.

  13. Development of a finger joint phantom for evaluation of frequency domain measurement systems.

    PubMed

    Netz, Uwe J; Scheel, Alexander K; Beuthan, Jürgen; Hielscher, Andreas H

    2006-01-01

    For development and test of new optical imaging devices, phantoms are widely used to emulate the tissue to be imaged. Phantom design gets more difficult the more complex the tissue is structured. We report on developing and testing a solid, stable finger joint phantom to simulate transillumination of finger joints in frequency-domain imaging systems. The phantom consists of the bone, capsule, skin, the capsule volume, and the joint gap. Silicone was used to build the solid parts and a glycerol-water solution for the fluid in the capsule volume and joint gap. The system to test the phantom is an optical frequency-domain scanning set-up. Different stages of joint inflammation as they occur in rheumatoid arthritis (BA) were emulated by assembling the phantom with capsule and fluid having different optical properties. Reliability of the phantom measurement was investigated by repeated assembling. The results show clear discrimination between different stages of joints within the signal deviation due to reassembling of the phantom.

  14. Development of a 64 channel ultrasonic high frequency linear array imaging system

    PubMed Central

    Hu, ChangHong; Zhang, Lequan; Cannata, Jonathan M.; Yen, Jesse; Shung, K. Kirk

    2011-01-01

    In order to improve the lateral resolution and extend the field of view of a previously reported 48 element 30 MHz ultrasound linear array and 16-channel digital imaging system, the development of a 256 element 30 MHz linear array and an ultrasound imaging system with increased channel count has been undertaken. This paper reports the design and testing of a 64 channel digital imaging system which consists of an analog front-end pulser/receiver, 64 channels of Time-Gain Compensation (TGC), 64 channels of high-speed digitizer as well as a beamformer. A Personal Computer (PC) is used as the user interface to display real-time images. This system is designed as a platform for the purpose of testing the performance of high frequency linear arrays that have been developed in house. Therefore conventional approaches were taken it its implementation. Flexibility and ease of use are of primary concern whereas consideration of cost-effectiveness and novelty in design are only secondary. Even so, there are many issues at higher frequencies but do not exist at lower frequencies need to be solved. The system provides 64 channels of excitation pulsers while receiving simultaneously at a 20 MHz–120 MHz sampling rate to 12-bits. The digitized data from all channels are first fed through Field Programmable Gate Arrays (FPGAs), and then stored in memories. These raw data are accessed by the beamforming processor to re-build the image or to be downloaded to the PC for further processing. The beamformer that applies delays to the echoes of each channel is implemented with the strategy that combines coarse (8.3ns) and fine delays (2 ns). The coarse delays are integer multiples of the sampling clock rate and are achieved by controlling the write enable pin of the First-In-First-Out (FIFO) memory to obtain valid beamforming data. The fine delays are accomplished with interpolation filters. This system is capable of achieving a maximum frame rate of 50 frames per second. Wire phantom

  15. Development of a 64 channel ultrasonic high frequency linear array imaging system.

    PubMed

    Hu, ChangHong; Zhang, Lequan; Cannata, Jonathan M; Yen, Jesse; Shung, K Kirk

    2011-12-01

    In order to improve the lateral resolution and extend the field of view of a previously reported 48 element 30 MHz ultrasound linear array and 16-channel digital imaging system, the development of a 256 element 30 MHz linear array and an ultrasound imaging system with increased channel count has been undertaken. This paper reports the design and testing of a 64 channel digital imaging system which consists of an analog front-end pulser/receiver, 64 channels of Time-Gain Compensation (TGC), 64 channels of high-speed digitizer as well as a beamformer. A Personal Computer (PC) is used as the user interface to display real-time images. This system is designed as a platform for the purpose of testing the performance of high frequency linear arrays that have been developed in house. Therefore conventional approaches were taken it its implementation. Flexibility and ease of use are of primary concern whereas consideration of cost-effectiveness and novelty in design are only secondary. Even so, there are many issues at higher frequencies but do not exist at lower frequencies need to be solved. The system provides 64 channels of excitation pulsers while receiving simultaneously at a 20-120 MHz sampling rate to 12-bits. The digitized data from all channels are first fed through Field Programmable Gate Arrays (FPGAs), and then stored in memories. These raw data are accessed by the beamforming processor to re-build the image or to be downloaded to the PC for further processing. The beamformer that applies delays to the echoes of each channel is implemented with the strategy that combines coarse (8.3 ns) and fine delays (2 ns). The coarse delays are integer multiples of the sampling clock rate and are achieved by controlling the write enable pin of the First-In-First-Out (FIFO) memory to obtain valid beamforming data. The fine delays are accomplished with interpolation filters. This system is capable of achieving a maximum frame rate of 50 frames per second. Wire phantom images

  16. Development of a portable system for checking radioactive sources using long wave radio frequency identification.

    PubMed

    Mori, K; Deji, S; Ito, S; Saze, T; Nishizawa, K

    2007-03-01

    A portable system for automatically checking radioactive sources stored in lead containers at low temperatures was developed in order to prevent the discharging of orphan sources and contaminated materials from a controlled area to the general public. A radio frequency identification (RFID) system using a long wave in a frequency range of 125 kHz was composed of identification tags, a reader, a notebook computer, and software. ID tags without batteries were devised by using integrated circuits with an electrically erasable programmable read-only memory of 250 bytes and antennas. This software consisted of operating and maintenance functions. The read range of the ID tags was adjusted to around 5 cm in order to avoid accidental contamination and for discriminating the multiple sources. A water layer of 6.9 cm had no influence on communication between the ID tags and the reader. The data of the ID tags stored at +4, -20, and -80 degrees C were precisely read 4 mo later. The influence of lead was completely removed by separating the ID tags more than 1.6 cm from the lead. A reader can exactly identify the data of the ID tags within 6.0 cm at a velocity less than 9.0 cm s(-1). Performance of the software was verified using mock data. Nine lists concerning registered, disposed, and missing sources, etc., were displayed on the computer monitor and printed out. An RFID system using long waves proved to be applicable for routinely checking radioactive sources.

  17. Development of a novel low frequency GPR system for ultra-deep detection in Mine

    NASA Astrophysics Data System (ADS)

    Xu, Xianlei; Peng, Suping; Yang, Feng

    2016-04-01

    Mine disasters sources is the main source of the underground coal mine accidents in China. This paper describes the development of a novel explosion proof ground penetrating radar (GPR) for mine disasters sources detection, aiming to solve the current problems of the small detection range and low precision in the mine advanced detection in China. A high performance unipolar pulse transmitting unit is developed by using avalanche transistors, and an effective pulse excitation source network. And a new pluggable combined low-frequency antenna involving three frequencies with 12.5MHz, 25 MHz and 50MHz, is designed and developed. The plate-type structure is designed, aiming to enhance the directivity of the antenna, and the achievement of the antenna impedance matching is implemented in the feed point based on the extensions interface design, enhancing the antenna bandwidth and reducing the standing wave interference. Moreover, a high precision stepper delay circuit is designed by transforming the number of the operational amplifier step and using the differential compensation between the metal-oxide semiconductor field effect transistors, aiming to improve the accuracy of the signal acquisition system. In order to adapt to the mine environment, the explosion-proof design is implemented for the GPR system, including the host, transmitter, receiver, battery box, antenna, and other components.Mine detection experiments is carried out and the results show: the novel GPR system can effectively detect the location and depth of the geological disasters source with the depth greater than30 m and the diameter greater than 3m, the maximum detection depth can be up to 80m, which break the current detection depth limitations within 30m, providing an effective technical support for the ultra-deep mine disasters detection and the safety problems in coal mine production.

  18. A Theory of the Visual System Biology Underlying Development of Spatial Frequency Lateralization

    ERIC Educational Resources Information Center

    Howard, Mary F.; Reggia, James A.

    2007-01-01

    The spatial frequency hypothesis contends that performance differences between the hemispheres on various visuospatial tasks are attributable to lateralized processing of the spatial frequency content of visual stimuli. Hellige has proposed that such lateralization could arise during infant development from the earlier maturation of the right…

  19. A Theory of the Visual System Biology Underlying Development of Spatial Frequency Lateralization

    ERIC Educational Resources Information Center

    Howard, Mary F.; Reggia, James A.

    2007-01-01

    The spatial frequency hypothesis contends that performance differences between the hemispheres on various visuospatial tasks are attributable to lateralized processing of the spatial frequency content of visual stimuli. Hellige has proposed that such lateralization could arise during infant development from the earlier maturation of the right…

  20. Development of Multiple-Frequency Ultrasonic Imaging System Using Multiple Resonance Piezoelectric Transducer

    NASA Astrophysics Data System (ADS)

    Akiyama, Iwaki; Yoshizumi, Natsuki; Saito, Shigemi; Wada, Yuji; Koyama, Daisuke; Nakamura, Kentaro

    2012-07-01

    The authors have developed a multiple frequency imaging system using a multiple resonance transducer (MRT) consisting of 1-3 composite materials with a low mechanical quality factor Q bonded together. The MRT has a structure consisting of thin and thick piezoelectric plates, two matching layers, and a backing layer. This makes it possible to obtain B-mode images of satisfactory resolution using ultrasonic pulses owing to their short duration. In this paper, the vibration property of the MRT derived through equivalent-circuit analysis is first shown. By utilizing the result, an MRT capable of transmitting ultrasonic pulses for generation of the images of biological tissues with satisfactory resolution is designed and prototyped. Setting the prototype transducer in the mechanical sector probe of commercial ultrasonic diagnosis equipment, the speckle reduction effect is demonstrated using images of various phantoms to mimic biological tissues and a human thyroid.

  1. Frequency domain measurement systems

    NASA Technical Reports Server (NTRS)

    Eischer, M. C.

    1978-01-01

    Stable frequency sources and signal processing blocks were characterized by their noise spectra, both discrete and random, in the frequency domain. Conventional measures are outlined, and systems for performing the measurements are described. Broad coverage of system configurations which were found useful is given. Their functioning and areas of application are discussed briefly. Particular attention is given to some of the potential error sources in the measurement procedures, system configurations, double-balanced-mixer-phase-detectors, and application of measuring instruments.

  2. Development of data communication system with ultra high frequency radio wave for implantable artificial hearts.

    PubMed

    Tsujimura, Shinichi; Yamagishi, Hiroto; Sankai, Yoshiyuki

    2009-01-01

    In order to minimize infection risks of patients with artificial hearts, wireless data transmission methods with electromagnetic induction or light have been developed. However, these methods tend to become difficult to transmit data if the external data transmission unit moves from its proper position. To resolve this serious problem, the purpose of this study is to develop a prototype wireless data communication system with ultra high frequency radio wave and confirm its performance. Due to its high-speed communication rate, low power consumption, high tolerance to electromagnetic disturbances, and secure wireless communication, we adopted Bluetooth radio wave technology for our system. The system consists of an internal data transmission unit and an external data transmission unit (53 by 64 by 16 mm, each), and each has a Bluetooth module (radio field intensity: 4 dBm, receiver sensitivity: -80 dBm). The internal unit also has a micro controller with an 8-channel 10-bit A/D converter, and the external unit also has a RS-232C converter. We experimented with the internal unit implanted into pig meat, and carried out data transmission tests to evaluate the performance of this system in tissue thickness of up to 3 mm. As a result, data transfer speeds of about 20 kbps were achieved within the communication distance of 10 m. In conclusion, we confirmed that the system can wirelessly transmit the data from the inside of the body to the outside, and it promises to resolve unstable data transmission due to accidental movements of an external data transmission unit.

  3. Frequency conversion system

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Waarts, Robert G. (Inventor)

    2001-01-01

    A frequency conversion system comprises first and second gain sources providing first and second frequency radiation outputs where the second gain source receives as input the output of the first gain source and, further, the second gain source comprises a Raman or Brillouin gain fiber for wave shifting a portion of the radiation of the first frequency output into second frequency radiation output to provided a combined output of first and second frequencies. Powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  4. Protocols development for security and privacy of radio frequency identification systems

    NASA Astrophysics Data System (ADS)

    Sabbagha, Fatin

    There are benefits to adopting radio frequency identification (RFID) technology, although there are methods of attack that can compromise the system. This research determined how that may happen and what possible solutions can keep that from happening. Protocols were developed to implement better security. In addition, new topologies were developed to handle the problems of the key management. Previously proposed protocols focused on providing mutual authentication and privacy between readers and tags. However, those protocols are still vulnerable to be attacked. These protocols were analyzed and the disadvantages shown for each one. Previous works assumed that the channels between readers and the servers were secure. In the proposed protocols, a compromised reader is considered along with how to prevent tags from being read by that reader. The new protocols provide mutual authentication between readers and tags and, at the same time, remove the compromised reader from the system. Three protocols are proposed. In the first protocol, a mutual authentication is achieved and a compromised reader is not allowed in the network. In the second protocol, the number of times a reader contacts the server is reduced. The third protocol provides authentication and privacy between tags and readers using a trusted third party. The developed topology is implemented using python language and simulates work to check the efficiency regarding the processing time. The three protocols are implemented by writing codes in C language and then compiling them in MSP430. IAR Embedded workbench is used, which is an integrated development environment with the C/C++ compiler to generate a faster code and to debug the microcontroller. In summary, the goal of this research is to find solutions for the problems on previously proposed protocols, handle a compromised reader, and solve key management problems.

  5. Development and testing of a frequency-agile optical parametric oscillator system for differential absorption lidar

    NASA Astrophysics Data System (ADS)

    Weibring, P.; Smith, J. N.; Edner, H.; Svanberg, S.

    2003-10-01

    An all-solid-state fast-tuning lidar transmitter for range- and temporally resolved atmospheric gas concentration measurements has been developed and thoroughly tested. The instrument is based on a commercial optical parametric oscillator (OPO) laser system, which has been redesigned with piezoelectric transducers mounted on the wavelength-tuning mirror and on the crystal angle tuning element in the OPO. Piezoelectric transducers similarly control a frequency-mixing stage and doubling stage, which have been incorporated to extend system capabilities to the mid-IR and UV regions. The construction allows the system to be tuned to any wavelength, in any order, in the range of the piezoelectric transducers on a shot-to-shot basis. This extends the measurement capabilities far beyond the two-wavelength differential absorption lidar method and enables simultaneous measurements of several gases. The system performance in terms of wavelength, linewidth, and power stability is monitored in real time by an étalon-based wave meter and gas cells. The tests showed that the system was able to produce radiation in the 220-4300-nm-wavelength region, with an average linewidth better than 0.2 cm-1 and a shot-to-shot tunability up to 160 cm-1 within 20 ms. The utility of real-time linewidth and wavelength measurements is demonstrated by the ability to identify occasional poor quality laser shots and disregard these measurements. Also, absorption cell measurements of methane and mercury demonstrate the performance in obtaining stable wavelength and linewidth during rapid scans in the mid-IR and UV regions.

  6. Development of an automatic frequency control system for an X-band (=9300 MHz) RF electron linear accelerator

    NASA Astrophysics Data System (ADS)

    Cha, Sungsu; Kim, Yujong; Lee, Byung Cheol; Park, Hyung Dal; Lee, Seung Hyun; Buaphad, Pikad

    2017-05-01

    KAERI is developing a 6 MeV X-band radio frequency (RF) electron linear accelerator for medical purposes. The proposed X-band accelerator consists of an e-gun, an accelerating structure, two solenoid magnets, two steering magnets, a magnetron, a modulator, and an automatic frequency control (AFC) system. The accelerating structure of the component consists of oxygen-free high-conductivity copper (OFHC). Therefore, the ambient temperature changes the volume, and the resonance frequency of the accelerating structure also changes. If the RF frequency of a 9300 MHz magnetron and the resonance frequency of the accelerating structure do not match, it can degrade the performance. That is, it will decrease the output power, lower the beam current, decrease the X-ray dose rate, increase the reflection power, and result in unstable operation of the accelerator. Accelerator operation should be possible at any time during all four seasons. To prevent humans from being exposed to radiation when it is operated, the accelerator should also be operable through remote monitoring and remote control. Therefore, the AFC system is designed to meet these requirements; it is configured based on the concept of a phase-locked loop (PLL) model, which includes an RF section, an intermediate frequency (IF) [1-3] section, and a local oscillator (LO) section. Some resonance frequency controllers use a DC motor, chain, and potentiometer to store the position and tune the frequency [4,5]. Our AFC system uses a step motor to tune the RF frequency of the magnetron. The maximum tuning turn number of our magnetron frequency tuning shaft is ten. Since the RF frequency of our magnetron is 9300±25 MHz, it gives 5 MHz (∵±25 MHz/10 turns → 50 MHz/10 turns =5 MHz/turn) frequency tuning per turn. The rotation angle of our step motor is 0.72° per step and the total step number per one rotation is 360°/0.72°=500 steps. Therefore, the tuning range per step is 10 kHz/step (=5 MHz per turn/500 steps per

  7. Development of a portable frequency-domain angle-resolved low coherence interferometry system

    NASA Astrophysics Data System (ADS)

    Pyhtila, John W.; Wax, Adam

    2007-02-01

    Improved methods for detecting dysplasia, or pre-cancerous growth, are a current clinical need. Random biopsy and subsequent diagnosis through histological analysis is the current gold standard in endoscopic surveillance for dysplasia. However, this approach only allows limited examination of the at-risk tissue and has the drawback of a long delay in time-to-diagnosis. In contrast, optical scattering spectroscopy methods offer the potential to assess cellular structure and organization in vivo, thus allowing for instantaneous diagnosis and increased coverage of the at-risk tissue. Angle-resolved low coherence interferometry (a/LCI), a novel scattering spectroscopy technique, combines the ability of low-coherence interferometry to isolate scattered light from sub-surface tissue layers with the ability of light scattering spectroscopy to obtain structural information on sub-wavelength scales, specifically by analyzing the angular distribution of the backscattered light. In application to examining tissue, a/LCI enables depthresolved quantitative measurements of changes in the size and texture of cell nuclei, which are characteristic biomarkers of dysplasia. The capabilities of a/LCI were demonstrated initially by detecting pre-cancerous changes in epithelial cells within intact, unprocessed, animal tissues. Recently, we have developed a new frequency-domain a/LCI system, with sub-second acquisition time and a novel fiber optic probe. Preliminary results using the fa/LCI system to examine human esophageal tissue in Barrett's esophagus patients demonstrate the clinical viability of the approach. In this paper, we present a new portable system which improves upon the design of the fa/LCI system to allow for higher quality data to be collected in the clinic. Accurate sizing of polystyrene microspheres and cell nuclei from ex vivo human esophageal tissue is presented. These results demonstrate the promise of a/LCI as a clinically viable diagnostic tool.

  8. A Web-Based Graphical Food Frequency Assessment System: Design, Development and Usability Metrics.

    PubMed

    Franco, Rodrigo Zenun; Alawadhi, Balqees; Fallaize, Rosalind; Lovegrove, Julie A; Hwang, Faustina

    2017-05-08

    Food frequency questionnaires (FFQs) are well established in the nutrition field, but there remain important questions around how to develop online tools in a way that can facilitate wider uptake. Also, FFQ user acceptance and evaluation have not been investigated extensively. This paper presents a Web-based graphical food frequency assessment system that addresses challenges of reproducibility, scalability, mobile friendliness, security, and usability and also presents the utilization metrics and user feedback from a deployment study. The application design employs a single-page application Web architecture with back-end services (database, authentication, and authorization) provided by Google Firebase's free plan. Its design and responsiveness take advantage of the Bootstrap framework. The FFQ was deployed in Kuwait as part of the EatWellQ8 study during 2016. The EatWellQ8 FFQ contains 146 food items (including drinks). Participants were recruited in Kuwait without financial incentive. Completion time was based on browser timestamps and usability was measured using the System Usability Scale (SUS), scoring between 0 and 100. Products with a SUS higher than 70 are considered to be good. A total of 235 participants created accounts in the system, and 163 completed the FFQ. Of those 163 participants, 142 reported their gender (93 female, 49 male) and 144 reported their date of birth (mean age of 35 years, range from 18-65 years). The mean completion time for all FFQs (n=163), excluding periods of interruption, was 14.2 minutes (95% CI 13.3-15.1 minutes). Female participants (n=93) completed in 14.1 minutes (95% CI 12.9-15.3 minutes) and male participants (n=49) completed in 14.3 minutes (95% CI 12.6-15.9 minutes). Participants using laptops or desktops (n=69) completed the FFQ in an average of 13.9 minutes (95% CI 12.6-15.1 minutes) and participants using smartphones or tablets (n=91) completed in an average of 14.5 minutes (95% CI 13.2-15.8 minutes). The median SUS

  9. Development of high frequency low weight power magnetics for aerospace power systems

    NASA Technical Reports Server (NTRS)

    Schwarze, G. E.

    1984-01-01

    A dominant design consideration in the development of space type power mangetic devices is the application of reliable thermal control methods to prevent device failure which is due to excessive temperature rises and hot temperatures in critical areas. The resultant design must also yield low weight, high efficiency, high reliability and maintainability, and long life. The weight savings and high efficiency that results by going to high frequency and unique thermal control techniques is demonstrated by the development of a 25 kVA, 20 kHz space type transformer under the power magnetics technology program. Work in the area of power rotary transformer is also discussed.

  10. Development and validation of reverberation-chamber type whole-body exposure system for mobile-phone frequency.

    PubMed

    Jung, K B; Kim, T H; Kim, J L; Doh, H J; Chung, Y C; Choi, J H; Pack, J K

    2008-01-01

    We developed whole-body exposure systems for in-vivo study at cellular (848.5 MHz) and Personal Communication System (PCS, 1,762.5 MHz) frequency, utilizing reverberation chamber. The field uniformities in the test area of the designed chambers were verified by simulation and measurement. In the whole-body exposure environment, Specific Absorption Rate (SAR) distributions inside of mice were calculated using Finite Difference Time Domain (FDTD) simulation. Key results are presented in this article.

  11. Development of Frequency-Division Multiplexing Readout System for Large-Format TES X-ray Microcalorimeter Arrays

    NASA Astrophysics Data System (ADS)

    Sakai, K.; Yamamoto, R.; Takei, Y.; Mitsuda, K.; Yamasaki, N. Y.; Hidaka, M.; Nagasawa, S.; Kohjiro, S.; Miyazaki, T.

    2016-07-01

    We are developing the frequency-division multiplexing (FDM) readout system aimed to realize the 400-pixel transition edge sensor (TES) microcalorimeter array for the DIOS mission as well as large-format arrays with more than a thousand of TES for future space missions such as the ATHENA mission. The developed system consists of the low-power superconducting quantum interference device (SQUID), the digital FDM electronics, and the analog front-end to bridge the SQUID and the digital electronics. Using the developed readout system, we performed a TES readout experiment and succeeded to multiplex four TES signals with the single-staged cryogenic setup. We have experienced two issues during the experiment: an excess noise and crosstalk. The brief overview of the developed system and the details, results, and issues of the TES multiplexing readout experiment is discussed.

  12. Development of a radio frequency heating system for sterilization of vacuum-packed fish in water.

    PubMed

    Uemura, Kunihiko; Kanafusa, Sumiyo; Takahashi, Chieko; Kobayashi, Isao

    2017-04-01

    We developed equipment that quickly and uniformly heats packed whole fish in circulating tap water using radio frequency (RF) heating. Four vacuumed plastic-packed Pacific sauries in tap water were set in a radial arrangement between coaxial cylindrical electrodes in a closed vessel. For sterilization testing, Bacillus subtilis spores added in the center of the sauries were counted after treatment. For quality assurance, meat color and backbone hardness were measured after treatment. The temperature at the center of the sauries was increased up to 130 °C for 19 min using 9 kW RF heating, and up to 119 °C for 45 min using conventional heating (CH) at 120 °C. B. subtilis spores were decreased by five logarithmic orders using RF heating and by four logarithmic orders using CH. The RF-treated meat was brighter than the CH-treated meat, and the RF-treated backbone was softer than CH-treated one.

  13. AUTOMATIC FREQUENCY CONTROL SYSTEM

    DOEpatents

    Hansen, C.F.; Salisbury, J.D.

    1961-01-10

    A control is described for automatically matching the frequency of a resonant cavity to that of a driving oscillator. The driving oscillator is disconnected from the cavity and a secondary oscillator is actuated in which the cavity is the frequency determining element. A low frequency is mixed with the output of the driving oscillator and the resultant lower and upper sidebands are separately derived. The frequencies of the sidebands are compared with the secondary oscillator frequency. deriving a servo control signal to adjust a tuning element in the cavity and matching the cavity frequency to that of the driving oscillator. The driving oscillator may then be connected to the cavity.

  14. FREQUENCY STABILIZING SYSTEM

    DOEpatents

    Kerns, Q.A.; Anderson, O.A.

    1960-05-01

    An electronic control circuit is described in which a first signal frequency is held in synchronization with a second varying reference signal. The circuit receives the first and second signals as inputs and produces an output signal having an amplitude dependent upon rate of phase change between the two signals and a polarity dependent on direction of the phase change. The output may thus serve as a correction signal for maintaining the desired synchronization. The response of the system is not dependent on relative phase angle between the two compared signals. By having practically no capacitance in the circuit, there is minimum delay between occurrence of a phase shift and a response in the output signal and therefore very fast synchronization is effected.

  15. Development of multi-frequency ESR system for high-pressure measurements up to 2.5 GPa.

    PubMed

    Sakurai, T; Fujimoto, K; Matsui, R; Kawasaki, K; Okubo, S; Ohta, H; Matsubayashi, K; Uwatoko, Y; Tanaka, H

    2015-10-01

    A new piston-cylinder pressure cell for electron spin resonance (ESR) has been developed. The pressure cell consists of a double-layer hybrid-type cylinder with internal components made of the ZrO2-based ceramics. It can generate a pressure of 2 GPa repeatedly and reaches a maximum pressure of around 2.5 GPa. A high-pressure ESR system using a cryogen-free superconducting magnet up 10T has also been developed for this hybrid-type pressure cell. The frequency region is from 50 GHz to 400 GHz. This is the first time a pressure above 2 GPa has been achieved in multi-frequency ESR system using a piston-cylinder pressure cell. We demonstrate its potential by showing the results of the high-pressure ESR of the S=1 system with the single ion anisotropy NiSnCl6·6H2O and the S=1/2 quantum spin system CsCuCl3. We performed ESR measurements of these systems above 2 GPa successfully. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Quantum systems under frequency modulation

    NASA Astrophysics Data System (ADS)

    Silveri, M. P.; Tuorila, J. A.; Thuneberg, E. V.; Paraoanu, G. S.

    2017-05-01

    We review the physical phenomena that arise when quantum mechanical energy levels are modulated in time. The dynamics resulting from changes in the transition frequency is a problem studied since the early days of quantum mechanics. It has been of constant interest both experimentally and theoretically since, with the simple two-state model providing an inexhaustible source of novel concepts. When the transition frequency of a quantum system is modulated, several phenomena can be observed, such as Landau-Zener-Stückelberg-Majorana interference, motional averaging and narrowing, and the formation of dressed states with the appearance of sidebands in the spectrum. Adiabatic changes result in the accumulation of geometric phases, which can be used to create topological states. In recent years, an exquisite experimental control in the time domain was gained through the parameters entering the Hamiltonian, and high-fidelity readout schemes allowed the state of the system to be monitored non-destructively. These developments were made in the field of quantum devices, especially in superconducting qubits, as a well as in atomic physics, in particular in ultracold gases. As a result of these advances, it became possible to demonstrate many of the fundamental effects that arise in a quantum system when its transition frequencies are modulated. The purpose of this review is to present some of these developments, from two-state atoms and harmonic oscillators to multilevel and many-particle systems.

  17. Quantum systems under frequency modulation.

    PubMed

    Silveri, M P; Tuorila, J A; Thuneberg, E V; Paraoanu, G S

    2017-05-01

    We review the physical phenomena that arise when quantum mechanical energy levels are modulated in time. The dynamics resulting from changes in the transition frequency is a problem studied since the early days of quantum mechanics. It has been of constant interest both experimentally and theoretically since, with the simple two-state model providing an inexhaustible source of novel concepts. When the transition frequency of a quantum system is modulated, several phenomena can be observed, such as Landau-Zener-Stückelberg-Majorana interference, motional averaging and narrowing, and the formation of dressed states with the appearance of sidebands in the spectrum. Adiabatic changes result in the accumulation of geometric phases, which can be used to create topological states. In recent years, an exquisite experimental control in the time domain was gained through the parameters entering the Hamiltonian, and high-fidelity readout schemes allowed the state of the system to be monitored non-destructively. These developments were made in the field of quantum devices, especially in superconducting qubits, as a well as in atomic physics, in particular in ultracold gases. As a result of these advances, it became possible to demonstrate many of the fundamental effects that arise in a quantum system when its transition frequencies are modulated. The purpose of this review is to present some of these developments, from two-state atoms and harmonic oscillators to multilevel and many-particle systems.

  18. Development and evaluation of intermediate frequency magnetic field exposure system for studies of in vitro biological effects.

    PubMed

    Fujita, Atsushi; Hirota, Izuo; Kawahara, Yoshinobu; Omori, Hideki

    2007-10-01

    We have developed an intermediate frequency (IF) magnetic field exposure system for in vitro studies. Since there are no previous studies on exposure to heating-frequency magnetic fields generated from an induction heating (IH) cook top, there is a strong need for such an exposure system and for biological studies of IF magnetic fields. This system mainly consists of a magnetic-field-generating coil housed inside an incubator, inside which cultured cells can be exposed to magnetic field. Two systems were prepared to allow the experiment to be conducted in a double-blind manner. The level of the generated magnetic field was set to 532 microT rms in the exposure space, 23 kHz, 80 times the value in the International Commission on Non-ionizing Radiation Protection (ICNIRP) guidelines, with a spatial field uniformity better than 3.8%. The waveforms were nearly sinusoidal. It was also confirmed that the parasitic electric field was 157 V/m rms and the induced electric field was 1.9 V/m rms. The temperature was maintained at 36.5 +/- 0.5 degrees C for 2 h. Furthermore, leaked magnetic flux density was 0.7 microT rms or lower at extremely low frequency (ELF) and IF in the stopped system when the other system was being operated, and the environmental magnetic flux density was 0.1 microT rms or lower at the center of the coils. As a result, it was confirmed that this system could be successfully used to evaluate the biological effects of exposure to IF magnetic fields.

  19. Frequency conversion system

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor)

    2001-01-01

    Laser diode pumped mid-IR wavelength sources include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  20. Sudden infant death syndrome: case-control frequency differences at genes pertinent to early autonomic nervous system embryologic development.

    PubMed

    Weese-Mayer, Debra E; Berry-Kravis, Elizabeth M; Zhou, Lili; Maher, Brion S; Curran, Mark E; Silvestri, Jean M; Marazita, Mary L

    2004-09-01

    We have previously identified polymorphisms in the serotonin transporter gene promoter region and in intron 2 that were more common among sudden infant death syndrome (SIDS) cases compared with control subjects. To elucidate further the genetic profile that might increase an infant's vulnerability to SIDS, we focused on the recognized relationship between autonomic nervous system (ANS) dysregulation and SIDS. We therefore studied genes pertinent to early embryologic development of the ANS, including MASH1, BMP2, PHOX2a, PHOX2b, RET, ECE1, EDN1, TLX3, and EN1 in 92 probands with SIDS and 92 gender- and ethnicity-matched control subjects. Eleven protein-changing rare mutations were identified in 14 of 92 SIDS cases among the PHOX2a, RET, ECE1, TLX3, and EN1 genes. Only 1 of these mutations (TLX3) was identified in 2 of 92 control subjects. Black infants accounted for 10 of these mutations in SIDS cases and 2 control subjects. Four protein-changing common polymorphisms were identified in BMP2, RET, ECE1, and EDN1, but the allele frequency did not differ between SIDS cases and control subjects. However, among SIDS cases, the allele frequency for the BMP2 common polymorphism demonstrated ethnic differences; among control subjects, the allele frequency for the BMP2 and the ECE1 common polymorphisms also demonstrated ethnic differences. These data represent further refinement of the genetic profile that might place an infant at risk for SIDS.

  1. Nanoelectromechanical systems: Nanodevice motion at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Henry Huang, Xue Ming; Zorman, Christian A.; Mehregany, Mehran; Roukes, Michael L.

    2003-01-01

    It has been almost forgotten that the first computers envisaged by Charles Babbage in the early 1800s were mechanical and not electronic, but the development of high-frequency nanoelectromechanical systems is now promising a range of new applications, including sensitive mechanical charge detectors and mechanical devices for high-frequency signal processing, biological imaging and quantum measurement. Here we describe the construction of nanodevices that will operate with fundamental frequencies in the previously inaccessible microwave range (greater than 1 gigahertz). This achievement represents a significant advance in the quest for extremely high-frequency nanoelectromechanical systems.

  2. Automatic oscillator frequency control system

    NASA Technical Reports Server (NTRS)

    Smith, S. F. (Inventor)

    1985-01-01

    A frequency control system makes an initial correction of the frequency of its own timing circuit after comparison against a frequency of known accuracy and then sequentially checks and corrects the frequencies of several voltage controlled local oscillator circuits. The timing circuit initiates the machine cycles of a central processing unit which applies a frequency index to an input register in a modulo-sum frequency divider stage and enables a multiplexer to clock an accumulator register in the divider stage with a cyclical signal derived from the oscillator circuit being checked. Upon expiration of the interval, the processing unit compares the remainder held as the contents of the accumulator against a stored zero error constant and applies an appropriate correction word to a correction stage to shift the frequency of the oscillator being checked. A signal from the accumulator register may be used to drive a phase plane ROM and, with periodic shifts in the applied frequency index, to provide frequency shift keying of the resultant output signal. Interposition of a phase adder between the accumulator register and phase plane ROM permits phase shift keying of the output signal by periodic variation in the value of a phase index applied to one input of the phase adder.

  3. Swept Frequency Laser Metrology System

    NASA Technical Reports Server (NTRS)

    Zhao, Feng (Inventor)

    2010-01-01

    A swept frequency laser ranging system having sub-micron accuracy that employs multiple common-path heterodyne interferometers, one coupled to a calibrated delay-line for use as an absolute reference for the ranging system. An exemplary embodiment uses two laser heterodyne interferometers to create two laser beams at two different frequencies to measure distance and motions of target(s). Heterodyne fringes generated from reflections off a reference fiducial X(sub R) and measurement (or target) fiducial X(sub M) are reflected back and are then detected by photodiodes. The measured phase changes Delta phi(sub R) and Delta phi (sub m) resulting from the laser frequency swept gives target position. The reference delay-line is the only absolute reference needed in the metrology system and this provides an ultra-stable reference and simple/economical system.

  4. Power enhanced frequency conversion system

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor); Waarts, Robert G. (Inventor)

    2001-01-01

    A frequency conversion system includes at least one source providing a first near-IR wavelength output including a gain medium for providing high power amplification, such as double clad fiber amplifier, a double clad fiber laser or a semiconductor tapered amplifier to enhance the power output level of the near-IR wavelength output. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Ra-man/Brillouin amplifier or oscillator between the high power source and the NFM device.

  5. Monolithically integrated absolute frequency comb laser system

    SciTech Connect

    Wanke, Michael C.

    2016-07-12

    Rather than down-convert optical frequencies, a QCL laser system directly generates a THz frequency comb in a compact monolithically integrated chip that can be locked to an absolute frequency without the need of a frequency-comb synthesizer. The monolithic, absolute frequency comb can provide a THz frequency reference and tool for high-resolution broad band spectroscopy.

  6. Proposal and Development of a High Voltage Variable Frequency Alternating Current Power System for Hybrid Electric Aircraft

    NASA Technical Reports Server (NTRS)

    Sadey, David J.; Taylor, Linda M.; Beach, Raymond F.

    2016-01-01

    The development of ultra-efficient commercial vehicles and the transition to low-carbon emission propulsion are seen as thrust paths within NASA Aeronautics. A critical enabler to these paths comes in the form of hybrid-electric propulsion systems. For megawatt-class systems, the best power system topology for these hybrid-electric propulsion systems is debatable. Current proposals within NASA and the Aero community suggest using a combination of AC and DC for power transmission. This paper proposes an alternative to the current thought model through the use of a primarily high voltage AC power generation, transmission, and distribution systems, supported by the Convergent Aeronautics Solutions (CAS) Project. This system relies heavily on the use of dual-fed induction machines, which provide high power densities, minimal power conversion, and variable speed operation. The paper presents background on the project along with the system architecture, development status and preliminary results.

  7. Proposal and Development of a High Voltage Variable Frequency Alternating Current Power System for Hybrid Electric Aircraft

    NASA Technical Reports Server (NTRS)

    Sadey, David J.; Taylor, Linda M.; Beach, Raymond F.

    2017-01-01

    The development of ultra-efficient commercial vehicles and the transition to low-carbon emission propulsion are seen as strategic thrust paths within NASA Aeronautics. A critical enabler to these paths comes in the form of hybrid electric propulsion systems. For megawatt-class systems, the best power system topology for these hybrid electric propulsion systems is debatable. Current proposals within NASA and the Aero community suggest using a combination of alternating current (AC) and direct current (DC) for power generation, transmission, and distribution. This paper proposes an alternative to the current thought model through the use of a primarily high voltage AC power system, supported by the Convergent Aeronautics Solutions (CAS) Project. This system relies heavily on the use of doubly-fed induction machines (DFIMs), which provide high power densities, minimal power conversion, and variable speed operation. The paper presents background on the activity along with the system architecture, development status, and preliminary results.

  8. Fundamental analysis and development of the current and voltage control method by changing the driving frequency for the transcutaneous energy transmission system.

    PubMed

    Miura, Hidekazu; Yamada, Akihiro; Shiraishi, Yasuyuki; Yambe, Tomoyuki

    2015-08-01

    We have been developing transcutaneous energy transmission system (TETS) for a ventricular assist device, shape memory alloy (SMA) fibered artificial organs and so on, the system has high efficiency and a compact size. In this paper, we summarize the development, design method and characteristics of the TETS. New control methods for stabilizing output voltage or current of the TETS are proposed. These methods are primary side, are outside of the body, not depending on a communication system from the inside the body. Basically, the TETS operates at the fixed frequency with a suitable compensation capacitor so that the internal impedance is minimalized and a flat load characteristic is obtained. However, when the coil shifted from the optimal position, the coupling factor changes and the output is fluctuated. TETS has a resonant property; its output can be controlled by changing the driving frequency. The continuous current to continuous voltage driving method was implemented by changing driving frequency and setting of limitation of low side frequency. This method is useful for battery charging system for electrically driven artificial hearts and also useful for SMA fibered artificial organs which need intermittent high peak power comsumption. In this system, the internal storage capacitor is charged slowly while the fibers are turned off and discharge the energy when the fibers are turned on. We examined the effect of the system. It was found that the size and maximum output of the TETS would able to be reduced.

  9. Variable frequency microwave furnace system

    DOEpatents

    Bible, Don W.; Lauf, Robert J.

    1994-01-01

    A variable frequency microwave furnace system (10) designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity (34) for testing or other selected applications. The variable frequency microwave furnace system (10) includes a microwave signal generator (12) or microwave voltage-controlled oscillator (14) for generating a low-power microwave signal for input to the microwave furnace. A first amplifier (18) may be provided to amplify the magnitude of the signal output from the microwave signal generator (12) or the microwave voltage-controlled oscillator (14). A second amplifier (20) is provided for processing the signal output by the first amplifier (18). The second amplifier (20) outputs the microwave signal input to the furnace cavity (34). In the preferred embodiment, the second amplifier (20) is a traveling-wave tube (TWT). A power supply (22) is provided for operation of the second amplifier (20). A directional coupler (24) is provided for detecting the direction of a signal and further directing the signal depending on the detected direction. A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load (28).

  10. Variable frequency microwave furnace system

    DOEpatents

    Bible, D.W.; Lauf, R.J.

    1994-06-14

    A variable frequency microwave furnace system designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity for testing or other selected applications. The variable frequency microwave furnace system includes a microwave signal generator or microwave voltage-controlled oscillator for generating a low-power microwave signal for input to the microwave furnace. A first amplifier may be provided to amplify the magnitude of the signal output from the microwave signal generator or the microwave voltage-controlled oscillator. A second amplifier is provided for processing the signal output by the first amplifier. The second amplifier outputs the microwave signal input to the furnace cavity. In the preferred embodiment, the second amplifier is a traveling-wave tube (TWT). A power supply is provided for operation of the second amplifier. A directional coupler is provided for detecting the direction of a signal and further directing the signal depending on the detected direction. A first power meter is provided for measuring the power delivered to the microwave furnace. A second power meter detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load. 5 figs.

  11. A low frequency RFI monitoring system

    NASA Astrophysics Data System (ADS)

    Amiri, Shahram; Shankar, N. Udaya; Girish, B. S.; Somashekar, R.

    Radio frequency interference (RFI) is a growing problem for research in radio astronomy particularly at wavelengths longer than 2m. For satisfactory operation of a radio telescope, several bands have been protected for radio astronomy observations by the International Telecommunication Union. Since the radiation from cosmic sources are typically 40 to 100 dB below the emission from services operating in unprotected bands, often the out-of-band emission limits the sensitivity of astronomical observations. Moreover, several radio spectral emissions from cosmic sources are present in the frequency range outside the allocated band for radio astronomy. Thus monitoring of RFI is essential before building a receiver system for low frequency radio astronomy. We describe the design and development of an RFI monitoring system operating in the frequency band 30 to 100 MHz. This was designed keeping in view our proposal to extend the frequency of operation of GMRT down to 40 MHz. The monitor is a PC based spectrometer recording the voltage output of a receiver connected to an antenna, capable of digitizing the low frequency RF directly with an 8 bit ADC and sampling bandwidths up to 16 MHz. The system can operate continuously in almost real-time with a loss of only 2% of data. Here we will present the systems design aspects and the results of RFI monitoring carried out at the Raman Research Institute, Bangalore and at the GMRT site in Khodad.

  12. Development of a Media Driven Online Assessment System: Improving Quality, Frequency, and Deployment of Grades and Feedback in Higher Education

    ERIC Educational Resources Information Center

    Jaurez, James J.

    2013-01-01

    Information communication technologies (ICT) in education is an expanding field, and within this field there is a need for development of effective systems for faculty and learners to communicate feedback and assess performance. The increasing migration of many academic disciplines and courses to an online format has prompted an increased need for…

  13. Development of a Media Driven Online Assessment System: Improving Quality, Frequency, and Deployment of Grades and Feedback in Higher Education

    ERIC Educational Resources Information Center

    Jaurez, James J.

    2013-01-01

    Information communication technologies (ICT) in education is an expanding field, and within this field there is a need for development of effective systems for faculty and learners to communicate feedback and assess performance. The increasing migration of many academic disciplines and courses to an online format has prompted an increased need for…

  14. Odd-frequency Superconductivity in Driven Systems

    NASA Astrophysics Data System (ADS)

    Triola, Christopher; Balatsky, Alexander

    We show that Berezinskii's classification of the symmetries of Cooper pair amplitudes in terms of parity under transformations that invert spin, space, time, and orbital degrees of freedom holds for driven systems even in the absence of translation invariance. We then discuss the conditions under which pair amplitudes which are odd in frequency can emerge in driven systems. Considering a model Hamiltonian for a superconductor coupled to an external driving potential, we investigate the influence of the drive on the anomalous Green's function, density of states, and spectral function. We find that the anomalous Green's function develops odd in frequency component in the presence of an external drive. Furthermore we investigate how these odd-frequency terms are related to satellite features in the density of states and spectral function. Supported by US DOE BES E 304.

  15. Odd-frequency superconductivity in driven systems

    NASA Astrophysics Data System (ADS)

    Triola, Christopher; Balatsky, Alexander V.

    2016-09-01

    We show that Berezinskii's classification of the symmetries of Cooper pair amplitudes holds for driven systems even in the absence of translation invariance. We then consider a model Hamiltonian for a superconductor coupled to an external driving potential and, treating the drive as a perturbation, we investigate the corrections to the anomalous Green's function, density of states, and spectral function. We find that in the presence of an external drive the anomalous Green's function develops terms that are odd in frequency and that the same mechanism responsible for these odd-frequency terms generates additional features in the density of states and spectral function.

  16. Development of a Multi-modal Tissue Diagnostic System Combining High Frequency Ultrasound and Photoacoustic Imaging with Lifetime Fluorescence Spectroscopy

    PubMed Central

    Sun, Yang; Stephens, Douglas N.; Park, Jesung; Sun, Yinghua; Marcu, Laura; Cannata, Jonathan M.; Shung, K. Kirk

    2010-01-01

    We report the development and validate a multi-modal tissue diagnostic technology, which combines three complementary techniques into one system including ultrasound backscatter microscopy (UBM), photoacoustic imaging (PAI), and time-resolved laser-induced fluorescence spectroscopy (TR-LIFS). UBM enables the reconstruction of the tissue microanatomy. PAI maps the optical absorption heterogeneity of the tissue associated with structure information and has the potential to provide functional imaging of the tissue. Examination of the UBM and PAI images allows for localization of regions of interest for TR-LIFS evaluation of the tissue composition. The hybrid probe consists of a single element ring transducer with concentric fiber optics for multi-modal data acquisition. Validation and characterization of the multi-modal system and ultrasonic, photoacoustic, and spectroscopic data coregistration were conducted in a physical phantom with properties of ultrasound scattering, optical absorption, and fluorescence. The UBM system with the 41 MHz ring transducer can reach the axial and lateral resolution of 30 and 65 μm, respectively. The PAI system with 532 nm excitation light from a Nd:YAG laser shows great contrast for the distribution of optical absorbers. The TR-LIFS system records the fluorescence decay with the time resolution of ~300 ps and a high sensitivity of nM concentration range. Biological phantom constructed with different types of tissues (tendon and fat) was used to demonstrate the complementary information provided by the three modalities. Fluorescence spectra and lifetimes were compared to differentiate chemical composition of tissues at the regions of interest determined by the coregistered high resolution UBM and PAI image. Current results demonstrate that the fusion of these techniques enables sequentially detection of functional, morphological, and compositional features of biological tissue, suggesting potential applications in diagnosis of tumors

  17. Single frequency RF powered ECG telemetry system

    NASA Technical Reports Server (NTRS)

    Ko, W. H.; Hynecek, J.; Homa, J.

    1979-01-01

    It has been demonstrated that a radio frequency magnetic field can be used to power implanted electronic circuitry for short range telemetry to replace batteries. A substantial reduction in implanted volume can be achieved by using only one RF tank circuit for receiving the RF power and transmitting the telemetered information. A single channel telemetry system of this type, using time sharing techniques, was developed and employed to transmit the ECG signal from Rhesus monkeys in primate chairs. The signal from the implant is received during the period when the RF powering radiation is interrupted. The ECG signal is carried by 20-microsec pulse position modulated pulses, referred to the trailing edge of the RF powering pulse. Satisfactory results have been obtained with this single frequency system. The concept and the design presented may be useful for short-range long-term implant telemetry systems.

  18. Heterodyne laser instantaneous frequency measurement system

    DOEpatents

    Wyeth, Richard W.; Johnson, Michael A.; Globig, Michael A.

    1990-01-01

    A heterodyne laser instantaneous frequency measurement system is disclosed. The system utilizes heterodyning of a pulsed laser beam with a continuous wave laser beam to form a beat signal. The beat signal is processed by a controller or computer which determines both the average frequency of the laser pulse and any changes or chirp of the frequency during the pulse.

  19. Heterodyne laser instantaneous frequency measurement system

    DOEpatents

    Wyeth, Richard W.; Johnson, Michael A.; Globig, Michael A.

    1989-01-01

    A heterodyne laser instantaneous frequency measurement system is disclosed. The system utilizes heterodyning of a pulsed laser beam with a continuous wave laser beam to form a beat signal. The beat signal is processed by a controller or computer which determines both the average frequency of the laser pulse and any changes or chirp of th frequency during the pulse.

  20. The Development of Children's Sensitivity to Bigram Frequencies When Spelling in Spanish, a Transparent Writing System

    ERIC Educational Resources Information Center

    Carrillo, María Soledad; Alegría, Jesús

    2014-01-01

    The aim of this study was to collect data concerning the sensitivity of 2nd-6th grade Spanish-speaking children towards orthographic regularities. In a first experiment, children were asked to spell words that begin with /b/, a sound that is inconsistently spelled "b" or "v", depending on the lexeme. Low frequency words were…

  1. The Development of Children's Sensitivity to Bigram Frequencies When Spelling in Spanish, a Transparent Writing System

    ERIC Educational Resources Information Center

    Carrillo, María Soledad; Alegría, Jesús

    2014-01-01

    The aim of this study was to collect data concerning the sensitivity of 2nd-6th grade Spanish-speaking children towards orthographic regularities. In a first experiment, children were asked to spell words that begin with /b/, a sound that is inconsistently spelled "b" or "v", depending on the lexeme. Low frequency words were…

  2. Multi-frequency communication system and method

    DOEpatents

    Carrender, Curtis Lee; Gilbert, Ronald W.

    2004-06-01

    A multi-frequency RFID remote communication system is provided that includes a plurality of RFID tags configured to receive a first signal and to return a second signal, the second signal having a first frequency component and a second frequency component, the second frequency component including data unique to each remote RFID tag. The system further includes a reader configured to transmit an interrogation signal and to receive remote signals from the tags. A first signal processor, preferably a mixer, removes an intermediate frequency component from the received signal, and a second processor, preferably a second mixer, analyzes the IF frequency component to output data that is unique to each remote tag.

  3. Development of multi-frequency ESR/EDMR system using a rectangular cavity equipped with waveguide window.

    PubMed

    Fukuda, Kunito; Asakawa, Naoki

    2016-11-01

    A straightforward method for a variable frequency electron spin resonance/electrically detected magnetic resonance (ESR/EDMR) spectroscopy using a C-band microwave cavity equipped with waveguide windows is presented. The method enables us to perform quasi-continuous multiple resonance frequency (MF-ESR/EDMR) experiments for electronic devices. The C-band microwave circuitry was selected because of larger available sample volume than that for conventional X-band one. All the measurements were performed using a combined sample of 2,2-diphenyl-1-picrylhydrazyl/ pn-junction Si diode. The present simple MF-ESR/EDMR method will be useful for the characterization of electronic and optoelectronic devices.

  4. Development of multi-frequency ESR/EDMR system using a rectangular cavity equipped with waveguide window

    NASA Astrophysics Data System (ADS)

    Fukuda, Kunito; Asakawa, Naoki

    2016-11-01

    A straightforward method for a variable frequency electron spin resonance/electrically detected magnetic resonance (ESR/EDMR) spectroscopy using a C-band microwave cavity equipped with waveguide windows is presented. The method enables us to perform quasi-continuous multiple resonance frequency (MF-ESR/EDMR) experiments for electronic devices. The C-band microwave circuitry was selected because of larger available sample volume than that for conventional X-band one. All the measurements were performed using a combined sample of 2,2-diphenyl-1-picrylhydrazyl/ pn-junction Si diode. The present simple MF-ESR/EDMR method will be useful for the characterization of electronic and optoelectronic devices.

  5. The LASI high-frequency ellipticity system

    SciTech Connect

    Sternberg, B.K.; Poulton, M.M.

    1995-12-31

    A high-frequency, high-resolution, electromagnetic (EM) imaging system has been developed for environmental geophysics surveys. Some key features of this system include: (1) rapid surveying to allow dense spatial sampling over a large area, (2) high-accuracy measurements which are used to produce a high-resolution image of the subsurface, (3) measurements which have excellent signal-to-noise ratio over a wide bandwidth (31 kHz to 32 MHz), (4) large-scale physical modeling to produce accurate theoretical responses over targets of interest in environmental geophysics surveys, (5) rapid neural network interpretation at the field site, and (6) visualization of complex structures during the survey.

  6. The LASI high-frequency ellipticity system

    SciTech Connect

    Sternberg, B.K.; Poulton, M.M.

    1995-10-01

    A high-frequency, high-resolution, electromagnetic (EM) imaging system has been developed for environmental geophysics surveys. Some key features of this system include: (1) rapid surveying to allow dense spatial sampling over a large area, (2) high-accuracy measurements which are used to produce a high-resolution image of the subsurface, (3) measurements which have excellent signal-to-noise ratio over a wide bandwidth (31 kHz to 32 MHz), (4) large-scale physical modeling to produce accurate theoretical responses over targets of interest in environmental geophysics surveys, (5) rapid neural network interpretation at the field site, and (6) visualization of complex structures during the survey.

  7. Flexible alternatives to constant frequency systems

    NASA Astrophysics Data System (ADS)

    Stewart-Wilson, John

    The use of hybrid systems in which variable frequency is used as generated, with a proportion being converted to constant frequency by electronic conversion, is examined as a flexible alternative to constant frequency systems. Here, some practical solutions to the technical issues raised by adopting the more flexible approach to electrical system generation are presented. In particular, attention is given to the frequency ranges used, impact on aircraft equipment, motor-driven equipment, transformer rectifier units, lighting, and avionics. The discussion also covers fan-assisted galley ovens, system architecture, special airworthiness requirements, and power quality.

  8. Development of a high-frequency in vivo transposon mutagenesis system for Synechocystis sp. PCC 6803 and Synechococcus elongatus PCC 7942.

    PubMed

    Watabe, Kazuyuki; Mimuro, Mamoru; Tsuchiya, Tohru

    2014-11-01

    Synechocystis sp. PCC 6803 (Synechocystis) is the first sequenced photosynthetic organism and has two advantages: natural transformation and light-activated heterotrophic growth. Such characteristics have mainly promoted reverse genetic analysis in this organism, however, to date approximately 50% of genes are still annotated as 'unknown protein' or 'hypothetical protein'. Therefore, forward genetic analysis is required for the identification of significant genes responsible for photosynthesis and other physiological phenomena among the genes of unknown function. The in vivo transposon mutagenesis system is one of the major methods for random mutagenesis. However, present in vivo transposon mutagenesis systems for cyanobacteria face problems such as relatively low frequency of transposition and repeated transposition in the host cells. In this study, we constructed vectors based on a mini-Tn5-derived vector that was designed to prevent repeated transposition. Our vectors carry a hyperactive transposase and optimized recognition sequence of transposase, which were reported to enhance frequency of transposition. Using the vector, we succeeded in highly frequent transposition (9×10(-3) per recipient cell) in Synechocystis. Transposon insertion sites of 10 randomly selected mutants indicated that the insertion sites spread throughout the genome with low sequence dependency. Furthermore, one of the 10 mutants exhibited the slow-growing phenotype, and the mutant was functionally complemented by using our expression vector. Our system also worked with another model cyanobacterium, Synechococcus elongatus PCC 7942, with high frequency. These results indicate that the developed system can be applied to the forward genetic analysis of a broad range of cyanobacteria. © The Author 2014. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  9. High frequency power distribution system

    NASA Technical Reports Server (NTRS)

    Patel, Mikund R.

    1986-01-01

    The objective of this project was to provide the technology of high frequency, high power transmission lines to the 100 kW power range at 20 kHz frequency. In addition to the necessary design studies, a 150 m long, 600 V, 60 A transmission line was built, tested and delivered for full vacuum tests. The configuration analysis on five alternative configurations resulted in the final selection of the three parallel Litz straps configuration, which gave a virtually concentric design in the electromagnetic sense. Low inductance, low EMI and flexibility in handling are the key features of this configuration. The final design was made after a parametric study to minimize the losses, weight and inductance. The construction of the cable was completed with no major difficulties. The R,L,C parameters measured on the cable agreed well with the calculated values. The corona tests on insulation samples showed a safety factor of 3.

  10. High frequency power distribution system

    NASA Astrophysics Data System (ADS)

    Patel, Mikund R.

    1986-04-01

    The objective of this project was to provide the technology of high frequency, high power transmission lines to the 100 kW power range at 20 kHz frequency. In addition to the necessary design studies, a 150 m long, 600 V, 60 A transmission line was built, tested and delivered for full vacuum tests. The configuration analysis on five alternative configurations resulted in the final selection of the three parallel Litz straps configuration, which gave a virtually concentric design in the electromagnetic sense. Low inductance, low EMI and flexibility in handling are the key features of this configuration. The final design was made after a parametric study to minimize the losses, weight and inductance. The construction of the cable was completed with no major difficulties. The R,L,C parameters measured on the cable agreed well with the calculated values. The corona tests on insulation samples showed a safety factor of 3.

  11. Development of Miniaturized Difference Frequency Generation, Fiber Optic, and Quantum Cascade Laser Systems in Conjunction With Integrated Electronics for Global Studies of Atmospheric Tracers Using UAVs.

    NASA Astrophysics Data System (ADS)

    Witinski, M. F.; Lapson, L. B.; Anderson, J. G.

    2007-12-01

    In order to harness the power of UAVs (Unmanned Aerial Vehicles) for in situ atmospheric monitoring of tracers such as CO2, N2O, CH4, and H2O, we have developed small, lightweight, single mode laser systems with co- developed integrated electronics. The laser sources are of various types including newly developed cavity- enhanced difference frequency generation (CE DFG), distributed feedback quantum cascade lasers (DFB QCLs), and new types of commercially available DFB diode lasers. All are continuous wave (cw) and thermo-electrically cooled, ensuring a high instrument duty cycle in a compact, low maintenance package. The light sources are collimated with miniature aspherical lenses and coupled into a home-built astigmatic Herriott cell for detection of the various targets using direct absorption. In parallel with the optical components, we have developed integrated electrical systems for laser control, data processing, and acquisition. A prototype instrument suite is described that illustrates the importance of parallel development of optical and electrical components in achieving an apparatus that is compact, fully automated, and highly capable scientifically. Although the emphasis here is on atmospheric tracers, this technology could be applied to spectroscopic measurements of other atmospheric species such as isotopes, free radicals, and reactive intermediates.

  12. Design development and manufacture of a breadboard radio frequency mass gauging system. Volume 1: Phase B final report

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The applicability of the RF Mode Counting technique for gauging liquid oxygen and liquid hydrogen under all attitude conditions was demonstrated using a vacuum jacketed test tank mounted on a remotely controlled gimbaling mechanism. In addition, the technique was successfully tested using liquid oxygen in a large NASA test tank as the tank was filled and emptied. To further substantiate the capabilities of the RF Mode Counting technique as applied to applications involving zero gravity conditions, a test system using benzene as a test fluid was flight tested in a KC-135 test aircraft. This testing involved a number of zero "g" maneuvers with various quantities of the test fluid. A series of tests were also performed to evaluate the relative effects of the presence of capillary liquid retention screens on the RF Gauging technique. These tests involved considerations of system Q reductions, RF leakage through retention screens, and surface wetting effects.

