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1

Microminiature radio frequency transmitter for communication and tracking applications  

NASA Astrophysics Data System (ADS)

A micro-miniature radio frequency (rf) transmitter has been developed and demonstrated by the Oak Ridge National Laboratory. The objective of the rf transmitter development was to maximize the transmission distance while drastically shrinking the overall transmitter size, including antenna. Based on analysis and testing, an application-specific integrated circuit (ASIC) with a 16-GHz gallium arsenide (GaAs) oscillator and integrated on-chip antenna was designed and fabricated using microwave monolithic integrated circuit (MMIC) technology. Details of the development and the results of various field tests are discussed. The rf transmitter is applicable to covert surveillance and tracking scenarios due to its small size of 2.2 multiplied by 2.2 mm, including the antenna. Additionally, the 16-GHz frequency is well above the operational range of consumer-grade radio scanners, providing a degree of protection from unauthorized interception. Variations of the transmitter design have been demonstrated for tracking and tagging beacons, transmission of digital data, and transmission of real-time analog video from a surveillance camera. Preliminary laboratory measurements indicate adaptability to direct-sequence spread-spectrum transmission, providing a low probability of intercept and/or detection. Concepts related to law enforcement applications are presented.

Crutcher, Richard I.; Emery, Mike S.; Falter, Kelly G.; Nowlin, C. H.; Rochelle, Jim M.; Clonts, Lloyd G.

1997-02-01

2

Radio frequency radiation (RFR) from TV and radio transmitters at a pilot region in Turkey.  

PubMed

For the last 30 y, the biological effects of non-ionising radiation (NIR: 0-300 GHz) have been a major topic in bioelectromagnetism. Since the number of radiofrequency (RF) systems operating in this frequency range has shown an incredible increase over the last few decades, the dangers of exposure to the fields generated thereby has become an important public health issue. In this study, the aim was to evaluate the level of RF electromagnetic radiation in Yenimahalle Sentepe Dededoruk Hill in Ankara, Turkey that is a multiple-transmitter site hosting 64 different TV and radio towers and one base station for mobile phone communication. The site has been of interest as it is nearby a residential community. Within the technical input data available on 31 of the radio and TV transmitters, the calculated radiation level in this particular region was found to be approximately four times higher than the permitted standards of Turkey, which are the same as the ICNIRP standards. Electromagnetic field measurement is needed in the site. PMID:19671591

Sirav, Bahriye; Seyhan, Nesrin

2009-08-11

3

Micro-miniature radio frequency transmitter for communication and tracking applications  

SciTech Connect

A micro-miniature radio frequency (rf) transmitter has been developed and demonstrated by the Oak Ridge National Laboratory. The objective of the rf transmitter development was to maximize the transmission distance while drastically shrinking the overall transmitter size, including antenna. Based on analysis and testing, an application-specific integrated circuit (ASIC) with a 16-GHz gallium arsenide (GaAs) oscillator and integrated on-chip antenna was designed and fabricated using microwave monolithic integrated circuit (MMIC) technology. Details of the development and the results of various field tests will be discussed. The rf transmitter is applicable to covert surveillance and tracking scenarios due to its small size of 2.2 x 2.2 mm, including the antenna. Additionally, the 16-GHz frequency is well above the operational range of consumer-grade radio scanners, providing a degree of protection from unauthorized interception. Variations of the transmitter design have been demonstrated for tracking and tagging beacons, transmission of digital data, and transmission of real-time analog video from a surveillance camera. Preliminary laboratory measurements indicate adaptability to direct-sequence spread-spectrum transmission, providing a low probability of intercept and/or detection. Concepts related to law enforcement applications will be presented.

Crutcher, R.I.; Emery, M.S.; Falter, K.G.; Nowlin, C.H. [Oak Ridge National Lab., TN (United States); Rochelle, J.M.; Clonts, L.G. [Univ. of Tennessee, Knoxville, TN (United States). Electrical Engineering Dept.

1996-12-31

4

SHIELDED-NEEDLE TECHNIQUE FOR SURGICALLY IMPLANTING RADIO-FREQUENCY TRANSMITTERS IN FISH  

EPA Science Inventory

Protruding whip antenna radio transmitters were implanted in fish with abdominal pelvic fins. This surgical technique enables the transmitter to be positioned anywhere in the peritoneal cavity without piercing vital organs through the use of a shielded needle to guide an antenna ...

5

Transmitter location system for frequencies below HF  

NASA Astrophysics Data System (ADS)

Differential phase measurement techniques and an apparatus for accurately locating unknown transmitters over great distances at radio frequencies below HF are presented. A network of separated, time- and phase-synchronized, pairs of receiving stations are discussed. The stations are comprised of vertical whip antennas that have a known base-line geometry. The antennas are used to accurately measure VLF phase differentials. The measured phase differences are compared against theoretical calculated values to provide highly accurate transmitter location information.

Westfall, Wallace D.

1991-12-01

6

Cancer Incidence near Radio and Television Transmitters in Great Britain  

Microsoft Academic Search

A small area study of cancer incidence, 1974-1986, near 20 high power television (TV) and frequency modulation (FM) radio transmitters in Great Britain was carried out to place in context the findings of an earlier study around the Sutton Coldfield transmitter. The national database of postcoded cancer registrations was used with population and socioeconomic data from the 1981 census. Cancers

Helen Dolk; Paul Elliott; Gavin Shaddick; Peter Walls; Bharat Thakrar

1997-01-01

7

Radio frequency interference  

Microsoft Academic Search

The article consists of a Powerpoint presentation on radio frequency interference. The areas discussed include: radio frequency interference; electromagnetic interference; mobile Internet device and wireless sensitivity requirement.

H. Skinner; K. Slattery

2008-01-01

8

Effects of implanted radio transmitters with percutaneous antennas on the behavior of Canada Geese  

USGS Publications Warehouse

We examined whether surgically-implanted radio transmitters with percutaneous antennas affected behavior of Lesser Canada Geese (Branta canadensis parvipes) in Anchorage, Alaska. We implanted either a 26-g VHF radio transmitter or a larger VHF radio that was the same mass (35 g) and shape as a satellite transmitter in the coelom of adult females captured during molt in 2000. A control group of females was marked with leg bands. We simultaneously observed behavior of radio-marked and control females from 4-62 d following capture. We observed no differences in the proportion of time birds in different treatments allocated among grazing, resting, comfort, walking, and alert behavior. Females in different treatments spent a similar proportion of time in the water. Implantation of radio transmitters did not affect the frequency of agonistic interactions. We conclude that coelomic radio transmitters with percutaneous antennas had minimal effects on the behavior of Canada Geese.

Hupp, J. W.; Ruhl, G. A.; Pearce, J. M.; Mulcahy, D. M.; Tomeo, M. A.

2003-01-01

9

DQPSK Receiver tolerance to transmitter frequency stability  

Microsoft Academic Search

In case of Differential Quadrature Phase Shift Keying transmission, the diode laser frequency instability affects the quality of the received signal. Free-running transmitters are employed to experimentally evaluate the tolerance of the interferometric DQPSK receiver to this instability. Heterodyne measure of the frequency offset is discussed for different transmitters. Experimental data are related both with BER performance and power penalty.

Lucia Marazzi; Paola Parolari; Pierpaolo Boffi; Rocco Siano; Matteo Feroldi; M. Martinelli

2006-01-01

10

Radio Frequency Motion Sensor Cable Studies.  

National Technical Information Service (NTIS)

The Radio Frequency Motion Sensor (RFMS) detects movement within interior areas by detecting the electromagnetic phase and amplitude changes caused by an intruder moving through an RF field. The RFMS consists of a transmitter, receiver, up to three transm...

R. D. Bailey

1985-01-01

11

Miniature stereo radio transmitter for simultaneous recording of multiple single-neuron signals from behaving owls  

Microsoft Academic Search

Wireless radiotelemetric transmission of neuronal activity is an elegant technique to study brain-behavior interaction in unrestrained animals. In the current study, a miniature FM-stereo radio transmitter is described that permitted simultaneous recordings from two microelectrodes in behaving barn owls. Input from two independent channels is multiplexed to form a stereo composite signal that modulates a radio frequency carrier. The high

Andreas Nieder

2000-01-01

12

Implanting a Radio Transmitter in a Burmese Python  

USGS Multimedia Gallery

Researchers implant a radio transmitter in a 16-foot, 155-pound female Burmese python (Python molurus) at the South Florida Research Center, Everglades National Park. Radio-tracking builds understanding of where pythons spend their time and therefore where they can be controlled in practice. Photo c...

2009-10-12

13

Transmitter Identifier Systems for CB Radio  

Microsoft Academic Search

The need for Automatic Transmitter Identifier Systems (ATIS) is justified based on rule compliance and television interference (TVI) problems. Federal Communications Commission (FCC) rule making activities relative to ATIS are reviewed. The functional requirements of an ATIS are proposed that will satisfy the rule compliance and TVI needs while at the same time provide selective calling (SELCALL) features. The potential

Stuart J. Lipoff

1977-01-01

14

Laser transmitter feed-forward linearization system for radio over fiber application  

Microsoft Academic Search

This paper introduces a laser transmitter feed-forward linearization system for Radio over Fiber application at frequency 5.2GHz. The system was modeled and simulated in Optisystem 8.0. Theoretical simulation has shown a reduction in the distortion to 20dB and above.

Y. S. Neo; S. M. Idrus; M. F. Rahmat; N. M. Kassim; S. Alifah

2010-01-01

15

Frequency agile OPO-based transmitters for multiwavelength DIAL  

SciTech Connect

We describe a first generation mid-infrared transmitter with pulse-to- pulse frequency agility and both wide and narrow band capability. This transmitter was used to make multicomponent DIAL measurements in the field.

Velsko, S.P.; Ruggiero, A.; Herman, M.

1996-09-01

16

Frequency agile OPO-based transmitters for multiwavelength DIAL  

SciTech Connect

We describe a first generation mid-infrared transmitter with pulse to pulse frequency agility and both wide and narrow band capability. This transmitter was used to make multicomponent Differential Absorption LIDAR (DIAL) measurements in the field.

Velsko, S.P.; Ruggiero, A.; Herman, M.

1996-09-01

17

Balun with passband characteristic for ultra-wideband (UWB) impulse radio transmitter  

Microsoft Academic Search

This paper presents on-chip balun with capacitors connected in series (BCCS) has three-order high pass frequency characteristic. It can be used to suppress the power spectral density (PSD) of UWB impulse radio (UWB-IR) signal within 0.961.61GHz. With proper value of capacitor, BCCS has sharper cutoff edge than the balun without capacitor connected, which is desired for UWB-IR transmitter. The balun

Ruibing Dong; Ramesh K. Pokharel; Haruichi Kanaya; Keiji Yoshida

2012-01-01

18

A space-frequency transmitter diversity technique for OFDM systems  

Microsoft Academic Search

A transmitter diversity technique for wireless communications over frequency selective fading channels is presented. The proposed technique utilizes orthogonal frequency division multiplexing (OFDM) to transform a frequency selective fading channel into multiple flat fading subchannels on which space-frequency processing is applied. Simulation results verify that in a slow fading environment the proposed space-frequency OFDM (SF-OFDM) transmitter diversity technique has the

King F. Lee; Douglas B. Williams

2000-01-01

19

RADIO FREQUENCY ATTENUATOR  

DOEpatents

A high peak power level r-f attenuator that is readily and easily insertable along a coaxial cable having an inner conductor and an outer annular conductor without breaking the ends thereof is presented. Spaced first and second flares in the outer conductor face each other with a slidable cylindrical outer conductor portion therebetween. Dielectric means, such as water, contact the cable between the flares to attenuate the radio-frequency energy received thereby. The cylindrical outer conductor portion is slidable to adjust the voltage standing wave ratio to a low level, and one of the flares is slidable to adjust the attenuation level. An integral dielectric container is also provided. (AFC)

Giordano, S.

1963-11-12

20

Hematological stress indices reveal no effect of radio-transmitters on wintering Hermit Thrushes  

Microsoft Academic Search

Radio-telemetry is often used to track birds, and several investigators have examined the possible effects of radio-transmitters on birds. One approach to this question is to determine if transmitters induce physiological stress. Using hematological indicators of stress (heterophil-lymphocyte (H\\/L) ratios), studies of captive birds have revealed no evidence that radio-transmitters cause stress. However, studies in captivity may not reflect conditions

Andrew K. Davis; Nora E. Diggs; Robert J. Cooper; Peter P. Marra

2008-01-01

21

Radio frequency picosecond phototube  

SciTech Connect

We propose a photon detector for recording low-level and ultra-fast optical signals, based on radio frequency (RF) analysis of low-energy photoelectrons (PEs). By using currently developed 500 MHz RF deflector, it is possible to scan circularly and detect single PEs, amplified in multi-channel plates (MCPs). The operation of the tube is investigated by means of thermionic electron source. It is demonstrated that the signals generated in the MCP can be processed event by event; by using available nanosecond electronics and that time resolution better than 20 ps can be achieved. Timing characteristics of the Cherenkov detector with RF phototube in a ''head-on'' geometry is investigated by means of Monte Carlo simulation.

A. Margaryan; R. Carlini; R. Ent; N. Grigoryan; K. Gyunashyan; O. Hashimoto; K. Hovater; M. Ispiryan; S. Knyazyan; B. Kross; S. Majewski; G. Marikyan; M. Mkrtchyan; L. Parlakyan; V. Popov; L. Tang; H. Vardanyan; C. Yan; S. Zhamkochyan; C. Zorn

2006-10-01

22

Doppler circular array antenna principle for determining azimuth angle of radio transmitter  

Microsoft Academic Search

Radio tracking is widely used in communication technology because it can determine the coordinate position of radio transmitter and the distance of rocket to the ground station in a similar manner toradar system. this paper describes a method of azimuth angle detection of transmitter based on doppler circullar array antenna. the difference of signal power when the antenna is switched

Risanuri Hidayat; Isnan Nur Rifai; Wahyu Widada; Andreas Prasetya Adi

2011-01-01

23

47 CFR 74.461 - Transmitter power.  

Code of Federal Regulations, 2011 CFR

... (a) Transmitter power is the power at the transmitter output terminals and delivered to the antenna, antenna transmission line, or any other impedance-matched, radio frequency load. For the purpose of this Subpart, the transmitter...

2011-10-01

24

47 CFR 74.461 - Transmitter power.  

Code of Federal Regulations, 2012 CFR

... (a) Transmitter power is the power at the transmitter output terminals and delivered to the antenna, antenna transmission line, or any other impedance-matched, radio frequency load. For the purpose of this Subpart, the transmitter...

2012-10-01

25

Primary Transmitter Discovery Based on Image Processing in Cognitive Radio  

NASA Astrophysics Data System (ADS)

The subject of secondary spectrum usage has been a hot research topic for some time now. Secondary users should be able to detect available primary frequency bands and use these spectrum opportunities without causing any harmful interference to primary users. The aim of this paper is to propose a new methodology, based on image processing techniques, which combines a number of sensed samples at different random geographical positions collected by secondary sensors, in order to build a map with the positions and coverage areas of the different primary transmitters. The results can be used to discover frequencies that can be used by a secondary market without causing interference to primary receivers and without any type of cooperation between primary and secondary networks.

Bolea, Liliana; Prez-Romero, Jordi; Agust, Ramn; Sallent, Oriol

26

Clamping of time scales and collation of frequencies in the frequency range of super-long radio waves  

Microsoft Academic Search

The frequency range of super-long radio waves was historically the first frequency range used for radio communication. Fifty to 55 years ago, almost all of radio (mainly spark transmitters and the corresponding receiving equipment) worked on frequencies below 60 kHz. The theory of propagation of super-long radio waves around the earth reached at that time a rather high development stage

M. V. Bolotnikov; A. D. Klykov

1972-01-01

27

Radio Frequency Identification  

NSDL National Science Digital Library

A wealth of information about RFID is available at this site (1), ranging from background material to case studies. A discussion highlighting the myriad of uses for RFID is included. Transponder News (2) offers several articles that explore the technology in greater detail. Two in particular look at current and future trends, while others are editorial essays and technical notes. Pacific Northwest National Laboratory (3) is involved in the development of advanced tags for RFID systems. The project's homepage outlines current research efforts for three different types of radio frequency tags, which are being designed for varying degrees of sophistication and functionality. While RFID technology can be very useful, the fact that information about items is collected remotely raises concerns about privacy and security. This issue is addressed in a research paper from the Massachusetts Institute of Technology (4). The authors review current RFID systems and their operation, and then propose a number of security mechanisms that could reduce the risk associated with their use. A paper presented at the 2002 European Wireless Conference (5) compares the performance of RFID systems that use ultra-high frequency (UHF) communications to those that use microwave communications. It is argued that although microwave-based devices, such as Bluetooth, are suitable for worldwide operation, systems that communicate in the UHF range have greater range and less interference. The introduction of RFID smart tags in goods is discussed in this article (6). Now that these tags are cheap enough to be attached to thousands of items, stores will be able to track goods as they are transferred from storehouses to retail shelves, thereby minimizing the possibility of loss or theft. RFID technology has found another use in the war with Iraq. An article from May 20, 2003 (7) describes wristbands embedded with an RFID chip. The status and position of a wounded soldier who is wearing such a wristband can be monitored while he or she is recovering at a medical facility. For additional updates on the development of RFID technology, RFID News (8) maintains current news about emerging standards, innovative applications, and general issues.

Leske, Cavin.

28

A CMOS UWB transmitter for possible use for medical and biological imaging based on radio-wave induced ultrasound.  

PubMed

Medical and biological imaging based on radio-wave induced ultrasound with a single source capable of irradiating multiple signals of different frequencies simultaneously can be implemented using ultra-wideband (UWB) technique. Development of a low-cost miniature UWB CMOS transmitter that can be used for this medical application is presented. The UWB transmitter designed using a 0.25-m CMOS process can generate and transmit both monocycle pulses from 140 to 350 ps and impulses from 100 to 300 ps which contain many concurrent frequencies such as 3.1-10.6 GHz of the UWB spectrum. PMID:24110982

Nguyen, Andrew; Nguyen, Cam

2013-07-01

29

Frequency Allocation; The Radio Spectrum.  

ERIC Educational Resources Information Center

|The Federal Communications Commission (FCC) assigns segments of the radio spectrum to categories of users, and specific frequencies within each segment to individual users. Since demand for channel space exceeds supply, the process is complex. The radio spectrum can be compared to a long ruler: the portion from 10-540 kiloHertz has been set aside

Federal Communications Commission, Washington, DC.

30

Miniature stereo radio transmitter for simultaneous recording of multiple single-neuron signals from behaving owls.  

PubMed

Wireless radiotelemetric transmission of neuronal activity is an elegant technique to study brain-behavior interaction in unrestrained animals. In the current study, a miniature FM-stereo radio transmitter is described that permitted simultaneous recordings from two microelectrodes in behaving barn owls. Input from two independent channels is multiplexed to form a stereo composite signal that modulates a radio frequency carrier. The high quality of broadcasted extracellular signals enabled separation of single units based on differences in spike waveforms. Recording several single cells from different electrodes allows the possibility of investigating correlations between small, distributed neuronal ensembles. Multi-channel radiotelemetry that meets the demands of modern electrophysiology might open a new perspective for combined behavioral/neurophysiological approaches in freely-behaving animals. PMID:10996376

Nieder, A

2000-09-15

31

Radio Frequency Interference: Radio Astronomy's Biggest Enemy  

NASA Astrophysics Data System (ADS)

As technology progresses, the demand for the usage of the electromagnetic spectrum increases with it. The development is so fast and prolific that clean band space for passive users such as Radio Astronomy is becoming ever so scarce. Even though, several spectral bands have been protected for Radio Astronomy by Federal Communication Commission (in the USA) under the recommendations of the International Telecommunication Union (ITU), pressure for making more spectral space commercially usable is extreme. Although these commercial usages make our modern living at all possible, often the extreme vulnerability of passive users are are not fully appreciated, resulting in unwanted emissions (RFI) in the Radio Astronomy Bands. Another source of RFI is the fact that many of the electronic devices used in the observatories themselves generate radio waves. If proper precautions are not taken, these can be received back through the Radio Telescope itself. This problem is referred to as internal RFI. The focus of this paper is the search and diminution of internal RFI in the Arecibo Observatory in Arecibo, Puerto Rico. Using a simple setup of a log-periodic antenna and a Spectrum Analyzer, spectra spanning a frequency range of 100 - 1800 MHZ were recorded in some areas of the Observatory and the new Visitor Center (AOVEF). The measurements disclosed sources of radio emission among some of the digital electronic equipment in the Equipment room and a few displays in the AOVEF. Most prominent of these was a 2.5 MHz comb spanning the entire range of the measurements emitted from the SRENDIP and AOFTM machines. The respective groups were informed and corrective shielding & isolations were implemented immediately. In AOVEF, three displays, some audio-visual equipment, and video/digital cameras used by the visitors were found to be "leaky". In future, the use of such cameras will be prohibited and the exhibits will be screened appropriately.

Acevedo, F.; Ghosh, Tapasi

1997-12-01

32

Effects of antenna length and material on output power and detection of miniature radio transmitters  

USGS Publications Warehouse

The optimal antenna of transmitters used in small aquatic animals is often a compromise between efficient radio wave propagation and effects on animal behavior. Radio transmission efficiency generally increases with diameter and length of the conductor, but increased antenna length or weight can adversely affect animal behavior. We evaluated the effects of changing antenna length and material on the subsequent tag output power, reception, and detection of tagged fish. In a laboratory, we compared the relative signal strengths in water of 150 MHz transmitters over a range of antenna lengths (from 6 to 30 cm) and materials (one weighing about half of the other). The peak relative signal strengths were at 20 and 22 cm, which are approximately one wavelength underwater at the test frequency. The peak relative signal strengths at these lengths were approximately 50% greater than those of 30 cm antennas, a length commonly used in fisheries research. Few significant differences were present in distances for the operator to hear or the telemetry receiver to decode transmitters from a boat-mounted receiving system based on antenna length, but the percent of tagged fish detected passing a hydroelectric dam fitted with an array of receiving systems was significantly greater at the antenna length with peak output power in laboratory tests. This study indicates careful choice of antenna length and material of small transmitters can be used to reduce weight and possible antenna effects on animal behavior, to maximize tag output power and detection, or to balance these factors based on the needs of the application. ?? 2007 Springer Science+Business Media B.V.

Beeman, J. W.; Bower, N.; Juhnke, S.; Dingmon, L.; Van Den, Tillaart, M.; Thomas, T.

2007-01-01

33

Loss from harlequin ducks of abdominally implanted radio transmitters equipped with percutaneous antennas  

USGS Publications Warehouse

We documented extrusion and loss of abdominally implanted radio transmitters with percutaneous antennas from adult female Harlequin Ducks (Histrionicus histrionicus). Birds were captured during wing molt (late August to mid-September) in 1995-1997. Of 44 Harlequin Ducks implanted with radios and recaptured, 7 (16%) had lost their transmitters and 5 (11%) had radios in the process of extruding. Most (11 of 12) extrusions and losses occurred in birds implanted with radios in 1996 and recaptured in 1997. We suggest that transmitter extrusions and losses were due largely to changes in transmitter design made between 1095 and 1996. Transmitters implanted in 1996 were cylindrical rather than spherical, had a flat end with an abrupt edge, and the lower portion of the antenna was reinforced. Radio losses occurred after the 7-mo monitoring period and caused no apparent harm to the birds. Investigators using implanted radios with percutaneous antennas for long-term projects should be aware of the potential for radio extrusion and should minimize the problem by using transmitters that have no sharp edges and that are wide, rather than narrow.

Mulcahy, D. M.; Esler, D.; Stoskopf, M. K.

1999-01-01

34

A high band impulse radio UWB transmitter for communication and localization  

Microsoft Academic Search

This paper describes a monolithic integrated transmitter intended for impulse radio (IR) Ultra-wide band (UWB) applications including indoor communication and indoor localization. The transmitter operates in the higher UWB band centered at 7.68 GHz and it is optimized for a pulse bandwidth of about 1.5 GHz. The transmitter generates single pulses with a repetition rate of 60 MHz and utilizes

Denys Martynenko; Gunter Fischer; Oleksiy Klymenko

2009-01-01

35

Radio Frequency Radiation Hazards.  

National Technical Information Service (NTIS)

Explains the biological (personnel) and non-biological (feed and fuel) effects of RF radiation. The frequency spectrum is explained and the difference between ionizing and non-ionizing radiation is illustrated.

1994-01-01

36

Performance evaluation of a Radio over Fiber (ROF) system subject to the transmitter's limitations for application in broadband networks  

Microsoft Academic Search

The increasing demand for high data rates in wireless networks indicates radio-over-fiber (RoF) as an excellent candidate for physical layer infrastructure in the development of future broadband communication systems. In this work, a thorough investigation on the performance of an intensity-modulation direct detection (IM-DD) RoF system utilizing orthogonal frequency division multiplexing (OFDM) is performed, emphasizing on the transmitter's impairments, and

Spiros Mikroulis; Sotiris Karabetsos; Evagelos Pikasis; Athanase A. Nassiopoulos

2008-01-01

37

Radio Frequency and Optical Metamaterials.  

National Technical Information Service (NTIS)

This research encompassed of study radio frequency (RF) and optical metamaterials. The RF study of metamaterials focuses on the polarization behavior of split-ring resonators (SRR) and wire-post (WP) elements and the spatially dispersive behavior of the S...

A. D. Drehman B. Turchinetz E. E. Crisman J. S. Derov T. H. O'Donnell

2013-01-01

38

Radio Frequency Plasma in Water  

Microsoft Academic Search

We generate a radio frequency (RF) plasma in water at an atmospheric pressure by applying an RF power of 13.56 MHz from an electrode. The plasma is in a bubble formed in water. On the basis of hydrogen spectral lines under the assumption of thermal equilibrium, the temperature of the plasma is estimated to be 4000-4500 K. Spectroscopic measurements show

Tsunehiro Maehara; Hiromichi Toyota; Makoto Kuramoto; Atsushi Iwamae; Atsushi Tadokoro; Shinobu Mukasa; Hiroshi Yamashita; Ayato Kawashima; Shinfuku Nomura

2006-01-01

39

Digital Channelizing Radio Frequency Receiver  

Microsoft Academic Search

HYPRES is developing a class of digital receivers featuring direct digitization at radio frequency (RF). Such a receiver consists of a wideband analog-to-digital converter (ADC) modulator and multiple digital channelizer units to extract different frequency bands-of-interest within the broad digitized spectrum. The single-bit oversampled data, from either a lowpass delta or bandpass delta-sigma modulator, are applied to one or more

Deepnarayan Gupta; Timur V. Filippov; Alexander F. Kirichenko; Dmitri E. Kirichenko; Igor V. Vernik; Anubhav Sahu; Saad Sarwana; Pavel Shevchenko; Andrei Talalaevskii; Oleg A. Mukhanov

2007-01-01

40

A mode-locked microchip laser optical transmitter for fiber radio  

Microsoft Academic Search

This paper is concerned with the optical domain generation of high-quality millimeter-wave signals for fiber-radio and other applications. The mode-locked millimeter-wave optical transmitter described is based on simple electrooptic microchip laser technology. The transmitter can be designed to operate from a few gigahertz to 100 GHz and beyond. The residual phase noise of the laser is below -100 dBc\\/Hz at

Amarildo J. C. Vieira; Peter R. Herczfeld; Arye Rosen; Michael Ermold; Eric E. Funk; William D. Jemison; Keith J. Williams

2001-01-01

41

Wireless charging using radio frequency  

Microsoft Academic Search

Wireless technologies such as mobiles, PDAs, laptops, pagers, sensors, embedded controllers etc. have become an integral part of an individual's day-to-day life. Everyone would have faced the problem of their devices going out of charge. This paper explores the possibilities of charging your cell phones wirelessly i. e. radio waves (30 KHz-30MHz). It is observed that the RF frequency can

Prashant Vikram; Sujay Shetty; Sujay Paralikar

2011-01-01

42

Effects of radio transmitters on the behavior of Red-headed Woodpeckers.  

SciTech Connect

ABSTRACT. Previous studies have revealed that radio-transmitters may affect bird behaviors, including feeding rates, foraging behavior, vigilance, and preening behavior. In addition, depending on the method of attachment, transmitters can potentially affect the ability of cavity-nesting birds to use cavities. Our objective was to evaluate effects of transmitters on the behavior of and use of cavities byRed-headedWoodpeckers (Melanerpes erythrocephalus). Using backpack harnesses, we attached 2.1-g transmitter packages that averaged 3.1% of body weight (range = 2.53.6%) to Red-headed Woodpeckers. We observed both radio-tagged (N = 23) and nonradio-tagged (N = 28) woodpeckers and determined the percentage of time spent engaged in each of five behaviors: flight, foraging, perching, preening, and territorial behavior. We found no difference between the two groups in the percentage of time engaged in each behavior. In addition, we found that transmitters had no apparent effect on use of cavities for roosting by radio-tagged woodpeckers (N = 25).We conclude that backpack transmitters weighing less than 3.6% of body weight had no impact on either their behavior or their ability to use cavities.

Vukovich, Mark; Kilgo, John, C.

2009-05-01

43

Effects of antenna length and material on output power and detection of miniature radio transmitters  

Microsoft Academic Search

The optimal antenna of transmitters used in small aquatic animals is often a compromise between efficient radio wave propagation\\u000a and effects on animal behavior. Radio transmission efficiency generally increases with diameter and length of the conductor,\\u000a but increased antenna length or weight can adversely affect animal behavior. We evaluated the effects of changing antenna\\u000a length and material on the subsequent

John W. Beeman; Neil Bower; Steve Juhnke; Laura Dingmon; Mike van den Tillaart; Tom Thomas

2007-01-01

44

Effects of antenna length and material on output power and detection of miniature radio transmitters  

Microsoft Academic Search

The optimal antenna of transmitters used in small aquatic animals is often a compromise between efficient radio wave propagation\\u000a and effects on animal behavior. Radio transmission efficiency generally increases with diameter and length of the conductor,\\u000a but increased antenna length or weight can adversely affect animal behavior. We evaluated the effects of changing antenna\\u000a length and material on the subsequent

John W. Beeman; Neil Bower; Steve Juhnke; Laura Dingmon; Mike van den Tillaart; Tom Thomas

45

Complication associated with abdominal surgical implantation of a radio transmitter in an American badger (Taxidea taxus).  

PubMed

Radio telemetry has greatly advanced the understanding of wild animal ecology. Telemetry studies must ensure that placement of transmitters does not influence the health and behavior of study animals. Here, 10 American badgers (Taxidea taxus) were implanted with beeswax-coated abdominal radio transmitters under general anesthesia and tracked for an average of 14 mo. Behavior and movements of all badgers indicated successful short-term recovery from implantation; however, three mortalities were observed between 5 mo and 15 mo after capture. Cause of death could not be determined for two badgers due to decomposition of the carcasses. A third badger that was recovered in good postmortem condition died from sepsis secondary to a transmitter-related omental torsion. This study indicates that there is some risk associated with abdominally implanted radio transmitters in badgers. Future studies involving implanted transmitters in mammals should focus on identifying safe and effective telemetry devices that do not affect the health of study animals. American badger, omental adhesion, peritoneal implant, telemetry, Taxidea taxus. PMID:20722276

Quinn, Jessica H; Gaffney, Patricia M; Gilardi, Kirsten; Murray, Michael; Jessup, David A; Johnson, Christine K

2010-03-01

46

47 CFR 95.628 - MedRadio transmitters.  

Code of Federal Regulations, 2011 CFR

...to and from a medical implant or medical body-worn device on that channel. The...MedRadio stations associated with medical body-worn devices, regardless of whether...provided that: (i) Such external body-worn operation is limited solely to...

2011-10-01

47

A Proposed Service Aid for the Receiver-Transmitter, Radio Rt-859/Apx-72.  

National Technical Information Service (NTIS)

The design and use of a proposed service aid for the Receiver-transmitter, Radio RT-859/APX-72 is described. The proposed service aid would follow the design used with the service aid constructed for the APX-72 Service Test Model. The service aid was desi...

E. C. Bean

1968-01-01

48

47 CFR 95.627 - MedRadio transmitters in the 401-406 MHz band.  

Code of Federal Regulations, 2012 CFR

...MedRadio stations associated with medical implant devices, which incorporate a frequency...MedRadio stations associated with medical implant devices, which do not incorporate...fully implanted permanent medical device that is intended to...

2012-10-01

49

Radio Frequency Charge Parity Meter  

NASA Astrophysics Data System (ADS)

We demonstrate a total charge parity measurement by detecting the radio frequency signal that is reflected by a lumped-element resonator coupled to a single InAs nanowire double quantum dot. The high frequency response of the circuit is used to probe the effects of the Pauli exclusion principle at interdot charge transitions. Even parity charge transitions show a striking magnetic field dependence that is due to a singlet-triplet transition, while odd parity transitions are relatively insensitive to a magnetic field. The measured response agrees well with cavity input-output theory, allowing accurate measurements of the interdot tunnel coupling and the resonator-charge coupling rate gc/2?17MHz.

Schroer, M. D.; Jung, M.; Petersson, K. D.; Petta, J. R.

2012-10-01

50

Coping with Radio Frequency Interference  

NASA Astrophysics Data System (ADS)

The radio spectrum is a finite resource, on which humanity makes many demands. And pressure on it is ever increasing with the development of new technology and ideas for radio services. After all, we all benefit from wifi and cell phones. Radio astronomers have a small percentage of the spectrum allocated to them at octave intervals in the metre-centimetre bands, and at important frequencies, such as that of the 21cm line of HI. Signals from other services, as well as from our own poorly-engineered equipment, sometimes contaminate our bands: these signals constitute RFI. These may totally obliterate the astronomical signal, or, in the case of CLOUDSAT, may be capable of completely destroying a receiver, which introduces us to the new possibility of 'destructive interference'. A geo-stationary satellite can block access to a piece of sky from one site. Good equipment design eliminates self-inflicted interference, while physical separation often provides adequate practical mitigation at many frequencies. However, new observatories end up being located in the West Australian desert or Antarctica. In future they may be on the back side of the Moon. But there is no Earth-bound protection via physical separation against satellite signals. Some mitigation can be achieved by frequent data dumps and the excision of RFI, or by real-time detection and blanking of the receiver, or by more sophisticated algoriths. Astronomers of necessity aim to achieve mitigation via coordination, at the local level, and by participating in spectrum management at the national and international levels. This involves them spending a lot of time in Geneva at the International Telegraphic Union protecting their access to spectrum, and access to clean spectrum from the L3 point and the far side of the Moon.

Lewis, B. M.

2009-01-01

51

Radio Frequency Plasma in Water  

NASA Astrophysics Data System (ADS)

We generate a radio frequency (RF) plasma in water at an atmospheric pressure by applying an RF power of 13.56 MHz from an electrode. The plasma is in a bubble formed in water. On the basis of hydrogen spectral lines under the assumption of thermal equilibrium, the temperature of the plasma is estimated to be 4000-4500 K. Spectroscopic measurements show that hydrogen and oxygen are excited in the plasma. The plasma is also obtained in tap water or NaCl solution with a high conductivity. In the solution, sodium spectral lines are observed. Colored water containing methylene blue is exposed to the plasma. The absorbence spectra of the colored water before and after exposure to the plasma suggest the decomposition of organic matter due to chemical reactions involving active species, such as OH-radicals.

Maehara, Tsunehiro; Toyota, Hiromichi; Kuramoto, Makoto; Iwamae, Atsushi; Tadokoro, Atsushi; Mukasa, Shinobu; Yamashita, Hiroshi; Kawashima, Ayato; Nomura, Shinfuku

2006-11-01

52

Orbiting Low Frequency Array for radio astronomy  

Microsoft Academic Search

Recently new and interesting science drivers have emerged for very low frequency radio astronomy from 0.3 MHz to 30 MHz. However Earth bound radio observations at these wavelengths are severely hampered by ionospheric distortions, man made interference, solar flares and even complete reflection below 10 MHz. OL- FAR is Orbiting Low Frequency ARray, a project whose aim is to develop

Raj Thilak Rajan; Steven Engelen; Mark Bentum; Chris Verhoeven

2011-01-01

53

High power radio frequency attenuation device  

Microsoft Academic Search

A resistor device for attenuating radio frequency power includes a radio frequency conductor connected to a series of fins formed of high relative magnetic permeability material. The fins are dimensional to accommodate the skin depth of the current conduction therethrough, as well as an inner heat conducting portion where current does not travel. Thermal connections for air or water cooling

Q. A. Kerns; H. W. Miller

1984-01-01

54

Observations on the movement of coarse gravel using implanted motion-sensing radio transmitters  

NASA Astrophysics Data System (ADS)

Motion-sensing radio transmitters were implanted in cobbles (72-92 mm diameter) and placed in a stream in south-west Idaho for 43 days during a snowmelt period. The radios transmit different pulse rates depending on whether the rocks are at rest or in motion. Every 30 s, a datalogger samples the receiver and records the pulse rate of the transmitters. Such information can be used to assess numerous properties of particle transport that are beyond the capabilities of conventional tracking methods. Conclusions include: (i) rocks are more likely to move on rising hydrograph limbs than on falling hydrograph limbs; (ii) the average Shields' parameter is 0.046; (iii) rocks move only a fraction of the time between initial and final motion during an event; (iv) the distributions of motion and rest periods are best modeled by gamma functions rather than exponential, but the distributions approach exponential as the tails are trimmed.

McNamara, James P.; Borden, Carter

2004-07-01

55

Optimum frequency of communication channel for indoor radio telemetry  

NASA Astrophysics Data System (ADS)

A major problem in application of radiotelemetry to biological research and medical practice is indoor interference caused by superposition of forward and reflected waves, with resulting signal fadeout. Avoidance of this effect requires that the radio transmitter operate at the optimum signal wavelength and the radio receiver be placed in the optimum location. A method of determining both is proposed on the basis of an experimental study and a theoretical model. Measurements are made with the Prima radiotelemetry system developed and built by A. A. Kvitka with others and V6-1 selective microvoltmeter, in an 8x5x3.5 cu m large room where the radio receiver is placed successively in three different locations (first in corner 0,0,0 m, then closer to the center 2.5,1.5,1.0 m and 1.25,0.75,1.0 m) while the radio transmitter on a dielectric post is moved around in 0.25 m steps successively in three horizontal planes 1, 1.5, 2 m, respectively, above the floor. Measurements are made at eight frequencies (60, 30, 20, 15, 12, 10, 8.89, 7.5 MHz).

Kvitka, A. A.; Podlepetskiy, B. I.; Chernysheva, S. D.

1985-10-01

56

Preferred Transmission Frequency for Size-Constrained Ultralow-Power Short-Range CMOS Oscillator Transmitters  

Microsoft Academic Search

A method is presented for minimizing the power consumption of size-constrained oscillator transmitters by selecting the preferred carrier frequency from among the standard ISM bands. The method has been applied to CMOS oscillator transmitters in which a single-turn loop antenna doubles as the inductor in the frequency-defining LC tank. A detailed model of the transmitter circuit, including the antenna, is

David C. Yates; Andrew S. Holmes

2009-01-01

57

Demonstration of space optical transmitter development for multiple high-frequency bands  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

58

Two low frequency surveys of radio galaxies  

Microsoft Academic Search

High resolution, low frequency observations are very efficient for surveying radio galaxies because of: (1) the wide field of view; and (2) the bias toward steep spectrum (lobe dominated) emission. Here I present preliminary results from two ongoing low frequency radio surveys: the 4 Meter All Sky Survey (4MASS) and the low frequency counterpart to the XMM-Large Scale Structure (XMM-LSS)

A. S Cohen; T. J. W Lazio; N. E Kassim; R. A Perley; W. D Cotton; J. Condon; H. J. A Rttgering; R. Wilman; P. Best; M. Pierre; M. Birkinshaw; A. Zanichelli

2003-01-01

59

47 CFR 2.815 - External radio frequency power amplifiers.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false External radio frequency power amplifiers. 2.815...COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES AND REGULATIONS Marketing of Radio-frequency Devices § 2.815...

2010-10-01

60

High power radio frequency attenuation device  

DOEpatents

A resistor device for attenuating radio frequency power includes a radio frequency conductor connected to a series of fins formed of high relative magnetic permeability material. The fins are dimensional to accommodate the skin depth of the current conduction therethrough, as well as an inner heat conducting portion where current does not travel. Thermal connections for air or water cooling are provided for the inner heat conducting portions of each fin. Also disclosed is a resistor device to selectively alternate unwanted radio frequency energy in a resonant cavity.

Kerns, Quentin A. (Bloomingdale, IL); Miller, Harold W. (Winfield, IL)

1984-01-01

61

Radio-frequency characteristics of graphene oxide  

NASA Astrophysics Data System (ADS)

We confirm graphene oxide, a two-dimensional carbon structure at the nanoscale level can be a strong candidate for high-efficient interconnector in radio-frequency range. In this paper, we investigate high frequency characteristics of graphene oxide in range of 0.5-40 GHz. Radio-frequency transmission properties were extracted as S-parameters to determine the intrinsic ac transmission of graphene sheets, such as the impedance variation dependence on frequency. The impedance and resistance of graphene sheets drastically decrease as frequency increases. This result confirms graphene oxide has high potential for transmitting signals at gigahertz ranges.

Kim, Whan Kyun; Jung, Young Mo; Cho, Joon Hyong; Kang, Ji Yoong; Oh, Ju Yeong; Kang, Hosung; Lee, Hee-Jo; Kim, Jae Hun; Lee, Seok; Shin, H. J.; Choi, J. Y.; Lee, S. Y.; Kim, Y. C.; Han, I. T.; Kim, J. M.; Yook, Jong-Gwan; Baik, Seunghyun; Jun, Seong Chan

2010-11-01

62

Heating of the nighttime D region by very low frequency transmitters  

Microsoft Academic Search

VLF signals propagating in the Earth-ionosphere waveguide are used to probe the heated nighttime D region over three U.S. Navy very low frequency (VLF,3-30 kHz) transmitters. Ionospheric cooling and heating are observed when a transmitter turns off and on in the course of normal operations. Heating by the 24.0-kHz NAA transmitter in Cutler, Maine, (1000 kW radiated power) was observed

Juan V. Rodriguez; Umran S. Inan; Timothy F. Bell

1994-01-01

63

Heating of the nighttime D region by very low frequency transmitters  

Microsoft Academic Search

VLF signals propagating in the Earth-ionosphere waveguide are used to probe the heated nighttime D region over three U.S. Navy very low frequency (VLF, 3-30 kHz) transmitters. Ionospheric cooling and heating are observed when a transmitter turns off and on in the course of normal operations. Heating by the 24.0-kHz NAA transmitter in Cutler, Maine, (1000 kW radiated power) was

Juan V. Rodriguez; Umran S. Inan; Timothy F. Bell

1994-01-01

64

Radio frequency hazard monitoring-USAKA  

NASA Astrophysics Data System (ADS)

This study provides the design of a network of sensors and procedures which will allow efficient and rapid mapping of RF power density and spectral data at a large number of ground station sensors surrounding the USAKA radars as a function of antenna pointing angles, transmitter power, and time of day. The system acts as a stand alone unit, powered by solar charged batteries. The sensor network is linked to a common control center, which collects, displays and archives the data. Communication between sensor units and the control center can use telephone or VHF radio links.

Brown, David H.

