Graphit-ceramic RF Faraday-thermal shield and plasma limiter

DOEpatents

Hwang, David L.; Hosea, Joel C.

1989-01-01

The present invention is directed to a process of brazing a ceramic mater to graphite. In particular, the brazing procedure is directed to the production of a novel brazed ceramic graphite product useful as a Faraday shield.

Electron beam gun with kinematic coupling for high power RF vacuum devices

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

Borchard, Philipp

An electron beam gun for a high power RF vacuum device has components joined by a fixed kinematic coupling to provide both precise alignment and high voltage electrical insulation of the components. The kinematic coupling has high strength ceramic elements directly bonded to one or more non-ductile rigid metal components using a high temperature active metal brazing alloy. The ceramic elements have a convex surface that mates with concave grooves in another one of the components. The kinematic coupling, for example, may join a cathode assembly and/or a beam shaping focus electrode to a gun stem, which is preferably composedmore » of ceramic. The electron beam gun may be part of a high power RF vacuum device such as, for example, a gyrotron, klystron, or magnetron.« less

High-Power X-Band Semiconductor RF Switch for Pulse Compression Systems of Future Colliders

NASA Astrophysics Data System (ADS)

Tantawi, Sami G.; Tamura, Fumihiko

2000-04-01

We describe the potential of semiconductor X-band RF switch arrays as a means of developing high power RF pulse compression systems for future linear colliders. The switch systems described here have two designs. Both designs consist of two 3dB hybrids and active modules. In the first design the module is composed of a cascaded active phase shifter. In the second design the module uses arrays of SPST (Single Pole Single Throw) switches. Each cascaded element of the phase shifter and the SPST switch has similar design. The active element consists of symmetrical three-port tee-junctions and an active waveguide window in the symmetrical arm of the tee-junction. The design methodology of the elements and the architecture of the whole switch system are presented. We describe the scaling law that governs the relation between power handling capability and number of elements. The design of the active waveguide window is presented. The waveguide window is a silicon wafer with an array of four hundred PIN/NIP diodes covering the surface of the window. This waveguide window is located in an over-moded TE01 circular waveguide. The results of high power RF measurements of the active waveguide window are presented. The experiment is performed at power levels of tens of megawatts at X-band.

Modification of the surface properties of glass-ceramic materials at low-pressure RF plasma stream

NASA Astrophysics Data System (ADS)

Tovstopyat, Alexander; Gafarov, Ildar; Galeev, Vadim; Azarova, Valentina; Golyaeva, Anastasia

2018-05-01

The surface roughness has a huge effect on the mechanical, optical, and electronic properties of materials. In modern optical systems, the specifications for the surface accuracy and smoothness of substrates are becoming even more stringent. Commercially available pre-polished glass-ceramic substrates were treated with the radio frequency (RF) inductively coupled (13.56 MHz) low-pressure plasma to clean the surface of the samples and decrease the roughness. Optical emission spectroscopy was used to investigate the plasma stream parameters and phase-shifted interferometry to investigate the surface of the specimen. In this work, the dependence of RF inductively coupled plasma on macroscopic parameters was investigated with the focus on improving the surfaces. The ion energy, sputtering rate, and homogeneity were investigated. The improvements of the glass-ceramic surfaces from 2.6 to 2.2 Å root mean square by removing the "waste" after the previous operations had been achieved.

Low-loss electromagnetic composites for RF and microwave applications.

PubMed

Wang, Hong; Yang, Haibo; Xiang, Feng; Yao, Xi

2011-09-01

Low-loss electromagnetic composites with high permittivity and permeability will benefit the miniaturization and multifunctional of RF devices. A kind of low-loss dielectric-magnetic ceramic-ceramic composite was developed by hybrid processing technology with the goal of integrating the dielectric properties and magnetic properties. The hybrid processing technology exhibits the advantage of lowered sintering temperatures for the composites while retaining good microstructure and high performance. By introducing elastomer as matrix, a kind of flexible low-loss dielectric-magnetic ceramic-polymer composite was prepared and studied. The obtained flexible dielectric-magnetic ceramic-polymer composite exhibited low loss and good mechanical properties. The results show good effects on lowering the dielectric loss and extending the cut-off magnetic frequency of the electromagnetic composite. Methods for tailoring the properties of the multifunctional composites were proposed and discussed.

Construction of vacuum system for Tristan accumulation ring

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

Ishimaru, H.; Horikoshi, G.; Kobayashi, M.

1983-08-01

An all aluminum-alloy vacuum system for the TRISTAN accumulation ring is now under construction. Aluminum and aluminum alloys are preferred materials for ultrahigh vacuum systems of large electron storage rings because of their good thermal conductivity, extremely low outgassing rate, and low residual radioactivity. Vacuum beam chambers for the dipole and quadrupole magnets are extruded using porthole dies. The aluminum alloy 6063-T6 provides superior performance in extrusion. For ultrahigh vacuum performance, a special extrusion technique is applied which, along with the outgassing procedure used, is described in detail. Aluminum alloy 3004 seamless elliptical bellows are inserted between the dipole andmore » quadrupole magnet chambers. These bellows are produced by the hydraulic forming of a seamless tube. The seamless bellows and the beam chambers are joined by fully automatic welding. The ceramic chambers for the kicker magnets, the fast bump magnets, and the slow beam intensity monitor are inserted in the aluminum alloy beam chambers. The ceramic chamber (98% alumina) and elliptical bellows are brazed with brazing sheets (4003-3003-4003) in a vacuum furnace. The brazing technique is described. The inner surface of the ceramic chamber is coated with a TiMo alloy by vacuum evaporation to permit a smooth flow of the RF wall current. Other suitable aluminum alloy components, including fittings, feedthroughs, gauges, optical windows, sputter ion pumps, turbomolecular pumps, and valves have been developed; their fabrication is described.« less

Stabilized chromium oxide film

DOEpatents

Nyaiesh, A.R.; Garwin, E.L.

1986-08-04

Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150A are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

Stabilized chromium oxide film

DOEpatents

Garwin, Edward L.; Nyaiesh, Ali R.

1988-01-01

Stabilized air-oxidized chromium films deposited on high-power klystron ceramic windows and sleeves having a thickness between 20 and 150.ANG. are useful in lowering secondary electron emission yield and in avoiding multipactoring and window failure due to overheating. The ceramic substrate for the film is chosen from alumina, sapphire or beryllium oxide.

Applying Fused Silica and Other Transparent Window Materials in Aerospace Applications

NASA Technical Reports Server (NTRS)

Salem, Jon

2017-01-01

A variety of transparent ceramics, such as AlONs and spinels, that were developed for military applications hold promise as spacecraft windows. Window materials in spacecraft such as the Space Shuttle must meet many requirements such as maintaining cabin pressure, sustaining thermal shock, and tolerating damage from hyper-velocity impact while providing superior optical characteristics. The workhorse transparent material for space missions from Apollo to the International Space Station has been fused silica due in part to its low density, low coefficient of expansion and optical quality. Despite its successful use, fused silica exhibits lower fracture toughness and impact resistance as compared to newer materials. Can these newer transparent ceramics lighten spacecraft window systems and might they be useful for applications such as phone screens? This presentation will compare recent optical ceramics to fused silica and demonstrate how weight can be saved.

Structural Design of Glass and Ceramic Components for Space System Safety

NASA Technical Reports Server (NTRS)

Bernstein, Karen S.

2007-01-01

Manned space flight programs will always have windows as part of the structural shell of the crew compartment. Astronauts and cosmonauts need to and enjoy looking out of the spacecraft windows at Earth, at approaching vehicles, at scientific objectives and at the stars. With few exceptions spacecraft windows have been made of glass, and the lessons learned over forty years of manned space flight have resulted in a well-defined approach for using this brittle, unforgiving material in NASA's vehicles, in windows and other structural applications. This chapter will outline the best practices that have developed at NASA for designing, verifying and accepting glass (and ceramic) windows and other components for safe and reliable use in any space system.

Sealed symmetric multilayered microelectronic device package with integral windows

DOEpatents

Peterson, Kenneth A.; Watson, Robert D.

2002-01-01

A sealed symmetric multilayered package with integral windows for housing one or more microelectronic devices. The devices can be a semiconductor chip, a CCD chip, a CMOS chip, a VCSEL chip, a laser diode, a MEMS device, or a IMEMS device. The multilayered package can be formed of a low-temperature cofired ceramic (LTCC) or high-temperature cofired ceramic (HTCC) multilayer processes with the windows being simultaneously joined (e.g. cofired) to the package body during LTCC or HTCC processing. The microelectronic devices can be flip-chip bonded and oriented so that the light-sensitive sides are optically accessible through the windows. The result is a compact, low-profile, sealed symmetric package, having integral windows that can be hermetically-sealed.

Electrical and Structural Properties Study of Layered Dielectric and Magnetic Composites and Blends Structures for RF and Microwave Applications

DTIC Science & Technology

2014-06-12

Graduação em Engenharia de Teleinformática (2012) 3- STUDY of THERMAL STABILITY of microwave Resonant frequency of (τf) of DIELETRICS and...SYNTHESIS of CERAMIC MATERIALS with NEAR-ZERO τf Marcelo Antonio Santos da Silva, Programa de Pós Graduação em Quimica (2012) 4- STUDY OF DIELECTRIC...PROPERTIES OF CERAMIC MATRIX SrBi2Nb2O9 (SBN) FOR USE IN RF AND MICROWAVE DEVICES, EMMANUELLE DE OLIVEIRA SANCHO PROGRAMA DE PÓS-GRADUAÇÃO EM ENGENHARIA

Investigation and Prediction of RF Window Performance in APT Accelerators

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

Humphries, S. Jr.

1997-05-01

The work described in this report was performed between November 1996 and May 1997 in support of the APT (Accelerator Production of Tritium) Program at Los Alamos National Laboratory. The goal was to write and to test computer programs for charged particle orbits in RF fields. The well-documented programs were written in portable form and compiled for standard personal computers for easy distribution to LANL researchers. They will be used in several APT applications including the following. Minimization of multipactor effects in the moderate {beta} superconducting linac cavities under design for the APT accelerator. Investigation of suppression techniques for electronmore » multipactoring in high-power RF feedthroughs. Modeling of the response of electron detectors for the protection of high power RF vacuum windows. In the contract period two new codes, Trak{_}RF and WaveSim, were completed and several critical benchmark etests were carried out. Trak{_}RF numerically tracks charged particle orbits in combined electrostatic, magnetostatic and electromagnetic fields. WaveSim determines frequency-domain RF field solutions and provides a key input to Trak{_}RF. The two-dimensional programs handle planar or cylindrical geometries. They have several unique characteristics.« less

Graphite-ceramic rf Faraday-thermal shield and plasma limiter

DOEpatents

Hwang, D.L.Q.; Hosea, J.C.

1983-05-05

The present invention is directed to a brazing procedure for joining a ceramic or glass material (e.g., Al/sub 2/O/sub 3/ or Macor) to graphite. In particular, the present invention is directed to a novel brazing procedure for the production of a brazed ceramic graphite product useful as a Faraday shield. The brazed ceramic graphite Faraday shield of the present invention may be used in Magnetic Fusion Devices (e.g., Princeton Large Torus Tokamak) or other high temperature resistant apparatus.

Multilayered Microelectronic Device Package With An Integral Window

DOEpatents

Peterson, Kenneth A.; Watson, Robert D.

2004-10-26

A microelectronic package with an integral window mounted in a recessed lip for housing a microelectronic device. The device can be a semiconductor chip, a CCD chip, a CMOS chip, a VCSEL chip, a laser diode, a MEMS device, or a IMEMS device. The package can be formed of a low temperature co-fired ceramic (LTCC) or high temperature cofired ceramic (HTCC) multilayered material, with the integral window being simultaneously joined (e.g. co-fired) to the package body during LTCC or HTCC processing. The microelectronic device can be flip-chip bonded and oriented so that a light-sensitive side is optically accessible through the window. The result is a compact, low profile package, having an integral window mounted in a recessed lip, that can be hermetically sealed.

Microelectronic device package with an integral window

DOEpatents

Peterson, Kenneth A.; Watson, Robert D.

2002-01-01

An apparatus for packaging of microelectronic devices, including an integral window. The microelectronic device can be a semiconductor chip, a CCD chip, a CMOS chip, a VCSEL chip, a laser diode, a MEMS device, or a IMEMS device. The package can include a cofired ceramic frame or body. The package can have an internal stepped structure made of one or more plates, with apertures, which are patterned with metallized conductive circuit traces. The microelectronic device can be flip-chip bonded on the plate to these traces, and oriented so that the light-sensitive side is optically accessible through the window. A cover lid can be attached to the opposite side of the package. The result is a compact, low-profile package, having an integral window that can be hermetically-sealed. The package body can be formed by low-temperature cofired ceramic (LTCC) or high-temperature cofired ceramic (HTCC) multilayer processes with the window being simultaneously joined (e.g. cofired) to the package body during LTCC or HTCC processing. Multiple chips can be located within a single package. The cover lid can include a window. The apparatus is particularly suited for packaging of MEMS devices, since the number of handling steps is greatly reduced, thereby reducing the potential for contamination.

Development of Alumina Ceramics Vacuum Chamber for J-PARC

NASA Astrophysics Data System (ADS)

Kinsho, Michikazu; Saito, Yoshio; Kabeya, Zenzaburo; Ogiwara, Norio

We successfully developed alumina ceramics vacuum chamber for the 3 GeV-RCS of J-PARC at JAEA. This chamber has titanium flanges and an outer RF shield to reduce duct impedance, and moreover TiN film is coated on the inside surface to preclude charge build up and to reduce secondary emitted electrons. The outgassing rate of the ceramics chamber measured by the conductance modulation method has a sufficiently low value of 1.2×10-8 Pa m3 s-1 m2 after 50 hours pumping. The temperature of the titanium flange became 45°C due to eddy current heating under dipole magnet operation. It was found that the radiation damage to the capacitor used for the RF shield of this duct was small, the capacitance only decreased by 7% after gamma ray irradiation of 30 MGy. In order to determine effect of the ceramics chamber on the proton beam, this ceramics chamber prepared for J-PARC was installed instead in the 12 GeV main ring at KEK-PS. The proton beam could be controlled to accelerate stably after installation, and thus it was found that this chamber did not influence the beam very much. This ceramics chamber is thus usable for the 3 GeV-RCS of J-PARC.

Multilayered microelectronic device package with an integral window

DOEpatents

Peterson, Kenneth A.; Watson, Robert D.

2003-01-01

An apparatus for packaging of microelectronic devices is disclosed, wherein the package includes an integral window. The microelectronic device can be a semiconductor chip, a CCD chip, a CMOS chip, a VCSEL chip, a laser diode, a MEMS device, or a IMEMS device. The package can comprise, for example, a cofired ceramic frame or body. The package has an internal stepped structure made of a plurality of plates, with apertures, which are patterned with metallized conductive circuit traces. The microelectronic device can be flip-chip bonded on the plate to these traces, and oriented so that the light-sensitive side is optically accessible through the window. A cover lid can be attached to the opposite side of the package. The result is a compact, low-profile package, having an integral window that can be hermetically-sealed. The package body can be formed by low-temperature cofired ceramic (LTCC) or high-temperature cofired ceramic (HTCC) multilayer processes with the window being simultaneously joined (e.g. cofired) to the package body during LTCC or HTCC processing. Multiple chips can be located within a single package, according to some embodiments. The cover lid can include a window. The apparatus is particularly suited for packaging of MEMS devices, since the number of handling steps is greatly reduced, thereby reducing the potential for contamination. The integral window can further include a lens for optically transforming light passing through the window. The package can include an array of binary optic lenslets made integral with the window. The package can include an electrically-switched optical modulator, such as a lithium niobate window attached to the package, for providing a very fast electrically-operated shutter.

Antireflective surface structures on optics for high energy lasers

NASA Astrophysics Data System (ADS)

Busse, Lynda E.; Florea, Catalin M.; Shaw, L. Brandon; Frantz, Jesse; Bayya, Shyam; Poutous, Menelaos K.; Joshi, Rajendra; Aggarwal, Ishwar D.; Sanghera, Jas S.

2014-02-01

We report results for antireflective surface structures (ARSS) fabricated directly into the surface of optics and lenses which are important as high energy (multi-kW) laser components, including fused silica windows and lenses, YAG crystals and ceramics and spinel ceramics. Very low reflection losses as well as high laser damage thresholds have been measured for optics with ARSS. Progress to scale up the process for large size windows will also be presented..

Low-loss spinel windows for high-energy lasers

NASA Astrophysics Data System (ADS)

Kim, Woohong; Baker, Colin; Villalobos, Guillermo; Bayya, Shyam; Hunt, Michael; Sadowski, Bryan; Aggarwal, Ishwar; Sanghera, Jasbinder

2014-05-01

Ideal exit aperture windows for high-energy laser (HEL) should possess low absorption and scattering losses and be environmentally rugged and strong in order to protect the laser gain medium without compromising the light propagating through the window. Spinel is an ideal candidate for this application due to its high mechanical strength, high thermal conductivity, and excellent optical transmission between 0.2~5 μm. However, spinel ceramics fabricated with commercial powders often show inhomogeneity and suffer from absorption and scattering caused by various types of intrinsic and extrinsic impurities present in the powders. Here, we report on a convenient and economical powder purification method to significantly lower the absorption loss of transparent spinel ceramics using commercial powders. Acid washing was successfully used to reduce absorption loss in spinel ceramic fabricated using commercial powder from >20,000 ppm/cm down to 75 ppm/cm.

Bi-level multilayered microelectronic device package with an integral window

DOEpatents

Peterson, Kenneth A.; Watson, Robert D.

2002-01-01

A bi-level, multilayered package with an integral window for housing a microelectronic device. The device can be a semiconductor chip, a CCD chip, a CMOS chip, a VCSEL chip, a laser diode, a MEMS device, or a IMEMS device. The multilayered package can be formed of a low-temperature cofired ceramic (LTCC) or high-temperature cofired ceramic (HTCC) multilayer processes with the window being simultaneously joined (e.g. cofired) to the package body during LTCC or HTCC processing. The microelectronic device can be flip-chip bonded and oriented so that the light-sensitive side is optically accessible through the window. A second chip can be bonded to the backside of the first chip, with the second chip being wirebonded to the second level of the bi-level package. The result is a compact, low-profile package, having an integral window that can be hermetically-sealed.

Thin CVD-diamond RF Pill-Box vacuum windows for LHCD systems

NASA Astrophysics Data System (ADS)

Ravera, G. L.; Ceccuzzi, S.; Cardinali, A.; Cesario, R.; Mirizzi, F.; Schettini, G.; Tuccillo, A. A.

2014-02-01

The preliminary assessment of a Lower Hybrid Current Drive (LHCD) system for the DEMOnstration power plant (DEMO) is mainly focused on the R&D needs of the less conventional RF components of the Main Transmission Line (MTL) and of the launcher. 500 kW, CW klystrons will be used to deliver the RF power to independent Passive Active Multijunction (PAM) launcher modules at 5 GHz. This paper describes the criteria followed to investigate the optimum solution for the RF window used as vacuum barrier between the MTL and the launcher, an open issue in the LHCD system for ITER too. The best candidate, capable of withstanding a power level of, or above, 0.5 MW in CW operation and to satisfy the electrical and thermonuclear requirements, is a Pill-Box assembly, based on a thin single disk of CVD-diamond as dielectric, water cooled at the edge. A thickness of 3 mm, much shorter than half a wavelength of the TE°11 mode in the dielectric as in the conventional window (unfeasible and too expensive with CVD-diamond at these frequencies), is sufficient to limit the exerted stress at the edge under the fracture stress for a maximum pressure applied of 0.9 MPa. In this paper the simulation results of conventional and thin CVD-diamond vacuum windows are presented comparing S-parameters, losses and electric fields in both matching condition and with VSWR = 2, using WR284 and WR229 as input/output rectangular waveguide.

VIS-IR transmitting BGG glass windows

NASA Astrophysics Data System (ADS)

Bayya, Shyam S.; Chin, Geoff D.; Sanghera, Jasbinder S.; Aggarwal, Ishwar D.

2003-09-01

BaO-Ga2O3-GeO2 (BGG) glasses have the desired properties for various window applications in the 0.5-5 μm wavelength region. These glasses are low cost alternatives to the currently used window materials. Fabrication of a high optical quality 18" diameter BGG glass window has been demonstrated with a transmitted wave front error of λ/10 at 632 nm. BGG substrates have also been successfully tested for environmental weatherability (MIL-F-48616) and rain erosion durability up to 300 mph. Preliminary EMI grids have been successfully applied on BGG glasses demonstrating attenuation of 20dB in X and Ku bands. Although the mechanical properties of BGG glasses are acceptable for various window applications, it is demonstrated here that the properties can be further improved significantly by the glassceramization process. The ceramization process does not add any significant cost to the final window material. The crystallite size in the present glass-ceramic limits its transmission to the 2-5 μm region.

Basic Research on Oxynitride Glasses.

DTIC Science & Technology

1982-07-01

The upsurge in interest in these glasses was originally motivated by their relevance to the processing of Si 3 1 4 -based ceramics (4, 5) when it was...are suggested by results obtained so far, among them refractory glass - ceramics , leach-resistant glasses , hardened optical windows, and Joining...compositions for ceramic - ceramic seals. Oxynitride Glass Synthesis The preparation of oxynitride glasses is more complex than preparation of conventional

Investigation of high temperature antennas for space shuttle

NASA Technical Reports Server (NTRS)

Kuhlman, E. A.

1973-01-01

The design and development of high temperature antennas for the space shuttle orbiter are discussed. The antenna designs were based on three antenna types, an annular slot (L-Band), a linear slot (C-Band), and a horn (C-Band). The design approach was based on combining an RF window, which provides thermal protection, with an off-the-shelf antenna. Available antenna window materials were reviewed and compared, and the materials most compatible with the design requirements were selected. Two antenna window design approaches were considered: one employed a high temperature dielectric material and a low density insulation material, and the other an insulation material usable for the orbiter thermal protection system. Preliminary designs were formulated and integrated into the orbiter structure. Simple electrical models, with a series of window configurations, were constructed and tested. The results of tests and analyses for the final antenna system designs are given and show that high temperature antenna systems consisting of off-the-shelf antennas thermally protected by RF windows can be designed for the Space Shuttle Orbiter.

RF to millimeter wave integration and module technologies

NASA Astrophysics Data System (ADS)

Vähä-Heikkilä, T.

2015-04-01

Radio Frequency (RF) consumer applications have boosted silicon integrated circuits (IC) and corresponding technologies. More and more functions are integrated to ICs and their performance is also increasing. However, RF front-end modules with filters and switches as well as antennas still need other way of integration. This paper focuses to RF front-end module and antenna developments as well as to the integration of millimeter wave radios. VTT Technical Research Centre of Finland has developed both Low Temperature Co-fired Ceramics (LTCC) and Integrated Passive Devices (IPD) integration platforms for RF and millimeter wave integrated modules. In addition to in-house technologies, VTT is using module and component technologies from other commercial sources.

Multi-frequency klystron designed for high efficiency

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

Jensen, Aaron

A multi-frequency klystron has an electron gun which generates a beam, a circuit of bunch-align-collect (BAC) tuned cavities that bunch the beam and amplify an RF signal, a collector where the beam is collected and dumped, and a standard output cavity and waveguide coupled to a window to output RF power at a fundamental mode to an external load. In addition, the klystron has additional bunch-align-collect (BAC) cavities tuned to a higher harmonic frequency, and a harmonic output cavity and waveguide coupled via a window to an additional external load.

Continuous Fiber Ceramic Composites

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

Fareed, Ali; Craig, Phillip A.

2002-09-01

Fiber-reinforced ceramic composites demonstrate the high-temperature stability of ceramics--with an increased fracture toughness resulting from the fiber reinforcement of the composite. The material optimization performed under the continuous fiber ceramic composites (CFCC) included a series of systematic optimizations. The overall goals were to define the processing window, to increase the robustinous of the process, to increase process yield while reducing costs, and to define the complexity of parts that could be fabricated.

Summary Report for the C50 Cryomodule Project

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

Drury, Michael; Davis, G; Fischer, John

2011-03-01

The Thomas Jefferson National Accelerator Facility has recently completed the C50 cryomodule refurbishment project. The goal of this project was to enable robust 6 GeV, 5 pass operation of the Continuous Electron Beam Accelerator Facility (CEBAF). The scope of the project included removal, refurbishment and reinstallation of ten CEBAF cryomodules at a rate of three per year. The refurbishment process included reprocessing of SRF cavities to eliminate field emission and to increase the nominal gradient from the original 5 MV/m to 12.5 MV/m. New 'dogleg' couplers were installed between the cavity and helium vessel flanges to intercept secondary electrons thatmore » produce arcing in the fundamental Power Coupler (FPC). Other changes included new ceramic RF windows for the air to vacuum interface of the FPC and improvements to the mechanical tuner. Damaged or worn components were replaced as well. All ten of the refurbished cryomodules are now installed in CEBAF and are currently operational. This paper will summarize the performance of the cryomodules.« less

Wave energy transmission apparatus for high-temperature environments

NASA Technical Reports Server (NTRS)

Buckley, John D. (Inventor); Edwards, William C. (Inventor); Kelliher, Warren C. (Inventor); Carlberg, Ingrid A. (Inventor)

2010-01-01

A wave energy transmission apparatus has a conduit made from a refractory oxide. A transparent, refractory ceramic window is coupled to the conduit. Wave energy passing through the window enters the conduit.

Characterization of a Compact Cryogenic Package Approach to Ion Trap Quantum Comuting

NASA Astrophysics Data System (ADS)

Spivey, Robert; Vrijsen, Geert; Ahn, Byeong-Hyeon; Hudek, Kai; Crain, Stephen; van Rynbach, Andre; Rachel, Noek; Kim, Jungsang

One challenge for the expansion of trapped ion systems to a large scale is the lack of repeatable integration technology to realize compact and stable operating environment. In this work, we present a novel ion trapping environment where conventional ultra-high vacuum (UHV) chambers are replaced with a sealed ceramic package operating in a cryogenic environment. A microfabricated surface ion trap mounted on a 100-pin ceramic pin grid array (CPGA) package is placed in a UHV environment. A titanium lid with windows for optical access is then attached to the CPGA via an indium seal which maintains the UHV conditions for the ion trap. The trap package assembly is operated at cryogenic temperatures (5K) in order to freeze out most of the residual background gas. Activated charcoal is used to pump remaining helium and hydrogen molecules. Metallic Yb ablated using a Q-switched Nd:YAG laser at 1,064 nm is used as the atomic source. A compact radio frequency resonant circuit is used to create the RF potential for trapping. A low output impedance amplifier drives a superconducting inductor of value 2 uH in series with the trap capacitance in order to produce 200V at 26 MHz with low heating at 5K. We present the experimental progress towards trapping ions in this compact cryogenic setup.

Fused Silica and Other Transparent Window Materials

NASA Technical Reports Server (NTRS)

Salem, Jon

2016-01-01

Several transparent ceramics, such as spinel and AlONs are now being produced in sufficient large areas to be used in space craft window applications. The work horse transparent material for space missions from Apollo to the International Space Station has been fused silica due in part to its low coefficient of expansion and optical quality. Despite its successful use, fused silica exhibits anomalies in its crack growth behavior, depending on environmental preconditioning and surface damage. This presentation will compare recent optical ceramics to fused silica and discuss sources of variation in slow crack growth behavior.

Effect of V2O5 Addition on the Phase Composition of Bi5FeTi3O15 Ceramic and RF/Microwave Dielectric Properties

NASA Astrophysics Data System (ADS)

Aguiar, F. A. A.; Sales, A. J. M.; Araújo, B. S.; Sabóia, K. D. A.; Filho, M. C. Campos; Sombra, A. S. B.; Ayala, A. P.; Fechine, P. B. A.

2017-04-01

Bi5FeTi3O15 (BFT) polycrystalline ceramic with the addition of different concentrations of V2O5 was obtained by a solid-state method. X-ray powder diffraction, Raman spectroscopy and scanning electron microscopy (SEM) were used to study the microstructure and crystalline phases of the ceramics. SEM images showed plate-like morphology with dimensions between 0.32 μm and 3.07 μm (grain size, average around 1.3 μm). For samples with V2O5 concentration below 5%, Raman spectra were mainly determined by the vibrational modes from BFT. Impedance spectroscopy was also performed to evaluate the dielectric properties at microwave and radio frequencies (RF). Two extra phases (Bi4V1.5Fe0.5O10.5 and Bi2Ti2O7) were found due to the chemical reaction between BFT and V2O5. These phases were responsible for the changes in the grain morphology and dielectric response. V2O5 addition increased the real part of the dielectric permittivity ( ɛ') and reduced the dielectric loss tangent (tan δ) values at the RF range of 10 Hz to 1 MHz. For microwave frequencies of 3-3.5 GHz, ɛ' and temperature coefficient of resonant frequency ( τ f) values ranged from 66.52 ppm/°C to 88.60 ppm/°C and -304.3 ppm/°C to -192.6 ppm/°C, respectively. Thereby, BFT ceramics with added V2O5 are good candidates to be used for microwave devices (e.g., cell phones).

Novel Cranial Implants of Yttria-Stabilized Zirconia as Acoustic Windows for Ultrasonic Brain Therapy.

PubMed

Gutierrez, Mario I; Penilla, Elias H; Leija, Lorenzo; Vera, Arturo; Garay, Javier E; Aguilar, Guillermo

2017-11-01

Therapeutic ultrasound can induce changes in tissues by means of thermal and nonthermal effects. It is proposed for treatment of some brain pathologies such as Alzheimer's, Parkinson's, Huntington's diseases, and cancer. However, cranium highly absorbs ultrasound reducing transmission efficiency. There are clinical applications of transcranial focused ultrasound and implantable ultrasound transducers proposed to address this problem. In this paper, biocompatible materials are proposed for replacing part of the cranium (cranial implants) based on low porosity polycrystalline 8 mol% yttria-stabilized-zirconia (8YSZ) ceramics as acoustic windows for brain therapy. In order to assess the viability of 8YSZ implants to effectively transmit ultrasound, various 8YSZ ceramics with different porosity are tested; their acoustic properties are measured; and the results are validated using finite element models simulating wave propagation to brain tissue through 8YSZ windows. The ultrasound attenuation is found to be linearly dependent on ceramics' porosity. Results for the nearly pore-free case indicate that 8YSZ is highly effective in transmitting ultrasound, with overall maximum transmission efficiency of ≈81%, compared to near total absorption of cranial bone. These results suggest that 8YSZ polycrystals could be suitable acoustic windows for ultrasound brain therapy at 1 MHz. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A new powder production route for transparent spinel windows: powder synthesis and window properties

NASA Astrophysics Data System (ADS)

Cook, Ronald; Kochis, Michael; Reimanis, Ivar; Kleebe, Hans-Joachim

2005-05-01

Spinel powders for the production of transparent polycrystalline ceramic windows have been produced using a number of traditional ceramic and sol-gel methods. We have demonstrated that magnesium aluminate spinel powders produced from the reaction of organo-magnesium compounds with surface modified boehmite precursors can be used to produce high quality transparent spinel parts. The new powder production method allows fine control over the starting particle size, size distribution, purity and stoichiometry. The new process involves formation of a boehmite sol-gel from the hydrolysis of aluminum alkoxides followed by surface modification of the boehmite nanoparticles using carboxylic acids. The resulting surface modified boehmite nanoparticles can then be metal exchanged at room temperature with magnesium acetylacetonate to make a precursor powder that is readily transformed into pure phase spinel.

Technique for Predicting the RF Field Strength Inside an Enclosure

NASA Technical Reports Server (NTRS)

Hallett, M.; Reddell, J.

1998-01-01

This Memorandum presents a simple analytical technique for predicting the RF electric field strength inside an enclosed volume in which radio frequency radiation occurs. The technique was developed to predict the radio frequency (RF) field strength within a launch vehicle's fairing from payloads launched with their telemetry transmitters radiating and to the impact of the radiation on the vehicle and payload. The RF field strength is shown to be a function of the surface materials and surface areas. The method accounts for RF energy losses within exposed surfaces, through RF windows, and within multiple layers of dielectric materials which may cover the surfaces. This Memorandum includes the rigorous derivation of all equations and presents examples and data to support the validity of the technique.

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

Read, Michael; Ives, Robert Lawrence; Marsden, David

The Phase II program developed an internal RF coupler that transforms the whispering gallery RF mode produced in gyrotron cavities to an HE11 waveguide mode propagating in corrugated waveguide. This power is extracted from the vacuum using a broadband, chemical vapor deposited (CVD) diamond, Brewster angle window capable of transmitting more than 1.5 MW CW of RF power over a broad range of frequencies. This coupling system eliminates the Mirror Optical Units now required to externally couple Gaussian output power into corrugated waveguide, significantly reducing system cost and increasing efficiency. The program simulated the performance using a broad range ofmore » advanced computer codes to optimize the design. Both a direct coupler and Brewster angle window were built and tested at low and high power. Test results confirmed the performance of both devices and demonstrated they are capable of achieving the required performance for scientific, defense, industrial, and medical applications.« less

Radio frequency coaxial feedthrough device

DOEpatents

Owens, Thomas L.; Baity, Frederick W.; Hoffman, Daniel J.; Whealton, John H.

1987-01-01

A radio frequency coaxial vacuum feedthrough is provided which utilizes a cylindrical ceramic vacuum break formed of an alumina ceramic. The cylinder is coaxially disposed and brazed between tapered coaxial conductors to form a vacuum sealed connection between a pressurized upstream coaxial transmission line and a utilization device located within a vacuum container. The feedthrough provides 50 ohm matched impedance RF feedthrough up to about 500 MHz at power levels in the multimegawatt range.

Broadband 19F TOCSY using BURBOP-based spin lock

NASA Astrophysics Data System (ADS)

Marchione, Alexander A.; Diaz, Elizabeth L.

2018-01-01

A train of BURBOP universal rotation pulses has been used to generate a spin lock sufficient to observe TOCSY correlations over a 46 kHz 19F spectral window (i.e. 122 ppm on a 9.4 T spectrometer). This spin lock requires lower RF field (γB1 = 15 kHz), and was employed over a wider spectral window, than previously reported DIPSI-2 spin locks. The BURBOP-based spin lock was effected for 80-160 ms periods with a 2% duty cycle without evidence of harm to the RF coil of the probehead. Spectral separation and full set of correlations were obtained for a mixture of perfluorocarbons.

Comparative study of plasma-deposited fluorocarbon coatings on different substrates

NASA Astrophysics Data System (ADS)

Farsari, E.; Kostopoulou, M.; Amanatides, E.; Mataras, D.; Rapakoulias, D. E.

2011-05-01

The deposition of hydrophobic fluorocarbon coatings from C2F6 and C2F6-H2 rf discharges on different substrates was examined. Polyester textile, glass and two different ceramic compounds were used as substrates. The effect of the total gas pressure, the rf power dissipation and the deposition time on the hydrophobic character of the samples was investigated. Films deposited on polyester textiles at low pressure (0.03 mbar) and power consumption (16 mW cm-2) using pure C2F6 presented the highest water contact angles (~150°). On the other hand, the addition of hydrogen was necessary in order to deposit stable hydrophobic coatings on glass and ceramic substrates. Coatings deposited on glass at intermediate deposition rates (~100 Å min-1) and pressures presented the highest angles (~105°). Concerning the heavy clay ceramics, samples treated in low-pressure (0.05 mbar) and low-power (16 mW cm-2) discharges showed the highest contact angles. The deposition time was found to play an important role in the hydrophobicity and long-term behaviour of porous and rough substrates.

7-T magnetic resonance imaging of the inner ear's anatomy by using dual four-element radiofrequency coil arrays and the VIBE sequence

NASA Astrophysics Data System (ADS)

Kim, Kyoung-Nam; Heo, Phil; Kim, Young-Bo; Han, Gyu-Cheol

2015-02-01

An ultra-high-field magnetic resonance (MR) scanner and a specially-optimized radiofrequency (RF) coil and sequence protocol are required to obtain high-resolution images of the inner ear that can noninvasively confirm pathologic diagnoses. In phantom studies, the MR signal distribution of the gradient echo MR images generated by using a customized RF coil was compared with that of a commercial volume coil. The MR signal intensity of the customized RF coil decreases rapidly from near the RF coil plane toward the exterior of the phantom. However, the signal sensitivity of this coil is superior on both sides of the phantom, corresponding to the petrous pyramid. In in-vivo 7-T MR imaging, a customized RF coil and a volumetric-interpolated breath-hold examination imaging sequence are employed for visualization of the inner ear's structure. The entire membranous portion of the cochlear and the three semicircular canals, including the ductus reunions, oval window, and round window with associated nervous tissue, were clearly depicted with sufficient spatial coverage for adequate inspection of the surrounding anatomy. Developments from a new perspective to inner ear imaging using the 7-T modality could lead to further improved image sensitivity and, thus, enable ultra-structural MR imaging.

Boron nitride housing cools transistors

NASA Technical Reports Server (NTRS)

1965-01-01

Boron nitride ceramic heat sink cools transistors in r-f transmitter and receiver circuits. Heat dissipated by the transistor is conducted by the boron nitride housing to the metal chassis on which it is mounted.

Variable frequency matching to a radiofrequency source immersed in vacuum

NASA Astrophysics Data System (ADS)

Charles, C.; Boswell, R. W.; Bish, A.

2013-09-01

A low-weight (0.12 kg) low-volume fixed ceramic capacitor impedance matching system is developed for frequency agile tuning of a radiofrequency (rf) Helicon plasma thruster. Three fixed groups of capacitors are directly mounted onto a two loop rf antenna with the thruster immersed in a vacuum chamber. Optimum plasma tuning at the resonance frequency is demonstrated via measurements of the load impedance, power transfer efficiency and plasma density versus driving frequency in the 12.882-14.238 MHz range. The resonance frequency with the plasma on is higher than the resonance frequency in vacuum. The minimum rf power necessary for ignition decreases when the ignition frequency is shifted downwards from the resonance frequency. This development has direct applications in space qualification and space use of rf plasma thrusters.

Novel particle and radiation sources and advanced materials

NASA Astrophysics Data System (ADS)

Mako, Frederick

2016-03-01

The influence Norman Rostoker had on the lives of those who had the pleasure of knowing him is profound. The skills and knowledge I gained as a graduate student researching collective ion acceleration has fueled a career that has evolved from particle beam physics to include particle and radiation source development and advanced materials research, among many other exciting projects. The graduate research performed on collective ion acceleration was extended by others to form the backbone for laser driven plasma ion acceleration. Several years after graduate school I formed FM Technologies, Inc., (FMT), and later Electron Technologies, Inc. (ETI). Currently, as the founder and president of both FMT and ETI, the Rostoker influence can still be felt. One technology that we developed is a self-bunching RF fed electron gun, called the Micro-Pulse Gun (MPG). The MPG has important applications for RF accelerators and microwave tube technology, specifically clinically improved medical linacs and "green" klystrons. In addition to electron beam and RF source research, knowledge of materials and material interactions gained indirectly in graduate school has blossomed into breakthroughs in materials joining technologies. Most recently, silicon carbide joining technology has been developed that gives robust helium leak tight, high temperature and high strength joints between ceramic-to-ceramic and ceramic-to-metal. This joining technology has the potential to revolutionize the ethylene production, nuclear fuel and solar receiver industries by finally allowing for the practical use of silicon carbide as furnace coils, fuel rods and solar receptors, respectively, which are applications that have been needed for decades.

Novel particle and radiation sources and advanced materials

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

Mako, Frederick

The influence Norman Rostoker had on the lives of those who had the pleasure of knowing him is profound. The skills and knowledge I gained as a graduate student researching collective ion acceleration has fueled a career that has evolved from particle beam physics to include particle and radiation source development and advanced materials research, among many other exciting projects. The graduate research performed on collective ion acceleration was extended by others to form the backbone for laser driven plasma ion acceleration. Several years after graduate school I formed FM Technologies, Inc., (FMT), and later Electron Technologies, Inc. (ETI). Currently,more » as the founder and president of both FMT and ETI, the Rostoker influence can still be felt. One technology that we developed is a self-bunching RF fed electron gun, called the Micro-Pulse Gun (MPG). The MPG has important applications for RF accelerators and microwave tube technology, specifically clinically improved medical linacs and “green” klystrons. In addition to electron beam and RF source research, knowledge of materials and material interactions gained indirectly in graduate school has blossomed into breakthroughs in materials joining technologies. Most recently, silicon carbide joining technology has been developed that gives robust helium leak tight, high temperature and high strength joints between ceramic-to-ceramic and ceramic-to-metal. This joining technology has the potential to revolutionize the ethylene production, nuclear fuel and solar receiver industries by finally allowing for the practical use of silicon carbide as furnace coils, fuel rods and solar receptors, respectively, which are applications that have been needed for decades.« less

Surface-enhanced Raman spectroscopy using silver-coated porous glass-ceramic substrates.

PubMed

Pan, Z; Zavalin, A; Ueda, A; Guo, M; Groza, M; Burger, A; Mu, R; Morgan, S H

2005-06-01

Surface-enhanced Raman scattering (SERS) has been studied using a silver-coated porous glass-ceramic material as a new type of substrate. The porous glass-ceramic is in the CaO-TiO2-P2O5 system prepared by controlled crystallization and subsequent chemical leaching of the dense glass-ceramic, leaving a solid skeleton with pores ranging in size from 50 nm to submicrometer. Silver was coated on the surface of the porous glass-ceramic by radio frequency (RF) sputtering or e-beam evaporation in vacuum. SERS spectra of excellent quality were obtained from several dyes and carboxylic acid molecules, including rhodamine 6G, crystal violet, isonicotinic acid, and benzoic acid, using this new substrate. This new substrate showed a good compatibility with these molecules. The porous glass ceramic with a nanometer-structured surface accommodated both test molecules and silver film. The absorbed molecules were therefore better interfaced with silver for surface-enhanced Raman scattering.

Economic Analysis of Costs Incurred from Chemical Exposures in the Workplace Resulting in Non-Carcinogenic Responses as Additional Justification for Pollution Prevention Projects

DTIC Science & Technology

1993-08-26

Exposure 1CI RfC / RfD Hazard Pathway Total Chemical Index (mg/kg-d) (a/kg-d) Qotient Hazard Eposure index Hazard Index Exposure Pathway: Inhalation...4229 3.0 71651 16.9 CONTAINER 15808 11.1 273386 17.3 DOOR/WINDOW/GATE/FENCE 1476 1.0 22778 15.4 FORM/FRAME/ MOLD 94 0.1 1555 16.5 RACK/SHELF 1332 0.9...DOOR/WINDOW/GATE/FENCE 0 0.0 0 0.0 FORM/FRAME/ MOLD 0 0.0 0 0.0 RACK/SHELF 0 0.0 0 0.0 SKID/PALLET 0 0.0 0 0.0 MACHINES 1 7.1 3 3.0 CASTING/FORGING

Formation of high-Tc YBa2Cu3O(7-delta) films on Y2BaCuO5 substrate

NASA Astrophysics Data System (ADS)

Wang, W. N.; Lu, H. B.; Lin, W. J.; Yao, P. C.; Hsu, H. E.

1988-07-01

High-Tc superconducting YBa2Cu3O(7-delta) films have been successfully prepared on green Y2BaCuO5 (2115) ceramic substrate. The films have been formed by RF sputtering and screen printing with post annealing at 925 C. Regarding superconducting features, the sharp resistivity drop with Tc onset around 95 K (midpoint 84 K) and 99 K (midpoint 89 K) has been observed for RF sputtered and printed films respectively. Both films show the excellent adhesion towards the 2115 substrate. Powder X-ray diffraction profiles indicate a majority of 1237 phase with preferred orientation for RF sputtered thin film.

Recycled Glass and Dredged Materials

DTIC Science & Technology

2007-03-01

stations, and is either source-separated or co-mingled with plastics, aluminum cans, ceramics , or colored glass containers. In the United States in...anything other than container glass ). The debris may contain contaminants including ceramics (from dishware, pottery, window glass , light bulbs...ERDC TN-DOER-T8 March 2007 Recycled Glass and Dredged Materials by Landris T. Lee, Jr. PURPOSE: This technical note explores the concepts

Genome-Wide Association Study for Carcass Traits in an Experimental Nelore Cattle Population

PubMed Central

Medeiros de Oliveira Silva, Rafael; Bonvino Stafuzza, Nedenia; de Oliveira Fragomeni, Breno; Miguel Ferreira de Camargo, Gregório; Matos Ceacero, Thaís; Noely dos Santos Gonçalves Cyrillo, Joslaine; Baldi, Fernando; Augusti Boligon, Arione; Zerlotti Mercadante, Maria Eugênia; Lino Lourenco, Daniela; Misztal, Ignacy; Galvão de Albuquerque, Lucia

2017-01-01

The purpose of this study was to identify genomic regions associated with carcass traits in an experimental Nelore cattle population. The studied data set contained 2,306 ultrasound records for longissimus muscle area (LMA), 1,832 for backfat thickness (BF), and 1,830 for rump fat thickness (RF). A high-density SNP panel (BovineHD BeadChip assay 700k, Illumina Inc., San Diego, CA) was used for genotyping. After genomic data quality control, 437,197 SNPs from 761 animals were available, of which 721 had phenotypes for LMA, 669 for BF, and 718 for RF. The SNP solutions were estimated using a single-step genomic BLUP approach (ssGWAS), which calculated the variance for windows of 50 consecutive SNPs and the regions that accounted for more than 0.5% of the additive genetic variance were used to search for candidate genes. The results indicated that 12, 18, and 15 different windows were associated to LMA, BF, and RF, respectively. Confirming the polygenic nature of the studied traits, 43, 65, and 53 genes were found in those associated windows, respectively for LMA, BF, and RF. Among the candidate genes, some of them, which already had their functions associated with the expression of energy metabolism, were found associated with fat deposition in this study. In addition, ALKBH3 and HSD17B12 genes, which are related in fibroblast death and metabolism of steroids, were found associated with LMA. The results presented here should help to better understand the genetic and physiologic mechanism regulating the muscle tissue deposition and subcutaneous fat cover expression of Zebu animals. The identification of candidate genes should contribute for Zebu breeding programs in order to consider carcass traits as selection criteria in their genetic evaluation. PMID:28118362

rf improvements for Spallation Neutron Source H- ion sourcea)

NASA Astrophysics Data System (ADS)

Kang, Y. W.; Fuja, R.; Goulding, R. H.; Hardek, T.; Lee, S.-W.; McCarthy, M. P.; Piller, M. C.; Shin, K.; Stockli, M. P.; Welton, R. F.

2010-02-01

The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering ˜38 mA H- beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.

rf improvements for Spallation Neutron Source H- ion source.

PubMed

Kang, Y W; Fuja, R; Goulding, R H; Hardek, T; Lee, S-W; McCarthy, M P; Piller, M C; Shin, K; Stockli, M P; Welton, R F

2010-02-01

The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering approximately 38 mA H(-) beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.

Preparation and Optical Properties of Infrared Transparent 3Y-TZP Ceramics.

PubMed

Wang, Chuanfeng; Mao, Xiaojian; Peng, Ya-Pei; Jiang, Benxue; Fan, Jintai; Xu, Yangyang; Zhang, Long; Zhao, Jingtai

2017-04-07

In the present study, a tough tetragonal zirconia polycrystalline (Y-TZP) material was developed for use in high-speed infrared windows and domes. The influence of the preparation procedure and the microstructure on the material's optical properties was evaluated by SEM and FT-IR spectroscopy. It was revealed that a high transmittance up to 77% in the three- to five-micrometer IR region could be obtained when the sample was pre-sintered at 1225 °C and subjected to hot isostatic pressing (HIP) at 1275 °C for two hours. The infrared transmittance and emittance at elevated temperature were also examined. The in-line transmittance remained stable as the temperature increased to 427 °C, with degradation being observed only near the infrared cutoff edge. Additionally, the emittance property of 3Y-TZP ceramic at high temperature was found to be superior to those of sapphire and spinel. Overall, the results indicate that Y-TZP ceramic is a potential candidate for high-speed infrared windows and domes.

Preparation and Optical Properties of Infrared Transparent 3Y-TZP Ceramics

PubMed Central

Wang, Chuanfeng; Mao, Xiaojian; Peng, Ya-Pei; Jiang, Benxue; Fan, Jintai; Xu, Yangyang; Zhang, Long; Zhao, Jingtai

2017-01-01

In the present study, a tough tetragonal zirconia polycrystalline (Y-TZP) material was developed for use in high-speed infrared windows and domes. The influence of the preparation procedure and the microstructure on the material’s optical properties was evaluated by SEM and FT-IR spectroscopy. It was revealed that a high transmittance up to 77% in the three- to five-micrometer IR region could be obtained when the sample was pre-sintered at 1225 °C and subjected to hot isostatic pressing (HIP) at 1275 °C for two hours. The infrared transmittance and emittance at elevated temperature were also examined. The in-line transmittance remained stable as the temperature increased to 427 °C, with degradation being observed only near the infrared cutoff edge. Additionally, the emittance property of 3Y-TZP ceramic at high temperature was found to be superior to those of sapphire and spinel. Overall, the results indicate that Y-TZP ceramic is a potential candidate for high-speed infrared windows and domes. PMID:28772753

Ultra-hard AlMgB14 coatings fabricated by RF magnetron sputtering from a stoichiometric target

NASA Astrophysics Data System (ADS)

Grishin, A. M.; Khartsev, S. I.; Böhlmark, J.; Ahlgren, M.

2015-01-01

For the first time hard aluminum magnesium boride films were fabricated by RF magnetron sputtering from a single stoichiometric ceramic AlMgB14 target. Optimized processing conditions (substrate temperature, target sputtering power and target-to-substrate distance) enable fabrication of stoichiometric in-depth compositionally homogeneous films with the peak values of nanohardness 88 GPa and Young's modulus 517 GPa at the penetration depth of 26 nm and, respectively, 35 and 275 GPa at 200 nm depth in 2 μm thick film.

A sputtered zirconia primer for improved thermal shock resistance of plasma sprayed ceramic turbine seals

NASA Technical Reports Server (NTRS)

Bill, R. C.; Sovey, J.; Allen, G. P.

1981-01-01

The development of plasma-sprayed yttria stabilized zirconia (YSZ) ceramic turbine blade tip seal components is discussed. The YSZ layers are quite thick (0.040 to 0.090 in.). The service potential of seal components with such thick ceramic layers is cyclic thermal shock limited. The most usual failure mode is ceramic layer delamination at or very near the interface between the plasma sprayed YSZ layer and the NiCrAlY bondcoat. Deposition of a thin RF sputtered YSZ primer to the bondcoat prior to deposition of the thick plasma sprayed YSZ layer was found to reduce laminar cracking in cyclic thermal shock testing. The cyclic thermal shock life of one ceramic seal design was increased by a factor of 5 to 6 when the sputtered YSZ primer was incorporated. A model based on thermal response of plasma sprayed YSZ particles impinging on the bondcoat surface with and without the sputtered YSZ primer provides a basis for understanding the function of the primer.

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

NASA Astrophysics Data System (ADS)

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

2012-02-01

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

Miniature lowpass filters in low loss 9k7 LTCC

DOE PAGES

Dai, Steve; Hsieh, Lung -Hwa

2015-07-01

DuPont 9k7 low temperature cofired ceramic (LTCC) is a low loss, or high quality factor Q, tape system targeting at radio frequency (RF) applications. This paper reports the effect of a critical process parameter, heating rate, on the densification and dielectric properties of the 9k7 LTCC. The role of competing densification and crystallization during the sintering of 9k7 is discussed. The high Q of DuPont 9K7 can be used to improve RF system performance, for example a better receiver noise figure, by designing embedded passive RF components such as inductors, capacitors and filters. As a result, miniaturized multilayer low passmore » filters (LPF) with a wide stopband were fabricated to showcase the technology.« less

Miniature lowpass filters in low loss 9k7 LTCC

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

Dai, Steve; Hsieh, Lung -Hwa

DuPont 9k7 low temperature cofired ceramic (LTCC) is a low loss, or high quality factor Q, tape system targeting at radio frequency (RF) applications. This paper reports the effect of a critical process parameter, heating rate, on the densification and dielectric properties of the 9k7 LTCC. The role of competing densification and crystallization during the sintering of 9k7 is discussed. The high Q of DuPont 9K7 can be used to improve RF system performance, for example a better receiver noise figure, by designing embedded passive RF components such as inductors, capacitors and filters. As a result, miniaturized multilayer low passmore » filters (LPF) with a wide stopband were fabricated to showcase the technology.« less

Miniature low-pass filter in low-loss 9k7 LTCC

DOE PAGES

Dai, Steve Xunhu; Hsieh, Lung -Hwa

2015-09-30

DuPont 9k7 low-temperature cofired ceramic (LTCC) is a low-loss, or high-quality-factor Q, tape system targeting at radio frequency (RF) applications. This paper reports on the effect of a critical process parameter, the heating rate, on the densification and dielectric properties of the 9k7 LTCC. The role of competing densification and crystallization during the sintering of 9k7 is discussed. The high Q of DuPont 9K7 can be used to improve RF system performance, for example a better receiver noise figure, by designing embedded passive RF components such as inductors, capacitors and filters. Furthermore, miniaturized multilayer low-pass filters (LPF) with a widemore » stopband were fabricated to showcase the technology.« less

Radiofrequency antenna for suppression of parasitic discharges in a helicon plasma thruster experiment.

PubMed

Takahashi, Kazunori

2012-08-01

A radiofrequency (rf) antenna for helicon plasma thruster experiments is developed and tested using a permanent magnets helicon plasma source immersed in a vacuum chamber. A magnetic nozzle is provided by permanent magnets arrays and an argon plasma is produced by a 13.56 MHz radiofrequency helicon-wave or inductively-coupled discharge. A parasitic discharge outside the source tube is successfully suppressed by covering the rf antenna with a ceramic ring and a grounded shield; a decrease in the ion saturation current of a Langmuir probe located outside the source tube is observed and the ion saturation current on axis increases simultaneously, compared with the case of a standard uncovered rf antenna. It is also demonstrated that the covered antenna can yield stable operation of the source.

Bi-level microelectronic device package with an integral window

DOEpatents

Peterson, Kenneth A.; Watson, Robert D.

2004-01-06

A package with an integral window for housing a microelectronic device. The integral window is bonded directly to the package without having a separate layer of adhesive material disposed in-between the window and the package. The device can be a semiconductor chip, CCD chip, CMOS chip, VCSEL chip, laser diode, MEMS device, or IMEMS device. The multilayered package can be formed of a LTCC or HTCC cofired ceramic material, with the integral window being simultaneously joined to the package during LTCC or HTCC processing. The microelectronic device can be flip-chip bonded so that the light-sensitive side is optically accessible through the window. The package has at least two levels of circuits for making electrical interconnections to a pair of microelectronic devices. The result is a compact, low-profile package having an integral window that is hermetically sealed to the package prior to mounting and interconnecting the microelectronic device(s).

Single level microelectronic device package with an integral window

DOEpatents

Peterson, Kenneth A.; Watson, Robert D.

2003-12-09

A package with an integral window for housing a microelectronic device. The integral window is bonded directly to the package without having a separate layer of adhesive material disposed in-between the window and the package. The device can be a semiconductor chip, CCD chip, CMOS chip, VCSEL chip, laser diode, MEMS device, or IMEMS device. The package can be formed of a multilayered LTCC or HTCC cofired ceramic material, with the integral window being simultaneously joined to the package during cofiring. The microelectronic device can be flip-chip interconnected so that the light-sensitive side is optically accessible through the window. A glob-top encapsulant or protective cover can be used to protect the microelectronic device and electrical interconnections. The result is a compact, low profile package having an integral window that is hermetically sealed to the package prior to mounting and interconnecting the microelectronic device.

Studies on RF sputtered (WO3)1-x (V2O5)x thin films for smart window applications

NASA Astrophysics Data System (ADS)

Meenakshi, M.; Sivakumar, R.; Perumal, P.; Sanjeeviraja, C.

2016-05-01

V2O5 doped WO3 targets for RF sputtering thin film deposition were prepared for various compositions. Thin films of (WO3)1-x (V2O5)x were deposited on to glass substrates using these targets. Structural characteristics of the prepared targets and thin films were studied using X-ray diffraction. Laser Raman studies were carried out on the thin films to confirm the compound formation.

Electrical and ferroelectric properties of RF sputtered PZT/SBN on silicon for non-volatile memory applications

NASA Astrophysics Data System (ADS)

Singh, Prashant; Jha, Rajesh Kumar; Singh, Rajat Kumar; Singh, B. R.

2018-02-01

We report the integration of multilayer ferroelectric film deposited by RF magnetron sputtering and explore the electrical characteristics for its application as the gate of ferroelectric field effect transistor for non-volatile memories. PZT (Pb[Zr0.35Ti0.65]O3) and SBN (SrBi2Nb2O9) ferroelectric materials were selected for the stack fabrication due to their large polarization and fatigue free properties respectively. Electrical characterization has been carried out to obtain memory window, leakage current density, PUND and endurance characteristics. Fabricated multilayer ferroelectric film capacitor structure shows large memory window of 17.73 V and leakage current density of the order 10-6 A cm-2 for the voltage sweep of -30 to +30 V. This multilayer gate stack of PZT/SBN shows promising endurance property with no degradation in the remnant polarization for the read/write iteration cycles upto 108.

Development of a 1-m plasma source for heavy ion beam charge neutralization

NASA Astrophysics Data System (ADS)

Efthimion, Philip C.; Gilson, Erik P.; Grisham, Larry; Davidson, Ronald C.; Yu, Simon; Waldron, William; Grant Logan, B.

2005-05-01

Highly ionized plasmas are being employed as a medium for charge neutralizing heavy ion beams in order to focus to a small spot size. Calculations suggest that plasma at a density of 1-100 times the ion beam density and at a length ˜0.1-1 m would be suitable for achieving a high level of charge neutralization. A radio frequency (RF) source was constructed at the Princeton Plasma Physics Laboratory (PPPL) in support of the joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization. Pulsing the source enabled operation at pressures ˜10 -6 Torr with plasma densities of 10 11 cm -3. Near 100% ionization was achieved. The plasma was 10 cm in length, but future experiments require a source 1 m long. The RF source does not easily scale to the length. Consequently, large-volume plasma sources based upon ferroelectric ceramics are being considered. These sources have the advantage of being able to increase the length of the plasma and operate at low neutral pressures. The source will utilize the ferroelectric ceramic BaTiO 3 to form metal plasma. A 1 m long section of the drift tube inner surface of NTX will be covered with ceramic. A high voltage (˜1-5 kV) is applied between the drift tube and the front surface of the ceramic by placing a wire grid on the front surface. Plasma densities of 10 12 cm -3 and neutral pressures ˜10 -6 Torr are expected. A test stand to produce 20 cm long plasma is being constructed and will be tested before a 1 m long source is developed.

Optical Characterization of Window Materials for Aerospace Applications

NASA Technical Reports Server (NTRS)

Tedjojuwono, Ken K.; Clark, Natalie; Humphreys, William M., Jr.

2013-01-01

An optical metrology laboratory has been developed to characterize the optical properties of optical window materials to be used for aerospace applications. Several optical measurement systems have been selected and developed to measure spectral transmittance, haze, clarity, birefringence, striae, wavefront quality, and wedge. In addition to silica based glasses, several optical lightweight polymer materials and transparent ceramics have been investigated in the laboratory. The measurement systems and selected empirical results for non-silica materials are described. These measurements will be used to form the basis of acceptance criteria for selection of window materials for future aerospace vehicle and habitat designs.

Controllable optical modulation of blue/green up-conversion fluorescence from Tm3+ (Er3+) single-doped glass ceramics upon two-step excitation of two-wavelengths

PubMed Central

Chen, Zhi; Kang, Shiliang; Zhang, Hang; Wang, Ting; Lv, Shichao; Chen, Qiuqun; Dong, Guoping; Qiu, Jianrong

2017-01-01

Optical modulation is a crucial operation in photonics for network data processing with the aim to overcome information bottleneck in terms of speed, energy consumption, dispersion and cross-talking from conventional electronic interconnection approach. However, due to the weak interactions between photons, a facile physical approach is required to efficiently manipulate photon-photon interactions. Herein, we demonstrate that transparent glass ceramics containing LaF3: Tm3+ (Er3+) nanocrystals can enable fast-slow optical modulation of blue/green up-conversion fluorescence upon two-step excitation of two-wavelengths at telecom windows (0.8–1.8 μm). We show an optical modulation of more than 1500% (800%) of the green (blue) up-conversion fluorescence intensity, and fast response of 280 μs (367 μs) as well as slow response of 5.82 ms (618 μs) in the green (blue) up-conversion fluorescence signal, respectively. The success of manipulating laser at telecom windows for fast-slow optical modulation from rear-earth single-doped glass ceramics may find application in all-optical fiber telecommunication areas. PMID:28368041

Studies on RF sputtered (WO{sub 3}){sub 1-x} (V{sub 2}O{sub 5}){sub x} thin films for smart window applications

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

Meenakshi, M.; Perumal, P.; Sivakumar, R.

2016-05-23

V{sub 2}O{sub 5} doped WO{sub 3} targets for RF sputtering thin film deposition were prepared for various compositions. Thin films of (WO{sub 3}){sub 1-x} (V{sub 2}O{sub 5}){sub x} were deposited on to glass substrates using these targets. Structural characteristics of the prepared targets and thin films were studied using X-ray diffraction. Laser Raman studies were carried out on the thin films to confirm the compound formation.

Scale up of large ALON® and spinel windows

NASA Astrophysics Data System (ADS)

Goldman, Lee M.; Kashalikar, Uday; Ramisetty, Mohan; Jha, Santosh; Sastri, Suri

2017-05-01

Aluminum Oxynitride (ALON® Transparent Ceramic) and Magnesia Aluminate Spinel (Spinel) combine broadband transparency with excellent mechanical properties. Their cubic structure means that they are transparent in their polycrystalline form, allowing them to be manufactured by conventional powder processing techniques. Surmet has scaled up its ALON® production capability to produce and deliver windows as large as 4.4 sq ft. We have also produced our first 6 sq ft window. We are in the process of producing 7 sq ft ALON® window blanks for armor applications; and scale up to even larger, high optical quality blanks for Recce window applications is underway. Surmet also produces spinel for customers that require superior transmission at the longer wavelengths in the mid wave infra-red (MWIR). Spinel windows have been limited to smaller sizes than have been achieved with ALON. To date the largest spinel window produced is 11x18-in, and windows 14x20-in size are currently in process. Surmet is now scaling up its spinel processing capability to produce high quality window blanks as large as 19x27-in for sensor applications.

Optimizing electrical conductivity and optical transparency of IZO thin film deposited by radio frequency (RF) magnetron sputtering

NASA Astrophysics Data System (ADS)

Zhang, Lei

Transparent conducting oxide (TCO) thin films of In2O3, SnO2, ZnO, and their mixtures have been extensively used in optoelectronic applications such as transparent electrodes in solar photovoltaic devices. In this project I deposited amorphous indium-zinc oxide (IZO) thin films by radio frequency (RF) magnetron sputtering from a In2O3-10 wt.% ZnO sintered ceramic target to optimize the RF power, argon gas flowing rate, and the thickness of film to reach the maximum conductivity and transparency in visible spectrum. The results indicated optimized conductivity and transparency of IZO thin film is closer to ITO's conductivity and transparency, and is even better when the film was deposited with one specific tilted angle. National Science Foundation (NSF) MRSEC program at University of Nebraska Lincoln, and was hosted by Professor Jeff Shields lab.

Low-profile wireless passive resonators for sensing

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

Gong, Xun; An, Linan

A resonator for sensing a physical or an environmental parameter includes a support having a top surface that provides a ground plane, and a polymer-derived ceramic (PDC) element positioned on the top surface including a PDC layer, and a metal patch on the PDC layer. The metal patch is electrically isolated from all surrounding structure, and the resonator has a resonant frequency that changes as a function of the physical or environmental parameter. A system for wirelessly sensing a physical or environmental parameter includes at least one resonator and a wireless RF reader located remotely from the resonator for transmittingmore » a wide-band RF interrogation signal that excites the resonator. The wireless RF reader detects a sensing signal retransmitted by the resonator and includes a processor for determining the physical or environmental parameter at the location of the resonator from the sensing signal.« less

Li-ion transport in all-solid-state lithium batteries with LiCoO 2 using NASICON-type glass ceramic electrolytes

NASA Astrophysics Data System (ADS)

Xie, J.; Imanishi, N.; Zhang, T.; Hirano, A.; Takeda, Y.; Yamamoto, O.

LiCoO 2 thin films were deposited on the NASICON-type glass ceramics, Li 1+ x+ yAl xTi 2- xSi yP 3- yO 12, by radio frequency (RF) magnetron sputtering and were annealed at different temperatures. The as-deposited and the annealed LiCoO 2 thin films were characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). It was found that the films exhibited a (1 0 4) preferred orientation after annealing and Co 3O 4 was observed by annealing over 500 °C due to the reaction between the LiCoO 2 and the glass ceramics. The effect of annealing temperature on the interfacial resistance of glass ceramics/LiCoO 2 and Li-ion transport in the bulk LiCoO 2 thin film was investigated by galvanostatic cycling, cyclic voltammetry (CV), potentiostatic intermittent titration technique (PITT) and electrochemical impedance spectroscopy (EIS) with the Li/PEO/glass ceramics/LiCoO 2 cell. The cell performance was limited by the Li-ion diffusion resistance in Ohara/LiCoO 2 interface as well as in bulk LiCoO 2.

Novel Ultrahigh Vacuum System for Chip-Scale Trapped Ion Quantum Computing

NASA Astrophysics Data System (ADS)

Chen, Shaw-Pin; Trapped Team

2011-05-01

This presentation reports the experimental results of an ultrahigh vacuum (UHV) system as a scheme to implement scalable trapped-ion quantum computers that use micro-fabricated ion traps as fundamental building blocks. The novelty of this system resides in our design, material selection, mechanical liability, low complexity of assembly, and reduced signal interference between DC and RF electrodes. Our system utilizes RF isolation and onsite-filtering topologies to attenuate AC signals generated from the resonator. We use a UHV compatible printed circuit board (PCB) material to perform DC routing, while the RF high and RF ground received separated routing via wire-wrapping. The standard PCB fabrication process enabled us to implement ceramic-based filter components adjacent to the chip trap. The DC electrodes are connected to air-side electrical feed through using four 25D adaptors made with polyether ether ketone (PEEK). The assembly process of this system is straight forward and in-chamber structure is self-supporting. We report on initial testing of this concept with a linear chip trap fabricated by the Sandia National Labs.

Trace and surface analysis of ceramic layers of solid oxide fuel cells by mass spectrometry.

PubMed

Becker, J S; Breuer, U; Westheide, J; Saprykin, A I; Holzbrecher, H; Nickel, H; Dietze, H J

1996-06-01

For the trace analysis of impurities in thick ceramic layers of a solid oxide fuel cell (SOFC) sensitive solid-state mass spectrometric methods, such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and radiofrequency glow discharge mass spectrometry (rf-GDMS) have been developed and used. In order to quantify the analytical results of LA-ICP-MS, the relative sensitivity coefficients of elements in a La(0.6)Sr(0.35)MnO(3) matrix have been determined using synthetic standards. Secondary ion mass spectrometry (SIMS) - as a surface analytical method - has been used to characterize the element distribution and diffusion profiles of matrix elements on the interface of a perovskite/Y-stabilized ZrO(2) layer. The application of different mass spectrometric methods for process control in the preparation of ceramic layers for the SOFC is described.

Genetics Home Reference: polymicrogyria

MedlinePlus

... Guerrini R, Katz N, Kimonis V, Lin JP, Lynch DR, Mohammed SN, Massey RF, McDonald M, Rogers RC, Splitt M, Stevens CA, Tischkowitz MD, Stoodley N, Leventer RJ, Pilz DT, Dobyns WB. Polymicrogyria and deletion 22q11.2 syndrome: window to the etiology of a common cortical ...

Modeling of surface-dominated plasmas: from electric thruster to negative ion source.

PubMed

Taccogna, F; Schneider, R; Longo, S; Capitelli, M

2008-02-01

This contribution shows two important applications of the particle-in-cell/monte Carlo technique on ion sources: modeling of the Hall thruster SPT-100 for space propulsion and of the rf negative ion source for ITER neutral beam injection. In the first case translational degrees of freedom are involved, while in the second case inner degrees of freedom (vibrational levels) are excited. Computational results show how in both cases, plasma-wall and gas-wall interactions play a dominant role. These are secondary electron emission from the lateral ceramic wall of SPT-100 and electron capture from caesiated surfaces by positive ions and atoms in the rf negative ion source.

Afghan Air Force University: Contract Requirements Were Generally Met, but Instances of Non Compliance, Poor Workmanship, and Inadequate Maintenance Need to Be Addressed

DTIC Science & Technology

2016-03-01

work included installing new doors and windows, new plumbing fixtures, and overhead lighting, fresh paint, and tile work in 15 buildings and new...ceramic tile work in some buildings. These issues can largely be attributed to USACE’s failure to (1) fully monitor the implementation of its three-phase...and 3 support structures. The building renovations largely consisted of replacing doors, windows, carpeting, tiles , bathroom fixtures, and fans, as

Monolithic control components for high power mm-waves

NASA Astrophysics Data System (ADS)

Armstrong, A.; Goodrich, J.; Moroney, W.; Wheeler, D.

1985-09-01

Monolithic PIN diode arrays are shown to provide significant advances in switching ratios, bandwidth, and high-power capability for millimeter control applications The PIN diodes are arranged in a series/parallel configuration and form an electronically controlled window for switching RF power by applying DC voltage. At Ka band, an SPST switch using the window array (WINAR) design typically has 0.6 dB insertion loss and 22 dB isolation over the 26.5 to 40.0 GHz band. The switch has over 500 W peak power and 25 W average power capability.

NASA/CARES dual-use ceramic technology spinoff applications

NASA Technical Reports Server (NTRS)

Powers, Lynn M.; Janosik, Lesley A.; Gyekenyesi, John P.; Nemeth, Noel N.