  13. A high frequency electromagnetic impedance imaging system

    SciTech Connect

    Tseng, Hung-Wen; Lee, Ki Ha; Becker, Alex

    2003-01-15

    Non-invasive, high resolution geophysical mapping of the shallow subsurface is necessary for delineation of buried hazardous wastes, detecting unexploded ordinance, verifying and monitoring of containment or moisture contents, and other environmental applications. Electromagnetic (EM) techniques can be used for this purpose since electrical conductivity and dielectric permittivity are representative of the subsurface media. Measurements in the EM frequency band between 1 and 100 MHz are very important for such applications, because the induction number of many targets is small and the ability to determine the subsurface distribution of both electrical properties is required. Earlier workers were successful in developing systems for detecting anomalous areas, but quantitative interpretation of the data was difficult. Accurate measurements are necessary, but difficult to achieve for high-resolution imaging of the subsurface. We are developing a broadband non-invasive method for accurately mapping the electrical conductivity and dielectric permittivity of the shallow subsurface using an EM impedance approach similar to the MT exploration technique. Electric and magnetic sensors were tested to ensure that stray EM scattering is minimized and the quality of the data collected with the high-frequency impedance (HFI) system is good enough to allow high-resolution, multi-dimensional imaging of hidden targets. Additional efforts are being made to modify and further develop existing sensors and transmitters to improve the imaging capability and data acquisition efficiency.

  14. An introduction to high frequency radioteletype systems

    NASA Astrophysics Data System (ADS)

    Pinnau, Roger R.

    1989-10-01

    A basic introductory guide is provided to modern High Frequency (HF) data communications systems. Described are modern commercial radioteletype systems, data communication protocols, and various secrets of the trade.

  15. 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.

  16. Development of a novel marking system for laparoscopic gastrectomy using endoclips with radio frequency identification tags: feasibility study in a canine model.

    PubMed

    Kojima, Fumitsugu; Sato, Toshihiko; Tsunoda, Shigeru; Takahata, Hiromi; Hamaji, Masatsugu; Komatsu, Teruya; Okada, Minoru; Sugiura, Tadao; Oshiro, Osamu; Sakai, Yoshiharu; Date, Hiroshi; Nakamura, Tatsuo

    2014-09-01

    Intraoperative identification of early gastric cancer is difficult to conduct during laparoscopic procedures. In this study, we investigated the feasibility and accuracy of a newly developed marking system using endoclips with radio frequency identification (RFID) tags in a canine model. RFID is a wireless near field communication technology. Among the open frequency bands available for medical use, 13.56 MHz is suitable for a surgical marking system because of the similar and linear signal decay both in air and in biological tissues. The proposed system consists of four parts: (a) endoclips with RFID tags, (b) endo-clip applier equipment, (c) laparoscopic locating probe, and (d) signal processing units with audio interface. In the experimental setting using canine models, RFID-tagged endoclips were applied to the mucosa of each dog's stomach. During the subsequent operation, the clips with RFID tags placed in five dogs were located by the detection of the RFID signal from the tag (RFID group), and the conventional clips in the other six dogs were located by finger palpation (FP group). The detected sites were marked by ablation on the serosal surface. Distance between the clips and the metal pin needles indicating ablated sites were measured with X-ray radiographs of the resected specimen. All clips were successfully detected by the marking system in the RFID group (10/10) and by finger palpation in the FP group (17/17). The medians of detection times were 31.5 and 25.0 s, respectively; the distances were 5.63 and 7.62 mm, respectively. The differences were not statistically significant. No adverse event related to the procedures was observed. Endoclips with RFID tags were located by our novel marking system in an experimental laparoscopic setting using canine stomachs with substantial accuracy comparable to conventional endoclips located by finger palpation through an open approach.

  17. The development of spatial frequency discrimination.

    PubMed

    Patel, Ashna; Maurer, Daphne; Lewis, Terri L

    2010-12-31

    We compared thresholds for discriminating spatial frequency for children aged 5, 7, and 9 years, and adults at two baseline spatial frequencies (1 and 3 cpd). In Experiment 1, the minimum change from baseline necessary to detect a change in spatial frequency from either baseline decreased with age from 34% in 5-year-olds to 11% in 7-year-olds, 8% in 9-year-olds, and 6% in adults. The data were best fit by an exponential function reflecting the rapid improvement in thresholds between 5 and 7 years of age and more gradual improvement thereafter (r(2) = 0.50, p < 0.0001). In Experiment 2, 5-year-olds' thresholds were higher than those of adults, even when memory demands were eliminated by presenting the two spatial frequencies side by side for an unlimited time. The pattern of development for sensitivity to spatial frequency (this study) resembles those for the development of sensitivity to orientation (T. L. Lewis, S. E. Chong, & D. Maurer, 2009) and contrast (D. Ellemberg, T. L. Lewis, C. H. Lui, & D. Maurer, 1999). The similar patterns are consistent with theories of common underlying mechanisms in primary visual cortex (A. Vincent & D. Regan, 1995; W. Zhu, M. Shelley, & R. Shapley, 2008) and suggest that those mechanisms continue to develop throughout childhood.

  18. The system design of a rubidium maser frequency standard

    NASA Technical Reports Server (NTRS)

    Xiong, C. X.

    1984-01-01

    The Rubidium Maser Frequency Standard is a precision frequency source with excellent short-term stability. A type PBR-II Rb maser frequency standard was developed by the Beijing Institute of Radio Metrology and Measurement (BIRMM). The time-domain frequency stability (two-sample variance) of this frequency standard is less than 1/5 times 10 to the 13th power for t=10ms yields 1.0s, fh=1.0 KHz. Two PBR-II frequency standards were used as reference frequency sources in a frequency stability measurement system. Some important system characteristics for the PBR-II Rb maser frequency standard such as phase noise and frequency stability transfer characteristics are discussed. Furthermore, the design of the frequency standard for optimum frequency stability of the output signal; the choice of a voltage controlled crystal oscillator for the frequency standard; the design of the phase-locked loop; and the frequency stability test results on the PBR-II are discussed.

  19. A low frequency rotational energy harvesting system

    NASA Astrophysics Data System (ADS)

    Febbo, M.; Machado, S. P.; Ramirez, J. M.; Gatti, C. D.

    2016-11-01

    This paper presents a rotary power scavenging unit comprised of two systems of flexible beams connected by two masses which are joined by means of a spring, considering a PZT (QP16N, Midé Corporation) piezoelectric sheet mounted on one of the beams. The energy harvesting (EH) system is mounted rigidly on a rotating hub. The gravitational force on the masses causes sustained oscillatory motion in the flexible beams as long as there is rotary motion. The intention is to use the EH system in the wireless autonomous monitoring of wind turbines under different wind conditions. Specifically, the development is oriented to monitor the dynamic state of the blades of a wind generator of 30 KW which rotates between 50 and 150 rpm. The paper shows a complete set of experimental results on three devices, modifying the amount of beams in the frame supporting the system. The results show an acceptable sustained voltage generation for the expected range, in the three proposed cases. Therefore, it is possible to use this system for generating energy in a low-frequency rotating environment. As an alternative, the system can be easily adapted to include an array of piezoelectric sheets to each of the beams, to provide more power generation.

  20. Trajectory of frequency stability in typical development

    PubMed Central

    Irimia, Andrei; Jeste, Shafali S.

    2015-01-01

    Introduction This work explores a feature of brain dynamics, metastability, by which transients are observed in functional brain data. Metastability is a balance between static (stable) and dynamic (unstable) tendencies in electrophysiological brain activity. Furthermore, metastability is a theoretical mechanism underlying the rapid synchronization of cell assemblies that serve as neural substrates for cognitive states, and it has been associated with cognitive flexibility. While much previous research has sought to characterize metastability in the adult human brain, few studies have examined metastability in early development, in part because of the challenges of acquiring adequate, noise free continuous data in young children. Methods To accomplish this endeavor, we studied a new method for characterizing the stability of EEG frequency in early childhood, as inspired by prior approaches for describing cortical phase resets in the scalp EEG of healthy adults. Specifically, we quantified the variance of the rate of change of the signal phase (i.e., frequency) as a proxy for phase resets (signal instability), given that phase resets occur almost simultaneously across large portions of the scalp. We tested our method in a cohort of 39 preschool age children (age = 53 ± 13.6 months). Results We found that our outcome variable of interest, frequency variance, was a promising marker of signal stability, as it increased with the number of phase resets in surrogate (artificial) signals. In our cohort of children, frequency variance decreased cross-sectionally with age (r = −0.47, p = 0.0028). Conclusions EEG signal stability, as quantified by frequency variance, increases with age in preschool age children. Future studies will relate this biomarker with the development of executive function and cognitive flexibility in children, with the overarching goal of understanding metastability in atypical development. PMID:25501709

  1. Design & development fo a 20-MW flywheel-based frequency regulation power plant : a study for the DOE Energy Storage Systems program.

    SciTech Connect

    Rounds, Robert; Peek, Georgianne Huff

    2009-01-01

    This report describes the successful efforts of Beacon Power to design and develop a 20-MW frequency regulation power plant based solely on flywheels. Beacon's Smart Matrix (Flywheel) Systems regulation power plant, unlike coal or natural gas generators, will not burn fossil fuel or directly produce particulates or other air emissions and will have the ability to ramp up or down in a matter of seconds. The report describes how data from the scaled Beacon system, deployed in California and New York, proved that the flywheel-based systems provided faster responding regulation services in terms of cost-performance and environmental impact. Included in the report is a description of Beacon's design package for a generic, multi-MW flywheel-based regulation power plant that allows accurate bids from a design/build contractor and Beacon's recommendations for site requirements that would ensure the fastest possible construction. The paper concludes with a statement about Beacon's plans for a lower cost, modular-style substation based on the 20-MW design.

  2. The Role of Time and Frequency in Future Systems

    NASA Technical Reports Server (NTRS)

    Stein, Samuel R.; Gifford, Al; Celano, Tom

    1996-01-01

    Over the past twenty years, the Global Positioning System (GPS) has revolutionized the performance and the geographical availability of time and frequency discrimination, while at the same time reducing the cost to the individual user. This paper examines the question of what comes next for time and frequency dissemination. The question has two motivations: How can improved performance be achieved in the future, and how can redundant sources of time and frequency be provided to critical systems? A model is developed for time and frequency dissemination based on the time management performed in GPS. Several candidate systems for future time and frequency distribution are identified. One system - SONET telecommunications - is discussed in detail. Performance requirements and hardware implementation are presented.

  3. Seismic isolation systems with distinct multiple frequencies

    DOEpatents

    Wu, Ting-shu; Seidensticker, Ralph W.

    1990-01-01

    A method and apparatus for isolating a building or other structure from smic vibratory motion which provides increased assurance that large horizontal motion of the structure will not occur than is provided by other isolation systems. Increased assurance that large horizontal motion will not occur is achieved by providing for change of the natural frequency of the support and structure system in response to displacement of the structure beyond a predetermined value. The natural frequency of the support and structure system may be achieved by providing for engaging and disengaging of the structure and some supporting members in response to motion of the supported structure.

  4. Allan deviation computations of a linear frequency synthesizer system using frequency domain techniques

    NASA Technical Reports Server (NTRS)

    Wu, Andy

    1995-01-01

    Allan Deviation computations of linear frequency synthesizer systems have been reported previously using real-time simulations. Even though it takes less time compared with the actual measurement, it is still very time consuming to compute the Allan Deviation for long sample times with the desired confidence level. Also noises, such as flicker phase noise and flicker frequency noise, can not be simulated precisely. The use of frequency domain techniques can overcome these drawbacks. In this paper the system error model of a fictitious linear frequency synthesizer is developed and its performance using a Cesium (Cs) atomic frequency standard (AFS) as a reference is evaluated using frequency domain techniques. For a linear timing system, the power spectral density at the system output can be computed with known system transfer functions and known power spectral densities from the input noise sources. The resulting power spectral density can then be used to compute the Allan Variance at the system output. Sensitivities of the Allan Variance at the system output to each of its independent input noises are obtained, and they are valuable for design trade-off and trouble-shooting.

  5. Frequency Measurement System of Optical Clocks Without a Flywheel Oscillator.

    PubMed

    Fujieda, Miho; Ido, Tetsuya; Hachisu, Hidekazu; Gotoh, Tadahiro; Takiguchi, Hiroshi; Hayasaka, Kazuhiro; Toyoda, Kenji; Yonegaki, Kenji; Tanaka, Utako; Urabe, Shinji

    2016-12-01

    We developed a system for the remote frequency comparison of optical clocks. The system does not require a flywheel oscillator at the remote end, making it possible to evaluate optical frequencies even in laboratories, where no stable microwave reference, such as an Rb clock, a Cs clock, or a hydrogen maser exists. The system is established by the integration of several systems: a portable carrier-phase two-way satellite frequency transfer station and a microwave signal generation system by an optical frequency comb from an optical clock. The measurement was as quick as a conventional method that employs a local microwave reference. We confirmed the system uncertainty and instability to be at the low 10(-15) level using an Sr lattice clock.

  6. High frequency, high power capacitor development

    NASA Technical Reports Server (NTRS)

    White, C. W.; Hoffman, P. S.

    1983-01-01

    A program to develop a special high energy density, high power transfer capacitor to operate at frequency of 40 kHz, 600 V rms at 125 A rms plus 600 V dc bias for space operation. The program included material evaluation and selection, a capacitor design was prepared, a thermal analysis performed on the design. Fifty capacitors were manufactured for testing at 10 kHz and 40 kHz for 50 hours at Industrial Electric Heating Co. of Columbus, Ohio. The vacuum endurance test used on environmental chamber and temperature plate furnished by Maxwell. The capacitors were energized with a special power conditioning apparatus developed by Industrial Electric Heating Co. Temperature conditions of the capacitors were monitored by IEHCo test equipment. Successful completion of the vacuum endurance test series confirmed achievement of the main goal of producing a capacitor or reliable operation at high frequency in an environment normally not hospitable to electrical and electronic components. The capacitor developed compared to a typical commercial capacitor at the 40 kHz level represents a decrease in size and weight by a factor of seven.

  7. High frequency, high power capacitor development

    NASA Astrophysics Data System (ADS)

    White, C. W.; Hoffman, P. S.

    1983-03-01

    A program to develop a special high energy density, high power transfer capacitor to operate at frequency of 40 kHz, 600 V rms at 125 A rms plus 600 V dc bias for space operation. The program included material evaluation and selection, a capacitor design was prepared, a thermal analysis performed on the design. Fifty capacitors were manufactured for testing at 10 kHz and 40 kHz for 50 hours at Industrial Electric Heating Co. of Columbus, Ohio. The vacuum endurance test used on environmental chamber and temperature plate furnished by Maxwell. The capacitors were energized with a special power conditioning apparatus developed by Industrial Electric Heating Co. Temperature conditions of the capacitors were monitored by IEHCo test equipment. Successful completion of the vacuum endurance test series confirmed achievement of the main goal of producing a capacitor or reliable operation at high frequency in an environment normally not hospitable to electrical and electronic components. The capacitor developed compared to a typical commercial capacitor at the 40 kHz level represents a decrease in size and weight by a factor of seven.

  8. Radio frequency multicusp ion source development (invited)

    NASA Astrophysics Data System (ADS)

    Leung, K. N.

    1996-03-01

    The radio-frequency (rf) driven multicusp source was originally developed for use in the Superconducting Super Collider injector. It has been demonstrated that the source can meet the H- beam current and emittance requirements for this application. By employing a porcelain-coated antenna, a clean plasma discharge with very long-life operation can be achieved. Today, the rf source is used to generate both positive and negative hydrogen ion beams and has been tested in various particle accelerator laboratories throughout the world. Applications of this ion source have been extended to other fields such as ion beam lithography, oil-well logging, ion implantation, accelerator mass spectrometry and medical therapy machines. This paper summarizes the latest rf ion source technology and development at the Lawrence Berkeley National Laboratory.

  9. Radio frequency multicusp ion source development (invited)

    SciTech Connect

    Leung, K.N.

    1996-03-01

    The radio-frequency (rf) driven multicusp source was originally developed for use in the Superconducting Super Collider injector. It has been demonstrated that the source can meet the H{sup {minus}} beam current and emittance requirements for this application. By employing a porcelain-coated antenna, a clean plasma discharge with very long-life operation can be achieved. Today, the rf source is used to generate both positive and negative hydrogen ion beams and has been tested in various particle accelerator laboratories throughout the world. Applications of this ion source have been extended to other fields such as ion beam lithography, oil-well logging, ion implantation, accelerator mass spectrometry and medical therapy machines. This paper summarizes the latest rf ion source technology and development at the Lawrence Berkeley National Laboratory. {copyright} {ital 1996 American Institute of Physics.}

  10. Frequency domain state-space system identification

    NASA Technical Reports Server (NTRS)

    Chen, Chung-Wen; Juang, Jer-Nan; Lee, Gordon

    1992-01-01

    An algorithm for identifying state-space models from frequency response data of linear systems is presented. A matrix-fraction description of the transfer function is employed to curve-fit the frequency response data, using the least-squares method. The parameters of the matrix-fraction representation are then used to construct the Markov parameters of the system. Finally, state-space models are obtained through the Eigensystem Realization Algorithm using Markov parameters. The main advantage of this approach is that the curve-fitting and the Markov parameter construction are linear problems which avoid the difficulties of nonlinear optimization of other approaches. Another advantage is that it avoids windowing distortions associated with other frequency domain methods.

  11. High-frequency ultrasonic wire bonding systems

    PubMed

    Tsujino; Yoshihara; Sano; Ihara

    2000-03-01

    The vibration characteristics of longitudinal-complex transverse vibration systems with multiple resonance frequencies of 350-980 kHz for ultrasonic wire bonding of IC, LSI or electronic devices were studied. The complex vibration systems can be applied for direct welding of semiconductor tips (face-down bonding, flip-chip bonding) and packaging of electronic devices. A longitudinal-complex transverse vibration bonding system consists of a complex transverse vibration rod, two driving longitudinal transducers 7.0 mm in diameter and a transverse vibration welding tip. The vibration distributions along ceramic and stainless-steel welding tips were measured at up to 980 kHz. A high-frequency vibration system with a height of 20.7 mm and a weight of less than 15 g was obtained.

  12. Beam Instrument Development System

    SciTech Connect

    DOOLITTLE, LAWRENCE; HUANG, GANG; DU, QIANG; SERRANO, CARLOS

    2016-01-08

    Beam Instrumentation Development System (BIDS) is a collection of common support libraries and modules developed during a series of Low-Level Radio Frequency (LLRF) control and timing/synchronization projects. BIDS includes a collection of Hardware Description Language (HDL) libraries and software libraries. The BIDS can be used for the development of any FPGA-based system, such as LLRF controllers. HDL code in this library is generic and supports common Digital Signal Processing (DSP) functions, FPGA-specific drivers (high-speed serial link wrappers, clock generation, etc.), ADC/DAC drivers, Ethernet MAC implementation, etc.

  13. SYNCHROTRON RADIO FREQUENCY PHASE CONTROL SYSTEM

    DOEpatents

    Plotkin, M.; Raka, E.C.; Snyder, H.S.

    1963-05-01

    A system for canceling varying phase changes introduced by connecting cables and control equipment in an alternating gradient synchrotron is presented. In a specific synchrotron embodiment twelve spaced accelerating stations for the proton bunches are utilized. In order to ensure that the protons receive their boost or kick at the exact instant necessary it is necessary to compensate for phase changes occurring in the r-f circuitry over the wide range of frequencies dictated by the accelerated velocities of the proton bunches. A constant beat frequency is utilized to transfer the r-f control signals through the cables and control equipment to render the phase shift constant and readily compensable. (AEC)

  14. Stabilized fiber-optic frequency distribution system

    NASA Technical Reports Server (NTRS)

    Primas, L. E.; Lutes, G. F.; Sydnor, R. L.

    1989-01-01

    A technique for stabilizing reference frequencies transmitted over fiber-optic cable in a frequency distribution system is discussed. The distribution system utilizes fiber-optic cable as the transmission medium to distribute precise reference signals from a frequency standard to remote users. The stability goal of the distribution system is to transmit a 100-MHz signal over a 22-km fiber-optic cable and maintain a stability of 1 part in 10(17) for 1000-second averaging times. Active stabilization of the link is required to reduce phase variations produced by environmental effects, and is achieved by transmitting the reference signal from the frequency standard to the remote unit and then reflecting back to the reference unit over the same optical fiber. By comparing the phase of the transmitted and reflected signals at the reference unit, phase variations of the remote signal can be measured. An error voltage derived from the phase difference between the two signals is used to add correction phase.

  15. Custom Turnkey Time and Frequency Systems: A structured, expandable approach

    NASA Astrophysics Data System (ADS)

    Wright, David F.

    1995-05-01

    Radiocode Clocks Ltd. have developed a Turnkey Time and Frequency Generation and Distribution, System strategy based upon a bus of three, 'core' signals from which any Time code, Pulse rate or Frequency can be produced. The heart of the system is a ruggedized 19 inch, 3U Single Eurocard chassis constructed from machined 10mm aluminum alloy plate and designed to meet stringent Military, Security and Telecommunications specifications. The chassis is fitted with an advanced multilayer backplane with separate ground planes for analog and digital signals ensuring no degradation of low noise frequency references in the proximity of high speed digital pulse transmissions. The system has been designed to be used in three possible configurations: 1) As a stand alone generation and distribution instrument; 2) As a primary distribution unit in a turnkey Time and Frequency system; and 3) As a secondary distribution unit at a remote location from the Turnkey Time and Frequency System providing regeneration of core signals and correction for transmission delays. When configured as a secondary distribution unit the system will continue to provide usable outputs when one, two or even all three of the 'core' signals are lost. The instrument's placement within a system as a possible single point of system failure has required the development of very high reliability translator, synthesizer, phase locked loop and distribution modules together with a comprehensive alarm and monitoring strategy.

  16. Custom Turnkey Time and Frequency Systems: A structured, expandable approach

    NASA Technical Reports Server (NTRS)

    Wright, David F.

    1995-01-01

    Radiocode Clocks Ltd. have developed a Turnkey Time and Frequency Generation and Distribution, System strategy based upon a bus of three, 'core' signals from which any Time code, Pulse rate or Frequency can be produced. The heart of the system is a ruggedized 19 inch, 3U Single Eurocard chassis constructed from machined 10mm aluminum alloy plate and designed to meet stringent Military, Security and Telecommunications specifications. The chassis is fitted with an advanced multilayer backplane with separate ground planes for analog and digital signals ensuring no degradation of low noise frequency references in the proximity of high speed digital pulse transmissions. The system has been designed to be used in three possible configurations: 1) As a stand alone generation and distribution instrument; 2) As a primary distribution unit in a turnkey Time and Frequency system; and 3) As a secondary distribution unit at a remote location from the Turnkey Time and Frequency System providing regeneration of core signals and correction for transmission delays. When configured as a secondary distribution unit the system will continue to provide usable outputs when one, two or even all three of the 'core' signals are lost. The instrument's placement within a system as a possible single point of system failure has required the development of very high reliability translator, synthesizer, phase locked loop and distribution modules together with a comprehensive alarm and monitoring strategy.

  17. The ONERA Airborne Multi Frequency SAR Imaging Systems (PREPRINT)

    DTIC Science & Technology

    2014-10-09

    The ONERA Airborne Multi-Frequency SAR Imaging Systems Olivier Ruault du Plessis Electromagnetism and Radar Department ONERA Salon de...Provence FRANCE Olivier.Ruault_du_Plessis@onera.fr Philippe Dreuillet Electromagnetism and Radar Department ONERA Palaiseau FRANCE...Philippe.Dreuillet@onera.fr Abstract—RAMSES-NG and SETHI, the airborne SAR systems developed by ONERA , integrate new generation of radar and optronics

  18. Biological effects of low-frequency pulsed magnetic fields on the embryonic central nervous system development. A histological and histochemical study.

    PubMed

    Roda, Olga; Garzón, Ingrid; Carriel, Víctor; Alaminos, Miguel; Sánchez-Montesinos, Indalecio

    2011-07-01

    Numerous experiments have yielded contradictory results on the harmful action of magnetic fields on embryonic development. Pulsed magnetic fields appear to be able to delay normal development of embryos. In the present study, fertilized Gallus domesticus eggs were exposed during incubation to pulsed magnetic fields (harmonic signals of 10 µT for 1 second with silences of 0.5 seconds) of 50 or 100 Hz frequency. Embryos extracted at 45 h of exposure to fields of 50 Hz or 100 Hz frequency had significantly (p<0.05) fewer somite pairs compared with controls of the same age. At 15 days of incubation, only embryos exposed to a 10 µT- 50 Hz field had a significantly (p<0.05) higher somatic weight. At 21 days of incubation, a significantly lower somatic weight (p<0.01) and development stage (p<0.05) was found in embryos exposed to a 10 µT-100 Hz field than in controls, while a lower development stage (p<0.05) alone was observed in those exposed to a 10 µT-50 Hz field. In addition, animals showed higher expression of the neural marker NSE (neural specific enolase) after 21 days of development as determined by immunohistochemistry, with very low expression of glycosaminoglycans identified by alcyan blue staining. These results suggest that pulsed magnetic fields may be able to hinder normal embryonic development in vivo and to alter normal neural function, at least at the intensities and frequencies analyzed in the present study.

  19. Autonomous Frequency-Domain System-Identification Program

    NASA Technical Reports Server (NTRS)

    Yam, Yeung; Mettler, Edward; Bayard, David S.; Hadaegh, Fred Y.; Milman, Mark H.; Scheid, Robert E.

    1993-01-01

    Autonomous Frequency Domain Identification (AU-FREDI) computer program implements system of methods, algorithms, and software developed for identification of parameters of mathematical models of dynamics of flexible structures and characterization, by use of system transfer functions, of such models, dynamics, and structures regarded as systems. Software considered collection of routines modified and reassembled to suit system-identification and control experiments on large flexible structures.

  20. Autonomous Frequency-Domain System-Identification Program

    NASA Technical Reports Server (NTRS)

    Yam, Yeung; Mettler, Edward; Bayard, David S.; Hadaegh, Fred Y.; Milman, Mark H.; Scheid, Robert E.

    1993-01-01

    Autonomous Frequency Domain Identification (AU-FREDI) computer program implements system of methods, algorithms, and software developed for identification of parameters of mathematical models of dynamics of flexible structures and characterization, by use of system transfer functions, of such models, dynamics, and structures regarded as systems. Software considered collection of routines modified and reassembled to suit system-identification and control experiments on large flexible structures.

  1. Development of Radio Frequency Diesel Particulate Filter Sensor and Controls for Advanced Low Pressure Drop Systems to Reduce Engine Fuel Consumption (06B)

    SciTech Connect

    Sappok, Alexander; Ragaller, Paul; Bromberg, Leslie

    2016-09-28

    This project developed a radio frequencybased sensor for accurate measurement of diesel particulate filter (DPF) loading with advanced low pressuredrop aftertreatment systems. The resulting technology demonstrated engine efficiency improvements through optimization of the combined engineaftertreatment system while reducing emissions, system cost, and complexity to meet the DOE program objectives.

  2. Static Frequency Converter System Installed and Tested

    NASA Technical Reports Server (NTRS)

    Brown, Donald P.; Sadhukhan, Debashis

    2003-01-01

    A new Static Frequency Converter (SFC) system has been installed and tested at the NASA Glenn Research Center s Central Air Equipment Building to provide consistent, reduced motor start times and improved reliability for the building s 14 large exhausters and compressors. The operational start times have been consistent around 2 min, 20 s per machine. This is at least a 3-min improvement (per machine) over the old variable-frequency motor generator sets. The SFC was designed and built by Asea Brown Boveri (ABB) and installed by Encompass Design Group (EDG) as part of a Construction of Facilities project managed by Glenn (Robert Scheidegger, project manager). The authors designed the Central Process Distributed Control Systems interface and control between the programmable logic controller, solid-state exciter, and switchgear, which was constructed by Gilcrest Electric.

  3. Development of a radio frequency ion source with multi-helicon plasma injectors for neutral beam injection system of Versatile Experiment Spherical Torus

    SciTech Connect

    Choe, Kyumin; Jung, Bongki; Chung, Kyoung-Jae; Hwang, Y. S.

    2014-02-15

    Despite of high plasma density, helicon plasma has not yet been applied to a large area ion source such as a driver for neutral beam injection (NBI) system due to intrinsically poor plasma uniformity in the discharge region. In this study, a radio-frequency (RF) ion source with multi-helicon plasma injectors for high plasma density with good uniformity has been designed and constructed for the NBI system of Versatile Experiment Spherical Torus at Seoul National University. The ion source consists of a rectangular plasma expansion chamber (120 × 120 × 120 mm{sup 3}), four helicon plasma injectors with annular permanent magnets and RF power system. Main feature of the source is downstream plasma confinement in the cusp magnetic field configuration which is generated by arranging polarities of permanent magnets in the helicon plasma injectors. In this paper, detailed design of the multi-helicon plasma injector and plasma characteristics of the ion source are presented.

  4. Liga developer apparatus system

    DOEpatents

    Boehme, Dale R.; Bankert, Michelle A.; Christenson, Todd R.

    2003-01-01

    A system to fabricate precise, high aspect ratio polymeric molds by photolithograpic process is described. The molds for producing micro-scale parts from engineering materials by the LIGA process. The invention is a developer system for developing a PMMA photoresist having exposed patterns comprising features having both very small sizes, and very high aspect ratios. The developer system of the present invention comprises a developer tank, an intermediate rinse tank and a final rinse tank, each tank having a source of high frequency sonic agitation, temperature control, and continuous filtration. It has been found that by moving a patterned wafer, through a specific sequence of developer/rinse solutions, where an intermediate rinse solution completes development of those portions of the exposed resist left undeveloped after the development solution, by agitating the solutions with a source of high frequency sonic vibration, and by adjusting and closely controlling the temperatures and continuously filtering and recirculating these solutions, it is possible to maintain the kinetic dissolution of the exposed PMMA polymer as the rate limiting step.

  5. Load Frequency Control of AC Microgrid Interconnected Thermal Power System

    NASA Astrophysics Data System (ADS)

    Lal, Deepak Kumar; Barisal, Ajit Kumar

    2017-08-01

    In this paper, a microgrid (MG) power generation system is interconnected with a single area reheat thermal power system for load frequency control study. A new meta-heuristic optimization algorithm i.e. Moth-Flame Optimization (MFO) algorithm is applied to evaluate optimal gains of the fuzzy based proportional, integral and derivative (PID) controllers. The system dynamic performance is studied by comparing the results with MFO optimized classical PI/PID controllers. Also the system performance is investigated with fuzzy PID controller optimized by recently developed grey wolf optimizer (GWO) algorithm, which has proven its superiority over other previously developed algorithm in many interconnected power systems.

  6. Development and in vivo testing of a high frequency endoscopic Raman spectroscopy system for potential applications in the detection of early colonic neoplasia.

    PubMed

    Short, Michael A; Wang, Wenbo; Tai, Isabella T; Zeng, Haishan

    2016-01-01

    The objective of this study was to build and test an adjunct system to a colonoscope for in vivo measurement of Raman spectra from colon tissue for potentially improving the detection of early cancers. The novelty of this system was that low cost fibre optic probes were used, without the addition of expensive optical filters. Good quality in vivo Raman spectra were successfully obtained with a 1 s integration time in the high frequency (HF) range from normal tissue and polyps of patients during a colonoscopy. The polyps were subsequently removed, and their pathology determined. The acquired in vivo Raman spectra showed clear changes between tissue with normal and tubular adenoma pathology. Further clinical study with this low cost HF Raman probe is warranted to fully test its clinical utility. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Extreme Low Frequency Acoustic Measurement System

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A. (Inventor); Zuckerwar, Allan J. (Inventor)

    2017-01-01

    The present invention is an extremely low frequency (ELF) microphone and acoustic measurement system capable of infrasound detection in a portable and easily deployable form factor. In one embodiment of the invention, an extremely low frequency electret microphone comprises a membrane, a backplate, and a backchamber. The backchamber is sealed to allow substantially no air exchange between the backchamber and outside the microphone. Compliance of the membrane may be less than ambient air compliance. The backplate may define a plurality of holes and a slot may be defined between an outer diameter of the backplate and an inner wall of the microphone. The locations and sizes of the holes, the size of the slot, and the volume of the backchamber may be selected such that membrane motion is substantially critically damped.

  8. Extreme low frequency acoustic measurement system

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A. (Inventor); Zuckerwar, Allan J. (Inventor)

    2013-01-01

    The present invention is an extremely low frequency (ELF) microphone and acoustic measurement system capable of infrasound detection in a portable and easily deployable form factor. In one embodiment of the invention, an extremely low frequency electret microphone comprises a membrane, a backplate, and a backchamber. The backchamber is sealed to allow substantially no air exchange between the backchamber and outside the microphone. Compliance of the membrane may be less than ambient air compliance. The backplate may define a plurality of holes and a slot may be defined between an outer diameter of the backplate and an inner wall of the microphone. The locations and sizes of the holes, the size of the slot, and the volume of the backchamber may be selected such that membrane motion is substantially critically damped.

  9. 47 CFR 80.385 - Frequencies for automated systems.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequencies for automated systems. 80.385... SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Automated Systems § 80.385 Frequencies for automated systems. This section describes the carrier frequencies for the Automated Maritime Telecommunications...

  10. 47 CFR 80.385 - Frequencies for automated systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequencies for automated systems. 80.385... SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Automated Systems § 80.385 Frequencies for automated systems. This section describes the carrier frequencies for the Automated Maritime Telecommunications...

  11. High-frequency H-PDLC optical chopper for frequency division multiplexing fluorescence confocal microscope system

    NASA Astrophysics Data System (ADS)

    Jiang, Yanmeng; Zheng, Jihong; Tang, Pingyu; Wang, Tingting; Huang, Aiqin; Zhou, Zengjun; Zhuang, Songlin

    2011-10-01

    The optical chopper array based on Holographic Polymer Dispersed Liquid Crystal (H-PDLC) working at high frequencies, for example 1KHz, 2KHz, and its application in an improved Frequency Division Multiplexed Fluorescence Confocal Microscope (FDMFCM) system are reported in this article. The system is a combination of the confocal microscopy and the frequency division multiplexing technique. Taking advantages of the optical chopper array based on H-PDLC that avoids mechanical movements, the FDMFCM system is able to obtain better Signal-Noise Ratio (SNR), smaller volume, more independent channels and more efficient scanning. What's more, the FDMCFM maintained the high special resolution ability and realized faster temporal resolution than pervious system. Using the proposed device, the FDMFCM system conducts successful parallel detection of rat neural cells. Fluorescence intensity signals from two different points on the specimen, which represent concentration of certain kind of proteins in the sample cells, are achieved. The experimental results show that the proposed H-PDLC optical chopper array has feasibility in FDMFCM system, which owes to its unique characteristics such as fast response, simple fabrication and lower consumption etc. With the development of H-PDLC based devices, there will be prospective in upgrading FDMFCM system's performance in the biomedical area.

  12. Piezoelectric Shaker Development for High Frequency Calibration of Accelerometers

    SciTech Connect

    Payne, Bev; Harper, Kari K.; Vogl, Gregory W.

    2010-05-28

    Calibration of vibration transducers requires sinusoidal motion over a wide frequency range with low distortion and low cross-axial motion. Piezoelectric shakers are well suited to generate such motion and are suitable for use with laser interferometric methods at frequencies of 3 kHz and above. An advantage of piezoelectric shakers is the higher achievable accelerations and displacement amplitudes as compared to electro-dynamic (ED) shakers. Typical commercial ED calibration shakers produce maximum accelerations from 100 m/s{sup 2} to 500 m/s{sup 2}. Very large ED shakers may produce somewhat higher accelerations but require large amplifiers and expensive cooling systems to dissipate heat. Due to the limitations in maximum accelerations by ED shakers at frequencies above 5 kHz, the amplitudes of the generated sinusoidal displacement are frequently below the resolution of laser interferometers used in primary calibration methods. This limits the usefulness of ED shakers in interferometric based calibrations at higher frequencies.Small piezoelectric shakers provide much higher acceleration and displacement amplitudes for frequencies above 5 kHz, making these shakers very useful for accelerometer calibrations employing laser interferometric measurements, as will be shown in this paper. These piezoelectric shakers have been developed and used at NIST for many years for high frequency calibration of accelerometers. This paper documents the construction and performance of a new version of these shakers developed at NIST for the calibration of accelerometers over the range of 3 kHz to 30 kHz and possibly higher. Examples of typical calibration results are also given.

  13. Tissue Viscoelasticity Measurement System by Simultaneous Multiple-Frequency Excitation

    NASA Astrophysics Data System (ADS)

    Miwa, Takashi; Yoshihara, Yuki; Kanzawa, Kouki; Parajuli, Raj Kumar; Yamakoshi, Yoshiki

    2012-07-01

    Tissue elasticity measurements by an ultrasonic wave are a promising technique for the qualitative diagnosis of tumors and liver diseases. The viscoelastic characteristics in soft tissue can be quantitatively evaluated by considering the frequency dependence of the velocity of the shear wave propagating in the tissue. To improve the reliability of the in vivo viscoelasticity measurement, we propose a novel elasticity imaging method using continuous vibration wave excitation, which was realized by developing a three dimensional ultrasonic (3D US) wave Doppler measurement system with multiple-frequency excitation. In vivo experiments on the brachial muscle were carried out in order to demonstrate the validity and effectiveness of the developed system. The experimental results show that this system can successfully measure the velocity of a shear wave propagating through a muscle layer. This system has the potential to obtain viscoelastic information from a target with high repeatability and reliability.

  14. Carrier: Interference ratios for frequency sharing between satellite systems transmitting frequency modulated and digital television signals

    NASA Technical Reports Server (NTRS)

    Barnes, S. P.

    1979-01-01

    Results are presented of subjective and quantitative tests describing the results of interference to a particular digital television system from a frequency modulated (FM) television system, and for interference to an FM television system from a digital television system.

  15. Development of frequency-agile high-repetition-rate CO{sub 2} DIAL systems for long range chemical remote sensing

    SciTech Connect

    Quick, C.R. Jr.; Fite, C.B.; Foy, B.R.; Jolin, J.; Mietz, D.E.

    1997-11-01

    Issues related to the development of direct detection, long-range CO{sub 2} DIAL systems for chemical detection and identification are presented and discussed including: data handling and display techniques for large, multi-{lambda} data sets, turbulence effects, slant path propagation, and speckle averaging. Data examples from various field campaigns and CO{sub 2} lidar platforms are used to illustrate the issues.

  16. A very wide frequency band pulsed/IF radar system

    NASA Technical Reports Server (NTRS)

    Jones, D. N.; Burnside, W. D.

    1988-01-01

    A pulsed/IF radar for compact range radar cross section measurements has been developed which converts RF returns to a fixed IF, so that amplification and grating may be performed at one frequency. This permits the use of components which have optimal performance at this frequency which results in a corresponding improvement in performance. Sensitivity and dynamic range are calculated for this system and compared with our old radar, and the effect of pulse width on clutter level is also studied. Sensitivity and accuracy tests are included to verify the performance of the radar.

  17. Large-N correlator systems for low frequency radio astronomy

    NASA Astrophysics Data System (ADS)

    Foster, Griffin

    Low frequency radio astronomy has entered a second golden age driven by the development of a new class of large-N interferometric arrays. The low frequency array (LOFAR) and a number of redshifted HI Epoch of Reionization (EoR) arrays are currently undergoing commission and regularly observing. Future arrays of unprecedented sensitivity and resolutions at low frequencies, such as the square kilometer array (SKA) and the hydrogen epoch of reionization array (HERA), are in development. The combination of advancements in specialized field programmable gate array (FPGA) hardware for signal processing, computing and graphics processing unit (GPU) resources, and new imaging and calibration algorithms has opened up the oft underused radio band below 300 MHz. These interferometric arrays require efficient implementation of digital signal processing (DSP) hardware to compute the baseline correlations. FPGA technology provides an optimal platform to develop new correlators. The significant growth in data rates from these systems requires automated software to reduce the correlations in real time before storing the data products to disk. Low frequency, widefield observations introduce a number of unique calibration and imaging challenges. The efficient implementation of FX correlators using FPGA hardware is presented. Two correlators have been developed, one for the 32 element BEST-2 array at Medicina Observatory and the other for the 96 element LOFAR station at Chilbolton Observatory. In addition, calibration and imaging software has been developed for each system which makes use of the radio interferometry measurement equation (RIME) to derive calibrations. A process for generating sky maps from widefield LOFAR station observations is presented. Shapelets, a method of modelling extended structures such as resolved sources and beam patterns has been adapted for radio astronomy use to further improve system calibration. Scaling of computing technology allows for the

  18. Unique frequency-shift-keyed demodulation system

    NASA Technical Reports Server (NTRS)

    Staloff, C.; Teltelbaum, S.

    1968-01-01

    Frequency-Shift-Keyed /FSK/ demodulator provides a frequency discriminator whose outputs are separate and applied to two identical decoding channels, one decoding binary ones and the other decoding binary zeros. This demodulator rejects data applied to it at any frequency higher than design.

  19. Formant frequency development: 15 to 36 months.

    PubMed

    Gilbert, H R; Robb, M P; Chen, Y

    1997-09-01

    Developmental characteristics of formant 1 (F1) and formant 2 (F2) are reported for spontaneous vocalizations produced by four young children. Each child was systematically sampled at between 15 and 36 months of age. Results indicated that both F1 and F2 remained relatively unchanged prior to 24 months of age. Significant decreases in average F1 and F2 occurred between 24 and 36 months. When F1 and F2 values were categorized according to tongue elevation and tongue advancement, the most significant changes were associated with high/back articulations. The pattern of formant frequencies noted in the present group of children appears to reflect developmental changes in vocal tract growth and reconfiguration.

  20. Development of a wearable multi-frequency impedance cardiography device.

    PubMed

    Weyer, Sören; Menden, Tobias; Leicht, Lennart; Leonhardt, Steffen; Wartzek, Tobias

    2015-02-01

    Cardiovascular diseases as well as pulmonary oedema can be early diagnosed using vital signs and thoracic bio-impedance. By recording the electrocardiogram (ECG) and the impedance cardiogram (ICG), vital parameters are captured continuously. The aim of this study is the continuous monitoring of ECG and multi-frequency ICG by a mobile system. A mobile measuring system, based on 'low-power' ECG, ICG and an included radio transmission is described. Due to the high component integration, a board size of only 6.5 cm×5 cm could be realized. The measured data can be transmitted via Bluetooth and visualized on a portable monitor. By using energy-efficient hardware, the system can operate for up to 18 hs with a 3 V battery, continuously sending data via Bluetooth. Longer operating times can be realized by decreased transfer rates. The relative error of the impedance measurement was less than 1%. The ECG and ICG measurements allow an approximate calculation of the heart stroke volume. The ECG and the measured impedance showed a high correlation to commercial devices (r=0.83, p<0.05). In addition to commercial devices, the developed system allows a multi-frequency measurement of the thoracic impedance between 5-150 kHz.

  1. S and Ku band frequency source development

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The results of the two part S- and Ku-band source development program are described. The S- and Ku-band sources were designed, fabricated, and evaluated. A high performance S- and Ku-band microwave signal source using state-of-the-art oscillator and microwave source technology was developed.

  2. The Development of Spatial Frequency Biases in Face Recognition

    ERIC Educational Resources Information Center

    Leonard, Hayley C.; Karmiloff-Smith, Annette; Johnson, Mark H.

    2010-01-01

    Previous research has suggested that a mid-band of spatial frequencies is critical to face recognition in adults, but few studies have explored the development of this bias in children. We present a paradigm adapted from the adult literature to test spatial frequency biases throughout development. Faces were presented on a screen with particular…

  3. The Development of Spatial Frequency Biases in Face Recognition

    ERIC Educational Resources Information Center

    Leonard, Hayley C.; Karmiloff-Smith, Annette; Johnson, Mark H.

    2010-01-01

    Previous research has suggested that a mid-band of spatial frequencies is critical to face recognition in adults, but few studies have explored the development of this bias in children. We present a paradigm adapted from the adult literature to test spatial frequency biases throughout development. Faces were presented on a screen with particular…

  4. Development of a variable frequency microwave processing system for post-curing of thermoset polymer matrix composite materials. Final report, 1 September 1994-28 February 1995

    SciTech Connect

    Johnson, A.

    1995-02-28

    Using a Variable frequency Microwave Furnace (VFMF) technology, Lambda Technologies has demonstrated the ability to tune to the optimum incident frequency for best coupling into a given material structure (e.g., polymer matrix composite, PMC), and then by sweeping around that incident center frequency, producing uniform energy distribution throughout the cavity and sample volume. Hence, the advantages of microwave energy---enhanced reaction rates, reduced process time, and heat generation at the molecular level---are now obtainable with controlled and uniform results compatible for commercial scale-up. The processing via VFMF is 8 - 10 times faster than conventional processing methods. The advantages of VFMF technology over single frequency microwave technology in achieving the uniform electromagnetic energy distribution required for rapid and reliable processing of advanced polymer composites are systematically demonstrated in the Phase I (Both Glass and Carbon fiber reinforced PMC were investigated). In addition, a numerical modeling program implemented during Phase I provided a foundation for the ability to predict field distribution and temperature profiles in various geometries (plate, disk and cylinder) and materials (glass and graphite fiber reinforced PMCs) when being heated with variable frequency microwave energy.

  5. Efficient system for wavenumber-frequency analysis of underwater structures

    NASA Astrophysics Data System (ADS)

    Boober, Walter H.; Morton, David; Gedney, Charles; Abbot, Philip

    1998-06-01

    A watertight housing was developed to a low a scanning laser vibrometer (SLV) system to work underwater. Compared to other underwater optical measurement systems, this system offers distinct advantages, including ease of adaptation to a variety of teste, no requirement to be near tank windows, and a simplified rigging system. The system was recently sued to successfully conduct a wavenumber frequency evaluation of the vibratory response of a submerged cylindrical shell. The technical issues in developing the housing and assuring the integrity of the SLV accuracy during transition to underwater use will be discussed. Also, problems encountered in maximizing return signal strength, preparation of the shell, and the process of on-sight data transfer for quick-look wavenumber-frequency analysis while data are being acquired will be presented. The cylindrical shell was excited with 100 to 5000 Hz chirp signals by a 44 N shaker that was attached axially at the center of a bulkhead. A scan consisted of 3 columns with 64 measurement points per column. The shell was rotated 11.25 degrees and the scan repeated to collect an array of 32 by 64 equally spaced points totalling 6144 measurements. The time of data acquisition was about 11 hours. This underwater housing permitted the type of measurements that are not readily available with other systems. With most other techniques the collection time would have been significantly longer. The transfer functions between the velocities measured at each scan location and the shaker force signal were computed as functions of frequency. The transfer functions computed for the center scan columns were then transformed into the wavevector domain using a 2D FFT program. Preliminary results show that the shell response is concentrated near zero circumferential wavenumber, due to the axial symmetry of the driving force. Further, the maximum shell response is also concentrated near the ring frequency of the cylinder, at an axial wavenumber of

  6. Sub-millimeter wave frequency heterodyne detector system

    NASA Technical Reports Server (NTRS)

    Siegel, Peter H. (Inventor); Dengler, Robert (Inventor); Mueller, Eric R. (Inventor)

    2010-01-01

    The present invention relates to sub-millimeter wave frequency heterodyne imaging systems. More specifically, the present invention relates to a sub-millimeter wave frequency heterodyne detector system for imaging the magnitude and phase of transmitted power through or reflected power off of mechanically scanned samples at sub-millimeter wave frequencies.

  7. Sub-millimeter wave frequency heterodyne detector system

    NASA Technical Reports Server (NTRS)

    Siegel, Peter H. (Inventor); Dengler, Robert (Inventor); Mueller, Eric R. (Inventor)

    2009-01-01

    The present invention relates to sub-millimeter wave frequency heterodyne imaging systems. More specifically, the present invention relates to a sub-millimeter wave frequency heterodyne detector system for imaging the magnitude and phase of transmitted power through or reflected power off of mechanically scanned samples at sub-millimeter wave frequencies.

  8. Development of Graphene for High Frequency Electronics

    NASA Astrophysics Data System (ADS)

    Robinson, Joshua; Snyder, David; Fanton, Mark; Hollander, Matthew; Labella, Michael; Trumbull, Kathleen; Cavalero, Randall; Weiland, Brian; The Pennsylvania State University Team

    2011-03-01

    The practicality and success of a graphene technology depends on the ability to regularly and controllably synthesize graphene; integrate it with metals and dielectrics; and to develop device designs that take advantage of graphene's unique properties. We demonstrate graphene synthesis on SiC(0001) and Sapphire with 1.5% variation in sheet resistance across 100mm wafers. Hall mobility measurements indicate that direct growth of graphene on sapphire leads to a 2x increase in mobility (2200 cm2 /Vs) compared to silicon sublimation from SiC(0001). Additionally, we have developed high quality ohmic contacts to graphene, which improves the contact resistance by nearly 6000x (5 x 10-8 Ohm-cm2) compared to untreated metal/graphene interfaces. Finally, we discuss integration of ultra-thin high-k dielectrics and their impact on graphene transport. Atomic layer deposited oxide heterostructures (seed not equal to overlayer) have deleterious effects on Hall mobility while homostructures lead to an increase in Hall mobility. Importantly, 5nm thick EBPVD Hf O2 gate dielectrics are successfully demonstrated and show improved Hall mobility, on-off ratio, and transconductance relative to Al 2 O3 gates and heterostructure gates.

  9. Application of multi-variable control for automatic frequency controller of HVDC transmission system

    SciTech Connect

    Sanpei, Masatoshi ); Kakehi, Atsuyuki; Takeda, Hideo )

    1994-04-01

    In an HVDC transmission system that links two ac power systems, the automatic frequency controller (AFC) calculates power to be interchanged between the two ac systems according to their frequencies thereby improving the frequency characteristics of the two power systems. This paper introduces a newly developed dc AFC system, which applies a multi-variable control to the dc system-based frequency control. It is capable of controlling the frequencies of the two ac systems optimally while maintaining their stability. This system was developed for one of Japan's HVDC transmission facilities and produced good results in a combined test using a power system simulator. The field installation will be completed in March 1993, when the AFC system will enter service.

  10. a Pre-Emphasis Technique to Broaden the Usable Frequency Range in Swept-Frequency Systems

    NASA Astrophysics Data System (ADS)

    Gammell, Paul M.; Maruvada, Subha; Liu, Yunbo; Harris, Gerald R.

    2010-02-01

    The usable frequency range of an ultrasonic swept-frequency system can be compromised because of transducer bandwidth limitations or sample frequency response and corresponding signal-to-noise (S/N) considerations. By adding a variable gain amplifier together with an arbitrary waveform generator that is synchronized with the frequency sweep, the dynamic range of the receiver can be accommodated over a wider frequency range. This pre-emphasis approach has been demonstrated for two applications: substitution calibration of hydrophones and attenuation measurements.

  11. Dual-Frequency Airborne Scanning Rain Radar Antenna System

    NASA Technical Reports Server (NTRS)

    Hussein, Ziad A.; Green, Ken

    2004-01-01

    A compact, dual-frequency, dual-polarization, wide-angle-scanning antenna system has been developed as part of an airborne instrument for measuring rainfall. This system is an upgraded version of a prior single-frequency airborne rain radar antenna system and was designed to satisfy stringent requirements. One particularly stringent combination of requirements is to generate two dual-polarization (horizontal and vertical polarizations) beams at both frequencies (13.405 and 35.605 GHz) in such a way that the beams radiated from the antenna point in the same direction, have 3-dB angular widths that match within 25 percent, and have low sidelobe levels over a wide scan angle at each polarization-and-frequency combination. In addition, the system is required to exhibit low voltage standing-wave ratios at both frequencies. The system (see figure) includes a flat elliptical scanning reflector and a stationary offset paraboloidal reflector illuminated by a common-aperture feed system that comprises a corrugated horn with four input ports one port for each of the four frequency-and-polarization combinations. The feed horn is designed to simultaneously (1) under-illuminate the reflectors 35.605 GHz and (2) illuminate the reflectors with a 15-dB edge taper at 13.405 GHz. The scanning mirror is rotated in azimuth to scan the antenna beam over an angular range of 20 in the cross-track direction for wide swath coverage, and in elevation to compensate for the motion of the aircraft. The design of common-aperture feed horn makes it possible to obtain the required absolute gain and low side-lobe levels in wide-angle beam scanning. The combination of the common-aperture feed horn with the small (0.3) focal-length-to-diameter ratio of the paraboloidal reflector makes it possible for the overall system to be compact enough that it can be mounted on a DC-8 airplane.

  12. 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

  13. Responses of an isolation system with distinct multiple frequencies

    SciTech Connect

    Wu, Ting-shu; Seidensticker, R.W.

    1991-01-01

    Base isolation systems are generally designed with a single natural frequency. A major concern for these isolation systems is that, if the dominant frequency of a future earthquake is equal or close to the system's natural frequency, the ground motion will be greatly amplified because of resonance,and the superstructure would suffer severe damages. This paper present an isolation system designed with two distinct frequencies. Its responses to different ground motions, including a harmonic motion, show that no excessive amplification will occur. Adoption of this isolation system would greatly enhance the safety of an isolated superstructure against future strong earthquakes. 3 refs., 4 figs., 2 tabs.

  14. Low-frequency radio navigation system

    NASA Technical Reports Server (NTRS)

    Wallis, D. E. (Inventor)

    1983-01-01

    A method of continuous wave navigation using four transmitters operating at sufficiently low frequencies to assure essentially pure groundwave operation is described. The transmitters are keyed to transmit constant bursts (1/4 sec) in a time-multiplexed pattern with phase modulation of at least one transmitter for identification of the transmitters and with the ability to identify the absolute phase of the modulated transmitter and the ability to modulate low rate data for transmission. The transmitters are optimally positioned to provide groundwave coverage over a service region of about 50 by 50 km for the frequencies selected in the range of 200 to 500 kHz, but their locations are not critical because of the beneficial effect of overdetermination of position of a receiver made possible by the fourth transmitter. Four frequencies are used, at least two of which are selected to provide optimal resolution. All transmitters are synchronized to an average phase as received by a monitor receiver.

  15. Magnetoencephalography Detection of High-Frequency Oscillations in the Developing Brain

    PubMed Central

    Leiken, Kimberly; Xiang, Jing; Zhang, Fawen; Shi, Jingping; Tang, Lu; Liu, Hongxing; Wang, Xiaoshan

    2014-01-01

    Increasing evidence from invasive intracranial recordings suggests that the matured brain generates both physiological and pathological high-frequency signals. The present study was designed to detect high-frequency brain signals in the developing brain using newly developed magnetoencephalography (MEG) methods. Twenty healthy children were studied with a high-sampling rate MEG system. Functional high-frequency brain signals were evoked by electrical stimulation applied to the index fingers. To determine if the high-frequency neuromagnetic signals are true brain responses in high-frequency range, we analyzed the MEG data using the conventional averaging as well as newly developed time-frequency analysis along with beamforming. The data of healthy children showed that very high-frequency brain signals (>1000 Hz) in the somatosensory cortex in the developing brain could be detected and localized using MEG. The amplitude of very high-frequency brain signals was significantly weaker than that of the low-frequency brain signals. Very high-frequency brain signals showed a much earlier latency than those of a low-frequency. Magnetic source imaging (MSI) revealed that a portion of the high-frequency signals was from the somatosensory cortex, another portion of the high-frequency signals was probably from the thalamus. Our results provide evidence that the developing brain generates high-frequency signals that can be detected with the non-invasive technique of MEG. MEG detection of high-frequency brain signals may open a new window for the study of developing brain function. PMID:25566015

  16. Frequency-agile THz-wave generation and detection system using nonlinear frequency conversion at room temperature.

    PubMed

    Guo, Ruixiang; Ikar'i, Tomofumi; Zhang, Jun; Minamide, Hiroaki; Ito, Hiromasa

    2010-08-02

    A surface-emitting THz parametric oscillator is set up to generate a narrow-linewidth, nanosecond pulsed THz-wave radiation. The THz-wave radiation is coherently detected using the frequency up-conversion in MgO: LiNbO(3) crystal. Fast frequency tuning and automatic achromatic THz-wave detection are achieved through a special optical design, including a variable-angle mirror and 1:1 telescope devices in the pump and THz-wave beams. We demonstrate a frequency-agile THz-wave parametric generation and THz-wave coherent detection system. This system can be used as a frequency-domain THz-wave spectrometer operated at room-temperature, and there are a high possible to develop into a real-time two-dimensional THz spectral imaging system.

  17. Microfabricated multi-frequency particle impedance characterization system

    SciTech Connect

    Fuller, C K; Hamilton, J; Ackler, H; Krulevitch, P; Boser, B; Eldredge, A; Becker, F; Yang, J; Gascoyne, P

    2000-03-01

    We have developed a microfabricated flow-through impedance characterization system capable of performing AC, multi-frequency measurements on cells and other particles. The sensor measures both the resistive and reactive impedance of passing particles, at rates of up to 100 particles per second. Its operational bandwidth approaches 10 MHz with a signal-to-noise ratio of approximately 40 dB. Particle impedance is measured at three or more frequencies simultaneously, enabling the derivation of multiple particle parameters. This constitutes an improvement to the well-established technique of DC particle sizing via the Coulter Principle. Human peripheral blood granulocyte radius, membrane capacitance, and cytoplasmic conductivity were measured (r = 4.1 {micro}m, C{sub mem} = 0.9 {micro}F/cm{sup 2}, {sigma}{sub int} = 0.66 S/m) and were found to be consistent with published values.

  18. Tracking and Data Relay Satellite System (TDRSS) frequency plan

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The functions of the Tracking and Data Relay Satellite System (TDRSS) are discussed. The primary purpose of the system is to transmit signals to and receive signals from earth orbiting user spacecraft, and provide data from which user spacecraft ephemerides can be calculated. The system configuration is described and illustrated. The frequency plan is analyzed to show the frequency coverage and the signal handling capability of the system. The characteristics of the components of the system are tabulated.

  19. Development of a four-frequency selective surface prototype spacecraft antenna

    NASA Astrophysics Data System (ADS)

    Hickey, Gregory S.; Wu, Te-Kao

    NASA-JPL's four-frequency telecommunication system design entails the creation and integration of a frequency-selective surface (FSS) subreflector into the high-gain antenna subsystem. The FSS design, which incorporates a periodic array of conducting elements on a kevlar/polymer composite structure, will be able to multiplex S, X, Ku, and Ka frequency-band wavelengths. Accounts are presented of the FSS's development, mechanical testing, and electrical testing.

  20. Development of a four-frequency selective surface prototype spacecraft antenna

    NASA Technical Reports Server (NTRS)

    Hickey, Gregory S.; Wu, Te-Kao

    1992-01-01

    NASA-JPL's four-frequency telecommunication system design entails the creation and integration of a frequency-selective surface (FSS) subreflector into the high-gain antenna subsystem. The FSS design, which incorporates a periodic array of conducting elements on a kevlar/polymer composite structure, will be able to multiplex S, X, Ku, and Ka frequency-band wavelengths. Accounts are presented of the FSS's development, mechanical testing, and electrical testing.