1991-10-01

65

Radio Frequency Nonionizing Radiation in a Community Exposed to Radio and Television Broadcasting  

PubMed Central

Exposure to radio frequency (RF) nonionizing radiation from telecommunications is pervasive in modern society. Elevated disease risks have been observed in some populations exposed to radio and television transmissions, although findings are inconsistent. This study quantified RF exposures among 280 residents living near the broadcasting transmitters for Denver, Colorado. RF power densities outside and inside each residence were obtained, and a global positioning system (GPS) identified geographic coordinates and elevations. A viewshed model within a geographic information system (GIS) characterized the average distance and percentage of transmitters visible from each residence. Data were collected at the beginning and end of a 2.5-day period, and some measurements were repeated 829 months later. RF levels logged at 1-min intervals for 2.5 days varied considerably among some homes and were quite similar among others. The greatest differences appeared among homes within 1 km of the transmitters. Overall, there were no differences in mean residential RF levels compared over 2.5 days. However, after a 1- to 2-year follow-up, only 25% of exterior and 38% of interior RF measurements were unchanged. Increasing proximity, elevation, and line-of-sight visibility were each associated with elevated RF exposures. At average distances from > 13 km, exterior RF measurements were 1330 times greater among homes that had > 50% of the transmitters visible compared with homes with ? 50% visibility at those distances. This study demonstrated that both spatial and temporal factors contribute to residential RF exposure and that GPS/GIS technologies can improve RF exposure assessment and reduce exposure misclassification.

Burch, James B.; Clark, Maggie; Yost, Michael G.; Fitzpatrick, Cole T.E.; Bachand, Annette M.; Ramaprasad, Jaya; Reif, John S.

2006-01-01

66

Radio frequency rectification on membrane bound pores.  

PubMed

Probing the interaction of biological systems with radio frequencies holds great promise for research and drug screening applications. While a common assumption is that biological systems do not operate at radio frequencies, we find that currents due to ion transport through channels and pores in cell membranes are in the pA to nA range. These values translate via the average current I = ne/tau(d) = nef to frequencies in the range of 1 MHz-1 GHz, where n is the average number of ions transported and tau(d) is the dwell time of the ions in the channel. It is thus desirable to have circuitry available which facilitates radio frequency spectroscopy of ion transport. This will yield real-time in vitro information on ion channel operation. Here we present measurements on the local interaction of a radio frequency signal with single ion channels and pores. We find radio frequency rectification and pumping on the channels and pores embedded in suspended bilipid membranes, recorded in direct current measurements. This electromagnetic modulation can be used to probe the dynamics of ion channel conformational changes. PMID:20081294

Ramachandran, Sujatha; Blick, Robert H; van der Weide, Daniel W

2010-01-18

67

Physics of low frequency radio emissions  

SciTech Connect

Radio sources of solar origin are the dominant feature of radio emissions at low frequencies. Solar radio sources are sporadic and very frequent during the maximum phase of the solar cycle; they may be very intense (more than 40 dB above the background) and they can be localized almost anywhere in the interplanetary medium. They represent a unique means to detect perturbations originating from the solar activity and to track their progression through the interplanetary medium and particularly into the Earth's environment.

Bougeret, J. (Department of Space Research, URA CNRS 264, Meudon Observatory, F-92195 Meudon Cedex (France))

1990-07-05

68

47 CFR 95.629 - LPRS transmitter frequencies.  

Code of Federal Regulations, 2011 CFR

...standard band frequencies. The channel bandwidth is 25 kHz. Channel No. Center frequency...indicates extra band frequencies. The channel bandwidth is 50 kHz. Channel No. Center frequency...indicates narrowband frequencies. The channel bandwidth is 5 kHz and the authorized...

2011-10-01

69

Narrowband, tunable, frequency-doubled, erbium-doped fiber-amplifed transmitter.  

PubMed

We report on the development of a fiber-based laser transmitter designed for active remote sensing spectroscopy. The transmitter uses a master oscillator power amplifier (MOPA) configuration with a distributed feedback diode-laser master oscillator and an erbium-doped fiber amplifier. The output from the MOPA is frequency-doubled with a periodically poled potassium titanium oxide phosphate crystal. With 35 W of single-frequency peak optical pump power, 8 W of frequency-doubled peak power was achieved. The utility of this single-frequency, wavelength tunable, power scalable laser was then demonstrated in a spectroscopic measurement of diatomic oxygen A band. PMID:17671540

Stephen, Mark; Krainak, Michael; Riris, Haris; Allan, Graham R

2007-08-01

70

Radio Frequency Signals in Jupiter's Atmosphere  

PubMed

During the Galileo probe's descent through Jupiter's atmosphere, under the ionosphere, the lightning and radio emission detector measured radio frequency signals at levels significantly above the probe's electromagnetic noise. The signal strengths at 3 and 15 kilohertz were relatively large at the beginning of the descent, decreased with depth to a pressure level of about 5 bars, and then increased slowly until the end of the mission. The 15-kilohertz signals show arrival direction anisotropies. Measurements of radio frequency wave forms show that the probe passed through an atmospheric region that did not support lightning within at least 100 kilometers and more likely a few thousand kilometers of the descent trajectory. The apparent opacity of the jovian atmosphere increases sharply at pressures greater than about 4 bars. PMID:8662576

Lanzerotti; Rinnert; Dehmel; Gliem; Krider; Uman; Bach

1996-05-10

71

MICROWAVE AND RADIO-FREQUENCY POWER APPLICATIONS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The potential for agricultural applications of radio-frequency (RF) energy for the solution of various problems in agricultural production, crop handling and storage, and product preservation and conditioning has been considered for many years. With the development of economical microwave power equ...

72

Radio-frequency radiation of storm clouds  

Microsoft Academic Search

It is proposed that the radio frequency radiation occurring during storms over water and during the disintegration of water droplets in storm clouds can be explained through the retardation of electrical discharges upon the destruction of water films. The electrical discharge, as in the balloelectric effect, takes the form of heavy and ultraheavy ions, escaping in all directions. The phenomenon

V. I. Arabadzhi; Y. S. Prokhorov; I. I. Epshteyn

1985-01-01

73

Radio Frequency Identification Applications in Smart Hospitals  

Microsoft Academic Search

Recent advances in radio frequency identification (RFID) technology are leading to promising means for significant enhancement of safety, quality and value of health care. In this paper, we give an overview of the state-of-art research in applications of RFID in hospitals. We outline the challenges in designing RFID based systems for hospitals, and point out open problems and future research

Huzaifa Al Nahas; Jitender S. Deogun

2007-01-01

74

Cost cutting using radio frequency inventory control.  

PubMed

Bar coding should be a staple in every hospital by now--but it's not. The author tells how bar coding and the use of radio frequency transmission of inventory data direct to their mainframe computer has saved them time and money. PMID:10117777

Weber, J

1992-05-01

75

Modification of the Earth's Ionosphere by Very Low-Frequency Transmitters  

Microsoft Academic Search

This dissertation concerns the design and implementation of a controlled experiment aimed at determining the extent to which very-low-frequency (VLF, 3-30 kHz) transmitters operating worldwide modify the Earth's ionosphere. VLF signals propagating in the Earth-ionosphere waveguide are used to probe the heated nighttime D region of the ionosphere (50-90 km altitude) over three U. S. Navy VLF transmitters. Ionospheric cooling

Juan Valentin Rodriguez

1994-01-01

76

A 900MHz low-power transmitter with fast frequency calibration for wireless sensor networks  

Microsoft Academic Search

A low-power transmitter designed for wireless sensor networks operating in a 900-MHz ISM band has been fabricated in 0.18-mum CMOS technology. The transmitter has a power efficiency as high as 26% while radiating an output signal of -2.9 dBm. It supports both OOK and BFSK modulation. A fast frequency calibration is developed to reduce the RF tuning time down to

Napong Panitantum; Kartikeya Mayaram; Terri S. Fiez

2008-01-01

77

Inflammatory reaction to fabric collars from percutaneous antennas attached to intracoelomic radio transmitters implanted in harlequin ducks (Histrionicus histrionicus)  

USGS Publications Warehouse

In wild birds implanted intracoelomically with radio transmitters, a synthetic fabric collar placed around the base of a percutaneous antenna is believed to function as a barrier to contamination of the coelom. We examined 13 fabric collars recovered from percutaneous antennas of radio transmitters implanted intracoelomically in harlequin ducks (Histrionicus histrionicus) 12 months earlier. Both the transmitters and antenna collars were encapsulated in fibrous connective tissue, with adhesions to internal organs. Histologically, bacteria were evident at the fabric-plastic interface in 8 of 10 collars examined in cross section and along the length of the collar in 3 collars examined longitudinally. Bacteria were confined within the fibrotic sheath surrounding the transmitter and the antenna collar in all birds. No evidence of chronic systemic effects secondary to implantation was present on hematologic or serum biochemical testing. These findings indicate that antenna collars do not prevent the entry of bacteria along the percutaneous antenna but may help stabilize the antenna and minimize coelomic contamination. We conclude that radio transmitters implanted into the coelom of harlequin ducks do not appear to cause significant health problems for at least 1 year after implantation. ?? 2007 by the Association of Avian Veterinarians.

Mulcahy, D. M.; Burek, K. A.; Esler, D.

2007-01-01

78

47 CFR 80.909 - Radiotelephone transmitter.  

Code of Federal Regulations, 2012 CFR

...RADIO SERVICES STATIONS IN THE MARITIME SERVICES Compulsory...Radiotelephone transmitter. (a) The medium frequency transmitter must have a peak envelope output power of at least 60 watts for...working frequency within the band 1605 to 2850 kHz...

2012-10-01

79

Nonlinear reflection of a high-frequency radio wave by the ionospheric grating created by another wave  

Microsoft Academic Search

A powerful O-mode radio wave of frequency ?0, launched from a ground-based transmitter into the equatorial ionosphere, forms a standing wave pattern below the critical layer, heating the electrons with spatial periodicity. Subsequent ambipolar redistribution of plasma creates a density ripple. When another radio wave, of higher-frequency ?, is launched into the ripple region, the oscillatory electron velocity due to

Ashok Kumar; R. Uma; V. K. Tripathi

2006-01-01

80

Extending the ICRF to Higher Radio Frequencies  

NASA Astrophysics Data System (ADS)

We present astrometric and imaging results for compact extragalactic objects observed with the Very Long Baseline Array at radio frequencies of 24 and 43 GHz. Data were obtained from ten 24-hour observing sessions made over an approximately 5-year period. These observations were motivated by the need to extend the International Celestial Reference Frame to higher radio frequencies to enable improved deep space navigation after 2015 and to improve state-of-the-art astrometry. With observations over five years we have achieved a precision at 24 GHz approaching that of the ICRF but unaccounted for systematic errors such as residual tropospheric and ionospheric refraction limit the overall accuracy of the catalogs. We conclude that the reduction in the effects due to source structure gained by observing at higher frequencies will result in an improved celestial reference frame and a pool of high-quality fiducial reference points for use in spacecraft navigation over the next decade.

Fey, Alan Lee; Boboltz, D.; Charlot, P.; Fomalont, E.; Lanyi, G.; Jacobs, C.; K-Q VLBI Survey Collaboration

2009-05-01

81

47 CFR 95.655 - Frequency capability.  

Code of Federal Regulations, 2012 CFR

...Services and Military Affiliate Radio System will not be certificated.) (b) All frequency determining circuitry (including crystals) and programming controls in each CB transmitter and in each GMRS transmitter must be internal to the transmitter and...

2012-10-01

82

47 CFR 95.655 - Frequency capability.  

Code of Federal Regulations, 2011 CFR

...Services and Military Affiliate Radio System will not be certificated.) (b) All frequency determining circuitry (including crystals) and programming controls in each CB transmitter and in each GMRS transmitter must be internal to the transmitter and...

2011-10-01

83

47 CFR 95.632 - MURS transmitter frequencies.  

Code of Federal Regulations, 2011 CFR

...154.600 MHz. (b) The authorized bandwidth is 11.25 kHz on frequencies 151...MHz and 151.940 MHz. The authorized bandwidth is 20.0 kHz on frequencies 154.570...designed to operate with a 6.25 kHz bandwidth. [65 FR 60877, Oct. 13,...

2011-10-01

84

Impact of Radio Frequency Refarming on Transit Communications.  

National Technical Information Service (NTIS)

The Federal Communications Commission has decided to use 'refarming' to help mitigate radio frequency congestion and increase spectrum efficiency in the private land mobile radio bands (frequencies below 512 MHz). Refarming is the term used for reduction ...

J. J. Maul J. J. Greichen

1996-01-01

85

SITE TECHNOLOGY CAPSULE: IITRI RADIO FREQUENCY HEATING TECHNOLOGY  

EPA Science Inventory

Radio frequency heating (RFH) technologies use electromagnetic energy in the radio frequency (RF) band to heat soil in situ, thereby potentially enhancing the performance of standard soil vapor extraction (SVE) technologies. Contaminants are removed from in situ soils and transfe...

86

Radio frequency interference at passive microwave earth observation frequencies  

Microsoft Academic Search

The retrieval of geophysical parameters of the Earth and its atmosphere from satellite observations fundamentally relies upon the accuracy of the measurements. The growth in communication technologies has led to the exploitation of regions of the electromagnetic spectrum hitherto primarily used for Earth observation. This article describes and maps the distribution of radio frequency interference in the microwave portion of

C. Kidd

2006-01-01

87

Wavelet Based Approach to Transmitter Identification.  

National Technical Information Service (NTIS)

Research is conducted to find a robust wavelet based algorithm for automatic identification of push to talk radio transmitters. Digital data at an intermediate frequency (IF) is preprocessed to translate it into a form applicable to wavelet analysis. The ...

R. D. Hippenstiel

1995-01-01

88

78 FR 13893 - Certain Radio Frequency Identification (RFID) Products and Components Thereof; Notice of...  

Federal Register 2010, 2011, 2012, 2013

...Certain Radio Frequency Identification (``RFID'') Products and Components Thereof...Certain Radio Frequency Identification (``RFID'') Products and Components Thereof...certain radio frequency identification (``RFID'') products and components...

2013-03-01

89

Optimum frequency band for radio polarization observations  

NASA Astrophysics Data System (ADS)

Polarized radio synchrotron emission from interstellar, intracluster and intergalactic magnetic fields is affected by frequency-dependent Faraday depolarization. The maximum polarized intensity depends on the physical properties of the depolarizing medium. New-generation radio telescopes such as Low Frequency Array (LOFAR), the Square Kilometre Array (SKA) and its precursors need a wide range of frequencies to cover the full range of objects. The optimum frequency of maximum polarized intensity (PI) is computed for the cases of depolarization in magneto-ionic media by regular magnetic fields (differential Faraday rotation) or by turbulent magnetic fields (internal or external Faraday dispersion), assuming that the Faraday spectrum of the medium is dominated by one component or that the medium is turbulent. Polarized emission from bright galaxy discs, spiral arms and cores of galaxy clusters are best observed at wavelengths below a few centimetres (at frequencies beyond about 10 GHz), haloes of galaxies and clusters around decimetre wavelengths (at frequencies below about 2 GHz). Intergalactic filaments need observations at metre wavelengths (frequencies below 300 MHz). Sources with extremely large intrinsic rotation measure | RM | or RM dispersion can be searched with mm-wave telescopes. Measurement of the PI spectrum allows us to derive the average Faraday | RM | or the Faraday dispersion within the source, as demonstrated for the case of the spiral galaxy NGC 6946. Periodic fluctuations in PI at low frequencies are a signature of differential Faraday rotation. Internal and external Faraday dispersion can be distinguished by the different slopes of the PI spectrum at low frequencies. A wide band around the optimum frequency is important to distinguish between varieties of depolarization effects.

Arshakian, Tigran G.; Beck, Rainer

2011-12-01

90

Radio frequency multicusp ion source development (invited)  

Microsoft Academic Search

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

K. N. Leung

1996-01-01

91

Radio frequency multicusp ion source development (invited)  

Microsoft Academic Search

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

K. N. Leung

1996-01-01

92

Radio Frequency Identification: A Panacea for Governments?  

Microsoft Academic Search

Radio frequency identification (RFID) has been used to improve business supply chain management for over 35years. As often\\u000a happens, private sector technology migrates to the public sector where it is adapted for use. RFID use in governments is spreading\\u000a far and wide at the federal and state levels with virtually no debate or performance analyses to inform adoption decisions.\\u000a Implementation

Barbara L. Neuby; Elizabeth Rudin

2008-01-01

93

Ionospheric heating with oblique waves. Volume 2: Applications to high-frequency radio propagation  

Microsoft Academic Search

This volume presents numerical calculations of ionospheric electron density perturbations and ground-level signal changes for several electric field distributions produced by high-frequency (HF) transmitters. This volume applies theory developed in earlier work (Vol. 1) to the problem of possible self-effects of powerful obliquely incident radio waves. Using the results from this earlier work, we use field-driven changes in ionospheric electron

R. M. Bloom; E. C. Field Jr.

1989-01-01

94

Design of a Fiber-Optic Transmitter for Microwave Analog Transmission with High Phase Stability.  

National Technical Information Service (NTIS)

The principal considerations in the design of fiber-optic transmitters for highly phase-stable radio frequency and microwave analog transmission are discussed. Criteria for a fiber-optic transmitter design with improved amplitude and phase-noise performan...

R. T. Logan G. F. Lutes L. E. Primas L. Maleki

1990-01-01

95

Transmitter Power Control for Co-channel Interference Management in Cellular Radio Systems  

Microsoft Academic Search

Transmitter power control is a necessity to combat "near-far" problems in radiosystems using receivers with limited "dynamic range" (such as conventional DSCDMAsystems). Transmitter power control, however, can also be used tocontrol cochannel interference, i.e. interference from other users using the samechannel (code or time slot). For this purpose, it has been shown that theoptimum transmitter power configuration is found by

Jens Zander Radio

1993-01-01

96

Photo-acoustic concave transmitter for generating high frequency focused ultrasound  

PubMed Central

We present a photo-acoustic concave transmitter to generate and subsequently focus high frequency ultrasound. Owing to a short time-duration of pulse laser beam, high frequency acoustic waves and tight focusing can be easily achieved. The transmitter consists of a light-absorbing film coated on a concave spherical structure. For detection, we used an optical microring ultrasound detector capable of covering a broadband and high frequency spectrum of photo-acoustic source. A spot width of ?44 ?m was obtained at the focal plane. As the finite size and the specific shape of the microring cause a geometrical effect on the detection process, especially for high frequency components, we performed a 2-D spatial signal processing to remove this effect and extract a pure pressure distribution. The aperture for acoustic focusing could be optically controlled by changing the size of pulse laser beam.

Baac, Hyoung Won; Ling, Tao; Ashkenazi, Shai; Huang, Sheng-Wen; Guo, L. Jay

2010-01-01

97

Photo-acoustic concave transmitter for generating high frequency focused ultrasound.  

PubMed

We present a photo-acoustic concave transmitter to generate and subsequently focus high frequency ultrasound. Owing to a short time-duration of pulse laser beam, high frequency acoustic waves and tight focusing can be easily achieved. The transmitter consists of a light-absorbing film coated on a concave spherical structure. For detection, we used an optical microring ultrasound detector capable of covering a broadband and high frequency spectrum of photo-acoustic source. A spot width of ?44 ?m was obtained at the focal plane. As the finite size and the specific shape of the microring cause a geometrical effect on the detection process, especially for high frequency components, we performed a 2-D spatial signal processing to remove this effect and extract a pure pressure distribution. The aperture for acoustic focusing could be optically controlled by changing the size of pulse laser beam. PMID:20689643

Baac, Hyoung Won; Ling, Tao; Ashkenazi, Shai; Huang, Sheng-Wen; Guo, L Jay

2010-02-11

98

Cubesat Missions for Low Frequency Radio Astronomy  

NASA Astrophysics Data System (ADS)

There have been many concepts and several mission proposals for low frequency radio interferometers in space during the past two decades. Most of these idea are based on multiple small spacecraft, each acting as one antenna element in a three-dimensional array. The science goals for single cubesats or arrays operating at frequencies near and below Earth's ionosphere cutoff span a wide range research areas from solar and planetary observations to galactic and extragalactic astronomy to cosmological observations of large-scale structure evolution before the epoch of reionization. Recently several groups have realized that the rapid progress in the capabilities of cubesats make them a logical basis for such mission concepts. A workshop on cubesat-based low frequency radio astronomy missions was held at the Keck Institute for Space Studies (KISS) at Caltech during July 2012. This paper will summarize the discussions and conclusions from that workshop. These include a number of future mission ideas based on cubesat technologies, as well as recommendations for near-term technology demonstrations that would reduce risk for many of the potential missions. Portions of this work were carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Support from the JPL Center for Academic Partnerships and KISS is gratefully acknowledged.

Jones, Dayton L.

2013-01-01

99

Radio frequency driven multicusp sources (invited)  

NASA Astrophysics Data System (ADS)

The radio frequency (rf)-driven multicusp source was originally developed for use in the superconducting super collider injector. The source can routinely provide 30 mA of H~ beam at 0.1% duty factor. By adding a minute quantity of cesium to the discharge, H- beam current in excess of 100 mA and e/H~1 has been achieved. The rf-driven H~ source is being further developed for 6% duty factor operation to be used in the national spallation neutron source. Application of the rf-driven multicusp source has been extended to radioactive ion beam production, ion projection lithography, and compact neutron tubes.

Leung, Ka-Ngo

1998-02-01

100

Inductive coupled radio frequency plasma bridge neutralizer  

NASA Astrophysics Data System (ADS)

A 13.56 MHz radio frequency plasma bridge neutralizer (rf-PBN) for ion thruster applications as well as ion beam surface processing of insulating materials is presented. The energy for the plasma excitation is inductively coupled into the plasma chamber. Because no components are located inside the plasma, the lifetime of the rf-PBN is expected to be very long. A compact tuning system adapts the input power to the plasma impedance. The electron current may be controlled over a wide range by the rf input power. An electron current of up to 1.6 A has been extracted.

Scholze, F.; Tartz, M.; Neumann, H.

2008-02-01

101

Inductive coupled radio frequency plasma bridge neutralizer.  

PubMed

A 13.56 MHz radio frequency plasma bridge neutralizer (rf-PBN) for ion thruster applications as well as ion beam surface processing of insulating materials is presented. The energy for the plasma excitation is inductively coupled into the plasma chamber. Because no components are located inside the plasma, the lifetime of the rf-PBN is expected to be very long. A compact tuning system adapts the input power to the plasma impedance. The electron current may be controlled over a wide range by the rf input power. An electron current of up to 1.6 A has been extracted. PMID:18315215

Scholze, F; Tartz, M; Neumann, H

2008-02-01

102

Inductive coupled radio frequency plasma bridge neutralizer  

SciTech Connect

A 13.56 MHz radio frequency plasma bridge neutralizer (rf-PBN) for ion thruster applications as well as ion beam surface processing of insulating materials is presented. The energy for the plasma excitation is inductively coupled into the plasma chamber. Because no components are located inside the plasma, the lifetime of the rf-PBN is expected to be very long. A compact tuning system adapts the input power to the plasma impedance. The electron current may be controlled over a wide range by the rf input power. An electron current of up to 1.6 A has been extracted.

Scholze, F.; Tartz, M.; Neumann, H. [Leibniz Institute of Surface Modification, Permoserstr. 15, D-04318 Leipzig (Germany)

2008-02-15

103

Surgical and immediate postrelease mortality of harlequin ducks (Histrionicus histrionicus) implanted with abdominal radio transmitters with percutaneous antennae  

USGS Publications Warehouse

Radiotelemetry is an essential tool in the study of free-ranging bird populations, and a variety of transmitter-attachment methods have been developed. A promising new method is abdominal implantation of a transmitter with a percutaneous antenna. Researchers using this technique should be concerned about and aware of mortality during surgery and during the immediate postrelease period (the 14-day period following surgery). Of 307 radio-implant surgeries performed between 1995 and 1997 in harlequin ducks (Histrionicus histrionicus), 7 (2.3%) deaths were documented during surgery or anesthetic recovery. Of 295 birds released with implanted radios, 10 (3.4%) died during the immediate postrelease period. Modifications to anesthetic procedures used in the 204 surgeries performed in 1996 and 1997 reduced mortality to 1.5% during surgery and 1.5% during the immediate postrelease period. Anesthetic modifications included intubation of all birds, placement of birds on an elevated platform that allowed the head to rest at a level lower than the body during surgery, placement of a heated water blanket under the birds during surgery, monitoring of body temperature, and use of electrocardiogram and Doppler ultrasound to monitor heart rates and arrhythmias. Low levels of mortality associated with abdominal implantation of radio transmitters may be unavoidable, but mortality can be minimized with adjustments to anesthetic technique. Copyright 1999 by American Association of Zoo Veterinarians.

Mulcahy, D. M.; Esler, D.

1999-01-01

104

Optical generation of radio-frequency power  

SciTech Connect

An optical technique for high-power radio-frequency (RF) signal generation is described. The technique uses a unique photodetector based on a traveling-wave design driven by an appropriately modulated light source. The traveling-wave photodetector (TWPD) exhibits simultaneously a theoretical quantum efficiency approaching 100 % and a very large electrical bandwidth. Additionally, it is capable of dissipating the high-power levels required for the RF generation technique. The modulated light source is formed by either the beating together of two lasers or by the direct modulation of a light source. A system example is given which predicts RF power levels of 100`s of mW`s at millimeter wave frequencies with a theoretical ``wall-plug`` efficiency approaching 34%.

Hietala, V.M.; Vawter, G.A.; Brennan, T.M.; Hammons, B.E.; Meyer, W.J.

1994-11-01

105

High-Speed $W$ Band Integrated Photonic Transmitter for Radio-Over-Fiber Applications  

Microsoft Academic Search

A high-speed -band integrated photonic trans- mitter is demonstrated. The presented integrated photonic transmitter is essentially developed with a near-ballistic uni-trav- eling-carrier photodiode integrated with a broadband front end through the flip-chip assembling technique. Technically, compared to our previous design, a -band bandpass filter is exploited to significantly increase the transmitter IF modulation bandwidth. The demonstrated integrated photonic transmitter has

Nan-Wei Chen; Hsuan-Ju Tsai; Fon-Ming Kuo; Jin-Wei Shi

2011-01-01

106

Characterization of optical microring ultrasound detector by using a high frequency focused photoacoustic transmitter  

PubMed Central

We characterize a response of optical microring resonator to high frequency focused ultrasound. To properly evaluate the response over high frequency and broadband spectrum, we use a photoacoustic concave transmitter generating and subsequently focusing the ultrasound. A detected focused profile reveals two types of spatial peaks due to the special ring-shaped detector geometry interacting with the high frequency focused ultrasound. Spectral analysis shows that those peaks are contributed by the main and the side lobes of focused ultrasound, respectively. Experimental focal widths agree with theoretical values within 2 ?m error, which can be attributed to the narrow width of waveguide.

Won Baac, Hyoung; Ling, Tao; Huang, Sheng-Wen; Ashkenazi, Shai; Guo, L. Jay

2009-01-01

107

K-Band Radio frequency Interference Survey of Southeastern Michigan  

Microsoft Academic Search

The Radio frequency Interference Survey of Earth (RISE) is a new type of instrument used to survey and characterize the presence of Radio Frequency Interference (RFI) that can affect microwave radiometers. It consists of a combined microwave radiometer and kurtosis spectrometer with broad frequency coverage and high temporal and spectral resolution. A K-Band airborne version has been built and flown

Shannon Curry; Michael Ahlers; Harvey Elliot; Steve Gross; Darren McKague; Sidharth Misra; John J. Puckett; Christopher Ruf

2010-01-01

108

Wideband micromachined capacitive microphones with radio frequency detection  

Microsoft Academic Search

Silicon microphones based on capacitive micromachined ultrasonic transducer membranes and radio frequency detection overcome many of the limitations in bandwidth, uniformity of response, and durability associated with micromachined condenser microphones. These membranes are vacuum-sealed to withstand submersion in water and have a flat mechanical response from dc up to ultrasonic frequencies. However, a sensitive radio frequency detection scheme is necessary

Sean T. Hansen; A. Sanli Ergun; William Liou; Bertram A. Auld; Butrus T. Khuri-Yakub

2004-01-01

109

Point-to-point measurement of radio frequency attenuation in South Polar ice  

NASA Astrophysics Data System (ADS)

For ultra high energy (UHE) electromagnetic showers in a dense medium, radio frequency Cherenkov emission is enhanced due to the Askaryan effect. Present and future detectors such as RICE, ANITA, ARIANNA and the Askaryan Radio Array (ARA) exploit this effect to detect UHE neutrinos interacting with Antarctic ice. The radio frequency electromagnetic wave attenuation length (the distance over which signal amplitude diminishes by a factor of 1/e due to absorption or scattering) is of tantamount importance as it determines the size scale and effective volume of these detectors. Previous attenuation measurements rely on reflections off the bedrock of signals from a surface-mounted transmitter. Using RICE in-ice transmitters and IceCube Radio Extension in-ice receivers, we are conducting a point-to-point attenuation measurement in the upper 1500 meters of South Polar ice, the region of interest for planned near-surface detectors such as ARA. We will present the analysis method as well as preliminary results.

Richman, Michael; Hoffman, Kara

2011-04-01

110

Interstellar Radio Communication and the Frequency Selection Problem  

Microsoft Academic Search

THE largest microwave radio telescope on Earth, at the Arecibo Observatory of the National Astronomy and Ionosphere Center, will soon have the capability of communicating with an identical radio telescope, if such exists, anywhere in the Galaxy. But such communication assumes some previous agreement between the transmitting and receiving civilizations, or mutual discovery of the chosen radio frequency, bandpass, information

F. D. Drake; Carl Sagan

1973-01-01

111

Radio frequency driven multicusp sources (invited)  

SciTech Connect

The radio frequency (rf)-driven multicusp source was originally developed for use in the superconducting super collider injector. The source can routinely provide 30 mA of H{sup {approximately}} beam at 0.1{percent} duty factor. By adding a minute quantity of cesium to the discharge, H{sup {minus}} beam current in excess of 100 mA and e/H{approximately}1 has been achieved. The rf-driven H{approximately} source is being further developed for 6{percent} duty factor operation to be used in the national spallation neutron source. Application of the rf-driven multicusp source has been extended to radioactive ion beam production, ion projection lithography, and compact neutron tubes.{copyright} {ital 1998 American Institute of Physics.}

Leung, K. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road-MS 5/119, University of California, Berkeley, California 94720 (United States)

1998-02-01

112

Radio frequency multicusp ion source development (invited)  

SciTech Connect

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.}

Leung, K.N. [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States)

1996-03-01

113

Radio-frequency quadrupole linear accelerator  

SciTech Connect

The radio-frequency quadrupole (RFQ) is a new linear accelerator concept in which rf electric fields are used to focus, bunch, and accelerate the beam. Because the RFQ can provide strong focusing at low velocities, it can capture a high-current dc ion beam from a low-voltage source and accelerate it to an energy of 1 MeV/nucleon within a distance of a few meters. A recent experimental test at the Los Alamos Scientific Laboratory (LASL) has confirmed the expected performance of this structure and has stimulated interest in a wide variety of applications. The general properties of the RFQ are reviewed and examples of applications of this new accelerator are presented.

Wangler, T.P.; Stokes, R.H.

1980-01-01

114

Nb3Sn for Radio Frequency Cavities  

SciTech Connect

In this article, the suitability of Nb3Sn to improve theperformance of superconducting Radio-Frequency (RF)cavities is discussed.The use of Nb3Sn in RF cavitiesis recognized as an enabling technology toretain a veryhigh cavity quality factor (Q0) at 4.2 K and tosignificantly improve the cavity accelerating efficiency per unitlength(Eacc). This potential arises through the fundamental properties ofNb3Sn. The properties that are extensively characterized in theliterature are, however, mainly related to improvements in currentcarrying capacity (Jc) in the vortex state. Much less is available forthe Meissner state, which is of key importance to cavities. Relevantdata, available for the Meissner state is summarized, and it is shown howthis already validates the use of Nb3Sn. In addition, missing knowledgeis highlighted and suggestions are given for further Meissner statespecific research.

Godeke, A.

2006-12-18

115

Micro-arcing in radio frequency plasmas  

NASA Astrophysics Data System (ADS)

Micro-arcing and breakdown of the wall plasma sheath in radio frequency (RF) plasmas is studied in a hollow cathode system, using a Langmuir probe to measure the floating potential. Micro-arcing was induced reproducibly by controlling the floating potential. By dc grounding the hollow cathode, a negative current can flow to ground resulting in a higher voltage sheath between the plasma and the earthed vacuum vessel. The wall arcing threshold of the plasma potential in this system is in the vicinity of 50 V. In the present system, the charging process to rebuild the plasma potential, which is about a few tens of milliseconds, is much slower than the microsecond discharge. The arcing frequency was found to depend strongly on the plasma potential and the pressure. We propose a mechanism for the dependence of the frequency of periodic micro-arcing based on the development of electron field emission sites. The measurement of floating potential is suggested as a useful parameter to monitor and prevent micro-arcing in RF plasmas.

Yin, Y.; Bilek, M. M. M.; McKenzie, D. R.; Boswell, R. W.; Charles, C.

2004-10-01

116

Assessment of Barotrauma Resulting from Rapid Decompression of Depth Acclimated Juvenile Chinook Salmon Bearing Radio Telemetry Transmitters  

SciTech Connect

A multifactor study was conducted by Battelle for the US Army Corps of Engineers to assess the significance of the presence of a radio telemetry transmitter on the effects of rapid decompression from simulated hydro turbine passage on depth acclimated juvenile run-of-the-river Chinook salmon. Study factors were: (1) juvenile chinook salmon age;, subyearling or yearling, (2) radio transmitter present or absent, (3) three transmitter implantation factors: gastric, surgical, and no transmitter, and (4) four acclimation depth factors: 1, 10, 20, and 40 foot submergence equivalent absolute pressure, for a total of 48 unique treatments. Exposed fish were examined for changes in behavior, presence or absence of barotrauma injuries, and immediate or delayed mortality. Logistic models were used to test hypotheses that addressed study objectives. The presence of a radio transmitter was found to significantly increase the risk of barotrauma injury and mortality at exposure to rapid decompression. Gastric implantation was found to present a higher risk than surgical implantation. Fish were exposed within 48 hours of transmitter implantation so surgical incisions were not completely healed. The difference in results obtained for gastric and surgical implantation methods may be the result of study design and the results may have been different if tested fish had completely healed surgical wounds. However, the test did simulate the typical surgical-release time frame for in-river telemetry studies of fish survival so the results are probably representative for fish passing through a turbine shortly following release into the river. The finding of a significant difference in response to rapid decompression between fish bearing radio transmitters and those not implies a bias may exist in estimates of turbine passage survival obtained using radio telemetry. However, the rapid decompression (simulated turbine passage) conditions used for the study represented near worst case exposure for fish passing through turbines. At this time, insufficient data exist about the distribution of river-run fish entering turbines, and particularly, the distribution of fish passing through turbine runners, to extrapolate study findings to the population of fish passing through FCRPS turbines. This study is the first study examining rapid decompression study to include acclimation depth as an experimental factor for physostomous fish. We found that fish acclimated to deeper depth were significantly more vulnerable to barotrauma injury and death. Insufficient information about the distribution of fish entering turbines and their depth acclimation currently exists to extrapolate these findings to the population of fish passing through turbines. However, the risk of barotrauma for turbine-passed fish could be particularly high for subyearling Chinook salmon that migrate downstream at deeper depths late in the early summer portion of the outmigration. Barotrauma injuries led to immediate mortality delayed mortality and potential mortality due to increased susceptibility to predation resulting from loss of equilibrium or swim bladder rupture.

Brown, Richard S.; Carlson, Thomas J.; Welch, Abigail E.; Stephenson, John R.; Abernethy, Cary S.; McKinstry, Craig A.; Theriault, Marie-Helene

2007-09-06

117

Committee on Radio Astronomy Frequencies (CRAF)  

NASA Astrophysics Data System (ADS)

The science of radio astronomy plays a key role in increasing our understanding of the environment and the universe in which we live. By its nature it is a passive service, so it never causes interference to other users of radio. On the other hand, it is becoming increasingly difficult to protect radio astronomy operations from radio interference as use of the spectrum increases for both terrestrial and space-borne communications.

Monstein, Chr.

2013-06-01

118

Demeter/ICE Experiment: Study of low frequency transmitter intensity variations  

NASA Astrophysics Data System (ADS)

We report on low frequency (LF) transmitter signal recorded by the 'Instrument Capteur Electrique' (ICE) experiment onboard the DEMETER micro-satellite. We mainly consider the signal emitted by the Brasov broadcasting station (25.60E, 45.75N) at frequency of about 153 kHz. We analyze the reception conditions of this transmitter several weeks before the occurrence of the Vrancea earthquakes, on October, 27th, 2004. Ground-based observations revealed the presence of sudden decrease of the Y-component of the magnetic field at Muntele Rosu Observatory (Romania), at about 68 km from the epicenter, as reported by Moldovan et al. (Rom. Journ. Phys., Vol. 54, Nos. 1-2, p. 249-261, Bucharest, 2009). In this contribution we attempt to check if the LF Brasov signal was also subject to similar disturbances as observed by the ground-station. We focus on the variation of the LF transmitter intensity levels, several weeks before and after the Vrancea earthquake occurrence. We discuss the physical parameters which may disturb the signal reception in particular the geomagnetic activity and the signal to noise ratios.

Boudjada, M. Y.; Moldovan, I.; Schwingenschuh, K.; Al-Haddad, E.; Biagi, P. F.; Parrot, M.

2012-04-01

119

Trirotron: triode rotating beam radio frequency amplifier  

DOEpatents

High efficiency amplification of radio frequencies to very high power levels including: establishing a cylindrical cloud of electrons; establishing an electrical field surrounding and coaxial with the electron cloud to bias the electrons to remain in the cloud; establishing a rotating electrical field that surrounds and is coaxial with the steady field, the circular path of the rotating field being one wavelength long, whereby the peak of one phase of the rotating field is used to accelerate electrons in a beam through the bias field in synchronism with the peak of the rotating field so that there is a beam of electrons continuously extracted from the cloud and rotating with the peak; establishing a steady electrical field that surrounds and is coaxial with the rotating field for high-energy radial acceleration of the rotating beam of electrons; and resonating the rotating beam of electrons within a space surrounding the second field, the space being selected to have a phase velocity equal to that of the rotating field to thereby produce a high-power output at the frequency of the rotating field.

Lebacqz, Jean V. (Stanford, CA)

1980-01-01

120

Heating of the nighttime D region by very low frequency transmitters  

SciTech Connect

VLF signals propagating in the Earth-ionosphere waveguide are used to probe the heated nighttime D region over three U.S. Navy very low frequency (VLF, 3-30 kHz) transmitters. Ionospheric cooling and heating are observed when a transmitter turns off and on in the course of normal operations. Heating by the 24.0-kHz NAA transmitter in Cutler, Maine, (1000 kW radiated power) was observed by this method in 41 of 52 off/on episodes during December 1992, increasing the amplitude and retarding the phase of 21.4-kHz NSS probe wave propagating from Annapolis, Maryland, to Gander, Newfoundland, by as much as 0.84 dB and 5.3{degree}, respectively. In 6 of these 41 episodes, the amplitude of the 28.5-kHz NAU probe wave propagating from Puerto Rico to Gander was also perturbed by as much as 0.29 dB. The latter observations were unexpected due to the > 770 km distance between NAA and the NAU-Gander great circle path. Heating by the NSS (21.4 kHz, 265 kW) and NLK (24.8 kHz, 850 kW) transmitters was observed serendipitously in data from earlier measurements of the amplitudes of VLF signals propagating in the Earth-ionosphere waveguide. A three-dimensional model of wave absorption and electron heating in a magnetized, weakly ionized plasma is used to calculate the extent and shape of the collision frequency (i.e., electron temperature) enhancement above a VLF transmitter. Heating by the NAA transmitter is predicted to increase the night-time D region electron temperature by as much as a factor of 3. The calculated changes in the D region conductivity are used in a three-dimensional model of propagation in the Earth-ionosphere waveguide to predict the effect of the heated patch on a subionospheric VLF probe wave. The range of predicted scattered field amplitudes is in general consistent with the observed signal perturbations. 25 refs., 9 figs., 6 tabs.

Rodriguez, J.V.; Inan, U.S.; Bell, T.F. [Stanford Univ., CA (United States)

1994-12-01

121

SITE TECHNOLOGY CAPSULE: IITRI RADIO FREQUENCY HEATING TECHNOLOGY  

EPA Science Inventory

Radio frequency heating (RFH) technologies use electromagnetic energy in the radio frequency i(RF) band to heat soil in-situ, thereby potentially enhancing the performances of standard soil vapor extraction (SVE) technologies. ontaminants are removed from in situ soils and transf...

122

DEMONSTRATION BULLETIN: RADIO FREQUENCY HEATING - KAI TECHNOLOGIES, INC.  

EPA Science Inventory

Radio frequency heating (RFH) is a process that uses electromagnetic energy in the radio frequency (RF) band to heat soil in situ, thereby potentially enhancing the performance of standard soil vapor extraction (SVE) technologies. An RFH system developed by KAI Technologies, I...

123

Final report: In situ radio frequency heating demonstration  

Microsoft Academic Search

A field demonstration of in situ radio frequency heating was performed at the Savannah River Site (SRS) as part of the US Department of Energy-Office of Technology Development`s Integrated Demonstration. The objective of the demonstration was to investigate the effectiveness of in situ radio frequency (RF) heating as an enhancement to vacuum extraction of residual solvents (primarily trichloroethylene and perchloroethylene)

T. R. Jarosch; R. J. Beleski; D. Faust

1994-01-01

124

High-power radio-frequency attenuation device  

Microsoft Academic Search

A resistor device for attenuating radio frequency power includes a radio frequency conductor connected to a series of fins formed of high relative magnetic permeability material. The fins are dimensional to accommodate the skin depth of the current conduction therethrough, as well as an inner heat conducting portion where current does not travel. Thermal connections for air or water cooling

Q. A. Kerns; H. W. Miller

1981-01-01

125

IN SITU AND SOIL DECONTAMINATION BY RADIO FREQUENCY HEATING  

EPA Science Inventory

In situ radio frequency heating is performed by applying electromagnetic energy in the radio frequency band to an array of electrodes placed in bore holes drilled through the contaminated soil. he process removes organic contaminants from large volumes of soil by volatilization, ...

126

Cassini Huygens mission : the exploration of the Saturn system. Radio science experiments : Radio Frequency Instrument Subsystem  

Microsoft Academic Search

Many of the Cassini radio science experiments will require very stable microwave signals from the ground station that are transponded phase coherently on board the spacecraft. The Radio Frequency Instrument Subsystem is designed to provide this latter capability with high performance downlink signals at S-band and Ka-band. The signal level and phase change at both frequencies will be monitored during

Bruno Perrot; Roberto Giordani

1998-01-01

127

Radio-frequency electromagnetic fields. The Skrunda Radio Location Station case  

Microsoft Academic Search

The Skrunda Radio Location Station in Latvia, an early warning radar system which operates in the 156 to 162 Mhz frequency range, has been in operation since 1971 and is scheduled to operate until 1998. Currently, information on the biological effects of radio frequency electromagnetic radiation emissions on plants is rare. A brief introduction to six papers in this issue

Guntis Br?melis; Valdis Balodis; Zanda Balode

1996-01-01

128

Mapping the radio sky with an interferometric network of low-frequency radio receivers  

NASA Astrophysics Data System (ADS)

The structure of the 100 kHz radio sky is determined with two interferometric networks of 10 radio receivers which are distributed over local areas of 1 1 km2 and 10 10 km2. The radio waves arrive at individual receiver pairs with small time differences which are used to determine the arrival direction of the electromagnetic waves including both the bearing and the elevation angle. The results show that the major part of the 100 kHz radio wave energy comes from the horizon at bearings which are consistent with known locations of Long Range Navigation (LORAN) transmitters. Some part of the radio wave energy arrives from the sky at elevation angles which are consistent with the first and second sky hop waves of LORAN transmissions. A minor part of the 100 kHz radio wave energy comes from lightning discharges at distances up to 1000 km with bearings which are consistent with lightning locations reported by the arrival time difference (ATD) lightning detection network of the UK Met Office. The angular resolution for mapping the radio sky depends on the network geometry, the instrumental timing accuracy, and on the signal-to-noise ratio of the radio waves. The resulting angular resolution of the interferometric networks used in this study is 1 in bearing at zero elevation and several degrees in elevation.