1994-01-01

NASA has developed software that enables American industry to establish the reliability and life of ceramic structures in a wide variety of 21st Century applications. Designing ceramic components to survive at higher temperatures than the capability of most metals and in severe loading environments involves the disciplines of statistics and fracture mechanics. Successful application of advanced ceramics material properties and the use of a probabilistic brittle material design methodology. The NASA program, known as CARES (Ceramics Analysis and Reliability Evaluation of Structures), is a comprehensive general purpose design tool that predicts the probability of failure of a ceramic component as a function of its time in service. The latest version of this software, CARESALIFE, is coupled to several commercially available finite element analysis programs (ANSYS, MSC/NASTRAN, ABAQUS, COSMOS/N4, MARC), resulting in an advanced integrated design tool which is adapted to the computing environment of the user. The NASA-developed CARES software has been successfully used by industrial, government, and academic organizations to design and optimize ceramic components for many demanding applications. Industrial sectors impacted by this program include aerospace, automotive, electronic, medical, and energy applications. Dual-use applications include engine components, graphite and ceramic high temperature valves, TV picture tubes, ceramic bearings, electronic chips, glass building panels, infrared windows, radiant heater tubes, heat exchangers, and artificial hips, knee caps, and teeth.

On the mechanisms of interference between mobile phones and pacemakers: parasitic demodulation of GSM signal by the sensing amplifier.

PubMed

Barbaro, V; Bartolini, P; Calcagnini, G; Censi, F; Beard, B; Ruggera, P; Witters, D

2003-06-07

The aim of this study was to investigate the mechanisms by which the radiated radiofrequency (RF) GSM (global system for mobile communication) signal may affect pacemaker (PM) function. We measured the signal at the output of the sensing amplifier of PMs with various configurations of low-pass filters. We used three versions of the same PM model: one with a block capacitor which short circuits high-frequency signals; one with a ceramic feedthrough capacitor, a hermetically sealed mechanism connecting the internal electronics to the external connection block, and one with both. The PMs had been modified to have an electrical shielded connection to the output of the sensing amplifier. For each PM, the output of the sensing amplifier was monitored under exposure to modulated and non-modulated RF signals, and to GSM signals (900 and 1800 MHz). Non-modulated RF signals did not alter the response of the PM sensing amplifier. Modulated RF signals showed that the block capacitor did not succeed in short circuiting the RF signal, which is somehow demodulated by the PM internal non-linear circuit elements. Such a demodulation phenomenon poses a critical problem because digital cellular phones use extremely low-frequency modulation (as low as 2 Hz). which can be mistaken for normal heartbeat.

Analytical response function for planar Ge detectors

NASA Astrophysics Data System (ADS)

García-Alvarez, Juan A.; Maidana, Nora L.; Vanin, Vito R.; Fernández-Varea, José M.

2016-04-01

We model the response function (RF) of planar HPGe x-ray spectrometers for photon energies between around 10 keV and 100 keV. The RF is based on the proposal of Seltzer [1981. Nucl. Instrum. Methods 188, 133-151] and takes into account the full-energy absorption in the Ge active volume, the escape of Ge Kα and Kβ x-rays and the escape of photons after one Compton interaction. The relativistic impulse approximation is employed instead of the Klein-Nishina formula to describe incoherent photon scattering in the Ge crystal. We also incorporate a simple model for the continuous component of the spectrum produced by the escape of photo-electrons from the active volume. In our calculations we include external interaction contributions to the RF: (i) the incoherent scattering effects caused by the detector's Be window and (ii) the spectrum produced by photo-electrons emitted in the Ge dead layer that reach the active volume. The analytical RF model is compared with pulse-height spectra simulated using the PENELOPE Monte Carlo code.

Continuous Particulate Filter State of Health Monitoring Using Radio Frequency Sensing

DOE PAGES

Sappok, Alexander; Ragaller, Paul; Herman, Andrew; ...

2018-04-03

Reliable means for on-board detection of particulate filter failures or malfunctions are needed to meet diagnostics (OBD) requirements. Detecting these failures, which result in tailpipe particulate matter (PM) emissions exceeding the OBD limit, over all operating conditions is challenging. Current approaches employ differential pressure sensors and downstream PM sensors, in combination with particulate filter and engine-out soot models. These conventional monitors typically operate over narrowly-defined time windows and do not provide a direct measure of the filter’s state of health. In contrast, radio frequency (RF) sensors, which transmit a wireless signal through the filter substrate provide a direct means formore » interrogating the condition of the filter itself. Here, this study investigated the use of RF sensors for the continuous measurement of filter trapping efficiency, which was compared to downstream measurements with an AVL Microsoot Sensor, and a PM sampling probe simulating the geometry and installation configuration of a conventional PM sensor. The study included several particulate filter failure modes, both above and below the OBD threshold. Finally, the results confirmed the use of RF sensors to provide a direct and continuous measure of the particulate filter’s state of health over a range of typical in-use operating conditions, thereby significantly increasing the time window over which filter failures may be detected.« less

PET Performance Evaluation of an MR-Compatible PET Insert

PubMed Central

Wu, Yibao; Catana, Ciprian; Farrell, Richard; Dokhale, Purushottam A.; Shah, Kanai S.; Qi, Jinyi; Cherry, Simon R.

2010-01-01

A magnetic resonance (MR) compatible positron emission tomography (PET) insert has been developed in our laboratory for simultaneous small animal PET/MR imaging. This system is based on lutetium oxyorthosilicate (LSO) scintillator arrays with position-sensitive avalanche photodiode (PSAPD) photodetectors. The PET performance of this insert has been measured. The average reconstructed image spatial resolution was 1.51 mm. The sensitivity at the center of the field of view (CFOV) was 0.35%, which is comparable to the simulation predictions of 0.40%. The average photopeak energy resolution was 25%. The scatter fraction inside the MRI scanner with a line source was 12% (with a mouse-sized phantom and standard 35 mm Bruker 1H RF coil), 7% (with RF coil only) and 5% (without phantom or RF coil) for an energy window of 350–650 keV. The front-end electronics had a dead time of 390 ns, and a trigger extension dead time of 7.32 μs that degraded counting rate performance for injected doses above ~0.75 mCi (28 MBq). The peak noise-equivalent count rate (NECR) of 1.27 kcps was achieved at 290 μCi (10.7 MBq). The system showed good imaging performance inside a 7-T animal MRI system; however improvements in data acquisition electronics and reduction of the coincidence timing window are needed to realize improved NECR performance. PMID:21072320

Towards a 1 MW, 170 GHz gyrotron design for fusion application

NASA Astrophysics Data System (ADS)

Kumar, Anil; Kumar, Nitin; Singh, Udaybir; Bhattacharya, Ranajoy; Yadav, Vivek; Sinha, A. K.

2013-03-01

The electrical design of different components of 1 MW, 170 GHz gyrotron such as, magnetron injection gun, cylindrical interaction cavity and collector and RF window is presented in this article. Recently, a new project related to the development of 170 GHz, 1 MW gyrotron has been started for the Indian Tokamak. TE34,10 mode is selected as the operating mode after studied the problem of mode competition. The triode type geometry is selected for the design of magnetron injection gun (MIG) to achieve the required beam parameters. The maximum transverse velocity spread of 3.28% at the velocity ratio of 1.34 is obtained in simulations for a 40 A, 80 kV electron beam. The RF output power of more than 1 MW with 36.5% interaction efficiency without depressed collector is predicted by simulation in single-mode operation at 170 GHz frequency. The simulated single-stage depressed collector of the gyrotron predicted the overall device efficiencies >55%. Due to the very good thermal conductivity and very weak dependency of the dielectric parameters on temperature, PACVD diamond is selected for window design for the transmission of RF power. The in-house developed code MIGSYN and GCOMS are used for initial geometry design of MIG and mode selection respectively. Commercially available simulation tools MAGIC and ANSYS are used for beam-wave interaction and mechanical analysis respectively.

Continuous Particulate Filter State of Health Monitoring Using Radio Frequency Sensing

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

Sappok, Alexander; Ragaller, Paul; Herman, Andrew

Reliable means for on-board detection of particulate filter failures or malfunctions are needed to meet diagnostics (OBD) requirements. Detecting these failures, which result in tailpipe particulate matter (PM) emissions exceeding the OBD limit, over all operating conditions is challenging. Current approaches employ differential pressure sensors and downstream PM sensors, in combination with particulate filter and engine-out soot models. These conventional monitors typically operate over narrowly-defined time windows and do not provide a direct measure of the filter’s state of health. In contrast, radio frequency (RF) sensors, which transmit a wireless signal through the filter substrate provide a direct means formore » interrogating the condition of the filter itself. Here, this study investigated the use of RF sensors for the continuous measurement of filter trapping efficiency, which was compared to downstream measurements with an AVL Microsoot Sensor, and a PM sampling probe simulating the geometry and installation configuration of a conventional PM sensor. The study included several particulate filter failure modes, both above and below the OBD threshold. Finally, the results confirmed the use of RF sensors to provide a direct and continuous measure of the particulate filter’s state of health over a range of typical in-use operating conditions, thereby significantly increasing the time window over which filter failures may be detected.« less

Optical Property Requirements for Glasses, Ceramics and Plastics in Spacecraft Window Systems

NASA Technical Reports Server (NTRS)

Estes, Lynda

2011-01-01

This is a preliminary draft of a standard published by the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) that is intended to provide uniform window optical design requirements in support of the development of human-rated spaceflight hardware. The material covered in this standard is based on data from extensive testing by the Advanced Sensing and Optical Measurement Branch at NASA Langley Research Center, and compiled into requirements format by the NASA JSC Structural Engineering Division. At the time of this initial document release, a broader technical community has not reviewed this standard. The technical content of this standard is primarily based on the Constellation Program Orion Crew Exploration Vehicle Window Optical Properties Requirements, CxP 72407, Baseline. Unlike other optical requirements documents available for human rated spacecraft, this document includes requirements that ensure functionality for windows that contain glass/ceramic and/or plastic window substrate materials. These requirements were derived by measuring the optical properties of fused silica and aluminosilicate glass window assemblies and ensuring that the performance of any window assembly that includes a plastic pane or panes will meet the performance level of the all-glass assemblies. The resulting requirements are based upon the performance and parameter metrology testing of a variety of materials, including glass, transparent ceramics, acrylics, and polycarbonates. In general, these requirements are minimum specifications for each optical parameter in order to achieve the function specified for each functional category, A through D. Because acrylic materials perform at a higher level than polycarbonates in the optics regime, and CxP/Orion is planning to use acrylic in the Orion spacecraft, these requirements are based heavily on metrology from that material. As a result, two of the current Category D requirements for plastics are cited in such a way that will result in the screening out of polycarbonates. It is acknowledged that many polycarbonates can perform the functions of Category D, such as piloting and imagery with lens with apertures up to 25mm, without performance issues. Therefore, this forward warns users that certain requirements, such as birefringence and wavefront, for Category D plastics need to be revised to allow those polycarbonates that perform adequately in Category D to be accepted, while at the same time, screen out those materials that do not perform up to par. At the time of document release, the requirements in question have been identified by a TBD beside the proposed requirement criteria (which is based upon acrylic performance). Vehicles that are designed with acrylic materials for windowpanes are encouraged to use the values presented in this document for all requirements, in order to ensure adequate optical performance.

Thin-film cadmium telluride photovoltaic cells

NASA Astrophysics Data System (ADS)

Compaan, A. D.; Bohn, R. G.

1994-09-01

This report describes work to develop and optimize radio-frequency (RF) sputtering for the deposition of thin films of cadmium telluride (CdTe) and related semiconductors for thin-film solar cells. Pulsed laser physical vapor deposition was also used for exploratory work on these materials, especially where alloying or doping are involved, and for the deposition of cadmium chloride layers. The sputtering work utilized a 2-in diameter planar magnetron sputter gun. The film growth rate by RF sputtering was studied as a function of substrate temperature, gas pressure, and RF power. Complete solar cells were fabricated on tin-oxide-coated soda-lime glass substrates. Currently, work is being done to improve the open-circuit voltage by varying the CdTe-based absorber layer, and to improve the short-circuit current by modifying the CdS window layer.

A systematic review on radiofrequency assisted laparoscopic liver resection: Challenges and window to excel.

PubMed

Reccia, Isabella; Kumar, Jayant; Kusano, Tomokazu; Zanellato, Artur; Draz, Ahmed; Spalding, Duncan; Habib, Nagy; Pai, Madhava

2017-09-01

Laparoscopic liver resection has progressively gained acceptance as a safe and effective procedure in the treatment of benign and malignant liver neoplasms. However, blood loss remains the major challenge in liver surgery. Several techniques and devices have been introduced in liver surgery in order to minimize intraoperative haemorrhage during parenchymal transection. Radiofrequency (RF)-assisted liver resection has been shown to be an effective method to minimize bleeding in open and laparoscopic liver resection. A number of RF devices for parenchymal transection have been designed to assist laparoscopic liver resections. Here we have reviewed the results of various RF devices in laparoscopic liver resection. A total 15 article were considered relevant for the evaluation of technical aspects and outcomes of RF-assisted liver resections in laparoscopic procedures. In these studies, 176 patients had laparoscopic liver resection using RF-assisted parenchymal coagulation. Two monopolar and three bipolar devices were employed. Blood loss was limited in most of the studies. The need of blood transfusions was limited to two cases in all the series. Conversion was necessary due to bleeding in 3 cases. Operative and transection times varied between studies. However, RF-assisted resection with bipolar devices appeared to have taken less time in comparison to other RF devices. RF-related complications were minimum, and only one case of in-hospital death due to hepatic failure was reported. Although RF has been used in a small minority of laparoscopic liver resections, laparoscopic RF-assisted liver resection for benign and malignant disease is a safe and feasible procedure associated with reduction in blood loss, low morbidity, and lower hospital mortality rates. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sol-gel, One Technology by Produced Nanohybrid with Anticorrosive Properties

NASA Astrophysics Data System (ADS)

Hernández-Padrón, Genoveva; García-Garduño, Margarita V.

The evolution of nanotechnology has been allowed modify the material properties since of chemical architecture. In this work, we development nanohybrids sol-gel process, silica particles are incorporated a functionalized polymer resin (type epoxy and/or phenolic) with carboxylic groups. When the metallic plate is coating formed film ceramic glass. The incorporation this particles into to polymeric matrix, allowed to obtain performance corrosive properties. The structural characteristics of the different materials prepared, phenolic resin (RF), the resin functionalized (RFF) and its corresponding hybrids (RF-SiO2 and RFF- SiO2), were studied by infrared spectroscopy and morphological changes were analyzed by scanning electron microscopy. Then cooper plates were coated with these materials to evaluate their corrosion performance. The corrosion performance evaluation for each of these coatings RF, RFF, RE- SiO2 and RFF- SiO2 were determined by the following tests: a misty saline chamber operated under accelerated corrosive conditions for corrosion advance measurement, abrasion and adhesion.

Conductor backed and shielded multi-layer coplanar waveguide designs on LTCC for RF carrier boards for packaging PICs

NASA Astrophysics Data System (ADS)

Marraccini, Philip J.; Jezzini, Moises A.; Peters, Frank H.

2016-05-01

Designing photonic integrated circuits (PICs) with packaging in mind is important since this impacts the performance of the final product. In coherent optical communication applications there are a large number of DC and RF lines that need routed to connect the PIC to the outer packaging. These RF lines should be impedance matched to the devices, isolated from each other, low loss and protected against electromagnetic interference (EMI) over the frequency range of interest to achieve the performance required for the application. Multilevel low temperature co-fired ceramic (LTCC) boards can be used as a carrier board connecting the PIC to the packaging due to its good RF performance, machinability, compatibility with hermetic sealing, and ability to integrate drivers into the board. Flexibility with layer numbers enables additional layers for shielding against electromagnetic interference or increased space for routing electrical connections. In this paper the design, simulations, and measured results for a set of 4 phase matched transmission lines in LTCC that would be used with an IQ MZM are presented. The measured 3dB bandwidth for a set of four phase matched transmission lines for an IQ MZM was measured to be 19.8 GHz.

Industrial waste utilization in the panels production for high buildings facade and socle facing

NASA Astrophysics Data System (ADS)

Vitkalova, Irina; Torlova, Anastasiya; Pikalov, Evgeniy; Selivanov, Oleg

2018-03-01

The research presents comprehensive utilization of such industrial waste as galvanic sludge, broken window glass as functional additives for producing ceramics for facade and socle paneling in high-rise construction. The basic charge component is low-plasticity clay, which does not allow producing high-quality products if used without any functional additives. The application of the mentioned above components broadens the resource base, reduces production cost and the mass of the products in comparison with the currently used facing ceramics. The decrease of product mass helps to reduce the load on the basement and to use ceramic material in high-rise construction more effectively. Additional advantage of the developed composition is the reducing of production energy intensity due to comparatively low pressing pressure and firing temperature thus reducing the overall production cost. The research demonstrates the experimental results of determining density, compressive strength, water absorption, porosity and frost resistance of the produced ceramic material. These characteristics prove that the material can be applied for high buildings outdoor paneling. Additional research results prove ecologic safety of the produced ceramic material.

Radiofrequency exposure in the Neonatal Medium Care Unit.

PubMed

Calvente, I; Vázquez-Pérez, A; Fernández, M F; Núñez, M I; Múñoz-Hoyos, A

2017-01-01

The aims of this study were to characterize electromagnetic fields of radiofrequency (RF-EMF) levels generated in a Neonatal Medium Care Unit and to analyze RF-EMF levels inside unit's incubators. Spot and long-term measurements were made with a dosimeter. The spot measurement mean was 1.51±0.48V/m. Higher values were found in the proximity to the window and to the incubator evaluated. Mean field strength for the entire period of 17h was 0.81 (±0.07)V/m and the maximum value was 1.58V/m for long-term RF-EMF measurements in the incubator. Values found during the night period were higher than those found during the day period. It is important to consider RF-EMF exposure levels in neonatal care units, due to some evidence of adverse health effects found in children and adults. Characterization of RF-EMF exposure may be important to further investigate the mechanisms and underlying effects of electromagnetic fields (EMF) on infant health. A prudent avoidance strategy should be adopted because newborns are at a vulnerable stage of development and the actual impact of EMF on premature infants is unknown. Copyright © 2016 Elsevier Inc. All rights reserved.

Macro-meso-microsystems integration in LTCC : LDRD report.

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

De Smet, Dennis J.; Nordquist, Christopher Daniel; Turner, Timothy Shawn

2007-03-01

Low Temperature Cofired Ceramic (LTCC) has proven to be an enabling medium for microsystem technologies, because of its desirable electrical, physical, and chemical properties coupled with its capability for rapid prototyping and scalable manufacturing of components. LTCC is viewed as an extension of hybrid microcircuits, and in that function it enables development, testing, and deployment of silicon microsystems. However, its versatility has allowed it to succeed as a microsystem medium in its own right, with applications in non-microelectronic meso-scale devices and in a range of sensor devices. Applications include silicon microfluidic ''chip-and-wire'' systems and fluid grid array (FGA)/microfluidic multichip modulesmore » using embedded channels in LTCC, and cofired electro-mechanical systems with moving parts. Both the microfluidic and mechanical system applications are enabled by sacrificial volume materials (SVM), which serve to create and maintain cavities and separation gaps during the lamination and cofiring process. SVMs consisting of thermally fugitive or partially inert materials are easily incorporated. Recognizing the premium on devices that are cofired rather than assembled, we report on functional-as-released and functional-as-fired moving parts. Additional applications for cofired transparent windows, some as small as an optical fiber, are also described. The applications described help pave the way for widespread application of LTCC to biomedical, control, analysis, characterization, and radio frequency (RF) functions for macro-meso-microsystems.« less

MULTIPLE POWER DENSITY WINDOWS AND THEIR POSSIBLE ORIGIN

EPA Science Inventory

We have previously reported that in vitro exposure of chick forebrain tissue to 50-Mz radiofrequency (RF) radiation, amplitude modulated (AM) at 16 Hz, would enhance the efflux of calcium ions only within two power density ranges: one spanning from 1.44 to 1.67 mW/cm2, and the ot...

Engineered Surfaces to Control Secondary Electron Yield for Multipactor Suppression

DTIC Science & Technology

2017-09-14

Radio Engineers ( IRE ) Transactions on Electron Devices. The first paper , published by Preist and Talcott, examined damage to RF windows in klystrons...Secondary electron emission data for aluminum referenced by Hatch in his 1961 paper showing a typical SEY (δ) curve (top) and typical energy...83 IRE : Institute of Radio Engineers

BROADENING OF THE RF POWER-DENSITY WINDOW FOR CALCIUM-ION EFFLUX FROM BRAIN TISSUE

EPA Science Inventory

Blackman, et. al. have reported enhanced efflux of calcium ions from chicken forebrains, exposed in vitro in a 50 ohm stripline to 147 MHz radiation, modulated sinusoidally at 16 Hz. When the spacing between the sample tubes was 3.8 cm on center, enhancement occurred at an incide...

Survival of Staphylococcus aureus exposed to UV radiation on the surface of ceramic tiles coated with TiO2.

PubMed

Szczawiński, J; Tomaszewski, H; Jackowska-Tracz, A; Szczawińska, M E

2011-01-01

The aim of this study was to determine and compare the antimicrobial activity of UV radiation of wavelength 253.7 nm (used in typical germicidal lamps) against Staphylococcus aureus on the surfaces of conventionally produced white ceramic wall tiles (matt and shiny) and the same tiles coated with TiO2 using three different methods: RF diode sputtering, atmospheric pressure chemical vapour deposition (APCVD) and spray pyrolysis deposition (SPD). Results clearly indicate that the bactericidal action of UV radiation is much stronger on the surfaces of tiles coated with TiO2 than on the tiles uncovered. The strongest bactericidal effect of UV radiation was found for film prepared by APCVD. Results of experiments for shiny and matt tiles did not differ statistically. The use of ceramic wall tiles coated with TiO2 films in hospitals, veterinary clinics, laboratories, food processing plants and other places where UV radiation is applied for disinfection should greatly improve the efficiency of this treatment.

Method of making an integral window hermetic fiber optic component

DOEpatents

Dalton, R.D.; Kramer, D.P.; Massey, R.T.; Waker, D.A.

1996-11-12

In the fabrication of igniters, actuators, detonators, and other pyrotechnic devices to be activated by a laser beam, an integral optical glass window is formed by placing a preform in the structural member of the device and then melting the glass and sealing it in place by heating at a temperature between the ceramming temperature of the glass and the melting point of the metal, followed by rapid furnace cooling to avoid devitrification. No other sealing material is needed to achieve hermeticity. A preferred embodiment of this type of device is fabricated by allowing the molten glass to flow further and form a plano-convex lens integral with and at the bottom of the window. The lens functions to decrease the beam divergence caused by refraction of the laser light passing through the window when the device is fired by means of a laser beam. 9 figs.

Method of making an integral window hermetic fiber optic component

DOEpatents

Dalton, Rick D.; Kramer, Daniel P.; Massey, Richard T.; Waker, Damon A.

1996-11-12

In the fabrication of igniters, actuators, detonators, and other pyrotechnic devices to be activated by a laser beam, an integral optical glass window is formed by placing a preform in the structural member of the device and then melting the glass and sealing it in place by heating at a temperature between the ceramming temperature of the glass and the melting point of the metal, followed by rapid furnace cooling to avoid devitrification. No other sealing material is needed to achieve hermeticity. A preferred embodiment of this type of device is fabricated by allowing the molten glass to flow further and form a plano-convex lens integral with and at the bottom of the window. The lens functions to decrease the beam divergence caused by refraction of the laser light passing through the window when the device is fired by means of a laser beam.

Wedding ring shaped excitation coil

DOEpatents

MacLennan, Donald A.; Tsai, Peter

2001-01-01

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

Ionic conductivity of cold-pressed ceramics from grinding of R0.95M0.05F2.95 solid electrolytes ( R = La, Nd; M = Ca, Sr, Ba) synthesized by reaction in melt

NASA Astrophysics Data System (ADS)

Sorokin, N. I.; Ivanovskaya, N. A.; Sobolev, B. P.

2014-03-01

Cold-pressed ceramics of fluorine-conducting solid electrolytes La1 - y M y F3 - y ( M = Ca, Sr, Ba) and Nd1 - y Ca y F3 - y with y = 0.95 have been synthesized in a melt of RF3 ( R = La, Nd) and MF2 components in a fluorinating atmosphere and ground in a ball mill. The as-prepared ceramics require annealing, during which their porosity decreases and the conductivity is stably increased (by a factor of 250 for the R 1 - y M y F3 - y composition at 293 K). The Nd0.95Ca0.05F2.95 and Nd0.95Ca0.05F2.95 compositions have a maximum ionic conductivity σ(293 K) ˜ 5 × 10-6 Sm/cm. This value is larger (by a factor of about 10) than σ (293 K) for the R 1 - y M y F3 - y ceramics of tysonite phases prepared by mechanochemical synthesis with the cold pressing of reaction products.

Radiofrequency exposure in the Neonatal Medium Care Unit

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

Calvente, I.

The aims of this study were to characterize electromagnetic fields of radiofrequency (RF-EMF) levels generated in a Neonatal Medium Care Unit and to analyze RF-EMF levels inside unit’s incubators. Spot and long-term measurements were made with a dosimeter. The spot measurement mean was 1.51±0.48 V/m. Higher values were found in the proximity to the window and to the incubator evaluated. Mean field strength for the entire period of 17 h was 0.81 (±0.07) V/m and the maximum value was 1.58 V/m for long-term RF-EMF measurements in the incubator. Values found during the night period were higher than those found duringmore » the day period. It is important to consider RF-EMF exposure levels in neonatal care units, due to some evidence of adverse health effects found in children and adults. Characterization of RF-EMF exposure may be important to further investigate the mechanisms and underlying effects of electromagnetic fields (EMF) on infant health. A prudent avoidance strategy should be adopted because newborns are at a vulnerable stage of development and the actual impact of EMF on premature infants is unknown. - Highlights: • The increasing use of RF-EMF suggests an urgent need for more research in this field. • Health consequences of RF-EMF exposure on infants are not well known. • Description of RF-EMF exposure is vital in further study mechanisms on infant health. • Considering newborns vulnerability, it is wise to adopt a prudent avoidance strategy.« less

Biaxial flexural strength of Turkom-Cera core compared to two other all-ceramic systems.

PubMed

Al-Makramani, Bandar Mohammed Abdullah; Razak, Abdul Aziz Abdul; Abu-Hassan, Mohamed Ibrahim

2010-12-01

Advances in all-ceramic systems have established predictable means of providing metal-free aesthetic and biocompatible materials. These materials must have sufficient strength to be a practical treatment alternative for the fabrication of crowns and fixed partial dentures. The aim of this study was to compare the biaxial flexural strength of three core ceramic materials. Three groups of 10 disc-shaped specimens (16 mm diameter x 1.2 mm thickness - in accordance with ISO-6872, 1995) were made from the following ceramic materials: Turkom-Cera Fused Alumina [(Turkom-Ceramic (M) Sdn Bhd, Puchong, Selangor, Malaysia)], In-Ceram (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany) and Vitadur-N (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany), which were sintered according to the manufacturer's recommendations. The specimens were subjected to biaxial flexural strength test in an universal testing machine at a crosshead speed of 0.5 mm/min. The definitive fracture load was recorded for each specimen and the biaxial flexural strength was calculated from an equation in accordance with ISO-6872. The mean biaxial flexural strength values were: Turkom-Cera: 506.8 ± 87.01 MPa, In-Ceram: 347.4 ± 28.83 MPa and Vitadur-N: 128.7 ± 12.72 MPa. The results were analyzed by the Levene's test and Dunnett's T3 post-hoc test (SPSS software V11.5.0 for Windows, SPSS, Chicago, IL, USA ) at a preset significance level of 5% because of unequal group variances (P<0.001). There was statistically significant difference between the three core ceramics (P<0.05). Turkom-Cera showed the highest biaxial flexural strength, followed by In-Ceram and Vitadur-N. Turkom-Cera core had significantly higher flexural strength than In-Ceram and Vitadur-N ceramic core materials.

Advances/applications of MAGIC and SOS

NASA Astrophysics Data System (ADS)

Warren, Gary; Ludeking, Larry; Nguyen, Khanh; Smithe, David; Goplen, Bruce

1993-12-01

MAGIC and SOS have been applied to investigate a variety of accelerator-related devices. Examples include high brightness electron guns, beam-RF interactions in klystrons, cold-test modes in an RFQ and in RF sources, and a high-quality, flexible, electron gun with operating modes appropriate for gyrotrons, peniotrons, and other RF sources. Algorithmic improvements for PIC have been developed and added to MAGIC and SOS to facilitate these modeling efforts. Two new field algorithms allow improved control of computational numerical noise and selective control of harmonic modes in RF cavities. An axial filter in SOS accelerates simulations in cylindrical coordinates. The recent addition of an export/import feature now allows long devices to be modeled in sections. Interfaces have been added to receive electromagnetic field information from the Poisson group of codes and from EGUN and to send beam information to PARMELA for subsequent tracing of bunches through beam optics. Post-processors compute and display beam properties including geometric, normalized, and slice emittances, and phase-space parameters, and video. VMS, UNIX, and DOS versions are supported, with migration underway toward windows environments.

Fast ferroelectric phase shifters for energy recovery linacs

DOE PAGES

Kazakov, S. Yu; Shchelkunov, S. V.; Yakovlev, V. P.; ...

2010-11-24

Fast phase shifters are described that use a novel barium strontium titanate ceramic that can rapidly change its dielectric constant as an external bias voltage is changed. These phase shifters promise to reduce by ~10 times the power requirements for the rf source needed to drive an energy recovery linac (ERL). Such phase shifters will be coupled with superconducting radiofrequency cavities so as to tune them to compensate for phase instabilities, whether beam-driven or those caused by microphonics. The most promising design is presented, which was successfully cold tested and demonstrated a switching speed of ~30 ns for 77 deg, correspondingmore » to < 0.5 ns per deg of rf phase. As a result, other crucial issues (losses, phase shift values, etc.) are discussed.« less

Ultraminiature Broadband Light Source and Method of Manufacturing Same

NASA Technical Reports Server (NTRS)

Tuma, Margaret L. (Inventor); Collura, Joseph S. (Inventor); Helvajian, Henry (Inventor); Pocha, Michael D. (Inventor); Meyer, Glenn A. (Inventor); McConaghy, Charles F. (Inventor); Olsen, Barry L. (Inventor); Hansen, William W. (Inventor)

2010-01-01

An ultraminiature light source using a double-spiral shaped tungsten filament includes end contact portions which are separated to allow for radial and length-wise unwinding of the spiral. The double-spiral filament is spaced relatively far apart at the end portions thereof so that contact between portions of the filament upon expansion is avoided. The light ource is made by fabricating a double-spiral ultraminiature tungsten filament from tungsten foil and housing the filament in a ceramic package having a reflective bottom and a well wherein the filament is suspended. A vacuum furnace brazing process attaches the filament to contacts of the ceramic package. Finally, a cover with a transparent window is attached onto the top of the ceramic package by solder reflow in a second vacuum furnace process to form a complete hermetically sealed package.

Ultraminiature broadband light source with spiral shaped filament

NASA Technical Reports Server (NTRS)

McConaghy, Charles F. (Inventor); Olsen, Barry L. (Inventor); Tuma, Margaret L. (Inventor); Collura, Joseph S. (Inventor); Pocha, Michael D. (Inventor); Helvajian, Henry (Inventor); Meyer, Glenn A. (Inventor); Hansen, William W (Inventor)

2012-01-01

An ultraminiature light source using a double-spiral shaped tungsten filament includes end contact portions which are separated to allow for radial and length-wise unwinding of the spiral. The double-spiral filament is spaced relatively far apart at the end portions thereof so that contact between portions of the filament upon expansion is avoided. The light source is made by fabricating a double-spiral ultraminiature tungsten filament from tungsten foil and housing the filament in a ceramic package having a reflective bottom and a well wherein the filament is suspended. A vacuum furnace brazing process attaches the filament to contacts of the ceramic package. Finally, a cover with a transparent window is attached onto the top of the ceramic package by solder reflow in a second vacuum furnace process to form a complete hermetically sealed package.

Circuit model of the ITER-like antenna for JET and simulation of its control algorithms

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

Durodié, Frédéric, E-mail: frederic.durodie@rma.ac.be; Křivská, Alena; Dumortier, Pierre

2015-12-10

The ITER-like Antenna (ILA) for JET [1] is a 2 toroidal by 2 poloidal array of Resonant Double Loops (RDL) featuring in-vessel matching capacitors feeding RF current straps in conjugate-T manner, a low impedance quarter-wave impedance transformer, a service stub allowing hydraulic actuator and water cooling services to reach the aforementioned capacitors and a 2nd stage phase-shifter-stub matching circuit allowing to correct/choose the conjugate-T working impedance. Toroidally adjacent RDLs are fed from a 3dB hybrid splitter. It has been operated at 33, 42 and 47MHz on plasma (2008-2009) while it presently estimated frequency range is from 29 to 49MHz. Atmore » the time of the design (2001-2004) as well as the experiments the circuit models of the ILA were quite basic. The ILA front face and strap array Topica model was relatively crude and failed to correctly represent the poloidal central septum, Faraday Screen attachment as well as the segmented antenna central septum limiter. The ILA matching capacitors, T-junction, Vacuum Transmission Line (VTL) and Service Stubs were represented by lumped circuit elements and simple transmission line models. The assessment of the ILA results carried out to decide on the repair of the ILA identified that achieving routine full array operation requires a better understanding of the RF circuit, a feedback control algorithm for the 2nd stage matching as well as tighter calibrations of RF measurements. The paper presents the progress in modelling of the ILA comprising a more detailed Topica model of the front face for various plasma Scrape Off Layer profiles, a comprehensive HFSS model of the matching capacitors including internal bellows and electrode cylinders, 3D-EM models of the VTL including vacuum ceramic window, Service stub, a transmission line model of the 2nd stage matching circuit and main transmission lines including the 3dB hybrid splitters. A time evolving simulation using the improved circuit model allowed to design and simulate the effectiveness of a feedback control algorithm for the 2nd stage matching and demonstrates the simultaneous matching and control of the 4 RDLs: 11 feedback loops control 21 actuators (8 capacitors, 4 phase shifters and 4 stubs for the 2nd stage matching, 4 main phase shifters controlling of the toroidal phasing and the electronically controlled phase between RF sources feeding top and bottom parts of the array and determines the poloidal phasing of the array which is solved explicitly at each time step) on (simulated) ELMy plasmas.« less

Small-window parametric imaging based on information entropy for ultrasound tissue characterization

PubMed Central

Tsui, Po-Hsiang; Chen, Chin-Kuo; Kuo, Wen-Hung; Chang, King-Jen; Fang, Jui; Ma, Hsiang-Yang; Chou, Dean

2017-01-01

Constructing ultrasound statistical parametric images by using a sliding window is a widely adopted strategy for characterizing tissues. Deficiency in spatial resolution, the appearance of boundary artifacts, and the prerequisite data distribution limit the practicability of statistical parametric imaging. In this study, small-window entropy parametric imaging was proposed to overcome the above problems. Simulations and measurements of phantoms were executed to acquire backscattered radiofrequency (RF) signals, which were processed to explore the feasibility of small-window entropy imaging in detecting scatterer properties. To validate the ability of entropy imaging in tissue characterization, measurements of benign and malignant breast tumors were conducted (n = 63) to compare performances of conventional statistical parametric (based on Nakagami distribution) and entropy imaging by the receiver operating characteristic (ROC) curve analysis. The simulation and phantom results revealed that entropy images constructed using a small sliding window (side length = 1 pulse length) adequately describe changes in scatterer properties. The area under the ROC for using small-window entropy imaging to classify tumors was 0.89, which was higher than 0.79 obtained using statistical parametric imaging. In particular, boundary artifacts were largely suppressed in the proposed imaging technique. Entropy enables using a small window for implementing ultrasound parametric imaging. PMID:28106118

Small-window parametric imaging based on information entropy for ultrasound tissue characterization

NASA Astrophysics Data System (ADS)

Tsui, Po-Hsiang; Chen, Chin-Kuo; Kuo, Wen-Hung; Chang, King-Jen; Fang, Jui; Ma, Hsiang-Yang; Chou, Dean

2017-01-01

Constructing ultrasound statistical parametric images by using a sliding window is a widely adopted strategy for characterizing tissues. Deficiency in spatial resolution, the appearance of boundary artifacts, and the prerequisite data distribution limit the practicability of statistical parametric imaging. In this study, small-window entropy parametric imaging was proposed to overcome the above problems. Simulations and measurements of phantoms were executed to acquire backscattered radiofrequency (RF) signals, which were processed to explore the feasibility of small-window entropy imaging in detecting scatterer properties. To validate the ability of entropy imaging in tissue characterization, measurements of benign and malignant breast tumors were conducted (n = 63) to compare performances of conventional statistical parametric (based on Nakagami distribution) and entropy imaging by the receiver operating characteristic (ROC) curve analysis. The simulation and phantom results revealed that entropy images constructed using a small sliding window (side length = 1 pulse length) adequately describe changes in scatterer properties. The area under the ROC for using small-window entropy imaging to classify tumors was 0.89, which was higher than 0.79 obtained using statistical parametric imaging. In particular, boundary artifacts were largely suppressed in the proposed imaging technique. Entropy enables using a small window for implementing ultrasound parametric imaging.

Thermal and Lorentz Force Analysis of Beryllium Windows for the Rectilinear Muon Cooling Channel

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

Luo, Tianhuan; Li, D.; Virostek, S.

Reduction of the 6-dimensional phase-space of a muon beam by several orders of magnitude is a key requirement for a Muon Collider. Recently, a 12-stage rectilinear ionization cooling channel has been proposed to achieve that goal. The channel consists of a series of low frequency (325 MHz-650 MHz) normal conducting pillbox cavities, which are enclosed with thin beryllium windows (foils) to increase shunt impedance and give a higher field on-axis for a given amount of power. These windows are subject to ohmic heating from RF currents and Lorentz force from the EM field in the cavity, both of which willmore » produce out of the plane displacements that can detune the cavity frequency. In this study, using the TEM3P code, we report on a detailed thermal and mechanical analysis for the actual Be windows used on a 325 MHz cavity in a vacuum ionization cooling rectilinear channel for a Muon Collider.« less

Thermal and Lorentz force analysis of beryllium windows for a rectilinear muon cooling channel

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

Luo, T.; Stratakis, D.; Li, D.

Reduction of the 6-dimensional phase-space of a muon beam by several orders of magnitude is a key requirement for a Muon Collider. Recently, a 12-stage rectilinear ionization cooling channel has been proposed to achieve that goal. The channel consists of a series of low frequency (325 MHz-650 MHz) normal conducting pillbox cavities, which are enclosed with thin beryllium windows (foils) to increase shunt impedance and give a higher field on-axis for a given amount of power. These windows are subject to ohmic heating from RF currents and Lorentz force from the EM field in the cavity, both of which willmore » produce out of the plane displacements that can detune the cavity frequency. In this study, using the TEM3P code, we report on a detailed thermal and mechanical analysis for the actual Be windows used on a 325 MHz cavity in a vacuum ionization cooling rectilinear channel for a Muon Collider.« less

Optical signal processing

NASA Technical Reports Server (NTRS)

Casasent, D.

1978-01-01

The article discusses several optical configurations used for signal processing. Electronic-to-optical transducers are outlined, noting fixed window transducers and moving window acousto-optic transducers. Folded spectrum techniques are considered, with reference to wideband RF signal analysis, fetal electroencephalogram analysis, engine vibration analysis, signal buried in noise, and spatial filtering. Various methods for radar signal processing are described, such as phased-array antennas, the optical processing of phased-array data, pulsed Doppler and FM radar systems, a multichannel one-dimensional optical correlator, correlations with long coded waveforms, and Doppler signal processing. Means for noncoherent optical signal processing are noted, including an optical correlator for speech recognition and a noncoherent optical correlator.

Ternary Sulfide Infrared Window Materials.

DTIC Science & Technology

1981-10-10

results. Oxalates of the two cations can also be used for those combinations where oxalates of good purity are available. The reaction is: CaCO3 + 2La(OH... hydrothermal condi- tions. At 3000C and 300 bars pressure, CaLa2S4 breaks down completely into a mixture of calcium and lanthanum hydroxides. 3.0 CERAMIC

Chalcogenide glasses and glass-ceramics: Transparent materials in the infrared for dual applications

NASA Astrophysics Data System (ADS)

Calvez, Laurent

2017-05-01

In this paper are described the different research activities that led to the awarding of the Lamb prize by the French Academy of Sciences in order to promote research work on the national defense of France. This research concerns the development of infrared materials for night vision and the development of thermal imagers useful for defense, but also for civilian applications. The contribution has been particularly innovative in different sectors: broadening of chalcogenide glasses window of transparency, IR glass-ceramics with high thermomechanical properties, and the design of a new way of synthesis of these materials by a mechanical process.

Trap Design and Construction for High-Power Multinuclear Magnetic Resonance Experiments

PubMed Central

Rispoli, Joseph V.; Dimitrov, Ivan E.; Cheshkov, Sergey; Malloy, Craig; Wright, Steven M.; McDougall, Mary P.

2016-01-01

Performing multinuclear experiments requires one or more radiofrequency (RF) coils operating at both the proton and second-nucleus frequencies; however, inductive coupling between coils must be mitigated to retain proton sensitivity and coil tuning stability. The inclusion of trap circuits simplifies placement of multinuclear RF coils while maintaining inter-element isolation. Of the commonly investigated non-proton nuclei, perhaps the most technically demanding is carbon-13, particularly when applying a proton decoupling scheme to improve the resulting spectra. This work presents experimental data for trap circuits withstanding high-power broadband proton decoupling of carbon-13 at 7 T. The advantages and challenges of building trap circuits with various inductor and capacitor components are discussed. Multiple trap designs are evaluated on the bench and utilized on an RF coil at 7 T to detect broadband proton-decoupled carbon-13 spectra from a lipid phantom. A particular trap design, built from a coaxial stub inductor and high-voltage ceramic chip capacitors, is highlighted owing to both its performance and adaptability for planar array coil elements with diverse spatial orientations. PMID:28529464

Manufacturing process scale-up of optical grade transparent spinel ceramic at ArmorLine Corporation

NASA Astrophysics Data System (ADS)

Spilman, Joseph; Voyles, John; Nick, Joseph; Shaffer, Lawrence

2013-06-01

While transparent Spinel ceramic's mechanical and optical characteristics are ideal for many Ultraviolet (UV), visible, Short-Wave Infrared (SWIR), Mid-Wave Infrared (MWIR), and multispectral sensor window applications, commercial adoption of the material has been hampered because the material has historically been available in relatively small sizes (one square foot per window or less), low volumes, unreliable supply, and with unreliable quality. Recent efforts, most notably by Technology Assessment and Transfer (TA and T), have scaled-up manufacturing processes and demonstrated the capability to produce larger windows on the order of two square feet, but with limited output not suitable for production type programs. ArmorLine Corporation licensed the hot-pressed Spinel manufacturing know-how of TA and T in 2009 with the goal of building the world's first dedicated full-scale Spinel production facility, enabling the supply of a reliable and sufficient volume of large Transparent Armor and Optical Grade Spinel plates. With over $20 million of private investment by J.F. Lehman and Company, ArmorLine has installed and commissioned the largest vacuum hot press in the world, the largest high-temperature/high-pressure hot isostatic press in the world, and supporting manufacturing processes within 75,000 square feet of manufacturing space. ArmorLine's equipment is capable of producing window blanks as large as 50" x 30" and the facility is capable of producing substantial volumes of material with its Lean configuration and 24/7 operation. Initial production capability was achieved in 2012. ArmorLine will discuss the challenges that were encountered during scale-up of the manufacturing processes, ArmorLine Optical Grade Spinel optical performance, and provide an overview of the facility and its capabilities.

Rugged sensor window materials for harsh environments

NASA Astrophysics Data System (ADS)

Bayya, Shyam; Villalobos, Guillermo; Kim, Woohong; Sanghera, Jasbinger; Hunt, Michael; Aggarwal, Ishwar D.

2014-09-01

There are several military or commercial systems operating in very harsh environments that require rugged windows. On some of these systems, windows become the single point of failure. These applications include sensor or imaging systems, high-energy laser weapons systems, submarine photonic masts, IR countermeasures and missiles. Based on the sea or land or air based platforms the window or dome on these systems must withstand wave slap, underwater or ground based explosions, or survive flight through heavy rain and sand storms while maintaining good optical transmission in the desired wavelength range. Some of these applications still use softer ZnS or fused silica windows because of lack of availability of rugged materials in shapes or sizes required. Sapphire, ALON and spinel are very rugged materials with significantly higher strengths compared to ZnS and fused silica. There have been recent developments in spinel, ALON and sapphire materials to fabricate in large sizes and conformal shapes. We have been developing spinel ceramics for several of these applications. We are also developing β-SiC as a transparent window material as it has higher hardness, strength, and toughness than sapphire, ALON and spinel. This paper gives a summary of our recent findings.

Glass and glass-ceramic photonic systems

NASA Astrophysics Data System (ADS)

Zur, Lidia; Thi Ngoc Tran, Lam; Meneghetti, Marcello; Varas, Stefano; Armellini, Cristina; Ristic, Davor; Chiasera, Alessandro; Scotognella, Francesco; Pelli, Stefano; Nunzi Conti, Gualtiero; Boulard, Brigitte; Zonta, Daniele; Dorosz, Dominik; Lukowiak, Anna; Righini, Giancarlo C.; Ramponi, Roberta; Ferrari, Maurizio

2017-02-01

The development of optically confined structure is a major topic in both basic and applied physics not solely ICT oriented but also concerning lighting, laser, sensing, energy, environment, biological and medical sciences, and quantum optics. Glasses and glass-ceramics activated by rare earth ions are the bricks of such structures. Glass-ceramics are nanocomposite systems that exhibit specific morphologic, structural and spectroscopic properties allowing developing new physical concepts, for instance the mechanism related to the transparency, as well as novel photonic devices based on the enhancement of the luminescence. The dependence of the final product on the specific parent glass and on the fabrication protocol still remain an important task of the research in material science. Looking to application, the enhanced spectroscopic properties typical of glass ceramic in respect to those of the amorphous structures constitute an important point for the development of integrated optics devices, including optical amplifiers, monolithic waveguide laser, novel sensors, coating of spherical microresonators, and up and down converters. This paper presents some results obtained by our consortium regarding glass-based photonics systems. We will comment the energy transfer mechanism in transparent glass ceramics taking as examples the up and down conversion systems and the role of SnO2 nanocrystals as sensitizers. Coating of spherical resonators by glass ceramics, 1D-Photonic Crystals for luminescence enhancement, laser action and disordered 1-D photonic structures will be also discussed. Finally, RF-Sputtered rare earth doped P2O5- SiO2-Al2O3-Na2O-Er2O3 planar waveguides, will be presented.

IMPATT Diodes Based on 〈111〉, 〈100〉, and 〈110〉 Oriented GaAs: A Comparative Study to Search the Best Orientation for Millimeter-Wave Atmospheric Windows

PubMed Central

Banerjee, Bhadrani; Tripathi, Anvita; Das, Adrija; Singh, Kumari Alka; Banerjee, J. P.

2015-01-01

The authors have carried out the large-signal (L-S) simulation of double-drift region (DDR) impact avalanche transit time (IMPATT) diodes based on 〈111〉, 〈100〉, and 〈110〉 oriented GaAs. A nonsinusoidal voltage excited (NSVE) L-S simulation technique is used to investigate both the static and L-S performance of the above-mentioned devices designed to operate at millimeter-wave (mm-wave) atmospheric window frequencies, such as 35, 94, 140, and 220 GHz. Results show that 〈111〉 oriented GaAs diodes are capable of delivering maximum RF power with highest DC to RF conversion efficiency up to 94 GHz; however, the L-S performance of 〈110〉 oriented GaAs diodes exceeds their other counterparts while the frequency of operation increases above 94 GHz. The results presented in this paper will be helpful for the future experimentalists to choose the GaAs substrate of appropriate orientation to fabricate DDR GaAs IMPATT diodes at mm-wave frequencies. PMID:27347524

The Use of Metal Filled Via Holes for Improving Isolation in LTCC RF and Wireless Multichip Packages

NASA Technical Reports Server (NTRS)

Ponchak, George E.; Chun, Donghoon; Yook, Jong-Gwan; Katehi, Linda P. B.

1999-01-01

LTCC MCMs (Low Temperature Cofired Ceramic MultiChip Module) for RF and wireless systems often use metal filled via holes to improve isolation between the stripline and microstrip interconnects. In this paper, results from a 3D-FEM electromagnetic characterization of microstrip and stripline interconnects with metal filled via fences for isolation are presented. It is shown that placement of a via hole fence closer than three times the substrate height to the transmission lines increases radiation and coupling. Radiation loss and reflections are increased when a short via fence is used in areas suspected of having high radiation. Also, via posts should not be separated by more than three times the substrate height for low radiation loss, coupling, and suppression of higher order modes in a package.

Ionic conductivity of binary fluorides of potassium and rare earth elements

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

Sorokin, N. I., E-mail: nsorokin1@yandex.ru

2016-01-15

The ionic conductivity s of KYF{sub 4} and K{sub 2}RF{sub 5} single crystals (R = Gd, Ho, Er) and KNdF{sub 4} and K{sub 2}RF{sub 5} ceramic samples (R = Dy, Er) has been studied in the temperature range of 340–500°C. A comparative analysis of the σ values for these objects has been performed. Binary fluorides of potassium and rare earth elements were synthesized by the hydrothermal method (temperature 480°C, pressure 100–150 MPa) in the R{sub 2}O{sub 3}–KF–H{sub 2}O systems. The σ values of tetraf luorides are 3 × 10{sup –5} S/cm (KYF{sub 4} single crystal) and 3 × 10{sup –6}more » S/cm (KNdF{sub 4} ceramics) at 435°C. A K{sub 2}ErF{sub 5} single crystal with σ = 1.2 × 10{sup –4} S/cm at 435°C has the maximum value of ionic conductivity among pentafluorides. The anisotropy of ionic transport was found in K{sub 2}HoF{sub 5} single crystals, σ{sub ∥c}/σ{sub ⊥c} = 2.5, where σ{sub ∥c} and σ{sub ⊥c} are, respectively, the conductivities along the crystallographic c axis and in the perpendicular direction.« less

High frequency inductive lamp and power oscillator

DOEpatents

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

2001-01-01

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

Material System Engineering for Advanced Electrocaloric Cooling Technology

NASA Astrophysics Data System (ADS)

Qian, Xiaoshi

Electrocaloric effect refers to the entropy change and/or temperature change in dielectrics caused by the electric field induced polarization change. Recent discovery of giant ECE provides an opportunity to realize highly efficient cooling devices for a broad range of applications ranging from household appliances to industrial applications, from large-scale building thermal management to micro-scale cooling devices. The advances of electrocaloric (EC) based cooling device prototypes suggest that highly efficient cooling devices with compact size are achievable, which could lead to revolution in next generation refrigeration technology. This dissertation focuses on both EC based materials and cooling devices with their recent advances that address practical issues. Based on better understandings in designing an EC device, several EC material systems are studied and improved to promote the performances of EC based cooling devices. In principle, applying an electric field to a dielectric would cause change of dipolar ordering states and thus a change of dipolar entropy. Giant ECE observed in ferroelectrics near ferroelectric-paraelectric (FE-PE) transition temperature is owing to the large dipolar orientation change, between random-oriented dipolar states in paraelectric phase and spontaneous-ordered dipolar states in ferroelectric phases, which is induced by external electric fields. Besides pursuing large ECE, studies on EC cooling devices indicated that EC materials are required to possess wide operational temperature window, in which large ECE can be maintained for efficient operations. Although giant ECE was first predicted in ferroelectric polymers, where the large effect exhibits near FEPE phase transition, the narrow operation temperature window poses obstacles for these normal ferroelectrics to be conveniently perform in wide range of applications. In this dissertation, we demonstrated that the normal ferroelectric polymers can be converted to relaxor ferroelectric polymers which possess both giant ECE (27 Kelvin temperature drop) and much wider operating temperature window (over 50 kelvin covering RT) by proper defect modification which delicately tailors ferroelectrics in meso-, micro- and molecular scales. In addition, in order to be practical, EC device requires EC material can be driven at low electric fields upon achieve the large ECE. It is demonstrated in this dissertation that by facially modifying materials structure in meso-, micro- and molecular scale, lowfield ECE can be greatly improved. Large ECE, induced by low electric fields and existing in wide temperature window, is a major improvement in EC materials for practical applications. Besides EC polymers, this thesis also investigated EC ceramics. Due to several unique opportunities offered by the EC ceramics, Ba(ZrxTi 1-x)O3 (BZT), that is studied. (i) This class of EC ceramics offers a possibility to explore the invariant critical point (ICP), which maximizes the number of coexistent phase and provides a nearly vanishing energy barrier for switching among different phases. As demonstrated in this thesis, the BZT bulk ceramics at x˜ 0.2 exhibits a large adiabatic temperature drop DeltaTc=4.5 K, a large isothermal entropy change DeltaS = 8 Jkg-1K-1, a large EC coefficient (|DeltaT c/DeltaE| = 0.52x10-6 KmV-1 and DeltaS/DeltaE=0.93x10 -6 Jmkg-1K-1V-1) over a wide operating temperature range Tspan>30K. (ii) The thermal conductivity of EC ceramics is in general, much higher than that of EC polymers, and consequently they will allow EC cooling configurations which are not accessible by the EC polymers. Moreover, in the same device configuration, the high thermal conductivity of EC ceramics (kappa> 5 W/mK, compared with EC polymer, ˜ 0.25 W/mK) allows higher operation frequency and therefore a higher cooling power. (iii) Well-established fabrication processes of multilayer ceramic capacitor (MLCC) provide a foundation for the EC ceramic toward mass production. In this thesis, BZT thick film double layers have been fabricated and large ECE has been directly measured. EC induced temperature drop (DeltaT) around 6.3 °C and entropy change (DeltaS) of 11.0 Jkg-1K -1 are observed under an electric field of DeltaE=14.6 MV/m at 40 °C was observed in BZT thick film double layers. The result encourages further investigations on ECE in MLCC for practical applications. (Abstract shortened by ProQuest.).

Al-/Ga-Doped ZnO Window Layers for Highly Efficient Cu₂ZnSn(S,Se)₄ Thin Film Solar Cells.

PubMed

Seo, Se Won; Seo, Jung Woo; Kim, Donghwan; Cheon, Ki-Beom; Lee, Doh-Kwon; Kim, Jin Young

2018-09-01

The successful use of Al-/Ga-doped ZnO (AGZO) thin films as a transparent conducting oxide (TCO) layer of a Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cell is demonstrated. The AGZO thin films were prepared by radio frequency (RF) sputtering. The structural, crystallographic, electrical, and optical properties of the AGZO thin films were systematically investigated. The photovoltaic properties of CZTSSe thin film solar cells incorporating the AGZO-based TCO layer were also reported. It has been found that the RF power and substrate temperature of the AGZO thin film are important factors determining the electrical, optical, and structural properties. The optimization process involving the RF power and the substrate temperature leads to good electrical and optical transmittance of the AGZO thin films. Finally, the CZTSSe solar cell with the AGZO TCO layer demonstrated a high conversion efficiency of 9.68%, which is higher than that of the conventional AZO counterpart by 12%.

Development of fundamental power coupler for C-ADS superconducting elliptical cavities

NASA Astrophysics Data System (ADS)

Gu, Kui-Xiang; Bing, Feng; Pan, Wei-Min; Huang, Tong-Ming; Ma, Qiang; Meng, Fan-Bo

2017-06-01

5-cell elliptical cavities have been selected for the main linac of the China Accelerator Driven sub-critical System (C-ADS) in the medium energy section. According to the design, each cavity should be driven with radio frequency (RF) energy up to 150 kW by a fundamental power coupler (FPC). As the cavities work with high quality factor and high accelerating gradient, the coupler should keep the cavity from contamination in the assembly procedure. To fulfil the requirements, a single-window coaxial type coupler was designed with the capabilities of handling high RF power, class 10 clean room assembly, and heat load control. This paper presents the coupler design and gives details of RF design, heat load optimization and thermal analysis as well as multipacting simulations. In addition, a primary high power test has been performed and is described in this paper. Supported by China ADS Project (XDA03020000) and National Natural Science Foundation of China (11475203)

Biaxial flexural strength of Turkom-Cera core compared to two other all-ceramic systems

PubMed Central

AL-MAKRAMANI, Bandar Mohammed Abdullah; RAZAK, Abdul Aziz Abdul; ABU-HASSAN, Mohamed Ibrahim

2010-01-01

Advances in all-ceramic systems have established predictable means of providing metal-free aesthetic and biocompatible materials. These materials must have sufficient strength to be a practical treatment alternative for the fabrication of crowns and fixed partial dentures. Objectives The aim of this study was to compare the biaxial flexural strength of three core ceramic materials. Material and methods Three groups of 10 disc-shaped specimens (16 mm diameter x 1.2 mm thickness - in accordance with ISO-6872, 1995) were made from the following ceramic materials: Turkom-Cera Fused Alumina [(Turkom-Ceramic (M) Sdn Bhd, Puchong, Selangor, Malaysia)], In-Ceram (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany) and Vitadur-N (Vita Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany), which were sintered according to the manufacturer's recommendations. The specimens were subjected to biaxial flexural strength test in a universal testing machine at a crosshead speed of 0.5 mm/min. The definitive fracture load was recorded for each specimen and the biaxial flexural strength was calculated from an equation in accordance with ISO-6872. Results The mean biaxial flexural strength values were: Turkom-Cera: 506.8±87.01 MPa, In-Ceram: 347.4±28.83 MPa and Vitadur-N: 128.7±12.72 MPa. The results were analyzed by the Levene's test and Dunnett's T3 post-hoc test (SPSS software V11.5.0 for Windows, SPSS, Chicago, IL, USA ) at a preset significance level of 5% because of unequal group variances (P<0.001). There was statistically significant difference between the three core ceramics (P<0.05). Turkom-Cera showed the highest biaxial flexural strength, followed by In-Ceram and Vitadur-N. Conclusions Turkom-Cera core had significantly higher flexural strength than In-Ceram and Vitadur-N ceramic core materials. PMID:21308292

"TPSX: Thermal Protection System Expert and Material Property Database"

NASA Technical Reports Server (NTRS)

Squire, Thomas H.; Milos, Frank S.; Rasky, Daniel J. (Technical Monitor)

1997-01-01

The Thermal Protection Branch at NASA Ames Research Center has developed a computer program for storing, organizing, and accessing information about thermal protection materials. The program, called Thermal Protection Systems Expert and Material Property Database, or TPSX, is available for the Microsoft Windows operating system. An "on-line" version is also accessible on the World Wide Web. TPSX is designed to be a high-quality source for TPS material properties presented in a convenient, easily accessible form for use by engineers and researchers in the field of high-speed vehicle design. Data can be displayed and printed in several formats. An information window displays a brief description of the material with properties at standard pressure and temperature. A spread sheet window displays complete, detailed property information. Properties which are a function of temperature and/or pressure can be displayed as graphs. In any display the data can be converted from English to SI units with the click of a button. Two material databases included with TPSX are: 1) materials used and/or developed by the Thermal Protection Branch at NASA Ames Research Center, and 2) a database compiled by NASA Johnson Space Center 9JSC). The Ames database contains over 60 advanced TPS materials including flexible blankets, rigid ceramic tiles, and ultra-high temperature ceramics. The JSC database contains over 130 insulative and structural materials. The Ames database is periodically updated and expanded as required to include newly developed materials and material property refinements.

A high power, pulsed, microwave amplifier for a synthetique aperture radar electrical model. Phase 1: Design

NASA Astrophysics Data System (ADS)

Atkinson, J. E.; Barker, G. G.; Feltham, S. J.; Gabrielson, S.; Lane, P. C.; Matthews, V. J.; Perring, D.; Randall, J. P.; Saunders, J. W.; Tuck, R. A.

1982-05-01

An electrical model klystron amplifier was designed. Its features include a gridded gun, a single stage depressed collector, a rare earth permanent magnet focusing system, an input loop, six rugged tuners and a coaxial line output section incorporating a coaxial-to-waveguide transducer and a pillbox window. At each stage of the design, the thermal and mechanical aspects were investigated and optimized within the framework of the RF specification. Extensive use was made of data from the preliminary design study and from RF measurements on the breadboard model. In an additional study, a comprehensive draft tube specification has been produced. Great emphasis has been laid on a second additional study on space-qualified materials and processes.

Radiofrequency attenuator and method

DOEpatents

Warner, Benjamin P [Los Alamos, NM; McCleskey, T Mark [Los Alamos, NM; Burrell, Anthony K [Los Alamos, NM; Agrawal, Anoop [Tucson, AZ; Hall, Simon B [Palmerston North, NZ

2009-01-20

Radiofrequency attenuator and method. The attenuator includes a pair of transparent windows. A chamber between the windows is filled with molten salt. Preferred molten salts include quarternary ammonium cations and fluorine-containing anions such as tetrafluoroborate (BF.sub.4.sup.-), hexafluorophosphate (PF.sub.6.sup.-), hexafluoroarsenate (AsF.sub.6.sup.-), trifluoromethylsulfonate (CF.sub.3SO.sub.3.sup.-), bis(trifluoromethylsulfonyl)imide ((CF.sub.3SO.sub.2).sub.2N.sup.-), bis(perfluoroethylsulfonyl)imide ((CF.sub.3CF.sub.2SO.sub.2).sub.2N.sup.-) and tris(trifluoromethylsulfonyl)methide ((CF.sub.3SO.sub.2).sub.3C.sup.-). Radicals or radical cations may be added to or electrochemically generated in the molten salt to enhance the RF attenuation.

Radiofrequency attenuator and method

DOEpatents

Warner, Benjamin P [Los Alamos, NM; McCleskey, T Mark [Los Alamos, NM; Burrell, Anthony K [Los Alamos, NM; Agrawal, Anoop [Tucson, AZ; Hall, Simon B [Palmerston North, NZ

2009-11-10

Radiofrequency attenuator and method. The attenuator includes a pair of transparent windows. A chamber between the windows is filled with molten salt. Preferred molten salts include quarternary ammonium cations and fluorine-containing anions such as tetrafluoroborate (BF.sub.4.sup.-), hexafluorophosphate (PF.sub.6.sup.-), hexafluoroarsenate (AsF.sub.6.sup.-), trifluoromethylsulfonate (CF.sub.3SO.sub.3.sup.-), bis(trifluoromethylsulfonyl)imide ((CF.sub.3SO.sub.2).sub.2N.sup.-), bis(perfluoroethylsulfonyl)imide ((CF.sub.3CF.sub.2SO.sub.2).sub.2N.sup.-) and tris(trifluoromethylsulfonyl)methide ((CF.sub.3SO.sub.2).sub.3 C.sup.-). Radicals or radical cations may be added to or electrochemically generated in the molten salt to enhance the RF attenuation.

Energy Saving Glass Lamination via Selective Radio Frequency Heating

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

Allan, Shawn M; Baranova, Inessa; Poley, Joseph

2012-02-27

This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates overmore » the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North America. The second task dealt with a study of current lamination processes in the various laminate industries, and development of concepts for integrating RF lamination into new or existing processes. The third task explored the use of a non-destructive technique for analyzing laminate adhesion with the University of Illinois at Urbana-Champaign. The fourth task focused on developing concepts for curved glass lamination using RF lamination. The fifth and sixth tasks together comprised an analysis of laminate product markets, ranking for applicability and commercialization potential, and the development of commercialization strategies for those products. In addition, throughout the project as new experimental data and conventional process data were obtained, the benefits analysis of RF lamination was refined. The goals of the project described above were achieved, positioning RF lamination for the next stage growth envisioned in the original Industrial Grand Challenge proposal. Working with Pilkington North America, lamination of flat autoglass with PVB was achieved, meeting all 16 stringent industry tests. In particular, PVB laminates made with RF lamination passed environmental tests including the high temperature, 120°C bake test, without significant formation of bubbles (defects). The adhesion of PVB to glass was measured using the pummel method. Adhesion values ranging from 1 to 7 out of 10 were obtained. The significant process parameters affecting the environmental and adhesion performance were identified through a designed experiment. Pre-lamination process variables including PVB storage humidity and the de-airing process (vacuum or nip rolling) were significant, as well as the level of pressure applied to the laminate during the RF process. Analysis of manufacturing with RF lamination equipment, based on the processes developed indicated that 3 RF presses could replace a typical auto-industry autoclave to achieve equal or greater throughput with possibly less capital cost and smaller footprint. Concepts for curved lamination identifying castable molds for prototyping were developed, which allowed Ceralink to obtain commitment to begin curved tooling development. The project significantly helped to advance RF lamination past the feasibility and novelty stage and into the realm of commercial acceptance as a viable alternative to autoclaves. The demonstration of autoclave-quality autoglass produced in just 1 minute with RF lamination, with validation by Pilkington, has fueled industry motivation to seriously consider RF lamination. The industry and other contacts and outreach made in the study of laminate markets (including 3 technical publications and 5 conference presentations), has resulted in a recent surge in RF lamination activity.« less

Energy Saving Glass Lamination via Selective Radio Frequency Heating

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

Allan, Shawn M.

2012-02-27

This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates overmore » the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North America. The second task dealt with a study of current lamination processes in the various laminate industries, and development of concepts for integrating RF lamination into new or existing processes. The third task explored the use of a non-destructive technique for analyzing laminate adhesion with the University of Illinois at Urbana-Champaign. The fourth task focused on developing concepts for curved glass lamination using RF lamination. The fifth and sixth tasks together comprised an analysis of laminate product markets, ranking for applicability and commercialization potential, and the development of commercialization strategies for those products. In addition, throughout the project as new experimental data and conventional process data were obtained, the benefits analysis of RF lamination was refined. The goals of the project described above were achieved, positioning RF lamination for the next stage growth envisioned in the original Industrial Grand Challenge proposal. Working with Pilkington North America, lamination of flat autoglass with PVB was achieved, meeting all 16 stringent industry tests. In particular, PVB laminates made with RF lamination passed environmental tests including the high temperature, 120 C bake test, without significant formation of bubbles (defects). The adhesion of PVB to glass was measured using the pummel method. Adhesion values ranging from 1 to 7 out of 10 were obtained. The significant process parameters affecting the environmental and adhesion performance were identified through a designed experiment. Pre-lamination process variables including PVB storage humidity and the de-airing process (vacuum or nip rolling) were significant, as well as the level of pressure applied to the laminate during the RF process. Analysis of manufacturing with RF lamination equipment, based on the processes developed indicated that 3 RF presses could replace a typical auto-industry autoclave to achieve equal or greater throughput with possibly less capital cost and smaller footprint. Concepts for curved lamination identifying castable molds for prototyping were developed, which allowed Ceralink to obtain commitment to begin curved tooling development. The project significantly helped to advance RF lamination past the feasibility and novelty stage and into the realm of commercial acceptance as a viable alternative to autoclaves. The demonstration of autoclave-quality autoglass produced in just 1 minute with RF lamination, with validation by Pilkington, has fueled industry motivation to seriously consider RF lamination. The industry and other contacts and outreach made in the study of laminate markets (including 3 technical publications and 5 conference presentations), has resulted in a recent surge in RF lamination activity.« less

Study of HV Dielectrics for High Frequency Operation in Linear & Nonlinear Transmission Lines & Simulation & Development of Hybrid Nonlinear Lines for RF Generation

DTIC Science & Technology

2015-08-27

applied reverse voltage [8], [9]. In this report, the experimental results of a varactor diode NLTL built with 30 sections are presented. Besides, Spice ...capacitive line (NLCL) using commercial BT and PZT ceramic capacitors. Corresponding NLCL Spice simulation is provided for comparison with experimental...the output pulse. In special for PZT, Spice simulation of a line with respective linear capacitors illustrates its weak nonlinearity as the

Study of HV Dielectrics for High Frequency Operation in Linear and Nonlinear Transmission Lines (NLTLs) and Simulation and Development of Hybrid Nonlinear Lines for RF Generation

DTIC Science & Technology

2016-01-27

presented. Besides, Spice simulation provides an excellent way of studying the NLTL principle operation by comparing them with the experimental...high voltage nonlinear capacitive line (NLCL) using commercial BT and PZT ceramic capacitors. Corresponding NLCL Spice simulation is provided for...which causes a long tail on the output pulse. In special for PZT, Spice simulation of a line with respective linear capacitors illustrates its weak

The effects of composition and sintering temperature on the silica foam fabricated by slurry method

NASA Astrophysics Data System (ADS)

Baharom, Syazwani; Ahmad, Sufizar; Taib, Hariati; Muda, Rizamarhaiza

2016-07-01

Reticulated ceramic or open pore ceramic foam is a well-known material which exhibits extremely high porosities, with a significant degree of interconnectivity that makes them desirable in a wide range of applications. There were broad types of ceramic foam fabrication method such as polymeric sponge method, direct foaming, and starch consolidation. In this study, the slurry method has been chosen to fabricate Silica (SiO2) foam. In this process, Polyurethane (PU) foam template was dipped into ceramic slurry and followed by drying and sintering to obtain foam which contains porosity in the range of 50% to 70%. The compositions of SiO2 were varied starting from 55 wt.%, 60 wt.%, 65 wt.% and 70 wt.%. The samples of SiO2 that have been dipped and dried were sintered at 900°C, 1000°C, 1100°C, and 1250°C. The sintered SiO2 ceramic foam samples were characterized to observe their morphology, and physical properties. Thus, the microstructure of the SiO2 ceramic foams samples was examined by Scanning Electron Microscopy (SEM), and Electron Dispersive Spectroscopy (EDS). Meanwhile, the physical properties of the SiO2 ceramic foam samples such as the total porosity (%) and bulk density were determined using Archimedes method. It was found that the density of ceramic foam produced was in the range of 0.25 g/cm3 up to 0.75 g/cm3, whereas the level of porosity percentage was in the range of 61.81% to 82.18% with the size of open pore or window cells were in between 141 µm up to 626 µm.