  1. DSN frequency and timing system, Mark 4-85

    NASA Technical Reports Server (NTRS)

    Falin, B. W.

    1985-01-01

    As part of the Deep Space Network (DSN) Mark IVA implementation program, the DSN frequency and timing system is currently undergoing changes. With the implementation of signal processing centers (SPC) at each deep space communications complex (DSCC), major changes to the frequency and timing distribution equipment were necessary. A functional description of the Mark IVA frequency and timing system (FTS) as it exists today and planned capabilities through 1988 is given.

  2. Accident Sequence Precursor Program Large Early Release Frequency Model Development

    SciTech Connect

    Brown, T.D.; Brownson, D.A.; Duran, F.A.; Gregory, J.J.; Rodrick, E.G.

    1999-01-04

    The objectives for the ASP large early release frequency (LERF) model development work is to build a Level 2 containment response model that would capture all of the events necessary to define LERF as outlined in Regulatory Guide 1.174, can be directly interfaced with the existing Level 1 models, is technically correct, can be readily modified to incorporate new information or to represent another plant, and can be executed in SAPHIRE. The ASP LERF models being developed will meet these objectives while providing the NRC with the capability to independently assess the risk impact of plant-specific changes proposed by the utilities that change the nuclear power plants' licensing basis. Together with the ASP Level 1 models, the ASP LERF models provide the NRC with the capability of performing equipment and event assessments to determine their impact on a plant's LERF for internal events during power operation. In addition, the ASP LERF models are capable of being updated to reflect changes in information regarding the system operations and phenomenological events, and of being updated to assess the potential for early fatalities for each LERF sequence. As the ASP Level 1 models evolve to include more analysis capabilities, the LERF models will also be refined to reflect the appropriate level of detail needed to demonstrate the new capabilities. An approach was formulated for the development of detailed LERF models using the NUREG-1150 APET models as a guide. The modifications to the SAPHIRE computer code have allowed the development of these detailed models and the ability to analyze these models in a reasonable time. Ten reference LERF plant models, including six PWR models and four BWR models, which cover a wide variety of containment and nuclear steam supply systems designs, will be complete in 1999. These reference models will be used as the starting point for developing the LERF models for the remaining nuclear power plants.

  3. 622-Mbps Orthogonal Frequency Division Multiplexing Modulator Developed

    NASA Technical Reports Server (NTRS)

    Nguyen, Na T.

    1999-01-01

    The Communications Technology Division at the NASA Lewis Research Center is developing advanced electronic technologies for the space communications and remote sensing systems of tomorrow. As part of the continuing effort to advance the state-of-the art in satellite communications and remote sensing systems, Lewis is developing a programmable Orthogonal Frequency Division Multiplexing (OFDM) modulator card for high-data-rate communication links. The OFDM modulator is particularly suited to high data-rate downlinks to ground terminals or direct data downlinks from near-Earth science platforms. It can support data rates up to 622 megabits per second (Mbps) and high-order modulation schemes such as 16-ary quadrature amplitude modulation (16-ary QAM) or 8- phase shift keying (8PSK). High order modulations can obtain the bandwidth efficiency over the traditional binary phase shift keying (BPSK) or quadrature phase shift keying (QPSK) modulator schemes. The OFDM modulator architecture can also be precompensated for channel disturbances and alleviate amplitude degradations caused by nonlinear transponder characteristics.

  4. NSLS-II Radio Frequency Systems

    SciTech Connect

    Rose J.; Gao F.; Goel, A.; Holub, B.; Kulpin, J.; Marques, C.; Yeddulla, M.

    2015-05-03

    The National Synchrotron Light Source II is a 3 GeV X-ray user facility commissioned in 2014. The NSLS-II RF system consists of the master oscillator, digital low level RF controllers, linac, booster and storage ring RF sub-systems, as well as a supporting cryogenic system. Here we will report on RF commissioning and early operation experience of the system.

  5. Development of high frequency annular array ultrasound transducers

    NASA Astrophysics Data System (ADS)

    Gottlieb, Emanuel John

    The advantage of ultrasonic annular arrays over conventional single element transducers has been in the ability to transmit focus at multiple points throughout the depth of field, as well as receive dynamic focus. Today, annular, linear and multidimensional array imaging systems are not commercially available at frequencies greater than 20 MHz. The fabrication technology used to develop a high frequency (>50 MHz) annular array transducer is presented. A 9 mum P(VDF-TrFE) film was bonded to gold annuli electrodes on the top layer of a two sided polyimide flexible circuit. Each annulus was separated by a 30 mum kerf and had several electroplated micro vias that connected to electrode traces on the bottom side of the polyimide flexible circuit. The array's performance was evaluated by measuring the electrical impedance, pulse echo response and crosstalk measurement for each element in the array. In order to improve device sensitivity each element was electrically matched to an impedance magnitude of 50 O and 0° phase at resonance. The average round trip insertion loss measured for the array and compensated for diffraction effects was -33.5 dB. The measured average center frequency and bandwidth of an element was 55 MHz and 47 respectively. The measured crosstalk between adjacent elements remained below -29 dB at the center frequency in water. A vertical wire phantom was imaged using a single focus transmit beamformer and dynamic focusing receive beamformer. This image showed a significant improvement in lateral resolution over a range of 9 mm after the dynamic focusing receive algorithm was applied. These results correlated well with predictions from a Field II simulation. After beamforming the minimum lateral resolution (-6 dB) was 108 mum at the focus. Preliminary ultrasound B-mode images of the rabbit eye using this transducer were shown in conjunction with a multi-channel digital beamformer. A feasibility study of designing and fabricating tunable copolymer

  6. A robust decentralized load frequency controller for interconnected power systems.

    PubMed

    Dong, Lili; Zhang, Yao; Gao, Zhiqiang

    2012-05-01

    A novel design of a robust decentralized load frequency control (LFC) algorithm is proposed for an inter-connected three-area power system, for the purpose of regulating area control error (ACE) in the presence of system uncertainties and external disturbances. The design is based on the concept of active disturbance rejection control (ADRC). Estimating and mitigating the total effect of various uncertainties in real time, ADRC is particularly effective against a wide range of parameter variations, model uncertainties, and large disturbances. Furthermore, with only two tuning parameters, the controller provides a simple and easy-to-use solution to complex engineering problems in practice. Here, an ADRC-based LFC solution is developed for systems with turbines of various types, such as non-reheat, reheat, and hydraulic. The simulation results verified the effectiveness of the ADRC, in comparison with an existing PI-type controller tuned via genetic algorithm linear matrix inequalities (GALMIs). The comparison results show the superiority of the proposed solution. Moreover, the stability and robustness of the closed-loop system is studied using frequency-domain analysis.

  7. Frequency Control Concerns in the North American Electric Power System

    SciTech Connect

    Kirby, B.J.

    2003-03-26

    This paper examines the relationship between system frequency, reliability and markets. It was prompted by the frequency deviations recently experienced at 2200 hours daily but is more generally concerned with the question of what frequency control is necessary. The paper does not provide new information or document new research. Nor is it intended to educate readers concerning power system engineering. Instead, the purpose is to reexamine well known truths concerning the power system and to freshly explore the basic relationship between frequency, reliability and markets: stepping back, if you will, to see if we are collectively missing something. The concern of this paper is with frequency and reliability. Off-nominal frequency can impact reliability and markets efficiency (as we are using the term here) in four ways. It could damage equipment (generation, transmission, or load). It could degrade the quality of the product being delivered to end users (too low and lights would flicker unacceptably, for example). It could result in the collapse of the power system itself (by triggering protective system actions, for example). Or it could result in overloading transmission lines as various generators try to restore system frequency impacting markets efficiency. Often these causes operate in concert. Generator protective systems take action to prevent generator damage, for example, but exacerbate the overall generation/load imbalance. The paper is divided into two sections. The Introduction is followed by a section titled ''A Perspective on Frequency Control'' which addresses the physical requirements of the power system and how market transactions interact with the physical system. The ''Frequency Standards and Control Performance'' section discusses the various NERC and regional reliability council policies that govern utility performance and how these relate to frequency and reliability. Finally, Conclusions are provided.

  8. Carrier - Interference ratios for frequency sharing between satellite systems transmitting frequency modulated and digital television signals

    NASA Technical Reports Server (NTRS)

    Barnes, S. P.

    1979-01-01

    As the data rates required for digitally encoded television are reduced, satellite systems employing the transmission of digitally encoded television will become attractive. It is likely that television transmitted in this format will be adjacent to or in the same frequency band as television transmissions in other modulation formats, so a knowledge of carrier to interference power ratios as a function of assessed picture quality will be required for frequency sharing between these different modulation formats. This paper presents the results of subjective and quantitative tests describing the results of interference to a particular digital television system from a frequency modulated (FM) television system, and for interference to an FM television system from a digital television system.

  9. Development of high precision digital driver of acoustic-optical frequency shifter for ROG

    NASA Astrophysics Data System (ADS)

    Zhang, Rong; Kong, Mei; Xu, Yameng

    2016-10-01

    We develop a high precision digital driver of the acoustic-optical frequency shifter (AOFS) based on the parallel direct digital synthesizer (DDS) technology. We use an atomic clock as the phase-locked loop (PLL) reference clock, and the PLL is realized by a dual digital phase-locked loop. A DDS sampling clock up to 320 MHz with a frequency stability as low as 10-12 Hz is obtained. By constructing the RF signal measurement system, it is measured that the frequency output range of the AOFS-driver is 52-58 MHz, the center frequency of the band-pass filter is 55 MHz, the ripple in the band is less than 1 dB@3MHz, the single channel output power is up to 0.3 W, the frequency stability is 1 ppb (1 hour duration), and the frequency-shift precision is 0.1 Hz. The obtained frequency stability has two orders of improvement compared to that of the analog AOFS-drivers. For the designed binary frequency shift keying (2-FSK) and binary phase shift keying (2-PSK) modulation system, the demodulating frequency of the input TTL synchronous level signal is up to 10 kHz. The designed digital-bus coding/decoding system is compatible with many conventional digital bus protocols. It can interface with the ROG signal detecting software through the integrated drive electronics (IDE) and exchange data with the two DDS frequency-shift channels through the signal detecting software.

  10. Telemetry Systems Radio Frequency (RF) Handbook

    DTIC Science & Technology

    2001-12-01

    1-11 Figure 1-9. OQPSK block diagram...space OQPSK offset quadrature phase-shift keying p-p peak-to-peak PAM pulse-amplitude modulation PCM pulse-code modulation PLD path length difference...11 Figure 1-8. QPSK block diagram. 1.3.2.2.3 Offset Quadrature Phase-Shift Keying ( OQPSK ) Systems. The OQPSK transmission system, also known as

  11. Beat frequency ultrasonic microsphere contrast agent detection system

    NASA Technical Reports Server (NTRS)

    Pretlow, III, Robert A. (Inventor); Yost, William T. (Inventor); Cantrell, Jr., John H. (Inventor)

    1997-01-01

    A system for and method of detecting and measuring concentrations of an ultrasonically-reflective microsphere contrast agent involving detecting non-linear sum and difference beat frequencies produced by the microspheres when two impinging signals with non-identical frequencies are combined by mixing. These beat frequencies can be used for a variety of applications such as detecting the presence of and measuring the flow rates of biological fluids and industrial liquids, including determining the concentration level of microspheres in the myocardium.

  12. Beat frequency ultrasonic microsphere contrast agent detection system

    NASA Technical Reports Server (NTRS)

    Pretlow, Robert A., III (Inventor); Yost, William T. (Inventor); Cantrell, John H., Jr. (Inventor)

    1995-01-01

    A system for and method of detecting and measuring concentrations of an ultrasonically-reflective microsphere contrast agent involving detecting non-linear sum and difference beat frequencies produced by the microspheres when two impinging signals with non-identical frequencies are combined by mixing. These beat frequencies can be used for a variety of applications such as detecting the presence of and measuring the flow rates of biological fluids and industrial liquids, including determining the concentration level of microspheres in the myocardium.

  13. Development and preliminary results of radio frequency ion source

    SciTech Connect

    Xie, Yahong Hu, Chundong; Jiang, Caichao; Chen, Yuqian; Gu, Yumin; Su, Renxue; Xie, Yuanlai; Liu, Zhimin

    2016-02-15

    A radio frequency (RF) ion source was designed and developed for neutral beam injector. A RF driver test bed was used with a RF generator with maximum power of 25 kW with 1 MHz frequency and a matching box. In order to study the characteristic of RF plasma generation, the capacitance in the matching box was adjusted with different cases. The results show that lower capacitance will better the stability of the plasma with higher RF power. In the future, new RF coils and matching box will be developed for plasma generators with higher RF power of 50 kW.

  14. Development and test of the Ball Aerospace optical frequency comb: a versatile measurement tool for aerospace applications

    NASA Astrophysics Data System (ADS)

    Wachs, Jordan; Leitch, James; Knight, Scott; Pierce, Robert; Adkins, Michael

    2016-07-01

    The Ball Fiber Optical Comb Demo is a lab-based system which is used to develop space applications for optical frequency combs. These developments utilize the broadband optical coherence of the frequency comb to expand the capabilities of ground test and orbital systems used for optical wave-front measurement, control of adaptive optics, precision ranging, and reference frequency stabilization. The work expands upon a NIST-developed all-fiber frequency comb that exhibits high stability in a compact, enclosed package. Previously demonstrated applications for frequency combs include: Spectroscopy, distance and velocity measurement, frequency conversion, and timing transfer. Results from the Ball system show the characterization and performance of a frequency comb system with a technological path-to-space. Demonstrations in high precision metrology and long distance ranging are also presented for application in adaptive and multi-body optical systems.

  15. Battery Performance in Frequency Modulated Amplification Systems.

    ERIC Educational Resources Information Center

    Lyon, David J.; Swain, Graeme D.

    1989-01-01

    This paper investigates one characteristic of FM radio hearing-aid systems as used in the education of hearing impaired children: battery performance. While batteries studied performed according to manufacturer's specifications, the importance of monitoring the charging procedure cannot be overemphasized. (Author/PB)

  16. Development and RF Evaluation of a Four-Frequency Selective Surface Spacecraft Subreflector Antenna

    NASA Technical Reports Server (NTRS)

    Hickey, George S.; Wu, Te-Kao

    1996-01-01

    NASA Jet Propulsion Laboratory has baselined a four frequency telecommunication system for the Cassini spacecraft antenna subsystems. This design required the design and development of a Frequency Selective Surface Subreflector (FSS) that is integrated into the High Gain Antenna Subsystem. This paper will discuss the development, mechanical and RF electrical testing of two alternate designs as flat panel prototypes that were conducted to verify the multifrequency design approach.

  17. Development of Frequency Stabilizing Scheme for Integrating Wind Power Generation into an Isolated Grid

    NASA Astrophysics Data System (ADS)

    Yamashita, Koji; Sakamoto, Orie; Kitauchi, Yoshihiro; Nanahara, Toshiya; Inoue, Toshio; Shiohama, Tomohiro; Fukuda, Hitoshi

    Integrating of wind power generation into small islands has been one of the demonstration projects in Okinawa prefecture. Since such integration could deteriorate power quality including frequency in an island grid, a frequency stabilizing system using flywheels has been installed into a small island. In order to establish a proper frequency stabilizing scheme for the small island, an accurate model of a diesel generator including governor is vital. Therefore, the model was developed based on the measured values of generator dump tests. A new frequency stabilizing scheme was also developed through time-domain simulation of the island grid model which consists of the above-mentioned diesel generator model and an equivalent load change representing wind power variation. The proper parameters of the scheme were derived considering role sharing between the diesel generators and the flywheels. The developed stabilizing scheme was applied to the flywheels in the island grid and revealed great performance for mitigating frequency variation.

  18. Controlled radio frequency vessel sealing system for surgical applications

    NASA Astrophysics Data System (ADS)

    Kennedy, Jenifer S.; Buysse, Steve; Chandler, James; Eggleston, Jeff; Taylor, Kenneth D.; Thomsen, Sharon L.

    1998-04-01

    A radio frequency tissue welding system has been developed for occlusion of vessels during surgery. The system is designed to replace commonly used mechanical clip and suture ligation techniques. Other energy based ligation techniques are limited to use on small structures (system consists of forceps and an RF electrosurgery generator, both of which are specifically designed for optimal tissue sealing. The method combines optimal pressure delivery to the tissue and energy delivery consisting of a high heat cycle, a low heat cycle and a cooling cycle. The generator output is also voltage limited and delivers high current in order to remodel the collagen in approximately 5 seconds with no sticking or charring. The vessel sealing system was compared to other energy based ligation techniques including ultrasonic sealing and other bipolar systems. The pressure required to burst the vessel was used for comparison. Average burst pressures on 3 - 7 mm arteries were 126 +/- 154 mmHg, 607 +/- 314 mmHg, and 913 +/- 304 mmHg for ultrasonic, standard bipolar, and vessel sealing, respectively. Histologic evaluation showed vessel wall fusion and minimal thermal damage to adjacent tissues for the vessel sealing system.

  19. Novel solutions to low-frequency problems with geometrically designed beam-waveguide systems

    NASA Technical Reports Server (NTRS)

    Imbriale, W. A.; Esquivel, M. S.; Manshadi, F.

    1995-01-01

    The poor low-frequency performance of geometrically designed beam-waveguide (BWG) antennas is shown to be caused by the diffraction phase centers being far from the geometrical optics mirror focus, resulting in substantial spillover and defocusing loss. Two novel solutions are proposed: (1) reposition the mirrors to focus low frequencies and redesign the high frequencies to utilize the new mirror positions, and (2) redesign the input feed system to provide an optimum solution for the low frequency. A novel use of the conjugate phase-matching technique is utilized to design the optimum low-frequency feed system, and the new feed system has been implemented in the JPL research and development BWG as part of a dual S-/X-band (2.3 GHz/8.45 GHz) feed system. The new S-band feed system is shown to perform significantly better than the original geometrically designed system.

  20. Advanced high frequency partial discharge measuring system

    NASA Technical Reports Server (NTRS)

    Karady, George G.

    1994-01-01

    This report explains the Advanced Partial Discharge Measuring System in ASU's High Voltage Laboratory and presents some of the results obtained using the setup. While in operation an insulation is subjected to wide ranging temperature and voltage stresses. Hence, it is necessary to study the effect of temperature on the behavior of partial discharges in an insulation. The setup described in this report can be used to test samples at temperatures ranging from -50 C to 200 C. The aim of conducting the tests described herein is to be able to predict the behavior of an insulation under different operating conditions in addition to being able to predict the possibility of failure.

  1. Frequency weighted system identification and linear quadratic controller design

    NASA Technical Reports Server (NTRS)

    Horta, Lucas G.; Phan, Minh; Juang, Jer-Nan; Longman, Richard W.; Sulla, Jeffrey L.

    1991-01-01

    Application of filters for frequency weighting of Markov parameters (pulse response functions) is described in relation to system/observer identification. The time domain identification approach recovers a model which has a pulse response weighted according to frequency. The identified model is composed of the original system and filters. The augmented system is in a form which can be used directly for frequency weighted linear quadratic controller design. Data from either single or multiple experiments can be used to recover the Markov parameters. Measured acceleration signals from a truss structure are used for system identification and the model obtained is used for frequency weighted controller design. The procedure makes the identification and controler design complementary problems.

  2. 7. Survivable low frequency communication system pathway, looking east ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. Survivable low frequency communication system pathway, looking east - Ellsworth Air Force Base, Delta Flight, Launch Control Facility, County Road CS23A, North of Exit 127, Interior, Jackson County, SD

  3. Nonlinear frequency-dependent synchronization in the developing hippocampus.

    PubMed

    Prida, L M; Sanchez-Andres, J V

    1999-07-01

    Synchronous population activity is present both in normal and pathological conditions such as epilepsy. In the immature hippocampus, synchronous bursting is an electrophysiological conspicuous event. These bursts, known as giant depolarizing potentials (GDPs), are generated by the synchronized activation of interneurons and pyramidal cells via GABAA, N-methyl-D-aspartate, and AMPA receptors. Nevertheless the mechanism leading to this synchronization is still controversial. We have investigated the conditions under which synchronization arises in developing hippocampal networks. By means of simultaneous intracellular recordings, we show that GDPs result from local cooperation of active cells within an integration period prior to their onset. During this time interval, an increase in the number of excitatory postsynaptic potentials (EPSPs) takes place building up full synchronization between cells. These EPSPs are correlated with individual action potentials simultaneously occurring in neighboring cells. We have used EPSP frequency as an indicator of the neuronal activity underlying GDP generation. By comparing EPSP frequency with the occurrence of synchronized GDPs between CA3 and the fascia dentata (FD), we found that GDPs are fired in an all-or-none manner, which is characterized by a specific threshold of EPSP frequency from which synchronous GDPs emerge. In FD, the EPSP frequency-threshold for GDP onset is 17 Hz. GDPs are triggered similarly in CA3 by appropriate periodic stimulation of mossy fibers. The frequency threshold for CA3 GDP onset is 12 Hz. These findings clarify the local mechanism of synchronization underlying bursting in the developing hippocampus, indicating that GDPs are fired when background levels of EPSPs or action potentials have built up full synchronization by firing at specific frequencies (>12 Hz). Our results also demonstrate that spontaneous EPSPs and action potentials are important for the initiation of synchronous bursts in the

  4. Spectroscopic Investigation of Materials for Frequency Agile Laser Systems.

    DTIC Science & Technology

    1985-01-01

    fluorescence spectra and lifetimes of divalent Rh, Ru, Pt, and Ir ions in alkali halide crystals are measured using pulsed nitrogen laser excitation...AD-Ai5t 73t SPECTROSCOPIC INVESTIGRTION OF MATERIALS FOR FREQUENCY t/ AGILE LASER SYSTEMS(U) OKLAHOMA STATE UNIV STILLWATER DEPT OF PHYSICS R C...INVESTIGATION OF MATERIALS FOR FREQUENCY AGILE LASER SYSTEMS Richard C. Powell, Ph.D. Principal Investigator Department of Physics OKLAHOMA STATE UNIVERSITY

  5. A frequency-routed satellite system concept using multiple orthogonally-polarized beams for frequency reuse

    NASA Technical Reports Server (NTRS)

    Rotholz, E.; White, B. E.

    1983-01-01

    The design concepts of a multibeam frequency-division multiplexed satellite system accessed by many moderately sized earth stations are outlined. In the system proposed here, traffic is routed from beam to beam through appropriate apportionment and filtering. Within a beam, the routing to particular users is achieved by conventional FDM. The optimum beam size, beam isolation, orthogonal polarization assignment to beams, the concept of beam groups yielding a simple transponder design, and the establishment of a frequency plan providing interference-free band assignments are discussed.

  6. Preliminary Results From the UNICIT High Frequency Microwave Palaeointensity System

    NASA Astrophysics Data System (ADS)

    Biggin, A.; Boehnel, H.; Walton, D.

    2002-05-01

    Two of the biggest problems encountered when using the Thellier method to obtain estimates of the geomagnetic field intensity in the past are thermochemical alteration occurring during the experiments and the time intensive nature of the experiments themselves. Together these factors frequently yield a frustratingly low ratio of success achieved to time spent in the laboratory. However this ratio can be much increased, if microwave radiation instead of conventional thermal energy is used to excite the ferromagnetic grains within samples. Following the recent success of the geomagnetism group at the University of Liverpool in using microwave radiation to perform palaeointensity experiments, a new system has been developed at the Earth science research unit (UNICIT) of UNAM in Querétaro, Mexico. Conceptually, it differs from the Liverpool system (described in the literature) only in that it is designed to use higher frequency microwave radiation (12 to 18 GHz as opposed to 8.5 GHz) as a more efficient means to excite the ferromagnetic systems of materials. The system has been used to perform modified Thellier palaeointensity experiments on volcanic samples which had previously had a full TRM imparted to them using a known field in the laboratory. The results of these experiments were very encouraging and will be presented. Currently, samples derived from recent volcanic material which has previously undergone conventional Thellier analysis are being studied using the microwave system. Results from these experiments will also be discussed.

  7. Microwave photonic system for instantaneous frequency measurement based on principles of "frequency-amplitude" conversion in fiber Bragg grating and additional frequency separation

    NASA Astrophysics Data System (ADS)

    Ivanov, Alexander A.; Morozov, Oleg G.; Andreev, Vladimir A.; Morozov, Gennady A.; Kuznetsov, Artem A.; Faskhutdinov, Lenar M.

    2017-04-01

    This article describes the design principles of optoelectronic system (OES) for instantaneous frequency measurement (IFM) of microwave signals based on the use of amplitude-phase modulation conversion of single optical carrier into symmetrical dual-frequency signal for additional frequency separation, its modulation by unknown frequency and subsequent "frequency-amplitude" measurement conversion in Fiber Bragg Grating (FBG) with Gaussian reflection profile. Such approach allows increasing of measurement resolution at low frequencies.

  8. ARTICLES: Some features of parametric conversion of infrared radiation in a system generating a difference frequency

    NASA Astrophysics Data System (ADS)

    Galaĭchuk, Yu A.; Strizhevskiĭ, V. L.; Yashkir, Yu N.

    1984-11-01

    A fluctuation theory is developed for the parametric conversion of infrared radiation utilizing four-photon difference frequency generation processes. An analysis is made of some features of optical parametric oscillation in this system allowing for sum frequency generation. Parametric "conversion" of quantum fluctuations to the frequency range of the infrared signal is discussed and it is shown that this effect increases the noise level.

  9. Frequency-difference-dependent stochastic resonance in neural systems

    NASA Astrophysics Data System (ADS)

    Guo, Daqing; Perc, Matjaž; Zhang, Yangsong; Xu, Peng; Yao, Dezhong

    2017-08-01

    Biological neurons receive multiple noisy oscillatory signals, and their dynamical response to the superposition of these signals is of fundamental importance for information processing in the brain. Here we study the response of neural systems to the weak envelope modulation signal, which is superimposed by two periodic signals with different frequencies. We show that stochastic resonance occurs at the beat frequency in neural systems at the single-neuron as well as the population level. The performance of this frequency-difference-dependent stochastic resonance is influenced by both the beat frequency and the two forcing frequencies. Compared to a single neuron, a population of neurons is more efficient in detecting the information carried by the weak envelope modulation signal at the beat frequency. Furthermore, an appropriate fine-tuning of the excitation-inhibition balance can further optimize the response of a neural ensemble to the superimposed signal. Our results thus introduce and provide insights into the generation and modulation mechanism of the frequency-difference-dependent stochastic resonance in neural systems.

  10. Precision Pointing System Development

    SciTech Connect

    BUGOS, ROBERT M.

    2003-03-01

    The development of precision pointing systems has been underway in Sandia's Electronic Systems Center for over thirty years. Important areas of emphasis are synthetic aperture radars and optical reconnaissance systems. Most applications are in the aerospace arena, with host vehicles including rockets, satellites, and manned and unmanned aircraft. Systems have been used on defense-related missions throughout the world. Presently in development are pointing systems with accuracy goals in the nanoradian regime. Future activity will include efforts to dramatically reduce system size and weight through measures such as the incorporation of advanced materials and MEMS inertial sensors.

  11. Low Frequency Radio-wave System for subsurface investigation

    NASA Astrophysics Data System (ADS)

    Soldovieri, Francesco; Gennarelli, Gianluca; Kudelya, Anatoliy; Denisov, Alexander

    2015-04-01

    Low frequency radio-wave methods (RWM) allow subsurface investigations in terms of lithological structure characterization, detection of filtration flows of ground water, anthropogenic and natural cavities. In this contribution, we present a RWM that exploits two coils working at frequencies of few MHz as transmitting and receiving antennas. The basic principle of this inductive method is as follows. The primary alternating electromagnetic field radiated by the transmitting coil induces eddy currents in the subsurface mainly due to the conductivity anomalies. These eddy currents generate a secondary (scattered) magnetic field which overlaps to the incident magnetic field and is detected by the receiving coil. Despite the simple operation of the system, the complexity of the electromagnetic scattering phenomenon at hand must be properly modeled to achieve adequate performance. Therefore, an advanced data processing technique, belonging to the class of the inverse scattering approaches, has been developed by the authors in a full 3D geometry. The proposed method allows to deal with data collected on a scanning surface under a dipole inductive profiling (DIP) modality, where the transmitting/receiving coils are moved simultaneously with fixed offset (multi-bistatic configuration). The hardware, called Dipole Inductive Radio-wave System (DIRS), is composed by an electronic unit and transmitting and receiving loop antennas radiating at frequencies of few MHz (2-4 MHz), which are installed on theodolite supports. The compactness of DIRS and its robustness to external electromagnetic interference offers the possibility to perform geophysical research up to the depth of some tens of meters and under several types of ground and water surfaces, vegetation, and weather conditions. The light weight and small size of system (the single antenna with support weights about 5 kg and has a diameter of 0.5m) allows two operators to perform geophysical research without disturbing the

  12. Switch over to the high frequency rf systems near transition

    SciTech Connect

    Brennan, J.M.; Wei, J.

    1988-01-01

    The purpose of this note is to point out that since bunch narrowing naturally occurs in the acceleration process in the vicinity of transition, it should be possible to switch over to the high frequency system close to transition when the bunch has narrowed enough to fit directly into the high frequency bucket. The advantage of this approach is the simplicity, no extra components or gymnastics are required of the low frequency system. The disadvantage, of course, is for protons which do not go through transition. But on the other hand, there is no shortage of intensity for protons and so it should be possible to keep the phase space area low for protons, and then matching to the high frequency bucket should be easily accomplished by adiabatic compression. 3 refs., 7 figs.

  13. Distributed Frequency Control of Prosumer-Based Electric Energy Systems

    SciTech Connect

    Nazari, MH; Costello, Z; Feizollahi, MJ; Grijalva, S; Egerstedt, M

    2014-11-01

    In this paper, we propose a distributed frequency regulation framework for prosumer-based electric energy systems, where a prosumer (producer-consumer) is defined as an intelligent agentwhich can produce, consume, and/or store electricity. Despite the frequency regulators being distributed, stability can be ensured while avoiding inter-area oscillations using a limited control effort. To achieve this, a fully distributed one-step model-predictive control protocol is proposed and analyzed, whereby each prosumer communicates solely with its neighbors in the network. The efficacy of the proposed frequency regulation framework is shown through simulations on two real-world electric energy systems of different scale and complexity. We show that prosumers can indeed bring frequency and power deviations to their desired values after small perturbations.

  14. Status of frequency and time support for NASA systems

    NASA Technical Reports Server (NTRS)

    Kuhnle, Paul F.; Kushmeider, Paul J.; Wardrip, S. Clark

    1994-01-01

    NASA has frequency and timing systems at many facilities and centers. Timing systems with specifications tighter than several microseconds are covered. These ground based systems support scientific experiments and spacecraft tracking for the following programs; NASA Satellite Laser Ranging (NSLR); Network Mission Operations Support (NMOS); Kennedy Space Center (KSC); Very Long Baseline Interferometry (VLBI); Tracking Data Relay Satellite System (TDRSS) Ground Terminal Network; and the Deep Space Network (DSN). Major equipment assemblies, specifications, performance, and requirements, both present and future, are presented.

  15. A novel, multichannel, comb-frequency Doppler backscatter system

    SciTech Connect

    Peebles, W. A.; Rhodes, T. L.; Hillesheim, J. C.; Zeng, L.; Wannberg, C.

    2010-10-15

    Doppler backscattering has emerged in recent years as a powerful diagnostic tool in high temperature fusion plasmas. The technique is sensitive to plasma turbulence flow and has been utilized to determine radial electric field and to study geodesic acoustic modes, zonal flows, and intermediate scale density turbulence. The current manuscript describes a novel technique for creating a stable, multichannel system covering the V-band frequency range (50-75 GHz) which enables simultaneous monitoring of turbulent flows and fluctuation levels at eight distinct spatial locations. The system is based on a high-frequency, low phase noise comb-frequency generator combined with a filter bank and quadrature detection system. The system is now in operation on DIII-D and has allowed monitoring of the flow and turbulence levels across the plasma radius during events such as the L-H transition.

  16. Recent developments in thermoacoustically-driven low-frequency projectors

    SciTech Connect

    Ward, W.C.; Merrigan, M.A.

    1992-05-01

    Thermoacoustic engines are a recent class of devices that can efficiently convert heat to acoustic energy without moving parts or intervening mechanisms. These engines have a natural potential for powering low-frequency sonar projectors with high reliability and efficiencies that cannot be matched by conventional technologies. A recent design study has produced thermoacoustic projector configurations that can execute standard projector performance requirements such as FM sweep and velocity magnitude and phase control in array environments for a wide range of positive and negative radiation resistances. The thermoacoustic driver is a vertically oriented, helium-filled resonator that contains a movable tuning element to vary the resonator frequency. It is coupled to a variable length water column that is tunable by a similar means to adjust the effective source impedance of the device. Modeling results indicate a sweep range of at least an octave for a single device, and maximum overall (heat-to-acoustic) conversion efficiencies of 25% at 50 Hz. Efficiency increases slightly at lower frequencies, and the lowest operational frequency is limited only by the size of the projector. Output power increases linearly with mean pressure, and at depths of 200 m or more, power densities in excess of 500 kW/m{sup 2} are achievable. Control aspects have been investigated, including rapid startup and shutdown that can be performed by manipulating the water tuning column. Future trends and development prospects are discussed. 4 refs.

  17. Recent developments in thermoacoustically-driven low-frequency projectors

    SciTech Connect

    Ward, W.C.; Merrigan, M.A.

    1992-01-01

    Thermoacoustic engines are a recent class of devices that can efficiently convert heat to acoustic energy without moving parts or intervening mechanisms. These engines have a natural potential for powering low-frequency sonar projectors with high reliability and efficiencies that cannot be matched by conventional technologies. A recent design study has produced thermoacoustic projector configurations that can execute standard projector performance requirements such as FM sweep and velocity magnitude and phase control in array environments for a wide range of positive and negative radiation resistances. The thermoacoustic driver is a vertically oriented, helium-filled resonator that contains a movable tuning element to vary the resonator frequency. It is coupled to a variable length water column that is tunable by a similar means to adjust the effective source impedance of the device. Modeling results indicate a sweep range of at least an octave for a single device, and maximum overall (heat-to-acoustic) conversion efficiencies of 25% at 50 Hz. Efficiency increases slightly at lower frequencies, and the lowest operational frequency is limited only by the size of the projector. Output power increases linearly with mean pressure, and at depths of 200 m or more, power densities in excess of 500 kW/m{sup 2} are achievable. Control aspects have been investigated, including rapid startup and shutdown that can be performed by manipulating the water tuning column. Future trends and development prospects are discussed. 4 refs.

  18. Development of a swallowing frequency meter using a laryngeal microphone.

    PubMed

    Tanaka, N; Nohara, K; Okuno, K; Kotani, Y; Okazaki, H; Matsumura, M; Sakai, T

    2012-06-01

    Disuse atrophy of swallowing-related organs is suspected when decreased swallowing frequency is seen in the elderly. However, swallowing frequency has not been examined in elderly people during daily life. We developed a swallowing frequency meter containing a laryngeal microphone that does not restrict the subject's ability to perform daily activities. In this study, the utility of the meter was assessed. Experiment 1: The ability of the meter to detect swallowing was examined. The subject was instructed to swallow saliva or foods at a voluntarily pace. During these procedures, swallowing events were simultaneously recorded by the meter, self-enumeration and videofluorography. As a result, all of the swallowing events identified by the meter coincided with the swallowing events identified by self-enumeration and videofluorography. Experiment 2: Swallowing sounds display various patterns both between and within individuals. Therefore, we examined the concordance rate between the number of swallowing events counted by the meter and that counted by self-enumeration in 15 subjects over a longer period than in experiment 1. The concordance rates calculated by two examiners between the meter and self-enumeration were 96·8 ± 4·5% and 98·9 ± 3·3% at rest and 95·2 ± 4·5% and 96·1 ± 4·1% during meals, respectively. Our findings indicate that this meter is useful for measuring the frequency of swallowing during daily situations.

  19. Development and optimization of acoustic bubble structures at high frequencies.

    PubMed

    Lee, Judy; Ashokkumar, Muthupandian; Yasui, Kyuichi; Tuziuti, Toru; Kozuka, Teruyuki; Towata, Atsuya; Iida, Yasuo

    2011-01-01

    At high ultrasound frequencies, active bubble structures are difficult to capture due to the decrease in timescale per acoustic cycle and size of bubbles with increasing frequencies. However the current study demonstrates an association between the spatial distribution of visible bubbles and that of the active bubble structure established in the path of the propagating acoustic wave. By monitoring the occurrence of these visible bubbles, the development of active bubbles can be inferred for high frequencies. A series of still images depicting the formation of visible bubble structures suggest that a strong standing wave field exists at early stages of wave propagation and weakens by the increase in the attenuation of the acoustic wave, caused by the formation of large coalesced bubbles. This attenuation is clearly demonstrated by the occurrence of a force which causes bubbles to be driven toward the liquid surface and limit standing wave fields to near the surface. This force is explained in terms of the acoustic streaming and traveling wave force. It is found that a strong standing wave field is established at 168 kHz. At 448 kHz, large coalesced bubbles can significantly attenuate the acoustic pressure amplitude and weaken the standing wave field. When the frequency is increased to 726 kHz, acoustic streaming becomes significant and is the dominant force behind the disruption of the standing wave structure. The disruption of the standing wave structure can be minimized under certain pulse ON and OFF ratios.

  20. Time and frequency transfer system using GNSS receiver

    NASA Astrophysics Data System (ADS)

    Wang, Jia-Lun; Huang, Shi-Yu; Liao, Chia-Shu

    2014-12-01

    Global Positioning System (GPS) time and frequency transfer is one of the most useful ways for the comparison of remote clocks, and the comparison results are very important for the calculation of International Atomic Time and UTC (Coordinated Universal Time). For the timing laboratories, it is necessary to calibrate and periodically evaluate their time transfer system to ensure the accuracy and long-term stability of their time and frequency comparison results. Once the calibration is achieved, it can be used as a standard for traceable time and frequency measurements. In this paper, we demonstrate Global Navigation Satellite System receiver calibration campaign between the National Time and Frequency Standard Laboratory of Telecommunication Laboratories in Taiwan and the Measurement Standards Laboratory in New Zealand. Two calibration strategies, receiver calibration and the link calibration, are adopted in this work. The receiver calibration is used for evaluating the performance of the proposed system in domestic traceability network in Taiwan. The link calibration is used for minimizing the total uncertainty budget in calculating UTC. Experimental results indicate that the expanded time and frequency uncertainty of the proposed system (with a coverage factor of k = 2) are less than 25 ns and 1.1 × 10-13, respectively, after 1 day of averaging. The accuracy of GPS time link is reported to be better than 2 ns in long-baseline link (10,000 km) in Asia-Pacific Zone.

  1. The NASA data systems standardization program - Radio frequency and modulation

    NASA Astrophysics Data System (ADS)

    Martin, W. L.

    The modifications being considered by the NASA-ESA Working Group (NEWG) for space-data-systems standardization to maximize the commonality of the NASA and ESA RF and modulation systems linking spaceborne scientific experiments with ground stations are summarized. The first phase of the NEWG project shows that the NASA MK-IVA Deep Space Network and Shuttle Interrogator (SI) systems in place or planned for 1985 are generally compatible with the ESA Network, but that communications involving the Tracking and Data Relay Satellite (TDRS) are incompatible due to its use of spread-spectrum modulation, pseudonoise ranging, multiple-access channels, and Mbit/s data rates. Topics under study for the post-1985 period include low-bit-rate capability for the ESA Network, an optional 8-kHz command subcarrier for the SI, fixing the spacecraft-transponder frequency-multiplication ratios for possible X-band uplinks or X-band nondeep-space downlinks, review of incompatible TDRS features, and development of the 32-GHz band.

  2. The NASA data systems standardization program - Radio frequency and modulation

    NASA Technical Reports Server (NTRS)

    Martin, W. L.

    1983-01-01

    The modifications being considered by the NASA-ESA Working Group (NEWG) for space-data-systems standardization to maximize the commonality of the NASA and ESA RF and modulation systems linking spaceborne scientific experiments with ground stations are summarized. The first phase of the NEWG project shows that the NASA MK-IVA Deep Space Network and Shuttle Interrogator (SI) systems in place or planned for 1985 are generally compatible with the ESA Network, but that communications involving the Tracking and Data Relay Satellite (TDRS) are incompatible due to its use of spread-spectrum modulation, pseudonoise ranging, multiple-access channels, and Mbit/s data rates. Topics under study for the post-1985 period include low-bit-rate capability for the ESA Network, an optional 8-kHz command subcarrier for the SI, fixing the spacecraft-transponder frequency-multiplication ratios for possible X-band uplinks or X-band nondeep-space downlinks, review of incompatible TDRS features, and development of the 32-GHz band.

  3. Development of the auditory system.

    PubMed

    Litovsky, Ruth

    2015-01-01

    Auditory development involves changes in the peripheral and central nervous system along the auditory pathways, and these occur naturally, and in response to stimulation. Human development occurs along a trajectory that can last decades, and is studied using behavioral psychophysics, as well as physiologic measurements with neural imaging. The auditory system constructs a perceptual space that takes information from objects and groups, segregates sounds, and provides meaning and access to communication tools such as language. Auditory signals are processed in a series of analysis stages, from peripheral to central. Coding of information has been studied for features of sound, including frequency, intensity, loudness, and location, in quiet and in the presence of maskers. In the latter case, the ability of the auditory system to perform an analysis of the scene becomes highly relevant. While some basic abilities are well developed at birth, there is a clear prolonged maturation of auditory development well into the teenage years. Maturation involves auditory pathways. However, non-auditory changes (attention, memory, cognition) play an important role in auditory development. The ability of the auditory system to adapt in response to novel stimuli is a key feature of development throughout the nervous system, known as neural plasticity.

  4. Development of the auditory system

    PubMed Central

    Litovsky, Ruth

    2015-01-01

    Auditory development involves changes in the peripheral and central nervous system along the auditory pathways, and these occur naturally, and in response to stimulation. Human development occurs along a trajectory that can last decades, and is studied using behavioral psychophysics, as well as physiologic measurements with neural imaging. The auditory system constructs a perceptual space that takes information from objects and groups, segregates sounds, and provides meaning and access to communication tools such as language. Auditory signals are processed in a series of analysis stages, from peripheral to central. Coding of information has been studied for features of sound, including frequency, intensity, loudness, and location, in quiet and in the presence of maskers. In the latter case, the ability of the auditory system to perform an analysis of the scene becomes highly relevant. While some basic abilities are well developed at birth, there is a clear prolonged maturation of auditory development well into the teenage years. Maturation involves auditory pathways. However, non-auditory changes (attention, memory, cognition) play an important role in auditory development. The ability of the auditory system to adapt in response to novel stimuli is a key feature of development throughout the nervous system, known as neural plasticity. PMID:25726262

  5. Cascade Distillation System Development

    NASA Technical Reports Server (NTRS)

    Callahan, Michael R.; Sargushingh, Miriam; Shull, Sarah

    2014-01-01

    NASA's Advanced Exploration Systems (AES) Life Support System (LSS) Project is chartered with de-veloping advanced life support systems that will ena-ble NASA human exploration beyond low Earth orbit (LEO). The goal of AES is to increase the affordabil-ity of long-duration life support missions, and to re-duce the risk associated with integrating and infusing new enabling technologies required to ensure mission success. Because of the robust nature of distillation systems, the AES LSS Project is pursuing develop-ment of the Cascade Distillation Subsystem (CDS) as part of its technology portfolio. Currently, the system is being developed into a flight forward Generation 2.0 design.

  6. 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.

  7. Development and Validation of Transferable Amide I Vibrational Frequency Maps for Peptides

    PubMed Central

    Wang, L.; Middleton, C. T.; Zanni, M. T.; Skinner, J. L.

    2012-01-01

    Infrared (IR) spectroscopy of the amide I band has been widely utilized for the analysis of peptides and proteins. Theoretical modeling of IR spectra of proteins requires an accurate and efficient description of the amide I frequencies. In this paper, amide I frequency maps for protein backbone and side chain groups are developed from experimental spectra and vibrational lifetimes of N-methylacetamide and acetamide in different solvents. The frequency maps, along with established nearest-neighbor frequency shift and coupling schemes, are then applied to a variety of peptides in aqueous solution and reproduce experimental spectra well. The frequency maps are designed to be transferable to different environments; therefore, they can be used for heterogeneous systems, such as membrane proteins. PMID:21405034

  8. High frequency data acquisition system for space shuttle main engine testing

    NASA Technical Reports Server (NTRS)

    Lewallen, Pat

    1987-01-01

    The high frequency data acquisition system developed for the Space Shuttle Main Engine (SSME) single engine test facility at the National Space Technology Laboratories is discussed. The real time system will provide engineering data for a complete set of SSME instrumentation (approx. 100 measurements) within 4 hours following engine cutoff, a decrease of over 48 hours from the previous analog tape based system.

  9. Frequency selective bolometer development at Argonne National Laboratory.

    SciTech Connect

    Datesman, A.; Pearson, J.; Wang, G.; Yefremenko, V.; Divan, R.; Downes, T.; Chang, C.; McMahon, J.; Meyer, S.; Carlstrom, J.; Logan, D.; Perera, T.; Wilson, G.; Novosad, V.; Univ. of Chicago; Univ. of Massachusetts

    2008-07-01

    We discuss the development, at Argonne National Laboratory, of a four-pixel camera suitable for photometry of distant dusty galaxies located by Spitzer and SCUBA, and for study of other millimeter-wave sources such as ultra-luminous infrared galaxies, the Sunyaev-Zeldovich (SZ) effect in clusters, and galactic dust. Utilizing Frequency Selective Bolometers (FSBs) with superconducting Transition-Edge Sensors (TESs), each of the camera's four pixels is sensitive to four colors, with frequency bands centered approximately at 150, 220, 270, and 360 GHz. The current generation of these devices utilizes proximity effect superconducting bilayers of Mo/Au or Ti/Au for TESs, along with frequency selective circuitry on membranes of silicon nitride 1 cm across and 1 micron thick. The operational properties of these devices are determined by this circuitry, along with thermal control structures etched into the membranes. These etched structures do not perforate the membrane, so that the device is both comparatively robust mechanically and carefully tailored in terms of its thermal transport properties. In this paper, we report on development of the superconducting bilayer TES technology and characterization of the FSB stacks. This includes the use of new materials, the design and testing of thermal control structures, the introduction of desirable thermal properties using buried layers of crystalline silicon underneath the membrane, detector stability control, and optical and thermal test results. The scientific motivation, FSB design, FSB fabrication, and measurement results are discussed.

  10. Enhanced Recovery Utilizing Variable Frequency Drives and a Distributed Power System

    SciTech Connect

    Randy Peden; Sanjiv Shah

    2005-07-26

    This report describes complete results of the project entitled ''Enhanced Recovery Utilizing Variable Frequency Drives and a Distributed Power System''. This demonstration project was initiated in July 2003 and completed in March 2005. The objective of the project was to develop an integrated power production/variable frequency drive system that could easily be deployed in the oil field that would increase production and decrease operating costs. This report describes all the activities occurred and documents results of the demonstration.

  11. Coding for Frequency - Shift - Keyed (FSK) Communication System

    DTIC Science & Technology

    1973-12-01

    COMMUNICATION SYSTEM ELECTRICAL ENGINEERING DEPARTMENT UNIVERSITY OF MISSOURI TECHNICAL REPORT AFATL-TR-73-245 DECEMBER 1973 ɛy J> % ̂ A... Communication System Dr. John J. Komo Distribui-.ion limited to ll—5—r" ■ ■ this report documents test f^T™^^^^^ limitation applied^eX m’ŕ^^ dist...FREQUENCY-SHIFT-KEYED COMMUNICATION SYSTEM . 3 III CYCLIC CODES .... 11 IV RANDOM ERROR-CORRECTING CODES V BURST ERROR-CORRECTING CODES

  12. Design and Development of Thermistor based Power Meter at 140 GHz Frequency Band

    NASA Astrophysics Data System (ADS)

    Roy, Rajesh; Kush, Abhimanyue Kumar; Dixit, Rajendra Prasad

    2011-12-01

    Design and development of thermistor based power meter at 140 gigahertz (GHz) frequency band have been presented. Power meter comprises power sensor, amplifier circuit and dialog based graphical user interface in visual C++ for the average power measurement. The output power level of a component or system is very critical design factor. Thus there was a need of a power meter for the development of millimeter wave components at 140 GHz frequency band. Power sensor has been designed and developed using NTC (Negative Temperature Coefficient) thermistors. The design aims at developing a direct, simple and inexpensive power meter that can be used to measure absolute power at 140 GHz frequency band. Due to absorption of 140 GHz frequencies, resistance of thermistor changes to a new value. This change in resistance of thermistor can be converted to a dc voltage change and amplified voltage change can be fed to computer through data acquisition card. Dialog based graphical user interface (GUI) has been developed in visual C++ language for average power measurement in dBm. WR6 standard rectangular waveguide is the input port for the sensor of power meter. Temperature compensation has been achieved. Moderate sensor return loss greater than 20 dB has been found over the frequency range 110 to 170 GHz. The response time of the power sensor is 10 second. Average power accuracy is better than ±0.25 dB within the power range from -10 to 10 dBm at 140 GHz frequency band.

  13. Frequency response analysis of IPMC actuators by an IR system

    NASA Astrophysics Data System (ADS)

    Bonomo, Claudia; Fortuna, Luigi; Giannone, Pietro; Graziani, Salvatore

    2005-05-01

    Ionic Polymer Metal Composites or IPMCs are emerging materials belonging to EAP class. They are of increasing interest in innovative applications due to several advantages respect to competing technologies (SMA, piezoelectric, etc.), such as the possibility to be used both as moving actuators and sensors, their lightness and the low actuation voltage. On the other hand their behaviour is not fully known and it is still subjected to deep investigations. In this perspective the development of a complete model, able to fully describe the electromechanical properties of the IPMC materials, is the aim of many research groups. To that purpose this work focuses on designing and realising a system to determine the frequency domain behaviour of an IPMC strip as actuator in order to collect information useful to model it. Here the IPMC deformation, caused by applying a voltage input signal across its thickness, is detected by using an infrared transmitter-receiver couple. This methodology is largely diffused and it is based on the acquisition of the intensity of the emitted ray after being reflected by the moving target, moreover it constitutes a low cost solution. Also a transducer is used to acquire information about the current absorbed by the device under test. For the specific application a conditioning circuitry and the software for signal processing has been designed and realised. Preliminary results show that the proposed system allows to infer a number of interesting properties of IPMC based actuators.

  14. An ultra-broadband low-frequency magnetic resonance system

    NASA Astrophysics Data System (ADS)

    Mandal, S.; Utsuzawa, S.; Cory, D. G.; Hürlimann, M.; Poitzsch, M.; Song, Y.-Q.

    2014-05-01

    MR probes commonly employ resonant circuits for efficient RF transmission and low-noise reception. These circuits are narrow-band analog devices that are inflexible for broadband and multi-frequency operation at low Larmor frequencies. We have addressed this issue by developing an ultra-broadband MR probe that operates in the 0.1-3 MHz frequency range without using conventional resonant circuits for either transmission or reception. This “non-resonant” approach significantly simplifies the probe circuit and allows robust operation without probe tuning while retaining efficient power transmission and low-noise reception. We also demonstrate the utility of the technique through a variety of NMR and NQR experiments in this frequency range.

  15. Arcjet system integration development

    NASA Technical Reports Server (NTRS)

    Zafran, Sidney

    1994-01-01

    Compatibility between an arcjet propulsion system and a communications satellite was verified by testing a Government-furnished, 1.4 kW hydrazine arcjet system with the FLTSATCOM qualification model satellite in a 9.1-meter (30-foot) diameter thermal-vacuum test chamber. Background pressure was maintained at 10(exp -5) torr during arcjet operation by cryopumping the thruster exhaust with an array of 5 K liquid helium cooled panels. Power for the arcjet system was obtained from the FLTSATCOM battery simulator. Spacecraft telemetry was monitored during each thruster firing period. No changes in telemetry data attributable to arcjet operation were detected in any of the tests. Electromagnetic compatibility data obtained included radiated emission measurements, conducted emission measurements, and cable coupling measurements. Significant noise was observed at lower frequencies. Above 500 MHz, radiated emissions were generally within limits, indicating that communication links at S-band and higher frequencies will not be affected. Other test data taken with a diagnostic array of calorimeters, radiometers, witness plates, and a residual gas analyzer evidenced compatible operation, and added to the data base for arcjet system integration. Two test series were conducted. The first series only included the arcjet and diagnostic array operating at approximately 0.1 torr background pressure. The second series added the qualification model spacecraft, a solar panel, and the helium cryopanels. Tests were conducted at 0.1 torr and 10(exp-5) torr. The arcjet thruster was canted 20 degrees relative to the solar panel axis, typical of the configuration used for stationkeeping thrusters on geosynchronous communications satellites.

  16. Arcjet system integration development

    NASA Astrophysics Data System (ADS)

    Zafran, Sidney

    1994-03-01

    Compatibility between an arcjet propulsion system and a communications satellite was verified by testing a Government-furnished, 1.4 kW hydrazine arcjet system with the FLTSATCOM qualification model satellite in a 9.1-meter (30-foot) diameter thermal-vacuum test chamber. Background pressure was maintained at 10(exp -5) torr during arcjet operation by cryopumping the thruster exhaust with an array of 5 K liquid helium cooled panels. Power for the arcjet system was obtained from the FLTSATCOM battery simulator. Spacecraft telemetry was monitored during each thruster firing period. No changes in telemetry data attributable to arcjet operation were detected in any of the tests. Electromagnetic compatibility data obtained included radiated emission measurements, conducted emission measurements, and cable coupling measurements. Significant noise was observed at lower frequencies. Above 500 MHz, radiated emissions were generally within limits, indicating that communication links at S-band and higher frequencies will not be affected. Other test data taken with a diagnostic array of calorimeters, radiometers, witness plates, and a residual gas analyzer evidenced compatible operation, and added to the data base for arcjet system integration. Two test series were conducted. The first series only included the arcjet and diagnostic array operating at approximately 0.1 torr background pressure. The second series added the qualification model spacecraft, a solar panel, and the helium cryopanels. Tests were conducted at 0.1 torr and 10(exp-5) torr. The arcjet thruster was canted 20 degrees relative to the solar panel axis, typical of the configuration used for stationkeeping thrusters on geosynchronous communications satellites.

  17. Developing Data System Engineers

    NASA Astrophysics Data System (ADS)

    Behnke, J.; Byrnes, J. B.; Kobler, B.

    2011-12-01

    In the early days of general computer systems for science data processing, staff members working on NASA's data systems would most often be hired as mathematicians. Computer engineering was very often filled by those with electrical engineering degrees. Today, the Goddard Space Flight Center has special position descriptions for data scientists or as they are more commonly called: data systems engineers. These staff members are required to have very diverse skills, hence the need for a generalized position description. There is always a need for data systems engineers to develop, maintain and operate the complex data systems for Earth and space science missions. Today's data systems engineers however are not just mathematicians, they are computer programmers, GIS experts, software engineers, visualization experts, etc... They represent many different degree fields. To put together distributed systems like the NASA Earth Observing Data and Information System (EOSDIS), staff are required from many different fields. Sometimes, the skilled professional is not available and must be developed in-house. This paper will address the various skills and jobs for data systems engineers at NASA. Further it explores how to develop staff to become data scientists.

  18. Visualization and Classification of Power System Frequency Data Streams

    SciTech Connect

    Bank, Jason N; Omitaomu, Olufemi A; Fernandez, Steven J; Liu, Yilu

    2009-01-01

    Two challenges in the realization of the smart grid technology are the ability to visualize the deluge of expected data streams for global situational awareness and the ability to detect disruptive and classify events from spatially-distributed high-speed power system frequency measurements while minimizing false alarms and eliminating missed detection. This paper presents an interactive visualization model for high speed power system frequency data streams that presents both local and global views of the data streams for decision making process. It also presents a K-Median for clustering and identifying disruptive events in spatially-distributed data streams. The results from experimental evaluation on a variety of datasets show that K-Median achieve better performance and empowers analysts with the ability to make sense of a deluge of frequency measurements in a real-time situation.

  19. Modal sensitivity for structural systems with repeated frequencies

    NASA Technical Reports Server (NTRS)

    Ojalvo, I. U.

    1987-01-01

    Repeated or closely packed modal frequencies are common physical occurrences for vibrating structures which are complex or possess multi-planes of symmetry. The computation of the sensitivity to structural modifications for these frequencies and mode shapes is made difficult by the fact that the mode shapes are not unique, since any linear combination of eigenvectors corresponding to a repeated eigenvalue is also an eigenvector. The work of Chen and Pan is extended, who used modal expansion techniques for accommodating the sensitivity analysis of structures with repeated eigenvalues. Starting with a discussion of the physical significance of sensitivity analysis for repeated frequency modes, a derivation is presented of the governing equations for the derivatives of a repeated eigenvalue. This is followed with a small example to illustrate the results. An efficient computation procedure, based upon an expansion of Nelson's ideas for large banded systems, is then proposed for systems with repeated or closely spaced eigenvalues.

  20. Power Systems Development Facility

    SciTech Connect

    Southern Company Services

    2009-01-31

    In support of technology development to utilize coal for efficient, affordable, and environmentally clean power generation, the Power Systems Development Facility (PSDF), located in Wilsonville, Alabama, has routinely demonstrated gasification technologies using various types of coals. The PSDF is an engineering scale demonstration of key features of advanced coal-fired power systems, including a Transport Gasifier, a hot gas particulate control device, advanced syngas cleanup systems, and high-pressure solids handling systems. This final report summarizes the results of the technology development work conducted at the PSDF through January 31, 2009. Twenty-one major gasification test campaigns were completed, for a total of more than 11,000 hours of gasification operation. This operational experience has led to significant advancements in gasification technologies.

  1. Low-frequency switching voltage regulators for terrestrial photovoltaic systems

    NASA Technical Reports Server (NTRS)

    Delombard, R.

    1984-01-01

    The photovoltaic technology project and the stand alone applications project are discussed. Two types of low frequency switching type regulators were investigated. The design, operating characteristics and field application of these regulators is described. The regulators are small in size, low in cost, very low in power dissipation, reliable and allow considerable flexibility in system design.

  2. Radio frequency telemetry system for sensors and actuators

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N. (Inventor); Miranda, Felix A. (Inventor)

    2003-01-01

    The present invention discloses and teaches apparatus for combining Radio Frequency (RF) technology with novel micro-inductor antennas and signal processing circuits for RF telemetry of real time, measured data, from microelectromechanical system (MEMS) sensors, through electromagnetic coupling with a remote powering/receiving device. Such technology has many applications, but is especially useful in the biomedical area.