Mezentsev, Andrew; Fllekrug, Martin

2013-08-01

129

Errors in radio-frequency quadrupole structures  

SciTech Connect

Performance degradation caused by certain radio-frequency quadrupole (RFQ) machine errors was studied using an efficient 3-D particle-tracing simulation code for a high-brightness example. Matched beams, for which no emittance growth occurs, exist for periodic structures and were used as input beams for particle tracing in the presence of errors. We considered both slowly varying and fast (random) errors that destroy periodicity. Random dipole errors cause emittance growth because of the mismatches they introduce and also result in a motion of the beam centroid that causes a reduction in acceptance. Because of the way RFQs are manufactured, the random error amplitudes can be kept below harmful levels. More important are the slow errors, which are harmful because they reduce acceptance even though they maintain a match (up to the point of particle loss). Slow dipole errors steer the beam toward the wall, and voltage deficiencies cause instabilities in the longitudinal direction resulting in particles not being accelerated to full energy.

Lysenko, W.P.

1983-01-01

130

Deposition of a conductive near-infrared cutoff filter by radio-frequency magnetron sputtering.  

PubMed

We have designed a conductive near-infrared (NIR) cutoff filter for display application, i.e., a modified low-emissivity filter based on the three periods of the basic design of [TiO2[Ti]Ag] TiO2] upon a glass substrate and investigated the optical, structural, chemical, and electrical properties of the conductive NIR cutoff filter prepared by a radio frequency magnetron sputtering system. The results show that the average transmittance is 61.1% in the visible, that the transmittance in the NIR is less than 6.6%, and that the sheet resistance and emissivity are 0.9 ohms/square (where square stands for a square film) and 0.012, respectively, suggesting that the conductive NIR cutoff filter can be employed as a shield against the hazard of electromagnetic waves as well as to cut off the NIR. PMID:12064381

Lee, Jang-Hoon; Lee, Seung-Hyu; Yoo, Kwang-Lim; Kim, Nam-Young; Hwangbo, Chang Kwon

2002-06-01

131

Deposition of transparent, conductive tin oxide films on glass using a radio-frequency induction heater  

NASA Astrophysics Data System (ADS)

Tin oxide films are often used as transparent, conductive coatings on glass in the scientific research setting. The standard approach of depositing these films in an oven leads to poor visibility of the substrate and thus inhibits the ready formation of uniform, low resistivity films. In this note we describe a simple tin oxide film deposition technique using a radio-frequency induction heater that allows for in situ visualization of the deposition process and resulting film. Uniform films having resistivities as low as 2 m? cm with transmittances of approximately 85% in the visible light spectrum were readily deposited.

Solano, I.; Schwoebel, P. R.

2009-12-01

132

A 24mm2 Quad-Band Single-Chip GSM Radio with Transmitter Calibration in 90nm Digital CMOS  

Microsoft Academic Search

The RF transceiver is built on the Digital RF Processor (DRP) technology. The ADPLL-based transmitter uses a polar architecture with all-digital PM-FM and AM paths. The receiver uses a discrete-time architecture in which the RF signal is directly sampled and processed using analog and DSP techniques. A 26 MHz digitally controlled crystal oscillator (DCXO) generates frequency reference (FREF) and has

R. B. Staszewski; D. Leipold; O. Eliezer; M. Entezari; K. Muhammad; I. Bashir; C.-M. Hung; J. Wallberg; P. Cruise; S. Rezeq; S. Vemulapalli; K. Waheed; N. Barton; M.-C. Lee; C. Fernando; K. Maggio; T. Jung; I. Elahi; S. Larson; T. Murphy; G. Feygin; I. Deng; T. Mayhugh; Y.-C. Ho; K.-M. Low; C. Lin; J. Jaehnig; J. Kerr; J. Mehta; S. Glock; T. Almholt; S. Bhatara

2008-01-01

133

Automatic Radio Telemetry Recording of Fish Temperature and Depth.  

National Technical Information Service (NTIS)

Radio frequency fish transmitters capable of relaying temperature or pressure information and a multichannel recording system were developed and used successfully in the field. Both transmitters operated on pulse rate variation with either temperature or ...

M. J. Ross V. B. Kuechle R. A. Reichle D. B. Siniff

1979-01-01

134

A low emission, low power non-linear frequency modulation based transmitter for implanted devices.  

PubMed

The paper proposes a low emission, non linear frequency modulator for transmitting neural signals. With the advent of embedded medical devices, designers need to start developing low Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI) devices. We propose a non-phase locked loop based frequency modulator. The modulator utilizes a ramp to encode the bit stream from the neural amplifier. In addition it utilizes a non linear signal to modulate the encoded signal leading to lowering of peak of power spectrum, a measure of electro-magnetic interference. The proposed algorithm has been implemented on 0.18 AMS technology and results presented. PMID:24109815

Saraswat, Ruchir; Rodriguez-Villegas, Esther

2013-07-01

135

77 FR 35426 - Certain Radio Frequency Integrated Circuits and Devices Containing Same; Institution of...  

Federal Register 2010, 2011, 2012, 2013

...No. 337-TA-848] Certain Radio Frequency Integrated Circuits...after importation of certain radio frequency integrated circuits...be obtained by accessing its internet server at http://www.usitc...after importation of certain radio frequency integrated...

2012-06-13

136

48 CFR 552.211-92 - Radio Frequency Identification (RFID) using passive tags.  

Code of Federal Regulations, 2010 CFR

...false Radio Frequency Identification (RFID) using passive tags. 552.211-92...211-92 Radio Frequency Identification (RFID) using passive tags. As prescribed...clause: Radio Frequency Identification (RFID) Using Passive Tags (JAN...

2010-10-01

137

High-power radio-frequency attenuation device  

DOEpatents

A resistor device for attenuating radio frequency power includes a radio frequency conductor connected to a series of fins formed of high relative magnetic permeability material. The fins are dimensional to accommodate the skin depth of the current conduction therethrough, as well as an inner heat conducting portion where current does not travel. Thermal connections for air or water cooling are provided for the inner heat conducting portions of each fin. Also disclosed is a resistor device to selectively alternate unwanted radio frequency energy in a resonant cavity.

Kerns, Q.A.; Miller, H.W.

1981-12-30

138

Electron density changes in the nightime D region due to heating by very-low-frequency transmitters  

SciTech Connect

Modification of the nighttime D region electron density (N[sub e]) due to heating by very-low-frequency (VLF) transmitters is investigated theoretically using a four-species model of the ion chemistry. The effects of a 100 kW, a 265 kW, and a 1000 kW VLF transmitter are calculated for three ambient N[sub e] profiles. Results indicate that N[sub e] is reduced by up to 26% at [approximately]80 km altitude over a 1000 kW transmitter. 24 refs., 4 figs., 1 tab.

Rodriguez, J.V.; Inan, U.S. (Stanford Univ., Stanford, CA (United States))

1994-01-15

139

Solar observations with a low frequency radio telescope  

NASA Astrophysics Data System (ADS)

We have set up a low frequency radio monitoring station for solar bursts at the Observatory of the Aristotle University in Thessaloniki. The station consists of a dual dipole phased array, a radio receiver and a dedicated computer with the necessary software installed. The constructed radio receiver is based on NASA's Radio Jove project. It operates continuously, since July 2010, at 20.1 MHz (close to the long-wavelength ionospheric cut-off of the radio window) with a narrow bandwidth (~5 kHz). The system is properly calibrated, so that the recorded data are expressed in antenna temperature. Despite the high interference level of an urban region like Thessaloniki (strong broadcasting shortwave radio stations, periodic experimental signals, CBs, etc), we have detected several low frequency solar radio bursts and correlated them with solar flares, X-ray events and other low frequency solar observations. The received signal is monitored in ordinary ASCII format and as audio signal, in order to investigate and exclude man-made radio interference. In order to exclude narrow band interference and calculate the spectral indices of the observed events, a second monitoring station, working at 36 MHz, is under construction at the village of Nikiforos near the town of Drama, about 130 km away of Thessaloniki. Finally, we plan to construct a third monitoring station at 58 MHz, in Thessaloniki. This frequency was revealed to be relatively free of interference, after a thorough investigation of the region.

Myserlis, I.; Seiradakis, J.; Dogramatzidis, M.

2012-01-01

140

An overview of backscattered radio frequency identification system (RFID)  

Microsoft Academic Search

A radio frequency identification (RFID) system is a wireless communication system in which the radio link between the base station and the transponders are furnished by the modulated backscattered waves. The present paper is intended to provide a brief description of various subsystems of the RFID. The various applications of RFID are discussed. Sample results on read\\/write range for a

K. V. S. Rao

1999-01-01

141

Overview of technical approaches to radio frequency interference mitigation  

Microsoft Academic Search

This overview provides an interface between lines of thought on radio frequency interference (RFI) mitigation in the fields of radio astronomy and signal processing. The goal is to explore the commonality of different approaches to help researchers in both fields interpret each other's concepts and jargon. The paper elaborates on the astronomers' concept of gain closure relations and how they

F. H. Briggs; J. Kocz

2005-01-01

142

DEMONSTRATION BULLETIN: RADIO FREQUENCY HEATING - IIT RESEARCH INSTITUTE  

EPA Science Inventory

Radio frequency heating (RFH) is a process that uses electromagnetic energy generated by radio waves to heat soil in situ, thereby potentially enhancing the performance of standard soil vapor extraction (SVE) technologies. An RFH system developed by the IIT Research Institute ...

143

Radio frequency overview of the high explosive radio telemetry project  

SciTech Connect

High explosive radio telemetry (HERT) is a project that is being developed jointly by Los Alamos National Laboratory and AlliedSignal Federal Manufacturing and Technologies. The ultimate goal is to develop a small, modular telemetry system capable of high-speed detection of explosive events, with an accuracy on the order of 10 nanoseconds. The reliable telemetry of this data, from a high-speed missile trajectory, is a very challenging opportunity. All captured data must be transmitted in less than 20 microseconds of time duration. This requires a high bits/Hertz microwave telemetry modulation code to insure transmission of the data with the limited time interval available.

Bracht, R. [Los Alamos National Lab., NM (United States); Dimsdle, J.; Rich, D.; Smith, F. [AlliedSignal Federal Manufacturing and Technologies, Kansas City, MO (United States)

1998-12-31

144

Deck Boxes for UHF SATCOM Radio Frequency Interference Study.  

National Technical Information Service (NTIS)

This report concerns itself with the design, construction, and utilization of a remotely controlled deck box assembly. This deck box assembly was used in conjunction with other specialized equipments for the study of radio frequency interference. This stu...

G. B. Parker J. E. Ohlson

1976-01-01

145

Principles and Applications of Radio Frequency Impedance Probes.  

National Technical Information Service (NTIS)

The underlying principle of the radio frequency plasma probe is presented. The resonance properties of the probe's equivalent circuit with and without external magnetic field are analyzed. The admittance of the equivalent circuit is shown to posses a pole...

S. T. Lai

1981-01-01

146

Radio Frequency Study of Atomic Structure and Spectra.  

National Technical Information Service (NTIS)

We have investigated the possibility of using radio-frequency techniques for the study of the spectra and structure of free atomic ions. After consideration of various methods of producing polarized ions and detecting their polarization we concluded that ...

L. W. Anderson

1969-01-01

147

Experimental Investigation of the Bennett Type Radio-Frequency Spectrometer.  

National Technical Information Service (NTIS)

Authors conducted experiments to study the static characteristics of a Bennett radio-frequency (RF) mass spectrometer. Bennett RF mass spectrometer is used to determine individual constituent contents in gaseous mixtures. The gaseous mixture is ionized by...

C. Zeng-tsu C. Shao-chiang R. Hua-chi Y. Cheng-an

1967-01-01

148

Security and Privacy in Radio-Frequency Identification Devices  

Microsoft Academic Search

Radio Frequency Identification (RFID) systems are a common and useful tool in manufacturing, supply chain management and retail inventory control. Optical barcodes, another common automatic identification system, have been a familiar packaging feature on consumer items for years.

Stephen August Weis

2003-01-01

149

A Real-Time Radio Frequency Spectrum analyzer  

Microsoft Academic Search

We use OptiSystem to demonstrate a technique to make Real-Time Radio Frequency Spectrum measurements through the combination of cross phase modulation, and the time domain analog to Fraunhofer Diffraction.

B. H. Hamel-Bissell; L. R. Chen

2010-01-01

150

Radio frequency-based optical transport network systems and methods  

US Patent & Trademark Office Database

The present disclosure provides radio frequency (RF)-based OTN systems and methods. This includes a framework to carry services over RF-based links without using SONET/SDH or asynchronous radio. In an exemplary embodiment, the present disclosure utilizes an OTN framework over RF. Additionally, the present disclosure can also apply to other non-OTN frameworks such as an extended Ethernet frame with forward error correction (FEC) over RF-based links. The present disclosure combines existing OTN FEC with a radio FEC or with an over-the-air FEC to reduce the OTN FEC. Additionally, the present disclosure utilizes unused overhead to communicate RF data rates between radios.

2012-06-19

151

Principles and applications of radio frequency impedance probes  

Microsoft Academic Search

The underlying principle of the radio frequency plasma probe is presented. The resonance properties of the probe's equivalent circuit with and without external magnetic field are analyzed. The admittance of the equivalent circuit is shown to possess a pole at the sheath hybrid frequency and a zero at the upper hybrid frequency. The phase of the admittance changes signature to

S. T. Lai

1981-01-01

152

Dielectric Losses at Radio Frequencies in Liquid Dielectrics  

Microsoft Academic Search

Dielectric losses and dielectric constants at radio frequencies for nitrobenzene, water and xylene.-The method of resistance variation was used to measure the phase difference psi and dielectric constant K for frequencies between 2 105 and 14 105 cycles\\/sec. Special cells were required. (1) Variation with frequency. The results agree approximately with the equations: For carefully dried nitrobenzene at

A. B. Bryan

1923-01-01

153

Active control of edge localized modes by radio frequency waves  

NASA Astrophysics Data System (ADS)

The effect of radio frequency wave driven torque on edge localized mode (ELM) activity is studied. It is shown that the radio frequency driven torque causes transition of type I giant ELMs to the benign grassy ELM behavior. The efficiency of this process scales directly with minor radius and inversely with the plasma density. It is argued that the technique of active ELM control will be efficient in the present for moderate-sized machines and in the future for large machines.

Avinash, K.; Diamond, P. H.

2000-11-01

154

Radio frequency electromagnetic fields: mild hyperthermia and safety standards  

Microsoft Academic Search

This chapter is a short review of literature that serves as the basis for current safe exposure recommendations by ICNIRP (International Commission on Non-Ionizing Radiation Protection, 1998). and the IEEE C95.1 (IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3kHz to 300GHz, 2005) for exposure to radio frequency electromagnetic radiation (RF-EMF). Covered here

John A. DAndrea; John M. Ziriax; Eleanor R. Adair

2007-01-01

155

Planetary and exoplanetary low frequency radio observations from the Moon  

NASA Astrophysics Data System (ADS)

We analyze the planetary and exoplanetary science that can be carried out with precursor as well as future low frequency radio instruments on the Moon, assessing the limiting noise sources, comparing them to the average and peak spectra of all planetary radio components as they will be seen from the Lunar surface or orbit. We identify which objectives will be accessible with each class of instrument, and discuss the interest of these observations compared to observations by planetary probes and to ground-based observations by large low-frequency radio arrays. The interest of goniopolarimetry is emphasized for pathfinder missions.

Zarka, P.; Bougeret, J.-L.; Briand, C.; Cecconi, B.; Falcke, H.; Girard, J.; Griemeier, J.-M.; Hess, S.; Klein-Wolt, M.; Konovalenko, A.; Lamy, L.; Mimoun, D.; Aminaei, A.

2012-12-01

156

Supplying the Power Requirements to a Sensor Network Using Radio Frequency Power Transfer  

PubMed Central

Wireless power transmission is a method of supplying power to small electronic devices when there is no wired connection. One way to increase the range of these systems is to use a directional transmitting antenna, the problem with this approach is that power can only be transmitted through a narrow beam and directly forward, requiring the transmitter to always be aligned with the sensor node position. The work outlined in this article describes the design and testing of an autonomous radio frequency power transfer system that is capable of rotating the base transmitter to track the position of sensor nodes and transferring power to that sensor node. The system's base station monitors the node's energy levels and forms a charge queue to plan charging order and maintain energy levels of the nodes. Results show a radio frequency harvesting circuit with a measured S11 value of ?31.5 dB and a conversion efficiency of 39.1%. Simulation and experimentation verified the level of power transfer and efficiency. The results of this work show a small network of three nodes with different storage types powered by a central base node.

Percy, Steven; Knight, Chris; Cooray, Francis; Smart, Ken

2012-01-01

157

The Current Status of Low Frequency Radio Astronomy from Space  

NASA Astrophysics Data System (ADS)

Ground-based radio astronomy is severely limited by the Earth's ionosphere. Below 15 -- 20 MHz, space-based radio observations are superior or even mandatory. Three different areas of astronomical research manifest themselves at low radio frequencies: solar, planetary, and galactic-extragalactic. Space-based observations of solar phenomena at low frequencies are a natural extension of high-frequency ground-based observations that have been carried out since the beginnings of radio astronomy. Measurements of known solar phenomena such as Types II and III bursts have been extended from the few solar radii altitude range reachable by ground-based techniques out to 1 AU and beyond. These space-based solar measurements have become critical in our developing an understanding of ``space weather." In contrast, non-thermal planetary radio emissions are almost exclusively a space radio astronomy phenomenon. With the exception of two components of Jupiter's complex radio spectrum, the magnetospheric and Auroral radio emissions of Earth, Jupiter, Saturn, Uranus, and Neptune have all been discovered by space radio astronomy techniques. For astrophysical applications, the lack of angular resolution from space at low frequencies has thwarted progress such that most areas still remain to be fully exploited. Results to date have only included overall cosmic background spectra and extremely crude (~1 steradian resolution) ``maps." In this overview we will briefly summarize the current status of science in the three areas of research and outline some future concepts for low-frequency, space-based instruments for solar, planetary, and astrophysical problems.

Kaiser, M. L.; Weiler, K. W.

158

Daily Radio Frequency Observations of Selected Objects  

Microsoft Academic Search

The authors present a list of 38 celestial objects that have been observed since January 1978 at 2.7 and 8.1 GHz with the Green Bank interferometer. The sources fall into three categories: radio stars, possibly galactic sources, and extragalactic sources.

B. J. Geldzahler; K. J. Johnston; J. H. Spencer; E. B. Waltman; W. J. Klepczynski; P. E. Angerhofer; D. R. Florkowski; D. D. McCarthy; D. N. Matsakis

1984-01-01

159

Magnetic pulsation generation by a powerful ground-based modulated HF radio transmitter  

Microsoft Academic Search

The Hall and Pedersen ionospheric conductivity disturbances produced by high power amplitude-modulated radio waves as a function of altitude for different initial electron density profiles are calculated. Disturbances of the integral Hall and Pedersen conductivities as well as the artificial magnetic pulsation amplitudes for different initial electron density profiles and different magnetic pulsation periods are calculated too. Some recommendations for

A. B. Pashin; E. G. Belova; W. B. Lyatsky

1995-01-01

160

Heating mechanisms in gold nanoparticles at radio frequencies.  

PubMed

Gold nanoparticles are under study as a potentially viable mechanism for hyperthermia tumor treatment in two regimes of the electromagnetic spectrum: laser and radio frequency excitation. Gold nanoparticles, nanorods and nanoshells have been applied with visible laser sources that excite the particles at or near their plasmon resonance frequency, and this mechanism has been well studied. The physical processes that describe the experimentally observed heating at radio frequencies (13.56 MHz) are not as well understood. Differing results have been reported in semi-solid phantom materials and liquid phase suspensions. This numerical modeling study was undertaken to inspect the relative importance of several candidate physical processes. PMID:22255603

Pearce, John A; Cook, Jason R

2011-01-01

161

INACTIVATION OF SACCHAROMYCES CEREVISIAE USING RADIO FREQUENCY ELECTRIC FIELDS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The application of radio frequency (RF) electric fields was investigated as a nonthermal alternative to thermal inactivation of microorganisms in liquids. A novel RF system was developed and produced frequencies in the range of 20 kHz to 60 kHz. Electric field strengths of 20 kV/cm and 30 kV/cm we...

162

Physical properties of conventional explosives deduced from radio frequency emissions  

Microsoft Academic Search

Los Alamos National Laboratory collected broadband radio frequency (RF) electric field change measurements from multiple detonations of high explosives (HE). Three types of HE were used: small cylinders of flake TNT, solid TNT, and PBX-9501. Low frequency signals (<80 MHz) were shot-to-shot repeatable and occurred within the first 100 s at measured amplitudes of about 2 V m at 35

Jeremiah D Harlin; Robert Nemzek

2008-01-01

163

Radio-Frequency Size-Effect Line Shape for Gallium.  

National Technical Information Service (NTIS)

Study of the frequency dependence of the radio-frequency size effect line shape allows a determination of the portion of that line shape which can be interpreted as arising from extremal orbit electrons on the Fermi surface whose wave vector is simply rel...

A. Fukumoto M. W. P. Strandberg

1966-01-01

164

Radio frequency hollow cathodes for the plasma processing technology  

Microsoft Academic Search

The present paper summarizes the main features of the hollow cathode discharges generated by a radio frequency (r.f.) instead of a d.c. field. The pressure of gas inside the hollow cathode is almost independent on the reactor pressure, which allows to generate discharge at high collision frequency and transport it into the low pressure reactor. The discharge forced out from

L. Brdo

1996-01-01

165

Advanced radio frequency materials for packaging of implantable biomedical devices  

Microsoft Academic Search

Most electronic biomedical implants are packaged with an epoxy coating that reduces the lifetime of the implant, or a metal casing that complicates wireless telemetry in a biological system. Advanced radio frequency (RF) materials commonly used in cell phones and high frequency devices have the ability to enhance implanted devices. Therefore this document analyzes the functionality and biocompatibility of implantable

Arthur Lawrence Chlebowski

2009-01-01

166

Radio Frequency Impedance Interrogation monitoring of hemodynamic parameters  

Microsoft Academic Search

Non-contact, non-invasive monitoring of hemodynamic parameters has long been deemed to be important to medical monitoring in a variety of environments. Radio Frequency Impedance Interrogation (RFII) measures hemodynamic function via resonance frequency coupling to a hydrophilic protein molecule. We examined the use of RFII for hemodynamic monitoring of human subjects during Lower Body Negative Pressure (LBNP) and physiological hemodynamic maneuvers

Marc O Griofa; Rebecca Blue; Robert Friedman; Kenneth Cohen; Philip Hamski; Andrew Pal; Robert Rinehart; Tom Merrick

2011-01-01

167

On the radio-frequency emission from the Geminga pulsar  

NASA Astrophysics Data System (ADS)

The famous neutron star Geminga was until quite lately the only pulsar undetected in the radio regime, though observed as a strong pulsating gamma- and X-ray source. Three independent groups from the Pushchino Radio Astronomy Observatory (Russia) reported recently the detection of pulsed radio emission from Geminga at 102.5 MHz, i.e., the first detection of the radio pulsar PSR J0633+1746 by Kuz'min & Losovskii, Malofeev & Malov and Shitov & Pugachev. This pulsar exhibits the weakest radio luminosity known. Its average pulse profile appears to be very wide, filling an entire 360 deg pulse window according to Kuz'min & Losovskii. We present a model explaining the peculiarities of the Geminga radio pulsar, based on the assumption that it is an almost aligned rotator. The electromagnetic waves generated in the inner magnetosphere reach the region within the light cylinder with a weak magnetic field (at distances of a few light cylinder radii), where they are strongly damped due to the cyclotron resonance with particles of magnetospheric electron-positron plasma. The lowest frequencies that can escape are determined by the value of the magnetic field in the region where the line of sight passes through the light cylinder. The specific viewing geometry of an almost aligned rotator implies that the observer's line of sight probes the emission region near the bundle of the last open field lines. This explains the unusually weak emission from Geminga's low-frequency radio pulsar.

Gil, Janusz A.; Khechinashvili, David G.; Melikidze, George I.

1998-08-01

168

The Use of a Solid State Analog Television Transmitter as a Superconducting Electron Gun Power Amplifier  

SciTech Connect

A solid state analog television transmitter designed for 200 MHz operation is being commissioned as a radio frequency power amplifier on the Wisconsin superconducting electron gun cavity. The amplifier consists of three separate radio frequency power combiner cabinets and one monitor and control cabinet. The transmitter employs rugged field effect transistors built into one kilowatt drawers that are individually hot swappable at maximum continuous power output. The total combined power of the transmitter system is 33 kW at 200 MHz, output through a standard coaxial transmission line. A low level radio frequency system is employed to digitally synthesize the 200 MHz signal and precisely control amplitude and phase.

J.G. Kulpin, K.J. Kleman, R.A. Legg

2012-07-01

169

Physics of Radio-Frequency Plasmas  

NASA Astrophysics Data System (ADS)

1. Introduction; 2. Plasma dynamics and equilibrium; 3. Bounded plasmas; 4. Radiofrequency sheaths; 5. Single frequency capacitively-coupled plasmas; 6. Multi-frequency capacitively-coupled plasmas; 7. Inductively-coupled plasmas; 8. Helicon plasmas; 9. Real plasmas; 10. Electrical measurements; Index.

Chabert, Pascal; Braithwaite, Nicholas

2011-02-01

170

Cosmic Radio-Frequency Radiation Near One Megacycle  

Microsoft Academic Search

Observations of cosmic radio-frequency radiation on frequencies of 2130 kc\\/sec, 1435 kc\\/sec, 900 kc\\/sec, and 520 kc\\/sec have been made, using a method of recording which effectively reduces interference from atmospherics. At these frequencies, the intensity of the radiation is approximately 10 - watt per square metre per cycle per second** per steradian. The ionospheric effects associated with observations near

Grote Reber; G. R. Ellis

1956-01-01

171

Progress on radio frequency auxiliary heating system designs in ITER  

SciTech Connect

ITER will require over 100 MW of auxiliary power for heating, on- and off-axis current drive, accessing the H-mode, and plasma shut-down. The Electron Cyclotron Range of Frequencies (ECRF) and Ion Cyclotron Range of Frequencies (ICRF) are two forms of Radio Frequency (RF) auxiliary power being developed for these applications. Design concepts for both the ECRF and ICRF systems are presented, key features and critical design issues are discussed, and projected performances outlined.

Makowski, M.; Bosia, G.; Elio, F.

1996-09-01

172

Radio-Controlled Cyborg Beetles: A Radio-Frequency System for Insect Neural Flight Control  

Microsoft Academic Search

We present the first report of radio control of a cyborg beetle in free-flight. The microsystem (Figs. 1,2) consisted of a radio-frequency receiver assembly, a micro battery and a live giant flower beetle platform (Mecynorhina polyphemus or Mecynorhina torquata). The assembly had six electrode stimulators implanted into the left and right optic lobes, brain, posterior pronotum (counter electrode), right and

H. SatoI; Y. Peeri; E. Baghoomian; C. W. Berry; M. M. Maharbiz

2009-01-01

173

Range and movement of resident holdover and hatchery brown trout tagged with radio transmitters in the Farmington River, Connecticut  

USGS Publications Warehouse

The 5.8-km West Branch Farmington River Trout Management Area (TMA) is one of Connecticut's premier catch-and-release fisheries for brown trout Salmo trutta. However, little is known about the behavior of brown trout in this system and to what extent brown trout emigrate from the TMA. The objectives of this study were to determine the movement, range, and emigration of resident holdover and newly stocked brown trout tagged with radio transmitters in the TMA. Transmitters were implanted into 22 first-year (mean total length = 314 mm) and 25 second-year (mean total length = 432 mm) holdover brown trout. Twenty catchable-size (mean total length = 290 mm) brown trout were also implanted with transmitters and released into the TMA. The mean range (distance between the extreme upstream and downstream locations) was greater for second-year holdover brown trout than for first-year holdover brown trout, and it was greater in fall than in winter. The movement (distance moved between successive locations) of holdover brown trout was greater in fall than in winter. Movement of first-year holdover brown trout was significantly related to discharge, water temperature, and the number of days between successive locations. Newly stocked brown trout exhibited the two largest ranges (5.3 and 4.7 km). The range of newly stocked brown trout was not different between seasons, but movement was greater in spring than in summer. Through 16 weeks poststocking, there was no discernable difference in the percentage of stocked brown trout dispersing in a predominantly upstream or downstream direction. Mean dispersal distances from the stocking location were 0.5 and 0.9 km at 2 and 12 weeks poststocking, respectively. Movement of newly stocked brown trout was positively related to discharge and negatively related to water temperature. A known 6% (4 of 67) of the tagged brown trout emigrated from the TMA, but up to 21% (14 of 67) of tagged fish could have left the study area if all missing fish were emigrants. ?? Copyright by the American Fisheries Society 2005.

Popoff, N. D.; Neumann, R. M.

2005-01-01

174

Radio frequency surface conductivity measurement apparatus for small samples  

NASA Astrophysics Data System (ADS)

We have designed and developed an apparatus for the measurement of surface conductivity on small samples of metals and superconductors used in radio frequency cavity applications. Here we present some results of surface conductivity measurements using this setup on small samples of brass and aluminum at nearly 4.06 GHz at room temperature. The measured complex surface conductivity of brass and aluminum at radio frequencies is found to be consistent with the measured values of dc conductivity on the same samples. The temperature range of the instrument will be extended down to 4.2K with the same method of measurement.

Chandra, Jagdish; Manekar, Meghmalhar

2012-06-01

175

SYNCHROTRON RADIO FREQUENCY PHASE CONTROL SYSTEM  

DOEpatents

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)

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

1963-05-01

176

Low frequency radio synthesis imaging of the galactic center region  

NASA Astrophysics Data System (ADS)

The Very Large Array radio interferometer has been equipped with new receivers to allow observations at 330 and 74 MHz, frequencies much lower than were previously possible with this instrument. Though the VLA dishes are not optimal for working at these frequencies, the system is successful and regular observations are now taken at these frequencies. However, new data analysis techniques are required to work at these frequencies. The technique of self- calibration, used to remove small atmospheric effects at higher frequencies, has been adapted to compensate for ionospheric turbulence in much the same way that adaptive optics is used in the optical regime. Faceted imaging techniques are required to compensate for the noncoplanar image distortion that affects the system due to the wide fields of view at these frequencies (~2.3 at 330 MHz and ~11 at 74 MHz). Furthermore, radio frequency interference is a much larger problem at these frequencies than in higher frequencies and novel approaches to its mitigation are required. These new techniques and new system are allowing for imaging of the radio sky at sensitivities and resolutions orders of magnitude higher than were possible with the low frequency systems of decades past. In this work I discuss the advancements in low frequency data techniques required to make high resolution, high sensitivity, large field of view measurements with the new Very Large Array low frequency system and then detail the results of turning this new system and techniques on the center of our Milky Way Galaxy. At 330 MHz I image the Galactic center region with roughly 10 inches resolution and 1.6 mJy beam -1 sensitivity. New Galactic center nonthermal filaments, new pulsar candidates, and the lowest frequency detection to date of the radio source associated with our Galaxy's central massive black hole result. At 74 MHz I image a region of the sky roughly 40 x 6 with, ~10 feet resolution. I use the high opacity of H II regions at 74 MHz to extract three-dimensional data on the distribution of Galactic cosmic ray emissivity, a measurement possible only at low radio frequencies.

Nord, Michael Evans

2005-11-01

177

Preening behavior of adult gyrfalcons tagged with backpack transmitters  

USGS Publications Warehouse

Radio transmitters provide data that enhance understanding of raptor biology (Walls and Kenward 2007) and are now used to answer a multitude of research questions (Meyburg and Fuller 2007). However, transmitters affect the birds that carry them (Barron et al. 2010), and it is important to document and evaluate such effects (Casper 2009). For example, decreased survival has been documented in Prairie Falcons (Falco mexicanus; Steenhof et al. 2006), Northern Goshawks (Accipiter gentilis; Reynolds et al. 2004), and Spotted Owls (Strix occidentalis; Paton et al. 1991) tagged with radio transmitters. However, no such effects were reported for Peregrine Falcons (Falco peregrinus; Fuller et al. 1998, McGrady et al. 2002) and a number of other species (Kenward 2001). White and Garrott (1990) noted that in general, animals tagged with radio transmitters often altered their behaviors for 114 d after release during an adjustment period that included increased preening and grooming frequencies. Although more than 90 Gyrfalcons (Falco rusticolus) have been tagged with radio transmitters (e.g., Burnham 2007, McIntyre et al. 2009, T. Booms unpubl. data), the effects of transmitters on this species are not well documented. Anecdotal information suggests some Gyrfalcons might be negatively affected by radio-tagging (Booms et al. 2008). As part of a study investigating Gyrfalcon breeding biology, we conducted opportunistic, focused observations on two radio-tagged adult female Gyrfalcons and their unmarked mates. We here describe and quantify preening behavior of Gyrfalcons shortly after radio-tagging.

Booms, T. L.; Schempf, P. F.; Fuller, M. R.

2011-01-01

178

Single-electron transistor as a radio-frequency mixer  

NASA Astrophysics Data System (ADS)

We demonstrate the use of the single-electron transistor as a radio-frequency mixer, based on the nonlinear dependence of current on gate charge. This mixer can be used for high-frequency, ultrasensitive charge measurements over a broad and tunable range of frequencies. We demonstrate operation of the mixer, using a lithographically defined thin-film aluminum transistor, in both the superconducting and normal states of aluminum, over frequencies from 10 to 300 MHz. We have operated the device both as a homodyne detector and as a phase-sensitive heterodyne mixer. We demonstrate a charge sensitivity of <4 x10-3 e/RADICAL:[[RADICAND:[Hz

Knobel, R.; Yung, C. S.; Cleland, A. N.

2002-07-01

179

Optical, thermal, and electrical monitoring of radio-frequency tissue modification  

NASA Astrophysics Data System (ADS)

Radio-frequency (rf) tissue fusion involves the sealing of tissue between two electrodes delivering rf currents. Applications include small bowel fusion following anastomosis. The mechanism of adhesion is poorly understood, but one hypothesis is that rf modification is correlated to thermal damage and dehydration. A multimodal monitoring system capable of acquiring tissue temperature, electrical impedance, and optical transmittance at 1325-nm wavelength during rf delivery by a modified Ligasure fusion tool is presented. Measurements carried out on single layers of ex vivo porcine small bowel tissue heated at ~500-kHz frequency are correlated with observation of water evaporation and histological studies on full seals. It is shown that the induced current generates a rapid quasilinear rise of temperature until the boiling point of water, that changes in tissue transmittance occur before impedance control is possible, and that a decrease in transmission occurs at typical denaturation temperatures. Experimental results are compared with a biophysical model for tissue temperature and a rate equation model for thermal damage.

Floume, Timmy; Syms, Richard R. A.; Darzi, Ara W.; Hanna, George B.

2010-01-01

180

Optical, thermal, and electrical monitoring of radio-frequency tissue modification.  

PubMed

Radio-frequency (rf) tissue fusion involves the sealing of tissue between two electrodes delivering rf currents. Applications include small bowel fusion following anastomosis. The mechanism of adhesion is poorly understood, but one hypothesis is that rf modification is correlated to thermal damage and dehydration. A multimodal monitoring system capable of acquiring tissue temperature, electrical impedance, and optical transmittance at 1325-nm wavelength during rf delivery by a modified Ligasure fusion tool is presented. Measurements carried out on single layers of ex vivo porcine small bowel tissue heated at approximately 500-kHz frequency are correlated with observation of water evaporation and histological studies on full seals. It is shown that the induced current generates a rapid quasilinear rise of temperature until the boiling point of water, that changes in tissue transmittance occur before impedance control is possible, and that a decrease in transmission occurs at typical denaturation temperatures. Experimental results are compared with a biophysical model for tissue temperature and a rate equation model for thermal damage. PMID:20210489

Floume, Timmy; Syms, Richard R A; Darzi, Ara W; Hanna, George B

181

Mechanism of low?frequency radio emissions in the heliosphere  

Microsoft Academic Search

We present a model for the generation of Langmuir waves in the outer heliosphere. We further invoke the nonlinear interaction between the Langmuir waves resulting in electromagnetic radiation, at the second harmonic of the plasma frequency, which is able to leave the source region. This model can provide a quantitative explanation of the remote observation of radio emissions at 2-3

Wieslaw M. Macek

1994-01-01

182

Authentication of Radio Frequency Identification Devices Using Electronic Characteristics  

ERIC Educational Resources Information Center

|Radio frequency identification (RFID) tags are low-cost devices that are used to uniquely identify the objects to which they are attached. Due to the low cost and size that is driving the technology, a tag has limited computational capabilities and resources. This limitation makes the implementation of conventional security protocols to prevent

Chinnappa Gounder Periaswamy, Senthilkumar

2010-01-01

183

Energy Saving Glass Lamination via Selective Radio Frequency Heating  

Microsoft Academic Search

Ceralink Inc. developed FastFuse, a rapid, new, energy saving process for lamination of glass and composites using radio frequency (RF) heating technology. The Inventions and Innovations program supported the technical and commercial research and development needed to elevate the innovation from bench scale to a self-supporting technology with significant potential for growth. The attached report provides an overview of the

Shawn M. Allan; Patricia M. Strickland; Holly S. Shulman

2009-01-01

184

Manipulability analysis and design of radio frequency ablation robot  

Microsoft Academic Search

Radio frequency ablation of non-resectable malignant tissue in a patientpsilas liver is a rapidly expanding treatment tool for clinicians, because the operation result is smaller incision, therefore there is significantly reduced tissue trauma and short recovery time. But, the minimally invasive surgery only experienced surgeons can do, and need a long time, which bring maximum burden to surgeons. A possible

Qinjun Du; Xueyi Zhang

2008-01-01

185

Recent Observations of the Very Low Frequency Interplanetary Radio Emission.  

National Technical Information Service (NTIS)

Observations of radio emissions in the frequency range of 2 to 3 kHz have been made in the distant heliosphere by the Voyager 1 and 2 plasma wave instruments. Based primarily on wideband observations made periodically throughout the cruise phases of the m...

W. S. Kurth D. A. Gurnett F. L. Scarf

1986-01-01

186

Radio-frequency energy in fusion power generation  

SciTech Connect

The history of radio-frequency (rf) energy in fusion experiments is reviewed, and the status of current efforts is described. Potential applications to tasks other than plasma heating are described, as are the research and development needs of rf energy technology.

Lawson, J.Q.; Becraft, W.R.; Hoffman, D.J.

1983-01-01

187

RADIO FREQUENCY ELECTRIC FIELDS PROCESSING OF ORANGE JUICE  

Technology Transfer Automated Retrieval System (TEKTRAN)

The nonthermal process of radio frequency electric fields (RFEF) has been shown to inactivate bacteria in apple juice at moderately low temperatures, but has yet to be extended to inactivate bacteria in orange juice. An 80 kW RFEF pasteurizer was used to process pulp-free orange juice at flow rates ...

188

MICROWAVE AND RADIO FREQUENCY POWER APPLICATIONS IN AGRICULTURE  

Technology Transfer Automated Retrieval System (TEKTRAN)

The potential for agricultural applications of radio-frequency (RF) energy for the solution of various problems in agricultural production, crop handling and storage, and product preservation and conditioning has been considered for many years. With the development of economical microwave power equ...

189

Measurement of Radio-Frequency Impedance with Networks Simulating Lines  

Microsoft Academic Search

The complex value of an impedance may be measured at radio frequencies by measuring voltage ratios on a transmission line terminated in the unknown impedance. The line may often be replaced advantageously by an equivalent network. Several new methods of carrying out the measurement have been developed and a study of the factors affecting the accuracy and the technique of

W. L. Barrow

1935-01-01

190

Radio Frequency (RF) Measurements for Human Detection, Tracking, and Identification.  

National Technical Information Service (NTIS)

This report describes a protocol that is to be used during radio frequency measurements of humans. The purpose of the experiment is to measure the unique radar signature of walking humans so that methods of detecting and classifying dismounts can be devel...

T. J. Pizzillo

2007-01-01

191

Global Measurements of Low-Frequency Radio Noise.  

National Technical Information Service (NTIS)

We report illustrative results obtained by Stanford University's global survey of ELF/VLF radio noise (frequencies in the range 10 Hz - 32 kHz). Particular comparison is made between the noise measurements made at high (polar) latitudes with those at lowe...

A. Bernardi A. C. Fraser-Smith M. E. Ladd P. R. McGill R. A. Helliwell

1992-01-01

192

Radio Frequency Probing Apparatus for Surface Acoustic Wave Devices.  

National Technical Information Service (NTIS)

Wafer probing apparatus especially adapted to probing surface acoustic wave (SAW) device die such as delay lines is disclosed: the apparatus includes a probe card especially suited to the radio frequency and multiple output nature of a SAW delay line toge...

F. Y. Cho M. Adamo D. E. Le Son

1984-01-01

193

Radio frequency probing apparatus for surface acoustic wave devices  

NASA Astrophysics Data System (ADS)

Wafer probing apparatus especially adapted to probing surface acoustic wave (SAW) device die such as delay lines is disclosed: the apparatus includes a probe card especially suited to the radio frequency and multiple output nature of a SAW delay line together with a computer-aided electronic system for exciting the delay line and evaluating its output.

Cho, F.; Adamo, M. D.; Leson, D. E.

1984-05-01

194

29. View of typical radio frequency monitor group electronic tubetype ...  

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

29. View of typical radio frequency monitor group electronic tube-type cabinet. System is water-cooled with antenna assist. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

195

Self-consistent simulations of multipacting in superconducting radio frequencies  

Microsoft Academic Search

Multipacting continues to be an important issue in Superconducting Radio Frequency (SRF) cavities, particularly near waveguide couplers. Most modern simulations of multipacting are not self-consistent, using the fields from a purely electromagnetic simulation to drive the motion of multipacting electrons. This approach works well for the onset on multipacting but as the electron density increases in the cavity it can

C. Nieter; S. Ovtchinnikov; D. N. Smithe; P. H. Stoltz; P. J. Mullowney

2007-01-01

196

Thin film processing by radio frequency hollow cathodes  

Microsoft Academic Search

The main features of the radio frequency (RF) hollow cathodes for thin film processing are summarized. The utilization of cylindrical RF hollow cathodes in both the plasma-enhanced chemical vapour deposition (PECVD) and the physical vapour deposition (PVD) of films is reviewed. An example of the high rate PECVD of SiN films is described in more detail. Gas metastables excited inside

L. Brdo; H. Barnkov; S. Berg

1997-01-01

197

Celestial Reference Frame Realizations at Multiple Radio Frequency Bands  

NASA Astrophysics Data System (ADS)

The International Celestial Reference Frame (ICRF) was adopted by the IAU in 1997 based on VLBI measurements at S/X - band (2.3/8.4 GHz) and complemented by HIPPARC OS measurements at optical frequencies. At that time, the IAU encouraged the astrometric community to extend the ICRF to additional frequency bands. In response, VLBI measurements have been made at 24, 32, and 43 GHz. Meanwhile, the 8.4 GHz work has been greatly improved with the release of the ICRF - 2 in 2009. This paper will discuss the programmatic and scientific motivations for extending the ICRF to these higher radio bands. Results to date will be summarized including evidence that these new high frequency frames are rapidly approaching the accuracy of the 8.4 GHz ICRF - 2. We will discuss the current limiting errors and prospects for the future accuracy of radio reference frames. In particular, we will discuss using multiple radio frames to characterize t he frequency dependent systematic noise floor from extended source morphology and core shift. Finally, given the potential of the Gaia optical mission for state - of - the - art astrometry, we will discuss simulations which show the potential for a radio - optical frame tie at the 10 - 15 ?as level of precision (1 - sigma). The research described in this paper was done under contract with NASA. Government sponsorship acknowledged. 2012 California Institute of Technology.