The effects of composition and sintering temperature on the silica foam fabricated by slurry method

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

Baharom, Syazwani, E-mail: hd140001@siswa.uthm.edu.my; Ahmad, Sufizar, E-mail: sufizar@uthm.edu.my; Taib, Hariati, E-mail: hariati@uthm.edu.my

Reticulated ceramic or open pore ceramic foam is a well-known material which exhibits extremely high porosities, with a significant degree of interconnectivity that makes them desirable in a wide range of applications. There were broad types of ceramic foam fabrication method such as polymeric sponge method, direct foaming, and starch consolidation. In this study, the slurry method has been chosen to fabricate Silica (SiO{sub 2}) foam. In this process, Polyurethane (PU) foam template was dipped into ceramic slurry and followed by drying and sintering to obtain foam which contains porosity in the range of 50% to 70%. The compositions ofmore » SiO{sub 2} were varied starting from 55 wt.%, 60 wt.%, 65 wt.% and 70 wt.%. The samples of SiO{sub 2} that have been dipped and dried were sintered at 900°C, 1000°C, 1100°C, and 1250°C. The sintered SiO{sub 2} ceramic foam samples were characterized to observe their morphology, and physical properties. Thus, the microstructure of the SiO{sub 2} ceramic foams samples was examined by Scanning Electron Microscopy (SEM), and Electron Dispersive Spectroscopy (EDS). Meanwhile, the physical properties of the SiO{sub 2} ceramic foam samples such as the total porosity (%) and bulk density were determined using Archimedes method. It was found that the density of ceramic foam produced was in the range of 0.25 g/cm{sup 3} up to 0.75 g/cm{sup 3}, whereas the level of porosity percentage was in the range of 61.81% to 82.18% with the size of open pore or window cells were in between 141 µm up to 626 µm.« less

Effect of thickness on optoelectrical properties of Nb-doped indium tin oxide thin films deposited by RF magnetron sputtering

NASA Astrophysics Data System (ADS)

Li, Shi-na; Ma, Rui-xin; Ma, Chun-hong; Li, Dong-ran; Xiao, Yu-qin; He, Liang-wei; Zhu, Hong-min

2013-05-01

Niobium-doped indium tin oxide (ITO:Nb) thin films are prepared on glass substrates with various film thicknesses by radio frequency (RF) magnetron sputtering from one piece of ceramic target material. The effects of thickness (60-360 nm) on the structural, electrical and optical properties of ITO: Nb films are investigated by means of X-ray diffraction (XRD), ultraviolet (UV)-visible spectroscopy, and electrical measurements. XRD patterns show the highly oriented (400) direction. The lowest resistivity of the films without any heat treatment is 3.1×10-4Ω·cm-1, and the resistivity decreases with the increase of substrate temperature. The highest Hall mobility and carrier concentration are 17.6 N·S and 1.36×1021 cm-3, respectively. Band gap energy of the films depends on substrate temperature, which varies from 3.48 eV to 3.62 eV.

Grain boundary-dominated electrical conduction and anomalous optical-phonon behaviour near the Neel temperature in YFeO3 ceramics

NASA Astrophysics Data System (ADS)

Raut, Subhajit; Babu, P. D.; Sharma, R. K.; Pattanayak, Ranjit; Panigrahi, Simanchalo

2018-05-01

We investigated the anomalous behaviour in the dielectric properties, occurring nearly at room temperature and at elevated temperatures (near the Neel temperature TN) of the polycrystalline samples of YFeO3 (YFO) ceramics. On the prepared YFO ceramics, the magnetic measurements showed the Neel temperature of YFO to be 650 K, below which the compound exhibited the weak ferromagnetic behaviour. X-ray photoelectron spectroscopy (XPS) shows the presence of Fe ions (Fe2+ and Fe3+ states) and also revealed the formation of the oxygen vacancies. The frequency dependence of the complex dielectric constant within the frequency domain of 100 Hz-1 MHz shows the presence of grain dominated dielectric relaxation over the thermal window of 300-373 K. The activation energy Eact.ɛ=0.611 eV extracted from the imaginary permittivity spectrum indicates the involvement of oxygen vacancies in the relaxation process. Above 493 K, the ac conductivity, complex impedance, and modulus studies revealed appreciable conduction and relaxation processes occurring in YFO ceramics with respective activation energies Eac t . σ=1.362 eV and Eac t . Z=1.345 eV , which suggests that the oxygen vacancies are also involved for the anomalous behaviour of the dielectric constant at elevated temperatures. The temperature dependent Raman spectroscopic measurements within the thermal window of 298-698 K showed anomalous variations of the line widths and frequencies of several Raman active modes above 473 K up to the vicinity of TN pointing towards the presence of admixtures of the electron-phonon and spin-phonon coupling in the system. A further study on the thermal variation of the B2g(4) mode frequency with [M(T)/MS]2 shows the occurrence of strong spin-phonon (s-p) coupling, while the line shape shows the presence of the Fano asymmetry, suggesting spin dependent electron-phonon (e-p) coupling in the system below TN.

Influence of Substrate Temperature on Structural, Electrical and Optical Properties of Ito Thin Films Prepared by RF Magnetron Sputtering

NASA Astrophysics Data System (ADS)

He, Bo; Zhao, Lei; Xu, Jing; Xing, Huaizhong; Xue, Shaolin; Jiang, Meng

2013-10-01

In this paper, we investigated indium-tin-oxide (ITO) thin films on glass substrates deposited by RF magnetron sputtering using ceramic target to find the optimal condition for fabricating optoelectronic devices. The structural, electrical and optical properties of the ITO films prepared at various substrate temperatures were investigated. The results indicate the grain size increases with substrate temperature increases. As the substrate temperature grew up, the resistivity of ITO films greatly decreased. The ITO film possesses high quality in terms of electrode functions, when substrate temperature is 480°C. The resistivity is as low as 9.42 × 10-5 Ω•cm, while the carrier concentration and mobility are as high as 3.461 × 1021 atom/cm3 and 19.1 cm2/Vṡs, respectively. The average transmittance of the film is about 95% in the visible region. The novel ITO/np-Silicon frame, which prepared by RF magnetron sputtering at 480°C substrate temperature, can be used not only for low-cost solar cell, but also for high quantum efficiency of UV and visible lights enhanced photodetector for various applications.

Compatibility of AlN with liquid lithium

NASA Astrophysics Data System (ADS)

Terai, T.; Suzuki, A.; Yoneoka, T.; Mitsuyama, T.

2000-12-01

Development of ceramic coatings is one of the most important subjects in liquid blanket research and development. Compatibility of sintered AlN and AlN coatings with liquid lithium, a candidate breeding material, was investigated. Sintered AlN with or without the sintering aid of Y 2O 3 examined in lithium at 773 K for 1390 h showed a slight decrease in electrical resistivity because of a reduction in Al 2O 3 impurity, though AlN and Y 2O 3 components themselves were subject to no severe corrosion. On the other hand, AlN ceramic coatings on SUS430 with high resistivity (> 10 11 Ω m) fabricated by the RF sputtering method disappeared in liquid lithium at 773 K in 56 h. This may be because cracks were formed due to the difference in thermal expansion between the coatings and the substrate or because the oxide formed between the two was removed by liquid lithium.

High frequency inductive lamp and power oscillator

DOEpatents

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

2000-01-01

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

Initial deposition of calcium phosphate ceramic on polystyrene and polytetrafluoroethylene by rf magnetron sputtering deposition

NASA Astrophysics Data System (ADS)

Feddes, B.; Wolke, J. G. C.; Jansen, J. A.; Vredenberg, A. M.

2003-03-01

Calcium phosphate (CaP) coatings can be applied to improve the biological performance of polymeric medical implants. A strong interfacial bond between ceramic and polymer is required for clinical applications. Because the chemical structure of an interface plays an important role in the adhesion of a coating, we studied the formation of the interface between CaP and polystyrene (PS) and polytetrafluoroethylene (PTFE). The coating was deposited in a radio frequency (rf) magnetron sputtering deposition system. Prior to the deposition, some samples received an oxygen plasma pretreatment. We found that the two substrates show a strongly different reactivity towards CaP. On PS a phosphorus and oxygen enrichment is present at the interface. This is understood from POx complexes that are able to bind to the PS. The effects of the plasma pretreatment are overruled by the deposition process itself. On PTFE, a calcium enrichment and an absence of phosphorus is found at the interface. The former is the result of CaF2-like material being formed at the interface. The latter may be the result of phosphorus reacting with escaping fluorine to a PF3 molecule, which than escapes from the material as a gas molecule. We found that the final structure of the interface is mostly controlled by the bombardment of energetic particles escaping either from the plasma or from the sputtering target. The work described here can be used to understand and improve the adhesion of CaP coatings deposited on medical substrates.

Electron Multipactor: Theory Review, Comparison and Modeling of Mitigation Techniques in ICEPIC

DTIC Science & Technology

2009-03-01

dielectric . This development includes space charge effects . 2.2.1 Conventions, Notations and Definitions...gigawatts, one percent of the RF energy would indeed be enough to cause failure in the dielectric window. For the case in which space charge effects are...buildup of the space - charges along the dielectric surface not allowing the number of multipactoring electrons to evolve beyond a certain point. 0 2 4 6

The impact of microwave stray radiation to in-vessel diagnostic components

NASA Astrophysics Data System (ADS)

Hirsch, M.; Laqua, H. P.; Hathiramani, D.; Oosterbeek, J.; Baldzuhn, J.; Biedermann, C.; v d Brand, H.; Cardella, A.; Erckmann, V.; Jimenez, R.; König, R.; Köppen, M.; Parquay, S.; Zhang, D.; W7-X Team

2014-08-01

Microwave stray radiation resulting from unabsorbed multiple reflected ECRH / ECCD beams may cause severe heating of microwave absorbing in-vessel components such as gaskets, bellows, windows, ceramics and cable insulations. In view of long-pulse operation of WENDELSTEIN-7X the MIcrowave STray RAdiation Launch facility, MISTRAL, allows to test in-vessel components in the environment of isotropic 140 GHz microwave radiation at power load of up to 50 kW/m2 over 30 min. The results show that both, sufficient microwave shielding measures and cooling of all components are mandatory. If shielding/cooling measures of in-vessel diagnostic components are not efficient enough, the level of stray radiation may be (locally) reduced by dedicated absorbing ceramic coatings on cooled structures.

Asset Management: Roof Maintenance and Facility Energy Retrofits

DTIC Science & Technology

2012-03-01

vapor low emission coatings. Floor finishes completed in ceramic stone tile were the most efficient floor coverings. Fixed insulated fiberglass window...been coined Asset Management which utilizes organizational levels of service, business case analysis, and risk analysis to address urgent...Force have left a number of facility systems such as roofs at risk to disrepair due to a lack of maintenance. Under the principles of asset

High Ionic Conductivity of Composite Solid Polymer Electrolyte via In Situ Synthesis of Monodispersed SiO2 Nanospheres in Poly(ethylene oxide).

PubMed

Lin, Dingchang; Liu, Wei; Liu, Yayuan; Lee, Hye Ryoung; Hsu, Po-Chun; Liu, Kai; Cui, Yi

2016-01-13

High ionic conductivity solid polymer electrolyte (SPE) has long been desired for the next generation high energy and safe rechargeable lithium batteries. Among all of the SPEs, composite polymer electrolyte (CPE) with ceramic fillers has garnered great interest due to the enhancement of ionic conductivity. However, the high degree of polymer crystallinity, agglomeration of ceramic fillers, and weak polymer-ceramic interaction limit the further improvement of ionic conductivity. Different from the existing methods of blending preformed ceramic particles with polymers, here we introduce an in situ synthesis of ceramic filler particles in polymer electrolyte. Much stronger chemical/mechanical interactions between monodispersed 12 nm diameter SiO2 nanospheres and poly(ethylene oxide) (PEO) chains were produced by in situ hydrolysis, which significantly suppresses the crystallization of PEO and thus facilitates polymer segmental motion for ionic conduction. In addition, an improved degree of LiClO4 dissociation can also be achieved. All of these lead to good ionic conductivity (1.2 × 10(-3) S cm(-1) at 60 °C, 4.4 × 10(-5) S cm(-1) at 30 °C). At the same time, largely extended electrochemical stability window up to 5.5 V can be observed. We further demonstrated all-solid-state lithium batteries showing excellent rate capability as well as good cycling performance.

A CW radiofrequency ion source for production of negative hydrogen ion beams for cyclotrons

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

Kalvas, T.; Tarvainen, O.; Komppula, J.

2015-04-08

A CW 13.56 MHz radiofrequency-driven ion source RADIS for production of H{sup −} and D{sup −} beams is under development for replacing the filament-driven ion source of the MCC30/15 cyclotron. The RF ion source has a 16-pole multicusp plasma chamber, an electromagnet-based magnetic filter and an external planar spiral RF antenna behind an AlN window. The extraction is a 5-electrode system with an adjustable puller electrode voltage for optimizing the beam formation, a water-cooled electron dump electrode and an accelerating einzel lens. At 2650 W of RF power, the source produces 1 mA of H{sup −} (2.6 mA/cm{sup 2}), which is the intensity neededmore » at injection for production of 200 µA H{sup +} with the filament-driven ion source. A simple pepperpot device has been developed for characterizing the beam emittance. Plans for improving the power efficiency with the use of a new permanent magnet front plate is discussed.« less

Effect of deposition parameters and heat-treatment on the microstructure, mechanical and electrochemical properties of hydroxyapatite/titanium coating deposited on Ti6Al4V by RF-magnetron sputtering

NASA Astrophysics Data System (ADS)

Qi, Jianwei; Chen, Zhangbo; Han, Wenjun; He, Danfeng; Yang, Yiming; Wang, Qingliang

2017-09-01

Functionally graded HA/Ti coatings were deposited on silicon and Ti6Al4V substrate by radio-frequency (RF) magnetron sputtering. The effect of RF-power, negative bias and heat-treatment on the microstructure, mechanical and electrochemical properties of the coatings were characterized by SEM, XRD, FTIR, AFM Nanoindentation and electrochemical workstation. The obtained results showed that the as-deposited HA/Ti coatings were characteristic of amorphous structure, which transformed into a crystal structure after heat-treatment, and reformed O-H peak. The content of crystallization was increasing with the increase of negative bias. A dense, homogenous, smooth and featured surface, and columnar cross-section structure was observed in SEM observation. AFM results showed that the surface roughness became higher after heat-treatment, and increased with increasing RF-power. The mechanical test indicated that the coating had a higher nanohardness (9.1 GPa) in the case of  -100 V and 250 W than that of Ti6Al4V substrate, and a critical load as high as 17  ±  3.5 N. The electrochemical test confirmed the HA/Ti coating served as a stable protecting barrier in improving the corrosion resistance, which the corrosion current density was 1.3% of Ti6Al4V, but it was significantly influenced by RF-power and negative bias. The contact angle test demonstrated that all the coatings exhibited favorable hydrophilic properties, and it decreased by 20-25% compared to that untreated samples. Thus all results indicated that magnetron sputtering is a promising way for fabricating a better biocompatible ceramic coating by adjusting deposition parameters and post-deposition heat treatments.

Fluid valve with wide temperature range

NASA Technical Reports Server (NTRS)

Kast, Howard Berdolt (Inventor)

1976-01-01

A fluid valve suitable for either metering or pressure regulating fluids at various temperatures is provided for a fuel system as may be utilized in an aircraft gas turbine engine. The valve includes a ceramic or carbon pad which cooperates with a window in a valve plate to provide a variable area orifice which remains operational during large and sometimes rapid variations in temperature incurred from the use of different fuels.

Breakthroughs in Low Profile Leaky Wave HPM Antennas

DTIC Science & Technology

2016-10-17

3D RF modeling, but the design time and effort will be greatly reduced compared to starting from scratch. The LWAs featured here exhibit beam...Section 4 present related and novel antenna designs that leverage some of the concepts from this research program. Section 5 and Section 6 present...parameters that we used previously for the wire-grill design in Figure 3, but this time with the intent to combine it with an acrylic (εr=2.55) window of

Crystallization, fluoridation and some properties of apatite thin films prepared through rf-sputtering from CaO-P2O5 glasses.

PubMed

Yamashita, K; Matsuda, M; Arashi, T; Umegaki, T

1998-07-01

Using calcium phosphate glass targets with the CaO/P2O5 molar ratios of 1.50-0.50, much lower than the stoichiometric value of 3.3 for hydroxyapatite, thin films of stoichiometric hydroxy-, nonstoichiometric oxyhydroxy- and Ca-deficient oxyhydroxy-apatites were prepared on alumina ceramic substrates by rf-sputtering followed by post-annealing. Based on the present results, a phase diagram for CaO-P2O5 at low temperatures in the ambience of air was depicted for thin films. The ambient H2O vapor had an influence on the phase diagram: Tricalcium phosphate was changed to apatite in the presence of H2O vapor. Dense fluorohydroxyapatite thin films were prepared by fluoridation of those apatite thin films at a low temperature such as 200 degrees C. In the present report, some functional properties of thin films thus prepared were also shown.

Receptive fields of visual neurons: the early years.

PubMed

Spillmann, Lothar

2014-01-01

This paper traces the history of the visual receptive field (RF) from Hartline to Hubel and Wiesel. Hartline (1938, 1940) found that an isolated optic nerve fiber in the frog could be excited by light falling on a small circular area of the retina. He called this area the RF, using a term first introduced by Sherrington (1906) in the tactile domain. In 1953 Kuffler discovered the antagonistic center-surround organization of cat RFs, and Barlow, Fitzhugh, and Kuffler (1957) extended this work to stimulus size and state of adaptation. Shortly thereafter, Lettvin and colleagues (1959) in an iconic paper asked "what the frog's eye tells the frog's brain". Meanwhile, Jung and colleagues (1952-1973) searched for the perceptual correlates of neuronal responses, and Jung and Spillmann (1970) proposed the term perceptive field (PF) as a psychophysical correlate of the RF. The Westheimer function (1967) enabled psychophysical measurements of the PF center and surround in human and monkey, which correlated closely with the underlying RF organization. The sixties and seventies were marked by rapid progress in RF research. Hubel and Wiesel (1959-1974), recording from neurons in the visual cortex of the cat and monkey, found elongated RFs selective for the shape, orientation, and position of the stimulus, as well as for movement direction and ocularity. These findings prompted the emergence in visual psychophysics of the concept of feature detectors selective for lines, bars, and edges, and contributed to a model of the RF in terms of difference of Gaussians (DOG) and Fourier channels. The distinction between simple, complex, and hypercomplex neurons followed. Although RF size increases towards the peripheral retina, its cortical representation remains constant due to the reciprocal relationship with the cortical magnification factor (M). This constitutes a uniform yardstick for M-scaled stimuli across the retina. Developmental studies have shown that RF properties are not fixed. RFs possess their full response inventory already at birth, but require the interaction with appropriate stimuli within a critical time window for refinement and consolidation. Taken together these findings paved the way for a better understanding of how objective properties of the external world are encoded to become subjective properties of the subjective, perceptual world.

Better ceramics through chemistry. 4

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

Zelinski, B.J.J.; Brinker, C.J.; Clark, D.E.

1990-01-01

At this year's meeting, research into the area of reaction mechanisms and kinetics of silicon species remained strong, while significant advances in the area of structure and properties of modified and unmodified metal alkoxide species were reported. The complementary area of processing in water based systems also received considerable attention with emphasis being placed on the hydrolysis behavior of ions in solution. The nature of particle/aggregate growth was also a major topic of discussion with papers being presented on the role of aggregation in particle growth and on the nature and rheology of concentrated suspensions. Important developments in the areamore » of mechanical properties of aerogels, fibers and films were presented as well as research into techniques for in situ monitoring of films during dip coating. Continued advances in applications which utilize solution derived ceramics were also reported. These applications included GRIN lenses, planar waveguides, optical filters and switches, transpiration cooled windows, dye-polymer composites for nonlinear optics, dielectrics and electro-optic materials including PLZT's and the niobates, and chemical sensors. Finally, one of the meeting highlights was a special evening session on biomimetics: ceramic processing in natural systems.« less

Potentially improved glasses from space environment

NASA Technical Reports Server (NTRS)

Nichols, R.

1977-01-01

The benefits of processing glasses in a low-gravity space environment are examined. Containerless processing, the absence of gravity driven convection, and lack of sedimentation are seen as potential advantages. Potential applications include the formation of glass-ceramics with a high content of active elements for ferromagnetic devices, the production of ultrapure chalcogenide glasses for laser windows and IR fiber optics, and improved glass products for use in optical systems and laser fusion targets.

ALON® Components With Tunable Dielectric Properties for High Power Accelerator Applications

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

Goldman, Lee M; Jha, Santosh K; Lobur, Nicole

There are challenges in linear particle accelerators associated with the need to suppress “higher order modes” (HOMs). HOMs are detrimental to accelerator operation as they are a source of beam instability. The absorption/suppression of HOMs and dissipation of the energy of higher order modes is vital to the function of these accelerators. Surmet has identified ALON® Optical Ceramic (Aluminum Oxynitride), a hard, durable ceramic that is fabricated through conventional powder processing techniques, as a potential material for HOM absorber. In this Phase I program, Surmet has produced new ALON-composite HOM absorber materials that function at both ambient and cryogenic temperatures.more » The composite materials were developed and evaluated in collaboration with Thomas Jefferson National Labs. Success in this Phase I and the potential Phase II will demonstrate the utility of ALON composite components for RF absorbing applications and lay the groundwork for commercialization of such products, with applications in basic science, medical and digital electronics industries.« less

Operating Experience and Reliability Improvements on the 5 kW CW Klystron at Jefferson Lab

NASA Astrophysics Data System (ADS)

Nelson, R.; Holben, S.

1997-05-01

With substantial operating hours on the RF system, considerable information on reliability of the 5 kW CW klystrons has been obtained. High early failure rates led to examination of the operating conditions and failure modes. Internal ceramic contamination caused premature failure of gun potting material and ultimate tube demise through arcing or ceramic fracture. A planned course of repotting and reconditioning of approximately 300 klystrons, plus careful attention to operating conditions and periodic analysis of operational data, has substantially reduced the failure rate. It is anticipated that implementation of planned supplemental monitoring systems for the klystrons will allow most catastrophic failures to be avoided. By predicting end of life, tubes can be changed out before they fail, thus minimizing unplanned downtime. Initial tests have also been conducted on this same klystron operated at higher voltages with resultant higher output power. The outcome of these tests will provide information to be considered for future upgrades to the accelerator.

Ultra-hard amorphous AlMgB14 films RF sputtered onto curved substrates

NASA Astrophysics Data System (ADS)

Grishin, A. M.; Putrolaynen, V. V.; Yuzvyuk, M. H.

2017-03-01

Recently, hard AlMgB14 (BAM) coatings were deposited for the first time by RF magnetron sputtering using a single stoichiometric ceramic target. High target sputtering power and sufficiently short target-to-substrate distance were found to be critical processing conditions. They enabled fabrication of stoichiometric in-depth compositionally homogeneous films with the peak values of nanohardness 88 GPa and Young’s modulus 517 GPa at the penetration depth of 26 nm and, respectively, 35 GPa and 275 GPa at 200 nm depth in 2 µm thick film (Grishin et al 2014 JETP Lett. 100 680). The narrow range of sufficiently short target-to-substrate distance makes impossible to coat non flat specimens. To achieve ultimate BAM films’ characteristics onto curved surfaces we developed two-step sputtering process. The first thin layer is deposited as a template at low RF power that facilitates a layered Frank van der Merwe mode growth of smooth film occurs. The next layer is grown at high RF target sputtering power. The affinity of subsequent flow of sputtered atoms to already evenly condensed template fosters the development of smooth film surface. As an example, we made BAM coating onto hemispherical 5 mm in diameter ball made from a hard tool steel and used as a head of a special gauge. Very smooth (6.6 nm RMS surface roughness) and hard AlMgB14 films fabricated onto commercial ball-shaped items enhance hardness of tool steel specimens by a factor of four.

VO2 Thermochromic Films on Quartz Glass Substrate Grown by RF-Plasma-Assisted Oxide Molecular Beam Epitaxy

PubMed Central

Zhang, Dong; Sun, Hong-Jun; Wang, Min-Huan; Miao, Li-Hua; Liu, Hong-Zhu; Zhang, Yu-Zhi; Bian, Ji-Ming

2017-01-01

Vanadium dioxide (VO2) thermochromic thin films with various thicknesses were grown on quartz glass substrates by radio frequency (RF)-plasma assisted oxide molecular beam epitaxy (O-MBE). The crystal structure, morphology and chemical stoichiometry were investigated systemically by X-ray diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses. An excellent reversible metal-to-insulator transition (MIT) characteristics accompanied by an abrupt change in both electrical resistivity and optical infrared (IR) transmittance was observed from the optimized sample. Remarkably, the transition temperature (TMIT) deduced from the resistivity-temperature curve was reasonably consistent with that obtained from the temperature-dependent IR transmittance. Based on Raman measurement and XPS analyses, the observations were interpreted in terms of residual stresses and chemical stoichiometry. This achievement will be of great benefit for practical application of VO2-based smart windows. PMID:28772673

Design and development of a 6 MW peak, 24 kW average power S-band klystron

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

Joshi, L.M.; Meena, Rakesh; Nangru, Subhash

2011-07-01

A 6 MW peak, 24 kW average power S-band Klystron is under development at CEERI, Pilani under an MoU between BARC and CEERI. The design of the klystron has been completed. The electron gun has been designed using TRAK and MAGIC codes. RF cavities have been designed using HFSS and CST Microwave Studio while the complete beam wave interaction simulation has been done using MAGIC code. The thermal design of collector and RF window has been done using ANSYS code. A Gun Collector Test Module (GCTM) was developed before making actual klystron to validate gun perveance and thermal design ofmore » collector. A high voltage solid state pulsed modulator has been installed for performance valuation of the tube. The paper will cover the design aspects of the tube and experimental test results of GCTM and klystron. (author)« less

'Putting your foot in it'! A window into clumsy behaviour.

PubMed

Sigmundsson, H; Whiting, H T; Ingvaldsen, R P

1999-07-01

Intra-modal matching by 7-year-old children diagnosed as having hand-eye co-ordination problems (HECP) and a control group of children without such problems was tested using a target location and matching task. The 'foot-hand' task required the children to locate a target pin with the 'big-toe' (felt target) and match the located target position with the hand, without vision. There were four conditions: location via right foot-matching the located target with the right hand (RfRh) and left hand (RfLh) and location via left foot-matching the located target with the left hand (LfLh) and right hand (LfRh). Both groups demonstrated better performance in the intra- as compared to the inter-hemispheric conditions, suggesting that the corpus callosum is not yet fully mature at this age. The HECP children showed inferior performance to the control children in three of the four conditions, the conditions where the right hemisphere was involved and/or information had to be transported across the corpus callosum (RfLh; LfLh; LfRh). Two possible explanations of these findings are put forward and discussed: right hemisphere insufficiency with or without dysfunctional corpus callosum.

IC Ku-band Impatt Amplifier. [solid state spacecraft transmitter

NASA Technical Reports Server (NTRS)

Sokolov, V.; Namordi, M. R.; Doerbeck, F. H.; Wisseman, W. R.

1979-01-01

High efficiency GaAs low-high-low IMPATTs were investigated. Theoretical analyses were employed to establish a design window for the material parameters to maximize microwave performance. Single mesa devices yielded typically 2 to 3 W with 16 to 23% efficiency in waveguide oscillator test circuits. IMPATTs with high reliability Pt/TiW/Pt/Au metallizations were subjected to temperature stress, non-rf bias-temperature stress, and rf bias-temperature stress. Assuming that temperature is the driving force behind the dominant failure mechanism, a mean-time-to-failure considerably greater than 500,000 hours is indicated by the stress tests. A 15 GHz, 4W, 56 dB gain microstrip amplifier was realized using GaAs FETs and IMPATTs. Power combining using a 3 db Lange coupler is employed in the power output stage having an intrinsic power-added efficiency of 15.7%. Overall dc-to-rf efficiency of the amplifier is 10.8%. The amplifier has greater than a 250 MHz, 1 db bandwidth; operates over the 0 deg to 50 C (base plate) temperature range with less than 0.5 db change in the power output; weighs 444 grams; and has a volume of 220 cu cm.

Genetic algorithm optimized triply compensated pulses in NMR spectroscopy

NASA Astrophysics Data System (ADS)

Manu, V. S.; Veglia, Gianluigi

2015-11-01

Sensitivity and resolution in NMR experiments are affected by magnetic field inhomogeneities (of both external and RF), errors in pulse calibration, and offset effects due to finite length of RF pulses. To remedy these problems, built-in compensation mechanisms for these experimental imperfections are often necessary. Here, we propose a new family of phase-modulated constant-amplitude broadband pulses with high compensation for RF inhomogeneity and heteronuclear coupling evolution. These pulses were optimized using a genetic algorithm (GA), which consists in a global optimization method inspired by Nature's evolutionary processes. The newly designed π and π / 2 pulses belong to the 'type A' (or general rotors) symmetric composite pulses. These GA-optimized pulses are relatively short compared to other general rotors and can be used for excitation and inversion, as well as refocusing pulses in spin-echo experiments. The performance of the GA-optimized pulses was assessed in Magic Angle Spinning (MAS) solid-state NMR experiments using a crystalline U-13C, 15N NAVL peptide as well as U-13C, 15N microcrystalline ubiquitin. GA optimization of NMR pulse sequences opens a window for improving current experiments and designing new robust pulse sequences.

Numerical design and analysis of parasitic mode oscillations for 95 GHz gyrotron beam tunnel

NASA Astrophysics Data System (ADS)

Kumar, Nitin; Singh, Udaybir; Yadav, Vivek; Kumar, Anil; Sinha, A. K.

2013-05-01

The beam tunnel, equipped with the high lossy ceramics, is designed for 95 GHz gyrotron. The geometry of the beam tunnel is optimized considering the maximum RF absorption (ideally 100%) and the suppression of parasitic oscillations. The excitation of parasitic modes is a concerning problem for high frequency, high power gyrotrons. Considering the problem of parasitic mode excitation in beam tunnel, a detail analysis is performed for the suppression of these kinds of modes. Trajectory code EGUN and CST Microwave Studio are used for the simulations of electron beam trajectory and electromagnetic analysis, respectively.

New klystron technology

NASA Astrophysics Data System (ADS)

Faillon, G.

1985-10-01

It is pointed out that klystrons representing high-power RF sources are mainly used in applications related to radars and scientific instrumentation. High peak power pulsed klystrons are discussed. It is found that a large number of linacs are powered by S-band klystrons (2.856 or 2.9985 GHz) with pulse durations of a few microseconds. Special precautions are being taken to insure that the breakdown voltage will not be reached, and very thin titanium coatings are employed to protect the ceramic against discharges. Attention is given to very large pulse width tubes, CW tubes, and limits of the power-frequency domain.

Classification and Prediction of RF Coupling inside A-320 and A-319 Airplanes using Feed Forward Neural Networks

NASA Technical Reports Server (NTRS)

Jafri, Madiha; Ely, Jay; Vahala, Linda

2006-01-01

Neural Network Modeling is introduced in this paper to classify and predict Interference Path Loss measurements on Airbus 319 and 320 airplanes. Interference patterns inside the aircraft are classified and predicted based on the locations of the doors, windows, aircraft structures and the communication/navigation system-of-concern. Modeled results are compared with measured data and a plan is proposed to enhance the modeling for better prediction of electromagnetic coupling problems inside aircraft.

Improved scatterer property estimates from ultrasound backscatter for small gate lengths using a gate-edge correction factor

NASA Astrophysics Data System (ADS)

Oelze, Michael L.; O'Brien, William D.

2004-11-01

Backscattered rf signals used to construct conventional ultrasound B-mode images contain frequency-dependent information that can be examined through the backscattered power spectrum. The backscattered power spectrum is found by taking the magnitude squared of the Fourier transform of a gated time segment corresponding to a region in the scattering volume. When a time segment is gated, the edges of the gated regions change the frequency content of the backscattered power spectrum due to truncating of the waveform. Tapered windows, like the Hanning window, and longer gate lengths reduce the relative contribution of the gate-edge effects. A new gate-edge correction factor was developed that partially accounted for the edge effects. The gate-edge correction factor gave more accurate estimates of scatterer properties at small gate lengths compared to conventional windowing functions. The gate-edge correction factor gave estimates of scatterer properties within 5% of actual values at very small gate lengths (less than 5 spatial pulse lengths) in both simulations and from measurements on glass-bead phantoms. While the gate-edge correction factor gave higher accuracy of estimates at smaller gate lengths, the precision of estimates was not improved at small gate lengths over conventional windowing functions. .

Impact interaction of shells and structural elements of spacecrafts with the particles of space debris and micrometeoroids

NASA Astrophysics Data System (ADS)

Gerasimov, A. V.; Pashkov, S. V.; Khristenko, Yu. F.

2017-10-01

Space debris formed during the launch and operation of spacecrafts in the circumterrestrial space, and the flows of micrometeoroids from the depths of space pose a real threat to manned and automatic vehicles. Providing the fracture resistance of aluminum, glass and ceramic spacecraft elements is an important practical task. These materials are widely used in spacecraft elements such as bodies, tanks, windows, glass in optical devices, heat shields, etc.

Testing and Modeling Ultra-High Temperature Ceramic (UHTC) Materials for Hypersonic Flight

DTIC Science & Technology

2011-11-01

temperatures exceed 2500 K . as they have here. E. Evidence of Volatilization Emission spectroscopy of electronically excited B , Si, and W atoms...specimens. After roughly 30 seconds around 2660 K , the surface temperature of sample 3.3 decays steadily, and the B , Si, and W atom emissions follow...175-189. 51Roine, A., HSC Chemistry for Windows, Version 5.11. Outokumpu Research Oy, Pori, Finland, (2006). 52Hirsch, K ., Roth, B ., Altmann, I

Nanograin Ceramic Optical Composite Window

DTIC Science & Technology

2005-07-15

parts are sintered in air at 1100 C̊. Table 1: Carbon content of the calcined Alumina- Zirconia powders analyzed by LECO Calcination Temperature Carbon...estimated particle size of the Alumina and Zirconia powders Material name Surface area (m2/g) Estimated particle size (nm) Alumina 315.7 4.7 Zirconia...200 300 400 500 600 700 800 900 1000 2-Theta - Scale 20 30 40 50 60 70 80 Figure 3: XRD patterns of zirconia powder prepared by sonochemical method

Development and demonstration of a water-window soft x-ray microscope using a Z-pinching capillary discharge source

NASA Astrophysics Data System (ADS)

Nawaz, M. F.; Jancarek, Alexandr; Nevrkla, Michal; Duda, Martin Jakub; Pina, Ladislav

2017-05-01

The development and demonstration of a soft X-ray (SXR) microscope, based on a Z-pinching capillary discharge source has been realized. The Z-pinching plasma acts as a source of SXR radiation. A ceramic capacitor bank is pulsed charged up to 80 kV, and discharged through a pre- ionized nitrogen filled ceramic capillary. The discharge current has an amplitude of 25 kA. Working within the water-window spectral region (λ = 2.88 nm), corresponding to the 1s2-1s2p quantum transition of helium-like nitrogen (N5+), the microscope has a potential in exploiting the natural contrast existing between the K-absorption edges of carbon and oxygen as the main constituents of biological materials, and hence imaging them with high spatial resolution. The SXR microscope uses the grazing incidence ellipsoidal condenser mirror for the illumination, and the Fresnel zone plate optics for the imaging of samples onto a BI-CCD camera. The half- pitch spatial resolution of 100 nm [1] was achieved, as demonstrated by the knife-edge test. In order to enhance the photon-flux at the sample plane, a new scheme for focusing the radiation, from multiple capillary sources has been investigated. Details about the source, and the construction of the microscope are presented and discussed.

Design challenges of EO polymer based leaky waveguide deflector for 40 Gs/s all-optical analog-to-digital converters

NASA Astrophysics Data System (ADS)

Hadjloum, Massinissa; El Gibari, Mohammed; Li, Hongwu; Daryoush, Afshin S.

2016-08-01

Design challenges and performance optimization of an all-optical analog-to-digital converter (AOADC) is presented here. The paper addresses both microwave and optical design of a leaky waveguide optical deflector using electro-optic (E-O) polymer. The optical deflector converts magnitude variation of the applied RF voltage into variation of deflection angle out of a leaky waveguide optical beam using the linear E-O effect (Pockels effect) as part of the E-O polymer based optical waveguide. This variation of deflection angle as result of the applied RF signal is then quantized using optical windows followed by an array of high-speed photodetectors. We optimized the leakage coefficient of the leaky waveguide and its physical length to achieve the best trade-off between bandwidth and the deflected optical beam resolution, by improving the phase velocity matching between lightwave and microwave on one hand and using pre-emphasis technique to compensate for the RF signal attenuation on the other hand. In addition, for ease of access from both optical and RF perspective, a via-hole less broad bandwidth transition is designed between coplanar pads and coupled microstrip (CPW-CMS) driving electrodes. With the best reported E-O coefficient of 350 pm/V, the designed E-O deflector should allow an AOADC operating over 44 giga-samples-per-seconds with an estimated effective resolution of 6.5 bits on RF signals with Nyquist bandwidth of 22 GHz. The overall DC power consumption of all components used in this AOADC is of order of 4 W and is dominated by power consumption in the power amplifier to generate a 20 V RF voltage in 50 Ohm system. A higher sampling rate can be achieved at similar bits of resolution by interleaving a number of this elementary AOADC at the expense of a higher power consumption.

Maternal exposure to ambient PM10 during pregnancy increases the risk of congenital heart defects: Evidence from machine learning models.

PubMed

Ren, Zhoupeng; Zhu, Jun; Gao, Yanfang; Yin, Qian; Hu, Maogui; Dai, Li; Deng, Changfei; Yi, Lin; Deng, Kui; Wang, Yanping; Li, Xiaohong; Wang, Jinfeng

2018-07-15

Previous research suggested an association between maternal exposure to ambient air pollutants and risk of congenital heart defects (CHDs), though the effects of particulate matter ≤10μm in aerodynamic diameter (PM 10 ) on CHDs are inconsistent. We used two machine learning models (i.e., random forest (RF) and gradient boosting (GB)) to investigate the non-linear effects of PM 10 exposure during the critical time window, weeks 3-8 in pregnancy, on risk of CHDs. From 2009 through 2012, we carried out a population-based birth cohort study on 39,053 live-born infants in Beijing. RF and GB models were used to calculate odds ratios for CHDs associated with increase in PM 10 exposure, adjusting for maternal and perinatal characteristics. Maternal exposure to PM 10 was identified as the primary risk factor for CHDs in all machine learning models. We observed a clear non-linear effect of maternal exposure to PM 10 on CHDs risk. Compared to 40μgm -3 , the following odds ratios resulted: 1) 92μgm -3 [RF: 1.16 (95% CI: 1.06, 1.28); GB: 1.26 (95% CI: 1.17, 1.35)]; 2) 111μgm -3 [RF: 1.04 (95% CI: 0.96, 1.14); GB: 1.04 (95% CI: 0.99, 1.08)]; 3) 124μgm -3 [RF: 1.01 (95% CI: 0.94, 1.10); GB: 0.98 (95% CI: 0.93, 1.02)]; 4) 190μgm -3 [RF: 1.29 (95% CI: 1.14, 1.44); GB: 1.71 (95% CI: 1.04, 2.17)]. Overall, both machine models showed an association between maternal exposure to ambient PM 10 and CHDs in Beijing, highlighting the need for non-linear methods to investigate dose-response relationships. Copyright © 2018 Elsevier B.V. All rights reserved.

Comparison of direct and alternating current vacuum ultraviolet lamps in atmospheric pressure photoionization.

PubMed

Vaikkinen, Anu; Haapala, Markus; Kersten, Hendrik; Benter, Thorsten; Kostiainen, Risto; Kauppila, Tiina J

2012-02-07

A direct current induced vacuum ultraviolet (dc-VUV) krypton discharge lamp and an alternating current, radio frequency (rf) induced VUV lamp that are essentially similar to lamps in commercial atmospheric pressure photoionization (APPI) ion sources were compared. The emission distributions along the diameter of the lamp exit window were measured, and they showed that the beam of the rf lamp is much wider than that of the dc lamp. Thus, the rf lamp has larger efficient ionization area, and it also emits more photons than the dc lamp. The ionization efficiencies of the lamps were compared using identical spray geometries with both lamps in microchip APPI mass spectrometry (μAPPI-MS) and desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS). A comprehensive view on the ionization was gained by studying six different μAPPI solvent compositions, five DAPPI spray solvents, and completely solvent-free DAPPI. The observed reactant ions for each solvent composition were very similar with both lamps except for toluene, which showed a higher amount of solvent originating oxidation products with the rf lamp than with the dc lamp in μAPPI. Moreover, the same analyte ions were detected with both lamps, and thus, the ionization mechanisms with both lamps are similar. The rf lamp showed a higher ionization efficiency than the dc lamp in all experiments. The difference between the lamp ionization efficiencies was greatest when high ionization energy (IE) solvent compositions (IEs above 10 eV), i.e., hexane, methanol, and methanol/water, (1:1 v:v) were used. The higher ionization efficiency of the rf lamp is likely due to the larger area of high intensity light emission, and the resulting larger efficient ionization area and higher amount of photons emitted. These result in higher solvent reactant ion production, which in turn enables more efficient analyte ion production. © 2012 American Chemical Society

Tailoring the surface chemical bond states of the NbN films by doping Ag: Achieving hard hydrophobic surface

NASA Astrophysics Data System (ADS)

Ren, Ping; Zhang, Kan; Du, Suxuan; Meng, Qingnan; He, Xin; Wang, Shuo; Wen, Mao; Zheng, Weitao

2017-06-01

Robust hydrophobic surfaces based on ceramics capable of withstanding harsh conditions such as abrasion, erosion and high temperature, are required in a broad range of applications. The metal cations with coordinative saturation or low electronegativity are commonly chosen to achieve the intrinsically hydrophobic ceramic by reducing Lewis acidity, and thus the ceramic systems are limited. In this work, we present a different picture that robust hydrophobic surface with high hardness (≥20 GPa) can be fabricated through doping Ag atoms into intrinsically hydrophilic ceramic film NbN by reactive co-sputtering. The transition of wettability from hydrophilic to hydrophobic of Nb-Ag-N films induced by Ag doping results from the appearance of Ag2O groups on the films surfaces through self-oxidation, because Ag cations (Ag+) in Ag2O are the filled-shell (4d105S0) electronic structure with coordinative saturation that have no tendency to interact with water. The results show that surface Ag2O benefited for hydrophobicity comes from the solute Ag atoms rather than precipitate metal Ag, in which the more Ag atoms incorporated into Nb-sublattice are able to further improve the hydrophobicity, whereas the precipitation of Ag nanoclusters would worsen it. The present work opens a window for fabricating robust hydrophobic surface through tailoring surface chemical bond states by doping Ag into transition metal nitrides.

A new technique for cranioplasty with L-shaped titanium plates and combination ceramic implants composed of hydroxyapatite and tricalcium phosphate (Ceratite).

PubMed

Miyake, H; Ohta, T; Tanaka, H

2000-02-01

The use of hydroxyapatite-based ceramics for cranioplasties has recently increased in Japan, because of the good cosmetic outcomes, biocompatibility, strength, osteoconductive properties, and lack of risk of disease transmission associated with these materials. However, miniplate fixation has not been possible for ceramic implants. We describe a new technique for miniplate fixation of ceramic implants. Combination ceramic implants composed of hydroxyapatite and tricalcium phosphate (Ceratite; NGK Spark Plug Co., Aichi, Japan) were used for cranioplasties. A slot and a pair of holes were cut in each Ceratite implant, for use as a fixation unit. We have also developed a new L-shaped titanium plate (HOMS Engineering Inc., Nagano, Japan) that fits into the fixation unit. We first insert an L-shaped titanium plate through the slot from the back surface of the Ceratite implant. We then bend the plate outward at the front surface of the Ceratite implant and fix it to the cranium of the patient with titanium screws. The Ceratite implant is usually firmly fixed to the cranium of the patient with three L-shaped titanium plates. Using L-shaped titanium plates and Ceratite implants, we successfully performed cranioplasties for seven patients with cranial defects resulting from external decompression craniotomies. The Ceratite implant exactly fit the bone window for each patient. Surgical maneuvers were simple and easy for all patients, permitting shorter operating times. All Ceratite implants were firmly fixed, and no postoperative infections have occurred. Our new technique for cranioplasty is simple and allows rigid fixation of Ceratite implants.

Flexible Dielectric Nanocomposites with Ultrawide Zero-Temperature Coefficient Windows for Electrical Energy Storage and Conversion under Extreme Conditions.

PubMed

Shehzad, Khurram; Xu, Yang; Gao, Chao; Li, Hanying; Dang, Zhi-Min; Hasan, Tawfique; Luo, Jack; Duan, Xiangfeng

2017-03-01

Polymer dielectrics offer key advantages over their ceramic counterparts such as flexibility, scalability, low cost, and high breakdown voltages. However, a major drawback that limits more widespread application of polymer dielectrics is their temperature-dependent dielectric properties. Achieving dielectric constants with low/zero-temperature coefficient (L/0TC) over a broad temperature range is essential for applications in diverse technologies. Here, we report a hybrid filler strategy to produce polymer composites with an ultrawide L/0TC window of dielectric constant, as well as a significantly enhanced dielectric value, maximum energy storage density, thermal conductivity, and stability. By creating a series of percolative polymer composites, we demonstrated hybrid carbon filler based composites can exhibit a zero-temperature coefficient window of 200 °C (from -50 to 150 °C), the widest 0TC window for all polymer composite dielectrics reported to date. We further show the electric and dielectric temperature coefficient of the composites is highly stable against stretching and bending, even under AC electric field with frequency up to 1 MHz. We envision that our method will push the functional limits of polymer dielectrics for flexible electronics in extreme conditions such as in hybrid vehicles, aerospace, power electronics, and oil/gas exploration.

A machine learning calibration model using random forests to improve sensor performance for lower-cost air quality monitoring

NASA Astrophysics Data System (ADS)

Zimmerman, Naomi; Presto, Albert A.; Kumar, Sriniwasa P. N.; Gu, Jason; Hauryliuk, Aliaksei; Robinson, Ellis S.; Robinson, Allen L.; Subramanian, R.

2018-01-01

Low-cost sensing strategies hold the promise of denser air quality monitoring networks, which could significantly improve our understanding of personal air pollution exposure. Additionally, low-cost air quality sensors could be deployed to areas where limited monitoring exists. However, low-cost sensors are frequently sensitive to environmental conditions and pollutant cross-sensitivities, which have historically been poorly addressed by laboratory calibrations, limiting their utility for monitoring. In this study, we investigated different calibration models for the Real-time Affordable Multi-Pollutant (RAMP) sensor package, which measures CO, NO2, O3, and CO2. We explored three methods: (1) laboratory univariate linear regression, (2) empirical multiple linear regression, and (3) machine-learning-based calibration models using random forests (RF). Calibration models were developed for 16-19 RAMP monitors (varied by pollutant) using training and testing windows spanning August 2016 through February 2017 in Pittsburgh, PA, US. The random forest models matched (CO) or significantly outperformed (NO2, CO2, O3) the other calibration models, and their accuracy and precision were robust over time for testing windows of up to 16 weeks. Following calibration, average mean absolute error on the testing data set from the random forest models was 38 ppb for CO (14 % relative error), 10 ppm for CO2 (2 % relative error), 3.5 ppb for NO2 (29 % relative error), and 3.4 ppb for O3 (15 % relative error), and Pearson r versus the reference monitors exceeded 0.8 for most units. Model performance is explored in detail, including a quantification of model variable importance, accuracy across different concentration ranges, and performance in a range of monitoring contexts including the National Ambient Air Quality Standards (NAAQS) and the US EPA Air Sensors Guidebook recommendations of minimum data quality for personal exposure measurement. A key strength of the RF approach is that it accounts for pollutant cross-sensitivities. This highlights the importance of developing multipollutant sensor packages (as opposed to single-pollutant monitors); we determined this is especially critical for NO2 and CO2. The evaluation reveals that only the RF-calibrated sensors meet the US EPA Air Sensors Guidebook recommendations of minimum data quality for personal exposure measurement. We also demonstrate that the RF-model-calibrated sensors could detect differences in NO2 concentrations between a near-road site and a suburban site less than 1.5 km away. From this study, we conclude that combining RF models with carefully controlled state-of-the-art multipollutant sensor packages as in the RAMP monitors appears to be a very promising approach to address the poor performance that has plagued low-cost air quality sensors.

An improved soft-chemistry approach to the preparation of spinel powders

NASA Astrophysics Data System (ADS)

Cook, Ronald

2007-04-01

Spinel powders for the production of transparent polycrystalline ceramic windows have been produced using a number of traditional ceramic and sol-gel methods. We have demonstrated that magnesium aluminate spinel powders produced from the reaction of organo-magnesium compounds with surface modified boehmite precursors can be used to produce high quality transparent spinel parts. In previous work, the spinel powders were prepared by the reaction of surface-modified boehmite nanoparticles with magnesium acetylacetonate. While the magnesium acetylacetonate can produce small quantities of high quality spinel powders, it use for large scale production of spinel powders is problematic. Through a thermodynamic analysis we have identified a new high-purity, low-cost, low-toxicity organomagnesium compound that reacts the with surface modified boehmite nanoparticles to produce a spinel precursor. The magnesium doped precursor readily transforms into pure phase spinel at temperature between 900°C and 1200°C.

Characterization of a Y-TZP Zirconia material for gas gun experiments

NASA Astrophysics Data System (ADS)

Goff, Michael; Millett, Jeremy; Whiteman, Glenn; Collinson, Mark; Ferguson, James

2017-06-01

A number of shots were carried out on the AWE single stage gas gun with Het-V diagnostics to determine the shock Hugoniot of a commercial Y-TZP Zirconia ceramic material (ρ 6.05 g/cc). Zirconia ceramic has a higher density and acoustic impedance than alumina, this allows for higher shock pressures to be achieved in impact velocity limited scenarios where conductive materials are not suitable. For example, when using electromagnetic particle velocity gauge diagnostics. The grade examined here was highly reflective to 1550 nm wavelengths, which negated the need for window materials when taking free surface velocity measurements. The shock Hugoniot was determined to be linear up to 13.4 GPa with the form Us = 5.82 + 2.20Up and the HEL was in the range of 7-9 GPa. Additionally data from lateral gauge shots examining the failure behavior of the material are reported on. ©British Crown Owned Copyright 2017/AWE

Ultra-broadband amplification properties of Ni2+-doped glass-ceramics amplifiers.

PubMed

Jiang, Chun

2009-04-13

The energy level, transition configuration and mathematical model of Ni(2+)-doped glass-ceramics amplifiers are presented for the first time, to the best of one's knowledge. A quasi-three-level system is employed to model the gain and noise characteristics of the doped system, and the rate and power propagation equations of the mathematical model are solved to analyze the effect of the active ion concentration, fiber length, pump power as well as thermal-quenching on the gain spectra. It is shown that our model is in agreement with experimental result, and when excited at longer wavelength, the center of gain spectra of the amplifier red shifts, the ultra-broad band room-temperature gain spectra can cover 1.25-1.65 microm range for amplification of signal in the low-loss windows of the all-wave fiber without absorption peak caused by OH group.

Core-shell structured ceramic nonwoven separators by atomic layer deposition for safe lithium-ion batteries

NASA Astrophysics Data System (ADS)

Shen, Xiu; Li, Chao; Shi, Chuan; Yang, Chaochao; Deng, Lei; Zhang, Wei; Peng, Longqing; Dai, Jianhui; Wu, Dezhi; Zhang, Peng; Zhao, Jinbao

2018-05-01

Safety is one of the most factors for lithium-ion batteries (LIBs). In this work, a novel kind of ceramic separator with high safety insurance is proposed. We fabricated the core-shell nanofiber separators for LIBs by atomic layer deposition (ALD) of 30 nm Al2O3 on the electrospinning nonwoven fiber of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). The separators show a pretty high heat resistance up to 200 °C without any shrinkage, an excellent fire-resistant property and a wide electrochemical window. Besides, with higher uptake and ionic conductivity, cells assembled with the novel separator shows better electrochemical performance. The ALD produced separators exhibit great potential in elaborate products like 3C communications and in energy field with harsh requirements for safety such as electric vehicles. The application of ALD on polymer fiber membranes brings a new strategy and opportunity for improving the safety of the advanced LIBs.

Complex permittivity measurements during high temperature recycling of space shuttle antenna window and dielectric heat shield materials

NASA Technical Reports Server (NTRS)

Bassett, H. L.; Bomar, S. H., Jr.

1973-01-01

The research performed and the data obtained on candidate space shuttle antenna window and heat shield materials are presented. The measurement technique employs a free-space focused beam microwave bridge for obtaining RF transmission data, and a device which rotates a sample holder which is heated on one side by natural gas-air flames. The surface temperature of each sample is monitored by IR pyrometry; embedded and rear surface thermocouples are also used in obtaining temperature data. The surface of the sample undergoing test is subjected to approximately the same temperature/time profile that occurs at a proposed antenna position on the space shuttle as it re-enters. The samples are cycled through ten of these temperature profiles to determine the recycling effects. Very little change was noted in the materials due to the recycling.

Influence of Post-Heat Treatment of ZnO:Al Transparent Electrode for Copper Indium Gallium Selenide Thin Film Solar Cell.

PubMed

Eom, Taewoo; Park, Jeong Eun; Park, Sang Yong; Park, Jeong Hoon; Bweupe, Jackson; Lim, Donggun

2018-09-01

Copper indium gallium selenide (CIGS) thin film solar cells have been regarded as a candidate for energy conversion devices owing to their high absorption coefficient, high temperature stability, and low cost. ZnO:Al thin film is commonly used in CIGS solar cells as a window layer. In this study, ZnO:Al films were deposited on glass under various post-heat temperature using RF sputtering to observe the characteristics of ZnO:Al films such as Hall mobility, carrier concentration, and resistivity; subsequently, the ZnO:Al films were applied to a CIGS solar cell as a window. CIGS solar cells fabricated with various ZnO:Al films were analyzed in order to investigate their influence. The test results showed that the improvement of ZnO:Al characteristics affects Jsc and Voc in the solar cell through reduced recombination and increase of optical property.

Glass and Glass-Ceramic Materials from Simulated Composition of Lunar and Martian Soils: Selected Properties and Potential Applications

NASA Technical Reports Server (NTRS)

Ray, C. S.; Sen, S.; Reis, S. T.; Kim, C. W.

2005-01-01

In-situ resource processing and utilization on planetary bodies is an important and integral part of NASA's space exploration program. Within this scope and context, our general effort is primarily aimed at developing glass and glass-ceramic type materials using lunar and martian soils, and exploring various applications of these materials for planetary surface operations. Our preliminary work to date have demonstrated that glasses can be successfully prepared from melts of the simulated composition of both lunar and martian soils, and the melts have a viscosity-temperature window appropriate for drawing continuous glass fibers. The glasses are shown to have the potential for immobilizing certain types of nuclear wastes without deteriorating their chemical durability and thermal stability. This has a direct impact on successfully and economically disposing nuclear waste generated from a nuclear power plant on a planetary surface. In addition, these materials display characteristics that can be manipulated using appropriate processing protocols to develop glassy or glass-ceramic magnets. Also discussed in this presentation are other potential applications along with a few selected thermal, chemical, and structural properties as evaluated up to this time for these materials.

Review of Leading Approaches for Mitigating Hypersonic Vehicle Communications Blackout and a Method of Ceramic Particulate Injection Via Cathode Spot Arcs for Blackout Mitigation

NASA Technical Reports Server (NTRS)

Gillman, Eric D.; Foster, John E.; Blankson, Isaiah M.

2010-01-01

Vehicles flying at hypersonic velocities within the atmosphere become enveloped in a "plasma sheath" that prevents radio communication, telemetry, and most importantly, GPS signal reception for navigation. This radio "blackout" period has been a problem since the dawn of the manned space program and was an especially significant hindrance during the days of the Apollo missions. An appropriate mitigation method must allow for spacecraft to ground control and ground control to spacecraft communications through the reentry plasma sheath. Many mitigation techniques have been proposed, including but not limited to, aerodynamic shaping, magnetic windows, and liquid injection. The research performed on these mitigation techniques over the years will be reviewed and summarized, along with the advantages and obstacles that each technique will need to overcome to be practically implemented. A unique approach for mitigating the blackout communications problem is presented herein along with research results associated with this method. The novel method involves the injection of ceramic metal-oxide particulate into a simulated reentry plasma to quench the reentry plasma. Injection of the solid ceramic particulates is achieved by entrainment within induced, energetic cathode spot flows.

Interconnected porous hydroxyapatite ceramics for bone tissue engineering

PubMed Central

Yoshikawa, Hideki; Tamai, Noriyuki; Murase, Tsuyoshi; Myoui, Akira

2008-01-01

Several porous calcium hydroxyapatite (HA) ceramics have been used clinically as bone substitutes, but most of them possessed few interpore connections, resulting in pathological fracture probably due to poor bone formation within the substitute. We recently developed a fully interconnected porous HA ceramic (IP-CHA) by adopting the ‘foam-gel’ technique. The IP-CHA had a three-dimensional structure with spherical pores of uniform size (average 150 μm, porosity 75%), which were interconnected by window-like holes (average diameter 40 μm), and also demonstrated adequate compression strength (10–12 MPa). In animal experiments, the IP-CHA showed superior osteoconduction, with the majority of pores filled with newly formed bone. The interconnected porous structure facilitates bone tissue engineering by allowing the introduction of mesenchymal cells, osteotropic agents such as bone morphogenetic protein or vasculature into the pores. Clinically, we have applied the IP-CHA to treat various bony defects in orthopaedic surgery, and radiographic examinations demonstrated that grafted IP-CHA gained radiopacity more quickly than the synthetic HA in clinical use previously. We review the accumulated data on bone tissue engineering using the novel scaffold and on clinical application in the orthopaedic field. PMID:19106069

Development and coupling analysis of active skin antenna

NASA Astrophysics Data System (ADS)

Zhou, Jinzhu; Huang, Jin; He, Qingqang; Tang, Baofu; Song, Liwei

2017-02-01

An active skin antenna is a multifunctional composite structure that can provide load-bearing structure and steerable beam pointing functions, and is usually installed in the structural surface of aircraft, warships, and armored vehicles. This paper presents an innovative design of the active skin antenna, which consists of a package layer, control and signal processing layer, and RF (radio frequency) layer. The RF layer is fabricated by low temperature co-fired ceramics, with 64 microstrip antenna elements, tile transmitting and receiving modules, microchannel heat sinks, and feeding networks integrated into a functional block 2.8 mm thick. In this paper, a full-sized prototype of an active skin antenna was designed, fabricated, and tested. Moreover, a coupling analysis method was presented to evaluate the mechanical and electromagnetic performance of the active skin antenna subjected to aerodynamic loads. A deformed experimental system was built to validate the effectiveness of the coupling analysis method, which was also implemented to evaluate the performance of the active skin antenna when subjected to aerodynamic pressure. The fabricated specimen demonstrated structural configuration feasibility, and superior environmental load resistance.

Superconductivity in BiPbCaSrCuO thin films

NASA Astrophysics Data System (ADS)

Fu, S. M.; Yang, H. C.; Chen, F. C.; Horng, H. E.; Jao, J. C.

1989-12-01

Thin films of BiPbCaSrCuO sample were prepared by RF sputtering from sintered ceramic targets. Single crystal of MgO(100) was selected as substrate. The sputtering was held at room temperature. Different annealing conditions were carried out to obtain optimum conditions. High temperature resistivity was measured in air to study the thermodynamic reaction of the sintered films. An resistivity anomaly was found in the first heating cycle which suggests a thermodynamic reaction. A temperature dependence of I c was measured to study the coupling of grains in the granular films in different temperature ranges and the results will be discussed.

RESCUE - Reduction of MRI SNR Degradation by Using an MR-Synchronous Low-Interference PET Acquisition Technique

NASA Astrophysics Data System (ADS)

Gebhardt, Pierre; Wehner, Jakob; Weissler, Bjoern; Frach, Thomas; Marsden, Paul K.; Schulz, Volkmar

2015-06-01

Devices aiming at combined Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI) to enable simultaneous PET/MR image acquisition have to fulfill demanding requirements to avoid mutual magneticas well as electromagnetic-field-related interferences which lead to image quality degradation. Particularly Radio-Frequency (RF)-field-related interferences between PET and MRI may lead to MRI SNR reduction, thereby deteriorating MR image quality. RF shielding of PET electronics is therefore commonly applied to reduce RF emission and lower the potential coupling into MRI RF coil(s). However, shields introduce eddy-current-induced MRI field distortions and should thus be minimized or ideally omitted. Although the MRI noise floor increase caused by a PET system might be acceptable for many MRI applications, some MRI protocols, such as fast or high-resolution MRI scans, typically suffer from low SNR and might need more attention regarding RF silence to preserve the intrinsic MRI SNR. For such cases, we propose RESCUE, an MRI-synchronously-gated PET data acquisition technique: By interrupting the PET acquisition during MR signal receive phases, PET-related RF emission may be minimized, leading to MRI SNR preservation. Our PET insert Hyperion IID using Philips Digital Photon Counting (DPC) sensors serves as the platform to demonstrate RESCUE. To make the DPC sensor suitable for RESCUE to be applied for many MRI sequences with acquisition time windows in the range of a few milliseconds, we present in this paper a new technique which enables rapid DPC sensor operation interruption by dramatically lowering the overhead time to interrupt and restart the sensor operation. Procedures to enter and leave gated PET data acquisition may imply sensitivity losses which add to the ones occurring during MRI RF acquisition. For the case of our PET insert, the new DPC quick-interruption technique yields a PET sensitivity loss reduction by a factor of 78 when compared to the loss introduced with the standard start/stop procedure. For instance, PET sensitivity losses related to overhead time are 2.9% in addition to the loss related to PET gating being equal to the MRI RF acquisition duty cycle (14.7%) for an exemplary T1-weighted 3D-FFE MRI sequence. MRI SNR measurement results obtained with one Singles Detection Module (SDM) using no RF shield demonstrate a noise floor reduction by a factor of 2.1, getting close to the noise floor level of the SNR reference scan (SDM off-powered) when RESCUE was active.

Subcarrier multiplexing tolerant dispersion transmission system employing optical broadband sources.

PubMed

Grassi, Fulvio; Mora, José; Ortega, Beatriz; Capmany, José

2009-03-16

This paper presents a novel SCM optical transmission system for next-generation WDM-PONs combining broadband optical sources and a Mach-Zehnder interferometric structure. The approach leeds to transport RF signals up to 50 GHz being compatible with RoF systems since a second configuration has been proposed in order to overcome dispersion carrier suppression effect using DSB modulation. The theoretical analysis validates the potentiality of the system also considering the effects of the dispersion slope over the transmission window. (c) 2009 Optical Society of America

Template-assisted formation of microsized nanocrystalline CeO2 tubes and their catalytic performance in the carboxylation of methanol

PubMed Central

Naumann, Meike; Schäfer, Christian; Brandner, Armin; Hofmann, Heiko J; Claus, Peter

2011-01-01

Summary Polymethylmethacrylate (PMMA)/ceria composite fibres were synthesized by using a sequential combination of polymer electrospinning, spray-coating with a sol, and a final calcination step to yield microstructured ceria tubes, which are composed of nanocrystalline ceria particles. The PMMA template is removed from the organic/inorganic hybrid material by radio frequency (rf) plasma etching followed by calcination of the ceramic green-body fibres. Microsized ceria (CeO2) tubes, with a diameter of ca. 0.75 µm, composed of nanocrystalline agglomerated ceria particles were thus obtained. The 1-D ceramic ceria material was characterized by X-ray diffraction, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV–vis and photoluminescence spectroscopy (PL), as well as thermogravimetric analysis (TGA). Its catalytic performance was studied in the direct carboxylation of methanol with carbon dioxide leading to dimethyl carbonate [(CH3O)2CO, DMC], which is widely employed as a phosgene and dimethyl sulfate substitute, and as well as a fuel additive. PMID:22259761

Study on electrostatic and electromagnetic probes operated in ceramic and metallic depositing plasmas

NASA Astrophysics Data System (ADS)

Styrnoll, T.; Bienholz, S.; Lapke, M.; Awakowicz, P.

2014-04-01

This paper discusses plasma probe diagnostics, namely the multipole resonance probe (MRP) and Langmuir probe (LP), operated in depositing plasmas. The aim of this work is to show that the combination of both probes provides stable and robust measurements and clear determination of plasma parameters for metallic and ceramic coating processes. The probes use different approaches to determine plasma parameters, e.g. electron density ne and electron temperature Te. The LP is a well-established plasma diagnostic, and its applicability in technological plasmas is well documented. The LP is a dc probe that performs a voltage sweep and analyses the measured current, which makes it insensitive against conductive metallic coating. However, once the LP is dielectrically coated with a ceramic film, its functionality is constricted. In contrast, the MRP was recently presented as a monitoring tool, which is insensitive to coating with dielectric ceramics. It is a new plasma diagnostic based on the concept of active plasma resonance spectroscopy, which uses the universal characteristic of all plasmas to resonate on or near the electron plasma frequency. The MRP emits a frequency sweep and the absorption of the signal, the |S11| parameter, is analysed. Since the MRP concept is based on electromagnetic waves, which are able to transmit dielectrics, it is insensitive to dielectric coatings. But once the MRP is metallized with a thin conductive film, no undisturbed RF-signal can be emitted into the plasma, which leads to falsified plasma parameter. In order to compare both systems, during metallic or dielectric coating, the probes are operated in a magnetron CCP, which is equipped with a titanium target. We present measurements in metallic and dielectric coating processes with both probes and elaborate advantages and problems of each probe operated in each coating environment.

Towards Self-Clocked Gated OCDMA Receiver

NASA Astrophysics Data System (ADS)

Idris, S.; Osadola, T.; Glesk, I.

2013-02-01

A novel incoherent OCDMA receiver with incorporated all-optical clock recovery for self-synchronization of a time gate for the multi access interferences (MAI) suppression and minimizing the effect of data time jitter in incoherent OCDMA system was successfully developed and demonstrated. The solution was implemented and tested in a multiuser environment in an out of the laboratory OCDMA testbed with two-dimensional wavelength-hopping time-spreading coding scheme and OC-48 (2.5 Gbp/s) data rate. The self-clocked all-optical time gate uses SOA-based fibre ring laser optical clock, recovered all-optically from the received OCDMA traffic to control its switching window for cleaning the autocorrelation peak from the surrounding MAI. A wider eye opening was achieved when the all-optically recovered clock from received data was used for synchronization if compared to a static approach with the RF clock being generated by a RF synthesizer. Clean eye diagram was also achieved when recovered clock is used to drive time gating.

Environmental urban lead exposure and blood lead levels in children of Mexico City.

PubMed Central

Romieu, I; Carreon, T; Lopez, L; Palazuelos, E; Rios, C; Manuel, Y; Hernandez-Avila, M

1995-01-01

Lead contamination is now a leading public health problem in Mexico. However, there are few data on the lead content of various environmental sources, and little is known about the contribution of these sources to the total lead exposure in the population of children residing in Mexico City. We conducted a cross-sectional study in a random sample of 200 children younger than 5 years of age who lived in one of two areas of Mexico City. Environmental samples of floor, window, and street dust, paint, soil, water, and glazed ceramics were obtained from the participants' households, as well as blood samples and dirt from the hands of the children. Blood lead levels ranged from 1 to 31 micrograms/dl with a mean of 9.9 micrograms/dl (SD 5.8 micrograms/dl). Forty-four percent of the children 18 months of age or older had blood lead levels exceeding 10 micrograms/dl. The lead content of environmental samples was low, except in glazed ceramic. The major predictors of blood lead levels were the lead content of the glazed ceramics used to prepare children's food, exposure to airborne lead due to vehicular emission, and the lead content of the dirt from the children's hands. We conclude that the major sources of lead exposure in Mexico City could be controlled by adequate public health programs to reinforce the use of unleaded gasoline and to encourage production and use of unleaded cookware instead of lead-glazed ceramics. PMID:8605853

Cassettes for solid-oxide fuel cell stacks and methods of making the same

DOEpatents

Weil, K. Scott; Meinhardt, Kerry D; Sprenkle, Vincent L

2012-10-23

Solid-oxide fuel cell (SOFC) stack assembly designs are consistently investigated to develop an assembly that provides optimal performance, and durability, within desired cost parameters. A new design includes a repeat unit having a SOFC cassette and being characterized by a three-component construct. The three components include an oxidation-resistant, metal window frame hermetically joined to an electrolyte layer of a multi-layer, anode-supported ceramic cell and a pre-cassette including a separator plate having a plurality of vias that provide electrical contact between an anode-side collector within the pre-cassette and a cathode-side current collector of an adjacent cell. The third component is a cathode-side seal, which includes a standoff that supports a cathode channel spacing between each of the cassettes in a stack. Cassettes are formed by joining the pre-cassette and the window frame.

Modeling and experimental characterization of Blackglas(TM) polymer pyrolysis to ceramic and thermodynamic characterization of Blackglas(TM) ceramic

NASA Astrophysics Data System (ADS)

Wang, Feng

2000-10-01

The transformation of Blackglas(TM) polymer to ceramic is characterized by TGA-RGA/MS, Si29 and C13 NMR. Si29 NMR reveals a dependence between the postcure temperature and the microstructure of the resin. The postcure temperature that appears to give optimal mechanical and oxidative properties of Blackglas(TM) ceramic is around 150°C. The pyrolysis processing models, which are the Lumped Parameters Model (LPM), the Mechanistic Kinetic Model (MKM) and the Redistribution Reaction Model (RRM), are developed to provide an effective window of processing parameters rather than a costly, time-consuming trial and error approach. The Lumped Parameters Model (LPM) is developed to study the effects of various parameters such as temperature, curing conditions and heating rates on mass loss during the pyrolysis of resin and green composites. It can be used for the model-predictive control of the pyrolysis process; The Mechanistic Kinetic Model (MKM) is developed on the basis of known chemistry and architecture of the polysiloxane for the transformation of Blackglas(TM) polymer to ceramic and the evolution of gases. The effects of various heating protocols on the outgassing kinetics have been studied to develop an optimum protocol for a rapid pyrolysis process which gives a composite with desirable mechanical properties; The Redistribution Reaction Model (RRM) is proposed to describe how the microcompositions of silicon oxycarbide change with respect to temperature, and to the ratio O/Si in the polymer precursor. A Thermodynamic Additivity Model (TAM) is developed to estimate the heat capacity, standard heat of formation and entropy of Blackglas(TM) ceramic by means of the Neumann Kopp rule and the available thermodynamic data of the Si-C and Si-O systems. Thermal stability of this ceramic is investigated by constructing predominance diagrams, and it is shown that the internal degradation reactions, which account for a significant loss of strength, will proceed further in the Blackglas(TM) matrix than in the Nicalon fibers. This probably will induce failure in the matrix at lower temperatures than in the fibers. The predominance diagrams also explain the high temperature oxidation, reduction and volatilization experiments on silicon and silicon carbide in high vacuum.

