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Sample records for sapphire interface velocities

  1. Order in nanometer thick intergranular films at Au-sapphire interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Baram, Mor [Department of Materials Engineering, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Garofalini, Stephen H. [Department of Materials Science and Engineering, Rutgers University, Piscataway, NJ 08854-8065 (United States); Kaplan, Wayne D., E-mail: kaplan@tx.technion.ac.il [Department of Materials Engineering, Technion-Israel Institute of Technology, Haifa 32000 (Israel)

    2011-08-15

    Highlights: {yields} Au particles were equilibrated on (0 0 0 1) sapphire in the presence of anorthite. {yields} 1.2 nm thick equilibrium films (complexions) were formed at the Au-sapphire interfaces. {yields} Quantitative HRTEM was used to study the atomistic structure of the films. {yields} Structural order was observed in the 1.2 nm thick films adjacent to the sapphire crystal. {yields} This demonstrates that ordering is an intrinsic part of equilibrium intergranular films. - Abstract: In recent years extensive studies on interfaces have shown that {approx}1 nm thick intergranular films (IGF) exist at interfaces in different material systems, and that IGF can significantly affect the materials' properties. However, there is great deal of uncertainty whether such films are amorphous or partially ordered. In this study specimens were prepared from Au particles that were equilibrated on sapphire substrates in the presence of anorthite glass, leading to the formation of 1.2 nm thick IGF at the Au-sapphire interfaces. Site-specific cross-section samples were characterized using quantitative high resolution transmission electron microscopy to study the atomistic structure of the films. Order was observed in the 1.2 nm thick films adjacent to the sapphire crystal in the form of 'Ca cages', experimentally demonstrating that ordering is an intrinsic part of IGF, as predicted from molecular dynamics and diffuse interface theory.

  2. Ultrafast third-harmonic generation from textured aluminum nitride-sapphire interfaces

    International Nuclear Information System (INIS)

    Stoker, D. S.; Keto, J. W.; Baek, J.; Wang, W.; Becker, M. F.; Kovar, D.

    2006-01-01

    We measured and modeled third-harmonic generation (THG) from an AlN thin film on sapphire using a time-domain approach appropriate for ultrafast lasers. Second-harmonic measurements indicated that polycrystalline AlN contains long-range crystal texture. An interface model for third-harmonic generation enabled an analytical representation of scanning THG (z-scan) experiments. Using it and accounting for Fresnel reflections, we measured the AlN-sapphire susceptibility ratio and estimated the susceptibility for aluminum nitride, χ xxxx (3) (3ω;ω,ω,ω)=1.52±0.25x10 -13 esu. The third-harmonic (TH) spectrum strongly depended on the laser focus position and sample thickness. The amplitude and phase of the frequency-domain interference were fit to the Fourier transform of the calculated time-domain field to improve the accuracy of several experimental parameters. We verified that the model works well for explaining TH signal amplitudes and spectral phase. Some anomalous features in the TH spectrum were observed, which we attributed to nonparaxial effects

  3. Change in equilibrium position of misfit dislocations at the GaN/sapphire interface by Si-ion implantation into sapphire—I. Microstructural characterization

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sung Bo, E-mail: bolee@snu.ac.kr; Han, Heung Nam, E-mail: hnhan@snu.ac.kr; Lee, Dong Nyung [Department of Materials Science and Engineering and Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul 151-744 (Korea, Republic of); Ju, Jin-Woo [Korea Photonics Technology Institute, Gwangju 500-779 (Korea, Republic of); Kim, Young-Min; Yoo, Seung Jo; Kim, Jin-Gyu [Korea Basic Science Institute, Daejeon 305-806 (Korea, Republic of)

    2015-07-15

    Much research has been done to reduce dislocation densities for the growth of GaN on sapphire, but has paid little attention to the elastic behavior at the GaN/sapphire interface. In this study, we have examined effects of the addition of Si to a sapphire substrate on its elastic property and on the growth of GaN deposit. Si atoms are added to a c-plane sapphire substrate by ion implantation. The ion implantation results in scratches on the surface, and concomitantly, inhomogeneous distribution of Si. The scratch regions contain a higher concentration of Si than other regions of the sapphire substrate surface, high-temperature GaN being poorly grown there. However, high-temperature GaN is normally grown in the other regions. The GaN overlayer in the normally-grown regions is observed to have a lower TD density than the deposit on the bare sapphire substrate (with no Si accommodated). As compared with the film on an untreated, bare sapphire, the cathodoluminescence defect density decreases by 60 % for the GaN layer normally deposited on the Si-ion implanted sapphire. As confirmed by a strain mapping technique by transmission electron microscopy (geometric phase analysis), the addition of Si in the normally deposited regions forms a surface layer in the sapphire elastically more compliant than the GaN overlayer. The results suggest that the layer can largely absorb the misfit strain at the interface, which produces the overlayer with a lower defect density. Our results highlight a direct correlation between threading-dislocation density in GaN deposits and the elastic behavior at the GaN/sapphire interface, opening up a new pathway to reduce threading-dislocation density in GaN deposits.

  4. Interface amorphization in hexagonal boron nitride films on sapphire substrate grown by metalorganic vapor phase epitaxy

    Science.gov (United States)

    Yang, Xu; Nitta, Shugo; Pristovsek, Markus; Liu, Yuhuai; Nagamatsu, Kentaro; Kushimoto, Maki; Honda, Yoshio; Amano, Hiroshi

    2018-05-01

    Hexagonal boron nitride (h-BN) films directly grown on c-plane sapphire substrates by pulsed-mode metalorganic vapor phase epitaxy exhibit an interlayer for growth temperatures above 1200 °C. Cross-sectional transmission electron microscopy shows that this interlayer is amorphous, while the crystalline h-BN layer above has a distinct orientational relationship with the sapphire substrate. Electron energy loss spectroscopy shows the energy-loss peaks of B and N in both the amorphous interlayer and the overlying crystalline h-BN layer, while Al and O signals are also seen in the amorphous interlayer. Thus, the interlayer forms during h-BN growth through the decomposition of the sapphire at elevated temperatures.

  5. Shock-Assisted Superficial Hexagonal-to-Cubic Phase Transition in GaN/Sapphire Interface Induced by Using Ultra-violet Laser Lift-Of Techniques

    International Nuclear Information System (INIS)

    Wei-Hua, Chen; Xiao-Dong, Hu; Xiang-Ning, Kang; Xu-Rong, Zhou; Xiao-Min, Zhang; Tong-Jun, Yu; Zhi-Jian, Yang; Ke, Xu; Guo-Yi, Zhang; Xu-Dong, Shan; Li-Ping, You

    2009-01-01

    Ultra-violet (KrF excimer laser, λ = 248 nm) laser lift-of (LLO) techniques have been operated to the GaN/sapphire structure to separate GaN from the sapphire substrate. Hexagonal to cubic phase transformation induced by the ultra-violet laser lift-of (UV-LLO) has been characterized by micro-Raman spectroscopy, micro-photoluminescence, along with high-resolution transmission electron microscopy (HRTEM). HRTEM indicates that UV-LLO induced phase transition takes place above the LLO interface, without phase transition under the LLO interface. The formed cubic GaN often exists as nanocrystal grains attaching on the bulk hexagonal GaN. The half-loop-cluster-like UV-LLO interface indicates that the LLO-induced shock waves has generated and played an assistant role in the decomposition of the hexagonal GaN and in the formation of cubic GaN grains at the LLO surface

  6. Impact of layer and substrate properties on the surface acoustic wave velocity in scandium doped aluminum nitride based SAW devices on sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Gillinger, M., E-mail: manuel.gillinger@tuwien.ac.at; Knobloch, T.; Schneider, M.; Schmid, U. [Institute of Sensor and Actuator Systems, TU Wien, 1040 Vienna (Austria); Shaposhnikov, K.; Kaltenbacher, M. [Institute of Mechanics and Mechatronics, TU Wien, 1040 Vienna (Austria)

    2016-06-06

    This paper investigates the performance of surface acoustic wave (SAW) devices consisting of reactively sputter deposited scandium doped aluminum nitride (Sc{sub x}Al{sub 1-x}N) thin films as piezoelectric layers on sapphire substrates for wireless sensor or for RF-MEMS applications. To investigate the influence of piezoelectric film thickness on the device properties, samples with thickness ranging from 500 nm up to 3000 nm are fabricated. S{sub 21} measurements and simulations demonstrate that the phase velocity is predominantly influenced by the mass density of the electrode material rather than by the thickness of the piezoelectric film. Additionally, the wave propagation direction is varied by rotating the interdigital transducer structures with respect to the crystal orientation of the substrate. The phase velocity is about 2.5% higher for a-direction compared to m-direction of the sapphire substrate, which is in excellent agreement with the difference in the anisotropic Young's modulus of the substrate corresponding to these directions.

  7. Acoustic mismatch model and thermal phonon radiation across a tin/sapphire interface with radiation temperatures between 1.6 and 3.7 K

    International Nuclear Information System (INIS)

    Bayrle, R.; Weis, O.

    1989-01-01

    Using a special sandwich arrangement consisting of a constantan film, an insulating oxide layer and a superconducting tin-tunnel junction evaporated on an a-cut sapphire, the temperature jump between tin and sapphire has been measured as function of thermal phonon flux under steady-state and transient conditions using rectangular current pulses in the constantan heater. The tunnel junction serves as a very fast thermometer with a time resolution in the nanosecond range. During the steady-state and the heatup interval, full agreement is found between experimental results, and the predictions of the acoustic mismatch model applied to the phonon transfer across the tin/sapphire interface and under the additional assumption that thermal equilibrium exists between electrons and phonons (one-temperature model). In contrast, very strong deviations are found during the cooling process which starts immediately after the end of the heating pulses. This observed nonequilibrium between electron and phonon system is discussed in more detail in a subsequent paper

  8. Neutron Transmission through Sapphire Crystals

    DEFF Research Database (Denmark)

    of simulations, in order to reproduce the transmission of cold neutrons through sapphire crystals. Those simulations were part of the effort of validating and improving the newly developed interface between the Monte-Carlo neutron transport code MCNP and the Monte Carlo ray-tracing code McStas....

  9. Methane flux across the air-water interface - Air velocity effects

    Science.gov (United States)

    Sebacher, D. I.; Harriss, R. C.; Bartlett, K. B.

    1983-01-01

    Methane loss to the atmosphere from flooded wetlands is influenced by the degree of supersaturation and wind stress at the water surface. Measurements in freshwater ponds in the St. Marks Wildlife Refuge, Florida, demonstrated that for the combined variability of CH4 concentrations in surface water and air velocity over the water surface, CH4 flux varied from 0.01 to 1.22 g/sq m/day. The liquid exchange coefficient for a two-layer model of the gas-liquid interface was calculated as 1.7 cm/h for CH4 at air velocity of zero and as 1.1 + 1.2 v to the 1.96th power cm/h for air velocities from 1.4 to 3.5 m/s and water temperatures of 20 C.

  10. High performance sapphire windows

    Science.gov (United States)

    Bates, Stephen C.; Liou, Larry

    1993-02-01

    High-quality, wide-aperture optical access is usually required for the advanced laser diagnostics that can now make a wide variety of non-intrusive measurements of combustion processes. Specially processed and mounted sapphire windows are proposed to provide this optical access to extreme environment. Through surface treatments and proper thermal stress design, single crystal sapphire can be a mechanically equivalent replacement for high strength steel. A prototype sapphire window and mounting system have been developed in a successful NASA SBIR Phase 1 project. A large and reliable increase in sapphire design strength (as much as 10x) has been achieved, and the initial specifications necessary for these gains have been defined. Failure testing of small windows has conclusively demonstrated the increased sapphire strength, indicating that a nearly flawless surface polish is the primary cause of strengthening, while an unusual mounting arrangement also significantly contributes to a larger effective strength. Phase 2 work will complete specification and demonstration of these windows, and will fabricate a set for use at NASA. The enhanced capabilities of these high performance sapphire windows will lead to many diagnostic capabilities not previously possible, as well as new applications for sapphire.

  11. Interface condition for the Darcy velocity at the water-oil flood front in the porous medium.

    Science.gov (United States)

    Peng, Xiaolong; Liu, Yong; Liang, Baosheng; Du, Zhimin

    2017-01-01

    Flood front is the jump interface where fluids distribute discontinuously, whose interface condition is the theoretical basis of a mathematical model of the multiphase flow in porous medium. The conventional interface condition at the jump interface is expressed as the continuous Darcy velocity and fluid pressure (named CVCM). Our study has inspected this conclusion. First, it is revealed that the principle of mass conservation has no direct relation to the velocity conservation, and the former is not the true foundation of the later, because the former only reflects the kinetic characteristic of the fluid particles at one position(the interface), but not the different two parts of fluid on the different side of the interface which required by the interface conditions. Then the reasonableness of CVCM is queried from the following three aspects:(1)Using Mukat's two phase seepage equation and the mathematical method of apagoge, we have disproved the continuity of each fluid velocity;(2)Since the analytical solution of the equation of Buckley-Leveret equations is acquirable, its velocity jumps at the flood front presents an appropriate example to disprove the CVCM;(3) The numerical simulation model gives impractical result that flood front would stop moving if CVCM were used to calculate the velocities at the interface between two gridcells. Subsequently, a new one, termed as Jump Velocity Condition Model (JVCM), is deduced from Muskat's two phase seepage equations and Darcy's law without taking account of the capillary force and compressibility of rocks and fluids. Finally, several cases are presented. And the comparisons of the velocity, pressure difference and the front position, which are given by JVCM, CVCM and SPU, have shown that the result of JVCM is the closest to the exact solution.

  12. Interface condition for the Darcy velocity at the water-oil flood front in the porous medium.

    Directory of Open Access Journals (Sweden)

    Xiaolong Peng

    Full Text Available Flood front is the jump interface where fluids distribute discontinuously, whose interface condition is the theoretical basis of a mathematical model of the multiphase flow in porous medium. The conventional interface condition at the jump interface is expressed as the continuous Darcy velocity and fluid pressure (named CVCM. Our study has inspected this conclusion. First, it is revealed that the principle of mass conservation has no direct relation to the velocity conservation, and the former is not the true foundation of the later, because the former only reflects the kinetic characteristic of the fluid particles at one position(the interface, but not the different two parts of fluid on the different side of the interface which required by the interface conditions. Then the reasonableness of CVCM is queried from the following three aspects:(1Using Mukat's two phase seepage equation and the mathematical method of apagoge, we have disproved the continuity of each fluid velocity;(2Since the analytical solution of the equation of Buckley-Leveret equations is acquirable, its velocity jumps at the flood front presents an appropriate example to disprove the CVCM;(3 The numerical simulation model gives impractical result that flood front would stop moving if CVCM were used to calculate the velocities at the interface between two gridcells. Subsequently, a new one, termed as Jump Velocity Condition Model (JVCM, is deduced from Muskat's two phase seepage equations and Darcy's law without taking account of the capillary force and compressibility of rocks and fluids. Finally, several cases are presented. And the comparisons of the velocity, pressure difference and the front position, which are given by JVCM, CVCM and SPU, have shown that the result of JVCM is the closest to the exact solution.

  13. Leveraging Python Interoperability Tools to Improve Sapphire's Usability

    Energy Technology Data Exchange (ETDEWEB)

    Gezahegne, A; Love, N S

    2007-12-10

    The Sapphire project at the Center for Applied Scientific Computing (CASC) develops and applies an extensive set of data mining algorithms for the analysis of large data sets. Sapphire's algorithms are currently available as a set of C++ libraries. However many users prefer higher level scripting languages such as Python for their ease of use and flexibility. In this report, we evaluate four interoperability tools for the purpose of wrapping Sapphire's core functionality with Python. Exposing Sapphire's functionality through a Python interface would increase its usability and connect its algorithms to existing Python tools.

  14. Frictional interactions in forming processes: New studies with transparent sapphire strip-drawing dies

    Science.gov (United States)

    Rao, R. S.; Lu, C. Y.; Wright, P. K.; Devenpeck, M. L.; Richmond, O.; Appleby, E. J.

    1982-05-01

    This research is concerned with the frictional interactions at the toolwork interfaces in the machining and strip-drawing processes. A novel feature is that transparent sapphire (single crystal Al2O3) is being used as the tool and die material. This allows the tribological features of the interface to be directly observed and recorded on movie-film. These qualitative studies provide information on the role of lubricants. In addition, techniques are being developed to quantify the velocity gradient along the interface. For example, in the drawing work it has been found that tracer markings (e.g. dye-spots), applied to the undrawn strip, remain intact during drawing and can be tracked along the sapphire/strip interface. Such data will be used as input to a finite-element, elasto-plastic-workhardening model of the deformation process. The latter can compute strip deformation characteristics, drawing forces and local coefficients of friction at the interface. Introductory results will be presented in this paper, obtained from drawing tin-plated mild steel with sapphire and cemented carbide dies. Drawing loads and die-separating forces will be presented and movie-films of the action of tracer markings at the interface shown. In order to demonstrate how this data can be used in an analysis of a large strain deformation process with friction, initial results from running the FIPDEF elasto-plastic code will be discussed. From a commercial viewpoint research on strip-drawing is of special interest to the can-making industry. From a physical viewpoint stripdrawing is of particular interest because it is a symmetrical, plane strain deformation and, in comparison with other metal processing operations, it is more readily modeled. However, until now the elasto-plastic codes that have been developed to predictively model drawing have had limitations: the most notable being that of quantifying the friction conditions at the die-work interface. Hence the specification of the

  15. Interface Based on Electrooculography for Velocity Control of a Robot Arm

    Directory of Open Access Journals (Sweden)

    Eduardo Iáñez

    2010-01-01

    Full Text Available This paper describes a technique based on electrooculography to control a robot arm. This technique detects the movement of the eyes, measuring the difference of potential between the cornea and the retina by placing electrodes around the ocular area. The processing algorithm developed to obtain the position of the eye at the blink of the user is explained. The output of the processing algorithm offers, apart from the direction, four different values (zero to three to control the velocity of the robot arm according to how much the user is looking in one direction. This allows controlling two degrees of freedom of a robot arm with the eyes movement. The blink has been used to mark some targets in tests. In this paper, the experimental results obtained with a real robot arm are shown.

  16. The Laser Damage Threshold for Materials and the Relation Between Solid-Melt and Melt-Vapor Interface Velocities

    International Nuclear Information System (INIS)

    Khalil, Osama Mostafa

    2010-01-01

    Numerous experiments have demonstrated and analytic theories have predicted that there is a threshold for pulsed laser ablation of a wide range of materials. Optical surface damage threshold is a very complex and important application of high-power lasers. Optical damage may also be considered to be the initial phase of laser ablation. In this work it was determined the time required and the threshold energy of a layer of thickness to heat up. We used the Finite Difference method to simulate the process of laser-target interaction in three cases. Namely, the case before melting begins using a continuous wave (c.w) laser source and a pulsed laser source, the case after the first change of state (from solid to melt), and the case after the second change of state (from melt to vapor). And also study the relation between the solid-melt and melt-vapor interface velocities to have a commonsense of the laser ablation process.

  17. Ti:Sapphire waveguide lasers

    NARCIS (Netherlands)

    Pollnau, Markus; Pashinin, P.P.; Grivas, C.; Laversenne, L.; Wilkinson, J.S.; Eason, R.W.; Shepherd, D.P.

    2007-01-01

    Titanium-doped sapphire is one of the most prominent laser materials and is appreciated for its excellent heat conductivity and broadband gain spectrum, allowing for a wide wavelength tunability and generation of ultrashort pulses. As one of the hardest materials, it can also serve as a model system

  18. Interfacial reactions between sapphire and Ag–Cu–Ti-based active braze alloys

    International Nuclear Information System (INIS)

    Ali, Majed; Knowles, Kevin M.; Mallinson, Phillip M.; Fernie, John A.

    2016-01-01

    The interfacial reactions between two commercially available Ag–Cu–Ti-based active braze alloys and sapphire have been studied. In separate experiments, Ag–35.3Cu–1.8Ti wt.% and Ag–26.7Cu–4.5Ti wt.% alloys have been sandwiched between pieces of R-plane orientated sapphire and heated in argon to temperatures between 750 and 900 °C for 1 min. The phases at the Ag–Cu–Ti/sapphire interfaces have been studied using selected area electron diffraction, energy dispersive X-ray spectroscopy and electron energy loss spectroscopy. Gradual and subtle changes at the Ag–Cu–Ti/sapphire interfaces were observed as a function of temperature, along with the formation of a transient phase that permitted wetting of the sapphire. Unequivocal evidence is shown that when the active braze alloys melt, titanium first migrates to the sapphire and reacts to dissolve up to ∼33 at.% oxygen, forming a nanometre-size polycrystalline layer with a chemical composition of Ti 2 O 1–x (x ≪ 1). Ti 3 Cu 3 O particles subsequently nucleate behind the Ti 2 O 1–x layer and grow to become a continuous micrometre-size layer, replacing the Ti 2 O 1–x layer. Finally at 845 °C, a nanometre-size γ-TiO layer forms on the sapphire to leave a typical interfacial structure of Ag–Cu/Ti 3 Cu 3 O/γ-TiO/sapphire consistent with that seen in samples of polycrystalline alumina joined to itself with these active braze alloys. These experimental observations have been used to establish a definitive bonding mechanism for the joining of sapphire with Ag–Cu alloys activated by small amounts of titanium.

  19. 'Sapphire' project. Objectives and outcomes

    International Nuclear Information System (INIS)

    Shkolnik, V.S.

    1997-01-01

    'Sapphire' Project contains the US assistance in purchasing/exporting 600 kg of highly enriched uranium from the State Holding Association 'Ulba' Uranium Plant, and compensatory equipment and service deliveries under the mutually concerted list. The compensatory payments were as separate projects in conformity with Kazakhstan enterprises needs, participation quota of which was determined by the Kazakhstan Government. Realization Milestones. Activity on Separate Projects: - basic 'Sapphire' part includes medical projects; - Kazakhstan Services were equipped with computers by the American International Development Agency for Taxation Services of Kazakhstan and by US Department of Energy for Monitoring preparation of Kazakhstan Atomic energy Agency. - 7 Research projects are being realized via the International Science and Technological Center; - export control. It has been realized as the equipment delivery under the concerted list; - equipping of nuclear materials accounting and control system at 'Ulba' Association enterprises

  20. Sapphire: Canada's Answer to Space-Based Surveillance of Orbital Objects

    Science.gov (United States)

    Maskell, P.; Oram, L.

    The Canadian Department of National Defence is in the process of developing the Canadian Space Surveillance System (CSSS) as the main focus of the Surveillance of Space (SofS) Project. The CSSS consists of two major elements: the Sapphire System and the Sensor System Operations Centre (SSOC). The space segment of the Sapphire System is comprised of the Sapphire Satellite - an autonomous spacecraft with an electro-optical payload which will act as a contributing sensor to the United States (US) Space Surveillance Network (SSN). It will operate in a circular, sunsynchronous orbit at an altitude of approximately 750 kilometers and image a minimum of 360 space objects daily in orbits ranging from 6,000 to 40,000 kilometers in altitude. The ground segment of the Sapphire System is composed of a Spacecraft Control Center (SCC), a Satellite Processing and Scheduling Facility (SPSF), and the Sapphire Simulator. The SPSF will be responsible for data transmission, reception, and processing while the SCC will serve to control and monitor the Sapphire Satellite. Surveillance data will be received from Sapphire through two ground stations. Following processing by the SPSF, the surveillance data will then be forwarded to the SSOC. The SSOC will function as the interface between the Sapphire System and the US Joint Space Operations Center (JSpOC). The JSpOC coordinates input from various sensors around the world, all of which are a part of the SSN. The SSOC will task the Sapphire System daily and provide surveillance data to the JSpOC for correlation with data from other SSN sensors. This will include orbital parameters required to predict future positions of objects to be tracked. The SSOC receives daily tasking instructions from the JSpOC to determine which objects the Sapphire spacecraft is required to observe. The advantage of this space-based sensor over ground-based telescopes is that weather and time of day are not factors affecting observation. Thus, space-based optical

  1. Sapphire capillary interstitial irradiators for laser medicine

    Science.gov (United States)

    Shikunova, I. A.; Dolganova, I. N.; Dubyanskaya, E. N.; Mukhina, E. E.; Zaytsev, K. I.; Kurlov, V. N.

    2018-04-01

    In this paper, we demonstrate instruments for laser radiation delivery based on sapphire capillary needles. Such sapphire irradiators (introducers) can be used for various medical applications, such as photodynamic therapy, laser hyperthermia, laser interstitial thermal therapy, and ablation of tumors of various organs. Unique properties of sapphire allow for effective redistribution of the heat, generated in biological tissues during their exposure to laser radiation. This leads to homogeneous distribution of the laser irradiation around the needle, and lower possibility of formation of the overheating focuses, as well as the following non-transparent thrombi.

  2. Dependence of adhesion strength between GaN LEDs and sapphire substrate on power density of UV laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Park, Junsu [Department of Nano-Manufacturing Technology, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Yuseong-Gu, Daejeon 34103 (Korea, Republic of); Sin, Young-Gwan [Department of Nano-Mechatronics, Korea University of Science and Technology (UST), 217 Gajeong-Ro, Yuseong-Gu, Daejeon 34113 (Korea, Republic of); Kim, Jae-Hyun [Department of Nano-Mechanics, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Yuseong-Gu, Daejeon 34103 (Korea, Republic of); Kim, Jaegu, E-mail: gugu99@kimm.re.kr [Department of Nano-Manufacturing Technology, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Yuseong-Gu, Daejeon 34103 (Korea, Republic of)

    2016-10-30

    Highlights: • Fundamental relationship between laser irradiation and adhesion strength, between gallium-nitride light emitted diode and sapphire substrate, is proposed during selective laser lift-off. • Two competing mechanisms affect adhesion at the irradiated interface between the GaN LED and sapphire substrate. • Ga precipitation caused by thermal decomposition and roughened interface caused by thermal damage lead to the considerable difference of adhesion strength at the interface. - Abstract: Selective laser lift-off (SLLO) is an innovative technology used to manufacture and repair micro-light-emitting diode (LED) displays. In SLLO, laser is irradiated to selectively separate micro-LED devices from a transparent sapphire substrate. The light source used is an ultraviolet (UV) laser with a wavelength of 266 nm, pulse duration of 20 ns, and repetition rate of 30 kHz. Controlled adhesion between a LED and the substrate is key for a SLLO process with high yield and reliability. This study examined the fundamental relationship between adhesion and laser irradiation. Two competing mechanisms affect adhesion at the irradiated interface between the GaN LED and sapphire substrate: Ga precipitation caused by the thermal decomposition of GaN and roughened interface caused by thermal damage on the sapphire. The competition between these two mechanisms leads to a non-trivial SLLO condition that needs optimization. This study helps understand the SLLO process, and accelerate the development of a process for manufacturing micro-LED displays via SLLO for future applications.

  3. The Influence of Surface Anisotropy Crystalline Structure on Wetting of Sapphire by Molten Aluminum

    Science.gov (United States)

    Aguilar-Santillan, Joaquin

    2013-05-01

    The wetting of sapphire by molten aluminum was investigated by the sessile drop technique from 1073 K to 1473 K (800 °C to 1200 °C) at PO2 <10-15 Pa under Ar atmosphere. This study focuses on sapphire crystalline structure and its principle to the interface. The planes " a" and " b" are oxygen terminated structures and wet more by Al, whereas the " c" plane is an aluminum terminated structure. A wetting transition at 1273 K (1000 °C) was obtained and a solid surface tension proves the capillarity trends of the couple.

  4. Characteristics of surface acoustic waves in (11\\bar 2 0)ZnO film/ R-sapphire substrate structures

    Science.gov (United States)

    Wang, Yan; Zhang, ShuYi; Xu, Jing; Xie, YingCai; Lan, XiaoDong

    2018-02-01

    (11\\bar 2 0)ZnO film/ R-sapphire substrate structure is promising for high frequency acoustic wave devices. The propagation characteristics of SAWs, including the Rayleigh waves along [0001] direction and Love waves along [1ī00] direction, are investigated by using 3 dimensional finite element method (3D-FEM). The phase velocity ( v p), electromechanical coupling coefficient ( k 2), temperature coefficient of frequency ( TCF) and reflection coefficient ( r) of Rayleigh wave and Love wave devices are theoretically analyzed. Furthermore, the influences of ZnO films with different crystal orientation on SAW properties are also investigated. The results show that the 1st Rayleigh wave has an exceedingly large k 2 of 4.95% in (90°, 90°, 0°) (11\\bar 2 0)ZnO film/ R-sapphire substrate associated with a phase velocity of 5300 m/s; and the 0th Love wave in (0°, 90°, 0°) (11\\bar 2 0)ZnO film/ R-sapphire substrate has a maximum k 2 of 3.86% associated with a phase velocity of 3400 m/s. And (11\\bar 2 0)ZnO film/ R-sapphire substrate structures can be used to design temperature-compensated and wide-band SAW devices. All of the results indicate that the performances of SAW devices can be optimized by suitably selecting ZnO films with different thickness and crystal orientations deposited on R-sapphire substrates.