Jacobs, Chris

2012-08-01

198

Radio frequency and infrared drying of sized textile warp yarns  

SciTech Connect

Drying sized textile warp yarns without contacting the warp is easily accomplished by either radio frequency or infrared techniques. Although the process is more expensive than conventional drying, the substantial savings accrued during subsequent weaving and finishing of the cloth can help keep the US textile industry competitive and support electrical load. 5 refs., 8 figs., 14 tabs.

Ruddick, H.G. (West Point Foundry and Machine Co., GA (USA))

1990-11-01

199

Impact of Proposed Radio Frequency Radiation Standards on Military Operations.  

National Technical Information Service (NTIS)

Research conducted in the past few years provides a better understanding of the way radio-frequency radiation (RFR) is absorbed and distributed in living systems. This has led to general agreement on a common denominator for assessing biological effects o...

J. C. Mitchell C. H. Durney A. W. Guy N. J. Roberts J. H. Krupp

1985-01-01

200

A primer on radio frequency identification for libraries  

Microsoft Academic Search

Purpose Radio Frequency Identification (RFID) is a location determination technology that has been receiving a lot of commercial attention in recent times, especially in the areas of asset tracking and supply chain management. The purpose of this paper is to outline a library prototype that utilises RFID in order to enhance and speed up the current customer book search

Kevin Curran; Martin Porter

2007-01-01

201

Radio-Frequency Technology Division: Programs, Activities, and Accomplishments, 2001.  

National Technical Information Service (NTIS)

The Radio-Frequency Technology Division is a critical national resource for a wide range of customers. U.S. industry is the primary customer both for the Division's measurement services and for technical support on the test and measurement methodology nec...

2002-01-01

202

Method of making radio frequency ion source antenna  

Microsoft Academic Search

In the method, the radio frequency (RF) antenna is made by providing a clean coil made of copper tubing or other metal conductor, which is coated with a tacky organic binder, and then with a powdered glass frit, as by sprinkling the frit uniformly over the binder. The coil is then heated internally in an inert gas atmosphere, preferably by

Kenneth W. Ehlers; Ka-Ngo Leung

1988-01-01

203

RADIO FREQUENCY VACUUM DRYING OF WOOD. II. EXPERIMENTAL MODEL EVALUATION  

Microsoft Academic Search

Thick specimens of two softwoods were dried in a laboratory radio frequency\\/vacuum (RF\\/V) dryer to investigate the evolution of internal moisture flow patterns. The total average moisture content and local temperatures and pressures were monitored as a function of time. A number of runs were carried out for different conditions of voltage, power density, ambient pressure, core temperature, and initial

Anastasios Koumoutsakos; Stavros Avramidis; Savvas G. Hatzikiriakos

2001-01-01

204

Predicting Thermal Efficiency in Timber Radio Frequency Vacuum Drying  

Microsoft Academic Search

In this work, the efficiency of transforming dielectric energy into evaporated water is analyzed for the case of timber radio frequency vacuum drying. Based on well-known heat and mass transfer equations, a simplified mathematical model is proposed that estimates the drying efficacy in regards to the thermo-physical properties of wood. Although not exact, the theoretical results are close to the

Diego Elustondo; Stavros Avramidis; Satoshi Shida

2004-01-01

205

Towards Optimization of Probe Placement for Radio-Frequency Ablation  

Microsoft Academic Search

We present a model for the optimal placement of mono- and bipolar probes in radio-frequency (RF) ablation. The model is based on a numerical computation of the probe's electric potential and of the steady state of the heat distribution during RF ablation. The optimization is performed by minimizing a temperature based objective functional under these constraining equations. The paper discusses

Inga Altrogge; Tim Krger; Tobias Preusser; Christof Bskens; Philippe L. Pereira; Diethard Schmidt; Andreas Weihusen; Heinz-otto Peitgen

2006-01-01

206

Operating a radio-frequency plasma source on water vapor  

Microsoft Academic Search

A magnetically enhanced radio-frequency (rf) plasma source operating on water vapor has an extensive list of potential applications. In this work, the use of a rf plasma source to dissociate water vapor for hydrogen production is investigated. This paper describes a rf plasma source operated on water vapor and characterizes its plasma properties using a Langmuir probe, a residual gas

Sonca V. T. Nguyen; John E. Foster; Alec D. Gallimore

2009-01-01

207

Advances in radio frequency and ohmic heating of meats  

Microsoft Academic Search

Interest in both radio frequency (RF) and ohmic heating of foods has increased in recent years. In particular, their application to meat products has been investigated. A critical factor is the dielectric constants of the products being heated. These have been measured for meats. In particular, the dielectric constant ??, dielectric loss factor ??, thermal heat capacity cp, thermal conductivity

B. M. McKenna; J. Lyng; N. Brunton; N. Shirsat

2006-01-01

208

New observations of the Geminga pulsar at low radio frequencies  

NASA Astrophysics Data System (ADS)

New evidence for the detection of Geminga at three low frequencies is presented. The observations were carried out on two sensitive transit radio telescopes in the range 42-112 MHz. We used three new digital receivers to detect the pulses and to obtain dynamic spectra. The exact value of the dispersion measure has been calculated.

Malofeev, V. M.; Malov, O. I.; Logvinenko, S. V.; Teplykh, D. A.

2013-03-01

209

Radio frequency interstitial thermal ablation of metastatic liver tumours  

Microsoft Academic Search

Introduction: Radio frequency thermal ablation (RFA) of focal liver metastatic lesions has received much recent attention as minimally invasive treatment of such pathologic entities. The purpose of the study was to evaluate the efficacy of RFA in the treatment of liver metastases from different tumors.Methods: In the period October 1998January 2001, 29 patients affected by 38 focal lesions, age range

Piero Rossi; Francesco M. Danza; V. M. Stolfi; N. Di Lorenzo; Giorgio Coscarella; A. Manzelli; A. Arturi; F. De Lisa; L. A. Prisco; Enrico Bock; A. L. Gaspari

2001-01-01

210

Achieving privacy and security in radio frequency identification  

Microsoft Academic Search

Radio Frequency Identification RFID systems are gaining popularity in a wide variety of applications like asset tracking, personnel identification, and sensor net- works. However, unique security and privacy issues arise in these systems because (a) low computation capabilities of RFID tags prevent the use of complicated cryptographic pro- tocols, and (b) wide deployment of tags opens up room for illegal

Aaditeshwar Seth; Mirza Beg

2006-01-01

211

Radio Frequency Electrical Transduction of Graphene Mechanical Resonators  

Microsoft Academic Search

We report radio frequency (RF) electrical readout of graphene mechanical resonators. The mechanical motion is actuated and detected directly by using a vector network analyzer (VNA), employing a local gate to minimize parasitic capacitance. Resist-free doubly-clamped samples with resonant frequency in MHz range, Q factor 10,000 at 77 K and signal-to-background ratio of over 20 dB, are demonstrated. In addition

Changyao Chen; Vikram Deshpande; Yuehang Xu; Frank Direnno; Alexander Gondarenko; David Heinz; Shuaimin Liu; Philip Kim; James Hone

2011-01-01

212

Radio frequency electrical transduction of graphene mechanical resonators  

Microsoft Academic Search

We report radio frequency (rf) electrical readout of graphene mechanical resonators. The mechanical motion is actuated and detected directly by using a vector network analyzer, employing a local gate to minimize parasitic capacitance. A resist-free doubly clamped sample with resonant frequency ~34 MHz, quality factor ~10 000 at 77 K, and signal-to-background ratio of over 20 dB is demonstrated. In

Yuehang Xu; Changyao Chen; Vikram V. Deshpande; Frank A. Direnno; Alexander Gondarenko; David B. Heinz; Shuaimin Liu; Philip Kim; James Hone

2010-01-01

213

Low level radio frequency control system for the european XFEL  

Microsoft Academic Search

The low-level radio frequency system (LLRF) for the superconducting cavities of the European X-FEL must provide exceptional stability of the accelerating RF field amplitude (0.01%) and phase (0.01 degrees) at a frequency of 1.3 GHz. These requirements must be achieved in pulsed operation mode with one klystron driving 32 cavities. It is thus necessary to design and build a modern

T. Jezynski; S. Simrock

2006-01-01

214

Time Flies! Radio Signals Used for Time and Frequency Measurements  

Microsoft Academic Search

The widespread use of the Global Positioning System (GPS) as a time and frequency measurement reference was discussed in the July-September 2001 issue of Cal Lab. This article describes other radio signals that serve as alternatives or backups to GPS. It describes signals used to calibrate and control frequency standards, and signals that synchronize time-of-day clocks in products including wristwatches,

Michael A. Lombardi NIST

215

Modulation of radio frequency signals by ULF waves  

Microsoft Academic Search

The ionospheric plasma is continually perturbed by ultra-low frequency (ULF; 1-100 mHz) plasma waves that are incident from the magnetosphere. In this paper we present a combined experimental and modeling study of the variation in radio frequency of signals propagating in the ionosphere due to the interaction of ULF wave energy with the ionospheric plasma. Modeling the interaction shows that

C. L. Waters; T. K. Yeoman; M. D. Sciffer; P. Ponomarenko; D. M. Wright

2007-01-01

216

Stabilization of magnetohydrodynamic modes by applied radio-frequency waves  

Microsoft Academic Search

A kinetic theory describing the nonlinear interaction of radio-frequency waves with low-frequency magnetohydrodynamic modes is presented. The calculation of the nonlinear force density on a fluid element includes both ponderomotive and sideband mode coupling terms and allows arbitrary rf wave polarization. Electromagnetic effects and wave--particle interactions are retained in the analysis. The influence of the nonlinear force on magnetohydrodynamic plasma

D. A. D'Ippolito; J. R. Myra

1986-01-01

217

Stabilization of magnetohydrodynamic modes by applied radio-frequency waves  

Microsoft Academic Search

A kinetic theory describing the nonlinear interaction of radio-frequency waves with low-frequency magnetohydrodynamic modes is presented. The calculation of the nonlinear force density on a fluid element includes both ponderomotive and sideband mode coupling terms and allows arbitrary rf wave polarization. Electromagnetic effects and waveparticle interactions are retained in the analysis. The influence of the nonlinear force on magnetohydrodynamic plasma

D. A. DIppolito; J. R. Myra

1986-01-01

218

New Observations of Geminga at Three Low Radio Frequencies  

NASA Astrophysics Data System (ADS)

In this report we present new evidence for the detection of Geminga at three low frequencies. The observations were carried out on two sensitive transit radio telescopes in the range 42-112 MHz. We used three new digital receivers to detect the pulses and to obtain dynamic spectra.The examples of mean pulse profiles and individual pulses are presented. Exact value of the dispersion measure have been calculated using the simultaneous observations at three frequencies.

Malofeev, V. M.; Malov, O. I.; Logvinenko, S. V.; Teplykh, D. A.

2012-12-01

219

Analysis of the Efficiency Improvement of a Directly-Driven Antenna- Based AM Transmitter.  

National Technical Information Service (NTIS)

The operation of a traditional radio transmitter is limited by the frequency range over which the antenna input impedance can be conjugately matched to the power amplifier output impedance. This limitation is particularly strong when an electrically-small...

O. O. Olaode W. D. Palmer W. T. Joines

2009-01-01

220

Design of a fiber-optic transmitter for microwave analog transmission with high phase stability  

NASA Astrophysics Data System (ADS)

The principal considerations in the design of fiber-optic transmitters for highly phase-stable radio frequency and microwave analog transmission are discussed. Criteria for a fiber-optic transmitter design with improved amplitude and phase-noise performance are developed through consideration of factors affecting the phase noise, including low-frequency laser-bias supply noise, the magnitude and proximity of external reflections into the laser, and temperature excursions of the laser-transmitter package.

Logan, R. T., Jr.; Lutes, G. F.; Primas, L. E.; Maleki, L.

1990-08-01

221

A 44GHz 8-element phased-array SiGe HBT transmitter RFIC with an injection-locked quadrature frequency multiplier  

Microsoft Academic Search

An 8-element 44-GHz phased-array direct up-conversion transmitter, based on a localized injection-locked quadrature oscillator, is fabricated in a SiGe HBT process. The transmitter includes an improved injection-locked quadrature frequency doubler, an LO active phase shifter, I\\/Q mixers, and an RF PA driver. The transmitter has approximately 20-dB conversion gain per element, continuous 360 phase-shift and a baseband I\\/Q bandwidth of

Sunghwan Kim; P. S. Gudem; Lawrence E. Larson

2010-01-01

222

Radio-Frequency Magnetometry Using a Single Electron Spin  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate a simple and robust protocol for the detection of weak radio-frequency magnetic fields using a single electron spin in diamond. Our method relies on spin locking, where the Rabi frequency of the spin is adjusted to match the MHz signal frequency. In a proof-of-principle experiment we detect a 7.5 MHz magnetic probe field of 40nT amplitude with <10kHz spectral resolution. Rotating-frame magnetometry may provide a direct and sensitive route to high-resolution spectroscopy of nanoscale nuclear spin signals.

Loretz, M.; Rosskopf, T.; Degen, C. L.

2013-01-01

223

TOPICAL REVIEW: Radio-frequency amplifiers based on dc SQUIDs  

NASA Astrophysics Data System (ADS)

SQUIDs are an attractive candidate for the amplification of low-level rf and microwave signals. Compared to semiconductor amplifiers, they offer lower noise and much lower power dissipation. Especially at frequencies below 1 GHz, the improvement in noise temperature compared to the best cold semiconductor amplifiers can be as high as 50; noise temperatures only slightly above the quantum limit have been achieved in this frequency range. This article will review the current status of radio-frequency amplifiers based on dc SQUIDs and provide detailed discussions of amplifier noise temperature, input and output impedance, and nonlinearities.

Mck, Michael; McDermott, Robert

2010-09-01

224

A simple, tunable, and highly sensitive radio-frequency sensor  

NASA Astrophysics Data System (ADS)

We report a radio frequency (RF) sensor that exploits tunable attenuators and phase shifters to achieve high-sensitivity and broad band frequency tunability. Three frequency bands are combined to enable sensor operations from ~20 MHz to ~38 GHz. The effective quality factor (Qeff) of the sensor is as high as ~3.8 106 with 200 ?l of water samples. We also demonstrate the measurement of 2-proponal-water-solution permittivity at 0.01 mole concentration level from ~1 GHz to ~10 GHz. Methanol-water solution and de-ionized water are used to calibrate the RF sensor for the quantitative measurements.

Cui, Yan; Sun, Jiwei; He, Yuxi; Wang, Zheng; Wang, Pingshan

2013-08-01

225

Intercontinental Frequency Comparison by Very Low-Frequency Radio Transmission  

Microsoft Academic Search

Studies of signals from Rugby, England, at 16 kc and 60 kc have given evidence that a single source of standard frequency can be made available at vlf on a world-wide basis. At a distance of 5200 km the Doppler effects in transmission seldom exceed 3 parts in 109, and a measurement can be made to 1 part in 109

John Pierce

1957-01-01

226

47 CFR 73.759 - Auxiliary transmitters.  

Code of Federal Regulations, 2012 CFR

...FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES International Broadcast Stations...of regular programs during maintenance or modification work on the main transmitter, necessitating...

2012-10-01

227

47 CFR 73.759 - Auxiliary transmitters.  

Code of Federal Regulations, 2011 CFR

...FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES International Broadcast Stations...of regular programs during maintenance or modification work on the main transmitter, necessitating...

2011-10-01

228

Adaptive transmission protocols for frequency-hop radio networks  

Microsoft Academic Search

ABSTRACT The focus,of this paper,is on,the,performance,of an adaptive,transmission,protocol,for,frequency-hop,(FH) radio,networks,in which,the,radios,can,adjust,the power in the transmitted,signal,and,the rate of a Reed-Solomon code,io respond,to variations,in partial-band,interfer- ence,and,propagation,loss. The adaptation,is based,on side information,from the FH receiveT and on informa- tion,derived,from,the,decoder.,The results,presented,in this paper,am,obtained,from,a simulation,of a wireless FH radio,network,in,which,the,characteristics,of the links are time-varying. These results demonstrate,that the adaptive,transmission,protocol,can,improve,the qual- ity of a link by adapting,to variations,in

J. Gass; M. Pursley; H. Russell; R. Saulitis; C Wilkins; J. Wysocarski

1998-01-01

229

Population density effect on radio frequencies interference (RFI) in radio astronomy  

NASA Astrophysics Data System (ADS)

Radio astronomical observation is infected by wide range of Radio Frequency Interference (RFI). We will also use information gathered from on-site RFI level measurements on selected 'good' areas generated by this study. After investigating a few suitable sites we will commence to the site and construct the RFI observation. Eventually, the best area we will be deciding from the observations soon. The result of this experiment will support our planning to build the first radio telescope in Malaysia. Radio observatories normally are located in remote area, in order to combat RFI from active spectrum users and radio noise produced in industrial or residential areas. The other solution for this problem is regulating the use of radio frequencies in the country (spectrum management). Measurement of RFI level on potential radio astronomical site can be done to measure the RFI levels at sites. Seven sites are chosen divide by three group, which is A, B and C. In this paper, we report the initial testing RFI survey for overall spectrum (0-2GHz) for those sites. The averaged RFI level above noise level at the three group sites are 19.0 (+/-1.79) dBm, 19.5 (+/-3.71) dBm and 17.0 (+/-3.71) dBm and the averaged RFI level above noise level for without main peaks are 20.1 (+/-1.77) dBm, 19.6 (+/-3.65) dBm and 17.2 (+/-1.43) dBm respectively.

Umar, Roslan; Abidin, Zamri Zainal; Ibrahim, Zainol Abidin; Hassan, Mohd Saiful Rizal; Rosli, Zulfazli; Hamidi, Zety Shahrizat

2012-06-01

230

Hidden Mine Shaft Detection With Remote Radio Transmitter Electromagnetics and Self- Potential Method  

NASA Astrophysics Data System (ADS)

Abandoned near subsurface mining constructions from the 19th and early 20th century in urbanized areas placed upon former ore mines near the city of Aachen (Germany), and in many other regions of the world, provide hazardous risks concerning possible collapses. In many cases, the exact locations of such constructions are not known anymore. For instance, to map covered shafts of one meter diameter on large survey areas, high resolution methods with rapid measurement progress are necessary. Enhanced developments of the traditional Very Low Frequency (VLF) technique such as VLF-gradient and Radiomagnetotellurics (RMT) fulfill these requirements. Continuous ground-contactless VLF-gradient survey quickly provides maps indicating the lateral electric resistivity heterogeneity distribution. Inversions of RMT data provide 2D-resistivity-depth sections and also the interpretation of Self-Potential data gives information about the nature of the VLF-gradient anomalies. The successful combination of the three methods for detecting mineshafts is presented for both an electromagnetic undisturbed and noisy location.

Bosch, F. P.; Gurk, M.

2008-12-01

231

Surveying abandoned mine shafts with Remote Radio Transmitter EM methods and Selfpotential  

NASA Astrophysics Data System (ADS)

Abandoned near subsurface mining constructions from the 19th and early 20th century in urbanized areas placed upon former ore mines near the city of Aachen (Germany), as well as in many other regions of the world, provide hazardous risks concerning possible collapses. In many cases, the exact locations of such constructions are not known anymore. For instance, to map covered shafts of one meter diameter on large survey areas, high resolution methods with rapid measurement progress are necessary. Enhanced developments of the traditional Very Low Frequency (VLF) technique such as VLF-gradient and Radiomagnetotellurics (RMT) fulfill these requirements. Continuous ground-contactless VLF-gradient survey quickly provides maps indicating the lateral electric resistivity heterogeneity distribution. Inversions of RMT data provide 2D-resistivity-depth sections and also the interpretation of Self-Potential data gives information about the nature of the VLF-gradient anomalies. The successful combination of the three methods for detecting mineshafts near to the city if Aachen is presented for both an electromagnetic undisturbed and noisy location.

Bosch, F. P.; Gurk, M.

2009-04-01

232

Analysis and Identification of Wiener-Hammerstein System in Frequency Domain Using Two-Tone Measurements for Nonlinear RF Transmitters  

Microsoft Academic Search

This paper presents analysis and identification method of Wiener-Hammerstein system to characterize a nonlinear RF transmitter in fundamental frequency zone. A two-tone signal is used to analyze and identify a Wiener-Hammerstein model. A RF signal is converted to basebandequivalent complex signal, and Wiener-Hammerstein model is considered to have a baseband equivalent complex polynomial and linear filters. For a two-tone input

Hyunchul Ku

2008-01-01

233

An Integrated SiGe-BiCMOS Low Noise Transmitter Chip with a Frequency Divider Chain for 77 GHz Applications  

Microsoft Academic Search

This paper presents a low noise transmitter chip for a 77 GHz FMCW radar system being comprised of push-pull voltage controlled oscillator with an output buffer, a frequency divider chain and a peak-to-peak detector. The measurements show an output power of approximately 11 dBm at each of the two differential 50 Omega loads over a wide tuning range. The measured

Akbar Ghazinour; P. Wennekers; Ralf Reuter; Yin Yi; Hao Li; T. Bohm; D. Jahn

2006-01-01

234

Dowsing can be interfered with by radio frequency radiation.  

PubMed

The soil radiation, watercourses and ores have been located for centuries by sensitive persons, dowsers. An ideomotoric explanation of the dowsing reaction, with no physical interaction, has been accepted. Our present re-analyses of some such results have shown, that there could be a physical phenomenon connecting the human reactions in field experiments, where the test subjects walked or were sitting in a slow-moving car, with the windows covered, and a dowsing rod in their hands was recorded. The correlations between the reaction points by test subjects in the moving car and the points by walking along the same path were highly significant. The correlation was not seen in all test locations. The distance between the test location and the radio tower, and the incidence angle of the transmitted radio wave, possibly had an effect on results. We hypothesize that the experiments carried out in the 20th century were interfered with by man-made radio frequency radiation, mainly FM radio and TV broadcasting, as test subjects' bodies absorbed the radio waves and unconscious hand movement reactions took place following the standing waves or intensity variations due to multipath propagation. PMID:22365422

Huttunen, Paavo; Niinimaa, Ahti; Myllyl, Risto

2012-02-23

235

Imaging interplanetary CMEs at radio frequency from solar polar orbit  

NASA Astrophysics Data System (ADS)

Coronal mass ejections (CMEs) represent a great concentration of mass and energy input into the lower corona. They have come to be recognized as the major driver of physical conditions change in the Sun-Earth system. Consequently, observations of CMEs are important for understanding and ultimately predicting space weather conditions. This paper discusses a proposed mission, the Solar Polar Orbit Radio Telescope (SPORT) mission, which will observe the propagation of interplanetary CMEs to distances of near 0.35 AU from the Sun. The orbit of SPORT is an elliptical solar polar orbit. The inclination angle between the orbit and ecliptic plane should be about 90. The main payload on board SPORT will be an imaging radiometer working at the meter wavelength band (radio telescope), which can follow the propagation of interplanetary CMEs. The images that are obtained by the radio telescope embody the brightness temperature of the objectives. Due to the very large size required for the antenna aperture of the radio telescope, we adopt interferometric imaging technology to reduce it. Interferometric imaging technology is based on indirect spatial frequency domain measurements plus Fourier transformation. The SPORT spacecraft will also be equipped with a set of optical and in situ measurement instruments such as a EUV solar telescope, a solar wind ion instrument, an energetic particle detector, a magnetometer, a wave detector and a solar radio burst spectrometer.

Wu, Ji; Sun, Weiying; Zheng, Jianhua; Zhang, Cheng; Liu, Hao; Yan, Jingye; Wang, Chi; Wang, Chuanbing; Wang, Shui

2011-09-01

236

Remote Sensing: Radio Frequency Detection for High School Physics Students  

NASA Astrophysics Data System (ADS)

In an effort to give high school students experience in real world science applications, we have partnered with Loranger High School in Loranger, LA to mentor 9 senior physics students in radio frequency electromagnetic detection. The effort consists of two projects: Mapping of 60 Hz noise around the Laser Interferometer Gravitational Wave Observatory (LIGO), and the construction of a 20 MHz radio telescope for observations of the Sun and Jupiter (Radio Jove, NASA). The results of the LIGO mapping will aid in strategies to reduce the 60 Hz line noise in the LIGO noise spectrum. The Radio Jove project will introduce students to the field of radio astronomy and give them better insight into the dynamic nature of large solar system objects. Both groups will work together in the early stages as they learn the basics of electromagnetic transmission and detection. The groups will document and report their progress regularly. The students will work under the supervision of three undergraduate mentors. Our program is designed to give them theoretical and practical knowledge in radiation and electronics. The students will learn how to design and test receiver in the lab and field settings.

Huggett, Daniel; Jeandron, Michael; Maddox, Larry; Yoshida, Sanichiro

2011-10-01

237

Analysis and Identification of Wiener-Hammerstein System in Frequency Domain Using Two-Tone Measurements for Nonlinear RF Transmitters  

NASA Astrophysics Data System (ADS)

This paper presents analysis and identification method of Wiener-Hammerstein system to characterize a nonlinear RF transmitter in fundamental frequency zone. A two-tone signal is used to analyze and identify a Wiener-Hammerstein model. A RF signal is converted to basebandequivalent complex signal, and Wiener-Hammerstein model is considered to have a baseband equivalent complex polynomial and linear filters. For a two-tone input signal, closed form descriptions of the output signal in the time domain and frequency domain are developed using a newly suggested nonlinearly modulated two-tone phasors (NMTP). The relationship between frequency terms of input and output signals in RF transmitters are represented with linear matrix-vector equation based on NMTP analysis. An advantage of the proposed method is its simplicity using closed form analysis and linear approximation. In addition, we can model a wideband system with relatively narrowband measurements by sweeping two-tone signal. The prediction of spectral regrowth and the predistortion performance for WiBro 1FA signal demonstrate the validity of the proposed approach in identifying the nonlinear RF transmitters.

Ku, Hyunchul

238

78 FR 49529 - Radio Frequency Wireless Technology in Medical Devices; Guidance for Industry and Food and Drug...  

Federal Register 2010, 2011, 2012, 2013

...2006D-0504) Radio Frequency Wireless Technology in Medical Devices; Guidance...entitled ``Radio Frequency Wireless Technology in Medical Devices; Guidance...of radio frequency (RF) wireless technology in medical devices....

2013-08-14

239

Adaptive filters revisited: Radio frequency interference mitigation in pulsar observations  

NASA Astrophysics Data System (ADS)

Pulsar detection and timing experiments are applications where adaptive filters seem eminently suitable tools for radio frequency interference (RFI) mitigation. We describe a novel variant which works well in field trials of pulsar observations centered on an observing frequency of 675 MHz and a bandwidth of 64 MHz and with 2-bit sampling. Adaptive filters have generally received bad press for RFI mitigation in radio astronomical observations with their most serious drawback being a spectral echo of the RFI embedded in the filtered signals. Pulsar observations are intrinsically less sensitive to this as they operate in the (pulsar period) time domain. The field trials have allowed us to identify those issues which limit the effectiveness of the adaptive filter. We conclude that adaptive filters can significantly improve pulsar observations in the presence of RFI.

Kesteven, M.; Hobbs, G.; Clement, R.; Dawson, B.; Manchester, R.; Uppal, T.

2005-05-01

240

Final report: In situ radio frequency heating demonstration  

SciTech Connect

A field demonstration of in situ radio frequency heating was performed at the Savannah River Site (SRS) as part of the US Department of Energy-Office of Technology Development`s Integrated Demonstration. The objective of the demonstration was to investigate the effectiveness of in situ radio frequency (RF) heating as an enhancement to vacuum extraction of residual solvents (primarily trichloroethylene and perchloroethylene) held in vadose zone clay deposits. Conventional soil vacuum extraction techniques are mass transfer limited because of the low permeabilities of the clays. By selectively heating the clays to temperatures at or above 100{degrees}C, the release or transport of the solvent vapors will be enhanced as a result of several factors including an increase in the contaminant vapor pressure and diffusivity and an increase in the effective permeability of the formation with the release of water vapor.

Jarosch, T.R.; Beleski, R.J.; Faust, D.

1994-01-05

241

Momentum Resolved Radio Frequency Spectroscopy in Trapped Fermi Gases  

SciTech Connect

We address recent momentum-resolved radio frequency (rf) spectroscopy experiments, showing how they yield more stringent tests than other comparisons with theory, associated with the ultracold Fermi gases. We demonstrate that, by providing a clear dispersion signature of pairing, they remove the ambiguity plaguing the interpretation of previous rf experiments. Our calculated spectral intensities are in semiquantitative agreement with the data. Even in the presence of a trap, the spectra are predicted to exhibit two BCS-like branches.

Chen Qijin [Zhejiang Institute of Modern Physics and Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027 (China); James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States); Levin, K. [James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States)

2009-05-15

242

Smart Switch Metamaterials for Multiband Radio Frequency Antennas  

Microsoft Academic Search

We investigate metalmatrix composite metamaterials with embedded electrical switches made of shape memory nickeltitanium (NiTi) for use in broadband radio frequency (RF) antennas. Experiments show that a NiTi ribbon can form an electrical contact that opens and closes depending on the NiTi phase being austenite or martensite. Finite element modeling of thermal gradients illustrates the phase change within the ribbon.

Paul J. Wolcott; Christopher D. Hopkins; Lanlin Zhang; Marcelo J. Dapino

2011-01-01

243

Longitudinal capture in the radio-frequency-quadrupole structure  

SciTech Connect

The radio-frequency-quadrupole (RFQ) linac structure not only can attain easily transverse focusing in the low-beta region, but also can obtain very high capture efficiency because of its low beta-lambda and low-particle rigidity. An optimization study of the zero space-charge longitudinal capture in an RFQ linac that yields configurations with large capture efficiency is described.

Inagaki, S.

1980-03-01

244

Radio frequency perforation of cardiac tissue: Modelling and experimental results  

Microsoft Academic Search

Radio frequency (RF) current delivered through a thin catheter can be used to perforate the pulmonary valve or the atrial\\u000a septum to treat pulmonary atresia in newborns. To understand better the mechanisms of RF perforation, a numerical model is\\u000a developed, and experiments are performed in isolated canine cardiac tissue. The model consists of a cylindrical domain with\\u000a a tissue layer

N. Shimko; P. Savard; K. Shah

2000-01-01

245

Radio frequency quadrupole linac for the superconducting super Collider  

Microsoft Academic Search

A 2.5 MeV, 428 MHz radio frequency quadrupole (RFQ) linac has been designed and fabricated by the Los Alamos National Laboratory and GAR Electroforming for the Superconducting Super Collider Laboratory. This device is a two segment accelerator fabricated from tellurium-copper (CDA14500) vane\\/cavity quadrants which are joined by electroforming. The structure incorporates an integral vacuum jacket and has no longitudinal rf

D. L. Schrage; L. M. Young; W. L. Clark; J. H. Billen; R. F. Depaula; A. C. Naranjo; G. H. Neuschaefer; P. L. Roybal; J. E. Stovall; K. Ray; R. Richter

1993-01-01

246

Interconnect Parasitic Extraction Tool for Radio-Frequency Integrated Circuits  

Microsoft Academic Search

\\u000a A tool to model interconnect parasitics in radio-frequency (RF) integrated circuits (RFICs) is presented. Accurate modeling\\u000a is achieved by combining a detailed RLC wire model together with a distributed RC substrate model. Wire geometry is fractured\\u000a to ensure accurate modeling of wave propagation as well as displacement current due to substrate losses. The wire model includes\\u000a resistance and coupled capacitance

Jrme Lescot; Franois J. R. Clment

2003-01-01

247

Particle simulations of radio-frequency glow discharges  

Microsoft Academic Search

Particle-in-cell (PIC) simulations are used to study the structure of radio-frequency (RF) glow discharges in helium between parallel-plate electrodes. The authors have examined a range of conditions and report on a variety of observed phenomena. Comparisons to experiment and analytical models are made, when possible. The differences between discharges in which secondary electrons play a key role in sustaining the

M. Surendra; David B. Graves

1991-01-01

248

SIMULATING LOW FREQUENCY RADIO IMAGES OF THE SUN  

NASA Astrophysics Data System (ADS)

At low radio frequencies, the strong density gradients in the large scale solar corona lead to significant refraction. This implies that interpretation of solar radio images must account for these refractive effects, and as the ray paths at different frequencies travel through different parts of the corona, multi-frequency observations can help unravel the density and temperature distributions in a range of coronal heights. While the refractive properties of the medium are determined by the electron number density (Ne), the brightness temperature (Tb) distribution in the resulting image is determined by the electron temperature (Te) and the absorption coefficient (?) distributions. In the solar chromosphere and corona the Ne and Te change by 2, and the ? changes by 7 orders of magnitude, leading to significant changes in the morphology and observed Tb of the solar images. We are developing a flexible and precise tool to simulate brightness temperature, Tb, images of the sun resulting from arbitrary electron density, Ne, and electron temperature, Te, distributions. Although this ray-tracing algorithm is being developed in context of the MWA, a radio interferometer which will operate in the 80-300 MHz band (Oberoi et al., 2009, Rightley et al., 2009), it is of much wider applicability. At high radio frequencies, some rays penetrate into the chromosphere, which has significantly different Ne distribution. This tool implements a mathematical method for smoothly "stitching" the chromospheric and coronal Ne distributions, which are very different functions. As an application of this tool, we present and contrast the brightness temperature images from two well regarded coronal models by Baumbach and Allen (1947) and Saito (1970), and the model for chromosphere by Cillie and Menzel (1935). We also investigate the impact of coronal features like streamers on brightness temperature images.

Benkevitch, L. V.; Oberoi, D.; Sokolov, I.

2009-12-01

249

Dynamic impedance measurements during radio-frequency heating of cornea  

Microsoft Academic Search

Hyperopia affects approximately 25% of the population. The aim of different heating modalities for the treatment of hyperopia is to steepen the central curvature of the cornea. Conductive keratoplasty (CK) involves the placement of radio-frequency (RF) lesions around a 7-mm-diameter ring concentric with the pupil of the eye. Dynamics of lesion formation during CK depend on corneal electrical impedance, which

Bernard Choi; Jihoon Kim; Ashley J. Welch; John A. Pearce

2002-01-01

250

Radio frequency cooking of ground, comminuted and muscle meat products  

Microsoft Academic Search

The effect of radio frequency (RF) cooking, on the quality (colour, water holding capacity, texture), heating rate, and temperature history of three types of meat products (ground, comminuted and muscle), was investigated after heating to centre temperature of 72C in a 1.5 kW RF heater operating at 27.12 MHz. The results were compared with that obtained from heating in a

L. Laycock; P. Piyasena; G. S. Mittal

2003-01-01

251

Radio frequency energy effects on microorganisms in foods  

Microsoft Academic Search

Liquids containing microorganisms were exposed to radio frequency (RF) energy to study non-thermal inactivation. RF energy was applied to the liquids while heat was simultaneously removed to control temperature. Turbulent flow was maintained to minimize localized heating. An 18 MHz RF processor applied an approximately 0.5 kV\\/cm electric field strength to the liquids. It was capable of pasteurizing the liquids

David J. Geveke; Michael Kozempel; O. Joseph Scullen; Chris Brunkhorst

2002-01-01

252

Radio frequency electric fields processing of orange juice  

Microsoft Academic Search

The non-thermal process of radio frequency electric fields (RFEF) has been shown to inactivate bacteria in apple juice at moderately low temperatures, but has yet to be extended to inactivate bacteria in orange juice. An 80kW RFEF pasteurizer was used to process pulp-free orange juice at flow rates of 1.0 and 1.4l\\/min. Escherichia coli K12 in orange juice was exposed

David J. Geveke; Christopher Brunkhorst; Xuetong Fan

2007-01-01

253

Synchrotron radiation at radio frequencies from cosmic ray air showers  

NASA Astrophysics Data System (ADS)

We review some of the properties of extensive cosmic ray air showers and describe a simple model of the radio-frequency radiation generated by shower electrons and positrons as they bend in the Earth's magnetic field. We perform simulations by calculating the trajectory and radiation of a few thousand charged shower particles. The results are then transformed to predict the strength and polarization of the electromagnetic radiation emitted by the whole shower.

Suprun, Denis A.; Gorham, Peter W.; Rosner, Jonathan L.

2003-11-01

254

Simulation of low radio frequency solar images using HART  

NASA Astrophysics Data System (ADS)

The diagnostic potential of low radio frequency (< 300 MHz) solar observations has long been recognized. The radio waves are refracted by the smoothly and slowly varying large scale coronal structure and scattered by the small scale inhomogeneities. In addition, the presence of coronal magnetic fields make the coronal plasma dichroic in nature implying that even the unpolarized thermal radiation picks up some degree of polarization depending upon the details of the magnetic field geometry. The very same effects which impart the low radio frequencies its rich diagnostic power, also complicate the interpretation of these observations to extract coronal physics. A detailed analysis of coronal brightness temperature images necessarily requires a sophisticated understanding of coronal propagation and a robust and flexible numerical implementation to serve as a simulation tool. In anticipation of the solar images from the new generation of capable low radio frequency interferometers like the Murchison Widefield Array (MWA), we have been working on the design and development of a coronal propagation simulation tool. Christened Haystack and AOSS Ray Tracer (HART), this tool traces rays through a corona with specified electron density and temperature distributions. HART computes the appropriate radiative transfer to obtain the brightness temperature for each of the rays. This results in a simulated image corresponding to a specified observing frequency in each of the Stokes parameters. In view of the large number of pixels expected in the eventual images from the MWA and other instruments, and the large number of spectral slices for which these images would need to be simulated, considerable attention was paid to developing and implementing a robust and numerically efficient multi-threaded ray tracing algorithm. Here we describe the salient features of the flexible HART framework, presenting the current status of its implementation and the plans for near term development.

Benkevitch, L. V.; Oberoi, D.; Benjamin, M. D.; Sokolov, I.

2011-12-01

255

Imaging Interplanetary CMEs at Radio Frequency From Solar Polar Orbit  

NASA Astrophysics Data System (ADS)

Coronal mass ejections (CMEs) are violent discharges of plasma and magnetic fields from the Sun's corona. They have come to be recognized as the major driver of physical conditions in the Sun-Earth system. Consequently, the detection of CMEs is important for un-derstanding and ultimately predicting space weather conditions. The Solar Polar Orbit Radio Telescope (SPORT) is a proposed mission to observe the propagation of interplanetary CMEs from solar polar orbit. The main payload (radio telescope) on board SPORT will be an in-terferometric imaging radiometer working at the meter wavelength band, which will follow the propagation of interplanetary CMEs from a distance of a few solar radii to near 1 AU from solar polar orbit. The SPORT spacecraft will also be equipped with a set of optical and in situ measurement instruments such as a EUV solar telescope, a solar wind plasma experiment, a solar wind ion composition instrument, an energetic particle detector, a wave detector, a mag-netometer and an interplanetary radio burst tracker. In this paper, we first describe the current shortage of interplanetary CME observations. Next, the scientific motivation and objectives of SPORT are introduced. We discuss the basic specifications of the main radio telescope of SPORT with reference to the radio emission mechanisms and the radio frequency band to be observed. Finally, we discuss the key technologies of the SPORT mission, including the con-ceptual design of the main telescope, the image retrieval algorithm and the solar polar orbit injection. Other payloads and their respective observation objectives are also briefly discussed. Key words: Interplanetary CMEs; Interferometric imaging; Solar polar orbit; Radiometer.

Wu, Ji; Sun, Weiying; Zheng, Jianhua; Zhang, Cheng; Wang, Chi; Wang, C. B.; Wang, S.

256

Experimental development and theoretical studies of radio-frequency absorbers  

NASA Astrophysics Data System (ADS)

A mathematical model based on the equivalence with a sequence of lossy transmission lines has been developed and applied, by numerical calculus, to the study of radio-frequency absorbers of piramidal shape, made of polyurethane foam impregnated with finely powered carbon black. The model has been used to find the expected performance of absorbers with different electrical conductivities in the microwave range of frequencies. The results agree with the measurements of reflectivity which have been previously obtained, by the arch method, during the phase of experimental development of the absorbers, when the carbon black concentration was progressively changed.

Massa, J. L. L. M.

1991-04-01

257

Weighted mean tropospheric temperature and transmittance determination at millimeter-wave frequencies for ground-based applications  

NASA Astrophysics Data System (ADS)

A simple model for the radiometric determination of tropospheric transmittance is based on an isothermal troposphere. In this model the key parameter is the weighted mean tropospheric temperature Tm, which characterizes the radiation and temperature properties of the troposphere. Statistical approaches in modeling this parameter are presented here by using ground temperature, ground relative humidity, and radiometer data. In order to determine the statistical coefficients for Tm modeling and the parameters used in the transmittance retrieval algorithm, radiosonde data were used in a millimeter-wave propagation model for a site in the Swiss central plane and an Alpine site. Various observing geometries at different millimeter-wave frequencies were considered. A determination of Tm from ground temperature was achieved with a rms error between 4-5 K for the low-altitude site and 3-4 K for the high-altitude site. By incorporating relative humidity or radiometer data, an improvement of up to 25% relative to these values results, depending on frequency and site. The zenith transmittance estimations for the low-altitude site with our best model have a rms error of 0.5% at 38 GHz, 1% at 94, 110, and 142 GHz, 1.5% at 115 GHz, 2% at 204 GHz, and 3.5% at 279 GHz, whereas for the high-altitude site all rms errors are below 1%. The inclusion of radiometric information at 20 and 31 GHz did not provide any additional improvement, which was confirmed by actual measurements at 142 GHz.

Ingold, T.; Peter, R.; KMpfer, N.

1998-07-01

258

Radio-frequency dressed atoms beyond the linear Zeeman effect  

NASA Astrophysics Data System (ADS)

We evaluate the impact that nonlinear Zeeman shifts have on resonant radio-frequency (RF) dressed traps in an atom-chip configuration. The degeneracy of the resonance between Zeeman levels is lifted at large intensities of a static field, modifying the spatial dependence of the atomic adiabatic potential. In this context, we find effects that are important for the next generation of atom chips with tight trapping: in particular, that the vibrational frequency of the atom trap is sensitive to the RF frequency and, depending on the sign of the Land factor, can produce significantly weaker, or tighter trapping when compared to the linear regime of the Zeeman effect. We take 87Rb as an example and find that it is possible for the trapping frequency on F = 1 to exceed that of the F = 2 hyperfine manifold.

Sinuco-Len, G.; Garraway, B. M.

2012-12-01

259

Inactivation of Saccharomyces cerevisiae with radio frequency electric fields.  

PubMed

The application of radio frequency (RF) electric fields as a nonthermal alternative to thermal inactivation of microorganisms in liquids was investigated. A novel RF system producing frequencies in the range of 20 to 60 kHz was developed. Electric field strengths of 20 and 30 kV/cm were applied to suspensions of Saccharomyces cerevisiae in water over a temperature range of 35 to 55 degrees C. The flow rate was 1.2 liters/min. The S. cerevisiae population was reduced by 2.1 +/- 0.1 log units following exposure to a 30-kV/cm field at 40 degrees C. The results of the present study provide the first evidence that strong RF electric fields inactivate microorganisms at moderately low temperatures. Increasing the field strength, the number of treatments, and the temperature enhanced inactivation. Frequency had no effect on inactivation over the range of frequencies studied. PMID:14503732

Geveke, David J; Brunkhorst, Christopher

2003-09-01

260

A reconfigurable multi-mode multi-band transmitter with integrated frequency synthesizer for short-range wireless communication  

NASA Astrophysics Data System (ADS)

A reconfigurable multi-mode direct-conversion transmitter (TX) with integrated frequency synthesizer (FS) is presented. The TX as well as the FS is designed with a flexible architecture and frequency plan, which helps to support all the 433/868/915 MHz ISM band signals, with the reconfigurable bandwidth from 250 kHz to 2 MHz. In order to save power and chip area, only one 1.8 GHz VCO is adopted to cover the whole frequency range. All the operation modes can be regulated in real time by configuring the integrated register-bank through an SPI interface. Implemented in 180 nm CMOS, the FS achieves a frequency coverage of 320-460 MHz and 620-920 MHz. The lowest phase noise can be -107 dBc/Hz at a 100 kHz offset and -126 dBc/Hz at a 1 MHz offset. The transmitter features a + 10.2 dBm peak output power with a +9.5 dBm 1-dB-compression point and 250 kHz/500 kHz/1 MHz/2 MHz reconfigurable signal bandwidth.