  3. Radio Frequency Telemetry System for Sensors and Actuators

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N. (Inventor); Miranda, Felix A. (Inventor)

    2003-01-01

    The present invention discloses and teaches apparatus for combining Radio Frequency (RF) technology with novel micro-inductor antennas and signal processing circuits for RF telemetry of real time, measured data, from microelectromechanical system (MEMS) sensors, through electromagnetic coupling with a remote poweringheceiving device. Such technology has many applications, but is especially useful in the biomedical area.

  4. Unified tensor model for space-frequency spreading-multiplexing (SFSM) MIMO communication systems

    NASA Astrophysics Data System (ADS)

    de Almeida, André LF; Favier, Gérard

    2013-12-01

    This paper presents a unified tensor model for space-frequency spreading-multiplexing (SFSM) multiple-input multiple-output (MIMO) wireless communication systems that combine space- and frequency-domain spreadings, followed by a space-frequency multiplexing. Spreading across space (transmit antennas) and frequency (subcarriers) adds resilience against deep channel fades and provides space and frequency diversities, while orthogonal space-frequency multiplexing enables multi-stream transmission. We adopt a tensor-based formulation for the proposed SFSM MIMO system that incorporates space, frequency, time, and code dimensions by means of the parallel factor model. The developed SFSM tensor model unifies the tensorial formulation of some existing multiple-access/multicarrier MIMO signaling schemes as special cases, while revealing interesting tradeoffs due to combined space, frequency, and time diversities which are of practical relevance for joint symbol-channel-code estimation. The performance of the proposed SFSM MIMO system using either a zero forcing receiver or a semi-blind tensor-based receiver is illustrated by means of computer simulation results under realistic channel and system parameters.

  5. Universal distribution of component frequencies in biological and technological systems

    PubMed Central

    Pang, Tin Yau; Maslov, Sergei

    2013-01-01

    Bacterial genomes and large-scale computer software projects both consist of a large number of components (genes or software packages) connected via a network of mutual dependencies. Components can be easily added or removed from individual systems, and their use frequencies vary over many orders of magnitude. We study this frequency distribution in genomes of ∼500 bacterial species and in over 2 million Linux computers and find that in both cases it is described by the same scale-free power-law distribution with an additional peak near the tail of the distribution corresponding to nearly universal components. We argue that the existence of a power law distribution of frequencies of components is a general property of any modular system with a multilayered dependency network. We demonstrate that the frequency of a component is positively correlated with its dependency degree given by the total number of upstream components whose operation directly or indirectly depends on the selected component. The observed frequency/dependency degree distributions are reproduced in a simple mathematically tractable model introduced and analyzed in this study. PMID:23530195

  6. Frequency bands of strongly nonlinear homogeneous granular systems.

    PubMed

    Lydon, Joseph; Jayaprakash, K R; Ngo, Duc; Starosvetsky, Yuli; Vakakis, Alexander F; Daraio, Chiara

    2013-07-01

    Recent numerical studies on an infinite number of identical spherical beads in Hertzian contact showed the presence of frequency bands [Jayaprakash, Starosvetsky, Vakakis, Peeters, and Kerschen, Nonlinear Dyn. 63, 359 (2011)]. These bands, denoted here as propagation and attenuation bands (PBs and ABs), are typically present in linear or weakly nonlinear periodic media; however, their counterparts are not intuitive in essentially nonlinear periodic media where there is a complete lack of classical linear acoustics, i.e., in "sonic vacua." Here, we study the effects of PBs and ABs on the forced dynamics of ordered, uncompressed granular systems. Through numerical and experimental techniques, we find that the dynamics of these systems depends critically on the frequency and amplitude of the applied harmonic excitation. For fixed forcing amplitude, at lower frequencies, the oscillations are large in amplitude and governed by strongly nonlinear and nonsmooth dynamics, indicating PB behavior. At higher frequencies the dynamics is weakly nonlinear and smooth, in the form of compressed low-amplitude oscillations, indicating AB behavior. At the boundary between the PB and the AB large-amplitude oscillations due to resonance occur, giving rise to collisions between beads and chaotic dynamics; this renders the forced dynamics sensitive to initial and forcing conditions, and hence unpredictable. Finally, we study asymptotically the near field standing wave dynamics occurring for high frequencies, well inside the AB.

  7. Universal distribution of component frequencies in biological and technological systems.

    PubMed

    Pang, Tin Yau; Maslov, Sergei

    2013-04-09

    Bacterial genomes and large-scale computer software projects both consist of a large number of components (genes or software packages) connected via a network of mutual dependencies. Components can be easily added or removed from individual systems, and their use frequencies vary over many orders of magnitude. We study this frequency distribution in genomes of ∼500 bacterial species and in over 2 million Linux computers and find that in both cases it is described by the same scale-free power-law distribution with an additional peak near the tail of the distribution corresponding to nearly universal components. We argue that the existence of a power law distribution of frequencies of components is a general property of any modular system with a multilayered dependency network. We demonstrate that the frequency of a component is positively correlated with its dependency degree given by the total number of upstream components whose operation directly or indirectly depends on the selected component. The observed frequency/dependency degree distributions are reproduced in a simple mathematically tractable model introduced and analyzed in this study.

  8. A Frequency-Domain Substructure System Identification Algorithm

    NASA Technical Reports Server (NTRS)

    Blades, Eric L.; Craig, Roy R., Jr.

    1996-01-01

    A new frequency-domain system identification algorithm is presented for system identification of substructures, such as payloads to be flown aboard the Space Shuttle. In the vibration test, all interface degrees of freedom where the substructure is connected to the carrier structure are either subjected to active excitation or are supported by a test stand with the reaction forces measured. The measured frequency-response data is used to obtain a linear, viscous-damped model with all interface-degree of freedom entries included. This model can then be used to validate analytical substructure models. This procedure makes it possible to obtain not only the fixed-interface modal data associated with a Craig-Bampton substructure model, but also the data associated with constraint modes. With this proposed algorithm, multiple-boundary-condition tests are not required, and test-stand dynamics is accounted for without requiring a separate modal test or finite element modeling of the test stand. Numerical simulations are used in examining the algorithm's ability to estimate valid reduced-order structural models. The algorithm's performance when frequency-response data covering narrow and broad frequency bandwidths is used as input is explored. Its performance when noise is added to the frequency-response data and the use of different least squares solution techniques are also examined. The identified reduced-order models are also compared for accuracy with other test-analysis models and a formulation for a Craig-Bampton test-analysis model is also presented.

  9. Resent developments in high-frequency surface-wave techniques

    NASA Astrophysics Data System (ADS)

    Xia, J.; Pan, Y.; Zeng, C.

    2012-12-01

    calculate phase velocities when wavelengths < 2.5 h (h is the thickness of the topmost layer). Both solutions have been verified using numerical modeling both in the time-space and the frequency-velocity domains. The algorithm that we newly developed can handle any arbitrary velocity models, which is the foundation of high-frequency Rayleigh-wave methods and is critical to near-surface applications. Seismic numerical modeling is a matured technique in oil/gas seismic exploration. Applying algorithms used in oil/gas industry to near-surface seismic modeling needs extra caution. Unconsolidated sediments are most common materials in near surface, which results in extremely high Poisson's ratios, such as 0.49. Numerical modeling of P-Sv data with the perfect match layer technique works successfully in oil/gas industry. When a Poisson's ratio of a medium is 0.38 or higher, however, it fails. With the multiaxial perfect match layer (MPML) technique, we successfully handle this problem of modeling high-frequency P-Sv data due to a medium with a Poisson's ratio being higher than 0.38. Modeling results of high-frequency P-Sv data with high Poisson's ratios in the time-space and the frequency-velocity domains demonstrate the beauty of the MPML.

  10. Load Frequency Control in Power System with Distributed Generation

    NASA Astrophysics Data System (ADS)

    Yukita, Kazuto; Ota, Takuya; Fujimoto, Koji; Goto, Yasuyuki; Ichiyanagi, Katuhiro

    This paper proposes a method to improve the load frequency control in a power system with distributed generation (DG). DG is assumed to include photovoltaic generation, wind power generation, fuel cells and etc. In this paper, a simulation is performed using a microgrid model or island model that is composed of a storage system with either wind power generation or photovoltaic generation system as the DG. The effectiveness of load frequency control (LFC) using a storage system is examined using a power transmission simulator. The model for the experiment has been composed of inverter, battery, synchronous generator and load. Using this model, the comparison examination was done in respect of output setting control and the case in which the PI control was used. As a result, when the output set-point control using power demand estimation method is executed, the control characteristic is very excellent.

  11. Vibrational resonances in biological systems at microwave frequencies.

    PubMed Central

    Adair, Robert K

    2002-01-01

    Many biological systems can be expected to exhibit resonance behavior involving the mechanical vibration of system elements. The natural frequencies of such resonances will, generally, be in the microwave frequency range. Some of these systems will be coupled to the electromagnetic field by the charge distributions they carry, thus admitting the possibility that microwave exposures may generate physiological effects in man and other species. However, such microwave excitable resonances are expected to be strongly damped by interaction with their aqueous biological environment. Although those dissipation mechanisms have been studied, the limitations on energy transfers that follow from the limited coupling of these resonances to the electromagnetic field have not generally been considered. We show that this coupling must generally be very small and thus the absorbed energy is so strongly limited that such resonances cannot affect biology significantly even if the systems are much less strongly damped than expected from basic dissipation models. PMID:11867434

  12. The optimal control frequency response problem in manual control. [of manned aircraft systems

    NASA Technical Reports Server (NTRS)

    Harrington, W. W.

    1977-01-01

    An optimal control frequency response problem is defined within the context of the optimal pilot model. The problem is designed to specify pilot model control frequencies reflective of important aircraft system properties, such as control feel system dynamics, airframe dynamics, and gust environment, as well as man machine properties, such as task and attention allocation. This is accomplished by determining a bounded set of control frequencies which minimize the total control cost. The bounds are given by zero and the neuromuscular control frequency response for each control actuator. This approach is fully adaptive, i.e., does not depend upon user entered estimates. An algorithm is developed to solve this optimal control frequency response problem. The algorithm is then applied to an attitude hold task for a bare airframe fighter aircraft case with interesting dynamic properties.

  13. Remote systems development

    NASA Technical Reports Server (NTRS)

    Olsen, R.; Schaefer, O.; Hussey, J.

    1992-01-01

    Potential space missions of the nineties and the next century require that we look at the broad category of remote systems as an important means to achieve cost-effective operations, exploration and colonization objectives. This paper addresses such missions, which can use remote systems technology as the basis for identifying required capabilities which must be provided. The relationship of the space-based tasks to similar tasks required for terrestrial applications is discussed. The development status of the required technology is assessed and major issues which must be addressed to meet future requirements are identified. This includes the proper mix of humans and machines, from pure teleoperation to full autonomy; the degree of worksite compatibility for a robotic system; and the required design parameters, such as degrees-of-freedom. Methods for resolution are discussed including analysis, graphical simulation and the use of laboratory test beds. Grumman experience in the application of these techniques to a variety of design issues are presented utilizing the Telerobotics Development Laboratory which includes a 17-DOF robot system, a variety of sensing elements, Deneb/IRIS graphics workstations and control stations. The use of task/worksite mockups, remote system development test beds and graphical analysis are discussed with examples of typical results such as estimates of task times, task feasibility and resulting recommendations for design changes. The relationship of this experience and lessons-learned to future development of remote systems is also discussed.

  14. TES development for a frequency selective bolometer camera.

    SciTech Connect

    Datesman, A. M.; Downes, T. P.; Perera, T. A.; Wang, G.; Yefremenko, V. G.; Pearson, J. E.; Novosad, V.; Divan, R.; Chang, C. L.; Logan, D. W.; Meyer, S. S.; Wilson , G. W.; Bleem, L. E.; Crites, A. T.; McMahon, J. J.; Carlstrom, J. E.; Materials Science Division; Kavli Inst. Cosmological Phys.; Univ. of Massachusetts

    2009-06-01

    We discuss the development, at Argonne National Laboratory (ANL), of a four-pixel camera with four spectral channels centered at 150, 220, 270, and 360 GHz. The scientific motivation involves photometry of distant dusty galaxies located by Spitzer and SCUBA, as well as the study of other millimeter-wave sources such as ultra-luminous infrared galaxies, the Sunyaev-Zeldovich effect in clusters, and galactic dust. The camera incorporates Frequency Selective Bolometer (FSB) and superconducting Transition-Edge Sensor (TES) technology. The current generation of TES devices we examine utilizes proximity effect superconducting bilayers of Mo/Au, Ti, or Ti/Au as TESs, located along with frequency selective absorbing structures on silicon nitride membranes. The detector incorporates lithographically patterned structures designed to address both TES device stability and detector thermal transport concerns. The membrane is not perforated, resulting in a detector which is comparatively robust mechanically. In this paper, we report on the development of the superconducting bilayer TES technology, the design and testing of the detector thermal transport and device stability control structures, optical and thermal test results, and the use of new materials.

  15. Development oF High Frequency Electromagnetic Mapping (HFEM) technology

    NASA Astrophysics Data System (ADS)

    Jesch, R. L.

    1982-04-01

    High frequency electromagnetic mapping (HFEM) techniques were developed for evaluating rubblized oil shale in the cold retort state in the modified in situ process. This technology development is also applicable for using HFEM techniques for diagnosing, monitoring, controlling and evaluating modified in situ retorts after they are ignited. The baseline data work required to design a high temperature sample holder and experiments for determining the EM properties of oil shale samples at elevated temperatures (200 to 500 C) are described. A theoretical approach is given for modeling oil shale retorts for electromagnetic sensing techniques by a spheroid with an average dielectric constant along with numerical results. Finally, the measurement results are given for the spent and raw shale samples that were obtained from portions of the ten half score samples plus the results of the electromagnetic transmission measurements taken on oil shale samples.

  16. Methods, Systems and Apparatuses for Radio Frequency Identification

    NASA Technical Reports Server (NTRS)

    Fink, Patrick W. (Inventor); Chu, Andrew W. (Inventor); Lin, Gregory Y. (Inventor); Kennedy, Timothy F. (Inventor); Ngo, Phong H. (Inventor); Brown, Dewey T. (Inventor); Byerly, Diane (Inventor)

    2016-01-01

    A system for radio frequency identification (RFID) includes an enclosure defining an interior region interior to the enclosure, and a feed for generating an electromagnetic field in the interior region in response to a signal received from an RFID reader via a radio frequency (RF) transmission line and, in response to the electromagnetic field, receiving a signal from an RFID sensor attached to an item in the interior region. The structure of the enclosure may be conductive and may include a metamaterial portion, an electromagnetically absorbing portion, or a wall extending in the interior region. Related apparatuses and methods for performing RFID are provided.

  17. Methods, Systems and Apparatuses for Radio Frequency Identification

    NASA Technical Reports Server (NTRS)

    Fink, Patrick W. (Inventor); Chu, Andrew W. (Inventor); Lin, Gregory Y. (Inventor); Kennedy, Timothy F. (Inventor); Ngo, Phong H. (Inventor); Brown, Dewey T. (Inventor); Byerly, Diane (Inventor); Boose, Haley C. (Inventor)

    2015-01-01

    A system for radio frequency identification (RFID) includes an enclosure defining an interior region interior to the enclosure, and a feed for generating an electromagnetic field in the interior region in response to a signal received from an RFID reader via a radio frequency (RF) transmission line and, in response to the electromagnetic field, receiving a signal from an RFID sensor attached to an item in the interior region. The structure of the enclosure may be conductive and may include a metamaterial portion, an electromagnetically absorbing portion, or a wall extending in the interior region. Related apparatuses and methods for performing RFID are provided.

  18. Methods, Systems and Apparatuses for Radio Frequency Identification

    NASA Technical Reports Server (NTRS)

    Fink, Patrick W. (Inventor); Chu, Andrew W. (Inventor); Lin, Gregory Y. (Inventor); Kennedy, Timothy F. (Inventor); Ngo, Phong H. (Inventor); Brown, Dewey T. (Inventor); Byerly, Diane (Inventor)

    2017-01-01

    A system for radio frequency identification (RFID) includes an enclosure defining an interior region interior to the enclosure, and a feed for generating an electromagnetic field in the interior region in response to a signal received from an RFID reader via a radio frequency (RF) transmission line and, in response to the electromagnetic field, receiving a signal from an RFID sensor attached to an item in the interior region. The structure of the enclosure may be conductive and may include a metamaterial portion, an electromagnetically absorbing portion, or a wall extending in the interior region. Related apparatuses and methods for performing RFID are provided.

  19. Heatpipe power system development

    SciTech Connect

    Houts, M.G.; Poston, D.I.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of the project was to develop a design approach that could enable the development of near-term, low-cost, space fission-power systems. Sixteen desired attributes were identified for such systems and detailed analyses were performed to verify that they are feasible. Preliminary design work was performed on one concept, the Heatpipe Power system (HPS). As a direct result of this project, funding was obtained from the National Aeronautics and Space Administration to build and test an HPS module. The module tests went well, and they now have funding to build a bimodal module.

  20. Description and test results of a variable speed, constant frequency generating system

    NASA Technical Reports Server (NTRS)

    Brady, F. J.

    1985-01-01

    The variable-speed, constant frequency generating system developed for the Mod-0 wind turbine is presented. This report describes the system as it existed at the conclusion of the project. The cycloconverter control circuit is described including the addition of field-oriented control. The laboratory test and actual wind turbine test results are included.

  1. Description and test results of a variable speed, constant frequency generating system

    NASA Astrophysics Data System (ADS)

    Brady, F. J.

    1985-12-01

    The variable-speed, constant frequency generating system developed for the Mod-0 wind turbine is presented. This report describes the system as it existed at the conclusion of the project. The cycloconverter control circuit is described including the addition of field-oriented control. The laboratory test and actual wind turbine test results are included.

  2. RSMASS system model development

    SciTech Connect

    Marshall, A.C.; Gallup, D.R.

    1998-07-01

    RSMASS system mass models have been used for more than a decade to make rapid estimates of space reactor power system masses. This paper reviews the evolution of the RSMASS models and summarizes present capabilities. RSMASS has evolved from a simple model used to make rough estimates of space reactor and shield masses to a versatile space reactor power system model. RSMASS uses unique reactor and shield models that permit rapid mass optimization calculations for a variety of space reactor power and propulsion systems. The RSMASS-D upgrade of the original model includes algorithms for the balance of the power system, a number of reactor and shield modeling improvements, and an automatic mass optimization scheme. The RSMASS-D suite of codes cover a very broad range of reactor and power conversion system options as well as propulsion and bimodal reactor systems. Reactor choices include in-core and ex-core thermionic reactors, liquid metal cooled reactors, particle bed reactors, and prismatic configuration reactors. Power conversion options include thermoelectric, thermionic, Stirling, Brayton, and Rankine approaches. Program output includes all major component masses and dimensions, efficiencies, and a description of the design parameters for a mass optimized system. In the past, RSMASS has been used as an aid to identify and select promising concepts for space power applications. The RSMASS modeling approach has been demonstrated to be a valuable tool for guiding optimization of the power system design; consequently, the model is useful during system design and development as well as during the selection process. An improved in-core thermionic reactor system model RSMASS-T is now under development. The current development of the RSMASS-T code represents the next evolutionary stage of the RSMASS models. RSMASS-T includes many modeling improvements and is planned to be more user-friendly. RSMASS-T will be released as a fully documented, certified code at the end of

  3. Expert Systems Development Methodology

    DTIC Science & Technology

    1989-07-28

    two volumes. Volume 1 is the Development Metodology and Volume 2 is an Evaluation Methodology containing methods for evaluation, validation and...system are written in an English -like language which almost anyone can understand. Thus programming in rule based systems can become "programming for...computers and others have little understanding about how computers work. The knowledge engineer must therefore be willing and able to teach the expert

  4. Frequency Selective Surface Based Bandpass Filter for THz Communication System

    NASA Astrophysics Data System (ADS)

    Das, Subrata; Reza, Khan Mamun; Habib, Md. Ahsan

    2012-11-01

    In this work, a band pass filter based on frequency selective surface (FSS) is presented. The resonance of the FSS is achieved by perforating slot type ring structure on an Aluminum layer. To ensure adequate mechanical strength, this structure is again supported by a dielectric layer. The physical dimensions of the FSS, i.e. ring radius, slot width, cell dimension and width of the layers all are responsible for the resonance behavior. In its electrical equivalent circuit, these dimensions act as inductor and capacitor. The center frequency of the designed filter is at 0.16 THz with a -3 dB bandwidth of 18 GHz. This filter can be utilized as a part of any THz communication system to achieve application specific frequency discrimination. The simulation has been carried by using commercial software-CST Microwave Studio. The performance of the fabricated FSS is evaluated by Microwave Vector Network Analyzer.

  5. Radio frequency communication system utilizing radiating transmission lines

    DOEpatents

    Struven, Warren C.

    1984-01-01

    A radio communication system for use in tunnels, mines, buildings or other shielded locations in which a pair of radiating transmission lines (30), (31) extend through such location in spaced coextensive relation to each other. Each transmission line (30), (31) has at least one unidirectional amplifier (32), (33) interposed therein with the sense of the unidirectional amplifier (32) of one transmission line (30) being opposite to the sense of the unidirectional amplifier (33) of the other transmission line (31). Each of the amplifiers (32), (33) has a gain which is less than the coupling loss between the transmission lines (30), (31). Two or more mobile transceivers (35) in the location served by the system are coupled to the transmission lines (30), (31) by electromagnetic wave propagation in space in order to communicate directly with each other at a given radio frequency within the frequency range of the system.

  6. New Frequency Step-Tunable Ecrh System for Asdex Upgrade

    NASA Astrophysics Data System (ADS)

    Wagner, D.; Leuterer, F.; Manini, A.; Monaco, F.; Münich, M.; Ryter, F.; Schütz, H.; Zohm, H.; Franke, T.; Heidinger, R.; Thumm, M.; Kasparek, W.; Gantenbein, G.; Litvak, A. G.; Popov, L. G.; Nichiporenko, V. O.; Myasnikov, V. E.; Denisov, G. G.; Tai, E. M.; Solyanova, E. A.; Malygin, S. A.

    2006-02-01

    A new broadband ECRH (Electron Cyclotron Resonance Heating) system is currently under construction at the ASDEX Upgrade tokamak. This system will employ multi-frequency gyrotrons step-tunable in the range 105 140 GHz. In its final stage the system will consist of 4 gyrotrons with a total power of 4 MW and a pulse length of 10 s. It employs a fast steerable launcher for feedback controlled deposition that allows for poloidal steering of 10° within 100 ms. Transmission line elements, such as corrugated waveguides, polarizer mirrors and vacuum windows, are designed to cope for this frequency band.

  7. The Engineering Development Array: A Low Frequency Radio Telescope Utilising SKA Precursor Technology

    NASA Astrophysics Data System (ADS)

    Wayth, Randall; Sokolowski, Marcin; Booler, Tom; Crosse, Brian; Emrich, David; Grootjans, Robert; Hall, Peter J.; Horsley, Luke; Juswardy, Budi; Kenney, David; Steele, Kim; Sutinjo, Adrian; Tingay, Steven J.; Ung, Daniel; Walker, Mia; Williams, Andrew; Beardsley, A.; Franzen, T. M. O.; Johnston-Hollitt, M.; Kaplan, D. L.; Morales, M. F.; Pallot, D.; Trott, C. M.; Wu, C.

    2017-08-01

    We describe the design and performance of the Engineering Development Array, which is a low-frequency radio telescope comprising 256 dual-polarisation dipole antennas working as a phased array. The Engineering Development Array was conceived of, developed, and deployed in just 18 months via re-use of Square Kilometre Array precursor technology and expertise, specifically from the Murchison Widefield Array radio telescope. Using drift scans and a model for the sky brightness temperature at low frequencies, we have derived the Engineering Development Array's receiver temperature as a function of frequency. The Engineering Development Array is shown to be sky-noise limited over most of the frequency range measured between 60 and 240 MHz. By using the Engineering Development Array in interferometric mode with the Murchison Widefield Array, we used calibrated visibilities to measure the absolute sensitivity of the array. The measured array sensitivity matches very well with a model based on the array layout and measured receiver temperature. The results demonstrate the practicality and feasibility of using Murchison Widefield Array-style precursor technology for Square Kilometre Array-scale stations. The modular architecture of the Engineering Development Array allows upgrades to the array to be rolled out in a staged approach. Future improvements to the Engineering Development Array include replacing the second stage beamformer with a fully digital system, and to transition to using RF-over-fibre for the signal output from first stage beamformers.

  8. A precise GPS-based time and frequency system

    NASA Technical Reports Server (NTRS)

    Mcnabb, Jack; Fossler, Earl

    1993-01-01

    An approach to implementing a compact, highly reliable and precise Master Time and Frequency subsystem usable in a variety of applications is described. These applications include, among others, Satellite Ground Terminals, Range Timing Stations, Communications Terminals, and Power Station Timing subsystems. All time and frequency output signals are locked to Universal Time via the GPS Satellite system. The system provides for continued output of precise signals in the event of GPS signal interruption from antenna or lead-in breakage or other causes. Cost/performance tradeoffs affecting system accuracy over the short, medium, and long term are discussed. A unique approach to redundant system design provides an architecture with the reliability advantage of triple-redundant majority voting and the cost advantages of dual-redundant elements. The system can be configured to output a variety of precise time and frequency signals and the design can be tailored to output as few, or as many, types and quantities of signals as are required by the application.

  9. LANL receiver system development

    SciTech Connect

    Laubscher, B.; Cooke, B.; Cafferty, M.; Olivas, N.

    1997-08-01

    The CALIOPE receiver system development at LANL is the story of two technologies. The first of these technologies consists of off-the-shelf mercury-cadmium-telluride (MCT) detectors and amplifiers. The vendor for this system is Kolmar Technologies. This system was fielded in the Tan Trailer I (TTI) in 1995 and will be referred to in this paper as GEN I. The second system consists of a MCT detector procured from Santa Barbara Research Center (SBRC) and an amplifier designed and built by LANL. This system was fielded in the Tan Trailer II (TTII) system at the NTS tests in 1996 and will be referred to as GEN II. The LANL CALIOPE experimental plan for 1996 was to improve the lidar system by progressing to a higher rep rate laser to perform many shots in a much shorter period of time. In keeping with this plan, the receiver team set a goal of developing a detector system that was background limited for the projected 100 nanosecond (ns) laser pulse. A set of detailed simulations of the DIAL lidar experiment was performed. From these runs, parameters such as optimal detector size, field of view of the receiver system, nominal laser return power, etc. were extracted. With this information, detector physics and amplifier electronic models were developed to obtain the required specifications for each of these components. These derived specs indicated that a substantial improvement over commercially available, off-the-shelf, amplifier and detector technologies would be needed to obtain the goals. To determine if the original GEN I detector was usable, the authors performed tests on a 100 micron square detector at cryogenic temperatures. The results of this test and others convinced them that an advanced detector was required. Eventually, a suitable detector was identified and a number of these single element detectors were procured from SBRC. These single element detectors were witness for the detector arrays built for another DOE project.

  10. Nonlinear systems for frequency conversion from IR to RF

    NASA Astrophysics Data System (ADS)

    Dolasinski, Brian D.

    The objective of this dissertation is to evaluate and develop novel sources for tunable narrowband IR generation, tunable narrowband THz generation, and ultra-wideband RF generation to be used in possible non-destructive evaluation systems. Initially a periodically poled Lithium Niobate (PPLN) based optical parametric amplifier (OPA) is designed using a double-pass configuration where a small part of the pump is used on the first pass to generate a signal, which is reflected and filtered by an off-axis etalon. The portion of the pump that is not phase matched on the first pass is retro-reflected back into the PPLN crystal and is co-aligned with the narrow bandwidth filtered signal and amplified. We demonstrate that the system is tunable in the 1.4 microm -1.6 microm signal range with a linewidth of 5.4 GHz. Next the outputs of seeded, dual periodically poled lithium niobate (PPLN) optical parametric amplifiers (OPA) are combined in the nonlinear crystal 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST) to produce a widely tunable narrowband THz source via difference frequency generation (DFG). We have demonstrated that this novel configuration enables the system to be seamlessly tuned, without mode-hops, from 1.2 THz to 26.3 THz with a minimum bandwidth of 3.1 GHz. The bandwidth of the source was measured by using the THz transmission spectrum of water vapor lines over a 3-meter path length. By selecting of the DFG pump wavelength to be at 1380 nm and the signal wavelength to tune over a range from 1380 nm to 1570 nm, we produced several maxima in the output THz spectrum that was dependent on the phase matching ability of the DAST crystal and the efficiency of our pyro-electric detector. Due to the effects of dispersive phase matching, filter absorption of the THz waves, and two-photon absorption multiple band gaps in the overall spectrum occur and are discussed. Employing the dual generator scheme, we have obtained THz images at several locations in the

  11. An ultra-broadband frequency-domain terahertz measurement system based on frequency conversion via DAST crystal with an optimized phase-matching condition

    NASA Astrophysics Data System (ADS)

    Qi, Feng; Fan, Shuzhen; Notake, Takashi; Nawata, Kouji; Matsukawa, Takeshi; Takida, Yuma; Minamide, Hiroaki

    2014-08-01

    By applying the frequency conversion technique to 4-dimethylamino-N-methyl-4-stilbazolium tosylate crystal, a monochromatic terahertz (THz) measurement system, including both generation and detection, has been developed over quite a broad frequency band, from 1.85 to 30 THz. In the case of frequency upconversion detection of THz waves, for the first time, we used gratings instead of filters to tackle the tough phase-matching conditions for broadband operations. By synchronizing the rotation of two gratings to extract the frequency upconverted signal, the infrared (IR) pumping beam can be tuned freely over 300 nm with decent diffraction efficiency and sufficient isolation between the weak frequency upconversion signal and the strong IR pumping beam to be realized. Such a large tuning range has overcome the limit of commercial filters with a fixed passband, while such a high optical density value has been beyond the limit of commercial tunable filters. Consequently, the proposed frequency domain system gives the largest THz frequency band. Unlike THz time-domain spectroscopy systems in which a fs laser is applied and broadband THz pulses are applied, our system works based on a ns laser and it can function at a single THz frequency with random frequency access ability from pulse to pulse.

  12. A novel dual-frequency loading system for studying mechanobiology of load-bearing tissue.

    PubMed

    Zhang, Chunqiu; Qiu, Lulu; Gao, Lilan; Guan, Yinjie; Xu, Qiang; Zhang, Xizheng; Chen, Qian

    2016-12-01

    In mechanobiological research, an appropriate loading system is an essential tool to mimic mechanical signals in a native environment. To achieve this goal, we have developed a novel loading system capable of applying dual-frequency loading including both a low-frequency high-amplitude loading and a high-frequency low-amplitude loading, according to the mechanical conditions experienced by bone and articular cartilage tissues. The low-frequency high-amplitude loading embodies the main force from muscular contractions and/or reaction forces while the high-frequency low-amplitude loading represents an assistant force from small muscles, ligaments and/or other tissue in order to maintain body posture during human activities. Therefore, such dual frequency loading system may reflect the natural characteristics of complex mechanical load on bone or articular cartilage than the single frequency loading often applied during current mechanobiological experiments. The dual-frequency loading system is validated by experimental tests using precision miniature plane-mirror interferometers. The dual-frequency loading results in significantly more solute transport in articular cartilage than that of the low-frequency high-amplitude loading regiment alone, as determined by quantitative fluorescence microscopy of tracer distribution in articular cartilage. Thus, the loading system can provide a new method to mimic mechanical environment in bone and cartilage, thereby revealing the in vivo mechanisms of mechanosensation, mechanotransduction and mass-transport, and improving mechanical conditioning of cartilage and/or bone constructs for tissue engineering. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. A development of a generalized frequency - domain transient program - FTP

    SciTech Connect

    Nagaoka, N.; Ametani, A. )

    1988-10-01

    A generalized frequency-domain transient program (FTP) is developed in the paper. The FTP is based on a frequency-time transform method adopting nodal analysis, admittance parameter and modal theories. Discontinuous and nonlinear elements are solved as initial condition problems using a piece-wise linear approximation of the nonlinear characteristics. The FTP is used to solve the transient and steady states of a network composed of an arbitrary interconnection of basic circuit elements. The FTP is structured to be compatible with the EMTP so that the same input data and output formats are those of the EMTP can be used. The present version of the FTP can deal with a network with over a hundred of nodes and branches. Comparisons of calculated results by the FTP with field test results and calculated results by the EMTP confirm a high accuracy and a satisfactory efficiency of the FTP. The FTP is of great advantage to offer the most accurate or theoretically exact solutions of transients on distributed-parameter lines.

  14. Development of high frequency and wide bandwidth Johnson noise thermometry

    SciTech Connect

    Crossno, Jesse; Liu, Xiaomeng; Kim, Philip; Ohki, Thomas A.; Fong, Kin Chung

    2015-01-12

    We develop a high frequency, wide bandwidth radiometer operating at room temperature, which augments the traditional technique of Johnson noise thermometry for nanoscale thermal transport studies. Employing low noise amplifiers and an analog multiplier operating at 2 GHz, auto- and cross-correlated Johnson noise measurements are performed in the temperature range of 3 to 300 K, achieving a sensitivity of 5.5 mK (110 ppm) in 1 s of integration time. This setup allows us to measure the thermal conductance of a boron nitride encapsulated monolayer graphene device over a wide temperature range. Our data show a high power law (T ∼ 4) deviation from the Wiedemann-Franz law above T ∼ 100 K.

  15. Design and development of mode launcher for high frequency Gyrotron

    NASA Astrophysics Data System (ADS)

    Alaria, Mukesh Kumar; Sinha, A. K.; Khatun, H.

    2016-03-01

    In this paper, we describe the design and development of helical cut smooth wall mode launcher for high frequency and high power Gyrotron. A Vlasov-type helical cut mode launcher for converting TE22,6 mode to a Gaussian mode has been designed for 120 GHz, 1 MW Gyrotron. The initial design of mode launcher has been optimized using LOT/SURF-3D software. The mode launcher diameter and length are optimized considering the minimum return loss and the minimum insertion loss by using CST microwave studio. The return loss (S11) and insertion loss (S21) performance of helical cut smooth wall mode launcher have been obtained using CST-Microwave Studio. The fabrication of Vlasov-type helical cut mode launcher for 120 GHz Gyrotron has also been carried out.

  16. Development of high frequency and wide bandwidth Johnson noise thermometry

    NASA Astrophysics Data System (ADS)

    Crossno, Jesse; Liu, Xiaomeng; Ohki, Thomas A.; Kim, Philip; Fong, Kin Chung

    2015-01-01

    We develop a high frequency, wide bandwidth radiometer operating at room temperature, which augments the traditional technique of Johnson noise thermometry for nanoscale thermal transport studies. Employing low noise amplifiers and an analog multiplier operating at 2 GHz, auto- and cross-correlated Johnson noise measurements are performed in the temperature range of 3 to 300 K, achieving a sensitivity of 5.5 mK (110 ppm) in 1 s of integration time. This setup allows us to measure the thermal conductance of a boron nitride encapsulated monolayer graphene device over a wide temperature range. Our data show a high power law (T ˜ 4) deviation from the Wiedemann-Franz law above T ˜ 100 K.

  17. System upgrades and performance evaluation of the spectrally agile, frequency incrementing reconfigurable (SAFIRE) radar system

    NASA Astrophysics Data System (ADS)

    Phelan, Brian R.; Ranney, Kenneth I.; Ressler, Marc A.; Clark, John T.; Sherbondy, Kelly D.; Kirose, Getachew A.; Harrison, Arthur C.; Galanos, Daniel T.; Saponaro, Philip J.; Treible, Wayne R.; Narayanan, Ram M.

    2017-05-01

    The U.S. Army Research Laboratory has developed the Spectrally Agile Frequency-Incrementing Reconfigurable (SAFIRE) radar, which is capable of imaging concealed/buried targets using forward- and side-looking configurations. The SAFIRE radar is vehicle-mounted and operates from 300 MHz-2 GHz; the step size can be adjusted in multiples of 1 MHz. It is also spectrally agile and capable of excising frequency bands, which makes it ideal for operation in congested and/or contested radio frequency (RF) environments. Furthermore, the SAFIRE radar receiver has a super-heterodyne architecture, which was designed so that intermodulation products caused by interfering signals could be easily filtered from the desired received signal. The SAFIRE system also includes electro-optical (EO) and infrared (IR) cameras, which can be fused with radar data and displayed in a stereoscopic augmented reality user interface. In this paper, recent upgrades to the SAFIRE system are discussed and results from the SAFIRE's initial field tests are presented.

  18. Trauma system development.

    PubMed

    Lendrum, R A; Lockey, D J

    2013-01-01

    The word 'trauma' describes the disease entity resulting from physical injury. Trauma is one of the leading causes of death worldwide and deaths due to injury look set to increase. As early as the 1970s, it became evident that centralisation of resources and expertise could reduce the mortality rate from serious injury and that organisation of trauma care delivery into formal systems could improve outcome further. Internationally, trauma systems have evolved in various forms, with widespread reports of mortality and functional outcome benefits when major trauma management is delivered in this way. The management of major trauma in England is currently undergoing significant change. The London Trauma System began operating in April 2010 and others throughout England became operational this year. Similar systems exist internationally and continue to be developed. Anaesthetists have been and continue to be involved with all levels of trauma care delivery, from the provision of pre-hospital trauma and retrieval teams, through to chronic pain management and rehabilitation of patients back into society. This review examines the international development of major trauma care delivery and the components of a modern trauma system.

  19. A combined method for computing frequency responses of proportionally damped systems

    NASA Astrophysics Data System (ADS)

    Wu, Baisheng; Yang, Shitong; Li, Zhengguang; Zheng, Shaopeng

    2015-08-01

    Frequency response analysis requires the evaluation of an associated function for a typically large number of frequencies. Direct method for performing these calculations is time-consuming. In this paper, a method is proposed for solving frequency responses of a mechanical system with proportional damping. The method combines modal superposition with a model order reduction. Only the modes corresponding to a frequency range which is a little bigger than that of interest are used for modal superposition. Complementary part of contribution of computed modes for frequency response is calculated by a model order reduction method. Basis vectors are obtained by applying preconditioned conjugate gradient method to a modified undamped system at the highest frequency of interest. The existing factorized stiffness matrix developed for partial eigensolutions is used as preconditioner. This computational methodology is illustrated by its applications to two frequency response problems. It is shown that the present method can remarkably reduce the CPU time required by the direct method to frequency response analysis.

  20. Wind Generation Participation in Power System Frequency Response: Preprint

    SciTech Connect

    Gevorgian, Vahan; Zhang, Yingchen

    2017-01-01

    The electrical frequency of an interconnected power system must be maintained close its nominal level at all times. Excessive under- and overfrequency excursions can lead to load shedding, instability, machine damage, and even blackouts. There is a rising concern in the electric power industry in recent years about the declining amount of inertia and primary frequency response (PFR) in many interconnections. This decline may continue due to increasing penetrations of inverter-coupled generation and the planned retirements of conventional thermal plants. Inverter-coupled variable wind generation is capable of contributing to PFR and inertia with a response that is different from that of conventional generation. It is not yet entirely understood how such a response will affect the system at different wind power penetration levels. The modeling work presented in this paper evaluates the impact of wind generation's provision of these active power control strategies on a large, synchronous interconnection. All simulations were conducted on the U.S. Western Interconnection with different levels of instantaneous wind power penetrations (up to 80%). The ability of wind power plants to provide PFR - and a combination of synthetic inertial response and PFR - significantly improved the frequency response performance of the system.

  1. Investigating Power System Primary and Secondary Reserve Interaction under High Wind Penetration Using Frequency Response Model

    SciTech Connect

    Tan, Jin; Zhang, Yingchen; Krad, Ibrahim; Gevorgian, Vahan; Ela, Erik

    2015-10-12

    Power system frequency needs to be maintained close to its nominal value at all times to avoid machine damage, under-frequency load-shedding and even blackouts. Adequate primary frequency response and secondary frequency response are the primary forces to correct an energy imbalance at the second to minute level. As wind energy becomes a larger portion of the world's energy portfolio, there are greater oppotunities for wind to provide frequency response services. This paper addresses one area of frequency control that has been missing in previous work - the reliabilty impacts and interactions between primary and secondary frequency control. The lack of a commercially available tools to simulate the interaction of these two responses has limited the energy industry's understanding of when the depletion of primary control reserve will impact the performance of secondary conrol response or vice versa. To investigate this issue, in this paper we develop a multi-area frequency response integration model with combined primary and secondary frequency control capabilities.

  2. Internal insulation system development

    NASA Technical Reports Server (NTRS)

    Gille, J. P.

    1973-01-01

    The development of an internal insulation system for cryogenic liquids is described. The insulation system is based on a gas layer concept in which capillary or surface tension effects are used to maintain a stable gas layer within a cellular core structure between the tank wall and the contained cryogen. In this work, a 1.8 meter diameter tank was insulated and tested with liquid hydrogen. Ability to withstand cycling of the aluminum tank wall to 450 K was a design and test condition.

  3. Ultra-wideband communication system prototype using orthogonal frequency coded SAW correlators.

    PubMed

    Gallagher, Daniel R; Kozlovski, Nikolai Y; Malocha, Donald C

    2013-03-01

    This paper presents preliminary ultra-wideband (UWB) communication system results utilizing orthogonal frequency coded SAW correlators. Orthogonal frequency coding (OFC) and pseudo-noise (PN) coding provides a means for spread-spectrum UWB. The use of OFC spectrally spreads a PN sequence beyond that of CDMA; allowing for improved correlation gain. The transceiver approach is still very similar to that of the CDMA approach, but provides greater code diversity. Use of SAW correlators eliminates many of the costly components that are typically needed in the intermediate frequency (IF) section in the transmitter and receiver, and greatly reduces the signal processing requirements. Development and results of an experimental prototype system with center frequency of 250 MHz are presented. The prototype system is configured using modular RF components and benchtop pulse generator and frequency source. The SAW correlation filters used in the test setup were designed using 7 chip frequencies within the transducer. The fractional bandwidth of approximately 29% was implemented to exceed the defined UWB specification. Discussion of the filter design and results are presented and are compared with packaged device measurements. A prototype UWB system using OFC SAW correlators is demonstrated in wired and wireless configurations. OFC-coded SAW filters are used for generation of a transmitted spread-spectrum UWB and matched filter correlated reception. Autocorrelation and cross-correlation system outputs are compared. The results demonstrate the feasibility of UWB SAW correlators for use in UWB communication transceivers.

  4. An Auto-Lock Laser System for Long Term Frequency Stabilization

    NASA Astrophysics Data System (ADS)

    Berthiaume, Robert; Vorozcovs, Andrew; Kumarakrishnan, A.

    2010-03-01

    We have developed a compact, digitally controlled system to automatically stabilize the frequency of an external cavity diode laser to an atomic resonance. The key component of the system is a low-cost single-board computer with A/D and D/A capability that acts as a specialized lock-in amplifier. The system performs pattern matching between Doppler-free peaks obtained by scanning the laser frequency and reference peaks stored in the processor's memory. The incoming spectral signals are compared with the reference waveforms using a sliding correlation algorithm, which determines the control voltage required for adjusting the laser frequency to the desired lock point. The system has a scan amplitude of less than 1MHz when locked and it can re-lock for frequency drifts up to 10 GHz without human intervention. The dependence of laser frequency stability on ambient temperature, humidity, and pressure has been investigated. The performance of the system is suitable for experiments in atom trapping and atom interferometry that require long-term laser frequency stabilization.

  5. Participation of non-conventional energy resources in power system frequency control

    NASA Astrophysics Data System (ADS)

    Aghazadeh Tabrizi, Mehriar

    Frequency control is one of the key issues in designing, planning and reliably operating a power system and is becoming more challenging as new complexities and uncertainties are introduced into the modern power systems. Traditionally, power system frequency has been controlled using conventional generation units' capabilities namely inertial, primary and secondary frequency responses. Limited fossil-based fuel resources, ever-increasing energy consumption and rising public awareness for environmental protection have created growing interest in use of non-conventional energy resources such as Wind Generation Resources (WGRs) and Solar Generation Resources (SGRs) which have unfavorable characteristics in comparison with conventional generation units such as lack of frequency response. The more conventional generation units are replaced by these resources, the more challenges power system operators will face in terms of power system frequency control. These challenges are further compounded due to less system inertia during off-peak hours or within small power systems. This dissertation mainly focuses on participation of SGRs and Interior Permanent Magnet Synchronous Generator (IPMSG) based WGRs in power system frequency control. Detailed information regarding dynamic modeling of power system including conventional generation units, SGRs and IPMSG based WGRs is provided. The frequency response of conventional generation units is compared with that of SGRs and IPMSG based WGRs. The control systems associated with IPMSG based WGR and SGR are modified in order to improve their frequency response capabilities. The effectiveness of the proposed control strategies is evaluated and confirmed via MATLAB based time-domain simulations for different scenarios. Moreover, application of Battery Energy Storage Systems (BESSs) in power system frequency regulation is discussed. The detailed dynamic model of BESSs is utilized to develop a simplified model suitable for Automatic

  6. Development of a Multi-Channel, High Frequency QRS Electrocardiograph

    NASA Technical Reports Server (NTRS)

    DePalma, Jude L.

    2003-01-01

    With the advent of the ISS era and the potential requirement for increased cardiovascular monitoring of crewmembers during extended EVAs, NASA flight surgeons would stand to benefit from an evolving technology that allows for a more rapid diagnosis of myocardial ischemia compared to standard electrocardiography. Similarly, during the astronaut selection process, NASA flight surgeons and other physicians would also stand to benefit from a completely noninvasive technology that, either at rest or during maximal exercise tests, is more sensitive than standard ECG in identifying the presence of ischemia. Perhaps most importantly, practicing cardiologists and emergency medicine physicians could greatly benefit from such a device as it could augment (or even replace) standard electrocardiography in settings where the rapid diagnosis of myocardial ischemia (or the lack thereof) is required for proper clinical decision-making. A multi-channel, high-frequency QRS electrocardiograph is currently under development in the Life Sciences Research Laboratories at JSC. Specifically the project consisted of writing software code, some of which contained specially-designed digital filters, which will be incorporated into an existing commercial software program that is already designed to collect, plot and analyze conventional 12-lead ECG signals on a desktop, portable or palm PC. The software will derive the high-frequency QRS signals, which will be analyzed (in numerous ways) and plotted alongside of the conventional ECG signals, giving the PC-viewing clinician advanced diagnostic information that has never been available previously in all 12 ECG leads simultaneously. After the hardware and software for the advanced digital ECG monitor have been fully integrated, plans are to use the monitor to begin clinical studies both on healthy subjects and on patients with known coronary artery disease in both the outpatient and hospital settings. The ultimate goal is to get the technology

  7. Characterizing DSN System Frequency Stability with Spacecraft Tracking Data

    NASA Technical Reports Server (NTRS)

    Pham, T.; Machuzak, R.; Bedrossian, A.

    2010-01-01

    This paper describes a recent effort in characterizing frequency stability performance of the ground system in the NASA Deep Space Network (DSN). Unlike the traditional approach where performance is obtained from special calibration sessions that are both time consuming and require manual setup, the new method taps into the daily spacecraft tracking data. This method significantly increases the amount of data available for analysis, roughly by two orders of magnitude; making it possible to conduct trend analysis with reasonable confidence. Since the system is monitored daily, any significant variation in performance can be detected timely. This helps the DSN maintain its performance commitment to customers.

  8. Microarray Genomic Systems Development

    DTIC Science & Technology

    2008-06-01

    D Canada Contract Report DRDC Suffield CR 2009-145 June 2008 V. Lam, M. Crichton , T. Dickinson Laing, and D.C. Mah Canada West Biosciences Inc...Genomic Systems Development V. Lam, M. Crichton , T. Dickinson Laing, and D.C. Mah Canada West Biosciences Inc. Canada West Biosciences Inc. 5429... Crichton , M.; Dickinson Laing, T.; Mah, D.C.; DRDC Suffield CR 2009- 145; Defence R&D Canada – Suffield; June 2008. Introduction: Conventional

  9. Performance of a laser frequency comb calibration system with a high-resolution solar echelle spectrograph

    NASA Astrophysics Data System (ADS)

    Doerr, H.-P.; Kentischer, T. J.; Steinmetz, T.; Probst, R. A.; Franz, M.; Holzwarth, R.; Udem, Th.; Hänsch, T. W.; Schmidt, W.

    2012-09-01

    Laser frequency combs (LFC) provide a direct link between the radio frequency (RF) and the optical frequency regime. The comb-like spectrum of an LFC is formed by exact equidistant laser modes, whose absolute optical frequencies are controlled by RF-references such as atomic clocks or GPS receivers. While nowadays LFCs are routinely used in metrological and spectroscopic fields, their application in astronomy was delayed until recently when systems became available with a mode spacing and wavelength coverage suitable for calibration of astronomical spectrographs. We developed a LFC based calibration system for the high-resolution echelle spectrograph at the German Vacuum Tower Telescope (VTT), located at the Teide observatory, Tenerife, Canary Islands. To characterize the calibration performance of the instrument, we use an all-fiber setup where sunlight and calibration light are fed to the spectrograph by the same single-mode fiber, eliminating systematic effects related to variable grating illumination.

  10. Frequency-Weighting Filter Selection, for H2 Control of Microgravity Isolation Systems: A Consideration of the "Implicit Frequency Weighting" Problem

    NASA Technical Reports Server (NTRS)

    Hampton, Roy David; Whorton, Mark S.

    1999-01-01

    Many space-science experiments need an active isolation system to provide them with the requisite microgravity environment. The isolation systems planned for use with the International Space Station (ISS) have been appropriately modeled using relative position, relative velocity, and acceleration states. In theory, frequency-weighting design filters can be applied to these state-space models, in order to develop optimal H2 or mixed-norm controllers with desired stability and performance characteristics. In practice, however, since there is a kinematic relationship among the various states, any frequency weighting applied to one state will implicitly weight other states. These implicit frequency-weighting effects must be considered, for intelligent frequency-weighting filter assignment. This paper suggests a rational approach to the assignment of frequency-weighting design filters, in the presence of the kinematic coupling among states that exists in the microgravity vibration isolation problem.

  11. Improving transient performance of adaptive control architectures using frequency-limited system error dynamics

    NASA Astrophysics Data System (ADS)

    Yucelen, Tansel; De La Torre, Gerardo; Johnson, Eric N.

    2014-11-01

    Although adaptive control theory offers mathematical tools to achieve system performance without excessive reliance on dynamical system models, its applications to safety-critical systems can be limited due to poor transient performance and robustness. In this paper, we develop an adaptive control architecture to achieve stabilisation and command following of uncertain dynamical systems with improved transient performance. Our framework consists of a new reference system and an adaptive controller. The proposed reference system captures a desired closed-loop dynamical system behaviour modified by a mismatch term representing the high-frequency content between the uncertain dynamical system and this reference system, i.e., the system error. In particular, this mismatch term allows the frequency content of the system error dynamics to be limited, which is used to drive the adaptive controller. It is shown that this key feature of our framework yields fast adaptation without incurring high-frequency oscillations in the transient performance. We further show the effects of design parameters on the system performance, analyse closeness of the uncertain dynamical system to the unmodified (ideal) reference system, discuss robustness of the proposed approach with respect to time-varying uncertainties and disturbances, and make connections to gradient minimisation and classical control theory. A numerical example is provided to demonstrate the efficacy of the proposed architecture.

  12. Disturbance Frequency Determines Morphology and Community Development in Multi-Species Biofilm at the Landscape Scale

    PubMed Central

    Milferstedt, Kim; Santa-Catalina, Gaëlle; Godon, Jean-Jacques; Escudié, Renaud; Bernet, Nicolas

    2013-01-01

    Many natural and engineered biofilm systems periodically face disturbances. Here we present how the recovery time of a biofilm between disturbances (expressed as disturbance frequency) shapes the development of morphology and community structure in a multi-species biofilm at the landscape scale. It was hypothesized that a high disturbance frequency favors the development of a stable adapted biofilm system while a low disturbance frequency promotes a dynamic biofilm response. Biofilms were grown in laboratory-scale reactors over a period of 55-70 days and exposed to the biocide monochloramine at two frequencies: daily or weekly pulse injections. One untreated reactor served as control. Biofilm morphology and community structure were followed on comparably large biofilm areas at the landscape scale using automated image analysis (spatial gray level dependence matrices) and community fingerprinting (single-strand conformation polymorphisms). We demonstrated that a weekly disturbed biofilm developed a resilient morphology and community structure. Immediately after the disturbance, the biofilm simplified but recovered its initial complex morphology and community structure between two biocide pulses. In the daily treated reactor, one organism largely dominated a morphologically simple and stable biofilm. Disturbances primarily affected the abundance distribution of already present bacterial taxa but did not promote growth of previously undetected organisms. Our work indicates that disturbances can be used as lever to engineer biofilms by maintaining a biofilm between two developmental states. PMID:24303024

  13. Traffic camera system development

    NASA Astrophysics Data System (ADS)

    Hori, Toshi

    1997-04-01

    The intelligent transportation system has generated a strong need for the development of intelligent camera systems to meet the requirements of sophisticated applications, such as electronic toll collection (ETC), traffic violation detection and automatic parking lot control. In order to achieve the highest levels of accuracy in detection, these cameras must have high speed electronic shutters, high resolution, high frame rate, and communication capabilities. A progressive scan interline transfer CCD camera, with its high speed electronic shutter and resolution capabilities, provides the basic functions to meet the requirements of a traffic camera system. Unlike most industrial video imaging applications, traffic cameras must deal with harsh environmental conditions and an extremely wide range of light. Optical character recognition is a critical function of a modern traffic camera system, with detection and accuracy heavily dependent on the camera function. In order to operate under demanding conditions, communication and functional optimization is implemented to control cameras from a roadside computer. The camera operates with a shutter speed faster than 1/2000 sec. to capture highway traffic both day and night. Consequently camera gain, pedestal level, shutter speed and gamma functions are controlled by a look-up table containing various parameters based on environmental conditions, particularly lighting. Lighting conditions are studied carefully, to focus only on the critical license plate surface. A unique light sensor permits accurate reading under a variety of conditions, such as a sunny day, evening, twilight, storms, etc. These camera systems are being deployed successfully in major ETC projects throughout the world.

  14. Recent developments and proposed schemes for trapped ion frequency standards. [trapped mercury ions for microwave and optical frequency standards

    NASA Technical Reports Server (NTRS)

    Maleki, L.

    1982-01-01

    Ion traps are exciting candidates as future precision frequency sources. Recent developments demonstrate that mercury ion frequency standards are capable of a stability performance comparable to commercial cesium standards. There is, however, considerable room for improvement with regard to the signal to noise problem. The 40 GHz microwave frequency implies that a careful design should be implemented to ensure the elimination of the unwanted side bands in the microwave pump signal. A long life, high performance light source to be used in a trapped mercury ion microwave standard must be developed and the long term performance of a trapped mercury ion microwave standard must be investigated. While newly proposed two photon pumping schemes in conjuction with mercury ions promise exciting developments for both microwave and optical frequency standards, other ions that may be potential candidates should be evaluated for their usefulness.

  15. Analytical estimates of secular frequencies for binary star systems

    NASA Astrophysics Data System (ADS)

    Bazsó, Á.; Pilat-Lohinger, E.

    2017-03-01

    Binary and multiple star systems are extreme environments for the formation and long-term presence of extrasolar planets. Circumstellar planets are subject to gravitational perturbations from the distant companion star, and this interaction leads to a long-period precession of their orbits. We investigate analytical models that allow to quantify these perturbations and calculate the secular precession frequency in the dynamical model of the restricted three-body problem. These models are applied to test cases and we discuss some of their shortcomings. In addition, we introduce a modified Laplace-Lagrange model which allows to obtain better frequency estimates than the traditional model for large eccentricities of the perturber. We then generalize this model to any number of perturbers, and present an application to the four-body problem.

  16. Multifunction tests of a frequency domain based flutter suppression system

    NASA Technical Reports Server (NTRS)

    Christhilf, David M.; Adams, William M., Jr.

    1992-01-01

    The process is described of analysis, design, digital implementation, and subsonic testing of an active control flutter suppression system for a full span, free-to-roll wind tunnel model of an advanced fighter concept. The design technique uses a frequency domain representation of the plant and used optimization techniques to generate a robust multi input/multi output controller. During testing in a fixed-in-roll configuration, simultaneous suppression of both symmetric and antisymmetric flutter was successfully shown. For a free-to-roll configuration, symmetric flutter was suppressed to the limit of the tunnel test envelope. During aggressive rolling maneuvers above the open-loop flutter boundary, simultaneous flutter suppression and maneuver load control were demonstrated. Finally, the flutter damping controller was reoptimized overnight during the test using combined experimental and analytical frequency domain data, resulting in improved stability robustness.

  17. Imaging capability of the higher-frequency subsystem of a dual-frequency acoustic lens sonar system

    NASA Astrophysics Data System (ADS)

    Lopes, Joseph L.; Paustian, Iris C.; Marciniak, Robert; Van Tol, Dave; Folds, Donald L.

    2000-07-01

    An experimental dual-frequency acoustic lens sonar system, designed to detect both buried and non-buried objects is described with emphasis on the higher frequency subsystem. The lower frequency subsystem (35 - 100 kHz) forms conical beams with beam widths near 5 degree(s) using discrete transducer elements in the lens focal plane for both transmission and reception. The higher frequency (1 - 2 MHz) lens system is designed to be contained within the volume of the lower frequency subsystem to create a compact dual-frequency system. The higher frequency system consists of three 20-cm long cylindrical lenses designed to form fan-shaped beams over a 20 degree(s) field of view. The retina is positioned 34 cm from the entrance aperture. A test array containing several discrete elements with 1.0-mm pitch has been designed for initial testing. The final system will use a retina with 80 - 100 elements. The imaging system is designed to generate images with cross-range resolutions from 0.1 degree(s) to 0.25 degree(s), and is designed to be tested in both bistatic or monostatic modes. In the monostatic mode, results of spatial multiplexing of beams in the ratio of 3, 4, and 5 will be compared. The system is designed to make a thorough parametric evaluation of imaging in the 1 - 2 MHz range over a wide range of angular resolutions and to relate design parameters to operational performance for forward looking systems.

  18. Development of streamflow drought severity- and magnitude-duration-frequency curves using the threshold level method

    NASA Astrophysics Data System (ADS)

    Sung, J. H.; Chung, E.-S.; Lee, K. S.