  5. Sapphire: A kinking nonlinear elastic solid

    Science.gov (United States)

    Basu, S.; Barsoum, M. W.; Kalidindi, S. R.

    2006-03-01

    Kinking nonlinear elastic (KNE) solids are a recently identified large class of solids that deform fully reversibly by the formation of dislocation-based kink bands [Barsoum et al. Phys. Rev. Lett. 92, 255508 (2004)]. We further conjectured that a high c/a ratio-that ensures that only basal slip is operative-is a sufficient condition for a solid to be KNE. The c/a ratio of sapphire is 2.73 and thus, if our conjecture is correct, it should be a KNE solid. Herein by repeatedly loading-up to 30 times-the same location of sapphire single crystals of two orientations-A and C-with a 1 μm radius spherical nanoindenter, followed by atomic force microscopy, we showed that sapphire is indeed a KNE solid. After pop-ins of the order of 100 nm, the repeated loadings give rise to fully reversible, reproducible hysteresis loops wherein the energy dissipated per unit volume per cycle Wd is of the order of 0.5 GJ/m3. Wd is due to the back and fro motion of the dislocations making up the incipient kink bands that are fully reversible. The results presented here strongly suggest that-like in graphite and mica-kink bands play a more critical role in the room temperature constrained deformation of sapphire than had hitherto been appreciated. Our interpretation is also in agreement with, and can explain most, recent nanoindentation results on sapphire.

  6. Sapphire Energy - Integrated Algal Biorefinery

    Energy Technology Data Exchange (ETDEWEB)

    White, Rebecca L. [Sapphire Energy, Inc., Columbus, NM (United States). Columbus Algal Biomass Farm; Tyler, Mike [Sapphire Energy, Inc., San Diego, CA (United States)

    2015-07-22

    Sapphire Energy, Inc. (SEI) is a leader in large-scale photosynthetic algal biomass production, with a strongly cohesive research, development, and operations program. SEI takes a multidiscipline approach to integrate lab-based strain selection, cultivation and harvest and production scale, and extraction for the production of Green Crude oil, a drop in replacement for traditional crude oil.. SEI’s technical accomplishments since 2007 have produced a multifunctional platform that can address needs for fuel, feed, and other higher value products. Figure 1 outlines SEI’s commercialization process, including Green Crude production and refinement to drop in fuel replacements. The large scale algal biomass production facility, the SEI Integrated Algal Biorefinery (IABR), was built in Luna County near Columbus, New Mexico (see fig 2). The extraction unit was located at the existing SEI facility in Las Cruces, New Mexico, approximately 95 miles from the IABR. The IABR facility was constructed on time and on budget, and the extraction unit expansion to accommodate the biomass output from the IABR was completed in October 2012. The IABR facility uses open pond cultivation with a proprietary harvesting method to produce algal biomass; this biomass is then shipped to the extraction facility for conversion to Green Crude. The operation of the IABR and the extraction facilities has demonstrated the critical integration of traditional agricultural techniques with algae cultivation knowledge for algal biomass production, and the successful conversion of the biomass to Green Crude. All primary unit operations are de-risked, and at a scale suitable for process demonstration. The results are stable, reliable, and long-term cultivation of strains for year round algal biomass production. From June 2012 to November 2014, the IABR and extraction facilities produced 524 metric tons (MT) of biomass (on a dry weight basis), and 2,587 gallons of Green Crude. Additionally, the IABR

  7. Defect formation and recrystallization in the silicon on sapphire films under Si{sup +} irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Shemukhin, A.A., E-mail: shemuhin@gmail.com [Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow (Russian Federation); Nazarov, A.V.; Balakshin, Yu. V. [Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow (Russian Federation); Chernysh, V.S. [Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow (Russian Federation); Faculty of Physics, Lomonosov Moscow State University, Moscow (Russian Federation)

    2015-07-01

    Silicon-on-sapphire (SOS) is one of the most promising silicon-on-insulator (SOI) technologies. SOS structures are widely used in microelectronics, but to meet modern requirements the silicon layer should be 100 nm thick or less. The problem is in amount of damage in the interface layer, which decreases the quality of the produced devices. In order to improve the crystalline structure quality SOS samples with 300 nm silicon layers were implanted with Si{sup +} ions with energies in the range from 180 up to 230 keV with fluences in the range from 10{sup 14} up to 5 × 10{sup 15} cm{sup −2} at 0 °C. The crystalline structure of the samples was studied with RBS and the interface layer was studied with SIMS after subsequent annealing. It has been found out that to obtain silicon films with high lattice quality it is necessary to damage the sapphire lattice near the silicon–sapphire interface. Complete destruction of the strongly defected area and subsequent recrystallization depends on the energy of implanted ions and the substrate temperature. No significant mixing in the interface layer was observed with the SIMS.

  8. Analysis of the effect of the fluid-structure interface on elastic wave velocity in cornea-like structures by OCE and FEM

    International Nuclear Information System (INIS)

    Han, Zhaolong; Li, Jiasong; Singh, Manmohan; Wu, Chen; Liu, Chih-hao; Raghunathan, Raksha; Larin, Kirill V; Vantipalli, Srilatha; Aglyamov, Salavat R; Twa, Michael D

    2016-01-01

    Air-pulse optical coherence elastography (OCE) is a promising technique for quantifying biomechanical properties of the cornea. This technique typically involves imaging and analysis of the propagation of the air-pulse induced elastic waves to reconstruct corneal biomechanical properties using an analytical model. However, the effect of the fluid-structure interface (FSI) at the corneal posterior surface on the elastic wave velocity is not accounted for in many models. In this study, we examined the effect of the FSI with OCE experiments on contact lenses with and without fluid in the posterior gap. Finite element models (FEM), also with and without the FSI, were constructed to simulate the elastic wave propagation based on the OCE measurements. The FEM and OCE results were in good agreement demonstrating the feasibility of the method. To further investigate the effect of the FSI, OCE experiments and subsequent FEM simulations were conducted on in situ rabbit corneas before and after rose bengal/green light corneal collagen cross-linking (RGX). Both the OCE experiments and the FE simulations demonstrated that the FSI significantly reduced the group velocity of the elastic wave, and thus, should be considered when determining corneal biomechanical properties from an appropriate mechanical model. By matching the FEM-calculated velocity to the OCE-measured velocity, the corneal elasticity was quantified. The Young’s modulus of the rabbit cornea before RGX was E  =  65  ±  10 kPa at a controlled intraocular pressure (IOP) of 15 mmHg. After RGX, the Young’s modulus increased to E  =  102  ±  7 kPa at the same IOP. (letter)

  9. Numerical investigation of thermal and residual stress of sapphire during c-axis vertical Bridgman growth process considering the solidification history effect

    Science.gov (United States)

    Hwang, Ji Hoon; Lee, Young Cheol; Lee, Wook Jin

    2018-01-01

    Sapphire single crystals have been highlighted for epitaxial of gallium nitride films in high-power laser and light emitting diode industries. In this study, the evolution of thermally induced stress in sapphire during the vertical Bridgman crystal growth process was investigated using a finite element model that simplified the real Bridgman process. A vertical Bridgman process of cylindrical sapphire crystal with a diameter of 50 mm was considered for the model. The solidification history effect during the growth was modeled by the quite element technique. The effects of temperature gradient, seeding interface shape and seeding position on the thermal stress during the process were discussed based on the finite element analysis results.

  10. Controllable laser thermal cleavage of sapphire wafers

    Science.gov (United States)

    Xu, Jiayu; Hu, Hong; Zhuang, Changhui; Ma, Guodong; Han, Junlong; Lei, Yulin

    2018-03-01

    Laser processing of substrates for light-emitting diodes (LEDs) offers advantages over other processing techniques and is therefore an active research area in both industrial and academic sectors. The processing of sapphire wafers is problematic because sapphire is a hard and brittle material. Semiconductor laser scribing processing suffers certain disadvantages that have yet to be overcome, thereby necessitating further investigation. In this work, a platform for controllable laser thermal cleavage was constructed. A sapphire LED wafer was modeled using the finite element method to simulate the thermal and stress distributions under different conditions. A guide groove cut by laser ablation before the cleavage process was observed to guide the crack extension and avoid deviation. The surface and cross section of sapphire wafers processed using controllable laser thermal cleavage were characterized by scanning electron microscopy and optical microscopy, and their morphology was compared to that of wafers processed using stealth dicing. The differences in luminous efficiency between substrates prepared using these two processing methods are explained.

  11. Research Progress and Development of Sapphire Fiber Sensor

    Directory of Open Access Journals (Sweden)

    Guochang ZHAO

    2014-07-01

    Full Text Available Sapphire fiber thermometers have become a new potential option in the field of high-temperature measurements. Recent research progress of sapphire fiber sensors is summarized; operational principles, advantages, disadvantages, and applications of sapphire fiber sensors are introduced. Research has shown that sapphire fiber sensors can be used to accurately measure very high temperatures in harsh environments and has been widely applied in fields such as aviation, metallurgy, the chemical industry, energy, and other high temperature measurement areas. Sapphire optical fiber temperature measurement technology will move toward miniaturization, intelligence following the advances in materials, micro-fabrication and communication technologies.

  12. Influence of interfacial reactions on the fiber push-out behavior in sapphire fiber-reinforced-NiAl(Yb) composites

    International Nuclear Information System (INIS)

    Tewari, S.N.; Asthana, R.; Tiwari, R.; Bowman, R.R.

    1993-01-01

    The influence of microstructure of the fiber-matrix interface on the fiber push-out behavior has been examined in sapphire fiber-reinforced NiAl and NiAl(Yb) matrix composites synthesized using powder metallurgy techniques combined with zone directional solidification (DS). The push-out stress-displacement curves were observed to consist of an initial 'pseudoelastic' region, wherein the stress increased linearly with displacement, followed by an 'inelastic' region, where the slope of the stress-displacement plot decreased until a maximum stress was reached, and the subsequent stress drop to a constant 'frictional' stress. Chemical reaction between the fiber and the matrix resulted in higher interfacial shear strength in powder cloth processed sapphire-NiAl(Yb) composites as compared to the sapphire-NiAl composites. Grain boundaries in contact with the fibers on the back face of the push-out samples were the preferred sites for crack nucleation in PM composites. The frictional stress was independent of the microstructure and processing variables for NiAl composites, but showed strong dependence on these variables for the NiAl(Yb) composites. The DS processing enhanced the fiber-matrix interfacial shear strength of feedstock PM-NiAl/sapphire composites. However, it reduced the interfacial shear strength of PM-NiAl(Yb)-sapphire composites

  13. Influence of TMAl preflow on AlN epitaxy on sapphire

    KAUST Repository

    Sun, Haiding; Wu, Feng; Park, Young Jae; Al tahtamouni, T. M.; Li, Kuang-Hui; Alfaraj, Nasir; Detchprohm, Theeradetch; Dupuis, Russell D.; Li, Xiaohang

    2017-01-01

    The trimethylaluminum (TMAl) preflow process has been widely applied on sapphire substrates prior to growing Al-polar AlN films by metalorganic chemical vapor deposition. However, it has been unclear how the TMAl preflow process really works. In this letter, we reported on carbon's significance in the polarity and growth mode of AlN films due to the TMAl preflow. Without the preflow, no trace of carbon was found at the AlN/sapphire interface and the films possessed mixed Al- and N-polarity. With the 5 s preflow, carbon started to precipitate due to the decomposition of TMAl, forming scattered carbon-rich clusters which were graphitic carbon. It was discovered that the carbon attracted surrounding oxygen impurity atoms and consequently suppressed the formation of AlxOyNz and thus N-polarity. With the 40 s preflow, the significant presence of carbon clusters at the AlN/sapphire interface was observed. While still attracting oxygen and preventing the N-polarity, the carbon clusters served as randomly distributed masks to further induce a 3D growth mode for the AlN growth. The corresponding epitaxial growth mode change is discussed.

  14. Influence of TMAl preflow on AlN epitaxy on sapphire

    KAUST Repository

    Sun, Haiding

    2017-05-12

    The trimethylaluminum (TMAl) preflow process has been widely applied on sapphire substrates prior to growing Al-polar AlN films by metalorganic chemical vapor deposition. However, it has been unclear how the TMAl preflow process really works. In this letter, we reported on carbon\\'s significance in the polarity and growth mode of AlN films due to the TMAl preflow. Without the preflow, no trace of carbon was found at the AlN/sapphire interface and the films possessed mixed Al- and N-polarity. With the 5 s preflow, carbon started to precipitate due to the decomposition of TMAl, forming scattered carbon-rich clusters which were graphitic carbon. It was discovered that the carbon attracted surrounding oxygen impurity atoms and consequently suppressed the formation of AlxOyNz and thus N-polarity. With the 40 s preflow, the significant presence of carbon clusters at the AlN/sapphire interface was observed. While still attracting oxygen and preventing the N-polarity, the carbon clusters served as randomly distributed masks to further induce a 3D growth mode for the AlN growth. The corresponding epitaxial growth mode change is discussed.

  15. Molecular beam epitaxy of InN layers on Sapphire, GaN and indium tin oxide

    Energy Technology Data Exchange (ETDEWEB)

    Denker, Christian; Landgraf, Boris; Schuhmann, Henning; Malindretos, Joerg; Seibt, Michael; Rizzi, Angela [IV. Physikalisches Institut, Georg-August-Universitaet Goettingen (Germany); Segura-Ruiz, Jaime; Gomez-Gomez, Maribel; Cantarero, Andres [Materials Science Institute, University of Valencia, Paterna (Spain)

    2009-07-01

    Among the group-III nitrides semiconductors, InN is the one with the narrowest gap (0.67 eV), lowest effective electron mass and highest peak drift velocity. It is therefore a very interesting material for several applications, in particular semiconductor solar cells. Furthermore, the high electron affinity makes it suitable also as electrode material for organic solar cells. InN layers were grown by molecular beam epitaxy on MOCVD GaN templates, on bare c-plane sapphire and on polycrystalline indium tin oxide. On all substrates the III-V ratio as well as the substrate temperature was varied. A RHEED analysis of InN growth on GaN showed a relatively sharp transition from N-rich and columnar growth to In-rich growth with droplet formation by increasing the In flux impinging on the surface. The InN layers on single crystalline substrates were characterized by SEM, AFM, XRD, PL and Raman. The InN layers on ITO were mainly analyzed with respect to the surface morphology with SEM. HRTEM in cross section gives insight into the structure of the interface to the ITO substrate.

  16. Interface control scheme for computer high-speed interface unit

    Science.gov (United States)

    Ballard, B. K.

    1975-01-01

    Control scheme is general and performs for multiplexed and dedicated channels as well as for data-bus interfaces. Control comprises two 64-pin, dual in-line packages, each of which holds custom large-scale integrated array built with silicon-on-sapphire complementary metal-oxide semiconductor technology.

  17. Reduced cost and improved figure of sapphire optical components

    Science.gov (United States)

    Walters, Mark; Bartlett, Kevin; Brophy, Matthew R.; DeGroote Nelson, Jessica; Medicus, Kate

    2015-10-01

    Sapphire presents many challenges to optical manufacturers due to its high hardness and anisotropic properties. Long lead times and high prices are the typical result of such challenges. The cost of even a simple 'grind and shine' process can be prohibitive. The high precision surfaces required by optical sensor applications further exacerbate the challenge of processing sapphire thereby increasing cost further. Optimax has demonstrated a production process for such windows that delivers over 50% time reduction as compared to traditional manufacturing processes for sapphire, while producing windows with less than 1/5 wave rms figure error. Optimax's sapphire production process achieves significant improvement in cost by implementation of a controlled grinding process to present the best possible surface to the polishing equipment. Following the grinding process is a polishing process taking advantage of chemical interactions between slurry and substrate to deliver excellent removal rates and surface finish. Through experiments, the mechanics of the polishing process were also optimized to produce excellent optical figure. In addition to reducing the cost of producing large sapphire sensor windows, the grinding and polishing technology Optimax has developed aids in producing spherical sapphire components to better figure quality. In addition to reducing the cost of producing large sapphire sensor windows, the grinding and polishing technology Optimax has developed aids in producing spherical sapphire components to better figure quality. Through specially developed polishing slurries, the peak-to-valley figure error of spherical sapphire parts is reduced by over 80%.

  18. Description of Project Sapphire. Revision 1

    International Nuclear Information System (INIS)

    Taylor, R.G.

    1995-01-01

    The mission of Project Sapphire was to repackage approximately 600 kg of highly enriched uranium (HEU) in the Republic of Kazakhstan into internationally acceptable shipping packages and transport the material to a storage location in the United States. There were four material types to be repackaged: metal; oxide; uranium/beryllium (U/Be) alloy; and residues from U/Be alloy production. Seven major steps described in this report were necessary for successful execution of the project: planning and training; readiness assessment; deployment; set up; process; take down; and transport. Nuclear criticality safety especially affected several of these steps

  19. Lattice dynamics of sapphire (corundum). Pt. 2

    International Nuclear Information System (INIS)

    Kappus, W.

    1975-01-01

    Theoretical models of the lattice dynamics of sapphire (α - Al 2 O 3 ), based on the assumption of rigid ions, have been fitted to measured phonons at the Gamma-point of the Brillouin zone. Short range interactions were taken into account by assuming 2-body interactions between touching ions. Additional 3-body interactions could not improve the fit significantly. Calculated dispersion curves are presented and compared with inelastic neutron scattering data. A good agreement for branches along the trigonal axis can be stated. (orig.) [de

  20. A Century of Sapphire Crystal Growth

    Science.gov (United States)

    2004-05-17

    should be aware that notwithstanding any other provision of law , no person shall be subject to a penalty for failing to comply with a collection of...and ruby were oxides of the elements aluminum and silicon.1 In 1817, J. L. Gay- Lussac found that pure aluminum oxide (also called alumina) could...thought to consist of Al2O3 and SiO2 •1817: Gay- Lussac : •1840: Rose: Found SiO2 in sapphire is from agate mortar used for grinding •1837-72: Gaudin

  1. Structure of the Dislocation in Sapphire

    DEFF Research Database (Denmark)

    Bilde-Sørensen, Jørgen; Thölen, A. R.; Gooch, D. J.

    1976-01-01

    Experimental evidence of the existence of 01 0 dislocations in the {2 0} prism planes in sapphire has been obtained by transmission electron microscopy. By the weak-beam technique it has been shown that the 01 0 dislocations may dissociate into three partials. The partials all have a Burgers vector...... of ⅓ 01 0 and are separated by two identical faults. The distance between two partials is in the range 75-135 Å, corresponding to a fault energy of 320±60 mJ/m2. Perfect 01 0 dislocations have also been observed. These dislocations exhibited either one or two peaks when imaged in the (03 0) reflection...

  2. On the laser lift-off of lightly doped micrometer-thick n-GaN films from substrates via the absorption of IR radiation in sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Voronenkov, V. V. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Virko, M. V.; Kogotkov, V. S.; Leonidov, A. A. [Peter the Great St. Petersburg Polytechnic University (Russian Federation); Pinchuk, A. V.; Zubrilov, A. S.; Gorbunov, R. I.; Latishev, F. E.; Bochkareva, N. I.; Lelikov, Y. S.; Tarkhin, D. V.; Smirnov, A. N.; Davydov, V. Y. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Sheremet, I. A. [Financial University under the Government of the Russian Federation (Russian Federation); Shreter, Y. G., E-mail: y.shreter@mail.ioffe.ru [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

    2017-01-15

    The intense absorption of CO{sub 2} laser radiation in sapphire is used to separate GaN films from GaN templates on sapphire. Scanning of the sapphire substrate by the laser leads to the thermal dissociation of GaN at the GaN/sapphire interface and to the detachment of GaN films from the sapphire. The threshold density of the laser energy at which n-GaN started to dissociate is 1.6 ± 0.5 J/cm{sup 2}. The mechanical-stress distribution and the surface morphology of GaN films and sapphire substrates before and after laser lift-off are studied by Raman spectroscopy, atomic-force microscopy, and scanning electron microscopy. A vertical Schottky diode with a forward current density of 100 A/cm{sup 2} at a voltage of 2 V and a maximum reverse voltage of 150 V is fabricated on the basis of a 9-μm-thick detached n-GaN film.

  3. Transmission Electron Microscopy (TEM) Sample Preparation of Si(1-x)Gex in c-Plane Sapphire Substrate

    Science.gov (United States)

    Kim, Hyun Jung; Choi, Sang H.; Bae, Hyung-Bin; Lee, Tae Woo

    2012-01-01

    The National Aeronautics and Space Administration-invented X-ray diffraction (XRD) methods, including the total defect density measurement method and the spatial wafer mapping method, have confirmed super hetero epitaxy growth for rhombohedral single crystalline silicon germanium (Si1-xGex) on a c-plane sapphire substrate. However, the XRD method cannot observe the surface morphology or roughness because of the method s limited resolution. Therefore the authors used transmission electron microscopy (TEM) with samples prepared in two ways, the focused ion beam (FIB) method and the tripod method to study the structure between Si1-xGex and sapphire substrate and Si1?xGex itself. The sample preparation for TEM should be as fast as possible so that the sample should contain few or no artifacts induced by the preparation. The standard sample preparation method of mechanical polishing often requires a relatively long ion milling time (several hours), which increases the probability of inducing defects into the sample. The TEM sampling of the Si1-xGex on sapphire is also difficult because of the sapphire s high hardness and mechanical instability. The FIB method and the tripod method eliminate both problems when performing a cross-section TEM sampling of Si1-xGex on c-plane sapphire, which shows the surface morphology, the interface between film and substrate, and the crystal structure of the film. This paper explains the FIB sampling method and the tripod sampling method, and why sampling Si1-xGex, on a sapphire substrate with TEM, is necessary.

  4. Synthesis of titanium sapphire by ion implantation

    International Nuclear Information System (INIS)

    Morpeth, L.D.; McCallum, J.C.; Nugent, K.W.

    1998-01-01

    Since laser action was first demonstrated in titanium sapphire (Ti:Al 2 O 3 ) in 1982, it has become the most widely used tunable solid state laser source. The development of a titanium sapphire laser in a waveguide geometry would yield an elegant, compact, versatile and highly tunable light source useful for applications in many areas including optical telecommunications. We are investigating whether ion implantation techniques can be utilised to produce suitable crystal quality and waveguide geometry for fabrication of a Ti:Al 2 O 3 waveguide laser. The implantation of Ti and O ions into c-axis oriented α-Al 2 O 3 followed by subsequent thermal annealing under various conditions has been investigated as a means of forming the waveguide and optimising the fraction of Ti ions that have the correct oxidation state required for laser operation. A Raman Microprobe is being used to investigate the photo-luminescence associated with Ti 3+ ion. Initial photoluminescence measurements of ion implanted samples are encouraging and reveal a broad luminescence profile over a range of ∼ .6 to .9 μm, similar to that expected from Ti 3+ . Rutherford Backscattering and Ion Channelling analysis have been used to study the crystal structure of the samples following implantation and annealing. This enables optimisation of the implantation parameters and annealing conditions to minimise defect levels which would otherwise limit the ability of light to propagate in the Ti:Al 2O 3 waveguide. (authors)

  5. Refractive index of r-cut sapphire under shock pressure range 5 to 65 GPa

    International Nuclear Information System (INIS)

    Cao, Xiuxia; Li, Jiabo; Li, Jun; Li, Xuhai; Xu, Liang; Wang, Yuan; Zhu, Wenjun; Meng, Chuanmin; Zhou, Xianming

    2014-01-01

    High-pressure refractive index of optical window materials not only can provide information on electronic polarizability and band-gap structure, but also is important for velocity correction in particle-velocity measurement with laser interferometers. In this work, the refractive index of r-cut sapphire window at 1550 nm wavelength was measured under shock pressures of 5–65 GPa. The refractive index (n) decreases linearly with increasing shock density (ρ) for shock stress above the Hugoniot elastic limit (HEL): n = 2.0485 (± 0.0197) − 0.0729 (± 0.0043)ρ, while n remains nearly a constant for elastic shocks. This behavior is attributed to the transition from elastic (below HEL) to heterogeneous plastic deformation (above HEL). Based on the obtained refractive index-density relationship, polarizability of the shocked sapphire was also obtained

  6. Synthesis of single-crystalline Al layers in sapphire

    International Nuclear Information System (INIS)

    Schlosser, W.; Lindner, J.K.N.; Zeitler, M.; Stritzker, B.

    1999-01-01

    Single-crystalline, buried aluminium layers were synthesized by 180 keV high-dose Al + ion implantation into sapphire at 500 deg. C. The approximately 70 nm thick Al layers exhibit in XTEM investigations locally abrupt interfaces to the single-crystalline Al 2 O 3 top layer and bulk, while thickness and depth position are subjected to variations. The layers grow by a ripening process of oriented Al precipitates, which at low doses exist at two different orientations. With increasing dose, precipitates with one out of the two orientations are observed to exist preferentially, finally leading to the formation of a single-crystalline layer. Al outdiffusion to the surface and the formation of spherical Al clusters at the surface are found to be competing processes to buried layer formation. The formation of Al layers is described by Rutherford Backscattering Spectroscopy (RBS), Cross-section transmission electron microscopy (XTEM) and Scanning electron microscopy (SEM) studies as a function of dose, temperature and substrate orientation

  7. Research and development of photovoltaic power system. Characterization and control of surface/interface recombination velocity of crystalline silicon thin films; Taiyoko hatsuden system no kenkyu kaihatsu. Silicon kessho usumaku ni okeru hyomen kaimen saiketsugo sokudo no hyoka to seigyo

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, H [Hokkaido University, Sapporo (Japan). Faculty of Engineering

    1994-12-01

    This paper reports the result obtained during fiscal 1994 on characterization and control of surface/interface recombination velocity of crystalline silicon thin films. To optimize design and manufacture of solar cells, it is necessary to identify correctly resistance factor (or doping) of bulk of materials, bulk minority carrier life, and recombination velocity on surface, passivation interface and electrode interface. A group in the Hokkaido University has been working since a few years ago on development of non-contact and non-destructive photo-luminescence surface level spectroscopy (PLS{sup 3}). A new non-contact C-V method was also introduced. Using these methods, basic discussions were given on possibility of separate measurements on surface/interface and bulk characteristics of solar cell materials. The PLS{sup 3} method and the non-contact C-V method were used for experimental discussions on evaluation of silicon mono-crystalline and poly-crystalline materials. Discussions were given on separate evaluations by using the DLTS method. 10 figs., 2 tabs.

  8. Polishing Sapphire Substrates by 355 nm Ultraviolet Laser

    Directory of Open Access Journals (Sweden)

    X. Wei

    2012-01-01

    Full Text Available This paper tries to investigate a novel polishing technology with high efficiency and nice surface quality for sapphire crystal that has high hardness, wear resistance, and chemical stability. A Q-switched 355 nm ultraviolet laser with nanosecond pulses was set up and used to polish sapphire substrate in different conditions in this paper. Surface roughness Ra of polished sapphire was measured with surface profiler, and the surface topography was observed with scanning electronic microscope. The effects of processing parameters as laser energy, pulse repetition rate, scanning speed, incident angle, scanning patterns, and initial surface conditions on surface roughness were analyzed.

  9. Nanostructured sapphire optical fiber for sensing in harsh environments

    Science.gov (United States)

    Chen, Hui; Liu, Kai; Ma, Yiwei; Tian, Fei; Du, Henry

    2017-05-01

    We describe an innovative and scalable strategy of transforming a commercial unclad sapphire optical fiber to an allalumina nanostructured sapphire optical fiber (NSOF) that overcomes decades-long challenges faced in the field of sapphire fiber optics. The strategy entails fiber coating with metal Al followed by subsequent anodization to form anodized alumina oxide (AAO) cladding of highly organized pore channel structure. We show that Ag nanoparticles entrapped in AAO show excellent structural and morphological stability and less susceptibility to oxidation for potential high-temperature surface-enhanced Raman Scattering (SERS). We reveal, with aid of numerical simulations, that the AAO cladding greatly increases the evanescent-field overlap both in power and extent and that lower porosity of AAO results in higher evanescent-field overlap. This work has opened the door to new sapphire fiber-based sensor design and sensor architecture.