Nan, Qi; Fan, Chen; Lingwei, Zhang; Xiaoman, Wang; Baoyong, Chi

2013-09-01

261

Linear polarization of molecular lines at radio frequencies  

NASA Astrophysics Data System (ADS)

Calculations of the linear polarization of molecular emission lines from interstellar clouds at radio frequencies are extended by taking into account several coupled rotational states of a diatomic molecule. The goal of the calculations is to provide improved predictions of polarization with which to evaluate the observational results of Wannier, Scoville, and Barvainis (1983). It is found that the inclusion of additional states tends to decrease the maximum polarizations by a factor of about 2, except during superthermal excitation. The maximum polarizations obtained for the J = 2 to 1 transition tend to be somewhat less than those for J = 1 to 0. The polarization effects for a single-dish radio telescope are also estimated.

Deguchi, S.; Watson, W. D.

1984-10-01

262

Galactic synchrotron emission from WIMPs at radio frequencies  

NASA Astrophysics Data System (ADS)

Dark matter annihilations in the Galactic halo inject relativistic electrons and positrons which in turn generate a synchrotron radiation when interacting with the galactic magnetic field. We calculate the synchrotron flux for various dark matter annihilation channels, masses, and astrophysical assumptions in the low-frequency range and compare our results with radio surveys from 22 MHz to 1420 MHz. We find that current observations are able to constrain particle dark matter with ``thermal'' annihilation cross-sections, i.e. (?v) = 3 10-26 cm3 s-1, and masses MDMlesssim10 GeV. We discuss the dependence of these bounds on the astrophysical assumptions, namely galactic dark matter distribution, cosmic rays propagation parameters, and structure of the galactic magnetic field. Prospects for detection in future radio surveys are outlined.

Fornengo, Nicolao; Lineros, Roberto A.; Regis, Marco; Taoso, Marco

2012-01-01

263

Apparatus for the detection of angles-of-arrival of radio frequency signals  

NASA Astrophysics Data System (ADS)

Incoming radio frequency signals from one or more remote transmitters, that may be changing or hopping in frequency, are received at two closely spaced antennas. A pair of Chirp-Z transform processors are respectively coupled to said antennas. The transform processors are operated in synchronism and produce a pair of sampled comb filter output responses, each of which comprises a multiple of frequency bins distributed over a given spectrum. The bins are read out of the Chirp-Z processors in a synchronous sequential order, and each bin is represented by a pair of signals in phase quadrature. The phase quadrature signals of corresponding bins are multiplied in a predetermined manner and the products thereof are selectively added and subtracted to provide a predetermined function (tan psi) of the phase difference (psi) between the signals incident on the pair of antennas. This predetermined function is coupled to a processor that calculates a trigonometric function (arc sine) thereof which is indicative of the angle-of-arrival of the incident wave(s).

Klose, D. R.; Czentirmai, G.; French, B. T.

1986-05-01

264

Using a Satellite Swarm for building a Space-based Radio Telescope for Low Frequencies  

Microsoft Academic Search

In radio astronomy, as in astronomy in general, a wide range of frequencies is observed as each spectral band offers a unique window to study astrophysical phenomena. In the recent years, new observatories have been designed and built at the extreme limits of the radio spectrum. For the low frequencies several Earth-based radio telescopes are constructed at this moment. In

Mark Bentum; A. J. Boonstra; C. J. M. Verhoeven; A. J. van der Veen; E. K. A. Gill; N. Saks; H. Falcke; M. Klein-Wolt; R. T. Rajan; S. J. Wijnholds; M. Arts; K. van't Klooster; F. Belin; A. Meijerink; B. Monna; J. Rotteveel; M. A. Boer; E. Bongers; E. Boom; E. van Tuijl; A. van Staveren

2010-01-01

265

Radio frequency electromagnetic fields: mild hyperthermia and safety standards.  

PubMed

This chapter is a short review of literature that serves as the basis for current safe exposure recommendations by ICNIRP (International Commission on Non-Ionizing Radiation Protection, 1998). and the IEEE C95.1 (IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz, 2005) for exposure to radio frequency electromagnetic radiation (RF-EMF). Covered here are topics on dosimetry, thermoregulatory responses, behavioral responses, and how these have been used to derive safe exposure limits for humans to RF-EMF. Energy in this portion of the electromagnetic spectrum, 3 kHz-300 GHz, can be uniquely absorbed and is different from ionizing radiation both in dosimetry and effects. The deposition of thermalizing energy deep in the body by exposure to RF-EMF fields provides a unique exception to the energy flows normally encountered by humans. Behavioral effects of RF-EMF exposure range from detection to complete cessation of trained behaviors. RF-EMF is detectable and can in most cases, presumably by thermal mechanisms, support aversion and disruption or complete cessation (work stoppage) of behavior. Safety standards are based on behavioral responses by laboratory animals to RF-EMF, enhanced by careful studies of human thermoregulatory responses at four specific RF frequencies, thereby providing a conservative level of protection from RF-EMF for humans. PMID:17645917

D'Andrea, John A; Ziriax, John M; Adair, Eleanor R

2007-01-01

266

Jupiter's low-frequency radio spectrum from Cassini\\/Radio and Plasma Wave Science (RPWS) absolute flux density measurements  

Microsoft Academic Search

We apply the calibration method developed by Dulk et al. [2001] to the data from the Cassini\\/Radio and Plasma Wave Science (RPWS) High-Frequency Receiver in order to derive flux density measurements of six components of the Jovian low-frequency radio spectrum over the full frequency range of the instrument (3.5 kHz to 16.1 MHz). The estimated accuracy is better than 50%,

P. Zarka; B. Cecconi; W. S. Kurth

2004-01-01

267

Occupational exposure to radio-frequency electromagnetic fields  

SciTech Connect

The paper considers occupational exposure to radio-frequency (RF) electromagnetic (EM) fields in industrial processes in near-field situations where electric and magnetic field strengths are monitored to assess the health hazard. Plastic materials are joined by an RF machine whose electrodes are not shielded and which may produce high level RF fields in the immediate vicinity, exceeding the ANSI standard. A physiotherapist may be exposed to high E and H fields using RF shortwave therapy, the maintenance personnel in FM/TV broadcast towers are subject to intense RF fields, and induction heating equipment used for forging, annealing and brazing can expose operators' hands to magnetic fields.

Mild, K.H.

1980-01-01

268

Innovative technology evaluation report, radio frequency heating, KAI Technologies, Inc.  

SciTech Connect

A demonstration of KAI Technologies in-situ radio frequency heating system for soil treatment was conducted from January 1994 to July 1994 at Kelly Air Force Base in San Antonio, Texas. This demonstration was conducted as a joint effort between the USEAP and the USAF. The technology was used to remove hydrocarbon contamination from a contaminated site that had been used during waste treatment and storage operations in the past. This report discusses the results of this demonstration and presents an economic analysis of the process.

Groeber, M.; Krietemeyer, S.; Saylor, E.

1995-04-01

269

Electrically detected magnetic resonance using radio-frequency reflectometry.  

PubMed

The authors demonstrate readout of electrically detected magnetic resonance at radio frequencies by means of a LCR tank circuit. Applied to a silicon field-effect transistor at millikelvin temperatures, this method shows a 25-fold increased signal-to-noise ratio of the conduction band electron spin resonance and a higher operational bandwidth of >300 kHz compared to the kilohertz bandwidth of conventional readout techniques. This increase in temporal resolution provides a method for future direct observations of spin dynamics in the electrical device characteristics. PMID:19947749

Huebl, H; Starrett, R P; McCamey, D R; Ferguson, A J; Willems van Beveren, L H

2009-11-01

270

Radio Frequency Identification (RFID) in Healthcare: A Literature Review.  

PubMed

Creating and maintaining a safe and high-quality health care environment is of great importance for global community. New technologies and their applications can help us achieve this goal. Radio-Frequency Identification (RIFD) technology is considered one of those technologies and even today there are some interesting deployments in the health industry. As a result, this work aims to present the basic idea behind RFID solutions, problems that can be addressed with the adoption of RFID and the benefits of relative applications. PMID:23823408

Kolokathi, Aikaterini; Rallis, Panagiotis

2013-01-01

271

Radio frequency-compensated Langmuir probe with auxiliary double probes.  

PubMed

A radio frequency (rf) compensation design using auxiliary double probes connected in parallel with a main measurement probe was developed for Langmuir probe diagnostics. This probe structure can reduce the sheath impedance of the main probe. In our probe design, the sheath capacitance of the probe can be increased and its sheath resistance can be decreased with increasing dc bias differential voltage between the auxiliary double probes. The I-V characteristic curve and electron energy distribution functions measured by our probe system had sufficient rf compensation performance in inductively coupled plasmas. PMID:20886976

Oh, Se-Jin; Oh, Seung-Ju; Chung, Chin-Wook

2010-09-01

272

Development of a radio frequency surface contour mapping system  

SciTech Connect

A radio-frequency based system is being developed for imaging the top surface of the contents of vessels used in coal processes including lockhoppers, gasifiers, and mixing chambers. The system will be designed to image a minimum of 25 pixels with a depth resolution of {+-}1 inch over ranges of 4 to 30 feet. The system must tolerate harsh environments as found in coal gasifiers with temperatures up to 1800 F and pressures up to 600 psig. The system will provide both a visual readout of the contour of the upper surface of a vessel`s contents via a computer monitor and a data interface to the process control system.

Buttermore, W.H.; Weber, W.H.; Straszheim

1994-10-01

273

Radio frequency identification systems technology in the surgical setting.  

PubMed

Radio frequency identification (RFID) is a technology that will have a profound impact on medicine and the operating room of the future. The purpose of this article is to provide an introduction to this exciting technology and a description of the problems in the perioperative environment that RFID might address to improve safety and increase productivity. Although RFID is still a nascent technology, applications are likely to become much more visible in patient care and treatment areas and will raise questions for practitioners. We also address both the current limitations and what appear to be reasonable near-future possibilities. PMID:16708157

Nagy, Paul; George, Ivan; Bernstein, Wendy; Caban, Jesus; Klein, Rosemary; Mezrich, Reuben; Park, Adrian

2006-03-01

274

Radio Frequency Magnetic Field Effects on Electron-Hole Recombination  

SciTech Connect

We present measurements of the spectrum (1--80MHz) of the effect of a weak ({approx}500 {mu}T ) radio frequency magnetic field on the electron-hole recombination of radical ion pairs in solution. Distinct spectra are observed for the pyrene anion/dimethylaniline cation radical pair in which one or both of the radicals are perdeuterated. The radical pair mechanism is developed theoretically and shown to account satisfactorily for both the magnetic field effect and the associated magnetic isotope effect.

Woodward, J. R.; Timmel, C. R.; McLauchlan, K. A.; Hore, P. J.

2001-08-13

275

Nonclassical crystallization of amorphous iron nanoparticles by radio frequency methods  

NASA Astrophysics Data System (ADS)

Amorphous iron nanoparticles were synthesized using an aqueous reduction in iron(II) sulfate with sodium borohydride and sodium citrate. Various radio frequency (rf) exposure times were investigated in order to determine trends in nonclassical crystallization. RF times from 15 to 300 s revealed an increase in crystallite size from 5 to 60 nm, as determined by powder x-ray diffraction. Also, solvent optimization revealed that ethanol produced the largest trends for increasing crystallite size without total oxidation of the samples. Magnetic characterization by room temperature vibrating sample magnetometry and high resolution transmission microscopy was performed to verify magnetic properties and particle morphology.

Carroll, K. J.; Pitts, J. A.; Zhang, Kai; Pradhan, A. K.; Carpenter, E. E.

2010-05-01

276

Plasma plume propagation characteristics of pulsed radio frequency plasma jet  

SciTech Connect

A 4 cm long helium cold atmospheric pressure plasma jet with pulsed radio frequency (rf) excitation was obtained by a copper electrode inside a quartz tube. The plasma bullet propagation characteristics common to the microseconds direct current pulse and kilohertz plasma jet is not observed in this case. The space-, time-, and wavelength-resolved optical emission profiles suggest the pulsed rf plasma channel out of the tube was strengthened by ions and metastables with longer life time than the rf period, and the plasma propagation was actually an illumination of the plasma channel caused by energetic electrons accelerated along the channel.

Liu, J. H.; Liu, X. Y.; Hu, K.; Liu, D. W.; Lu, X. P. [Advanced Electromagnetic Engineering and Technology Laboratory, Huazhong University of Science and Technology, WuHan, HuBei 430074 (China); Iza, F.; Kong, M. G. [Department of Electronic and Electrical Engineering, Loughborough University, Leicestershire LE11 3TU (United Kingdom)

2011-04-11

277

Implantable Radio Frequency Identification Sensors: Wireless Power and Communication  

PubMed Central

There are significant technical challenges in the development of a fully implantable wirelessly powered neural interface. Challenges include wireless transmission of sufficient power to the implanted device to ensure reliable operation for decades without replacement, minimizing tissue heating, and adequate reliable communications bandwidth. Overcoming these challenges is essential for the development of implantable closed loop system for the treatment of disorders ranging from epilepsy, incontinence, stroke and spinal cord injury. We discuss the development of the wireless power, communication and control for a Radio-Frequency Identification Sensor (RFIDS) system with targeted power range for a 700mV, 30 to 40uA load attained at ?2dBm.

Hutchens, Chriswell; Rennaker, Robert L.; Venkataraman, Srinivasan; Ahmed, Rehan; Liao, Ran; Ibrahim, Tamer

2013-01-01

278

Radio-frequency quadrupole: general properties and specific applications  

SciTech Connect

The radio-frequency quadrupole (RFQ) linac structure is being developed for the acceleration of low-velocity ions. Recent experimental tests have confirmed its expected performance and have led to an increased interest in a wide range of possible applications. The general properties of RFQ accelerators are reviewed and beam dynamics simulation results are presented for their use in a variety of accelerating systems. These include the low-beta sections of the Fusion Materials Irradiation Test Accelerator, a 200-MHz proton linear accelerator, and a xenon accelerator for heavy ion fusion.

Stokes, R.H.; Crandall, K.R.; Hamm, R.W.

1980-01-01

279

Multifrequency radio frequency sensing with photonics-assisted spectrum compression.  

PubMed

We propose and demonstrate a multifrequency radio frequency (RF) spectrum estimation technology. With photonic assistance, a multifrequency RF signal ranging from 0 to 1GHz is highly spectrally compressed and sensed using a single analog-to-digital converter with analog bandwidth of 42.6MHz. By calculating the cross correlation of pseudo random binary sequence and the encoded signal, up to 40 RF tones are precisely recognized without large computational load. The employment of optical mixing decreased the cost and increased the performance compared to its electrical counterpart. The theory and performance are also discussed. PMID:24177100

Yin, Feifei; Gao, Yuyang; Dai, Yitang; Zhang, Junyi; Xu, Kun; Zhang, Ziping; Li, Jianqiang; Lin, Jintong

2013-11-01

280

Heating mechanisms in radio-frequency-driven ultracold plasmas  

NASA Astrophysics Data System (ADS)

Several mechanisms by which an external electromagnetic field influences the temperature of a plasma are studied analytically and specialized to the system of an ultracold plasma (UCP) driven by a uniform radio-frequency (rf) field. Heating through collisional absorption is reviewed and applied to UCPs. Furthermore, it is shown that the rf field modifies the three-body recombination process by ionizing electrons from intermediate high-lying Rydberg states and upshifting the continuum threshold, resulting in a suppression of three-body recombination. Heating through collisionless absorption associated with the finite plasma size is calculated in detail, revealing a temperature threshold below which collisionless absorption is ineffective.

Smorenburg, P. W.; Kamp, L. P. J.; Luiten, O. J.

2012-06-01

281

Effect of economic techniques on radio frequency utilization  

NASA Astrophysics Data System (ADS)

This thesis compares the efficacy of spectrum assignment and allocation using a market based system with the current government controlled regulatory system. In making this comparison, a brief review of the spectrum and its radio communication uses is given. An examination of the current system--historical, organizational and political--is also presented. The spectrum is then discussed as a resource in relation to its economic characteristics: supply, demand, opportunity costs, prices, externalities and property rights. Although the spectrum is a unique resource as compared to most other natural resources, this conclusion is no valid reason for not allowing the establishment of a spectrum market exists. An examination of how such a market might be established and operated, and the implications of such a market are then discussed, with an example of how this market would operate in the Land Mobile Radio Services. To better illustrate this point, a brief history of land mobile radio, its technology and applications, and current allocation and assignment mechanisms is also presented. This study concludes by discussing the importance of the frequency spectrum to economic growth, summarizes the advantages and disadvantages of both marketplace and government regulation, and proposes that a market trial be instituted to test the viability of a spectral market.

Fox, Richard N.

1991-03-01

282

Source Localization in a Cognitive Radio Environment Consisting of Frequency and Spatial Mobility.  

National Technical Information Service (NTIS)

Cognitive radio presents a unique challenge to source localization in that the radio has the ability to adapt to the environment, thus rendering current localization techniques ineffective due to a shifting combination of spatial, frequency, and temporal ...

A. Adams

2011-01-01

283

Bandwidth-Substitution Technique for Absolute Measurement of Power at All Radio Frequencies.  

National Technical Information Service (NTIS)

A highly sensitive technique for making absolute measurements of power at all radio frequencies is described. This technique surmounts the primary shortcomings of the other existing techniques in that it permits absolute measurement of power at all radio ...

A. Singer J. M. Minkowski

1976-01-01

284

Anomalous Capacitive Sheath with Deep Radio Frequency Electric Field Penetration  

SciTech Connect

A novel nonlinear effect of anomalously deep penetration of an external radio-frequency electric field into a plasma is described. A self-consistent kinetic treatment reveals a transition region between the sheath and the plasma. Because of the electron velocity modulation in the sheath, bunches in the energetic electron density are formed in the transition region adjusted to the sheath. The width of the region is of order V(subscript T)/omega, where V(subscript T) is the electron thermal velocity, and w is frequency of the electric field. The presence of the electric field in the transition region results in a cooling of the energetic electrons and an additional heating of the cold electrons in comparison with the case when the transition region is neglected.

Igor D. Kaganovich

2002-01-18

285

Hermetic aluminum radio frequency interconnection and method for making  

DOEpatents

The present invention provides a light-weight, hermetic coaxial radio-frequency (RF) interconnection having an electrically conductive outer housing made of aluminum or an aluminum alloy, a central electrical conductor made of ferrous or non-ferrous material, and a cylinder of dielectric material comprising a low-melting-temperature, high-thermal-expansion aluminophosphate glass composition for hermetically sealing between the aluminum-alloy outer housing and the ferrous or non-ferrous center conductor. The entire RF interconnection assembly is made permanently hermetic by thermally fusing the center conductor, glass, and housing concurrently by bringing the glass to the melt point by way of exposure to an atmospheric temperature sufficient to melt the glass, less than 540.degree. C., but that does not melt the center conductor or the outer aluminum or aluminum alloy housing. The composition of the glass used is controlled to provide a suitable low dielectric constant so that an appropriate electrical characteristic impedance, for example 50 ohms, can be achieved for an electrical interconnection that performs well at high radio frequencies and also provides an interconnection maintaining a relatively small physical size.

Kilgo, Riley D. (Albuquerque, NM); Kovacic, Larry (Albuquerque, NM); Brow, Richard K. (Rolla, MO)

2000-01-01

286

Humeral remodeling and soft tissue injury of the wings caused by backpack harnesses for radio transmitters in New Zealand Takah? (Porphyrio hochstetteri).  

PubMed

Backpack harnesses are commonly used to attach radio and satellite transmitters to a wide range of bird species for research and conservation management. They are an integral part of the conservation management of the New Zealand Takah? (Porphyrio hochstetteri), an endangered flightless rail. Radio transmitters mounted on backpack harnesses enable the birds to be tracked in their remaining native range of remote, mountainous Fiordland, New Zealand. We evaluated 26 Takah? retrospectively at necropsy by gross examination, radiography, and computed tomography to assess damage from the backpack harness. Ten birds that had never worn a harness had no evidence of wing injury. Of the 16 birds that had worn a harness, 10 (63%) had superficial soft tissue injury to skin or patagium or more severe injury, such as remodeling of the distal humerus at the harness cord-wing interface, or pathologic fractures. Such injuries are hypothesized to be associated with discomfort, increased risk of infection or fracture, and therefore reduced fitness. These findings have implications for all avian species deployed with backpack harnesses. PMID:23778604

Michael, Sarah; Gartrell, Brett; Hunter, Stuart

2013-07-01

287

Evaporative cooling in a radio-frequency trap  

SciTech Connect

A theoretical investigation for implementing a scheme of forced evaporative cooling in radio-frequency (rf) adiabatic potentials is presented. Supposing the atoms to be trapped in a combination of a dc magnetic field and a rf field at frequency {omega}{sub 1}, the cooling procedure is facilitated using a second rf source at frequency {omega}{sub 2}. This second rf field produces a controlled coupling between the spin states dressed by {omega}{sub 1}. The evaporation is then possible in a pulsed or continuous mode. In the pulsed case, atoms with a given energy are transferred into untrapped dressed states by abruptly switching off the {omega}{sub 2} coupling. In the continuous case, it is possible for energetic atoms to adiabatically follow the doubly dressed states and escape out of the trap. Our results also show that when {omega}{sub 1} and {omega}{sub 2} are separated by at least the Rabi frequency associated with {omega}{sub 1}, additional evaporation zones appear which can make this process more efficient.

Garrido Alzar, Carlos L.; Perrin, Helene; Lorent, Vincent [Laboratoire de Physique des Lasers, CNRS-Universite Paris 13, Villetaneuse (France); Garraway, Barry M. [Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH (United Kingdom)

2006-11-15

288

Effect of radio frequency discharge power on dusty plasma parameters  

SciTech Connect

The parameters of a two-dimensional dusty plasma consisting of six, 9 mum diameter particles trapped inside a radio frequency (rf) plasma sheath have been measured as a function of rf power in a 13.5 mtorr (1.8 Pa) argon discharge. The center-of-mass and breathing frequencies are found by projecting the cluster's Brownian motion onto the associated normal mode. The center-of-mass frequency (i.e., radial confinement) is insensitive to rf power. The Debye shielding parameter kappa, as found from the breathing frequency, increases from approx =0.5 to 2 as the square root of rf power. The Debye length decreases from approx =2.7 to 0.7 mm as the inverse of the square root of rf power. The average particle charge qapprox =-17 000e is effectively independent of rf power. These results are consistent with an electron temperature that is independent of rf power and an ion density that is directly proportional to rf power, where the Debye length is determined by the ion density in combination with the electron temperature.

Sheridan, T. E. [Department of Physics and Astronomy, Ohio Northern University, Ada, Ohio 45810 (United States)

2009-08-01

289

Effect of radio frequency discharge power on dusty plasma parameters  

NASA Astrophysics Data System (ADS)

The parameters of a two-dimensional dusty plasma consisting of six, 9 ?m diameter particles trapped inside a radio frequency (rf) plasma sheath have been measured as a function of rf power in a 13.5 mtorr (1.8 Pa) argon discharge. The center-of-mass and breathing frequencies are found by projecting the cluster's Brownian motion onto the associated normal mode. The center-of-mass frequency (i.e., radial confinement) is insensitive to rf power. The Debye shielding parameter ?, as found from the breathing frequency, increases from ~0.5 to 2 as the square root of rf power. The Debye length decreases from ~2.7 to 0.7 mm as the inverse of the square root of rf power. The average particle charge q~-17 000e is effectively independent of rf power. These results are consistent with an electron temperature that is independent of rf power and an ion density that is directly proportional to rf power, where the Debye length is determined by the ion density in combination with the electron temperature.

Sheridan, T. E.

2009-08-01

290

Simulator for optimization of radio-frequency pulses in magnetic resonance imaging  

Microsoft Academic Search

The surface coils being driven by radio-frequency pulses are often a primary choice in magnetic resonance imaging for both radio-frequency excitation and reception of weak magnetic resonance imaging signals from the volume of interest. The advantages of the surface coils compared to the volume coils are the minimized radio-frequency power deposition in tissue and the improved detection sensitivity due to

Johanna berg

291

The Radio Frequency Subsystem and Radio Science on the MESSENGER Mission  

NASA Astrophysics Data System (ADS)

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Radio Frequency (RF) Telecommunications Subsystem is used to send commands to the spacecraft, transmit information on the state of the spacecraft and science-related observations, and assist in navigating the spacecraft to and in orbit about Mercury by providing precise observations of the spacecrafts Doppler velocity and range in the line of sight to Earth. The RF signal is transmitted and received at X-band frequencies (7.2 GHz uplink, 8.4 GHz downlink) by the NASA Deep Space Network. The tracking data from MESSENGER will contribute significantly to achieving the missions geophysics objectives. The RF subsystem, as the radio science instrument, will help determine Mercurys gravitational field and, in conjunction with the Mercury Laser Altimeter instrument, help determine the topography of the planet. Further analysis of the data will improve the knowledge of the planets orbital ephemeris and rotation state. The rotational state determination includes refined measurements of the obliquity and forced physical libration, which are necessary to characterize Mercurys core state.

Srinivasan, Dipak K.; Perry, Mark E.; Fielhauer, Karl B.; Smith, David E.; Zuber, Maria T.

2007-08-01

292

78 FR 43916 - Certain Radio Frequency Identification (RFID) Products and Components Thereof; Commission...  

Federal Register 2010, 2011, 2012, 2013

...INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-875] Certain Radio Frequency Identification (RFID) Products and Components Thereof; Commission Determination Not To Review an Initial Determination Terminating...

2013-07-22

293

Advanced techniques for enhancing wireless RF transmitters' power efficiency  

Microsoft Academic Search

This paper expounds on power efficiency enhancement techniques that are sought for the reduction of power consumption of wireless radio frequency power amplifiers (RFPA) and transmitters. The paper will focus on advanced power amplification architectures such as doherty power amplifiers (DPA), linear amplification using nonlinear components (LINC), envelop elimination and restoration (EER) and envelope tracking (ET) techniques. Overview on each

Slim Boumaiza

2008-01-01

294

Momentum Resolved Radio Frequency Spectroscopy in Trapped Polarized Gases  

NASA Astrophysics Data System (ADS)

With recent advances in momentum resolved radio frequency (RF) spectroscopy, both experiment and theory, one can consider doing analogous experiments on polarized Fermi gases. In this talk we present predictions for the behavior of the fermionic spectral functions in the majority and minority bands. By truncating the integrated trap contributions at varying radii, the spectral functions will reflect the increase in the local polarization from nearly zero at the center to large values at the edges. We present predictions for these spectral functions and discuss their implications for future experiments.[4pt] [1] Stewart, J T et al. Nature 454, 744 (2008)[0pt] [2] Chen, Q. and Levin, K. Phys. Rev. Lett. 102, 190402 (2009)[0pt] [3] Chen, Q. et al. Rep. Prog. Phys. 72, 122501 (2009)

Levin, Kathryn; Chien, Chih-Chun; Guo, Hao

2011-03-01

295

Quartz antenna for radio frequency ion source operation  

SciTech Connect

Radio-frequency (rf) driven multicusp ion sources developed at the Lawrence Berkeley National Laboratory use an internal induction coil (antenna) for plasma generation. The copper rf-antenna with a thin layer of porcelain coating, which is presently used, cannot fully satisfy the increasing demands on source cleanliness and antenna lifetime under high power cw or pulsed operation in applications where water cooling is not possible. A quartz antenna has been designed and operated in the multicusp ion source. It has been demonstrated that the overall performance of the new antenna exceeds that of the regular porcelain-coated antenna. It can be operated with a long lifetime in different discharge plasmas. The quartz antenna has also been tested at the Paul Scherrer Institute for cw source operation at rf power higher than 5 kW. Results demonstrated that the antenna can survive under dense plasma discharge operations. {copyright} {ital 1998 American Institute of Physics.}

Lee, Y.; Gough, R.A.; Leung, K.N.; Perkins, L.T.; Pickard, D.S.; Vujic, J.; Wu, L.K. [Lawrence Berkeley National Laboratory, University of California, Berkeley, California (United States); Olivo, M.; Einenkel, H. [Paul Scherrer Institute (PSI), CH-5232 Villigen-PSI (Switzerland)

1998-02-01

296

Fiducialization of Superconducting Radio Frequency Cryomodules at Jefferson Lab  

SciTech Connect

During the early 1990's the Continuous Electron Beam Accelerator Facility (CEBAF), was under construction in Newport News, Virginia. The facility was to be the first of its kind in that it was to provide a continuous beam of electrons for experimental physics at energies of several GeV. One of the key elements of this unique machine was the 338 superconducting radio frequency (SRF) cavities built into 42 cryomodules and arranged in two linacs. These were linked by arcs of conventional magnets which allowed recirculation through the linacs up to five times, in order to achieve the design energy of 4GeV. Within each cryomodule the cavities were aligned and referenced to external fiducials allowing alignment on the design beampath. This paper describes the process developed to achieve this, how it evolved with improving instrumentation, and the results obtained. Suggestions for alternative methods which may prove useful for future projects are also discussed.

C. J. Curtis; J. Dahlberg; W. Oren; J. Preble; K. Tremblay

2006-09-26

297

Security risks associated with radio frequency identification in medical environments.  

PubMed

Radio frequency identification (RFID) is a form of wireless communication that is used to identify assets and people. RFID has significant benefits to the medical environment. However, serious security threats are present in RFID systems that must be addressed in a medical environment. Of particular interest are threats to patient privacy and safety based on interception of messages, interruption of communication, modification of data, and fabrication of messages and devices. This paper presents an overview of these security threats present in RFID systems in a medical environment and provides guidance on potential solutions to these threats. This paper provides a roadmap for researchers and implementers to address the security issues facing RFID in the medical space. PMID:22048780

Hawrylak, Peter J; Schimke, Nakeisha; Hale, John; Papa, Mauricio

2011-11-03

298

Electron Transport by Radio Frequency Waves in Tokamak Plasmas  

SciTech Connect

A relativistic kinetic description for momentum and spatial diffusion of electrons by radio frequency (RF) waves and non-axisymmetric magnetic field perturbations in a tokamak is formulated. The Lie perturbation technique is used to obtain a non-singular, time dependent evolution equation for resonant and non-resonant electron diffusion in momentum space and diffusion in configuration space. The kinetic equation for the electron distribution function is different from the usual quasilinear equations as it includes interactions that are non-Markovian. It is suitable for studying wave-particle interaction in present tokamaks and in ITER. A primary goal of RF waves, and, in particular, of electron cyclotron waves, in ITER is to control instabilities like the neoclassical tearing mode (NTM). Non-axisymmetric effects due to NTMs are included in the kinetic formalism.

Ram, A. K. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139. (United States); Kominis, Y.; Hizanidis, K. [National Technical University of Athens, Association EURATOM-Hellenic Republic, Zografou, Athens 15773 (Greece)

2009-11-26

299

Electron beam diagnostics for a superconducting radio frequency photoelectron injector  

SciTech Connect

A superconducting radio frequency (SRF) photoelectron injector is currently under construction by a collaboration of BESSY, DESY, FZD, and MBI. The project aims at the design and setup of a continuous-wave SRF injector including a diagnostics beamline for the ELBE free electron laser (FEL) and to address R and D issues on low emittance injectors for future light sources such as the BESSY FEL. Of critical importance for the injector performance is the control of the electron beam parameters. For this reason a compact diagnostics beamline is under development, serving a multitude of operation settings. In this paper the layout and the rationale of the diagnostics beamline are described. Furthermore detailed information on specific components is given, together with results from laboratory tests and data taking.

Kamps, Thorsten; Boehlick, Daniel; Dirsat, Marc; Lipka, Dirk; Quast, Torsten; Rudolph, Jeniffa; Schenk, Mario [Berliner Elektronenspeicherring-Gesellschaft fuer Synchrotronstrahlung, BESSY Albert-Einstein-Strasse 15, 12489 Berlin (Germany); Arnold, Andre; Staufenbiel, Friedrich; Teichert, Jochen [Forschungszentrum Dresden-Rossendorf, FZD, Bautzner Landstrasse 128, 01328 Dresden (Germany); Klemz, Guido; Will, Ingo [Max-Born-Institut Berlin, MBI, Max-Born-Strasse 2 A, 12489 Berlin (Germany)

2008-09-15

300

Implantable radio frequency identification sensors: wireless power and communication.  

PubMed

There are significant technical challenges in the development of a fully implantable wirelessly powered neural interface. Challenges include wireless transmission of sufficient power to the implanted device to ensure reliable operation for decades without replacement, minimizing tissue heating, and adequate reliable communications bandwidth. Overcoming these challenges is essential for the development of implantable closed loop system for the treatment of disorders ranging from epilepsy, incontinence, stroke and spinal cord injury. We discuss the development of the wireless power, communication and control for a Radio-Frequency Identification Sensor (RFIDS) system with targeted power range for a 700 mV, 30 to 40 uA load attained at -2 dBm. PMID:22254944

Hutchens, Chriswell; Rennaker, Robert L; Venkataraman, Srinivasan; Ahmed, Rehan; Liao, Ran; Ibrahim, Tamer

2011-01-01

301

Design and fabrication of the BNL radio frequency quadrupole  

SciTech Connect

The Brookhaven National Laboratory polarized H/sup -/ injection program for the AGS will utilize a Radio Frequency Quadrupole for acceleration between the polarized source and the Alvarez Linac. Although operation will commence with a few ..mu.. amperes of H/sup -/ current, it is anticipated that future polarized H/sup -/ sources will have a considerably improved output. The RFQ will operate at 201.25 MHz and will be capable of handling a beam current of 0.02 amperes with a duty cycle of 0.25%. The resulting low average power has allowed novel solutions to the problems of vane alignment, rf current contacts, and removal of heat from the vanes. The cavity design philosophy will be discussed together with the thermodynamics of heat removal from the vane. Details of the fabrication will be presented with a status report.

McKenzie-Wilson, R.B.

1983-01-01

302

SUPERCONDUCTING RADIO-FREQUENCY MODULES TEST FACILITY OPERATING EXPERIENCE  

SciTech Connect

Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R and D). Four major SRF test areas are being constructed to enable vertical and horizontal cavity testing, as well as cryomodule testing. The existing Fermilab cryogenic infrastructure has been modified to service the SRF R and D needs. The project's first stage has been successfully completed, which allows for distribution of cryogens for a single-cavity cryomodule using the existing Cryogenic Test Facility (CTF) that houses three Tevatron satellite refrigerators. The cooling capacity available for cryomodule testing at Meson Detector Building (MDB) results from the liquefaction capacity of the CTF cryogenic system. The cryogenic system for a single 9-cell cryomodule is currently operational. The paper describes the status, challenges and operational experience of the initial phase of the project.

Soyars, W.; Bossert, R.; Darve, C.; Degraff, B.; Klebaner, A.; Martinez, A.; Pei, L.; Theilacker, J. [Fermi National Accelerator Laboratory Batavia, IL, 60510 (United States)

2008-03-16

303

Superconducting radio-frequency modules test faciilty operating experience  

SciTech Connect

Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R&D). Four major SRF test areas are being constructed to enable vertical and horizontal cavity testing, as well as cryomodule testing. The existing Fermilab cryogenic infrastructure has been modified to service Fermilab SRF R&D needs. The first stage of the project has been successfully completed, which allows for distribution of cryogens for a single cavity cryomodule using the existing Cryogenic Test Facility (CTF) that houses three Tevatron satellite refrigerators. The cooling capacity available for cryomodule testing at MDB results from the liquefaction capacity of the CTF cryogenic system. The cryogenic system for a single 9-cell cryomodule is currently operational. The paper describes the status, challenges and operational experience of the initial phase of the project.

Soyars, W.; Bossert, R.; Darve, C.; Degraff, B.; Klebaner, A.; Martinez, A.; Pei, L.; Theilacker, J.; /Fermilab

2007-07-01

304

Quartz antenna for radio frequency ion source operation  

NASA Astrophysics Data System (ADS)

Radio-frequency (rf) driven multicusp ion sources developed at the Lawrence Berkeley National Laboratory use an internal induction coil (antenna) for plasma generation. The copper rf-antenna with a thin layer of porcelain coating, which is presently used, cannot fully satisfy the increasing demands on source cleanliness and antenna lifetime under high power cw or pulsed operation in applications where water cooling is not possible. A quartz antenna has been designed and operated in the multicusp ion source. It has been demonstrated that the overall performance of the new antenna exceeds that of the regular porcelain-coated antenna. It can be operated with a long lifetime in different discharge plasmas. The quartz antenna has also been tested at the Paul Scherrer Institute for cw source operation at rf power higher than 5 kW. Results demonstrated that the antenna can survive under dense plasma discharge operations.

Lee, Y.; Gough, R. A.; Leung, K. N.; Perkins, L. T.; Pickard, D. S.; Vujic, J.; Wu, L. K.; Olivo, M.; Einenkel, H.

1998-02-01

305

NbN thin films for superconducting radio frequency cavities  

NASA Astrophysics Data System (ADS)

NbN thin films have the potential to be incorporated into radio frequency cavities in a multilayer coating to overcome the fundamental field gradient limit of 50 MV m-1 for the bulk niobium based technology that is currently implemented in particle accelerators. In addition to having a larger critical field value than bulk niobium, NbN films develop smoother surfaces which are optimal for cavity performance and lead to fewer losses. Here, we present a study on the correlation of film deposition parameters, surface morphology, microstructure, transport properties and superconducting properties of NbN thin films. We have achieved films with bulk-like lattice parameters and superconducting transition temperatures. These NbN films have a lower surface roughness than similarly grown niobium films of comparable thickness. The potential application of NbN thin films in accelerator cavities is discussed.

Roach, W. M.; Skuza, J. R.; Beringer, D. B.; Li, Z.; Clavero, C.; Lukaszew, R. A.

2012-12-01

306

Radio-frequency superimposed direct current magnetron sputtered Ga:ZnO transparent conducting thin films  

NASA Astrophysics Data System (ADS)

The utilization of radio-frequency (RF) superimposed direct-current (DC) magnetron sputtering deposition on the properties of gallium doped ZnO (GZO) based transparent conducting oxides has been examined. The GZO films were deposited using 76.2 mm diameter ZnO:Ga2O3 (5 at. % Ga vs. Zn) ceramic oxide target on heated non-alkaline glass substrates by varying total power from 60 W to 120 W in steps of 20 W and at various power ratios of RF to DC changing from 0 to 1 in steps of 0.25. The GZO thin films grown with pure DC, mixed approach, and pure RF resulted in conductivities of 2200 +/- 200 S/cm, 3920 +/- 600 S/cm, and 3610 +/- 400 S/cm, respectively. X-ray diffraction showed all films have wurtzite ZnO structure with the c-axis oriented perpendicular to the substrate. The films grown with increasing RF portion of the total power resulted in the improvement of crystallographic texture with smaller full-width half maximum in ? and broadening of optical gap with increased carrier concentration via more efficient doping. Independent of the total sputtering power, all films grown with 50% or higher RF power portion resulted in high mobility (~28 +/- 1 cm2/Vs), consistent with observed improvements in crystallographic texture. All films showed optical transmittance of ~90% in the visible range.

Sigdel, Ajaya K.; Ndione, Paul F.; Perkins, John D.; Gennett, Thomas; van Hest, Maikel F. A. M.; Shaheen, Sean E.; Ginley, David S.; Berry, Joseph J.

2012-05-01

307

Radio-Frequency Superimposed Direct Current Magnetron Sputtered Ga:ZnO Transparent Conducting Thin Films  

SciTech Connect

The utilization of radio-frequency (RF) superimposed direct-current (DC) magnetron sputtering deposition on the properties of gallium doped ZnO (GZO) based transparent conducting oxides has been examined. The GZO films were deposited using 76.2 mm diameter ZnO:Ga{sub 2}O{sub 3} (5 at. % Ga vs. Zn) ceramic oxide target on heated non-alkaline glass substrates by varying total power from 60 W to 120 W in steps of 20 W and at various power ratios of RF to DC changing from 0 to 1 in steps of 0.25. The GZO thin films grown with pure DC, mixed approach, and pure RF resulted in conductivities of 2200 {+-} 200 S/cm, 3920 {+-} 600 S/cm, and 3610 {+-} 400 S/cm, respectively. X-ray diffraction showed all films have wurtzite ZnO structure with the c-axis oriented perpendicular to the substrate. The films grown with increasing RF portion of the total power resulted in the improvement of crystallographic texture with smaller full-width half maximum in {chi} and broadening of optical gap with increased carrier concentration via more efficient doping. Independent of the total sputtering power, all films grown with 50% or higher RF power portion resulted in high mobility ({approx}28 {+-} 1 cm{sup 2}/Vs), consistent with observed improvements in crystallographic texture. All films showed optical transmittance of {approx}90% in the visible range.

Sigdel, A. K.; Ndione, P. F.; Perkins, J. D.; Gennett, T.; van Hest, M. F. A. M.; Shaheen, S. E.; Ginley, D. S.; Berry, J. J.

2012-05-01

308

CMOS neurostimulation ASIC with 100 channels, scaleable output, and bidirectional radio-frequency telemetry.  

PubMed

100-channel neurostimulation circuit comprising a complementary metal oxide semiconductor (CMOS), application-specific integrated circuit (ASIC) has been designed, constructed and tested. The ASIC forms a significant milestone and an integral component of a 100-electrode neurostimulation system being developed by the authors. The system comprises an externally worn transmitter and a body implantable stimulator. The purpose of the system is to communicate both data and power across tissue via radio-frequency (RF) telemetry such that externally programmable, constant current, charge balanced, biphasic stimuli may be delivered to neural tissue at 100 unique sites. An intrinsic reverse telemetry feature of the ASIC has been designed such that information pertaining to the device function, reconstruction of the stimulation voltage waveform, and the measurement of impedance may be obtained through noninvasive means. To compensate for the paucity of data pertaining to the stimulation thresholds necessary in evoking a physiological response, the ASIC has been designed with scaleable current output. The ASIC has been designed primarily as a treatment of degenerative disorders of the retina whereby the 100 channels are to be utilized in the delivery of a pattern of stimuli of varying intensity and or duty cycle to the surviving neural tissue of the retina. However, it is conceivable that other fields of neurostimulation such as cochlear prosthetics and functional electronic stimulation may benefit from the employment of the system. PMID:11296881

Suaning, G J; Lovell, N H

2001-02-01

309

Radio-frequency superimposed direct current magnetron sputtered Ga:ZnO transparent conducting thin films  

SciTech Connect

The utilization of radio-frequency (RF) superimposed direct-current (DC) magnetron sputtering deposition on the properties of gallium doped ZnO (GZO) based transparent conducting oxides has been examined. The GZO films were deposited using 76.2 mm diameter ZnO:Ga{sub 2}O{sub 3} (5 at. % Ga vs. Zn) ceramic oxide target on heated non-alkaline glass substrates by varying total power from 60 W to 120 W in steps of 20 W and at various power ratios of RF to DC changing from 0 to 1 in steps of 0.25. The GZO thin films grown with pure DC, mixed approach, and pure RF resulted in conductivities of 2200 {+-} 200 S/cm, 3920 {+-} 600 S/cm, and 3610 {+-} 400 S/cm, respectively. X-ray diffraction showed all films have wurtzite ZnO structure with the c-axis oriented perpendicular to the substrate. The films grown with increasing RF portion of the total power resulted in the improvement of crystallographic texture with smaller full-width half maximum in {chi} and broadening of optical gap with increased carrier concentration via more efficient doping. Independent of the total sputtering power, all films grown with 50% or higher RF power portion resulted in high mobility ({approx}28 {+-} 1 cm{sup 2}/Vs), consistent with observed improvements in crystallographic texture. All films showed optical transmittance of {approx}90% in the visible range.