    2013-12-01

    This study developed a comprehensive method to quantify streamflow drought severity and magnitude based on a traditional frequency analysis. Two types of curve were developed: the streamflow drought severity-duration-frequency (SDF) curve and the streamflow drought magnitude-duration-frequency (MDF) curve (e.g., a rainfall intensity-duration-frequency curve). Severity was represented as the total water deficit volume for the specific drought duration, and magnitude was defined as the daily average water deficit. The variable threshold level method was introduced to set the target instream flow requirement, which can significantly affect the streamflow drought severity and magnitude. The four threshold levels utilized were fixed, monthly, daily, and desired yield for water use. The threshold levels for the desired yield differed considerably from the other levels and represented more realistic conditions because real water demands were considered. The streamflow drought severities and magnitudes from the four threshold methods could be derived at any frequency and duration from the generated SDF and MDF curves. These SDF and MDF curves are useful in designing water resources systems for streamflow drought and water supply management.

  19. The development of a tunable, single-frequency ultraviolet laser source for UV filtered Rayleigh scattering

    NASA Technical Reports Server (NTRS)

    Finkelstein, N.; Gambogi, J.; Lempert, Walter R.; Miles, Richard B.; Rines, G. A.; Finch, A.; Schwarz, R. A.

    1995-01-01

    We present the development of a flexible, high power, narrow line width, tunable ultraviolet source for diagnostic application. By frequency tripling the output of a pulsed titanium-sapphire laser, we achieve broadly tunable (227-360 nm) ultraviolet light with high quality spatial and spectral resolution. We also present the characterization of a mercury vapor cell which provides a narrow band, sharp edge absorption filter at 253.7 nm. These two components form the basis for the extension of the Filtered Rayleigh Scattering technique into the ultraviolet. The UV-FRS system is comprised of four pieces: a single frequency, cw tunable Ti:Sapphire seeding source; a high-powered pulsed Ti:Sapphire oscillator; a third harmonic generator system; and an atomic mercury vapor filter. In this paper we discuss the development and characterization of each of these elements.

  20. Method of implementing frequency encoded multiplexer and demultiplexer systems using nonlinear semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Garai, Sisir Kumar; Mukhopadhyay, Sourangshu

    2009-11-01

    Multiplexing and demultiplexing are the essential parts of any communication network. In case of optical multiplexing and demultiplexing the coding of the data as well as the coding of control signals are most important issues. Many encoding/decoding mechanisms have already been developed in optical communication technology. Recently frequency encoding technique has drawn some special interest to the scientific communities. The advantage of frequency encoding technique over any other techniques is that as the frequency is fundamental character of any signal so it remains unaltered in reflection, refraction, absorption, etc. during transmission of the signal and therefore the system will execute the operation with reliability. On the other hand, the switching speed of semiconductor optical amplifiers (SOA) is sufficiently high with property of best on/off contrast ratio. In our present communication we propose a method of implementing a '4-to-1' multiplexer (MUX) and a '1-to-4' demultiplexer (DEMUX) exploiting the switching character of nonlinear SOA with the use of frequency encoded control signals. To implement the '4-to-1' MUX and '1-to-4' DEMUX system, the frequency selection by multiquantum well (MQW)-grating filter-based SOA has been used for frequency routing purpose. At the same time, the polarization rotation character of SOA has also been exploited to get the desired purpose. Here the fast switching action of SOA with reliable frequency encoded control input signals, it is possible to achieve a faithful MUX/DEMUX service at tera-Hz operational speed.

  1. Optical Reflection Measurement System Using A Swept Modulation Frequency Technique

    NASA Astrophysics Data System (ADS)

    Braun, David M.; Leyde, Kent W.

    1989-03-01

    A measurement system has been developed capable of mea-suring reflected optical power as low as 0.0025% with a spot size diam-eter of 24 Am. One application for this system is the characterization of small-area photodetectors. The operation of the measurement system is simple, allowing the operator to quickly make multiple reflection measurements, and it does not require a darkroom. The measurement system merges a microscope, for visual alignment and focusing of the laser beam, with a lightwave component analyzer using modulation vec-tor error correction. A measurement comparison between the analyzer-based system and a power-meter-based system showed that each sys-tem can measure reflections as low as 0.0025%. However, the analyzer-based system offers the advantage of identifying the location and magnitude of system reflections. The system operates at a wavelength of 1310 nm.

  2. Frequency dependent and transient characteristics of substation grounding systems

    SciTech Connect

    Grcev, L.D. Heimbach, M.

    1997-01-01

    In spite of the existence of a number of analytical models aimed for transient analysis of large grounding systems, more detailed analysis of the influence of different parameters on the transient performance of large ground grids subjected to lightning current impulse is not available. This paper presents analysis of the influence of soil conductivity, location of feed point, grid size, depth, conductor separation, ground rods, and shape of the lightning current impulse, on the transient performance of ground grids with sizes ranging from 10 x 10 m{sup 2} to 120 x 120 m{sup 2} and with 4 to 124 meshes. Maximal transient ground potential rise and frequency dependent impedance are analyzed in time and frequency domain, respectively. Computations are made with computer model based on the electromagnetic field theory approach, taking accurately into account frequency dependent characteristics of large ground grids. Instead of usual simple approximations of the lightning current impulse, recorded channel base currents from triggered lightning are used for the time domain analysis.

  3. Optimal Frequency-Domain System Realization with Weighting

    NASA Technical Reports Server (NTRS)

    Juang, Jer-Nan; Maghami, Peiman G.

    1999-01-01

    Several approaches are presented to identify an experimental system model directly from frequency response data. The formulation uses a matrix-fraction description as the model structure. Frequency weighting such as exponential weighting is introduced to solve a weighted least-squares problem to obtain the coefficient matrices for the matrix-fraction description. A multi-variable state-space model can then be formed using the coefficient matrices of the matrix-fraction description. Three different approaches are introduced to fine-tune the model using nonlinear programming methods to minimize the desired cost function. The first method uses an eigenvalue assignment technique to reassign a subset of system poles to improve the identified model. The second method deals with the model in the real Schur or modal form, reassigns a subset of system poles, and adjusts the columns (rows) of the input (output) influence matrix using a nonlinear optimizer. The third method also optimizes a subset of poles, but the input and output influence matrices are refined at every optimization step through least-squares procedures.

  4. Active low-frequency vertical vibration isolation system for precision measurements

    NASA Astrophysics Data System (ADS)

    Wu, Kang; Li, Gang; Hu, Hua; Wang, Lijun

    2017-01-01

    Low-frequency vertical vibration isolation systems play important roles in precision measurements to reduce seismic and environmental vibration noise. Several types of active vibration isolation systems have been developed. However, few researches focus on how to optimize the test mass install position in order to improve the vibration transmissibility. An active low-frequency vertical vibration isolation system based on an earlier instrument, the Super Spring, is designed and implemented. The system, which is simple and compact, consists of two stages: a parallelogram-shaped linkage to ensure vertical motion, and a simple spring-mass system. The theoretical analysis of the vibration isolation system is presented, including terms erroneously ignored before. By carefully choosing the mechanical parameters according to the above analysis and using feedback control, the resonance frequency of the system is reduced from 2.3 to 0.03 Hz, a reduction by a factor of more than 75. The vibration isolation system is installed as an inertial reference in an absolute gravimeter, where it improved the scatter of the absolute gravity values by a factor of 5. The experimental results verifies the improved performance of the isolation system, making it particularly suitable for precision experiments. The improved vertical vibration isolation system can be used as a prototype for designing high-performance active vertical isolation systems. An improved theoretical model of this active vibration isolation system with beam-pivot configuration is proposed, providing fundamental guidelines for vibration isolator design and assembling.

  5. Analysis of secured Optical Orthogonal Frequency Division Multiplexed System

    NASA Astrophysics Data System (ADS)

    Gill, Harsimranjit Singh; Bhatia, Kamaljit Singh; Gill, Sandeep Singh

    2017-05-01

    In this paper, security issues for optical orthogonal frequency division multiplexed (OFDM) systems are emphasized. The encryption has been done on the data of coded OFDM symbols using data encryption standard (DES) algorithm before transmitting through the fiber. The results obtained justify that the DES provides better security to the input data without further bandwidth requirement. The data is transmitted to a distance of 1,000 km in a single-mode fiber with 16-quadrature amplitude modulation. The peak-to-average power ratio and optical signal-to-noise ratio of secure coded OFDM signal is fairly better than the conventional OFDM signal.

  6. Highly sensitive passive radio frequency identification based sensor systems.

    PubMed

    Wissenwasser, J; Vellekoop, M; Heer, R

    2010-02-01

    A novel platform for sensor applications based on radio frequency (rf) identification technology, where passive tags are powered by the rf-field of a reader, is presented. The sophisticated energy harvesting system of the tag enables a blanking of the rf-field for a defined period, while supplying the tag electronics with a highly stable voltage and a power of 25 mW for 100 ms. During this time, span measurements can be performed without interferences of the rf-field. The presented tags work without batteries and are designed for impedance measurements on microbiological cell cultures under physiological relevant conditions as well as in harsh environments.

  7. Highly sensitive passive radio frequency identification based sensor systems

    NASA Astrophysics Data System (ADS)

    Wissenwasser, J.; Vellekoop, M.; Heer, R.

    2010-02-01

    A novel platform for sensor applications based on radio frequency (rf) identification technology, where passive tags are powered by the rf-field of a reader, is presented. The sophisticated energy harvesting system of the tag enables a blanking of the rf-field for a defined period, while supplying the tag electronics with a highly stable voltage and a power of 25 mW for 100 ms. During this time, span measurements can be performed without interferences of the rf-field. The presented tags work without batteries and are designed for impedance measurements on microbiological cell cultures under physiological relevant conditions as well as in harsh environments.

  8. SIRU development. Volume 1: System development

    NASA Technical Reports Server (NTRS)

    Gilmore, J. P.; Cooper, R. J.

    1973-01-01

    A complete description of the development and initial evaluation of the Strapdown Inertial Reference Unit (SIRU) system is reported. System development documents the system mechanization with the analytic formulation for fault detection and isolation processing structure; the hardware redundancy design and the individual modularity features; the computational structure and facilities; and the initial subsystem evaluation results.

  9. Control of drug release from capsules using high frequency energy transmission systems.

    PubMed

    Gröning, R; Bensmann, H; Müller, R S

    2008-11-19

    In the present investigations new drug delivery systems have been developed, which are controlled by a computer and a high frequency energy transmission system. The capsules consist of a drug reservoir, a high frequency receiver, a gas generating section and a piston to pump a drug solution or drug suspension out of the reservoir. Mechanical energy is generated inside the capsule through electrolysis, if a 27 MHz high frequency field is in resonance with the receiver inside the capsule. Two different miniaturised oscillatory circuits were constructed, which act as the receivers in the capsules. Tramadol was used in release experiments as a model drug. Delayed and pulsed release profiles were obtained. A computer-controlled system was constructed, in which the programmed release profiles are compared with the actual release of the drug.

  10. Power Systems Development Facility

    SciTech Connect

    2003-07-01

    This report discusses Test Campaign TC12 of the Kellogg Brown & Root, Inc. (KBR) Transport Gasifier train with a Siemens Westinghouse Power Corporation (SW) particle filter system at the Power Systems Development Facility (PSDF) located in Wilsonville, Alabama. The Transport Gasifier is an advanced circulating fluidized-bed reactor designed to operate as either a combustor or a gasifier using a particulate control device (PCD). While operating as a gasifier, either air or oxygen can be used as the oxidant. Test run TC12 began on May 16, 2003, with the startup of the main air compressor and the lighting of the gasifier start-up burner. The Transport Gasifier operated until May 24, 2003, when a scheduled outage occurred to allow maintenance crews to install the fuel cell test unit and modify the gas clean-up system. On June 18, 2003, the test run resumed when operations relit the start-up burner, and testing continued until the scheduled end of the run on July 14, 2003. TC12 had a total of 733 hours using Powder River Basin (PRB) subbituminous coal. Over the course of the entire test run, gasifier temperatures varied between 1,675 and 1,850 F at pressures from 130 to 210 psig.

  11. A modular multiple use system for precise time and frequency measurement and distribution

    NASA Technical Reports Server (NTRS)

    Reinhardt, V. S.; Adams, W. S.; Lee, G. M.; Bush, R. L.

    1978-01-01

    A modular CAMAC based system is described which was developed to meet a variety of precise time and frequency measurement and distribution needs. The system was based on a generalization of the dual mixer concept. By using a 16 channel 100 ns event clock, the system can intercompare the phase of 16 frequency standards with subpicosecond resolution. The system has a noise floor of 26 fs and a long term stability on the order of 1 ps or better. The system also used a digitally controlled crystal oscillator in a control loop to provide an offsettable 5 MHz output with subpicosecond phase tracking capability. A detailed description of the system is given including theory of operation and performance. A method to improve the performance of the dual mixer technique is discussed when phase balancing of the two input ports cannot be accomplished.

  12. Advanced Dewatering Systems Development

    SciTech Connect

    R.H. Yoon; G.H. Luttrell

    2008-07-31

    A new fine coal dewatering technology has been developed and tested in the present work. The work was funded by the Solid Fuels and Feedstocks Grand Challenge PRDA. The objective of this program was to 'develop innovative technical approaches to ensure a continued supply of environmentally sound solid fuels for existing and future combustion systems with minimal incremental fuel cost.' Specifically, this solicitation is aimed at developing technologies that can (i) improve the efficiency or economics of the recovery of carbon when beneficiating fine coal from both current production and existing coal slurry impoundments and (ii) assist in the greater utilization of coal fines by improving the handling characteristics of fine coal via dewatering and/or reconstitution. The results of the test work conducted during Phase I of the current project demonstrated that the new dewatering technologies can substantially reduce the moisture from fine coal, while the test work conducted during Phase II successfully demonstrated the commercial viability of this technology. It is believed that availability of such efficient and affordable dewatering technology is essential to meeting the DOE's objectives.

  13. Development and application of a low-frequency FBG vibration sensor

    NASA Astrophysics Data System (ADS)

    Nan, Qiu-ming

    2010-10-01

    Dynamic monitoring is part of bridge structural health monitoring. Real-time and online monitoring for bridge's dynamic performance is an important technology means for model updating, damage detection of structure and security evaluation of bridge. Nowadays dynamic monitoring system is generally installed on new long-span bridges. Vibration sensor is key part of the technology means. Vibration of a large-scale bridge belongs to low frequency one, but traditional electromagnetic vibration sensors are restricted for use in the field due to such defects as signal unable to long distance transmission, hard to measure ultra-low frequency vibration, so it is inevitable and imminent to develop a novel-type vibration sensor instead of them. Aiming at the above-mentioned problems, the author in the paper develops a low-frequency vibration sensor with double-cantilever beam structure, based on fiber Bragg grating (FBG) and matching filtering demodulation. Some experiments are done to study its sensing properties and the results indicate that it has good temperature compensation, its natural frequency is about 35Hz, measurement bandwidth from 0.1Hz to 20Hz, sensitivity is 1000mv/g or so, linearity degree is over 0.9992, repeatability is superior to 2.4%, acceleration measurement range is 1g, and cross anti-interference is 5.6%. Such sensors have been successfully used on Wuhan Tianxingzhou Yangtze River Bridge(WTYRB). The most transmission distance of measurement signal is 10km or so and the lowest measurement frequency is 0.24 Hz. The application results show it can detect accurately dynamic properties of vital areas of the bridge and can meet the demands for dynamic measurement. To sum up, the sensor developed in the paper can overcome the shortcomings of electromagnetic sensors and has very good sensing properties, so it is very suitable to be used for low-frequency vibration measurement.

  14. H- radio frequency source development at the Spallation Neutron Source

    SciTech Connect

    Welton, Robert F; Pennisi, Terry R; Roseberry, Ron T; Stockli, Martin P

    2012-01-01

    The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent {approx}38 mA peak current in the linac and an availability of {approx}90%. H{sup -} beam pulses ({approx}1 ms, 60 Hz) are produced by a Cs-enhanced, multicusp ion source closely coupled with an electrostatic low energy beam transport (LEBT), which focuses the 65 kV beam into a radio frequency quadrupole accelerator. The source plasma is generated by RF excitation (2 MHz, {approx}60 kW) of a copper antenna that has been encased with a thickness of {approx}0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of {approx}99%. Recent increases in duty-factor and RF power have made antenna failures a leading cause of downtime. This report first identifies the physical mechanism of antenna failure from a statistical inspection of {approx}75 antennas which ran at the SNS, scanning electron microscopy studies of antenna surface, and cross sectional cuts and analysis of calorimetric heating measurements. Failure mitigation efforts are then described which include modifying the antenna geometry and our acceptance/installation criteria. Progress and status of the development of the SNS external antenna source, a long-term solution to the internal antenna problem, are then discussed. Currently, this source is capable of delivering comparable beam currents to the baseline source to the SNS and, an earlier version, has briefly demonstrated unanalyzed currents up to {approx}100 mA (1 ms, 60 Hz) on the test stand. In particular, this paper discusses plasma ignition (dc and RF plasma guns), antenna reliability, magnet overheating, and insufficient beam persistence.

  15. H- radio frequency source development at the Spallation Neutron Source.

    PubMed

    Welton, R F; Dudnikov, V G; Gawne, K R; Han, B X; Murray, S N; Pennisi, T R; Roseberry, R T; Santana, M; Stockli, M P; Turvey, M W

    2012-02-01

    The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent ∼38 mA peak current in the linac and an availability of ∼90%. H(-) beam pulses (∼1 ms, 60 Hz) are produced by a Cs-enhanced, multicusp ion source closely coupled with an electrostatic low energy beam transport (LEBT), which focuses the 65 kV beam into a radio frequency quadrupole accelerator. The source plasma is generated by RF excitation (2 MHz, ∼60 kW) of a copper antenna that has been encased with a thickness of ∼0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of ∼99%. Recent increases in duty-factor and RF power have made antenna failures a leading cause of downtime. This report first identifies the physical mechanism of antenna failure from a statistical inspection of ∼75 antennas which ran at the SNS, scanning electron microscopy studies of antenna surface, and cross sectional cuts and analysis of calorimetric heating measurements. Failure mitigation efforts are then described which include modifying the antenna geometry and our acceptance∕installation criteria. Progress and status of the development of the SNS external antenna source, a long-term solution to the internal antenna problem, are then discussed. Currently, this source is capable of delivering comparable beam currents to the baseline source to the SNS and, an earlier version, has briefly demonstrated unanalyzed currents up to ∼100 mA (1 ms, 60 Hz) on the test stand. In particular, this paper discusses plasma ignition (dc and RF plasma guns), antenna reliability, magnet overheating, and insufficient beam persistence.

  16. H- radio frequency source development at the Spallation Neutron Sourcea)

    NASA Astrophysics Data System (ADS)

    Welton, R. F.; Dudnikov, V. G.; Gawne, K. R.; Han, B. X.; Murray, S. N.; Pennisi, T. R.; Roseberry, R. T.; Santana, M.; Stockli, M. P.; Turvey, M. W.

    2012-02-01

    The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent ˜38 mA peak current in the linac and an availability of ˜90%. H- beam pulses (˜1 ms, 60 Hz) are produced by a Cs-enhanced, multicusp ion source closely coupled with an electrostatic low energy beam transport (LEBT), which focuses the 65 kV beam into a radio frequency quadrupole accelerator. The source plasma is generated by RF excitation (2 MHz, ˜60 kW) of a copper antenna that has been encased with a thickness of ˜0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of ˜99%. Recent increases in duty-factor and RF power have made antenna failures a leading cause of downtime. This report first identifies the physical mechanism of antenna failure from a statistical inspection of ˜75 antennas which ran at the SNS, scanning electron microscopy studies of antenna surface, and cross sectional cuts and analysis of calorimetric heating measurements. Failure mitigation efforts are then described which include modifying the antenna geometry and our acceptance/installation criteria. Progress and status of the development of the SNS external antenna source, a long-term solution to the internal antenna problem, are then discussed. Currently, this source is capable of delivering comparable beam currents to the baseline source to the SNS and, an earlier version, has briefly demonstrated unanalyzed currents up to ˜100 mA (1 ms, 60 Hz) on the test stand. In particular, this paper discusses plasma ignition (dc and RF plasma guns), antenna reliability, magnet overheating, and insufficient beam persistence.

  17. System identification and controller design using experimental frequency response data

    NASA Technical Reports Server (NTRS)

    Irwin, R. Dennis

    1990-01-01

    Recent findings from modeling and controller design for the NASA-Marshall Single Structure Control Facility have raised questions regarding the ability of modern control design techniques and modern modeling techniques to deal effectively with the stringent modeling and control design requirements of Large Space Structure Control. A brief and general discussion is presented of the results of studies into the modeling and control issues performed under sponsorship of the NASA/ASEE Summer Faculty Fellowship Program. Several issues are addressed. The first is a study of a modeling technique based on least squares identification of individual transfer functions from measured frequency response data. The second is a study of multiobjective optimization techniques applied to the modeling, or system identification, problem. The third issue is a study into the question of whether multiobjective optimization approaches can be effectively used for control system design using only frequency response data, thereby bypassing the difficult modeling problem. The last issue studied involves the resolution of seeming discrepancies between predicted and measured control computer time delays in the Single Structure Control Facility.

  18. Experimental laboratory system to generate high frequency test environments

    SciTech Connect

    Gregory, D.L.; Paez, T.L.

    1991-01-01

    This is an extension of two previous analytical studies to investigate a technique for generating high frequency, high amplitude vibration environments. These environments are created using a device attached to a common vibration exciter that permits multiple metal on metal impacts driving a test surface. These analytical studies predicted that test environments with an energy content exceeding 10 kHz could be achieved using sinusoidal and random shaker excitations. The analysis predicted that chaotic vibrations yielding random like test environments could be generated from sinusoidal inputs. In this study, a much simplified version of the proposed system was fabricated and tested in the laboratory. Experimental measurements demonstrate that even this simplified system, utilizing a single impacting object, can generate environments on the test surface with significant frequency content in excess of 40 kHz. Results for sinusoidal shaker inputs tuned to create chaotic impact response are shown along with the responses due to random vibration shaker inputs. The experiments and results are discussed. 4 refs., 5 figs.

  19. Fault detection in rotor bearing systems using time frequency techniques

    NASA Astrophysics Data System (ADS)

    Chandra, N. Harish; Sekhar, A. S.

    2016-05-01

    Faults such as misalignment, rotor cracks and rotor to stator rub can exist collectively in rotor bearing systems. It is an important task for rotor dynamic personnel to monitor and detect faults in rotating machinery. In this paper, the rotor startup vibrations are utilized to solve the fault identification problem using time frequency techniques. Numerical simulations are performed through finite element analysis of the rotor bearing system with individual and collective combinations of faults as mentioned above. Three signal processing tools namely Short Time Fourier Transform (STFT), Continuous Wavelet Transform (CWT) and Hilbert Huang Transform (HHT) are compared to evaluate their detection performance. The effect of addition of Signal to Noise ratio (SNR) on three time frequency techniques is presented. The comparative study is focused towards detecting the least possible level of the fault induced and the computational time consumed. The computation time consumed by HHT is very less when compared to CWT based diagnosis. However, for noisy data CWT is more preferred over HHT. To identify fault characteristics using wavelets a procedure to adjust resolution of the mother wavelet is presented in detail. Experiments are conducted to obtain the run-up data of a rotor bearing setup for diagnosis of shaft misalignment and rotor stator rubbing faults.

  20. A versatile power converter for high-frequency link systems

    NASA Technical Reports Server (NTRS)

    Sood, Pradeep K.; Lipo, Thomas A.; Hansen, Irving G.

    1988-01-01

    A single-phase HF link appears to be an attractive alternative to the dc link commonly used in power conversion systems. Here, a power converter suitable for one-step conversion of the single-phase HF link voltage to the three-phase LF voltages typically required for interfacing with system sources and loads is proposed. The converter utilizes zero-voltage switching principles to minimize switching losses and an easy-to-implement technique of pulse-density modulation for the control of the amplitude, frequency, and waveshape of the synthesized LF signals. Adaptation of the proposed topology for power conversion to single-phase ac and dc voltage or current outputs is shown to be straightforward. The feasibility of the proposed power circuit and the control technique has been experimentally verified.

  1. Discrete pulse modulation strategies for high-frequency inverter systems

    NASA Astrophysics Data System (ADS)

    Venkataramanan, Giri; Divan, Deepakraj M.; Jahns, Thomas M.

    1993-07-01

    High-performance, high-frequency inverter systems for UPS (uninterruptible power system) applications cannot be easily realized using conventional hard-switched PWM inverter topologies. Adoption of typical soft-switched inverters such as the resonant dc link inverter require the use of discrete pulse modulation strategies. New controller structures are necessary to cope with stringent voltage regulation and distortion constraints in the presence of unbalanced and nonlinear loads. A controller that utilizes a load current feedforward strategy with a cost function current regulator to achieve excellent transient performance characteristics is presented. Voltage regulation is ensured using a synchronous frame regulator. Detailed simulation and experimental results verifying the concepts are presented. Although this work focuses on soft-switching inverters, the control concepts can be applied to conventional hard-switching inverters as well.

  2. SIT-5 system development.

    NASA Technical Reports Server (NTRS)

    Hyman, J., Jr.

    1972-01-01

    A 5-cm structurally integrated ion thruster (SIT-5) has been developed for attitude control and stationkeeping of synchronous satellites. With two-dimension thrust-vectoring grids, a first generation unit has demonstrated a thrust of 0.56 mlb at a beam voltage of 1200 V, total mass efficiency of 64%, and electrical efficiency of 46.8%. Structural integrity is demonstrated with a dielectric-coated grid for shock (30 G), sinusoidal (9 G), and random (19.9 G rms) accelerations. System envelope is 31.8 cm long by 13.9 cm flange bolt circle, with a mass of 8.5 kg, including 6.2 kg mercury propellant. Characteristics of a second-generation unit indicate significant performance gains.

  3. System and method for tuning adjusting the central frequency of a laser while maintaining frequency stabilization to an external reference

    NASA Technical Reports Server (NTRS)

    Livas, Jeffrey (Inventor); Thorpe, James I. (Inventor); Numata, Kenji (Inventor)

    2011-01-01

    A method and system for stabilizing a laser to a frequency reference with an adjustable offset. The method locks a sideband signal generated by passing an incoming laser beam through the phase modulator to a frequency reference, and adjusts a carrier frequency relative to the locked sideband signal by changing a phase modulation frequency input to the phase modulator. The sideband signal can be a single sideband (SSB), dual sideband (DSB), or an electronic sideband (ESB) signal. Two separate electro-optic modulators can produce the DSB signal. The two electro-optic modulators can be a broadband modulator and a resonant modulator. With a DSB signal, the method can introduce two sinusoidal phase modulations at the phase modulator. With ESB signals, the method can further drive the optical phase modulator with an electrical signal with nominal frequency OMEGA(sub 1) that is phase modulated at a frequency OMEGA(sub 2)

  4. Power Systems Development Facility

    SciTech Connect

    Southern Company Services

    2004-04-30

    This report discusses Test Campaign TC15 of the Kellogg Brown & Root, Inc. (KBR) Transport Gasifier train with a Siemens Power Generation, Inc. (SPG) particle filter system at the Power Systems Development Facility (PSDF) located in Wilsonville, Alabama. The Transport Gasifier is an advanced circulating fluidized-bed reactor designed to operate as either a combustor or gasifier using a particulate control device (PCD). While operating as a gasifier, either air or oxygen can be used as the oxidant. Test run TC15 began on April 19, 2004, with the startup of the main air compressor and the lighting of the gasifier startup burner. The Transport Gasifier was shutdown on April 29, 2004, accumulating 200 hours of operation using Powder River Basin (PRB) subbituminous coal. About 91 hours of the test run occurred during oxygen-blown operations. Another 6 hours of the test run was in enriched-air mode. The remainder of the test run, approximately 103 hours, took place during air-blown operations. The highest operating temperature in the gasifier mixing zone mostly varied from 1,800 to 1,850 F. The gasifier exit pressure ran between 200 and 230 psig during air-blown operations and between 110 and 150 psig in oxygen-enhanced air operations.

  5. POWER SYSTEMS DEVELOPMENT FACILITY

    SciTech Connect

    Unknown

    2002-11-01

    This report discusses test campaign GCT4 of the Kellogg Brown & Root, Inc. (KBR) transport reactor train with a Siemens Westinghouse Power Corporation (Siemens Westinghouse) particle filter system at the Power Systems Development Facility (PSDF) located in Wilsonville, Alabama. The transport reactor is an advanced circulating fluidized-bed reactor designed to operate as either a combustor or a gasifier using one of two possible particulate control devices (PCDs). The transport reactor was operated as a pressurized gasifier during GCT4. GCT4 was planned as a 250-hour test run to continue characterization of the transport reactor using a blend of several Powder River Basin (PRB) coals and Bucyrus limestone from Ohio. The primary test objectives were: Operational Stability--Characterize reactor loop and PCD operations with short-term tests by varying coal-feed rate, air/coal ratio, riser velocity, solids-circulation rate, system pressure, and air distribution. Secondary objectives included the following: Reactor Operations--Study the devolatilization and tar cracking effects from transient conditions during transition from start-up burner to coal. Evaluate the effect of process operations on heat release, heat transfer, and accelerated fuel particle heat-up rates. Study the effect of changes in reactor conditions on transient temperature profiles, pressure balance, and product gas composition. Effects of Reactor Conditions on Synthesis Gas Composition--Evaluate the effect of air distribution, steam/coal ratio, solids-circulation rate, and reactor temperature on CO/CO{sub 2} ratio, synthesis gas Lower Heating Value (LHV), carbon conversion, and cold and hot gas efficiencies. Research Triangle Institute (RTI) Direct Sulfur Recovery Process (DSRP) Testing--Provide syngas in support of the DSRP commissioning. Loop Seal Operations--Optimize loop seal operations and investigate increases to previously achieved maximum solids-circulation rate.

  6. High Frequency Mechanical Pyroshock Simulations for Payload Systems

    SciTech Connect

    BATEMAN,VESTA I.; BROWN,FREDERICK A.; CAP,JEROME S.; NUSSER,MICHAEL A.

    1999-12-15

    Sandia National Laboratories (SNL) designs mechanical systems with components that must survive high frequency shock environments including pyrotechnic shock. These environments have not been simulated very well in the past at the payload system level because of weight limitations of traditional pyroshock mechanical simulations using resonant beams and plates. A new concept utilizing tuned resonators attached to the payload system and driven with the impact of an airgun projectile allow these simulations to be performed in the laboratory with high precision and repeatability without the use of explosives. A tuned resonator has been designed and constructed for a particular payload system. Comparison of laboratory responses with measurements made at the component locations during actual pyrotechnic events show excellent agreement for a bandwidth of DC to 4 kHz. The bases of comparison are shock spectra. This simple concept applies the mechanical pyroshock simulation simultaneously to all components with the correct boundary conditions in the payload system and is a considerable improvement over previous experimental techniques and simulations.

  7. Design of variable frequency endoscope ultrasonic digital imaging system

    NASA Astrophysics Data System (ADS)

    Li, Ya-nan; Bai, Bao-ping; Chen, Xiao-dong; Zhao, Qiang; Deng, Hao-ran; Wang, Yi; Yu, Dao-yin

    2013-12-01

    This paper presented a real-time endoscope ultrasonic digital imaging system, which was based on FPGA and applied for gastrointestinal examination. Four modules, scan-line data processing module, coordinate transformation and interpolation algorithm module, cache reading and writing control module and transmitting and receiving control module were included in this FPGA based system. Through adopting different frequency ultrasound probes in a single insertion of endoscope, the system showed a high speed data processing mechanism capable of achieving images with various display effects. A high-precision modified coordinate calibration CORDIC (HMCC-CORDIC) algorithm was employed to realize coordinate transformation and interpolation simultaneously, while the precision and reliability of the algorithm could be greatly improved through utilizing the pipeline structure based on temporal logic. Also, system real-time control by computer could be achieved through operating under the condition of USB2.0 interface. The corresponding experimental validations proved the feasibility and the correctness of the proper data processing mechanism, the HMCC-CORDIC algorithm and the USB real-time control. Finally, the specific experimental sample, a tissue mimicking phantom, was imaged in real-time (25 frames per second) by an endoscope ultrasonic imaging system with image size 1024×1024. The requirements for clinical examination could be well satisfied with the imaging parameters discussed above.

  8. System and method for constructing filters for detecting signals whose frequency content varies with time

    DOEpatents

    Qian, Shie; Dunham, Mark E.

    1996-01-01

    A system and method for constructing a bank of filters which detect the presence of signals whose frequency content varies with time. The present invention includes a novel system and method for developing one or more time templates designed to match the received signals of interest and the bank of matched filters use the one or more time templates to detect the received signals. Each matched filter compares the received signal x(t) with a respective, unique time template that has been designed to approximate a form of the signals of interest. The robust time domain template is assumed to be of the order of w(t)=A(t)cos{2.pi..phi.(t)} and the present invention uses the trajectory of a joint time-frequency representation of x(t) as an approximation of the instantaneous frequency function {.phi.'(t). First, numerous data samples of the received signal x(t) are collected. A joint time frequency representation is then applied to represent the signal, preferably using the time frequency distribution series (also known as the Gabor spectrogram). The joint time-frequency transformation represents the analyzed signal energy at time t and frequency .function., P(t,f), which is a three-dimensional plot of time vs. frequency vs. signal energy. Then P(t,f) is reduced to a multivalued function f(t), a two dimensional plot of time vs. frequency, using a thresholding process. Curve fitting steps are then performed on the time/frequency plot, preferably using Levenberg-Marquardt curve fitting techniques, to derive a general instantaneous frequency function .phi.'(t) which best fits the multivalued function f(t), a trajectory of the joint time-frequency domain representation of x(t). Integrating .phi.'(t) along t yields .phi.(t), which is then inserted into the form of the time template equation. A suitable amplitude A(t) is also preferably determined. Once the time template has been determined, one or more filters are developed which each use a version or form of the time template.

  9. A distributed fiber optic sensor system for dike monitoring using Brillouin optical frequency domain analysis

    NASA Astrophysics Data System (ADS)

    Nöther, Nils; Wosniok, Aleksander; Krebber, Katerina; Thiele, Elke

    2008-03-01

    We report on the development of a complete system for spatially resolved detection of critical soil displacement in river embankments. The system uses Brillouin frequency domain analysis (BOFDA) for distributed measurement of strain in silica optical fibers. Our development consists of the measurement unit, an adequate coating for the optical fibers and a technique to integrate the coated optical fibers into geotextiles as they are commonly used in dike construction. We present several laboratory and field tests that prove the capability of the system to detect areas of soil displacement as small as 2 meters. These are the first tests of truly distributed strain measurements on optical fibers embedded into geosynthetics.

  10. A method of developing frequency encoded multi-bit optical data comparator using semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Garai, Sisir Kumar

    2011-02-01

    Optical data comparator is the part and parcel of arithmetic and logical unit of any optical data processor and it is working as a building block in a larger optical circuit, as an optical switch in all optical header processing and optical packet switching based all optical telecommunications system. In this article the author proposes a method of developing an all optical single bit comparator unit and subsequently extending the proposal to develop a n-bit comparator exploiting the nonlinear rotation of the state of polarization of the probe beam in semiconductor optical amplifier (SOA). Here the dataset to be compared are taken in frequency encoded/decoded form throughout the communication. The major advantages of frequency encoding over all other conventional techniques are that as the frequency of any signal is fundamental one so it can preserve its identity throughout the communication of optical signal and minimizes the probability of bit error problem. For frequency routing purpose optical add/drop multiplexer (ADM) is used which not only route the pump beams properly but also to amplify the pump beams efficiently. Switching speed of 'MZI-SOA switch' as well as SOA based switches are very fast with good on-off contrast ratio and as a result it is possible to obtain very fast action of optical data comparator.

  11. Development of a frequency-separated knob with variable change rates by rotation speed.

    PubMed

    Kim, Huhn; Ham, Dong-Han

    2014-11-01

    The principle of frequency separation is a design method to display different information or feedback in accordance with the frequency of interaction between users and systems. This principle can be usefully applied to the design of knobs. Particularly, their rotation speed can be a meaningful criterion for applying the principle. Hence a knob can be developed, which shows change rates varying depending on its rotation speed. Such a knob would be more efficient than conventional knobs with constant change rate. We developed a prototype of frequency-separated knobs that has different combinations of the number of rotation speed steps and the size of the variation of change rate. With this prototype, we conducted an experiment to examine whether a speed frequency-separated knob enhances users' task performance. The results showed that the newly designed knob was effective in enhancing task performance, and that task efficiency was the best when its change rate increases exponentially and its rotation speed has three steps. We conducted another experiment to investigate how a more rapid exponential increase of change rate and a more number of steps of rotation speed influence users' task performance. The results showed that merely increasing both the size of the variation of change rates and the number of speed steps did not result in better task performance. Although two experimental results cannot easily be generalized to other contexts, they still offer practical information useful for designing a speed frequency-separated knob in various consumer electronics and control panels of industrial systems. Copyright © 2014 Elsevier Ltd and The Ergonomics Society. All rights reserved.

  12. Analytical simulation of water system capacity reliability, 1. Modified frequency-duration analysis

    NASA Astrophysics Data System (ADS)

    Hobbs, Benjamin F.; Beim, Gina K.

    1988-09-01

    The problem addressed is the computation of the unavailability and expected unserved demand of a water supply system having random demand, finished water storage, and unreliable capacity components. Examples of such components include pumps, treatment plants, and aqueducts. Modified frequency-duration analysis estimates these reliability statistics by, first, calculating how often demand exceeds available capacity and, second, comparing the amount of water in storage with how long such capacity deficits last. This approach builds upon frequency-duration methods developed by the power industry for analyzing generation capacity deficits. Three versions of the frequency-duration approach are presented. Two yield bounds to system unavailability and unserved demand and the third gives an estimate of their true values between those bounds.

  13. Low-frequency oscillation in a narrow vibrated granular system

    NASA Astrophysics Data System (ADS)

    Oyarte Gálvez, Loreto; van der Meer, Devaraj

    2015-11-01

    The analogy of the behaviour of granular materials with that of fluids has motivated much appealing research. An important example is a vertically shaken granular bed which exhibits fluid-like behavior, such as the Leidenfrost effect where a dense layer of grains floats on top of a gaseous layer, just like when a liquid droplet floats on its own vapour above a hot plate. When the shaking energy is increased the granular bed transits from the Leidenfrost to the convection state, for which a precursor is expected in the form of an oscillation of the bed as a whole. This precursor was observed numerically like an oscillation in the motion of the dense part, where the frequency of this oscillation is much lower than the frequency of the injected energy, and appears more relevant when the system is getting closer to the convective state. We built a setup that permits the observation of the granular Leidenfrost effect for a wide range of driving parameters. More specifically, a monodisperse granular material is contained in a transparent box and vertically shaken, and a fast camera is used to study its dynamics. The presence of a LFO is directly measured by images analysis and shows a good agreement with the previous numerical and experimental works.

  14. Development Of Frequency Transfer Via Optical Fiber Link at NICT

    DTIC Science & Technology

    2008-12-01

    al., 2006 “Comparison between frequency standards in Europe and the USA at the 10-15 uncertainty level,” Metrologia , 43, 109-120. [4] H. Kiuchi, T...M. Hosokawa, 2008, “Evaluation of caesium atomic fountain NICT-CsF1,” Metrologia , 45, 139-148. [12] M. Kumagai, H. Ito, G. Santarelli, C. Locke, J

  15. Design, development, and acceleration trials of radio-frequency quadrupole.

    PubMed

    Rao, S V L S; Jain, Piyush; Pande, Rajni; Roy, Shweta; Mathew, Jose V; Kumar, Rajesh; Pande, Manjiri; Krishnagopal, S; Gupta, S K; Singh, P

    2014-04-01

    A deuteron radio frequency quadrupole (RFQ) accelerator has been designed, fabricated, and tested at BARC, which will be used for neutron generation. The RFQ operates at a frequency of 350 MHz and needs an inter-vane voltage of 44 kV to accelerate the deuteron beam to 400 keV within a length of 1.03 m. The error analysis shows that the offset of two opposite vanes in the same direction by 100 μm leads to a change in resonant frequency by 1.3 MHz and a significant change of fields in the quadrants (∼±40% with respect to average field). From the 3D analysis, we have observed that the unwanted dipole mode frequencies are very near to the quadrupole mode frequency which will make structure sensitive to the perturbations. In order to move the dipole modes away from the quadrupole modes, we have used the dipole stabilizer rods. The 5 wire transmission line theory was used to study the perturbative analysis of the RFQ and based on this a computer program has been written to tune the cavity to get required field distribution. Based on these studies, a 1.03 m long RFQ made of OFE copper has been fabricated and tested. Even though the RFQ was designed for deuteron (D(+)) beam, we tested it by accelerating both the proton (H(+)) and D(+) beams. The RFQ was operated in pulsed mode and accelerated both H(+) and D(+) beams to designed values of 200 and 400 keV, respectively. The measured parameters are in good agreement with the designed values validating our simulations and fabrication processes. In this paper, simulations, RF measurements, and beam commissioning results are presented.

  16. Design, development, and acceleration trials of radio-frequency quadrupole

    SciTech Connect

    Rao, S. V. L. S. Jain, Piyush; Pande, Rajni; Roy, Shweta; Mathew, Jose V.; Kumar, Rajesh; Pande, Manjiri; Krishnagopal, S.; Gupta, S. K.; Singh, P.

    2014-04-15

    A deuteron radio frequency quadrupole (RFQ) accelerator has been designed, fabricated, and tested at BARC, which will be used for neutron generation. The RFQ operates at a frequency of 350 MHz and needs an inter-vane voltage of 44 kV to accelerate the deuteron beam to 400 keV within a length of 1.03 m. The error analysis shows that the offset of two opposite vanes in the same direction by 100 μm leads to a change in resonant frequency by 1.3 MHz and a significant change of fields in the quadrants (∼±40% with respect to average field). From the 3D analysis, we have observed that the unwanted dipole mode frequencies are very near to the quadrupole mode frequency which will make structure sensitive to the perturbations. In order to move the dipole modes away from the quadrupole modes, we have used the dipole stabilizer rods. The 5 wire transmission line theory was used to study the perturbative analysis of the RFQ and based on this a computer program has been written to tune the cavity to get required field distribution. Based on these studies, a 1.03 m long RFQ made of OFE copper has been fabricated and tested. Even though the RFQ was designed for deuteron (D{sup +}) beam, we tested it by accelerating both the proton (H{sup +}) and D{sup +} beams. The RFQ was operated in pulsed mode and accelerated both H{sup +} and D{sup +} beams to designed values of 200 and 400 keV, respectively. The measured parameters are in good agreement with the designed values validating our simulations and fabrication processes. In this paper, simulations, RF measurements, and beam commissioning results are presented.

  17. Method for determiantion of the frequency-contrast characteristics of electronic-optic systems

    NASA Astrophysics Data System (ADS)

    Mardirossian, Garo; Zhekov, Zhivko

    The frequency-contrast characteristics is an important criterion to judge the quality of electronic-optic systems, which boast an increasing application in space research, astronomy, martial art etc. The paper provides a brief description of the methods for determining the frequency-contrast characteristics of optic systems, developed at the Space Research Institute of the Bulgarian Academy of Science. The suggested methods have been used to develop a couple of electronic-optic systems participated in the designed ground-based and aerospace scientific-research equipment. Based on the obtained practical results, the conclusion was made that the methods provide to obtain sufficiently precise data, which coincide well with the results, obtained when using other methods.

  18. Supervisory development system

    SciTech Connect

    Arthur, P.L.; Norlach, D.L.

    1985-03-01

    The Supervisory Development System (SDS) consists of a series of training inputs which are designed to meet the training needs of a newly appointed manufacturing supervisor. Each training component has been carefully designed to insure that a new supervisor receives training which is job related and coincides with growth on the job. The SDS is initiated with appointment of the new supervisor and extends to eighteen months after appointment. Mobil's Marketing and Refining Division's U.S. operations are headquartered in Fairfax, Virginia. The Manufacturing function has five refineries located in Beaumont, Texas; Ferndale, Washington; Joliet, Illinois; Paulsboro, New Jersey; and Torrance, California. New first-line supervisors are appointed at a rate of about seven per year in one refinery and up to fifteen or twenty per year in others. First-line supervisors in Mobil's refineries are similar to those found in other refineries. To the hourly rate or blue collar employee, the first-level supervisor represents the company. They are responsible for providing work direction, improving performance, and operating efficiently within a safe environment.

  19. Electrochemical system and method for electropolishing superconductive radio frequency cavities

    DOEpatents

    Taylor, E. Jennings; Inman, Maria E.; Hall, Timothy

    2015-04-14

    An electrochemical finishing system for super conducting radio frequency (SCRF) cavities including a low viscosity electrolyte solution that is free of hydrofluoric acid, an electrode in contact with the electrolyte solution, the SCRF cavity being spaced apart from the electrode and in contact with the electrolyte solution and a power source including a first electrical lead electrically coupled to the electrode and a second electrical lead electrically coupled to the cavity, the power source being configured to pass an electric current between the electrode and the workpiece, wherein the electric current includes anodic pulses and cathodic pulses, and wherein the cathodic pulses are interposed between at least some of the anodic pulses. The SCRF cavity may be vertically oriented during the finishing process.

  20. Discrete pulse modulation strategies for high-frequency inverter systems

    SciTech Connect

    Venkataramanan, G. . Dept. of Electrical Engineering); Divan, D.M. . Dept. of Electrical and Computer Engineering); Jahns, T.M. )

    1993-07-01

    High-performance high-frequency inverter systems for UPS applications represent a demanding application that cannot be easily realized using conventional hard-switched PWM inverter topologies. Adoption of typical soft-switched inverters such as the resonant dc link inverter require the use of discrete pulse modulation strategies. New controller structures are necessary to cope with stringent voltage regulation and distortion constraints in the presence of unbalanced and nonlinear loads. This paper presents a controller that utilizes load current feed-forward strategy with a cost function current regulator to achieve excellent transient performance characteristics. Voltage regulation is ensured using a synchronous frame regulator. Detailed simulation and experimental results verifying the concepts are presented. Although this paper focuses on soft-switching inverters, the control concepts can be applied to conventional hard-switching inverters as well.

  1. Relationships Between the Performance of Time/Frequency Standards and Navigation/Communication Systems

    NASA Technical Reports Server (NTRS)

    Hellwig, H.; Stein, S. R.; Walls, F. L.; Kahan, A.

    1978-01-01

    The relationship between system performance and clock or oscillator performance is discussed. Tradeoffs discussed include: short term stability versus bandwidth requirements; frequency accuracy versus signal acquisition time; flicker of frequency and drift versus resynchronization time; frequency precision versus communications traffic volume; spectral purity versus bit error rate, and frequency standard stability versus frequency selection and adjustability. The benefits and tradeoffs of using precise frequency and time signals are various levels of precision and accuracy are emphasized.

  2. System and method for constructing filters for detecting signals whose frequency content varies with time

    DOEpatents

    Qian, S.; Dunham, M.E.

    1996-11-12

    A system and method are disclosed for constructing a bank of filters which detect the presence of signals whose frequency content varies with time. The present invention includes a novel system and method for developing one or more time templates designed to match the received signals of interest and the bank of matched filters use the one or more time templates to detect the received signals. Each matched filter compares the received signal x(t) with a respective, unique time template that has been designed to approximate a form of the signals of interest. The robust time domain template is assumed to be of the order of w(t)=A(t)cos(2{pi}{phi}(t)) and the present invention uses the trajectory of a joint time-frequency representation of x(t) as an approximation of the instantaneous frequency function {phi}{prime}(t). First, numerous data samples of the received signal x(t) are collected. A joint time frequency representation is then applied to represent the signal, preferably using the time frequency distribution series. The joint time-frequency transformation represents the analyzed signal energy at time t and frequency f, P(t,f), which is a three-dimensional plot of time vs. frequency vs. signal energy. Then P(t,f) is reduced to a multivalued function f(t), a two dimensional plot of time vs. frequency, using a thresholding process. Curve fitting steps are then performed on the time/frequency plot, preferably using Levenberg-Marquardt curve fitting techniques, to derive a general instantaneous frequency function {phi}{prime}(t) which best fits the multivalued function f(t). Integrating {phi}{prime}(t) along t yields {phi}{prime}(t), which is then inserted into the form of the time template equation. A suitable amplitude A(t) is also preferably determined. Once the time template has been determined, one or more filters are developed which each use a version or form of the time template. 7 figs.

  3. Random vibration of linear and nonlinear structural systems with singular matrices: A frequency domain approach

    NASA Astrophysics Data System (ADS)

    Kougioumtzoglou, I. A.; Fragkoulis, V. C.; Pantelous, A. A.; Pirrotta, A.

    2017-09-01

    A frequency domain methodology is developed for stochastic response determination of multi-degree-of-freedom (MDOF) linear and nonlinear structural systems with singular matrices. This system modeling can arise when a greater than the minimum number of coordinates/DOFs is utilized, and can be advantageous, for instance, in cases of complex multibody systems where the explicit formulation of the equations of motion can be a nontrivial task. In such cases, the introduction of additional/redundant DOFs can facilitate the formulation of the equations of motion in a less labor intensive manner. Specifically, relying on the generalized matrix inverse theory, a Moore-Penrose (M-P) based frequency response function (FRF) is determined for a linear structural system with singular matrices. Next, relying on the M-P FRF a spectral input-output (excitation-response) relationship is derived in the frequency domain for determining the linear system response power spectrum. Further, the above methodology is extended via statistical linearization to account for nonlinear systems. This leads to an iterative determination of the system response mean vector and covariance matrix. Furthermore, to account for singular matrices, the generalization of a widely utilized formula that facilitates the application of statistical linearization is proved as well. The formula relates to the expectation of the derivatives of the system nonlinear function and is based on a Gaussian response assumption. Several linear and nonlinear MDOF structural systems with singular matrices are considered as numerical examples for demonstrating the validity and applicability of the developed frequency domain methodology.

  4. High Frequency Monitoring System of Groundwater Level in Sheliao

    NASA Astrophysics Data System (ADS)

    Lee, C.; Chia, Y.; Chuang, P.

    2012-12-01

    Long-term groundwater monitoring had been executed since 1950s in Taiwan. In 1980s, with improving technology, various types of automatic reorders of groundwater level had become the most widely used equipment in groundwater monitoring. Among these devices, submersible pressure transducer is frequently selected to monitor groundwater level for its high frequency and high resolution. In this study, it is chosen to monitor groundwater level change in Sheliao well. On the other hand, factors which might influence the performance of recorded data were excluded in the early stage of establishment as well. And the final approach is to achieve a comprehensive understanding of the minor groundwater level change of Sheliao well, and specify its connection between precipitation, atmosphere, earth tide and earthquake. The Shelia well is located in central Taiwan, constructed in an unconfined aquifer, recorded hourly groundwater level change since 1997. We tried to establish a 1 Hz sampling rate pressure-sensing system in 2011 June. The groundwater level was monitored in a resolution of 2-mm. According to the records, several small-scale of fluctuations were observed and were all correlate well to the earthquakes. However, during the time that no earthquake occurred, some short-term fluctuations were still occurred, performed in a different pattern to those induced by earthquakes. After further investigation, those anomalous fluctuations of groundwater level were found corresponded to precipitation quite well. The fluctuations were observed under some specific condition, which involving different range of accumulated precipitation, rainfall intensity, and rainfall duration. The result implied groundwater level in Sheliao well changes with loading effect result from runoff on the ground surface and infiltration. And the earth tide lead to regularly change was also observed. We conclude that Sheliao can be characterized as a partial-confined aquifer with high frequency and high

  5. A real-time smart sensor for high-resolution frequency estimation in power systems.

    PubMed

    Granados-Lieberman, David; Romero-Troncoso, Rene J; Cabal-Yepez, Eduardo; Osornio-Rios, Roque A; Franco-Gasca, Luis A

    2009-01-01

    Power quality monitoring is a theme in vogue and accurate frequency measurement of the power line is a major issue. This problem is particularly relevant for power generating systems since the generated signal must comply with restrictive standards. The novelty of this work is the development of a smart sensor for real-time high-resolution frequency measurement in accordance with international standards for power quality monitoring. The proposed smart sensor utilizes commercially available current clamp, hall-effect sensor or resistor as primary sensor. The signal processing is carried out through the chirp z-transform. Simulations and experimental results show the efficiency of the proposed smart sensor.

  6. Graphene nanoelectromechanical systems as stochastic-frequency oscillators.

    PubMed

    Miao, Tengfei; Yeom, Sinchul; Wang, Peng; Standley, Brian; Bockrath, Marc

    2014-06-11

    We measure the quality factor Q of electrically driven few-layer graphene drumhead resonators, providing an experimental demonstration that Q ∼ 1/T, where T is the temperature. We develop a model that includes intermodal coupling and tensioned graphene resonators. Because the resonators are atomically thin, out-of-plane fluctuations are large. As a result, Q is mainly determined by stochastic frequency broadening rather than frictional damping, in analogy to nuclear magnetic resonance. This model is in good agreement with experiment. Additionally, at larger drives the resonance line width is enhanced by nonlinear damping, in qualitative agreement with recent theory of damping by radiation of in-plane phonons. Parametric amplification produced by periodic thermal expansion from the ac drive voltage yields an anomalously large line width at the largest drives. Our results contribute toward a general framework for understanding the mechanisms of dissipation and spectral line broadening in atomically thin membrane resonators.

  7. Blind estimation of carrier frequency offset, I/Q imbalance and DC offset for OFDM systems

    NASA Astrophysics Data System (ADS)

    Liu, Tao; Li, Hanzhang

    2012-12-01

    Sensitivity to carrier frequency offset (CFO) is one of the biggest drawbacks of orthogonal frequency division multiplexing (OFDM) system. A lot of CFO estimation algorithms had been studied for compensation of CFO in OFDM system. However, with the adoption of direct-conversion architecture (DCA), which introduces additional impairments such as dc offset (DCO) and in-phase/quadrature (I/Q) imbalance in OFDM system, the established CFO estimation algorithms suffer from performance degradation. In our previous study, we developed a blind CFO, I/Q imbalance and DCO estimation algorithm for OFDM systems with DCA. In this article, we propose an alternative algorithm with reduced computation complexity and better accuracy. Performance of the proposed algorithm is demonstrated by simulations.

  8. The Radio Frequency Health Node Wireless Sensor System

    NASA Technical Reports Server (NTRS)

    Valencia, J. Emilio; Stanley, Priscilla C.; Mackey, Paul J.

    2009-01-01

    The Radio Frequency Health Node (RFHN) wireless sensor system differs from other wireless sensor systems in ways originally intended to enhance utility as an instrumentation system for a spacecraft. The RFHN can also be adapted to use in terrestrial applications in which there are requirements for operational flexibility and integrability into higher-level instrumentation and data acquisition systems. As shown in the figure, the heart of the system is the RFHN, which is a unit that passes commands and data between (1) one or more commercially available wireless sensor units (optionally, also including wired sensor units) and (2) command and data interfaces with a local control computer that may be part of the spacecraft or other engineering system in which the wireless sensor system is installed. In turn, the local control computer can be in radio or wire communication with a remote control computer that may be part of a higher-level system. The remote control computer, acting via the local control computer and the RFHN, cannot only monitor readout data from the sensor units but can also remotely configure (program or reprogram) the RFHN and the sensor units during operation. In a spacecraft application, the RFHN and the sensor units can also be configured more nearly directly, prior to launch, via a serial interface that includes an umbilical cable between the spacecraft and ground support equipment. In either case, the RFHN wireless sensor system has the flexibility to be configured, as required, with different numbers and types of sensors for different applications. The RFHN can be used to effect realtime transfer of data from, and commands to, the wireless sensor units. It can also store data for later retrieval by an external computer. The RFHN communicates with the wireless sensor units via a radio transceiver module. The modular design of the RFHN makes it possible to add radio transceiver modules as needed to accommodate additional sets of wireless sensor

  9. Automated frequency domain system identification of a large space structure

    NASA Technical Reports Server (NTRS)

    Yam, Y.; Bayard, D. S.; Hadaegh, F. Y.; Mettler, E.; Milman, M. H.

    1989-01-01

    This paper presents the development and experimental results of an automated on-orbit system identification method for large flexible spacecraft that yields estimated quantities to support on-line design and tuning of robust high performance control systems. The procedure consists of applying an input to the plant, obtaining an output, and then conducting nonparametric identification to yield the spectral estimate of the system transfer function. A parametric model is determined by curve fitting the spectral estimate to a rational transfer function. The identification method has been demonstrated experimentally on the Large Spacecraft Control Laboratory in JPL.

  10. Intelligent pumping system developed

    SciTech Connect

    Not Available

    1983-06-01

    The oil field's first intelligent rod pumping system designed specifically to reduce the cost of pumping oil wells now is a reality. As a plus benefit, the system (called Liftronic) is compact and quiet. The new system combines an efficient mechanical design with a computer control system to reduce pumping costs. The unit stands less than 8 ft high, or approx. one-fourth the height of a comparable beam unit. It also mounts directly on the wellhead. The entire system can be concealed behind a fence or enclosed within a small building to make it a more attractive neighbor in residential, commercial, or recreational areas. It is useful also for agricultural areas where overhead irrigation systems restrict the use of many oil field pumping systems.

  11. POWER SYSTEMS DEVELOPMENT FACILITY

    SciTech Connect

    Unknown

    2002-05-01

    This report discusses test campaign GCT3 of the Halliburton KBR transport reactor train with a Siemens Westinghouse Power Corporation (Siemens Westinghouse) particle filter system at the Power Systems Development Facility (PSDF) located in Wilsonville, Alabama. The transport reactor is an advanced circulating fluidized-bed reactor designed to operate as either a combustor or a gasifier using one of two possible particulate control devices (PCDs). The transport reactor was operated as a pressurized gasifier during GCT3. GCT3 was planned as a 250-hour test run to commission the loop seal and continue the characterization of the limits of operational parameter variations using a blend of several Powder River Basin coals and Bucyrus limestone from Ohio. The primary test objectives were: (1) Loop Seal Commissioning--Evaluate the operational stability of the loop seal with sand and limestone as a bed material at different solids circulation rates and establish a maximum solids circulation rate through the loop seal with the inert bed. (2) Loop Seal Operations--Evaluate the loop seal operational stability during coal feed operations and establish maximum solids circulation rate. Secondary objectives included the continuation of reactor characterization, including: (1) Operational Stability--Characterize the reactor loop and PCD operations with short-term tests by varying coal feed, air/coal ratio, riser velocity, solids circulation rate, system pressure, and air distribution. (2) Reactor Operations--Study the devolatilization and tar cracking effects from transient conditions during transition from start-up burner to coal. Evaluate the effect of process operations on heat release, heat transfer, and accelerated fuel particle heat-up rates. Study the effect of changes in reactor conditions on transient temperature profiles, pressure balance, and product gas composition. (3) Effects of Reactor Conditions on Syngas Composition--Evaluate the effect of air distribution, steam

  12. Method of detecting system function by measuring frequency response

    NASA Technical Reports Server (NTRS)

    Morrison, John L. (Inventor); Morrison, William H. (Inventor); Christophersen, Jon P. (Inventor)

    2012-01-01

    Real-time battery impedance spectrum is acquired using a one-time record. Fast Summation Transformation (FST) is a parallel method of acquiring a real-time battery impedance spectrum using a one-time record that enables battery diagnostics. An excitation current to a battery is a sum of equal amplitude sine waves of frequencies that are octave harmonics spread over a range of interest. A sample frequency is also octave and harmonically related to all frequencies in the sum. The time profile of this signal has a duration that is a few periods of the lowest frequency. The voltage response of the battery, average deleted, is the impedance of the battery in the time domain. Since the excitation frequencies are known and octave and harmonically related, a simple algorithm, FST, processes the time record by rectifying relative to the sine and cosine of each frequency. Another algorithm yields real and imaginary components for each frequency.