  10. Neutron transmission of single-crystal sapphire filters

    International Nuclear Information System (INIS)

    Adib, M.; Kilany, M.; Habib, N.; Fathallah, M.

    2005-01-01

    An additive formula is given that permits the calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of sapphire temperature and crystal parameters. We have developed a computer program that allows calculations of the thermal neutron transmission for the sapphire rhombohedral structure and its equivalent trigonal structure. The calculated total cross-section values and effective attenuation coefficient for single-crystalline sapphire at different temperatures are compared with measured values. Overall agreement is indicated between the formula fits and experimental data. We discuss the use of sapphire single crystal as a thermal neutron filter in terms of the optimum crystal thickness, mosaic spread, temperature, cutting plane and tuning for efficient transmission of thermal-reactor neutrons. (author)

  11. Neutron Transmission of Single-crystal Sapphire Filters

    Science.gov (United States)

    Adib, M.; Kilany, M.; Habib, N.; Fathallah, M.

    2005-05-01

    An additive formula is given that permits the calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of sapphire temperature and crystal parameters. We have developed a computer program that allows calculations of the thermal neutron transmission for the sapphire rhombohedral structure and its equivalent trigonal structure. The calculated total cross-section values and effective attenuation coefficient for single-crystalline sapphire at different temperatures are compared with measured values. Overall agreement is indicated between the formula and experimental data. We discuss the use of sapphire single crystal as a thermal neutron filter in terms of the optimum cystal thickness, mosaic spread, temperature, cutting plane and tuning for efficient transmission of thermal-reactor neutrons.

  12. Neutron transmission of single-crystal sapphire filters

    International Nuclear Information System (INIS)

    Adib, M.; Kilany, M.; Habib, N.; Fathallah, M.

    2004-01-01

    A simple additive formula is given that permits the calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of sapphire temperature and crystal parameters. We have developed a computer program that allows calculations of the thermal neutron transmission for the sapphire rhombohedral structure and its equivalent trigonal structure. The calculated total cross-section values and effective attenuation coefficient for mono-crystalline sapphire at different temperatures are compared with measured values. Overall agreement is indicated between the formula fits and experimental data. We discuss the use of sapphire single-crystal as a thermal neutron filter in terms of the optimum crystal thickness, mosaic spread, temperature, cutting plane and tuning for efficient transmission of thermal-reactor neutrons

  13. Oleophobic properties of the step-and-terrace sapphire surface

    Energy Technology Data Exchange (ETDEWEB)

    Muslimov, A. E., E-mail: amuslimov@mail.ru; Butashin, A. V.; Kanevsky, V. M. [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Research Center “Crystallography and Photonics” (Russian Federation)

    2017-03-15

    Sapphire is widely used in production of optical windows for various devices due to its mechanical and optical properties. However, during operation the surface can be affected by fats, oils, and other organic contaminations. Therefore, it is important to improve the oleophobic properties of sapphire windows. In this study, we investigate the interaction of a supersmooth sapphire surface with oleic acid droplets, which imitate human finger printing. It is established that chemical–mechanical polishing with additional annealing in air, which leads to the formation of an atomically smooth sapphire surface, makes it possible to significantly improve the oleophobic properties of the surface. The results are analyzed using the Ventsel–Deryagin homogeneous wetting model.

  14. Reliability improvement methods for sapphire fiber temperature sensors

    Science.gov (United States)

    Schietinger, C.; Adams, B.

    1991-08-01

    Mechanical, optical, electrical, and software design improvements can be brought to bear in the enhancement of fiber-optic sapphire-fiber temperature measurement tool reliability in harsh environments. The optical fiber thermometry (OFT) equipment discussed is used in numerous process industries and generally involves a sapphire sensor, an optical transmission cable, and a microprocessor-based signal analyzer. OFT technology incorporating sensors for corrosive environments, hybrid sensors, and two-wavelength measurements, are discussed.

  15. Wetting phenomena of Al-Cu alloys on sapphire below 800 deg. C

    International Nuclear Information System (INIS)

    Klinter, Andreas J.; Leon-Patino, Carlos A.; Drew, Robin A.L.

    2010-01-01

    Using a modified dispensed drop method, a decrease in contact angle on sapphire from pure aluminum to low-copper-containing Al alloys (7-12 wt.%) was found; with higher copper additions θ transitions to the non-wetting regime. Atomic force microscopy on long-term samples showed a significantly increased surface roughness beneath the drop. Using high-resolution transmission electron microscopy, the reaction product at the interface was identified as CuAl 2 O 4 for Al-7Cu and Al 2 O 3 for an Al-99.99 drop. X-ray photoelectron spectroscopy further confirmed the formation of CuAl 2 O 4 under CuAl 2 drops. Spinel formation is caused by reaction of the alloy with residual oxygen in the furnace that is transported along the interface as modeled by thermodynamic simulations. The formation of CuAl 2 O 4 causes the reduced σ sl and hence the improved wettability of sapphire by low-copper-containing alloys compared to pure aluminum. The main reason for the increase in θ with higher copper contents is the increasing σ lv of the alloy.

  16. Wetting phenomena of Al-Cu alloys on sapphire below 800 deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Klinter, Andreas J., E-mail: andreas.klinter@mail.mcgill.ca [Mining and Materials Engineering, McGill University, M.H. Wong Building, 3610 University Street, Montreal, QC, H3A 2B2 (Canada); Leon-Patino, Carlos A. [Instituto de Investigaciones Metalurgicas, Universidad Michoacana de San Nicolas de Hidalgo, Apdo. Postal 888, CP 58000 Morelia, Michoacan (Mexico); Drew, Robin A.L. [Faculty of Engineering and Computer Science, Concordia University, 1455 Maisonneuve Blvd, EV 2.169, Montreal, QC, H3G 1M8 (Canada)

    2010-02-15

    Using a modified dispensed drop method, a decrease in contact angle on sapphire from pure aluminum to low-copper-containing Al alloys (7-12 wt.%) was found; with higher copper additions {theta} transitions to the non-wetting regime. Atomic force microscopy on long-term samples showed a significantly increased surface roughness beneath the drop. Using high-resolution transmission electron microscopy, the reaction product at the interface was identified as CuAl{sub 2}O{sub 4} for Al-7Cu and Al{sub 2}O{sub 3} for an Al-99.99 drop. X-ray photoelectron spectroscopy further confirmed the formation of CuAl{sub 2}O{sub 4} under CuAl{sub 2} drops. Spinel formation is caused by reaction of the alloy with residual oxygen in the furnace that is transported along the interface as modeled by thermodynamic simulations. The formation of CuAl{sub 2}O{sub 4} causes the reduced {sigma}{sub sl} and hence the improved wettability of sapphire by low-copper-containing alloys compared to pure aluminum. The main reason for the increase in {theta} with higher copper contents is the increasing {sigma}{sub lv} of the alloy.

  17. Evaluating the Type of Light Transmittance in Mono Crystalline, Poly Crystalline and Sapphire Brackets- An Invitro Spectrofluorometer Study.

    Science.gov (United States)

    Mohamed, Jauhar P; Kommi, Pradeep Babu; Kumar, M Senthil; Hanumanth; Venkatesan; Aniruddh; Arvinth; Kumar, Arani Nanda

    2016-08-01

    Group 3 (sapphire ceramic brackets) i.e., Group 2 showed the highest light absorption and the least translucency followed by groups 1 and 3. Shear bond strength results were 2.4 mpa, 1.9 mpa and 3.6 mpa for groups 1,2 and 3 respectively. Superior shear bond strength was recorded in group 3 (sapphire ceramic brackets). ARI results showed that group 3 had increased bond between bracket adhesive interfaces when compared to the other 2 groups. From this study, it has been concluded that sapphire ceramic brackets (Group 3) was superior in translucency and shear bond strength followed by monocrystalline and polycrystalline ceramic brackets.

  18. High energy iron ion implantation into sapphire

    International Nuclear Information System (INIS)

    Allen, W.R.; Pedraza, D.F.

    1990-01-01

    Sapphire specimens of c-axis orientation were implanted at room temperature with iron ions at energies of 1.2 and of 2 MeV to various fluences up to 8 x 10 16 cm -2 . The damage induced by the implantations was assessed by Rutherford backscattering spectroscopy in random and channeling geometries. Dechanneling in both sublattices was observed to saturate for all implantation conditions. Disorder in the aluminum sublattice was found to increase with depth at a significantly slower rate than in the oxygen sublattice. In the oxygen sublattice, a relative yield, χ, of 0.80 ± 0.11 was attained at a depth of 0.1 μm and remained constant up to the measured depth of 0.45 μm. In the aluminum sublattice, the disorder increased with depth and the dechanneling asymptotically approached χ =0.70 ± 0.04 at 0.45 μm. These results are discussed and compared with those for shallower Fe implantations obtained by other researchers

  19. Tuning the sapphire EFG process to the growth of Al2O3/YAG/ZrO2:Y eutectic

    Science.gov (United States)

    Carroz, L.; Duffar, T.

    2018-05-01

    In this work, a model is proposed, in order to analytically study the working point of the Edge defined Film-fed Growth (EFG) pulling of crystal plates. The model takes into account the heat equilibrium at the interface and the pressure equilibrium across the meniscus. It is validated on an industrial device dedicated to the pulling of sapphire ribbons. Then, the model is applied to pulling ceramic alloy plates, of the ternary eutectic Al2O3/YAG/ZrO2:Y. This allowed understanding the experimental difficulties of pulling this new material and suggested improvements of the control software. From these results, pulling net shaped ceramic alloy plates was successful in the same industrial equipment as used for sapphire.

  20. A peek into the history of sapphire crystal growth

    Science.gov (United States)

    Harris, Daniel C.

    2003-09-01

    After the chemical compositions of sapphire and ruby were unraveled in the middle of the 19th century, chemists set out to grow artificial crystals of these valuable gemstones. In 1885 a dealer in Geneva began to sell ruby that is now believed to have been created by flame fusion. Gemnologists rapidly concluded that the stones were artificial, but the Geneva ruby stimulated A. V. L. Verneuil in Paris to develop a flame fusion process to produce higher quality ruby and sapphire. By 1900 there was brisk demand for ruby manufactured by Verneuil's method, even though Verneuil did not publicly announce his work until 1902 and did not publish details until 1904. The Verneuil process was used with little alteration for the next 50 years. From 1932-1953, S. K. Popov in the Soviet Union established a capability for manufacturing high quality sapphire by the Verneuil process. In the U.S., under government contract, Linde Air Products Co. implemented the Verneuil process for ruby and sapphire when European sources were cut off during World War II. These materials were essential to the war effort for jewel bearings in precision instruments. In the 1960s and 1970s, the Czochralski process was implemented by Linde and its successor, Union Carbide, to make higher crystal quality material for ruby lasers. Stimulated by a government contract for structural fibers in 1966, H. LaBelle invented edge-defined film-fed growth (EFG). The Saphikon company, which is currently owned by Saint-Gobain, evolved from this effort. Independently and simultaneously, Stepanov developed edge-defined film-fed growth in the Soviet Union. In 1967 F. Schmid and D. Viechnicki at the Army Materials Research Lab grew sapphire by the heat exchanger method (HEM). Schmid went on to establish Crystal Systems, Inc. around this technology. Rotem Industries, founded in Israel in 1969, perfected the growth of sapphire hemispheres and near-net-shape domes by gradient solidification. In the U.S., growth of near

  1. Spatial chirp in Ti:sapphire multipass amplifier

    International Nuclear Information System (INIS)

    Li Wenkai; Lu Jun; Li Yanyan; Guo Xiaoyang; Wu Fenxiang; Yu Linpeng; Wang Pengfei; Xu Yi; Leng Yuxin

    2017-01-01

    The spatial chirp generated in the Ti:sapphire multipass amplifier is numerically investigated based on the one-dimensional (1D) and two-dimensional (2D) Frantz–Nodvik equations. The simulation indicates that the spatial chirp is induced by the spatially inhomogeneous gain, and it can be almost eliminated by utilization of proper beam profiles and spot sizes of the signal and pump pulses, for example, the pump pulse has a top-hatted beam profile and the signal pulse has a super-Gaussian beam profile with a relatively larger spot size. In this way, a clear understanding of spatial chirp mechanisms in the Ti:sapphire multipass amplifier is proposed, therefore we can effectively almost eliminate the spatial chirp and improve the beam quality of a high-power Ti:sapphire chirped pulse amplifier system. (paper)

  2. Interfacial thermal resistance between high-density polyethylene (HDPE) and sapphire

    International Nuclear Information System (INIS)

    Zheng Kun; Ma Yong-Mei; Wang Fo-Song; Zhu Jie; Tang Da-Wei

    2014-01-01

    To improve the thermal conductivity of polymeric composites, the numerous interfacial thermal resistance (ITR) inside is usually considered as a bottle neck, but the direct measurement of the ITR is hardly reported. In this paper, a sandwich structure which consists of transducer/high density polyethylene (HDPE)/sapphire is prepared to study the interface characteristics. Then, the ITRs between HDPE and sapphire of two samples with different HDPE thickness values are measured by time-domain thermoreflectance (TDTR) method and the results are ∼ 2 × 10 −7 m 2 ·K·W −1 . Furthermore, a model is used to evaluate the importance of ITR for the thermal conductivity of composites. The model's analysis indicates that reducing the ITR is an effective way of improving the thermal conductivity of composites. These results will provide valuable guidance for the design and manufacture of polymer-based thermally conductive materials. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  3. Wetting behavior of liquid Fe-C-Ti alloys on sapphire

    International Nuclear Information System (INIS)

    Gelbstein, M.; Froumin, N.; Frage, N.

    2008-01-01

    Wetting behavior in the (Fe-C-Ti)/sapphire system was studied at 1823 K. The wetting angle between sapphire and Fe-C alloys is higher than 90 deg. (93 deg. and 105 deg. for the alloys with 1.4 and 3.6 at.% C, respectively). The presence of Ti improves the wetting of the iron-carbon alloys, especially for the alloys with carbon content of 3.6 at.%. The addition of 5 at.% Ti to Fe-3.6 at.% C provides a contact angle of about 30 deg., while the same addition to Fe-1.4 at.% C decreases the wetting angle to 70 deg. only. It was established that the wetting in the systems is controlled by the formation of a titanium oxicarbide layer at the interface, which composition and thickness depend on C and Ti contents in the melt. The experimental observations are well accounted for by a thermodynamic analysis of the Fe-Ti-Al-O-C system

  4. Sea level characterization of a 1100 g sapphire bolometer

    CERN Document Server

    Pécourt, S; Bobin, C; Coron, N; Jesus, M D; Hadjout, J P; Leblanc, J W; Marcillac, P D

    1999-01-01

    A first characterization of a 1100 g sapphire bolometer, performed at sea level and at a working temperature of 40 mK, is presented. Despite perturbations coming from the high-radioactive background and cosmic rays, calibration spectra could be achieved with an internal alpha source and a sup 5 sup 7 Co gamma-ray source: the experimental threshold is 25 keV, while the FWHM resolution is 17.4 keV for the 122 keV peak. Possible heat release effects are discussed, and a new limit of 9x10 sup - sup 1 sup 4 W/g is obtained for sapphire.

  5. Sapphire-fiber-based distributed high-temperature sensing system.

    Science.gov (United States)

    Liu, Bo; Yu, Zhihao; Hill, Cary; Cheng, Yujie; Homa, Daniel; Pickrell, Gary; Wang, Anbo

    2016-09-15

    We present, for the first time to our knowledge, a sapphire-fiber-based distributed high-temperature sensing system based on a Raman distributed sensing technique. High peak power laser pulses at 532 nm were coupled into the sapphire fiber to generate the Raman signal. The returned Raman Stokes and anti-Stokes signals were measured in the time domain to determine the temperature distribution along the fiber. The sensor was demonstrated from room temperature up to 1200°C in which the average standard deviation is about 3.7°C and a spatial resolution of about 14 cm was achieved.

  6. SERS Raman Sensor Based on Diameter-Modulated Sapphire Fiber

    Energy Technology Data Exchange (ETDEWEB)

    Shimoji, Yutaka

    2010-08-09

    Surface enhanced Raman scattering (SERS) has been observed using a sapphire fiber coated with gold nano-islands for the first time. The effect was found to be much weaker than what was observed with a similar fiber coated with silver nanoparticles. Diameter-modulated sapphire fibers have been successfully fabricated on a laser heated pedestal growth system. Such fibers have been found to give a modest increase in the collection efficiency of induced emission. However, the slow response of the SERS effect makes it unsuitable for process control applications.

  7. Microscopic origin of the optical processes in blue sapphire.

    Science.gov (United States)

    Bristow, Jessica K; Parker, Stephen C; Catlow, C Richard A; Woodley, Scott M; Walsh, Aron

    2013-06-11

    Al2O3 changes from transparent to a range of intense colours depending on the chemical impurities present. In blue sapphire, Fe and Ti are incorporated; however, the chemical process that gives rise to the colour has long been debated. Atomistic modelling identifies charge transfer from Ti(III) to Fe(III) as being responsible for the characteristic blue appearance.

  8. Microscopic origin of the optical processes in blue sapphire

    OpenAIRE

    Bristow, JK; Parker, SC; Catlow, CRA; Woodley, SM; Walsh, A

    2013-01-01

    Al2O3 changes from transparent to a range of intense colours depending on the chemical impurities present. In blue sapphire, Fe and Ti are incorporated; however, the chemical process that gives rise to the colour has long been debated. Atomistic modelling identifies charge transfer from Ti(III) to Fe(III) as being responsible for the characteristic blue appearance.

  9. Antireflection coatings for intraocular lenses of sapphire and fianite

    Energy Technology Data Exchange (ETDEWEB)

    Babin, A.A.; Konoplev, Yu.N.; Mamaev, Yu.A. [Inst. of Applied Physics, Nizhnii Novgorod (Russian Federation)] [and others

    1995-10-01

    Broadband antireflection coatings for intraocular lenses of sapphire and fianite are calculated and implemented practically. Their residual reflectance in the liquid with a refracting index of 1.336 is below 0.2% from each face virtually over the entire visible region. 7 refs., 2 figs., 2 tabs.

  10. Oxidation states of Fe and Ti in blue sapphire

    International Nuclear Information System (INIS)

    Wongrawang, P; Wongkokua, W; Monarumit, N; Thammajak, N; Wathanakul, P

    2016-01-01

    X-ray absorption near-edge spectroscopy (XANES) can be used to study the oxidation state of a dilute system such as transition metal defects in solid-state samples. In blue sapphire, Fe and Ti are defects that cause the blue color. Inter-valence charge transfer (IVCT) between Fe 2+ and Ti 4+ has been proposed to describe the optical color’s origin. However, the existence of divalent iron cations has not been thoroughly investigated. Fluorescent XANES is therefore employed to study K-edge absorptions of Fe and Ti cations in various blue sapphire samples including natural, synthetic, diffused and heat-treated sapphires. All the samples showed an Fe absorption edge at 7124 eV, corresponding to the Fe 3+ state; and Ti at 4984 eV, corresponding to Ti 4+ . From these results, we propose Fe 3+ -Ti 4+ mixed acceptor states located at 1.75 eV and 2.14 eV above the valence band of corundum, that correspond to 710 nm and 580 nm bands of UV–vis absorption spectra, to describe the cause of the color of blue sapphire. (paper)

  11. Neurosurgery contact handheld probe based on sapphire shaped crystal

    Science.gov (United States)

    Shikunova, I. A.; Stryukov, D. O.; Rossolenko, S. N.; Kiselev, A. M.; Kurlov, V. N.

    2017-01-01

    A handheld contact probe based on sapphire shaped crystal is developed for intraoperative spectrally-resolved optical diagnostics, laser coagulation and aspiration of malignant brain tissue. The technology was integrated into the neurosurgical workflow for intraoperative real-time identification and removing of invasive brain cancer.

  12. Scintillation of sapphire under particle excitation at low temperature

    International Nuclear Information System (INIS)

    Amare, J; Beltran, B; Cebrian, S; Coron, N; Dambier, G; GarcIa, E; Gomez, H; Irastorza, I G; Leblanc, J; Luzon, G; Marcillac, P de; Martinez, M; Morales, J; Ortiz de Solorzano, A; Pobes, C; Puimedon, J; Redon, T; RodrIguez, A; Ruz, J; Sarsa, M L; Torres, L; Villar, J A

    2006-01-01

    The scintillation properties of undoped sapphire at very low temperature have been studied in the framework of the ROSEBUD (Rare Objects SEarch with Bolometers UnDerground) Collaboration devoted to dark matter searches. We present an estimation of its light yield under gamma, alpha and neutron excitation

  13. Single-transverse-mode Ti:sapphire rib waveguide laser

    NARCIS (Netherlands)

    Grivas, C.; Shepherd, D.P.; May-Smith, T.C.; Eason, R.W.; Pollnau, Markus

    2005-01-01

    Laser operation of Ti:sapphire rib waveguides fabricated using photolithography and ion beam etching in pulsed laser deposited layers is reported. Polarized laser emission was observed at 792.5 nm with an absorbed pump power threshold of 265 mW, which is more than a factor of 2 lower in comparison

  14. Temperature-modulated annealing of c-plane sapphire for long-range-ordered atomic steps

    International Nuclear Information System (INIS)

    Yatsui, Takashi; Kuribara, Kazunori; Sekitani, Tsuyoshi; Someya, Takao; Yoshimoto, Mamoru

    2016-01-01

    High-quality single-crystalline sapphire is used to prepare various semiconductors because of its thermal stability. Here, we applied the tempering technique, which is well known in the production of chocolate, to prepare a sapphire substrate. Surprisingly, we successfully realised millimetre-range ordering of the atomic step of the sapphire substrate. We also obtained a sapphire atomic step with nanometre-scale uniformity in the terrace width and atomic-step height. Such sapphire substrates will find applications in the preparation of various semiconductors and devices. (paper)

  15. Optimizing Ti:Sapphire laser for quantitative biomedical imaging

    Science.gov (United States)

    James, Jeemol; Thomsen, Hanna; Hanstorp, Dag; Alemán Hérnandez, Felipe Ademir; Rothe, Sebastian; Enger, Jonas; Ericson, Marica B.

    2018-02-01

    Ti:Sapphire lasers are powerful tools in the field of scientific research and industry for a wide range of applications such as spectroscopic studies and microscopic imaging where tunable near-infrared light is required. To push the limits of the applicability of Ti:Sapphire lasers, fundamental understanding of the construction and operation is required. This paper presents two projects, (i) dealing with the building and characterization of custom built tunable narrow linewidth Ti:Sapphire laser for fundamental spectroscopy studies; and the second project (ii) the implementation of a fs-pulsed commercial Ti:Sapphire laser in an experimental multiphoton microscopy platform. For the narrow linewidth laser, a gold-plated diffraction grating with a Littrow geometry was implemented for highresolution wavelength selection. We demonstrate that the laser is tunable between 700 to 950 nm, operating in a pulsed mode with a repetition rate of 1 kHz and maximum average output power around 350 mW. The output linewidth was reduced from 6 GHz to 1.5 GHz by inserting an additional 6 mm thick etalon. The bandwidth was measured by means of a scanning Fabry Perot interferometer. Future work will focus on using a fs-pulsed commercial Ti:Sapphire laser (Tsunami, Spectra physics), operating at 80 MHz and maximum average output power around 1 W, for implementation in an experimental multiphoton microscopy set up dedicated for biomedical applications. Special focus will be on controlling pulse duration and dispersion in the optical components and biological tissue using pulse compression. Furthermore, time correlated analysis of the biological samples will be performed with the help of time correlated single photon counting module (SPCM, Becker&Hickl) which will give a novel dimension in quantitative biomedical imaging.

  16. Epitaxial growth of InN on c-plane sapphire by pulsed laser deposition with r.f. nitrogen radical source

    International Nuclear Information System (INIS)

    Ohta, J.; Fujioka, H.; Honke, T.; Oshima, M.

    2004-01-01

    We have grown InN films on c-plane sapphire substrates by pulsed laser deposition (PLD) with a radio frequency nitrogen radical source for the first time and investigated the effect of the substrate surface nitridation on the structural and electrical properties of InN films with reflection high energy electron diffraction (RHEED), atomic force microscope, the Hall effect measurements and high-resolution X-ray diffraction (HRXRD). RHEED and HRXRD characterizations revealed that high-quality InN grows epitaxially on sapphire by PLD and its epitaxial relationship is InN (0 0 0 1) parallel sapphire (0 0 0 1) and InN [2 -1 -1 0] parallel sapphire [1 0 -1 0]. The InN crystalline quality and the electron mobility are improved by the substrate nitridation process. The area of the pits at the InN surface is reduced by the substrate nitridation process probably due to the reduction in the interface energy between InN and the substrate. The full width at half maximum of the -1 -1 2 4 X-ray rocking curve for InN grown by the present technique without using any buffer layers was as small as 34.8 arcmin. These results indicate that the present technique is promising for the growth of the high-quality InN films

  17. Single-Crystal Sapphire Optical Fiber Sensor Instrumentation

    Energy Technology Data Exchange (ETDEWEB)

    Pickrell, Gary [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States); Scott, Brian [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States); Wang, Anbo [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States); Yu, Zhihao [Virginia Polytechnic Inst. & State Univ., Blacksburg, VA (United States)

    2013-12-31

    This report summarizes technical progress on the program “Single-Crystal Sapphire Optical Fiber Sensor Instrumentation,” funded by the National Energy Technology Laboratory of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. This project was completed in three phases, each with a separate focus. Phase I of the program, from October 1999 to April 2002, was devoted to development of sensing schema for use in high temperature, harsh environments. Different sensing designs were proposed and tested in the laboratory. Phase II of the program, from April 2002 to April 2009, focused on bringing the sensor technologies, which had already been successfully demonstrated in the laboratory, to a level where the sensors could be deployed in harsh industrial environments and eventually become commercially viable through a series of field tests. Also, a new sensing scheme was developed and tested with numerous advantages over all previous ones in Phase II. Phase III of the program, September 2009 to December 2013, focused on development of the new sensing scheme for field testing in conjunction with materials engineering of the improved sensor packaging lifetimes. In Phase I, three different sensing principles were studied: sapphire air-gap extrinsic Fabry-Perot sensors; intensity-based polarimetric sensors; and broadband polarimetric sensors. Black body radiation tests and corrosion tests were also performed in this phase. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. At the beginning of Phase II, in June 2004, the BPDI sensor was tested at the Wabash River coal gasifier

  18. Neutron method for NDA in the Sapphire Project

    International Nuclear Information System (INIS)

    Lewis, K.D.

    1995-01-01

    The implementation of Project Sapphire, the top-secret mission to the Republic of Kazakhstan to recover weapons-grade nuclear materials, consisted of four major elements: (1) repacking of fissile material from Kazakh containers into suitable U.S. containers; (2) nondestructive analyses (NDA) to quantify the 235 U content of each container for nuclear criticality safety and compliance purposes; (3) packaging of the fissile material containers into 6M/2R drums, which are internationally approved for shipping fissile material; and (4) shipping or transport of the recovered fissile material to the United States. This paper discusses the development and application of a passive neutron counting technique used in the NDA phase of the Sapphire operations to analyze uranium/beryllium (U/Be) alloys and compounds for 235 U content

  19. A neutron method for NDA analysis in the SAPPHIRE Project

    International Nuclear Information System (INIS)

    Lewis, K.D.