Sigdel, Ajaya K.; Shaheen, Sean E. [Department of Physics and Astronomy, University of Denver, Denver, Colorado 80208 (United States); National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Ndione, Paul F.; Perkins, John D.; Gennett, Thomas; Hest, Maikel F. A. M. van; Ginley, David S.; Berry, Joseph J. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

2012-05-01

310

Very low frequency radio signatures of transient luminous events above thunderstorms  

NASA Astrophysics Data System (ADS)

Lightning discharges emit intense optical and acoustic energy, in the form of lightning and thunder, respectively, but a large amount of energy is emitted as radio-frequency electromagnetic pulses (EMP). These pulses can be detected thousands of kilometers away, thanks to efficient propagation in the waveguide formed by the conducting Earth and the overlying ionosphere. In addition, intense discharges interact with the overlying ionosphere at 80-100 km altitude. The EMP-ionosphere interaction is directly observed in one manifestation as the bright transient optical emissions known as "elves", but in addition, the interaction can directly modify the free electron density in the nighttime lower ionosphere. Modifications of the ionospheric electron density can be detected via subionospheric Very Low Frequency (VLF) remote sensing. In this method, coherent signals from powerful VLF transmitters, built for submarine communication and operated by the Navy, are monitored and their amplitude and phase are tracked in time. The variations of these signais are used to sense ionospheric modifications through rapid changes in the received amplitude and/or phase when the transmitted signal propagates through an ionospheric perturbation. When these perturbations are caused by lightning, they are known as "Early VLF" perturbations, due to the negligible delay between the lightning discharge and the appearance of the VLF signal change, whereas lightning-induced electron precipitation (LEP) events have a delay of 1--2 seconds. In this work, correlations between VLF signatures and optical events are used to show that these Early VLF events may be the signature of ionospheric modification by in-cloud (IC) lightning discharges. While the more impressive cloud-to-ground (CG) lightning discharges are more commonly observed and better understood, they are outnumbered in occurrence 3:1 by IC discharges, whose effects may be relatively stronger in the overlying ionosphere. We use a 3D time-domain model of the lightning EMP-ionosphere interaction to calculate expected ionospheric density changes from IC discharges. We find that bursts of IC-EMPs can significantly modify the lower ionosphere, with both increases and decreases in electron density. We then use a frequency-domain model of the VLF transmitter signal propagation in the Earth-ionosphere waveguide to a receiver to show that these density changes are consistent with measurements. Our results demonstrate that these Early VLF events, which are ubiquitous in VLF data, are signatures of the effects of in-cloud lightning, and that they can be used to quantify the effects of IC lightning on the ionosphere during an intense thunderstorm.

Marshall, Robert Andrew

311

Benefits of three frequency ionospheric corrections in Radio Occultation soundings  

NASA Astrophysics Data System (ADS)

The Finnish Meteorological Institute (FMI) has assessed the potential benefits from using the third transmission frequency of the next generation GNSS systems in the sounding of the atmosphere with Radio Occultation (RO). This research has been performed in the framework of the Ionospheric Effects in GNSS Radio Occultation Data study funded by EUMETSAT. The objective of this study was to analyze the advantages of three frequency soundings as part of the planning of the future EUMETSAT satellite missions. The research has been performed by simulating the three frequency transmissions of the next generation GPS and GALILEO systems with the EGOPS (End-to-end GNSS Occultation Performance Simulator) software package developed by the international EGOPS consortium. EGOPS allows simulations of RO missions by propagating the orbits of the transmitting and receiving satellites, determining the geodetic locations and geometries of the soundings and ray tracings of the signals propagation paths. In the study we have ensured that all specified conditions are met by simulating over 1700 occultation soundings. The simulations included both the GPS and the future GALILEO constellations and signals. A LEO satellite at the orbit of the EUMETSAT Metop-A has been used to simulate an RO receiver. The global distribution of the occultations ensured that all occultation times and geometries of interest have been covered. Three solar activity levels have been used to simulated solar minimum, normal and solar maximum conditions. Two ionospheric correction techniques taking benefit of the third GNSS frequency have been tested in the study. The first tested method was a three-frequency linear combination technique. This method is an expansion of the two frequency linear combination that is currently widely used in GNSS navigation and in RO data processing. The disadvantage of this approach is that the noise level in the retrieved bending angle profile is significantly increased. The second tested methods is an ionospheric ambiguity removal with a combination of widelane (WL) and extra-widelane (EWL) signals. This method does not increase the noise level as much as the linear combination method, but is computationally slightly more complex and requires combining code phase observations with the carrier phase observations. The results of the simulations and the retrievals have been rigorously analyzed both statistically and by investigating selected individual observations. The results indicate that ionospheric correction with three frequencies can significantly reduce the ionospheric error in the neutral atmosphere sounding in the heights of 35 - 60 km. This can potentially increase the useful height range of RO soundings in operational NWP (Numerical Weather Prediction) and climate monitoring. This result is very important because very few atmospheric sounding techniques can provide global information from the upper stratosphere and lower mesosphere region. This presentation will show the results of the performed study including descriptions of the simulations and the tested ionospheric correction techniques. The bending angle retrieval accuracy benefits will be quantified both statistically and by analysis of selected complex signal propagation cases. Finally, the presentation will also address the potential benefits of three frequency soundings in space weather observations by RO.

Luntama, J.

2008-12-01

312

Adaptation of the code rate and transmitter power in frequency-hop communications  

Microsoft Academic Search

An adaptive transmission technique for frequency-hop packet transmission is described and its performance is evaluated for certain channels with unknown or time-varying parameters. The power in the transmitted signal and the rate of the error-control code are adapted in a way that provides energy-efficient communications. The slow-frequency-hop packet transmissions have several bits per hop and several hops per packet. Feedback

Michael B. Pursley; Clint S. Wilkins

2004-01-01

313

Thin Film Encapsulation of Radio Frequency (RF) Microelectromechanical Systems (MEMS) Switches.  

National Technical Information Service (NTIS)

Microelectromechanical systems (MEMS) radio frequency (RF) switches have been shown to have excellent electrical performance over a wide range of frequencies. However, cost-effective packaging techniques for MEMS switches do not currently exist. This thes...

E. D. Marsh

2004-01-01

314

Tracking electric field exposure levels through radio frequency dosimetry  

SciTech Connect

The radio-frequency (rf) dosimeter developed by the Oak Ridge National Laboratory is a portable, pocket-sized cumulative-dose recording device designed to detect and record the strengths and durations of electric fields present in the work areas of naval vessels. The device measures an integrated dose and records the electric fields that exceed the permissible levels set by the American National Standards Institute. Features of the rf dosimeter include a frequency range of 30 MHz to 10 GHz and a three-dimensional sensor. Data obtained with the rf dosimeter will be used to determine the ambient field-strength profile for shipboard personnel over an extended time. Readings are acquired and averaged over a 6-min period corresponding to the rise time of the core body temperature. These values are stored for up to 6 months, after which the data are transferred to a computer via the dosimeter's serial port. The rf dosimeter should increase knowledge of the levels of electric fields to which individuals are exposed. 5 refs., 4 figs.

Ewing, P.D.; Moore, M.R.; Rochelle, R.W.; Thomas, R.S.; Hess, R.A.; Hoffheins, B.S.

1991-01-01

315

1.8 GHz Radio Frequency signal radiation effects on human health  

Microsoft Academic Search

Radio Frequency (RF) radiation effects are strictly relying on few critical factors, ie frequency, period of exposure and distance. Certain frequency ranges are absorbed in body tissue more than the other frequency range. The second factor is the duration of exposure. Where, over the period of time, the body will absorb more RF frequencies which hence will worsened the human

Azizah Ahmad; Rusnani Ariffin; Norhayati Mohd Noor; Meor Adzmey Sagiruddin

2011-01-01

316

Radio Frequency HeatingA Prospective Leather Drying System for Future  

Microsoft Academic Search

Drying is one of the important operations influencing finished product quality and leather is no exception. Newer drying methods are being explored worldwide in order to enhance the productivity and quality. Radio frequency (RF) heating is being increasingly applied for industrial applications such as drying of wood, paper, and textiles. Investigations on the use of radio frequency heating for leather

P. A. Balakrishnan; N. Vedaraman; V. John Sundar; C. Muralidharan; G. Swaminathan

2004-01-01

317

Fuzzy PID Control With alpha Factor for Medical Robot of Radio Frequency Ablation  

Microsoft Academic Search

Radio frequency ablation is a simple, safe and potentially effective treatment for patients with liver tumors. Despite all recent therapeutic advancements, however, intra-procedural target localization, precise and consistent placement of the tissue ablator device are still unresolved problems. Therefore, we study radio frequency liver tumors ablation medical robot that typically require precise placement of the ablator tool to meet the

Qinjun Du; Xueyi Zhang

2006-01-01

318

An Educational MATLAB Based Software for a Better Understanding of Radio Frequency Modulations  

Microsoft Academic Search

A MATLAB-based application is introduced here in order to show graphically how radio frequency modulation works. This work show how students of radio frequency courses can learn the different types of modulations varying the most important parameters of each modulation and using different signal sources. The examples presented in the article are a demonstration of how MATLAB can be used

David Moratal-Prez; Francisco Jos Mora-Mas; Antonio Cebrin

319

Surface Planar Ion Chip for Linear Radio-Frequency Paul Traps  

Microsoft Academic Search

We propose a surface planar ion chip which forms a linear radio frequency Paul ion trap. The electrodes reside in the two planes of a chip, and the trap axis is located above the chip surface. Its electric field and potential distribution are similar to the standard linear radio frequency Paul ion trap. This ion trap geometry may be greatly

Jin-Yin Wan; Qiu-Zhi Qu; Zi-Chao Zhou; Xiao-Lin Li; Yu-Zhu Wang; Liang Liu

2007-01-01

320

Radio Frequency Heating of Foods: Principles, Applications and Related PropertiesA Review  

Microsoft Academic Search

Radio frequency (RF) heating is a promising technology for food applications because of the associated rapid and uniform heat distribution, large penetration depth and lower energy consumption. Radio frequency heating has been successfully applied for drying, baking and thawing of frozen meat and in meat processing. However, its use in continuous pasteurization and sterilization of foods is rather limited. During

Punidadas Piyasena; Chantal Dussault; Tatiana Koutchma; H. S. Ramaswamy; G. B. Awuah

2003-01-01

321

SAW integrated modules for 800MHz cellular radio portable telephones with new frequency allocations  

Microsoft Academic Search

Several technologies are developed to achieve broader band surface-acoustic-wave (SAW) filters for portable telephones used in an 800-MHz wideband (25-MHz) cellular radio system. The design and realization of a transmitter final stage filter (high-power filter) and a prefilter (high-performance filter) are examined from initial specification to final device operation. An insertion loss of less than 2 dB and a rejection

MITSUTAKA HIKITA; TOYOJI TABUCHI; YOSHIKATSU ISHIDA; KAZUHITO KUROSAWA; KUNIHIRO HAMADA

1989-01-01

322

Simultaneous occupational exposure to FM and UHF transmitters.  

PubMed

Occupational exposure caused by large broadcasting transmitters exceeds current reference levels. As it is common for different radio and TV transmitters to share the location, we analysed combined exposure on a 40-m high mast. The frequency modulation (FM) transmitter, located between the 10th and 30th metre, had the power of 25 kW, whereas an ultra-high frequency (UHF) transmitter of 5 kW occupied the top 8 m of the mast. Measured and calculated values of the electric field strength exceeded the reference levels up to 10 times; however, the results for the specific absorption rate (SAR) values show that the reference levels are very conservative for FM exposure, i.e., basic restrictions are not exceeded even when the reference levels are exceeded 10 times. However, for UHF exposure the reference levels are not conservative; they give a good prediction of real exposure. PMID:22721535

Vali?, Bla; Kos, Bor; Gajek, Peter

2012-01-01

323

EFFICIENT ESTIMATION OF HUMAN FIELD EXPOSURE THREATS FOR VEHICLES WITH INTERNAL TRANSMITTERS AT MICROWAVE FREQUENCIES  

Microsoft Academic Search

Simple estimates for the statistical properties of electromagnetic field distributions in vehicles are proposed for assessing human exposure threats for internal sources at microwave frequencies. Illustrations are provided for a range of vehicles including cars, trucks, trains and aircraft. The estimates are based on the power balance method for electrically large cavities, with the additional assumptions that the windows are

A. R. Ruddle

2009-01-01

324

Signal processing approaches to radio frequency interference (RFI) suppression  

NASA Astrophysics Data System (ADS)

Ultra-wideband radar (UWB) has been shown to be among the most powerful techniques available for underground and obscured object detection. The value of such systems is that they combine the penetration enhancement associated with VHF/UHF (and lower) frequencies with the resolution of wide absolute bandwidth. Such systems necessarily make use of much of the frequency spectrum already in heavy use by other services, such as television and mobile communications. Although this spectral overlap provides occasion for adverse consequences in both directions, to date the principal consequence has been often-severe impact on UWB radar measurements. Even in remote locations, the average interference power often exceeds receiver noise by many dB, becoming the limiting factor on system sensitivity. Nor are UWB radar designers free to overcome this interference by increasing radar power, since regulatory sanction for UWB operation will depend on maintaining sufficiently low spectral power densities to assure that other, prior, services are not appreciably degraded. Given the importance of radio frequency interference (RFI) on practical ultrawide band ground penetrating radar systems, it is important to consider how and to what extent the effects of RFI noise may be reduced. The overall problem of RFI and its impacts will be described and several signal processing approaches to removal of RFI will be discussed. These include spectral estimation and coherent subtraction algorithms and various filter approaches, which have been developed and applied by the signal processing community in other contexts. These methods will be applied to several different real-world experimental data sets, and quantitative measures of the effectiveness of each of these algorithms in removing RFI noise will be presented. Although computationally-intensive, most of the techniques to be described achieve substantial increases in S/RFI without requiring concomitant increases in radar average power.

Braunstein, Matthew; Ralston, James M.; Sparrow, David A.

1994-06-01

325

Experimental characterization of radio frequency microthermal thruster performance  

NASA Astrophysics Data System (ADS)

Microsatellite (<100 kg) propulsion is a young field that has not yet produced technologies more commercially viable than cold gas thrusters. Design constraints rule out much of traditional propulsion, requiring new and nonobvious technologies to advance the state of the art and enable longer and more flexible missions. The radio frequency microthermal thruster is shown to be worth thorough study for this application. A basic analytical model is constructed to look at expected performance, and the theory behind that model is explained. Calibration and the challenges in working with extremely low forces and displacements are also examined. The results of extensive testing on this thruster type are presented. Important trends are confirmed and validated, such as a linearity of specific impulse with power, and consistent nonlinearities with frequency and mass flow rate. Additionally, tests indicate a nonlinear relationship between applied frequency and thruster internal geometry that can more than triple the heating occurring in the thruster. Further tests focus on this relationship, and find more information about how these parameters couple are found to be primarily due to induced inefficiencies in stochastic heating and the inability of a vibrating voltage sheath to transfer energy into the flow. Additionally, first steps towards optimizing a design for performance are taken, such as analyzing the effect of adding a converging/diverging nozzle and finding an optimal length of inner electrode to be exposed to plasma. Overall, specific impulses of up to 85 seconds are found with argon as the propellant, doubling cold gas specific impulse, and an error on specific impulse is calculated to be less than 3% in either direction. These results after only slight efforts at design optimization indicate much more improvement is possible with this technology that would make an RF microthermal thruster viable as a commercial product.

Williams, Shae E.

326

Post-growth annealing study of heavily Ga-doped zinc oxide grown by radio frequency magnetron sputtering  

NASA Astrophysics Data System (ADS)

Heavily doped Ga-doped ZnO (resistivity 8 10-4 ? cm and optical transmittance 96%) were fabricated by radio frequency magnetron sputtering. Post-growth annealing studies in H2-Ar and pure Ar atmospheres were conducted. No noticeable thermal-induced change in the Ga depth profile or in the Ga chemical state was found in both atmospheres up to 600 C. The Burstein-Moss effect was exhibited in the effective optical band gap, and the cathodoluminescence (CL) photon energy of the near band edge emission. CL emission related to VZn persisted after the 600 C annealing. The thermal evolutions of the carrier concentrations were nearly identical for both annealing atmospheres. The carrier mobility increased upon annealing in H2/Ar and remained effectively unchanged in pure Ar. The observed changes in carrier concentration and mobility were tentatively associated with VZn, or other compensating defects, which have concentrations as high as 1019-1020 cm-3.

Pak, C. M.; Su, S. C.; Ling, C. C.; Lu, Y. M.; Zhu, D. L.

2013-04-01

327

State-of-the-Art Survey of Radio Frequencies Available for Tactical Battlefield Radios in Frequency Bands Above 30 MHz.  

National Technical Information Service (NTIS)

The combat radio used by the fighting units (battalion and below) of the U.S. Army is the Single Channel Ground/Air Radio System (SINCGARS). This radio system operates effectively except that the available bandwidth is insufficient to avoid channel conges...

A. R. Downs

1997-01-01

328

Statistical correlation of spectral broadening in VLF transmitter signal and low-frequency ionospheric turbulence from observation on DEMETER satellite  

NASA Astrophysics Data System (ADS)

In our earlier papers we have found the effect of VLF transmitter signal depression over epicenters of the large earthquakes from observation on the French DEMETER satellite that can be considered as new method of global diagnostics of seismic influence on the ionosphere. At present paper we investigate a possibility VLF signal-ionospheric turbulence interaction using additional characteristic of VLF signal-spectrum broadening. This characteristic is important for estimation of the interaction type: linear or nonlinear scattering. Our main results are the following: - There are two zones of increased spectrum broadening, which are centered near magnetic latitudes ?=10 and ?=40. Basing on the previous case study research and ground ionosonde registrations, probably it is evidence of nonlinear (active) scattering of VLF signal on the ionospheric turbulence. However occurrence rate of spectrum broadening in the middle-latitude area is higher than in the near-equatorial zone (~15 20% in comparison with ~100% in former area) that is probably coincides with the rate of ionospheric turbulence. - From two years statistics of observation in the selected 3 low-latitude regions and 1 middle-latitude region inside reception area of VLF signal from NWC transmitter we find a correlation of spectrum broadening neither with ion-cyclotron noise (f=150 500 Hz), which possibly means poor representation of the turbulence by the noise due to its mixture with natural ELF emission (which correlates with whistler), nor with magnetic storm activity. - We find rather evident correlation of ion-cyclotron frequency noise, VLF signal depression and weak correlation of spectrum broadening with seismicity in the middle-latitude region over Japan. But in the low-latitude regions we do not find such a correlation. Statistical decrease of VLF signal supports our previous case study results. However rather weak spectrum broadening-seismicity statistical correlation means probably that passive scattering prevails upon nonlinear (active) one.

Rozhnoi, A.; Solovieva, M.; Molchanov, O.; Akentieva, O.; Berthelier, J. J.; Parrot, M.; Biagi, P. F.; Hayakawa, M.

2008-10-01

329

The method of matching resonance frequencies in coupled transmitter PVDF\\/TRFE diaphragms  

Microsoft Academic Search

The influence of thermal aging on the resonance frequency and electric impedance of polyvinylidenefluoride (PVDF) type polymer films was studied with the aim to apply thermal treatment to modify and tune the parameters of polymer electromechanical transducers. Results of our study show that thermal treatment of PVDF\\/TRFE 75\\/25 copolymer in the temperature range 50 to 125C (10 min) can be

B. Hilczer; J. Kulek; E. Markiewicz; L. Szczesniak

2000-01-01

330

47 CFR 101.129 - Transmitter location.  

Code of Federal Regulations, 2011 CFR

...101.129 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.129 Transmitter location. (a) The applicant must...

2011-10-01

331

Terrestrial VLF transmitter injection into the magnetosphere  

NASA Astrophysics Data System (ADS)

Very Low Frequency (VLF, 3-30 kHz) radio waves emitted from ground sources (transmitters and lightning) strongly impact the radiation belts, driving electron precipitation via whistler-electron gyroresonance, and contributing to the formation of the slot region. However, calculations of the global impacts of VLF waves are based on models of trans-ionospheric propagation to calculate the VLF energy reaching the magnetosphere. Limited comparisons of these models to individual satellite passes have found that the models may significantly (by >20 dB) overestimate amplitudes of ground based VLF transmitters in the magnetosphere. To form a much more complete empirical picture of VLF transmitter energy reaching the magnetosphere, we present observations of the radiation pattern from a number of ground-based VLF transmitters by averaging six years of data from the DEMETER satellite. We divide the slice at 700 km altitude above a transmitter into pixels and calculate the average field for all satellite passes through each pixel. There are enough data to see 25 km features in the radiation pattern, including the modal interference of the subionospheric signal mapped upwards. Using these data, we deduce the first empirical measure of the radiated power into the magnetosphere from these transmitters, for both daytime and nighttime, and at both the overhead and geomagnetically conjugate region. We find no detectable variation of signal intensity with geomagnetic conditions at low and mid latitudes (L < 2.6). We also present evidence of ionospheric heating by one VLF transmitter which modifies the trans-ionospheric absorption of signals from other transmitters passing through the heated region.

Cohen, M. B.; Inan, U. S.

2012-08-01

332

Programmable Multichannel Sonobuoy Transmitter.  

National Technical Information Service (NTIS)

A programmable phase-locked loop frequency synthesizer for a multi-channel sonobuoy transmitter is disclosed. The phase-locked loop, including a counter/dividr utilizing variable modulus prescaling techniques, is modulated at its voltage-controlled oscill...

A. M. Bates W. H. Sandford M. T. Junod

1984-01-01

333

The driving frequency effects on the atmospheric pressure corona jet plasmas from low frequency to radio frequency  

SciTech Connect

Lately, the atmospheric pressure jet type corona plasma, which has been typically driven by dc to low frequency (LF: several tens of kHz), is often generated by using radio frequency of 13.56 MHz. Yet, the relationship between the plasma and its driving frequency has seldom been investigated. Hence, in this study, dependence of the atmospheric pressure corona plasma characteristics on the driving frequency was explored experimentally from LF to rf (5 kHz-13.56 MHz). The plasmas generated by the driving frequency under 2 MHz were cylindrical shape of several tens of millimeters long while the 13.56 MHz plasma is spherical and a few millimeters long. As the driving frequency was increased, the plasma length became shortened. At the lower driving frequencies (below 2 MHz), the plasmas existed as positive streamer and negative glow for each half period of the applied voltage, but the discharge was more continuous in time for the 13.56 MHz plasma. It was inferred from the measured I-V curves that the higher driving frequency induced higher discharge currents, and the gas temperature was increased as the driving frequency was increased.

Kim, Dan Bee [Division of Physical Metrology, Korea Research Institute of Standards and Science, 209 Gajeongno, Yuseong-gu, Daejeon 305-340 (Korea, Republic of); Jung, H.; Gweon, B.; Rhee, J. K.; Choe, W. [Department of Physics, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Moon, S. Y. [LG Electronics Advanced Research Institute, 16 Woomyeon-Dong, Seocho-Gu, Seoul 137-724 (Korea, Republic of)

2011-04-15

334

Controlled radio frequency vessel sealing system for surgical applications  

NASA Astrophysics Data System (ADS)

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 (

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

1998-04-01

335

Supercomputer Simulation of Radio-frequency Hepatic Tumor Ablation  

NASA Astrophysics Data System (ADS)

We simulate the thermal and electrical processes, involved in the radio-frequency (RF) ablation procedure. The mathematical model consists of two parts-electrical and thermal. The energy from the applied AC voltage is determined first, by solving the Laplace equation to find the potential distribution. After that, the electric field intensity and the current density are directly calculated. Finally, the heat transfer equation is solved to determine the temperature distribution. Heat loss due to blood perfusion is also accounted for. The representation of the computational domain is based on a voxel mesh. Both partial differential equations are discretized in space via linear conforming FEM. After the space discretization, the backward Euler scheme is used for the time stepping. Large-scale linear systems arise from the FEM discretization. Moreover, they are ill-conditioned, due to the strong coefficient jumps and the complex geometry of the problem. Therefore, efficient parallel solution methods are required. The developed parallel solver is based on the preconditioned conjugate gradient (PCG) method. As a preconditioner, we use BoomerAMG-a parallel algebraic multigrid implementation from the package Hypre, developed in LLNL, Livermore. Parallel numerical tests, performed on the IBM Blue Gene/P massively parallel computer are presented.

Kosturski, N.; Margenov, S.

2010-11-01

336

Spectroscopic Measurements of Radio Frequency Plasmas in Supercritical Fluids  

SciTech Connect

Spectroscopic measurements of radio frequency (rf) plasma were performed under high pressure CO{sub 2} conditions (5 and 7 MPa) and supercritical (sc)CO{sub 2} conditions (8-20 MPa). The temperatures evaluated from C{sub 2} Swan bands increased from 3600 K to 4600 K with increasing pressure. The broadening and shifting of the O I line profile ({approx}777 nm) of rf plasma was observed under scCO{sub 2} conditions. The width of the line profile increased with increasing pressure. The reason for the broadening and shifting is still unclear because the present theory used to explain them is not valid for such high pressure conditions. Further, the broadening of the Ar I line profile ({approx}811.5 nm) in rf plasmas was observed under atmospheric Ar (0.1 MPa), high pressure Ar conditions (1-4 MPa), and scAr condition (5 MPa); the observation of the O I line profile in CO{sub 2} plasmas is difficult in this pressure range owing to its weak intensity therein. Similar to the case of the O I line in CO{sub 2} plasmas, the reason for the broadening of the Ar I line profile at 5 MPa is unclear.

Maehara, Tsunehiro [Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan); Iwamae, Atsushi [Graduate School of Engineering, Kyoto University, Kyoto 606-8501 (Japan); Kawashima, Ayato [Faculty of Agriculture, Ehime University, Matsuyama 790-8566 (Japan)

2010-10-29

337

The Stabiliy of Radio-Frequency Plasma Treated Polydimethylsiloxane Surface  

PubMed Central

Polydimethylsiloxane (PDMS) is a widely used material for manufacturing lab-on-chip devices. However, the hydrophobic nature of PDMS is a disadvantage in micro-fluidic systems. To transform the hydrophobic PDMS surface to hydrophilic it has been treated with radio frequency (RF) air plasma at 150, 300 and 500 mtorr pressure for up to 30 minutes. Following the surface treatment, the PDMS specimens were stored in air, deionized water or 0.14 M NaCl solution at 4 C, 20 C, and 70 C. The change in the hydrophilicity (wettability) of the PDMS surfaces has been followed by contact angle measurements and Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR) Spectroscopy as a function of time. As an effect of the RF plasma treatment the contact angles measured on PDMS surfaces dropped from 1134 degrees to 93 degrees. The chamber pressure and the treatment time had no or negligible effect on the results. However, the PDMS surface gradually lost its hydrophilic properties in time. The rate of this process is influenced by the difference in the dielectric constants of the PDMS and its ambient environment. It has been the smallest at low temperatures in deionized water and largest at high temperatures in air. Apparently, the OH groups generated on the PDMS surface during the plasma treatment tend towards a more hydrophilic/less hydrophobic environment during the relaxation processes. The correlation between FTIRATR spectral information and contact angle data supports this interpretation.

Chen, I-Jane

2008-01-01

338

Noninvasive radio frequency for skin tightening and body contouring.  

PubMed

The medical use of radio frequency (RF) is based on an oscillating electrical current forcing collisions between charged molecules and ions, which are then transformed into heat. RF heating occurs irrespective of chromophore or skin type and is not dependent on selective photothermolysis. RF can be delivered using monopolar, bipolar, and unipolar devices, and each method has theoretical limits of depth penetration. A variant of bipolar delivery is fractional RF delivery. In monopolar configurations, RF will penetrate deeply and return via a grounding electrode. Multiple devices are available and are detailed later in the text. RF thermal stimulation is believed to result in a microinflammatory process that promotes new collagen. By manipulating skin cooling, RF can also be used for heating and reduction of fat. Currently, the most common uses of RF-based devices are to noninvasively manage and treat skin tightening of lax skin (including sagging jowls, abdomen, thighs, and arms), as well as wrinkle reduction, cellulite improvement, and body contouring. PMID:24049924

Weiss, Robert A

2013-03-01

339

Radio-frequency plasma transducer for use in harsh environments  

SciTech Connect

We describe a compact transducer used to generate and modulate low-intensity radio-frequency atmospheric pressure plasma (RF-APP) for high temperature gap measurement and generation of air-coupled ultrasound. The new transducer consists of a quarter-wave transmission line where the ground return path is a coaxial solenoid winding. The RF-APP is initiated at the open end of the transmission line and stabilized by passive negative feedback between the electrical impedance of the plasma and the energy stored in the solenoid. The electrical impedance of the plasma was measured at the lower-voltage source end of the transducer, eliminating the need to measure kilovolt-level voltages near the discharge. We describe the use of a 7 MHz RF-APP prototype as a harsh-environment clearance sensor to demonstrate the suitability of plasma discharges for a common nondestructive inspection application. Clearance measurements of 0-5 mm were performed on a rotating calibration target with a measurement precision of 0.1 mm and a 20 kHz sampling rate.

May, Andrew; Andarawis, Emad [GE Global Research, 1 Research Circle, Niskayuna, New York 12309 (United States)

2007-10-15

340

Operating a radio-frequency plasma source on water vapor.  

PubMed

A magnetically enhanced radio-frequency (rf) plasma source operating on water vapor has an extensive list of potential applications. In this work, the use of a rf plasma source to dissociate water vapor for hydrogen production is investigated. This paper describes a rf plasma source operated on water vapor and characterizes its plasma properties using a Langmuir probe, a residual gas analyzer, and a spectrometer. The plasma source operated first on argon and then on water vapor at operating pressures just over 300 mtorr. Argon and water vapor plasma number densities differ significantly. In the electropositive argon plasma, quasineutrality requires n(i) approximately = n(e), where n(i) is the positive ion density. But in the electronegative water plasma, quasineutrality requires n(i+) = n(i-) + n(e). The positive ion density and electron density of the water vapor plasma are approximately one and two orders of magnitude lower, respectively, than those of argon plasma. These results suggest that attachment and dissociative attachment are present in electronegative water vapor plasma. The electron temperature for this water vapor plasma source is between 1.5 and 4 eV. Without an applied axial magnetic field, hydrogen production increases linearly with rf power. With an axial magnetic field, hydrogen production jumps to a maximum value at 500 W and then saturates with rf power. The presence of the applied axial magnetic field is therefore shown to enhance hydrogen production. PMID:19725651

Nguyen, Sonca V T; Foster, John E; Gallimore, Alec D

2009-08-01

341

Radio-frequency measurement of an asymmetric single electron transistor  

NASA Astrophysics Data System (ADS)

Since the invention of the radio-frequency single-electron transistor (RF-SET) by Schoelkopf et al.,[1] most measurements have focused on the symmetric single electron transistor. It has been shown, however, that the symmetric SET has a rather low measurement efficiency in its normal working regime.[2][3] Recently, it has been pointed out that an asymmetric SET can be considerably more efficient than a symmetric SET as a quantum amplifier. In this case the measurement efficiency of the asymmetric SET becomes similar to that of the quantum point contact (QPC) detector which can approach the quantum limit. We investigate the asymmetric SET by fabricating Al/AlOx SETs with junction areas 40x40 nm^2 and 40x80nm^2 and total resistance of about 25k?. The results of RF and DC characterization of such asymmetric SETs will be discussed. [1] R. J. Schoelkopf, P. Wahlgren, A. A. Kozhevnikov, P. Delsing, D. E. Prober, Science, 280, 1242 (1998). [2] A. N. Korotkov, Phys. Rev. B, 63, 085312 (2001); 63, 115403 (2001). [3] D. Mozyrsky, I. Martin, and M. B. Hastings, Phys. Rev. Lett., 92, 018303 (2004). [4] S. A. Gurvitz and G. P. Berman, Phys. Rev. B, 72 , 073303(2005).

Ji, Zhongqing; Xue, Weiwei; Rimberg, A. J.

2007-03-01

342

Radio frequency perforation of cardiac tissue: modelling and experimental results.  

PubMed

Radio frequency (RF) current delivered through a thin catheter can be used to perforate the pulmonary valve or the atrial septum to treat pulmonary atresia in newborns. To understand better the mechanisms of RF perforation, a numerical model is developed, and experiments are performed in isolated canine cardiac tissue. The model consists of a cylindrical domain with a tissue layer between two blood layers. The finite-difference method is used to compute both the potential and temperature distributions. When the tissue temperature exceeds 100 degrees C in all points that are directly in front of the catheter, these points are considered to be instantly vaporised, and the catheter advances over these points. The computed temperature time course coincides with measured temperature at small voltages (< 16 V). Simulated perforation occurs when the voltage exceeds a threshold of 70-80 V for a catheter diameter of 0.30-0.44 mm, which coincides with experimental observations in the myocardium. A voltage exceeding this perforation threshold tends to decrease tissue damage. Shorter electrodes (0.7 mm as against 2.4 mm) with smaller diameters produce a more rapid perforation. In conclusion, numerical simulations provide insights into aspects of RF perforation, such as electrode size, current, speed of perforation and collateral damage. PMID:11094817

Shimko, N; Savard, P; Shah, K

2000-09-01

343

Radio frequency coil technology for small-animal MRI.  

PubMed

A review of the theory, technology, and use of radio frequency (RF) coils for small-animal MRI is presented. It includes a brief overview of MR signal-to-noise (S/N) analysis and discussions of the various coils commonly used in small-animal MR: surface coils, linear volume coils, birdcages, and their derivatives. The scope is limited to mid-range coils, i.e. coils where the product (fd) of the frequency f and the coil diameter d is in the range 2-30 MHz-m. Common applications include mouse brain and body coils from 125 to 750 MHz, rat body coils up to 500 MHz, and small surface coils at all fields. In this regime, all the sources of loss (coil, capacitor, sample, shield, and transmission lines) are important. All such losses may be accurately captured in some modern full-wave 3D electromagnetics software, and new simulation results are presented for a selection of surface coils using Microwave Studio 2006 by Computer Simulation Technology, showing the dramatic importance of the "lift-off effect". Standard linear circuit simulators have been shown to be useful in optimization of complex coil tuning and matching circuits. There appears to be considerable potential for trading S/N for speed using phased arrays, especially for a larger field of view. Circuit simulators are shown to be useful for optimal mismatching of ultra-low-noise preamps based on the enhancement-mode pseudomorphic high-electron-mobility transistor for optimal coil decoupling in phased arrays. Cryogenically cooled RF coils are shown to offer considerable opportunity for future gains in S/N in smaller samples. PMID:17451180

Doty, F David; Entzminger, George; Kulkarni, Jatin; Pamarthy, Kranti; Staab, John P

2007-05-01

344

Effects of radio frequency bias frequency and radio frequency bias pulsing on SiO{sub 2} feature etching in inductively coupled fluorocarbon plasmas  

SciTech Connect

The effect of radio frequency (rf) bias frequency on SiO{sub 2} feature etching using inductively coupled fluorocarbon plasmas is investigated. It is found that the rf bias frequency can have an important effect on SiO{sub 2} feature etch rate, microtrenching phenomena, and SiO{sub 2}-to-photoresist etch selectivity. In addition, the effect of rf bias pulsing on inductively coupled fluorocarbon plasma SiO{sub 2} etching has been studied and a model that describes the data well is presented. The model assumes that fluorocarbon deposition occurs while the rf bias is off, fluorocarbon etching occurs during the first part of time that the bias is on, and substrate etching occurs once the fluorocarbon material has been removed from the substrate. (c) 2000 American Vacuum Society.

Schaepkens, M. [Physics Department, University at Albany, Albany, New York 12222 (United States); Oehrlein, G. S. [Physics Department, University at Albany, Albany, New York 12222 (United States); Cook, J. M. [Lam Research Corporation, Fremont, California 94538-6470 (United States)

2000-03-01

345

Adhoc electromagnetic compatibility testing of non-implantable medical devices and radio frequency identification  

PubMed Central

Background The use of radiofrequency identification (RFID) in healthcare is increasing and concerns for electromagnetic compatibility (EMC) pose one of the biggest obstacles for widespread adoption. Numerous studies have documented that RFID can interfere with medical devices. The majority of past studies have concentrated on implantable medical devices such as implantable pacemakers and implantable cardioverter defibrillators (ICDs). This study examined EMC between RFID systems and non-implantable medical devices. Methods Medical devices were exposed to 19 different RFID readers and one RFID active tag. The RFID systems used covered 5 different frequency bands: 125134kHz (low frequency (LF)); 13.56MHz (high frequency (HF)); 433MHz; 915MHz (ultra high frequency (UHF])) and 2.4GHz. We tested three syringe pumps, three infusion pumps, four automatic external defibrillators (AEDs), and one ventilator. The testing procedure is modified from American National Standards Institute (ANSI) C63.18, Recommended Practice for an On-Site, Ad Hoc Test Method for Estimating Radiated Electromagnetic Immunity of Medical Devices to Specific Radio-Frequency Transmitters. Results For syringe pumps, we observed electromagnetic interference (EMI) during 13 of 60 experiments (22%) at a maximum distance of 59cm. For infusion pumps, we observed EMI during 10 of 60 experiments (17%) at a maximum distance of 136cm. For AEDs, we observed EMI during 18 of 75 experiments (24%) at a maximum distance of 51cm. The majority of the EMI observed was classified as probably clinically significant or left the device inoperable. No EMI was observed for all medical devices tested during exposure to 433MHz (two readers, one active tag) or 2.4GHz RFID (two readers). Conclusion Testing confirms that RFID has the ability to interfere with critical medical equipment. Hospital staff should be aware of the potential for medical device EMI caused by RFID systems and should be encouraged to perform on-site RF immunity tests prior to RFID system deployment or prior to placing new medical devices in an RFID environment. The methods presented in this paper are time-consuming and burdensome and suggest the need for standard test methods for assessing the immunity of medical devices to RFID systems.

2013-01-01

346

Low-power radio-frequency ICs for portable communications  

Microsoft Academic Search

The contributions of integrated circuits to the RF front-end of wireless receivers and transmitters operating in broadcast and personal communications bands are surveyed. It is seen from this that when ICs enable a rethinking of the RF architecture, the wireless device can sometimes become significantly smaller, and consume much less power. Examples are taken from FM broadcast receivers, pagers, and

ASAD A. ABIDI

1995-01-01

347

Radio frequency sputtered Al:ZnO-Ag transparent conductor: A plasmonic nanostructure with enhanced optical and electrical properties  

NASA Astrophysics Data System (ADS)

Optimization of metal-based transparent conductors (MTCs) made of silver and aluminium-doped zinc oxide (AZO) prepared by radio-frequency (r.f.) sputtering has been carried out through tuning of metal film properties. The influence of morphology and related plasmonic features of AZO/Ag/AZO MTCs on their optical and electrical performance is demonstrated and it is shown that the nominal thickness of the silver layer itself is not the most crucial value determining the MTC performance. The MTC performance has been optimized by a search of deposition conditions ensuring fractal-type metal layer formation up to a certain coalescence state that enables full gaining from silver optical properties, including its plasmonic features. For 150 W- and 200 W-deposited silver, MTCs with maximum transmittance as high as 83.6% have been obtained. These coatings have a figure of merit as good as 0.01 ?-1 and a remarkably wide spectral transparency region: transmittance higher than 70% down to 1200 nm for 200W-samples. Modelling of the MTC coatings is proposed additionally, based on variable angle spectroscopic ellipsometric measurements, which takes into account the variation of the optical properties of silver when deposited in various conditions and embedded in a semiconductor stack.

Sytchkova, Anna; Luisa Grilli, Maria; Rinaldi, Antonio; Vedraine, Sylvain; Torchio, Philippe; Piegari, Angela; Flory, Franois

2013-09-01

348

Langmuir probe characterization of low-frequency oscillations in a radio-frequency SF6 plasma  

NASA Astrophysics Data System (ADS)

A low-frequency oscillation (<100 Hz) has been observed in a low-pressure (1-50 mTorr) radio-frequency (RF) inductively coupled plasma, produced in sulfur hexafluoride. Langmuir probe studies have characterized this oscillation with respect to RF power, gas pressure and probe proximity to the antenna. The experimental parameter space within which this oscillation is observed is mapped with respect to power and pressure for the reaction chamber in use. The oscillation is observed in Langmuir probe currents for positive probe bias, and has a strong dependence on experimental conditions, as well as probe position within the chamber. The propagation speed of the instability away from the source is found to be 16 m s-1.

Barlow, A. J.; Deslandes, A.; Quinton, J. S.

2011-12-01

349

Variable low-frequency radio emission of the solar system and galactic objects  

NASA Astrophysics Data System (ADS)

There are many physical processes and propagation effects for the producing the time variable radio emission just at the low frequencies (at the decameter wavelength). The study of this radio emission is the important part of the modern radio astronomy. Strong progress in the development of the radio telescopes, methods and instrumentation allowed to start the corresponding investigations at new quality and quantity levels. It related to the implementation of the world largest UTR-2 radio telescope (effective area is more than 100 000 sq.m) more high sensitive at frequencies less than 30 MHz. During last years many new observations were carried out with this radio telescope and many new effects have been detected for the Sun, planets, interplanetary medium, exoplanets as well as various kinds of the stars.

Konovalenko, Alexander; Kolyadin, Vladimir; Rucker, Helmut; Zakharenko, Vyacheslav; Zarka, Philippe; Griessmeier, Jean-M.; Denis, Loran; Melnik, Valentin; Litvinenko, Galina; Zaitsev, Valerij; Falkovich, Igor; Ulyanov, Oleg; Sidorchuk, Mikhail; Stepkin, Sergej; Stanislavskij, Alexander; Kalinichenko, Nikolaj; Boiko, Nastja; Vasiljiva, Iaroslavna; Mukha, Dmytro; Koval, Artem

2013-04-01

350

Automatic radio telemetry recording of fish temperature and depth  

Microsoft Academic Search

Radio frequency fish transmitters capable of relaying temperature or pressure information and a multichannel recording system were developed and used successfully in the field. Both transmitters operated on pulse rate variation with either temperature or depth. Design considerations for temperature and pressure dependant pulse rates are discussed, including power supply variation, sensitivity ranges, drift, size, power consumption and temperature variation.

M. J. Ross; V. B. Kuechle; R. A. Reichle; D. B. Siniff

1979-01-01

351

Radio frequency needle hyperthermia of normal and cancerous animal tissue  

NASA Astrophysics Data System (ADS)

Capacitative radio frequency (RF) was met with little success when used to treat human cancer. Conductive rf needle hyperthermia (RFNH) is used successfully for human tissue ablation in neurosurgery, cardiology, and recently in urology. RFNH ablates tissue by causing thermal damage limited to the vicinity of the rf needle. We conducted a series of studies to evaluate the effect of RFNH on cancerous and normal tissue. RFNH was applied to normal porcine livers during open surgery. Liver function tests were elevated two days post treatment, then returned to normal. Pigs were sequentially sacrificed. RFNH induced lesions were found to be maximal in size on days 2 - 4 post treatment and later became smaller as liver regenerated. Phase 2 included mice bearing two subcutaneous murine bladder tumors (MBT2). The rf needle was inserted into both tumors of each mouse, but rf current was applied to one tumor only. Energies of 3 to 7.5 watts were applied for 30 seconds to 5 minutes using a 0.02 inch needle. Mice were sacrificed 0, 1, and 3 days after treatment. Necrotic lesions 0.5 - 1.2 cm in diameter were found within the treated tumors. In phase 3, mice bearing a single 8 - 18 mm subcutaneous tumor were treated by RFNH aiming for complete tumor destruction. All control mice died of huge tumors within 31 days. Treated mice were alive with no signs of tumor when sacrificed 60 days after treatment. In phase 3 RFNH is capable of complete tumor eradication with little damage to surrounding normal tissue. It may have clinical applications for percutaneous endoscopic and laparoscopic treatment of tumors.