  13. Method of detecting system function by measuring frequency response

    DOEpatents

    Morrison, John L [Butte, MT; Morrison, William H [Manchester, CT; Christophersen, Jon P [Idaho Falls, ID

    2012-04-03

    Real-time battery impedance spectrum is acquired using a one-time record. Fast Summation Transformation (FST) is a parallel method of acquiring a real-time battery impedance spectrum using a one-time record that enables battery diagnostics. An excitation current to a battery is a sum of equal amplitude sine waves of frequencies that are octave harmonics spread over a range of interest. A sample frequency is also octave and harmonically related to all frequencies in the sum. The time profile of this signal has a duration that is a few periods of the lowest frequency. The voltage response of the battery, average deleted, is the impedance of the battery in the time domain. Since the excitation frequencies are known and octave and harmonically related, a simple algorithm, FST, processes the time record by rectifying relative to the sine and cosine of each frequency. Another algorithm yields real and imaginary components for each frequency.

  14. Method of detecting system function by measuring frequency response

    DOEpatents

    Morrison, John L.; Morrison, William H.; Christophersen, Jon P.; Motloch, Chester G.

    2013-01-08

    Methods of rapidly measuring an impedance spectrum of an energy storage device in-situ over a limited number of logarithmically distributed frequencies are described. An energy storage device is excited with a known input signal, and a response is measured to ascertain the impedance spectrum. An excitation signal is a limited time duration sum-of-sines consisting of a select number of frequencies. In one embodiment, magnitude and phase of each frequency of interest within the sum-of-sines is identified when the selected frequencies and sample rate are logarithmic integer steps greater than two. This technique requires a measurement with a duration of one period of the lowest frequency. In another embodiment, where selected frequencies are distributed in octave steps, the impedance spectrum can be determined using a captured time record that is reduced to a half-period of the lowest frequency.

  15. Development of a Multi-frequency Interferometer Telescope for Radio Astronomy (MITRA)

    NASA Astrophysics Data System (ADS)

    Ingala, Dominique Guelord Kumamputu

    2015-03-01

    This dissertation describes the development and construction of the Multi-frequency Interferometer Telescope for Radio Astronomy (MITRA) at the Durban University of Technology. The MITRA station consists of 2 antenna arrays separated by a baseline distance of 8 m. Each array consists of 8 Log-Periodic Dipole Antennas (LPDAs) operating from 200 MHz to 800 MHz. The design and construction of the LPDA antenna and receiver system is described. The receiver topology provides an equivalent noise temperature of 113.1 K and 55.1 dB of gain. The Intermediate Frequency (IF) stage was designed to produce a fixed IF frequency of 800 MHz. The digital Back-End and correlator were implemented using a low cost Software Defined Radio (SDR) platform and Gnu-Radio software. Gnu-Octave was used for data analysis to generate the relevant received signal parameters including total power, real, and imaginary, magnitude and phase components. Measured results show that interference fringes were successfully detected within the bandwidth of the receiver using a Radio Frequency (RF) generator as a simulated source. This research was presented at the IEEE Africon 2013 / URSI Session Mauritius, and published in the proceedings.

  16. Multi-frequency AOM for multi-beam laser scanning exposure system

    NASA Astrophysics Data System (ADS)

    Shinada, Hidetoshi

    2016-10-01

    Digital printing systems recorded on films or computer to plates (CTPs) have been required to improve their productivity and image quality. Under the circumstance, a printing technology of the multi-beam laser scanning for the drum capstan system, which is almost the same as optics configuration as the flat bed system, was developed using a newly developed multi-frequency acousto-optic modulator (AOM) as a key device instead of ultra-fast scanning devices toward a main scan direction. The multi-frequency AOM was developed with phased array-type transducers, achieving a wider bandwidth of over 160 MHz. The design consisted of a simultaneous three beams generation with interlace scan to avoid the beat effect by adjacent Doppler-shifted beams, which consequently attained the fastest recording speed of 5.0 mm/s compared with 2.0-3.0 mm/s of existing systems in those days. Furthermore, a couple of critical parameters of the multi-frequency AOM are studied, for example, a treatment of third-order intermodulation and also beat effect in connection with photosensitive media. As a result, the necessity of interlaces scanning to obtain good image quality without beat effect and also to allow a lower laser power to apply is proposed.

  17. SCHOOL CONSTRUCTION SYSTEMS DEVELOPMENT PROJECT.

    ERIC Educational Resources Information Center

    BOICE, JOHN,; AND OTHERS

    ONE-HUNDRED MANUFACTURERS EXPRESSED INTEREST IN BIDDING FOR A SYSTEM ON SCHOOL CONSTRUCTION CALLED SCSD OR SCHOOL CONSTRUCTION SYSTEMS DEVELOPMENT TO THE FIRST CALIFORNIA COMMISSION ON SCHOOL CONSTRUCTION SYSTEMS. TWENTY-TWO BUILDINGS COMPRISED THE PROJECT. THE OBJECTIVE WAS TO DEVELOP AN INTEGRATED SYSTEM OF STANDARD SCHOOL BUILDING COMPONENTS…

  18. Experimental investigation of a variable speed constant frequency electric generating system from a utility perspective

    NASA Technical Reports Server (NTRS)

    Herrera, J. I.; Reddoch, T. W.; Lawler, J. S.

    1985-01-01

    As efforts are accelerated to improve the overall capability and performance of wind electric systems, increased attention to variable speed configurations has developed. A number of potentially viable configurations have emerged. Various attributes of variable speed systems need to be carefully tested to evaluate their performance from the utility points of view. With this purpose, the NASA experimental variable speed constant frequency (VSCF) system has been tested. In order to determine the usefulness of these systems in utility applications, tests are required to resolve issues fundamental to electric utility systems. Legitimate questions exist regarding how variable speed generators will influence the performance of electric utility systems; therefore, tests from a utility perspective, have been performed on the VSCF system and an induction generator at an operating power level of 30 kW on a system rated at 200 kVA and 0.8 power factor.

  19. Frequency distribution of coliforms in water distribution systems.

    PubMed Central

    Christian, R R; Pipes, W O

    1983-01-01

    Nine small water distribution systems were sampled intensively to determine the patterns of dispersion of coliforms. The frequency distributions of confirmed coliform counts were compatible with either the negative-binomial or the lognormal distribution. They were not compatible with either the Poisson or Poisson-plus-added zeroes distribution. The implications of the use of the lognormal distributional model were further evaluated because of its previous use in water quality studies. The geometric means from 14 data sets ranged from 10(-6) to 0.2 coliforms per 100 ml, and the geometric standard deviations were between 10 and 100, with one exception. If the lognormal model is representative of the coliform distribution; the arithmetic mean sample count is a poor estimator of the true mean coliform density, and the probability of water in a distribution system containing small patches with large coliform densities without detection by routine monitoring is finite. These conclusions have direct bearing on the interpretation of microbiological quality standards for drinking water. PMID:6830219

  20. On Frequencies of Small Oscillations of Some Dynamical Systems Associated with Root Systems

    NASA Astrophysics Data System (ADS)

    Perelomov, A. M.

    In the paper by F. Calogero and author [Commun. Math. Phys. 59 (1978) 109-116] the formula for frequencies of small oscillations of the Sutherland system ($A_l$ case) was found. In present note the generalization of this formula for the case of arbitrary root system is given.

  1. High-Frequency Wireless and Electrodeless Quartz Crystal Microbalance Developed as Immunosensor

    NASA Astrophysics Data System (ADS)

    Ogi, Hirotsugu; Motohisa, Kazuma; Hatanaka, Kenichi; Ohmori, Toshinobu; Hirao, Masahiko; Nishiyama, Masayoshi

    2007-07-01

    A wireless and electrodeless high-frequency quartz crystal microbalance (QCM) was developed for monitoring biochemical reactions in real time without using any labeling procedures. An analytical vibrational calculation for a multilayered plate showed that the QCM sensitivity significantly deteriorates when metallic electrodes are present on the crystal surfaces, indicating the importance of an electrodeless QCM biosensor. The 30-μm-thick electrodeless QCM immunosensor was excited, and its mechanical vibration was detected contactlessly using an antenna located outside the QCM cells. The homebuilt QCM system was used to detect human immunoglobulin G (hIgG) using staphylococcal protein A (SPA) immobilized on the crystal surface and to demonstrate the higher sensitivity of the electrodeless QCM than that of the conventional QCM. The 30-μm-thick QCM, with a 54 MHz fundamental frequency, successfully monitored the hIgG-SPA binding reaction for a hIgG concentration of 100 pg/mL.

  2. [The Spatial-Frequency Characteristics of the Visual System in Schizophrenia].

    PubMed

    Shoshina, I I; Shelepin, Y E; Vershinina, E A; Novikova, K O

    2015-01-01

    In order to determine the spatial-frequancy characteristics of the visual system of healthy subjects and patients with schizophrenia, we used the contrast comparison of two Gabor gratings with sinusoidal distribution of brightness. The Gabor gratings have low, medium or high spatial frequencies; the neurons of magnocellular and parvocellular channels are sensitive to these frequencies to different extents. We found an increase in sensitivity to the contrast when comparing the gratings with low frequencies (to which magnocellular channels are most sensitive) in the patients with first-episode schizophrenia who had not receive long-term antipsychotic treatment, as compared with the control group. On the contrary, the sensitivity to the gratings with medium and high spatial frequencies in this group of patients was lower, as well as in patients with first-episode schizophrenia who had received long-term treatment. The patients with chronic schizophrenia showed a decrease in contrast sensitivity in all tested ranges of frequencies. We obtained supplementary evidence of the enhancement of internal noise in the visual system of the patients with schizophrenia. The results help us to explain the clinical data on the development of visual perceptual diorders at different stages of schizophrenia.

  3. Exploration Medical System Technical Development

    NASA Technical Reports Server (NTRS)

    McGuire, K.; Middour, C.; Cerro, J.; Burba, T.; Hanson, A.; Reilly, J.; Mindock, J.

    2017-01-01

    The Exploration Medical Capability (ExMC) Element systems engineering goals include defining the technical system needed to implement exploration medical capabilities for Mars. This past year, scenarios captured in the medical system concept of operations laid the foundation for systems engineering technical development work. The systems engineering team analyzed scenario content to identify interactions between the medical system, crewmembers, the exploration vehicle, and the ground system. This enabled the definition of functions the medical system must provide and interfaces to crewmembers and other systems. These analyses additionally lead to the development of a conceptual medical system architecture. The work supports the ExMC community-wide understanding of the functional exploration needs to be met by the medical system, the subsequent development of medical system requirements, and the system verification and validation approach utilizing terrestrial analogs and precursor exploration missions.

  4. Career Development: A Systems Approach.

    ERIC Educational Resources Information Center

    Slavenski, Lynn

    1987-01-01

    The author describes a comprehensive career development system implemented by Coca-Cola USA. The system's objectives are (1) to promote from within, (2) to develop talent for the future, (3) to make managers responsible for development efforts, and (4) to make individuals ultimately responsible for their development. (CH)

  5. Career Development: A Systems Approach.

    ERIC Educational Resources Information Center

    Slavenski, Lynn

    1987-01-01

    The author describes a comprehensive career development system implemented by Coca-Cola USA. The system's objectives are (1) to promote from within, (2) to develop talent for the future, (3) to make managers responsible for development efforts, and (4) to make individuals ultimately responsible for their development. (CH)

  6. A flight-like absolute optical frequency reference based on iodine for laser systems at 1064 nm

    NASA Astrophysics Data System (ADS)

    Döringshoff, K.; Schuldt, T.; Kovalchuk, E. V.; Stühler, J.; Braxmaier, C.; Peters, A.

    2017-06-01

    We present an absolute optical frequency reference based on precision spectroscopy of hyperfine transitions in molecular iodine ^{127}I_2 for laser systems operating at 1064 nm. A quasi-monolithic spectroscopy setup was developed, integrated, and tested with respect to potential deployment in space missions that require frequency stable laser systems. We report on environmental tests of the setup and its frequency stability and reproducibility before and after each test. Furthermore, we report on the first measurements of the frequency stability of the iodine reference with an unsaturated absorption cell which will greatly simplify its application in space missions. Our frequency reference fulfills the requirements on the frequency stability for planned space missions such as LISA or NGGM.

  7. Compact Superconducting Radio-frequency Accelerators and Innovative RF Systems

    SciTech Connect

    Kephart, Robert; Chattopadhyay, Swaapan; Milton, Stephen

    2015-04-10

    We will present several new technical and design breakthroughs that enable the creation of a new class of compact linear electron accelerators for industrial purposes. Use of Superconducting Radio-Frequency (SRF) cavities allow accelerators less than 1.5 M in length to create electron beams beyond 10 MeV and with average beam powers measured in 10’s of KW. These machines can have the capability to vary the output energy dynamically to produce brehmstrahlung x-rays of varying spectral coverage for applications such as rapid scanning of moving cargo for security purposes. Such compact accelerators will also be cost effective for many existing and new industrial applications. Examples include radiation crosslinking of plastics and rubbers, creation of pure materials with surface properties radically altered from the bulk, modification of bulk or surface optical properties of materials, sterilization of medical instruments animal solid or liquid waste, and destruction of organic compounds in industrial waste water effluents. Small enough to be located on a mobile platform, such accelerators will enable new remediation methods for chemical and biological spills and/or in-situ crosslinking of materials. We will describe one current design under development at Fermilab including plans for prototype and value-engineering to reduce costs. We will also describe development of new nano-structured field-emitter arrays as sources of electrons, new methods for fabricating and cooling superconducting RF cavities, and a new novel RF power source based on magnetrons with full phase and amplitude control.

  8. Development of Frequency Based Taste Receptors Using Bioinspired Glucose Nanobiosensor.

    PubMed

    TermehYousefi, Amin; Tateno, Katsumi; Bagheri, Samira; Tanaka, Hirofumi

    2017-05-09

    A method to fabricate a bioinspired nanobiosensor using electronic-based artificial taste receptors for glucose diagnosis is presented. Fabricated bioinspired glucose nanobiosensor designated based on an artificial taste bud including an amperometric glucose biosensor and taste bud-inspired circuits. In fact, the design of the taste bud-inspired circuits was inspired by the signal-processing mechanism of taste nerves which involves two layers. The first, known as a type II cell, detects the glucose by glucose oxidase and transduces the current signal obtained for the pulse pattern is conducted to the second layer, called type III cell, to induce synchronisation of the neural spiking activity. The oscillation results of fabricated bioinspired glucose nanobiosensor confirmed an increase in the frequency of the output pulse as a function of the glucose concentration. At high glucose concentrations, the bioinspired glucose nanobiosensor showed a pulse train of alternating short and long interpulse intervals. A computational analysis performed to validate the hypothesis, which was successfully reproduced the alternating behaviour of bioinspired glucose our nanobiosensor by increasing the output frequency and alternation of pulse intervals according to the reduction in the resistivity of the biosensor.

  9. Theoretical analysis and system design of two-photon based optical frequency standards

    NASA Astrophysics Data System (ADS)

    Burger, J. P.; Jivan, P.; Matthee, C.; Kritzinger, R.; Hussein, H.; Terra, O.

    2014-06-01

    The National Metrology Institute of South Africa (NMISA) is developing a new optical frequency standard based on the Rubidium two-photon transition in collaboration with the National Institute of Standards (NIS, Egypt) that will use both bulk and fiber optics in the system. This is system is called A-POD; an acronym for a portable photonic oscillator device. Rubidium two-photon standards can yield relatively simple and precise standards that are compatible with standard Ti:Sapphire optical frequency combs, as well as the need for a precise frequency standard in the optical telecommunication domain and for measurement of length with a visible beam. The robustness and transportability of the standard are important considerations for the optical frequency standard. This projects implements a framework for better two-photon standards that can be highly accurate, and possibly compete with much more complex clocks in the metrology environment, and especially so in the smaller national metrology institutes found in the developing world. This paper discusses the design constraints and the development considerations towards the optical setup. The robustness and transportability was greatly improved via the usage of optical fiber in the light source of the system, or even in atom-light interaction region. Of particular importance are the beam parameters inside the atomic interaction area. The extent of Doppler broadening and the intensity dependent line shift have to be optimized within practical extents, where both these aspects are affected by the beam shape and optical geometry. A way to fully treat the optical beam effects together with atomic movement is proposed. Furthermore a method is proposed to do real time compensation of intensity dependent light shift, which could have major applicability to frequency standards in general - the complexity is shifted from physical setups to digital signal processing, which is easily adaptable and stable.

  10. Digital low level rf control system with four different intermediate frequencies for the International Linear Collider

    NASA Astrophysics Data System (ADS)

    Wibowo, Sigit Basuki; Matsumoto, Toshihiro; Michizono, Shinichiro; Miura, Takako; Qiu, Feng; Liu, Na

    2017-09-01

    A field programmable gate array-based digital low level rf (LLRF) control system will be used in the International Linear Collider (ILC) in order to satisfy the rf stability requirements. The digital LLRF control system with four different intermediate frequencies has been developed to decrease the required number of analog-to-digital converters in this system. The proof of concept of this technique was demonstrated at the Superconducting RF Test Facility in the High Energy Accelerator Research Organization, Japan. The amplitude and phase stability has fulfilled the ILC requirements.

  11. Time domain and frequency domain design techniques for model reference adaptive control systems

    NASA Technical Reports Server (NTRS)

    Boland, J. S., III

    1971-01-01

    Some problems associated with the design of model-reference adaptive control systems are considered and solutions to these problems are advanced. The stability of the adapted system is a primary consideration in the development of both the time-domain and the frequency-domain design techniques. Consequentially, the use of Liapunov's direct method forms an integral part of the derivation of the design procedures. The application of sensitivity coefficients to the design of model-reference adaptive control systems is considered. An application of the design techniques is also presented.

  12. Frequency control in micro-grid power system combined with electrolyzer system and fuzzy PI controller

    NASA Astrophysics Data System (ADS)

    Li, Xiangjun; Song, Yu-Jin; Han, Soo-Bin

    The widespread use of various kinds of distributed power sources would impact the quality of the power supply within a micro-grid power system, causing many control problems. This paper focuses on the stability of micro-grid operation and discusses the control techniques of combining a micro-turbine with the fuel cell and electrolyzer hybrid system to expand the micro-grid system's ability to solve power quality issues resulting from frequency fluctuations. The paper examines the feasibility of fuel cell and electrolyzer hybrid system control, especially dynamic control of an electrolyzer system, to secure a real power balance and enhance the operational capability of load frequency control. The proposed control and monitoring system can be considered to be a means of power quality control, both to improve the frequency fluctuations caused by random power fluctuations on the generation and load sides and to relax tie-line power flow fluctuations caused by frequency fluctuations in the interconnected micro-grid power system.

  13. Developing Interim Systems

    NASA Technical Reports Server (NTRS)

    Caetta, J.

    1997-01-01

    One of the recent challenges in the aerospace industry has been to smoothly transition operations-oriented computer systems to meet increasing demands on smaller budgets. Sometimes the best solution is not affordable, but the current situation is equally untenable.

  14. [Design of low-intermediate frequency electrotherapy and pain assessment system].

    PubMed

    Liang, Chunyan; Tian, Xuelong; Yu, Xuehong; Luo, Hongyan

    2014-06-01

    Aiming at the single treatment and the design separation between treatment and assessment in electrotherapy equipment, a kind of system including low-intermediate frequency treatment and efficacy evaluation was developed. With C8051F020 single-chip microcomputer as the core and the circuit design and software programming used, the system realized the random switch of therapeutic parameters, the collection, display and data storage of pressure pain threshold in the assessment. Experiment results showed that the stimulus waveform, current intensity, frequency, duty ratio of the system output were adjustable, accurate and reliable. The obtained pressure pain threshold had a higher accuracy (< 0.3 N) and better stability, guiding the parameter choice in the precise electrical stimulation. It, therefore, provides a reliable technical support for the treatment and curative effect assessment.

  15. An animal tracking system for behavior analysis using radio frequency identification.

    PubMed

    Catarinucci, Luca; Colella, Riccardo; Mainetti, Luca; Patrono, Luigi; Pieretti, Stefano; Secco, Andrea; Sergi, Ilaria

    2014-09-01

    Evaluating the behavior of mice and rats has substantially contributed to the progress of research in many scientific fields. Researchers commonly observe recorded video of animal behavior and manually record their observations for later analysis, but this approach has several limitations. The authors developed an automated system for tracking and analyzing the behavior of rodents that is based on radio frequency identification (RFID) in an ultra-high-frequency bandwidth. They provide an overview of the system's hardware and software components as well as describe their technique for surgically implanting passive RFID tags in mice. Finally, the authors present the findings of two validation studies to compare the accuracy of the RFID system versus commonly used approaches for evaluating the locomotor activity and object exploration of mice.

  16. A Laser Frequency Comb System for Absolute Calibration of the VTT Echelle Spectrograph

    NASA Astrophysics Data System (ADS)

    Doerr, H.-P.; Steinmetz, T.; Holzwarth, R.; Kentischer, T.; Schmidt, W.

    2012-10-01

    A wavelength calibration system based on a laser frequency comb (LFC) was developed in a co-operation between the Kiepenheuer-Institut für Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut für Quantenoptik, Garching, Germany for permanent installation at the German Vacuum Tower Telescope (VTT) on Tenerife, Canary Islands. The system was installed successfully in October 2011. By simultaneously recording the spectra from the Sun and the LFC, for each exposure a calibration curve can be derived from the known frequencies of the comb modes that is suitable for absolute calibration at the meters per second level. We briefly summarize some topics in solar physics that benefit from absolute spectroscopy and point out the advantages of LFC compared to traditional calibration techniques. We also sketch the basic setup of the VTT calibration system and its integration with the existing echelle spectrograph.

  17. Control-oriented high-frequency turbomachinery modeling: General one-dimensional model development

    SciTech Connect

    Badmus, O.O.; Eveker, K.M.; Nett, C.N.

    1995-07-01

    In this paper, an approach for control-oriented high-frequency turbomachinery modeling previously developed by the authors is applied to develop one-dimensional unsteady compressible viscous flow models for a generic turbojet engine and a generic compression system. The authors begin by developing models for various components commonly fund in turbomachinery systems. These components include: ducting without combustion, blading, ducting with combustion, heat soak, blading with heat soak, inlet, nozzle, abrupt area change with incurred total pressure lose, flow splitting, bleed, mixing, and the spool. Once the component models have been developed, they are combined to form system models for a generic turbojet engine and a generic compression system. These models are developed so that they can be easily modified and used with appropriate maps to form a model for a specific rig. It is shown that these system models are explicit (i.e., can be solved with any standard ODE solver without iteration) due to the approach used in their development. Furthermore, since the nonlinear models are explicit, explicit analytical linear models can be derived from the nonlinear models. The procedure for developing these analytical linear models is discussed. An interesting feature of the models developed here is the use of effective lengths within the models, as functions of axial Mach number and nondimensional rotational speed, for rotating components. These effective lengths account for the helical path of the flow as it moves through a rotating component. Use of these effective lengths in the unsteady conservation equations introduces a nonlinear dynamic lag consistent with experimentally observed compressor lag and replaces less accurate linear first-order empirical lags proposed to account for this phenomenon. Models of the type developed here are expected to prove useful in the design and simulation of (integrated) surge control and rotating stall avoidance schemes.

  18. Design of an exposimetry system for analysis of high-frequency ultrasound devices

    NASA Astrophysics Data System (ADS)

    Snook, Kevin A.; Huang, Bin; Smith, Nadine B.; Shung, K. Kirk

    2001-05-01

    An exposimetry system for characterization of high frequency ultrasound fields has been developed and built. By extrapolating the recommendations of the AIUM and IEC standards to higher frequencies, an exposimetry system operating above 15 MHz was outlined. The system incorporates a five degrees-of-freedom positioning system, including three automated translational motors that provide 0.5 micron resolution. Two manual rotational axes utilize a worm-gear and concentric cylinder arrangement to insure orthogonal rotational adjustment. Overall bandwidth of the system is 100 MHz and is limited by the type of hydrophone used. Using a calibrated 0.04 mm diameter needle-type hydrophone, measurements of single element transducers of 25-50 MHz have been made. LiNbO3 and PVDF transducers of f-numbers from 2-3 have been tested and 2D intensity beam profiles plotted. Results from a 50 MHz LiNbO3 transducer show good agreement between empirical (8.6 mm) and theoretical (9.0 mm) focal points. The -3 dB beamwidth was also measured (108 micron) to be comparable to that of the calculated value (86 micron). It is shown that this system provides a good means for characterization and analysis of the beam profiles of high frequency transducers.

  19. Emergency and operational low and medium frequency band radio communications system for underground mines

    SciTech Connect

    Stolarczyk, L.G. )

    1991-07-01

    This paper reports on a minewide low- and medium-frequency radio system has been developed and installed in coal and metalliferous mines. The radio system established reliable emergency communications between mine personnel on the surface, in working areas, or traveling in designated escapeway. The system also provides operational communications to improve coordination among working groups in the underground mining complex. The radio system utilizes two robust radio signal transmission modes to establish underground radio coverage areas. The seam transmission mode occurs when layers of coal, trona, potash, quartzite, or gilsonite are surrounded by more electrically conductive sediment layers. The layering forms a natural waveguide for transmission of medium-frequency (MF) band (300 to 23 000 kHz) radio signals. The conductor transmission line mode waveguide occurs when electrical conductors, such as ac power distribution cable, conveyor belt structures, steel pipe, and rail are in place in mine passageways. The conductor transmission waveguide attenuation rate is lowest in the low-frequency and (30 to 300 kHz). Safety is inherent in the system design since robust radio signal transmission modes are likely to survive events such as rock falls, fire, or explosion. Since the conductor utilities are necessary parts of the underground mine infrastructure, transmission line installation and maintenance cost can be avoided in the radio system.

  20. Linear Frequency Modulated Signals VS Orthogonal Frequency Division Multiplexing Signals for Synthetic Aperture Radar Systems

    DTIC Science & Technology

    2014-06-01

    frequency modulation (LFM), communications radar 15. NUMBER OF PAGES 161 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT Unclassified 18...116 APPENDIX MATLAB CODES ...........................................................................117 LIST OF...results obtained for the range imaging case and two-dimensional case, respectively. All simulations were conducted in MATLAB , and the code was derived

  1. Development and Characterization of a Ytterbium-171 Miniature Ion Trap Frequency Standard

    NASA Astrophysics Data System (ADS)

    Partner, Heather L.

    This dissertation reports on the development of a low-power, high-stability miniature atomic frequency standard based on 171Yb+ ions. The ions are buffer-gas cooled and held in a linear quadrupole trap that is integrated into a sealed, getter-pumped vacuum package, and interrogated on the 12.6 GHz hyperfine transition. We hope to achieve a long-term fractional frequency stability of 10-14 with this miniature clock while consuming only 50 mW of power and occupying a volume of 5 cm 3, as part of a project funded to rapidly develop an advanced miniaturized frequency standard that has exceptional long-term stability. I discuss our progress through several years of development on this project. We began by building a relatively conventional tabletop clock system to act as a "test bed" for future components and for testing new techniques in a controlled environment. We moved on to develop and test several designs of miniature ion-trap vacuum packages, while also developing techniques for various aspects of the clock operation, including ion loading, laser and magnetic field stabilization, and a low power ion trap drive. The ion traps were modeled using boundary element software to assist with the design and parameter optimization of new trap geometries. We expect a novel trap geometry made using a material that is new to ion traps to lead to an exceptionally small ion trap vacuum package in the next phase of the project. To achieve the long-term stability required, we have also considered the sensitivity of the clock frequency to magnetic fields. A study of the motion of the individual ions in a room-temperature cloud in the trap was performed. The purpose of this simulation was to understand the effect of both spatially varying and constant magnetic fields on the clock resonance and therefore the operation of the clock. These effects were studied experimentally and theoretically for several traps. In summary, this dissertation is a contribution to the design, development

  2. Development of frequency modulation reflectometer for Korea Superconducting Tokamak Advanced Research tokamak

    NASA Astrophysics Data System (ADS)

    Seo, Seong-Heon; Park, Jinhyung; Wi, H. M.; Lee, W. R.; Kim, H. S.; Lee, T. G.; Kim, Y. S.; Kang, Jin-Seob; Bog, M. G.; Yokota, Y.; Mase, A.

    2013-08-01

    Frequency modulation reflectometer has been developed to measure the plasma density profile of the Korea Superconducting Tokamak Advanced Research tokamak. Three reflectometers are operating in extraordinary polarization mode in the frequency range of Q band (33.6-54 GHz), V band (48-72 GHz), and W band (72-108 GHz) to measure the density up to 7 × 1019 m-3 when the toroidal magnetic field is 2 T on axis. The antenna is installed inside of the vacuum vessel. A new vacuum window is developed by using 50 μm thick mica film and 0.1 mm thick gold gasket. The filter bank of low pass filter, notch filter, and Faraday isolator is used to reject the electron cyclotron heating high power at attenuation of 60 dB. The full frequency band is swept in 20 μs. The mixer output is directly digitized with sampling rate of 100 MSamples/s. The phase is obtained by using wavelet transform. The whole hardware and software system is described in detail and the measured density profile is presented as a result.

  3. 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.

  4. Development of frequency modulation reflectometer for Korea Superconducting Tokamak Advanced Research tokamak

    SciTech Connect

    Seo, Seong-Heon; Wi, H. M.; Lee, W. R.; Kim, H. S.; Lee, T. G.; Kim, Y. S.; Park, Jinhyung; Kang, Jin-Seob; Bog, M. G.; Yokota, Y.; Mase, A.

    2013-08-15

    Frequency modulation reflectometer has been developed to measure the plasma density profile of the Korea Superconducting Tokamak Advanced Research tokamak. Three reflectometers are operating in extraordinary polarization mode in the frequency range of Q band (33.6–54 GHz), V band (48–72 GHz), and W band (72–108 GHz) to measure the density up to 7 × 10{sup 19} m{sup −3} when the toroidal magnetic field is 2 T on axis. The antenna is installed inside of the vacuum vessel. A new vacuum window is developed by using 50 μm thick mica film and 0.1 mm thick gold gasket. The filter bank of low pass filter, notch filter, and Faraday isolator is used to reject the electron cyclotron heating high power at attenuation of 60 dB. The full frequency band is swept in 20 μs. The mixer output is directly digitized with sampling rate of 100 MSamples/s. The phase is obtained by using wavelet transform. The whole hardware and software system is described in detail and the measured density profile is presented as a result.

  5. Development of frequency modulation reflectometer for Korea Superconducting Tokamak Advanced Research tokamak.

    PubMed

    Seo, Seong-Heon; Park, Jinhyung; Wi, H M; Lee, W R; Kim, H S; Lee, T G; Kim, Y S; Kang, Jin-Seob; Bog, M G; Yokota, Y; Mase, A

    2013-08-01

    Frequency modulation reflectometer has been developed to measure the plasma density profile of the Korea Superconducting Tokamak Advanced Research tokamak. Three reflectometers are operating in extraordinary polarization mode in the frequency range of Q band (33.6-54 GHz), V band (48-72 GHz), and W band (72-108 GHz) to measure the density up to 7 × 10(19) m(-3) when the toroidal magnetic field is 2 T on axis. The antenna is installed inside of the vacuum vessel. A new vacuum window is developed by using 50 μm thick mica film and 0.1 mm thick gold gasket. The filter bank of low pass filter, notch filter, and Faraday isolator is used to reject the electron cyclotron heating high power at attenuation of 60 dB. The full frequency band is swept in 20 μs. The mixer output is directly digitized with sampling rate of 100 MSamples/s. The phase is obtained by using wavelet transform. The whole hardware and software system is described in detail and the measured density profile is presented as a result.

  6. Neuro-Fuzzy Computational Technique to Control Load Frequency in Hydro-Thermal Interconnected Power System

    NASA Astrophysics Data System (ADS)

    Prakash, S.; Sinha, S. K.

    2015-09-01

    In this research work, two areas hydro-thermal power system connected through tie-lines is considered. The perturbation of frequencies at the areas and resulting tie line power flows arise due to unpredictable load variations that cause mismatch between the generated and demanded powers. Due to rising and falling power demand, the real and reactive power balance is harmed; hence frequency and voltage get deviated from nominal value. This necessitates designing of an accurate and fast controller to maintain the system parameters at nominal value. The main purpose of system generation control is to balance the system generation against the load and losses so that the desired frequency and power interchange between neighboring systems are maintained. The intelligent controllers like fuzzy logic, artificial neural network (ANN) and hybrid fuzzy neural network approaches are used for automatic generation control for the two area interconnected power systems. Area 1 consists of thermal reheat power plant whereas area 2 consists of hydro power plant with electric governor. Performance evaluation is carried out by using intelligent (ANFIS, ANN and fuzzy) control and conventional PI and PID control approaches. To enhance the performance of controller sliding surface i.e. variable structure control is included. The model of interconnected power system has been developed with all five types of said controllers and simulated using MATLAB/SIMULINK package. The performance of the intelligent controllers has been compared with the conventional PI and PID controllers for the interconnected power system. A comparison of ANFIS, ANN, Fuzzy and PI, PID based approaches shows the superiority of proposed ANFIS over ANN, fuzzy and PI, PID. Thus the hybrid fuzzy neural network controller has better dynamic response i.e., quick in operation, reduced error magnitude and minimized frequency transients.

  7. Series Bosch System Development

    NASA Technical Reports Server (NTRS)

    Abney, Morgan B.; Evans, Christopher; Mansell, Matt; Swickrath, Michael

    2012-01-01

    State-of-the-art (SOA) carbon dioxide (CO2) reduction technology for the International Space Station produces methane as a byproduct. This methane is subsequently vented overboard. The associated loss of hydrogen ultimately reduces the mass of oxygen that can be recovered from CO2 in a closed-loop life support system. As an alternative to SOA CO2 reduction technology, NASA is exploring a Series-Bosch system capable of reducing CO2 with hydrogen to form water and solid carbon. This results in 100% theoretical recovery of oxygen from metabolic CO2. In the past, Bosch-based technology did not trade favorably against SOA technology due to a high power demand, low reaction efficiencies, concerns with carbon containment, and large resupply requirements necessary to replace expended catalyst cartridges. An alternative approach to Bosch technology, labeled "Series-Bosch," employs a new system design with optimized multi-stage reactors and a membrane-based separation and recycle capability. Multi-physics modeling of the first stage reactor, along with chemical process modeling of the integrated system, has resulted in a design with potential to trade significantly better than previous Bosch technology. The modeling process and resulting system architecture selection are discussed.

  8. A multi-frequency EIT system design based on telecommunication signal processors.

    PubMed

    Robitaille, Nicolas; Guardo, Robert; Maurice, Isabelle; Hartinger, Alzbeta E; Gagnon, Hervé

    2009-06-01

    A multi-frequency electrical impedance tomography system for cardiopulmonary monitoring has been designed with specialized digital signal processors developed primarily for the telecommunications sector. The system consists of two modules: a scan-head and a base-station. The scan-head, located close to the patient's torso, contains front-end circuits for measuring transfer impedance with a 16-electrode array. The base-station, placed at the bedside, comprises 16 direct digital synthesizers, 32 digital down-converters, digital circuits to control the data acquisition sequence and a USB-2.0 microcontroller. At every step of the scan sequence, the system simultaneously measures four complex variables at eight frequencies. These variables are the potential difference between the selected pair of sense electrodes, the currents applied by the source and sink electrodes, and the current flowing through the ground electrode. Frequencies are programmable from 10 kHz to 2 MHz with a resolution of 2 mHz. Characterization tests were performed with a precision mesh phantom connected to the scan-head. For a 5 Hz frame rate, the mean signal-to-noise ratio and accuracy are, respectively, 43 dB and 95.4% for eight frequencies logarithmically spaced from 70 to 950 kHz. In vitro and in vivo time-difference images have been reconstructed.

  9. High Temperature VSCF (Variable Speed Constant Frequency) Generator System

    DTIC Science & Technology

    1989-04-01

    be’ing developed to reduce size and weight on all production programs. Monsanto OS-124 oil properties were used for heat transfer and fluid flow...is an important design consideration for higher temperature operation. Use of a lower expansion and stronger composite material such as cast AZ91 mg...systems were investigated. Figures 5 through 7 give a comparison of the tensile properties of composites with the properties of an unreinforced alloy. It

  10. A frequency scanning method for the identification of harmonic instabilities in HVDC systems

    SciTech Connect

    Jiang, X.; Gole, A.M.

    1995-10-01

    A Frequency Scanning Method is introduced in the paper to obtain a more accurate frequency characteristic for identifying harmonic instability in HVdc systems. An example of the application is used to identify the resonance frequencies in the CIGRE benchmark model. The paper shows that the Benchmark model is not tuned to the resonance frequency that it was designed for. Using the scanning method, the resonance frequency of the benchmark model may be shifted to demonstrate a simulation of core-saturation type instability.

  11. Analog Techniques for Measuring the Frequency Response of Linear Physical Systems Excited by Frequency-Sweep Inputs

    NASA Technical Reports Server (NTRS)

    Reed, Wilmer H., III; Hall, Albert W.; Barker, Lawrence E., Jr.

    1960-01-01

    Data-reduction methods using general-purpose analog computer equipment and compatible testing techniques for determining the frequency response of linear physical systems are examined. The techniques considered may be classed as steady state or transient depending on the method of excitation. The relative merits of periodic, slow sweep, and transient (rapid sweep) forcing functions are discussed and applications are given that relate to dynamic-response tests of aeroelastic systems. Two frequency-sweep-input methods are considered in detail. one case the sweep rate is sufficiently slow that the response is approximately the same as that for steady-state conditions. With this input the frequency response can be evaluated and displayed in real time while the test is in progress. Errors due to treating sweep data as steady state can be eliminated, when desired, by reanalyzing tape-recorded time histories of the input and output as transient rather than as periodic data. In the second method the frequency-response function is deter- mined from the system's transient response to a very rapid sweep input. The purpose of frequency sweep in this case is to provide sufficient harmonic content in the input to overcome noise while keeping the test time as short as possible. tests and limited flight-test data presented herein, it appears that a transient-type rapid-sweep forcing function offers a considerable saving in test time while preserving the accuracy possible with steady-state sinusoidal inputs.

  12. Commissioning of a multiple-frequency modulation smoothing by spectral dispersion demonstration system on OMEGA EP

    NASA Astrophysics Data System (ADS)

    Kruschwitz, B. E.; Kelly, J. H.; Dorrer, C.; Okishev, A. V.; Waxer, L. J.; Balonek, G.; Begishev, I. A.; Bittle, W.; Consentino, A.; Cuffney, R.; Hill, E.; Marozas, J. A.; Moore, M.; Roides, R. G.; Zuegel, J. D.

    2013-02-01

    A one-dimensional smoothing by spectral dispersion (SSD) demonstration system for smoothing focal-spot nonuniformities using multiple modulation frequencies (multi-FM SSD) was commissioned on one long-pulse beamline of OMEGA EP—the first use of such a system in a high-energy laser. System models of frequency modulation-to-amplitude modulation (FM-to-AM) conversion in the OMEGA EP beamline and final optics were used to develop an AM budget. The AM budget in turn provided a UV power limit of 0.85 TW, based on accumulation of B-integral in the final optics. The front end of the demonstration system utilized a National Ignition Facility preamplifier module (PAM) with a custom SSD grating inserted into the PAM's multipass amplifier section. The dispersion of the SSD grating was selected to cleanly propagate the dispersed SSD bandwidth through various pinholes in the system while maintaining sufficient focal-spot smoothing performance. A commissioning plan was executed that systematically introduced the new features of the demonstration system into OMEGA EP. Ultimately, the OMEGA EP beamline was ramped to the UV power limit with various pulse shapes. The front-end system was designed to provide flexibility in pulse shaping. Various combinations of pickets and nanosecond-scale drive pulses were demonstrated, with multi-FM SSD selectively applied to portions of the pulse. Analysis of the dispersion measured by the far-field diagnostics at the outputs of the infrared beamline and the frequency-conversion crystals indicated that the SSD modulation spectrum was maintained through both the beamline and the frequency-conversion process. At the completion of the plan, a series of equivalent-target-plane measurements with distributed phase plates installed were conducted that confirmed the expected timeintegrated smoothing of the focal spot.

  13. R&D of an LLRF control system for a 162.5 MHz radio frequency system

    NASA Astrophysics Data System (ADS)

    Wen, Liang-Hua; Wang, Xian-Wu; He, Yuan; Chang, Wei; Zhang, Rui-Feng; Zhang, Sheng-Hu; Zhu, Zheng-Long; Li, Chun-Long; Shi, Long-Bo; Zhang, Rui

    2013-08-01

    This paper describes a low level radio frequency control system that was developed by the Institute of Modern Physics Chinese Academy of Sciences, and will be used in Injector II of the China-ADS project. The LLRF control system consists of an RF modulated front end, fast analog-to-digital converter (ADC) modules, and a digital signal processing board based on a field programmable gate array. The system has been tested on a room temperature cavity with 12-hr, and the results illustrate that the stability of amplitude and phase achieved ±0.32% and ±0.35 degrees, respectively.

  14. Development of a prototype compact fibre frequency synthesiser for mobile femtosecond optical clocks

    SciTech Connect

    Pivtsov, V S; Korel', I I; Koliada, N A; Farnosov, S A; Denisov, V I; Nyushkov, B N

    2014-06-30

    A prototype compact fibre frequency synthesiser based on a femtosecond erbium fibre laser and an original hybrid highly nonlinear fibre is developed and preliminarily studied. This synthesiser will ensure an extremely low relative instability of synthesised frequencies (down to 10{sup -17}) with the use of a corresponding optical standard and will be used in mobile optical clocks. The realised frequency stabilisation principle makes the synthesiser universal and allows it to transfer the frequency stability of various types of optical standards to the synthesised radio- and optical frequencies. (extreme light fields and their applications)

  15. Development of a high speed wideband frequency tunable infrared laser source for real time wind turbine array sensing applications

    NASA Astrophysics Data System (ADS)

    Mitchell, Philip; Janssen, Adrian; Partov Poor, Bahar

    2011-05-01

    This paper reports the development of an infra-red circa 193THz (~1.5μm) frequency tunable laser source selected and evaluated for photonic environment sensing systems. LIDAR (LIght Detection And Ranging) offers a method of remote wind speed measurement. Widespread deployment of the technique has been limited by the expense and complexity of LIDAR systems. However development of systems based on optical fiber and photonic components from the telecommunications industry promises improvements in cost, compactness, and reliability, so that it becomes viable to consider deployment of such systems on large wind turbines for the advance detection of fluctuations of wind speed. A monolithic multi-section laser, originally designed as a tunable source for telecommunications applications, has been modified and re-evaluated as a source for sensing applications, based on the technique of coherent laser radar (CLR), and coherent doppler LIDAR (CDL). A tunable frequency optical source should fulfil specific technical criteria to fulfil the applications requirements; speed of frequency selection, absolute accuracy of emitted frequency, spectral purity, and stability. Custom electronics and firmware were developed to realise an improvement in frequency switching speed by a factor of 10 relative to equivalent commercially available telecoms (DBR) sources, satisfying the target application requirements. An overview of the sensing architecture is presented, a detailed description of the fast tuning process described, including the custom hardware and firmware, and specifically the laser energising sequence. The results of the laser module are then presented with detailed consideration of the target application.

  16. Frequency domain modeling and dynamic characteristics evaluation of existing wind turbine systems

    NASA Astrophysics Data System (ADS)

    Chiang, Chih-Hung; Yu, Chih-Peng

    2016-04-01

    It is quite well accepted that frequency domain procedures are suitable for the design and dynamic analysis of wind turbine structures, especially for floating offshore wind turbines, since random wind loads and wave induced motions are most likely simulated in the frequency domain. This paper presents specific applications of an effective frequency domain scheme to the linear analysis of wind turbine structures in which a 1-D spectral element was developed based on the axially-loaded member. The solution schemes are summarized for the spectral analyses of the tower, the blades, and the combined system with selected frequency-dependent coupling effect from foundation-structure interactions. Numerical examples demonstrate that the modal frequencies obtained using spectral-element models are in good agreement with those found in the literature. A 5-element mono-pile model results in less than 0.3% deviation from an existing 160-element model. It is preliminarily concluded that the proposed scheme is relatively efficient in performing quick verification for test data obtained from the on-site vibration measurement using the microwave interferometer.

  17. Liquid Cooled Variable Speed Constant Frequency (VSCF) Converter Device Development.

    DTIC Science & Technology

    1982-06-01

    into a rod, slices can be geometries and materials . Evaluation of steady made. The pipe wall holds the wires together, state performance can be done...the same above mentioned VSCF development period, the Air Force Materials Laboratory was leading the effort in the development of Rare Earth...solder preform be speci- fied on the drawings for future reference. Indalloy 151 solder is used to bond together the various materials making up the

  18. System Description and First Application of an FPGA-Based Simultaneous Multi-Frequency Electrical Impedance Tomography.

    PubMed

    Aguiar Santos, Susana; Robens, Anne; Boehm, Anna; Leonhardt, Steffen; Teichmann, Daniel

    2016-07-25

    A new prototype of a multi-frequency electrical impedance tomography system is presented. The system uses a field-programmable gate array as a main controller and is configured to measure at different frequencies simultaneously through a composite waveform. Both real and imaginary components of the data are computed for each frequency and sent to the personal computer over an ethernet connection, where both time-difference imaging and frequency-difference imaging are reconstructed and visualized. The system has been tested for both time-difference and frequency-difference imaging for diverse sets of frequency pairs in a resistive/capacitive test unit and in self-experiments. To our knowledge, this is the first work that shows preliminary frequency-difference images of in-vivo experiments. Results of time-difference imaging were compared with simulation results and shown that the new prototype performs well at all frequencies in the tested range of 60 kHz-960 kHz. For frequency-difference images, further development of algorithms and an improved normalization process is required to correctly reconstruct and interpreted the resulting images.

  19. System Description and First Application of an FPGA-Based Simultaneous Multi-Frequency Electrical Impedance Tomography

    PubMed Central

    Aguiar Santos, Susana; Robens, Anne; Boehm, Anna; Leonhardt, Steffen; Teichmann, Daniel

    2016-01-01

    A new prototype of a multi-frequency electrical impedance tomography system is presented. The system uses a field-programmable gate array as a main controller and is configured to measure at different frequencies simultaneously through a composite waveform. Both real and imaginary components of the data are computed for each frequency and sent to the personal computer over an ethernet connection, where both time-difference imaging and frequency-difference imaging are reconstructed and visualized. The system has been tested for both time-difference and frequency-difference imaging for diverse sets of frequency pairs in a resistive/capacitive test unit and in self-experiments. To our knowledge, this is the first work that shows preliminary frequency-difference images of in-vivo experiments. Results of time-difference imaging were compared with simulation results and shown that the new prototype performs well at all frequencies in the tested range of 60 kHz–960 kHz. For frequency-difference images, further development of algorithms and an improved normalization process is required to correctly reconstruct and interpreted the resulting images. PMID:27463715

  20. SCCS System SW Development

    NASA Technical Reports Server (NTRS)

    Beale, David Michael

    2014-01-01

    The original project to be completed, GenSim, was a Generic Simulator for Application Control Language scripts. This would mock the systems on which the scripts were meant to be run on so that you could run tests without access to the machine. Soon after the project was started, a different project took priority. Unit testing the Application Services Framework code became the focus of the team because of approaching deadlines. Communication was very important to ensure that code wasn't being duplicated and to keep the team up to date with what mock files are available to them. Because of this, daily meetings were conducted until the testing was complete.

  1. 47 CFR 90.357 - Frequencies for LMS systems in the 902-928 MHz band.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequencies for LMS systems in the 902-928 MHz... SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Intelligent Transportation Systems Radio Service § 90.357 Frequencies for LMS systems in the 902-928 MHz band. (a) Multilateration LMS systems will be...

  2. 47 CFR 90.357 - Frequencies for LMS systems in the 902-928 MHz band.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Intelligent Transportation Systems Radio Service § 90.357 Frequencies for LMS systems in the 902-928 MHz band. (a) Multilateration LMS systems will be... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequencies for LMS systems in the 902-928 MHz...

  3. 47 CFR 90.357 - Frequencies for LMS systems in the 902-928 MHz band.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Intelligent Transportation Systems Radio Service § 90.357 Frequencies for LMS systems in the 902-928 MHz band. (a) Multilateration LMS systems will be... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequencies for LMS systems in the 902-928 MHz...

  4. 47 CFR 90.357 - Frequencies for LMS systems in the 902-928 MHz band.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Intelligent Transportation Systems Radio Service § 90.357 Frequencies for LMS systems in the 902-928 MHz band. (a) Multilateration LMS systems will be... 47 Telecommunication 5 2011-10-01 2011-10-01 false Frequencies for LMS systems in the 902-928...

  5. Algae-P Relationships, Thresholds, and Frequency Distributions Guide Nutrient Criterion Development

    EPA Science Inventory

    The complementary use of frequency distribution methods and stressor-response relationships that we used to develop candidates for TP criteria in this study should provide the fundamental analytical basis for criteria development to protect multiple attributes in ecosystems where...

  6. Cellular computational generalized neuron network for frequency situational intelligence in a multi-machine power system.

    PubMed

    Wei, Yawei; Venayagamoorthy, Ganesh Kumar

    2017-09-01

    To prevent large interconnected power system from a cascading failure, brownout or even blackout, grid operators require access to faster than real-time information to make appropriate just-in-time control decisions. However, the communication and computational system limitations of currently used supervisory control and data acquisition (SCADA) system can only deliver delayed information. However, the deployment of synchrophasor measurement devices makes it possible to capture and visualize, in near-real-time, grid operational data with extra granularity. In this paper, a cellular computational network (CCN) approach for frequency situational intelligence (FSI) in a power system is presented. The distributed and scalable computing unit of the CCN framework makes it particularly flexible for customization for a particular set of prediction requirements. Two soft-computing algorithms have been implemented in the CCN framework: a cellular generalized neuron network (CCGNN) and a cellular multi-layer perceptron network (CCMLPN), for purposes of providing multi-timescale frequency predictions, ranging from 16.67 ms to 2 s. These two developed CCGNN and CCMLPN systems were then implemented on two different scales of power systems, one of which installed a large photovoltaic plant. A real-time power system simulator at weather station within the Real-Time Power and Intelligent Systems (RTPIS) laboratory at Clemson, SC, was then used to derive typical FSI results. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Engineering monitoring expert system's developer

    NASA Technical Reports Server (NTRS)

    Lo, Ching F.

    1991-01-01

    This research project is designed to apply artificial intelligence technology including expert systems, dynamic interface of neural networks, and hypertext to construct an expert system developer. The developer environment is specifically suited to building expert systems which monitor the performance of ground support equipment for propulsion systems and testing facilities. The expert system developer, through the use of a graphics interface and a rule network, will be transparent to the user during rule constructing and data scanning of the knowledge base. The project will result in a software system that allows its user to build specific monitoring type expert systems which monitor various equipments used for propulsion systems or ground testing facilities and accrues system performance information in a dynamic knowledge base.

  8. Spatial and frequency averaging techniques for a polarimetric scatterometer system

    SciTech Connect

    Monakov, A.A.; Stjernman, A.S.; Nystroem, A.K. ); Vivekanandan, J. )

    1994-01-01

    An accurate estimation of backscattering coefficients for various types of rough surfaces is the main theme of remote sensing. Radar scattering signals from distributed targets exhibit fading due to interference associated with coherent scattering from individual scatterers within the resolution volume. Uncertainty in radar measurements which arises as a result of fading is reduced by averaging independent samples. Independent samples are obtained by collecting the radar returns from nonoverlapping footprints (spatial averaging) and/or nonoverlapping frequencies (frequency agility techniques). An improved formulation of fading characteristics for the spatial averaging and frequency agility technique is derived by taking into account the rough surface scattering process. Kirchhoff's approximation is used to describe rough surface scattering. Expressions for fading decorrelation distance and decorrelation bandwidth are derived. Rough surface scattering measurements are performed between L and X bands. Measured frequency and spatial correlation coefficients show good agreement with theoretical results.

  9. Systems and methods for determining radio frequency interference

    NASA Technical Reports Server (NTRS)

    Johannsen, K. G.; Sabaroff, S.; Henry, V. F. (Inventor)

    1978-01-01

    The presence, frequency and amplitude of radio frequency interference superimposed on communication links originating from a terrestrial region and including a relay in a geostationary spacecraft are determined by pointing a narrow beam antenna on the satellite at the terrestrial region. The level of noise radiated from the region to the antenna is measured at a terrestrial station that is usually remote from the region. Calibrating radio signals having a plurality of predetermined EIRP's (Effective Isotropic Radiated Power) and frequencies in the spectrum are transmitted from the region through the spacecraft narrow beam antenna back to the station. At the station, the levels of the received calibrating signals are separately measured for each of the frequency bands and EIRP's.

  10. An improved offset generator developed for Allan deviation measurement of ultra stable frequency standards

    NASA Technical Reports Server (NTRS)

    Hamell, Robert L.; Kuhnle, Paul F.; Sydnor, Richard L.

    1992-01-01

    Measuring the performance of ultra stable frequency standards such as the Superconducting Cavity Maser Oscillator (SCMO) necessitates improvement of some test instrumentation. The frequency stability test equipment used at JPL includes a 1 Hz Offset Generator to generate a beat frequency between a pair of 100 MHz signals that are being compared. The noise floor of the measurement system using the current Offset Generator is adequate to characterize stability of hydrogen masers, but it is not adequate for the SCMO. A new Offset Generator with improved stability was designed and tested at JPL. With this Offset Generator and a new Zero Crossing Detector, recently developed at JPL, the measurement flow was reduced by a factor of 5.5 at 1 second tau, 3.0 at 1000 seconds, and 9.4 at 10,000 seconds, compared against the previous design. In addition to the new circuit designs of the Offset Generator and Zero Crossing Detector, tighter control of the measurement equipment environment was required to achieve this improvement. The design of this new Offset Generator are described, along with details of the environment control methods used.

  11. An improved offset generator developed for Allan deviation measurement of ultra stable frequency standards

    NASA Technical Reports Server (NTRS)

    Hamell, Robert L.; Kuhnle, Paul F.; Sydnor, Richard L.

    1992-01-01

    Measuring the performance of ultra stable frequency standards such as the Superconducting Cavity Maser Oscillator (SCMO) necessitates improvement of some test instrumentation. The frequency stability test equipment used at JPL includes a 1 Hz Offset Generator to generate a beat frequency between a pair of 100 MHz signals that are being compared. The noise floor of the measurement system using the current Offset Generator is adequate to characterize stability of hydrogen masers, but it is not adequate for the SCMO. A new Offset Generator with improved stability was designed and tested at JPL. With this Offset Generator and a new Zero Crossing Detector, recently developed at JPL, the measurement flow was reduced by a factor of 5.5 at 1 second tau, 3.0 at 1000 seconds, and 9.4 at 10,000 seconds, compared against the previous design. In addition to the new circuit designs of the Offset Generator and Zero Crossing Detector, tighter control of the measurement equipment environment was required to achieve this improvement. The design of this new Offset Generator are described, along with details of the environment control methods used.

  12. Progress in low-frequency radio astronomy and I.S. Shklovskii's contribution to its development

    NASA Astrophysics Data System (ADS)

    Konovalenko, A. A.

    2017-04-01

    Radio astronomy at decameter wavelengths is currently undergoing very active development. Large-scale, new generation low-frequency radio telescopes are being constructed and already used in many countries around the world. As before, the largest, most sensitive, and most versatile telescope at decameter wavelengths is the Ukrainian UTR-2 radio telescope operating at 8-32 MHz, which has an effective area of more than 105 m2 and an angular resolution of about 0.5°, as well as the URAN interferometric system based on the UTF-2. Many studies that have been carried out on these facilities have been based on important results and far-sighted predictions of Shklovskii. These include, in particular, studies of dynamical spectra and the brightness distributions of the sporadic and quiescent decameter radio emission of the hot solar corona, complex, broadband radio spectroscopy of the interstellar medium, and multi-frequency monitoring of secular decreases in the flux densities of supernova remnants. The coordinated use of highly effective existing and newly constructed radio telescopes joined into ground networks, as well as specialized space missions, are opening new prospects for low-frequency radio astronomy.

  13. A FEMTOSECOND-LEVEL FIBER-OPTICS TIMING DISTRIBUTION SYSTEM USING FREQUENCY-OFFSET INTERFEROMETRY

    SciTech Connect

    Staples, J.W.; Byrd, J.; Doolittle, L.; Huang, G.; Wilcox, R.

    2009-10-17

    An optical fiber-based frequency and timing distribution system based on the principle of heterodyne interferometry has been in development at LBNL for several years. The fiber drift corrector has evolved from an RF-based to an optical-based system, from mechanical correctors (piezo and optical trombone) to fully electronic, and the electronics from analog to fully digital, all using inexpensive off-the-shelf commodity fiber components. Short-term optical phase jitter and long-term phase drift are both in the femtosecond range over distribution paths of 2 km or more.

  14. A novel control system for automatically locking a diode laser frequency to a selected gas absorption line

    NASA Astrophysics Data System (ADS)

    Dong, Lei; Yin, Wangbao; Ma, Weiguang; Jia, Suotang

    2007-05-01

    A novel control system has been developed for avoiding manual operation during traditional frequency locking. The control system uses a computer with a commercial data acquisition card. This accomplishes the whole operation of frequency locking, including generating ramp, searching locking point, engaging a proportional-integral-differential (PID) regulator at the proper time and outputting PID compensation signal. Moreover, a new method has also been employed to make the novel control system accurately identify the locking points of all absorption lines within the scanning range, so that the laser frequency can be automatically firmly brought onto any selected absorption line centre without any adjusting time. The operation of the system, the ability to identify absorption lines and the performance of the frequency locking were discussed in detail. Successful tests were made with two different lasers: external cavity diode lasers and distributed feedback diode lasers.