    1995-01-01

    The implementation of Project SAPPHIRE, the top secret mission to the Republic of Kazakhstan to recover weapons grade nuclear materials, consisted of four major elements: (1) the re-packing of fissile material from Kazakh containers into suitable US containers; (2) nondestructive analyses (NDA) to quantify the U-235 content of each container for Nuclear Criticality Safety and compliance purposes; (3) the packaging of the fissile material containers into 6M/2R drums, which are internationally approved for shipping fissile material; and (4) the shipping or transport of the recovered fissile material to the United States. This paper discusses the development and application of a passive neutron counting technique used in the NDA phase of SAPPHIRE operations to analyze uranium/beryllium (U/Be) alloys and compounds for U-235 content

  20. Characterization of single crystal uranium-oxide thin films grown via reactive-gas magnetron sputtering on yttria-stabilized zirconia and sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Strehle, Melissa M.; Heuser, Brent J., E-mail: bheuser@illinois.edu; Elbakhshwan, Mohamed S.; Han Xiaochun; Gennardo, David J.; Pappas, Harrison K.; Ju, Hyunsu

    2012-06-30

    The microstructure and valence states of three single crystal thin film systems, UO{sub 2} on (11{sup Macron }02) r-plane sapphire, UO{sub 2} on (001) yttria-stabilized zirconia, and U{sub 3}O{sub 8} on (11{sup Macron }02) r-plane sapphire, grown via reactive-gas magnetron sputtering are analyzed primarily with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy (UPS). XRD analysis indicates the growth of single crystal domains with varying degrees of mosaicity. XPS and UPS analyses yield U-4f, U-5f, O-1s, and O-2p electron binding energies consistent with reported bulk values. A change from p-type to n-type semiconductor behavior induced by preferential sputtering of oxygen during depth profile analysis was observed with both XPS and UPS. Trivalent cation impurities (Nd and Al) in UO{sub 2} lower the Fermi level, shifting the XPS spectral weight. This observation is consistent with hole-doping of a Mott-Hubbard insulator. The uranium oxide-(11{sup Macron }02) sapphire system is unstable with respect to Al interdiffusion across the film-substrate interface at elevated temperature. - Highlights: Black-Right-Pointing-Pointer Single crystal uranium-oxides grown on sapphire and yttria-stabilized zirconia. Black-Right-Pointing-Pointer Anion and cation valence states studied by photoelectron emission spectroscopy. Black-Right-Pointing-Pointer Trivalent Nd and Al impurities lower the Fermi level. Black-Right-Pointing-Pointer Uranium-oxide films on sapphire found to be unstable with respect to Al interdiffusion.

  1. Structural characterization of ZnO films grown by molecular beam epitaxy on sapphire with MgO buffer

    International Nuclear Information System (INIS)

    Pecz, B.; El-Shaer, A.; Bakin, A.; Mofor, A.-C.; Waag, A.; Stoemenos, J.

    2006-01-01

    The structural characteristics of the ZnO film grown on sapphire substrate using a thin MgO buffer layer were studied using transmission electron microscopy and high-resolution x-ray diffraction. The growth was carried out in a modified plasma-molecular beam epitaxy system. The observed misfit dislocations were well confined at the sapphire overgrown interface exhibiting domain matching epitaxy, where the integral multiples of lattice constants match across the interface. The main extended defects in the ZnO film were the threading dislocations having a mean density of 4x10 9 cm -2 . The formation of the MgO buffer layer as well as the ZnO growth were monitored in situ by reflection high-energy electron diffraction. The very thin ∼1 nm, MgO buffer layer can partially interdiffuse with the ZnO as well as react with the Al 2 O 3 substrate forming an intermediate epitaxial layer having the spinel (MgO/Al 2 O 3 ) structure

  2. Implementation of ZnO/ZnMgO strained-layer superlattice for ZnO heteroepitaxial growth on sapphire

    Science.gov (United States)

    Petukhov, Vladimir; Bakin, Andrey; Tsiaoussis, Ioannis; Rothman, Johan; Ivanov, Sergey; Stoemenos, John; Waag, Andreas

    2011-05-01

    The main challenge in fabrication of ZnO-based devices is the absence of reliable p-type material. This is mostly caused by insufficient crystalline quality of the material and not well-enough-developed native point defect control of ZnO. At present high-quality ZnO wafers are still expensive and ZnO heteroepitaxial layers on sapphire are the most reasonable alternative to homoepitaxial layers. But it is still necessary to improve the crystalline quality of the heteroepitaxial layers. One of the approaches to reduce defect density in heteroepitaxial layers is to introduce a strained-layer superlattice (SL) that could stop dislocation propagation from the substrate-layer interface. In the present paper we have employed fifteen periods of a highly strained SL structure. The structure was grown on a conventional double buffer layer comprising of high-temperature MgO/low-temperature ZnO on sapphire. The influence of the SLs on the properties of the heteroepitaxial ZnO layers is investigated. Electrical measurements of the structure with SL revealed very high values of the carrier mobility up to 210 cm2/Vs at room temperature. Structural characterization of the obtained samples showed that the dislocation density in the following ZnO layer was not reduced. The high mobility signal appears to come from the SL structure or the SL/ZnO interface.

  3. Photonics of 2D gold nanolayers on sapphire surface

    Energy Technology Data Exchange (ETDEWEB)

    Muslimov, A. E., E-mail: amuslimov@mail.ru; Butashin, A. V.; Nabatov, B. V. [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Research Center “Crystallography and Photonics” (Russian Federation); Konovko, A. A.; Belov, I. V.; Gizetdinov, R. M.; Andreev, A. V. [Moscow State University (Russian Federation); Kanevsky, V. M. [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Research Center “Crystallography and Photonics” (Russian Federation)

    2017-03-15

    Gold layers with thicknesses of up to several nanometers, including ordered and disordered 2D nanostructures of gold particles, have been formed on sapphire substrates; their morphology is described; and optical investigations are carried out. The possibility of increasing the accuracy of predicting the optical properties of gold layers and 2D nanostructures using quantum-mechanical models based on functional density theory calculation techniques is considered. The application potential of the obtained materials in photonics is estimated.

  4. Time dependent temperature distribution in pulsed Ti:sapphire lasers

    Science.gov (United States)

    Buoncristiani, A. Martin; Byvik, Charles E.; Farrukh, Usamah O.

    1988-01-01

    An expression is derived for the time dependent temperature distribution in a finite solid state laser rod for an end-pumped beam of arbitrary shape. The specific case of end pumping by circular (constant) or Gaussian beam is described. The temperature profile for a single pump pulse and for repetitive pulse operation is discussed. The particular case of the temperature distribution in a pulsed titanium:sapphire rod is considered.

  5. An injection modelocked Ti-sapphire laser for synchronous photoinjection

    International Nuclear Information System (INIS)

    Hovater, C.; Poelker, M.

    1997-01-01

    The CEBAF 4 GeV accelerator has recently begun delivering spin-polarized electrons for nuclear physics experiments. Spin-polarized electrons are emitted from a GaAs photocathode that is illuminated with pulsed laser light from a diode laser system synchronized to the injector chopping frequency (499 MHz). The present diode laser system is compact, reliable and relatively maintenance-free; however, output power is limited to less than 500 mW. In an effort to obtain higher average power and thereby prolong the effective operating lifetime of the source, they have constructed an injection modelocked Ti-sapphire laser with picosecond pulsewidths and gigahertz repetition rates. Modelocked operation is obtained through gain modulation within the Ti-sapphire crystal as a result of injection seeding with a gain-switched diode laser. Unlike conventional modelocked lasers, the pulse repetition rate of this laser can be discretely varied by setting the seed laser repetition rate equal to multiples of the Ti-sapphire laser cavity fundamental frequency. They observe pulse repetition rates from 223 MHz (fundamental) to 1,560 MHz (seventh harmonic) with average output power of 700 mW for all repetition rates. Pulsewidths ranged from 21 to 39 ps (FWHM) under various pump laser conditions

  6. Thermal neutron scattering kernels for sapphire and silicon single crystals

    International Nuclear Information System (INIS)

    Cantargi, F.; Granada, J.R.; Mayer, R.E.

    2015-01-01

    Highlights: • Thermal cross section libraries for sapphire and silicon single crystals were generated. • Debye model was used to represent the vibrational frequency spectra to feed the NJOY code. • Sapphire total cross section was measured at Centro Atómico Bariloche. • Cross section libraries were validated with experimental data available. - Abstract: Sapphire and silicon are materials usually employed as filters in facilities with thermal neutron beams. Due to the lack of the corresponding thermal cross section libraries for those materials, necessary in calculations performed in order to optimize beams for specific applications, here we present the generation of new thermal neutron scattering kernels for those materials. The Debye model was used in both cases to represent the vibrational frequency spectra required to feed the NJOY nuclear data processing system in order to produce the corresponding libraries in ENDF and ACE format. These libraries were validated with available experimental data, some from the literature and others obtained at the pulsed neutron source at Centro Atómico Bariloche

  7. Microstructure evolution in carbon-ion implanted sapphire

    International Nuclear Information System (INIS)

    Orwa, J. O.; McCallum, J. C.; Jamieson, D. N.; Prawer, S.; Peng, J. L.; Rubanov, S.

    2010-01-01

    Carbon ions of MeV energy were implanted into sapphire to fluences of 1x10 17 or 2x10 17 cm -2 and thermally annealed in forming gas (4% H in Ar) for 1 h. Secondary ion mass spectroscopy results obtained from the lower dose implant showed retention of implanted carbon and accumulation of H near the end of range in the C implanted and annealed sample. Three distinct regions were identified by transmission electron microscopy of the implanted region in the higher dose implant. First, in the near surface region, was a low damage region (L 1 ) composed of crystalline sapphire and a high density of plateletlike defects. Underneath this was a thin, highly damaged and amorphized region (L 2 ) near the end of range in which a mixture of i-carbon and nanodiamond phases are present. Finally, there was a pristine, undamaged sapphire region (L 3 ) beyond the end of range. In the annealed sample some evidence of the presence of diamond nanoclusters was found deep within the implanted layer near the projected range of the C ions. These results are compared with our previous work on carbon implanted quartz in which nanodiamond phases were formed only a few tens of nanometers from the surface, a considerable distance from the projected range of the ions, suggesting that significant out diffusion of the implanted carbon had occurred.

  8. Critical thickness for Nb nanofilm on sapphire substrate: a critical analysis using finite element method

    International Nuclear Information System (INIS)

    Kumar, Arun; Subramaniam, Anandh

    2009-01-01

    Full text: On growth beyond critical thickness, interfacial misfit dislocations partially relax the misfit strains, in epitaxially grown nanofilms. In this study the stress state and growth of nanofilms is simulated using Finite Element Method (FEM); by imposing stress-free strains, corresponding to the lattice mismatch between Nb nanofilm and Sapphire substrate. On growth of the Nb nanofilm, a triangular network of edge misfit dislocations nucleates at the (0001) Al2ο3 || (111) Nb , interface. Using a combined simulation of a coherently strained nanofilm and an edge dislocation, the equilibrium criterion for the nucleation of an edge dislocation is determined. Theoretical analyses in literature use only the component of the Burger's vector parallel to the interface, which is an erroneous description of the stress state and energetics of the system. In this investigation the full interfacial edge dislocation is simulated using standard commercially available software and comparisons are made with results available in literature to bring out the utility of the methodology

  9. Spectroscopic properties for identifying sapphire samples from Ban Bo Kaew, Phrae Province, Thailand

    Science.gov (United States)

    Mogmued, J.; Monarumit, N.; Won-in, K.; Satitkune, S.

    2017-09-01

    Gemstone commercial is a high revenue for Thailand especially ruby and sapphire. Moreover, Phrae is a potential gem field located in the northern part of Thailand. The studies of spectroscopic properties are mainly to identify gemstone using advanced techniques (e.g. UV-Vis-NIR spectrophotometry, FTIR spectrometry and Raman spectroscopy). Typically, UV-Vis-NIR spectrophotometry is a technique to study the cause of color in gemstones. FTIR spectrometry is a technique to study the functional groups in gem-materials. Raman pattern can be applied to identify the mineral inclusions in gemstones. In this study, the natural sapphires from Ban Bo Kaew were divided into two groups based on colors including blue and green. The samples were analyzed by UV-Vis-NIR spectrophotometer, FTIR spectrometer and Raman spectroscope for studying spectroscopic properties. According to UV-Vis-NIR spectra, the blue sapphires show higher Fe3+/Ti4+ and Fe2+/Fe3+ absorption peaks than those of green sapphires. Otherwise, green sapphires display higher Fe3+/Fe3+ absorption peaks than blue sapphires. The FTIR spectra of both blue and green sapphire samples show the absorption peaks of -OH,-CH and CO2. The mineral inclusions such as ferrocolumbite and rutile in sapphires from this area were observed by Raman spectroscope. The spectroscopic properties of sapphire samples from Ban Bo Kaew, Phrae Province, Thailand are applied to be the specific evidence for gemstone identification.

  10. Effect of coating thickness on interfacial shear behavior of zirconia-coated sapphire fibers in a polycrystalline alumina matrix

    International Nuclear Information System (INIS)

    Hellmann, J.R.; Chou, Y.S.

    1995-01-01

    The effect of zirconia (ZrO 2 ) interfacial coatings on the interfacial shear behavior in sapphire reinforced alumina was examined in this study. Zirconia coatings of thicknesses ranging from 0.15 to 1.45 μm were applied to single crystal sapphire (Saphikon) fibers using a particulate loaded sol dipping technique. After calcining at 1,100 C in air, the coated fibers were incorporated into a polycrystalline alumina matrix via hot pressing. Interfacial shear strength and sliding behavior of the coated fibers was examined using thin-slice indentation fiber pushout and pushback techniques. In all cases, debonding and sliding occurred at the interface between the fibers and the coating. The coatings exhibited a dense microstructure and led to a higher interfacial shear strength (> 240 MPa) and interfacial sliding stress (> 75 MPa) relative to previous studies on the effect of a porous interphase on interfacial properties. The interfacial shear strength decreased with increasing fiber coating thickness (from 389 ± 59 to 241 ± 43 MPa for 0.15 to 1.45 microm thick coatings, respectively). Sliding behavior exhibited load modulation with increasing displacement during fiber sliding which is characteristic of fiber roughness-induced stick-slip. The high interfacial shear strengths and sliding stresses measured in this study, as well as the potentially strength degrading surface reconstruction observed on the coated fibers after hot pressing and heat treatment, indicate that dense zirconia coatings are not suitable candidates for optimizing composite toughness and strength in the sapphire fiber reinforced alumina system

  11. Detection of beryllium treatment of natural sapphires by NRA

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, P.C., E-mail: carolina.gutierrez@uam.e [Centro de Micro-Analisis de Materiales (CMAM), Universidad Autonoma de Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Ynsa, M.-D.; Climent-Font, A. [Centro de Micro-Analisis de Materiales (CMAM), Universidad Autonoma de Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Dpto. Fisica Aplicada C-12, Universidad Autonoma de Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Calligaro, T. [Centre de Recherche et de Restauration des musees de France C2RMF, CNRS-UMR171, 14 quai Francois Mitterrand, 75001 Paris (France)

    2010-06-15

    Since the 1990's, artificial treatment of natural sapphires (Al{sub 2}O{sub 3} crystals coloured by impurities) by diffusion of beryllium at high temperature has become a growing practice. This process permits to enhance the colour of these gemstones, and thus to increase their value. Detection of such a treatment - diffusion of tens of {mu}g/g of beryllium in Al{sub 2}O{sub 3} crystals - is usually achieved using high sensitivity techniques like laser-ablation inductively coupled plasma mass spectrometry (LA-ICP/MS) or laser-induced breakdown spectrometry (LIBS) which are unfortunately micro-destructive (leaving 50-100-{mu}m diameter craters on the gems). The simple and non-destructive alternative method proposed in this work is based on the nuclear reaction {sup 9}Be({alpha}, n{gamma}){sup 12}C with an external helium ion beam impinging on the gem directly placed in air. The 4439 keV prompt {gamma}-ray tagging Be atoms are detected with a high efficiency bismuth germanate scintillator. Beam dose is monitored using the 2235 keV prompt {gamma}-ray produced during irradiation by the aluminium of the sapphire matrix through the {sup 27}Al({alpha}, p{gamma}){sup 30}Si nuclear reaction. The method is tested on a series of Be-treated sapphires previously analyzed by LA-ICP/MS to determine the optimal conditions to obtain a peak to background appropriate to reach the required {mu}g/g sensitivity. Using a 2.8-MeV external He beam and a beam dose of 200 {mu}C, beryllium concentrations from 5 to 16 {mu}g/g have been measured in the samples, with a detection limit of 1 {mu}g/g.

  12. Superconducting accelerometer using niobium-on-sapphire rf resonator

    International Nuclear Information System (INIS)

    Blair, D.G.

    1979-01-01

    An accelerometer is described which uses a rf niobium-on-sapphire resonator as its sensor element. The accelerometer uses a magnetically levitated spool as a test mass and the spool modulates the inductance of the resonator; its position is servo controlled to maintain the resonator at the external rf excitation frequency. The accelerometer has high sensitivity over the full audio frequency range, but is optimized for frequencies between 100 Hz and 1 kHz, where the calculated displacement sensitivity approaches 10 -15 cm for a 1 Hz measurement bandwidth. The system noise sources are analyzed and possible improvements are discussed

  13. Ultrafast, ultrahigh-peak power Ti:sapphire laser system

    Energy Technology Data Exchange (ETDEWEB)

    Yamakawa, Koichi; Aoyama, Makoto; Matsuoka, Shinichi; Akahane, Yutaka; Kase, Teiji; Nakano, Fumihiko; Sagisaka, Akito [Advanced Photon Research Center, Kansai Research Establishment, Japan Atomic Energy Research Inst., Kizu, Kyoto (Japan)

    2001-01-01

    We review progress in the generation of multiterawatt optical pulses in the 10-fs range. We describe a design, performance and characterization of a Ti:sapphire laser system based on chirped-pulse amplification, which has produced a peak power in excess of 100-TW with sub-20-fs pulse durations and an average power of 19-W at a 10-Hz repetition rate. We also discuss extension of this system to the petawatt power level and potential applications in the relativistic, ultrahigh intensity regimes. (author)

  14. Flashlamp pumped Ti-sapphire laser for ytterbium glass chirped pulse amplification

    Energy Technology Data Exchange (ETDEWEB)

    Nishimura, Akihiko; Ohzu, Akira; Sugiyama, Akira [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; and others

    1998-03-01

    A flashlamp pumped Ti:sapphire laser is designed for ytterbium glass chirped pulse amplification. A high quality Ti:sapphire rod and a high energy long pulse discharging power supply are key components. The primary step is to produce the output power of 10 J per pulse at 920 nm. (author)

  15. Analysis and modification of blue sapphires from Rwanda by ion beam techniques

    Science.gov (United States)

    Bootkul, D.; Chaiwai, C.; Tippawan, U.; Wanthanachaisaeng, B.; Intarasiri, S.

    2015-12-01

    Blue sapphire is categorised in a corundum (Al2O3) group. The gems of this group are always amazed by their beauties and thus having high value. In this study, blue sapphires from Rwanda, recently came to Thai gemstone industry, are chosen for investigations. On one hand, we have applied Particle Induced X-ray Emission (PIXE), which is a highly sensitive and precise analytical technique that can be used to identify and quantify trace elements, for chemical analysis of the sapphires. Here we have found that the major element of blue sapphires from Rwanda is Al with trace elements such as Fe, Ti, Cr, Ga and Mg as are commonly found in normal blue sapphire. On the other hand, we have applied low and medium ion implantations for color improvement of the sapphire. It seems that a high amount of energy transferring during cascade collisions have altered the gems properties. We have clearly seen that the blue color of the sapphires have been intensified after nitrogen ion bombardment. In addition, the gems were also having more transparent and luster. The UV-Vis-NIR measurement detected the modification of their absorption properties, implying of the blue color increasing. Here the mechanism of these modifications is postulated and reported. In any point of view, the bombardment by using nitrogen ion beam is a promising technique for quality improvement of the blue sapphire from Rwanda.

  16. Characterization of sapphire: For its material properties at high temperatures

    Science.gov (United States)

    Bal, Harman Singh

    There are numerous needs for sensing, one of which is in pressure sensing for high temperature application such as combustion related process and embedded in aircraft wings for reusable space vehicles. Currently, silicon based MEMS technology is used for pressure sensing. However, due to material properties the sensors have a limited range of approximately 600 °C which is capable of being pushed towards 1000 °C with active cooling. This can introduce reliability issues when you add more parts and high flow rates to remove large amounts of heat. To overcome this challenge, sapphire is investigated for optical based pressure transducers at temperatures approaching 1400 °C. Due to its hardness and chemical inertness, traditional cutting and etching methods used in MEMS technology are not applicable. A method that is being investigated as a possible alternative is laser machining using a picosecond laser. In this research, we study the material property changes that occur from laser machining and quantify the changes with the experimental results obtained by testing sapphire at high-temperature with a standard 4-point bending set-up.

  17. Thermal stress resistance of ion implanted sapphire crystals

    International Nuclear Information System (INIS)

    Gurarie, V.N.; Jamieson, D.N.; Szymanski, R.; Orlov, A.V.; Williams, J.S.; Conway, M.

    1999-01-01

    Monocrystals of sapphire have been subjected to ion implantation with 86 keV Si - and 80 keV Cr - ions to doses in the range of 5x10 14 -5x10 16 cm -2 prior to thermal stress testing in a pulsed plasma. Above a certain critical dose ion implantation is shown to modify the near-surface structure of samples by introducing damage, which makes crack nucleation easier under the applied stress. The effect of ion dose on the stress resistance is investigated and the critical doses which produce a noticeable change in the stress resistance are determined. The critical dose for Si ions is shown to be much lower than that for Cr - ions. However, for doses exceeding 2x10 16 cm -2 the stress resistance parameter decreases to approximately the same value for both implants. The size of the implantation-induced crack nucleating centers and the density of the implantation-induced defects are considered to be the major factors determining the stress resistance of sapphire crystals irradiated with Si - and Cr - ions

  18. Nonlinearity Mechanism and Correction of Sapphire Fiber Temperature Sensor on Blackbody Cavity

    Directory of Open Access Journals (Sweden)

    Tiejun Cao

    2014-06-01

    Full Text Available Based on the principle of blackbody radiation, sapphire optic fiber temperature sensor has been more widely used in recent years, and its temperature range is between 800 ~ 2000 oC, and the response time is in 10-2 magnitude, and transient temperature measurement can be high precision in harsh environments. Nonlinear constraints on sapphire fiber temperature sensor affect the accuracy and stability of the sensor. In order to solve the nonlinear problems which exist in the measurement, at first, the sapphire fiber optic temperature sensor temperature measurement principle and nonlinear generation mechanism are studied; secondly piecewise linear interpolation and spline interpolation linearization algorithm is designed with combining the nonlinear characteristics of sapphire optical fiber temperature sensor, and the program is designed on its linear and associated signal processing. Experimental results show that a good linearization of sapphire fiber optic temperature sensor can been achieved in this method.

  19. Electronic structure analysis of GaN films grown on r- and a-plane sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Monu; Krishna TC, Shibin; Aggarwal, Neha [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory (CSIR-NPL), Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-NPL Campus, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Vihari, Saket [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory (CSIR-NPL), Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Gupta, Govind, E-mail: govind@nplindia.org [Physics of Energy Harvesting Division, CSIR-National Physical Laboratory (CSIR-NPL), Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-NPL Campus, Dr. K.S. Krishnan Marg, New Delhi 110012 (India)

    2015-10-05

    Graphical abstract: Substrate orientation induced changes in surface chemistry, band bending, hybridization states, electronic properties and surface morphology of epitaxially grown GaN were investigated via photoemission spectroscopic and Atomic Force Microscopic measurements. - Highlights: • Electronic structure and surface properties of GaN film grown on r/a-plane sapphire. • Downward band bending (0.5 eV) and high surface oxide is observed for GaN/a-sapphire. • Electron affinity and ionization energy is found to be higher for GaN/a-sapphire. - Abstract: The electronic structure and surface properties of epitaxial GaN films grown on r- and a-plane sapphire substrates were probed via spectroscopic and microscopic measurements. X-ray photoemission spectroscopic (XPS) measurements were performed to analyse the surface chemistry, band bending and valence band hybridization states. It was observed that GaN/a-sapphire display a downward band bending of 0.5 eV and possess higher amount of surface oxide compared to GaN/r-sapphire. The valence band (VB) investigation revealed that the hybridization corresponds to the interactions of Ga 4s and Ga 4p orbitals with N 2p orbital, and result in N2p–Ga4p, N2p–Ga4s{sup ∗}, mixed and N2p–Ga4s states. The energy band structure and electronic properties were measured via ultraviolet photoemission spectroscopic (UPS) experiments. The band structure analysis and electronic properties calculations divulged that the electron affinity and ionization energy of GaN/a-sapphire were 0.3 eV higher than GaN/r-sapphire film. Atomic Force Microscopic (AFM) measurements revealed faceted morphology of GaN/r-sapphire while a smooth pitted surface was observed for GaN/a-sapphire film, which is closely related to surface oxide coverage.

  20. α-Ga2O3 grown by low temperature atomic layer deposition on sapphire

    Science.gov (United States)

    Roberts, J. W.; Jarman, J. C.; Johnstone, D. N.; Midgley, P. A.; Chalker, P. R.; Oliver, R. A.; Massabuau, F. C.-P.

    2018-04-01

    α-Ga2O3 is a metastable phase of Ga2O3 of interest for wide bandgap engineering since it is isostructural with α-In2O3 and α-Al2O3. α-Ga2O3 is generally synthesised under high pressure (several GPa) or relatively high temperature (∼500 °C). In this study, we report the growth of α-Ga2O3 by low temperature atomic layer deposition (ALD) on sapphire substrate. The film was grown at a rate of 0.48 Å/cycle, and predominantly consists of α-Ga2O3 in the form of (0001) -oriented columns originating from the interface with the substrate. Some inclusions were also present, typically at the tips of the α phase columns and most likely comprising ε-Ga2O3. The remainder of the Ga2O3 film - i.e. nearer the surface and between the α-Ga2O3 columns, was amorphous. The film was found to be highly resistive, as is expected for undoped material. This study demonstrates that α-Ga2O3 films can be grown by low temperature ALD and suggests the possibility of a new range of ultraviolet optoelectronic and power devices grown by ALD. The study also shows that scanning electron diffraction is a powerful technique to identify the different polymorphs of Ga2O3 present in multiphase samples.

  1. Cracking of GaN on sapphire from etch-process-induced nonuniformity in residual thermal stress

    International Nuclear Information System (INIS)

    Lacroix, Yves; Chung, Sung-Hoon; Sakai, Shiro

    2001-01-01

    An experiment was performed to explain the appearance of cracks along mesa structures during the processing of GaN device layers grown on sapphire substrates. Micro-Raman spectroscopy was used to measure the position-dependent stress in the GaN layer. We show evidence that the stress at the interface with the substrate may be larger along the mesa structures than that of the as-grown layer, and that this increase in stress can be enough to induce cracks along mesa structures during processing. We report on the formation of cracks that propagate guided by the nonuniformity of the stress induced by the formation of mesa structures in the GaN layer, independent of crystal direction. The understanding of cracking mechanisms has implications in GaN-based device structures that require heteroepitaxial growth of layers with different lattice size and thermal expansion coefficients. [copyright] 2001 American Institute of Physics

  2. Surface study of irradiated sapphires from Phrae Province, Thailand using AFM

    Science.gov (United States)

    Monarumit, N.; Jivanantaka, P.; Mogmued, J.; Lhuaamporn, T.; Satitkune, S.

    2017-09-01

    The irradiation is one of the gemstone enhancements for improving the gem quality. Typically, there are many varieties of irradiated gemstones in the gem market such as diamond, topaz, and sapphire. However, it is hard to identify the gemstones before and after irradiation. The aim of this study is to analyze the surface morphology for classifying the pristine and irradiated sapphires using atomic force microscope (AFM). In this study, the sapphire samples were collected from Phrae Province, Thailand. The samples were irradiated by high energy electron beam for a dose of ionizing radiation at 40,000 kGy. As the results, the surface morphology of pristine sapphires shows regular atomic arrangement, whereas, the surface morphology of irradiated sapphires shows the nano-channel observed by the 2D and 3D AFM images. The atomic step height and root mean square roughness have changed after irradiation due to the micro-structural defect on the sapphire surface. Therefore, this study is a frontier application for sapphire identification before and after irradiation.

  3. Optical and structural behaviour of Mn implanted sapphire

    International Nuclear Information System (INIS)

    Marques, C.; Franco, N.; Kozanecki, A.; Silva, R.C. da; Alves, E.