Shalhav, Arieh; Ramon, J.; Goldwasser, Benad; Nativ, Ofer; Cherniack, Ramy; Zajdel, Liliana

1994-12-01

352

Assessment of radio frequency ablation treatment of hepatic tumors  

NASA Astrophysics Data System (ADS)

It is fundamentally important that all cancerous cells be adequately destroyed during Radio Frequency Ablation (RFA) procedures. To help achieve this goal, probe manufacturers advise physicians to increase the treatment region by one centimeter (1cm) in all directions around the diseased tissue. This enlarged treatment region provides a buffer to insure that cancer cells that migrated into surrounding tissue are adequately treated and necrose. Even though RFA is a minimally invasive, image-guided procedure, it is difficult for physicians to confidently follow the specified treatment protocol. In this paper we visually assess an RFA treatment by comparing a registered image set containing the untreated tumor, including the 1 cm safety boundary, to that of an image set containing the treated region acquired one month after surgery. For this study, we used Computerized Tomography images as both the tumor and treated regions are visible. To align the image sets of the abdomen, we investigate three different registration techniques; an affine transform that minimizes the correlation ratio, a point (or landmark) based 3D thin-plate spline approach, and a nonlinear B-spline elastic registration methodology. We found the affine registration technique simple and easy to use because it is fully automatic. Unfortunately, this method resulted in the largest visible discrepancy between the liver in the fused images. The thin-plate spline technique required the physician to identify corresponding landmarks in both image sets, but resulted in better visual accuracy in the fused images. Finally, the non-linear, B-spline, elastic registration technique used the registration results of the thin-plate spline method as a starting point and then required a significant amount of computation to determine its transformation, but also provided the most visually accurate fused image set.

Hemler, Paul F.; McCreedy, Evan S.; Cheng, Ruida; Wood, Brad; McAuliffe, Matthew J.

2006-03-01

353

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

PubMed

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. PMID:22380234

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

354

H- radio frequency source development at the Spallation Neutron Source  

NASA Astrophysics Data System (ADS)

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.

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

355

Three-dimensional effects for radio frequency antenna modeling  

SciTech Connect

Electromagnetic field calculations for radio frequency (rf) antennas in two dimensions (2-D) neglect finite antenna length effects as well as the feeders leading to the main current strap. Comparisons with experiments indicate that these 2-D calculations can overestimate the loading of the antenna and fail to give the correct reactive behavior. To study the validity of the 2-D approximation, the Multiple Antenna Implementation System (MAntIS) has been used to perform 3-D modeling of the power spectrum, plasma loading, and inductance for a relevant loop antenna design. Effects on antenna performance caused by feeders to the main current strap, conducting sidewalls, and finite phase velocity are considered. The plasma impedance matrix for the loading calculation is generated by use of the ORION-1D code. The 3-D model is benchmarked with the 2-D model in the 2-D limit. For finite-length antennas, inductance calculations are found to be in much more reasonable agreement with experiments for 3-D modeling than for the 2-D estimates. The modeling shows that the feeders affect the launched power spectrum in an indirect way by forcing the driven rf current to return in the antenna sidewalls rather than in the plasma as in the 2-D model. Thus, the feeders have much more influence than the plasma on the currents that return in the sidewall. It has also been found that poloidal dependencies in the plasma impedance matrix can reduce the loading from that predicted in the 2-D model. For some plasma parameters, the combined 3-D effects can lead to a reduction in the predicted loading by as much as a factor of 2 from that given by the 2-D model.

Carter, M.D.; Batchelor, D.B.; Stallings, D.C.

1993-09-01

356

Development of a superconducting radio frequency photoelectron injector  

NASA Astrophysics Data System (ADS)

A superconducting radio frequency (RF) photoelectron injector (SRF gun) is under development at the Research Center Dresden Rossendorf. This project aims mainly at replacing the present thermionic gun of the superconducting electron linac ELBE. Thereby the beam quality is greatly improved. Especially, the normalized transverse emittance can be reduced by up to one order of magnitude depending on the operating conditions. The length of the electron bunches will be shortened by about two orders of magnitude making the present bunchers in the injection beam line dispensable. The maximum obtainable bunch charge of the present thermionic gun amounts to 80 pC. The SRF gun is designed to deliver also higher bunch charge values up to 2.5 nC. Therefore, this gun can be used also for advanced facilities such as energy recovery linacs (ERLs) and soft X-ray FELs. The SRF gun is designed as a 312 cell cavity structure with three cells basically TESLA cells supplemented by a newly developed gun cell and a choke filter. The exit energy is projected to be 9.5 MeV. In this paper, we present a description of the design of the SRF gun with special emphasis on the physical and technical problems arising from the necessity of integrating a photocathode into the superconducting cavity structure. Preparation, transfer, cooling and alignment of the photocathode are discussed. In designing the SRF gun cryostat for most components wherever possible the technical solutions were adapted from the ELBE cryostat in some cases with major modifications. As concerns the status of the project the design is finished, most parts are manufactured and the gun is being assembled. Some of the key components are tested in special test arrangements such as cavity warm tuning, cathode cooling, the mechanical behavior of the tuners and the effectiveness of the magnetic screening of the cavity.

Arnold, A.; Bttig, H.; Janssen, D.; Kamps, T.; Klemz, G.; Lehmann, W. D.; Lehnert, U.; Lipka, D.; Marhauser, F.; Michel, P.; Mller, K.; Murcek, P.; Schneider, Ch.; Schurig, R.; Staufenbiel, F.; Stephan, J.; Teichert, J.; Volkov, V.; Will, I.; Xiang, R.

2007-07-01

357

Low radio frequency observation of Nova Delphini 2013  

NASA Astrophysics Data System (ADS)

Nova Delphini 2013 (ATel #5279), a very fast (ATel #5297), optically bright FeII type classical nova on a CO white dwarf (ATel #5282, #5304, #5337), was observed with the Giant Metrewave Radio Telescope (GMRT) on August 28, 2013 (~2 weeks after the outburst). No radio continuum counterpart is detected at the position of the nova down to the 3sigma flux density limit of 150 microJy at 1.3 GHz. Earlier observations with the VLA and the CARMA also detected no radio emission at 5 - 96 GHz (ATel #5298), constraining the distance to be more than 2 kpc.

Roy, Nirupam; Kantharia, Nimisha G.; Dutta, Prasun; Anupama, G. C.; Ashok, N. M.; Banerjee, Dipankar P. K.

2013-09-01

358

Radiation effects on communication performance of radio frequency identification tags.  

PubMed

Radioactive materials (sources) are managed by bookkeeping and stocktaking. The radiation protection section staffs should check the sources manually. Annual effective dose concerning stocktaking of them are estimated at some mSv concerning fingers. A radio frequency identification (RFID) tag's absorbed dose is estimated at some dozen Gy. RFID for stocktaking automatically was devised. Radiation effects on the communication performance of RFID tags were investigated by using response times and read ranges as indices. The RFID system was composed of a computer, a detector, and transponders (tag) consisting of an integrated circuit chip and an antenna. The tag is joined to the source for identification. The tags were irradiated at doses between 5 and 5,000 Gy by an x-ray irradiator. The response times and the read ranges were tracked from 40 to 23,200 min after irradiation. Relative read ranges fluctuated between 0.9 and 1.1 in the dose region less than 2,000 Gy, but fluctuated greatly in the dose region beyond 2,000 Gy. Malfunctioning tags appeared from 3,000 Gy, and all tags malfunctioned in the dose region over 4,500 Gy. The threshold dose leading to malfunction was determined to be 2,100 Gy. Time variation of relative read ranges was classified into four patterns. The pattern shifted from pattern 1 to 4 when the dose was increased. The relative read ranges lengthened in pattern 1. The relative read rages were approximately 1.0 in pattern 2. The read ranges tentatively shortened, then recovered in pattern 3. The tags malfunctioned in pattern 4. Once the tags malfunctioned, they never recovered their performance. Radiation enhances or deteriorates communication performance depending on dosage. Tags can spontaneously recover from radiation deterioration. The time variation of the read ranges can be illustrated by enhancement, deterioration, and recovery. The mechanism of four patterns is explained based on the variation of the frequency harmonization strength and activation voltage by irradiation. The annual effective dose of radiation protection section staffs can be reduced considerably. PMID:20938239

Mori, Kazuyuki; Meng, Zhaowu; Kikuchi, Hirosumi; Kataoka, Yasuhide; Nakazato, Kazuhisa; Deji, Shizuhiko; Ito, Shigeki; Saze, Takuya; Hirota, Masahiro; Nishizawa, Kunihide

2010-11-01

359

Comparison of radio transmission at X-band frequencies in suburban and urban areas  

Microsoft Academic Search

Measurements were made at a frequency of 11.2 GHz of the signal strength received by a fixed-base station from a mobile transmitter. Distributions of the instantaneous and rms signal levels are compared for data taken in New York City and suburban New Providence, N. J.

D. Reudink

1972-01-01

360

Inhibition of a Demand Pacemaker and Interference with Monitoring Equipment by Radio-frequency Transmissions  

Microsoft Academic Search

During the initial testing of Radio Leicester a swept-frequency technique for testing radio antennae was shown to affect demand pacemakers by inhibition of the pacing impulse and to interfere with physiological monitoring equipment. Adequate filtering of demand pacemakers is necessary to eliminate this interference. There is no evidence that such testing has any effect on the function of fixed-rate pacemakers.

Bryan A. Pickers; M. J. Goldberg

1969-01-01

361

A reliable frequency lock detection for Software-Defined Radio (SDR) systems  

Microsoft Academic Search

This work proposes a new approach on the frequency lock detection suitable for high QAM modulations which are used in many reconfigurable Software-Defined-Radio (SDR) systems. This work contains a reliable mechanism to enable a radio system working under very low signal-to-noise ratio (SNR) environments, with high coding gain scenarios such as TPC, LDPC, etc.

D. N. Vo

2010-01-01

362

Radio Frequency IDentification (RFID) working, design considerations and modelling of antenna  

Microsoft Academic Search

RFID is the acronym of radio frequency identification. It represents a new automated data-capture technology, based on the extraction of data contained in devices called RFID tags or transponders by wireless radio technologies. In the RFID appellation we find RF. For memory, who says RF says laws of the physics such as, laws of Maxwell and those of Biot and

Nejah NASRI; Nacer KACHOURI; Mounir SAMET; Laurent Andrieux

2008-01-01

363

Frequency and phase fluctuations of radio waves during propagation in the Venus atmosphere  

Microsoft Academic Search

Radio-occultation data on the Venus atmosphere obtained with the Venera-10 probe are used to analyze the effect of atmospheric irregularities on frequency and phase fluctuations of radio waves at a wavelength of 32 cm; the experiments were carried out in March 1976. It is shown that, as in the case of amplitude fluctuations, when the line of sight is removed

A. I. Efimov; V. M. Razmanov; T. S. Timofeeva; O. I. Iakovlev

1982-01-01

364

Using radio frequency identification in agent-based control systems for industrial applications  

Microsoft Academic Search

The radio frequency identification (RFID) is a technology for automatic identification of items, particularly in supply chain, but it is becoming increasingly important for industrial applications. Unlike barcode technology that detects the optical signals reflected from barcode labels, RFID uses radio waves to transmit the information from an RFID tag affixed to the physical object. In contrast to today most

Pavel Vrba; Filip Macurek; Vladimr Mark

2008-01-01

365

Radio Frequency Field Calculations for Plasma Heating Simulations in VASIMR  

NASA Astrophysics Data System (ADS)

(VASIMR)1 is plasma heating by ion-cyclotron RF heating (ICRF). Mathematical simulation helps to design an ICRF antenna, i.e. make maximal absorption of RF power into the plasma in the resonance area. Another goal of a particle simulation is design of a magnetic nozzle and optimize the performance of VASIMR2. field in the plasma, 2) ion density and velocity, 3) ion-cyclotron radio-frequency electromagnetic field. The assumptions of quasineutral and collisionless plasma are based on the range of operating VASIMR parameters. Carlo simulations for systems of million of particles in a reasonable time and without the need for a powerful supercomputer. The particle to grid weighting method is used for calculating the ion density, which is used for recalculation of the electric potential and RF field. dimensional problem to a weighted sum over two-dimensional solutions. Absorption is introduced in the cold plasma model by adding an imaginary collision frequency to the RF driven frequency, which is equivalent to adding an imaginary particle mass in the dielectric tensor elements. static and RF fields using the VASIMR code2. The VASIMR and EMIR codes are then iterated to estimate the ICRF effects on the plasma density. The iteration is performed by calculating the RF fields with the EMIR code, and using these fields to follow nonlinear ion trajectories with the VASIMR code on the gyro-frequency time scale. The ion trajectories are used to generate RF power absorption values and a density input for the next EMIR calculation. The codes are iterated until the density profile becomes reasonably stable, then the collisional absorption parameter in the EMIR code is adjusted and the iteration is continued until the power deposited by the RF system matches the power absorbed by the ion trajectories in a global sense. electric field. The solved algebraic system of equations is represented by ill-conditioned 18-diagonal matrix with complex elements. Since early development of the EMIR code, the frontal method direct solver was used. That solver requires large CPU time and RAM, which both are proportional to Nr Nz2, for a grid of the size Nr x Nz. These requirements make almost impossible to use existent EMIR solver on PC to obtain RF fields with good accuracy. system. The suggested iterative method is Modified Incomplete Cholesky Preconditioned Conjugate Gradient Squared solver4. The solver involves a couple of the control parameters, which let a user tune the code to make iterations converge as fast as possible for a particular grid. Since the iterative solver does not require large RAM, and works much faster than the direct solver, the new algorithm lets us resolve RF fields on a PC with required accuracy. REFERENCES 1. Chang Daz F.R., "Research Status of The Variable Specific Impulse Magnetoplasma Rocket", Proc. 39th Annual Meeting of the Division of Plasma Physics (Pittsburgh, PA, 1997), Bulletin of APS, 42 2057. 2. Ilin A.V., Chang Daz F.R., Squire J.P. and Carter M.D. "Monte Carlo Particle Dynamics in a Variable Specific Impulse Magnetoplasma Rocket", (Proceedings of Open Systems' 98), Transactions of Fusion Technology, 35 330 - 334 (1999). 3. Jaeger E.F., Batchelor D.B., Weitzner H. and Whealton J.H. "ICRF Wave Propagation And Absorption in Tokamak And Mirror Magnetic Fields - A Full-wave Calculation", Computer Physics Com., 40 33 - 64 (1986). 4. Ilin, A. V., Bagheri, B., Scott, L. R., Briggs, J. M., and McCammon, J. A. "Parallelization of Poisson-Boltzmann and Brownian Dynamics calculation", Parallel Computing in Computational Chemistry, ACB Books, Washington D.C., (1995) 170-185.

Ilin, A. V.; Daz, F. R. Chang; Squire, J. P.; Carter, M. D.

2002-01-01

366

Review of radio-frequency, nonlinear effects on the ionosphere  

SciTech Connect

Modification of the ionosphere by high power radio waves in the megahertz band has been intensively investigated over the past two decades. This research has yielded advances in aeronomy, geophysics, and plasma physics with applications to radio communication and has provided a fruitful interaction of radio theorists and experimentalists. There being almost no linear effects of powerful radio waves on the ionosphere, we concentrate on the nonlinear effects. To put the subject in perspective we trace its history beginning in the early 1930s and highlight the important events up to the late 1960s. We then shift to a phenomenological approach and deal in order with ohmic heating, parametric instabilities, self-focusing and kilometer-scale irregularities, meter-scale irregularities, and a collection of recently discovered effects. We conclude with the observation that stronger international cooperation would benefit this research, and describe a list of promising, difficult challenges.

Gordon, W.E.; Duncan, L.M.

1983-01-01

367

Radio frequency observations of galactic X-ray sources  

Microsoft Academic Search

Fourteen galactic X-ray sources were surveyed with the VLA at 1.4 GHz in search of radio morphologies similar to that of Sco X-1. Five objects were detected, and substantially improved positions are presented for three of these. In two cases, optical counterparts are suggested. The radio\\/X-ray source 1820-304 is found to lie within 7arcsec of the core of the globular

B. J. Geldzahler

1983-01-01

368

REGENERATION AND REACTIVATION OF CARBON ADSORBENTS BY RADIO FREQUENCY INDUCTION HEATING  

EPA Science Inventory

1. Electrical Properties of Adsorbents: We measured the electric permittivity of four commercially available carbon adsorbents (supplied by Wesvaco Inc) over the radio frequency range (1 to 40 MHz). Westvaco is by far the largest volume supplier of activated carbon...

369

Defense Logistics: Better Strategic Planning Can Help Ensure DOD's Successful Implementation of Passive Radio Frequency Identification.  

National Technical Information Service (NTIS)

The Department of Defense (DOD) has had problems with tracking and identifying inventory for many years, most recently in Operation Iraqi Freedom. One of several tools DOD is using to address these inventory problems is radio frequency identification (RFI...

2005-01-01

370

76 FR 9714 - Defense Federal Acquisition Regulation Supplement; Passive Radio Frequency Identification (DFARS...  

Federal Register 2010, 2011, 2012, 2013

...of passive Radio Frequency Identification (RFID). DATES: Comments on the proposed rule should...identification, to-- --Clarify that the RFID requirement pertains solely to ``passive RFID''; --Supply a link to a web site in...

2011-02-22

371

Radio Frequency Hearing Aids: The Need for Complementary and Compatible Channel Allocation.  

ERIC Educational Resources Information Center

|The article discusses the use of radio frequency hearing aids, which provide a practical means of improving the signal-to-noise ratio of conventional hearing aids used by the aurally handicapped. (Author/DLS)|

Burgess, Vic; And Others

1979-01-01

372

Studies on the Effect of Radio-Frequency Waves in Biological Macromolecules.  

National Technical Information Service (NTIS)

The effect of radio-frequency electric fields on various biologic materials was examined. Particularly, the effects on alcohol dehydrogenase and DNA were carefully investigated. To avoid the effects of heating, a pulsed electric field was used, and sample...

S. Takashima

1965-01-01

373

Base-level management of radio-frequency radiation-protection program. Final report  

SciTech Connect

AFOEHL developed this report to assist the base-level aerospace medical team manage their radio-frequency radiation-protection program. This report supersedes USAFOEHL Report 80-42, 'A Practical R-F Guide for BEES.'

Rademacher, S.E.; Montgomery, N.D.

1989-04-01

374

Base-level management of radio-frequency radiation-protection program. Final report  

SciTech Connect

AFOEHL developed this report to assist the base-level aerospace medical team manage their radio-frequency radiation protection program. This report supersedes USAFOEHL Report 80-42, 'A practical R-F Guide for BEES.'

Rademacher, S.E.; Montgomery, N.D.

1989-04-01

375

Random Access Algorithm for Frequency Hopped Spread Spectrum Packet Radio Networks.  

National Technical Information Service (NTIS)

The authors consider packet radio multi-user spread-spectrum environments, where frequency hopping spread spectrum techniques are deployed for protection against intelligent adversaries. When the users in such environments are mobile and bursty, random ac...

M. Georgiopoulos P. Papantoni-Kazakos

1986-01-01

376

THE ELECTRICAL PROPERTIES OF CHLORITE TREMOLITE MARBLE MEASURED FOR A RANGE OF RADIO FREQUENCIES  

Microsoft Academic Search

This article attempts to present a simple approach to measuring the electrical properties of rocks over the frequency range from 50MHz to 950MHz. These electrical properties, and especially the resonating frequency points, may prove useful in the transfer of radio frequency energy to rock samples for precomminution treatment of run of mine ore. The rock sample that was used consists

James Swart; Peter Mendonidis; Christo Pienaar

2009-01-01

377

Low frequency solar radio astronomy at the Indian Institute of Astrophysics (IIA)  

NASA Astrophysics Data System (ADS)

IIA is presently involved in the expansion of its existing radioheliograph operating in the frequency 120-40 MHz at the Gauribidanur radio observatory located about 80 km north of Bangalore. Once completed, the expanded array will have an angular resolution of ? 1' at a typical frequency of 100 MHz. This paper describes the development of solar radio astronomy activities at IIA since 1952 when the first observations were carried out.

Ramesh, R.

378

FORTE observations of lightning radio-frequency signatures: Capabilities and basic results  

Microsoft Academic Search

The FORTE satellite, launched on August 29, 1997, carries both radio-frequency-receiver and optical (imaging and photometric) payloads for the study of lightning. The radio-frequency (RF) data for the first 7 months of operation are described, both to illustrate the satellite{close_quote}s capabilities and to explain the basic statistical findings so far. FORTE{close_quote}s multichannel RF trigger system represents a significant advance in

Abram R. Jacobson; Stephen O. Knox; Robert Franz; Donald C. Enemark

1999-01-01

379

RADIO FREQUENCY-HOT WATER DIPS FOR POSTHARVEST CODLING MOTH CONTROL IN APPLES  

Microsoft Academic Search

A combination radio frequency-hot water dip method was examined as a potential quarantine treatment against fifth instars of the codling moth, Cydia pomonella L. (Lepidoptera: Tortricidae), in apples, Malus sylvestris (L.) var. domestica (Borkh.) Mansf., which were intended for export to Japan. The apples were initially exposed to 27.12-MHz radio frequency energy at 12 kW for 2.75 min and were

J. D. HANSEN; S. R. DRAKE; M. L. HEIDT; M. A. WATKINS; J. TANG; S. WANG

2006-01-01

380

A low-power OOK ultra-wideband transmitter with power cycling and spectral flexibility  

Microsoft Academic Search

This paper presents a reconfigurable 0.13 ?m CMOS impulse radio ultra-wideband transmitter which supports the on-off keying modulation scheme. The transmitter allows for control of the center frequency and bandwidth of the output spectrum, thus providing large spectrum flexibility. A power cycling scheme is implemented to reduce the power consumption, and allows the system to operate within stringent power requirements.

Raslen Hamdi; Kamel Elkhenissi; Dominic Deslandes; Frederic Nabki

2010-01-01

381

Radio frequency radiation risk: A study focused on wireless telephones  

NASA Astrophysics Data System (ADS)

The focus of this dissertation is radio frequency radiation (RFR) from wireless telephony handsets and the risk assessment conducted for purposes of protecting health from this RFR. In the United States, the Federal Communications Commission (FCC) promulgates and enforces occupational and public health exposure limits for wireless telephone handsets. The FCC has relied upon the risk assessment of the Institute of Electrical and Electronics Engineers (IEEE) Standards Coordinating Committee 28 (SCC-28) in crafting these exposure limits. Using qualitative research methods of policy analysis, the procedures used by SCC-28, the people who make up SCC-28, and the results of SCC-28 efforts were evaluated. The objective was to determine if SCC-28 adequately evaluated wireless RFR health effects research to substantiate its partial body exposure limit recommendations, those pertinent to exposure of the human head from wireless telephone handsets. This is critical because the SCC-28 recommendations have been the primary basis for FCC regulations on exposures from the wireless telephone handsets. The research methods employed were a systematic evaluation of published and unpublished comments and interview. The systematic evaluation of published and unpublished comments consisted of an analysis of records of activity in the minutes of SCC-28 as well as the collective perspectives of other knowledgeable individuals and groups in publications. This evaluation also included an in-depth literature review of hundreds of primary research publications designed to assess the nature and quality of wireless RFR health effects data available to risk assessors. Interview was accomplished using a detailed questionnaire. The National Academy of Sciences (NAS) criteria for risk assessment in the federal government were used to as the framework with which to assess the functions of SCC-28. To assess the recommendations of the results of SCC-28 risk assessment, the RFR health effects research literature was analyzed. This analysis examined whether evidence of risk was available and adequately considered in light of the judgements of authoritative individuals and organizations. Review of the health effects literature does not indicate significant risk from wireless telephone RFR, though much more research and risk assessment is needed to rule out low levels of risk. (Abstract shortened by UMI.)

Irwin, William Edward, III

382

Radio Frequency Station - Beam Dynamics Interaction in Circular Accelerators  

SciTech Connect

The longitudinal beam dynamics in circular accelerators is mainly defined by the interaction of the beam current with the accelerating Radio Frequency (RF) stations. For stable operation, Low Level RF (LLRF) feedback systems are employed to reduce coherent instabilities and regulate the accelerating voltage. The LLRF system design has implications for the dynamics and stability of the closed-loop RF systems as well as for the particle beam, and is very sensitive to the operating range of accelerator currents and energies. Stability of the RF loop and the beam are necessary conditions for reliable machine operation. This dissertation describes theoretical formalisms and models that determine the longitudinal beam dynamics based on the LLRF implementation, time domain simulations that capture the dynamic behavior of the RF station-beam interaction, and measurements from the Positron-Electron Project (PEP-II) and the Large Hadron Collider (LHC) that validate the models and simulations. These models and simulations are structured to capture the technical characteristics of the system (noise contributions, non-linear elements, and more). As such, they provide useful results and insight for the development and design of future LLRF feedback systems. They also provide the opportunity to study diverse longitudinal beam dynamics effects such as coupled-bunch impedance driven instabilities and single bunch longitudinal emittance growth. Coupled-bunch instabilities and RF station power were the performance limiting effects for PEP-II. The sensitivity of the instabilities to individual LLRF parameters, the effectiveness of alternative operational algorithms, and the possible tradeoffs between RF loop and beam stability were studied. New algorithms were implemented, with significant performance improvement leading to a world record current during the last PEP-II run of 3212 mA for the Low Energy Ring. Longitudinal beam emittance growth due to RF noise is a major concern for LHC. Simulations studies and measurements were conducted that clearly show the correlation between RF noise and longitudinal bunch emittance, identify the major LLRF noise contributions, and determine the RF component dominating this effect. With these results, LHC upgrades and alternative algorithms are evaluated to reduce longitudinal emittance growth during operations. The applications of this work are described with regard to future machines and analysis of new technical implementations, as well as to possible future work which would continue the directions of this dissertation.

Mastoridis, Themistoklis; /Stanford U., Elect. Eng. Dept. /SLAC

2011-03-01

383

Indication of radio frequency interference (RFI) sources for solar burst monitoring in Malaysia  

NASA Astrophysics Data System (ADS)

Apart of monitoring the Sun project, the Radio Frequency Interference (RFI) surveying in the region of (1-1200) MHz has been conducted. The main objective of this surveying is to test and qualify the potential of monitoring a continuous radio emission of Solar in Malaysia. This work is also an initiative of International Space Weather Initiative (ISWI) project where Malaysia is one of the country that participate a e-Callisto Spectrometer network in order to study the behavior of Solar radio burst in frequency of (45-800) MHz region which will be install in this October. Detail results will indicate the potential of monitoring a solar in Malaysia.

Hamidi, Z. S.; Abidin, Z. Z.; Ibrahim, Z. A.; Shariff, N. N. M.

2012-06-01

384

TUNE MODULATION FROM BEAM BEAM INTERACTION AND UNEQUAL RADIO FREQUENCIES IN RHIC.  

SciTech Connect

The two RHIC rings have independent rf systems to accommodate different species. Thus, the radio frequencies can differ when the phase and radial loops are closed, and the if frequencies of the two rings are not synchronized. A radio frequency difference leads to longitudinally moving beam crossing points. When the crossing points are between the beam splitting dipoles, the beams experience the beam-beam interaction. Outside the interaction region the beam-beam interaction is switched off. In this way the tune is modulated. A computation of the tune modulation depth, pulse shape and frequency is presented. Tune modulation measurements are shown.

FISCHER,W.CAMERON,P.PEGGS,S.SATOGATA,T.

2003-05-19

385

Type III solar radio burst storms observed at low frequencies  

Microsoft Academic Search

Storms of type III solar radio bursts observed from 5.4 to 0.2 MHz, indicate the quasicontinuous production of type III events observable for a half solar rotation but persisting in some cases for well over a complete rotation. The characteristics of these storms, including the dependance of occurrence and apparent drift rates on the disc position of the associated active

Joseph Fainberg; R. G. Stone

1970-01-01

386

Radio-Frequency Induction for Checking Fire Detectors.  

National Technical Information Service (NTIS)

A new method of testing fire detectors in the glove-box lines has been developed. The method includes heating the fire detector by a strong electromagnetic field which induces eddy currents in the metal case of the fire detector. Developed as a radio-freq...

H. J. Aarts W. B. Evans L. W. Utley

1976-01-01

387

Power absorption in electrically asymmetric dual frequency capacitive radio frequency discharges  

SciTech Connect

The symmetry of capacitive radio frequency discharges can be controlled via the electrical asymmetry effect by driving one electrode with a fundamental frequency and its second harmonic. In such electrically asymmetric discharges, the mean ion energies at both electrodes are controlled separately from the ion flux by tuning the phase angle {theta} between the harmonics at fixed voltage amplitudes. Here, the question why the ion flux is nearly independent of {theta} is answered by investigating the power absorbed by the electrons P{sub e} as a function of {theta} and time experimentally, by a particle in cell simulation, and an analytical model. The dynamics of P{sub e} is understood by the model and is found to be strongly affected by the choice of {theta}. However, on time average, P{sub e} is nearly constant, independently of {theta}. Thus, the ion flux remains approximately constant. In addition, it is shown that the absolute value of the individual voltages across the powered and grounded electrode sheath vary linearly with the dc self-bias. However, their sum remains constant. This yields, in combination with the constancy of the ion flux, a constant power absorbed by the ions and, in conclusion, a total power absorption that is independent of {theta}.

Schuengel, E.; Czarnetzki, U. [Institute for Plasma and Atomic Physics, Ruhr-University Bochum, 44780 Bochum (Germany); Schulze, J. [Institute for Plasma and Atomic Physics, Ruhr-University Bochum, 44780 Bochum (Germany); Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest (Hungary); Donko, Z. [Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest (Hungary)

2011-01-15

388

Frequency-domain equalization of mobile radio and terrestrial broadcast channels  

Microsoft Academic Search

For mobile radio and terrestrial broadcast applications, we compare orthogonal frequency-division multiplexing (OFDM) and single-carrier transmission with frequency-domain equalization. With respect to our earlier results, we include channel coding and frequency-domain interleaving which are necessary for OFDM systems on multipath fading channels characterized by deep notches in the signal spectrum. Our results indicate that a single-carrier system with a frequency-domain

H. Sari; G. Karam; I. Jeanclaudle

1994-01-01

389

Radio bursts with rapid frequency variations - Lace bursts  

Microsoft Academic Search

The Ondrejov radiospectrograph operating in the 0.8-2.0 GHz frequency range recorded in recent years (1998-2000), three (August 10, 1998; August 17, 1999; June 27, 2000) unique bursts with rapid frequency variations (lace bursts) lasting for several minutes. On August 17, 1999, the same burst was recorded simultaneously by the Brazilian Solar Spectroscope in the 1.0-2.5 GHz frequency range. The frequency

M. Karlick; M. Brta; K. Jiricka; H. Mszrosov; H. S. Sawant; F. C. R. Fernandes; J. R. Cecatto

2001-01-01

390

Modified transmitter attachment method for adult ducks  

USGS Publications Warehouse

The value of radio telemetry for waterfowl research depends on the availability of suitable methods of attaching transmitters. In previous studies, external transmitters attached to adult Mallards (Anas platyrhynchos) with sutures and glue did not stay on birds reliably. In an attempt to improve transmitter retention, a method of attachment was tested in which 4-g transmitters were attached mid-dorsally with sutures and with a stainless steel anchor-shaped wire inserted subcutaneously (anchor transmitters). Field tests indicated that all of 26 female Mallards and 63 of 65 female Gadwalls (Anas strepera) retained their anchor transmitters during 4369 bird-days of monitoring during nesting and brood rearing. Survival rates of females with anchor transmitters compared favorably with those reported from other studies. In this study, females with and without anchor transmitters did not differ with respect to survival rates of their ducklings. The anchor transmitter may be suitable for a variety of field studies on numerous species.

Pietz, P. J.; Brandt, D. A.; Krapu, G. L.; Buhl, D. A.

1995-01-01

391

Type III solar radio burst storms observed at low frequencies  

Microsoft Academic Search

The analysis of a storm of type III solar radio bursts observed in August 1968 between 5 and 0.2 MHz by the RAE-1 satellite has yielded the storm morphology, a possible relation to meter and decameter storms, and an average exciter speed of 0.37 c between 10 and 40 R? (Fainberg and Stone, 1970a, b). A continuation of the analysis,

Joseph Fainberg; R. G. Stone

1971-01-01

392

Read distance performance and variation of 5 low-frequency radio frequency identification panel transceiver manufacturers.  

PubMed

Use of electronic animal identification technologies by livestock managers is increasing, but performance of these technologies can be variable when used in livestock production environments. This study was conducted to determine whether 1) read distance of low-frequency radio frequency identification (RFID) transceivers is affected by type of transponder being interrogated; 2) read distance variation of low-frequency RFID transceivers is affected by transceiver manufacturer; and 3) read distance of various transponder-transceiver manufacturer combinations meet the 2004 United States Animal Identification Plan (USAIP) bovine standards subcommittee minimum read distance recommendation of 60 cm. Twenty-four transceivers (n = 5 transceivers per manufacturer for Allflex, Boontech, Farnam, and Osborne; n = 4 transceivers for Destron Fearing) were tested with 60 transponders [n = 10 transponders per type for Allflex full duplex B (FDX-B), Allflex half duplex (HDX), Destron Fearing FDX-B, Farnam FDX-B, and Y-Tex FDX-B; n = 6 for Temple FDX-B (EM Microelectronic chip); and n = 4 for Temple FDX-B (HiTag chip)] presented in the parallel orientation. All transceivers and transponders met International Organization for Standardization 11784 and 11785 standards. Transponders represented both one-half duplex and full duplex low-frequency air interface technologies. Use of a mechanical trolley device enabled the transponders to be presented to the center of each transceiver at a constant rate, thereby reducing human error. Transponder and transceiver manufacturer interacted (P < 0.0001) to affect read distance, indicating that transceiver performance was greatly dependent upon the transponder type being interrogated. Twenty-eight of 30 combinations of transceivers and transponders evaluated met the minimum recommended USAIP read distance. The mean read distance across all 30 combinations was 45.1 to 129.4 cm. Transceiver manufacturer and transponder type interacted to affect read distance variance (P < 0.05). Maximum read distance performance of low-frequency RFID technologies with low variance can be achieved by selecting specific transponder-transceiver combinations. PMID:20407068

Ryan, S E; Blasi, D A; Anglin, C O; Bryant, A M; Rickard, B A; Anderson, M P; Fike, K E

2010-04-20

393

Silicon photonic on-chip spectral shaper for ultra-broadband radio frequency arbitrary waveform generation  

Microsoft Academic Search

Silicon photonics technology attracts increasing interest in lightwave communication systems, as well as in high speed interconnection within or in-between central processing units (CPUs). A novel application of silicon photonics is in the microwave area: high carrier frequency of lightwave and ultra-compact optical devices on a silicon platform enable an integrated solution for certain broadband Radio Frequency (RF) applications, such

Hao Shen

2010-01-01

394

Exposure to radio frequency radiation emitted by cell phone and mortality in chick embryos (Gallus domesticus)  

Microsoft Academic Search

The rapidly increasing use of cell phones since late 1990s has caused a general concern on the possible hazardous health effects of exposure to radio frequency electro-magnetic radiation (EMR) emitted by them. While considering the bio- logical effects of EMR on the human body, its intensity, frequency of radiation and duration of exposure are important determinants. Many researchers have reported

I. V. Ingole; S. K. Ghosh

2006-01-01

395

Gas Breakdown of Radio Frequency Glow Discharges in Helium at near Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

A one-dimensional self-consistent fluid model was developed for radio frequency glow discharge in helium at near atmospheric pressure, and was employed to study the gas breakdown characteristics in terms of breakdown voltage. The effective secondary electron emission coefficient and the effective electric field for ions were demonstrated to be important for determining the breakdown voltage of radio frequency glow discharge at near atmospheric pressure. The constant of A was estimated to be 644 cm-1Torr-1, which was proportional to the first Townsend coefficient and could be employed to evaluate the gas breakdown voltage. The reduction in the breakdown voltage of radio frequency glow discharge with excitation frequency was studied and attributed to the electron trapping effect in the discharge gap.

Liu, Xinkun; Xu, Jinzhou; Cui, Tongfei; Guo, Ying; Zhang, Jing; Shi, Jianjun

2013-07-01

396

Radio frequency interference mitigation with phase-only adaptive beam forming  

NASA Astrophysics Data System (ADS)

Connected radio interferometers are sometimes used in the tied array mode: signals from antenna elements are coherently added and the sum signal applied to a very long baseline interferometry (VLBI) back-end or pulsar-processing machine. Usually, there is no computer-controlled amplitude weighting in the existing radio interferometer facilities. Radio frequency interference (RFI) mitigation with phase-only adaptive beam forming is proposed for this mode of observation. Small phase perturbations are introduced in each of the antenna's signals. The values of these perturbations are optimized in such a way that the signal from a radio source of interest is preserved and RFI signals are suppressed. An evolutionary programming algorithm is used for this task. Computer simulations, made for both one-dimensional and two-dimensional array setups, show considerable suppression of RFI and acceptable changes to the main array beam in the radio source direction.

Fridman, P. A.

2005-05-01

397

Weighted mean tropospheric temperature and transmittance determination at millimeter-wave frequencies for ground-based applications  

Microsoft Academic Search

A simple model for the radiometric determination of tropospheric transmittance is based on an isothermal troposphere. In this model the key parameter is the weighted mean tropospheric temperature Tm, which characterizes the radiation and temperature properties of the troposphere. Statistical approaches in modeling this parameter are presented here by using ground temperature, ground relative humidity, and radiometer data. In order

T. Ingold; R. Peter; N. Kmpfer

1998-01-01

398

Parametric decay of high-frequency radio waves of high intensity in an ionospheric plasma  

Microsoft Academic Search

The parametric instability of ionospheric plasma in a field of intense radio waves in the meter range is discussed. In particular, the decay of high-frequency radio waves into Langmuir and transverse electromagnetic (i.e., stimulated Raman scattering) and into ion-acoustic and electromagnetic waves (i.e., stimulated Brillouin scattering) is considered. A calculation of the threshold fields and increments of perturbation growth number

A. S. Abyzov; A. S. Bakai; G. K. Solodovnikov

1981-01-01

399

Experimental Study of Radio Frequency Transmission over Standard and High-Bandwidth Multimode Optical Fibers  

Microsoft Academic Search

We experimentally study radio frequency (RF) transmission over several standard (core diameter 62.5 gm) and high-bandwidth (core diameter 50 ?m) multimode fibers (MMFs) with a wide range of bandwidths (170 MHzkm to 2600 MHzkm). Performance of the radio-over-fiber (RoF) link is assessed in terms of the error vector magnitude (EVM). An IEEE 802.11b\\/gwirless access point and a MMF link using

Michael Sauer; Andrey Kobyakov; J. E. Hurley; J. George

2005-01-01

400

Frequency effects on the electron density and {alpha}-{gamma} mode transition in atmospheric radio frequency discharges  

SciTech Connect

In this paper, a one-dimensional model is explored to investigate the frequency effects on the characteristics of atmospheric radio frequency discharges at a given power. The simulation data and analytical results show that the improvement of electron density can be observed with better discharge stability by increasing excitation frequency in an appropriate range. Using the analytical equations deduced from the model, the mean electron density could be inferred by means of the measured parameters. The {alpha}-{gamma} mode transition especially in high frequency discharges is also analytically discussed based on the theoretical equations.

Zhang Yuantao [Shandong Provincial Key Lab of UHV Technology and Gas Discharge Physics, School of Electrical Engineering, Shandong University, Jinan, Shandong Province 250061 (China); Cui Shaoyan [School of Mathematics and Information, Ludong University, Yantai, Shandong Province 264025 (China)

2011-08-15

401

Dielectric properties of salmon ( Oncorhynchus keta) and sturgeon ( Acipenser transmontanus) caviar at radio frequency (RF) and microwave (MW) pasteurization frequencies  

Microsoft Academic Search

Radio frequency (RF) and microwave (MW) heating provide an important advantage of more rapid heat penetration in pasteurization processes for heat labile high value foods, which to date, have only been pasteurized by conductive heating. The objectives of this work were to determine the dielectric constant, loss factor and power penetration depth for salmon (0.8% and 2.3% total salt) and

Murad Al-Holy; Yifen Wang; Juming Tang; Barbara Rasco

2005-01-01

402

Frequency Characteristics Measurement of Overhead High-Voltage Power-Line in Low Radio-Frequency Range  

Microsoft Academic Search

This paper presents measurement results of frequency characteristics of the high-voltage power line in low radio-frequency range: amplitude and phase characteristic, group delay, and input impedance. Measurement results for the 400-kV overhead power-line under operation are presented together with the developed measurement methodology. The methodology provides a method to measure amplitude and phase characteristics, group delay and the return loss

M. Zajc; N. Suljanovic; A. Mujcic; J. F. Tasic

2007-01-01

403

Response of radio frequency superconducting quantum interference devices to electromagnetic interferencea)  

Microsoft Academic Search

A number of applications of high-temperature superconductor radio frequency superconducting quantum interference devices (rf SQUIDs) require a certain immunity of these sensors against electromagnetic interference (EMI). We have investigated effects of electromagnetic radiation in the high-frequency and ultrahigh-frequency range on various types of rf SQUIDs. It has been found that EMI of sufficient field strength reduces the voltage versus flux

M. Mueck; J. Dechert; J. Gail; M. Kreutzbruck; S. Schoene; R. Weidl

1995-01-01

404

Robotic Assisted Radio-Frequency Ablation of Liver Tumors - Randomized Patient Study  

PubMed Central

The minimally invasive treatment of liver tumors represents an alternative to the open surgery approach. Radio-frequency ablation destroys a tumor by delivering radio-frequency energy through a needle probe. Traditionally, the probe is placed manually using imaging feedback. New approaches use robotic devices to accurately place the instrument at the target. The authors developed an image-guided robotic system for percutaneous interventions using computed tomography. The paper presents a randomized patient study comparing the manual versus robotic needle placement for radio-frequency ablation procedures of liver tumors. The results of this study show that in our case robotic interventions were a very viable solution. Several treatment parameters such as radiation exposures and procedure-times were found to be significantly improved in the robotic case.

Patriciu, A; Awad, M; Solomon, S.B.; Choti, M; Mazilu, D; Kavoussi, L; Stoianovici, D

2011-01-01

405

UTag: Long-range Ultra-wideband Passive Radio Frequency Tags  

SciTech Connect

Long-range, ultra-wideband (UWB), passive radio frequency (RF) tags are key components in Radio Frequency IDentification (RFID) system that will revolutionize inventory control and tracking applications. Unlike conventional, battery-operated (active) RFID tags, LLNL's small UWB tags, called 'UTag', operate at long range (up to 20 meters) in harsh, cluttered environments. Because they are battery-less (that is, passive), they have practically infinite lifetimes without human intervention, and they are lower in cost to manufacture and maintain than active RFID tags. These robust, energy-efficient passive tags are remotely powered by UWB radio signals, which are much more difficult to detect, intercept, and jam than conventional narrowband frequencies. The features of long range, battery-less, and low cost give UTag significant advantage over other existing RFID tags.

Dowla, F

2007-03-14

406

Time delay measurements of current primary FAA air/ground transmitters and receivers  

NASA Astrophysics Data System (ADS)

The results of tests performed by ACW-300B, Spectrum Engineering Group, in determining the amount of time delay present in various air/ground communications equipment are detailed. This test was comprised of an Federal Aviation Administration (FAA) Air Navigation Ground Radio Transmitter (AN-GRT-21) and an FAA Air Navigation Ground Radio Receiver (AN-GRR-23): two aircraft transceivers, a King KTR-905 very high frequency (VHF) transceiver, and a Collins VHF-251 Technical Standard Order (TSO) transceiver

Petro, John; Randazzo, Philip

1993-06-01

407

Non-detection at Venus of high-frequency radio signals characteristic of terrestrial lightning.  