  15. Cyber security with radio frequency interferences mitigation study for satellite systems

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Wei, Sixiao; Chen, Genshe; Tian, Xin; Shen, Dan; Pham, Khanh; Nguyen, Tien M.; Blasch, Erik

    2016-05-01

    Satellite systems including the Global Navigation Satellite System (GNSS) and the satellite communications (SATCOM) system provide great convenience and utility to human life including emergency response, wide area efficient communications, and effective transportation. Elements of satellite systems incorporate technologies such as navigation with the global positioning system (GPS), satellite digital video broadcasting, and information transmission with a very small aperture terminal (VSAT), etc. The satellite systems importance is growing in prominence with end users' requirement for globally high data rate transmissions; the cost reduction of launching satellites; development of smaller sized satellites including cubesat, nanosat, picosat, and femtosat; and integrating internet services with satellite networks. However, with the promising benefits, challenges remain to fully develop secure and robust satellite systems with pervasive computing and communications. In this paper, we investigate both cyber security and radio frequency (RF) interferences mitigation for satellite systems, and demonstrate that they are not isolated. The action space for both cyber security and RF interferences are firstly summarized for satellite systems, based on which the mitigation schemes for both cyber security and RF interferences are given. A multi-layered satellite systems structure is provided with cross-layer design considering multi-path routing and channel coding, to provide great security and diversity gains for secure and robust satellite systems.

  16. Development of a new concept automatic frequency controller for an ultrasmall C-band linear accelerator guide.

    PubMed

    Kamino, Yuichiro; Tsukuda, Kazuhiro; Kokubo, Masaki; Miura, Sadao; Hirai, Etsuro; Hiraoka, Masahiro; Ishikawa, Junzo

    2007-08-01

    We are developing a four-dimensional, image-guided radiotherapy system with a gimbaled x-ray head. The system has pursuing irradiation capability in addition to precise irradiation capability, owing to its agile x-ray head. The moving x-ray head requires a very small C-band accelerator guide. The heat intensity of the accelerator guide is much higher than that of conventional S-band medical linear accelerators. The resonance frequency varies over almost 1.0 MHz with a thermal time constant of about 30 s. An automatic frequency controller (AFC) is employed to compensate for this variation in resonance frequency. Furthermore, we noted that fast AFC response is important for step-and-shoot intensity modulation radiotherapy (IMRT), in which the beam is turned on and off frequently. Therefore, we invented a digital AFC, based on a new concept, to provide effective compensation for the thermal characteristics of the accelerator guide and to ensure stable and optimized x-ray treatment. An important aspect of the performance of the AFC is the capture-frequency range over which the AFC can seek, lock on to, and track the resonance frequency. The conventional, analog AFC used in S-band medical linear accelerators would have a capture-frequency range of about 0.9 MHz, if applied to our accelerator guide, and would be inappropriate. Conversely, our new AFC has a capture-frequency range of 24 MHz, which is well suited to our accelerator guide. The design concept behind this new AFC has been developed and verified. A full prototype system was constructed and tested on an existing accelerator guide at the rated x-ray output (500 cGy/min) of our radiotherapy system, with a pulse-repetition frequency of 300 Hz. The AFC acquired the resonance frequency of the accelerator guide within 0.15 s after beam-on, and provided stable tracking and adjustment of the frequency of the microwave source to the resonance frequency of the accelerator guide. With a planned improvement of the

  17. SPECTRON, a neutron noise measurement system in frequency domain.

    PubMed

    de Izarra, G; Jammes, C; Geslot, B; Di Salvo, J; Destouches, C

    2015-11-01

    This paper is dedicated to the presentation and validation of SPECTRON, a novel neutron noise measurement system developed at CEA Cadarache. The device is designed for the measurement of the β(eff) parameter (effective fraction of delayed neutrons) of experimental nuclear reactors using the Cohn-α method. An integrated electronic system is used to record the current from fission chambers. Spectra computed from measurement data are processed by a dedicated software in order to estimate the reactor transfer function and then the effective fraction of delayed neutrons as well as the prompt neutron generation time. After a review of the pile noise measurement method in current mode, the SPECTRON architecture is presented. Then, the validation procedure is described and experimental results are shown, supporting the proper functioning of this new measurement system. It is shown that every technical requirement needed for correct measurement of neutron noise is fulfilled. Measurements performed at MINERVE and EOLE, two experimental nuclear reactors at CEA Cadarache, in real conditions allowed us to validate SPECTRON.

  18. System Control Applications of Low-Power Radio Frequency Devices

    NASA Astrophysics Data System (ADS)

    van Rensburg, Roger

    2017-09-01

    This paper conceptualizes a low-power wireless sensor network design for application employment to reduce theft of portable computer devices used in educational institutions today. The aim of this study is to design and develop a reliable and robust wireless network that can eradicate accessibility of a device’s human interface. An embedded system supplied by an energy harvesting source, installed on the portable computer device, may represent one of multiple slave nodes which request regular updates from a standalone master station. A portable computer device which is operated in an undesignated area or in a field perimeter where master to slave communication is restricted, indicating a possible theft scenario, will initiate a shutdown of its operating system and render the device unusable. Consequently, an algorithm in the device firmware may ensure the necessary steps are executed to track the device, irrespective whether the device is enabled. Design outcomes thus far indicate that a wireless network using low-power embedded hardware, is feasible for anti-theft applications. By incorporating one of the latest Bluetooth low-energy, ANT+, ZigBee or Thread wireless technologies, an anti-theft system may be implemented that has the potential to reduce major portable computer device theft in institutions of digitized learning.

  19. SPECTRON, a neutron noise measurement system in frequency domain

    SciTech Connect

    Izarra, G. de; Jammes, C. Destouches, C.; Geslot, B.; Di Salvo, J.

    2015-11-15

    This paper is dedicated to the presentation and validation of SPECTRON, a novel neutron noise measurement system developed at CEA Cadarache. The device is designed for the measurement of the β{sub eff} parameter (effective fraction of delayed neutrons) of experimental nuclear reactors using the Cohn-α method. An integrated electronic system is used to record the current from fission chambers. Spectra computed from measurement data are processed by a dedicated software in order to estimate the reactor transfer function and then the effective fraction of delayed neutrons as well as the prompt neutron generation time. After a review of the pile noise measurement method in current mode, the SPECTRON architecture is presented. Then, the validation procedure is described and experimental results are shown, supporting the proper functioning of this new measurement system. It is shown that every technical requirement needed for correct measurement of neutron noise is fulfilled. Measurements performed at MINERVE and EOLE, two experimental nuclear reactors at CEA Cadarache, in real conditions allowed us to validate SPECTRON.

  20. Managing Risk in Systems Development.

    ERIC Educational Resources Information Center

    DePaoli, Marilyn M.; And Others

    Stanford University's use of a risk assessment methodology to improve the management of systems development projects is discussed. After examining the concepts of hazard, peril, and risk as they relate to the system development process, three ways to assess risk are covered: size, structure, and technology. The overall objective for Stanford…

  1. Managing Risk in Systems Development.

    ERIC Educational Resources Information Center

    DePaoli, Marilyn M.; And Others

    Stanford University's use of a risk assessment methodology to improve the management of systems development projects is discussed. After examining the concepts of hazard, peril, and risk as they relate to the system development process, three ways to assess risk are covered: size, structure, and technology. The overall objective for Stanford…

  2. An Instructional Systems Development Process.

    ERIC Educational Resources Information Center

    Campbell, Clifton P.

    Instructional systems development (ISD) is a systems approach to curriculum development and instructional delivery. It is oriented toward occupational needs with an emphasis on what it is that students must learn to perform specific tasks, what facilities best provide a setting for the neccessary learning, and what instructional methods and media…

  3. Development of frequency step tunable 1 MW gyrotron at 131 to 146.5 GHz

    SciTech Connect

    Samartsev, A.; Gantenbein, G.; Dammertz, G.; Illy, S.; Kern, S.; Leonhardt, W.; Schlaich, A.; Schmid, M.; Thumm, M.

    2011-07-01

    Effective control of power absorption in tokamaks and stellarators could be achieved by the frequency tuning of ECH and CD power delivered by high-power gyrotrons. In this report some results of the development of a frequency tunable gyrotron with fused-silica Brewster window are presented. Excitation of several modes at 1 MW power level in the range of frequencies from 131 to 146.5 GHz is achieved. (author)

  4. Development of high power radio frequency components for fusion plasma heating. Final report, Revision 3

    SciTech Connect

    1997-09-11

    The purpose of this CRADA was to develop advanced microwave heating systems for both ion cyclotron heating and electron cyclotron heating for magnetic fusion reactors. This involved low-frequency (UHF), high-power (millimeter-wave) microwave components, such as antennas, windows, and matching elements. This CRADA also involved developing conceptual designs for new microwave sources. General Atomics built and tested the distributed cooled window and provided LLNL with transmission and reflection test data in order to then benchmark the EM computer codes. The combline antenna built and analyzed by LLNL was based on a GA design. GA provided LLNL with a number of niobium plates for hot pressing and provided the necessary guidance to allow successful bonding. GA representatives were on site at LLNL on numerous occasions to consult and give guidance on the ferroelectric tuner, combline antenna and distributed window analysis.

  5. A Low Cost Automated Monitoring System for Landslides Using Dual Frequency GPS

    NASA Astrophysics Data System (ADS)

    Mills, H.; Edwards, S.

    2006-12-01

    Landslides are an existing and permanent threat to societies across the globe, generating financial and human losses whenever and wherever they occur. Drawing together the strands of science that provide increased understanding of landslide triggers through accurate modelling is therefore vital for the development of mitigation and management strategies. Together with climatic and geomorphological data a key input here is information on the precise location and timing of landslide events. However, the detailed monitoring of landslides and precursor movements is generally limited to episodic campaigns where limiting factors include equipment and mobilisation costs, time constraints and spatial resolution. This research has developed a geodetic tool of benefit to scientists involved in the development of closely coupled models that seek to explain trigger mechanisms such as rainfall duration and intensity and changes in groundwater pressure to actual real land movements. A fully automated low cost dual frequency GPS station for the continuous in-situ monitoring of landslide sites has been developed. System configuration combines a dual frequency GPS receiver, PC board with a GPRS modem and power supply to deliver 24hr/365day operation capability. Individual components have been chosen to provide the highest accuracies while minimising power consumption resulting in a system around half that of equivalent commercial systems. Measurement point-costs can be further reduced through the use of antenna switching and multi antenna arrays. Continuous data is delivered via mobile phone uplink and processed automatically using geodetic software. The developed system has been extensively tested on a purpose built platform capable of simulating ground movements. Co-mounted antennas have allowed direct comparisons with more expensive geodetic GPS receivers. The system is capable of delivering precise 3D coordinates with a 9 mm rms. The system can be up-scaled resulting in the

  6. Dynamic model based novel findings in power systems analysis and frequency measurement verification

    NASA Astrophysics Data System (ADS)

    Kook, Kyung Soo

    This study selects several new advanced topics in power systems, and verifies their usefulness using the simulation. In the study on ratio of the equivalent reactance and resistance of the bulk power systems, the simulation results give us the more correct value of X/R of the bulk power system, which can explain why the active power compensation is also important in voltage flicker mitigation. In the application study of the Energy Storage System(ESS) to the wind power, the new model implementation of the ESS connected to the wind power is proposed, and the control effect of ESS to the intermittency of the wind power is verified. Also this study conducts the intensive simulations for clarifying the behavior of the wide-area power system frequency as well as the possibility of the on-line instability detection. In our POWER IT Laboratory, since 2003, the U.S. national frequency monitoring network (FNET) has been being continuously operated to monitor the wide-area power system frequency in the U.S. Using the measured frequency data, the event of the power system is triggered, and its location and scale are estimated. This study also looks for the possibility of using the simulation technologies to contribute the applications of FNET, finds similarity of the event detection orders between the frequency measurements and the simulations in the U.S. Eastern power grid, and develops the new methodology for estimating the event location based on the simulated N-1 contingencies using the frequency measurement. It has been pointed out that the simulation results can not represent the actual response of the power systems due to the inevitable limit of modeling power systems and different operating conditions of the systems at every second. However, in the circumstances that we need to test such an important infrastructure supplying the electric energy without taking any risk of it, the software based simulation will be the best solution to verify the new technologies in

  7. Method of Detecting System Function by Measuring Frequency Response

    NASA Technical Reports Server (NTRS)

    Morrison, John L. (Inventor); Morrison, William H. (Inventor)

    2008-01-01

    Real time battery impedance spectrum is acquired using one time record, Compensated Synchronous Detection (CSD). This parallel method enables battery diagnostics. The excitation current to a test battery is a sum of equal amplitude sin waves of a few frequencies spread over range of interest. The time profile of this signal has duration that is a few periods of the lowest frequency. The voltage response of the battery, average deleted, is the impedance of the battery in the time domain. Since the excitation frequencies are known, synchronous detection processes the time record and each component, both magnitude and phase, is obtained. For compensation, the components, except the one of interest, are reassembled in the time domain. The resulting signal is subtracted from the original signal and the component of interest is synchronously detected. This process is repeated for each component.

  8. Method of detecting system function by measuring frequency response

    DOEpatents

    Morrison, John L.; Morrison, William H.

    2008-07-01

    Real time battery impedance spectrum is acquired using one time record, Compensated Synchronous Detection (CSD). This parallel method enables battery diagnostics. The excitation current to a test battery is a sum of equal amplitude sin waves of a few frequencies spread over range of interest. The time profile of this signal has duration that is a few periods of the lowest frequency. The voltage response of the battery, average deleted, is the impedance of the battery in the time domain. Since the excitation frequencies are known, synchronous detection processes the time record and each component, both magnitude and phase, is obtained. For compensation, the components, except the one of interest, are reassembled in the time domain. The resulting signal is subtracted from the original signal and the component of interest is synchronously detected. This process is repeated for each component.

  9. Advancements in frequency-domain methods for rotorcraft system identification

    NASA Technical Reports Server (NTRS)

    Tischler, Mark B.

    1989-01-01

    A new method for frequency-domain identification of rotorcraft dynamics is presented. Nonparametric frequency-response identification and parametric transfer-function modeling methods are extended to allow the extraction of state-space (stability and control derivative) representations. An interactive computer program DERIVID is described for the iterative solution of the multi-input/multi-output frequency-response matching approach used in the identification. Theoretical accuracy methods are used to determine the appropriate model structure and degree-of-confidence in the identified parameters. The method is applied to XV-15 tilt-rotor aircraft data in hover. Bare-airframe stability and control derivatives for the lateral/directional dynamics are shown to compare favorably with models previously obtained using time-domain identification methods and the XV-15 simulation program.

  10. Advancements in frequency-domain methods for rotorcraft system identification

    NASA Technical Reports Server (NTRS)

    Tischler, Mark B.

    1988-01-01

    A new method for frequency-domain identification of rotorcraft dynamics is presented. Nonparametric frequency-response identification and parametric tranfer-function modeling methods are extended to allow the extraction of state-space (stability and control derivative) representations. An interactive computer program DERIVID is described for the iterative solution of the multi-input/multi-output frequency-response matching approach used in the identification. Theoretical accuracy methods are used to determine the appropriate model structure and degree-of-confidence in the identified parameters. The method is applied to XV-15 tilt-rotor aircraft data in hover. Bare-airframe stability and control derivatives for the lateral/directional dynamics are shown to compare favorably with models previously obtained using time-domain identification methods and the XV-15 simulation program.

  11. Properties and Frequency Conversion of High-Brightness Diode-Laser Systems

    NASA Astrophysics Data System (ADS)

    Boller, Klaus-Jochen; Beier, Bernard; Wallenstein, Richard

    An overview of recent developments in the field of high-power, high-brightness diode-lasers, and the optically nonlinear conversion of their output into other wavelength ranges, is given. We describe the generation of continuous-wave (CW) laser beams at power levels of several hundreds of milliwatts to several watts with near-perfect spatial and spectral properties using Master-Oscillator Power-Amplifier (MOPA) systems. With single- or double-stage systems, using amplifiers of tapered or rectangular geometry, up to 2.85 W high-brightness radiation is generated at wavelengths around 810nm with AlGaAs diodes. Even higher powers, up to 5.2W of single-frequency and high spatial quality beams at 925nm, are obtained with InGaAs diodes. We describe the basic properties of the oscillators and amplifiers used. A strict proof-of-quality for the diode radiation is provided by direct and efficient nonlinear optical conversion of the diode MOPA output into other wavelength ranges. We review recent experiments with the highest power levels obtained so far by direct frequency doubling of diode radiation. In these experiments, 100mW single-frequency ultraviolet light at 403nm was generated, as well as 1W of single-frequency blue radiation at 465nm. Nonlinear conversion of diode radiation into widely tunable infrared radiation has recently yielded record values. We review the efficient generation of widely tunable single-frequency radiation in the infrared with diode-pumped Optical Parametric Oscillators (OPOs). With this system, single-frequency output radiation with powers of more than 0.5W was generated, widely tunable around wavelengths of 2.1,m and 1.65,m and with excellent spectral and spatial quality. These developments are clear indicators of recent advances in the field of high-brightness diode-MOPA systems, and may emphasize their future central importance for applications within a vast range of optical

  12. Airborne Turbulence Warning System Development

    NASA Technical Reports Server (NTRS)

    Bogue, Rod

    2003-01-01

    This viewgraph presentation provides information on the development of a system by which aircraft pilots will be warned of turbulence. This networked system of in situ sensors will be mounted on various aircraft all of which are linked through a ground based parabolic antenna. As its end result, this system will attempt to reduce the number of accidents arising from turbulence.

  13. Expert systems development and application

    NASA Technical Reports Server (NTRS)

    Duke, E. L.; Regenie, V. A.

    1985-01-01

    Current research in the application of expert systems to problems in the flight research environment is discussed. In what is anticipated to be a broad research area, a real time expert system flight status monitor has been identified as the initial project. This real time expert system flight status monitor is described in terms of concept, application, development, and schedule.

  14. ISE System Development Methodology Manual

    SciTech Connect

    Hayhoe, G.F.

    1992-02-17

    The Information Systems Engineering (ISE) System Development Methodology Manual (SDM) is a framework of life cycle management guidelines that provide ISE personnel with direction, organization, consistency, and improved communication when developing and maintaining systems. These guide-lines were designed to allow ISE to build and deliver Total Quality products, and to meet the goals and requirements of the US Department of Energy (DOE), Westinghouse Savannah River Company, and Westinghouse Electric Corporation.

  15. 47 CFR 80.385 - Frequencies for automated systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... System (AMTS) and for other automated multi-station systems. (a) Automated Maritime Telecommunications System (AMTS). (1) The Automated Maritime Communications System (AMTS) is an automated maritime... stations for public correspondence communications with ship stations and units on land. AMTS...

  16. 47 CFR 80.385 - Frequencies for automated systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... System (AMTS) and for other automated multi-station systems. (a) Automated Maritime Telecommunications System (AMTS). (1) The Automated Maritime Communications System (AMTS) is an automated maritime... stations for public correspondence communications with ship stations and units on land. AMTS...

  17. 47 CFR 80.385 - Frequencies for automated systems.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... System (AMTS) and for other automated multi-station systems. (a) Automated Maritime Telecommunications System (AMTS). (1) The Automated Maritime Communications System (AMTS) is an automated maritime... stations for public correspondence communications with ship stations and units on land. AMTS...

  18. Radio Frequency Identification (RFID) and communication technologies for solid waste bin and truck monitoring system.

    PubMed

    Hannan, M A; Arebey, Maher; Begum, R A; Basri, Hassan

    2011-12-01

    This paper deals with a system of integration of Radio Frequency Identification (RFID) and communication technologies for solid waste bin and truck monitoring system. RFID, GPS, GPRS and GIS along with camera technologies have been integrated and developed the bin and truck intelligent monitoring system. A new kind of integrated theoretical framework, hardware architecture and interface algorithm has been introduced between the technologies for the successful implementation of the proposed system. In this system, bin and truck database have been developed such a way that the information of bin and truck ID, date and time of waste collection, bin status, amount of waste and bin and truck GPS coordinates etc. are complied and stored for monitoring and management activities. The results showed that the real-time image processing, histogram analysis, waste estimation and other bin information have been displayed in the GUI of the monitoring system. The real-time test and experimental results showed that the performance of the developed system was stable and satisfied the monitoring system with high practicability and validity. Copyright © 2011 Elsevier Ltd. All rights reserved.

  19. 77 FR 52317 - Record of Decision for Surveillance Towed Array Sensor System Low Frequency Active Sonar

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-29

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF DEFENSE Department of the Navy Record of Decision for Surveillance Towed Array Sensor System Low Frequency Active... Array Sensor System Low Frequency Active (SURTASS LFA) sonar systems with certain...

  20. 47 CFR 80.383 - Vessel Traffic Services (VTS) system frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Vessel Traffic Services (VTS) system... SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Vessel Traffic Services System (vts) § 80.383 Vessel Traffic Services (VTS) system frequencies. This section describes the...

  1. 47 CFR 80.383 - Vessel Traffic Services (VTS) system frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Vessel Traffic Services (VTS) system... SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Vessel Traffic Services System (vts) § 80.383 Vessel Traffic Services (VTS) system frequencies. This section describes the...

  2. 47 CFR 80.383 - Vessel Traffic Services (VTS) system frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Vessel Traffic Services (VTS) system... SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Vessel Traffic Services System (vts) § 80.383 Vessel Traffic Services (VTS) system frequencies. This section describes the...

  3. 47 CFR 80.383 - Vessel Traffic Services (VTS) system frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Vessel Traffic Services (VTS) system... SPECIAL RADIO SERVICES STATIONS IN THE MARITIME SERVICES Frequencies Vessel Traffic Services System (vts) § 80.383 Vessel Traffic Services (VTS) system frequencies. This section describes the...

  4. First Principles Modeling of RFQ Cooling System and Resonant Frequency Responses for Fermilab’s PIP-II Injector Test

    DOE PAGES

    Edelen, J. P.; Edelen, A. L.; Bowring, D.; ...

    2016-12-23

    In this study we develop an a priori method for simulating dynamic resonant frequency and temperature responses in a radio frequency quadrupole (RFQ) and its associated water-based cooling system respectively. Our model provides a computationally efficient means to evaluate the transient response of the RFQ over a large range of system parameters. The model was constructed prior to the delivery of the PIP-II Injector Test RFQ and was used to aid in the design of the water-based cooling system, data acquisition system, and resonance control system. Now that the model has been validated with experimental data, it can confidently bemore » used to aid in the design of future RFQ resonance controllers and their associated water-based cooling systems. Finally, without any empirical fitting, it has demonstrated the ability to predict absolute temperature and frequency changes to 11% accuracy on average, and relative changes to 7% accuracy.« less

  5. First Principles Modeling of RFQ Cooling System and Resonant Frequency Responses for Fermilab’s PIP-II Injector Test

    SciTech Connect

    Edelen, J. P.; Edelen, A. L.; Bowring, D.; Chase, B. E.; Steimel, J.; Biedron, S. G.; Milton, S. V.

    2016-12-23

    In this study we develop an a priori method for simulating dynamic resonant frequency and temperature responses in a radio frequency quadrupole (RFQ) and its associated water-based cooling system respectively. Our model provides a computationally efficient means to evaluate the transient response of the RFQ over a large range of system parameters. The model was constructed prior to the delivery of the PIP-II Injector Test RFQ and was used to aid in the design of the water-based cooling system, data acquisition system, and resonance control system. Now that the model has been validated with experimental data, it can confidently be used to aid in the design of future RFQ resonance controllers and their associated water-based cooling systems. Finally, without any empirical fitting, it has demonstrated the ability to predict absolute temperature and frequency changes to 11% accuracy on average, and relative changes to 7% accuracy.

  6. Autonomous Rubidium Clock Weak Frequency Jump Detector for Onboard Navigation Satellite System.

    PubMed

    Khare, Akshay; Arora, Rajat; Banik, Alak; Mehta, Sanjay D

    2016-02-01

    Frequency jumps are common in rubidium frequency sources. They affect the estimation of user position in navigational satellite systems. These jumps must be detected and corrected immediately as they have direct impact on the navigation system integrity. A novel weak frequency jump detector is proposed based on a Kalman filter with a multi-interval approach. This detector can be applied for both "sudden" and "slow" frequency transitions. In this detection method, noises of clock data are reduced by Kalman filtering, for accurate estimation of jump size with less latency. Analysis on in-orbit rubidium atomic frequency standard (RAFS) phase telemetry data shows that the detector can be used for fast detection and correction of weak frequency jumps. Furthermore, performance comparison of different existing frequency jump detection techniques with the proposed detector is discussed. A multialgorithm-based strategy is proposed depending on the jump size and latency for onboard navigation satellites having RAFS as the primary frequency source.

  7. System for transmitting low frequency analog signals over AC power lines

    DOEpatents

    Baker, Steven P.; Durall, Robert L.; Haynes, Howard D.

    1989-09-05

    A system for transmitting low frequency analog signals over AC power lines using FM modulation. A low frequency analog signal to be transmitted is first applied to a voltage-to-frequency converter where it is converted to a signal whose frequency varies in proportion to the analog signal amplitude. This signal is then used to modulate the carrier frequency of an FM transmitter coupled to an AC power line. The modulation signal frequency range in selected to be within the response band of the FM transmitter. The FM modulated carrier signal is received by an FM receiver coupled to the AC power line, demodulated and the demodulated signal frequency is converted by a frequency-to-voltage converter back to the form of the original low frequency analog input signal.

  8. A system for tranmitting low frequency analog signals over ac power lines

    DOEpatents

    Baker, S.P.; Durall, R.L.; Haynes, H.D.

    1987-07-30

    A system for transmitting low frequency analog signals over ac power lines using FM modulation. A low frequency analog signal to be transmitted is first applied to a voltage-to-frequency converter where it is converted to a signal whose frequency varies in proportion to the analog signal amplitude. This signal is then used to modulate the carrier frequency of an FM transmitter coupled to an ac power line. The modulation signal frequency range is selected to be within the response band of the FM transmitter. The FM modulated carrier signal is received by an FM receiver coupled to the ac power line, demodulated and the demodulated signal frequency is converted by a frequency-to-voltage converter back to the form of the original low frequency analog input signal. 4 figs.

  9. System for transmitting low frequency analog signals over AC power lines

    DOEpatents

    Baker, Steven P.; Durall, Robert L.; Haynes, Howard D.

    1989-01-01

    A system for transmitting low frequency analog signals over AC power lines using FM modulation. A low frequency analog signal to be transmitted is first applied to a voltage-to-frequency converter where it is converted to a signal whose frequency varies in proportion to the analog signal amplitude. This signal is then used to modulate the carrier frequency of an FM transmitter coupled to an AC power line. The modulation signal frequency range in selected to be within the response band of the FM transmitter. The FM modulated carrier signal is received by an FM receiver coupled to the AC power line, demodulated and the demodulated signal frequency is converted by a frequency-to-voltage converter back to the form of the original low frequency analog input signal.

  10. On tune deafness (dysmelodia): frequency, development, genetics and musical background.

    PubMed

    Kalmus, H; Fry, D B

    1980-05-01

    With the aid of the Distorted Tunes Test a group of British adults could be established whose melodic aptitude was below a certain level and whom we called tune deaf. They are only a fraction of those popularly called tone deaf. The Distorted Tunes Test is only slightly correlated with pitch discrimination, short term tonal memory or number memory. In children ability to pass the Distorted Tunes Test develops at greatly varying speeds and to a varying degree, reaching stability in adolescence. Tune deafness has a familial distribution and segregates in a way suggesting an autosomal dominant trait with imperfect penetrance. Some degree of positive assortative mating has been established. Some people, unfamiliar with the British melodies which form the basis of the test, pass it. This indicates the existence of a partly innate and partly acquired competence to judge what is acceptable and what is not, within the tradition of Western popular or classical music. This seems to indicate the existence of some deep structure of tonality, comparable with Chomsky's deep language structure. Asians who have not been much exposed to this kind of music find the task very difficult.

  11. Issues in expert system development

    SciTech Connect

    Baer, C.L.

    1988-03-01

    The explicit representation of domain knowledge and its separation from the processes which manipulate it and the representation formalism particular to artificial intelligence allow expert systems to solve problems which are characterized by a high combinatoric complexity or which are sufficiently ill defined as to not have reasonable software engineering solutions. The expert system approach to problem-solving differs radically from it conventional system development counterpart. This paper defines the expert system and introduces the production system architecture. The relative strengths and weaknesses of expert system and software engineering approaches to problem solving are discussed. Also addressed are criteria for identifying problems amenable to expert system solution and some justification for system development.

  12. Dielectric properties of almond shells in the development of radio frequency and microwave pasteurization

    USDA-ARS?s Scientific Manuscript database

    To develop pasteurization treatments based on radio frequency (RF) or microwave energy, dielectric properties of almond shells were determined using an open-ended coaxial-probe with an impedance analyzer over a frequency range of 10 to 1800 MHz. Both the dielectric constant and loss factor of almond...

  13. The Development of Polysemy and Frequency Use in English Second Language Speakers

    ERIC Educational Resources Information Center

    Crossley, Scott; Salsbury, Tom; McNamara, Danielle

    2010-01-01

    Spoken language data were collected from six adult second language (L2) English learners over a year-long period in order to explore the development of word polysemy and frequency use. The data were analyzed both quantitatively and qualitatively. In the first analysis, the growth of WordNet polysemy values and CELEX word frequency values were…

  14. Higher-order modulations of fs laser pulses for GHz frequency domain photon migration system.

    PubMed

    Lin, Huang-Yi; Cheng, Nanyu; Tseng, Sheng-Hao; Chan, Ming-Che

    2014-02-24

    Except the fundamental modulation frequency, by higher-order-harmonic modulations of mode-locked laser pulses and a simple frequency demodulation circuit, a novel approach to GHz frequency-domain-photon-migration (FDPM) system was reported. With this novel approach, a wide-band modulation frequency comb is available without any external modulation devices and the only electronics to extract the optical attenuation and phase properties at a selected modulation frequency in FDPM systems are good mixers and lock-in devices. This approach greatly expands the frequency range that could be achieved by conventional FDPM systems and suggests that our system could extract much more information from biological tissues than the conventional FDPM systems. Moreover, this demonstration will be beneficial for discerning the minute change of tissue properties.

  15. Linear Optimization of Frequency Spectrum Assignments Across System

    DTIC Science & Technology

    2016-03-01

    selection tools, frequency allocation, transmission optimization, electromagnetic maneuver warfare, electronic protection, assignment model 15. NUMBER... ELECTROMAGNETIC MANEUVER WARFARE .............................5  B.  THE SPECTRUM AS THE NEWEST DOMAIN ..................................6  C.  A FULL...concept AW air warfare CM communications CNO Chief of Naval Operations DT data transmission EA electronic attack EME electromagnetic

  16. Heterogeneity measures in hydrological frequency analysis: review and new developments

    NASA Astrophysics Data System (ADS)

    Requena, Ana I.; Chebana, Fateh; Ouarda, Taha B. M. J.

    2017-03-01

    Some regional procedures to estimate hydrological quantiles at ungauged sites, such as the index-flood method, require the delineation of homogeneous regions as a basic step for their application. The homogeneity of these delineated regions is usually tested providing a yes/no decision. However, complementary measures that are able to quantify the degree of heterogeneity of a region are needed to compare regions, evaluate the impact of particular sites, and rank the performance of different delineating methods. Well-known existing heterogeneity measures are not well-defined for ranking regions, as they entail drawbacks such as assuming a given probability distribution, providing negative values and being affected by the region size. Therefore, a framework for defining and assessing desirable properties of a heterogeneity measure in the regional hydrological context is needed. In the present study, such a framework is proposed through a four-step procedure based on Monte Carlo simulations. Several heterogeneity measures, some of which commonly known and others which are derived from recent approaches or adapted from other fields, are presented and developed to be assessed. The assumption-free Gini index applied on the at-site L-variation coefficient (L-CV) over a region led to the best results. The measure of the percentage of sites for which the regional L-CV is outside the confidence interval of the at-site L-CV is also found to be relevant, as it leads to more stable results regardless of the regional L-CV value. An illustrative application is also presented for didactical purposes, through which the subjectivity of commonly used criteria to assess the performance of different delineation methods is underlined.

  17. Carrier-frequency synchronization system for improved amplitude modulation and television broadcast reception

    DOEpatents

    Smith, Stephen F.; Moore, James A.

    2003-05-13

    Systems and methods are described for carrier-frequency synchronization for improved AM and TV broadcast reception. A method includes synchronizing a carrier frequency of a broadcast signal with a remote reference frequency. An apparatus includes a reference signal receiver; a phase comparator coupled to the reference signal receiver; a voltage controlled oscillator coupled to the phase comparator; and a radio frequency output coupled to the voltage controlled oscillator.

  18. An expert system to analyze high frequency dependent data for the space shuttle main engine turbopumps

    NASA Technical Reports Server (NTRS)

    Garcia, Raul C., Jr.

    1987-01-01

    The prototype expert system ADDAMX identifies selected sinusoid frequencies from spectral data graphs as speed frequencies and harmonics from each turbopump, frequency feed through from one turbopump to another, frequencies generated by turbopump bearings, pseudo 3N for the phase 2 high pressure fuel turbopump, and electrical noise. ADDAMX does the analysis in an interactive or batch mode and the results can be displayed on the screen or hardcopy.

  19. Development of a frequency regulation duty-cycle for standardized energy storage performance testing

    DOE PAGES

    Rosewater, David; Ferreira, Summer

    2016-05-25

    The US DOE Protocol for uniformly measuring and expressing the performance of energy storage systems, first developed in 2012 through inclusive working group activities, provides standardized methodologies for evaluating an energy storage system’s ability to supply specific services to electrical grids. This article elaborates on the data and decisions behind the duty-cycle used for frequency regulation in this protocol. Analysis of a year of publicly available frequency regulation control signal data from a utility was considered in developing the representative signal for this use case. Moreover, this showed that signal standard deviation can be used as a metric for aggressivenessmore » or rigor. From these data, we select representative 2 h long signals that exhibit nearly all of dynamics of actual usage under two distinct regimens, one for average use and the other for highly aggressive use. Our results were combined into a 24-h duty-cycle comprised of average and aggressive segments. The benefits and drawbacks of the selected duty-cycle are discussed along with its potential implications to the energy storage industry.« less

  20. Development of a frequency regulation duty-cycle for standardized energy storage performance testing

    SciTech Connect

    Rosewater, David; Ferreira, Summer

    2016-05-25

    The US DOE Protocol for uniformly measuring and expressing the performance of energy storage systems, first developed in 2012 through inclusive working group activities, provides standardized methodologies for evaluating an energy storage system’s ability to supply specific services to electrical grids. This article elaborates on the data and decisions behind the duty-cycle used for frequency regulation in this protocol. Analysis of a year of publicly available frequency regulation control signal data from a utility was considered in developing the representative signal for this use case. Moreover, this showed that signal standard deviation can be used as a metric for aggressiveness or rigor. From these data, we select representative 2 h long signals that exhibit nearly all of dynamics of actual usage under two distinct regimens, one for average use and the other for highly aggressive use. Our results were combined into a 24-h duty-cycle comprised of average and aggressive segments. The benefits and drawbacks of the selected duty-cycle are discussed along with its potential implications to the energy storage industry.

  1. Development of a frequency regulation duty-cycle for standardized energy storage performance testing

    SciTech Connect

    Rosewater, David; Ferreira, Summer

    2016-05-25

    The US DOE Protocol for uniformly measuring and expressing the performance of energy storage systems, first developed in 2012 through inclusive working group activities, provides standardized methodologies for evaluating an energy storage system’s ability to supply specific services to electrical grids. This article elaborates on the data and decisions behind the duty-cycle used for frequency regulation in this protocol. Analysis of a year of publicly available frequency regulation control signal data from a utility was considered in developing the representative signal for this use case. Moreover, this showed that signal standard deviation can be used as a metric for aggressiveness or rigor. From these data, we select representative 2 h long signals that exhibit nearly all of dynamics of actual usage under two distinct regimens, one for average use and the other for highly aggressive use. Our results were combined into a 24-h duty-cycle comprised of average and aggressive segments. The benefits and drawbacks of the selected duty-cycle are discussed along with its potential implications to the energy storage industry.

  2. Planar Lithographed Superconducting LC Resonators for Frequency-Domain Multiplexed Readout Systems

    NASA Astrophysics Data System (ADS)

    Rotermund, K.; Barch, B.; Chapman, S.; Hattori, K.; Lee, A.; Palaio, N.; Shirley, I.; Suzuki, A.; Tran, C.

    2016-07-01

    Cosmic microwave background (CMB) polarization experiments are increasing the number of transition edge sensor (TES) bolometers to increase sensitivity. In order to maintain low thermal loading of the sub-Kelvin stage, the frequency-domain multiplexing (FDM) factor has to increase accordingly. FDM is achieved by placing TES bolometers in series with inductor-capacitor (LC) resonators, which select the readout frequency. The multiplexing factor can be raised with a large total readout bandwidth and small frequency spacing between channels. The inductance is kept constant to maintain a uniform readout bandwidth across detectors, while the maximum acceptable value is determined by bolometer stability. Current technology relies on commercially available ceramic chip capacitors. These have high scatter in their capacitance thereby requiring large frequency spacing. Furthermore, they have high equivalent series resistance (ESR) at higher frequencies and are time consuming and tedious to hand assemble via soldering. A solution lies in lithographed, planar spiral inductors (currently in use by some experiments) combined with interdigitated capacitors on a silicon (Si) substrate. To maintain reasonable device dimensions, we have reduced trace and gap widths of the LCs to 4 \\upmu m. We increased the inductance from 16 to 60 \\upmu H to achieve a higher packing density, a requirement for FDM systems with large multiplexing factors. Additionally, the Si substrate yields low ESR values across the entire frequency range and lithography makes mass production of LC pairs possible. We reduced mutual inductance between inductors by placing them in a checkerboard pattern with the capacitors, thereby increasing physical distances between adjacent inductors. We also reduce magnetic coupling of inductors with external sources by evaporating a superconducting ground plane onto the backside of the substrate. We report on the development of lithographed LCs in the 1-5 MHz range for use

  3. Control system architecture of QUIJOTE multi-frequency instrument

    NASA Astrophysics Data System (ADS)

    Gómez-Reñasco, María. F.; Aguiar, Marta; Herreros, José Miguel; Hoyland, Roger J.; Sánchez de la Rosa, Vicente; Vega-Moreno, Afrodisio; Viera-Curbelo, Teodora; Génova-Santos, Ricardo; López-Caraballo, Carlos; Rebolo, Rafael; Rubiño-Martín, Jose Alberto

    2012-09-01

    The QUIJOTE-CMB experiment has been described in previous publications. Here we describe the architecture of the control system, hardware and software, of the QUIJOTE I instrument (MFI). It is a multi-channel instrument with five separate polarimeters: two of which operate at 10-14 GHz, two of which operate at 16-20 GHz, and a central polarimeter at 26-36 GHz. Each polarimeter can rotate at a speed of up to 1 Hz and also can move to discrete angular positions which allow the linear polar parameters Q, U and I to be derived. The instrument is installed in an alt-azimuth telescope which implements several operational modes: movement around the azimuth axis at a constant velocity while the elevation axis is held at a fixed elevation; tracking of a sky object; and raster of a rectangular area both in horizontal and sky coordinates. The control system of both, telescope and instrument, is based in the following technologies: an LXI-VXI bus is used for the signal acquisition system; an EtherCAT bus implements software PLCs developed in TwinCAT to perform the movement of the 5 polarimeters and the 2 axes of the telescope. Science signal, angular positions of the 5 polarimeters and telescope coordinates are sampled at up to 4000 Hz. All these data are correlated by a time stamp obtained from an external GPS clock implementing the Precise Time Protocol-1588 which provides synchronization to less than 1 microsecond. The control software also acquires housekeeping (HK) from the different subsystems. LabVIEW implements the instrument user interface.

  4. Development of Intensity-Duration-Frequency curves at ungauged sites: risk management under changing climate

    NASA Astrophysics Data System (ADS)

    Liew, San Chuin; Raghavan, Srivatsan V.; Liong, Shie-Yui

    2014-12-01

    The impact of a changing climate is already being felt on several hydrological systems both on a regional and sub-regional scale of the globe. Southeast Asia is one of the regions strongly affected by climate change. With climate change, one of the anticipated impacts is an increase in the intensity and frequency of extreme rainfall which further increase the region's flood catastrophes, human casualties and economic loss. Optimal mitigation measures can be undertaken only when stormwater systems are designed using rainfall Intensity-Duration-Frequency (IDF) curves derived from a long and good quality rainfall data. Developing IDF curves for the future climate can be even more challenging especially for ungauged sites. The current practice to derive current climate's IDF curves for ungauged sites is, for example, to `borrow' or `interpolate' data from regions of climatologically similar characteristics. Recent measures to derive IDF curves for present climate was performed by extracting rainfall data from a high spatial resolution Regional Climate Model driven by ERA-40 reanalysis dataset. This approach has been demonstrated on an ungauged site (Java, Indonesia) and the results were quite promising. In this paper, the authors extend the application of the approach to other ungauged sites particularly in Peninsular Malaysia. The results of the study undoubtedly have significance contribution in terms of local and regional hydrology (Malaysia and Southeast Asian countries). The anticipated impacts of climate change especially increase in rainfall intensity and its frequency appreciates the derivation of future IDF curves in this study. It also provides policy makers better information on the adequacy of storm drainage design, for the current climate at the ungauged sites, and the adequacy of the existing storm drainage to cope with the impacts of climate change.

  5. Propagation effects on satellite systems at frequencies below 10 GHz: A handbook for satellite systems design

    NASA Technical Reports Server (NTRS)

    Flock, Warren L.

    1987-01-01

    Frequencies below 10 GHz continue to be used for a large portion of satellite service, and new applications, including mobile satellite service and the global positioning system, use frequencies below 10 GHz. As frequency decreases below 10 GHz, attenuation due to precipitation and gases decreases and ionospheric effects increase. Thus the ionosphere, which can be largely neglected above 10 GHz, receives major attention. Although attenuation and depolarization due to rain are less severe below 10 GHz than above, they are nevertheless still important and constitute another major topic. The handbook emphasizes the propagation effects on satellite communications but material that is pertinent to radio navigation and positioning systems and deep-space telecommunications is included as well. Chapter 1 through 7 describe the various propagation impairments, and Chapter 9 is devoted to the estimation or calculation of the magnitudes of these effects for use in system design. Chapter 10 covers link power budget equations and the role of propagation effects in these equations. Chapter 8 deals with the complex subject of interference between space and terrestrial systems.

  6. Data management system advanced development

    NASA Technical Reports Server (NTRS)

    Douglas, Katherine; Humphries, Terry

    1990-01-01

    The Data Management System (DMS) Advanced Development task provides for the development of concepts, new tools, DMS services, and for the testing of the Space Station DMS hardware and software. It also provides for the development of techniques capable of determining the effects of system changes/enhancements, additions of new technology, and/or hardware and software growth on system performance. This paper will address the built-in characteristics which will support network monitoring requirements in the design of the evolving DMS network implementation, functional and performance requirements for a real-time, multiprogramming, multiprocessor operating system, and the possible use of advanced development techniques such as expert systems and artificial intelligence tools in the DMS design.

  7. Hunting for dark matter with ultra-stable fibre as frequency delay system.

    PubMed

    Yang, Wanpeng; Li, Dawei; Zhang, Shuangyou; Zhao, Jianye

    2015-07-10

    Many cosmological observations point towards the existence of dark-matter(DM) particles and consider them as the main component of the matter content of the universe. The goal of revealing the nature of dark-matter has triggered the development of new, extremely sensitive detectors. It has been demonstrated that the frequencies and phases of optical clock have a transient shift during the DMs' arrival due to the DM-SM(Standard Model) coupling. A simple, reliable and feasible experimental scheme is firstly proposed in this paper, based on "frequency-delay system" to search dark-matter by "self-frequency comparison" of an optical clock. During the arrival of a dark-matter, frequency discrepancy is expected between two signals with a short time difference(~ms) of the same optical clock to exhibit the interaction between atoms and dark-matter. Furthermore, this process can determine the exact position of dark-matter when it is crossing the optical clocks, therefore a network of detecting stations located in different places is recommended to reduce the misjudgment risk to an acceptable level.

  8. The word frequency effect: a review of recent developments and implications for the choice of frequency estimates in German.

    PubMed

    Brysbaert, Marc; Buchmeier, Matthias; Conrad, Markus; Jacobs, Arthur M; Bölte, Jens; Böhl, Andrea

    2011-01-01

    We review recent evidence indicating that researchers in experimental psychology may have used suboptimal estimates of word frequency. Word frequency measures should be based on a corpus of at least 20 million words that contains language participants in psychology experiments are likely to have been exposed to. In addition, the quality of word frequency measures should be ascertained by correlating them with behavioral word processing data. When we apply these criteria to the word frequency measures available for the German language, we find that the commonly used Celex frequencies are the least powerful to predict lexical decision times. Better results are obtained with the Leipzig frequencies, the dlexDB frequencies, and the Google Books 2000-2009 frequencies. However, as in other languages the best performance is observed with subtitle-based word frequencies. The SUBTLEX-DE word frequencies collected for the present ms are made available in easy-to-use files and are free for educational purposes.

  9. ECG reconstruction based on the injection of a multi-frequency signal in capacitive measurement systems.

    PubMed

    Serteyn, A; Vullings, R; Meftah, M; Bergmans, J W M

    2014-01-01

    Many healthcare and lifestyle applications could benefit from capacitive measurement systems for unobtrusive ECG monitoring. However, a key technical challenge remains: the susceptibility of such systems to motion artifacts and common-mode interferences. With this in mind, we developed a novel method to reduce various types of artifacts present in capacitive ECG measurement systems. The objective is to perform ECG reconstruction and channel balancing in an automated and continuous manner. The proposed method consists of a) modeling the measurement system; b) specifically parameterizing the reconstruction equation; and c) adaptively estimating the parameters. A multi-frequency injection signal serves to estimate and track the variations of the different parameters of the reconstruction equation. A preliminary investigation on the validity of the method has been performed in both simulation and lab environment: the method shows benefits in terms of common-mode interference and motion artifact reduction, resulting in improved R-peak detection.

  10. SOC Synchronization Control Method of Electric Vehicles Considering Customers' Convenience for Suppression of System Frequency Fluctuation

    NASA Astrophysics Data System (ADS)

    Shimizu, Koichiro; Masuta, Taisuke; Ota, Yutaka; Yokoyama, Akihiko

    Nowadays, a large integration of photovoltaic and wind power generations causes an imbalance between supply and demand in power systems because their outputs are intermittent. To solve the mentioned problem, Vehicle-to-Grid (V2G), which is one of the smart grid technologies, has gained much attention. Under the concept of V2G, batteries of Electric Vehicles (EVs) can be used as Battery Storage Energy Systems (BESS) in the power system. In this paper, we are developing a new Load Frequency Control (LFC) method using EVs, which is named the State Of Charge (SOC) synchronization control. In the proposal control method, a number of EVs in the power system can be considered as one large-capacity BESS. Moreover, the EVs can be plugged-in/out whenever the users want to and can store the sufficient energy for the next trip at plug-out.

  11. Frequency measurement of a Sr lattice clock using an SI-second-referenced optical frequency comb linked by a global positioning system (GPS)

    NASA Astrophysics Data System (ADS)

    Hong, Feng-Lei; Takamoto, Masao; Higashi, Ryoichi; Fukuyama, Yasuhiro; Jiang, Jie; Katori, Hidetoshi

    2005-07-01

    We have established a transportable frequency measurement system using an optical frequency comb linked to a commercial Cs atomic clock, which is in turn linked to international atomic time (TAI) through global positioning system (GPS) time. An iodine-stabilized Nd:YAG laser is used as a flywheel in the frequency measurement system. This system is used to measure the absolute frequency of the clock transition of 87Sr in an optical lattice. We obtained a fractional uncertainty of 2×10-14 in the frequency measurement with a total averaging time of ~ 105 s over 9 days.

  12. Frequency measurement of a Sr lattice clock using an SI-second-referenced optical frequency comb linked by a global positioning system (GPS).

    PubMed

    Hong, Feng-Lei; Takamoto, Masao; Higashi, Ryoichi; Fukuyama, Yasuhiro; Jiang, Jie; Katori, Hidetoshi

    2005-07-11

    We have established a transportable frequency measurement system using an optical frequency comb linked to a commercial Cs atomic clock, which is in turn linked to international atomic time (TAI) through global positioning system (GPS) time. An iodine-stabilized Nd:YAG laser is used as a flywheel in the frequency measurement system. This system is used to measure the absolute frequency of the clock transition of (87)Sr in an optical lattice. We obtained a fractional uncertainty of 2x10(-14) in the frequency measurement with a total averaging time of ~ 10(5) s over 9 days.

  13. Coordinated control of wind generation and energy storage for power system frequency regulation

    NASA Astrophysics Data System (ADS)

    Baone, Chaitanya Ashok

    Large-scale centralized synchronous generators have long been the primary actors in exercising active power and frequency control, and much of the existing grid control framework is predicated upon their dynamic terminal characteristics. Important among these characteristics is the inertia of such generators. These play key roles in determining the electromechanical stability of the electric power grid. Modern wind generator systems are partially or fully connected to the grid through power electronic interfaces, and hence do not present the same level of inertial coupling. The absence of inertial frequency response from modern wind generator systems is a topic of growing concern in power engineering practice, as the penetration of wind generation is expected to grow dramatically in the next few years. Solutions proposed in the literature have sought to address this problem by seeking to mimic the inherent inertial response characteristics of traditional synchronous generators via control loops added to wind generators. Recent literature has raised concerns regarding this approach, and the work here will further examine its shortcomings, motivating approaches that seek to optimally design for the characteristics of the equipment exercising the control, rather than forcing new technologies to mimic the characteristics of synchronous machines. In particular, this work will develop a new approach to power system frequency regulation, with features suited to distributed energy storage devices such as grid-scale batteries and wind turbine speed and blade pitch control. The dynamic characteristics of these new technologies are treated along with existing mechanisms, such as synchronous machine governor control, to develop a comprehensive multi-input control design approach. To make the method practically feasible for geographically distributed power systems, an observer-based distributed control design utilizing phasor measurement unit (PMU) signals along with local

  14. Controls system developments for the ERL facility

    SciTech Connect

    Jamilkowski, J.; Altinbas, Z.; Gassner, D.; Hoff, L.; Kankiya, P.; Kayran, D.; Miller, T.; Olsen, R.; Sheehy, B.; Xu, W.

    2011-10-07

    The BNL Energy Recovery LINAC (ERL) is a high beam current, superconducting RF electron accelerator that is being commissioned to serve as a research and development prototype for a RHIC facility upgrade for electron-ion collision (eRHIC). Key components of the machine include a laser, photocathode, and 5-cell superconducting RF cavity operating at a frequency of 703 MHz. Starting with a foundation based on existing ADO software running on Linux servers and on the VME/VxWorks platforms developed for RHIC, we are developing a controls system that incorporates a wide range of hardware I/O interfaces that are needed for machine R&D. Details of the system layout, specifications, and user interfaces are provided.

  15. The dual-frequency method for ultrasonic assessment of skeletal system

    NASA Astrophysics Data System (ADS)

    Tatarinov, A. M.; Egorov, V. P.; Sarvazyan, A. P.

    2009-10-01

    The article is a review of the new dual-frequency method in axial bone quantitative ultrasonometry for assessment of changes in cortical bones in osteoporosis. The method is based on the use of two frequencies for the generation of flexural and longitudinal ultrasonic waves, which opens possibilities for differential diagnostics of changes in various components of the state of the skeletal system, such as cortical layer thickness, porosity, and elastic properties of tissue. The axial scanning and composition of two-dimensional acoustic profiles of bones are carried out with the purpose of using topographic variations in the acoustic properties for diagnostics of the state of a bone. Results of laboratory and clinical tests of Bone UltraSonic Scanner (BUSS) developed in Artann Laboratories on the basis of the stated principles are presented. The sensitivity of measured characteristics to progression of osteoporosis and the detectability of early changes in bones related to this disease are shown.

  16. Intercontinental time and frequency transfer using a global positioning system timing receiver

    NASA Technical Reports Server (NTRS)

    Clements, P. A.

    1983-01-01

    The DSN has a requirement to maintain knowledge of the frequency offset between DSN stations with 3 x 10 to the minus 13th power and time offset within 10 microseconds. It is further anticipated that in the 1987-1990 era the requirement for knowledge of time offset between DSN stations will be less than 10 nanoseconds. JPL is using the Global Positioning System (GPS) Space Vehicles, as a development project, to transfer time and frequency over intercontinental distances between stations of the DSN and between the DSN and other agencies. JPL has installed GPS timing receivers at its tracking station near Barstow, California, and at its tracking station near Madrid, Spain. The details of the experiment and the data are reported. There is a discussion of the ultimate capabilities of these techniques for meeting the functional requirements of the DSN.

  17. Caregivers' suffix frequencies and suffix acquisition by language impaired, late talking, and typically developing children.

    PubMed

    Warlaumont, Anne S; Jarmulowicz, Linda

    2012-11-01

    Acquisition of regular inflectional suffixes is an integral part of grammatical development in English and delayed acquisition of certain inflectional suffixes is a hallmark of language impairment. We investigate the relationship between input frequency and grammatical suffix acquisition, analyzing 217 transcripts of mother-child (ages 1 ; 11-6 ; 9) conversations from the CHILDES database. Maternal suffix frequency correlates with previously reported rank orders of acquisition and with child suffix frequency. Percentages of children using a suffix are consistent with frequencies in caregiver speech. Although late talkers acquire suffixes later than typically developing children, order of acquisition is similar across populations. Furthermore, the third person singular and past tense verb suffixes, weaknesses for children with language impairment, are less frequent in caregiver speech than the plural noun suffix, a relative strength in language impairment. Similar findings hold across typical, SLI and late talker populations, suggesting that frequency plays a role in suffix acquisition.

  18. Control considerations for high frequency, resonant, power processing equipment used in large systems

    NASA Technical Reports Server (NTRS)

    Mildice, J. W.; Schreiner, K. E.; Wolff, F.

    1987-01-01

    Addressed is a class of resonant power processing equipment designed to be used in an integrated high frequency (20 KHz domain), utility power system for large, multi-user spacecraft and other aerospace vehicles. It describes a hardware approach, which has been the basis for parametric and physical data used to justify the selection of high frequency ac as the PMAD baseline for the space station. This paper is part of a larger effort undertaken by NASA and General Dynamics to be sure that all potential space station contractors and other aerospace power system designers understand and can comfortably use this technology, which is now widely used in the commercial sector. In this paper, we will examine control requirements, stability, and operational modes; and their hardware impacts from an integrated system point of view. The current space station PMAD system will provide the overall requirements model to develop an understanding of the performance of this type of system with regard to: (1) regulation; (2) power bus stability and voltage control; (3) source impedance; (4) transient response; (5) power factor effects; and (6) limits and overloads.

  19. Control considerations for high frequency, resonant, power processing equipment used in large systems

    NASA Technical Reports Server (NTRS)

    Mildice, J. W.; Schreiner, K. E.; Wolff, F.

    1987-01-01

    Addressed is a class of resonant power processing equipment designed to be used in an integrated high frequency (20 KHz domain), utility power system for large, multi-user spacecraft and other aerospace vehicles. It describes a hardware approach, which has been the basis for parametric and physical data used to justify the selection of high frequency ac as the PMAD baseline for the space station. This paper is part of a larger effort undertaken by NASA and General Dynamics to be sure that all potential space station contractors and other aerospace power system designers understand and can comfortably use this technology, which is now widely used in the commercial sector. In this paper, we will examine control requirements, stability, and operational modes; and their hardware impacts from an integrated system point of view. The current space station PMAD system will provide the overall requirements model to develop an understanding of the performance of this type of system with regard to: (1) regulation; (2) power bus stability and voltage control; (3) source impedance; (4) transient response; (5) power factor effects, and (6) limits and overloads.

  20. A Versatile and Reproducible Multi-Frequency Electrical Impedance Tomography System

    PubMed Central

    Avery, James; Dowrick, Thomas; Faulkner, Mayo; Goren, Nir; Holder, David

    2017-01-01

    A highly versatile Electrical Impedance Tomography (EIT) system, nicknamed the ScouseTom, has been developed. The system allows control over current amplitude, frequency, number of electrodes, injection protocol and data processing. Current is injected using a Keithley 6221 current source, and voltages are recorded with a 24-bit EEG system with minimum bandwidth of 3.2 kHz. Custom PCBs interface with a PC to control the measurement process, electrode addressing and triggering of external stimuli. The performance of the system was characterised using resistor phantoms to represent human scalp recordings, with an SNR of 77.5 dB, stable across a four hour recording and 20 Hz to 20 kHz. In studies of both haeomorrhage using scalp electrodes, and evoked activity using epicortical electrode mats in rats, it was possible to reconstruct images matching established literature at known areas of onset. Data collected using scalp electrode in humans matched known tissue impedance spectra and was stable over frequency. The experimental procedure is software controlled and is readily adaptable to new paradigms. Where possible, commercial or open-source components were used, to minimise the complexity in reproduction. The hardware designs and software for the system have been released under an open source licence, encouraging contributions and allowing for rapid replication. PMID:28146122

  1. An efficient frequency response solution for nonproportionally damped systems

    NASA Technical Reports Server (NTRS)

    Conti, Paul; Rule, William K.

    1987-01-01

    A method is presented to accurately and economically calculate steady state frequency responses based on the analysis of large finite element models with nonproportional damping effects. The new method is a hybrid of the traditional nonproportional and proportional damping solution methods. It captures the advantages of each computational approach without the burden of their respective shortcomings, as demonstrated with comparative analysis performed on a large finite element model.