Ion Energy and Ion Flux Distributions of CF4/Ar/O2 Inductively Coupled Plasmas in a GEC Cell

NASA Technical Reports Server (NTRS)

Rao, M. V. V. S.; Cruden, Brett; Sharma, Surendra; Meyyappan, Meyya

2001-01-01

Knowledge of ion kinetics in plasma processing gas mixtures, such as CF4:Ar:O2, is important for understanding plasma assisted etching and deposition of materials. Ion energies and ion fluxes were measured in this mixture for 80:10:10, 60:20:20, and 40:30:30 mixture ratios in the pressure range of 10-50 mTorr, and at 200 and 300 W of RF power. Ions from plasma, sampled through a 10 micron orifice in the center of the lower plane electrode, were energy and mass analyzed by a combination of electrostatic energy and quadrupole mass filters. CFx(+) (x = 1 - 3), F2(+), F(+), C(+) from CF4, Ar(+) from Ar, and O2(+) and O(+) from O2, and by-product ions SiFx(+)(x = 1 - 3) from etching of quartz coupling window, COFx(+)(x = 1 - 3), CO(+), CO2(+), and OF(+) were detected. In all conditions ion flux decreases with increase of pressure but increase with increase of RF power. Ar(+) signal decreases with increase of pressure while CF3(+), which is the dominant ion at all conditions, increases with increase in pressure. The loss mechanism for Ar(+) and increase of CF3(+) is due to large cross section for Ar(+) + CF4 yields Ar + CF3(+) + F. Ion energies, which range from 15-25 eV depending on plasma operating conditions, are nearly Gaussian. By-product ion signals are higher at lower pressures indicating stronger plasma interaction with quartz window.

New method for characterizing electron mediators in microbial systems using a thin-layer twin-working electrode cell.

PubMed

Hassan, Md Mahamudul; Cheng, Ka Yu; Ho, Goen; Cord-Ruwisch, Ralf

2017-01-15

Microbial biofilms are significant ecosystems where the existence of redox gradients drive electron transfer often via soluble electron mediators. This study describes the use of two interfacing working electrodes (WEs) to simulate redox gradients within close proximity (250µm) for the detection and quantification of electron mediators. By using a common counter and reference electrode, the potentials of the two WEs were independently controlled to maintain a suitable "voltage window", which enabled simultaneous oxidation and reduction of electron mediators as evidenced by the concurrent anodic and cathodic currents, respectively. To validate the method, the electrochemical properties of different mediators (hexacyanoferrate, HCF, riboflavin, RF) were characterized by stepwise shifting the "voltage window" (ranging between 25 and 200mV) within a range of potentials after steady equilibrium current of both WEs was established. The resulting differences in electrical currents between the two WEs were recorded across a defined potential spectrum (between -1V and +0.5V vs. Ag/AgCl). Results indicated that the technique enabled identification (by the distinct peak locations at the potential scale) and quantification (by the peak of current) of the mediators for individual species as well as in an aqueous mixture. It enabled a precise determination of mid-potentials of the externally added mediators (HCF, RF) and mediators produced by pyocyanin-producing Pseudomonas aeruginosa (WACC 91) culture. The twin working electrode described is particularly suitable for studying mediator-dependent microbial electron transfer processes or simulating redox gradients as they exist in microbial biofilms. Copyright © 2016 Elsevier B.V. All rights reserved.

Flash water-window x-ray generator with a ferrite capillary

NASA Astrophysics Data System (ADS)

Sato, Eiichi; Sagae, Michiaki; Ichimaru, Toshio; Takayama, Kazuyoshi; Sakamaki, Kimio; Tamakawa, Yoshiharu

1997-12-01

The fundamental study on a flash water-window x-ray generator is described. This generator is composed of a high-voltage power supply, a polarity-inversion high-voltage pulser, a krytron pulser as a trigger device, an oil-diffusion pump, and a vacuum chamber with a capillary. A combined ceramic condenser of about 5 nF in the pulser is charged up to 70 kV by the power supply, and the electric charges in the condenser are discharged to the capillary in the tube after closing a gap switch by the krytron pulser. In the present work, the chamber is evacuated by the pump with a pressure of about 1 by 10-3 Pa, and the titanium anode and cathode electrodes are employed to produce L-series characteristic x rays in the water-window range. The diameter and the length of the ferrite capillary are 2.0 and 30 mm, respectively. Both the cathode voltage and the discharge current displayed damped oscillations. The peak values of the voltage and current increased when the charging voltage was increased, and their maximum values were minus 24 kV and 2.8 kA, respectively. The pulse durations of the water-window x-rays were nearly equivalent to those of the damped oscillations of the voltage and current, and their values were less than 10 microseconds.

High Field In Vivo 13C Magnetic Resonance Spectroscopy of Brain by Random Radiofrequency Heteronuclear Decoupling and Data Sampling

NASA Astrophysics Data System (ADS)

Li, Ningzhi; Li, Shizhe; Shen, Jun

2017-06-01

In vivo 13C magnetic resonance spectroscopy (MRS) is a unique and effective tool for studying dynamic human brain metabolism and the cycling of neurotransmitters. One of the major technical challenges for in vivo 13C-MRS is the high radio frequency (RF) power necessary for heteronuclear decoupling. In the common practice of in vivo 13C-MRS, alkanyl carbons are detected in the spectra range of 10-65ppm. The amplitude of decoupling pulses has to be significantly greater than the large one-bond 1H-13C scalar coupling (1JCH=125-145 Hz). Two main proton decoupling methods have been developed: broadband stochastic decoupling and coherent composite or adiabatic pulse decoupling (e.g., WALTZ); the latter is widely used because of its efficiency and superb performance under inhomogeneous B1 field. Because the RF power required for proton decoupling increases quadratically with field strength, in vivo 13C-MRS using coherent decoupling is often limited to low magnetic fields (<= 4 Tesla (T)) to keep the local and averaged specific absorption rate (SAR) under the safety guidelines established by the International Electrotechnical Commission (IEC) and the US Food and Drug Administration (FDA). Alternately, carboxylic/amide carbons are coupled to protons via weak long-range 1H-13C scalar couplings, which can be decoupled using low RF power broadband stochastic decoupling. Recently, the carboxylic/amide 13C-MRS technique using low power random RF heteronuclear decoupling was safely applied to human brain studies at 7T. Here, we review the two major decoupling methods and the carboxylic/amide 13C-MRS with low power decoupling strategy. Further decreases in RF power deposition by frequency-domain windowing and time-domain random under-sampling are also discussed. Low RF power decoupling opens the possibility of performing in vivo 13C experiments of human brain at very high magnetic fields (such as 11.7T), where signal-to-noise ratio as well as spatial and temporal spectral resolution are more favorable than lower fields.

STS-114: Discovery Day 6 Post MMT Meeting

NASA Technical Reports Server (NTRS)

2005-01-01

Wane Hill, Deputy Manager of the Space Shuttle Program, and Steve Poulos, Manager, Orbiter Project Office discussed damage assessments caused during ascent. Steve further detailed the damage analysis and assessments with chart presentation of composite tile damage and gap filler sites evaluation, protruding ceramic shim, left wing tile damage, comparisons of ground test results versus FD5 focused inspection, and the window 1 blanket. Gap fillers, the STS-73, thermal protection, temperature range, heating and heating range, aerodynamics, aerothermodynamics, risk, foam damage, tile adhesions, and extravehicular activities are topics covered with the News media.

Evaluation of the Effect of Radiofrequency Radiation Emitted From Wi-Fi Router and Mobile Phone Simulator on the Antibacterial Susceptibility of Pathogenic Bacteria Listeria monocytogenes and Escherichia coli.

PubMed

Taheri, M; Mortazavi, S M J; Moradi, M; Mansouri, S; Hatam, G R; Nouri, F

2017-01-01

Mobile phones and Wi-Fi radiofrequency radiation are among the main sources of the exposure of the general population to radiofrequency electromagnetic fields (RF-EMF). Previous studies have shown that exposure of microorganisms to RF-EMFs can be associated with a wide spectrum of changes ranged from the modified bacterial growth to the alterations of the pattern of antibiotic resistance. Our laboratory at the nonionizing department of the Ionizing and Non-ionizing Radiation Protection Research Center has performed experiments on the health effects of exposure to animal models and humans to different sources of electromagnetic fields such as cellular phones, mobile base stations, mobile phone jammers, laptop computers, radars, dentistry cavitrons, magnetic resonance imaging, and Helmholtz coils. On the other hand, we have previously studied different aspects of the challenging issue of the ionizing or nonionizing radiation-induced alterations in the susceptibility of microorganisms to antibiotics. In this study, we assessed if the exposure to 900 MHz GSM mobile phone radiation and 2.4 GHz radiofrequency radiation emitted from common Wi-Fi routers alters the susceptibility of microorganisms to different antibiotics. The pure cultures of Listeria monocytogenes and Escherichia coli were exposed to RF-EMFs generated either by a GSM 900 MHz mobile phone simulator and a common 2.4 GHz Wi-Fi router. It is also shown that exposure to RF-EMFs within a narrow level of irradiation (an exposure window) makes microorganisms resistant to antibiotics. This adaptive phenomenon and its potential threats to human health should be further investigated in future experiments. Altogether, the findings of this study showed that exposure to Wi-Fi and RF simulator radiation can significantly alter the inhibition zone diameters and growth rate for L monocytogenes and E coli. These findings may have implications for the management of serious infectious diseases.

Evaluation of the Effect of Radiofrequency Radiation Emitted From Wi-Fi Router and Mobile Phone Simulator on the Antibacterial Susceptibility of Pathogenic Bacteria Listeria monocytogenes and Escherichia coli

PubMed Central

Taheri, M.; Mansouri, S.; Hatam, G. R.; Nouri, F.

2017-01-01

Mobile phones and Wi-Fi radiofrequency radiation are among the main sources of the exposure of the general population to radiofrequency electromagnetic fields (RF-EMF). Previous studies have shown that exposure of microorganisms to RF-EMFs can be associated with a wide spectrum of changes ranged from the modified bacterial growth to the alterations of the pattern of antibiotic resistance. Our laboratory at the nonionizing department of the Ionizing and Non-ionizing Radiation Protection Research Center has performed experiments on the health effects of exposure to animal models and humans to different sources of electromagnetic fields such as cellular phones, mobile base stations, mobile phone jammers, laptop computers, radars, dentistry cavitrons, magnetic resonance imaging, and Helmholtz coils. On the other hand, we have previously studied different aspects of the challenging issue of the ionizing or nonionizing radiation-induced alterations in the susceptibility of microorganisms to antibiotics. In this study, we assessed if the exposure to 900 MHz GSM mobile phone radiation and 2.4 GHz radiofrequency radiation emitted from common Wi-Fi routers alters the susceptibility of microorganisms to different antibiotics. The pure cultures of Listeria monocytogenes and Escherichia coli were exposed to RF-EMFs generated either by a GSM 900 MHz mobile phone simulator and a common 2.4 GHz Wi-Fi router. It is also shown that exposure to RF-EMFs within a narrow level of irradiation (an exposure window) makes microorganisms resistant to antibiotics. This adaptive phenomenon and its potential threats to human health should be further investigated in future experiments. Altogether, the findings of this study showed that exposure to Wi-Fi and RF simulator radiation can significantly alter the inhibition zone diameters and growth rate for L monocytogenes and E coli. These findings may have implications for the management of serious infectious diseases. PMID:28203122

ALON GRIN optics for visible-MWIR applications

NASA Astrophysics Data System (ADS)

Nag, Nagendra; Jha, Santosh; Sastri, Suri; Goldman, Lee M.; McCarthy, Peter; Schmidt, Greg R.; Bentley, Julie L.; Moore, Duncan T.

2016-05-01

Surmet continuously strives to develop novel, advanced optical ceramics products for current and future defense and commercial systems. Using conventional powder processing techniques, Surmet has made substantial progress in its ability to manufacture large ALON® sensor windows, lenses, domes and transparent armor. In addition to transparency, Surmet has demonstrated the ability to incorporate other capabilities into its optical ceramic components, including: EMI shielding, heating, internal antennas and cooling channels. Working closely with the University of Rochester, Surmet has developed gradient index (GRIN) optics in ALON for use in the visible through the MWIR applications. Surmet has demonstrated the ability to tailor the refractive index of ALON® Optical Ceramic by either varying its composition or through the addition of dopants. Smooth axial and radial gradient profiles with ~0.055 change in refractive index, over depths of 1-8 mm (axial) and over 20 mm radius (radial) have been demonstrated. Initial design studies have shown that such elements provide unique capabilities. Radial gradients in particular, with their optical power contribution, provide additional degrees of freedom for color correction in broadband imaging systems. Surmet continues to mature ALON® GRIN technology along with the associated metrology. Surmet is committed to the development of its ALON® GRIN capability as well as finding insertion opportunities in novel imaging solutions for military and other commercial systems.

Design of 28 GHz, 200 kW Gyrotron for ECRH Applications

NASA Astrophysics Data System (ADS)

Yadav, Vivek; Singh, Udaybir; Kumar, Nitin; Kumar, Anil; Deorani, S. C.; Sinha, A. K.

2013-01-01

This paper presents the design of 28 GHz, 200 kW gyrotron for Indian TOKAMAK system. The paper reports the designs of interaction cavity, magnetron injection gun and RF window. EGUN code is used for the optimization of electron gun parameters. TE03 mode is selected as the operating mode by using the in-house developed code GCOMS. The simulation and optimization of the cavity parameters are carried out by using the Particle-in-cell, three dimensional (3-D)-electromagnetic simulation code MAGIC. The output power more than 250 kW is achieved.

Proceedings of the Symposium on Electromagnetic Windows (17th) Held at Georgia Institute of Technology, Engineering Experiment Station, Atlanta, Georgia on 25-27 July 1984. Part 2

DTIC Science & Technology

1984-01-01

and that a residual 1100 quadratic phase error across the aperture remained uncorrected. K --] In Fig.4 the measured far field pattern of the horn...The radio frequency (RF) source consists of a 10-mW klystron at 35 GHz which is phase locked to a stable 5 MHz crystal oscillator . The 35 GHz sig...electronics, the purchased components have worked to specifica- tions, but our earliest work was delayed by phase locked oscillator instabil- ities until

Progress in joining, reuse, and customization of WR284 waveguide in the laboratory

NASA Astrophysics Data System (ADS)

Clark, Mike; Flanagan, Ken; Milhone, Jason; Nonn, Paul; Forest, Cary

2017-10-01

A system of five 20 kW magnetrons is being installed for the Big Red Ball (BRB) to produce and heat the plasma with 2.45GHz RF energy. An existing system of two 6 kW magentrons of the same frequency is actively used for the same purpose on Plasma Couette Experiment Upgrade (PCX-U). In each experiment, the RF is transmitted to the vessel via WR284 waveguide. Waveguide occasionally needs to be disassembled, modified and rebuilt for different reasons such as physics interests, ongoing problems (arcing), or efficient utilization of laboratory space. Reuse of disassembled waveguide parts is desirable for cost savings. Methods of assembly, disassembly, and modification of waveguide will be discussed. Also, frequently used designs of chokes, windows, and limiters will be shown. Materials used include copper, brass, and even aluminum. The vacuum vessel of PCX-U is a 1 meter diameter, 1 meter tall cylinder comprised of ¼'' thick stainless steel. PCX-U has one removable end. The vacuum vessel of the BRB is a 3 meter diameter, sphere comprised of two hemispheres of 1-¼'' thick cast A356 aluminum. Rings comprised of hundreds of SmCo magnets in each vessel create a cusp field to contain the plasma and provide a resonance surface for the RF. Supported by NSF and DoE.

The application of "double isolation" in Fourier transform ion cyclotron resonance sustained off-resonance irradiation collisionally-induced dissociation tandem mass spectrometry to remove labile isobaric impurities.

PubMed

Gates, Paul J; Lopes, Norberto P; Pinto, Emani; Colepicolo, Pio; Cardozo, Karina H M

2011-01-01

This study reports the application of "double isolation" in sustained off-resonance irradiation collisionally-induced dissociation tandem mass spectrometry (SORI-CID-MS/MS) to remove radio- frequency (RF) fragment ions of very close mass isobaric ions (0.02 m/z apart). Analyses were performed with a fraction of a biological extract isolated from a macroalgae containing the mycosporine-like amino acid asterina-330. Direct isolation of the precursor ion by narrowing the isolation window proved ineffective as it impinged upon the required ion thus substantially reducing its intensity. By increasing the correlated sweep time, ejection efficiency of the isolation was improved, but caused the unwanted side-effect of RF fragmentation of labile ions. Finally, by skipping the ion activation step and performing a second isolation (in the MS(3) module) the RF fragments from the first isolation were removed leaving a very pure isolation of the required precursor ion and allowed a very clean CID fragmentation. We demonstrated that the m/z 272.1351 ion is derived from the loss of NH(3) from m/z 289.1620 isobaric impurity and is not related to asterina-330. This application represents a powerful tool to remove unwanted ions in the MS/MS spectrum that result from fragmentation of isobaric ions.

The Japanese Positron Factory

NASA Astrophysics Data System (ADS)

Okada, S.; Sunaga, H.; Kaneko, H.; Takizawa, H.; Kawasuso, A.; Yotsumoto, K.; Tanaka, R.

1999-06-01

The Positron Factory has been planned at Japan Atomic Energy Research Institute (JAERI). The factory is expected to produce linac-based monoenergetic positron beams having world-highest intensities of more than 1010e+/sec, which will be applied for R&D of materials science, biotechnology and basic physics & chemistry. In this article, results of the design studies are demonstrated for the following essential components of the facilities: 1) Conceptual design of a high-power electron linac with 100 MeV in beam energy and 100 kW in averaged beam power, 2) Performance tests of the RF window in the high-power klystron and of the electron beam window, 3) Development of a self-driven rotating electron-to-positron converter and the performance tests, 4) Proposal of multi-channel beam generation system for monoenergetic positrons, with a series of moderator assemblies based on a newly developed Monte Carlo simulation and the demonstrative experiment, 5) Proposal of highly efficient moderator structures, 6) Conceptual design of a local shield to suppress the surrounding radiation and activation levels.

Variable transmittance electrochromic windows

NASA Astrophysics Data System (ADS)

Rauh, R. D.

1983-11-01

Electrochromic apertures based on RF sputtered thin films of WO3 are projected to have widely different sunlight attenuation properties when converted to MxWO3 (M = H, Li, Na, Ag, etc.), depending on the initial preparation conditions. Amorphous WO3, prepared at low temperature, has a coloration spectrum centered in the visible, while high temperature crystalline WO3 attenuates infrared light most efficiently, but appears to become highly reflective at high values of x. The possibility therefore exists of producing variable light transmission apertures of the general form (a-MxWO3/FIC/c-WO3), where the FIC is an ion conducting thin film, such as LiAlF4 (for M = Li). The attenuation of 90% of the solar spectrum requires an injected charge of 30 to 40 mcoul/sq cm in either amorphous or crystalline WO3, corresponding to 0.2 Whr/sq m per coloration cycle. In order to produce windows with very high solar transparency in the bleached form, new counter electrode materials must be found with complementary electrochromism to WO3.

Fabrication and Physical Properties of Titanium Nitride/Hydroxyapatite Composites on Polyether Ether Ketone by RF Magnetron Sputtering Technique

NASA Astrophysics Data System (ADS)

Nupangtha, W.; Boonyawan, D.

2017-09-01

Titanium nitride (TiN) coatings have been used very successfully in a variety of applications because of their excellent properties, such as the high hardness meaning good wear resistance and also used for covering medical implants. Hydroxyapatite is a bioactive ceramic that contributes to the restoration of bone tissue, which together with titanium nitride may contribute to obtaining a superior composite in terms of mechanical and bone tissue interaction matters. This paper aims to explain how to optimize deposition conditions for films synthesis on PEEK by varying sputtering parameters such as nitrogen flow rate and direction, deposition time, d-s (target-to-substrate distance) and 13.56 MHz RF power. The plasma conditions used to deposit films were monitored by the optical emission spectroscopy (OES). Titanium nitride/Hydroxyapatite composite films were performed by gas mixture with nitrogen and argon ratio of 1:3 and target-to-substrate distance at 8 cm. The gold colour, as-deposited film was found on PEEK with high hardness and higher surface energy than uncoated PEEK. X-ray diffraction characterization study was carried to study the crystal structural properties of these composites.

60-MW test using the 30-MW klystrons for the KEKB project

NASA Astrophysics Data System (ADS)

Fukuda, S.; Michizono, S.; Nakao, K.; Saito, Y.; Anami, S.

1995-07-01

The B-Factory is a future plan, requiring an energy upgrade of the KEK linac from 2.5 GeV to 8.0 GeV (KEKB Project). This paper describes the recent development of an S-band high-power pulse klystron to be used as the PF-linac rf-source of the B-Factory. This tube is a modified version of the existing 30-MW tube, which produces 51 MW at a 310 kV beam voltage by optimizing the focusing magnetic field. In order to increase the reliability, the cathode diameter, the gun housing, and the insulation ceramic-seal were enlarged. This tube was redesigned so as to have the same characteristics as the test results of 30-MW tubes at a higher applied voltage without changing the rf interaction region. Four prototype tubes have been manufactured; final test results showed that these new tubes produce an output power of more than 50 MW at 310 kV with an efficiency of 46%. Recently this tube has produced more than 60 MW at a 350 kV beam voltage for a demonstration test. A comparison between the FCI-code prediction and the test results is also given in this paper.

RF H-minus ion source development in China spallation neutron source

NASA Astrophysics Data System (ADS)

Chen, W.; Ouyang, H.; Xiao, Y.; Liu, S.; Lü, Y.; Cao, X.; Huang, T.; Xue, K.

2017-08-01

China Spallation Neutron Source (CSNS) phase-I project currently uses a Penning surface plasma H- ion source, which has a life time of several weeks with occasional sparks between high voltage electrodes. To extend the life time of the ion source and prepare for the CSNS phase-II, we are trying to develop a RF negative hydrogen ion source with external antenna. The configuration of the source is similar to the DESY external antenna ion source and SNS ion source. However several changes are made to improve the stability and the life time. Firstly, Si3N4 ceramic with high thermal shock resistance, and high thermal conductivity is used for plasma chamber, which can endure an average power of 2000W. Secondly, the water-cooled antenna is brazed on the chamber to improve the energy efficiency. Thirdly, cesium is injected directly to the plasma chamber if necessary, to simplify the design of the converter and the extraction. Area of stainless steel exposed to plasma is minimized to reduce the sputtering and degassing. Instead Mo, Ta, and Pt coated materials are used to face the plasma, which makes the self-cleaning of the source possible.

Association between the electromyographic fatigue threshold and ventilatory threshold.

PubMed

Camata, T V; Lacerda, T R; Altimari, L R; Bortolloti, H; Fontes, E B; Dantas, J L; Nakamura, F Y; Abrão, T; Chacon-Mikahil, M P T; Moraes, A C

2009-01-01

The objective of this study is to verify the coincidence between the occurrence of the electromyographic fatigue threshold (EMGth) and the ventilatory threshold (Vth) in an incremental test in the cyclosimulator, as well as to compare the calculation of the RMS from the EMG signal using different time windows. Thirteen male cyclists (73.7 +/- 12.4 kg and 174.3 +/- 6.2 cm) performed a ramp incremental test (TI) in a cyclosimulator until voluntary exhaustion. Before the start of each TI subjects had the active bipolar electrodes placed over the superficial muscles of the quadriceps femoris (QF) of the right leg: rectus femoris (RF), vastus medialis (VM) and vastus lateralis (VL). The paired student's t test, pearson's correlation coefficient and the analysis method described by Bland and Altman for the determination of the concordance level were used for statistical analysis. The significance level adopted was P < 0.05. Although no significant differences were found between Vth and the EMGth calculated from windows of 2, 5, 10, 30 and 60 seconds in the studied muscles, it is suggested that the EMGth values determined from the calculation of the RMS curve with windows of 5 and 10 seconds seem to be more appropriate for the calculation of the RMS curve and determination of EMGth from visual inspection.

Industrial 30-kW CO2 laser with fast axial gas flow and rf excitation

NASA Astrophysics Data System (ADS)

Habich, Uwe; Loosen, Peter; Hertzler, Christoph; Wollermann-Windgasse, Reinhard

1996-03-01

A CO2 laser with fast axial gas flow was set up and operated with a maximum cw output power above 30 kW. The laser makes use of 8 rf-excited discharges which were optimized regarding to the gas-flow, to the discharge homogeneity and to the optical properties of the gain medium. Results of experimental investigation of these topics are described as well as performance characteristics of the laser system equipped with a stable and an unstable resonator, respectively. With an unstable resonator and an aerodynamic window for the extraction of the beam the laser system gives a beam quality which is close to the diffraction limit for this type of resonator. Disregarding the difficulties which are related to the definition and measurement of beam quality for unstable resonators, the beam quality could be described as M2 equals 3. Measured far field intensity profiles in the focal plane of a focusing optics are presented as well as the beam propagation behavior near focus. First results of applications in materials processing are discussed.

Electromechanical properties of engineered lead free potassium sodium niobate based materials =

NASA Astrophysics Data System (ADS)

Rafiq, Muhammad Asif

K0.5Na0.5NbO3 (KNN), is the most promising lead free material for substituting lead zirconate titanate (PZT) which is still the market leader used for sensors and actuators. To make KNN a real competitor, it is necessary to understand and to improve its properties. This goal is pursued in the present work via different approaches aiming to study KNN intrinsic properties and then to identify appropriate strategies like doping and texturing for designing better KNN materials for an intended application. Hence, polycrystalline KNN ceramics (undoped, non-stoichiometric; NST and doped), high-quality KNN single crystals and textured KNN based ceramics were successfully synthesized and characterized in this work. Polycrystalline undoped, non-stoichiometric (NST) and Mn doped KNN ceramics were prepared by conventional ceramic processing. Structure, microstructure and electrical properties were measured. It was observed that the window for mono-phasic compositions was very narrow for both NST ceramics and Mn doped ceramics. For NST ceramics the variation of A/B ratio influenced the polarization (P-E) hysteresis loop and better piezoelectric and dielectric responses could be found for small stoichiometry deviations (A/B = 0.97). Regarding Mn doping, as compared to undoped KNN which showed leaky polarization (P-E) hysteresis loops, B-site Mn doped ceramics showed a well saturated, less-leaky hysteresis loop and a significant properties improvement. Impedance spectroscopy was used to assess the role of Mn and a relation between charge transport - defects and ferroelectric response in K0.5Na0.5NbO3 (KNN) and Mn doped KNN ceramics could be established. At room temperature the conduction in KNN which is associated with holes transport is suppressed by Mn doping. Hence Mn addition increases the resistivity of the ceramic, which proved to be very helpful for improving the saturation of the P-E loop. At high temperatures the conduction is dominated by the motion of ionized oxygen vacancies whose concentration increases with Mn doping. Single crystals of potassium sodium niobate (KNN) were grown by a modified high temperature flux method. A boron-modified flux was used to obtain the crystals at a relatively low temperature. XRD, EDS and ICP analysis proved the chemical and crystallographic quality of the crystals. The grown KNN crystals exhibit higher dielectric permittivity (29,100) at the tetragonal-to-cubic phase transition temperature, higher remnant polarization (19.4 ?C/cm2) and piezoelectric coefficient (160 pC/N) when compared with the standard KNN ceramics. KNN single crystals domain structure was characterized for the first time by piezoforce response microscopy. It could be observed that - oriented potassium sodium niobate (KNN) single crystals reveal a long range ordered domain pattern of parallel 180° domains with zig-zag 90° domains. From the comparison of KNN Single crystals to ceramics, It is argued that the presence in KNN single crystal (and absence in KNN ceramics) of such a long range order specific domain pattern that is its fingerprint accounts for the improved properties of single crystals. These results have broad implications for the expanded use of KNN materials, by establishing a relation between the domain patterns and the dielectric and ferroelectric response of single crystals and ceramics and by indicating ways of achieving maximised properties in KNN materials. (Abstract shortened by ProQuest.).

Experimental Verification of the Use of Metal Filled Via Hole Fences for Crosstalk Control of Microstrip Lines in LTCC Packages

NASA Technical Reports Server (NTRS)

Ponchak, George E.; Chun, Donghoon; Yook, Jong-Gwan; Katehi, Linda P. B.

2001-01-01

Coupling between microstrip lines in dense RF packages is a common problem that degrades circuit performance. Prior three-dimensional-finite element method (3-D-FEM) electromagnetic simulations have shown that metal filled via hole fences between two adjacent microstrip lines actually Increases coupling between the lines: however, if the top of the via posts are connected by a metal strip, coupling is reduced. In this paper, experimental verification of the 3-D-FEM simulations is demonstrated for commercially fabricated low temperature cofired ceramic (LTCC) packages. In addition, measured attenuation of microstrip lines surrounded by the shielding structures is presented and shows that shielding structures do not change the attenuation characteristics of the line.

Atomic Oxygen Durability Evaluation of a UV Curable Ceramer Protective Coating

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; Karniotis, Christina A.; Dworak, David; Soucek, Mark

2004-01-01

The exposure of most silicones to atomic oxygen in low Earth orbit (LEO) results in the oxidative loss of methyl groups with a gradual conversion to oxides of silicon. Typically there is surface shrinkage of oxidized silicone protective coatings which leads to cracking of the partially oxidized brittle surface. Such cracks widen and branch crack with continued atomic oxygen exposure ultimately allowing atomic oxygen to reach any hydrocarbon polymers under the silicone coating. A need exists for a paintable silicone coating that is free from such surface cracking and can be effectively used for protection of polymers and composites in LEO. A new type of silicone based protective coating holding such potential was evaluated for atomic oxygen durability in an RF atomic oxygen plasma exposure facility. The coating consisted of a UV curable inorganic/organic hybrid coating, known as a ceramer, which was fabricated using a methyl substituted polysiloxane binder and nanophase silicon-oxo-clusters derived from sol-gel precursors. The polysiloxane was functionalized with a cycloaliphatic epoxide in order to be cured at ambient temperature via a cationic UV induced curing mechanism. Alkoxy silane groups were also grafted onto the polysiloxane chain, through hydrosilation, in order to form a network with the incorporated silicon-oxo-clusters. The prepared polymer was characterized by H-1 and Si-29 NMR, FT-IR, and electrospray ionization mass spectroscopy. The paper will present the results of atomic oxygen protection ability of thin ceramer coatings on Kapton H as evaluated over a range of atomic oxygen fluence levels.

High Frequency GaAs Bulk Acousto-Optic Devices For Modulators And Frequency Shifters At 1.3um And 1.5um In Fiber-Optics

NASA Astrophysics Data System (ADS)

Soos, J. I.; Rosemeier, R. G.

1989-02-01

The edge of a transmission window for a GaAs Bragg cell starts about lum, which allows this material to be used for infrared fiber-optic applications, especially at 1.3um and 1.5um. The single crystal of GaAs is acoustically anisotropic and has the highest figure of merit, M2, along <111> direction for a longitudinal mode sound wave. Recently, Brimrose has designed and fabricated an acousto-optic modulator from GaAs operating at a carrier frequency of 2.3 GHz with a diffraction efficiency of 4%/RF watt.

Preliminary results from the Small Negative Ion Facility (SNIF) at CCFE

NASA Astrophysics Data System (ADS)

Zacks, J.; McAdams, R.; Booth, J.; Flinders, K.; Holmes, A. J. T.; Simmonds, M.; Stevens, B.; Stevenson, P.; Surrey, E.; Warder, S.; Whitehead, A.; Young, D.

2013-02-01

At Culham Centre for Fusion Energy, a new beam extraction test facility has been built with the purpose of studying and enhancing negative ion beam production and transport. The multipole hydrogen ion source is based on a RF generated plasma using a continuous 5kW power supply operating at the industrial standard frequency of 13.56MHz. The cylindrical source has a diameter of 30cm and a depth of 20cm, with a flat spiral antenna driving the source through a quartz window. The magnet configuration is arranged to produce a dipole filter field across the ion source close to the plasma grid. The plasma load is matched to the RF generator using a Pi matching network. The accelerator uses a single extraction aperture of 14mm diameter, with a biased insert for electron suppression. The accelerator is a triode design with a beam energy of up to 30kV. The beamline consists of a turbomolecular pumped vacuum tank with an instrumented beam dump and ports for additional diagnostics. The ITER Neutral Beam source operates with the enhancement of caesium, which, when scaled up to a reactor, will be heavily consumed. The small size of SNIF allows for fast turn around of modifications and alternative materials to caesium can be tested. A full description of the facility and planned diagnostics is given. Initial results are presented, including measurements and calculations of the plasma load on the RF generator, and beam extraction measurements.

Lead-free BNT-based composite materials: enhanced depolarization temperature and electromechanical behavior.

PubMed

Bai, Wangfeng; Zheng, Peng; Wen, Fei; Zhang, Jingji; Chen, Daqin; Zhai, Jiwei; Ji, Zhenguo

2017-11-14

The development of (Bi 0.5 Na 0.5 )TiO 3 -based solid solutions with both high depolarization temperature T d and excellent piezoelectric and electromechanical properties for practical application is intractable because improved thermal stability is usually accompanied by a deterioration in piezoelectric and electromechanical performance. Herein, we report a 0-3 type 0.93(Bi 0.5 Na 0.5 )TiO 3 -0.07BaTiO 3  : 30 mol%ZnO composite (BNT-7BT : 0.3ZnO), in which the ZnO nanoparticles exist in two forms, to resolve the abovementioned long-standing obstacle. In this composite, Zn ions fill the boundaries of BNT-7BT grains, and residual Zn ions diffuse into the BNT-7BT lattice, as confirmed by XRD, Raman spectroscopy, and microstructure analysis. The BNT-7BT composite ceramics with a 0-3 type connectivity exhibited enhanced frequency-dependent electromechanical properties, fatigue characteristics, and thermal stabilities. More importantly, low poling field-driven large piezoelectric properties were observed for the composite ceramics as compared to the case of the pure BNT-7BT solid solution. A mechanism related to the ZnO-driven phase transition from the rhombohedral to tetragonal phase and built-in electric field to partially compensate the depolarization field was proposed to explain the achieved outstanding piezoelectric performance. This is the first time that the thermal stability, electromechanical behavior, and low poling field-driven high piezoelectric performance of BNT-based ceramics have been simultaneously optimized. Thus, our study provides a referential methodology to achieve novel piezoceramics with excellent piezoelectricity by composite engineering and opens up a new development window for the utilization of conventional BNT-based and other lead-free ceramics in practical applications.

Time-resolved chromatographic analysis and mechanisms in adsorption and catalysis.

PubMed

Roubani-Kalantzopoulou, Fani

2009-03-06

The main object of this review is the study of fundamentals of adsorption and heterogeneous catalysis, a benefit for the understanding of adsorptive and catalytic properties. This work aims to define and record, with the utmost accuracy, the phenomena and the possible reactions. A new methodology for the study of the adsorption is presented, which is a version of the well-known inverse gas chromatography. This reversed-flow inverse gas chromatography (RF-IGC) is technically very simple, and it is combined with a mathematical analysis that gives the possibility for the estimation of various physicochemical parameters related to adsorbent or catalyst characterization, under conditions compatible with the operation of real adsorbents and catalysts. On this base, this methodology has been successfully applied to the study of the impact of air pollutants, volatile organic and/or inorganic, on many solids such as marbles, ceramics, oxide-pigments of works of art, building materials, authentic statues of the Greek Archaeological Museums. Moreover, this methodology proved to be a powerful tool for studying the topography of active sites of heterogeneous surfaces in the nano-scale domain. Thus, some very important local quantities for the surface chemistry have been determined experimentally for many solids including thin films. These physicochemical local quantities (among which adsorption energy and entropy, surface diffusion coefficient, probability density function) have been determined from the experimental pairs of height of extra chromatographic peaks and time by a nonlinear least-squares method, through personal computer programs written in GW BASIC and lately in FORTRAN. Through the time-resolved analysis the surface characterization of the examined materials took place. In addition, the kinetic constants responsible for adsorption/desorption and surface chemical reactions have also been calculated. Thus, important answers have been provided to the following essential questions: (1) Can RF-IGC define the gnostic regions of adsorption/desorption, surface diffusion, surface reaction? Yes, irrefutably and undeniably. (2) Can RF-IGC deal with issues of catalysis, the existence of more than one reaction? Certainly yes. Indeed, it is impressive to observe the reactions "on line". (3) Can RF-IGC identify peaks of products and reactants simultaneously? Certainly yes. (4) Can RF-IGC be applied to thin films in a nano-scale domain? The answer is "definitely yes". (5) Can it kinetically follow the above? Yes, again.

The influence of target erosion grade in the optoelectronic properties of AZO coatings growth by magnetron sputtering

NASA Astrophysics Data System (ADS)

Zubizarreta, C.; G-Berasategui, E.; Ciarsolo, I.; Barriga, J.; Gaspar, D.; Martins, R.; Fortunato, E.

2016-09-01

Aluminum-doped zinc oxide (AZO) transparent conductor coating has emerged as promising substitute to tin-doped indium oxide (ITO) as electrode in optoelectronic applications such as photovoltaics or light emitting diodes (LEDs). Besides its high transmission in the visible spectral region and low resistivity, AZO presents a main advantage over other candidates such as graphene, carbon nanotubes or silver nanowires; it can be deposited using the technology industrially implemented to manufacture ITO layers, the magnetron sputtering (MS). This is a productive, reliable and green manufacturing technique. But to guarantee the robustness, reproducibility and reliability of the process there are still some issues to be addressed, such as the effect and control of the target state. In this paper a thorough study of the influence of the target erosion grade in developed coatings has been performed. AZO films have been deposited from a ceramic target by RF MS. Structure, optical transmittance and electrical properties of the produced coatings have been analyzed as function of the target erosion grade. No noticeable differences have been found neither in optoelectronic properties nor in the structure of the coatings, indicating that the RF MS is a stable and consistent process through the whole life of the target.

Thin films sputtered from Ba{sub 2}NdFeNb{sub 4}O{sub 15} multiferroic targets on BaFe{sub 12}O{sub 19} coated substrates

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

Bodeux, Romain; Univ. Bordeaux, ICMCB, UPR 9048, F-33600 Pessac; Michau, Dominique, E-mail: dominique.michau@icmcb.cnrs.fr

2016-09-15

Highlights: • Synthesis of Ba{sub 2}NdFeNb{sub 4}O{sub 15}/BaFe{sub 12}O{sub 19} (BaM) heterostructures by RF magnetron sputtering. • Growth of TTB layer were retained regardless of the underlayer (Pt bottom electrode or BaM). • Dielectric and magnetic properties were obtained from the Pt/TTB/BaM/Pt stacks. - Abstract: Ba{sub 2}NdFeNb{sub 4}O{sub 15} tetragonal tungsten bronze (TTB)/BaFe{sub 12}O{sub 19} (BaM) hexaferrite bilayers have been grown by RF magnetron sputtering on Pt/TiO{sub 2}/SiO{sub 2}/Si (PtS) substrates. The BaM layer is textured along (0 0 1) while the TTB layer is multioriented regardless of the PtS or BaM/PtS substrate. Dielectric properties of TTB films are similarmore » to those of bulk, i.e., ε ∼ 150 and a magnetic hysteresis loop is obtained from TTB/BaM bilayers, thanks to the BaM component. This demonstrates the possibility of transferring to 2 dimensional structures the composite multiferroic system TTB/BaM previously identified in 3 dimensional bulk ceramics.« less

Dynamic electromechanical characterization of the ferroelectric ceramic PZT 95/5

NASA Astrophysics Data System (ADS)

Setchell, R. E.; Chhabildas, L. C.; Furnish, M. D.; Montgomery, S. T.; Holman, G. T.

1998-07-01

Shock-induced depoling of the ferroelectric ceramic PZT 95/5 has been utilized in pulsed power applications for many years. Recently, new design and certification requirements have generated a strong interest in numerically simulating the operation of pulsed power devices. Because of a scarcity of relevant experimental data obtained within the past twenty years, we have initiated an extensive experimental study of the dynamic behavior of this material in support of simulation efforts. The experiments performed to date have been limited to examining the behavior of unpoled material. Samples of PZT 95/5 have been shocked to axial stresses from 0.5 to 5.0 GPa in planar impact experiments. Impact face conditions have been recorded using PVDF stress gauges, and transmitted wave profiles have been recorded either at window interfaces or at a free surface using laser interferometry (VISAR). The results significantly extend the stresses examined in prior studies of unpoled material, and ensure that a comprehensive experimental characterization of the mechanical behavior under shock loading is available for continuing development of PZT 95/5 material models.

Variable transmittance electrochromic windows

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

Rauh, R.D.

1983-11-01

Electrochromic apertures based on RF sputtered thin films of WO3 are projected to have widely different sunlight attenuation properties when converted to MxWO3 (M H, Li, Na, Ag, etc.), depending on the initial preparation conditions. Amorphous WO3, prepared at low temperature, has a coloration spectrum centered in the visible, while high temperature crystalline WO3 attenuates infrared light most efficiently, but appears to become highly reflective at high values of x. The possibility therefore exists of producing variable light transmission apertures of the general form (a-MxWO3/FIC/c-WO3), where the FIC is an ion conducting thin film, such as LiAlF4 (for M Li).more » The attenuation of 90% of the solar spectrum requires an injected charge of 30 to 40 mcoul/sq cm in either amorphous or crystalline WO3, corresponding to 0.2 Whr/sq m per coloration cycle. In order to produce windows with very high solar transparency in the bleached form, new counter electrode materials must be found with complementary electrochromism to WO3.« less

Manufacturing and metrology for IR conformal windows and domes

NASA Astrophysics Data System (ADS)

Ferralli, Ian; Blalock, Todd; Brunelle, Matt; Lynch, Timothy; Myer, Brian; Medicus, Kate

2017-05-01

Freeform and conformal optics have the potential to dramatically improve optical systems by enabling systems with fewer optical components, reduced aberrations, and improved aerodynamic performance. These optical components differ from standard components in their surface shape, typically a non-symmetric equation based definition, and material properties. Traditional grinding and polishing tools are unable to handle these freeform shapes. Additionally, standard metrology tools cannot measure these surfaces. Desired substrates are typically hard ceramics, including poly-crystalline alumina or aluminum oxynitride. Notwithstanding the challenges that the hardness provides to manufacturing, these crystalline materials can be highly susceptible to grain decoration creating unacceptable scatter in optical systems. In this presentation, we will show progress towards addressing the unique challenges of manufacturing conformal windows and domes. Particular attention is given to our robotic polishing platform. This platform is based on an industrial robot adapted to accept a wide range of tooling and parts. The robot's flexibility has provided us an opportunity to address the unique challenges of conformal windows. Slurries and polishing active layers can easily be changed to adapt to varying materials and address grain decoration. We have the flexibility to change tool size and shape to address the varying sizes and shapes of conformal optics. In addition, the robotic platform can be a base for a deflectometry-based metrology tool to measure surface form error. This system, whose precision is independent of the robot's positioning accuracy, will allow us to measure optics in-situ saving time and reducing part risk. In conclusion, we will show examples of the conformal windows manufactured using our developed processes.

High-power hybrid plasma spraying of large yttria-stabilized zirconia powder

NASA Astrophysics Data System (ADS)

Huang, Heji; Eguchi, Keisuke; Yoshida, Toyonobu

2006-03-01

To testify to the advantage of large ceramic powder spraying, numerical simulations and experimental studies on the behavior of large yttria-stabilized zirconia (YSZ) powder in a high-power hybrid plasma spraying process have been carried out. Numeric predictions and experimental results showed that, with the high radio frequency (RF) input power of 100 kW, the most refractory YSZ powder with particle sizes as large as 88 μm could be fully melted and well-flattened splats could be formed. A large degree of flattening (ξ) of 4.7 has been achieved. The improved adhesive strength between the large splat and the substrate was confirmed based on the measurement of the crack density inside of the splats. A thick YSZ coating >300 μm was successfully deposited on a large CoNiCrAlY-coated Inconel substrate (50×50×4 mm in size). The ultradense microstructure without clear boundaries between the splats and the clean and crack-free interface between the top-coat and the bond-coat also indicate the good adhesion. These results showed that highpower hybrid plasma spraying of large ceramic powder is a very promising process for deposition of highquality coatings, especially in the application of thermal barrier coatings (TBCs).

A Novel Application of Machine Learning Methods to Model Microcontroller Upset Due to Intentional Electromagnetic Interference

NASA Astrophysics Data System (ADS)

Bilalic, Rusmir

A novel application of support vector machines (SVMs), artificial neural networks (ANNs), and Gaussian processes (GPs) for machine learning (GPML) to model microcontroller unit (MCU) upset due to intentional electromagnetic interference (IEMI) is presented. In this approach, an MCU performs a counting operation (0-7) while electromagnetic interference in the form of a radio frequency (RF) pulse is direct-injected into the MCU clock line. Injection times with respect to the clock signal are the clock low, clock rising edge, clock high, and the clock falling edge periods in the clock window during which the MCU is performing initialization and executing the counting procedure. The intent is to cause disruption in the counting operation and model the probability of effect (PoE) using machine learning tools. Five experiments were executed as part of this research, each of which contained a set of 38,300 training points and 38,300 test points, for a total of 383,000 total points with the following experiment variables: injection times with respect to the clock signal, injected RF power, injected RF pulse width, and injected RF frequency. For the 191,500 training points, the average training error was 12.47%, while for the 191,500 test points the average test error was 14.85%, meaning that on average, the machine was able to predict MCU upset with an 85.15% accuracy. Leaving out the results for the worst-performing model (SVM with a linear kernel), the test prediction accuracy for the remaining machines is almost 89%. All three machine learning methods (ANNs, SVMs, and GPML) showed excellent and consistent results in their ability to model and predict the PoE on an MCU due to IEMI. The GP approach performed best during training with a 7.43% average training error, while the ANN technique was most accurate during the test with a 10.80% error.

Changes in Quadriceps Muscle Activity During Sustained Recreational Alpine Skiing

PubMed Central

Kröll, Josef; Müller, Erich; Seifert, John G.; Wakeling, James M.

2011-01-01

During a day of skiing thousands of repeated contractions take place. Previous research on prolonged recreational alpine skiing show that physiological changes occur and hence some level of fatigue is inevitable. In the present paper the effect of prolonged skiing on the recruitment and coordination of the muscle activity was investigated. Six subjects performed 24 standardized runs. Muscle activity during the first two (PREskiing) and the last two (POSTskiing) runs was measured from the vastus lateralis (VL) and rectus femoris (RF) using EMG and quantified using wavelet and principal component analysis. The frequency content of the EMG signal shifted in seven out of eight cases significantly towards lower frequencies with highest effects observed for RF on outside leg. A significant pronounced outside leg loading occurred during POSTskiing and the timing of muscle activity peaks occurred more towards turn completion. Specific EMG frequency changes were observed at certain time points throughout the time windows and not over the whole double turn. It is suggested that general muscular fatigue, where additional specific muscle fibers have to be recruited due to the reduced power output of other fibers did not occur. The EMG frequency decrease and intensity changes for RF and VL are caused by altered timing (coordination) within the turn towards a most likely more uncontrolled skiing technique. Hence, these data provide evidence to suggest recreational skiers alter their skiing technique before a potential change in muscle fiber recruitment occurs. Key points The frequency content of the EMG signal shifted in seven out of eight cases significantly towards lower frequencies with highest effects observed for RF. General muscular fatigue, where additional specific fibers have to be recruited due to the reduced power output of other fibers, did not occur. A modified skiing style towards a less functional and hence more uncontrolled skiing technique seems to be a key issue with respect to the influence on muscle recruitment for applied prolonged skiing session. PMID:24149299

Integral resistors and capacitors for mixed-signal packages using electroless plating and polymer-ceramic nanocomposites

NASA Astrophysics Data System (ADS)

Chahal, Premjeet

In this work, new approaches to achieving integral resistors and capacitors on large area substrates at low temperatures in a high density wiring (HDW) environment using non-vacuum deposition techniques are introduced. This includes the use of polymer-ceramic nanocomposites for integral capacitors and electroless plating for integral resistors. From the literature review it is believed that resistors in the range of 5--50 ohm/square and capacitors in the range of 1--20 nF/cm2 can satisfy most of the mixed-signal application needs. The proposed materials can satisfy this need as demonstrated in this work. Several test vehicles were fabricated and measured to characterize the material properties, and demonstrate conventional and novel circuits for mixed-signal applications. To begin with, several polymer-ceramic combinations were analyzed under varying conditions to gain a fundamental understanding of the material system. Experimental advances have been made to achieve high dielectric constant values for both epoxy-ceramic and polyimide-ceramic systems. These material systems in general can satisfy specific capacitances in the range of 1--22 nF/cm2. These materials were found to be stable into the GHz range and have low loss-tangent. For electroless resistors, several plating baths were studied and a combination of Ni-P/Ni-W-P was found to produce the best results. Uniform plating was achieved through better nucleation of PdCl2 catalyst through the use of organosilane surface treatment. The Ni-P/Ni-W-P films produced sheet resistance in the range of 5--50 ohm/square and TCR below 50 ppm/°C. The material is stable into the GHz range. Upon optimizing the electrical properties and processing of capacitors and resistors, several test vehicles were fabricated to demonstrate some conventional and novel passive structures for RF and mixed-signal applications (e.g., filters, delay lines, etc.). Some of the structures were modeled using MDS and PSPICE and a good correlation between measured and modeled results were obtained. Capacitors on large area PWB substrates using meniscus coating are also demonstrated with a typical capacitance of 10 nF/cm2. The yield of the capacitor structures is found to be affected by the surface roughness of the bottom copper electrode. Resistors have been demonstrated on 6″ x 6″ substrates using a simple set-up.

Silicon Oil DC200(R)5CST as AN Alternative Coolant for Cvd Diamond Windows

NASA Astrophysics Data System (ADS)

Vaccaro, A.; Aiello, G.; Meier, A.; Schere, T.; Schreck, S.; Spaeh, P.; Strauss, D.; Gantenbein, G.

2011-02-01

The production of high power mm-wave radiation is a key technology in large fusion devices, since it is required for localized plasma heating and current drive. Transmission windows are necessary to keep the vacuum in the gyrotron system and also act as tritium barriers. With its excellent optical, thermal and mechanical properties, synthetic CVD (Chemical Vapor Deposition) diamond is the state of the art material for the cw transmission of the mm-wave beams produced by high power gyrotrons. The gyrotrons foreseen for the W7-X stellarator are designed for cw operation with 1 MW output power at 140 GHz. The output window unit is designed by TED (Thales Electron Devices, France) using a single edge circumferentially cooled CVD-diamond disc with an aperture of 88 mm. The window unit is cooled by de-ionized water which is considered as chemical aggressive and might cause corrosion in particular at the brazing. The use of a different coolant such as silicon oil could prevent this issue. The cooling circuit has been simulated by steady-state CFD analysis. A total power generation of 1 kW (RF transmission losses) with pure Gaussian distribution has been assumed for the diamond disc. The performance of both water and the industrial silicon oil DC200(R) have been investigated and compared with a focus on the temperature distribution on the disc, the pressure drop across the cooling path and the heat flux distribution. Although the silicon oil has a higher viscosity (~x5), lower heat capacity (~x1/2) and lower thermal conductivity (~x1/3), it has proven to be a good candidate as alternative to water.

The 2D analytic signal for envelope detection and feature extraction on ultrasound images.

PubMed

Wachinger, Christian; Klein, Tassilo; Navab, Nassir

2012-08-01

The fundamental property of the analytic signal is the split of identity, meaning the separation of qualitative and quantitative information in form of the local phase and the local amplitude, respectively. Especially the structural representation, independent of brightness and contrast, of the local phase is interesting for numerous image processing tasks. Recently, the extension of the analytic signal from 1D to 2D, covering also intrinsic 2D structures, was proposed. We show the advantages of this improved concept on ultrasound RF and B-mode images. Precisely, we use the 2D analytic signal for the envelope detection of RF data. This leads to advantages for the extraction of the information-bearing signal from the modulated carrier wave. We illustrate this, first, by visual assessment of the images, and second, by performing goodness-of-fit tests to a Nakagami distribution, indicating a clear improvement of statistical properties. The evaluation is performed for multiple window sizes and parameter estimation techniques. Finally, we show that the 2D analytic signal allows for an improved estimation of local features on B-mode images. Copyright © 2012 Elsevier B.V. All rights reserved.

Highly conducting and preferred <220> oriented boron doped nc–Si films for window layers in nc–Si solar cells

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

Mondal, Praloy; Das, Debajyoti, E-mail: erdd@iacs.res.in

2016-05-23

Growth and optimization of the boron dopednanocrystalline silicon (nc-Si) films have been studied by varyingthe gaspressure applied to the hydrogendiluted silane plasma in RF (13.56 MHz) plasma-enhanced chemical vapor deposition (PECVD) system, using diborane (B{sub 2}H{sub 6}) as the dopant gas. High magnitudeof electrical conductivity (~10{sup 2} S cm{sup −1}) and<220>orientedcrystallographic lattice planes have been obtained with high crystalline volume fraction (~86 %) at an optimum pressure of 2.5 Torr. XRD and Raman studies reveal good crystallinity with preferred orientation, suitable for applications in stacked layer devices, particularly in nc–Si solar cells.

Effect of grain size on optical transmittance of birefringent polycrystalline ceramics

NASA Astrophysics Data System (ADS)

Wen, Tzu-Chien

Polycrystalline ceramics are increasingly used for fabricating windows and domes for the mid infra-red regime (3-5 mum) due to their superior durability as compared to glass and the lower cost of their fabrication and finishing relative to single crystals without significant compromise in optical properties. Due to the noncubic structure, MgF2 and Al2O3 are birefringent ceramics. Birefringence causes scatter of light at the grain boundaries and diminishes in-line transmittance and optical performance. This dissertation presents experimental results and analyses of the grain-size and wavelength dependence of the in-line transmittance of polycrystalline MgF2 and Al2O3. Chapter 2 presents experimental results and analyses of light transmission in polycrystalline MgF2 as a function of the mean grain size at different wavelengths. The scattering coefficient of polycrystalline MgF 2 increased linearly with the mean grain size and inversely with the square of the wavelength of light. These trends are consistent with theoretical models based on both a limiting form of the Raleigh-Gans-Debye theory of particle scattering and light retardation theories that take refractive-index variations along the light path. Chapter 3 investigates the applicability of particle light scattering theories to light attenuation in birefringent polycrystalline ceramics by measuring light transmittance in a model two-phase system. The system consisted of microspheres of silica dispersed in a solution of glycerol in water. It was found that RGD theory showed the systematic deviation for higher particle volume fraction (φ > 0.2) and larger particle size (d p > 1 mum). This result suggested that light scattering models based on single particle scattering are unlikely to provide viable physical explanation for the effect of grain size on light transmittance in birefringent polycrystalline ceramics due to the high volume fraction in dense polycrystalline ceramics. Chapter 4 analyses light transmission properties of polycrystalline Al 2O3 using theories of wave propagation in random media. Fully dense polycrystalline Al2O3 was fabricated using a pressure filtration method. By obtaining the Delta n2 measured from EBSD, the wave retardation theories of Raman and Viswanathan and Kahan et al. provided upper and lower bounds for the theoretical predictions of light transmittance as a function of mean intercept length.

Detection and display of acoustic window for guiding and training cardiac ultrasound users

NASA Astrophysics Data System (ADS)

Huang, Sheng-Wen; Radulescu, Emil; Wang, Shougang; Thiele, Karl; Prater, David; Maxwell, Douglas; Rafter, Patrick; Dupuy, Clement; Drysdale, Jeremy; Erkamp, Ramon

2014-03-01

Successful ultrasound data collection strongly relies on the skills of the operator. Among different scans, echocardiography is especially challenging as the heart is surrounded by ribs and lung tissue. Less experienced users might acquire compromised images because of suboptimal hand-eye coordination and less awareness of artifacts. Clearly, there is a need for a tool that can guide and train less experienced users to position the probe optimally. We propose to help users with hand-eye coordination by displaying lines overlaid on B-mode images. The lines indicate the edges of blockages (e.g., ribs) and are updated in real time according to movement of the probe relative to the blockages. They provide information about how probe positioning can be improved. To distinguish between blockage and acoustic window, we use coherence, an indicator of channel data similarity after applying focusing delays. Specialized beamforming was developed to estimate coherence. Image processing is applied to coherence maps to detect unblocked beams and the angle of the lines for display. We built a demonstrator based on a Philips iE33 scanner, from which beamsummed RF data and video output are transferred to a workstation for processing. The detected lines are overlaid on B-mode images and fed back to the scanner display to provide users real-time guidance. Using such information in addition to B-mode images, users will be able to quickly find a suitable acoustic window for optimal image quality, and improve their skill.

Development and experimental study of large size composite plasma immersion ion implantation device

NASA Astrophysics Data System (ADS)

Falun, SONG; Fei, LI; Mingdong, ZHU; Langping, WANG; Beizhen, ZHANG; Haitao, GONG; Yanqing, GAN; Xiao, JIN

2018-01-01

Plasma immersion ion implantation (PIII) overcomes the direct exposure limit of traditional beam-line ion implantation, and is suitable for the treatment of complex work-piece with large size. PIII technology is often used for surface modification of metal, plastics and ceramics. Based on the requirement of surface modification of large size insulating material, a composite full-directional PIII device based on RF plasma source and metal plasma source is developed in this paper. This device can not only realize gas ion implantation, but also can realize metal ion implantation, and can also realize gas ion mixing with metal ions injection. This device has two metal plasma sources and each metal source contains three cathodes. Under the condition of keeping the vacuum unchanged, the cathode can be switched freely. The volume of the vacuum chamber is about 0.94 m3, and maximum vacuum degree is about 5 × 10-4 Pa. The density of RF plasma in homogeneous region is about 109 cm-3, and plasma density in the ion implantation region is about 1010 cm-3. This device can be used for large-size sample material PIII treatment, the maximum size of the sample diameter up to 400 mm. The experimental results show that the plasma discharge in the device is stable and can run for a long time. It is suitable for surface treatment of insulating materials.

IRIS TOXICOLOGICAL REVIEW AND SUMMARY ...

EPA Pesticide Factsheets

Cerium is a member of the lanthanoid series of rare earth metals. It is also the most abundant and most reactive of the rare earth metals. Cerium oxidizes at room temperature and forms a variety of salt compounds including oxides, hydroxides, sulfates and chlorides. Cerium is used in a variety of ways and is present in many products. For example, cerium is used as a catalyst in emission control systems for gasoline engines, and most recently, as a fuel borne catalyst for diesel engines. In addition, cerium is found in carbon arc lamps, the polishing of lens and mirrors, high temperature ceramics, and the printing and lithographic industries. Cerium is released to the environment as salt compounds from the various uses listed above. This assessment will present reference values for the noncancer effects (RfD and RfC), where supported by the available data, and a cancer evaluation of cerium and cerium compounds. The assessment will be subject to internal review and external peer review along with Agency review. The final product will reflect the Agency's opinion on the toxicity of Cerium and cerium compounds. The U.S. EPA is conducting a new health assessment of cerium (stable) and compounds that will appear on the Agency's online database, the Integrated Risk Information System (IRIS). IRIS is an EPA database containing Agency scientific positions on potential adverse human health effects that may result from chronic (or lifetime) exposure to chemicals i

New Glass Serves as Window to Cutting-edge Lasers

NASA Technical Reports Server (NTRS)

2004-01-01

Since 1997, Marshall Space Flight Center s Electrostatic Levitator (ESL) facility has been used to study the characteristics of new metals, ceramics, and glass compounds - in both their hot molten states and as they are cooled to form solid materials. The ESL provides a unique way to test such substances without having to make contact with a container or crucible that would contaminate the sample. Simply put, objects analyzed in the levitator's chamber float in mid-air with no visible means of support or containment, suspended only by static electricity. While a sample object is levitated, a laser beam heats it until it melts so that scientists can measure its physical properties without interference from a container.

Generation of flash x-rays using a mercury-anode radiation tube

NASA Astrophysics Data System (ADS)

Oizumi, Teiji; Sato, Eiichi; Sagae, Michiaki; Hayasi, Yasuomi; Tamakawa, Yoshiharu; Yanagisawa, Toru

1993-02-01

The constructions and the radiographic characteristics of a flash x-ray generator having a liquid-anode radiation tube are described. This generator consisted of the following essential components: a high-voltage power supply, a combined ceramic condenser of 10.7 nF, an oil- diffusion pump, an oil circulator, a trigger device, and a flash x-ray tube. The x-ray tube was of a triode and was composed of the following major devices: a mercury anode, a rod-shaped graphite cathode, a trigger electrode made from a copper wire, an x-ray window made from a polyethyleneterephthalate film, and a glass tube body. The ceramic condenser was charged from 40 to 60 kV by a power supply, and the electric charges in the condenser were discharged to the x-ray tube after the triggering. The maximum tube voltage was equivalent to the initial charged voltage of the condenser, and the tube current was less than 0.7 kA. The pulse widths of the flash x rays had values of about 1 microsecond(s) , and the time-integrated x-ray intensity was about 2.4 (mu) C/kg at 0.26 m per pulse with a charged voltage of 60 kV.

Blue-light digital communication in underwater environments utilizing orbital angular momentum

NASA Astrophysics Data System (ADS)

Baghdady, Joshua; Miller, Keith; Osler, Sean; Morgan, Kaitlyn; Li, Wenzhe; Johnson, Eric; Cochenour, Brandon

2016-05-01

Underwater optical communication has recently become the topic of much investigation as the demands for underwater data transmission have rapidly grown in recent years. The need for reliable, high-speed, secure underwater communication has turned increasingly to blue-light optical solutions. The blue-green visible wavelength window provides an attractive solution to the problem of underwater data transmission thanks to its low attenuation, where traditional RF solutions used in free-space communications collapse. Beginning with GaN laser diodes as the optical source, this work explores the encoding and transmission of digital data across underwater environments of varying turbidities. Given the challenges present in an underwater environment, such as the mechanical and optical turbulences that make proper alignment difficult to maintain, it is desirable to achieve extremely high data rates in order to allow the time window of alignment between the transmitter and receiver to be as small as possible. In this paper, work is done to increase underwater data rates through the use of orbital angular momentum. Results are shown for a range of data rates across a variety of channel types ranging in turbidity from that of a clear ocean to a dirty harbor.

Practical experience and challenges in the operation of medical cyclotron.

PubMed

Kumar, Rajeev; Sonkawade, Rajendra G; Pandey, Anil K; Tripathi, Madhavi; Damle, Nishikant A; Kumar, Praveen; Bal, Chandra S

2017-01-01

The aim of this article was to share 10 years of operational experience of medical cyclotron and to provide working knowledge on the same. This experience has helped us gain working knowledge on cyclotron operation with practical points, which may help in improving F yield, minimizing the breakdown time, and help in the prevention of the occurrence of unusual events. Our facility has a self-shielded radioisotope delivery system eclipse 111 medical cyclotron with an 11 MeV proton beam in use for the past 10 years to produce positron emitters - namely, F, N, and F-2 gas - for PET imaging. During F production, we have followed a set protocol comprising the following: monitoring target pressure, rinsing the target with O water just immediately after bombardment, ion source feedback, radiofrequency (RF) feedback, and recording any unusual events that occurred during the operation. Besides this, enrichment of O water, target volume, target current, energy of the beam, variation in argon pressure on the target, bombardment duration, target status (new or old target or total number of previous bombardments on the same target), status of the delivery lines from target to the radiochemistry module (old or new) were also recorded. Rinsing with O water immediately after bombardment increases the life of the target and delivery line. The frequent problems encountered were with the ion source, RF, and target foil rupture. These problems were solved by rebuilding the ion source, changing the fuse of RF, and rebuilding the target. F yield can be increased by rinsing with O water immediately after bombardment. The effect of target leak - that is, rupture of vacuum window - can be avoided by immediate stoppage of bombardment.

RF Magnetron Sputtering Deposited W/Ti Thin Film For Smart Window Applications

NASA Astrophysics Data System (ADS)

Oksuz, Lutfi; Kiristi, Melek; Bozduman, Ferhat; Uygun Oksuz, Aysegul

2014-10-01

Electrochromic (EC) devices can change reversible and persistent their optical properties in the visible region (400-800 nm) upon charge insertion/extraction according to the applied voltage. A complementary type EC is a device containing two electrochromic layers, one of which is anodically colored such as vanadium oxide (V2 O5) while the other cathodically colored such as tungsten oxide (WO3) which is separated by an ionic conduction layer (electrolyte). The use of a solid electrolyte such as Nafion eliminates the need for containment of the liquid electrolyte, which simplifies the cell design, as well as improves safety and durability. In this work, the EC device was fabricated on a ITO/glass slide. The WO3-TiO2 thin film was deposited by reactive RF magnetron sputtering using a 2-in W/Ti (9:1%wt) target with purity of 99.9% in a mixture gas of argon and oxygen. As a counter electrode layer, V2O5 film was deposited on an ITO/glass substrate using V2O3 target with the same conditions of reactive RF magnetron sputtering. Modified Nafion was used as an electrolyte to complete EC device. The transmittance spectra of the complementary EC device was measured by optical spectrophotometry when a voltage of +/-3 V was applied to the EC device by computer controlled system. The surface morphology of the films was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) (Fig. 2). The cyclic voltammetry (CV) for EC device was performed by sweeping the potential between +/-3 V at a scan rate of 50 mV/s.

Correlation-based discrimination between cardiac tissue and blood for segmentation of 3D echocardiographic images

NASA Astrophysics Data System (ADS)

Saris, Anne E. C. M.; Nillesen, Maartje M.; Lopata, Richard G. P.; de Korte, Chris L.

2013-03-01

Automated segmentation of 3D echocardiographic images in patients with congenital heart disease is challenging, because the boundary between blood and cardiac tissue is poorly defined in some regions. Cardiologists mentally incorporate movement of the heart, using temporal coherence of structures to resolve ambiguities. Therefore, we investigated the merit of temporal cross-correlation for automated segmentation over the entire cardiac cycle. Optimal settings for maximum cross-correlation (MCC) calculation, based on a 3D cross-correlation based displacement estimation algorithm, were determined to obtain the best contrast between blood and myocardial tissue over the entire cardiac cycle. Resulting envelope-based as well as RF-based MCC values were used as additional external force in a deformable model approach, to segment the left-ventricular cavity in entire systolic phase. MCC values were tested against, and combined with, adaptive filtered, demodulated RF-data. Segmentation results were compared with manually segmented volumes using a 3D Dice Similarity Index (3DSI). Results in 3D pediatric echocardiographic images sequences (n = 4) demonstrate that incorporation of temporal information improves segmentation. The use of MCC values, either alone or in combination with adaptive filtered, demodulated RF-data, resulted in an increase of the 3DSI in 75% of the cases (average 3DSI increase: 0.71 to 0.82). Results might be further improved by optimizing MCC-contrast locally, in regions with low blood-tissue contrast. Reducing underestimation of the endocardial volume due to MCC processing scheme (choice of window size) and consequential border-misalignment, could also lead to more accurate segmentations. Furthermore, increasing the frame rate will also increase MCC-contrast and thus improve segmentation.

Convenient and large-scale synthesis of nitrogen-rich hierarchical porous carbon spheres for supercapacitors and CO2 capture

NASA Astrophysics Data System (ADS)

Chang, Binbin; Zhang, Shouren; Yin, Hang; Yang, Baocheng

2017-08-01

Herein, considering the great potential of nitrogen-doped hierarchical porous carbons in energy storage and CO2 capture, we designed a convenient and easily large-scale production strategy for preparing nitrogen-doped hierarchical porous carbon sphere (NHPCS) materials. In this synthesis route, spherical resorcinol-formaldehyde (RF) resins were selected as carbon precursor, and then the ZnCl2-impregnated RF resin spheres were carbonized in a NH3 atmosphere at a temperature range of 600-800 °C. During the one-step heat-treatment process, nitrogen atom could be efficiently incorporated into the carbon skeleton, and the interconnected and hierarchical pore structure with different micro/mesopore proportion could be generated and tuned by adjusting the activating agent ZnCl2 dosage and carbonization temperature. The resultant nitrogen-doped hierarchical porous carbon sphere materials exhibited a satisfactory charge storage capacity, and the optimal sample of NHPCS-2-8 with a high mesopore proportion obtained at 800 °C with a ZnCl2/RF mass ratio of 2:1 presented a specific capacitance of 273.8 F g-1 at a current density of 0.5 A g-1. More importantly, the assembled NHPCS-2-8-based symmetric capacitor displayed a high energy density of 17.2 Wh kg-1 at a power density of 178.9 W kg-1 within a voltage window of 0 ∼ 1.8 V in 0.5 M Na2SO4 aqueous electrolyte. In addition, the CO2 capture application of these NHPCS materials was also explored, and the optimal sample of NHPCS-0-8 with a large micropore proportion prepared at 800 °C exhibited an exceptional CO2 uptake capacity at ambient pressures of up to 4.23 mmol g-1 at 0 °C.

Multipactor experiment on a dielectric surface

NASA Astrophysics Data System (ADS)

Anderson, Rex Beach, III

2001-12-01

Multipactor is an electron multiplication process, or electron avalanche, that occurs on metallic and dielectric surfaces in the presence of rf microwave fields. Just as a rock avalanche only needs one rock to cause a larger slide of destruction, one electron under multipactor conditions can cause a tremendous amount of damage to electrical components. Multipactor is a nuisance that can cause excessive noise in communication satellites and radar, and damage to vacuum windows in particle accelerators. Single-surface multipactor on dielectrics is responsible for poor transmission properties of vacuum windows and can eventually lead to vacuum window failure. The repercussions of multipactor affect a wide range of people. For example, a civilian placing a call on a cell phone, or a captain dependent on radar for his ship's safety could both be affected by multipactor. In order to combat this expensive annoyance, a unique experiment to investigate single-surface multipactor on a dielectric surface was developed and tested. The motivation of this thesis is to introduce a novel experiment for multipactor that is designed to verify theoretical calculations and explore the physics behind the phenomenon. The compact apparatus consists of a small brass microwave cavity in a high vacuum system. Most single-surface multipactor experiments consist of a large resonant ring wave guide with a MW power supply. This experiment is the first to utilize a high Q resonant cavity and kW-level power supply to create multipactor on a dielectric surface. The small brass resonant cavity has an inner length of 9.154 cm with an inner diameter of 9.045 cm. A pulsed, variable frequency microwave source at ˜2.4 GHz, 2 kW peak excites the TE111 mode with a strong electric field parallel to a dielectric plate (˜0.2 cm thickness) that is inserted at the mid-plane of the cavity. The microwave pulses from the power supply are monitored by calibrated microwave diodes. These calibrated diodes along with a bead pull perturbation method are used to calculate the threshold rf fields at the dielectric surface when multipactor occurs. This experiment is the first to measure electron current from the dielectric using an electron probe. The electron probe provides temporal measurements of the multipactor electron current with respect to the microwave pulses. Another unique electron diagnostic utilized in this multipactor experiment is phosphor. Phosphor on the dielectric surface is used to detect multipactor electrons by photoemission. Phosphors with different excitation energies are used as a crude electron energy analyzer. Experimental results from these diagnostics match well with theoretical calculations.