    2006-01-01

    Sapphire single crystals were implanted at room temperature with 180 keV manganese ions to fluences up to 1.8 x 10 17 cm -2 . The samples were annealed at 1000 deg. C in oxidizing or reducing atmosphere. Surface damage was observed after implantation of low fluences, the amorphous phase being observed after implantation of 5 x 10 16 cm -2 , as seen by Rutherford backscattering spectroscopy under channelling conditions. Thermal treatments in air annealed most of the implantation related defects and promoted the redistribution of the manganese ions, in a mixed oxide phase. X-ray diffraction studies revealed the presence of MnAl 2 O 4 . On the contrary, similar heat treatments in vacuum led to enhanced out diffusion of Mn while the matrix remained highly damaged. The analysis of laser induced luminescence performed after implantation showed the presence of an intense red emission

  4. Site location and optical properties of Eu implanted sapphire

    International Nuclear Information System (INIS)

    Marques, C.; Wemans, A.; Maneira, M.J.P.; Kozanecki, A.; Silva, R.C. da; Alves, E.

    2005-01-01

    Synthetic colourless transparent (0 0 0 1) sapphire crystals were implanted at room temperature with 100 keV europium ions to fluences up to 1 x 10 16 cm -2 . Surface damage is observed at low fluences, as seen by Rutherford backscattering spectrometry under channelling conditions. Optical absorption measurements revealed a variety of structures, most probably related to F-type defects characteristic of implantation damage. Thermal treatments in air or in vacuum up to 1000 deg. C do not produce noticeable changes both in the matrix or the europium profiles. However, the complete recovery of the implantation damage and some redistribution of the europium ions is achieved after annealing at 1300 deg. C in air. Detailed lattice site location studies performed for various axial directions allowed to assess the damage recovery and the incorporation of the Eu ions into well defined crystallographic sites, possibly in an oxide phase also inferred from optical absorption measurements

  5. The SAPPHIRE and 50 MT projects at BWXT, Lynchburg, VA

    International Nuclear Information System (INIS)

    Thiele, R.; Horn, B.; Coates, C.W.; Stainback, J.R.

    2001-01-01

    Full text: When the SAPPHIRE project for the down-blending of HEU material of Khazak origin was initiated in 1996 at BWX Technologies (BWXT) formally Babcock and Wilcox in Lynchburg, VA and the Agency was requested to apply its specially designed safeguards measures to the process with a view to provide assurance to the international community that down-blending had actually taken place as stipulated in the USA-Khazak agreement a learning process was initiated from this effort culminating in the current 50 MT downblending process at the same facility with BWXT, the USA Authorities, and the Agency as partners in this technologically advanced enterprise aimed at the downgrading of a substantial quantity of weapons grade material. In the present paper an overview is provided of the road leading to an effective, and mutually agreeable safeguards approach for carrying out verifications in the sensitive environment of a facility devoted to HEU uranium processing. (author)

  6. CMOS Silicon-on-Sapphire RF Tunable Matching Networks

    Directory of Open Access Journals (Sweden)

    Chamseddine Ahmad

    2006-01-01

    Full Text Available This paper describes the design and optimization of an RF tunable network capable of matching highly mismatched loads to 50 at 1.9 GHz. Tuning was achieved using switched capacitors with low-loss, single-transistor switches. Simulations show that the performance of the matching network depends strongly on the switch performances and on the inductor losses. A 0.5 m silicon-on-sapphire (SOS CMOS technology was chosen for network implementation because of the relatively high-quality monolithic inductors achievable in the process. The matching network provides very good matching for inductive loads, and acceptable matching for highly capacitive loads. A 1 dB compression point greater than dBm was obtained for a wide range of load impedances.

  7. Polar and Nonpolar Gallium Nitride and Zinc Oxide based thin film heterostructures Integrated with Sapphire and Silicon

    Science.gov (United States)

    Gupta, Pranav

    This dissertation work explores the understanding of the relaxation and integration of polar and non-polar of GaN and ZnO thin films with Sapphire and silicon substrates. Strain management and epitaxial analysis has been performed on wurtzitic GaN(0001) thin films grown on c-Sapphire and wurtzitic non-polar a-plane GaN(11-20) thin films grown on r-plane Sapphire (10-12) by remote plasma atomic nitrogen source assisted UHV Pulsed Laser Deposition process. It has been established that high-quality 2-dimensional c-axis GaN(0001) nucleation layers can be grown on c-Sapphire by PLD process at growth temperatures as low as ˜650°C. Whereas the c-axis GaN on c-sapphire has biaxially negative misfit, the crystalline anisotropy of the a-plane GaN films on r-Sapphire results in compressive and tensile misfits in the two major orthogonal directions. The measured strains have been analyzed in detail by X-ray, Raman spectroscopy and TEM. Strain relaxation in GaN(0001)/Sapphire thin film heterostructure has been explained by the principle of domain matched epitaxial growth in large planar misfit system and has been demonstrated by TEM study. An attempt has been made to qualitatively understand the minimization of free energy of the system from the strain perspective. Analysis has been presented to quantify the strain components responsible for the compressive strain observed in the GaN(0001) thin films on c-axis Sapphire substrates. It was also observed that gallium rich deposition conditions in PLD process lead to smoother nucleation layers because of higher ad-atom mobility of gallium. We demonstrate near strain relaxed epitaxial (0001) GaN thin films grown on (111) Si substrates using TiN as intermediate buffer layer by remote nitrogen plasma assisted UHV pulsed laser deposition (PLD). Because of large misfits between the TiN/GaN and TiN/Si systems the TIN buffer layer growth occurs via nucleation of interfacial dislocations under domain matching epitaxy paradigm. X-ray and

  8. Sapphire/TiAl composites - structure and properties

    International Nuclear Information System (INIS)

    Povarova, K.B.; Antonova, A.V.; Mileiko, S.T.; Sarkissyan, N.S.

    2001-01-01

    Ti-Al-intermetallic-based alloys with lamellar microstructure, -γ(TiAl) +α 2 (Ti 3 Al) are characterized by a high melting point of 1460 o C, a low density of ∼3.9 g/cm 3 , a high gas corrosion resistance up to a temperature of about 900 o C, a high creep resistance up to a temperature of about 800 o C, and a sufficiently high fracture toughness at low temperatures, up to 30 Mpa x m 1/2 . Hence, they are considered as excellent matrices for fibres of high melting point. Unlike well-developed SiC/TiAl composites, which have an obvious upper limit for the usage temperature due to SiC/TiAl interaction, Sapphire/TiAl composites remain nearly unknown because fibres to be used in such composites have not been really available. At the present time, such fibres are developed in Solid State Physics Inst. of RAS. The results of preliminary creep tests of Al 2 O 3 /TiAl composites obtained by using pressure casting have shown that usage of such composite systems shifts the temperature limit for light structural materials in terms of creep resistance to, at least, 1050 o C: creep strength on 100 h time base reaches 120 MPa at that temperature. It occurs also that Sapphire-fibres/TiAl-matrix composite specimens have an increased gas corrosion resistance by more than one order of the magnitudes as compared with that of the matrix alloy. (author)

  9. Analysis and modification of blue sapphires from Rwanda by ion beam techniques

    Energy Technology Data Exchange (ETDEWEB)

    Bootkul, D., E-mail: mo_duangkhae@hotmail.com [Department of General Science - Gems & Jewelry, Faculty of Science, Srinakharinwirot University, Bangkok 10110 (Thailand); Chaiwai, C.; Tippawan, U. [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Wanthanachaisaeng, B. [Gems Enhancement Research Unit, Faculty of Gems, Burapha University, Chanthaburi Campus, Chanthaburi 22170 (Thailand); Intarasiri, S., E-mail: saweat@gmail.com [Science and Technology Research Institute, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2015-12-15

    Highlights: • Ion beam analysis is an effective method for detecting trace elements. • Ion beam treatment is able to improve optical and color appearances of the blue sapphire from Rwanda. • These alternative methods can be extended to jewelry industry for large scale application. - Abstract: Blue sapphire is categorised in a corundum (Al{sub 2}O{sub 3}) group. The gems of this group are always amazed by their beauties and thus having high value. In this study, blue sapphires from Rwanda, recently came to Thai gemstone industry, are chosen for investigations. On one hand, we have applied Particle Induced X-ray Emission (PIXE), which is a highly sensitive and precise analytical technique that can be used to identify and quantify trace elements, for chemical analysis of the sapphires. Here we have found that the major element of blue sapphires from Rwanda is Al with trace elements such as Fe, Ti, Cr, Ga and Mg as are commonly found in normal blue sapphire. On the other hand, we have applied low and medium ion implantations for color improvement of the sapphire. It seems that a high amount of energy transferring during cascade collisions have altered the gems properties. We have clearly seen that the blue color of the sapphires have been intensified after nitrogen ion bombardment. In addition, the gems were also having more transparent and luster. The UV–Vis–NIR measurement detected the modification of their absorption properties, implying of the blue color increasing. Here the mechanism of these modifications is postulated and reported. In any point of view, the bombardment by using nitrogen ion beam is a promising technique for quality improvement of the blue sapphire from Rwanda.

  10. Analysis and modification of blue sapphires from Rwanda by ion beam techniques

    International Nuclear Information System (INIS)

    Bootkul, D.; Chaiwai, C.; Tippawan, U.; Wanthanachaisaeng, B.; Intarasiri, S.

    2015-01-01

    Highlights: • Ion beam analysis is an effective method for detecting trace elements. • Ion beam treatment is able to improve optical and color appearances of the blue sapphire from Rwanda. • These alternative methods can be extended to jewelry industry for large scale application. - Abstract: Blue sapphire is categorised in a corundum (Al_2O_3) group. The gems of this group are always amazed by their beauties and thus having high value. In this study, blue sapphires from Rwanda, recently came to Thai gemstone industry, are chosen for investigations. On one hand, we have applied Particle Induced X-ray Emission (PIXE), which is a highly sensitive and precise analytical technique that can be used to identify and quantify trace elements, for chemical analysis of the sapphires. Here we have found that the major element of blue sapphires from Rwanda is Al with trace elements such as Fe, Ti, Cr, Ga and Mg as are commonly found in normal blue sapphire. On the other hand, we have applied low and medium ion implantations for color improvement of the sapphire. It seems that a high amount of energy transferring during cascade collisions have altered the gems properties. We have clearly seen that the blue color of the sapphires have been intensified after nitrogen ion bombardment. In addition, the gems were also having more transparent and luster. The UV–Vis–NIR measurement detected the modification of their absorption properties, implying of the blue color increasing. Here the mechanism of these modifications is postulated and reported. In any point of view, the bombardment by using nitrogen ion beam is a promising technique for quality improvement of the blue sapphire from Rwanda.

  11. Effect of power history on the shape and the thermal stress of a large sapphire crystal during the Kyropoulos process

    Science.gov (United States)

    Nguyen, Tran Phu; Chuang, Hsiao-Tsun; Chen, Jyh-Chen; Hu, Chieh

    2018-02-01

    In this study, the effect of the power history on the shape of a sapphire crystal and the thermal stress during the Kyropoulos process are numerically investigated. The simulation results show that the thermal stress is strongly dependent on the power history. The thermal stress distributions in the crystal for all growth stages produced with different power histories are also studied. The results show that high von Mises stress regions are found close to the seed of the crystal, the highly curved crystal surface and the crystal-melt interface. The maximum thermal stress, which occurs at the crystal-melt interface, increases significantly in value as the crystal expands at the crown. After this, there is reduction in the maximum thermal stress as the crystal lengthens. There is a remarkable enhancement in the maximum von Mises stress when the crystal-melt interface is close to the bottom of the crucible. There are two obvious peaks in the maximum Von Mises stress, at the end of the crown stage and in the final stage, when cracking defects can form. To alleviate this problem, different power histories are considered in order to optimize the process to produce the lowest thermal stress in the crystal. The optimal power history is found to produce a significant reduction in the thermal stress in the crown stage.

  12. Influence of different aspect ratios on the structural and electrical properties of GaN thin films grown on nanoscale-patterned sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Fang-Wei [Department of Electrophysics, National Chiao-Tung University, Hsinchu 300, Taiwan (China); Ke, Wen-Cheng, E-mail: wcke@mail.ntust.edu.tw [Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Cheng, Chun-Hong; Liao, Bo-Wei; Chen, Wei-Kuo [Department of Electrophysics, National Chiao-Tung University, Hsinchu 300, Taiwan (China)

    2016-07-01

    Highlights: • Nanoscale patterned sapphire substrate was prepared by anodic-aluminum-oxide etching mask. • Influence of aspect ratio of NPSS on structural and electrical properties of GaN films was studied. • Low dislocation density and high carrier mobility of GaN films were grown on high aspect ratio NPSS. - Abstract: This study presents GaN thin films grown on nanoscale-patterned sapphire substrates (NPSSs) with different aspect ratios (ARs) using a homemade metal-organic chemical vapor deposition system. The anodic aluminum oxide (AAO) technique is used to prepare the dry etching mask. The cross-sectional view of the scanning electron microscope image shows that voids exist between the interface of the GaN thin film and the high-AR (i.e. ∼2) NPSS. In contrast, patterns on the low-AR (∼0.7) NPSS are filled full of GaN. The formation of voids on the high-AR NPSS is believed to be due to the enhancement of the lateral growth in the initial growth stage, and the quick-merging GaN thin film blocks the precursors from continuing to supply the bottom of the pattern. The atomic force microscopy images of GaN on bare sapphire show a layer-by-layer surface morphology, which becomes a step-flow surface morphology for GaN on a high-AR NPSS. The edge-type threading dislocation density can be reduced from 7.1 × 10{sup 8} cm{sup −2} for GaN on bare sapphire to 4.9 × 10{sup 8} cm{sup −2} for GaN on a high-AR NPSS. In addition, the carrier mobility increases from 85 cm{sup 2}/Vs for GaN on bare sapphire to 199 cm{sup 2}/Vs for GaN on a high-AR NPSS. However, the increased screw-type threading dislocation density for GaN on a low-AR NPSS is due to the competition of lateral growth on the flat-top patterns and vertical growth on the bottom of the patterns that causes the material quality of the GaN thin film to degenerate. Thus, the experimental results indicate that the AR of the particular patterning of a NPSS plays a crucial role in achieving GaN thin film with

  13. Frequency-doubled diode laser for direct pumping of Ti:sapphire lasers

    DEFF Research Database (Denmark)

    Müller, André; Jensen, Ole Bjarlin; Unterhuber, Angelika

    2012-01-01

    . However, the superior electro-optical efficiency of the diode laser improves the overall efficiency of the Ti:sapphire laser by a factor > 2. The optical spectrum emitted by the Ti:sapphire laser shows a spectral width of 112 nm (FWHM). Based on autocorrelation measurements, pulse widths of less than 20...... fs are measured. These results open the opportunity of establishing diode laser pumped Ti:sapphire lasers for e.g. biophotonic applications like retinal optical coherence tomography or pumping of photonic crystal fibers for CARS microscopy.......A single-pass frequency doubled high-power tapered diode laser emitting nearly 1.3 W of green light suitable for direct pumping of Ti:sapphire lasers generating ultrashort pulses is demonstrated. The pump efficiencies reached 75 % of the values achieved with a commercial solid-state pump laser...

  14. MBE growth and characterization of ZnTe epilayers on m-plane sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Nakasu, Taizo; Sun, Wei-Che; Yamashita, Sotaro; Aiba, Takayuki; Taguri, Kosuke [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kobayashi, Masakazu [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, 2-8-26, Tokyo 169-0051 (Japan); Asahi, Toshiaki [Technology Development Center, JX Nippon Mining and Metals Corporation, Hitachi 317-0056 (Japan); Togo, Hiroyoshi [NTT Microsystem Integration Laboratories, Atsugi 243-0198 (Japan)

    2014-07-15

    ZnTe epilayers were grown on transparent (10-10) oriented (m -plane) sapphire substrates by molecular beam epitaxy (MBE). Pole figure imaging was used to study the domain distribution within the layer. (211)-oriented ZnTe domains were formed on m -plane sapphire. The presence of only one kind of (211) ZnTe domain formed on the 2 -tilted m -plane sapphire substrates was confirmed. Thus, single domain (211) ZnTe epilayers can be grown on the m -plane sapphire using MBE. Although differences in the crystal structure and lattice mismatch are large, precise control of the substrate surface lattice arrangement result in the formation of high-quality epitaxial layers. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Crystal orientation mechanism of ZnTe epilayers formed on different orientations of sapphire substrates by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Nakasu, T.; Yamashita, S.; Aiba, T.; Hattori, S.; Sun, W.; Taguri, K.; Kazami, F.; Kobayashi, M.

    2014-01-01

    The electrooptic effect in ZnTe has recently attracted research attention, and various device structures using ZnTe have been explored. For application to practical terahertz wave detector devices based on ZnTe thin films, sapphire substrates are preferred because they enable the optical path alignment to be simplified. ZnTe/sapphire heterostructures were focused upon, and ZnTe epilayers were prepared on highly mismatched sapphire substrates by molecular beam epitaxy. Epitaxial relationships between the ZnTe thin films and the sapphire substrates with their various orientations were investigated using an X-ray diffraction pole figure method. (0001) c-plane, (1-102) r-plane, (1-100) m-plane, and (11-20) a-plane oriented sapphire substrates were used in this study. The epitaxial relationship between ZnTe and c-plane sapphire was found to be (111) ZnTe//(0001) sapphire with an in-plane orientation relationship of [−211] ZnTe//[1-100] sapphire. It was found that the (211)-plane ZnTe layer was grown on the m-plane of the sapphire substrates, and the (100)-plane ZnTe layer was grown on the r-plane sapphire. When the sapphire substrates were inclined from the c-plane towards the m-axis direction, the orientation of the ZnTe thin films was then tilted from the (111)-plane to the (211)-plane. The c-plane of the sapphire substrates governs the formation of the (111) ZnTe domain and the ZnTe epilayer orientation. These crystallographic features were also related to the atom arrangements of ZnTe and sapphire.

  16. Review and perspective: Sapphire optical fiber cladding development for harsh environment sensing

    Science.gov (United States)

    Chen, Hui; Buric, Michael; Ohodnicki, Paul R.; Nakano, Jinichiro; Liu, Bo; Chorpening, Benjamin T.

    2018-03-01

    The potential to use single-crystal sapphire optical fiber as an alternative to silica optical fibers for sensing in high-temperature, high-pressure, and chemically aggressive harsh environments has been recognized for several decades. A key technological barrier to the widespread deployment of harsh environment sensors constructed with sapphire optical fibers has been the lack of an optical cladding that is durable under these conditions. However, researchers have not yet succeeded in incorporating a high-temperature cladding process into the typical fabrication process for single-crystal sapphire fibers, which generally involves seed-initiated fiber growth from the molten oxide state. While a number of advances in fabrication of a cladding after fiber-growth have been made over the last four decades, none have successfully transitioned to a commercial manufacturing process. This paper reviews the various strategies and techniques for fabricating an optically clad sapphire fiber which have been proposed and explored in published research. The limitations of current approaches and future prospects for sapphire fiber cladding are discussed, including fabrication methods and materials. The aim is to provide an understanding of the past research into optical cladding of sapphire fibers and to assess possible material systems for future research on this challenging problem for harsh environment sensors.

  17. Structural and electronic characterization of graphene grown by chemical vapor deposition and transferred onto sapphire

    International Nuclear Information System (INIS)

    Joucken, Frédéric; Colomer, Jean-François; Sporken, Robert; Reckinger, Nicolas

    2016-01-01

    Highlights: • CVD graphene is transferred onto sapphire. • Transport measurements reveal relatively low charge carriers mobility. • Scanning probe microscopy experiments reveal the presence of robust contaminant layers between the graphene and the sapphire, responsible for the low carriers mobility. - Abstract: We present a combination of magnetotransport and local probe measurements on graphene grown by chemical vapor deposition on copper foil and subsequently transferred onto a sapphire substrate. A rather strong p-doping is observed (∼9 × 10 12 cm −2 ) together with quite low carrier mobility (∼1350 cm 2 /V s). Atomic force and tunneling imaging performed on the transport devices reveals the presence of contaminants between sapphire and graphene, explaining the limited performance of our devices. The transferred graphene displays ridges similar to those observed whilst graphene is still on the copper foil. We show that, on sapphire, these ridges are made of different thicknesses of the contamination layer and that, contrary to what was reported for hBN or certain transition metal dichalcogenides, no self-cleansing process of the sapphire substrate is observed.

  18. Kinetic Interface

    DEFF Research Database (Denmark)

    2009-01-01

    A kinetic interface for orientation detection in a video training system is disclosed. The interface includes a balance platform instrumented with inertial motion sensors. The interface engages a participant's sense of balance in training exercises.......A kinetic interface for orientation detection in a video training system is disclosed. The interface includes a balance platform instrumented with inertial motion sensors. The interface engages a participant's sense of balance in training exercises....

  19. Molecular dynamics simulation of electron trapping in the sapphire lattice

    International Nuclear Information System (INIS)

    Rambaut, C.; Oh, K.H.; Fayeulle, S.; Kohanoff, J.

    1995-10-01

    Energy storage and release in dielectric materials can be described on the basis of the charge trapping mechanism. Most phenomenological aspects have been recently rationalized in terms of the space charge mode. Dynamical aspects are studied here by performing Molecular Dynamics simulations. We show that an excess electron introduced into the sapphire lattice (α -Al 2 O 3 ) can be trapped only at a limited number of sites. The energy gained by allowing the electron to localize in these sites is of the order of 4-5 eV, in good agreement with the results of the space charge model. Displacements of the neighboring ions due to the implanted charge are shown to be localized in a small region of about 5 A. Detrapping is observed at 250 K. The ionic displacements turn out to play an important role in modifying the potential landscape by lowering, in a dynamical way, the barriers that cause localization at low temperature. (author). 18 refs, 7 figs, 2 tabs

  20. Investigation of the photoluminescence properties of Au/ZnO/sapphire and ZnO/Au/sapphire films by experimental study and electromagnetic simulation

    International Nuclear Information System (INIS)

    Zeng, Yong; Zhao, Yan; Jiang, Yijian

    2015-01-01

    Highlights: • Photoluminescent properties from Au/ZnO/sapphire and ZnO/Au/sapphire structures have been investigated. • The enhancement of UV intensity is a result of the enhanced electric field intensity of the 325 nm excitation light. • Electron transfer which induced by the local surface may be also account for the enhancement of UV emissions. • The suppression of the visible emissions might be due to the flowing of electrons in the defect states to the Au. - Abstract: Photoluminescent properties from Au/ZnO/sapphire and ZnO/Au/sapphire structures have been investigated. It is found that due to the co-interaction between the incident light and local surface plasmons, the ultraviolet (UV) emissions from the two structures were both enhanced and the visible emissions related to the defects were suppressed. By the means of electromagnetic simulation, it indicates that the enhancement of UV intensity is a result of the enhanced electric field intensity of the 325 nm excitation light, which is induced by localized surface plasmons resonance (LSPR). On the other hand, electron transfer which is induced by the local surface also account for the enhancement of UV emissions. The suppression of the visible emissions might be due to the flowing of electrons in the defect states to the Au, which caused the reduction of the electrons in the defect states

  1. Solar wind stream interfaces

    International Nuclear Information System (INIS)

    Gosling, J.T.; Asbridge, J.R.; Bame, S.J.; Feldman, W.C.

    1978-01-01

    Measurements aboard Imp 6, 7, and 8 reveal that approximately one third of all high-speed solar wind streams observed at 1 AU contain a sharp boundary (of thickness less than approx.4 x 10 4 km) near their leading edge, called a stream interface, which separates plasma of distinctly different properties and origins. Identified as discontinuities across which the density drops abruptly, the proton temperature increases abruptly, and the speed rises, stream interfaces are remarkably similar in character from one stream to the next. A superposed epoch analysis of plasma data has been performed for 23 discontinuous stream interfaces observed during the interval March 1971 through August 1974. Among the results of this analysis are the following: (1) a stream interface separates what was originally thick (i.e., dense) slow gas from what was originally thin (i.e., rare) fast gas; (2) the interface is the site of a discontinuous shear in the solar wind flow in a frame of reference corotating with the sun; (3) stream interfaces occur at speeds less than 450 km s - 1 and close to or at the maximum of the pressure ridge at the leading edges of high-speed streams; (4) a discontinuous rise by approx.40% in electron temperature occurs at the interface; and (5) discontinuous changes (usually rises) in alpha particle abundance and flow speed relative to the protons occur at the interface. Stream interfaces do not generally recur on successive solar rotations, even though the streams in which they are embedded often do. At distances beyond several astronomical units, stream interfaces should be bounded by forward-reverse shock pairs; three of four reverse shocks observed at 1 AU during 1971--1974 were preceded within approx.1 day by stream interfaces. Our observations suggest that many streams close to the sun are bounded on all sides by large radial velocity shears separating rapidly expanding plasma from more slowly expanding plasma

  2. Investigation of iron film-substrate interfaces using Rutherford backscattering and channeling techniques

    International Nuclear Information System (INIS)

    Maheswaran, S.; Thevuthasan, S.

    1999-01-01

    Thin films of α-Fe 2 O 3 (0001) (hematite) were epitaxially grown on Al 2 O 3 (0001) substrates using the new molecular beam epitaxy (MBE) system at the Environmental Molecular Sciences Laboratory (EMSL). We have investigated the interface between the hematite films and sapphire substrates using Rutherford Backscattering (RBS) and channeling experiments. Theoretical simulations were performed using VEGAS code to investigate the surface and interface structural properties of the films

  3. Semipolar GaN grown on m-plane sapphire using MOVPE

    Energy Technology Data Exchange (ETDEWEB)

    Wernicke, Tim; Netzel, Carsten; Weyers, Markus [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Berlin (Germany); Kneissl, Michael [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Berlin (Germany); Institute of Solid State Physics, Technical University of Berlin (Germany)

    2008-07-01

    We have investigated the MOVPE growth of semipolar gallium nitride (GaN) films on (10 anti 1 0) m-plane sapphire substrates. Specular GaN films with a RMS roughness (10 x 10 {mu}m{sup 2}) of 15.2 nm were obtained and an arrowhead like structure aligned along[ anti 2 113] is prevailing. The orientation relationship was determined by XRD and yielded (212){sub GaN} parallel (10 anti 10){sub sapphire} and [anti 2113]{sub GaN} parallel [0001]{sub sapphire} as well as [anti 2113]{sub GaN} parallel [000 anti 1]{sub sapphire}. PL spectra exhibited near band edge emission accompanied by a strong basal plane stacking fault emission. In addition lower energy peaks attributed to prismatic plane stacking faults and donor acceptor pair emission appeared in the spectrum. With similar growth conditions also (1013) GaN films on m-plane sapphire were obtained. In the later case we found that the layer was twinned, crystallites with different c-axis orientation were present. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Sapphire scintillation tests for cryogenic detectors in the Edelweiss dark matter search

    Energy Technology Data Exchange (ETDEWEB)

    Luca, M

    2007-07-15

    Identifying the matter in the universe is one of the main challenges of modern cosmology and astrophysics. An important part of this matter seems to be made of non-baryonic particles. Edelweiss is a direct dark matter search using cryogenic germanium bolometers in order to look for particles that interact very weakly with the ordinary matter, generically known as WIMPs (weakly interacting massive particles). An important challenge for Edelweiss is the radioactive background and one of the ways to identify it is to use a larger variety of target crystals. Sapphire is a light target which can be complementary to the germanium crystals already in use. Spectroscopic characterization studies have been performed using different sapphire samples in order to find the optimum doping concentration for good low temperature scintillation. Ti doped crystals with weak Ti concentrations have been used for systematic X ray excitation tests both at room temperature and down to 30 K. The tests have shown that the best Ti concentration for optimum room temperature scintillation is 100 ppm and 50 ppm at T = 45 K. All concentrations have been checked by optical absorption and fluorescence. After having shown that sapphire had interesting characteristics for building heat-scintillation detectors, we have tested if using a sapphire detector was feasible within a dark matter search. During the first commissioning tests of Edelweiss-II, we have proved the compatibility between a sapphire heat scintillation detector and the experimental setup. (author)

  5. Nanoscratch Characterization of GaN Epilayers on c- and a-Axis Sapphire Substrates

    Directory of Open Access Journals (Sweden)

    Wen Hua-Chiang

    2010-01-01

    Full Text Available Abstract In this study, we used metal organic chemical vapor deposition to form gallium nitride (GaN epilayers on c- and a-axis sapphire substrates and then used the nanoscratch technique and atomic force microscopy (AFM to determine the nanotribological behavior and deformation characteristics of the GaN epilayers, respectively. The AFM morphological studies revealed that pile-up phenomena occurred on both sides of the scratches formed on the GaN epilayers. It is suggested that cracking dominates in the case of GaN epilayers while ploughing during the process of scratching; the appearances of the scratched surfaces were significantly different for the GaN epilayers on the c- and a-axis sapphire substrates. In addition, compared to the c-axis substrate, we obtained higher values of the coefficient of friction (μ and deeper penetration of the scratches on the GaN a-axis sapphire sample when we set the ramped force at 4,000 μN. This discrepancy suggests that GaN epilayers grown on c-axis sapphire have higher shear resistances than those formed on a-axis sapphire. The occurrence of pile-up events indicates that the generation and motion of individual dislocation, which we measured under the sites of critical brittle transitions of the scratch track, resulted in ductile and/or brittle properties as a result of the deformed and strain-hardened lattice structure.