PubMed

The detection of impulsive low-frequency (10 to 80 kHz) radio signals, and separate very-low-frequency (approximately 100 Hz) radio 'whistler' signals provided the first evidence for lightning in the atmosphere of Venus. Later, a small number of impulsive high-frequency (100 kHz to 5.6 MHz) radio signals, possibly due to lightning, were also detected. The existence of lightning at Venus has, however, remained controversial. Here we report the results of a search for high-frequency (0.125 to 16 MHz) radio signals during two close fly-bys of Venus by the Cassini spacecraft. Such signals are characteristic of terrestrial lightning, and are commonly heard on AM (amplitude-modulated) radios during thunderstorms. Although the instrument easily detected signals from terrestrial lightning during a later fly-by of Earth (at a global flash rate estimated to be 70 s(-1), which is consistent with the rate expected for terrestrial lightning), no similar signals were detected from Venus. If lightning exists in the venusian atmosphere, it is either extremely rare, or very different from terrestrial lightning. PMID:11201733

Gurnett, D A; Zarka, P; Manning, R; Kurth, W S; Hospodarsky, G B; Averkamp, T F; Kaiser, M L; Farrell, W M

2001-01-18

408

Impact of gate resistance in graphene radio frequency transistors  

NASA Astrophysics Data System (ADS)

The effect of gate resistance on the high frequency device properties of graphene transistors is explored. Decreasing this resistance does not alter the current gain cutoff frequency (fT), but it does allow for the power gain cutoff frequency (fmax) to be increased. Analysis of this effect reveals that the relative rate of change between fT and fmax is most sensitive to the relationship between the parasitic resistance in the device channel and the output conductance, a manifestation of device scaling in the triode regime. This result underlies the importance of a small output conductance in the scaling of graphene transistors.

Farmer, Damon B.; Valdes-Garcia, Alberto; Dimitrakopoulos, Christos; Avouris, Phaedon

2012-10-01

409

Health Aspects of Radio-Frequency Electromagnetic Radiation.  

National Technical Information Service (NTIS)

Many of the nonionizing electromagnetic radiation at certain frequencies, power levels, and exposure durations can produce biological effects or injury depending on multiple physical and biological variables. The pathophysiology is reviewed of exposure to...

M. Grandolfo

1974-01-01

410

Performance of a Frequency Hopping Radio at HF,  

National Technical Information Service (NTIS)

The report presents measurements made on the frequency hopping HF channel over an ionospheric path. The channel is compared to mathematical channel models, i.e. the discrete memoryless channel (DMC) and the Gilbert channel. Computer simulations with respe...

G. Hedby

1987-01-01

411

47 CFR 22.377 - Certification of transmitters.  

Code of Federal Regulations, 2011 CFR

...transmitters used in the Public Mobile Services, including those used with signal boosters, in-building radiation systems and cellular repeaters, must be certificated for use in the radio services regulated under this part. Transmitters must be...

2012-10-01

412

Structure of Sagittarius C observed at radio frequencies  

NASA Astrophysics Data System (ADS)

As discussed by Sofue and Handa (1984), two large radio continuum arcs cross the Galactic equator in the vicinity of the Galactic center. One arc, at longitude + 0.2 deg, brightens considerably over a 50 pc region nearest Sgr A, to which it is apparently connected by a remarkable set of curved filaments as reported by Yusef-Zadeh et al. (1984), the internal arc structure near Sgr A exhibits a unique series of parallel streamers. Here it is shown that Sgr C, located near the base of the second arc at l of about 359.45 deg, strongly resembles Sgr A and is connected to a filament which forms the brightest part of that arc. While there is no evidence that the Milky Way has a double nucleus, similarity between the Sgr A and C complexes suggests that some of the same striking phenomena can be studied at two locations near the Galactic center.

Liszt, H. S.

1985-06-01

413

Layer-like Structure of Radio-Frequency Discharge with Dust Particles  

SciTech Connect

In this paper we are carried out the computer simulation of the dust particles dynamics in the radio frequency discharges at the microgravity conditions using PIC/MCC method for electrons and ions and hydrodynamics model for dust particles. The moving of dust particles is governed by the electrostatic force, ion and neutral drag forces, which are averaged over period of RF discharge. The obtained results show that dust particles form layers with sharp boundaries in the discharge chamber that is response on the instability of the radio-frequency discharge.

Kravchenko, O. Y.; Vakulenko, A. V.; Lisitchenko, T. Y.; Levada, G. I. [National Taras Shevchenko University of Kyiv, Volodymirs'ka str. 64, 01033 Kyiv (Ukraine)

2008-09-07

414

An ultrasensitive radio-frequency single-electron transistor working up to 4.2 K  

Microsoft Academic Search

We present the measurement of a radio-frequency single-electron transistor that displays a very high charge sensitivity of 1.9 mue\\/Hz at 4.2 K. At 40 mK, the charge sensitivity is 0.9 and 1.0 mue\\/Hz in the superconducting and normal state, respectively. The sensitivity was measured as a function of radio frequency amplitude at three different temperatures; 40 mK, 1.8, and 4.2

Henrik Brenning; Sergey Kafanov; Tim Duty; Sergey Kubatkin; Per Delsing

2006-01-01

415

Numerical analysis of radio-frequency sheath-plasma interactions in the ion cyclotron range of frequencies  

SciTech Connect

A new finite element numerical scheme for analyzing self-consistent radio-frequency (RF) sheath-plasma interaction problems in the ion cyclotron range of frequencies is applied to various problems represented by simplified models for the tokamak scrape-off layer. The present code incorporates a modified boundary condition, which is called a sheath boundary condition, that couples the radio-frequency waves and sheaths at the material boundaries by treating the sheath as a thin vacuum layer. A series of numerical analyses in one- and two-dimensional domains show several important physical properties, such as the existence of multiple roots, hysteresis effects, presence and characteristics of the sheath-plasma waves, and the phase shift of a reflected slow wave, some of which are newly identified by introducing a spatially varying plasma density and background magnetic field.

Kohno, H. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Myra, J. R.; D'Ippolito, D. A. [Lodestar Research Corporation, 2400 Central Avenue P-5, Boulder, Colorado 80301 (United States)

2012-01-15

416

Effects of solar and geomagnetic activities on the sub-ionospheric very low frequency transmitter signals received by the DEMETER micro-satellite  

NASA Astrophysics Data System (ADS)

In the framework of seismic precursor electromagnetic investigations, we analyzed the very low frequency (VLF) amplitude signals recorded by the Instrument Champ Electrique (ICE) experiment on board the DEMETER micro-satellite. The sun-synchronous orbits of the micro-satellite allowed us to cover an invariant latitude of between -65 and +65 in a time interval of about 40 min. We considered four transmitter signals emitted by stations in Europe (France, FTU, 18.3 kHz; Germany, DFY, 16.58 kHz),Asia (Japan, JP, 17.8 kHz) and Australia (Australia, NWC, 19.8 kHz). We studied the variations of these VLF signals, taking into consideration: the signal-to-noise ratio, sunspots, and the geomagnetic activity. We show that the degree of correlation in periods of high geomagnetic and solar activities is, on average, about 40%. Such effects can be fully neglected in the period of weak activity. We also find that the solar activity can have a more important effect on the VLF transmitter signal than the geomagnetic activity. Our data are combined with models where the coupling between the lithosphere, atmosphere and ionosphere is essential to explain how ionospheric disturbances scatter the VLF transmitter signal.

Boudjada, Mohammed Yahia; Schwingenschuh, Konrad; Al-Haddad, Emad; Parrot, Michel; Galopeau, Patrick H. M.; Besser, Bruno; Stangl, Guenter; Voller, Wolfgang

2012-04-01

417

47 CFR 90.461 - Direct and remote control of transmitters.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 false Direct and remote control of transmitters. 90.461 Section 90...PRIVATE LAND MOBILE RADIO SERVICES Transmitter Control § 90.461 Direct and remote control of transmitters. (a) In...

2012-10-01

418

47 CFR 90.461 - Direct and remote control of transmitters.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 false Direct and remote control of transmitters. 90.461 Section 90...PRIVATE LAND MOBILE RADIO SERVICES Transmitter Control § 90.461 Direct and remote control of transmitters. (a) In...

2011-10-01

419

A COMBINED LOW-RADIO FREQUENCY/X-RAY STUDY OF GALAXY GROUPS. I. GIANT METREWAVE RADIO TELESCOPE OBSERVATIONS AT 235 MHz AND 610 MHz  

SciTech Connect

We present new Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz of 18 X-ray bright galaxy groups. These observations are part of an extended project, presented here and in future papers, which combines low-frequency radio and X-ray data to investigate the interaction between central active galactic nuclei (AGNs) and the intra-group medium (IGM). The radio images show a very diverse population of group-central radio sources, varying widely in size, power, morphology, and spectral index. Comparison of the radio images with Chandra and XMM-Newton X-ray images shows that groups with significant substructure in the X-ray band and marginal radio emission at {approx}>1 GHz host low-frequency radio structures that correlate with substructures in IGM. Radio-filled X-ray cavities, the most evident form of AGN/IGM interaction in our sample, are found in half of the systems and are typically associated with small, low-, or mid-power double radio sources. Two systems, NGC5044 and NGC4636, possess multiple cavities, which are isotropically distributed around the group center, possibly due to group weather. In other systems the radio/X-ray correlations are less evident. However, the AGN/IGM interaction can manifest itself through the effects of the high-pressure medium on the morphology, spectral properties, and evolution of the radio-emitting plasma. In particular, the IGM can confine fading radio lobes in old/dying radio galaxies and prevent them from dissipating quickly. Evidence for radio emission produced by former outbursts that co-exist with current activity is found in six groups of the sample.

Giacintucci, Simona [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); O'Sullivan, Ewan; Vrtilek, Jan; David, Laurence P.; Mazzotta, Pasquale; Gitti, Myriam; Jones, Christine; Forman, William R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Raychaudhury, Somak; Ponman, Trevor [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Venturi, Tiziana [INAF-Istituto di Radioastronomia, via Gobetti 101, I-40129, Bologna (Italy); Athreya, Ramana M. [IISER, Pune, Maharashtra 411 008 (India); Clarke, Tracy E. [Naval Research Laboratory, 4555 Overlook Avenue SW, Code 7213, Washington, DC 20375 (United States); Murgia, Matteo [INAF-Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, I-09012 Capoterra (Italy); Ishwara-Chandra, C. H., E-mail: simona@astro.umd.edu [National Centre for Radio Astrophysics, TIFR, Post Bag No. 3, Ganeshkhind, Pune 411 007 (India)

2011-05-10

420

Excitation of a magnetospheric maser through modification of the Earth's ionosphere by high-power HF radio emission from a ground-based transmitter  

SciTech Connect

A method for controlled excitation of a magnetospheric maser through the production of artificial density ducts by high-power HF radio emission from the Earth's surface has been proposed and implemented in an in-situ experiment. Artificial density ducts allow one to affect the maser resonator system and the excitation and propagation of low-frequency electromagnetic waves in a disturbed magnetic flux tube. The experimental data presented here were obtained at the mid-latitude Sura heating facility. The characteristics of electromagnetic and plasma disturbances at outer-ionosphere altitudes were measured using the onboard equipment of the DEMETER satellite as it passed through the magnetic flux tube rested on the region of intense generation of artificial ionospheric turbulence.

Markov, G. A., E-mail: markov@rf.unn.ru; Belov, A. S., E-mail: alexis-belov@yandex.ru [Lobachevsky Nizhni Novgorod State University (Russian Federation); Frolov, V. L.; Rapoport, V. O. [Radiophysical Research Institute (Russian Federation); Parrot, M. [Environment Physics and Chemistry Laboratory (France)

2010-01-15

421

Magnetic field probes for use in radio frequency plasma  

SciTech Connect

An impedance analyzer has been used in the characterization of a magnetic induction probe (B-dot probe) for use in plasma. The role of the impedance analyzer was to determine the frequency response of a B-dot probe up to 100 MHz. The probe was specifically designed to take measurements in rf plasma driven at 13.56 MHz. Probe sensitivity and calibration are considered based on the impedance values obtained when a B-dot probe is swept over a wide frequency range. Effects such as unbalanced loads based on transmission line inductances and termination impedance are shown to be limiting factors on the probes useful frequency range. The use of an impedance analyzer allows these effects to readily be characterized.

Reilly, Michael P.; Miley, George H. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, 104 S. Wright Street, 216 Talbot Laboratory, MC-234 Urbana, Illinois 61801 (United States); Lewis, William [ERC Inc. Knight High School, 37423 70th Street East, Palmdale, California 93552 (United States)

2009-05-15

422

On the noise correlation matrix for multiple radio frequency coils.  

PubMed

Noise correlation between multiple receiver coils is discussed using principles of statistical physics. Using the general fluctuation-dissipation theorem we derive the prototypic correlation formula originally determined by Redpath (Magn Res Med 1992;24:85-89), which states that correlation of current spectral noise depends on the real part of the inverse impedance matrix at a given frequency. A distinct correlation formula is also derived using the canonical partition function, which states that correlation of total current noise over the entire frequency spectrum depends on the inverse inductance matrix. The Kramers-Kronig relation is used to equate the inverse inductance matrix to the spectral integral of the inverse impedance matrix, implying that the total noise is equal to the summation of the spectral noise over the entire frequency spectrum. Previous conflicting arguments on noise correlation may be reconciled by differentiating between spectral and total noise correlation. These theoretical derivations are verified experimentally using two-coil arrays. PMID:17654588

Brown, Ryan; Wang, Yi; Spincemaille, Pascal; Lee, Ray F

2007-08-01

423

Dual-frequency Vega radio sounding of Comet Halley  

SciTech Connect

Radiophysical effects observed by Vega 1 and 2 as they passed through Comet Halley are presented and analyzed. Variations in the amplitude and frequency of the centimeter and decimeter signals, and the normalized phase difference of the two coherent signals are examined. From the Vega 1 data obtained on March 6, 1986, it is observed that the two signals began to rise in frequency as the spacecraft approached the comet; however, no frequency shift was detected by Vega 2 on March 9, 1986. A peak electron column density of 7.5 x 10 to the 12th/sq cm and a local electron space density of 2000-3000/cu cm were derived from the Vega 1 normalized phase differential data, and from the Vega 2 data, the peak electron column density was estimated as 3.5 x 10 to the 12th/sq cm and the local electron space density as 1000-2000/cu cm. 5 references.

Savich, N.A.; Altunin, V.I.; Andreev, V.E.; Basos, IU.F.; Boguslavskaia, N.E.E.

1986-10-01

424

Transmitters using Power Amplifiers  

Microsoft Academic Search

TWT amplifiers have traditionally been used for microwave communications links requiring high power amplifiers. The mean-time-before-failure (MTBF) of traveling wave tube amplifiers (TWTAs) is low compared to solid state power amplifiers and generally limits the communication system performance. The frequency and power capabilities of solid state amplifiers using FETs and IMPATT devices have been advancing rapidly in recent years. Transmitters

J. Goel; S. Yuan

1984-01-01

425

The Attenuation vs Frequency Characteristics of VLF Radio Waves  

Microsoft Academic Search

The theoretical dependence on frequency of the attenuation of the wave guide modes in vlf propagation is discussed in some detail. It is indicated that most of the published experimental data between 1 and 30 kc was compatible with the sharply bounded model of the ionosphere with a reflecting height of about 70 km during the day and 90 km

James Wait

1957-01-01

426

An ASIC for transponder for radio frequency identification system  

Microsoft Academic Search

Presented is a novel and effective design of a batteryless, self-powered RFID transponder. It is compatible with the TIRIS, the popular RFID system by the Texas Instruments. Data transmission uses FSK modulation and the circuit is designed such that the output frequencies are implicitly determined, independent of the load of the antenna. The major part of the design uses digital

Sau-Mou Wu; Jeng-Rern Yang; Tzen-Yi Liu

1996-01-01

427

Radio interferometric imaging of spatial structure that varies with time and frequency  

NASA Astrophysics Data System (ADS)

The spatial-frequency coverage of a radio interferometer is increased by combining samples acquired at different times and observing frequencies. However, astrophysical sources often contain complicated spatial structure that varies within the time-range of an observation, or the bandwidth of the receiver being used, or both. Image reconstruction algorithms can been designed to model time and frequency variability in addition to the average intensity distribution, and provide an improvement over traditional methods that ignore all variability. This paper describes an algorithm designed for such structures, and evaluates it in the context of reconstructing three-dimensional time-varying structures in the solar corona from radio interferometric measurements between 5 GHz and 15 GHz using existing telescopes such as the EVLA and at angular resolutions better than that allowed by traditional multi-frequency analysis algorithms.

Rau, Urvashi

2012-10-01

428

Low power radio-frequency and microwave effects on human electroencephalogram and behavior.  

PubMed

In a pilot study of ten human subjects, temporary changes in brain waves and behavior were seen on exposure to power densities lower than 10(-12) W/cm2, which is substantially below typical urban levels. Frequencies included .1 to 960 MHz continuous and 8.5 to 9.6 GHz pulse-modulated waves. Since the relaxation frequency of protein-bound water is considered to fall between 100 and 1,000 MHz, absorptions and quantum effects may be the mechanistic basis for the electroencephalogram changes observed in most of the subjects produced by 10(-15) W/cm2 cw radio-frequency energy of between 130 and 960 MHz. Constructive and destructive interference patterns from standing waves within the skull possibly interact with the bioelectric generators in the brain, since electroencephalogram wave amplitudes and frequencies increased or decreased respectively at different radio wavelengths. PMID:751078

Bise, W

1978-01-01

429

Multifrequency light curves of low-frequency variable radio sources  

NASA Astrophysics Data System (ADS)

Light curves for the low-frequency variable sources AO 0235 + 16, NRAO 140, PKS 1117 + 14, DA 406, CTA 102, and 3C 454.3, obtained in monthly observations at 318, 430, and 606 MHz using the 305-m telescope at Arecibo and in bimonthly observations at 880 MHz and 1.4 GHz using the 91-m Green Bank transit telescope during 1980-1983, are presented and analyzed. AO 0235 + 16 is found to have basically canonical variability which is attributed to relativistically moving evolving synchrotron components; but in the other sources, strong simultaneous variations at 318, 430, and 606 MHz are observed to be greatly diminished in amplitude at 880 MHz and 1.4 GHz, confirming the existence of the intermediate-frequency gap at about 1 GHz proposed by Spangler and Cotton (1981). The possibility that a second variability mechanism is active in these sources is explored.

Altschuler, D. R.; Broderick, J. J.; Dennison, B.; Mitchell, K. J.; Odell, S. L.; Condon, J. J.; Payne, H. E.

1984-12-01

430

Measuring Neutrino Masses Using Radio-Frequency Techniques  

NASA Astrophysics Data System (ADS)

We describe a new technique by which the energy spectrum of low energy electrons can be extracted. The technique relies on the detection and measurement of coherent radiation created from the cyclotron motion of charged particles, such as electrons, in strong magnetic fields. The technique proposed relies on the principle that the frequency of cyclotron radiation emitted by the particle depends inversely on its Lorentz boost. Detection and measurement of the coherent radiation emitted is tantamount to measuring the kinetic energy of the electron. As the technique inherently involves the measurement of a frequency in a non-destructive manner, it can, in principle, achieve a high degree of precision and accuracy; estimated to be better than 1 part in 106 for electrons with kinetic energies between 5 and 50 keV. One immediate application of this technique is in the measurement of the endpoint spectrum from tritium beta decay, which is directly sensitive to the absolute mass scale of neutrinos.

Formaggio, J. A.; Project 8 Collaboration

2012-07-01

431

Dynamics of ion-ion plasmas under radio frequency bias  

Microsoft Academic Search

A time-dependent one-dimensional fluid model was developed to study the dynamics of a positive ion-negative ion (ion-ion) plasma under the influence of a rf bias voltage. The full ion momentum and continuity equations were coupled to the Poisson equation for the electrostatic field. Special emphasis was placed on the effect of applied bias frequency. Due to the lower temperature and

Vikas Midha; Demetre J. Economou

2001-01-01

432

Limits on Radio Frequency Flux Density Changes in Sgr A*  

NASA Astrophysics Data System (ADS)

We report new limits on changes low frequency emission for Sgr A* based on Jansky VLA observations obtained on 2013 April 26. Data were obtained through the NRAO Service Observing program (https://science.nrao.edu/science/service-observing/service-observing). The JVLA is currently in the compact D-configuration, providing low resolution observations in which Sgr A* is heavily confused by diffuse structure associated with Sgr A West and East.

Bower, Geoffrey C.; Brunthaler, Andreas; Falcke, Heino

2013-04-01

433

Diffraction of High-Frequency Radio Waves around the Earth  

Microsoft Academic Search

This paper reports nonoptical height-gain measurements on a remarkably uniform desert link at frequencies of 25, 63, 170, 520, 1,000, 3,300, and 9,375 Mc using horizontal polarization. It has been shown that when the index of refraction of the atmosphere is a linear function of elevation, the problem of refraction and diffraction may be represented approximately by a problem in

M. D. ROCCOf; J. B. Smyth

1949-01-01

434

Use of Radio Frequency Identification for Targeted Advertising: A Collaborative Filtering Approach Using Bayesian Networks  

Microsoft Academic Search

This article discusses a potential application of radio frequency identification (RFID) and collaborative filtering for targeted advertising in grocery stores. Every day hundreds of items in grocery stores are marked down for promotional purposes. Whether these promotions are effective or not depends primarily on whether the customers are aware of them or not, and secondarily whether the customers are interested

Esma Nur Cinicioglu; Prakash P. Shenoy; Canan Kocabasoglu

2007-01-01

435

AN IMPROVED METHOD FOR RADIO FREQUENCY DIRECTION FINDING USING WIRELESS SENSOR NETWORKS  

Microsoft Academic Search

We present the design of a remotely deployable distributed wireless antenna system formed from wireless sensor network nodes. Specifically, the focus is on enhancing the detection range of a distributed wireless antenna system. The primary objective is to create a methodology to steer the beam in the desired direction to enhance radio frequency (RF) direction finding and follow-on signal reception.

Mickey S. Batson; John C. McEachen; Murali Tummala

436

A Method for Fast Radio Frequency Direction Finding Using Wireless Sensor Networks  

Microsoft Academic Search

We present the design of a remotely deployable distributed wireless antenna system formed from wireless sensor network nodes. Specifically, the focus is on enhancing the detection range of a distributed wireless antenna system. The primary objective is to create a methodology to steer the beam in the desired direction to enhance radio frequency (RF) direction finding and follow-on signal reception.

Mickey S. Batson; John C. Mceachen; Murali Tummala

2008-01-01

437

A Novel RF Sensing Circuit Using Injection Locking and Frequency Demodulation for Cognitive Radio Applications  

Microsoft Academic Search

A novel RF sensing circuit for a cognitive radio to sense spectral environment is proposed using injection locking and frequency demodulation techniques. The research starts with deriving a generalized locking equation for oscillators as a theoretical basis, and then develops the sensing principle and circuit architecture to a practical and useful level. To accurately evaluate the sensing performance, a discrete

Chien-Jung Li; Fu-Kang Wang; Tzyy-Sheng Horng; Kang-Chun Peng

2009-01-01

438

Radio frequency (rf) plasma spheroidized HA powders: powder characterization and spark plasma sintering behavior  

Microsoft Academic Search

The present study describes the synthesis of spheroidized hydroxyapatite (HA) powders using a radio frequency (rf) inductively coupled plasma (ICP) torch. The spheroidized powders were consolidated through a spark plasma sintering (SPS) system. The microstructure and crystallographic phases in the synthesized powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Raman spectrometry. Results

J. L. Xu; K. A. Khor; Y. W. Gu; R. Kumar; P. Cheang

2005-01-01

439

Radio Frequency Heat Treatments to Disinfest Dried Pulses of Cowpea Weevil  

Technology Transfer Automated Retrieval System (TEKTRAN)

To explore the potential of radio frequency (RF) heat treatments as an alternative to chemical fumigants for disinfestation of dried pulses, the relative heat tolerance and dielectric properties of different stages of the cowpea weevil (Callosobruchus maculatus) was determined. Among the immature st...

440

Radio Frequency Electric Fields Inactivation of Escherichia coli in Apple Cider  

Technology Transfer Automated Retrieval System (TEKTRAN)

Apple cider has been implicated in several outbreaks. Thermal pasteurization eliminates this threat, but it can detrimentally affect the quality of the cider. A nonthermal process using radio frequency electric fields (RFEF) was developed to pasteurize cider. An 80 kW RFEF pilot plant system was ...

441

Effects of Dielectric Barriers in Radio-Frequency Atmospheric Glow Discharges  

Microsoft Academic Search

This paper reports the effects of introducing dielectric barriers to radio-frequency (RF) atmospheric pressure glow discharges (APGD) that have hitherto employed bare electrodes. The resulting atmospheric RF dielectric barrier discharges (DBD) are experimentally shown to retain their large volume without constriction at very large currents, well above the maximum current at which conventional RF APGD with bare electrodes can maintain

Jianjun J. Shi; Dawei W. Liu; Michael G. Kong

2007-01-01

442

Characterization of radio frequency heating of fresh fruits influenced by dielectric properties  

Microsoft Academic Search

Because of its fast and volumetric nature, radio frequency (RF) heating has been looked upon as a way to overcome the problems associated with conventional heating methods used for disinfestation of fruits. But non-uniform heating within fruits is a major obstacle in adaptation of this technology. In this study, RF heating patterns influenced by dielectric properties (DPs) of fruits were

S. L. Birla; S. Wang; J. Tang; G. Tiwari

2008-01-01

443

Inactivation of Lactobacillus plantarum in apple cider using radio frequency electric fields  

Technology Transfer Automated Retrieval System (TEKTRAN)

Radio frequency electric fields (RFEF) processing is effective at inactivating Gram negative bacteria in fruit juices at moderately low temperatures, but has yet to be shown to be effective at reducing Gram positive bacteria. Lactobacillus plantarum ATCC 49445, a Gram positive bacterium, was inocula...

444

Radio Frequency Electric Fields Inactivation of Lactobacillus plantarum in Apple Cider  

Technology Transfer Automated Retrieval System (TEKTRAN)

Radio frequency electric fields (RFEF) nonthermal processing has recently been shown to be effective at reducing Escherichia coli in fruit juices. While considerable effort and progress have been made in studying the effect of RFEF processing on this gram negative bacteria, there is a total lack of...

445

Radio frequency identification An innovative solution to guide dexterous prosthetic hands  

Microsoft Academic Search

Dexterous manipulation of a multi-fingered prosthetic hand requires far more cognitive effort compared to typical 1 degree of freedom hands, which hinders their acceptance clinically. This paper presents a Myoelectrically-Operated Radio Frequency Identification (RFID) Prosthetic Hand (MORPH); an implementation of RFID with a myoelectric prosthetic hand as a means to amplify the controllable degrees of freedom. Contextual information from an

Matthew S. Trachtenberg; Girish Singhal; Rahul Kaliki; Ryan J. Smith; Nitish V. Thakor

2011-01-01

446

Toward a Universal Radio Frequency System for Special Operations Forces. Abbreviated Version.  

National Technical Information Service (NTIS)

Two overarching needs of the U.S. Special Operations Command (SOCOM) drove this study by the Committee on Universal Radio Frequency System for Special Operations Forces: (1) reduce the quantity and weight of equipment carried on a mission and (2) add futu...

2009-01-01

447

RADIO FREQUENCY MEASUREMENTS FOR SENSING MOISTURE IN SMALL SAMPLES OF PEANUTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

A method developed earlier for estimating the moisture content of single peanut kernels from radio-frequency impedance measurements on a parallel-plate capacitor, holding the kernel between the plates, was used for estimating the moisture content of small samples of 6 to 8 kernels. Parallel plates...

448

Sharing Between the Broadcast Service and VHF Radio RT-F200 in Frequency Hopping Mode.  

National Technical Information Service (NTIS)

Several reports on interference caused by Frequency Hopping radios are reviewed. A theoretical model based on ITU-R 1S.851-1 is developed and validated against data obtained from measurements made at Department of Communications and the Arts Laboratories....

G. G. Glenn

1996-01-01

449

Selected Issues in DoD's Radio Frequency Identification (RFID) Implementation.  

National Technical Information Service (NTIS)

This report describes the full scope of the Department of Defense (DoD) Radio Frequency Identification (RFID) activities with the purpose of identifying RFID-related issues specific to the Defense Logistics Agency (DLA). It summarizes DoD Components' stat...

C. Youngblut S. H. Nash M. S. Nash

2006-01-01

450

A Hybrid Model for Radio Wave Propagation Through Frequency Selective Structures (FSS)  

Microsoft Academic Search

A novel hybrid model is presented to study the radio wave propagation through frequency selective structures (FSS) used to control propagation in an outdoor to indoor building environment. This hybrid model is based on combining ray-tracing with a commercial tool, Computer Simulation Technology (CST) Microwave Studio. Numerical results of the hybrid model have been compared with those of a full

Ming Yang; Anthony K. Brown

2010-01-01

451

Super-hydrophobicity and oleophobicity of silicone rubber modified by CF 4 radio frequency plasma  

Microsoft Academic Search

Owing to excellent electric properties, silicone rubber (SIR) has been widely employed in outdoor insulator. For further improving its hydrophobicity and service life, the SIR samples are treated by CF4 radio frequency (RF) capacitively coupled plasma. The hydrophobic and oleophobic properties are characterized by static contact angle method. The surface morphology of modified SIR is observed by atom force microscope

Song-Hua Gao; Li-Hua Gao; Ke-Sheng Zhou

2011-01-01

452

Influence of annealing on thermoelectric properties of bismuth telluride films grown via radio frequency magnetron sputtering  

Microsoft Academic Search

Bismuth telluride films were prepared via radio frequency magnetron sputtering. Mixed powders with different composition were used as sputtering targets. Influence of the annealing temperature on surface topography, crystal structure and thermoelectric properties of the films has been investigated. It was found that the grain size increased and the surface roughness decreased with a rising annealing temperature. X-ray diffraction analysis

Hu Huang; Wei-ling Luan; Shan-tung Tu

2009-01-01

453

Scheme to funnel ion beams with a radio-frequency quadrupole  

SciTech Connect

We describe a proposed method to funnel ion beams using a new form of the radio-frequency quadrupole (RFQ) structure. This RFQ accepts two bunched ion beams and combines them into a single final beam with interlaced microstructure pulses. It also provides uninterrupted periodic transverse focusing to facilitate the funneling of beams with high current and low emittance.

Stokes, R.H.; Minerbo, G.N.

1985-01-01

454

Developing hot air assisted radio frequency drying for in-shell Macadamia nuts  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dehydration offers a means of preserving foods in a stable and safe condition as it reduces water activity and extends shelf-life of perishable agricultural products. The purpose of this study was to develop radio frequency (RF) drying protocols for in-shell macadamia nuts based on conventional hot ...

455

Method for Automated Monitoring of Hand Hygiene Adherence without Radio-Frequency Identification  

PubMed Central

Many efforts to automatically measure hand hygiene activity depend on radio-frequency identification equipment or similar technology that can be expensive to install. We have developed a method for automatically tracking the use of hand hygiene dispensers before healthcare workers enter (or after they exit) patient rooms that is easily and quickly deployed without permanent hardware.

Polgreen, Philip M.; Hlady, Christopher S.; Severson, Monica A.; Segre, Alberto M.; Herman, Ted

2011-01-01

456

Radio frequency identification tagging : Supplier attitudes to implementation in the grocery retail sector  

Microsoft Academic Search

Purpose The principal rationale for this study is to investigate the implications of the introduction of radio frequency identification (RFID) tagging on suppliers. Emphasis concerns the impact it is likely to have on suppliers to the UK grocery retail market. Design\\/methodology\\/approach Primary research focuses on UK grocery suppliers' perception, with two specific research questions: What are the implications

Martin Hingley; Susan Taylor; Charlotte Ellis

2007-01-01

457

Computer simulation of radio frequency heating of model fruit immersed in water  

Microsoft Academic Search

This study investigated the effect of different factors on temperature distribution within a spherical object in a parallel plate radio frequency (RF) heating system. A finite element-computer simulation program FEMLAB was used to solve the electromagnetic and NavierStoke equations for developing a model to study the effect of dielectric properties of a model fruit and its surrounding medium. The

S. L. Birla; S. Wang; J. Tang

2008-01-01

458

Numerical Studies on a Radio Frequency Hologram and Its Use in Antenna Measurements.  

National Technical Information Service (NTIS)

The objective of this thesis is to develop a numerical tool for analyzing the radio frequency hologram, and thus to advance the development of the hologram CATR for antenna measurements. An accurate simulation method is needed as the success of the hologr...

J. Ala Laurinaho

2000-01-01

459

Comment on enhancement of forbidden nuclear beta decay by high-intensity radio-frequency fields  

Microsoft Academic Search

A recent claim that forbidden nuclear beta decay can, by the application of a high-intensity radio-frequency field, be enhanced by many orders of magnitude is contested. The effect is shown to be nonexistent, at least within the theoretical model which has been adopted thus far.

W. Becker; R. R. Schlicher; M. O. Scully

1984-01-01

460

New method of carbon onion growth by radio-frequency plasma-enhanced chemical vapor deposition  

Microsoft Academic Search

Large quantities of carbon onions with high purity were synthesized by radio-frequency plasma-enhanced chemical vapor deposition. The produced carbon onions are solid, clean and can be separated easily from the catalytic particles. The formation of onions is based on the formation of many cages in successive stages from the core to the surface. Around the edge of a carbon onion,

X. H Chen; F. M Deng; J. X Wang; H. S Yang; G. T Wu; X. B Zhang; J. C Peng; W. Z Li

2001-01-01

461

Heating uniformity and differential heating of insects in almonds associated with radio frequency energy  

Technology Transfer Automated Retrieval System (TEKTRAN)

Radio frequency (RF) treatments have potential as alternatives to chemical fumigation for phytosanitary disinfestation treatments in the dried nut industry. To develop effective RF treatment protocols for almonds, it is desirable to determine heating uniformity and the occurrence of differential hea...

462

A Low-Frequency Distributed Aperture Array for Radio Astronomy in Space  

Microsoft Academic Search

The frequency band below 30 MHz is one of the last unexplored bands in radio astronomy. This band is well suited for studying the early cosmos at high hydrogen redshifts, the so-called dark ages, extragalactic surveys, (extra) solar planetary bursts, and high energy particle physics. In addition, space research such as space weather tomography, are also areas of scientific interest.

Albert-Jan Boonstra; Noah Saks; Heino Falcke; Marc Klein-Wolt; Ark Bentum; Raj Thilak Rajan; Ir. Stefan J. Wijnholds; Michel Arts; Kees van-T Klooster; Frederik Belien

2010-01-01

463

Dose Dependence of Acetylcholinesterase Activity in Neuroblastoma Cells Exposed to Modulated Radio-Frequency Electromagnetic Radiation.  

National Technical Information Service (NTIS)

Radio-frequency electromagnetic radiation (RFR) at 915 and at 147 MHz, when sinusoidally amplitude modulated (AM) at 16 Hz, has been shown to enhance release of calcium ions from neuroblastoma cells in culture. The dose-response relation is unusual, consi...

S. K. Dutta K. Das B. Ghosh C. F. Blackman

1992-01-01

464

Radio Frequency Identification (RFID) and communication technologies for solid waste bin and truck monitoring system  

Microsoft Academic Search

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

M. A. Hannan; Maher Arebey; R. A. Begum; Hassan Basri

2011-01-01

465

Radio-Frequency Energy Delivery to the Anal Canal for the Treatment of Fecal Incontinence  

Microsoft Academic Search

PURPOSE: In this prospective study we investigated the feasibility, safety, and efficacy of radio-frequency energy delivery deep to the mucosa of the anal canal for the treatment of fecal incontinence. METHODS: We studied ten patients with fecal incontinence of varying causes. All patients underwent anoscopy, anorectal manometry, endorectal ultrasound, and pudendal nerve terminal motor latency testing at baseline and six

Takeshi Takahashi; Sandra Garcia-Osogobio; MiguelAngel Valdovinos; Wilbert Mass; Ramiro Jimenez; LuisAlfonso Jauregui; Juan Bobadilla; Carlos Belmonte; Peter S. Edelstein; David S. Utley

2002-01-01

466

Evaluation of a Radio Frequency Identification (RFID) Library System: Preliminary Results  

Microsoft Academic Search

The literature has indicated that libraries in developed countries are fast growing early adopters of Radio Frequency Identification (RFID) technology. The adoption of RFID in supply chain has reported superior growth, spurred by mandate compliance from global retailers such as Wal-Mart and Target. Numerous tests have been performed in a variety of supply chain environment to determine the performance requirements,

Paul Golding; Vanesa Tennant

2008-01-01

467

Radio-frequency-identification for security and media circulation in libraries  

Microsoft Academic Search

Radio frequency identification (RFID) systems have been in use in libraries for five years for book identification, for self-checkout, for anti-theft control, for inventory control, and for sorting and conveying of library books and AV materials. These applications can lead to significant savings in labour costs, enhance customer service, and lower book theft and can provide a constant record update

Christian Kern

2004-01-01

468

Work in Progress: Performance and Reliability of Radio Frequency Identification (RFID) Library System  

Microsoft Academic Search

The literature has indicated that libraries in developed countries are fast growing early adopters of radio frequency identification (RFID) technology. The other sector of early adopters is distributors who use the technology primarily in the supply chain. The literature abounds with studies on perceived and expected problems with RFID in the supply chain but is sparse on performance and reliability

Paul Golding; Vanesa Tennant

2007-01-01

469

Biological stress responses to radio frequency electromagnetic radiation: are mobile phones really so (heat) shocking?  

Microsoft Academic Search

Cells phenotypically adapt to alterations in their intra- and extracellular environment via organised alterations to gene and protein expression. Many chemical and physical stimuli are known to drive such responses, including the induction of oxidative stress and heat shock. Increasing use of mobile telephony in our society, has brought focus on the potential for radio frequency (microwave) electromagnetic radiation to

Ian A Cotgreave

2005-01-01

470

Electronics and Electrical Engineering Laboratory Radio-Frequency Technology Division. Programs, Activities, and Accomplishments.  

National Technical Information Service (NTIS)

The Radio-Frequency Technology Division is a critical national resource for a wide range of customers. U.S. industry is the primary customer for both the Division's measurement services and for technical support on the test and measurement methodology nec...

2000-01-01

471

Low frequency radio wave propagation in the Atlantic and Mediterranean areas  

Microsoft Academic Search

Data from eighteen long range aircraft flights are compared with the wave hop propagation model of Berry, and areas of agreement and disagreement noted. The field strength of low frequency radio waves from transmitting stations in Iceland, Scotland, Morocco, and Greece was measured under daytime and nighttime conditions. The nighttime waves at about 1 mm seem to oscillate with distance

F. J. Kelly; F. J. Rhoads; D. J. Baker; J. A. Murray

1982-01-01

472

EFFECTS OF RADIO FREQUENCY WAVES ON FUNGAL COLONIZATION OF STYROBLOCK CONTAINERS  

Microsoft Academic Search

Fungal pathogens tend to accumulate within styroblock containers, which are reused to produce successive crops of container-grown seedlings. Most nurseries treat reused containers by immersing them in hot water for varying time periods. The efficacy of radio frequency waves (RFs) to reduce levels of selected groups of fungi within styroblock containers was evaluated. RFs were effective only on containers that

R. L. James; Andy Trent

473

Characterizing Species Composition in Radio-Frequency Plasma Produced from Water Vapor  

Microsoft Academic Search

Using hydrogen as an energy carrier has the potential to address the need to reduce oil consumption and pollution. However, hydrogen is only as clean as the method employed for its production. This work experimentally investigates an unconventional method of hydrogen production by breaking up water molecules in a radio-frequency plasma. This paper demonstrates that this proposed method can successfully

Sonca Nguyen; Kristina Lemmer; John Foster; Alec Gallimore

2007-01-01

474

Method of making radio frequency ion source antenna and such antenna  

Microsoft Academic Search

In the method, the radio frequency (rf) antenna is made by providing a clean coil made of copper tubing or other metal conductor, which is coated with a tacky organic binder, and then with a powdered glass frit, as by sprinkling the frit uniformly over the binder. The coil is then heated internally in an inert gas atmosphere, preferably by

K. W. Ehlers; K. N. Leung

1985-01-01

475

The Hexagon Pattern Formed in Radio Frequency Dielectric Barrier Discharge at Atmospheric Pressure  

Microsoft Academic Search

Hexagon-arranged pattern is formed in a dielectric barrier discharge employing a radio frequency power source, where argon mixed with a small concentration of nitrogen was used as discharge gas. The pattern formations were observed through a water electrode. In this paper, the influence of applied voltage and the concentration of nitrogen in the mixture gases on the pattern formation were

Sen Li; Zhongwei Liu; Huiping Cai; Qiang Chen

2011-01-01

476

Orientation of RF (Radio Frequency)-Sputter-Deposited MoS2 Films.  

National Technical Information Service (NTIS)

A theory to predict the orientation of radio frequency (rf) sputter deposited MoS2 films with respect to the substrate surface is presented. Oxygen containing species such as H2O and -OH are postulated to be active sites that force crystallites to form wi...

P. A. Bertrand

1989-01-01

477

INFLUENCE OF MASHED POTATO DIELECTRIC PROPERTIES AND CIRCULATING WATER ELECTRIC CONDUCTIVITY ON RADIO FREQUENCY HEATING  

Microsoft Academic Search

Experiments and computer simulations were conducted to systematically investigate the influence of mashed potato dielectric properties and circulating water electric conductivity on electromagnetic field distribution, heating rate, and heating pattern in packaged food during radio frequency (RF) heating processes in a 6 kW, 27 MHz laboratory scale RF heating system. Both experimental and simulation results indicated that for the selected

Jian Wang; Robert G. Olsen; Juming Tang; Zhongwei Tang

478

Decomposition of polyethylene in radio-frequency nitrogen and water steam plasmas under reduced pressures  

Microsoft Academic Search

The possibility of radio-frequency (RF) nitrogen and water steam plasmas under reduced pressures for gasification of plastic waste as a thermal recycling method has been investigated in order to develop an innovative method for directly recycling plastic waste to hydrogen, synthesis gases or fuels. The products of pyrolysis were analyzed and classified into gaseous fraction and solid soot; and analytical

L. Tang; H. Huang

2007-01-01

479

High power water load for microwave and millimeter-wave radio frequency sources  

Microsoft Academic Search

A high power water load for microwave and millimeter wave radio frequency sources has a front wall including an input port for the application of RF power, a cylindrical dissipation cavity lined with a dissipating material having a thickness which varies with depth, and a rear wall including a rotating reflector for the reflection of wave energy inside the cylindrical

R. L. Ives; Y. M. Mizuhara; R. V. Schumacher; R. P. Pendleton

1999-01-01

480

Radio-Frequency Method for Measuring the Water Content of Liquids  

Microsoft Academic Search

The method for radio-frequency measurements of water content in nonaqueous liquids is improved, and a procedure for measuring the concentration of water emulsified in oils and diesel fuels is described. Correlations between the composition of emulsions studied and the attenuation of the energy of electromagnetic radiation passing through the emulsions are revealed.

V. A. Bannyi; A. V. Makarevich; L. S. Pinchuk; B. G. An

2002-01-01

481

Temperature distributions of radio-frequency plasma in water by spectroscopic analysis  

Microsoft Academic Search

Distributions of emission intensity from radicals, electron temperature, and rotational temperature at a radio frequency of 27.12 MHz plasma in water are clarified by detailed spectroscopy measurement. Through this investigation, the following were observed. The points of maximum emission intensity of Halpha, Hbeta, O (777 nm), and O (845 nm) are almost the same, while that of OH shifts upward.

Shinobu Mukasa; Shinfuku Nomura; Hiromichi Toyota; Tsunehiro Maehara; Fumiaki Abe; Ayato Kawashima

2009-01-01