Building and Testing a Superconductivity Measurement Platform for a Helium Cryostat

NASA Astrophysics Data System (ADS)

Rose, Heath; Ostrander, Joshua; Wu, Jim; Ramos, Roberto

2013-03-01

Superconductivity experiments using Josephson junctions are an excellent environment to study quantum mechanics and materials science. A standard electrical transport technique uses filtered four wire measurement of these superconducting devices. We report our experience as undergraduates in a liberal arts college in building and testing an experimental platform anchored on the cold-finger of a helium cryostat and designed for performing differential conductance measurements in Josephson junctions. To filter out RF, we design, build and test cryogenic filters using ceramic capacitors and inductors and thermocoax cables. We also use fixed attenuators for thermal anchoring and use miniature connectors to connect wires and coax to a sample box. We report on progress in our diagnostic measurements as well as low-temperature tunneling experiments to probe the structure of the energy gap in both single- and multi-gapped superconductors. We acknowledge the support of the National Science Foundation through NSF Grant DMR-1206561.

Process for producing Ti-Cr-Al-O thin film resistors

DOEpatents

Jankowski, Alan F.; Schmid, Anthony P.

2001-01-01

Thin films of Ti-Cr-Al-O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti-Cr-Al-O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti-Cr-Al-O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti-Cr-Al-O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

Flat panel display using Ti-Cr-Al-O thin film

DOEpatents

Jankowski, Alan F.; Schmid, Anthony P.

2002-01-01

Thin films of Ti--Cr--Al--O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti--Cr--Al--O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti--Cr--Al--O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti--Cr--Al--O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

TI--CR--AL--O thin film resistors

DOEpatents

Jankowski, Alan F.; Schmid, Anthony P.

2000-01-01

Thin films of Ti--Cr--Al--O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti--Cr--Al--O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti--Cr--Al--O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti--Cr--Al--O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

High-Temperature RF Probe Station For Device Characterization Through 500 deg C and 50 GHz

NASA Technical Reports Server (NTRS)

Schwartz, Zachary D.; Downey, Alan N.; Alterovitz, Samuel A.; Ponchak, George E.; Williams, W. D. (Technical Monitor)

2003-01-01

A high-temperature measurement system capable of performing on-wafer microwave testing of semiconductor devices has been developed. This high temperature probe station can characterize active and passive devices and circuits at temperatures ranging from room temperature to above 500 C. The heating system uses a ceramic heater mounted on an insulating block of NASA shuttle tile material. The temperature is adjusted by a graphical computer interface and is controlled by the software-based feedback loop. The system is used with a Hewlett-Packard 8510C Network Analyzer to measure scattering parameters over a frequency range of 1 to 50 GHz. The microwave probes, cables, and inspection microscope are all shielded to protect from heat damage. The high temperature probe station has been successfully used to characterize gold transmission lines on silicon carbide at temperatures up to 540 C.

Silicon Solar Cell Process Development, Fabrication and Analysis, Phase 1

NASA Technical Reports Server (NTRS)

Yoo, H. I.; Iles, P. A.; Tanner, D. P.

1979-01-01

Solar cells from RTR ribbons, EFG (RF and RH) ribbons, dendritic webs, Silso wafers, cast silicon by HEM, silicon on ceramic, and continuous Czochralski ingots were fabricated using a standard process typical of those used currently in the silicon solar cell industry. Back surface field (BSF) processing and other process modifications were included to give preliminary indications of possible improved performance. The parameters measured included open circuit voltage, short circuit current, curve fill factor, and conversion efficiency (all taken under AM0 illumination). Also measured for typical cells were spectral response, dark I-V characteristics, minority carrier diffusion length, and photoresponse by fine light spot scanning. the results were compared to the properties of cells made from conventional single crystalline Czochralski silicon with an emphasis on statistical evaluation. Limited efforts were made to identify growth defects which will influence solar cell performance.

Carbon-free induction furnace

DOEpatents

Holcombe, Cressie E.; Masters, David R.; Pfeiler, William A.

1985-01-01

An induction furnace for melting and casting highly pure metals and alloys such as uranium and uranium alloys in such a manner as to minimize contamination of the melt by carbon derived from the materials and the environment within the furnace. The subject furnace is constructed of carbon free materials and is housed within a conventional vacuum chamber. The furnace comprises a ceramic oxide crucible for holding the charge of metal or alloy. The heating of the crucible is achieved by a plasma-sprayed tungsten susceptor surrounding the crucible which, in turn, is heated by an RF induction coil separated from the susceptor by a cylinder of inorganic insulation. The furnace of the present invention is capable of being rapidly cycled from ambient temperatures to about 1650.degree. C. for effectively melting uranium and uranium alloys without the attendant carbon contamination problems previously encountered when using carbon-bearing furnace materials.

Non-carbon induction furnace

DOEpatents

Holcombe, C.E.; Masters, D.R.; Pfeiler, W.A.

1984-01-06

The present invention is directed to an induction furnace for melting and casting highly pure metals and alloys such as uranium and uranium alloys in such a manner as to minimize contamination of the melt by carbon derived from the materials and the environment within the furnace. The subject furnace is constructed of non-carbon materials and is housed within a conventional vacuum chamber. The furnace comprises a ceramic oxide crucible for holding the charge of metal or alloys. The heating of the crucible is achieved by a plasma-sprayed tungsten susceptor surrounding the crucible which, in turn, is heated by an rf induction coil separated from the susceptor by a cylinder of inorganic insulation. The furnace of the present invention is capable of being rapidly cycled from ambient temperatures to about 1650/sup 0/C for effectively melting uranium and uranium alloys without the attendant carbon contamination problems previously encountered when using carbon-bearing furnace materials.

Development of a portable therapeutic and high intensity ultrasound system for military, medical, and research use

PubMed Central

Lewis, George K.; Olbricht, William L.

2008-01-01

We have developed a portable high power ultrasound system with a very low output impedance amplifier circuit (less than 0.3 Ω) that can transfer more than 90% of the energy from a battery supply to the ultrasound transducer. The system can deliver therapeutic acoustical energy waves at lower voltages than those in conventional ultrasound systems because energy losses owing to a mismatched impedance are eliminated. The system can produce acoustic power outputs over the therapeutic range (greater then 50 W) from a PZT-4, 1.54 MHz, and 0.75 in diameter piezoelectric ceramic. It is lightweight, portable, and powered by a rechargeable battery. The portable therapeutic ultrasound unit has the potential to replace “plug-in” medical systems and rf amplifiers used in research. The system is capable of field service on its internal battery, making it especially useful for military, ambulatory, and remote medical applications. PMID:19045903

Production and characterization of large-area sputtered selective solar absorber coatings

NASA Astrophysics Data System (ADS)

Graf, Wolfgang; Koehl, Michael; Wittwer, Volker

1992-11-01

Most of the commercially available selective solar absorber coatings are produced by electroplating. Often the reproducibility or the durability of their optical properties is not very satisfying. Good reproducibility can be achieved by sputtering, the technique for the production of low-(epsilon) coatings for windows. The suitability of this kind of deposition technique for flat-plate solar absorber coatings based on the principle of ceramic/metal composites was investigated for different material combinations, and prototype collectors were manufactured. The optical characterization of the coatings is based on spectral measurements of the near-normal/hemispherical and the angle-dependent reflectance in the wavelength-range 0.38 micrometers - 17 micrometers . The durability assessment was carried out by temperature tests in ovens and climatic chambers.

Status of the Perpendicular Biased 2nd Harmonic Cavity for the Fermilab Booster

DOE PAGES

Tan, C. Y.; Dey, J. E.; Duel, K. L.; ...

2017-05-01

This is a status report on the 2nd harmonic cavity for the Fermilab Booster as part of the Proton Improvement Plan (PIP) for increasing beam transmission efficiency, and thus reducing losses. A set of tuner rings has been procured and is undergoing quality control tests. The Y567 tube for driving the cavity has been successfully tested at both injection and extraction frequencies. A cooling scheme for the tuner and cavity has been developed after a thorough thermal analysis of the system. RF windows have been procured and substantial progress has been made on the mechanical designs of the cavity andmore » the bias solenoid. Finally, the goal is to have a prototype cavity ready for testing by the end of 2017.« less

Status of the Perpendicular Biased 2nd Harmonic Cavity for the Fermilab Booster

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

Tan, C. Y.; Dey, J. E.; Duel, K. L.

This is a status report on the 2nd harmonic cavity for the Fermilab Booster as part of the Proton Improvement Plan (PIP) for increasing beam transmission efficiency, and thus reducing losses. A set of tuner rings has been procured and is undergoing quality control tests. The Y567 tube for driving the cavity has been successfully tested at both injection and extraction frequencies. A cooling scheme for the tuner and cavity has been developed after a thorough thermal analysis of the system. RF windows have been procured and substantial progress has been made on the mechanical designs of the cavity andmore » the bias solenoid. Finally, the goal is to have a prototype cavity ready for testing by the end of 2017.« less

History of development of polycrystalline optical spinel in the U.S.

NASA Astrophysics Data System (ADS)

Harris, Daniel C.

2005-05-01

Optical quality polycrystalline spinel (MgAl2O4) has been sought as a visible- and infrared-transmitting material since the 1960s because of its potential for transparent armor and durable sensor windows. Its physical properties were known from synthetic crystals available since ~1950 from Linde Air Products. In the late 1960s, methods to process powder into transparent, polycrystalline spinel were investigated at North Carolina State University, General Electric Co., AVCO, and Westinghouse, mainly with Government support. The leading figure in the development of polycrystalline spinel was Don Roy, who began work on spinel at Coors Ceramics around 1970, initially for transparent armor. In the late 1970s, both Coors Ceramics and Raytheon Research Division were funded to make spinel for the infrared dome of the Advanced Short-Range Air-to-Air Missile, an application that disappeared by 1980. In the late 1980s, there was another burst of activity when spinel was a candidate for the Stinger Missile. By 1990, Raytheon had dropped spinel and the material was spun off by Coors Ceramics to Alpha Optical Systems, whose technical effort was led by Don Roy. With low commercial sales potential for spinel, Alpha was dissolved in 1993. RCS Technologies took over a Government contract seeking 200-mm spinel domes for the Harrier aircraft, but this effort ended in 1996 and RCS was dissolved. In 1998, the Army enlisted TA&T to make spinel for transparent armor. Other potential applications appeared and TA&T received numerous Government development contracts. Demand for the still-unavailable spinel drew Surmet to begin development in 2002. In early 2005, spinel is under active development at TA&T and Surmet.

Do radio frequencies of medical instruments common in the operating room interfere with near-infrared spectroscopy signals?

NASA Astrophysics Data System (ADS)

Shadgan, Babak; Molavi, Behnam; Reid, W. D.; Dumont, Guy; Macnab, Andrew J.

2010-02-01

Background: Medical and diagnostic applications of near infrared spectroscopy (NIRS) are increasing, especially in operating rooms (OR). Since NIRS is an optical technique, radio frequency (RF) interference from other instruments is unlikely to affect the raw optical data, however, NIRS data processing and signal output could be affected. Methods: We investigated the potential for three common OR instruments: an electrical cautery, an orthopaedic drill and an imaging system, to generate electromagnetic interference (EMI) that could potentially influence NIRS signals. The time of onset and duration of every operation of each device was recorded during surgery. To remove the effects of slow changing physiological variables, we first used a lowpass filter and then selected 2 windows with variable lengths around the moment of device onset. For each instant, variances (energy) and means of the signals in the 2 windows were compared. Results: Twenty patients were studied during ankle surgery. Analysis shows no statistically significant difference in the means and variance of the NIRS signals (p < 0.01) during operation of any of the three devices for all surgeries. Conclusion: This method confirms the instruments evaluated caused no significant interference. NIRS can potentially be used without EMI in clinical environments such as the OR.

High field side launch of RF waves: A new approach to reactor actuators

NASA Astrophysics Data System (ADS)

Wallace, G. M.; Baek, S. G.; Bonoli, P. T.; Faust, I. C.; LaBombard, B. L.; Lin, Y.; Mumgaard, R. T.; Parker, R. R.; Shiraiwa, S.; Vieira, R.; Whyte, D. G.; Wukitch, S. J.

2015-12-01

Launching radio frequency (RF) waves from the high field side (HFS) of a tokamak offers significant advantages over low field side (LFS) launch with respect to both wave physics and plasma material interactions (PMI). For lower hybrid (LH) waves, the higher magnetic field opens the window between wave accessibility (n∥≡c k∥/ω >√{1 -ωpi 2/ω2+ωpe 2/ωce 2 }+ωp e/|ωc e| ) and the condition for strong electron Landau damping (n∥˜√{30 /Te } with Te in keV), allowing LH waves from the HFS to penetrate into the core of a burning plasma, while waves launched from the LFS are restricted to the periphery of the plasma. The lower n∥ of waves absorbed at higher Te yields a higher current drive efficiency as well. In the ion cyclotron range of frequencies (ICRF), HFS launch allows for direct access to the mode conversion layer where mode converted waves absorb strongly on thermal electrons and ions, thus avoiding the generation of energetic minority ion tails. The absence of turbulent heat and particle fluxes on the HFS, particularly in double null configuration, makes it the ideal location to minimize PMI damage to the antenna structure. The quiescent SOL also eliminates the need to couple LH waves across a long distance to the separatrix, as the antenna can be located close to plasma without risking damage to the structure. Improved impurity screening on the HFS will help eliminate the long-standing issues of high Z impurity accumulation with ICRF. Looking toward a fusion reactor, the HFS is the only possible location for a plasma-facing RF antenna that will survive long-term. By integrating the antenna into the blanket module it is possible to improve the tritium breeding ratio compared with an antenna occupying an equatorial port plug. Blanket modules will require remote handling of numerous cooling pipes and electrical connections, and the addition of transmission lines will not substantially increase the level of complexity. The obvious engineering challenges associated with locating antenna structures on the HFS can be overcome if HFS antennas are incorporated in the overall experimental design from the start. The Advanced Divertor and radio frequency eXperiment(ADX) will include LH and ICRF antennas located on the HFS. Compact antenna designs based on proven technologies (e.g. multi-junction and "4-way splitter" antennas) fit within the available space on the HFS of ADX. Field aligned ICRF antennas are also located on the HFS. The ADX vacuum vessel design includes dedicated space for transmission lines, pressure windows, and vacuum feedthrus for accessing the HFS wall.

Experimental results of the 140 GHz, 1 MW long-pulse gyrotron for W7-X

NASA Astrophysics Data System (ADS)

Koppenburg, K.; Arnold, A.; Borie, E.; Dammertz, G.; Giguet, E.; Heidinger, R.; Illy, S.; Kuntze, M.; Le Cloarec, G.; Legrand, F.; Leonhardt, W.; Lievin, C.; Neffe, G.; Piosczyk, B.; Schmid, M.; Thumm, M.

2003-02-01

Gyrotrons at high frequency with high output power are mainly developed for microwave heating and current drive in plasmas for thermonuclear fusion. For the stellarator Wendelstein 7-X now under construction at IPP Greifswald, Germany, a 10 MW ECRH system is foreseen. A 1 MW, 140 GHz long-pulse gyrotron has been designed and a pre-prototype (Maquette) has been constructed and tested in an European collaboration between FZK Karlsruhe, CRPP Lausanne, IPF Suttgart, IPP Greifswald, CEA Cadarache and TED Vélizy [1]. The cylindrical cavity is designed for operating in the TE28,8 mode. It is a standard tapered cavity with linear input downtaper and a non-linear uptaper. The diameter of the cylindrical part is 40.96 mm. The transitions between tapers and straight section are smoothly rounded to avoid mode conversion. The TE28,8-cavity mode is transformed to a Gaussian TEM0,0 output mode by a mode converter consisting of a rippled-wall waveguide launcher followed by a three mirror system. The output window uses a single, edge cooled CVD-diamond disk with an outer diameter of 106 mm, a window aperture of 88 mm and a thickness of 1.8 mm corresponding to four half wavelengths. The collector is at ground potential, and a depression voltage for energy recovery can be applied to the cavity and to the first two mirrors. Additional normal-conducting coils are employed to the collector in order to produce an axial magnetic field for sweeping the electron beam with a frequency of 7 Hz. A temperature limited magnetron injection gun without intermediate anode ( diode type ) is used. In short pulse operation at the design current of 40 A an output power of 1 MW could be achieved for an accelerating voltage of 82 kV without depression voltage and with a depression voltage of 25 kV an output power of 1.15 MW at an accelerating voltage of 84 kV has been measured. For these values an efficiency of 49% was obtained. At constant accelerating voltages, the output power did not change up to depression voltages of 33 kV. The output beam of the gyrotron is injected into an RF-tight microwave chamber which is equipped with two water-cooled mirrors directing the beam towards the 1 MW water load. The second mirror inside the microwave chamber contains a directional output coupler formed by a row of holes in the mirror surface. A diode detector is connected to the directional coupler and the forward power can be determined once the signal has been calibrated. This was performed by calorimetric measurement of the RF wave in short-pulse measurements. The mode purity of the Gaussian beam was measured by an IR camera and a thin dielectric target plate placed at different positions across the RF beam. The measured beam distribution agrees very well with the theoretical predictions. After some problems with the RF load, long-pulse operation was performed: The power measurements were done by the signal of the diode detector placed at the second mirror. The measured output power of the calorimetric RF-load normally shows values reduced by about 20%. Output powers of 1 MW could be achieved for 10 s, and an energy as high as 90 MJ per pulse has been produced with an output power of 0.64 MW. The pulse lengths were mainly determined by the preset values, and due to lack of experimental time no attempt was made to increase the pulse length. Only for a 100 s pulse with 0.74 MW output power, a limitation was found due to a pressure increase beyond about 10-7mbar. The gyrotron was sent back to the manufacturer Thales Electron Devices for a visual inspection, and an improved prototype was built and delivered to Forschungszentrum Karlsruhe in the middle of April 2002.

3D ultrasound Nakagami imaging for radiation-induced vaginal fibrosis

NASA Astrophysics Data System (ADS)

Yang, Xiaofeng; Rossi, Peter; Shelton, Joseph; Bruner, Debrorah; Tridandapani, Srini; Liu, Tian

2014-03-01

Radiation-induced vaginal fibrosis is a debilitating side-effect affecting up to 80% of women receiving radiotherapy for their gynecological (GYN) malignancies. Despite the significant incidence and severity, little research has been conducted to identify the pathophysiologic changes of vaginal toxicity. In a previous study, we have demonstrated that ultrasound Nakagami shape and PDF parameters can be used to quantify radiation-induced vaginal toxicity. These Nakagami parameters are derived from the statistics of ultrasound backscattered signals to capture the physical properties (e.g., arrangement and distribution) of the biological tissues. In this paper, we propose to expand this Nakagami imaging concept from 2D to 3D to fully characterize radiation-induced changes to the vaginal wall within the radiation treatment field. A pilot study with 5 post-radiotherapy GYN patients was conducted using a clinical ultrasound scanner (6 MHz) with a mechanical stepper. A serial of 2D ultrasound images, with radio-frequency (RF) signals, were acquired at 1 mm step size. The 2D Nakagami shape and PDF parameters were calculated from the RF signal envelope with a sliding window, and then 3D Nakagami parameter images were generated from the parallel 2D images. This imaging method may be useful as we try to monitor radiation-induced vaginal injury, and address vaginal toxicities and sexual dysfunction in women after radiotherapy for GYN malignancies.

Interlock system for machine protection of the KOMAC 100-MeV proton linac

NASA Astrophysics Data System (ADS)

Song, Young-Gi

2015-02-01

The 100-MeV proton linear accelerator of the Korea Multi-purpose Accelerator Complex (KOMAC) has been developed. The beam service started this year after performing the beam commissioning. If the very sensitive and essential equipment is to be protected during machine operation, a machine interlock system is required, and the interlock system has been implemented. The purpose of the interlock system is to shut off the beam when the radio-frequency (RF) and ion source are unstable or a beam loss occurs. The interlock signal of the KOMAC linac includes a variety of sources, such as the beam loss, RF and high-voltage converter modulator faults, and fast closing valves of the vacuum window at the beam lines and so on. This system consists of a hardware-based interlock system using analog circuits and a software-based interlock system using an industrial programmable logic controller (PLC). The hardware-based interlock system has been fabricated, and the requirement has been satisfied with the results being within 10 µs. The software logic interlock system using the PLC has been connected to the framework of with the experimental physics and industrial control system (EPICS) to integrate a variety of interlock signals and to control the machine components when an interlock occurs. This paper will describe the design and the construction of the machine interlock system for the KOMAC 100-MeV linac.

Neutron resonance spin-echo upgrade at the three-axis spectrometer FLEXX

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

Groitl, F., E-mail: felix.groitl@psi.ch; Quintero-Castro, D. L.; Habicht, K.

2015-02-15

We describe the upgrade of the neutron resonance spin-echo setup at the cold neutron triple-axis spectrometer FLEXX at the BER II neutron source at the Helmholtz-Zentrum Berlin. The parameters of redesigned key components are discussed, including the radio frequency (RF) spin-flip coils, the magnetic shield, and the zero field coupling coils. The RF-flippers with larger beam windows allow for an improved neutron flux transfer from the source to the sample and further to the analyzer. The larger beam cross sections permit higher coil inclination angles and enable measurements on dispersive excitations with a larger slope of the dispersion. Due tomore » the compact design of the spin-echo units in combination with the increased coil tilt angles, the accessible momentum-range in the Larmor diffraction mode is substantially enlarged. In combination with the redesigned components of the FLEXX spectrometer, including the guide, the S-bender polarizer, the double focusing monochromator, and a Heusler crystal analyzer, the count rate increased by a factor of 15.5, and the neutron beam polarization is enhanced. The improved performance extends the range of feasible experiments, both for inelastic scattering on excitation lifetimes in single crystals, and for high-resolution Larmor diffraction. The experimental characterization of the instrument components demonstrates the reliable performance of the new neutron resonance spin-echo option, now available for the scientific community at FLEXX.« less

Artificial ionospheric modification: The Metal Oxide Space Cloud experiment

NASA Astrophysics Data System (ADS)

Caton, Ronald G.; Pedersen, Todd R.; Groves, Keith M.; Hines, Jack; Cannon, Paul S.; Jackson-Booth, Natasha; Parris, Richard T.; Holmes, Jeffrey M.; Su, Yi-Jiun; Mishin, Evgeny V.; Roddy, Patrick A.; Viggiano, Albert A.; Shuman, Nicholas S.; Ard, Shaun G.; Bernhardt, Paul A.; Siefring, Carl L.; Retterer, John; Kudeki, Erhan; Reyes, Pablo M.

2017-05-01

Clouds of vaporized samarium (Sm) were released during sounding rocket flights from the Reagan Test Site, Kwajalein Atoll in May 2013 as part of the Metal Oxide Space Cloud (MOSC) experiment. A network of ground-based sensors observed the resulting clouds from five locations in the Republic of the Marshall Islands. Of primary interest was an examination of the extent to which a tailored radio frequency (RF) propagation environment could be generated through artificial ionospheric modification. The MOSC experiment consisted of launches near dusk on two separate evenings each releasing 6 kg of Sm vapor at altitudes near 170 km and 180 km. Localized plasma clouds were generated through a combination of photoionization and chemi-ionization (Sm + O → SmO+ + e-) processes producing signatures visible in optical sensors, incoherent scatter radar, and in high-frequency (HF) diagnostics. Here we present an overview of the experiment payloads, document the flight characteristics, and describe the experimental measurements conducted throughout the 2 week launch window. Multi-instrument analysis including incoherent scatter observations, HF soundings, RF beacon measurements, and optical data provided the opportunity for a comprehensive characterization of the physical, spectral, and plasma density composition of the artificial plasma clouds as a function of space and time. A series of companion papers submitted along with this experimental overview provide more detail on the individual elements for interested readers.

Experiments with planar inductive ion source meant for creation of H+ beams.

PubMed

Vainionpaa, J H; Kalvas, T; Hahto, S K; Reijonen, J

2007-06-01

In this article the effects of different engineering parameters of rf-driven ion sources with an external spiral antenna and a quartz rf window are studied. This article consists of three main topics: the effect of source geometry on the operation gas pressure, the effect of source materials and magnetic confinement on extracted current density and ion species, and the effect of different antenna geometries on the extracted current density. The effect of source geometry was studied using three cylindrical plasma chambers with different inner diameters. The chamber materials were studied using two materials, aluminum (Al) and alumina (Al(2)O(3)). The removable 14 magnet multicusp confinement arrangement enabled us to compare the effects of the two wall materials with and without the magnetic confinement. The highest measured proton fractions were measured using Al(2)O(3) plasma chamber and no multicusp confinement. For the compared ion sources the source with multicusp confinement and Al(2)O(3) plasma chamber yields the highest current densities. Multicusp confinement increased the maximum extracted current by up to a factor of 2. Plasma production with different antenna geometries were also studied. The highest current density was achieved using 4.5 loop solenoid antenna with 6.0 cm diameter. A slightly lower current density with lower pressure was achieved using a tightly wound 3 loop spiral antenna with 3.3 cm inner diameter and 6 cm outer diameter.

Innovative ceramic slab lasers for high power laser applications

NASA Astrophysics Data System (ADS)

Lapucci, Antonio; Ciofini, Marco

2005-09-01

Diode Pumped Solid State Lasers (DPSSL) are gaining increasing interest for high power industrial application, given the continuous improvement in high power diode laser technology reliability and affordability. These sources open new windows in the parameter space for traditional applications such as cutting , welding, marking and engraving for high reflectance metallic materials. Other interesting applications for this kind of sources include high speed thermal printing, precision drilling, selective soldering and thin film etching. In this paper we examine the most important DPSS laser source types for industrial applications and we describe in details the performances of some slab laser configurations investigated at our facilities. The different architectures' advantages and draw-backs are briefly compared in terms of performances, system complexity and ease of scalability to the multi-kW level.

Infrared and Raman spectroscopy study of AsS chalcogenide films prepared by plasma-enhanced chemical vapor deposition.

PubMed

Mochalov, Leonid; Dorosz, Dominik; Kudryashov, Mikhail; Nezhdanov, Aleksey; Usanov, Dmitry; Gogova, Daniela; Zelentsov, Sergey; Boryakov, Aleksey; Mashin, Alexandr

2018-03-15

AsS chalcogenide films, where As content is 60-40at.%, have been prepared via a RF non-equilibrium low-temperature argon plasma discharge, using volatile As and S as the precursors. Optical properties of the films were studied in UV-visible-NIR region in the range from 0.2 to 2.5μm. Infrared and Raman spectroscopy have been employed for the elucidation of the molecular structure of the newly developed material. It was established that PECVD films possess a higher degree of transparency (up to 80%) and a wider transparency window (>20μm) in comparison with the "usual" AsS thin films, prepared by different thermal methods, which is highly advantageous for certain applications. Copyright © 2017 Elsevier B.V. All rights reserved.

NMOS contact resistance reduction with selenium implant into NiPt silicide

NASA Astrophysics Data System (ADS)

Rao, K. V.; Khaja, F. A.; Ni, C. N.; Muthukrishnan, S.; Darlark, A.; Lei, J.; Peidous, I.; Brand, A.; Henry, T.; Variam, N.; Erokhin, Y.

2012-11-01

A 25% reduction in NMOS contact resistance (Rc) was achieved by Selenium implantation into NiPt silicide film in VIISta Trident high-current single-wafer implanter. The Trident implanter is designed for shallow high-dose implants with high beam currents to maintain high throughput (for low CoO), with improved micro-uniformity and no energy contamination. The integration of Se implant was realized using a test chip dedicated to investigating silicide/junction related electrical properties and testable after silicidation. The silicide module processes were optimized, including the pre-clean (prior to RF PVD NiPt dep) and pre- and post-implant anneals. A 270°C soak anneal was used for RTP1, whereas a msec laser anneal was employed for RTP2 with sufficient process window (800-850°C), while maintaining excellent junction characteristics without Rs degradation.

Use of sol-gels as solid matrixes for simultaneous multielement determination by radio frequency glow discharge optical emission spectrometry: determinations of suspended particulate matter.

PubMed

Davis, W Clay; Knippel, Brad C; Cooper, Julia E; Spraul, Bryan K; Rice, Jeanette K; Smith, Dennis W; Marcus, R Kenneth

2003-05-15

A new approach for the analysis of particulate matter by radio frequency glow discharge optical emission spectrometry (rf-GD-OES) is described. Dispersion of the particles in a sol-gel sample matrix provides a convenient means of generating a thin film suitable for sputter-sampling into the discharge. Acid-catalyzed sol-gel glasses synthesized from tetramethyl orthosilicate were prepared and spun-cast on glass substrates. The resultant thin films on glass substrates were analyzed to determine the discharge operating conditions and resultant sputtering characteristics while a number of optical emission lines of the film components were monitored. Slurries of powdered standard reference materials NIST SRM 1884a (Portland Cement) and NIST SRM 2690 (Coal Fly Ash) dispersed in the sols were cast into films in the same manner. Use of the sol-gels as sample matrixes allows for background subtraction through the use of analytical blanks and may facilitate the generation of calibration curves via readily synthesized, matrix-matched analytical standards in solids analysis. Detection limits were determined for minor elements via the RSDB method to be in the range of 1-10 microg/g in Portland Cement and Coal Fly Ash samples for the elements Al, Fe, Mg, S, and Si. Values for Ca were in the range of 15-35 microg/g. This preliminary study demonstrates the possibility of incorporating various insoluble species, including ceramics and geological specimens in powder form, into a solid matrix for further analysis by either rf-GD-OES or MS.

Metal oxide nanostructures for gas detection

NASA Astrophysics Data System (ADS)

Maziarz, Wojciech; Pisarkiewicz, Tadeusz; Rydosz, Artur; Wysocka, Kinga; Czyrnek, Grzegorz

2013-07-01

Currently, most of gas sensors on the market are produced in thin or thick film technologies with the use of ceramic substrates. It is expected that the miniature sensors needed in portable applications will be based on one-dimensional structures due to their low power consumption, fast and stable time response, small dimensions and possibility of embedding in integrated circuit together with signal conditioning electronics. The authors manufactured resistance type gas sensors based on ZnO and WO3 nanostructures. ZnO:Al nanorods with good cristallinity were obtained with electrodeposition method, while ZnO:Al nanofibres with varying diameters were obtained by electrospinning method. The sensors were built as a nanowire network. WO3 films with nanocrystalline surface were manufactured by deposition of a three layer WO3/W/WO3 structure by RF sputtering and successive annealing of the structure in appropriate temperature range. In effect a uniform nanostructurized metal oxide layer was formed. Investigation of sensors characteristics revealed good sensitivity to nitrogen dioxide at temperatures lower than these for conventional conductometric type sensors.

Flexoelectricity in barium strontium titanate thin film

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

Kwon, Seol Ryung; Huang, Wenbin; Yuan, Fuh-Gwo

2014-10-06

Flexoelectricity, the linear coupling between the strain gradient and the induced electric polarization, has been intensively studied as an alternative to piezoelectricity. Especially, it is of interest to develop flexoelectric devices on micro/nano scales due to the inherent scaling effect of flexoelectric effect. Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} thin film with a thickness of 130 nm was fabricated on a silicon wafer using a RF magnetron sputtering process. The flexoelectric coefficients of the prepared thin films were determined experimentally. It was revealed that the thin films possessed a transverse flexoelectric coefficient of 24.5 μC/m at Curie temperature (∼28 °C) and 17.44 μC/m at 41 °C. Themore » measured flexoelectric coefficients are comparable to that of bulk BST ceramics, which are reported to be 10–100 μC/m. This result suggests that the flexoelectric thin film structures can be effectively used for micro/nano-sensing devices.« less

Recent advancements in supporting materials for immobilised photocatalytic applications in waste water treatment.

PubMed

Srikanth, B; Goutham, R; Badri Narayan, R; Ramprasath, A; Gopinath, K P; Sankaranarayanan, A R

2017-09-15

The aim of this paper is to provide a review on the usage of different anchoring media (supports) for immobilising commonly employed photocatalysts for degradation of organic pollutants. The immobilisation of nano-sized photocatalysts can eliminate costly and impractical post-treatment recovery of spent photocatalysts in largescale operations. Some commonly employed immobilisation aids such as glass, carbonaceous substances, zeolites, clay and ceramics, polymers, cellulosic materials and metallic agents that have been previously discussed by various research groups have been reviewed. The study revealed that factors such as high durability, ease of availability, low density, chemical inertness and mechanical stability are primary factors responsible for the selection of suitable supports for catalysts. Common techniques for immobilisation namely, dip coating, cold plasma discharge, polymer assisted hydrothermal decomposition, RF magnetron sputtering, photoetching, solvent casting, electrophoretic deposition and spray pyrolysis have been discussed in detail. Finally, some common techniques adopted for the characterisation of the catalyst particles and their uses are also discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

The oxidation of TaBe sub 12 and NbBe sub 12 coatings on niobium

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

Courtright, E.L.

1990-01-01

The oxidation behavior of tantalum and niobium beryllide coatings on niobium were evaluated. Intermetallic bond layers consisting of Ir{sub 3}Ta and Ir{sub 3}Nb were used to butter the large thermal expansion mismatch between the beryllide coatings and underlying niobium substrate. All coatings were applied by Triode Sputtering except for a final environmental protection layer of stabilized zirconia deposited by RF Diode using a ceramic target. Severe delamination and spalling occurred during cyclic oxidation exposure, even at temperatures as low as 925{degrees}C, indicating that the bond layer did not prevent the differential expansion stresses from reaching the delamination failure threshold, particularlymore » at the edges and corners. Hot pressed samples of the two beryllide compounds were also exposed to a similar cyclic oxidation history, but, in contrast to the coatings, exhibited excellent oxidation resistance to temperatures as high as 1370{degrees}C. 9 refs., 8 figs., 1 tab.« less

Next Generation H- Ion Sources for the SNS

NASA Astrophysics Data System (ADS)

Welton, R. F.; Stockli, M. P.; Murray, S. N.; Crisp, D.; Carmichael, J.; Goulding, R. H.; Han, B.; Tarvainen, O.; Pennisi, T.; Santana, M.

2009-03-01

The U.S. Spallation Neutron Source (SNS) is the leading accelerator-based, pulsed neutron-scattering facility, currently in the process of ramping up neutron production. In order to insure meeting operational requirements as well as providing for future facility beam power upgrades, a multifaceted H- ion source development program is ongoing. This work discusses several aspects of this program, specifically the design and first beam measurements of an RF-driven, external antenna H- ion source based on an A1N ceramic plasma chamber, elemental and chromate Cs-systems, and plasma ignition gun. Unanalyzed beam currents of up to ˜100 mA (60 Hz, 1 ms) have been observed and sustained currents >60 mA (60 Hz, 1 ms) have been demonstrated on the test stand. Accelerated beam currents of ˜40 mA have also been demonstrated into the SNS front end. Data are also presented describing the first H- beam extraction experiments from a helicon plasma generator based on the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine design.

An anion-immobilized composite electrolyte for dendrite-free lithium metal anodes

PubMed Central

Zhao, Chen-Zi; Zhang, Xue-Qiang; Cheng, Xin-Bing; Zhang, Rui; Xu, Rui; Chen, Peng-Yu; Peng, Hong-Jie; Huang, Jia-Qi

2017-01-01

Lithium metal is strongly regarded as a promising electrode material in next-generation rechargeable batteries due to its extremely high theoretical specific capacity and lowest reduction potential. However, the safety issue and short lifespan induced by uncontrolled dendrite growth have hindered the practical applications of lithium metal anodes. Hence, we propose a flexible anion-immobilized ceramic–polymer composite electrolyte to inhibit lithium dendrites and construct safe batteries. Anions in the composite electrolyte are tethered by a polymer matrix and ceramic fillers, inducing a uniform distribution of space charges and lithium ions that contributes to a dendrite-free lithium deposition. The dissociation of anions and lithium ions also helps to reduce the polymer crystallinity, rendering stable and fast transportation of lithium ions. Ceramic fillers in the electrolyte extend the electrochemically stable window to as wide as 5.5 V and provide a barrier to short circuiting for realizing safe batteries at elevated temperature. The anion-immobilized electrolyte can be applied in all–solid-state batteries and exhibits a small polarization of 15 mV. Cooperated with LiFePO4 and LiNi0.5Co0.2Mn0.3O2 cathodes, the all–solid-state lithium metal batteries render excellent specific capacities of above 150 mAh⋅g−1 and well withstand mechanical bending. These results reveal a promising opportunity for safe and flexible next-generation lithium metal batteries. PMID:28973945

Terahop and Lawrence Livermore National LaboratoryStructural Fire RF Testing

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

Haugen, P; Pratt, G

The Georgia Public Safety Training Center's Live Fire Training Facility in Forsyth, GA is a three story structure constructed of rebar-reinforced concrete wall and floors. All the door and window coverings on the building are constructed of thick, plate metal to withstand the high temperatures generated inside the building during training exercises. All of the building's walls and floors are 1-foot thick, and regular concrete columns run up along the inside of the wall increasing the thickness to 20-inches in those locations. A center concrete staircase divides the structure in half. For typical exercises, fires are started in the backmore » right corner of the building on the first floor and in the front right corner on the second floor as shown in Figure 2. Due to the high heat generated during these exercises, measured at 300 F on the floor and 700 F near the ceilings, there were limited locations at which equipment could be placed that did not incorporate heat shielding, such as the Lawrence Livermore National Laboratory's UWB system. However, upon inspection of the building, two preferable locations were identified in which equipment could be placed that would be protected from the temperature extremes generated by the fires. These locations are identified in Figure 2 as the tested TX locations. These were preferred locations because, while they protected the hardware from temperature extremes, they also force the RF transmission path through the building to cross very near the fire locations and anticipated plasma generation regions. Both of the locations listed in Figure 2 were tested by the UWB equipment and found to be suitable deployment locations to establish a solid RF link for data collection. The transmission location on the first floor was ultimately chosen for use during the actual exercises because it was accessible to the data collection team during the exercises. This allowed them to remove the hardware once the testing was complete without having to wait for the entire day of exercises to complete. Unfortunately, RF transmission directly through the central location of the fire on the first floor was not possible, so the transmission path had to be shifted approximately 6-feet off the side of the fire's center. The corner where the fire was located on the first floor was re-enforced with a mixture of concrete and metal fibers for heat resistance. This material was highly reflective, permitting very little RF energy to pass through it. This phenomenon was also observed and verified by Terahop's testing, discussed in the next section. An image of these re-enforced walls and a close up of the actual wall material containing the metal fibers can bee seen in Figure 3.« less

The sonic window: second generation results

NASA Astrophysics Data System (ADS)

Walker, William F.; Fuller, Michael I.; Brush, Edward V.; Eames, Matthew D. C.; Owen, Kevin; Ranganathan, Karthik; Blalock, Travis N.; Hossack, John A.

2006-03-01

Medical Ultrasound Imaging is widely used clinically because of its relatively low cost, portability, lack of ionizing radiation, and real-time nature. However, even with these advantages ultrasound has failed to permeate the broad array of clinical applications where its use could be of value. A prime example of this untapped potential is the routine use of ultrasound to guide intravenous access. In this particular application existing systems lack the required portability, low cost, and ease-of-use required for widespread acceptance. Our team has been working for a number of years to develop an extremely low-cost, pocket-sized, and intuitive ultrasound imaging system that we refer to as the "Sonic Window." We have previously described the first generation Sonic Window prototype that was a bench-top device using a 1024 element, fully populated array operating at a center frequency of 3.3 MHz. Through a high degree of custom front-end integration combined with multiplexing down to a 2 channel PC based digitizer this system acquired a full set of RF data over a course of 512 transmit events. While initial results were encouraging, this system exhibited limitations resulting from low SNR, relatively coarse array sampling, and relatively slow data acquisition. We have recently begun assembling a second-generation Sonic Window system. This system uses a 3600 element fully sampled array operating at 5.0 MHz with a 300 micron element pitch. This system extends the integration of the first generation system to include front-end protection, pre-amplification, a programmable bandpass filter, four sample and holds, and four A/D converters for all 3600 channels in a set of custom integrated circuits with a combined area smaller than the 1.8 x 1.8 cm footprint of the transducer array. We present initial results from this front-end and present benchmark results from a software beamformer implemented on the Analog Devices BF-561 DSP. We discuss our immediate plans for further integration and testing. This second prototype represents a major reduction in size and forms the foundation of a fully functional, fully integrated, pocket sized prototype.

Multiple conversion between the genes encoding bacterial class-I release factors

PubMed Central

Ishikawa, Sohta A.; Kamikawa, Ryoma; Inagaki, Yuji

2015-01-01

Bacteria require two class-I release factors, RF1 and RF2, that recognize stop codons and promote peptide release from the ribosome. RF1 and RF2 were most likely established through gene duplication followed by altering their stop codon specificities in the common ancestor of extant bacteria. This scenario expects that the two RF gene families have taken independent evolutionary trajectories after the ancestral gene duplication event. However, we here report two independent cases of conversion between RF1 and RF2 genes (RF1-RF2 gene conversion), which were severely examined by procedures incorporating the maximum-likelihood phylogenetic method. In both cases, RF1-RF2 gene conversion was predicted to occur in the region encoding nearly entire domain 3, of which functions are common between RF paralogues. Nevertheless, the ‘direction’ of gene conversion appeared to be opposite from one another—from RF2 gene to RF1 gene in one case, while from RF1 gene to RF2 gene in the other. The two cases of RF1-RF2 gene conversion prompt us to propose two novel aspects in the evolution of bacterial class-I release factors: (i) domain 3 is interchangeable between RF paralogues, and (ii) RF1-RF2 gene conversion have occurred frequently in bacterial genome evolution. PMID:26257102

Status of Europe's contribution to the ITER EC system

NASA Astrophysics Data System (ADS)

Albajar, F.; Aiello, G.; Alberti, S.; Arnold, F.; Avramidis, K.; Bader, M.; Batista, R.; Bertizzolo, R.; Bonicelli, T.; Braunmueller, F.; Brescan, C.; Bruschi, A.; von Burg, B.; Camino, K.; Carannante, G.; Casarin, V.; Castillo, A.; Cauvard, F.; Cavalieri, C.; Cavinato, M.; Chavan, R.; Chelis, J.; Cismondi, F.; Combescure, D.; Darbos, C.; Farina, D.; Fasel, D.; Figini, L.; Gagliardi, M.; Gandini, F.; Gantenbein, G.; Gassmann, T.; Gessner, R.; Goodman, T. P.; Gracia, V.; Grossetti, G.; Heemskerk, C.; Henderson, M.; Hermann, V.; Hogge, J. P.; Illy, S.; Ioannidis, Z.; Jelonnek, J.; Jin, J.; Kasparek, W.; Koning, J.; Krause, A. S.; Landis, J. D.; Latsas, G.; Li, F.; Mazzocchi, F.; Meier, A.; Moro, A.; Nousiainen, R.; Purohit, D.; Nowak, S.; Omori, T.; van Oosterhout, J.; Pacheco, J.; Pagonakis, I.; Platania, P.; Poli, E.; Preis, A. K.; Ronden, D.; Rozier, Y.; Rzesnicki, T.; Saibene, G.; Sanchez, F.; Sartori, F.; Sauter, O.; Scherer, T.; Schlatter, C.; Schreck, S.; Serikov, A.; Siravo, U.; Sozzi, C.; Spaeh, P.; Spichiger, A.; Strauss, D.; Takahashi, K.; Thumm, M.; Tigelis, I.; Vaccaro, A.; Vomvoridis, J.; Tran, M. Q.; Weinhorst, B.

2015-03-01

The electron cyclotron (EC) system of ITER for the initial configuration is designed to provide 20MW of RF power into the plasma during 3600s and a duty cycle of up to 25% for heating and (co and counter) non-inductive current drive, also used to control the MHD plasma instabilities. The EC system is being procured by 5 domestic agencies plus the ITER Organization (IO). F4E has the largest fraction of the EC procurements, which includes 8 high voltage power supplies (HVPS), 6 gyrotrons, the ex-vessel waveguides (includes isolation valves and diamond windows) for all launchers, 4 upper launchers and the main control system. F4E is working with IO to improve the overall design of the EC system by integrating consolidated technological advances, simplifying the interfaces, and doing global engineering analysis and assessments of EC heating and current drive physics and technology capabilities. Examples are the optimization of the HVPS and gyrotron requirements and performance relative to power modulation for MHD control, common qualification programs for diamond window procurements, assessment of the EC grounding system, and the optimization of the launcher steering angles for improved EC access. Here we provide an update on the status of Europe's contribution to the ITER EC system, and a summary of the global activities underway by F4E in collaboration with IO for the optimization of the subsystems.

Windowed R-PDLF recoupling: a flexible and reliable tool to characterize molecular dynamics.

PubMed

Gansmüller, Axel; Simorre, Jean-Pierre; Hediger, Sabine

2013-09-01

This work focuses on the improvement of the R-PDLF heteronuclear recoupling scheme, a method that allows quantification of molecular dynamics up to the microsecond timescale in heterogeneous materials. We show how the stability of the sequence towards rf-imperfections, one of the main sources of error of this technique, can be improved by the insertion of windows without irradiation into the basic elements of the symmetry-based recoupling sequence. The impact of this modification on the overall performance of the sequence in terms of scaling factor and homonuclear decoupling efficiency is evaluated. This study indicates the experimental conditions for which precise and reliable measurement of dipolar couplings can be obtained using the popular R18(1)(7) recoupling sequence, as well as alternative symmetry-based R sequences suited for fast MAS conditions. An analytical expression for the recoupled dipolar modulation has been derived that applies to a whole class of sequences with similar recoupling properties as R18(1)(7). This analytical expression provides an efficient and precise way to extract dipolar couplings from the experimental dipolar modulation curves. We hereby provide helpful tools and information for tailoring R-PDLF recoupling schemes to specific sample properties and hardware capabilities. This approach is particularly well suited for the study of materials with strong and heterogeneous molecular dynamics where a precise measurement of dipolar couplings is crucial. Copyright © 2013 Elsevier Inc. All rights reserved.

Environmental Management vitrification activities

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

Krumrine, P.H.

1996-05-01

Both the Mixed Waste and Landfill Stabilization Focus Areas as part of the Office of Technology Development efforts within the Department of Energy`s (DOE) Environmental Management (EM) Division have been developing various vitrification technologies as a treatment approach for the large quantities of transuranic (TRU), TRU mixed and Mixed Low Level Wastes that are stored in either landfills or above ground storage facilities. The technologies being developed include joule heated, plasma torch, plasma arc, induction, microwave, combustion, molten metal, and in situ methods. There are related efforts going into development glass, ceramic, and slag waste form windows of opportunity formore » the diverse quantities of heterogeneous wastes needing treatment. These studies look at both processing parameters, and long term performance parameters as a function of composition to assure that developed technologies have the right chemistry for success.« less

Solar heated fluidized bed gasification system

NASA Technical Reports Server (NTRS)

Qader, S. A. (Inventor)

1981-01-01

A solar-powered fluidized bed gasification system for gasifying carbonaceous material is presented. The system includes a solar gasifier which is heated by fluidizing gas and steam. Energy to heat the gas and steam is supplied by a high heat capacity refractory honeycomb which surrounds the fluid bed reactor zone. The high heat capacity refractory honeycomb is heated by solar energy focused on the honeycomb by solar concentrator through solar window. The fluid bed reaction zone is also heated directly and uniformly by thermal contact of the high heat capacity ceramic honeycomb with the walls of the fluidized bed reactor. Provisions are also made for recovering and recycling catalysts used in the gasification process. Back-up furnace is provided for start-up procedures and for supplying heat to the fluid bed reaction zone when adequate supplies of solar energy are not available.

Plasma Physics Challenges of MM-to-THz and High Power Microwave Generation

NASA Astrophysics Data System (ADS)

Booske, John

2007-11-01

Homeland security and military defense technology considerations have stimulated intense interest in mobile, high power sources of millimeter-wave to terahertz regime electromagnetic radiation, from 0.1 to 10 THz. While sources at the low frequency end, i.e., the gyrotron, have been deployed or are being tested for diverse applications such as WARLOC radar and active denial systems, the challenges for higher frequency sources have yet to be completely met for applications including noninvasive sensing of concealed weapons and dangerous agents, high-data-rate communications, and high resolution spectroscopy and atmospheric sensing. The compact size requirements for many of these high frequency sources requires miniscule, micro-fabricated slow wave circuits with high rf ohmic losses. This necessitates electron beams with not only very small transverse dimensions but also very high current density for adequate gain. Thus, the emerging family of mm-to-THz e-beam-driven vacuum electronics devices share many of the same plasma physics challenges that currently confront ``classic'' high power microwave (HPM) generators [1] including bright electron sources, intense beam transport, energetic electron interaction with surfaces and rf air breakdown at output windows. Multidimensional theoretical and computational models are especially important for understanding and addressing these challenges. The contemporary plasma physics issues, recent achievements, as well as the opportunities and outlook on THz and HPM will be addressed. [1] R.J. Barker, J.H. Booske, N.C. Luhmann, and G.S. Nusinovich, Modern Microwave and Millimeter-Wave Power Electronics (IEEE/Wiley, 2005).

Seeing visual word forms: spatial summation, eccentricity and spatial configuration.

PubMed

Kao, Chien-Hui; Chen, Chien-Chung

2012-06-01

We investigated observers' performance in detecting and discriminating visual word forms as a function of target size and retinal eccentricity. The contrast threshold of visual words was measured with a spatial two-alternative forced-choice paradigm and a PSI adaptive method. The observers were to indicate which of two sides contained a stimulus in the detection task, and which contained a real character (as opposed to a pseudo- or non-character) in the discrimination task. When the target size was sufficiently small, the detection threshold of a character decreased as its size increased, with a slope of -1/2 on log-log coordinates, up to a critical size at all eccentricities and for all stimulus types. The discrimination threshold decreased with target size with a slope of -1 up to a critical size that was dependent on stimulus type and eccentricity. Beyond that size, the threshold decreased with a slope of -1/2 on log-log coordinates before leveling out. The data was well fit by a spatial summation model that contains local receptive fields (RFs) and a summation across these filters within an attention window. Our result implies that detection is mediated by local RFs smaller than any tested stimuli and thus detection performance is dominated by summation across receptive fields. On the other hand, discrimination is dominated by a summation within a local RF in the fovea but a cross RF summation in the periphery. Copyright © 2012 Elsevier Ltd. All rights reserved.

Optimization of a reversed-phase-high-performance thin-layer chromatography method for the separation of isoniazid, ethambutol, rifampicin and pyrazinamide in fixed-dose combination antituberculosis tablets.

PubMed

Shewiyo, D H; Kaale, E; Risha, P G; Dejaegher, B; Smeyers-Verbeke, J; Vander Heyden, Y

2012-10-19

This paper presents the development of a new RP-HPTLC method for the separation of pyrazinamide, isoniazid, rifampicin and ethambutol in a four fixed-dose combination (4 FDC) tablet formulation. It is a single method with two steps in which after plate development pyrazinamide, isoniazid and rifampicin are detected at an UV wavelength of 280 nm. Then ethambutol is derivatized and detected at a VIS wavelength of 450 nm. Methanol, ethanol and propan-1-ol were evaluated modifiers to form alcohol-water mobile phases. Systematic optimization of the composition of each alcohol in the mobile phase was carried out using the window diagramming concept to obtain the best separation. Examination of the Rf distribution of the separated compounds showed that separation of the compounds with the mobile phase containing ethanol at the optimal fraction was almost situated within the optimal Rf-values region of 0.20-0.80. Therefore, ethanol was selected as organic modifier and the optimal mobile phase composition was found to be ethanol, water, glacial acetic acid (>99% acetic acid) and 37% ammonia solution (70/30/5/1, v/v/v/v). The method is new, quick and cheap compared to the actual method in the International Pharmacopoeia for the assay of the 4 FDC tablets, which involves the use of two separate HPLC methods. Copyright © 2012 Elsevier B.V. All rights reserved.

Tasking and control of a squad of robotic vehicles

NASA Astrophysics Data System (ADS)

Lewis, Christopher L.; Feddema, John T.; Klarer, Paul

2001-09-01

Sandia National Laboratories have developed a squad of robotic vehicles as a test-bed for investigating cooperative control strategies. The squad consists of eight RATLER vehicles and a command station. The RATLERs are medium-sized all-electric vehicles containing a PC104 stack for computation, control, and sensing. Three separate RF channels are used for communications; one for video, one for command and control, and one for differential GPS corrections. Using DGPS and IR proximity sensors, the vehicles are capable of autonomously traversing fairly rough terrain. The control station is a PC running Windows NT. A GUI has been developed that allows a single operator to task and monitor all eight vehicles. To date, the following mission capabilities have been demonstrated: 1. Way-Point Navigation, 2. Formation Following, 3. Perimeter Surveillance, 4. Surround and Diversion, and 5. DGPS Leap Frog. This paper describes the system and briefly outlines each mission capability. The DGPS Leap Frog capability is discussed in more detail. This capability is unique in that it demonstrates how cooperation allows the vehicles to accurately navigate beyond the RF communication range. One vehicle stops and uses its corrected GPS position to re-initialize its receiver to become the DGPS correction station for the other vehicles. Error in position accumulates each time a new vehicle takes over the DGPS duties. The accumulation in error is accurately modeled as a random walk phenomenon. This paper demonstrates how useful accuracy can be maintained beyond the vehicle's range.

Plasma cleaning of ITER first mirrors

NASA Astrophysics Data System (ADS)

Moser, L.; Marot, L.; Steiner, R.; Reichle, R.; Leipold, F.; Vorpahl, C.; Le Guern, F.; Walach, U.; Alberti, S.; Furno, I.; Yan, R.; Peng, J.; Ben Yaala, M.; Meyer, E.

2017-12-01

Nuclear fusion is an extremely attractive option for future generations to compete with the strong increase in energy consumption. Proper control of the fusion plasma is mandatory to reach the ambitious objectives set while preserving the machine’s integrity, which requests a large number of plasma diagnostic systems. Due to the large neutron flux expected in the International Thermonuclear Experimental Reactor (ITER), regular windows or fibre optics are unusable and were replaced by so-called metallic first mirrors (FMs) embedded in the neutron shielding, forming an optical labyrinth. Materials eroded from the first wall reactor through physical or chemical sputtering will migrate and will be deposited onto mirrors. Mirrors subject to net deposition will suffer from reflectivity losses due to the deposition of impurities. Cleaning systems of metallic FMs are required in more than 20 optical diagnostic systems in ITER. Plasma cleaning using radio frequency (RF) generated plasmas is currently being considered the most promising in situ cleaning technique. An update of recent results obtained with this technique will be presented. These include the demonstration of cleaning of several deposit types (beryllium, tungsten and beryllium proxy, i.e. aluminium) at 13.56 or 60 MHz as well as large scale cleaning (mirror size: 200 × 300 mm2). Tests under a strong magnetic field up to 3.5 T in laboratory and first experiments of RF plasma cleaning in EAST tokamak will also be discussed. A specific focus will be given on repetitive cleaning experiments performed on several FM material candidates.

Multitarget detection algorithm for automotive FMCW radar

NASA Astrophysics Data System (ADS)

Hyun, Eugin; Oh, Woo-Jin; Lee, Jong-Hun

2012-06-01

Today, 77 GHz FMCW (Frequency Modulation Continuous Wave) radar has strong advantages of range and velocity detection for automotive applications. However, FMCW radar brings out ghost targets and missed targets in multi-target situations. In this paper, in order to resolve these limitations, we propose an effective pairing algorithm, which consists of two steps. In the proposed method, a waveform with different slopes in two periods is used. In the 1st pairing processing, all combinations of range and velocity are obtained in each of two wave periods. In the 2nd pairing step, using the results of the 1st pairing processing, fine range and velocity are detected. In that case, we propose the range-velocity windowing technique in order to compensate for the non-ideal beat-frequency characteristic that arises due to the non-linearity of the RF module. Based on experimental results, the performance of the proposed algorithm is improved compared with that of the typical method.

Numerical Design of Megawatt Gyrotron with 120 GHz Frequency and 50% Efficiency for Plasma Fusion Application

NASA Astrophysics Data System (ADS)

Kumar, Nitin; Singh, Udaybir; Kumar, Anil; Bhattacharya, Ranajoy; Singh, T. P.; Sinha, A. K.

2013-02-01

The design of 120 GHz, 1 MW gyrotron for plasma fusion application is presented in this paper. The mode selection is carried out considering the aim of minimum mode competition, minimum cavity wall heating, etc. On the basis of the selected operating mode, the interaction cavity design and beam-wave interaction computation are carried out by using the PIC code. The design of triode type Magnetron Injection Gun (MIG) is also presented. Trajectory code EGUN, synthesis code MIGSYN and data analysis code MIGANS are used in the MIG designing. Further, the design of MIG is also validated by using the another trajectory code TRAK. The design results of beam dumping system (collector) and RF window are also presented. Depressed collector is designed to enhance the overall tube efficiency. The design study confirms >1 MW output power with tube efficiency around 50% (with collector efficiency).

Self-consistent simulation of radio frequency multipactor on micro-grooved dielectric surface

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

Cai, Libing; Wang, Jianguo, E-mail: wanguiuc@mail.xjtu.edu.cn; Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024

2015-02-07

The multipactor plays a key role in the surface breakdown on the feed dielectric window irradiated by high power microwave. To study the suppression of multipactor, a 2D electrostatic PIC-MCC simulation code was developed. The space charge field, including surface deposited charge and multipactor electron charge field, is obtained by solving 2D Poisson's equation in time. Therefore, the simulation is self-consistent and does not require presetting a fixed space charge field. By using this code, the self-consistent simulation of the RF multipactor on the periodic micro-grooved dielectric surface is realized. The 2D space distributions of the multipactor electrons and spacemore » charge field are presented. From the simulation results, it can be found that only half slopes have multipactor discharge when the slope angle exceeds a certain value, and the groove presents a pronounced suppression effect on the multipactor.« less

Influence of gold nanoparticles on the 805 nm gain in Tm3+/Yb3+ codoped PbO-GeO2 pedestal waveguides

NASA Astrophysics Data System (ADS)

de Assumpção, T. A. A.; Camilo, M. E.; Alayo, M. I.; da Silva, D. M.; Kassab, L. R. P.

2017-10-01

The production and characterization of pedestal waveguides based on PbO-GeO2 amorphous thin films codoped with Tm3+/Yb3+, with and without gold nanoparticles (NPs), are reported. Pedestal structure was obtained by conventional photolithography and plasma etching. Tm3+/Yb3+ codoped PGO amorphous thin film was obtained by RF Magnetron Sputtering deposition and used as core layer in the pedestal optical waveguide. The minimum propagation losses in the waveguide were 3.6 dB/cm at 1068 nm. The internal gain at 805 nm was enhanced and increased to 8.67 dB due to the presence of gold NPs. These results demonstrate for the first time that Tm3+/Yb3+ codoped PbO-GeO2 waveguides are promising for first telecom window and integrated photonics, especially for applications on fiber network at short distances.

Agile lensing-based non-contact liquid level optical sensor for extreme environments

NASA Astrophysics Data System (ADS)

Reza, Syed Azer; Riza, Nabeel A.

2010-09-01

To the best of the author's knowledge, demonstrated is the first opto-fluidic technology- based sensor for detection of liquid levels. An opto-fluidic Electronically Controlled Variable Focus Lens (ECVFL) is used to change the spatial intensity profile of the low power optical beam falling on the liquid surface. By observing, tuning and measuring the liquid surface reflected intensity profile to reach its smallest size, the liquid level is determined through a beam spot size versus ECVFL focal length calibration table. Using a 50 μW 632.8 nm laser wavelength liquid illuminating beam, a proof-of-concept sensor is tested using engine oil, vegetable oil, and detergent fluid with measured liquid levels over a 75 cm range. This non-contact Radio Frequency (RF) modulation-free sensor is particularly suited for hazardous fluids in window-accessed sealed containers including liquid carrying vessels in Electromagnetic Interference (EMI) rich environments.

Structural insights into eRF3 and stop codon recognition by eRF1

PubMed Central

Cheng, Zhihong; Saito, Kazuki; Pisarev, Andrey V.; Wada, Miki; Pisareva, Vera P.; Pestova, Tatyana V.; Gajda, Michal; Round, Adam; Kong, Chunguang; Lim, Mengkiat; Nakamura, Yoshikazu; Svergun, Dmitri I.; Ito, Koichi; Song, Haiwei

2009-01-01

Eukaryotic translation termination is mediated by two interacting release factors, eRF1 and eRF3, which act cooperatively to ensure efficient stop codon recognition and fast polypeptide release. The crystal structures of human and Schizosaccharomyces pombe full-length eRF1 in complex with eRF3 lacking the GTPase domain revealed details of the interaction between these two factors and marked conformational changes in eRF1 that occur upon binding to eRF3, leading eRF1 to resemble a tRNA molecule. Small-angle X-ray scattering analysis of the eRF1/eRF3/GTP complex suggested that eRF1's M domain contacts eRF3's GTPase domain. Consistently, mutation of Arg192, which is predicted to come in close contact with the switch regions of eRF3, revealed its important role for eRF1's stimulatory effect on eRF3's GTPase activity. An ATP molecule used as a crystallization additive was bound in eRF1's putative decoding area. Mutational analysis of the ATP-binding site shed light on the mechanism of stop codon recognition by eRF1. PMID:19417105

Ion source with external RF antenna

DOEpatents

Leung, Ka-Ngo; Ji, Qing; Wilde, Stephen

2005-12-13

A radio frequency (RF) driven plasma ion source has an external RF antenna, i.e. the RF antenna is positioned outside the plasma generating chamber rather than inside. The RF antenna is typically formed of a small diameter metal tube coated with an insulator. An external RF antenna assembly is used to mount the external RF antenna to the ion source. The RF antenna tubing is wound around the external RF antenna assembly to form a coil. The external RF antenna assembly is formed of a material, e.g. quartz, which is essentially transparent to the RF waves. The external RF antenna assembly is attached to and forms a part of the plasma source chamber so that the RF waves emitted by the RF antenna enter into the inside of the plasma chamber and ionize a gas contained therein. The plasma ion source is typically a multi-cusp ion source.

Radiofrequency Thermal Ablation: Increase in Lesion Diameter with Continuous Acetic Acid Infusion

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

Lubienski, Andreas; Duex, Markus; Lubienski, Katrin

Purpose. To evaluate the influence of continuous infusion of acetic acid 50% during radiofrequency ablation (RFA) on the size of the thermal lesion produced. Methods. Radiofrequency (RF) was applied to excised bovine liver by using an expandable needle electrode with 10 retractable tines (LeVeen Needle Electrode, RadioTherapeutics, Sunnyvale, CA) connected to a commercially available RF generator (RF 2000, RadioTherapeutics, Sunnyvale, CA). Experiments were performed using three different treatment modalities: RF only (n = 15), RF with continuous saline 0.9% infusion (n = 15), and RF with continuous acetic acid 50% infusion (n = 15). RF duration, power output, tissue impedance,more » and time to a rapid rise in impedance were recorded. The ablated lesions were evaluated both macroscopically and histologically. Results. The ablated lesions appeared as spherical or ellipsoid, well-demarcated pale areas with a surrounding brown rim with both RF only and RF plus saline 0.9% infusion. In contrast, thermolesions generated with RF in combination with acetic acid 50% infusion were irregular in shape and the central portion was jelly-like. Mean diameter of the coagulation necrosis was 22.3 {+-} 2.1 mm (RF only), 29.2 {+-} 4.8 mm (RF + saline 0.9%) and 30.7 {+-} 5.7 mm (RF + acetic acid 50%), with a significant increase in the RF plus saline 0.9% and RF plus acetic acid 50% groups compared with RF alone. Time to a rapid rise in impedance was significantly prolonged in the RF plus saline 0.9% and RF plus acetic acid 50% groups compared with RF alone. Conclusions. A combination of RF plus acetic acid 50% infusion is able to generate larger thermolesions than RF only or RF combined with saline 0.9% infusion.« less

The processed isoform of the translation termination factor eRF3 localizes to the nucleus to interact with the ARF tumor suppressor

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

Hashimoto, Yoshifumi; Kumagai, Naomichi; Hosoda, Nao

2014-03-14

Highlights: • So far, eRF3 has been thought to function exclusively in the cytoplasm. • eRF3 is a nucleo-cutoplasmic shuttling protein. • eRF3 has a leptomycin-sensitive nuclear export signal (NES). • Removal of NES by proteolytic cleavage allows eRF3 to translocate to the nucleus. • The processed eRF3 (p-eRF3) interacts with a nuclear tumor suppressor ARF. - Abstract: The eukaryotic releasing factor eRF3 is a multifunctional protein that plays pivotal roles in translation termination as well as the initiation of mRNA decay. eRF3 also functions in the regulation of apoptosis; eRF3 is cleaved at Ala73 by an as yet unidentifiedmore » protease into processed isoform of eRF3 (p-eRF3), which interacts with the inhibitors of apoptosis proteins (IAPs). The binding of p-eRF3 with IAPs leads to the release of active caspases from IAPs, which promotes apoptosis. Although full-length eRF3 is localized exclusively in the cytoplasm, p-eRF3 localizes in the nucleus as well as the cytoplasm. We here focused on the role of p-eRF3 in the nucleus. We identified leptomycin-sensitive nuclear export signal (NES) at amino acid residues 61–71 immediately upstream of the cleavage site Ala73. Thus, the proteolytic cleavage of eRF3 into p-eRF3 leads to release an amino-terminal fragment containing NES to allow the relocalization of eRF3 into the nucleus. Consistent with this, p-eRF3 more strongly interacted with the nuclear ARF tumor suppressor than full-length eRF3. These results suggest that while p-eRF3 interacts with IAPs to promote apoptosis in the cytoplasm, p-eRF3 also has some roles in regulating cell death in the nucleus.« less

Sulfophenyl-Functionalized Reduced Graphene Oxide Networks on Electrospun 3D Scaffold for Ultrasensitive NO₂ Gas Sensor.

PubMed

Zou, Bin; Guo, Yunlong; Shen, Nannan; Xiao, Anshan; Li, Mingjun; Zhu, Liang; Wan, Pengbo; Sun, Xiaoming

2017-12-19

Ultrasensitive room temperature real-time NO₂ sensors are highly desirable due to potential threats on environmental security and personal respiratory. Traditional NO₂ gas sensors with highly operated temperatures (200-600 °C) and limited reversibility are mainly constructed from semiconducting oxide-deposited ceramic tubes or inter-finger probes. Herein, we report the functionalized graphene network film sensors assembled on an electrospun three-dimensional (3D) nanonetwork skeleton for ultrasensitive NO₂ sensing. The functional 3D scaffold was prepared by electrospinning interconnected polyacrylonitrile (PAN) nanofibers onto a nylon window screen to provide a 3D nanonetwork skeleton. Then, the sulfophenyl-functionalized reduced graphene oxide (SFRGO) was assembled on the electrospun 3D nanonetwork skeleton to form SFRGO network films. The assembled functionalized graphene network film sensors exhibit excellent NO₂ sensing performance (10 ppb to 20 ppm) at room temperature, reliable reversibility, good selectivity, and better sensing cycle stability. These improvements can be ascribed to the functionalization of graphene with electron-withdrawing sulfophenyl groups, the high surface-to-volume ratio, and the effective sensing channels from SFRGO wrapping onto the interconnected 3D scaffold. The SFRGO network-sensing film has the advantages of simple preparation, low cost, good processability, and ultrasensitive NO₂ sensing, all advantages that can be utilized for potential integration into smart windows and wearable electronic devices for real-time household gas sensors.

Negative ion source with external RF antenna

DOEpatents

Leung, Ka-Ngo; Hahto, Sami K.; Hahto, Sari T.

2007-02-13

A radio frequency (RF) driven plasma ion source has an external RF antenna, i.e. the RF antenna is positioned outside the plasma generating chamber rather than inside. The RF antenna is typically formed of a small diameter metal tube coated with an insulator. An external RF antenna assembly is used to mount the external RF antenna to the ion source. The RF antenna tubing is wound around the external RF antenna assembly to form a coil. The external RF antenna assembly is formed of a material, e.g. quartz, which is essentially transparent to the RF waves. The external RF antenna assembly is attached to and forms a part of the plasma source chamber so that the RF waves emitted by the RF antenna enter into the inside of the plasma chamber and ionize a gas contained therein. The plasma ion source is typically a multi-cusp ion source. A converter can be included in the ion source to produce negative ions.

The image variations in mastoid segment of facial nerve and sinus tympani in congenital aural atresia by HRCT and 3D VR CT.

PubMed

Wang, Zhen; Hou, Qian; Wang, Pu; Sun, Zhaoyong; Fan, Yue; Wang, Yun; Xue, Huadan; Jin, Zhengyu; Chen, Xiaowei

2015-09-01

To find the variations of middle ear structures including the spatial pattern of mastoid segment of facial nerve and the shapes of the sinus tympani in patients with congenital aural atresia (CAA) by using the high-resolution (HR) CT and 3D volume rendered (VR) CT images. HRCT was performed in 25 patients with congenital aural atresia including six bilateral atresia patients (n=25, 21 males, 4 females, mean age 13.8 years, range 6-19). Along the long axis of the posterior semicircular canal ampulla, the oblique axial multiplanar reconstruction (MPR) was set to view the depiction of the round window and the mastoid segment of facial nerve. Volumetric rending technique was used to demonstrate the morphologic features. HRCT and 3D VR findings in atresia ears were compared with those in 19 normal ears of the unilateral ears of atresia patients. On the basic plane, the horizontal line distances between the mastoid segment of the facial nerve and the round window (h-RF) in atresia ears significantly decreased compared to the control ears (P<0.05). There was a significant negative correlation between the sinus tympani area (a-ST) and the distance between the horizontal lines of FN and RW midpoint (h-RF) (P<0.05). The mean area of sinus tympani in atresia group is larger (P<0.05). The shapes of the sinus tympani were classified into three categories: the cup-shaped, the pear-shaped and the boot-shaped. Area measurement indicated that the boot-shaped sinus tympani was a special variation with a large area, which only appears in CAA group. There were a significant difference between the area of the boot-shaped group and the other two groups (P<0.05). The morphologic differences of ST and other middle ear structures can also be observed visually in 3D VR CT images. HRCT and 3D VR CT could help a better understanding of different kinds of variations in mastoid segment of facial nerve and sinus tympani in CAA ears. And it may further help surgeons to make the correct decision for hearing rehabilitation. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

IRIS Update Batch 1, Group 1

EPA Science Inventory

Update the following IRIS chemical dose-response assessments: Barium (cancer, RfC), o-Cresol (RfD, cancer), carbon disulfied (RfD, RfC), 1,1-Dichloroethane (cancer), 2,4-Dimethylphenol (RfD), 1,4-Dibromobenzene (RfD), 1-chloro-1,1-difluroelfane (RfC, Acetyl chloride (cancer),2,4...