  6. Use of sapphire as a neutron damage monitor for pressure vessel steels

    International Nuclear Information System (INIS)

    Pells, G.P.; Fudge, A.J.; Murphy, M.J.; Watt, S.

    1989-01-01

    Single crystal α-Al 2 O 3 (sapphire) has been neutron irradiated over a range of dose, dose rate and neutron energy spectra at temperatures from 60 to 310 0 C. Values of optical absorption at 400 nm, the peak of the aluminum vacancy absorption band, were plotted against damage dose expressed in terms of dpa of Al in sapphire obtained from measurements of induced radio-activity in activation foils irradiated with the sapphires and from calculation of the neutron energy spectrum at the irradiation position. The neutron energy spectrum was calculated using modern neutron transport computer codes and adjusted in the light of measurements obtained from multiple foil activation experiments. A simple response curve was obtained for all sapphires irradiated at temperatures between 220 to 310 0 C and for sapphires irradiated below 200 0 C which had been annealed at 290 0 C irrespective of dose rate or neutron beam energy spectrum. The single response curve for irradiations performed in a variety of neutron energy spectra validate the neutron energy spectrum computational procedures

  7. (211) oriented ZnTe growth on m-plane sapphire by MBE

    Energy Technology Data Exchange (ETDEWEB)

    Nakasu, Taizo [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kobayashi, Masakazu [Department of Electrical Engineering and Bioscience, Waseda University, Tokyo 169-8555 (Japan); Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, 2-8-26, Tokyo 169-0051 (Japan); Togo, Hiroyoshi [NTT Microsystem Integration Laboratories, Atugi-shi 243-0198 (Japan); Asahi, Toshiaki [Technology Development Center, JX Nippon Mining and Metals Corporation, Hitachi-shi 317-0056 (Japan)

    2013-11-15

    Single-crystalline and single domain ZnTe thin films are sought for high-performance terahertz wave detectors, and ZnTe/sapphire heterostructures were considered since the Electro-Optical (EO) effect could be obtained only from epilayers. ZnTe epilayers were grown on m-plane sapphire substrates by molecular beam epitaxy, and the potential of single domain epilayers was explored. Through the X-ray diffraction pole figure measurement it was confirmed that one (100) oriented ZnTe domain along with two kinds of (211) oriented domains were formed on the m-plane sapphire when the layer was grown at 340 C. When the layer was grown at 350 C, the (211) oriented domain dominated the film. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Contribution to the microwave characterisation of superconductive materials by means of sapphire resonators

    International Nuclear Information System (INIS)

    Hanus, Xavier

    1993-01-01

    The objective of this research thesis is to find a compact resonant structure which would allow the residual surface impedance of superconductive samples to be simply, quickly and economically characterised. The author first explains why he decided to use a sapphire single-crystal as inner dielectric, given some performance reached by resonant structures equipped with such inner dielectrics, and given constraints adopted from the start. He explains the origin of microwave losses which appear in this type of resonant structure, i.e. respectively the surface impedance as far as metallic losses are concerned, and the sapphire dielectric loss angle for as far as dielectric losses are concerned. The experimental installation and the principle of microwave measurements are described. The performance of different possible solutions of resonant structures from starting criteria is presented. The solution of the cavity-sapphire with a TE 011 resonant mode is derived [fr

  9. High Temperature Testing with Sapphire Fiber White-Light Michelson Interferometers

    Science.gov (United States)

    Barnes, A.; Pedrazzani, J.; May, R.; Murphy, K.; Tran, T.; Coate, J.

    1996-01-01

    In the design of new aerospace materials, developmental testing is conducted to characterize the behavior of the material under severe environmental conditions of high stress, temperature, and vibration. But to test these materials under extreme conditions requires sensors that can perform in harsh environments. Current sensors can only monitor high temperature test samples using long throw instrumentation, but this is inherently less accurate than a surface mounted sensor, and provides no means for fabrication process monitoring. A promising alternative is the use of sapphire optical fiber sensors. Sapphire is an incredibly rugged material, being extremely hard (9 mhos), chemically inert, and having a melting temperature (over 2000 C). Additionally, there is a extensive background of optical fiber sensors upon which to draw for sapphire sensor configurations.

  10. Kerr-lens mode-locked Ti:Sapphire laser pumped by a single laser diode

    Science.gov (United States)

    Kopylov, D. A.; Esaulkov, M. N.; Kuritsyn, I. I.; Mavritskiy, A. O.; Perminov, B. E.; Konyashchenko, A. V.; Murzina, T. V.; Maydykovskiy, A. I.

    2018-04-01

    The performance of a Ti:sapphire laser pumped by a single 461 nm laser diode is presented for both the continuous-wave and the mode-locked regimes of operation. We introduce a simple astigmatism correction scheme for the laser diode beam consisting of two cylindrical lenses affecting the pump beam along the fast axis of the laser diode, which provides the mode-matching between the nearly square-shaped pump beam and the cavity mode. The resulting efficiency of the suggested Ti:Sapphire oscillator pumped by such a laser diode is analyzed for the Ti:sapphire crystals of 3 mm, 5 mm and 10 mm in length. We demonstrate that such a system provides the generation of ultrashort pulses up to 15 fs in duration with the repetition rate of 87 MHz, the average power being 170 mW.

  11. Fabrication of Ternary AgPdAu Alloy Nanoparticles on c-Plane Sapphire by the Systematical Control of Film Thickness and Deposition Sequence

    Science.gov (United States)

    Kunwar, Sundar; Pandey, Puran; Sui, Mao; Bastola, Sushil; Lee, Jihoon

    2018-06-01

    In this work, a systematic study on the fabrication of ternary AgPdAu alloy nanoparticles (NPs) on c-plane sapphire (0001) is presented and the corresponding structural and optical characteristics are demonstrated. The metallic trilayers of various thicknesses and deposition orders are annealed in a controlled manner (400 °C to 900 °C) to induce the solid-state dewetting that yields the various structural configurations of AgPdAu alloy NPs. The dewetting of relatively thicker trilayers (15 nm) is gradually progressed with void nucleation, growth, and coalescence, isolated NP formation, and shape transformation, along with the temperature control. For 6 nm thickness, owing to the sufficient dewetting of trilayers along with enhanced diffusion, dense and small spherical alloy NPs are fabricated. Depending on the specific growth condition, the surface diffusion and interdiffusion of metal atoms, surface and interface energy minimization, Rayleigh instability, and equilibrium configuration are correlated to describe the fabrication of ternary alloy NPs. Ternary alloy NPs exhibit morphology-dependent ultraviolet-visible-near infrared (UV-VIS-NIR) reflectance properties such as the inverse relationship of average reflectance with the surface coverage, absorption enhancement in specific regions, and reflectance maxima in UV and NIR regions. In addition, Raman spectra depict the six active phonon modes of sapphires and their intensity and position modulation by the alloy NPs.

  12. Towards rhombohedral SiGe epitaxy on 150mm c-plane sapphire substrates

    Science.gov (United States)

    Duzik, Adam J.; Park, Yeonjoon; Choi, Sang H.

    2015-04-01

    Previous work demonstrated for the first time the ability to epitaxially grow uniform single crystal diamond cubic SiGe (111) films on trigonal sapphire (0001) substrates. While SiGe (111) forms two possible crystallographic twins on sapphire (0001), films consisting primarily of one twin were produced on up to 99.95% of the total wafer area. This permits new bandgap engineering possibilities and improved group IV based devices that can exploit the higher carrier mobility in Ge compared to Si. Models are proposed on the epitaxy of such dissimilar crystal structures based on the energetic favorability of crystallographic twins and surface reconstructions. This new method permits Ge (111) on sapphire (0001) epitaxy, rendering Ge an economically feasible replacement for Si in some applications, including higher efficiency Si/Ge/Si quantum well solar cells. Epitaxial SiGe films on sapphire showed a 280% increase in electron mobility and a 500% increase in hole mobility over single crystal Si. Moreover, Ge possesses a wider bandgap for solar spectrum conversion than Si, while the transparent sapphire substrate permits an inverted device structure, increasing the total efficiency to an estimated 30-40%, much higher than traditional Si solar cells. Hall Effect mobility measurements of the Ge layer in the Si/Ge/Si quantum well structure were performed to demonstrate the advantage in carrier mobility over a pure Si solar cell. Another application comes in the use of microelectromechanical devices technology, where high-resistivity Si is currently used as a substrate. Sapphire is a more resistive substrate and offers better performance via lower parasitic capacitance and higher film carrier mobility over the current Si-based technology.

  13. Interface Consistency

    DEFF Research Database (Denmark)

    Staunstrup, Jørgen

    1998-01-01

    This paper proposes that Interface Consistency is an important issue for the development of modular designs. Byproviding a precise specification of component interfaces it becomes possible to check that separately developedcomponents use a common interface in a coherent matter thus avoiding a very...... significant source of design errors. Awide range of interface specifications are possible, the simplest form is a syntactical check of parameter types.However, today it is possible to do more sophisticated forms involving semantic checks....

  14. Multiphoton imaging with a novel compact diode-pumped Ti:sapphire oscillator

    DEFF Research Database (Denmark)

    König, Karsten; Andersen, Peter E.; Le, Tuan

    2015-01-01

    Multiphoton laser scanning microscopy commonly relies on bulky and expensive femtosecond lasers. We integrated a novel minimal-footprint Ti:sapphire oscillator, pumped by a frequency-doubled distributed Bragg reflector tapered diode laser, into a clinical multiphoton tomograph and evaluated its...... imaging capability using different biological samples, i.e. cell monolayers, corneal tissue, and human skin. With the novel laser, the realization of very compact Ti:sapphire-based systems for high-quality multiphoton imaging at a significantly size and weight compared to current systems will become...

  15. Controlling material birefringence in sapphire via self-assembled, sub-wavelength defects

    Science.gov (United States)

    Singh, Astha; Sharma, Geeta; Ranjan, Neeraj; Mittholiya, Kshitij; Bhatnagar, Anuj; Singh, B. P.; Mathur, Deepak; Vasa, Parinda

    2018-02-01

    Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. Generally, this is an intrinsic optical property of a material and cannot be altered. Here, we report a novel technique—direct laser writing—that enables us to control the natural, material birefringence of sapphire over a broad range of wavelengths. The broadband form birefringence originating from self-assembled, periodic array of sub-wavelength (˜ 50-200 nm) defects created by laser writing, can enhance, suppress or maintain the material birefringence of sapphire without affecting its transparency range in visible or its surface quality.

  16. Interfacial structure of V2AlC thin films deposited on (112-bar 0)-sapphire

    International Nuclear Information System (INIS)

    Sigumonrong, Darwin P.; Zhang, Jie; Zhou, Yanchun; Music, Denis; Emmerlich, Jens; Mayer, Joachim; Schneider, Jochen M.

    2011-01-01

    Local epitaxy between V 2 AlC and sapphire without intentionally or spontaneously formed seed layers was observed by transmission electron microscopy. Our ab initio calculations suggest that the most stable interfacial structure is characterized by the stacking sequence ...C-V-Al-V//O-Al..., exhibiting the largest work of separation for the configurations studied and hence strong interfacial bonding. It is proposed that a small misfit accompanied by strong interfacial bonding enable the local epitaxial growth of V 2 AlC on (112-bar 0)-sapphire.

  17. Design of all solid state tunable single-mode Ti: sapphire laser for nuclear industry

    International Nuclear Information System (INIS)

    Lee, J.H.; Nam, S.M.; Lee, Y.J.; Lee, J.M.; Horn, Roland E.; Wendt, Klaus

    1999-01-01

    We designed a Ti:Sapphire laser pumped by a diode laser pumped solid state laser (DPSSL). The DPSSL was intra-cavity frequency doubled and it had 20 W output power. The Ti:Sapphire laser was designed for single longitudinal mode lasing. For single mode lasing, the laser used several solid etalons. We simulated temporal evolution of the laser pulse and single pass amplification rate of the photons in each modes from rate equations. From the result, we found that single mode lasing is viable in this cavity

  18. Interface models

    DEFF Research Database (Denmark)

    Ravn, Anders P.; Staunstrup, Jørgen

    1994-01-01

    This paper proposes a model for specifying interfaces between concurrently executing modules of a computing system. The model does not prescribe a particular type of communication protocol and is aimed at describing interfaces between both software and hardware modules or a combination of the two....... The model describes both functional and timing properties of an interface...

  19. Superhilac real-time velocity measurements

    International Nuclear Information System (INIS)

    Feinberg, B.; Meaney, D.; Thatcher, R.; Timossi, C.

    1987-03-01

    Phase probes have been placed in several external beam lines at the LBL heavy ion linear accelerator (SuperHILAC) to provide non-destructive velocity measurements independent of the ion being accelerated. The existing system has been improved to provide the following features: a display refresh rate better than twice per second, a sensitive pseudo-correlation technique to pick out the signal from the noise, simultaneous measurements of up to four ion velocities when more than one beam is being accelerated, and a touch-screen operator interface. These improvements allow the system to be used as a routine tuning aid and beam velocity monitor

  20. Time-resolved light emission of a, c, and r-cut sapphires shock-compressed to 65 GPa

    Science.gov (United States)

    Liu, Q. C.; Zhou, X. M.

    2018-04-01

    To investigate light emission and dynamic deformation behaviors, sapphire (single crystal Al2O3) samples with three crystallographic orientations (a, c, and r-cut) were shock-compressed by the planar impact method, with final stress ranges from 47 to 65 GPa. Emission radiance and velocity versus time profiles were simultaneously measured with a fast pyrometer and a Doppler pin system in each experiment. Wave profile results show anisotropic elastic-plastic transitions, which confirm the literature observations. Under final shock stress of about 52 GPa, lower emission intensity is observed in the r-cut sample, in agreement with the previous report in the literature. When final shock stress increases to 57 GPa and 65 GPa, spectral radiance histories of the r-cut show two stages of distinct features. In the first stage, the emission intensity of r-cut is lower than those of the other two, which agrees with the previous report in the literature. In the second stage, spectral radiance of r-cut increases with time at much higher rate and it finally peaks over those of the a and c-cut. These observations (conversion of intensified emission in the r-cut) may indicate activation of a second slip system and formation of shear bands which are discussed with the resolved shear stress calculations for the slip systems in each of the three cuts under shock compression.

  1. Antiphase inversion domains in lithium cobaltite thin films deposited on single-crystal sapphire substrates

    International Nuclear Information System (INIS)

    Zheng, S.J.; Fisher, C.A.J.; Hitosugi, T.; Kumatani, A.; Shiraki, S.; Ikuhara, Y.H.; Kuwabara, A.; Moriwake, H.; Oki, H.; Ikuhara, Y.

    2013-01-01

    Antiphase inversion domains in LiCoO 2 thin films prepared by pulsed laser deposition on sapphire single-crystal substrates are analyzed using a combination of (scanning) transmission electron microscopy and first-principles calculations. Domains form epitaxially on the substrates with orientation relationships of [112 ¯ 0] LiCoO 2 (0001) LiCoO 2 //[11 ¯ 00] α-Al 2 O 3 (0001) α-Al 2 O 3 and [1 ¯ 1 ¯ 20] LiCoO 2 (0001) LiCoO 2 //[11 ¯ 00] α-Al 2 O 3 (0001) α-Al 2 O 3 . In addition, substrate/film interfaces with the above orientation relationships always have the same stacking sequence of Al–O–Co–O–Li–O. This is confirmed to be the most energetically stable stacking arrangement according to first-principles calculations. Individual domains form as a result of steps one (0 0 0 1) O–Al–O spacing in height on the otherwise flat substrate surface. Because the orientation of adjacent (0 0 0 1) AlO 6 octahedra in Al 2 O 3 are rotated by 180°, while LiO 6 and CoO 6 octahedra in LiCoO 2 are all aligned in the same direction, substrate steps produce LiCoO 2 domains rotated 180° relative to their neighbors. The similar size of oxygen octahedra in the two materials also means that the step height is close to the layer spacing in LiCoO 2 , so that (0 0 0 1) Li and Co layers of adjacent domains are shifted by one layer relative to each other at each domain boundary, aligning Li layers with Co layers across the boundary. The combination of these two effects generates antiphase inversion domains. The domain boundaries effectively sever Li-ion diffusion pathways in the (0 0 0 1) planes between domains and thus are expected to have a detrimental effect on Li-ion conductivity

  2. Visual observation of gas hydrates nucleation and growth at a water - organic liquid interface

    Science.gov (United States)

    Stoporev, Andrey S.; Semenov, Anton P.; Medvedev, Vladimir I.; Sizikov, Artem A.; Gushchin, Pavel A.; Vinokurov, Vladimir A.; Manakov, Andrey Yu.

    2018-03-01

    Visual observation of nucleation sites of methane and methane-ethane-propane hydrates and their further growth in water - organic liquid - gas systems with/without surfactants was carried out. Sapphire Rocking Cell RCS6 with transparent sapphire cells was used. The experiments were conducted at the supercooling ΔTsub = 20.2 °C. Decane, toluene and crude oils were used as organics. Gas hydrate nucleation occurred on water - metal - gas and water - sapphire - organic liquid three-phase contact lines. At the initial stage of growth hydrate crystals rapidly covered the water - gas or water - organics interfaces (depending on the nucleation site). Further hydrate phase accrete on cell walls (sapphire surface) and into the organics volume. At this stage, growth was accompanied by water «drawing out» from under initial hydrate film formed at water - organic interface. Apparently, it takes place due to water capillary inflow in the reaction zone. It was shown that the hydrate crystal morphology depends on the organic phase composition. In the case of water-in-decane emulsion relay hydrate crystallization was observed in the whole sample, originating most likely due to the hydrate crystal intergrowth through decane. Contacts of such crystals with adjacent water droplets result in rapid hydrate crystallization on this droplet.

  3. High energy (MeV) ion beam modifications of sputtered MoS2 coatings on sapphire

    International Nuclear Information System (INIS)

    Bhattacharya, R.S.; Rai, A.K.; Erdemir, A.

    1991-01-01

    The present article reports on the results of our investigations of high-energy (MeV) ion irradiation on the microstructural and tribological properties of dc magnetron sputtered MoS 2 films. Films of thicknesses 500-7500 A were deposited on NaCl, Si and sapphire substrates and subsequently ion irradiated by 2 MeV Ag + ions at a dose of 5x10 15 cm -2 . Scanning and transmission electron microscopy. Rutherford backscattering and X-ray diffraction techniques were utilized to study the structural, morphological and compositional changes of the film due to ion irradiation. The friction coefficient and sliding life were determined by pin-on-disc tests. Both as-deposited and ion-irradiated films were found to be amorphous having a stoichiometry of MoS 1.8 . A low friction coefficient in the range 0.03-0.04 was measured for both as-deposited and ion-irradiated films. However, the sliding life of ion-irradiated film was found to increase more than tenfold compared to as-deposited films indicating improved bonding at the interface. (orig.)

  4. Polarity inversion of AlN film grown on nitrided a-plane sapphire substrate with pulsed DC reactive sputtering

    Directory of Open Access Journals (Sweden)

    Marsetio Noorprajuda

    2018-04-01

    Full Text Available The effect of oxygen partial pressure (PO2 on polarity and crystalline quality of AlN films grown on nitrided a-plane sapphire substrates by pulsed direct current (DC reactive sputtering was investigated as a fundamental study. The polarity inversion of AlN from nitrogen (−c-polarity to aluminum (+c-polarity occurred during growth at a high PO2 of 9.4×103 Pa owing to Al-O octahedral formation at the interface of nitrided layer and AlN sputtered film which reset the polarity of AlN. The top part of the 1300 nm-thick AlN film sputtered at the high PO2 was polycrystallized. The crystalline quality was improved owing to the high kinetic energy of Al sputtered atom in the sputtering phenomena. Thinner AlN films were also fabricated at the high PO2 to eliminate the polycrystallization. For the 200 nm-thick AlN film sputtered at the high PO2, the full width at half-maximum values of the AlN (0002 and (10−12 X-ray diffraction rocking curves were 47 and 637 arcsec, respectively.

  5. "You Hafta Push": Using Sapphire's Novel to Teach Introduction to American Government

    Science.gov (United States)

    Pappas, Christine

    2007-01-01

    Using fiction in the classroom can dramatize public policy issues and political science concepts, therefore, making them more real and relevant to students. Sapphire's 1996 novel "Push" puts a face on welfare, rape, incest, child abuse, educational inequalities, homophobia, and AIDS. I also use this novel to discuss the public policy process,…

  6. Thermal healing of the sub-surface damage layer in sapphire

    International Nuclear Information System (INIS)

    Pinkas, Malki; Lotem, Haim; Golan, Yuval; Einav, Yeheskel; Golan, Roxana; Chakotay, Elad; Haim, Avivit; Sinai, Ela; Vaknin, Moshe; Hershkovitz, Yasmin; Horowitz, Atara

    2010-01-01

    The sub-surface damage layer formed by mechanical polishing of sapphire is known to reduce the mechanical strength of the processed sapphire and to degrade the performance of sapphire based components. Thermal annealing is one of the methods to eliminate the sub-surface damage layer. This study focuses on the mechanism of thermal healing by studying its effect on surface topography of a- and c-plane surfaces, on the residual stresses in surface layers and on the thickness of the sub-surface damage layer. An atomically flat surface was developed on thermally annealed c-plane surfaces while a faceted roof-top topography was formed on a-plane surfaces. The annealing resulted in an improved crystallographic perfection close to the sample surface as was indicated by a noticeable decrease in X-ray rocking curve peak width. Etching experiments and surface roughness measurements using white light interferometry with sub-nanometer resolution on specimens annealed to different extents indicate that the sub-surface damage layer of the optically polished sapphire is less than 3 μm thick and it is totally healed after thermal treatment at 1450 deg. C for 72 h.

  7. Micromachining and dicing of sapphire, gallium nitride and micro LED devices with UV copper vapour laser

    International Nuclear Information System (INIS)

    Gu, E.; Jeon, C.W.; Choi, H.W.; Rice, G.; Dawson, M.D.; Illy, E.K.; Knowles, M.R.H.

    2004-01-01

    Gallium nitride (GaN) and sapphire are important materials for fabricating photonic devices such as high brightness light emitting diodes (LEDs). These materials are strongly resistant to wet chemical etching and also, low etch rates restrict the use of dry etching. Thus, to develop alternative high resolution processing and machining techniques for these materials is important in fabricating novel photonic devices. In this work, a repetitively pulsed UV copper vapour laser (255 nm) has been used to machine and dice sapphire, GaN and micro LED devices. Machining parameters were optimised so as to achieve controllable machining and high resolution. For sapphire, well-defined grooves 30 μm wide and 430 μm deep were machined. For GaN, precision features such as holes on a tens of micron length scale have been fabricated. By using this technique, compact micro LED chips with a die spacing 100 and a 430 μm thick sapphire substrate have been successfully diced. Measurements show that the performances of LED devices are not influenced by the UV laser machining. Our results demonstrate that the pulsed UV copper vapour laser is a powerful tool for micromachining and dicing of photonic materials and devices

  8. Large scale metal-free synthesis of graphene on sapphire and transfer-free device fabrication.

    Science.gov (United States)

    Song, Hyun Jae; Son, Minhyeok; Park, Chibeom; Lim, Hyunseob; Levendorf, Mark P; Tsen, Adam W; Park, Jiwoong; Choi, Hee Cheul

    2012-05-21

    Metal catalyst-free growth of large scale single layer graphene film on a sapphire substrate by a chemical vapor deposition (CVD) process at 950 °C is demonstrated. A top-gated graphene field effect transistor (FET) device is successfully fabricated without any transfer process. The detailed growth process is investigated by the atomic force microscopy (AFM) studies.

  9. Secondary electron emission of sapphire tungsten molybdenum and titanium for Maxwellian incident electrons

    International Nuclear Information System (INIS)

    Saussez-Hublet, M.-C.; Harbour, P.J.

    1980-06-01

    The second electron emission coefficient of various materials, namely titanium, molybdenum, tungsten and sapphire, has been calculated for a Maxwellian energy distribution from data for a normally incident monoenergetic beam of primary electrons. The most significant difference from the monoenergetic case occurs at low energies. In addition the influence of the incident angle of the electrons is discussed. (author)

  10. Neutron reflectivity study of substrate surface chemistry effects on supported phospholipid bilayer formation on (1120) sapphire.

    Energy Technology Data Exchange (ETDEWEB)

    Oleson, Timothy A. [University of Wisconsin, Madison; Sahai, Nita [University of Akron; Wesolowski, David J [ORNL; Dura, Joseph A [ORNL; Majkrzak, Charles F [ORNL; Giuffre, Anthony J. [University of Wisconsin, Madison

    2012-01-01

    Oxide-supported phospholipid bilayers (SPBs) used as biomimetric membranes are significant for a broad range of applications including improvement of biomedical devices and biosensors, and in understanding biomineralization processes and the possible role of mineral surfaces in the evolution of pre-biotic membranes. Continuous-coverage and/or stacjed SPBs retain properties (e.,g. fluidity) more similar to native biological membranes, which is desirable for most applications. Using neutron reflectivity, we examined face coverage and potential stacking of dipalmitoylphosphatidylcholine (DPPC) bilayers on the (1120) face of sapphire (a-Al2O3). Nearly full bilayers were formed at low to neutral pH, when the sapphire surface is positively charged, and at low ionic strength (l=15 mM NaCl). Coverage decreased at higher pH, close to the isoelectric point of sapphire, and also at high I>210mM, or with addition of 2mM Ca2+. The latter two effects are additive, suggesting that Ca2+ mitigates the effect of higher I. These trends agree with previous results for phospholipid adsorption on a-Al2O3 particles determined by adsorption isotherms and on single-crystal (1010) sapphire by atomic force microscopy, suggesting consistency of oxide surface chemistry-dependent effects across experimental techniques.

  11. Theoretical studies on lattice-oriented growth of single-walled carbon nanotubes on sapphire

    Science.gov (United States)

    Li, Zhengwei; Meng, Xianhong; Xiao, Jianliang

    2017-09-01

    Due to their excellent mechanical and electrical properties, single-walled carbon nanotubes (SWNTs) can find broad applications in many areas, such as field-effect transistors, logic circuits, sensors and flexible electronics. High-density, horizontally aligned arrays of SWNTs are essential for high performance electronics. Many experimental studies have demonstrated that chemical vapor deposition growth of nanotubes on crystalline substrates such as sapphire offers a promising route to achieve such dense, perfectly aligned arrays. In this work, a theoretical study is performed to quantitatively understand the van der Waals interactions between SWNTs and sapphire substrates. The energetically preferred alignment directions of SWNTs on A-, R- and M-planes and the random alignment on the C-plane predicted by this study are all in good agreement with experiments. It is also shown that smaller SWNTs have better alignment than larger SWNTs due to their stronger interaction with sapphire substrate. The strong vdW interactions along preferred alignment directions can be intuitively explained by the nanoscale ‘grooves’ formed by atomic lattice structures on the surface of sapphire. This study provides important insights to the controlled growth of nanotubes and potentially other nanomaterials.