  2. System frequency support of permanent magnet synchronous generator-based wind power plant

    NASA Astrophysics Data System (ADS)

    Wu, Ziping

    With ever-increasing penetration of wind power into modern electric grids all over the world, a trending replacement of conventional synchronous generators by large wind power plants will likely result in the poor overall frequency regulation performance. On the other hand, permanent magnet synchronous generator wind Turbine System (PMSG-WTG) with full power back to back converters tends to become one of the most promising wind turbine technologies thanks to various advantages. It possesses a significant amount of kinetic energy stored in the rotating mass of turbine blades, which can be utilized to enhance the total inertia of power system. Additionally, the deloaded operation and decoupled control of active and reactive power make it possible for PMSG-WTG to provide a fast frequency regulation through full-power converter. First of all, a comprehensive and in-depth survey is conducted to analyze the motivations for incorporating the inertial response and frequency regulation of VSWT into the system frequency regulation. Besides, control classifications, fundamental control concepts and advanced control schemes implemented for auxiliary frequency support of individual WT or wind power plant are elaborated along with a comparison of the potential frequency regulation capabilities of four major types of WTs. Secondly, a Controls Advanced Research Turbine2-Permanent Magnet Synchronous Generator wind turbine (CART2-PMSG) integrated model representing the typical configuration and operation characteristics of PMSG-WT is established in Matlab/Simulink,. Meanwhile, two different rotor-side converter control schemes, including rotor speed-based control and active power-based control, are integrated into this CART2-PMSG integrated model to perform Maximum Power Point Tracking (MPPT) operation over a wide range of wind speeds, respectively. Thirdly, a novel comprehensive frequency regulation (CFR) control scheme is developed and implemented into the CART2-PMSG model based

  3. Syntactic Complexity and Frequency in the Neurocognitive Language System.

    PubMed

    Yang, Yun-Hsuan; Marslen-Wilson, William D; Bozic, Mirjana

    2017-09-01

    Prominent neurobiological models of language follow the widely accepted assumption that language comprehension requires two principal mechanisms: a lexicon storing the sound-to-meaning mapping of words, primarily involving bilateral temporal regions, and a combinatorial processor for syntactically structured items, such as phrases and sentences, localized in a left-lateralized network linking left inferior frontal gyrus (LIFG) and posterior temporal areas. However, recent research showing that the processing of simple phrasal sequences may engage only bilateral temporal areas, together with the claims of distributional approaches to grammar, raise the question of whether frequent phrases are stored alongside individual words in temporal areas. In this fMRI study, we varied the frequency of words and of short and long phrases in English. If frequent phrases are indeed stored, then only less frequent items should generate selective left frontotemporal activation, because memory traces for such items would be weaker or not available in temporal cortex. Complementary univariate and multivariate analyses revealed that, overall, simple words (verbs) and long phrases engaged LIFG and temporal areas, whereas short phrases engaged bilateral temporal areas, suggesting that syntactic complexity is a key factor for LIFG activation. Although we found a robust frequency effect for words in temporal areas, no frequency effects were found for the two phrasal conditions. These findings support the conclusion that long and short phrases are analyzed, respectively, in the left frontal network and in a bilateral temporal network but are not retrieved from memory in the same way as simple words during spoken language comprehension.

  4. Radio frequency systems for present and future accelerators

    SciTech Connect

    Raka, E.C.

    1987-01-01

    Rf systems are described for the FNAL Main Ring and Tevatron Ring, CERN SPS and LEP, and HERA proton acceleration system, CERN PS e/sup +/e/sup minus/ acceleration system, and CERN EPA monochromatic cavity. Low impedance rf systems in CERN ISR, the Brookhaven CBA, and SSC are also discussed.

  5. INSTRUMENTS AND METHODS OF INVESTIGATION: Spectral and spectral-frequency methods of investigating atmosphereless bodies of the Solar system

    NASA Astrophysics Data System (ADS)

    Busarev, Vladimir V.; Prokof'eva-Mikhailovskaya, Valentina V.; Bochkov, Valerii V.

    2007-06-01

    A method of reflectance spectrophotometry of atmosphereless bodies of the Solar system, its specificity, and the means of eliminating basic spectral noise are considered. As a development, joining the method of reflectance spectrophotometry with the frequency analysis of observational data series is proposed. The combined spectral-frequency method allows identification of formations with distinctive spectral features, and estimations of their sizes and distribution on the surface of atmospherelss celestial bodies. As applied to investigations of asteroids 21 Lutetia and 4 Vesta, the spectral frequency method has given us the possibility of obtaining fundamentally new information about minor planets.

  6. Development and beam test of a continuous wave radio frequency quadrupole accelerator

    NASA Astrophysics Data System (ADS)

    Ostroumov, P. N.; Mustapha, B.; Barcikowski, A.; Dickerson, C.; Kolomiets, A. A.; Kondrashev, S. A.; Luo, Y.; Paskvan, D.; Perry, A.; Schrage, D.; Sharamentov, S. I.; Sommer, R.; Toter, W.; Zinkann, G.

    2012-11-01

    The front end of any modern ion accelerator includes a radio frequency quadrupole (RFQ). While many pulsed ion linacs successfully operate RFQs, several ion accelerators worldwide have significant difficulties operating continuous wave (CW) RFQs to design specifications. In this paper we describe the development and results of the beam commissioning of a CW RFQ designed and built for the National User Facility: Argonne Tandem Linac Accelerator System (ATLAS). Several innovative ideas were implemented in this CW RFQ. By selecting a multisegment split-coaxial structure, we reached moderate transverse dimensions for a 60.625-MHz resonator and provided a highly stabilized electromagnetic field distribution. The accelerating section of the RFQ occupies approximately 50% of the total length and is based on a trapezoidal vane tip modulation that increased the resonator shunt impedance by 60% in this section as compared to conventional sinusoidal modulation. To form an axially symmetric beam exiting the RFQ, a very short output radial matcher with a length of 0.75βλ was developed. The RFQ is designed as a 100% oxygen-free electronic (OFE) copper structure and fabricated with a two-step furnace brazing process. The radio frequency (rf) measurements show excellent rf properties for the resonator, with a measured intrinsic Q equal to 94% of the simulated value for OFE copper. An O5+ ion beam extracted from an electron cyclotron resonance ion source was used for the RFQ commissioning. In off-line beam testing, we found excellent coincidence of the measured beam parameters with the results of beam dynamics simulations performed using the beam dynamics code TRACK, which was developed at Argonne. These results demonstrate the great success of the RFQ design and fabrication technology developed here, which can be applied to future CW RFQs.

  7. A frequency up-converting harvester based on internal resonance in 2-DOF nonlinear systems

    NASA Astrophysics Data System (ADS)

    Wu, Yipeng; Qiu, Jinhao; Ji, Hongli

    2016-11-01

    This paper reports the design and experimental testing of a novel frequency up- converting piezoelectric energy harvester. The harvester is firstly approximated as a 2-degree- of-freedom cubic nonlinear system instead of the general Duffing systems. A 1:3 internal resonance innovatively applied in the frequency up-conversion approach is thoroughly investigated. Finally, the theoretical dynamic model confirmed by the experimental results clearly shows the effect of the frequency up-conversion.

  8. Firmware Development Improves System Efficiency

    NASA Technical Reports Server (NTRS)

    Chern, E. James; Butler, David W.

    1993-01-01

    Most manufacturing processes require physical pointwise positioning of the components or tools from one location to another. Typical mechanical systems utilize either stop-and-go or fixed feed-rate procession to accomplish the task. The first approach achieves positional accuracy but prolongs overall time and increases wear on the mechanical system. The second approach sustains the throughput but compromises positional accuracy. A computer firmware approach has been developed to optimize this point wise mechanism by utilizing programmable interrupt controls to synchronize engineering processes 'on the fly'. This principle has been implemented in an eddy current imaging system to demonstrate the improvement. Software programs were developed that enable a mechanical controller card to transmit interrupts to a system controller as a trigger signal to initiate an eddy current data acquisition routine. The advantages are: (1) optimized manufacturing processes, (2) increased throughput of the system, (3) improved positional accuracy, and (4) reduced wear and tear on the mechanical system.

  9. A NARX damper model for virtual tuning of automotive suspension systems with high-frequency loading

    NASA Astrophysics Data System (ADS)

    Alghafir, M. N.; Dunne, J. F.

    2012-02-01

    A computationally efficient NARX-type neural network model is developed to characterise highly nonlinear frequency-dependent thermally sensitive hydraulic dampers for use in the virtual tuning of passive suspension systems with high-frequency loading. Three input variables are chosen to account for high-frequency kinematics and temperature variations arising from continuous vehicle operation over non-smooth surfaces such as stone-covered streets, rough or off-road conditions. Two additional input variables are chosen to represent tuneable valve parameters. To assist in the development of the NARX model, a highly accurate but computationally excessive physical damper model [originally proposed by S. Duym and K. Reybrouck, Physical characterization of non-linear shock absorber dynamics, Eur. J. Mech. Eng. M 43(4) (1998), pp. 181-188] is extended to allow for high-frequency input kinematics. Experimental verification of this extended version uses measured damper data obtained from an industrial damper test machine under near-isothermal conditions for fixed valve settings, with input kinematics corresponding to harmonic and random road profiles. The extended model is then used only for simulating data for training and testing the NARX model with specified temperature profiles and different valve parameters, both in isolation and within quarter-car vehicle simulations. A heat generation and dissipation model is also developed and experimentally verified for use within the simulations. Virtual tuning using the quarter-car simulation model then exploits the NARX damper to achieve a compromise between ride and handling under transient thermal conditions with harmonic and random road profiles. For quarter-car simulations, the paper shows that a single tuneable NARX damper makes virtual tuning computationally very attractive.

  10. Formulation of frequency stability limited by laser intrinsic noise in feedback systems.

    PubMed

    Hori, Teruhito; Araya, Akito; Moriwaki, Shigenori; Mio, Norikatsu

    2009-01-10

    We investigated the influence of amplitude modulation (AM) noise and phase modulation (PM) noise of a laser source on the frequency stability in frequency stabilization systems. We estimated the frequency stability and evaluated the efficacy of a noise reduction technique (the Doppler-trend subtraction method) of a laser diode frequency stabilization system, where enhanced intensity noise arising from PM-to-AM noise conversion through a reference gas cell is reduced using the technique employed in modulation transfer spectroscopy. To evaluate the relationship between the laser's intrinsic noise and its frequency stability, we performed noise spectrum measurements and formulated frequency stability in addition to measuring Allan standard deviation. As a result, it is found that the extra noise generated in PM-to-AM conversion is efficiently removed by the Doppler-trend subtraction method and that within the feedback bandwidth, the frequency stability becomes 1 order of magnitude better than that without the method.

  11. Dynamics of male meiotic recombination frequency during plant development using Fluorescent Tagged Lines in Arabidopsis thaliana

    PubMed Central

    Li, Fan; De Storme, Nico; Geelen, Danny

    2017-01-01

    Meiotic homologous recombination plays a central role in creating genetic variability, making it an essential biological process relevant to evolution and crop breeding. In this study, we used pollen-specific fluorescent tagged lines (FTLs) to measure male meiotic recombination frequency during the development of Arabidopsis thaliana. Interestingly, a subset of pollen grains consistently shows loss of fluorescence expression in tested lines. Using nine independent FTL intervals, the spatio-temporal dynamics of male recombination frequency was assessed during plant development, considering both shoot type and plant age as independent parameters. In most genomic intervals assayed, male meiotic recombination frequency is highly consistent during plant development, showing no significant change between different shoot types and during plant aging. However, in some genomic regions, such as I1a and I5a, a small but significant effect of either developmental position or plant age were observed, indicating that the meiotic CO frequency in those intervals varies during plant development. Furthermore, from an overall view of all nine genomic intervals assayed, both primary and tertiary shoots show a similar dynamics of increasing recombination frequency during development, while secondary and lateral shoots remain highly stable. Our results provide new insights in the dynamics of male meiotic recombination frequency during plant development. PMID:28211906

  12. Dynamics of male meiotic recombination frequency during plant development using Fluorescent Tagged Lines in Arabidopsis thaliana.

    PubMed

    Li, Fan; De Storme, Nico; Geelen, Danny

    2017-02-13

    Meiotic homologous recombination plays a central role in creating genetic variability, making it an essential biological process relevant to evolution and crop breeding. In this study, we used pollen-specific fluorescent tagged lines (FTLs) to measure male meiotic recombination frequency during the development of Arabidopsis thaliana. Interestingly, a subset of pollen grains consistently shows loss of fluorescence expression in tested lines. Using nine independent FTL intervals, the spatio-temporal dynamics of male recombination frequency was assessed during plant development, considering both shoot type and plant age as independent parameters. In most genomic intervals assayed, male meiotic recombination frequency is highly consistent during plant development, showing no significant change between different shoot types and during plant aging. However, in some genomic regions, such as I1a and I5a, a small but significant effect of either developmental position or plant age were observed, indicating that the meiotic CO frequency in those intervals varies during plant development. Furthermore, from an overall view of all nine genomic intervals assayed, both primary and tertiary shoots show a similar dynamics of increasing recombination frequency during development, while secondary and lateral shoots remain highly stable. Our results provide new insights in the dynamics of male meiotic recombination frequency during plant development.

  13. Breast cancer margin detection with a single frequency terahertz imaging system

    NASA Astrophysics Data System (ADS)

    Yngvesson, Sigfrid K.; Karellas, Andrew; Glick, Stephen; Khan, Ashraf; Siqueira, Paul R.; Kelly, Patrick A.; St. Peter, Benjamin

    2016-03-01

    The ability to discern malignant from benign tissue in excised human breast specimens in Breast Conservation Surgery (BCS) was evaluated using a prototype single frequency terahertz radiation. Terahertz (THz) images of the specimens in reflection mode were obtained by employing a gas laser source and mechanical scanning. The images were correlated with optical histological micrographs of the same specimens, and a mean discrimination of 73% was found for five out of six samples using Receiver Operating Characteristic (ROC) analysis. This result is similar to what has previously been obtained using Terahertz pulsed imaging (TPI) techniques. We will discuss the specific advantages of Single frequency THz imaging (SFTI) compared with TPI for potentially allowing the development of much faster, more compact and less expensive cancer imaging systems that could be adapted for employment in the operating room. The system design and characterization of the prototype SFTI system are discussed in detail. The initial results are encouraging but further development of the technology and clinical evaluation is needed to evaluate its feasibility in the clinical environment.

  14. A digital frequency stabilization system of external cavity diode laser based on LabVIEW FPGA

    NASA Astrophysics Data System (ADS)

    Liu, Zhuohuan; Hu, Zhaohui; Qi, Lu; Wang, Tao

    2015-10-01

    Frequency stabilization for external cavity diode laser has played an important role in physics research. Many laser frequency locking solutions have been proposed by researchers. Traditionally, the locking process was accomplished by analog system, which has fast feedback control response speed. However, analog system is susceptible to the effects of environment. In order to improve the automation level and reliability of the frequency stabilization system, we take a grating-feedback external cavity diode laser as the laser source and set up a digital frequency stabilization system based on National Instrument's FPGA (NI FPGA). The system consists of a saturated absorption frequency stabilization of beam path, a differential photoelectric detector, a NI FPGA board and a host computer. Many functions, such as piezoelectric transducer (PZT) sweeping, atomic saturation absorption signal acquisition, signal peak identification, error signal obtaining and laser PZT voltage feedback controlling, are totally completed by LabVIEW FPGA program. Compared with the analog system, the system built by the logic gate circuits, performs stable and reliable. User interface programmed by LabVIEW is friendly. Besides, benefited from the characteristics of reconfiguration, the LabVIEW program is good at transplanting in other NI FPGA boards. Most of all, the system periodically checks the error signal. Once the abnormal error signal is detected, FPGA will restart frequency stabilization process without manual control. Through detecting the fluctuation of error signal of the atomic saturation absorption spectrum line in the frequency locking state, we can infer that the laser frequency stability can reach 1MHz.

  15. Development of a stereofluoroscopy system

    NASA Technical Reports Server (NTRS)

    Rivers, D. B.

    1979-01-01

    A technique of 3-D video imaging, was developed for use on manned missions for observation and control of remote manipulators. An improved medical diagnostic fluoroscope with a stereo, real-time output was also developed. An explanation of how this system works, and recommendations for future work in this area are presented.

  16. Development of Vocational Training Systems.

    ERIC Educational Resources Information Center

    Commission of the European Communities, Brussels (Belgium). Directorate-General for Education, Training, and Youth.

    The EUROTECNET program was implemented to develop and improve vocational training policies and systems to meet the challenges of change in the economic and social situation through the development of innovative responses and actions. Each Member State of the European Community was asked to identify one issue of strategic and critical importance to…

  17. Influence of the viscoelastic properties of the respiratory system on the energetically optimum breathing frequency.

    PubMed

    Bates, J H; Milic-Emili, J

    1993-01-01

    We hypothesized that the viscoelastic properties of the respiratory system should have significant implications for the energetically optimal frequency of breathing, in view of the fact that these properties cause marked dependencies of overall system resistance and elastance on frequency. To test our hypothesis we simulated two models of canine and human respiratory system mechanics during sinusoidal breathing and calculated the inspiratory work (WI) and pressure-time integral (PTI) per minute under both resting and exercise conditions. The two models were a two-compartment viscoelastic model and a single-compartment model. Requiring minute alveolar ventilation to be fixed, we found that both models predicted almost identical optimum breathing frequencies. The calculated PTI was very insensitive to increases in breathing frequency above the optimal frequencies, while WI was found to increase slowly with frequency above its optimum. In contrast, both WI and PTI increased sharply as frequency decreased below their respective optima. A sensitivity analysis showed that the model predictions were very insensitive to the elastance and resistance values chosen to characterize tissue viscoelasticity. We conclude that the WI criterion for choosing the frequency of breathing is compatible with observations in nature, whereas the optimal frequency predictions of the PTI are rather too high. Both criteria allow for a fairly wide margin of choice in frequency above the optimum values without incurring excessive additional energy expenditure. Furthermore, contrary to our expectations, the viscoelastic properties of the respiratory system tissues do not pose a noticeable problem to the respiratory controller in terms of energy expenditure.

  18. Gramian-Preserving Frequency Transformation for Linear Discrete-Time State-Space Systems

    NASA Astrophysics Data System (ADS)

    Koshita, Shunsuke; Tanaka, Satoru; Abe, Masahide; Kawamata, Masayuki

    This paper proposes the Gramian-preserving frequency transformation for linear discrete-time state-space systems. In this frequency transformation, we replace each delay element of a discrete-time system with an allpass system that has a balanced realization. This approach can generate transformed systems that have the same controllability/observability Gramians as those of the original system. From this result, we show that the Gramian-preserving frequency transformation gives us transformed systems with different magnitude characteristics, but with the same structural property with respect to the Gramians as that of the original system. This paper also presents a simple method for realization of the Gramian-preserving frequency transformation. This method makes use of the cascaded normalized lattice structure of allpass systems.

  19. Frequency domain analysis and synthesis of lumped parameter systems using nonlinear least squares techniques

    NASA Technical Reports Server (NTRS)

    Hays, J. R.

    1969-01-01

    Lumped parametric system models are simplified and computationally advantageous in the frequency domain of linear systems. Nonlinear least squares computer program finds the least square best estimate for any number of parameters in an arbitrarily complicated model.

  20. The NASA/JPL three-frequency polarimetric AIRSAR system

    NASA Technical Reports Server (NTRS)

    Van Zyl, J.; Carande, R.; Lou, Y.; Miller, T.; Wheeler, K.

    1992-01-01

    The NASA/Jet Propulsion Laboratory Airborne Synthetic Aperture Radar (JPL AIRSAR) system has now completed four flight campaigns. The authors describe the current state of this system and provide insight into how flight seasons are planned for this instrument. The data processors and data products are described. A table containing relevant system parameters is provided.

  1. Performance analysis of modified Asymmetrically-Clipped Optical Orthogonal Frequency-Division Multiplexing systems

    NASA Astrophysics Data System (ADS)

    Mohamed, Salma D.; Shalaby, Hossam M. H.; Andonovic, Ivan; Aly, Moustafa H.

    2016-12-01

    A modification to the Asymmetrically-Clipped Optical Orthogonal Frequency-Division Multiplexing (ACO-OFDM) technique is proposed through unipolar encoding. A performance analysis of the Bit Error Rate (BER) is developed and Monte Carlo simulations are carried out to verify the analysis. Results are compared to that of the corresponding ACO-OFDM system under the same bit energy and transmission rate; an improvement of 1 dB is obtained at a BER of 10-4 . In addition, the performance of the proposed system in the presence of atmospheric turbulence is investigated using single-input multiple-output (SIMO) configuration and its performance under that environment is compared to that of ACO-OFDM. Energy improvements of 4 dB and 2.2 dB are obtained at a BER of 10-4 for SIMO systems of 1 and 2 photodetectors at the receiver for the case of strong turbulence, respectively.

  2. A flexible active and reactive power control strategy for a variable speed constant frequency generating system

    SciTech Connect

    Tang, Y.; Xu, L.

    1995-07-01

    Variable-speed constant-frequency generating systems are used in wind power, hydro power, aerospace, and naval power generations to enhance efficiency and reduce friction. In these applications, an attractive candidate is the slip power recovery system comprising of doubly excited induction machine or doubly excited brushless reluctance machine and PWM converters with a dc link. In this paper, a flexible active and reactive power control strategy is developed, such that the optimal torque-speed profile of the turbine can be followed and overall reactive power can be controlled, while the machine copper losses have been minimized. At the same time, harmonics injected into the power network has also been minimized. In this manner, the system can function as both a high-efficient power generator and a flexible reactive power compensator.

  3. Ozone concentration-monitoring photoacoustic system based on a frequency-quadrupled Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Ajtai, T.; Filep, Á.; Varga, A.; Motika, G.; Bozóki, Z.; Szabó, G.

    2010-10-01

    A novel type of system based on a frequency-quadrupled Nd:YAG laser light source at 266 nm and a dual-cell photoacoustic detection unit was developed, and its applicability for ozone-concentration measurement with a minimum detectable ozone concentration of about 100 pptV was demonstrated. The instrument was calibrated against an ozone generator, and it was installed at a regional environmental monitoring station to be operated in parallel with a commercial UV-absorption photometry based ozone-monitoring instrument. While good agreement between the readings of the two systems was found, the photoacoustic system outperformed its optical absorption based counterpart as far as minimum detectable concentration and measurement accuracy is concerned.

  4. A multi-frequency electrical impedance tomography system for real-time 2D and 3D imaging

    NASA Astrophysics Data System (ADS)

    Yang, Yunjie; Jia, Jiabin

    2017-08-01

    This paper presents the design and evaluation of a configurable, fast multi-frequency Electrical Impedance Tomography (mfEIT) system for real-time 2D and 3D imaging, particularly for biomedical imaging. The system integrates 32 electrode interfaces and the current frequency ranges from 10 kHz to 1 MHz. The system incorporates the following novel features. First, a fully adjustable multi-frequency current source with current monitoring function is designed. Second, a flexible switching scheme is developed for arbitrary sensing configuration and a semi-parallel data acquisition architecture is implemented for high-frame-rate data acquisition. Furthermore, multi-frequency digital quadrature demodulation is accomplished in a high-capacity Field Programmable Gate Array. At last, a 3D imaging software, visual tomography, is developed for real-time 2D and 3D image reconstruction, data analysis, and visualization. The mfEIT system is systematically tested and evaluated from the aspects of signal to noise ratio (SNR), frame rate, and 2D and 3D multi-frequency phantom imaging. The highest SNR is 82.82 dB on a 16-electrode sensor. The frame rate is up to 546 fps at serial mode and 1014 fps at semi-parallel mode. The evaluation results indicate that the presented mfEIT system is a powerful tool for real-time 2D and 3D imaging.

  5. High-Power, High-Frequency Si-Based (SiGe) Transistors Developed

    NASA Technical Reports Server (NTRS)

    Ponchak, George E.

    2002-01-01

    Future NASA, DOD, and commercial products will require electronic circuits that have greater functionality and versatility but occupy less space and cost less money to build and integrate than current products. System on a Chip (SOAC), a single semiconductor substrate containing circuits that perform many functions or containing an entire system, is widely recognized as the best technology for achieving low-cost, small-sized systems. Thus, a circuit technology is required that can gather, process, store, and transmit data or communications. Since silicon-integrated circuits are already used for data processing and storage and the infrastructure that supports silicon circuit fabrication is very large, it is sensible to develop communication circuits on silicon so that all the system functions can be integrated onto a single wafer. Until recently, silicon integrated circuits did not function well at the frequencies required for wireless or microwave communications, but with the introduction of small amounts of germanium into the silicon to make silicon-germanium (SiGe) transistors, silicon-based communication circuits are possible. Although microwavefrequency SiGe circuits have been demonstrated, there has been difficulty in obtaining the high power from their transistors that is required for the amplifiers of a transmitter, and many researchers have thought that this could not be done. The NASA Glenn Research Center and collaborators at the University of Michigan have developed SiGe transistors and amplifiers with state-of-the-art output power at microwave frequencies from 8 to 20 GHz. These transistors are fabricated using standard silicon processing and may be integrated with CMOS integrated circuits on a single chip. A scanning electron microscope image of a typical SiGe heterojunction bipolar transistor is shown in the preceding photomicrograph. This transistor achieved a record output power of 550 mW and an associated power-added efficiency of 33 percent at 8

  6. Frequency-based design of Adaptive Optics systems

    NASA Astrophysics Data System (ADS)

    Agapito, Guido; Battistelli, Giorgio; Mari, Daniele; Selvi, Daniela; Tesi, Alberto; Tesi, Pietro

    2013-12-01

    The problem of reducing the effects of wavefront distortion and structural vibrations inground-based telescopes is addressed within a modal-control framework. The proposed approach aimsat optimizing the parameters of a given modal stabilizing controller with respect to a performance criterionwhich reflects the residual phase variance and is defined on a sampled frequency domain. Thisframework makes it possible to account for turbulence and vibration profiles of arbitrary complexity(even empirical power spectral densities from data), while the controller order can be kept at a desiredvalue. Moreover it is possible to take into account additional requirements, as robustness in the presenceof disturbances whose intensity and frequency profile vary with time. The proposed design procedureresults in solving a minmax problem and can be converted into a linear programming problem withquadratic constraints, for which there exist several standard optimization techniques. The optimizationstarts from a given stabilizing controller which can be either a non-model-based controller (in this caseno identification effort is required), or a model-based controller synthesized by means of turbulence andvibration models of limited complexity. In this sense the approach can be viewed not only as alternative,but also as cooperative with other control design approaches. The results obtained by means of anEnd-to-End simulator are shown to emphasize the power of the proposed method.

  7. Frequency transformation in the auditory lemniscal thalamocortical system.

    PubMed

    Imaizumi, Kazuo; Lee, Charles C

    2014-01-01

    The auditory lemniscal thalamocortical (TC) pathway conveys information from the ventral division of the medial geniculate body to the primary auditory cortex (A1). Although their general topographic organization has been well characterized, functional transformations at the lemniscal TC synapse still remain incompletely codified, largely due to the need for integration of functional anatomical results with the variability observed with various animal models and experimental techniques. In this review, we discuss these issues with classical approaches, such as in vivo extracellular recordings and tracer injections to physiologically identified areas in A1, and then compare these studies with modern approaches, such as in vivo two-photon calcium imaging, in vivo whole-cell recordings, optogenetic methods, and in vitro methods using slice preparations. A surprising finding from a comparison of classical and modern approaches is the similar degree of convergence from thalamic neurons to single A1 neurons and clusters of A1 neurons, although, thalamic convergence to single A1 neurons is more restricted from areas within putative thalamic frequency lamina. These comparisons suggest that frequency convergence from thalamic input to A1 is functionally limited. Finally, we consider synaptic organization of TC projections and future directions for research.

  8. The effects of radio-frequency electromagnetic fields on T cell function during development

    PubMed Central

    Ohtani, Shin; Ushiyama, Akira; Maeda, Machiko; Ogasawara, Yuki; Wang, Jianqing; Kunugita, Naoki; Ishii, Kazuyuki

    2015-01-01

    With the widespread use of radio-frequency devices, it is increasingly important to understand the biological effects of the associated electromagnetic fields. Thus, we investigated the effects of radio-frequency electromagnetic fields (RF-EMF) on T cell responses during development due to the lack of science-based evidence for RF-EMF effects on developmental immune systems. Sprague Dawley (SD) rats were exposed to 2.14-GHz wideband code division multiple-access (W-CDMA) RF signals at a whole-body specific absorption rate (SAR) of 0.2 W/kg. Exposures were performed for a total of 9 weeks spanning in utero development, lactation and the juvenile period. Rats were continuously exposed to RF-EMF for 20 h/day, 7 days/week. Comparisons of control and exposed rats using flow cytometry revealed no changes in the numbers of CD4/CD8 T cells, activated T cells or regulatory T cells among peripheral blood cells, splenocytes and thymocytes. Expression levels of 16 genes that regulate the immunological Th1/Th2 paradigm were analyzed using real-time PCR in the spleen and thymus tissues of control and RF-EMF–exposed rats. Although only the Il5 gene was significantly regulated in spleen tissues, Il4, Il5 and Il23a genes were significantly upregulated in thymus tissues following exposure to RF-EMF. However, ELISAs showed no changes in serum IL-4 protein concentrations. These data indicate no adverse effects of long-term RF-EMF exposure on immune-like T cell populations, T cell activation, or Th1/Th2 balance in developing rats, although significant transcriptional effects were observed. PMID:25835473

  9. The effects of radio-frequency electromagnetic fields on T cell function during development.

    PubMed

    Ohtani, Shin; Ushiyama, Akira; Maeda, Machiko; Ogasawara, Yuki; Wang, Jianqing; Kunugita, Naoki; Ishii, Kazuyuki

    2015-05-01

    With the widespread use of radio-frequency devices, it is increasingly important to understand the biological effects of the associated electromagnetic fields. Thus, we investigated the effects of radio-frequency electromagnetic fields (RF-EMF) on T cell responses during development due to the lack of science-based evidence for RF-EMF effects on developmental immune systems. Sprague Dawley (SD) rats were exposed to 2.14-GHz wideband code division multiple-access (W-CDMA) RF signals at a whole-body specific absorption rate (SAR) of 0.2 W/kg. Exposures were performed for a total of 9 weeks spanning in utero development, lactation and the juvenile period. Rats were continuously exposed to RF-EMF for 20 h/day, 7 days/week. Comparisons of control and exposed rats using flow cytometry revealed no changes in the numbers of CD4/CD8 T cells, activated T cells or regulatory T cells among peripheral blood cells, splenocytes and thymocytes. Expression levels of 16 genes that regulate the immunological Th1/Th2 paradigm were analyzed using real-time PCR in the spleen and thymus tissues of control and RF-EMF-exposed rats. Although only the Il5 gene was significantly regulated in spleen tissues, Il4, Il5 and Il23a genes were significantly upregulated in thymus tissues following exposure to RF-EMF. However, ELISAs showed no changes in serum IL-4 protein concentrations. These data indicate no adverse effects of long-term RF-EMF exposure on immune-like T cell populations, T cell activation, or Th1/Th2 balance in developing rats, although significant transcriptional effects were observed. © The Author 2015. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

  10. Simulated vibrational sum frequency generation from a multilayer thin film system with two active interfaces.

    PubMed

    O'Brien, Daniel B; Massari, Aaron M

    2013-04-21

    In the field of surface-specific vibrational sum frequency generation spectroscopy (VSFG) on organic thin films, optical interferences combined with the two-interface problem presents a challenge in terms of qualitative assessment of the data and quantitative modeling. The difficulty is amplified when considering systems comprised of more than a single material thin film layer. Recently, in our lab we have developed a generalized model that describes thin film interference in interface-specific nonlinear optical spectroscopies from arbitrary multilayer systems. Here, we apply the model to simulate VSFG spectra from the simplest multilayer: a system of two thin films, one of which is an organic small molecule and the other is a dielectric layer on a semiconductor substrate system where we idealize that the organic interfaces are equally VSFG active. Specifically, we consider the molecule N,N'-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) deposited on a silicon wafer with a thermally grown oxide dielectric. We present results for the four polarization experiments that sample the nonzero nonlinear susceptibility elements of macroscopically centrosymmetric materials (ssp, sps, pss, and ppp) and in two mIR frequency windows (the imide carbonyl stretches around 1680 cm(-1) and the alkyl stretches around 2900 cm(-1)) as a function of both thin film thicknesses with fixed input beam angles. We use frequency dependent refractive indices for all materials. The goal is to illustrate some of the intricacies contained in the intensity data of such systems. Of particular interest is the effect of the relative polar orientation of modes at the interfaces and the possibility of designing a system where the collected signal is exclusively attributable to a single interface. Our calculations indicate that in order to unambiguously identify the relative polar orientation one must experimentally vary an additional system parameter such as thin film thickness or input beam angle

  11. Note: Stability control of intermediate frequencies of a three laser far-infrared polarimeter-interferometer system.

    PubMed

    Yu, Jiang-Tao; Li, He-Ping; Nie, Qiu-Yue; Zou, Zhi-Yong; Liu, Hai-Qing; Bao, Cheng-Yu; Jie, Yin-Xian; Li, Zhan-Xian

    2016-12-01

    Stability of the intermediate frequency (IF) in the far-infrared polarimeter-interferometer diagnostic system is critically important for the long pulse discharge experiments on the EAST tokamak. In this note, a real-time remote/local IF stability control system is described. The measured plasma parameters, including the Faraday rotation angle, electron density, lower hybrid wave, and plasma current, are obtained with the aid of this newly developed IF stability control system.

  12. Note: Stability control of intermediate frequencies of a three laser far-infrared polarimeter-interferometer system

    NASA Astrophysics Data System (ADS)

    Yu, Jiang-Tao; Li, He-Ping; Nie, Qiu-Yue; Zou, Zhi-Yong; Liu, Hai-Qing; Bao, Cheng-Yu; Jie, Yin-Xian; Li, Zhan-Xian

    2016-12-01

    Stability of the intermediate frequency (IF) in the far-infrared polarimeter-interferometer diagnostic system is critically important for the long pulse discharge experiments on the EAST tokamak. In this note, a real-time remote/local IF stability control system is described. The measured plasma parameters, including the Faraday rotation angle, electron density, lower hybrid wave, and plasma current, are obtained with the aid of this newly developed IF stability control system.

  13. Expert System Development Methodology (ESDM)

    NASA Technical Reports Server (NTRS)

    Sary, Charisse; Gilstrap, Lewey; Hull, Larry G.

    1990-01-01

    The Expert System Development Methodology (ESDM) provides an approach to developing expert system software. Because of the uncertainty associated with this process, an element of risk is involved. ESDM is designed to address the issue of risk and to acquire the information needed for this purpose in an evolutionary manner. ESDM presents a life cycle in which a prototype evolves through five stages of development. Each stage consists of five steps, leading to a prototype for that stage. Development may proceed to a conventional development methodology (CDM) at any time if enough has been learned about the problem to write requirements. ESDM produces requirements so that a product may be built with a CDM. ESDM is considered preliminary because is has not yet been applied to actual projects. It has been retrospectively evaluated by comparing the methods used in two ongoing expert system development projects that did not explicitly choose to use this methodology but which provided useful insights into actual expert system development practices and problems.

  14. Method and system for air-driven pump monitoring based on frequency analysis of the acoustic signal

    NASA Astrophysics Data System (ADS)

    Ida, Nathan; Ciocan, Razvan

    2002-07-01

    A method for early failure detection for elastic diaphragms during their operation is described in this paper. The method is based on frequency analysis of the acoustic signal obtained from an air-driven pump. A fully digital system for frequency analysis based on a personal computer was developed for practical implementation of this method. The system was tested in the laboratory and in plant conditions. In laboratory, diaphragms with different artificial flaws were mounted in the pump and the corresponding spectra recorded. The results helped to set the parameters for in-plant experiments. These experiments were between three and fourteen days. During this time the system performed acquisition and data processing at 10 second apart. Three in-plant experiments have shown that a failure initiation event can be detected from frequency behavior analysis for each test and that a subsequent failure occurs. All failures indicated by the system have been confirmed by visual inspection.

  15. Development of Very Low Frequency Self-Nulling Probe for Inspection of Thick Layered Aluminum Structures

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Namkung, Min

    1998-01-01

    It is clear from simple skin depth considerations that steady state electromagnetic inspection of thick multi-layered conductors requires low frequency excitation. Conventional pickup sensors, however, lose sensitivity at lower frequencies. Giant magneto resistive materials offer a unique alternative for very low frequency electromagnetic NDE due to their high sensitivity to low frequency fields, small size, ease of use, and low cost. This paper outlines the development and testing of a Very Low Frequency Self-Nulling Probe incorporating a GMR sensor. The initial test results show flaw detectability at depths up to 1 cm in aluminum 2024. Optimization of the probe design based upon finite element modeling and GMR sensor characteristics (including hysteresis, linearity and saturation) is under way.

  16. Occupational exposure to intermediate frequency and extremely low frequency magnetic fields among personnel working near electronic article surveillance systems.

    PubMed

    Roivainen, Päivi; Eskelinen, Tuomo; Jokela, Kari; Juutilainen, Jukka

    2014-05-01

    Cashiers are potentially exposed to intermediate frequency (IF) magnetic fields at their workplaces because of the electronic article surveillance (EAS) systems used in stores to protect merchandise against theft. This study aimed at investigating occupational exposure of cashiers to IF magnetic fields in Finnish stores. Exposure to extremely low frequency (ELF) magnetic fields was also evaluated because cashiers work near various devices operating with 50 Hz electric power. The peak magnetic flux density was measured for IF magnetic fields, and was found to vary from 0.2 to 4 µT at the cashier's seat. ELF magnetic fields from 0.03 to 4.5 µT were found at the cashier's seat. These values are much lower than exposure limits. However, according to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) occupational reference levels for IF magnetic fields (141 µT for the peak field) were exceeded in some cases (maximum 189 µT) for short periods of time when cashiers walked through the EAS gates. As the ICNIRP reference levels do not define any minimum time for exposure, additional investigations are recommended to determine compliance with basic restrictions. Even if the basic restrictions are not exceeded, persons working near EAS devices represent an exceptional group of workers with respect to exposure to electromagnetic fields. This group could serve as a basis for epidemiological studies addressing possible health effects of IF magnetic fields. Compliance with the reference levels for IF fields was evaluated using both broadband measurement of peak fields and the ICNIRP summation rule for multiple frequencies. The latter was generally more conservative, and the difference between the two methods was large (>10-fold) for EAS systems using a 58 kHz signal with complex waveform. This indicates that the ICNIRP multiple frequency rule can be unnecessarily conservative when measuring complex waveforms. © 2014 Wiley Periodicals, Inc.

  17. A frequency averaging framework for the solution of complex dynamic systems

    PubMed Central

    Lecomte, Christophe

    2014-01-01

    A frequency averaging framework is proposed for the solution of complex linear dynamic systems. It is remarkable that, while the mid-frequency region is usually very challenging, a smooth transition from low- through mid- and high-frequency ranges is possible and all ranges can now be considered in a single framework. An interpretation of the frequency averaging in the time domain is presented and it is explained that the average may be evaluated very efficiently in terms of system solutions. PMID:24910518

  18. A comparative study of frequency offset estimations in real and complex OFDM systems using different algorithms

    NASA Astrophysics Data System (ADS)

    Sahu, Swagatika; Mohanty, Saumendra; Srivastav, Richa

    2013-01-01

    Orthogonal Frequency Division Multiplexing (OFDM) is an emerging multi-carrier modulation scheme, which has been adopted for several wireless standards such as IEEE 802.11a and HiperLAN2, etc. A well-known problem of OFDM is its sensitivity to frequency offset between the transmitted and received carrier frequencies. In (OFDM) system Carrier frequency offsets (CFOs) between the transmitter and the receiver destroy the orthogonality between carriers and degrade the system performance significantly. The main problem with frequency offset is that it introduces interference among the multiplicity of carriers in the OFDM signal.The conventional algorithms given by P. Moose and Schmidl describes how carrier frequency offset of an OFDM system can be estimated using training sequences. Simulation results show that the improved carrier frequency offset estimation algorithm which uses a complex training sequence for frequency offset estimation, performs better than conventional P. Moose and Schmidl algorithm, which can effectively improve the frequency estimation accuracy and provides a wide acquisition range for the carrier frequency offset with low complexity. This paper introduces the BER comparisons of different algorithms with the Improved Algorithms for different Real and Complex modulations schemes, considering random carrier offsets . This paper also introduces the BER performances with different CFOs for different Real and Complex modulation schemes for the Improved algorithm.

  19. Narrow linewidth laser system realized by linewidth transfer using a fiber-based frequency comb for the magneto-optical trapping of strontium.

    PubMed

    Akamatsu, Daisuke; Nakajima, Yoshiaki; Inaba, Hajime; Hosaka, Kazumoto; Yasuda, Masami; Onae, Atsushi; Hong, Feng-Lei

    2012-07-02

    A narrow linewidth diode laser system at 689 nm is realized by phase-locking an extended cavity diode laser to one tooth of a narrow linewidth optical frequency comb. The optical frequency comb is phase-locked to a narrow linewidth laser at 1064 nm, which is frequency stabilized to a high-finesse optical cavity. We demonstrate the magneto-optical trapping of Sr using an intercombination transition with the developed laser system.

  20. Modeling of thermoacoustic systems using the nonlinear frequency domain method.

    PubMed

    de Jong, J A; Wijnant, Y H; Wilcox, D; de Boer, A

    2015-09-01

    When modeling thermoacoustic (TA) devices at high amplitude, nonlinear effects such as time-average mass flows, and the generation of higher harmonics can no longer be neglected. Thus far, modeling these effects in TA devices required a generally computationally costly time integration of the nonlinear governing equations. In this paper, a fast one-dimensional nonlinear model for TA devices is presented, which omits this costly time integration by directly solving the periodic steady state. The model is defined in the frequency domain, which eases the implementation of phase delays due to viscous resistance and thermoacoustic heat exchange. As a demonstration, the model is used to solve an experimental standing wave thermoacoustic engine. The obtained results agree with experimental results, as well as with results from a nonlinear time domain model from the literature. The low computational cost of this model opens the possibility to do optimization studies using a nonlinear TA model.

  1. Adaptive SSVEP-based BCI system with frequency and pulse duty-cycle stimuli tuning design.

    PubMed

    Shyu, Kuo-Kai; Chiu, Yun-Jen; Lee, Po-Lei; Liang, Jia-Ming; Peng, Shao-Hwo

    2013-09-01

    This study aims to design a steady state visual evoked potentials (SSVEP) based brain-computer interface (BCI) system with only three electrodes. It is known that low frequency flickering induces more intensive SSVEP, but might cause users feel uncomfortable and easily tired. Therefore, this paper proposes a novel middle/high frequency flickering stimulus. However, users show different SSVEP responses when gazing at the same stimuli. It is improper to design fixed frequency flickering stimuli for all users. This study firstly proposes a strategy to adjust the stimuli frequency for each user that could cause better SSVEP. Moreover, to further enhance the SSVEP, this study incorporates flickering duty-cycle for stimuli design, which has been discussed less for SSVEP-based BCI systems. The proposed system consists of two modes, flicker frequency/duty-cycle selection mode and application mode. The flicker frequency/duty-cycle selection mode obtains two best frequencies between 24 and 36 Hz with their related optimal duty-cycle. Then the system goes into the application mode to control the devices. A new fact that has been found is that the optimal flicker frequency and duty-cycle do not vary with time. It means once the optical flicker frequency and duty-cycle is determined the first time, flicker frequency/duty-cycle selection mode does not need to operate the next time. Furthermore, the phase coding technology is used to extend the one command/one frequency to multi command/one frequency. Experimental results show the proposed system has good performance with average accuracy 95% and average command transfer interval 4.4925 s per command.

  2. Decentralized robust frequency control for power systems subject to wind power variability

    NASA Astrophysics Data System (ADS)

    Liu, Juhua

    As the penetration of wind energy generation increases in electric power systems, the frequency performance degrades mainly for two reasons. First, the intermittency of wind power introduces additional generation-load imbalance in the system, causing frequency to deviate from nominal values. Second, modern wind turbine generators are often decoupled from the grid by power electronics, making the wind turbines contribute no inertia to the grid. When more conventional generation is displaced by such wind generation, the total system inertia will decrease and the grid is more susceptible to generation-load imbalance. Therefore, frequency control must be revisited and enhanced in order to accommodate large-scale integration of wind energy. This dissertation mainly concerns the re-design of generator compensators to improve frequency performance of power systems when the penetration of wind power is high. Hinfinity methods can be used to synthesize controllers to achieve stability and robust performance in the presence disturbances. However, standard Hinfinity methods tend to produce complex controllers when the order of the system is high. Furthermore, when standard Hinfinity methods are continued with a naive decentralized control design, the resulting decentralized controllers may compete against each other and lead to instability. Therefore, we develop a passivity-based decentralized control framework for power system frequency control. A storage function is derived from the entropy of individual generators. Tellegen's theorem is invoked to derive the storage function for the entire power network. With this storage function, the power network is shown to be passive with respect to a supply rate, which is the sum of decentralized input-output products. Stability can then be assured when passive controllers are connected in negative feedback interconnection to the system. Proportional-integral-derivative (PID) controllers with positive gains are passive controllers

  3. Recent developments in fiber-based optical frequency comb and its applications

    NASA Astrophysics Data System (ADS)

    Xia, Wei; Chen, Xuzong

    2016-04-01

    Fiber-based optical frequency combs, characterized by compact configuration and outstanding optical properties, have been developed into state-of-the-art precision instruments which are no longer used just for optical frequency metrology, but for a number of applications, including optical clocks, attosecond science, exoplanet searches, medical diagnostics, physicochemical processes control and advanced manufacturing. This short perspective presents some of the milestones and highlights in the evolution of fiber-based optical frequency combs and the technical revolution that are brought by them for a wide range of applications. Along the way, both the challenges and opportunities in the future development of the fiber-based optical frequency comb technology have been described as well.

  4. Development of a Wideband VLBI System (GALA-V)

    NASA Astrophysics Data System (ADS)

    Sekido, Mamoru; Takefuji, Kazuhiro; Ujihara, Hideki; Tsutsumi, Masanori; Miyauchi, Yuka; Hasegawa, Shingo; Hobiger, Thomas; Ichikawa, Ryuichi; Koyama, Yasuhiro

    2014-12-01

    The VLBI group of the National Institute of Information and Communications Technology (NICT) has been developing a wideband VLBI observation system, which is semi-compliant with the VGOS system. Two small-diameter, transportable antennas and a 34-m antenna are prepared for wideband observations at the 3-14 GHz frequency range. This project, named ``GALA-V'', is intended to be used for precise frequency comparisons between widely separated atomic frequency standards. Several new challenges are being addressed in this project: (1) development of a wideband feed with narrow beam width for a large-diameter Cassegrain antenna, (2) development of a direct RF sampling data acquisition system, which samples the RF analog signal at 16 GHz. A prototype of the new wideband feed has been installed on the 34-m antenna at the end of 2013. The current status of this GALA-V project development is described in this report.

  5. Development of a low-frequency physiotherapeutic device for diabetes manipulated by microcontroller.

    PubMed

    Guo, Jin-Song; Gong, Jian

    2001-01-01

    OBJECTIVE: To develop a physiotherapeutic device for diabetes that generates special low-frequency waveform manipulated by a microcontroller. METHODS: A microcontoller and a digital-to-analog converter were utilized along with a keyboard and LED display circuit, to generate desired low-frequecy waveform with the assistance of a software. RESULTS: The complex waveform generated by this device met the demands for diabetes physiotherapy, and the frequency and amplitude could be freely adjusted. CONCLUSIONS: The utilization of a digital-to-analog converter controlled by a microcontroller can very well serve the purpose of a low-frequency physiotherapy for diabetes.

  6. Comparison of Bus Frequency Models for Power System Electro-mechanical Simulations

    NASA Astrophysics Data System (ADS)

    Li, Changgang; Yu, Yawei; Sun, Yanli

    2017-05-01

    With more and more frequency-related devices interconnected into power grid, accurate frequency estimation becomes important for power system electro-mechanical simulations. This paper reviewed the methods for calculation of bus frequency including difference method, difference method with low-pass filter. Trapezoidal method and damping trapezoidal method which are commonly used in numerical computation are also discussed in this paper for the calculation of bus frequency. In order to analyze advantages and disadvantages of these methods in the aspect of numerical accuracy and stability, a comparison is made on their amplitude-frequency and phase-frequency characteristics. Voltage angle samples from both ideal function and numerical simulation are provided to test the performance of these methods on estimating bus frequency.

  7. Automotive Stirling engine systems development

    NASA Technical Reports Server (NTRS)

    Richey, A. E.

    1984-01-01

    The objective of the Automotive Stirling Engine (ASE) program is to develop a Stirling engine for automotive use that provides a 30 percent improvement in fuel economy relative to a comparable internal-combustion engine while meeting emissions goals. This paper traces the engine systems' development efforts focusing on: (1) a summary of engine system performance for all Mod I engines; (2) the development, program conducted for the upgraded Mod I; and (3) vehicle systems work conducted to enhance vehicle fuel economy. Problems encountered during the upgraded Mod I test program are discussed. The importance of the EPA driving cycle cold-start penalty and the measures taken to minimize that penalty with the Mod II are also addressed.

  8. Laser system for Doppler cooling of ytterbium ion in an optical frequency standard

    SciTech Connect

    Chepurov, S V; Lugovoy, A A; Kuznetsov, S N

    2014-06-30

    A laser system for Doppler cooling of ytterbium ion on the {sup 2}S{sub 1/2} → {sup 2}P{sub 1/2} transition in a single-ion optical frequency standard is developed. The second harmonic of a semiconductor laser with a wavelength of 739 nm is used for cooling. The laser frequency is doubled in a nonlinear BiBO crystal embedded in a ring resonator, which also serves as a reference for laser frequency stabilisation. Second-harmonic power of ∼100 μW is generated at a wavelength of 369.5 nm. Diode laser radiation is modulated by an electro-optic modulator at 14.75 GHz to generate a sideband exciting the {sup 2}S{sub 1/2} (F = 0) → {sup 2}P{sub 1/2} (F = 1) hyperfine component of the cooling transition that is not excited by resonant cooling light. The sideband relative intensity of a few percent proved to be sufficient to reduce the ion dwelling time in the {sup 2}S{sub 1/2} (F = 0) state to less than 10{sup -4} s and increase the cooling efficiency. (extreme light fields and their applications)

  9. PWM Switching Frequency Effects on Eddy Current Sensors for Magnetically Suspended Flywheel Systems

    NASA Technical Reports Server (NTRS)

    Jansen, Ralph; Lebron, Ramon; Dever, Timothy P.; Birchenough, Arthur G.

    2003-01-01

    A flywheel magnetic bearing (MB) pulse width modulated power amplifier (PWM) configuration is selected to minimize noise generated by the PWMs in the flywheel position sensor system. Two types of noise are addressed: beat frequency noise caused by variations in PWM switching frequencies, and demodulation noise caused by demodulation of high order harmonics of the switching voltage into the MB control band. Beat frequency noise is eliminated by synchronizing the PWM switch frequencies, and demodulation noise is minimized by selection of a switching frequency which does not have harmonics at the carrier frequency of the sensor. The recommended MB PWM system has five synchronized PWMs switching at a non-integer harmonic of the sensor carrier.

  10. Ionospheric total-electron-content estimation for single-frequency Global-positioning-system receivers

    SciTech Connect

    Smith, C.A.

    1987-01-01

    The ionosphere delays transmissions from the Global Positioning System (GPS), as well as those from other satellite systems. At the GPS frequencies (L-Band), this delay is directly proportional to the total ionospheric electron content (TEC) along the line-of-sight to the satellite. Classified receivers have access to 2 frequencies to allow them to measure this delay through the difference in the ionospheric effect at the 2 frequencies, but commercial, single-frequency receivers have had no direct method for estimating the ionospheric delay; they have had to rely on a TEC prediction. Two methods are described for single-frequency GPS receivers to estimate the ionospheric TEC directly. These methods take advantage of the dispersive nature of the ionosphere at L-Band frequencies, which causes a phase advance of the carrier that is opposite to the group delay of the GPS code and data.

  11. Application of a modified complementary filtering technique for increased aircraft control system frequency bandwidth in high vibration environment

    NASA Technical Reports Server (NTRS)

    Garren, J. F., Jr.; Niessen, F. R.; Abbott, T. S.; Yenni, K. R.

    1977-01-01

    A modified complementary filtering technique for estimating aircraft roll rate was developed and flown in a research helicopter to determine whether higher gains could be achieved. Use of this technique did, in fact, permit a substantial increase in system frequency bandwidth because, in comparison with first-order filtering, it reduced both noise amplification and control limit-cycle tendencies.

  12. Frequency selectivity, multistability, and oscillations emerge from models of genetic regulatory systems.

    PubMed

    Smolen, P; Baxter, D A; Byrne, J H

    1998-02-01

    To examine the capability of genetic regulatory systems for complex dynamic activity, we developed simple kinetic models that incorporate known features of these systems. These include autoregulation and stimulus-dependent phosphorylation of transcription factors (TFs), dimerization of TFs, crosstalk, and feedback. The simplest model manifested multiple stable steady states, and brief perturbations could switch the model between these states. Such transitions might explain, for example, how a brief pulse of hormone or neurotransmitter could elicit a long-lasting cellular response. In slightly more complex models, oscillatory regimes were identified. The addition of competition between activating and repressing TFs provided a plausible explanation for optimal stimulus frequencies that give maximal transcription. Such optimal frequencies are suggested by recent experiments comparing training paradigms for long-term memory formation and examining changes in mRNA levels in repetitively stimulated cultured cells. In general, the computational approach illustrated here, combined with appropriate experiments, provides a conceptual framework for investigating the function of genetic regulatory systems.

  13. 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.

  14. Development of a frequency-tunable optical phase lock loop (OPLL) for high resolution fiber optic distributed sensing

    NASA Astrophysics Data System (ADS)

    Kuperschmidt, Vladimir; Stolpner, Lew; Mols, Peter; Alalusi, Mazin; Mehnert, Axel; Barsan, Radu; Ansari, Farhad

    2011-04-01

    We report on the development of a precision-tunable, dual wavelength, optical light source suitable for high performance fiber optic Brillouin scattering distributed sensing. The design is based on an Optical Phase Locked Loop (OPLL) system using novel narrow linewidth, low frequency noise and high stability PLANEX external cavity semiconductor. The inherent wavelength stability of PLANEX lasers (typically an order of magnitude better that any DFB laser on the market) enable the OPLL to operate continuously over a wide ambient temperature range without degradation in wavelength locking performance. The OPLL architecture is implemented with polarization maintaining (PM) components and has a very low beat frequency jitter on the order of few kHz. The OPLL frequency tuning range is between 8 and 14 GHz, with fast tuning of sweep steps on the order of 100 μsec. Such a frequency tuning range covers practically all corresponding temperature and strain sensing applications based on the measurement of the frequency shift produced by spontaneous or stimulated Brillouin scattering, and thus is a versatile and enabling technology for both BOTDA/BOTDR distributed sensing systems.

  15. Noise-Induced Phase Locking and Frequency Mixing in an Optical Bistable System with Delayed Feedback

    NASA Astrophysics Data System (ADS)

    Misono, Masatoshi; Miyakawa, Kenji

    2011-11-01

    The interplay between stochastic resonance (SR) and coherence resonance (CR) is experimentally studied in an optical bistable system with a time-delayed feedback loop. We demonstrate that the phase of the noise-induced motion is locked to that of the periodic input when the ratio of their frequencies is a simple rational number. We also demonstrate that the interplay between SR and CR generates frequency-mixed modes, and that the efficiency of frequency mixing is enhanced by the optimum noise.

  16. Low-latency digital frequency synthesizer using the residue number system

    NASA Technical Reports Server (NTRS)

    Chren, William A., Jr.

    1993-01-01

    A low-latency frequency synthesizer using the Direct Digital Synthesis (DDS) technique has been designed. Called the Residue Assisted Frequency Synthesizer (RAFS), it exhibits frequency switching times which are reduced by more than 50 percent below previously published designs. The switching speed advantage is made possible by the use of the Residue Number System, which allows the pipeline lengths in the Phase Accumulator and other circuitry to be reduced significantly.

  17. Two-frequency information recording in a three-level system using stimulated photon echo

    SciTech Connect

    Garnaeva, G I; Nefediev, L A; Akhmedshina, E N; Garnaev, R N

    2015-07-31

    The process of recording and reproducing information in a three-level system using stimulated photon echo is studied as a function of the amount of information embedded in the first and second two-frequency object laser pulses. It is shown that two-frequency information recording leads to an increase in the power of the stimulated photon echo response on one frequency transition and to its reduction on the other. (laser applications and other topics in quantum electronics)

  18. Very High Frequency Monitoring System for Engine Gearbox and Generator Health Management (Postprint)

    DTIC Science & Technology

    2007-09-18

    Application of Health and Usage Monitoring System (HUMS) Technologies to Wind Turbine Drive Trains,” WindPower 2005, Denver, CO, May 15-18, 2005...AFRL-RZ-WP-TP-2008-2043 VERY HIGH FREQUENCY MONITORING SYSTEM FOR ENGINE GEARBOX AND GENERATOR HEALTH MANAGEMENT (POSTPRINT) Matthew J...2649 5b. GRANT NUMBER 4. TITLE AND SUBTITLE VERY HIGH FREQUENCY MONITORING SYSTEM FOR ENGINE GEARBOX AND GENERATOR HEALTH MANAGEMENT (POSTPRINT

  19. Characterization of an intraluminal differential frequency-domain photoacoustics system

    NASA Astrophysics Data System (ADS)

    Lashkari, Bahman; Son, Jungik; Liang, Simon; Castelino, Robin; Foster, F. Stuart; Courtney, Brian; Mandelis, Andreas

    2016-03-01

    Cardiovascular related diseases are ranked as the second highest cause of death in Canada. Among the most important cardiovascular diseases is atherosclerosis. Current methods of diagnosis of atherosclerosis consist of angiography, intravascular ultrasound (IVUS) and optical coherence tomography (OCT). None of these methods possesses adequate sensitivity, as the ideal technique should be capable of both depth profiling, as well as functional imaging. An alternative technique is photoacoustics (PA) which can perform deep imaging and spectroscopy. The presented study explores the application of wavelength-modulated differential photoacoustic radar (WM-DPAR) for characterizing arterial vessels. The wavelength-modulated differential photoacoustic technique was shown to be able to substantially increase the dynamic range and sensitivity of hemoglobin oxygenation level detection. In this work the differential PA technique was used with a very high frequency modulation range. To perform spectroscopic PA imaging, at least two wavelengths are required. The selected wavelengths for this work are 1210 nm and 980 nm. 1210 nm corresponds to the maximum optical absorption coefficient of cholesterol and cholesteryl esters which are the main constituents of plaques. Since water, elastin and collagen also have high absorption coefficients at 1210 nm, this wavelength alone cannot provide very high sensitivity and specificity. The additional wavelength, 980 nm corresponds to high absorption coefficient of those constituents of healthy artery tissue. The simultaneous application of the abovementioned wavelengths can provide higher sensitivity and improved specificity in detecting lipids in the arterial vessels.

  20. Communications and logic systems at millimeter wave frequencies

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Activities in materials development, lithography, FET experiments, and mixer diode fabrication are reported. In addition, articles are presented which address leakage effects in n-GaAs MESFET's and lateral nonuniform doping in GaAs MESFET's.