Rf Feedback free electron laser

DOEpatents

Brau, Charles A.; Swenson, Donald A.; Boyd, Jr., Thomas J.

1981-01-01

A free electron laser system and electron beam system for a free electron laser which use rf feedback to enhance efficiency. Rf energy is extracted from an electron beam by decelerating cavities and returned to accelerating cavities using rf returns such as rf waveguides, rf feedthroughs, etc. This rf energy is added to rf klystron energy to lower the required input energy and thereby enhance energy efficiency of the system.

Airborne characterization of smoke marker ratios from prescribed burning

NASA Astrophysics Data System (ADS)

Sullivan, A. P.; May, A. A.; Lee, T.; McMeeking, G. R.; Kreidenweis, S. M.; Akagi, S. K.; Yokelson, R. J.; Urbanski, S. P.; Collett, J. L., Jr.

2014-05-01

A Particle-into-Liquid Sampler - Total Organic Carbon and fraction collector system was flown aboard aTwin Otter aircraft sampling prescribed burning emissions in South Carolina in November2011 to obtain smoke marker measurements. The fraction collector provided 2 min time-integrated off-line samples for carbohydrate (i.e., smoke markers levoglucosan, mannosan, galactosan) analysis by high-performance anion-exchange chromatography with pulsed amperometric detection. Each fire location appeared to have aunique Δ levoglucosan / Δ water-soluble organic carbon (WSOC) ratio (RF01/RF02/RF03/RF05 = 0.163 ± 0.007 μg C μg C-1, RF08 = 0.115 ± 0.011 μg C μg C-1, RF09A = 0.072 ± 0.028 μg C μg C-1, RF09B = 0.042 ± 0.008 μg C μg C-1). These ratios were comparable to those obtained from controlled laboratory burns and suggested that the emissions sampled during RF01/RF02/RF03/RF05 were dominated by the burning of grasses, RF08 by leaves, RF09A by needles, and RF09B by marsh grasses. These findings were further supported by the Δ galactosan / Δ levoglucosan ratios (RF01/RF02/RF03/RF05 = 0.067 ± 0.004 μg μg-1, RF08 = 0.085 ± 0.009 μg μg-1, RF09A = 0.101 ± 0.029 μg μg-1) obtained as well as by the ground-based fuel and filter sample analyses during RF01/RF02/RF03/RF05. Differences between Δ potassium / Δ levoglucosan ratios obtained for these prescribed fires vs. laboratory-scale measurements suggest that some laboratory burns may not accurately represent potassium emissions from prescribed burns. The Δ levoglucosan / Δ WSOC ratio had no clear dependence on smoke age or fire dynamics suggesting that this ratio is more dependent on the type of fuel being burned. Levoglucosan was stable over a timescale of at least 1.5 h and could be useful to help estimate the air quality impacts of biomass burning.

Rf feedback free electron laser

DOEpatents

Brau, C.A.; Swenson, D.A.; Boyd, T.J. Jr.

1979-11-02

A free electron laser system and electron beam system for a free electron laser are provided which use rf feedback to enhance efficiency. Rf energy is extracted from an electron beam by decelerating cavities and returned to accelerating cavities using rf returns such as rf waveguides, rf feedthroughs, etc. This rf energy is added to rf klystron energy to lower the required input energy and thereby enhance energy efficiency of the system.

Phase stable RF transport system

DOEpatents

Curtin, Michael T.; Natter, Eckard F.; Denney, Peter M.

1992-01-01

An RF transport system delivers a phase-stable RF signal to a load, such as an RF cavity of a charged particle accelerator. A circuit generates a calibration signal at an odd multiple frequency of the RF signal where the calibration signal is superimposed with the RF signal on a common cable that connects the RF signal with the load. Signal isolating diplexers are located at both the RF signal source end and load end of the common cable to enable the calibration to be inserted and extracted from the cable signals without any affect on the RF signal. Any phase shift in the calibration signal during traverse of the common cable is then functionally related to the phase shift in the RF signal. The calibration phase shift is used to control a phase shifter for the RF signal to maintain a stable RF signal at the load.

Mineral resources of Peru's ancient societies

USGS Publications Warehouse

Brooks, W.E.

2003-01-01

Northern Peru has an exceptionally rich archaeological heritage that includes metalwork, ceramics and textiles. The success of at least a half-dozen pre-Columbian societies dating back 3,000 years and subsequent Spanish colonization in the 1400s has rested on the effective use of northern Peru's abundant resources. In the summer of 2000, my son Matt and I learned about that connection firsthand by volunteering at the Santa Rita B archaeological site in the Chao Valley near Trujillo in northern Peru. Riding donkey-back through the Andes and talking with local people, we got our hands dirty in the rich archaeology and geology of the area. We were able to correlate mineral occurrences to their various roles in society - opening a window into the region's fascinating past. From construction to metallurgy, pre-Columbian societies flourished and advanced because of their understanding and use of the available mineral resources.

200 MW S-band traveling wave resonant ring development at IHEP

NASA Astrophysics Data System (ADS)

Zhou, Zu-Sheng; Chi, Yun-Long; Git, Meng-Ping; Pei, Guo-Xi

2010-03-01

The resonant-ring is a traveling wave circuit, which is used to produce high peak power with comparatively smaller stored energy. The application to be considered is its use as a high power simulator mainly for testing the klystron ceramic output window, as well as for high power microwave transmission devices. This paper describes the principle of a resonant ring and introduces the structure and property of the newly constructed traveling wave resonant ring at IHEP. Our goal is to produce a 200 MW class resonant ring at 2.856 GHz with a pulse length of 2 μs and repetition rate of 25 Hz. The installation, commissioning and testing of the ring have been completed and a peak power of 200 MW at 3 μs has been achieved. The conditioning results show that all the parameters of the resonant ring reach the design goals.

Laser dispersing of ceramic powders into Al-alloys

NASA Astrophysics Data System (ADS)

Jendrzejewski, Rafał; Van Acker, Karel; Vanhoyweghen, Dirk

2007-02-01

The general objective of the work was formation of highly wear resistant metal matrix composite (MMC) surface layers on aluminium based Al 6061 alloy by means of laser dispersing. The surface of the substrate is locally melted by the high power diode laser beam and simultaneously powder particles are injected into molten material. The optimal process parameter window for the laser dispersing of SiC in Al 6061 has been found. The measured values of the wear rates of the sample with dispersed SiC particles are about seven times lower than that of the reference Al-substrates. Results show that laser dispersing is highly promising technology to improve the surface, mainly wear properties of light metals. However the possibilities of industrial application are still limited due to considerable laser beam power and preheating temperature applied as well low productivity because of low scanning speed, and therefore further investigations are required.

Design of the new couplers for C-ADS RFQ

NASA Astrophysics Data System (ADS)

Shi, Ai-Min; Sun, Lie-Peng; Zhang, Zhou-Li; Xu, Xian-Bo; Shi, Long-Bo; Li, Chen-Xing; Wang, Wen-Bin

2015-04-01

A new special coupler with a kind of bowl-shaped ceramic window for a proton linear accelerator named the Chinese Accelerator Driven System (C-ADS) at the Institute of Modern Physics (IMP) has been simulated and constructed and a continuous wave (CW) beam commissioning through a four-meter long radio frequency quadruple (RFQ) was completed by the end of July 2014. In the experiments of conditioning and beam, some problems were promoted gradually such as sparking and thermal issues. Finally, two new couplers were passed with almost 110 kW CW power and 120 kW pulsed mode, respectively. The 10 mA intensity beam experiments have now been completed, and the couplers during the operation had no thermal or electro-magnetic problems. The detailed design and results are presented in the paper. Supported by Strategic Priority Research Program of Chinese Academy of Sciences (XDA03020500)

STS-114: Discovery Day 6 Post MMT Meeting

NASA Technical Reports Server (NTRS)

2005-01-01

Wayne Hale, Space Shuttle Deputy Program Manager and Steve Poulos, Orbiter Program Manager, discuss the damage assessment from the tiles that came off the Space Shuttle Discovery during launch. Poulos presents charts and discusses in detail the following topics: 1) Composite Tile Damage/Gap Filler Sites Evaluation; 2) Protruding Ceramic Shim Aft of the Nose Landing Gear Door (NLGD); 3) Protruding Chine Gap Filler; 4) RH NLGD Tile Damage; 5) RH NLGD Damage Analysis; 6) Left Wing Tile Damage; 7) Comparison of Ground Test Results vs. FD5 Focused Inspection; 8) Current Status: Focused Inspection 721L07-01 ITVC FD5 Image of Panel 7L Apex 9) Current Status: Focused Inspection Lower Panel 7L721L07-02; 10) Current Status Focused Inspection 721L10-02 Lower Panel 10L Close-up view; and 11) Window 1 Blanket. The presentation ends with a question and answer period from the news media.

Airborne characterization of smoke marker ratios from prescribed burning

NASA Astrophysics Data System (ADS)

Sullivan, A. P.; May, A. A.; Lee, T.; McMeeking, G. R.; Kreidenweis, S. M.; Akagi, S. K.; Yokelson, R. J.; Urbanski, S. P.; Collett, J. L., Jr.

2014-10-01

A Particle-Into-Liquid Sampler - Total Organic Carbon (PILS-TOC) and fraction collector system was flown aboard a Twin Otter aircraft sampling prescribed burning emissions in South Carolina in November 2011 to obtain smoke marker measurements. The fraction collector provided 2 min time-integrated offline samples for carbohydrate (i.e., smoke markers levoglucosan, mannosan, and galactosan) analysis by high-performance anion-exchange chromatography with pulsed amperometric detection. Each fire location appeared to have a unique Δlevoglucosan/Δwater-soluble organic carbon (WSOC) ratio (RF01/RF02/RF03/RF05 = 0.163 ± 0.007 μg C μg-1 C, RF08 = 0.115 ± 0.011 μg C μg-1 C, RF09A = 0.072 ± 0.028 μg C μg-1 C, and RF09B = 0.042 ± 0.008 μg C μg-1 C, where RF means research flight). These ratios were comparable to those obtained from controlled laboratory burns and suggested that the emissions sampled during RF01/F02/RF03/RF05 were dominated by the burning of grasses, RF08 by leaves, RF09A by needles, and RF09B by marsh grasses. These findings were further supported by the Δgalactosan/Δlevoglucosan ratios (RF01/RF02/RF03/RF05 = 0.067 ± 0.004 μg μg-1, RF08 = 0.085 ± 0.009 μg μg-1, and RF09A = 0.101 ± 0.029 μg μg-1) obtained as well as by the ground-based fuel and filter sample analyses during RF01/RF02/RF03/RF05. Differences between Δpotassium/Δlevoglucosan ratios obtained for these prescribed fires vs. laboratory-scale measurements suggest that some laboratory burns may not accurately represent potassium emissions from prescribed burns. The Δlevoglucosan/ΔWSOC ratio had no clear dependence on smoke age or fire dynamics suggesting that this ratio is more dependent on the type of fuel being burned. Levoglucosan was stable over a timescale of at least 1.5 h and could be useful to help estimate the air quality impacts of biomass burning.

Single electron beam rf feedback free electron laser

DOEpatents

Brau, C.A.; Stein, W.E.; Rockwood, S.D.

1981-02-11

A free electron laser system and electron beam system for a free electron laser which uses rf feedback to enhance efficiency are described. Rf energy is extracted from a single electron beam by decelerating cavities and energy is returned to accelerating cavities using rf returns, such as rf waveguides, rf feedthroughs, resonant feedthroughs, etc. This rf energy is added to rf klystron energy to reduce the required input energy and thereby enhance energy efficiency of the system.

Growth, microstructure and electrical properties of sputter-deposited hafnium oxide (HfO2) thin films grown using HfO2 ceramic target

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

Aguirre, B.; Vemuri, R. S.; Zubia, David

2011-01-01

Hafnium oxide (HfO₂) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(100) substrates under varying growth temperature (Ts). HfO₂ ceramic target has been employed for sputtering while varying the Ts from room temperature to 500⁰C during deposition. The effect of Ts on the growth and microstructure of deposited HfO₂ films has been studied using grazing incidence x-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive x-ray spectrometry (EDS). The results indicate that the effect of Ts is significant on the growth, surface and interface structure, morphology and chemical composition ofmore » the HfO₂ films. Structural characterization indicates that the HfO₂ films grown at Ts<200 ⁰C are amorphous while films grown at Ts>200 ⁰C are nanocrystalline. An amorphous-to-crystalline transition occurs at Ts=200 ⁰C. Nanocrystalline HfO₂ films crystallized in a monoclinic structure with a (-111) orientation. XPS measurements indicated the high surface-chemical quality and stoichiometric nature of the grown HfO₂ films. An interface layer (IL) formation occurs due to reaction at the HfO₂-Si interface for HfO₂ films deposited at Ts>200 ⁰C. The thickness of IL increases with increasing Ts. XPS and EDS at the HfO₂-Si cross-section indicate the IL is a (Hf, Si)-O compound. The electrical characterization using capacitance-voltage measurements indicate that the dielectric constant decreases from 25 to 16 with increasing Ts.« less

Experimental FSO network availability estimation using interactive fog condition monitoring

NASA Astrophysics Data System (ADS)

Turán, Ján.; Ovseník, Łuboš

2016-12-01

Free Space Optics (FSO) is a license free Line of Sight (LOS) telecommunication technology which offers full duplex connectivity. FSO uses infrared beams of light to provide optical broadband connection and it can be installed literally in a few hours. Data rates go through from several hundreds of Mb/s to several Gb/s and range is from several 100 m up to several km. FSO link advantages: Easy connection establishment, License free communication, No excavation are needed, Highly secure and safe, Allows through window connectivity and single customer service and Compliments fiber by accelerating the first and last mile. FSO link disadvantages: Transmission media is air, Weather and climate dependence, Attenuation due to rain, snow and fog, Scattering of laser beam, Absorption of laser beam, Building motion and Air pollution. In this paper FSO availability evaluation is based on long term measured data from Fog sensor developed and installed at TUKE experimental FSO network in TUKE campus, Košice, Slovakia. Our FSO experimental network has three links with different physical distances between each FSO heads. Weather conditions have a tremendous impact on FSO operation in terms of FSO availability. FSO link availability is the percentage of time over a year that the FSO link will be operational. It is necessary to evaluate the climate and weather at the actual geographical location where FSO link is going to be mounted. It is important to determine the impact of a light scattering, absorption, turbulence and receiving optical power at the particular FSO link. Visibility has one of the most critical influences on the quality of an FSO optical transmission channel. FSO link availability is usually estimated using visibility information collected from nearby airport weather stations. Raw data from fog sensor (Fog Density, Relative Humidity, Temperature measured at each ms) are collected and processed by FSO Simulator software package developed at our Department. Based on FSO link data the FSO link and experimental FSO network availability was estimated for years from 2007 up to 2015. The average FSO network availability up to 98,3378 % was measured (for the BER 10-9). From the experimental data also Hybrid RF/FSO link availability was evaluated. As the weather conditions for FSO and RF link are complementary (FSO works well in rain and RF works well in fog) Hybrid FSO/RF system long time average availability was much better up to 99,9986 %.

SLAC pulsed X-ray facility

NASA Astrophysics Data System (ADS)

Ipe, N. E.; McCall, R. C.; Baker, E. D.

1986-05-01

The Stanford Linear Accelerator Center (SLAC) operates a high energy (up to 33 GeV) linear accelerator delivering pulses up to a few microseconds wide. The pulsed nature of the electron beam creates problems in the detection and measurement of radiation both from the accelerator beam and the klystrons that provide the RF power for the accelerator. Hence, a pulsed X-ray facility has been built at SLAC mainly for the purpose of testing the response of different radiation detection instruments to pulsed radiation fields. The X-ray tube consists of an electron gun with a control grid. This provides a stream of pulsed electrons that can be accelerated towards a confined target-window. The window is made up of aluminum 0.051 cm (20 mils) thick, plated on the vacuum side with a layer of gold 0.0006 cm (1/4 mil) thick. The frequency of electron pulses can be varied by an internal pulser from 60 to 360 pulses per second with pulse widths of 360 ns to 5 ms. The pulse amplitude can be varied over a wide range of currents. An external pulser can be used to obtain other frequencies or special pulse shapes. The voltage across the gun can be varied from 0 to 100 kV. The major part of the X-ray tube is enclosed in a large walk-in-cabinet made of 1.9 cm (3/4 in) plywood and lined with 0.32 cm (1/8 in) lead to make a very versatile facility.

Mutation at Tyrosine in AMLRY (GILRY Like) Motif of Yeast eRF1 on Nonsense Codons Suppression and Binding Affinity to eRF3

PubMed Central

Akhmaloka; Susilowati, Prima Endang; Subandi; Madayanti, Fida

2008-01-01

Termination translation in Saccharomyces cerevisiae is controlled by two interacting polypeptide chain release factors, eRF1 and eRF3. Two regions in human eRF1, position at 281-305 and position at 411-415, were proposed to be involved on the interaction to eRF3. In this study we have constructed and characterized yeast eRF1 mutant at position 410 (correspond to 415 human eRF1) from tyrosine to serine residue resulting eRF1(Y410S). The mutations did not affect the viability and temperature sensitivity of the cell. The stop codons suppression of the mutant was analyzed in vivo using PGK-stop codon-LACZ gene fusion and showed that the suppression of the mutant was significantly increased in all of codon terminations. The suppression on UAG codon was the highest increased among the stop codons by comparing the suppression of the wild type respectively. In vitro interaction between eRF1 (mutant and wild type) to eRF3 were carried out using eRF1-(His)6 and eRF1(Y410S)-(His)6 expressed in Escherichia coli and indigenous Saccharomyces cerevisiae eRF3. The results showed that the binding affinity of eRF1(Y410S) to eRF3 was decreased up to 20% of the wild type binding affinity. Computer modeling analysis using Swiss-Prot and Amber version 9.0 programs revealed that the overall structure of eRF1(Y410S) has no significant different with the wild type. However, substitution of tyrosine to serine triggered the structural change on the other motif of C-terminal domain of eRF1. The data suggested that increasing stop codon suppression and decreasing of the binding affinity of eRF1(Y410S) were probably due to the slight modification on the structure of the C-terminal domain. PMID:18463713

Porcine MuRF2 and MuRF3: molecular cloning, expression and association analysis with muscle production traits.

PubMed

Shen, H; Zhao, S H; Cao, J H; Li, X Y; Fan, B

2011-11-01

Muscle specific RING finger protein2 (MuRF2) and Muscle specific RING finger protein3(MuRF3) are two important members of the muscle specific RING finger protein family, which are especially expressed in cardiac and skeletal muscle tissues and play critical roles during the myocyte differentiation, development and morphogenesis. In this study, the molecular characteristics of porcine MuRF2 and MuRF3 gene were reported, and furthermore two variants of MuRF2 were identified. The tissue distribution pattern analyses revealed that MuRF2-b and MuRF3 mRNA was exclusively expressed in striated muscle tissues while MuRF2-a had a low-level expression in liver tissue. Real-time quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) results displayed MuRF2 mRNA expression levels were significantly varied at three stages of fetal skeletal muscle in Landrace pigs, and the expression of MuRF2-a was lower than that of MuRF2-b in all stages. An essencial region of -396 to -22 for transcription was identified at the 5'UTR of porcine MuRF2 gene, while no active regulatory fragment found in the 5'UTR of mouse MuRF2. A single nucleotide polymorphism (SNP), c.915G > A was identified in MuRF2 exon 5. A HinfI PCR-RFLP was developed for SNP genotyping in two different pig populations. Association of the genotypes with growth and carcass traits showed that different genotypes of MuRF2 were significantly (P < 0.05) associated with average daily gain on test, carcass weight and carcass length. The study suggested that the porcine MuRF2 and MuRF3 genes are involved in the muscle growth and development, and can be considered as potential candidate genes affecting muscle production traits in the pig.

Further improvements in conducting and transparent properties of ZnO:Ga films with perpetual c-axis orientation: Materials optimization and application in silicon solar cells

NASA Astrophysics Data System (ADS)

Mondal, Praloy; Das, Debajyoti

2017-07-01

Technologically appropriate device friendly ZnO:Ga films have been prepared at a low growth temperature (100 °C) by changing the RF power (P) applied to the magnetron plasma. Structurally preferred c-axis orientation of the ZnO:Ga network has been attained with I〈002〉/I〈103〉 > 5. The c-axis oriented grains of wurtzite ZnO:Ga grows geometrically and settles in tangentially, providing favorable conduction path for stacked layer devices. Nano-sheet like structures produced at the surface are interconnected and provide conducting path across the surface; however, those accommodate a lot of pores in between that help better light trapping and reduce the reflection loss. The optimized ZnO:Ga thin film prepared at RF power of 200 W has 〈002〉 oriented grains of average size ∼10 nm and exhibits a very high conductivity ∼200 S cm-1 and elevated transmission (∼93% at 500 nm) in the visible range. The optimized ZnO:Ga film has been used as the transparent conducting oxide (TCO) window layer of RF-PECVD grown silicon thin film solar cells in glass/TCO/p-i-n-Si/Al configuration. The characteristics of identically prepared p-i-n-Si solar cells are compared by replacing presently developed ZnO:Ga TCO with the best quality U-type SnO2 coated Asahi glass substrates. The ZnO:Ga coated glass substrate offers a higher open circuit voltage (VOC) and the higher fill factor (FF). The ZnO:Ga film being more stable in hydrogen plasma than its SnO2 counterpart, maintains a high transparency to the solar radiation and improves the VOC, while reduced diffusion of Zn across the p-layer creates less defects at the p-i interface in Si:H cells and thereby, increases the FF. Nearly identical conversion efficiency is preserved for both TCO substrates. Excellent c-axis orientation even at low growth temperature promises improved device performance by extended parametric optimization.

Predicting Failure Under Laboratory Conditions: Learning the Physics of Slow Frictional Slip and Dynamic Failure

NASA Astrophysics Data System (ADS)

Rouet-Leduc, B.; Hulbert, C.; Riviere, J.; Lubbers, N.; Barros, K.; Marone, C.; Johnson, P. A.

2016-12-01

Forecasting failure is a primary goal in diverse domains that include earthquake physics, materials science, nondestructive evaluation of materials and other engineering applications. Due to the highly complex physics of material failure and limitations on gathering data in the failure nucleation zone, this goal has often appeared out of reach; however, recent advances in instrumentation sensitivity, instrument density and data analysis show promise toward forecasting failure times. Here, we show that we can predict frictional failure times of both slow and fast stick slip failure events in the laboratory. This advance is made possible by applying a machine learning approach known as Random Forests1(RF) to the continuous acoustic emission (AE) time series recorded by detectors located on the fault blocks. The RF is trained using a large number of statistical features derived from the AE time series signal. The model is then applied to data not previously analyzed. Remarkably, we find that the RF method predicts upcoming failure time far in advance of a stick slip event, based only on a short time window of data. Further, the algorithm accurately predicts the time of the beginning and end of the next slip event. The predicted time improves as failure is approached, as other data features add to prediction. Our results show robust predictions of slow and dynamic failure based on acoustic emissions from the fault zone throughout the laboratory seismic cycle. The predictions are based on previously unidentified tremor-like acoustic signals that occur during stress build up and the onset of macroscopic frictional weakening. We suggest that the tremor-like signals carry information about fault zone processes and allow precise predictions of failure at any time in the slow slip or stick slip cycle2. If the laboratory experiments represent Earth frictional conditions, it could well be that signals are being missed that contain highly useful predictive information. 1Breiman, L. Random forests. Machine Learning 45, 5-32 (2001). 2Rouet-Leduc, B. C. Hulbert, N. Lubbers, K. Barros and P. A. Johnson, Learning the physics of failure, in review (2016).

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

Brajnik, G., E-mail: gabriele.brajnik@elettra.eu; Carrato, S.; Bassanese, S.

At Elettra, the Italian synchrotron light source, an internal project has been started to develop an electron beam position monitor capable of achieving sub-micron resolution with a self-compensation feature. In order to fulfil these requirements, a novel RF front end has been designed. A high isolation coupler combines the input signals with a known pilot tone which is generated by the readout system. This allows the parameters of the four channels to be continuously calibrated, by compensating the different responses of each channel. A similar technique is already known, but for the first time experimental results have shown the improvementmore » in resolution due to this method. The RF chain was coupled with a 4-channel digitizer based on 160 MHz, 16 bits ADCs and an Altera Stratix FPGA. At first, no additional processing was done in the FPGA, collecting only the raw data from the ADCs; the position was calculated through the FFT of each signal. A simulation was also performed to verify the analytic relation between spatial resolution and signal-to-noise ratio; this was very useful to better understand the behaviour of the system with different sources of noise (aperture jitter, thermal noise, etc.). The experimental data were compared with the simulation, showing indeed a perfect agreement with the latter and confirming the capability of the system to reach sub-micrometric accuracy. Therefore, the use of the pilot tone greatly improves the quality of the system, correcting the drifts and increasing the spatial resolution by a factor of 4 in a time window of 24 hours.« less

Dark current, breakdown, and magnetic field effects in a multicell, 805MHz cavity

NASA Astrophysics Data System (ADS)

Norem, J.; Wu, V.; Moretti, A.; Popovic, M.; Qian, Z.; Ducas, L.; Torun, Y.; Solomey, N.

2003-07-01

We present measurements of dark currents and x rays in a six cell 805MHz cavity, taken as part of an rf development program for muon cooling, which requires high power, high stored energy, low frequency cavities operating in a strong magnetic field. We have done the first systematic study of the behavior of high power rf in a strong (2.5 4T) magnetic field. Our measurements extend over a very large dynamic range in current and provide good fits to the Fowler-Nordheim field emission model assuming mechanical structures produce field enhancements at the surface. The locally enhanced field intensities we derive at the tips of these emitters are very large, (˜10 GV/m), and should produce tensile stresses comparable to the tensile strength of the copper cavity walls and should be capable of causing breakdown events. We also compare our data with estimates of tensile stresses from a variety of accelerating structures. Preliminary studies of the internal surface of the cavity and window are presented, which show splashes of copper with many sharp cone shaped protrusions and wires which can explain the experimentally measured field enhancements. We discuss a “cold copper” breakdown mechanism and briefly review alternatives. We also discuss a number of effects due to the 2.5T solenoidal fields on the cavity such as altered field emission due to mechanical deformation of emitters, and dark current ring beams, which are produced from the irises by E×B drifts during the nonrelativistic part of the acceleration process.

A novel power spectrum calculation method using phase-compensation and weighted averaging for the estimation of ultrasound attenuation.

PubMed

Heo, Seo Weon; Kim, Hyungsuk

2010-05-01

An estimation of ultrasound attenuation in soft tissues is critical in the quantitative ultrasound analysis since it is not only related to the estimations of other ultrasound parameters, such as speed of sound, integrated scatterers, or scatterer size, but also provides pathological information of the scanned tissue. However, estimation performances of ultrasound attenuation are intimately tied to the accurate extraction of spectral information from the backscattered radiofrequency (RF) signals. In this paper, we propose two novel techniques for calculating a block power spectrum from the backscattered ultrasound signals. These are based on the phase-compensation of each RF segment using the normalized cross-correlation to minimize estimation errors due to phase variations, and the weighted averaging technique to maximize the signal-to-noise ratio (SNR). The simulation results with uniform numerical phantoms demonstrate that the proposed method estimates local attenuation coefficients within 1.57% of the actual values while the conventional methods estimate those within 2.96%. The proposed method is especially effective when we deal with the signal reflected from the deeper depth where the SNR level is lower or when the gated window contains a small number of signal samples. Experimental results, performed at 5MHz, were obtained with a one-dimensional 128 elements array, using the tissue-mimicking phantoms also show that the proposed method provides better estimation results (within 3.04% of the actual value) with smaller estimation variances compared to the conventional methods (within 5.93%) for all cases considered. Copyright 2009 Elsevier B.V. All rights reserved.

Wireless sensor network

NASA Astrophysics Data System (ADS)

Perotti, Jose M.; Lucena, Angel R.; Mullenix, Pamela A.; Mata, Carlos T.

2006-05-01

Current and future requirements of aerospace sensors and transducers demand the design and development of a new family of sensing devices, with emphasis on reduced weight, power consumption, and physical size. This new generation of sensors and transducers will possess a certain degree of intelligence in order to provide the end user with critical data in a more efficient manner. Communication between networks of traditional or next-generation sensors can be accomplished by a Wireless Sensor Network (WSN) developed by NASA's Instrumentation Branch and ASRC Aerospace Corporation at Kennedy Space Center (KSC), consisting of at least one central station and several remote stations and their associated software. The central station is application-dependent and can be implemented on different computer hardware, including industrial, handheld, or PC-104 single-board computers, on a variety of operating systems: embedded Windows, Linux, VxWorks, etc. The central stations and remote stations share a similar radio frequency (RF) core module hardware that is modular in design. The main components of the remote stations are an RF core module, a sensor interface module, batteries, and a power management module. These modules are stackable, and a common bus provides the flexibility to stack other modules for additional memory, increased processing, etc. WSN can automatically reconfigure to an alternate frequency if interference is encountered during operation. In addition, the base station will autonomously search for a remote station that was perceived to be lost, using relay stations and alternate frequencies. Several wireless remote-station types were developed and tested in the laboratory to support different sensing technologies, such as resistive temperature devices, silicon diodes, strain gauges, pressure transducers, and hydrogen leak detectors.

Myoeletric indices of fatigue adopting different rest intervals during leg press sets.

PubMed

Miranda, Humberto; Maia, Marianna; de Oliveira, Carlos G; Farias, Déborah; da Silva, Jurandir B; Lima, Vicente P; Willardson, Jeffrey M; Paz, Gabriel A

2018-01-01

The purpose of this study was to examine the acute effect of different rest intervals between multiple sets of the 45° angled leg press exercise (LP45) on surface electromyographic (SEMG) spectral and amplitude indices of fatigue. Fifteen recreationally trained females performed three protocols in a randomized crossover design; each consisting of four sets of 10 repetitions with 1 (P1), 3 (P3), or 5 (P5) minute rest intervals between sets. Each set was performed with 70% of the LP45 ten-repetition maximum load. The SEMG data for biceps femoris (BF), vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) muscles was then evaluated. The SEMG amplitude change in the time coefficient (CRMS) and spectral fatigue index (Cf5) indicated higher levels of fatigue for all muscles evaluated during the P3 protocol versus the P1 and P5 protocols (p ≤ 0.05), respectively. The RF and VL muscles showed greater fatigue levels by the second and third sets; whereas, greater fatigue was shown in the VM and BF muscles by the fourth set (p ≤ 0.05). A three-minute rest interval between sets might represent a neuromuscular window between a fatigue stated and fully recovered state in the context of neural activation. Moreover, a three minute rest interval between sets might allow for consistent recruitment of high threshold motor units over multiple sets, and thus promote a more effective stimulus for strength gains. Copyright © 2017 Elsevier Ltd. All rights reserved.

A Comparison of Space and Ground Based Facility Environmental Effects for FEP Teflon. Revised

NASA Technical Reports Server (NTRS)

Rutledge, Sharon K.; Banks, Bruce A.; Kitral, Michael

1998-01-01

Fluorinated Ethylene Propylene (FEP) Teflon is widely used as a thermal control material for spacecraft, however, it is susceptible to erosion, cracking, and subsequent mechanical failure in low Earth orbit. One of the difficulties in determining whether FEP Teflon will survive during a mission is the wide disparity of erosion rates observed for this material in space and in ground based facilities. Each environment contains different levels of atomic oxygen, ions, and vacuum ultraviolet (VUV) radiation in addition to parameters such as the energy of the arriving species and temperature. These variations make it difficult to determine what is causing the observed differences in erosion rates. This paper attempts to narrow down which factors affect the erosion rate of FEP Teflon through attempting to change only one environmental constituent at a time. This was attempted through the use of a single simulation facility (plasma asher) environment with a variety of Faraday cages and VUV transparent windows. Isolating one factor inside of a radio frequency (RF) plasma proved to be very difficult. Two observations could be made. First, it appears that the erosion yield of FEP Teflon with respect to that of polyimide Kapton is not greatly affected by the presence or lack of VUV radiation present in the RF plasma and the relative erosion yield for the FEP Teflon may decrease with increasing fluence. Second, shielding from charged particles appears to lower the relative erosion yield of the FEP to approximately that observed in space, however it is difficult to determine for sure whether ions, electrons, or some other components are causing the enhanced erosion.

Nonenzymatic free-cholesterol detection via a modified highly sensitive macroporous gold electrode with platinum nanoparticles.

PubMed

Lee, Yi-Jae; Park, Jae-Yeong

2010-12-15

A sensitive macroporous Au electrode with a highly rough surface obtained through the use of with Pt nanoparticles (macroporous Au-/nPts) is reported. It has been designed for nonenzymatic free-cholesterol biosensor applications. A macroporous Au-/nPts electrode was fabricated by electroplating Pt nanoparticles onto a coral-like shaped macroporous Au electrode structure. The macroporous Au-/nPts electrode was physically characterized by field emission scanning electron microscopy (FESEM). It was confirmed that the Pt nanoparticles were well deposited on the surface of the macroporous Au electrode. The porosity and window pore size of the macroporous Au electrode were 50% and 100-300 nm, respectively. The electroplated Pt nanoparticle size was approximately 10-20 nm. Electrochemical experiments showed that the macroporous Au-/nPts exhibited a much larger surface activation area (roughness factor (RF)=2024.7) than the macroporous Au electrode (RF=46.07). The macroporous Au-/nPts also presented a much stronger electrocatalytic activity towards cholesterol oxidation than does the macroporous Au electrode. At 0.2 V, the electrode responded linearly up to a 5 mM cholesterol concentration in a neutral media, with a detection limit of 0.015 mM and detection sensitivity of 226.2 μA mM(-1) cm(-2). Meanwhile, interfering species such as ascorbic acid (AA), acetaminophen (AP), and uric acid (UA), were effectively avoided. This novel nonenzymatic detection electrode has strong applications as an electrochemically based cholesterol biosensor. Copyright © 2010 Elsevier B.V. All rights reserved.

Spontaneous Magnetic Alignment by Yearling Snapping Turtles: Rapid Association of Radio Frequency Dependent Pattern of Magnetic Input with Novel Surroundings

PubMed Central

Landler, Lukas; Painter, Michael S.; Youmans, Paul W.; Hopkins, William A.; Phillips, John B.

2015-01-01

We investigated spontaneous magnetic alignment (SMA) by juvenile snapping turtles using exposure to low-level radio frequency (RF) fields at the Larmor frequency to help characterize the underlying sensory mechanism. Turtles, first introduced to the testing environment without the presence of RF aligned consistently towards magnetic north when subsequent magnetic testing conditions were also free of RF (‘RF off → RF off’), but were disoriented when subsequently exposed to RF (‘RF off → RF on’). In contrast, animals initially introduced to the testing environment with RF present were disoriented when tested without RF (‘RF on → RF off’), but aligned towards magnetic south when tested with RF (‘RF on → RF on’). Sensitivity of the SMA response of yearling turtles to RF is consistent with the involvement of a radical pair mechanism. Furthermore, the effect of RF appears to result from a change in the pattern of magnetic input, rather than elimination of magnetic input altogether, as proposed to explain similar effects in other systems/organisms. The findings show that turtles first exposed to a novel environment form a lasting association between the pattern of magnetic input and their surroundings. However, under natural conditions turtles would never experience a change in the pattern of magnetic input. Therefore, if turtles form a similar association of magnetic cues with the surroundings each time they encounter unfamiliar habitat, as seems likely, the same pattern of magnetic input would be associated with multiple sites/localities. This would be expected from a sensory input that functions as a global reference frame, helping to place multiple locales (i.e., multiple local landmark arrays) into register to form a global map of familiar space. PMID:25978736

Spontaneous magnetic alignment by yearling snapping turtles: rapid association of radio frequency dependent pattern of magnetic input with novel surroundings.

PubMed

Landler, Lukas; Painter, Michael S; Youmans, Paul W; Hopkins, William A; Phillips, John B

2015-01-01

We investigated spontaneous magnetic alignment (SMA) by juvenile snapping turtles using exposure to low-level radio frequency (RF) fields at the Larmor frequency to help characterize the underlying sensory mechanism. Turtles, first introduced to the testing environment without the presence of RF aligned consistently towards magnetic north when subsequent magnetic testing conditions were also free of RF ('RF off → RF off'), but were disoriented when subsequently exposed to RF ('RF off → RF on'). In contrast, animals initially introduced to the testing environment with RF present were disoriented when tested without RF ('RF on → RF off'), but aligned towards magnetic south when tested with RF ('RF on → RF on'). Sensitivity of the SMA response of yearling turtles to RF is consistent with the involvement of a radical pair mechanism. Furthermore, the effect of RF appears to result from a change in the pattern of magnetic input, rather than elimination of magnetic input altogether, as proposed to explain similar effects in other systems/organisms. The findings show that turtles first exposed to a novel environment form a lasting association between the pattern of magnetic input and their surroundings. However, under natural conditions turtles would never experience a change in the pattern of magnetic input. Therefore, if turtles form a similar association of magnetic cues with the surroundings each time they encounter unfamiliar habitat, as seems likely, the same pattern of magnetic input would be associated with multiple sites/localities. This would be expected from a sensory input that functions as a global reference frame, helping to place multiple locales (i.e., multiple local landmark arrays) into register to form a global map of familiar space.

Radiofrequency ablation for hepatocellular carcinoma: a prospective comparison of four radiofrequency devices.

PubMed

Lin, Shi-Ming; Lin, Chen-Chun; Chen, Wei-Ting; Chen, Yi-Chen; Hsu, Chao-Wei

2007-09-01

To compare the effectiveness of ablation techniques for hepatocellular carcinoma (HCC) with the use of four radiofrequency (RF) devices. One hundred patients with 133 HCC lesions no larger than 4 cm were treated with one of four RF devices: RF 2000 (maximum power, 100 W) and RF 3000 generators (maximum power, 200 W) with LeVeen expandable electrodes with a maximum dimension of 3.5 cm or 4 cm, internally cooled single electrode with a thermal dimension of 3 cm, and a RITA RF generator with expandable electrodes with a maximum dimension of 5 cm. Numbers of RF sessions needed per HCC to achieve complete necrosis were 1.4 +/- 0.5 with the RF 2000 device and greater than 1.1 +/- 0.3 with the other three devices (P < .05). The RF 2000 device required a more interactive algorithm than the RF 3000 device. Session times per patient were 31.7 minutes +/- 13.2 in the RF 2000 group and longer than 16.6 minutes +/- 7.5 in the RF 3000 group, 28.3 minutes +/- 12 in the RITA device group, and 27.1 minutes +/- 12 with the internally cooled electrode device (P < .005 for RF 2000 vs other devices and for RF 3000 vs RITA or internally cooled electrode device). Complete necrosis and local tumor progression rates at 2 years in the RF 2000, RF 3000, RITA, and internally cooled electrode device groups were 91.1%, 97.1%, 96.7%, and 96.8% and 12%, 8%, 8.2%, and 8.3%, respectively (P = .37). Ablation with the RF 3000 device required a shorter time than the other three devices and required a less interactive algorithm than the RF 2000 device. However, complete necrosis and local tumor progression rates were similar among devices.

Method of making a continuous ceramic fiber composite hot gas filter

DOEpatents

Hill, Charles A.; Wagner, Richard A.; Komoroski, Ronald G.; Gunter, Greg A.; Barringer, Eric A.; Goettler, Richard W.

1999-01-01

A ceramic fiber composite structure particularly suitable for use as a hot gas cleanup ceramic fiber composite filter and method of making same from ceramic composite material has a structure which provides for increased strength and toughness in high temperature environments. The ceramic fiber composite structure or filter is made by a process in which a continuous ceramic fiber is intimately surrounded by discontinuous chopped ceramic fibers during manufacture to produce a ceramic fiber composite preform which is then bonded using various ceramic binders. The ceramic fiber composite preform is then fired to create a bond phase at the fiber contact points. Parameters such as fiber tension, spacing, and the relative proportions of the continuous ceramic fiber and chopped ceramic fibers can be varied as the continuous ceramic fiber and chopped ceramic fiber are simultaneously formed on the porous vacuum mandrel to obtain a desired distribution of the continuous ceramic fiber and the chopped ceramic fiber in the ceramic fiber composite structure or filter.

Simultaneous radiofrequency (RF) heating and magnetic resonance (MR) thermal mapping using an intravascular MR imaging/RF heating system.

PubMed

Qiu, Bensheng; El-Sharkawy, Abdel-Monem; Paliwal, Vaishali; Karmarkar, Parag; Gao, Fabao; Atalar, Ergin; Yang, Xiaoming

2005-07-01

Previous studies have confirmed the possibility of using an intravascular MR imaging guidewire (MRIG) as a heating source to enhance vascular gene transfection/expression. This motivated us to develop a new intravascular system that can perform MR imaging, radiofrequncy (RF) heating, and MR temperature monitoring simultaneously in an MR scanner. To validate this concept, a series of mathematical simulations of RF power loss along a 0.032-inch MRIG and RF energy spatial distribution were performed to determine the optimum RF heating frequency. Then, an RF generator/amplifier and a filter box were built. The possibility for simultaneous RF heating and MR thermal mapping of the system was confirmed in vitro using a phantom, and the obtained thermal mapping profile was compared with the simulated RF power distribution. Subsequently, the feasibility of simultaneous RF heating and temperature monitoring was successfully validated in vivo in the aorta of living rabbits. This MR imaging/RF heating system offers a potential tool for intravascular MR-mediated, RF-enhanced vascular gene therapy.

Improved optoelectronics properties of ITO-based transparent conductive electrodes with the insertion of Ag/Ni under-layer

NASA Astrophysics Data System (ADS)

Ali, Ahmad Hadi; Abu Bakar, Ahmad Shuhaimi; Hassan, Zainuriah

2014-10-01

ITO-based transparent conductive electrodes (TCE) with Ag/Ni thin metal under-layer were deposited on Si and glass substrates by thermal evaporator and RF magnetron sputtering system. Ceramic ITO with purity of 99.99% and In2O3:SnO2 weight ratio of 90:10 was used as a target at room temperature. Post-deposition annealing was performed on the TCE at moderate temperature of 500 °C, 600 °C and 700 °C under N2 ambient. It was observed that the structural properties, optical transmittance, electrical characteristics and surface morphology were improved significantly after the post-annealing process. Post-annealed ITO/Ag/Ni at 600 °C shows the best quality of TCE with figure-of-merit (FOM) of 1.5 × 10-2 Ω-1 and high optical transmittance of 83% at 470 nm as well as very low electrical resistivity of 4.3 × 10-5 Ω-cm. The crystalline quality and surface morphological plays an important role in determining the quality of the TCE multilayer thin films properties.

Multifunctional graded dielectrics fabricated using dry powder printing

NASA Astrophysics Data System (ADS)

Good, Austin J.; Roper, David; Good, Brandon; Yarlagadda, Shridhar; Mirotznik, Mark S.

2017-09-01

The ability to fabricate multifunctional devices that combine good structural properties with embedded electromagnetic functionality has many practical applications, including antireflective surfaces for structural radomes, load bearing conformal antennas, integrated RF transmission lines and passive beam forming networks. We describe here a custom made 3D printer that can print high dielectric constant ceramic powders within a low-loss structural composite substrate to produce mechanically robust parts with integrated graded dielectric properties. We fabricated a number of these parts and evaluated their anisotropic dielectric properties by determining the complete permittivity tensor of the printed samples as a function of local powder weight. This data was then experimentally validated using two practical examples: a Chebyshev antireflective stack and a 2D passive beamsteering network. The results of both electromagnetic systems displayed acceptable agreement between the simulated and measured results. This agreement shows that powder printing is a potential approach for fabricating spatially graded dielectric electromagnetic systems. This paper was submitted for review on 15 February 2017. The project is funded by the Office of Naval Research, Code 331.

Electrical Conducting and Mechanism of Oxygen-Deficient Tin Oxide Films Deposited by RF Magnetron Sputtering at Various O2/Ar Ratios

NASA Astrophysics Data System (ADS)

Wang, Qi; Wang, Chengbiao; Lv, Changchun; Wang, Yang; Peng, Zhijian; Fu, Xiuli

Oxygen-deficient tin oxide thin films were prepared by radiofrequency magnetron sputtering with a sintered non-stoichiometric tin oxide ceramic target under an atmosphere of various ratios of O2/Ar from pure Ar to 1:1. X-ray diffraction analysis showed that the thin films were polycrystalline with relatively strong (1 1 0), (1 0 1) and (2 1 1) diffraction peaks. Scanning electron microscopy observation revealed that the thin films prepared at different O2/Ar ratios were all of relatively dense and homogeneous structure. With increasing O2/Ar ratio, the grain size of the films decreased slightly, and their chemical composition became close to the stoichiometric SnO2; but the deposition rate as well as film thickness increased first and then decreased sharply. It was revealed that the main defect in obtained films was oxygen vacancy (VO), and as the O2/Ar ratio increased, the concentration of VO fell down monotonously, which would lead to an increased electrical resistivity.

Abrasion resistant low friction and ultra-hard magnetron sputtered AlMgB14 coatings

NASA Astrophysics Data System (ADS)

Grishin, A. M.

2016-04-01

Hard aluminum magnesium boride films were fabricated by RF magnetron sputtering from a single stoichiometric AlMgB14 ceramic target. X-ray amorphous AlMgB14 films are very smooth. Their roughness does not exceed the roughness of Si wafer and Corning glass used as the substrates. Dispersion of refractive index and extinction coefficient were determined within 300 to 2500 nm range for the film deposited onto Corning glass. Stoichiometric in-depth compositionally homogeneous 2 μm thick films on the Si(100) wafer possess the peak values of nanohardness 88 GPa and Young’s modulus 517 GPa at the penetration depth of 26 nm and, respectively, 35 GPa and 275 GPa at 200 nm depth. Friction coefficient was found to be 0.06. The coating scratch adhesion strength of 14 N was obtained as the first chipping of the coating whereas its spallation failure happened at 21 N. These critical loads and the work of adhesion, estimated as high as 18.4 J m-2, surpass characteristics of diamond like carbon films deposited onto tungsten carbide-cobalt (WC-Co) substrates.

The continued development of the Spallation Neutron Source external antenna H- ion sourcea)

NASA Astrophysics Data System (ADS)

Welton, R. F.; Carmichael, J.; Desai, N. J.; Fuga, R.; Goulding, R. H.; Han, B.; Kang, Y.; Lee, S. W.; Murray, S. N.; Pennisi, T.; Potter, K. G.; Santana, M.; Stockli, M. P.

2010-02-01

The U.S. Spallation Neutron Source (SNS) is an accelerator-based, pulsed neutron-scattering facility, currently in the process of ramping up neutron production. In order to ensure that the SNS will meet its operational commitments as well as provide for future facility upgrades with high reliability, we are developing a rf-driven, H- ion source based on a water-cooled, ceramic aluminum nitride (AlN) plasma chamber. To date, early versions of this source have delivered up to 42 mA to the SNS front end and unanalyzed beam currents up to ˜100 mA (60 Hz, 1 ms) to the ion source test stand. This source was operated on the SNS accelerator from February to April 2009 and produced ˜35 mA (beam current required by the ramp up plan) with availability of ˜97%. During this run several ion source failures identified reliability issues, which must be addressed before the source re-enters production: plasma ignition, antenna lifetime, magnet cooling, and cooling jacket integrity. This report discusses these issues, details proposed engineering solutions, and notes progress to date.

Measured performance of the GTA rf systems

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

Denney, P.M.; Jachim, S.P.

1993-06-01

This paper describes the performance of the RF systems on the Ground Test Accelerator (GTA). The RF system architecture is briefly described. Among the RF performance results presented are RF field flatness and stability, amplitude and phase control resolution, and control system bandwidth and stability. The rejection by the RF systems of beam-induced disturbances, such as transients and noise, are analyzed. The observed responses are also compared to computer-based simulations of the RF systems for validation.

Measured performance of the GTA rf systems

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

Denney, P.M.; Jachim, S.P.

1993-01-01

This paper describes the performance of the RF systems on the Ground Test Accelerator (GTA). The RF system architecture is briefly described. Among the RF performance results presented are RF field flatness and stability, amplitude and phase control resolution, and control system bandwidth and stability. The rejection by the RF systems of beam-induced disturbances, such as transients and noise, are analyzed. The observed responses are also compared to computer-based simulations of the RF systems for validation.

Method of forming a ceramic matrix composite and a ceramic matrix component

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

de Diego, Peter; Zhang, James

A method of forming a ceramic matrix composite component includes providing a formed ceramic member having a cavity, filling at least a portion of the cavity with a ceramic foam. The ceramic foam is deposited on a barrier layer covering at least one internal passage of the cavity. The method includes processing the formed ceramic member and ceramic foam to obtain a ceramic matrix composite component. Also provided is a method of forming a ceramic matrix composite blade and a ceramic matrix composite component.

Auxiliary coil controls temperature of RF induction heater

NASA Technical Reports Server (NTRS)

1966-01-01

Auxiliary coil controls the temperature of an RF induction furnace that is powered by a relatively unstable RF generator. Manual or servoed adjustments of the relative position of the auxiliary coil, which is placed in close proximity to the RF coil, changes the looseness of the RF coil and hence the corresponding heating effect of its RF field.

The friction and wear of ceramic/ceramic and ceramic/metal combinations in sliding contact

NASA Technical Reports Server (NTRS)

Sliney, Harold E.; Dellacorte, Christopher

1993-01-01

The tribological characteristics of ceramics sliding on ceramics are compared to those of ceramics sliding on a nickel based turbine alloy. The friction and wear of oxide ceramics and silicon-based ceramics in air at temperatures from room ambient to 900 C (in a few cases to 1200 C) were measured for a hemispherically-tipped pin on a flat sliding contact geometry. In general, especially at high temperature, friction and wear were lower for ceramic/metal combinations than for ceramic/ceramic combinations. The better tribological performance for ceramic/metal combinations is attributed primarily to the lubricious nature of the oxidized surface of the metal.

Flight-vehicle materials, structures, and dynamics - Assessment and future directions. Vol. 3 - Ceramics and ceramic-matrix composites

NASA Technical Reports Server (NTRS)

Levine, Stanley R. (Editor)

1992-01-01

The present volume discusses ceramics and ceramic-matrix composites in prospective aerospace systems, monolithic ceramics, transformation-toughened and whisker-reinforced ceramic composites, glass-ceramic matrix composites, reaction-bonded Si3N4 and SiC composites, and chemical vapor-infiltrated composites. Also discussed are the sol-gel-processing of ceramic composites, the fabrication and properties of fiber-reinforced ceramic composites with directed metal oxidation, the fracture behavior of ceramic-matrix composites (CMCs), the fatigue of fiber-reinforced CMCs, creep and rupture of CMCs, structural design methodologies for ceramic-based materials systems, the joining of ceramics and CMCs, and carbon-carbon composites.

HLA-DRB1 Analysis Identified a Genetically Unique Subset within Rheumatoid Arthritis and Distinct Genetic Background of Rheumatoid Factor Levels from Anticyclic Citrullinated Peptide Antibodies.

PubMed

Hiwa, Ryosuke; Ikari, Katsunori; Ohmura, Koichiro; Nakabo, Shuichiro; Matsuo, Keitaro; Saji, Hiroh; Yurugi, Kimiko; Miura, Yasuo; Maekawa, Taira; Taniguchi, Atsuo; Yamanaka, Hisashi; Matsuda, Fumihiko; Mimori, Tsuneyo; Terao, Chikashi

2018-04-01

HLA-DRB1 is the most important locus associated with rheumatoid arthritis (RA) and anticitrullinated protein antibodies (ACPA). However, fluctuations of rheumatoid factor (RF) over the disease course have made it difficult to define fine subgroups according to consistent RF positivity for the analyses of genetic background and the levels of RF. A total of 2873 patients with RA and 2008 healthy controls were recruited. We genotyped HLA-DRB1 alleles for the participants and collected consecutive data of RF in the case subjects. In addition to RF+ and RF- subsets, we classified the RF+ subjects into group 1 (constant RF+) and group 2 (seroconversion). We compared HLA-DRB1 alleles between the RA subsets and controls and performed linear regression analysis to identify HLA-DRB1 alleles associated with maximal RF levels. Omnibus tests were conducted to assess important amino acid positions. RF positivity was 88%, and 1372 and 970 RF+ subjects were classified into groups 1 and 2, respectively. RF+ and RF- showed similar genetic associations to ACPA+ and ACPA- RA, respectively. We found that shared epitope (SE) was more enriched in group 2 than 1, p = 2.0 × 10 -5 , and that amino acid position 11 showed a significant association between 1 and 2, p = 2.7 × 10 -5 . These associations were independent of ACPA positivity. SE showed a tendency to be negatively correlated with RF titer (p = 0.012). HLA-DRB1*09:01, which reduces ACPA titer, was not associated with RF levels (p = 0.70). The seroconversion group was shown to have distinct genetic characteristics. The genetic architecture of RF levels is different from that of ACPA.

Mentalization in adults with attention deficit hyperactivity disorder: Comparison with controls and patients with borderline personality disorder.

PubMed

Perroud, Nader; Badoud, Deborah; Weibel, Sébastien; Nicastro, Rosetta; Hasler, Roland; Küng, Anne-Lise; Luyten, Patrick; Fonagy, Peter; Dayer, Alexandre; Aubry, Jean-Michel; Prada, Paco; Debbané, Martin

2017-10-01

Emotion dysregulation and interpersonal hardships constitute core features of borderline personality disorder (BPD). Research has established the link between these core dysregulations and fluctuations in the capacity to appreciate the mental states that underlie behavior (mentalizing, operationalized as reflective functioning (RF)). As emotion dysregulation and interpersonal hardships also characterize adults with attention deficit hyperactivity disorder (ADHD), this study sought to examine the potential RF impairments affecting this population. 101 adults with ADHD, 108 with BPD and 236 controls were assessed using the RF questionnaire (RFQ), evaluating how individuals employ information about mental states to better understand their own and others' behaviors. The RFQ comprises two dimensions, certainty (RF_c) and uncertainty (RF_u) about mental states. RF scores helped distinguish ADHD from controls, but also from BPD (F = 48.1 (2/441) ; p < 0.0001 for RF_c and F = 92.5 (2/441) ; p < 0.0001 for RF_u). The ADHD group showed intermediary RF scores compared to the controls (b = -0.70; p < 0.0001 and b = 0.89; p < 0.0001 for RF_c and RF_u) and BPD group (b = 0.44; p = 0.001 and b = -0.56; p = 0.001 for RF_c and RF_u). Lower RF scores correlated with poor anger control and high levels of impulsivity. Higher severity of ADHD (more attentional and hyperactive/impulsive symptoms) was correlated with RF impairments. In conclusion, RF may constitute an important process underlying attentional, hyperactive/impulsive as well as emotional symptoms in ADHD; it should therefore be considered in the assessment of these patients. Copyright © 2017 Elsevier B.V. All rights reserved.

Study of RF breakdown and multipacting in accelerator components

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

Pande, Manjiri; Singh, P., E-mail: manjiri@barc.gov.in, E-mail: psingh@barc.gov.in

2014-07-01

Radio frequency (RF) structures that are part of accelerators and energy sources, operate with sinusoidally varying electromagnetic fields under high RF energy. Here, RF breakdown and multipacting take place in RF structures and limit their performance. Electron field emission processes in a RF structure are precursors for breakdown processes. RF breakdown is a major phenomena affecting and causing the irreversible damage to RF structures. Breakdown rate and the damage induced by the breakdowns are its important properties. The damage is related to power absorbed during breakdown, while the breakdown rate is determined by the amplitudes of surface electric and magneticmore » fields, geometry, metal surface preparation and conditioning history. It limits working power and produces irreversible surface damage. The breakdown limit depends on the RF circuit, structure geometry, RF frequency, input RF power, pulse width, materials used, surface processing technique and surface electric and magnetic fields. Multipactor (MP) is a low power, electron multiplication based resonance breakdown phenomenon in vacuum and is often observed in RF structures. A multipactor discharge is undesirable, as it can create a reactive component that detunes the resonant cavities and components, generates noise in communication system and induces gas desorption from the conductor surfaces. In RF structures, certain conditions are required to generate multipacting. (author)« less

Local Multi-Channel RF Surface Coil versus Body RF Coil Transmission for Cardiac Magnetic Resonance at 3 Tesla: Which Configuration Is Winning the Game?

PubMed

Weinberger, Oliver; Winter, Lukas; Dieringer, Matthias A; Els, Antje; Oezerdem, Celal; Rieger, Jan; Kuehne, Andre; Cassara, Antonino M; Pfeiffer, Harald; Wetterling, Friedrich; Niendorf, Thoralf

2016-01-01

The purpose of this study was to demonstrate the feasibility and efficiency of cardiac MR at 3 Tesla using local four-channel RF coil transmission and benchmark it against large volume body RF coil excitation. Electromagnetic field simulations are conducted to detail RF power deposition, transmission field uniformity and efficiency for local and body RF coil transmission. For both excitation regimes transmission field maps are acquired in a human torso phantom. For each transmission regime flip angle distributions and blood-myocardium contrast are examined in a volunteer study of 12 subjects. The feasibility of the local transceiver RF coil array for cardiac chamber quantification at 3 Tesla is demonstrated. Our simulations and experiments demonstrate that cardiac MR at 3 Tesla using four-channel surface RF coil transmission is competitive versus current clinical CMR practice of large volume body RF coil transmission. The efficiency advantage of the 4TX/4RX setup facilitates shorter repetition times governed by local SAR limits versus body RF coil transmission at whole-body SAR limit. No statistically significant difference was found for cardiac chamber quantification derived with body RF coil versus four-channel surface RF coil transmission. Our simulation also show that the body RF coil exceeds local SAR limits by a factor of ~2 when driven at maximum applicable input power to reach the whole-body SAR limit. Pursuing local surface RF coil arrays for transmission in cardiac MR is a conceptually appealing alternative to body RF coil transmission, especially for patients with implants.

Structural Ceramics Database

National Institute of Standards and Technology Data Gateway

SRD 30 NIST Structural Ceramics Database (Web, free access)   The NIST Structural Ceramics Database (WebSCD) provides evaluated materials property data for a wide range of advanced ceramics known variously as structural ceramics, engineering ceramics, and fine ceramics.

Fracture strength of three all-ceramic systems: Top-Ceram compared with IPS-Empress and In-Ceram.

PubMed

Quran, Firas Al; Haj-Ali, Reem

2012-03-01

The purpose of this study was to investigate the fracture loads and mode of failure of all-ceramic crowns fabricated using Top-Ceram and compare it with all-ceramic crowns fabricated from well-established systems: IPS-Empress II, In-Ceram. Thirty all-ceramic crowns were fabricated; 10 IPS-Empress II, 10 In-Ceram alumina and 10 Top-Ceram. Instron testing machine was used to measure the loads required to introduce fracture of each crown. Mean fracture load for In-Ceram alumina [941.8 (± 221.66) N] was significantly (p > 0.05) higher than those of Top-Ceram and IPS-Empress II. There was no statistically significant difference between Top-Ceram and IPS-Empress II mean fracture loads; 696.20 (+222.20) and 534 (+110.84) N respectively. Core fracture pattern was highest seen in Top- Ceram specimens.

New type of x-ray-wafer image intensifier with CsI-CsI/MCP photocathodes: its design and assessment

NASA Astrophysics Data System (ADS)

Xiang, Shiming; Zhao, Hong

1993-04-01

The article introduces a new type of x-ray wafer image intensifier with a double proximity focusing system, (Phi) 50 CsI-CsI/MCP photocathode, and a series of welding constructions of glass window or ceramic components with metal rings. This kind of x-ray image intensifier has been widely used in the field of medical diagnosis and industrial non-destructive detection by means of sophisticated portable x-ray diagnoscopes, featuring a number of satisfactory performances such as low x-ray dosage, miniature x-ray tube and power supply, high output brightness and good resolution, light weight, small volume, low cost, and easy operation without any condition constrained by working environment and illumination. In the paper, the authors have given a series of formulae to determine characteristic parameters of the device, i.e., the quantum detection efficiencies of both reflection mode (CsI/MCP) and transmission mode (glass window CsI/MCP) photocathode, the brightness conversion factor, and resolution. The relations of the mentioned parameters with the performances of constituent components, which include CsI photocathodes layer thickness, MCP bias angle and gain, phosphor screen conversion efficiency, and double proximity focusing distances, are also briefly analyzed. The analysis thought and methods mentioned in the paper have been successfully used for the optimal design and assessment work of our devices and shows that they have a good coincidence with experimental results.

MISSE 6, 7 and 8 Materials Sample Experiments from the International Space Station Materials and Processes Team

NASA Technical Reports Server (NTRS)

Kravchenko, Michael; ORourke, Mary Jane; Golden, Johnny; Finckenor, Miria; Leatherwood, Michael; Alred, John

2010-01-01

The International Space Station Materials and Processes (ISS M&P) team has multiple material samples on MISSE 6, 7 and 8 to observe Low Earth Orbit (LEO) environmental effects on Space Station materials. Optical properties, thickness/mass loss, surface elemental analysis, visual and microscopic analysis for surface change are some of the techniques employed in this investigation. The ISS M&P team has participated in previous MISSE activities in order to better characterize the LEO effects on Space Station materials. This investigation will further this effort. Results for the following MISSE 6 samples materials will be presented: a comparison of anodize and chemical conversion coatings on various aluminum alloys, electroless nickel; AZ93 white ceramic thermal control coating with and without Teflon; Hyzod(TM) polycarbonate used to temporarily protect ISS windows; Russian quartz window material; reformulated Teflon (TM) coated Beta Cloth (Teflon TM without perfluorooctanoic acid (PFOA)) and a Dutch version of beta cloth. Discussion for current and future MISSE materials experiments will be presented. MISSE 7 samples are: deionized water sealed anodized aluminum Photofoil(TM); indium tin oxide (ITO)- coated Kapton(TM) used as thermo-optical surfaces; mechanically scribed tin-plated beryllium-copper samples for "tin pest" growth ( alpha/Beta transformation); Crew Exploration Vehicle (CEV) parachute soft goods. MISSE 8 sample: exposed "scrim cloth" (fiberglass weave) from the ISS solar array wing material, Davlyn fiberglass sleeve material, Permacel and Intertape protective tapes, and ITO-coated Kapton.

Durability of feldspathic veneering ceramic on glass-infiltrated alumina ceramics after long-term thermocycling.

PubMed

Mesquita, A M M; Ozcan, M; Souza, R O A; Kojima, A N; Nishioka, R S; Kimpara, E T; Bottino, M A

2010-01-01

This study compared the bond strength durability of a feldspathic veneering ceramic to glass-infiltrated reinforced ceramics in dry and aged conditions. Disc shaped (thickness: 4 mm, diameter: 4 mm) of glass-infiltrated alumina (In-Ceram Alumina) and glass-infiltrated alumina reinforced by zirconia (In-Ceram Zirconia) core ceramic specimens (N=48, N=12 per groups) were constructed according to the manufacturers' recommendations. Veneering ceramic (VITA VM7) was fired onto the core ceramics using a mold. The core-veneering ceramic assemblies were randomly divided into two conditions and tested either immediately after specimen preparation (Dry) or following 30000 thermocycling (5-55 ºC±1; dwell time: 30 seconds). Shear bond strength test was performed in a universal testing machine (cross-head speed: 1 mm/min). Failure modes were analyzed using optical microscope (x20). The bond strength data (MPa) were analyzed using ANOVA (α=0.05). Thermocycling did not decrease the bond strength results for both In-Ceram Alumina (30.6±8.2 MPa; P=0.2053) and In-Ceram zirconia (32.6±9 MPa; P=0.3987) core ceramic-feldspathic veneering ceramic combinations when compared to non-aged conditions (28.1±6.4 MPa, 29.7±7.3 MPa, respectively). There were also no significant differences between adhesion of the veneering ceramic to either In-Ceram Alumina or In-Ceram Zirconia ceramics (P=0.3289). Failure types were predominantly a mixture of adhesive failure between the veneering and the core ceramic together with cohesive fracture of the veneering ceramic. Long-term thermocycling aging conditions did not impair the adhesion of the veneering ceramic to the glass-infiltrated alumina core ceramics tested.

Characterisation of three novel giant viruses reveals huge diversity among viruses infecting Prymnesiales (Haptophyta).

PubMed

Johannessen, Torill Vik; Bratbak, Gunnar; Larsen, Aud; Ogata, Hiroyuki; Egge, Elianne S; Edvardsen, Bente; Eikrem, Wenche; Sandaa, Ruth-Anne

2015-02-01

We have isolated three novel lytic dsDNA-viruses from Raunefjorden (Norway) that are putative members of the Mimiviridae family, namely Haptolina ericina virus RF02 (HeV RF02), Prymnesium kappa virus RF01 (PkV RF01), and Prymnesium kappa virus RF02 (PkV RF02). Each of the novel haptophyte viruses challenges the common conceptions of algal viruses with respect to host range, phylogenetic affiliation and size. PkV RF01 has a capsid of ~310 nm and is the largest algal virus particle ever reported while PkV RF01 and HeV RF02 were able to infect different species, even belonging to different genera. Moreover, PkV RF01 and HeV RF02 infected the same hosts, but phylogenetic analysis placed them in different groups. Our results reveal large variation among viruses infecting closely related microalgae, and challenge the common conception that algal viruses have narrow host range, and phylogeny reflecting their host affiliation. Copyright © 2014 Elsevier Inc. All rights reserved.

Insulated laser tube structure and method of making same

DOEpatents

Dittbenner, Gerald R.

1999-01-01

An insulated high temperature ceramic laser tube having substantially uniform insulation along the length of the tube is disclosed having particulate ceramic insulation positioned between the outer wall of the ceramic laser tube and the inner surface of tubular ceramic fiber insulation which surrounds the ceramic laser tube. The particulate ceramic insulation is preferably a ceramic capable of sintering to the outer surface of the ceramic laser tube and to the inner surface of the tubular ceramic fiber insulation. The addition of the particulate ceramic insulation to fill all the voids between the ceramic laser tube and the fibrous ceramic insulation permits the laser tube to be operated at a substantially uniform temperature throughout the length of the laser tube.

Ultra-high vacuum photoelectron linear accelerator

DOEpatents

Yu, David U.L.; Luo, Yan

2013-07-16

An rf linear accelerator for producing an electron beam. The outer wall of the rf cavity of said linear accelerator being perforated to allow gas inside said rf cavity to flow to a pressure chamber surrounding said rf cavity and having means of ultra high vacuum pumping of the cathode of said rf linear accelerator. Said rf linear accelerator is used to accelerate polarized or unpolarized electrons produced by a photocathode, or to accelerate thermally heated electrons produced by a thermionic cathode, or to accelerate rf heated field emission electrons produced by a field emission cathode.

Local Multi-Channel RF Surface Coil versus Body RF Coil Transmission for Cardiac Magnetic Resonance at 3 Tesla: Which Configuration Is Winning the Game?

PubMed Central

Winter, Lukas; Dieringer, Matthias A.; Els, Antje; Oezerdem, Celal; Rieger, Jan; Kuehne, Andre; Cassara, Antonino M.; Pfeiffer, Harald; Wetterling, Friedrich; Niendorf, Thoralf

2016-01-01

Introduction The purpose of this study was to demonstrate the feasibility and efficiency of cardiac MR at 3 Tesla using local four-channel RF coil transmission and benchmark it against large volume body RF coil excitation. Methods Electromagnetic field simulations are conducted to detail RF power deposition, transmission field uniformity and efficiency for local and body RF coil transmission. For both excitation regimes transmission field maps are acquired in a human torso phantom. For each transmission regime flip angle distributions and blood-myocardium contrast are examined in a volunteer study of 12 subjects. The feasibility of the local transceiver RF coil array for cardiac chamber quantification at 3 Tesla is demonstrated. Results Our simulations and experiments demonstrate that cardiac MR at 3 Tesla using four-channel surface RF coil transmission is competitive versus current clinical CMR practice of large volume body RF coil transmission. The efficiency advantage of the 4TX/4RX setup facilitates shorter repetition times governed by local SAR limits versus body RF coil transmission at whole-body SAR limit. No statistically significant difference was found for cardiac chamber quantification derived with body RF coil versus four-channel surface RF coil transmission. Our simulation also show that the body RF coil exceeds local SAR limits by a factor of ~2 when driven at maximum applicable input power to reach the whole-body SAR limit. Conclusion Pursuing local surface RF coil arrays for transmission in cardiac MR is a conceptually appealing alternative to body RF coil transmission, especially for patients with implants. PMID:27598923

Radio Astronomy Software Defined Receiver Project

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

Vacaliuc, Bogdan; Leech, Marcus; Oxley, Paul

The paper describes a Radio Astronomy Software Defined Receiver (RASDR) that is currently under development. RASDR is targeted for use by amateurs and small institutions where cost is a primary consideration. The receiver will operate from HF thru 2.8 GHz. Front-end components such as preamps, block down-converters and pre-select bandpass filters are outside the scope of this development and will be provided by the user. The receiver includes RF amplifiers and attenuators, synthesized LOs, quadrature down converters, dual 8 bit ADCs and a Signal Processor that provides firmware processing of the digital bit stream. RASDR will interface to a usermore » s PC via a USB or higher speed Ethernet LAN connection. The PC will run software that provides processing of the bit stream, a graphical user interface, as well as data analysis and storage. Software should support MAC OS, Windows and Linux platforms and will focus on such radio astronomy applications as total power measurements, pulsar detection, and spectral line studies.« less

Deep inductively coupled plasma etching of ELO-GaN grown with high fill factor

NASA Astrophysics Data System (ADS)

Gao, Haiyong; Lee, Jaesoong; Ni, Xianfeng; Leach, Jacob; Özgür, Ümit; Morkoç, Hadis

2011-02-01

The epitaxial lateral overgrowth (ELO) gallium nitride (GaN) was grown with high fill factor using metal organic chemical vapor deposition (MOCVD). The inductively coupled plasma (ICP) etching of ELO-GaN based on Cl2/Ar/SiCl4 gas mixture was performed. Surface properties of ELO-GaN subjected to ICP etching have been investigated and optimized etching condition in ELO-GaN with ICP etching is presented. Radiofrequency (RF) power and the flow rate of Cl2 gas were modified during the experiments. The window region, wing region and the edge region of ELO-GaN pattern present different etching characteristics. Different etching conditions were studied to get the minimized plasma-induced damage, relatively high etching rates, and excellent surface profiles. Etch depths of the etched ELO-GaN with smooth surface up to about 19 μm were achieved. The most suitable three-step etching condition is discussed with the assessment based on the morphology observation of the etched surface of ELO-GaN patterns.

Dose controlled low energy electron irradiator for biomolecular films

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

Kumar, S. V. K., E-mail: svkk@tifr.res.in; Tare, Satej T.; Upalekar, Yogesh V.