  12. Vanadium-rich ruby and sapphire within Mogok Gemfield, Myanmar: implications for gem color and genesis

    Science.gov (United States)

    Zaw, Khin; Sutherland, Lin; Yui, Tzen-Fu; Meffre, Sebastien; Thu, Kyaw

    2015-01-01

    Rubies and sapphires are of both scientific and commercial interest. These gemstones are corundum colored by transition elements within the alumina crystal lattice: Cr3+ yields red in ruby and Fe2+, Fe3+, and Ti4+ ionic interactions color sapphires. A minor ion, V3+ induces slate to purple colors and color change in some sapphires, but its role in coloring rubies remains enigmatic. Trace element and oxygen isotope composition provide genetic signatures for natural corundum and assist geographic typing. Here, we show that V can dominate chromophore contents in Mogok ruby suites. This raises implications for their color quality, enhancement treatments, geographic origin, exploration and exploitation and their comparison with rubies elsewhere. Precise LA-ICP-MS analysis of ruby and sapphire from Mogok placer and in situ deposits reveal that V can exceed 5,000 ppm, giving V/Cr, V/Fe and V/Ti ratios up to 26, 78, and 97 respectively. Such values significantly exceed those found elsewhere suggesting a localized geological control on V-rich ruby distribution. Our results demonstrate that detailed geochemical studies of ruby suites reveal that V is a potential ruby tracer, encourage comparisons of V/Cr-variation between ruby suites and widen the scope for geographic typing and genesis of ruby. This will allow more precise comparison of Asian and other ruby fields and assist confirmation of Mogok sources for rubies in historical and contemporary gems and jewelry.

  13. Transmittance enhancement of sapphires with antireflective subwavelength grating patterned UV polymer surface structures by soft lithography.

    Science.gov (United States)

    Lee, Soo Hyun; Leem, Jung Woo; Yu, Jae Su

    2013-12-02

    We report the total and diffuse transmission enhancement of sapphires with the ultraviolet curable SU8 polymer surface structures consisting of conical subwavelength gratings (SWGs) at one- and both-side surfaces for different periods. The SWGs patterns on the silicon templates were transferred into the SU8 polymer film surface on sapphires by a simple and cost-effective soft lithography technique. For the fabricated samples, the surface morphologies, wetting behaviors, and optical characteristics were investigated. For theoretical optical analysis, a rigorous coupled-wave analysis method was used. At a period of 350 nm, the sample with SWGs on SU8 film/sapphire exhibited a hydrophobic surface and higher total transmittance compared to the bare sapphire over a wide wavelength of 450-1000 nm. As the period of SWGs was increased, the low total transmittance region of < 85% was shifted towards the longer wavelengths and became broader while the diffuse transmittance was increased (i.e., larger haze ratio). For the samples with SWGs at both-side surfaces, the total and diffuse transmittance spectra were further enhanced compared to the samples with SWGs at one-side surface. The theoretical optical calculation results showed a similar trend to the experimentally measured data.

  14. Erbium medium temperature localised doping into lithium niobate and sapphire: A comparative study

    Czech Academy of Sciences Publication Activity Database

    Nekvindová, P.; Macková, Anna; Peřina, Vratislav; Červená, Jarmila; Čapek, P.; Schrofel, J.; Špirková, J.; Oswald, Jiří

    90-91, - (2003), s. 559-564 ISSN 1012-0394 Institutional research plan: CEZ:AV0Z1048901 Keywords : lithium niobate * sapphire * erbium Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 0.687, year: 2003

  15. Light refraction in sapphire plates with a variable angle of crystal optical axis to the surface

    International Nuclear Information System (INIS)

    Vetrov, V. N.; Ignatenkov, B. A.

    2013-01-01

    The modification of sapphire by inhomogeneous plastic deformation makes it possible to obtain plates with a variable angle of inclination of the crystal optical axis to the plate surface. The refraction of light in this plate at perpendicular and oblique incidence of a parallel beam of rays is considered. The algorithm of calculating the refractive index of extraordinary ray and the birefringence is proposed.

  16. Interface stability during rapid directional solidification

    International Nuclear Information System (INIS)

    Hoglund, D.E.; Aziz, M.J.

    1992-01-01

    This paper reports that at the solidification velocities observed during pulsed laser annealing, the planar interface between solid and liquid is stabilized by capillarity and nonequilibrium effects such as solute trapping. The authors used Rutherford backscattering and electron microscopy to determine the nonequilibrium partition coefficient and critical concentration for breakdown of the planar interface as a function of interface velocity for Sn-implanted silicon. This allows the authors to test the applicability of the Mulliins-Sekerka stability theory to interfaces not in local equilibrium and to test the Coriell-Sekerka and other theories for oscillatory instabilities

  17. High resolution electron microscopy studies of interfaces between Al2O3 substrates and MBE grown Nb films

    International Nuclear Information System (INIS)

    Mayer, J.; Ruhle, M.; Dura, J.; Flynn, C.P.

    1991-01-01

    This paper reports on single crystal niobium films grown by Molecular Beam Epitaxy (MBE) on (001) S sapphire substrates. Cross-sectional specimens with thickness of 2 O 3 interface could be investigated by high resolution electron microscopy (HREM). The orientation relationship between the metal film and the ceramic substrate was verified by selected area diffraction: (111) Nb parallel (0001) S and [1 bar 10] Nb parallel [2 bar 1 bar 10] S . The atomistic structure of the interface was identified by HREM

  18. Nerve conduction velocity

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/003927.htm Nerve conduction velocity To use the sharing features on this page, please enable JavaScript. Nerve conduction velocity (NCV) is a test to see ...

  19. The velocity of sound

    International Nuclear Information System (INIS)

    Beyer, R.T.

    1985-01-01

    The paper reviews the work carried out on the velocity of sound in liquid alkali metals. The experimental methods to determine the velocity measurements are described. Tables are presented of reported data on the velocity of sound in lithium, sodium, potassium, rubidium and caesium. A formula is given for alkali metals, in which the sound velocity is a function of shear viscosity, atomic mass and atomic volume. (U.K.)

  20. Testing of Sapphire Optical Fiber and Sensors in Intense Radiation Fields When Subjected to Very High Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Blue, Thomas [The Ohio State Univ., Columbus, OH (United States); Windl, Wolfgang [The Ohio State Univ., Columbus, OH (United States)

    2017-12-15

    The primary objective of this project was to determine the optical attenuation and signal degradation of sapphire optical fibers & sensors (temperature & strain), in-situ, operating at temperatures up to 1500°C during reactor irradiation through experiments and modeling. The results will determine the feasibility of extending sapphire optical fiber-based instrumentation to extremely high temperature radiation environments. This research will pave the way for future testing of sapphire optical fibers and fiber-based sensors under conditions expected in advanced high temperature reactors.

  1. Development of frequency tunable Ti:sapphire laser and dye laser pumped by a pulsed Nd:YAG laser

    International Nuclear Information System (INIS)

    Yi, Jong Hoon; Horn, Roland; Wendt, K.

    2001-01-01

    We investigated lasing characteristics of two kinds of tunable laser, liquid dye laser and solid Ti:sapphire crystal laser, pumped by high pulse repetition rate Nd:YAG laser. Dye laser showed drastically reduced pulsewidth compared with that of pump laser and it also contained large amount of amplified spontaneous emission. Ti:sapphire laser showed also reduced pulsewidth. But, the laser conversion pump laser and Ti:sapphire laser pulse, we used a Brewster-cut Pockel's cell for Q-switching. The laser was frequency doubled by a type I BBO crystal outside of the cavity.

  2. Organic interfaces

    NARCIS (Netherlands)

    Poelman, W.A.; Tempelman, E.

    2014-01-01

    This paper deals with the consequences for product designers resulting from the replacement of traditional interfaces by responsive materials. Part 1 presents a theoretical framework regarding a new paradigm for man-machine interfacing. Part 2 provides an analysis of the opportunities offered by new

  3. Interface Realisms

    DEFF Research Database (Denmark)

    Pold, Søren

    2005-01-01

    This article argues for seeing the interface as an important representational and aesthetic form with implications for postmodern culture and digital aesthetics. The interface emphasizes realism due in part to the desire for transparency in Human-Computer Interaction (HCI) and partly...

  4. Microprocessor interfacing

    CERN Document Server

    Vears, R E

    2014-01-01

    Microprocessor Interfacing provides the coverage of the Business and Technician Education Council level NIII unit in Microprocessor Interfacing (syllabus U86/335). Composed of seven chapters, the book explains the foundation in microprocessor interfacing techniques in hardware and software that can be used for problem identification and solving. The book focuses on the 6502, Z80, and 6800/02 microprocessor families. The technique starts with signal conditioning, filtering, and cleaning before the signal can be processed. The signal conversion, from analog to digital or vice versa, is expl

  5. Reduction of Residual Stresses in Sapphire Cover Glass Induced by Mechanical Polishing and Laser Chamfering Through Etching

    Directory of Open Access Journals (Sweden)

    Shih-Jeh Wu

    2016-10-01

    Full Text Available Sapphire is a hard and anti-scratch material commonly used as cover glass of mobile devices such as watches and mobile phones. A mechanical polishing using diamond slurry is usually necessary to create mirror surface. Additional chamfering at the edge is sometimes needed by mechanical grinding. These processes induce residual stresses and the mechanical strength of the sapphire work piece is impaired. In this study wet etching by phosphate acid process is applied to relief the induced stress in a 1” diameter sapphire cover glass. The sapphire is polished before the edge is chamfered by a picosecond laser. Residual stresses are measured by laser curvature method at different stages of machining. The results show that the wet etching process effectively relief the stress and the laser machining does not incur serious residual stress.

  6. Ga2O3-In2O3 thin films on sapphire substrates: Synthesis and ultraviolet photoconductivity

    Science.gov (United States)

    Muslimov, A. E.; Butashin, A. V.; Kolymagin, A. B.; Nabatov, B. V.; Kanevsky, V. M.

    2017-11-01

    The structure and electrical and optical properties of β-Ga2O3-In2O3 thin films on sapphire substrates with different orientations have been investigated. The samples have been prepared by annealing of gallium-indium metallic films on sapphire substrates in air at different gallium-to-indium ratios in the initial mixture. The photoconductivity of these structures in the solar-blind ultraviolet spectral region has been examined.

  7. Interface Anywhere

    Data.gov (United States)

    National Aeronautics and Space Administration — Current paradigms for crew interfaces to the systems that require control are constrained by decades old technologies which require the crew to be physically near an...

  8. Growth optimization for thick crack-free GaN layers on sapphire with HVPE

    Energy Technology Data Exchange (ETDEWEB)

    Richter, E.; Hennig, Ch.; Kissel, H.; Sonia, G.; Zeimer, U.; Weyers, M. [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, 12489 Berlin (Germany)

    2005-05-01

    Conditions for optimized growth of thick GaN layers with crack-free surfaces by HVPE are reported. It was found that a 1:1 mixture of H{sub 2}/N{sub 2} as carrier gas leads to the lowest density of cracks in the surface. Crack formation also depends on the properties of the GaN/sapphire templates used. Best results have been obtained for 5 {mu}m thick GaN/sapphire templates grown by MOVPE with medium compressive strain {epsilon}{sub zz} of about 0.05%. But there is no simple dependence of the crack formation on the strain status of the starting layer indicating that the HVPE growth of GaN can itself introduce strong tensile strain. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Development of Cr,Nd:GSGG laser as a pumping source of Ti:sapphire laser

    International Nuclear Information System (INIS)

    Tamura, Koji; Arisawa, Takashi

    1999-08-01

    Since efficiency of Cr,Nd doped gadolinium scandium gallium garnet (GSGG) laser is in principle higher than that of Nd:YAG laser, it can be a highly efficient pumping source for Ti:sapphire laser. We have made GSGG laser, and measured its oscillation properties. It was two times more efficient than Nd:YAG laser at free running mode operation. At Q-switched mode operation, fundamental output of 50 mJ and second harmonics output of 8 mJ were obtained. The developed laser had appropriate spatial profile, temporal duration, long time stability for solid laser pumping. Ti:sapphire laser oscillation was achieved by the second harmonics of GSGG laser. (author)

  10. Electrical parameters of silicon on sapphire; influence on aluminium gate MOS devices performances

    International Nuclear Information System (INIS)

    Suat, J.P.; Borel, J.

    1976-01-01

    The question is the quality level of the substrate obtained with MOS technologies on silicon on an insulating substrate. Experimental results are presented on the main electrical parameters of MOS transistors made on silicon on sapphire, e.g. mean values and spreads of: threhold voltage and surface mobilities of transistors, breakdown voltages, and leakage currents of diodes. These devices have been made in three different technologies: enhancement P. channel technology, depletion-enhancement P. channel technology, and complementary MOS technology. These technologies are all aluminium gate processes with standard design rules and 5μm channel length. Measurements show that presently available silicon on sapphire can be considered as a very suitable substrate for many MOS digital applications (but not for dynamic circuits) [fr

  11. Structural, transport and microwave properties of 123/sapphire films: Thickness effect

    Energy Technology Data Exchange (ETDEWEB)

    Predtechensky, MR.; Smal, A.N.; Varlamov, Y.D. [Institute of Thermophysics, Novosibirsk (Russian Federation)] [and others

    1994-12-31

    The effect of thickness and growth conditions on the structure and microwave properties has been investigated for the 123/sapphire films. It has been shown that in the conditions of epitaxial growth and Al atoms do not diffuse from substrate into the film and the films with thickness up to 100nm exhibit the excellent DC properties. The increase of thickness of GdBaCuO films causes the formation of extended line-mesh defects and the increase of the surface resistance (R{sub S}). The low value of surface resistance R{sub S}(75GHz,77K)=20 mOhm has been obtained for the two layer YBaCuO/CdBaCuO/sapphire films.

  12. Growth of cubic InN on r-plane sapphire

    International Nuclear Information System (INIS)

    Cimalla, V.; Pezoldt, J.; Ecke, G.; Kosiba, R.; Ambacher, O.; Spiess, L.; Teichert, G.; Lu, H.; Schaff, W.J.

    2003-01-01

    InN has been grown directly on r-plane sapphire substrates by plasma-enhanced molecular-beam epitaxy. X-ray diffraction investigations have shown that the InN layers consist of a predominant zinc blende (cubic) structure along with a fraction of the wurtzite (hexagonal) phase which content increases with proceeding growth. The lattice constant for zinc blende InN was found to be a=4.986 A. For this unusual growth of a metastable cubic phase on a noncubic substrate an epitaxial relationship was proposed where the metastable zinc blende phase grows directly on the r-plane sapphire while the wurtzite phase arises as the special case of twinning in the cubic structure

  13. Detection of solar neutrinos with a torsion balance with sapphire crystal

    Science.gov (United States)

    Cruceru, M.; Nicolescu, G.

    2018-01-01

    The solar neutrinos (antineutrinos) are detected with a dedicated torsion balance in the case when they interact coherently on stiff crystals (sapphire with high Debye temperature ∼1000K and lead with ∼100K Debye temperature). The balance consists in two equal masses of lead and sapphire, of 25g. An autocollimator coupled to this balance measures small rotation angles of the balance. The force with which neutrino flux interacts with these crystals is between 10-5 dyn and 10-8 dyn, comparable with that reported in Weber’s experiments [1]. A diurnal effect is observed for solar neutrinos due to the rotation of the Earth around its own axes. The solar neutrino flux obtained at the site of our experiment is ∼3.8*1010neutrinos/cm2*s [2]. Experimental data for neutrinos signals from this high sensitivity torsion balance are presented and commented [3].

  14. Contamination-Free Graphene Transfer from Cu-Foil and Cu-Thin-Film/Sapphire

    Directory of Open Access Journals (Sweden)

    Jaeyeong Lee

    2017-12-01

    Full Text Available The separation of graphene grown on metallic catalyst by chemical vapor deposition (CVD is essential for device applications. The transfer techniques of graphene from metallic catalyst to target substrate usually use the chemical etching method to dissolve the metallic catalyst. However, this causes not only high material cost but also environmental contamination in large-scale fabrication. We report a bubble transfer method to transfer graphene films to arbitrary substrate, which is nondestructive to both the graphene and the metallic catalyst. In addition, we report a type of metallic catalyst, which is 700 nm of Cu on sapphire substrate, which is hard enough to endure against any procedure in graphene growth and transfer. With the Cr adhesion layer between sapphire and Cu film, electrochemically delaminated graphene shows great quality during several growth cycles. The electrochemical bubble transfer method can offer high cost efficiency, little contamination and environmental advantages.

  15. Direct pumping of ultrashort Ti:sapphire lasers by a frequency doubled diode laser

    DEFF Research Database (Denmark)

    Müller, André; Jensen, Ole Bjarlin; Unterhuber, Angelika

    2011-01-01

    electro-optical efficiency of the diode laser. Autocorrelation measurements show that pulse widths of less than 20 fs can be expected with an average power of 52 mW when using our laser. These results indicate the high potential of direct diode laser pumped Ti: sapphire lasers to be used in applications....... When using our diode laser system, the optical conversion efficiencies from green to near-infrared light reduces to 75 % of the values achieved with the commercial pump laser. Despite this reduction the overall efficiency of the Ti: sapphire laser is still increased by a factor > 2 due to the superior...... like retinal optical coherence tomography (OCT) or pumping of photonic crystal fibers for CARS (coherent anti-stokes Raman spectroscopy) microscopy....

  16. Gold wetting effects on sapphire irradiated with GeV uranium ions

    International Nuclear Information System (INIS)

    Ramos, S.M.M.

    1997-01-01

    Single crystals of α-Al 2 O 3 were irradiated with 238 U ions using two different energies: 3.4 MeV/u and 1.7 MeV/u. The irradiations were performed at a temperature of ∼80 K, with fluences ranging from 1.2 x 10 12 to 2.5 x 10 12 ions cm -2 . After irradiation, thin gold films were deposited on the sapphire surfaces by using a sputtering method. Subsequent annealing in air at a temperature of 723 and 923 K were applied to investigate the influence of the pre-damage on the adhesion of the gold layer on the sapphire surface. Rutherford backscattering analysis and scanning electron microscopy performed in both virgin and irradiated areas, show that the pre-irradiation damage inhibits the gold film of breaking up into islands after annealing. A wetting effect, which could depend on the damage morphology, is clearly observed. (orig.)

  17. Sapphire implant based neuro-complex for deep-lying brain tumors phototheranostics

    Science.gov (United States)

    Sharova, A. S.; Maklygina, YU S.; Yusubalieva, G. M.; Shikunova, I. A.; Kurlov, V. N.; Loschenov, V. B.

    2018-01-01

    The neuro-complex as a combination of sapphire implant optical port and osteoplastic biomaterial "Collapan" as an Aluminum phthalocyanine nanoform photosensitizer (PS) depot was developed within the framework of this study. The main goals of such neuro-complex are to provide direct access of laser radiation to the brain tissue depth and to transfer PS directly to the pathological tissue location that will allow multiple optical phototheranostics of the deep-lying tumor region without repeated surgical intervention. The developed complex spectral-optical properties research was carried out by photodiagnostics method using the model sample: a brain tissue phantom. The optical transparency of sapphire implant allows obtaining a fluorescent signal with high accuracy, comparable to direct measurement "in contact" with the tissue.

  18. Facet Appearance on the Lateral Face of Sapphire Single-Crystal Fibers during LHPG Growth

    Directory of Open Access Journals (Sweden)

    Liudmila D. Iskhakova

    2016-08-01

    Full Text Available Results of the study of the lateral surface of single-crystal (SC sapphire fibers grown along crystallographic directions [ 0001 ] and [ 11 2 ¯ 0 ] by the LHPG method are presented. The appearance or absence of faceting of the lateral surface of the fibers depending on the growth direction is analyzed. The crystallographic orientation of the facets is investigated. The microstructure of the samples is investigated with the help of an optical microscope and a JSM-5910LV scanning electronic microscope (JEOL. The crystallographic orientations of the facets on the SC sapphire fiber surface are determined by electron backscatter diffraction (EBSD. The seed orientation is studied by means of XRD techniques.

  19. High velocity properties of the dynamic frictional force between ductile metals

    International Nuclear Information System (INIS)

    Hammerberg, James Edward; Hollan, Brad L.; Germann, Timothy C.; Ravelo, Ramon J.

    2010-01-01

    The high velocity properties of the tangential frictional force between ductile metal interfaces seen in large-scale NonEquilibrium Molecular Dynamics (NEMD) simulations are characterized by interesting scaling behavior. In many cases a power law decrease in the frictional force with increasing velocity is observed at high velocities. We discuss the velocity dependence of the high velocity branch of the tangential force in terms of structural transformation and ultimate transition, at the highest velocities, to confined fluid behavior characterized by a critical strain rate. The particular case of an Al/Al interface is discussed.

  20. Laser ablation of dental calculus at 400 nm using a Ti:sapphire laser

    Science.gov (United States)

    Schoenly, Joshua E.; Seka, Wolf; Rechmann, Peter

    2009-02-01

    A Nd:YAG laser-pumped, frequency-doubled Ti:sapphire laser is used for selective ablation of calculus. The laser provides calculus removal. This is in stark contrast with tightly focused Gaussian beams that are energetically inefficient and lead to irreproducible results. Calculus is well ablated at high fluences >=2J/cm2 stalling occurs below this fluence because of photobleaching. Healthy hard tissue is not removed at fluences <=3 J/cm2.

  1. Femtosecond Ti:sapphire cryogenic amplifier with high gain and MHz repetition rate

    DEFF Research Database (Denmark)

    Dantan, Aurelien Romain; Laurat, Julien; Ourjoumtsev, Alexei

    2007-01-01

    We demonstrate high gain amplification of 160-femtosecond pulses in a compact double-pass cryogenic Ti:sapphire amplifier. The setup involves a negative GVD mirrors recompression stage, and operates with a repetition rate between 0.2 and 4 MHz with a continuous pump laser. Amplification factors a...... as high as 17 and 320 nJ Fourier-limited pulses are obtained at a 800 kHz repetition rate....

  2. A microwave exciter for Cs frequency standards based on a sapphire-loaded cavity oscillator.

    Science.gov (United States)

    Koga, Y; McNeilage, C; Searls, J H; Ohshima, S

    2001-01-01

    A low noise and highly stable microwave exciter system has been built for Cs atomic frequency standards using a tunable sapphire-loaded cavity oscillator (SLCO), which works at room temperature. This paper discusses the successful implementation of a control system for locking the SLCO to a long-term reference signal and reports an upper limit of the achieved frequency tracking error 6 x 10(-15) at tau = 1 s.

  3. Second Breakdown Susceptibility of Silicon-On-Sapphire Diodes having Systematically Different Geometries.

    Science.gov (United States)

    1980-05-30

    Sunshine’s experiments less enlight - ening than they might otherwise have been. First, changes in optical transmittance could not be correlated directly to...silicon- on-sapphire technology ) and the orientation of the silicon surface ex- posed to the oxide layer44 ,46 ,4 7,51. Not enough data were taken to at...success. With rapid progress of semi- conductor technology , such simplified and largely intuitive methods proved to be inadequate for dealing with

  4. Transformation of a Plane Wavefront in Hemispherical Lenses Made of Leuco-Sapphire

    Science.gov (United States)

    Vetrov, V. N.; Ignatenkov, B. A.; Yakobson, V. E.

    2018-01-01

    An algorithm for wavefront calculation of ordinary and extraordinary waves after propagation through hemispherical components made of a uniaxial crystal is developed. The influence of frequency dispersion of n o and n e , as well as change in the direction of the optic axis of the crystal, on extraordinary wavefront in hemispheres made of from leuco-sapphire and a plastically deformed analog thereof is determined.

  5. Sub-100 fs high average power directly blue-diode-laser-pumped Ti:sapphire oscillator

    Science.gov (United States)

    Rohrbacher, Andreas; Markovic, Vesna; Pallmann, Wolfgang; Resan, Bojan

    2016-03-01

    Ti:sapphire oscillators are a proven technology to generate sub-100 fs (even sub-10 fs) pulses in the near infrared and are widely used in many high impact scientific fields. However, the need for a bulky, expensive and complex pump source, typically a frequency-doubled multi-watt neodymium or optically pumped semiconductor laser, represents the main obstacle to more widespread use. The recent development of blue diodes emitting over 1 W has opened up the possibility of directly diode-laser-pumped Ti:sapphire oscillators. Beside the lower cost and footprint, a direct diode pumping provides better reliability, higher efficiency and better pointing stability to name a few. The challenges that it poses are lower absorption of Ti:sapphire at available diode wavelengths and lower brightness compared to typical green pump lasers. For practical applications such as bio-medicine and nano-structuring, output powers in excess of 100 mW and sub-100 fs pulses are required. In this paper, we demonstrate a high average power directly blue-diode-laser-pumped Ti:sapphire oscillator without active cooling. The SESAM modelocking ensures reliable self-starting and robust operation. We will present two configurations emitting 460 mW in 82 fs pulses and 350 mW in 65 fs pulses, both operating at 92 MHz. The maximum obtained pulse energy reaches 5 nJ. A double-sided pumping scheme with two high power blue diode lasers was used for the output power scaling. The cavity design and the experimental results will be discussed in more details.

  6. Formation of Au nanoparticles in sapphire by using Ar ion implantation and thermal annealing

    International Nuclear Information System (INIS)

    Zhou, L.H.; Zhang, C.H.; Yang, Y.T.; Li, B.S.; Zhang, L.Q.; Fu, Y.C.; Zhang, H.H.

    2009-01-01

    In this paper, we present results of the synthesis of gold nanoclusters in sapphire, using Ar ion implantation and annealing in air. Unlike the conventional method of Au implantation followed by thermal annealing, Au was deposited on the surface of m- and a- cut sapphire single crystal samples including those pre-implanted with Ar ions. Au atoms were brought into the substrate by subsequent implantation of Ar ions to form Au nanoparticles. Samples were finally annealed stepwisely in air at temperatures ranging from 400 to 800 deg. C and then studied using UV-vis absorption spectrometry, transmission electron microscopy and Rutherford backscattered spectrometry. Evidence of the formation Au nanoparticles in the sapphire can be obtained from the characteristic surface plasmon resonance (SPR) absorption band in the optical absorption spectra or directly from the transmission electron microscopy. The results of optical absorption spectra indicate that the specimen orientations and pre-implantation also influence the size and the volume fraction of Au nanoparticles formed. Theoretical calculations using Maxwell-Garnett effective medium theory supply a good interpretation of the optical absorption results.

  7. Metalorganic vapor phase epitaxy of AlN on sapphire with low etch pit density

    Science.gov (United States)

    Koleske, D. D.; Figiel, J. J.; Alliman, D. L.; Gunning, B. P.; Kempisty, J. M.; Creighton, J. R.; Mishima, A.; Ikenaga, K.

    2017-06-01

    Using metalorganic vapor phase epitaxy, methods were developed to achieve AlN films on sapphire with low etch pit density (EPD). Key to this achievement was using the same AlN growth recipe and only varying the pre-growth conditioning of the quartz-ware. After AlN growth, the quartz-ware was removed from the growth chamber and either exposed to room air or moved into the N2 purged glove box and exposed to H2O vapor. After the quartz-ware was exposed to room air or H2O, the AlN film growth was found to be more reproducible, resulting in films with (0002) and (10-12) x-ray diffraction (XRD) rocking curve linewidths of 200 and 500 arc sec, respectively, and EPDs < 100 cm-2. The EPD was found to correlate with (0002) linewidths, suggesting that the etch pits are associated with open core screw dislocations similar to GaN films. Once reproducible AlN conditions were established using the H2O pre-treatment, it was found that even small doses of trimethylaluminum (TMAl)/NH3 on the quartz-ware surfaces generated AlN films with higher EPDs. The presence of these residual TMAl/NH3-derived coatings in metalorganic vapor phase epitaxy (MOVPE) systems and their impact on the sapphire surface during heating might explain why reproducible growth of AlN on sapphire is difficult.

  8. Study of sapphire probe tip wear when scanning on different materials

    International Nuclear Information System (INIS)

    Nicolet, Anaïs; Küng, Alain; Meli, Felix

    2012-01-01

    The accuracy of today's coordinate measuring machines (CMM) has reached a level at which exact knowledge of each component is required. The role of the probe tip is particularly crucial as it is in contact with the sample surface. Understanding how the probe tip wears off will help to narrow the measurement errors. In this work, wear of a sapphire sphere was studied for different scanning conditions and with different sample materials. Wear depth on the probe was investigated using an automated process in situ on the METAS micro-CMM and completed by measurements with an atomic force microscope. We often found a linear dependence between the wear depth and the scan length ranging from 0.5 to 9 nm m −1 , due to variations in scan speed, contact force or sample material. In the case of steel, the wear rate is proportional to the scan speed, while for aluminum several processes seem to interact. A large amount of debris was visible after the tests. Except for aluminum, wear was visible only on the sphere and not on the sample. Sapphire/steel is the worst combination in terms of wear, whereas the combination sapphire/ceramic exhibits almost no wear. (paper)

  9. Water velocity meter

    Science.gov (United States)

    Roberts, C. W.; Smith, D. L.