2016-03-15

We have developed a multi target, Low Energy Electron (LEE), precise dose controlled irradiator for biomolecular films. Up to seven samples can be irradiated one after another at any preset electron energy and dose under UHV conditions without venting the chamber. In addition, one more sample goes through all the steps except irradiation, which can be used as control for comparison with the irradiated samples. All the samples are protected against stray electron irradiation by biasing them at −20 V during the entire period, except during irradiation. Ethernet based communication electronics hardware, LEE beam control electronics and computer interface weremore » developed in house. The user Graphical User Interface to control the irradiation and dose measurement was developed using National Instruments Lab Windows CVI. The working and reliability of the dose controlled irradiator has been fully tested over the electron energy range of 0.5 to 500 eV by studying LEE induced single strand breaks to ΦX174 RF1 dsDNA.« less

CO2 lasers and applications II; Proceedings of the Third European Congress on Optics, The Hague, Netherlands, Mar. 12-14, 1990

NASA Technical Reports Server (NTRS)

Opower, Hans (Editor)

1990-01-01

Recent advances in CO2 laser technology and its applications are examined. Topics discussed include the excitation of CO2 lasers by microwave discharge, a compact RF-excited 12-kW CO2 laser, a robotic laser for three-dimensional cutting and welding, three-dimensional CO2-laser material processing with gantry machine systems, and a comparison of hollow metallic waveguides and optical fibers for transmitting CO2-laser radiation. Consideration is given to an aerodynamic window with a pump cavity and a supersonic jet, cutting and welding Al using a high-repetition-rate pulsed CO2 laser, speckle reduction in CO2 heterodyne laser radar systems, high-power-laser float-zone crystal growth, melt dynamics in surface processing with laser radiation, laser hardfacing, surface melting of AlSi10Mg with CO2 laser radiation, material processing with Cu-vapor lasers, light-induced flow at a metal surface, and absorption measurements in high-power CW CO2-laser processing of materials.

A new classification system for all-ceramic and ceramic-like restorative materials.

PubMed

Gracis, Stefano; Thompson, Van P; Ferencz, Jonathan L; Silva, Nelson R F A; Bonfante, Estevam A

2015-01-01

Classification systems for all-ceramic materials are useful for communication and educational purposes and warrant continuous revisions and updates to incorporate new materials. This article proposes a classification system for ceramic and ceramic-like restorative materials in an attempt to systematize and include a new class of materials. This new classification system categorizes ceramic restorative materials into three families: (1) glass-matrix ceramics, (2) polycrystalline ceramics, and (3) resin-matrix ceramics. Subfamilies are described in each group along with their composition, allowing for newly developed materials to be placed into the already existing main families. The criteria used to differentiate ceramic materials are based on the phase or phases present in their chemical composition. Thus, an all-ceramic material is classified according to whether a glass-matrix phase is present (glass-matrix ceramics) or absent (polycrystalline ceramics) or whether the material contains an organic matrix highly filled with ceramic particles (resin-matrix ceramics). Also presented are the manufacturers' clinical indications for the different materials and an overview of the different fabrication methods and whether they are used as framework materials or monolithic solutions. Current developments in ceramic materials not yet available to the dental market are discussed.

Design and Calibration of an RF Actuator for Low-Level RF Systems

NASA Astrophysics Data System (ADS)

Geng, Zheqiao; Hong, Bo

2016-02-01

X-ray free electron laser (FEL) machines like the Linac Coherent Light Source (LCLS) at SLAC require high-quality electron beams to generate X-ray lasers for various experiments. Digital low-level RF (LLRF) systems are widely used to control the high-power RF klystrons to provide a highly stable RF field in accelerator structures for beam acceleration. Feedback and feedforward controllers are implemented in LLRF systems to stabilize or adjust the phase and amplitude of the RF field. To achieve the RF stability and the accuracy of the phase and amplitude adjustment, low-noise and highly linear RF actuators are required. Aiming for the upgrade of the S-band Linac at SLAC, an RF actuator is designed with an I/Qmodulator driven by two digital-to-analog converters (DAC) for the digital LLRF systems. A direct upconversion scheme is selected for RF actuation, and an on-line calibration algorithm is developed to compensate the RF reference leakage and the imbalance errors in the I/Q modulator, which may cause significant phase and amplitude actuation errors. This paper presents the requirements on the RF actuator, the design of the hardware, the calibration algorithm, and the implementation in firmware and software and the test results at LCLS.

Accuracy of Voltage Signal Measurement During Radiofrequency Delivery Through the SMARTTOUCH Catheter.

PubMed

Safavi-Naeini, Payam; Zafar-Awan, Dreema; Zhu, Hongjian; Zablah, Gerardo; Ganapathy, Anand V; Rasekh, Abdi; Saeed, Mohammad; Razavi, Joanna Esther Molina; Razavi, Mehdi

2017-01-01

Current methods for measuring voltage during radiofrequency (RF) ablation (RFA) necessitate turning off the ablation catheter. If voltage could be accurately read without signal attenuation during RFA, turning off the catheter would be unnecessary, allowing continuous ablation. We evaluated the accuracy of the Thermocool SMARTTOUCH catheter for measuring voltage while RF traverses the catheter. We studied 26 patients undergoing RFA for arrhythmias. A 7.5F SMARTTOUCH catheter was used for sensing voltage and performing RFA. Data were collected from the Carto-3 3-dimensional mapping system. Voltages were measured during ablation (RF-ON) and immediately before or after ablation (RF-OFF). In evaluating the accuracy of RF-ON measurements, we utilized the RF-OFF measure as the gold standard. We measured 465 voltage signals. The median values were 0.2900 and 0.3100 for RF-ON and RF-OFF, respectively. Wilcoxon signed rank testing showed no significant difference in these values (P = 0.608). The intraclass correlation coefficient (ICC) was 0.96, indicating that voltage measurements were similarly accurate during RF-OFF versus RF-ON. Five patients had baseline atrial fibrillation (AF), for whom 82 ablation points were measured; 383 additional ablation points were measured for the remaining patients. The voltages measured during RF-ON versus RF-OFF were similar in the presence of AF (P = 0.800) versus non-AF rhythm (P = 0.456) (ICC, 0.96 for both). Voltage signal measurement was similarly accurate during RF-ON versus RF-OFF independent of baseline rhythm. Physicians should consider not turning off the SMARTTOUCH ablation catheter when measuring voltage during RFA. © 2016 Wiley Periodicals, Inc.

Topological, chemical and electro-optical characteristics of riboflavin-doped artificial and natural DNA thin films

NASA Astrophysics Data System (ADS)

Gnapareddy, Bramaramba; Dugasani, Sreekantha Reddy; Son, Junyoung; Park, Sung Ha

2018-02-01

DNA is considered as a useful building bio-material, and it serves as an efficient template to align functionalized nanomaterials. Riboflavin (RF)-doped synthetic double-crossover DNA (DX-DNA) lattices and natural salmon DNA (SDNA) thin films were constructed using substrate-assisted growth and drop-casting methods, respectively, and their topological, chemical and electro-optical characteristics were evaluated. The critical doping concentrations of RF ([RF]C, approx. 5 mM) at given concentrations of DX-DNA and SDNA were obtained by observing the phase transition (from crystalline to amorphous structures) of DX-DNA and precipitation of SDNA in solution above [RF]C. [RF]C are verified by analysing the atomic force microscopy images for DX-DNA and current, absorbance and photoluminescence (PL) for SDNA. We study the physical characteristics of RF-embedded SDNA thin films, using the Fourier transform infrared spectrum to understand the interaction between the RF and DNA molecules, current to evaluate the conductance, absorption to understand the RF binding to the DNA and PL to analyse the energy transfer between the RF and DNA. The current and UV absorption band of SDNA thin films decrease up to [RF]C followed by an increase above [RF]C. By contrast, the PL intensity illustrates the reverse trend, as compared to the current and UV absorption behaviour as a function of the varying [RF]. Owing to the intense PL characteristic of RF, the DNA lattices and thin films with RF might offer immense potential to develop efficient bio-sensors and useful bio-photonic devices.

Topological, chemical and electro-optical characteristics of riboflavin-doped artificial and natural DNA thin films

PubMed Central

Gnapareddy, Bramaramba; Son, Junyoung

2018-01-01

DNA is considered as a useful building bio-material, and it serves as an efficient template to align functionalized nanomaterials. Riboflavin (RF)-doped synthetic double-crossover DNA (DX-DNA) lattices and natural salmon DNA (SDNA) thin films were constructed using substrate-assisted growth and drop-casting methods, respectively, and their topological, chemical and electro-optical characteristics were evaluated. The critical doping concentrations of RF ([RF]C, approx. 5 mM) at given concentrations of DX-DNA and SDNA were obtained by observing the phase transition (from crystalline to amorphous structures) of DX-DNA and precipitation of SDNA in solution above [RF]C. [RF]C are verified by analysing the atomic force microscopy images for DX-DNA and current, absorbance and photoluminescence (PL) for SDNA. We study the physical characteristics of RF-embedded SDNA thin films, using the Fourier transform infrared spectrum to understand the interaction between the RF and DNA molecules, current to evaluate the conductance, absorption to understand the RF binding to the DNA and PL to analyse the energy transfer between the RF and DNA. The current and UV absorption band of SDNA thin films decrease up to [RF]C followed by an increase above [RF]C. By contrast, the PL intensity illustrates the reverse trend, as compared to the current and UV absorption behaviour as a function of the varying [RF]. Owing to the intense PL characteristic of RF, the DNA lattices and thin films with RF might offer immense potential to develop efficient bio-sensors and useful bio-photonic devices. PMID:29515837

High temperature ceramics for automobile gas turbines. Part 2: Development of ceramic components

NASA Technical Reports Server (NTRS)

Walzer, P.; Koehler, M.; Rottenkolber, P.

1978-01-01

The development of ceramic components for automobile gas turbine engines is described with attention given to the steady and unsteady thermal conditions the ceramics will experience, and their anti-corrosion and strain-resistant properties. The ceramics considered for use in the automobile turbines include hot-pressed Si3N4, reaction-sintered, isostatically pressed Si3N4, hot-pressed SiC, reaction-bonded SiC, and glass ceramics. Attention is given to the stress analysis of ceramic structures and the state of the art of ceramic structural technology is reviewed, emphasizing the use of ceramics for combustion chambers and ceramic shrouded turbomachinery (a fully ceramic impeller).

RF/optical shared aperture for high availability wideband communication RF/FSO links

DOEpatents

Ruggiero, Anthony J; Pao, Hsueh-yuan; Sargis, Paul

2014-04-29

An RF/Optical shared aperture is capable of transmitting and receiving optical signals and RF signals simultaneously. This technology enables compact wide bandwidth communications systems with 100% availability in clear air turbulence, rain and fog. The functions of an optical telescope and an RF reflector antenna are combined into a single compact package by installing an RF feed at either of the focal points of a modified Gregorian telescope.

RF/optical shared aperture for high availability wideband communication RF/FSO links

DOEpatents

Ruggiero, Anthony J; Pao, Hsueh-yuan; Sargis, Paul

2015-03-24

An RF/Optical shared aperture is capable of transmitting and receiving optical signals and RF signals simultaneously. This technology enables compact wide bandwidth communications systems with 100% availability in clear air turbulence, rain and fog. The functions of an optical telescope and an RF reflector antenna are combined into a single compact package by installing an RF feed at either of the focal points of a modified Gregorian telescope.

Synthesis of ultrafine Si3N4 powder in RF-RF plasma

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

Sato, Michitaka; Nishio, Hiroaki

1991-10-01

A newly designed plasma-CVD apparatus mounted with the RF-RF type plasma torch was introduced to synthesize ultrafine powders of silicon nitride (Si3N4). The RF-RF plasma system (the combination of a main (lower) and controlling (upper) RF plasma) improved the stability of simple RF plasma and solved the impurity problem of dc-RF hybrid plasma. The reaction of SiCl4 and NH3, which were radially injected into the tail flames of the upper and lower plasmas, respectively, yielded near-stoichiometric amorphous powders of Si3N4. The nitrogen content in the products largely depended on the flow rate of the quenching gas, a mixture of NH3more » (reactant) and H2. The oxygen content and metal impurities are 2-3 wt pct and less than 200 ppm, respectively. The powder particles had an average diameter of about 15 nm with a narrow size distribution, and showed extreme air sensitivity. Conspicuous crystallazation and particle growth occurred when heated at temperatures above 1400 C. These results suggested that the RF-RF system was a potential reactor for the synthesis of ultrafine powders with excellent sinterability at relatively low temperatures. 9 refs.« less

High-powered microwave ablation with a small-gauge, gas-cooled antenna: initial ex vivo and in vivo results.

PubMed

Lubner, Meghan G; Hinshaw, J Louis; Andreano, Anita; Sampson, Lisa; Lee, Fred T; Brace, Christopher L

2012-03-01

To evaluate the performance of a gas-cooled, high-powered microwave system. Investigators performed 54 ablations in ex vivo bovine livers using three devices-a single 17-gauge cooled radiofrequency(RF) electrode; a cluster RF electrode; and a single 17-gauge, gas-cooled microwave (MW) antenna-at three time points (n = 6 at 4 minutes, 12 minutes, and 16 minutes). RF power was applied using impedance-based pulsing with maximum 200 W generator output. MW power of 135 W at 2.45 GHz was delivered continuously. An approved in vivo study was performed using 13 domestic pigs. Hepatic ablations were performed using single applicators and the above-mentioned MW and RF generator systems at treatment times of 2 minutes (n = 7 MW, n = 6 RF), 5 minutes (n = 23 MW, n = 8 RF), 7 minutes (n = 11 MW, n = 6 RF), and 10 minutes (n = 7 MW, n = 9 RF). Mean transverse diameter and length of the ablation zones were compared using analysis of variance (ANOVA) with post-hoc t tests and Wilcoxon rank-sum tests. Single ex vivo MW ablations were larger than single RF ablations at all time points (MW mean diameter range 3.5-4.8 cm 4-16 minutes; RF mean diameter range 2.6-3.1 cm 4-16 minutes) (P < .05). There was no difference in mean diameter between cluster RF and MW ablations (RF 3.3-4.4 cm 4-16 minutes; P = .4-.9). In vivo lesion diameters for MW (and RF) were as follows: 2.6 cm ± 0.72 (RF 1.5 cm ± 0.14), 3.6 cm ± 0.89 (RF 2.0 cm ± 0.4), 3.4 cm ± 0.87 (RF 1.8 cm ± 0.23), and 3.8 cm ± 0.74 (RF 2.1 cm ± 0.3) at 2 minutes, 5 minutes, 7 minutes, and 10 minutes (P < .05 all time points). Gas-cooled, high-powered MW ablation allows the generation of large ablation zones in short times. Copyright © 2012 SIR. Published by Elsevier Inc. All rights reserved.

Associations of rheumatoid factor and anti-citrullinated peptide antibody with disease progression and treatment outcomes in patients with rheumatoid arthritis.

PubMed

Katchamart, Wanruchada; Koolvisoot, Ajchara; Aromdee, Emvalee; Chiowchanwesawakit, Praveena; Muengchan, Chayawee

2015-10-01

The objective of this study was to investigate the association of rheumatoid factor (RF) and anti-citrullinated peptide antibodies (ACPA) status with disease progression and treatment outcomes in patients with rheumatoid arthritis (RA). A total of 276 adult patients who fulfilled the American College of Rheumatology 1987 classification criteria for RA were recruited from the Rheumatology clinic, Siriraj Hospital, from January 2011 to December 2012. Demographic, clinical, and laboratory data were collected at baseline and every 3 months up to 1 year of follow-up. RF and ACPA were measured at baseline. Radiography of the hands and feet was performed at baseline and 1 year. Patients with RF+/ACPA+ had significantly more severe disease activity and impaired functional status than those who had RF-/ACPA-. Although they received more aggressive treatment with methotrexate and combination of non-biologic, disease-modifying antirheumatic drug than other groups, fewer patients in this group achieved remission at 1 year of follow-up, especially when compared to RF-/ACPA- group (12 vs. 18 %). For radiographic erosion, patients with the presence of either RF or ACPA had a higher proportion of hand erosion than seronegative patients at baseline (77, 73, 83, and 32 %, p < 0.001 for RF+/ACPA+, RF+/ACPA-, RF-/ACPA+, and RF-/ACPA-, respectively). After 1 year of follow-up, patients who developed new erosion at the hands were more prevalent in RF+/ACPA+ (32 %) and RF+/ACPA- (33 %) groups. However, "newly developed" feet erosion was most common in RF+/ACPA- group (40 %) than in other groups. Patients with positive either RF or ACPA or both have more severe and aggressive disease that requires intensive treatment to improve outcomes.

Methylation of bacterial release factors RF1 and RF2 is required for normal translation termination in vivo.

PubMed

Mora, Liliana; Heurgué-Hamard, Valérie; de Zamaroczy, Miklos; Kervestin, Stephanie; Buckingham, Richard H

2007-12-07

Bacterial release factors RF1 and RF2 are methylated on the Gln residue of a universally conserved tripeptide motif GGQ, which interacts with the peptidyl transferase center of the large ribosomal subunit, triggering hydrolysis of the ester bond in peptidyl-tRNA and releasing the newly synthesized polypeptide from the ribosome. In vitro experiments have shown that the activity of RF2 is stimulated by Gln methylation. The viability of Escherichia coli K12 strains depends on the integrity of the release factor methyltransferase PrmC, because K12 strains are partially deficient in RF2 activity due to the presence of a Thr residue at position 246 instead of Ala. Here, we study in vivo RF1 and RF2 activity at termination codons in competition with programmed frameshifting and the effect of the Ala-246 --> Thr mutation. PrmC inactivation reduces the specific termination activity of RF1 and RF2(Ala-246) by approximately 3- to 4-fold. The mutation Ala-246 --> Thr in RF2 reduces the termination activity in cells approximately 5-fold. After correction for the decrease in level of RF2 due to the autocontrol of RF2 synthesis, the mutation Ala-246 --> Thr reduced RF2 termination activity by approximately 10-fold at UGA codons and UAA codons. PrmC inactivation had no effect on cell growth in rich media but reduced growth considerably on poor carbon sources. This suggests that the expression of some genes needed for optimal growth under such conditions can become growth limiting as a result of inefficient translation termination.

System for damping vibrations in a turbine

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

Roberts, III, Herbert Chidsey; Johnson, Curtis Alan; Taxacher, Glenn Curtis

2015-11-24

A system for damping vibrations in a turbine includes a first rotating blade having a first ceramic airfoil, a first ceramic platform connected to the first ceramic airfoil, and a first root connected to the first ceramic platform. A second rotating blade adjacent to the first rotating blade includes a second ceramic airfoil, a second ceramic platform connected to the second ceramic airfoil, and a second root connected to the second ceramic platform. A non-metallic platform damper has a first position in simultaneous contact with the first and second ceramic platforms.

Challenges and Opportunities in Design, Fabrication, and Testing of High Temperature Joints in Ceramics and Ceramic Composites

NASA Technical Reports Server (NTRS)

Singh, M.; Levine, S. R. (Technical Monitor)

2001-01-01

Ceramic joining has been recognized as an enabling technology for successful utilization of advanced ceramics and composite materials. A number of joint design and testing issues have been discussed for ceramic joints in silicon carbide-based ceramics and fiber-reinforced composites. These joints have been fabricated using an affordable, robust ceramic joining technology (ARCJoinT). The microstructure and good high temperature mechanical capability (compressive and flexural strengths) of ceramic joints in silicon carbide-based ceramics and composite materials are reported.

Airborne RF Measurement System and Analysis of Representative Flight RF Environment

NASA Technical Reports Server (NTRS)

Koppen, Sandra V.; Ely, Jay J.; Smith, Laura J.; Jones, Richard A.; Fleck, Vincent J.; Salud, Maria Theresa; Mielnik, John

2007-01-01

Environmental radio frequency (RF) data over a broad band of frequencies were needed to evaluate the airspace around several airports. An RF signal measurement system was designed using a spectrum analyzer connected to an aircraft VHF/UHF navigation antenna installed on a small aircraft. This paper presents an overview of the RF measurement system and provides analysis of a sample of RF signal measurement data over a frequency range of 30 MHz to 1000 MHz.

Exposure to 1800 MHz radiofrequency radiation impairs neurite outgrowth of embryonic neural stem cells.

PubMed

Chen, Chunhai; Ma, Qinlong; Liu, Chuan; Deng, Ping; Zhu, Gang; Zhang, Lei; He, Mindi; Lu, Yonghui; Duan, Weixia; Pei, Liping; Li, Min; Yu, Zhengping; Zhou, Zhou

2014-05-29

A radiofrequency electromagnetic field (RF-EMF) of 1800 MHz is widely used in mobile communications. However, the effects of RF-EMFs on cell biology are unclear. Embryonic neural stem cells (eNSCs) play a critical role in brain development. Thus, detecting the effects of RF-EMF on eNSCs is important for exploring the effects of RF-EMF on brain development. Here, we exposed eNSCs to 1800 MHz RF-EMF at specific absorption rate (SAR) values of 1, 2, and 4 W/kg for 1, 2, and 3 days. We found that 1800 MHz RF-EMF exposure did not influence eNSC apoptosis, proliferation, cell cycle or the mRNA expressions of related genes. RF-EMF exposure also did not alter the ratio of eNSC differentiated neurons and astrocytes. However, neurite outgrowth of eNSC differentiated neurons was inhibited after 4 W/kg RF-EMF exposure for 3 days. Additionally, the mRNA and protein expression of the proneural genes Ngn1 and NeuroD, which are crucial for neurite outgrowth, were decreased after RF-EMF exposure. The expression of their inhibitor Hes1 was upregulated by RF-EMF exposure. These results together suggested that 1800 MHz RF-EMF exposure impairs neurite outgrowth of eNSCs. More attention should be given to the potential adverse effects of RF-EMF exposure on brain development.

[Comparison of color reappearance between metal-ceram restoration and foundry-ceram restoration using crystaleye spectrophotometer].

PubMed

Shi, Tao; Zhang, Ning; Kong, Fan-wen; Zhan, De-song

2010-10-01

To study the color reappearance effect of metal-ceram restoration and foundry-ceram restoration using Crystaleye spectrophotometer. 58 metal-ceram restorations and 58 foundry-ceram restorations according to the result of the Crystaleye spectrophotometer were made respectively. The deltaE between restorations and natural teeth as referenced were analyzed. And satisfaction of dentists and patients were evaluated. The deltaE between metal-ceram restorations and natural teeth was 7.13 +/- 0.74. The deltaE between foundry-ceram restorations and teeth was 1.47 +/- 0.84. There were statistical differences between the deltaE (P < 0.01). The satisnatural faction of dentists and patients to the foundry-ceram restorations were higher than to the metal-ceram restorations (P < 0.05). Crystaleye spectrophotometer can provide accurate reference for foundry-ceram restoration, but for metal-ceram restoration it is not accurate.

RF Conditioning of the Photo-Cathode RF Gun at the Advanced Photon Source - NWA RF Measurements

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

Smith, T. L.; DiMonte, N.; Nassiri, A.

A new S-band Photo-cathode (PC) gun was recently installed and RF conditioned at the Advanced Photon Source (APS) Injector Test-stand (ITS) at Argonne National Lab (ANL). The APS PC gun is a LCLS type gun fabricated at SLAC [1]. The PC gun was delivered to the APS in October 2013 and installed in the APS ITS in December 2013. At ANL, we developed a new method of fast detection and mitigation of the guns internal arcs during the RF conditioning process to protect the gun from arc damage and to RF condition more efficiently. Here, we report the results ofmore » RF measurements for the PC gun and an Auto-Restart method for high power RF conditioning.« less

Low-density resin impregnated ceramic article and method for making the same

NASA Technical Reports Server (NTRS)

Tran, Huy K. (Inventor); Henline, William D. (Inventor); Hsu, Ming-ta S. (Inventor); Rasky, Daniel J. (Inventor); Riccitiello, Salvatore R. (Inventor)

1997-01-01

A low-density resin impregnated ceramic article advantageously employed as a structural ceramic ablator comprising a matrix of ceramic fibers. The fibers of the ceramic matrix are coated with an organic resin film. The organic resin can be a thermoplastic resin or a cured thermosetting resin. In one embodiment, the resin is uniformly distributed within the ceramic article. In a second embodiment, the resin is distributed so as to provide a density gradient along at least one direction of the ceramic article. The resin impregnated ceramic article is prepared by providing a matrix of ceramic fibers; immersing the matrix of ceramic fibers in a solution of a solvent and an organic resin infiltrant; and removing the solvent to form a resin film on the ceramic fibers.

[Ceramic-on-ceramic bearings in total hip arthroplasty (THA)].

PubMed

Sentürk, U; Perka, C

2015-04-01

The main reason for total hip arthroplasty (THA) revision is the wear-related aseptic loosening. Younger and active patients after total joint replacement create high demands, in particular, on the bearings. The progress, especially for alumina ceramic-on-ceramic bearings and mixed ceramics have solved many problems of the past and lead to good in vitro results. Modern ceramics (alumina or mixed ceramics containing alumina) are extremely hard, scratch-resistant, biocompatible, offer a low coefficient of friction, superior lubrication and have the lowest wear rates in comparison to all other bearings in THA. The disadvantage of ceramic is the risk of material failure, i.e., of ceramic fracture. The new generation of mixed ceramics (delta ceramic), has reduced the risk of head fractures to 0.03-0.05 %, but the risk for liner fractures remains unchanged at about 0.02 %. Assuming a non-impinging component implantation, ceramic-on-ceramic bearings have substantial advantages over all other bearings in THA. Due to the superior hardness, ceramic bearings produce less third body wear and are virtually impervious to damage from instruments during the implantation process. A specific complication for ceramic-on-ceramic bearings is "squeaking". The high rate of reported squeaking (0.45 to 10.7 %) highlights the importance of precise implant positioning and the stem and patient selection. With precise implant positioning this problem is rare with many implant designs and without clinical relevance. The improved tribology and the presumable resulting implant longevity make ceramic-on-ceramic the bearing of choice for young and active patients. Georg Thieme Verlag KG Stuttgart · New York.

Transmission of Er:YAG laser through different dental ceramics.

PubMed

Sari, Tugrul; Tuncel, Ilkin; Usumez, Aslihan; Gutknecht, Norbert

2014-01-01

The aim of this study was to determine the erbium-doped yttrium aluminum garnet (Er:YAG) laser transmission ratio through different dental ceramics with different thicknesses. Laser debonding procedure of adhesively luted all-ceramic restorations is based on the transmission of laser energy through the ceramic and the ablation of resin cement, because of the transmitted laser energy. Five different dental ceramics were evaluated in this study: sintered zirconium-oxide core ceramic, monolithic zirconium-oxide ceramic, feldspathic ceramic, leucite-reinforced glass ceramic, and lithium disilicate-reinforced glass ceramic. Two ceramic discs with different thicknesses (0.5 and 1 mm) were fabricated for each group. Ceramic discs were placed between the sensor membrane of the laser power meter and the tip of the contact handpiece of an Er:YAG laser device with the aid of a custom- made acrylic holder. The transmission ratio of Er:YAG laser energy (500 mJ, 2 Hz, 1 W, 1000 μs) through different ceramic discs was measured with the power meter. Ten measurements were made for each group and the results were analyzed with two way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) tests. The highest transmission ratio was determined for lithium disilicate-reinforced ceramic with 0.5 mm thickness (88%) and the lowest was determined for feldspathic ceramic with 1 mm thickness (44%). The differences among the different ceramics and between the different thicknesses were significant (p<0.05). Ceramic type and thickness should be taken into consideration to adjust the laser irradiation parameters during laser debonding of adhesively luted all-ceramic restorations.

Application of RF-MEMS-Based Split Ring Resonators (SRRs) to the Implementation of Reconfigurable Stopband Filters: A Review

PubMed Central

Martín, Ferran; Bonache, Jordi

2014-01-01

In this review paper, several strategies for the implementation of reconfigurable split ring resonators (SRRs) based on RF-MEMS switches are presented. Essentially three types of RF-MEMS combined with split rings are considered: (i) bridge-type RF-MEMS on top of complementary split ring resonators CSRRs; (ii) cantilever-type RF-MEMS on top of SRRs; and (iii) cantilever-type RF-MEMS integrated with SRRs (or RF-MEMS SRRs). Advantages and limitations of these different configurations from the point of view of their potential applications for reconfigurable stopband filter design are discussed, and several prototype devices are presented. PMID:25474378

Airborne RF Measurement System (ARMS) and Analysis of Representative Flight RF Environment

NASA Technical Reports Server (NTRS)

Koppen, Sandra V.; Ely, Jay J.; Smith, Laura J.; Jones, Richard A.; Fleck, Vincent J.; Salud, Maria Theresa; Mielnik, John J.

2007-01-01

Environmental radio frequency (RF) data over a broad band of frequencies (30 MHz to 1000 MHz) were obtained to evaluate the electromagnetic environment in airspace around several airports. An RF signal measurement system was designed utilizing a spectrum analyzer connected to the NASA Lancair Columbia 300 aircraft's VHF/UHF navigation antenna. This paper presents an overview of the RF measurement system and provides analysis of sample RF signal measurement data. This aircraft installation package and measurement system can be quickly returned to service if needed by future projects requiring measurement of an RF signal environment or exploration of suspected interference situations.

Method of making a modified ceramic-ceramic composite

DOEpatents

Weaver, Billy L.; McLaughlin, Jerry C.; Stinton, David P.

1995-01-01

The present invention provides a method of making a shaped ceramic-ceramic composite articles, such as gas-fired radiant heat burner tubes, heat exchangers, flame dispersers, and other furnace elements, having a formed-on ceramic-ceramic composite thereon.

Use of a radio frequency shield during 1.5 and 3.0 Tesla magnetic resonance imaging: experimental evaluation.

PubMed

Favazza, Christopher P; King, Deirdre M; Edmonson, Heidi A; Felmlee, Joel P; Rossman, Phillip J; Hangiandreou, Nicholas J; Watson, Robert E; Gorny, Krzysztof R

2014-01-01

Radiofrequency (RF) shields have been recently developed for the purpose of shielding portions of the patient's body during magnetic resonance imaging (MRI) examinations. We present an experimental evaluation of a commercially available RF shield in the MRI environment. All tests were performed on 1.5 T and 3.0 T clinical MRI scanners. The tests were repeated with and without the RF shield present in the bore, for comparison. Effects of the shield, placed within the scanner bore, on the RF fields generated by the scanner were measured directly using tuned pick-up coils. Attenuation, by as much as 35 dB, of RF field power was found inside the RF shield. These results were supported by temperature measurements of metallic leads placed inside the shield, in which no measurable RF heating was found. In addition, there was a small, simultaneous detectable increase (∼1 dB) of RF power just outside the edges of the shield. For these particular scanners, the autocalibrated RF power levels were reduced for scan locations prescribed just outside the edges of the shield, which corresponded with estimations based on the pick-up coil measurements. Additionally, no significant heating during MRI scanning was observed on the shield surface. The impact of the RF shield on the RF fields inside the magnet bore is likely to be dependent on the particular model of the RF shield or the MRI scanner. These results suggest that the RF shield could be a valuable tool for clinical MRI practices.

Use of a radio frequency shield during 1.5 and 3.0 Tesla magnetic resonance imaging: experimental evaluation

PubMed Central

Favazza, Christopher P; King, Deirdre M; Edmonson, Heidi A; Felmlee, Joel P; Rossman, Phillip J; Hangiandreou, Nicholas J; Watson, Robert E; Gorny, Krzysztof R

2014-01-01

Radiofrequency (RF) shields have been recently developed for the purpose of shielding portions of the patient’s body during magnetic resonance imaging (MRI) examinations. We present an experimental evaluation of a commercially available RF shield in the MRI environment. All tests were performed on 1.5 T and 3.0 T clinical MRI scanners. The tests were repeated with and without the RF shield present in the bore, for comparison. Effects of the shield, placed within the scanner bore, on the RF fields generated by the scanner were measured directly using tuned pick-up coils. Attenuation, by as much as 35 dB, of RF field power was found inside the RF shield. These results were supported by temperature measurements of metallic leads placed inside the shield, in which no measurable RF heating was found. In addition, there was a small, simultaneous detectable increase (∼1 dB) of RF power just outside the edges of the shield. For these particular scanners, the autocalibrated RF power levels were reduced for scan locations prescribed just outside the edges of the shield, which corresponded with estimations based on the pick-up coil measurements. Additionally, no significant heating during MRI scanning was observed on the shield surface. The impact of the RF shield on the RF fields inside the magnet bore is likely to be dependent on the particular model of the RF shield or the MRI scanner. These results suggest that the RF shield could be a valuable tool for clinical MRI practices. PMID:25378957

Minnesota Multiphasic Personality Inventory-2-Restructured Form (MMPI-2-RF) scores generated from the MMPI-2 and MMPI-2-RF test booklets: internal structure comparability in a sample of criminal defendants.

PubMed

Tarescavage, Anthony M; Alosco, Michael L; Ben-Porath, Yossef S; Wood, Arcangela; Luna-Jones, Lynn

2015-04-01

We investigated the internal structure comparability of Minnesota Multiphasic Personality Inventory-2-Restructured Form (MMPI-2-RF) scores derived from the MMPI-2 and MMPI-2-RF booklets in a sample of 320 criminal defendants (229 males and 54 females). After exclusion of invalid protocols, the final sample consisted of 96 defendants who were administered the MMPI-2-RF booklet and 83 who completed the MMPI-2. No statistically significant differences in MMPI-2-RF invalidity rates were observed between the two forms. Individuals in the final sample who completed the MMPI-2-RF did not statistically differ on demographics or referral question from those who were administered the MMPI-2 booklet. Independent t tests showed no statistically significant differences between MMPI-2-RF scores generated with the MMPI-2 and MMPI-2-RF booklets on the test's substantive scales. Statistically significant small differences were observed on the revised Variable Response Inconsistency (VRIN-r) and True Response Inconsistency (TRIN-r) scales. Cronbach's alpha and standard errors of measurement were approximately equal between the booklets for all MMPI-2-RF scales. Finally, MMPI-2-RF intercorrelations produced from the two forms yielded mostly small and a few medium differences, indicating that discriminant validity and test structure are maintained. Overall, our findings reflect the internal structure comparability of MMPI-2-RF scale scores generated from MMPI-2 and MMPI-2-RF booklets. Implications of these results and limitations of these findings are discussed. © The Author(s) 2014.

Development of an X-Band 50 MW Multiple Beam Klystron

NASA Astrophysics Data System (ADS)

Song, Liqun; Ferguson, Patrick; Ives, R. Lawrence; Miram, George; Marsden, David; Mizuhara, Max

2003-12-01

Calabazas Creek Research, Inc. is developing an X-band 50 MW multiple beam klystron (MBK) on a DOE SBIR Phase II grant. The electrical design and preliminary mechanical design were completed on the Phase I. This MBK consists of eight discrete klystron circuits driven by eight electron beams located symmetrically on a circle with a radius of 6.3 cm. Each beam operates at 190 kV and 66 A. The eight beam electron gun is in development on a DOE SBIR Phase II grant. Each circuit consists of an input cavity, two gain cavities, three penultimate cavities, and a three cavity output circuit operating in the PI/2 mode. Ring resonators were initially proposed for the complete circuit; however, low beam — wave interaction resulted in the necessity to use discrete cavities for all eight circuits. The input cavities are coupled via hybrid waveguides to ensure constant drive power amplitude and phase. The output circuits can either be combined using compact waveguide twists driving a TE01 high power window or combined into a TM04 mode converter driving the same TE01 window. The gain and efficiency for a single circuit has been optimized using KLSC, a 2 1/2D large signal klystron code. Simulations for a single circuit predict an efficiency of 53% for a single output cavity and 55% for the three cavity output resonator. The total RF output power for this MBK is 55 MW. During the Phase II emphasis will be given to cost reduction techniques resulting in a robust — high efficient — long life high power amplifier.

Investigation of the delay time distribution of high power microwave surface flashover

NASA Astrophysics Data System (ADS)

Foster, J.; Krompholz, H.; Neuber, A.

2011-01-01

Characterizing and modeling the statistics associated with the initiation of gas breakdown has proven to be difficult due to a variety of rather unexplored phenomena involved. Experimental conditions for high power microwave window breakdown for pressures on the order of 100 to several 100 torr are complex: there are little to no naturally occurring free electrons in the breakdown region. The initial electron generation rate, from an external source, for example, is time dependent and so is the charge carrier amplification in the increasing radio frequency (RF) field amplitude with a rise time of 50 ns, which can be on the same order as the breakdown delay time. The probability of reaching a critical electron density within a given time period is composed of the statistical waiting time for the appearance of initiating electrons in the high-field region and the build-up of an avalanche with an inherent statistical distribution of the electron number. High power microwave breakdown and its delay time is of critical importance, since it limits the transmission through necessary windows, especially for high power, high altitude, low pressure applications. The delay time distribution of pulsed high power microwave surface flashover has been examined for nitrogen and argon as test gases for pressures ranging from 60 to 400 torr, with and without external UV illumination. A model has been developed for predicting the discharge delay time for these conditions. The results provide indications that field induced electron generation, other than standard field emission, plays a dominant role, which might be valid for other gas discharge types as well.

Jacketed lamp bulb envelope

DOEpatents

MacLennan, Donald A.; Turner, Brian P.; Gitsevich, Aleksandr; Bass, Gary K.; Dolan, James T.; Kipling, Kent; Kirkpatrick, Douglas A.; Leng, Yongzhang; Levin, Izrail; Roy, Robert J.; Shanks, Bruce; Smith, Malcolm; Trimble, William C.; Tsai, Peter

2001-01-01

A jacketed lamp bulb envelope includes a ceramic cup having an open end and a partially closed end, the partially closed end defining an aperture, a lamp bulb positioned inside the ceramic cup abutting the aperture, and a reflective ceramic material at least partially covering a portion of the bulb not abutting the aperture. The reflective ceramic material may substantially fill an interior volume of the ceramic cup not occupied by the bulb. The ceramic cup may include a structural feature for aiding in alignment of the jacketed lamp bulb envelope in a lamp. The ceramic cup may include an external flange about a periphery thereof. One example of a jacketed lamp bulb envelope includes a ceramic cup having an open end and a closed end, a ceramic washer covering the open end of the ceramic cup, the washer defining an aperture therethrough, a lamp bulb positioned inside the ceramic cup abutting the aperture, and a reflective ceramic material filling an interior volume of the ceramic cup not occupied by the bulb. A method of packing a jacketed lamp bulb envelope of the type comprising a ceramic cup with a lamp bulb disposed therein includes the steps of filling the ceramic cup with a flowable slurry of reflective material, and applying centrifugal force to the cup to pack the reflective material therein.

Method of producing a carbon coated ceramic membrane and associated product

DOEpatents

Liu, Paul K. T.; Gallaher, George R.; Wu, Jeffrey C. S.

1993-01-01

A method of producing a carbon coated ceramic membrane including passing a selected hydrocarbon vapor through a ceramic membrane and controlling ceramic membrane exposure temperature and ceramic membrane exposure time. The method produces a carbon coated ceramic membrane of reduced pore size and modified surface properties having increased chemical, thermal and hydrothermal stability over an uncoated ceramic membrane.

Reflective Functioning in Parents of School-Aged Children

PubMed Central

Borelli, Jessica L.; St. John, H. Kate; Cho, Evelyn; Suchman, Nancy E.

2016-01-01

Parental reflective functioning (RF) has garnered tremendous support as a predictor of secure attachment in infancy, though little work has examined RF among parents of older children. In this study, we used a high-risk community sample of parent–child dyads (N = 117) to explore whether parental RF comprises self- and child-focused factors, whether parental RF is associated with parent and child attachment security, and whether parental RF mediates the association between parent and child attachment security. Results suggested that parental RF can be characterized as having both self- and child-focused components, and that child-focused parental RF is associated with child but not parent attachment security. Further, child-focused parental RF indirectly mediates the association between parent attachment avoidance and child attachment security. These findings extend previous work on parental RF to parents of school-age children and, in so doing, inform developmental models of attachment relationships in middle childhood. Discussion focuses on the importance of these findings in informing theory, prevention, clinical practice, and policy. PMID:26618938

Selective RF pulses in NMR and their effect on coupled and uncoupled spin systems

NASA Astrophysics Data System (ADS)

Slotboom, J.

1993-10-01

This thesis describes various aspects of the usage of shaped RF-pulses for volume selection and spectral editing. Contents: Introduction--The History of Magnetic Resonance in a Nutshell, and The Usage of RF Pulses in Contemporary MRS and MRI; Theoretical and Practical Aspects of Localized NMR Spectroscopy; The Effects of RF Pulse Shape Discretization on the Spatially Selective Performance; Design of Frequency-Selective RF Pulses by Optimizing a Small Number of Pulse Parameters; A Single-Shot Localization Pulse Sequence Suited for Coils with Inhomogeneous RF Fields Using Adiabatic Slice-Selective RF Pulses; The Bloch Equations for an AB System and the Design of Spin State Selective RF Pulses for Coupled Spin Systems; The Effects of Frequency Selective RF Pulses on J Coupled Spin-1/2 Systems; A Quantitative (1)H MRS in vivo Study of the Effects of L-Ornithine-L-Aspartate on the Development of Mild Encephalopathy Using a Single Shot Localization Technique Based on SAR Reduced Adiabatic 2(pi) Pulses.

Low Density Resin Impregnated Ceramic Article Having an Average Density of 0.15 to 0.40 G/CC

NASA Technical Reports Server (NTRS)

Tran, Huy K. (Inventor); Henline, William D. (Inventor); Hsu, Ming-ta S. (Inventor); Rasky, Daniel J. (Inventor); Riccitiello, Salvatore R. (Inventor)

1996-01-01

A low-density resin impregnated ceramic article advantageously employed as a structural ceramic ablator comprising a fired preform of ceramic fibers. The fibers of the ceramic preform are coated with an organic resin film. The organic resin can be a thermoplastic resin or a cured thermosetting resin. In one embodiment, the resin is uniformly distributed within the ceramic article. In a second embodiment, the resin is distributed so as to provide a density gradient along at least one direction of the ceramic article. The resin impregnated ceramic article is prepared by providing a fired preform of ceramic fibers; immersing the preform of ceramic fibers in a solution of a solvent and an organic resin infiltrant; and removing the solvent to form a resin film on the ceramic fibers.

Failure of a novel ceramic-on-ceramic hip resurfacing prosthesis.

PubMed

Matharu, Gulraj S; Daniel, Joseph; Ziaee, Hena; McMinn, Derek J W

2015-03-01

We report the early failure of five ceramic-on-ceramic hip resurfacings (CoCHRs). The ceramic used for the acetabular liner was a novel ceramic-composite (two thirds polyurethane and one third alumina ceramic). All cases were revised for increasing metal ion levels (blood cobalt 3.93-208.0 μg/l and chromium 1.57-17.5 μg/l) due to ceramic liner fracture and/or accelerated wear of the ceramic femoral head coating. Patients underwent bearing exchange and revision using primary hip arthroplasty implants at a mean of 3.0 years following CoCHR. Intraoperatively all patients had metallosis. At 1 to 2 years of follow-up blood metal ions normalized with no complications. We do not recommend this particular type of ceramic-on-ceramic bearing for hip resurfacing. Copyright © 2014 Elsevier Inc. All rights reserved.

Portfolio: Ceramics.

ERIC Educational Resources Information Center

Hardy, Jane; And Others

1982-01-01

Describes eight art activities using ceramics. Elementary students created ceramic tiles to depict ancient Egyptian and medieval European art, made ceramic cookie stamps, traced bisque plates on sketch paper, constructed clay room-tableaus, and designed clay relief masks. Secondary students pit-fired ceramic pots and designed ceramic Victorian…

Lack of effect of dietary nucleotide supplementation on erythrocyte 2,3-diphosphoglycerate concentration. A study on preterm neonates.

PubMed

Scopesi, Fabio; Canini, Silvana; Arioni, Cesare; Mazzella, Massimo; Gazzolo, Diego; Lantieri, Pasquale B; Bonacci, Wanda; Serra, Giovanni

2006-06-01

Recently we demonstrated an increased 2,3-diphosphoglycerate (2,3-DPG) erythrocyte concentration in rat pups subjected to nucleotide-enriched artificial feeding. The present study was carried out to test the hypothesis that a possible increase in 2,3-DPG concentration can also be obtained in human neonates who are fed nucleotide-enriched formula. Preterm neonates born or referred to the neonatal intensive care unit of the G. Gaslini Hospital, Genoa University, with a gestational age >30 weeks and <37 weeks were enrolled in our randomized trial. Recruitment took place within 48-72 hours from birth. Only newborns of mothers deciding not to breast-feed were eligible to be randomized for the supplemented group (FN) or non-supplemented group (RF). Breast-fed newborns were considered the control group (C). The study window (for supplementation and blood samples) was restricted to the first two weeks following birth (from the 2nd (t1) to the 16th (t2) day of life). At the end of our study, only 21 neonates were eligible for statistical analysis. The stimulating action of dietary nucleotides on 2,3-DPG concentration failed to be demonstrated; increases in 2,3-DPG concentration that were observed in newborns fed with nucleotide supplemented formula (FN) were comparable to those observed in newborns fed with regular formula (RF) and breast-fed newborns. The EC recommendation for the amount of nucleotides allowed in formula milk does not seem to be high enough to have positive effects on 2,3-DPG synthesis. Whether this possible 'pharmacological' effect can be achieved by a higher intake of ingested nucleotides and/or a change in the proportions of single nucleotides contained in milk formulas remain interesting end points to be elucidated.

Properties and Clinical Application of Three Types of Dental Glass-Ceramics and Ceramics for CAD-CAM Technologies

PubMed Central

Ritzberger, Christian; Apel, Elke; Höland, Wolfram; Peschke, Arnd; Rheinberger, Volker M.

2010-01-01

The main properties (mechanical, thermal and chemical) and clinical application for dental restoration are demonstrated for three types of glass-ceramics and sintered polycrystalline ceramic produced by Ivoclar Vivadent AG. Two types of glass-ceramics are derived from the leucite-type and the lithium disilicate-type. The third type of dental materials represents a ZrO2 ceramic. CAD/CAM technology is a procedure to manufacture dental ceramic restoration. Leucite-type glass-ceramics demonstrate high translucency, preferable optical/mechanical properties and an application as dental inlays, onlays and crowns. Based on an improvement of the mechanical parameters, specially the strength and toughness, the lithium disilicate glass-ceramics are used as crowns; applying a procedure to machine an intermediate product and producing the final glass-ceramic by an additional heat treatment. Small dental bridges of lithium disilicate glass-ceramic were fabricated using a molding technology. ZrO2 ceramics show high toughness and strength and were veneered with fluoroapatite glass-ceramic. Machining is possible with a porous intermediate product.

rf power system for thrust measurements of a helicon plasma source.

PubMed

Kieckhafer, Alexander W; Walker, Mitchell L R

2010-07-01

A rf power system has been developed, which allows the use of rf plasma devices in an electric propulsion test facility without excessive noise pollution in thruster diagnostics. Of particular importance are thrust stand measurements, which were previously impossible due to noise. Three major changes were made to the rf power system: first, the cable connection was changed from a balanced transmission line to an unbalanced coaxial line. Second, the rf power cabinet was placed remotely in order to reduce vibration-induced noise in the thrust stand. Finally, a relationship between transmission line length and rf was developed, which allows good transmission of rf power from the matching network to the helicon antenna. The modified system was tested on a thrust measurement stand and showed that rf power has no statistically significant contribution to the thrust stand measurement.

Influence of ceramic thickness and ceramic materials on fracture resistance of posterior partial coverage restorations.

PubMed

Bakeman, E M; Rego, N; Chaiyabutr, Y; Kois, J C

2015-01-01

This study evaluated the influence of ceramic thickness and ceramic materials on fracture resistance of posterior partial coverage ceramic restorations. Forty extracted molars were allocated into four groups (n=10) to test for two variables: 1) the thickness of ceramic (1 mm or 2 mm) and 2) the ceramic materials (a lithium disilicate glass-ceramic [IPS e.max] or leucite-reinforced glass ceramic [IPS Empress]). All ceramic restorations were luted with resin cement (Variolink II) on the prepared teeth. These luted specimens were loaded to failure in a universal testing machine, in the compression mode, with a crosshead speed of 1.0 mm/min. The data were analyzed using two-way analysis of variance and the Tukey Honestly Significantly Different multiple comparison test (α =0.05). The fracture resistance revealed a significant effect for materials (p<0.001); however, the thickness of ceramic was not significant (p=0.074), and the interaction between the thickness of ceramic and the materials was not significant (p=0.406). Mean (standard deviation) fracture resistance values were as follows: a 2-mm thickness of a lithium disilicate bonded to tooth structure (2505 [401] N) revealed a significantly higher fracture resistance than did a 1-mm thickness of leucite-reinforced (1569 [452] N) and a 2-mm thickness of leucite-reinforced ceramic bonded to tooth structure (1716 [436] N) (p<0.05). There was no significant difference in fracture resistance values between a lithium disilicate ceramic at 1-mm thickness (2105 [567] N) and at 2-mm thickness. Using a lithium disilicate glass ceramic for partial coverage restoration significantly improved fracture resistance compared to using a leucite-reinforced glass ceramic. The thickness of ceramic had no significant effect on fracture resistance when the ceramics were bonded to the underlying tooth structure.

Fracture mode during cyclic loading of implant-supported single-tooth restorations.

PubMed

Hosseini, Mandana; Kleven, Erik; Gotfredsen, Klaus

2012-08-01

Fracture of veneering ceramics in zirconia-based restorations has frequently been reported. Investigation of the fracture mode of implant-supported ceramic restorations by using clinically relevant laboratory protocols is needed. This study compared the mode of fracture and number of cyclic loads until veneering fracture when ceramic and metal ceramic restorations with different veneering ceramics were supported by implants. Thirty-two implant-supported single-tooth restorations were fabricated. The test group was composed of 16 ceramic restorations of zirconia abutment-retained crowns with zirconia copings veneered with glass-ceramics (n=8) and feldspathic ceramics (n=8). The control group was composed of 16 metal ceramic restorations of titanium abutment-retained crowns with gold alloy copings veneered with glass (n=8) and feldspathic ceramics (n=8). The palatal surfaces of the crowns were exposed to cyclic loading of 800 N with a frequency of 2 Hz, which continued to 4.2 million cycles or until fracture of the copings, abutments, or implants. The number of cycles and the fracture modes were recorded. The fracture modes were analyzed by descriptive analysis and the Mann-Whitney test (α=.05). The differences in loading cycles until veneering fracture were estimated with the Cox proportional hazards analysis. Veneering fracture was the most frequently observed fracture mode. The severity of fractures was significantly more in ceramic restorations than in metal ceramic restorations. Significantly more loading cycles until veneering fracture were estimated with metal ceramic restorations veneered with glass-ceramics than with other restorations. The metal ceramic restorations demonstrated fewer and less severe fractures and resisted more cyclic loads than the ceramic restorations, particularly when the metal ceramic crowns were veneered with glass-ceramics. Copyright © 2012 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Exposure to 1800 MHz radiofrequency radiation impairs neurite outgrowth of embryonic neural stem cells

PubMed Central

Chen, Chunhai; Ma, Qinlong; Liu, Chuan; Deng, Ping; Zhu, Gang; Zhang, Lei; He, Mindi; Lu, Yonghui; Duan, Weixia; Pei, Liping; Li, Min; Yu, Zhengping; Zhou, Zhou

2014-01-01

A radiofrequency electromagnetic field (RF-EMF) of 1800 MHz is widely used in mobile communications. However, the effects of RF-EMFs on cell biology are unclear. Embryonic neural stem cells (eNSCs) play a critical role in brain development. Thus, detecting the effects of RF-EMF on eNSCs is important for exploring the effects of RF-EMF on brain development. Here, we exposed eNSCs to 1800 MHz RF-EMF at specific absorption rate (SAR) values of 1, 2, and 4 W/kg for 1, 2, and 3 days. We found that 1800 MHz RF-EMF exposure did not influence eNSC apoptosis, proliferation, cell cycle or the mRNA expressions of related genes. RF-EMF exposure also did not alter the ratio of eNSC differentiated neurons and astrocytes. However, neurite outgrowth of eNSC differentiated neurons was inhibited after 4 W/kg RF-EMF exposure for 3 days. Additionally, the mRNA and protein expression of the proneural genes Ngn1 and NeuroD, which are crucial for neurite outgrowth, were decreased after RF-EMF exposure. The expression of their inhibitor Hes1 was upregulated by RF-EMF exposure. These results together suggested that 1800 MHz RF-EMF exposure impairs neurite outgrowth of eNSCs. More attention should be given to the potential adverse effects of RF-EMF exposure on brain development. PMID:24869783

Radiofrequency fields in MAS solid state NMR probes

NASA Astrophysics Data System (ADS)

Tošner, Zdeněk; Purea, Armin; Struppe, Jochem O.; Wegner, Sebastian; Engelke, Frank; Glaser, Steffen J.; Reif, Bernd

2017-11-01

We present a detailed analysis of the radiofrequency (RF) field over full volume of a rotor that is generated in a solenoid coil. On top of the usually considered static distribution of amplitudes along the coil axis we describe dynamic radial RF inhomogeneities induced by sample rotation. During magic angle spinning (MAS), the mechanical rotation of the sample about the magic angle, a spin packet travels through areas of different RF fields and experiences periodical modulations of both the RF amplitude and the phase. These modulations become particularly severe at the end regions of the coil where the relative RF amplitude varies up to ±25% and the RF phase changes within ±30°. Using extensive numerical simulations we demonstrate effects of RF inhomogeneity on pulse calibration and for the ramped CP experiment performed at a wide range of MAS rates. In addition, we review various methods to map RF fields using a B0 gradient along the sample (rotor axis) for imaging purposes. Under such a gradient, a nutation experiment provides directly the RF amplitude distribution, a cross polarization experiment images the correlation of the RF fields on the two channels according to the Hartmann-Hahn matching condition, while a spin-lock experiment allows to calibrate the RF amplitude employing the rotary resonance recoupling condition. Knowledge of the RF field distribution in a coil provides key to understand its effects on performance of a pulse sequence at the spectrometer and enables to set robustness requirements in the experimental design.

De-repression of RaRF-mediated RAR repression by adenovirus E1A in the nucleolus.

PubMed

Um, Soo-Jong; Youn, Hye Sook; Kim, Eun-Joo

2014-02-21

Transcriptional activity of the retinoic acid receptor (RAR) is regulated by diverse binding partners, including classical corepressors and coactivators, in response to its ligand retinoic acid (RA). Recently, we identified a novel corepressor of RAR called the retinoic acid resistance factor (RaRF) (manuscript submitted). Here, we report how adenovirus E1A stimulates RAR activity by associating with RaRF. Based on immunoprecipitation (IP) assays, E1A interacts with RaRF through the conserved region 2 (CR2), which is also responsible for pRb binding. The first coiled-coil domain of RaRF was sufficient for this interaction. An in vitro glutathione-S-transferase (GST) pull-down assay was used to confirm the direct interaction between E1A and RaRF. Further fluorescence microscopy indicated that E1A and RaRF were located in the nucleoplasm and nucleolus, respectively. However, RaRF overexpression promoted nucleolar translocation of E1A from the nucleoplasm. Both the RA-dependent interaction of RAR with RaRF and RAR translocation to the nucleolus were disrupted by E1A. RaRF-mediated RAR repression was impaired by wild-type E1A, but not by the RaRF binding-defective E1A mutant. Taken together, our data suggest that E1A is sequestered to the nucleolus by RaRF through a specific interaction, thereby leaving RAR in the nucleoplasm for transcriptional activation. Copyright © 2014 Elsevier Inc. All rights reserved.

Nonlinear fracture of concrete and ceramics

NASA Technical Reports Server (NTRS)

Kobayashi, Albert S.; Du, Jia-Ji; Hawkins, Niel M.; Bradt, Richard C.

1989-01-01

The nonlinear fracture process zones in an impacted unnotched concrete bend specimen, a prenotched ceramic bend specimen, and an unnotched ceramic/ceramic composite bend specimen were estimated through hybrid experimental numerical analysis. Aggregate bridging in concrete, particulate bridging in ceramics, and fiber bridging in ceramic/ceramic composite are modeled by Barenblatt-type cohesive zones which are incorporated into the finite-element models of the bend specimens. Both generation and propagation analyses are used to estimate the distribution of crack closure stresses in the nonlinear fracture process zones. The finite-element models are then used to simulate fracture tests consisting of rapid crack propagation in an impacted concrete bend specimen, and stable crack growth and strain softening in a ceramic and ceramic/ceramic composite bend specimens.

[Manufacture and clinical application of 215 IPS-Empress casting ceramic restorations].

PubMed

Zhao, Na; Zhou, Jian

2008-08-01

To explore the manufacture and clinical application of IPS-Empress casting ceramic restorations. The problems in manufacture and clinical operation of 215 casting ceramic restorations were analyzed. In 215 casting ceramic restorations, 12 (5.58%) casting ceramic restorations were affected by clinical design or application, 15 (6.98%) casting ceramic restorations were affected by some manufacture problems, and 14 (6.51%) casting ceramic restorations were affected by clinical try-in. Through 2-3 years' follow-up, the achievement ratio of 215 IPS-Empress casting ceramic restorations was 94.88%, and 11 casting ceramic restorations were affected by some problems. Beauty and simultaneous enamel wear are the characteristics of casting ceramic restorations. But because of its brittle, the indications should be strictly selected.

Method of producing a carbon coated ceramic membrane and associated product

DOEpatents

Liu, P.K.T.; Gallaher, G.R.; Wu, J.C.S.

1993-11-16

A method is described for producing a carbon coated ceramic membrane including passing a selected hydrocarbon vapor through a ceramic membrane and controlling ceramic membrane exposure temperature and ceramic membrane exposure time. The method produces a carbon coated ceramic membrane of reduced pore size and modified surface properties having increased chemical, thermal and hydrothermal stability over an uncoated ceramic membrane. 12 figures.

Y-TZP ceramic processing from coprecipitated powders: a comparative study with three commercial dental ceramics.

PubMed

Lazar, Dolores R R; Bottino, Marco C; Ozcan, Mutlu; Valandro, Luiz Felipe; Amaral, Regina; Ussui, Valter; Bressiani, Ana H A

2008-12-01

(1) To synthesize 3mol% yttria-stabilized zirconia (3Y-TZP) powders via coprecipitation route, (2) to obtain zirconia ceramic specimens, analyze surface characteristics, and mechanical properties, and (3) to compare the processed material with three reinforced dental ceramics. A coprecipitation route was used to synthesize a 3mol% yttria-stabilized zirconia ceramic processed by uniaxial compaction and pressureless sintering. Commercially available alumina or alumina/zirconia ceramics, namely Procera AllCeram (PA), In-Ceram Zirconia Block (CAZ) and In-Ceram Zirconia (IZ) were chosen for comparison. All specimens (6mmx5mmx5mm) were polished and ultrasonically cleaned. Qualitative phase analysis was performed by XRD and apparent densities were measured on the basis of Archimedes principle. Ceramics were also characterized using SEM, TEM and EDS. The hardness measurements were made employing Vickers hardness test. Fracture toughness (K(IC)) was calculated. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's test (alpha=0.05). ANOVA revealed that the Vickers hardness (p<0.0001) and fracture toughness (p<0.0001) were affected by the ceramic materials composition. It was confirmed that the PA ceramic was constituted of a rhombohedral alumina matrix, so-called alpha-alumina. Both CAZ and IZ ceramics presented tetragonal zirconia and alpha-alumina mixture of phases. The SEM/EDS analysis confirmed the presence of aluminum in PA ceramic. In the IZ and CAZ ceramics aluminum, zirconium and cerium in grains involved by a second phase containing aluminum, silicon and lanthanum were identified. PA showed significantly higher mean Vickers hardness values (H(V)) (18.4+/-0.5GPa) compared to vitreous CAZ (10.3+/-0.2GPa) and IZ (10.6+/-0.4GPa) ceramics. Experimental Y-TZP showed significantly lower results than that of the other monophased ceramic (PA) (p<0.05) but it showed significantly higher fracture toughness (6.0+/-0.2MPam(1/2)) values when compared to the other tested ceramics (p<0.05). The coprecipitation method used to synthesize zirconia powders and the adopted ceramic processing conditions led to ceramics with mechanical properties comparable to commercially available reinforced ceramic materials.

Using antennas separated in flight direction to avoid effect of emitter clock drift in geolocation

DOEpatents

Ormesher, Richard C.; Bickel, Douglas L

2012-10-23

The location of a land-based radio frequency (RF) emitter is determined from an airborne platform. RF signaling is received from the RF emitter via first and second antennas. In response to the received RF signaling, signal samples for both antennas are produced and processed to determine the location of the RF emitter.

The RF Probe: providing space situational awareness through broad-spectrum detection and characterization

NASA Astrophysics Data System (ADS)

Zenick, Raymond; Kohlhepp, Kimberly; Partch, Russell

2004-09-01

AeroAstro's patented RF Probe is a system designed to address the needs of spacecraft developers and operators interested in measuring and analyzing near-field RF emissions emanating from a nearby spacecraft of interest. The RF Probe consists of an intelligent spectrum analyzer with digital signal processing capabilities combined with a calibrated, wide-bandwidth antenna and RF front end that covers the 50 kHz to 18 GHz spectrum. It is capable of acquiring signal level and signal vector information, classifying signals, assessing the quality of a satellite"s transponders, and characterizing near-field electromagnetic emissions. The RF Probe is intended for either incorporation as part of a suite of spacecraft sensors, or as a stand-alone sensor on spacecraft or other platforms such as Unmanned Aerial Vehicles (UAVs). The RF Probe was initially conceived as a tool to detect and aid in diagnosis of malfunctions in a spacecraft of interest. However, the utility of the RF Probe goes far beyond this initial concept, spanning a wide range of military applications. Most importantly, the RF Probe can provide space situational awareness for critical on-orbit assets by detecting externally induced RF fields, aiding in protection against potentially devastating attacks.

Development of a dual-pulse RF driver for an S-band (= 2856 MHz) RF electron linear accelerator

NASA Astrophysics Data System (ADS)

Cha, Sungsu; Kim, Yujong; Lee, Byeong-No; Lee, Byung Cheol; Cha, Hyungki; Ha, Jang Ho; Park, Hyung Dal; Lee, Seung Hyun; Kim, Hui Su; Buaphad, Pikad

2016-04-01

The radiation equipment research division of Korea Atomic Energy Research Institute has developed a Container Inspection System (CIS) using a Radio Frequency (RF) electron linear accelerator for port security. The primary purpose of the CIS is to detect nuclear materials and explosives, as well country-specific prohibited substances, e.g., smuggled. The CIS consists of a 9/6 MeV dualenergy electron linear accelerator for distinguishing between organic and inorganic materials. The accelerator consists of an electron gun, an RF accelerating structure, an RF driver, a modulator, electromagnets, a cooling system, a X-ray generating target, X-ray collimator, a detector, and a container moving system. The RF driver is an important part of the configuration because it is the RF power source: it supplies the RF power to the accelerating structure. A unique aspect of the RF driver is that it generates dual RF power to generate dual energy (9/6 MeV). The advantage of this RF driver is that it can allow the pulse width to vary and can be used to obtain a wide range of energy output, and pulse repetition rates up to 300 Hz. For this reason, 140 W (5 MW - 9 MeV) and 37 W (3.4 MW - 6 MeV) power outputs are available independently. A high power test for 20 minutes demonstrate that stable dual output powers can be generated. Moreover, the dual power can be applied to the accelerator which has stable accelerator operation. In this paper, the design, fabrication and high power test of the RF driver for the RF electron linear accelerator (linac) are presented.

Identification of IRX1 as a Risk Locus for Rheumatoid Factor Positivity in Rheumatoid Arthritis in a Genome-Wide Association Study.

PubMed

Julià, Antonio; Blanco, Francisco; Fernández-Gutierrez, Benjamín; González, Antonio; Cañete, Juan D; Maymó, Joan; Alperi-López, Mercedes; Olivè, Alex; Corominas, Héctor; Martínez-Taboada, Víctor; González-Álvaro, Isidoro; Fernandez-Nebro, Antonio; Erra, Alba; Sánchez-Fernández, Simón; Alonso, Arnald; López-Lasanta, María; Tortosa, Raül; Codó, Laia; Lluis Gelpi, Josep; García-Montero, Andrés C; Bertranpetit, Jaume; Absher, Devin; Myers, Richard M; Tornero, Jesús; Marsal, Sara

2016-06-01

Rheumatoid factor (RF) is a well-established diagnostic and prognostic biomarker in rheumatoid arthritis (RA). However, ∼20% of RA patients are negative for this anti-IgG antibody. To date, only variation at the HLA-DRB1 gene has been associated with the presence of RF. This study was undertaken to identify additional genetic variants associated with RF positivity. A genome-wide association study (GWAS) for RF positivity was performed using an Illumina Quad610 genotyping platform. A total of 937 RF-positive and 323 RF-negative RA patients were genotyped for >550,000 single-nucleotide polymorphisms (SNPs). Association testing was performed using an allelic chi-square test implemented in Plink software. An independent cohort of 472 RF-positive and 190 RF-negative RA patients was used to validate the most significant findings. In the discovery stage, a SNP in the IRX1 locus on chromosome 5p15.3 (SNP rs1502644) showed a genome-wide significant association with RF positivity (P = 4.13 × 10(-8) , odds ratio [OR] 0.37 [95% confidence interval (95% CI) 0.26-0.53]). In the validation stage, the association of IRX1 with RF was replicated in an independent group of RA patients (P = 0.034, OR 0.58 [95% CI 0.35-0.97] and combined P = 1.14 × 10(-8) , OR 0.43 [95% CI 0.32-0.58]). To our knowledge, this is the first GWAS of RF positivity in RA. Variation at the IRX1 locus on chromosome 5p15.3 is associated with the presence of RF. Our findings indicate that IRX1 and HLA-DRB1 are the strongest genetic factors for RF production in RA. © 2016, American College of Rheumatology.

Review of the Reference Dose and Reference Concentration Processes Document

EPA Pesticide Factsheets

Summarizes the review and deliberations of the Risk Assessment Forum’s RfD/RfC Technical Panel and its recommendations for improvements in oral referencedose/inhalation reference concentration (RfD/RfC) process.

Joining engineering ceramics

NASA Astrophysics Data System (ADS)

Loehman, Ronald E.

Methods for joining ceramics are outlined with attention given to their fundamental properties, and some examples of ceramic bonding in engineering ceramic systems are presented. Ceramic-ceramic bonds using no filler material include diffusion and electric-field bonding and ceramic welding, and bonds with filler materials can be provided by Mo-Mn brazing, microwave joining, and reactive nonmetallic liquid bonding. Ceramic-metal joints can be effected with filler material by means of the same ceramic-ceramic processes and without filler material by means of use of molten glass or diffusion bonding. Key properties of the bonding processes include: bonds with discontinuous material properties, energies that are positive relative to the bulk material, and unique chemical and mechanical properties. The processes and properties are outlined for ceramic-metal joints and for joining silicon nitride, and the factors that control wetting, adhesion, and reaction on the atomic scale are critical for establishing successful joints.

The effect of five kinds of surface treatment agents on the bond strength to various ceramics with thermocycle aging.

PubMed

Noda, Yukari; Nakajima, Masatoshi; Takahashi, Masahiro; Mamanee, Teerapong; Hosaka, Keiichi; Takagaki, Tomohiro; Ikeda, Masaomi; Foxton, Richard M; Tagami, Junji

2017-11-29

This study evaluated the effects of ceramic surface treatment agents on shear bond strengths to ceramic materials with and without thermocycling. Ceramic plates were prepared from feldspathic ceramic; AAA, lithium disilicate ceramic material; IPS e.max Press, zirconia ceramic; Lava. Ceramic surfaces were pretreated with one of five surface treatment agents (Clearfil PhotoBond mixed with Porcelainbond activator (PB), Clearfil SE One mixed with Porcelainbond activator (SO), Ceramic Primer (CP), Universal Primer (UP), Scotchbond Universal (SU)), and then a resin cement (Clapearl DC) was filled. After 0, 5,000, and 10,000 thermocycles, micro-shear bond strengths between ceramic-cement interfaces were determined. SU exhibited significantly lower initial bond strength to AAA and e.max than PB, SO, CP, and UP. For Lava, PB, SO, CP and SU exhibited higher initial bond strengths than UP. Thermocycles reduced bond strengths to all the ceramic materials with any surface treatment.

Biomechanical Assessment of Restored Mandibular Molar by Endocrown in Comparison to a Glass Fiber Post-Retained Conventional Crown: 3D Finite Element Analysis.

PubMed

Helal, Mohammed Abu; Wang, Zhigang

2017-10-25

To compare equivalent and contact stresses in a mandibular molar restored by all-ceramic crowns through two methods: ceramic endocrowns and ceramic crowns supported by fiber-reinforced composite (FRC) posts and core, by using 3D finite element analysis during normal masticatory load. Three 3D models of a mandibular first molar were made and labeled as such: intact molar with no restoration (A); ceramic endocrown-restored molar (B); ceramic crown supported by FRC posts and core restored molar (C). By using 3D FE analysis with contact components, normal masticatory load was simulated. The mvM stresses in all models were calculated. Maximal mvM stresses in the ceramic of restorations, dentin, and luting cement were contrasted among models and to values of materials' strength. Contact shear and tensile stresses in the restoration/tooth interface around restorations were also calculated. The highest mvM stress levels in the enamel and dentin for the tooth restored by ceramic endocrown were lower in the crown ceramic than in tooth restored with FRC posts and all-ceramic crowns; however, in the resin adhesive cement interface it was lower for ceramic crown supported by FRC posts than the in ceramic endocrown restoration. The maximum contact shear and tensile stress values along the restoration/tooth interface of ceramic endocrowns were lower than those with ceramic crowns supported by FRC posts. Ceramic endocrown restorations presented a lower mvM stress level in dentin than the conventional ceramic crowns supported by FRC posts and core. Ceramic endocrown restorations in molars are less susceptible to damage than those with conventional ceramic crowns retained by FRC posts. Ceramic endocrowns properly cemented in molars must not be fractured or loosen during normal masticatory load. Therefore, ceramic endocrowns are advised as practicable, minimally invasive, and esthetic restorations for root canal treated mandibular molars. © 2017 by the American College of Prosthodontists.

CEBAF Upgrade Cryomodule Component Testing in the Horizontal Test Bed (HTB)

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

I.E. Campisi; B. Carpenter; G.K. Davis

2001-06-01

The planned upgrade of the CEBAF electron accelerator includes the development of an improved cryomodule. Several components differ substantially from the original CEBAF cryomodule; these include: the new 7-cell, 1.5 GHz cavities with integral helium vessel, a new, backlash-free cavity tuner, the waveguide coupler with its room-temperature ceramic window, and the HOM damping filters. In order to test the design features and performance of the new components, a horizontal cryostat (Horizontal Test Bed) has been constructed which allows testing with a turn around time of less than three weeks. This cryostat provides the environment for testing one or two cavities,more » with associated auxiliary components, in a condition similar to that of a real cryomodule. A series of tests has been performed on a prototype 7-cell cavity and the above-mentioned systems. In this paper the results of the tests on the cryostat, on the cavity performance, on its coupler, on the tuner characteristics, and on the microphonics behavior will be reported.« less

Low temperature biosynthesis of Li2O-MgO-P2O5-TiO2 nanocrystalline glass with mesoporous structure exhibiting fast lithium ion conduction.

PubMed

Du, Xiaoyong; He, Wen; Zhang, Xudong; Ma, Jinyun; Wang, Chonghai; Li, Chuanshan; Yue, Yuanzheng

2013-04-01

We demonstrate a biomimetic synthesis methodology that allows us to create Li2O-MgO-P2O5-TiO2 nanocrystalline glass with mesoporous structure at lower temperature. We design a 'nanocrystal-glass' configuration to build a nanoarchitecture by means of yeast cell templates self-assembly followed by the controlled in-situ biomineralization of materials on the cell wall. Electrochemically active nanocrystals are used as the lamellar building blocks of mesopores, and the semiconductive glass phase can act both as the 'glue' between nanocrystals and functionalized component. The Li2O-MgO-P2O5-TiO2 nanocrystalline glass exhibits outstanding thermal stability, high conductivity and wide potential window. This approach could be applied to many other multicomponent glass-ceramics to fabricate mesoporous conducting materials for solid-state lithium batteries. Copyright © 2012 Elsevier B.V. All rights reserved.

A hydrothermal atomic force microscope for imaging in aqueous solution up to 150 °C

NASA Astrophysics Data System (ADS)

Higgins, Steven R.; Eggleston, Carrick M.; Knauss, Kevin G.; Boro, Carl O.

1998-08-01

We present the design of a contact atomic force microscope (AFM) that can be used to image solid surfaces in aqueous solution up to 150 °C and 6 atm. The main features of this unique AFM are: (1) an inert gas pressurized microscope base containing stepper motor for coarse advance and the piezoelectric tube scanner; (2) a chemically inert membrane separating these parts from the fluid cell; (3) a titanium fluid cell with fluid inlet-outlet ports, a thermocouple port, and a sapphire optical window; (4) a resistively heated ceramic booster heater for the fluid cell to maintain the temperature of solutions sourced from a hydrothermal bomb; and (5) mass flow control. The design overcomes current limitations on the temperature and pressure range accessible to AFM imaging in aqueous solutions. Images taken at temperature and pressure are presented, demonstrating the unit-cell scale (<1 nm) vertical resolution of the AFM under hydrothermal conditions.

Edward Burne-Jones' Heavenly Conception: A Biblical Cosmos

NASA Astrophysics Data System (ADS)

Cheney, L. D. G.

2016-01-01

Edward Burne-Jones was a Pre-Raphaelite artist and designer, who collaborated with William Morris on many decorative arts (stained glass windows, book illustrations, ceramic and tapestry designs). He was a founding partner in the firm Morris, Marshall, Faulkner & Company. Burne-Jones composed The Days of Creation between 1870 and 1876 for the Morris firm. These paintings were executed in gouache and gold paint, and cartoons were made for tile and in stained glass, for the Church of St. Editha at Tamworth in Staffordshire. Burne-Jones' creation was highly praised and elegantly described by Oscar Wilde: “The picture is divided into six compartments, each representing a day in the Creation of the World, under the symbol of an angel holding a crystal globe, within which is shown the work of a day.” This paper will examine how Burne-Jones visualized an unusual celestial creation where angels holding magical spheres unveil the divine manifestation for the creation of a terrestrial realm. He created a cosmic utopia of the natural world.

Prevalence and Clinical Characteristics of Refractory Hypertension.

PubMed

Armario, Pedro; Calhoun, David A; Oliveras, Anna; Blanch, Pedro; Vinyoles, Ernest; Banegas, Jose R; Gorostidi, Manuel; Segura, Julián; Ruilope, Luis M; Dudenbostel, Tanja; de la Sierra, Alejandro

2017-12-07

We aimed to estimate the prevalence of refractory hypertension (RfH) and to determine the clinical differences between these patients and resistant hypertensives (RH). Secondly, we assessed the prevalence of white-coat RfH and clinical differences between true- and white-coat RfH patients. The present analysis was conducted on the Spanish Ambulatory Blood Pressure Monitoring Registry database containing 70 997 treated hypertensive patients. RH and RfH were defined by the presence of elevated office blood pressure (≥140 and/or 90 mm Hg) in patients treated with at least 3 (RH) and 5 (RfH) antihypertensive drugs. White-coat RfH was defined by RfH with normal (<130/80 mm Hg) 24-hour blood pressure. A total of 11.972 (16.9%) patients fulfilled the standard criteria of RH, and 955 (1.4%) were considered as having RfH. Compared with RH patients, those with RfH were younger, more frequently male, and after adjusting for age and sex, had increased prevalence of target organ damage, and previous cardiovascular disease. The prevalence of white coat RfH was lower than white-coat RH (26.7% versus 37.1%, P <0.001). White-coat RfH, in comparison with those with true RfH, showed a lower prevalence of both left ventricular hypertrophy (22% versus 29.7%; P =0.018) and microalbuminuria (28.3% versus 42.9%; P =0.047). The prevalence of RfH was low and these patients had a greater cardiovascular risk profile compared with RH. One out of 4 patients with RfH have normal 24-hour blood pressure and less target organ damage, thus indicating the important role of ambulatory blood pressure monitoring in guiding antihypertensive therapy in difficult-to-treat patients. © 2017 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley.

Mutagenic and morphologic impacts of 1.8GHz radiofrequency radiation on human peripheral blood lymphocytes (hPBLs) and possible protective role of pre-treatment with Ginkgo biloba (EGb 761).

PubMed

Esmekaya, Meric Arda; Aytekin, Ebru; Ozgur, Elcin; Güler, Göknur; Ergun, Mehmet Ali; Omeroğlu, Suna; Seyhan, Nesrin

2011-12-01

The mutagenic and morphologic effects of 1.8GHz Global System for Mobile Communications (GSM) modulated RF (radiofrequency) radiation alone and in combination with Ginkgo biloba (EGb 761) pre-treatment in human peripheral blood lymphocytes (hPBLs) were investigated in this study using Sister Chromatid Exchange (SCE) and electron microscopy. Cell viability was assessed with 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) reduction assay. The lymphocyte cultures were exposed to GSM modulated RF radiation at 1.8GHz for 6, 8, 24 and 48h with and without EGb 761. We observed morphological changes in pulse-modulated RF radiated lymphocytes. Longer exposure periods led to destruction of organelle and nucleus structures. Chromatin change and the loss of mitochondrial crista occurred in cells exposed to RF for 8h and 24h and were more pronounced in cells exposed for 48h. Cytoplasmic lysis and destruction of membrane integrity of cells and nuclei were also seen in 48h RF exposed cells. There was a significant increase (p<0.05) in SCE frequency in RF exposed lymphocytes compared to sham controls. EGb 761 pre-treatment significantly decreased SCE from RF radiation. RF radiation also inhibited cell viability in a time dependent manner. The inhibitory effects of RF radiation on the growth of lymphoctes were marked in longer exposure periods. EGb 761 pre-treatment significantly increased cell viability in RF+EGb 761 treated groups at 8 and 24h when compared to RF exposed groups alone. The results of our study showed that RF radiation affects cell morphology, increases SCE and inhibits cell proliferation. However, EGb 761 has a protective role against RF induced mutagenity. We concluded that RF radiation induces chromosomal damage in hPBLs but this damage may be reduced by EGb 761 pre-treatment. Copyright © 2011 Elsevier B.V. All rights reserved.

Cultural Resource Investigation of the Dworshak Reservoir Project, North Fork Clearwater River, Northern Idaho.

DTIC Science & Technology

1983-01-01

Rhanius purshiana), ninebark (Physocarpus malvaceus), ocean spray (Holodiscus discolor) , elderberry ( Sambucus canadensis) , huckleberry (Vaccinium...sherd 2.1.6.1 Ceramic White rim sherd 2.1.7.1 Ceramic White rim sherd 2.1.8.1 Ceramic Rim sherd w/ flower design 2.1.9.1 Ceramic Rim sherd w/ flower design...2.1.10.1 Ceramic Rim sherd w/ flower design 2.1.11.1 Ceramic Rim sherd w/ flower design 2.1.12.1 Ceramic Rim sherd wd 2.1.13.1 Ceramic Body sherd

RF study and 3-D simulations of a side-coupling thermionic RF-gun

NASA Astrophysics Data System (ADS)

Rimjaem, S.; Kusoljariyakul, K.; Thongbai, C.

2014-02-01

A thermionic RF-gun for generating ultra-short electron bunches was optimized, developed and used as a source at a linac-based THz radiation research laboratory of the Plasma and Beam Physics Research Facility, Chiang Mai University, Thailand. The RF-gun is a π/2-mode standing wave structure, which consists of two S-band accelerating cells and a side-coupling cavity. The 2856 MHz RF wave is supplied from an S-band klystron to the gun through the waveguide input-port at the cylindrical wall of the second cell. A fraction of the RF power is coupled from the second cell to the first one via a side-coupling cavity. Both the waveguide input-port and the side-coupling cavity lead to an asymmetric geometry of the gun. RF properties and electromagnetic field distributions inside the RF-gun were studied and numerically simulated by using computer codes SUPERFISH 7.19 and CST Microwave Studio 2012©. RF characterizations and tunings of the RF-gun were performed to ensure the reliability of the gun operation. The results from 3D simulations and measurements are compared and discussed in this paper. The influence of asymmetric field distributions inside the RF-gun on the electron beam properties was investigated via 3D beam dynamics simulations. A change in the coupling-plane of the side-coupling cavity is suggested to improve the gun performance.

Segmented lasing tube for high temperature laser assembly

DOEpatents

Sawicki, Richard H.; Alger, Terry W.; Finucane, Raymond G.; Hall, Jerome P.

1996-01-01

A high temperature laser assembly capable of withstanding operating temperatures in excess of 1500.degree. C. is described comprising a segmented cylindrical ceramic lasing tube having a plurality of cylindrical ceramic lasing tube segments of the same inner and outer diameters non-rigidly joined together in axial alignment; insulation of uniform thickness surround the walls of the ceramic lasing tube; a ceramic casing, preferably of quartz, surrounding the insulation; and a fluid cooled metal jacket surrounds the ceramic casing. In a preferred embodiment, the inner surface of each of the ceramic lasing tube segments are provided with a pair of oppositely spaced grooves in the wall thereof parallel to the center axis of the segmented cylindrical ceramic lasing tube, and both of the grooves and the center axis of the segmented cylindrical ceramic lasing tube lie in a common plane, with the grooves in each ceramic lasing tube segment in circumferential alignment with the grooves in the adjoining ceramic lasing tube segments; and one or more ceramic plates, all lying in a common plane to one another and with the central axis of the segmented ceramic lasing tube, are received in the grooves to provide additional wall area in the segmented ceramic lasing tube for collision and return to ground state of metastable metal atoms within the segmented ceramic lasing tube.

rf power system for thrust measurements of a helicon plasma source

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

Kieckhafer, Alexander W.; Walker, Mitchell L. R.

2010-07-15

A rf power system has been developed, which allows the use of rf plasma devices in an electric propulsion test facility without excessive noise pollution in thruster diagnostics. Of particular importance are thrust stand measurements, which were previously impossible due to noise. Three major changes were made to the rf power system: first, the cable connection was changed from a balanced transmission line to an unbalanced coaxial line. Second, the rf power cabinet was placed remotely in order to reduce vibration-induced noise in the thrust stand. Finally, a relationship between transmission line length and rf was developed, which allows goodmore » transmission of rf power from the matching network to the helicon antenna. The modified system was tested on a thrust measurement stand and showed that rf power has no statistically significant contribution to the thrust stand measurement.« less

Adjusting dental ceramics: An in vitro evaluation of the ability of various ceramic polishing kits to mimic glazed dental ceramic surface.

PubMed

Steiner, René; Beier, Ulrike S; Heiss-Kisielewsky, Irene; Engelmeier, Robert; Dumfahrt, Herbert; Dhima, Matilda

2015-06-01

During the insertion appointment, the practitioner is often faced with the need to adjust ceramic surfaces to fit a restoration to the adjacent or opposing dentition and soft tissues. The purpose of this study was to assess the ceramic surface smoothness achieved with various commercially available ceramic polishing kits on different commonly used ceramic systems. The reliability of the cost of a polishing kit as an indicator of improved surface smoothness was assessed. A total of 350 ceramic surfaces representing 5 commonly available ceramic systems (IPS Empress Esthetic, IPS e.max Press, Cergo Kiss, Vita PM 9, Imagine PressX) were treated with 5 types of ceramic polishing systems (Cerapreshine, 94006C, Ceramiste, Optrafine, Zenostar) by following the manufacturers' guidelines. The surface roughness was measured with a profilometer (Taylor Hobson; Precision Taylor Hobson Ltd). The effects of ceramic systems and polishing kits of interest on surface roughness were analyzed by 2-way ANOVA, paired t test, and Bonferroni corrected significance level. The ceramic systems and polishing kits statistically affected surface roughness (P<.001).The polishing kit Zenostar on IPS e.max Press created the smoothest ceramic surface. No correlation could be established between the high cost of the polishing kit and low surface roughness. None of the commonly used ceramic polishing kits could create a surface smoother than that of glazed ceramic (P<.001). The inclusion of a diamond polishing paste step is recommended to improve surface smoothness (P<.001). The cost of ceramic polishing kits is not recommended as a reliable indicator of better performance of ceramic polishing kits (P>.30). Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Bipolar radiofrequency ablation of the kidney: comparison with monopolar radiofrequency ablation.

PubMed

Nakada, Stephen Y; Jerde, Travis J; Warner, Thomas F; Wright, Andrew S; Haemmerich, Dieter; Mahvi, David M; Lee, Fred T

2003-12-01

We report initial ex vivo and in vivo studies using bipolar radiofrequency (RF) ablation of porcine kidneys. An internal ground electrode is positioned in the kidney opposite the RF electrode, resulting in ablation of all the intervening renal tissue. Ex vivo preparations of 10 porcine kidneys were perfused continuously with Ringer's solution and treated with either standard external grounded RF (N = 3) or bipolar RF ablation with 1 (N = 2), 2 (N = 3), or 3 (N = 2) cm of separation between the ground probe and the RF probe using a Model 30 RITA generator (RITA, Mountain View, CA). Target temperatures were 90 degrees C for 8 minutes. Gross and histologic assessments were made acutely. Four domestic pigs were treated with monopolar RF ablation of the lower pole of one kidney and bipolar RF with a 12-mm separation between the probes of the contralateral lower pole. Animals were harvested 48 hours later to maximize tissue damage for gross measurements and histologic evaluation. Ex vivo studies revealed grossly monopolar lesions 1.5 cm in maximum diameter and 1.75 cm(3) in volume. In comparison, bipolar lesions were 2.8 cm in maximum diameter and 10.3 cm(3) in volume using 3 cm of electrode separation. There was histologic evidence of cell death in all specimens. In vivo studies showed two distinct gross lesions with RF: one blanched and one hemorrhagic. Using bipolar RF, larger blanched lesions were achievable than with monopolar RF (2.80 cm(3) v 1.63 cm(3)). Overall, the combinations of blanched and hemorrhagic lesions were similar with monopolar and bipolar RF (5.01 v 5.31 cm(3)). Histologic evaluation verified cell death in the blanched lesions and rare areas of normal tissue in the hemorrhagic lesions. As shown by ex vivo data, bipolar RF can create larger lesions than does monopolar RF. In vivo, at 48 hours, both blanched and hemorrhagic gross lesions were seen using RF. In this model, blanched lesions predominated when performing bipolar RF.

Characterization techniques to predict mechanical behaviour of green ceramic bodies fabricated by ceramic microstereolithography

NASA Astrophysics Data System (ADS)

Adake, Chandrashekhar V.; Bhargava, Parag; Gandhi, Prasanna

2018-02-01

Ceramic microstereolithography (CMSL) has emerged as solid free form (SFF) fabrication technology in which complex ceramic parts are fabricated from ceramic suspensions which are formulated by dispersing ceramic particles in UV curable resins. Ceramic parts are fabricated by exposing ceramic suspension to computer controlled UV light which polymerizes resin to polymer and this polymer forms rigid network around ceramic particles. A 3-dimensional part is created by piling cured layers one over the other. These ceramic parts are used to build microelectromechanical (MEMS) devices after thermal treatment. In many cases green ceramic parts can be directly utilized to build MEMS devices. Hence characterization of these parts is essential in terms of their mechanical behaviour prior to their use in MEMS devices. Mechanical behaviour of these green ceramic parts depends on cross link density which in turn depends on chemical structure of monomer, concentrations of photoinitiator and UV energy dose. Mechanical behaviour can be determined with the aid of nanoindentation. And extent of crosslinking can be verified with the aid of DSC. FTIR characterization is used to analyse (-C=C-) double bond conversion. This paper explains characterization tools to predict the mechanical behaviour of green ceramic bodies fabricated in CMSL

Radiofrequency fields in MAS solid state NMR probes.

PubMed

Tošner, Zdeněk; Purea, Armin; Struppe, Jochem O; Wegner, Sebastian; Engelke, Frank; Glaser, Steffen J; Reif, Bernd

2017-11-01

We present a detailed analysis of the radiofrequency (RF) field over full volume of a rotor that is generated in a solenoid coil. On top of the usually considered static distribution of amplitudes along the coil axis we describe dynamic radial RF inhomogeneities induced by sample rotation. During magic angle spinning (MAS), the mechanical rotation of the sample about the magic angle, a spin packet travels through areas of different RF fields and experiences periodical modulations of both the RF amplitude and the phase. These modulations become particularly severe at the end regions of the coil where the relative RF amplitude varies up to ±25% and the RF phase changes within ±30°. Using extensive numerical simulations we demonstrate effects of RF inhomogeneity on pulse calibration and for the ramped CP experiment performed at a wide range of MAS rates. In addition, we review various methods to map RF fields using a B 0 gradient along the sample (rotor axis) for imaging purposes. Under such a gradient, a nutation experiment provides directly the RF amplitude distribution, a cross polarization experiment images the correlation of the RF fields on the two channels according to the Hartmann-Hahn matching condition, while a spin-lock experiment allows to calibrate the RF amplitude employing the rotary resonance recoupling condition. Knowledge of the RF field distribution in a coil provides key to understand its effects on performance of a pulse sequence at the spectrometer and enables to set robustness requirements in the experimental design. Copyright © 2017 Elsevier Inc. All rights reserved.

Psychodynamic profile and reflective functioning in patients with bulimia nervosa.

PubMed

Mathiesen, Birgit Bork; Pedersen, Signe Holm; Sandros, Charlotte; Katznelson, Hannah; Wilczek, Alexander; Poulsen, Stig; Lunn, Susanne

2015-10-01

The aim of this study was to examine the general psychological functioning of patients suffering from bulimia nervosa (BN) using the Karolinska Psychodynamic Profile (KAPP). Furthermore, KAPP data and data from the Reflective Functioning scale (RF), measuring the ability to mentalize, were combined in order to examine differences in alexithymia, impulse control and affect regulation in patients with high or low RF. Seventy patients with BN were interviewed with both the KAPP and the Adult Attachment Interview (AAI) from which RF is coded. Differences in KAPP scores of patients with high or low RF were analyzed. Most of the patients with BN were found to have a personality structure within the normal or neurotic range (n=50 of 70). BN patients with a high RF had significantly lower scores on KAPP's alexithymia scale than patients with a low RF score, demonstrating that poor mentalizing is related to alexithymia. Concurrently, patients with high RF showed problems with impulse control and coping with aggressive affects according to KAPP scores. Although BN patients with high RF showed good capacities for describing their mental states, they still had difficulties regulating the emotions and impulses related to these states. Among patients suffering from BN, patients with high RF were significantly less alexithymic than low RF patients. The findings of this study are limited by the relatively small numbers of participants especially in the RF subgroups, posing a danger of not finding as significant existing differences in character pathology between high and low RF groups. Copyright © 2015 Elsevier Inc. All rights reserved.

Simulation of Impact Phenomena on the Composite Structures Containing Ceramic Plates and High Entropy Alloys

NASA Astrophysics Data System (ADS)

Geantă, V.; Cherecheș, T.; Lixandru, P.; Voiculescu, I.; Ștefănoiu, R.; Dragnea, D.; Zecheru, T.; Matache, L.

2017-06-01

Due to excellent mechanical properties, high entropy alloys from the system AlxCrFeCoNi can be used successfully to create composite structures containing both metallic and ceramic plates, which resists at dynamic load during high speeds impact (like projectiles, explosion). The paper presents four different composite structures made from a combination of metallic materials and ceramics plates: duralumin-ceramics, duralumin-ceramics-HEA, HEA-ceramics-HEA, HEA-ceramics-duralumin. Numerical simulation of impact behavior of the composite structures was performed by virtual methods, taking into account the mechanical properties of both materials. The best results were obtained using composite structures HEA-ceramics-HEA, HEA-ceramics-duralumin.

Environmental durability of ceramics and ceramic composites

NASA Technical Reports Server (NTRS)

Fox, Dennis S.

1992-01-01

An account is given of the current understanding of the environmental durability of both monolithic ceramics and ceramic-matrix composites, with a view to the prospective development of methods for the characterization, prediction, and improvement of ceramics' environmental durability. Attention is given to the environmental degradation behaviors of SiC, Si3N4, Al2O3, and glass-ceramic matrix compositions. The focus of corrosion prevention in Si-based ceramics such as SiC and Si3N4 is on the high and low sulfur fuel combustion-product effects encountered in heat engine applications of these ceramics; sintering additives and raw material impurities are noted to play a decisive role in ceramics' high temperature environmental response.

Improvements in Technique of NMR Imaging and NMR Diffusion Measurements in the Presence of Background Gradients.

NASA Astrophysics Data System (ADS)

Lian, Jianyu

In this work, modification of the cosine current distribution rf coil, PCOS, has been introduced and tested. The coil produces a very homogeneous rf magnetic field, and it is inexpensive to build and easy to tune for multiple resonance frequency. The geometrical parameters of the coil are optimized to produce the most homogeneous rf field over a large volume. To avoid rf field distortion when the coil length is comparable to a quarter wavelength, a parallel PCOS coil is proposed and discussed. For testing rf coils and correcting B _1 in NMR experiments, a simple, rugged and accurate NMR rf field mapping technique has been developed. The method has been tested and used in 1D, 2D, 3D and in vivo rf mapping experiments. The method has been proven to be very useful in the design of rf coils. To preserve the linear relation between rf output applied on an rf coil and modulating input for an rf modulating -amplifying system of NMR imaging spectrometer, a quadrature feedback loop is employed in an rf modulator with two orthogonal rf channels to correct the amplitude and phase non-linearities caused by the rf components in the rf system. The modulator is very linear over a large range and it can generate an arbitrary rf shape. A diffusion imaging sequence has been developed for measuring and imaging diffusion in the presence of background gradients. Cross terms between the diffusion sensitizing gradients and background gradients or imaging gradients can complicate diffusion measurement and make the interpretation of NMR diffusion data ambiguous, but these have been eliminated in this method. Further, the background gradients has been measured and imaged. A dipole random distribution model has been established to study background magnetic fields Delta B and background magnetic gradients G_0 produced by small particles in a sample when it is in a B_0 field. From this model, the minimum distance that a spin can approach a particle can be determined by measuring and <{bf G}_sp{0 }{2}>. From this model, the particle concentration in a sample can be determined by measuring the lineshape of a free induction decay (fid).

Heart Rate Detection During Sleep Using a Flexible RF Resonator and Injection-Locked PLL Sensor.

PubMed

Kim, Sung Woo; Choi, Soo Beom; An, Yong-Jun; Kim, Byung-Hyun; Kim, Deok Won; Yook, Jong-Gwan

2015-11-01

Novel nonintrusive technologies for wrist pulse detection have been developed and proposed as systems for sleep monitoring using three types of radio frequency (RF) sensors. The three types of RF sensors for heart rate measurement on wrist are a flexible RF single resonator, array resonators, and an injection-locked PLL resonator sensor. To verify the performance of the new RF systems, we compared heart rates between presleep time and postsleep onset time. Heart rates of ten subjects were measured using the RF systems during sleep. All three RF devices detected heart rates at 0.2 to 1 mm distance from the skin of the wrist over clothes made of cotton fabric. The wrist pulse signals of a flexible RF single resonator were consistent with the signals obtained by a portable piezoelectric transducer as a reference. Then, we confirmed that the heart rate after sleep onset time significantly decreased compared to before sleep. In conclusion, the RF system can be utilized as a noncontact nonintrusive method for measuring heart rates during sleep.

RF low-level control for the Linac4 H{sup −} source

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

Butterworth, A., E-mail: andrew.butterworth@cern.ch; Grudiev, A.; Lettry, J.

2015-04-08

The H{sup −} source for the Linac4 accelerator at CERN uses an RF driven plasma for the production of H{sup −}. The RF is supplied by a 2 MHz RF tube amplifier with a maximum power output of 100 kW and a pulse duration of up to 2 ms. The low-level RF signal generation and measurement system has been developed using standard CERN controls electronics in the VME form factor. The RF frequency and amplitude reference signals are generated using separate arbitrary waveform generator channels. The frequency and amplitude are both freely programmable over the duration of the RF pulse, which allowsmore » fine-tuning of the excitation. Measurements of the forward and reverse RF power signals are performed via directional couplers using high-speed digitizers, and permit the estimation of the plasma impedance and deposited power via an equivalent circuit model. The low-level RF hardware and software implementations are described, and experimental results obtained with the Linac4 ion sources in the test stand are presented.« less

C6, C7, and C8 perfluoroalkyl-substituted phosphinic acids.

PubMed

Singh, R P; Shreeve, J M

2000-04-17

Reaction of red phosphorus with RfI in a 1:2 molar ratio at 230 degrees C led to the formation of a mixture of (Rf)2PI and (Rf)PI2 (Rf = C6F13, C7F15, C8F17) in about a 70:30 ratio, respectively. These mixtures were separated by vacuum distillation. (Rf)2PI (Rf = C6F13, C7F15) are yellow liquids whereas (C8F17)2PI is a yellow solid. Oxidation of (Rf)2PI with excess NO2 led to (Rf)2P(O)OH (Rf = C6F13, C7F15, C8F17) in > 90% isolated yields after aqueous hydrolysis of the anhydride intermediates. These highly fluorinated phosphinic acids are white solids with sharp melting points and are highly soluble in methyl sulfoxide (DMSO) and 1,1,2-trichlorotrifluoroethane. However, solubility in chloroform and methylene dichloride is low. These perfluoroalkylphosphinic acids were characterized by IR, NMR (1H, 19F, and 31P), and mass spectra and elemental analysis.

Tribological properties of structural ceramics

NASA Technical Reports Server (NTRS)

Buckley, D. H.; Miyoshi, K.

1985-01-01

The tribological and lubricated behavior of both oxide and nonoxide ceramics are reviewed in this chapter. Ceramics are examined in contact with themselves, other harder materials and metals. Elastic, plastic and fracture behavior of ceramics in solid state contact is discussed. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as has been observed with metals. Grit size effects in two and three body abrasive wear are observed for ceramics. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Surface contaminants affect friction and adhesive wear. For example, carbon on silicon carbide and chlorine on aluminum oxide reduce friction while oxygen on metal surfaces in contact with ceramics increases friction. Lubrication increases the critical load necessary to initiate fracture of ceramics both in indentation and with sliding or rubbing. Ceramics compositions both as coatings and in composites are described for the high temperature lubrication of both alloys and ceramics.

Ceramic media amended with metal oxide for the capture of viruses in drinking water.

PubMed

Brown, J; Sobsey, M D

2009-04-01

Ceramic materials that can adsorb and/or inactivate viruses in water may find widespread application in low-tech drinking-water treatment technologies in developing countries, where porous ceramic filters and ceramic granular media filters are increasingly promoted for that purpose. We examined the adsorption and subsequent inactivation of bacteriophages MS2 and (phiX-174 on five ceramic media in batch adsorption studies to determine media suitability for use in a ceramic water filter application. The media examined were a kaolinitic ceramic medium and four kaolinitic ceramic media amended with iron or aluminium oxides that had been incorporated into the kaolinitic clays before firing. Batch adsorption tests indicate increased sorption and inactivation of surrogate viruses by media amended with Fe and Al oxide, with FeOOH-amended ceramic inactivating all bacteriophages up to 8 log10. Unmodified ceramic was a poor adsorbent of bacteriophages at less than 1 log10 adsorption-inactivation and high recovery of sorbed phages. These studies suggest that contact with ceramic media, modified with electropositive Fe or Al oxides, can reduce bacteriophages in waters to a greater extent than unmodified ceramic.

Effect of Ceramic Particle Velocity on Cold Spray Deposition of Metal-Ceramic Coatings

NASA Astrophysics Data System (ADS)

Sova, A.; Kosarev, V. F.; Papyrin, A.; Smurov, I.

2011-01-01

In this paper, metal-ceramic coatings are cold sprayed taking into account the spray parameters of both metal and ceramic particles. The effect of the ceramic particle velocity on the process of metal-ceramic coating formation and the coating properties is analyzed. Copper and aluminum powders are used as metal components. Two fractions of aluminum oxide and silicon carbide are sprayed in the tests. The ceramic particle velocity is varied by the particle injection into different zones of the gas flow: the subsonic and supersonic parts of the nozzle and the free jet after the nozzle exit. The experiments demonstrated the importance of the ceramic particle velocity for the stability of the process: Ceramic particles accelerated to a high enough velocity penetrate into the coating, while low-velocity ceramic particles rebound from its surface.

Advanced Turbine Technology Applications Project (ATTAP)

NASA Technical Reports Server (NTRS)

1992-01-01

ATTAP activities during the past year included test-bed engine design and development, ceramic component design, materials and component characterization, ceramic component process development and fabrication, ceramic component rig testing, and test-bed engine fabrication and testing. Significant technical challenges remain, but all areas exhibited progress. Test-bed engine design and development included engine mechanical design, combustion system design, alternate aerodynamic designs of gasifier scrolls, and engine system integration aimed at upgrading the AGT-5 from a 1038 C (1900 F) metal engine to a durable 1372 C (2500 F) structural ceramic component test-bed engine. ATTAP-defined ceramic and associated ceramic/metal component design activities completed include the ceramic gasifier turbine static structure, the ceramic gasifier turbine rotor, ceramic combustors, the ceramic regenerator disk, the ceramic power turbine rotors, and the ceramic/metal power turbine static structure. The material and component characterization efforts included the testing and evaluation of seven candidate materials and three development components. Ceramic component process development and fabrication proceeded for the gasifier turbine rotor, gasifier turbine scroll, gasifier turbine vanes and vane platform, extruded regenerator disks, and thermal insulation. Component rig activities included the development of both rigs and the necessary test procedures, and conduct of rig testing of the ceramic components and assemblies. Test-bed engine fabrication, testing, and development supported improvements in ceramic component technology that permit the achievement of both program performance and durability goals. Total test time in 1991 amounted to 847 hours, of which 128 hours were engine testing, and 719 were hot rig testing.

Rf2a and rf2b transcription factors

DOEpatents

Beachy, Roger N.; Petruccelli, Silvana; Dai, Shunhong

2007-10-02

A method of activating the rice tungro bacilliform virus (RTBV) promoter in vivo is disclosed. The RTBV promoter is activated by exposure to at least one protein selected from the group consisting of Rf2a and Rf2b.

Characterization of superconducting radiofrequency breakdown by two-mode excitation

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

Eremeev, Grigory V.; Palczewski, Ari D.

2014-01-14

We show that thermal and magnetic contributions to the breakdown of superconductivity in radiofrequency (RF) fields can be separated by applying two RF modes simultaneously to a superconducting surface. We develop a simple model that illustrates how mode-mixing RF data can be related to properties of the superconductor. Within our model the data can be described by a single parameter, which can be derived either from RF or thermometry data. Our RF and thermometry data are in good agreement with the model. We propose to use mode-mixing technique to decouple thermal and magnetic effects on RF breakdown of superconductors.

Comparison of approaches to rheumatic fever surveillance across Organisation for Economic Co-operation and Development countries.

PubMed

Oliver, Jane; Baker, Michael G; Pierse, Nevil; Carapetis, Jonathan

2015-11-01

Rheumatic fever (RF) prevention, control and surveillance are increasingly important priorities in New Zealand (NZ) and Australia. We compared RF surveillance across Organisation for Economic Co-operation and Development (OECD) member countries to assist in benchmarking and identifying useful approaches. A structured literature review was completed using Medline and PubMed databases, investigating RF incidence rates. Surveillance methods were noted. Health department websites were searched to assess whether addressing RF was a Government priority. Of 32 OECD member countries, nine reported RF incidence rates after 1999. Highest rates were seen in indigenous Australians, and NZ Māori and Pacific peoples. NZ and Australian surveillance systems are highly developed, with notification and register data compiled regularly. Only these two Governments appeared to prioritise RF surveillance and control. Other countries relied mainly on hospitalisation data. There is a lack of standardisation across incidence rate calculations. Israel and Italy may have relatively high RF rates among developed countries. RF lingers in specific populations in OECD member countries. At a minimum, RF registers are needed in higher incidence countries. Countries with low RF incidences should periodically review surveillance information to ensure rates are not increasing. © 2015 The Authors. Journal of Paediatrics and Child Health © 2015 Paediatrics and Child Health Division (Royal Australasian College of Physicians).

[Percutaneous ablation of malignant kidney tumors in rabbits by low frequency radio energy].

PubMed

Moskovitz, B; Nativ, O; Sabo, E; Barbara, Y; Mordohovich, D; Kaftori, Y; Shalhav, A; Goldwasser, B

1998-01-01

Radio-frequency (RF) current has been used successfully to ablate normal human tissue. To investigate further the clinical application of this modality in tumors, we studied the potential of using RF percutaneously to destroy experimental kidney tumors. 35 outbred albino rabbits underwent direct-implantation of renal VX2 tumor during open surgery. After 21 days, ultrasonography was performed to show tumor presence and size. A shielded RF needle was designed to be inserted percutaneously through an introduction needle. An electrical insulation shield covering the RF needle was retractable, controlling the length of exposure of the RF needle inside the tissue. 22 days after tumor implantation, RF was applied via this special needle using a ZoMed International RF generator. In one group of rabbits the procedure was performed under direct vision during open surgery, while in another group treatment was percutaneous, the needle guided by palpation of the tumor. Rabbits were killed 3 days later and revealed 4-25 mm intra-tumoral RF-induced lesions. A direct relation was found between lesion size and the power and duration of RF applied (at 7.5 W, R = 0.48, and P = 0.32). Based on our preliminary results we can conclude that RF may have clinical applications in the near future for percutaneous local tumor control in parenchymal organs.

Land cover and land use mapping of the iSimangaliso Wetland Park, South Africa: comparison of oblique and orthogonal random forest algorithms

NASA Astrophysics Data System (ADS)

Bassa, Zaakirah; Bob, Urmilla; Szantoi, Zoltan; Ismail, Riyad

2016-01-01

In recent years, the popularity of tree-based ensemble methods for land cover classification has increased significantly. Using WorldView-2 image data, we evaluate the potential of the oblique random forest algorithm (oRF) to classify a highly heterogeneous protected area. In contrast to the random forest (RF) algorithm, the oRF algorithm builds multivariate trees by learning the optimal split using a supervised model. The oRF binary algorithm is adapted to a multiclass land cover and land use application using both the "one-against-one" and "one-against-all" combination approaches. Results show that the oRF algorithms are capable of achieving high classification accuracies (>80%). However, there was no statistical difference in classification accuracies obtained by the oRF algorithms and the more popular RF algorithm. For all the algorithms, user accuracies (UAs) and producer accuracies (PAs) >80% were recorded for most of the classes. Both the RF and oRF algorithms poorly classified the indigenous forest class as indicated by the low UAs and PAs. Finally, the results from this study advocate and support the utility of the oRF algorithm for land cover and land use mapping of protected areas using WorldView-2 image data.

Pregnant Women Models Analyzed for RF Exposure and Temperature Increase in 3T RF Shimmed Birdcages

PubMed Central

Murbach, Manuel; Neufeld, Esra; Samaras, Theodoros; Córcoles, Juan; Robb, Fraser J.; Kainz, Wolfgang; Kuster, Niels

2017-01-01

Purpose MRI is increasingly used to scan pregnant patients. We investigated the effect of 3 Tesla (T) two-port radiofrequency (RF) shimming in anatomical pregnant women models. Theory and Methods RF shimming improves B1+ uniformity, but may at the same time significantly alter the induced current distribution and result in large changes in both the level and location of the absorbed RF energy. In this study, we evaluated the electrothermal exposure of pregnant women in the third, seventh, and ninth month of gestation at various imaging landmarks in RF body coils, including modes with RF shimming. Results Although RF shimmed configurations may lower the local RF exposure for the mother, they can increase the thermal load on the fetus. In worst-case configurations, whole-body exposure and local peak temperatures—up to 40.8°C—are equal in fetus and mother. Conclusions Two-port RF shimming can significantly increase the fetal exposure in pregnant women, requiring further research to derive a very robust safety management. For the time being, restriction to the CP mode, which reduces fetal SAR exposure compared with linear-horizontal polarization modes, may be advisable. Results from this study do not support scanning pregnant patients above the normal operating mode. PMID:27174499

Method of sintering ceramic materials

DOEpatents

Holcombe, Cressie E.; Dykes, Norman L.

1992-01-01

A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density.

Measuring Fracture Times Of Ceramics

NASA Technical Reports Server (NTRS)

Shlichta, Paul J.; Bister, Leo; Bickler, Donald G.

1989-01-01

Electrical measurements complement or replace fast cinematography. Electronic system measures microsecond time intervals between impacts of projectiles on ceramic tiles and fracture tiles. Used in research on ceramics and ceramic-based composite materials such as armor. Hardness and low density of ceramics enable them to disintegrate projectiles more efficiently than metals. Projectile approaches ceramic tile specimen. Penetrating foil squares of triggering device activate display and recording instruments. As ceramic and resistive film break oscilloscope plots increase in electrical resistance of film.

Alumina-based ceramic composite

DOEpatents

Alexander, Kathleen B.; Tiegs, Terry N.; Becher, Paul F.; Waters, Shirley B.

1996-01-01

An improved ceramic composite comprising oxide ceramic particulates, nonoxide ceramic particulates selected from the group consisting of carbides, borides, nitrides of silicon and transition metals and mixtures thereof, and a ductile binder selected from the group consisting of metallic, intermetallic alloys and mixtures thereof is described. The ceramic composite is made by blending powders of the ceramic particulates and the ductile to form a mixture and consolidating the mixture of under conditions of temperature and pressure sufficient to produce a densified ceramic composite.

TU-H-CAMPUS-IeP3-04: Evaluation of Changes in Quantitative Ultrasound Parameters During Prostate Radiotherapy

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

Najafi, M; El Kaffas, A; Han, B

Purpose: Clarity Autoscan ultrasound monitoring system allows acquisition of raw radiofrequency (RF) ultrasound data prior and during radiotherapy. This enables the computation of 3D Quantitative Ultrasound (QUS) tissue parametric maps from. We aim to evaluate whether QUS parameters undergo changes with radiotherapy and thus potentially be used as early predictors and/or markers of treatment response in prostate cancer patients. Methods: In-vivo evaluation was performed under IRB protocol to allow data collection in prostate patients treated with VMAT whereby prostate was imaged through the acoustic window of the perineum. QUS spectroscopy analysis was carried out by computing a tissue power spectrummore » normalized to the power spectrum obtained from a quartz to remove system transfer function effects. A ROI was selected within the 3D image volume of the prostate. Because longitudinal registration was optimal, the same features could be used to select ROIs at roughly the same location in images acquired on different days. Parametric maps were generated within the rectangular ROIs with window sizes that were approximately 8 times the wavelength of the ultrasound. The mid-band fit (MBF), spectral slope (SS) and spectral intercept (SI) QUS parameters were computed for each window within the ROI and displayed as parametric maps. Quantitative parameters were obtained by averaging each of the spectral parameters over the whole ROI. Results: Data was acquired for over 21 treatment fractions. Preliminary results show changes in the parametric maps. MBF values decreased from −33.9 dB to −38.7 dB from pre-treatment to the last day of treatment. The spectral slope increased from −1.1 a.u. to −0.5 a.u., and spectral intercept decreased from −28.2 dB to −36.3 dB over the 21 treatment regimen. Conclusion: QUS parametric maps change over the course of treatment which warrants further investigation in their potential use for treatment planning and predicting treatment outcomes. Research was supported by Elekta.« less

Ceramic oxide powders and the formation thereof

DOEpatents

Katz, Joseph L.; Hung, Cheng-Hung

1993-01-01

Ceramic oxide powders and a method for their preparation. Ceramic oxide powders are obtained using a flame process whereby two or more precursors of ceramic oxides are introduced into a counterflow diffusion flame burner wherein said precursors are converted into ceramic oxide powders. The morphology, particle size, and crystalline form of the ceramic oxide powders are determined by process conditions.

Ceramic Laser Materials

PubMed Central

Sanghera, Jasbinder; Kim, Woohong; Villalobos, Guillermo; Shaw, Brandon; Baker, Colin; Frantz, Jesse; Sadowski, Bryan; Aggarwal, Ishwar

2012-01-01

Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG) ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements. PMID:28817044

Slice-selective RF pulses for in vivo B1+ inhomogeneity mitigation at 7 tesla using parallel RF excitation with a 16-element coil.

PubMed

Setsompop, Kawin; Alagappan, Vijayanand; Gagoski, Borjan; Witzel, Thomas; Polimeni, Jonathan; Potthast, Andreas; Hebrank, Franz; Fontius, Ulrich; Schmitt, Franz; Wald, Lawrence L; Adalsteinsson, Elfar

2008-12-01

Slice-selective RF waveforms that mitigate severe B1+ inhomogeneity at 7 Tesla using parallel excitation were designed and validated in a water phantom and human studies on six subjects using a 16-element degenerate stripline array coil driven with a butler matrix to utilize the eight most favorable birdcage modes. The parallel RF waveform design applied magnitude least-squares (MLS) criteria with an optimized k-space excitation trajectory to significantly improve profile uniformity compared to conventional least-squares (LS) designs. Parallel excitation RF pulses designed to excite a uniform in-plane flip angle (FA) with slice selection in the z-direction were demonstrated and compared with conventional sinc-pulse excitation and RF shimming. In all cases, the parallel RF excitation significantly mitigated the effects of inhomogeneous B1+ on the excitation FA. The optimized parallel RF pulses for human B1+ mitigation were only 67% longer than a conventional sinc-based excitation, but significantly outperformed RF shimming. For example the standard deviations (SDs) of the in-plane FA (averaged over six human studies) were 16.7% for conventional sinc excitation, 13.3% for RF shimming, and 7.6% for parallel excitation. This work demonstrates that excitations with parallel RF systems can provide slice selection with spatially uniform FAs at high field strengths with only a small pulse-duration penalty. (c) 2008 Wiley-Liss, Inc.

Non-Equilibrium Plasma MHD Electrical Power Generation at Tokyo Tech

NASA Astrophysics Data System (ADS)

Murakami, T.; Okuno, Y.; Yamasaki, H.

2008-02-01

This paper reviews the recent activities on radio-frequency (rf) electromagnetic-field-assisted magnetohydrodynamic (MHD) power generation experiments at the Tokyo Institute of Technology. An inductively coupled rf field (13.56 MHz) is continuously supplied to the disk-shaped Hall-type MHD generator. The first part of this paper describes a method of obtaining increased power output from a pure Argon plasma MHD power generator by incorporating an rf power source to preionize and heat the plasma. The rf heating enhances ionization of the Argon and raises the temperature of the free electron population above the nominally low 4500 K temperatures obtained without rf heating. This in turn enhances the plasma conductivity making MHD power generation feasible. We demonstrate an enhanced power output when rf heating is on approximately 5 times larger than the input power of the rf generator. The second part of this paper is a demonstration of a physical phenomenon of the rf-stabilization of the ionization instability, that had been conjectured for some time, but had not been seen experimentally. The rf heating suppresses the ionization instability in the plasma behavior and homogenizes the nonuniformity of the plasma structures. The power-generating performance is significantly improved with the aid of the rf power under wide seeding conditions. The increment of the enthalpy extraction ratio of around 2% is significantly greater than the fraction of the net rf power, that is, 0.16%, to the thermal input.

Workgroup report: base stations and wireless networks-radiofrequency (RF) exposures and health consequences.

PubMed

Valberg, Peter A; van Deventer, T Emilie; Repacholi, Michael H

2007-03-01

Radiofrequency (RF) waves have long been used for different types of information exchange via the air waves--wireless Morse code, radio, television, and wireless telephone (i.e., construction and operation of telephones or telephone systems). Increasingly larger numbers of people rely on mobile telephone technology, and health concerns about the associated RF exposure have been raised, particularly because the mobile phone handset operates in close proximity to the human body, and also because large numbers of base station antennas are required to provide widespread availability of service to large populations. The World Health Organization convened an expert workshop to discuss the current state of cellular-telephone health issues, and this article brings together several of the key points that were addressed. The possibility of RF health effects has been investigated in epidemiology studies of cellular telephone users and workers in RF occupations, in experiments with animals exposed to cell-phone RF, and via biophysical consideration of cell-phone RF electric-field intensity and the effect of RF modulation schemes. As summarized here, these separate avenues of scientific investigation provide little support for adverse health effects arising from RF exposure at levels below current international standards. Moreover, radio and television broadcast waves have exposed populations to RF for > 50 years with little evidence of deleterious health consequences. Despite unavoidable uncertainty, current scientific data are consistent with the conclusion that public exposures to permissible RF levels from mobile telephone and base stations are not likely to adversely affect human health.

Workgroup Report: Base Stations and Wireless Networks—Radiofrequency (RF) Exposures and Health Consequences

PubMed Central

Valberg, Peter A.; van Deventer, T. Emilie; Repacholi, Michael H.

2007-01-01

Radiofrequency (RF) waves have long been used for different types of information exchange via the airwaves—wireless Morse code, radio, television, and wireless telephony (i.e., construction and operation of telephones or telephonic systems). Increasingly larger numbers of people rely on mobile telephone technology, and health concerns about the associated RF exposure have been raised, particularly because the mobile phone handset operates in close proximity to the human body, and also because large numbers of base station antennas are required to provide widespread availability of service to large populations. The World Health Organization convened an expert workshop to discuss the current state of cellular-telephone health issues, and this article brings together several of the key points that were addressed. The possibility of RF health effects has been investigated in epidemiology studies of cellular telephone users and workers in RF occupations, in experiments with animals exposed to cell-phone RF, and via biophysical consideration of cell-phone RF electric-field intensity and the effect of RF modulation schemes. As summarized here, these separate avenues of scientific investigation provide little support for adverse health effects arising from RF exposure at levels below current international standards. Moreover, radio and television broadcast waves have exposed populations to RF for > 50 years with little evidence of deleterious health consequences. Despite unavoidable uncertainty, current scientific data are consistent with the conclusion that public exposures to permissible RF levels from mobile telephony and base stations are not likely to adversely affect human health. PMID:17431492

Simulation of RF power and multi-cusp magnetic field requirement for H- ion sources

NASA Astrophysics Data System (ADS)

Pathak, Manish; Senecha, V. K.; Kumar, Rajnish; Ghodke, Dharmraj. V.

2016-12-01

A computer simulation study for multi-cusp RF based H- ion source has been carried out using energy and particle balance equation for inductively coupled uniformly dense plasma considering sheath formation near the boundary wall of the plasma chamber for RF ion source used as high current injector for 1 Gev H- Linac project for SNS applications. The average reaction rates for different reactions responsible for H- ion production and destruction have been considered in the simulation model. The RF power requirement for the caesium free H- ion source for a maximum possible H- ion beam current has been derived by evaluating the required current and RF voltage fed to the coil antenna using transformer model for Inductively Coupled Plasma (ICP). Different parameters of RF based H- ion source like excited hydrogen molecular density, H- ion density, RF voltage and current of RF antenna have been calculated through simulations in the presence and absence of multicusp magnetic field to distinctly observe the effect of multicusp field. The RF power evaluated for different H- ion current values have been compared with the experimental reported results showing reasonably good agreement considering the fact that some RF power will be reflected from the plasma medium. The results obtained have helped in understanding the optimum field strength and field free regions suitable for volume emission based H- ion sources. The compact RF ion source exhibits nearly 6 times better efficiency compare to large diameter ion source.

Hyperspectral Microwave Atmospheric Sounder (HyMas) - New Capability in the CoSMIR-CoSSIR Scanhead

NASA Technical Reports Server (NTRS)

Hilliard, L. M.; Racette, P. E.; Blackwell, W.; Galbraith, C.; Thompson, E.

2015-01-01

Lincoln Laboratory and NASA's Goddard Space Flight Center have teamed to re-use an existing instrument platform, the CoSMIRCoSSIR system for atmospheric sounding, to develop a new capability in hyperspectral filtering, data collection, and display. The volume of the scanhead accomodated an intermediate frequency processor(IFP), that provides the filtering and digitization of the raw data and the interoperable remote component (IRC) adapted to CoSMIR, CoSSIR, and HyMAS that stores and archives the data with time tagged calibration and navigation data.The first element of the work is the demonstration of a hyperspectral microwave receiver subsystem that was recently shown using a comprehensive simulation study to yield performance that substantially exceeds current state-of-the-art. Hyperspectral microwave sounders with 100 channels offer temperature and humidity sounding improvements similar to those obtained when infrared sensors became hyperspectral, but with the relative insensitivity to clouds that characterizes microwave sensors. Hyperspectral microwave operation is achieved using independent RF antennareceiver arrays that sample the same areavolume of the Earths surfaceatmosphere at slightly different frequencies and therefore synthesize a set of dense, finely spaced vertical weighting functions. The second, enabling element of the proposal is the development of a compact 52-channel Intermediate Frequency processor module. A principal challenge in the development of a hyperspectral microwave system is the size of the IF filter bank required for channelization. Large bandwidths are simultaneously processed, thus complicating the use of digital back-ends with associated high complexities, costs, and power requirements. Our approach involves passive filters implemented using low-temperature co-fired ceramic (LTCC) technology to achieve an ultra-compact module that can be easily integrated with existing RF front-end technology. This IF processor is universally applicable to other microwave sensing missions requiring compact IF spectrometry.The data include 52 operational channels with low IF module volume (100cm3) and mass (300g) and linearity better than 0.3 over a 330K dynamic range.

The Limit of Resolution and Detectability of the ArcCHECK QA Phantom in small field Volumetric Modulated Arc Therapy and Stereotactic Radiosurgery Quality Assurance

NASA Astrophysics Data System (ADS)

Geiler, Michael

Yittrium Iron Garnet Y3Fe6O12 and Lithium ferrite LiFe5O8 mono and poly crystals were investigated for their spinwave linewidth ΔHk, ferromagnetic resonance linewidth ΔH and complex magnetic losses μ’ and μ’’ at L and S bands. Conventional methods of Spinwave linewidth typically require very high power microwave sources and associated high power components. Therefore, we developed a Dielectric Resonator (DR) based test method that allows for measurement of ΔHk using low power, common microwave laboratory equipment, while providing additional capability to measure the other relevant magnetic material characteristics. The samples used in this research were 0.030” diameter, abrasive milled spheres provided by Pacific Ceramics Inc, and Ferrisphere Inc. and included a variety of standard off-the-shelf material offerings. The saturation magnetization Ms of the samples ranged from 75 Gauss to 3700 Gauss. The ΔH and ΔHk of the samples were in the ranges of 0.5 to 200 Oersteds, and 0.5 to 30 Oersteds, respectively. Practical frequencies of operation for this system are 1 GHz to 20 GHz with less than 20W required RF power. Operation below 1 GHz and up to 40 GHz is possible. Reduction of intrinsic Ms in YIG in achieved by doping with Gadolinium and/or Aluminum. These additions were found to affect the microwave properties of the materials as well. Dopants like Cobalt, Manganese and Holmium do not effect the saturation magnetization but they do alter the high power microwave properties of the material similarly to Gd and Al. Several DRs were designed and modeled using Ansys HFSS electromagnetic finite element solver. We designed experiments that allow the measurement of all relevant microwave properties in one convenient test setup. This includes simultaneous control of multiple variables including RF field, frequency and power, and DC field strength.

Three-year clinical evaluation of two ceramic crown systems: a preliminary study.

PubMed

Etman, Maged K; Woolford, M J

2010-02-01

The clinical performance and failure mechanisms of recently introduced ceramic crown systems used to restore posterior teeth have not been adequately examined. The purpose of this prospective clinical study was to evaluate and compare the clinical performance of 2 new ceramic crown systems with that of metal ceramic crowns using modified United States Public Health Services (USPHS) criteria. Ninety posterior teeth requiring crown restorations in 48 patients were randomized into 3 equal groups (n=30) for which different crown systems were used: an experimental hot-pressed glass ceramic based on a modified lithium disilicate ceramic (IPS e.max Press), an alumina-coping-based ceramic (Procera AllCeram), and a metal ceramic (Simidur S 2 veneered with IPS Classic Porcelain). The crowns were assessed over 3 years using the modified USPHS criteria. Crowns that developed visible cracks were sectioned and removed, and the surfaces were analyzed using a scanning electron microscope (SEM). The data were analyzed using the Kruskal-Wallis nonparametric statistical test, followed by the Mann-Whitney test with Bonferroni correction (alpha=.05). USPHS evaluation showed that the IPS e.max Press and metal ceramic crowns experienced fewer clinical changes than Procera AllCeram. Visible roughness, wear, and deformity were noticed in occlusal contact areas of Procera AllCeram crowns. SEM images showed well defined wear facets in both ceramic crown systems. Kruskal-Wallis tests showed a significant difference (P<.05) in Alpha scores among the 3 crown systems. Mann-Whitney tests showed significant differences among groups. IPS e.max Press crowns demonstrated clinical behavior comparable to Procera AllCeram and metal ceramic crowns, but the wear resistance of this crown type was superior to the Procera AllCeram crowns, according to modified USPHS criteria.

Ceramic dental biomaterials and CAD/CAM technology: state of the art.

PubMed

Li, Raymond Wai Kim; Chow, Tak Wah; Matinlinna, Jukka Pekka

2014-10-01

Ceramics are widely used as indirect restorative materials in dentistry because of their high biocompatibility and pleasing aesthetics. The objective is to review the state of the arts of CAD/CAM all-ceramic biomaterials. CAD/CAM all-ceramic biomaterials are highlighted and a subsequent literature search was conducted for the relevant subjects using PubMed followed by manual search. Developments in CAD/CAM technology have catalyzed researches in all-ceramic biomaterials and their applications. Feldspathic glass ceramic and glass infiltrated ceramic can be fabricated by traditional laboratory methods or CAD/CAM. The advent of polycrystalline ceramics is a direct result of CAD/CAM technology without which the fabrication would not have been possible. The clinical uses of these ceramics have met with variable clinical success. Multiple options are now available to the clinicians for the fabrication of aesthetic all ceramic restorations. Copyright © 2014 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Characterization and reduction of gradient-induced eddy currents in the RF shield of a TEM resonator.

PubMed

Alecci, Marcello; Jezzard, Peter

2002-08-01

Radiofrequency (RF) shields that surround MRI transmit/receive coils should provide effective RF screening, without introducing unwanted eddy currents induced by gradient switching. Results are presented from a detailed examination of an effective RF shield design for a prototype transverse electromagnetic (TEM) resonator suitable for use at 3 Tesla. It was found that effective RF shielding and low eddy current sensitivity could be achieved by axial segmentation (gap width = 2.4 mm) of a relatively thick (35 microm) copper shield, etched on a kapton polyimide substrate. This design has two main advantages: first, it makes the TEM less sensitive to the external environment and RF interference; and second, it makes the RF shield mechanically robust and easy to handle and assemble. Copyright 2002 Wiley-Liss, Inc.

Thermal and dynamic range characterization of a photonics-based RF amplifier

NASA Astrophysics Data System (ADS)

Noque, D. F.; Borges, R. M.; Muniz, A. L. M.; Bogoni, A.; Cerqueira S., Arismar, Jr.

2018-05-01

This work reports a thermal and dynamic range characterization of an ultra-wideband photonics-based RF amplifier for microwave and mm-waves future 5G optical-wireless networks. The proposed technology applies the four-wave mixing nonlinear effect to provide RF amplification in analog and digital radio-over-fiber systems. The experimental analysis from 300 kHz to 50 GHz takes into account different figures of merit, such as RF gain, spurious-free dynamic range and RF output power stability as a function of temperature. The thermal characterization from -10 to +70 °C demonstrates a 27 dB flat photonics-assisted RF gain over the entire frequency range under real operational conditions of a base station for illustrating the feasibility of the photonics-assisted RF amplifier for 5G networks.

Efficient Radio Frequency Inductive Discharges in Near Atmospheric Pressure Using Immittance Conversion Topology

NASA Astrophysics Data System (ADS)

Razzak, M. Abdur; Takamura, Shuichi; Uesugi, Yoshihiko; Ohno, Noriyasu

A radio frequency (rf) inductive discharge in atmospheric pressure range requires high voltage in the initial startup phase and high power during the steady state sustainment phase. It is, therefore, necessary to inject high rf power into the plasma ensuring the maximum use of the power source, especially where the rf power is limited. In order to inject the maximum possible rf power into the plasma with a moderate rf power source of few kilowatts range, we employ the immittance conversion topology by converting a constant voltage source into a constant current source to generate efficient rf discharge by inductively coupled plasma (ICP) technique at a gas pressure with up to one atmosphere in argon. A novel T-LCL immittance circuit is designed for constant-current high-power operation, which is practically very important in the high-frequency range, to provide high effective rf power to the plasma. The immittance conversion system combines the static induction transistor (SIT)-based radio frequency (rf) high-power inverter circuit and the immittance conversion elements including the rf induction coil. The basic properties of the immittance circuit are studied by numerical analysis and verified the results by experimental measurements with the inductive plasma as a load at a relatively high rf power of about 4 kW. The performances of the immittance circuit are also evaluated and compared with that of the conventional series resonance circuit in high-pressure induction plasma generation. The experimental results reveal that the immittance conversion circuit confirms injecting higher effective rf power into the plasma as much as three times than that of the series resonance circuit under the same operating conditions and same dc supply voltage to the inverter, thereby enhancing the plasma heating efficiency to generate efficient rf inductive discharges.

Radiofrequency Cauterization with Biopsy Introducer Needle

PubMed Central

Pritchard, William F.; Wray-Cahen, Diane; Karanian, John W.; Hilbert, Stephen; Wood, Bradford J.

2014-01-01

PURPOSE The principal risks of needle biopsy are hemorrhage and implantation of tumor cells in the needle tract. This study compared hemorrhage after liver and kidney biopsy with and without radiofrequency (RF) ablation of the needle tract. MATERIALS AND METHODS Biopsies of liver and kidney were performed in swine through introducer needles modified to allow RF ablation with the distal 2 cm of the needle. After each biopsy, randomization determined whether the site was to undergo RF ablation during withdrawal of the introducer needle. Temperature was measured with a thermistor stylet near the needle tip, with a target temperature of 70°C–100°C with RF ablation. Blood loss was measured as grams of blood absorbed in gauze at the puncture site for 2 minutes after needle withdrawal. Selected specimens were cut for gross examination. RESULTS RF ablation reduced bleeding compared with absence of RF ablation in liver and kidney (P < .01), with mean blood loss reduced 63% and 97%, respectively. Mean amounts of blood loss (±SD) in the liver in the RF and no-RF groups were 2.03 g ± 4.03 (CI, 0.53–3.54 g) and 5.50 g ± 5.58 (CI, 3.33–7.66 g), respectively. Mean amounts of blood loss in the kidney in the RF and no-RF groups were 0.26 g ± 0.32 (CI, −0.01 to 0.53 g) and 8.79 g ± 7.72 (CI, 2.34–15.24 g), respectively. With RF ablation, thermal coagulation of the tissue surrounding the needle tract was observed. CONCLUSION RF ablation of needle biopsy tracts reduced hemorrhage after biopsy in the liver and kidney and may reduce complications of hemorrhage as well as implantation of tumor cells in the tract. PMID:14963187

Ceramic inspection system

DOEpatents

Werve, Michael E [Modesto, CA

2006-05-16

A system for inspecting a ceramic component. The ceramic component is positioned on a first rotary table. The first rotary table rotates the ceramic component. Light is directed toward the first rotary table and the rotating ceramic component. A detector is located on a second rotary table. The second rotary table is operably connected to the first rotary table and the rotating ceramic component. The second rotary table is used to move the detector at an angle to the first rotary table and the rotating ceramic component.

Method of sintering ceramic materials

DOEpatents

Holcombe, C.E.; Dykes, N.L.

1992-11-17

A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density. 2 figs.

Alumina-based ceramic composite

DOEpatents

Alexander, K.B.; Tiegs, T.N.; Becher, P.F.; Waters, S.B.

1996-07-23

An improved ceramic composite comprising oxide ceramic particulates, nonoxide ceramic particulates selected from the group consisting of carbides, borides, nitrides of silicon and transition metals and mixtures thereof, and a ductile binder selected from the group consisting of metallic, intermetallic alloys and mixtures thereof is described. The ceramic composite is made by blending powders of the ceramic particulates and the ductile to form a mixture and consolidating the mixture of under conditions of temperature and pressure sufficient to produce a densified ceramic composite. 5 figs.

Ferroelectric ceramics in a pyroelectric accelerator

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

Shchagin, A. V., E-mail: shchagin@kipt.kharkov.ua; Belgorod State University, Belgorod 308015; Miroshnik, V. S.

2015-12-07

The applicability of polarized ferroelectric ceramics as a pyroelectric in a pyroelectric accelerator is shown by experiments. The spectra of X-ray radiation of energy up to tens of keV, generated by accelerated electrons, have been measured on heating and cooling of the ceramics in vacuum. It is suggested that curved layers of polarized ferroelectric ceramics be used as elements of ceramic pyroelectric accelerators. Besides, nanotubes and nanowires manufactured from ferroelectric ceramics are proposed for the use in nanometer-scale ceramic pyroelectric nanoaccelerators for future applications in nanotechnologies.

The history of ceramic filters.

PubMed

Fujishima, S

2000-01-01

The history of ceramic filters is surveyed. Included is the history of piezoelectric ceramics. Ceramic filters were developed using technology similar to that of quartz crystal and electro-mechanical filters. However, the key to this development involved the theoretical analysis of vibration modes and material improvements of piezoelectric ceramics. The primary application of ceramic filters has been for consumer-market use. Accordingly, a major emphasis has involved mass production technology, leading to low-priced devices. A typical ceramic filter includes monolithic resonators and capacitors packaged in unique configurations.

Comparison of the load at fracture of Turkom-Cera to Procera AllCeram and In-Ceram all-ceramic restorations.

PubMed

AL-Makramani, Bandar M A; Razak, Abdul A A; Abu-Hassan, Mohamed I

2009-08-01

This study investigated the occlusal fracture resistance of Turkom-Cerafused alumina compared to Procera AllCeram and In-Ceram all-ceramic restorations. Sixmaster dies were duplicated from the prepared maxillary first premolar tooth using nonprecious metal alloy (Wiron 99). Ten copings of 0.6 mm thickness were fabricated from each type of ceramic, for a total of thirty copings. Two master dies were used for each group, and each of them was used to lute five copings. All groups were cemented with resin luting cement Panavia F according to manufacturer's instructions and received a static load of 5 kg during cementation. After 24 hours of distilled water storage at 37 degrees C, the copings were vertically compressed using a universal testing machine at a crosshead speed of 1 mm/min. The results of the present study showed the following mean loads at fracture: Turkom-Cera (2184 +/- 164 N), In-Ceram (2042 +/- 200 N), and Procera AllCeram (1954 +/- 211 N). ANOVA and Scheffe's post hoc test showed that the mean load at fracture of Turkom-Cera was significantly different from Procera AllCeram (p < 0.05). Scheffe's post hoc test showed no significant difference between the mean load at fracture of Turkom-Cera and In-Ceram or between the mean load at fracture of In-Ceram and Procera AllCeram. Because Turkom-Cera demonstrated equal to or higher loads at fracture than currently accepted all-ceramic materials, it would seem to be acceptable for fabrication of anterior and posterior ceramic crowns.

1950 MHz Electromagnetic Fields Ameliorate Aβ Pathology in Alzheimer’s Disease Mice

PubMed Central

Jeong, Ye Ji; Kang, Ga-Young; Kwon, Jong Hwa; Choi, Hyung-Do; Pack, Jeong-Ki; Kim, Nam; Lee, Yun-Sil; Lee, Hae-June

2015-01-01

The involvement of radiofrequency electromagnetic fields (RF-EMF) in the neurodegenerative disease, especially Alzheimer’s disease (AD), has received wide consideration, however, outcomes from several researches have not shown consistency. In this study, we determined whether RF-EMF influenced AD pathology in vivo using Tg-5xFAD mice as a model of AD-like amyloid β (Aβ) pathology. The transgenic (Tg)-5xFAD and wild type (WT) mice were chronically exposed to RF-EMF for 8 months (1950 MHz, SAR 5W/kg, 2 hrs/day, 5 days/week). Notably, chronic RF-EMF exposure significantly reduced not only Aβ plaques, APP, and APP carboxyl-terminal fragments (CTFs) in whole brain including hippocampus and entorhinal cortex but also the ratio of Aβ42 and Aβ40 peptide in the hippocampus of Tg-5xFAD mice. We also found that parenchymal expression of β-amyloid precursor protein cleaving enzyme 1(BACE1) and neuroinflammation were inhibited by RF-EMF exposure in Tg-5xFAD. In addition, RF-EMF was shown to rescue memory impairment in Tg-5xFAD. Moreover, gene profiling from microarray data using hippocampus of WT and Tg-5xFAD following RF-EMF exposure revealed that 5 genes (Tshz2, Gm12695, St3gal1, Isx and Tll1), which are involved in Aβ, are significantly altered inTg-5xFAD mice, exhibiting different responses to RF-EMF in WT or Tg-5xFAD mice; RF-EMF exposure in WT mice showed similar patterns to control Tg-5xFAD mice, however, RF-EMF exposure in Tg-5xFAD mice showed opposite expression patterns. These findings indicate that chronic RF-EMF exposure directly affects Aβ pathology in AD but not in normal brain. Therefore, RF-EMF has preventive effects against AD-like pathology in advanced AD mice with a high expression of Aβ, which suggests that RF-EMF can have a beneficial influence on AD. PMID:26017559

REACTION $pi$$sup -$ + p $Yields$ $pi$$sup -$ + $pi$$sup +$ + n FROM 360 TO 800 Mev

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

Kirz, J.; Schwartz, J.; Tripp, R.D.

1963-10-31

The reaction ceramic materia /sup -/ + p ons in pyrolyti ceramic materia /sup -/ + ceramic materia /sup +/ + n is sLLawrence Radiation Laboratory's 72-in. hydrogen bubble chamber. Events are located by scanning the pictures for ceramic materia /sup +/ tracks. Cross sections, Dalitz plots, and ceramic materia /sup +/ ceramic materia /sup -/ d please delete abstract 26339

Ceramic oxide powders and the formation thereof

DOEpatents

Katz, J.L.; Chenghung Hung.

1993-12-07

Ceramic oxide powders and a method for their preparation. Ceramic oxide powders are obtained using a flame process whereby two or more precursors of ceramic oxides are introduced into a counterflow diffusion flame burner wherein said precursors are converted into ceramic oxide powders. The morphology, particle size, and crystalline form of the ceramic oxide powders are determined by process conditions. 14 figures.

Method for preparing thin-walled ceramic articles of configuration

DOEpatents

Holcombe, C.E.; Powell, G.L.

1975-11-01

A method for preparing a hollow thin-walled ceramic product is described. Ceramic powder is plasma-sprayed onto a concave surface of a substrate having a coefficient of thermal expansion less than that of the ceramic. The coated substrate is heated to sinter the ceramic and then cooled to effect a separation of the ceramic product from the substrate. (auth)

A review on the advances in 3D printing and additive manufacturing of ceramics and ceramic matrix composites for optical applications

NASA Astrophysics Data System (ADS)

Goodman, William A.

2017-09-01

This paper provides a review of advances in 3D printing and additive manufacturing of ceramic and ceramic matrix composites for optical applications. Dr. Goodman has been pioneering additive manufacturing of ceramic matrix composites since 2008. He is the inventor of HoneySiC material, a zero-CTE additively manufactured carbon fiber reinforced silicon carbide ceramic matrix composite, briefly mentioned here. More recently Dr. Goodman has turned his attention to the direct printing of ceramics for optical applications via various techniques including slurry and laser sintering of silicon carbide and other ceramic materials.

Ferromagnetic resonance induced large microwave magnetodielectric effect in cerium doped Y3Fe5O12 ferrites

PubMed Central

Chen, Fu; Wang, Xian; Nie, Yan; Li, Qifan; Ouyang, Jun; Feng, Zekun; Chen, Yajie; Harris, Vincent G.

2016-01-01

In recent years, multifunctional materials contained simultaneous ferroelectric and ferromagnetic ordering have been realized. Here, a real time room temperature adaptive materials system, which demonstrates an RF magnetodielectric (MD) response, i.e., CexY3−xFe5O12 (x = 0, 0.05, 0.1, 0.15, 0.2), is reported. The magnetic and dielectric properties of Ce-doped YIG microwave ferrites processed by a traditional ceramic route have been measured over a frequency range of 4–8 GHz (C-band). The substitution of Ce not only enhances the microwave electromagnetic properties of the YIG, but also modulates the magnetodielectric response. The maximum magnetodielectric response in Ce-doped YIG sample ranges in magnitude from approximately +5% to −5% under an applied field of 1.78 kOe. This effect was attributed to electron fluctuations on the Fe cation sites. Furthermore, the magnitude of the MD response was shown to be enhanced by the cerium content. It is believed that research of the magnetodielectric effect in YIG ferrites is of great importance to the development of next generation multifunctional adaptive microwave materials, devices and integrated circuits. PMID:27320039