    1970-01-01

    Simple, inexpensive drag sphere velocity meter with a zero to 6 ft/sec range measures steady-state flow. When combined with appropriate data acquisition system, it is suited to applications where large numbers of simultaneous measurements are needed for current mapping or velocity profile determination.

  10. Estimation of vector velocity

    DEFF Research Database (Denmark)

    2000-01-01

    Using a pulsed ultrasound field, the two-dimensional velocity vector can be determined with the invention. The method uses a transversally modulated ultrasound field for probing the moving medium under investigation. A modified autocorrelation approach is used in the velocity estimation. The new...

  11. Structural properties of Pt/TiO{sub 2}/Pt heterostructure grown on sapphire substrate—Influence of annealing processes

    Energy Technology Data Exchange (ETDEWEB)

    Roch, Tomas, E-mail: roch@fmph.uniba.sk; Durina, Pavol; Grancic, Branislav; Gregor, Maros; Plecenik, Tomas; Truchly, Martin; Mikula, Marian; Satrapinskyy, Leonid; Kus, Peter; Plecenik, Andrej

    2014-09-01

    Highlights: • Pt/TiO{sub 2}/Pt, Pt/TiO{sub 2} and TiO{sub 2}/Pt stacks were grown on (c-cut) Al{sub 2}O{sub 3} and annealed at 600 °C. • Pt/TiO{sub 2}/Pt contains both TiO{sub 2}-anatase (27%) and rutile (73%) phases after annealing. • Pt/TiO{sub 2} contains both anatase and rutile, TiO{sub 2}/Pt anatase phase only. • Epitaxial relationship of bottom platinum: Pt(1 1 1)[1–10]||sub(0 0 0 1)[11{sup ¯}00]. • Platinum top layer is uniaxially oriented: Pt(1 1 1)||sub(0 0 0 1). - Abstract: Simple gas sensors based on resistivity change of TiO{sub 2} thin films using combined top and bottom metallic contacts are very promising. In this work influence of ex situ annealing in ambient air on structure of TiO{sub 2} thin film stacked between two platinum contact layers has been studied. The layers were deposited using DC magnetron sputtering on unheated c-cut sapphire substrates. For lowering of the Schottky barrier at the Pt–TiO{sub 2} interfaces and for improved crystalline stability, ex situ annealing at 600 °C in air was carried out. In order to study separately influence of top and bottom platinum layers on crystal structure, also reference samples Pt/TiO{sub 2}/Al{sub 2}O{sub 3} and TiO{sub 2}/Pt/Al{sub 2}O{sub 3} have been prepared. Non-ambient X-ray diffraction measurement during annealing process and X-ray pole figures after annealing has been measured. Near epitaxial relationship was observed for bottom Pt layer grown on c-cut sapphire substrate: Pt(1 1 1)[11{sup ¯}0]||Al{sub 2}O{sub 3}(0 0 0 1)[11{sup ¯}00]. Inner titania layer shows randomly oriented both TiO{sub 2}-rutile (R) and anatase (A) phases with the volumetric ratio of R/A ∼ 2.7. If prepared without top Pt contact layer, the TiO{sub 2} transforms during annealing to random single anatase phase. The TiO{sub 2} layer overgrown with only single Pt top contact layer shows randomly oriented both rutile and anatase phases with volumetric ratio R/A ∼ 2.3. The top Pt layer on TiO{sub 2

  12. The SCEC Unified Community Velocity Model (UCVM) Software Framework for Distributing and Querying Seismic Velocity Models

    Science.gov (United States)

    Maechling, P. J.; Taborda, R.; Callaghan, S.; Shaw, J. H.; Plesch, A.; Olsen, K. B.; Jordan, T. H.; Goulet, C. A.

    2017-12-01

    Crustal seismic velocity models and datasets play a key role in regional three-dimensional numerical earthquake ground-motion simulation, full waveform tomography, modern physics-based probabilistic earthquake hazard analysis, as well as in other related fields including geophysics, seismology, and earthquake engineering. The standard material properties provided by a seismic velocity model are P- and S-wave velocities and density for any arbitrary point within the geographic volume for which the model is defined. Many seismic velocity models and datasets are constructed by synthesizing information from multiple sources and the resulting models are delivered to users in multiple file formats, such as text files, binary files, HDF-5 files, structured and unstructured grids, and through computer applications that allow for interactive querying of material properties. The Southern California Earthquake Center (SCEC) has developed the Unified Community Velocity Model (UCVM) software framework to facilitate the registration and distribution of existing and future seismic velocity models to the SCEC community. The UCVM software framework is designed to provide a standard query interface to multiple, alternative velocity models, even if the underlying velocity models are defined in different formats or use different geographic projections. The UCVM framework provides a comprehensive set of open-source tools for querying seismic velocity model properties, combining regional 3D models and 1D background models, visualizing 3D models, and generating computational models in the form of regular grids or unstructured meshes that can be used as inputs for ground-motion simulations. The UCVM framework helps researchers compare seismic velocity models and build equivalent simulation meshes from alternative velocity models. These capabilities enable researchers to evaluate the impact of alternative velocity models in ground-motion simulations and seismic hazard analysis applications

  13. Fe-N{sub x}/C assisted chemical–mechanical polishing for improving the removal rate of sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Li, E-mail: xl0522@126.com [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Shenzhen Key Laboratory of Micro/Nano Manufacturing, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057 (China); Zou, Chunli; Shi, Xiaolei [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Shenzhen Key Laboratory of Micro/Nano Manufacturing, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057 (China); Pan, Guoshun, E-mail: pangs@tsinghua.edu.cn [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Shenzhen Key Laboratory of Micro/Nano Manufacturing, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057 (China); Luo, Guihai; Zhou, Yan [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Shenzhen Key Laboratory of Micro/Nano Manufacturing, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057 (China)

    2015-07-15

    Highlights: • A novel non-noble metal catalyst (Fe-N{sub x}/C) was prepared. • Fe-N{sub x}/C shows remarkable catalytic activity for improving the removal rate of sapphire in alkaline solution. • The optimum CMP removal by Fe-N{sub x}/C yielded a superior surface finish of 0.078 nm the average roughness. • Fe{sub 2}O{sub 3}, Fe{sub 3}O{sub 4}, pyridinic N as well as pyrrolic N group possibly serving as the catalytic sites. • A soft hydration layer (boehmite, AlO(OH)) was generated on the surface of sapphire during CMP process. - Abstract: In this paper, a novel non-noble metal catalyst (Fe-N{sub x}/C) is used to improve the removal mass of sapphire as well as obtain atomically smooth sapphire wafer surfaces. The results indicate that Fe-N{sub x}/C shows good catalytic activity towards sapphire removal rate. And the material removal rates (MRRs) are found to vary with the catalyst content in the polishing fluid. Especially that when the polishing slurry mixes with 16 ppm Fe-N{sub x}/C shows the maximum MRR and its removal mass of sapphire is 38.43 nm/min, more than 15.44% larger than traditional CMP using the colloidal silicon dioxide (SiO{sub 2}) without Fe-N{sub x}/C. Catalyst-assisted chemical–mechanical polishing of sapphire is studied with X-ray photoelectron spectroscopy (XPS). It is found that the formation of a soft hydration layer (boehmite, γ-AlOOH or γ-AlO(OH)) on sapphire surface facilitates the material removal and achieving fine surface finish on basal plane. Abrasives (colloid silica together with magnetite, ingredient of Fe-N{sub x}/C) with a hardness between boehmite and sapphire polish the c-plane of sapphire with good surface finish and efficient removal. Fe{sub 2}O{sub 3}, Fe{sub 3}O{sub 4}, pyridinic N as well as pyrrolic N group would be the catalytical active sites and accelerate this process. Surface quality is characterized with atomic force microscopy (AFM). The optimum CMP removal by Fe-N{sub x}/C also yields a superior

  14. Effect of Ti:sapphire laser on shear bond strength of orthodontic brackets to ceramic surfaces.

    Science.gov (United States)

    Erdur, Emire Aybuke; Basciftci, Faruk Ayhan

    2015-08-01

    With increasing demand for orthodontic treatments in adults, orthodontists continue to debate the optimal way to prepare ceramic surfaces for bonding. This study evaluated the effects of a Ti:sapphire laser on the shear bond strength (SBS) of orthodontic brackets bonded to two ceramic surfaces (feldspathic and IPS Empress e-Max) and the results were compared with those using two other lasers (Er:YAG and Nd:YAG) and 'conventional' techniques, i.e., sandblasting (50 µm) and hydrofluoric (HF) acid. In total, 150 ceramic discs were prepared and divided into two groups. In each group, the following five subgroups were prepared: Ti:sapphire laser, Nd:YAG laser, Er:YAG laser, sandblasting, and HF acid. Mandibular incisor brackets were bonded using a light-cured adhesive. The samples were stored in distilled water for 24 hours at 37°C and then thermocycled. Extra samples were prepared and examined using scanning electron microscopy (SEM). SBS testing was performed and failure modes were classified. ANOVA and Tukey's HSD tests were used to compare SBS among the five subgroups (P < 0.05). Feldspathic and IPS Empress e-Max ceramics had similar SBS values. The Ti:sapphire femtosecond laser (16.76 ± 1.37 MPa) produced the highest mean bond strength, followed by sandblasting (12.79 ± 1.42 MPa) and HF acid (11.28 ± 1.26 MPa). The Er:YAG (5.43 ± 1.21 MPa) and Nd:YAG laser (5.36 ± 1.04 MPa) groups were similar and had the lowest SBS values. More homogeneous and regular surfaces were observed in the ablation pattern with the Ti:sapphire laser than with the other treatments by SEM analysis. Within the limitations of this in vitro study, Ti:sapphire laser- treated surfaces had the highest SBS values. Therefore, this technique may be useful for the pretreatment of ceramic surfaces as an alternative to 'conventional' techniques. © 2015 Wiley Periodicals, Inc.

  15. Designing Interfaces

    CERN Document Server

    Tidwell, Jenifer

    2010-01-01

    Despite all of the UI toolkits available today, it's still not easy to design good application interfaces. This bestselling book is one of the few reliable sources to help you navigate through the maze of design options. By capturing UI best practices and reusable ideas as design patterns, Designing Interfaces provides solutions to common design problems that you can tailor to the situation at hand. This updated edition includes patterns for mobile apps and social media, as well as web applications and desktop software. Each pattern contains full-color examples and practical design advice th

  16. An Advantage of the Equivalent Velocity Spectroscopy for Femtsecond Pulse Radiolysis

    CERN Document Server

    Kondoh, Takafumi; Tagawa, Seiichi; Tomosada, Hiroshi; Yang Jin Feng; Yoshida, Yoichi

    2005-01-01

    For studies of electron beam induced ultra-fast reaction process, femtosecond(fs) pulse radiolysis is under construction. To realize fs time resolution, fs electron and analyzing light pulses and their jitter compensation system are needed. About a 100fs electron pulse was generated by a photocathode RF gun linac and a magnetic pulse compressor. Synchronized Ti: Sapphire laser have a puleswidth about 160fs. And, it is significant to avoid degradation of time resolution caused by velocity difference between electron and analyzing light in a sample. In the 'Equivalent velocity spectroscopy' method, incident analyzing light is slant toward electron beam with an angle associated with refractive index of sample. Then, to overlap light wave front and electron pulse shape, electron pulse shape is slanted toward the direction of travel. As a result of the equivalent velocity spectroscopy for hydrated electrons, using slanted electron pulse shape, optical absorption rise time was about 1.4ps faster than normal electro...

  17. Preparation of YBCO on YSZ layers deposited on silicon and sapphire by MOCVD: influence of the intermediate layer on the quality of the superconducting film

    International Nuclear Information System (INIS)

    Garcia, G.; Casado, J.; Llibre, J.; Doudkowski, M.; Santiso, J.; Figueras, A.; Schamm, S.; Dorignac, D.; Grigis, C.; Aguilo, M.

    1995-01-01

    YSZ buffer layers were deposited on silicon and sapphire by MOCVD. The layers deposited on silicon were highly oriented along [100] direction without in-plane orientation, probably because the existence of the SiO 2 amorphous interlayer. In contrast, epitaxial YSZ was obtained on (1-102) sapphire showing an in-plane texture defined by the following relationships: (100) YSZ // (1-102) sapphire and (110) YSZ // (01-12) sapphire. Subsequently, YBCO films were deposited on YSZ by MOCVD. Structural, morphological and electrical characterization of the superconducting layers were correlated with the in-plane texture of the buffer layers. (orig.)

  18. Interface unit

    NARCIS (Netherlands)

    Keyson, D.V.; Freudenthal, A.; De Hoogh, M.P.A.; Dekoven, E.A.M.

    2001-01-01

    The invention relates to an interface unit comprising at least a display unit for communication with a user, which is designed for being coupled with a control unit for at least one or more parameters in a living or working environment, such as the temperature setting in a house, which control unit

  19. Efficient continuous-wave and passively Q-switched pulse laser operations in a diffusion-bonded sapphire/Er:Yb:YAl3(BO3)4/sapphire composite crystal around 1.55 μm.

    Science.gov (United States)

    Chen, Yujin; Lin, Yanfu; Huang, Jianhua; Gong, Xinghong; Luo, Zundu; Huang, Yidong

    2018-01-08

    A composite crystal consisting of a 1.5-mm-thick Er:Yb:YAl 3 (BO 3 ) 4 crystal between two 1.2-mm-thick sapphire crystals was fabricated by the thermal diffusion bonding technique. Compared with a lone Er:Yb:YAl 3 (BO 3 ) 4 crystal measured under the identical experimental conditions, higher laser performances were demonstrated in the sapphire/Er:Yb:YAl 3 (BO 3 ) 4 /sapphire composite crystal due to the reduction of the thermal effects. End-pumped by a 976 nm laser diode in a hemispherical cavity, a 1.55 μm continuous-wave laser with a maximum output power of 1.75 W and a slope efficiency of 36% was obtained in the composite crystal when the incident pump power was 6.54 W. Passively Q-switched by a Co 2+ :MgAl 2 O 4 crystal, a 1.52 μm pulse laser with energy of 10 μJ and repetition frequency of 105 kHz was also realized in the composite crystal. Pulse width was 315 ns. The results show that the sapphire/Er:Yb:YAl 3 (BO 3 ) 4 /sapphire composite crystal is an excellent active element for 1.55 μm laser.

  20. Velocity Feedback Experiments

    Directory of Open Access Journals (Sweden)

    Chiu Choi

    2017-02-01

    Full Text Available Transient response such as ringing in a control system can be reduced or removed by velocity feedback. It is a useful control technique that should be covered in the relevant engineering laboratory courses. We developed velocity feedback experiments using two different low cost technologies, viz., operational amplifiers and microcontrollers. These experiments can be easily integrated into laboratory courses on feedback control systems or microcontroller applications. The intent of developing these experiments was to illustrate the ringing problem and to offer effective, low cost solutions for removing such problem. In this paper the pedagogical approach for these velocity feedback experiments was described. The advantages and disadvantages of the two different implementation of velocity feedback were discussed also.

  1. The critical ionization velocity

    International Nuclear Information System (INIS)

    Raadu, M.A.

    1980-06-01

    The critical ionization velocity effect was first proposed in the context of space plasmas. This effect occurs for a neutral gas moving through a magnetized plasma and leads to rapid ionization and braking of the relative motion when a marginal velocity, 'the critical velocity', is exceeded. Laboratory experiments have clearly established the significance of the critical velocity and have provided evidence for an underlying mechanism which relies on the combined action of electron impact ionization and a collective plasma interaction heating electrons. There is experimental support for such a mechanism based on the heating of electrons by the modified two-stream instability as part of a feedback process. Several applications to space plasmas have been proposed and the possibility of space experiments has been discussed. (author)

  2. High Velocity Gas Gun

    Science.gov (United States)

    1988-01-01

    A video tape related to orbital debris research is presented. The video tape covers the process of loading a High Velocity Gas Gun and firing it into a mounted metal plate. The process is then repeated in slow motion.

  3. Interface superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Gariglio, S., E-mail: stefano.gariglio@unige.ch [DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève (Switzerland); Gabay, M. [Laboratoire de Physique des Solides, Bat 510, Université Paris-Sud 11, Centre d’Orsay, 91405 Orsay Cedex (France); Mannhart, J. [Max Planck Institute for Solid State Research, 70569 Stuttgart (Germany); Triscone, J.-M. [DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève (Switzerland)

    2015-07-15

    Highlights: • We discuss interfacial superconductivity, a field boosted by the discovery of the superconducting interface between LaAlO. • This system allows the electric field control and the on/off switching of the superconducting state. • We compare superconductivity at the interface and in bulk doped SrTiO. • We discuss the role of the interfacially induced Rashba type spin–orbit. • We briefly discuss superconductivity in cuprates, in electrical double layer transistor field effect experiments. • Recent observations of a high T{sub c} in a monolayer of FeSe deposited on SrTiO{sub 3} are presented. - Abstract: Low dimensional superconducting systems have been the subject of numerous studies for many years. In this article, we focus our attention on interfacial superconductivity, a field that has been boosted by the discovery of superconductivity at the interface between the two band insulators LaAlO{sub 3} and SrTiO{sub 3}. We explore the properties of this amazing system that allows the electric field control and on/off switching of superconductivity. We discuss the similarities and differences between bulk doped SrTiO{sub 3} and the interface system and the possible role of the interfacially induced Rashba type spin–orbit. We also, more briefly, discuss interface superconductivity in cuprates, in electrical double layer transistor field effect experiments, and the recent observation of a high T{sub c} in a monolayer of FeSe deposited on SrTiO{sub 3}.

  4. Heat transfer at a sapphire - Indium interface in the 30 mK - 300 mK temperature range

    NARCIS (Netherlands)

    Liberadzka, J.; Koettig, T.; Bremer, J.; Van Der Post, C. C.W.; Ter Brake, H. J.M.

    2017-01-01

    Within the framework of the AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) project a direct measurement of the Earth's gravitational acceleration on antihydrogen will be carried out. In order to obtain satisfactory precision of the measurement, the thermal movement of the

  5. Alignment control and atomically-scaled heteroepitaxial interface study of GaN nanowires.

    Science.gov (United States)

    Liu, Qingyun; Liu, Baodan; Yang, Wenjin; Yang, Bing; Zhang, Xinglai; Labbé, Christophe; Portier, Xavier; An, Vladimir; Jiang, Xin

    2017-04-20

    Well-aligned GaN nanowires are promising candidates for building high-performance optoelectronic nanodevices. In this work, we demonstrate the epitaxial growth of well-aligned GaN nanowires on a [0001]-oriented sapphire substrate in a simple catalyst-assisted chemical vapor deposition process and their alignment control. It is found that the ammonia flux plays a key role in dominating the initial nucleation of GaN nanocrystals and their orientation. Typically, significant improvement of the GaN nanowire alignment can be realized at a low NH 3 flow rate. X-ray diffraction and cross-sectional scanning electron microscopy studies further verified the preferential orientation of GaN nanowires along the [0001] direction. The growth mechanism of GaN nanowire arrays is also well studied based on cross-sectional high-resolution transmission electron microscopy (HRTEM) characterization and it is observed that GaN nanowires have good epitaxial growth on the sapphire substrate following the crystallographic relationship between (0001) GaN ∥(0001) sapphire and (101[combining macron]0) GaN ∥(112[combining macron]0) sapphire . Most importantly, periodic misfit dislocations are also experimentally observed in the interface region due to the large lattice mismatch between the GaN nanowire and the sapphire substrate, and the formation of such dislocations will favor the release of structural strain in GaN nanowires. HRTEM analysis also finds the existence of "type I" stacking faults and voids inside the GaN nanowires. Optical investigation suggests that the GaN nanowire arrays have strong emission in the UV range, suggesting their crystalline nature and chemical purity. The achievement of aligned GaN nanowires will further promote the wide applications of GaN nanostructures toward diverse high-performance optoelectronic nanodevices including nano-LEDs, photovoltaic cells, photodetectors etc.

  6. Comparison of stress states in GaN films grown on different substrates: Langasite, sapphire and silicon

    Science.gov (United States)

    Park, Byung-Guon; Saravana Kumar, R.; Moon, Mee-Lim; Kim, Moon-Deock; Kang, Tae-Won; Yang, Woo-Chul; Kim, Song-Gang

    2015-09-01

    We demonstrate the evolution of GaN films on novel langasite (LGS) substrate by plasma-assisted molecular beam epitaxy, and assessed the quality of grown GaN film by comparing the experimental results obtained using LGS, sapphire and silicon (Si) substrates. To study the substrate effect, X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and photoluminescence (PL) spectra were used to characterize the microstructure and stress states in GaN films. Wet etching of GaN films in KOH solution revealed that the films deposited on GaN/LGS, AlN/sapphire and AlN/Si substrates possess Ga-polarity, while the film deposited on GaN/sapphire possess N-polarity. XRD, Raman and PL analysis demonstrated that a compressive stress exist in the films grown on GaN/LGS, AlN/sapphire, and GaN/sapphire substrates, while a tensile stress appears on AlN/Si substrate. Comparative analysis showed the growth of nearly stress-free GaN films on LGS substrate due to the very small lattice mismatch ( 3.2%) and thermal expansion coefficient difference ( 7.5%). The results presented here will hopefully provide a new framework for the further development of high performance III-nitride-related devices using GaN/LGS heteroepitaxy.

  7. Sapphire: a better material for atomization and in situ collection of silver volatile species for atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Musil, Stanislav, E-mail: stanomusil@biomed.cas.cz; Matoušek, Tomáš; Dědina, Jiří

    2015-06-01

    Sapphire is presented as a high temperature and corrosion resistant material of an optical tube of an atomizer for volatile species of Ag generated by the reaction with NaBH{sub 4}. The modular atomizer design was employed which allowed to carry out the measurements in two modes: (i) on-line atomization and (ii) in situ collection (directly in the optical tube) by means of excess of O{sub 2} over H{sub 2} in the carrier gas during the trapping step and vice versa in the volatilization step. In comparison with quartz atomizers, the sapphire tube atomizer provides a significantly increased atomizer lifetime as well as substantially improved repeatability of the Ag in situ collection signals shapes. In situ collection of Ag in the sapphire tube atomizer was highly efficient (> 90%). Limit of detection in the on-line atomization mode and in situ collection mode, respectively, was 1.2 ng ml{sup −1} and 0.15 ng ml{sup −1}. - Highlights: • Sapphire was tested as a new material of an atomizer tube for Ag volatile species. • Two measurement modes were investigated: on-line atomization and in situ collection. • In situ collection of Ag was highly efficient (> 90%) with LOD of 0.15 ng ml{sup −1}. • No devitrification of the sapphire tube observed in the course of several months.

  8. Interface learning

    DEFF Research Database (Denmark)

    Thorhauge, Sally

    2014-01-01

    "Interface learning - New goals for museum and upper secondary school collaboration" investigates and analyzes the learning that takes place when museums and upper secondary schools in Denmark work together in local partnerships to develop and carry out school-related, museum-based coursework...... for students. The research focuses on the learning that the students experience in the interface of the two learning environments: The formal learning environment of the upper secondary school and the informal learning environment of the museum. Focus is also on the learning that the teachers and museum...... professionals experience as a result of their collaboration. The dissertation demonstrates how a given partnership’s collaboration affects the students’ learning experiences when they are doing the coursework. The dissertation presents findings that museum-school partnerships can use in order to develop...

  9. N-polar InGaN-based LEDs fabricated on sapphire via pulsed sputtering

    OpenAIRE

    Kohei Ueno; Eiji Kishikawa; Jitsuo Ohta; Hiroshi Fujioka

    2017-01-01

    High-quality N-polar GaN epitaxial films with an atomically flat surface were grown on sapphire (0001) via pulsed sputtering deposition, and their structural and electrical properties were investigated. The crystalline quality of N-polar GaN improves with increasing film thickness and the full width at half maximum values of the x-ray rocking curves for 0002 and 101¯2 diffraction were 313 and 394 arcsec, respectively, at the film thickness of 6μm. Repeatable p-type doping in N-polar GaN films...

  10. A higher-order-mode fiber delivery for Ti:Sapphire femtosecond lasers

    DEFF Research Database (Denmark)

    Jespersen, Kim Giessmann; Le, Tuan; Grüner-Nielsen, Lars Erik

    2010-01-01

    We report the first higher-order-mode fiber with anomalous dispersion at 800nm and demonstrate its potential in femtosecond pulse delivery for Ti:Sapphire femtosecond lasers. We obtain 125fs pulses after propagating a distance of 3.6 meters in solid-silica fiber. The pulses could be further...... compressed in a quartz rod to nearly chirp-free 110fs pulses. Femtosecond pulse delivery is achieved by launching the laser output directly into the delivery fiber without any pre-chirping of the input pulse. The demonstrated pulse delivery scheme suggests scaling to >20meters for pulse delivery in harsh...

  11. Single-crystalline AlN growth on sapphire using physical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Cardenas-Valencia, Andres M., E-mail: andres.cardenas@sri.co [SRI International (United States); Onishi, Shinzo; Rossie, Benjamin [SRI International (United States)

    2011-02-07

    A novel technique for growing single crystalline aluminum nitride (AlN) films is presented. The novelty of the technique, specifically, comes from the use of an innovative physical vapor deposition magnetron sputtering tool, which embeds magnets into the target material. A relatively high deposition rates is achieved ({approx}0.2 {mu}m/min), at temperatures between 860 and 940 {sup o}C. The AlN, grown onto sapphire, is single-crystalline as evidenced by observation using transmission electron microscopy. Tool configuration and growth conditions are discussed, as well as a first set of other analytical results, namely, x-ray diffraction and ultraviolet-visible transmission spectrophotometry.

  12. Numerical simulation of terahertz-wave propagation in photonic crystal waveguide based on sapphire shaped crystal

    International Nuclear Information System (INIS)

    Zaytsev, Kirill I; Katyba, Gleb M; Mukhina, Elena E; Kudrin, Konstantin G; Karasik, Valeriy E; Yurchenko, Stanislav O; Kurlov, Vladimir N; Shikunova, Irina A; Reshetov, Igor V

    2016-01-01

    Terahertz (THz) waveguiding in sapphire shaped single crystal has been studied using the numerical simulations. The numerical finite-difference analysis has been implemented to characterize the dispersion and loss in the photonic crystalline waveguide containing hollow cylindrical channels, which form the hexagonal lattice. Observed results demonstrate the ability to guide the THz-waves in multi-mode regime in wide frequency range with the minimal power extinction coefficient of 0.02 dB/cm at 1.45 THz. This shows the prospectives of the shaped crystals for highly-efficient THz waveguiding. (paper)

  13. Response of Seven Crystallographic Orientations of Sapphire Crystals to Shock Stresses of 16 to 86 GPa

    OpenAIRE

    Kanel, G. I.; Nellis, W. J.; Savinykh, A. S.; Razorenov, S. V.; Rajendran, A. M.

    2009-01-01

    Shock-wave profiles of sapphire (single-crystal Al2O3) with seven crystallographic orientations were measured with time-resolved VISAR interferometry at shock stresses in the range 16 to 86 GPa. Shock propagation was normal to the surface of each cut. The angle between the c-axis of the hexagonal crystal structure and the direction of shock propagation varied from 0 for c-cut up to 90 degrees for m-cut in the basal plane. Based on published shock-induced transparencies, shock-induced optical ...

  14. Possible pitfalls in search of magnetic order in thin films deposited on single crystalline sapphire substrates

    International Nuclear Information System (INIS)

    Salzer, R.; Spemann, D.; Esquinazi, P.; Hoehne, R.; Setzer, A.; Schindler, K.; Schmidt, H.; Butz, T.

    2007-01-01

    We have studied the field and temperature dependence of the magnetic moment of single crystalline sapphire substrates with different surface orientations. All the substrates show a ferromagnetic behavior that partially changes after surface cleaning. The amount of magnetic impurities in the substrates was determined by particle induced X-ray emission. The overall analysis of the data indicates that the magnetic impurities very likely contribute to the measured ferromagnetic behavior but does not rule out completely intrinsic contributions. Our work stresses the necessity to use other than bulk characterization methods for the study of weak ferromagnetic signals of thin films grown on oxide substrates

  15. Characteristics of InGaN-Based Light-Emitting Diodes on Patterned Sapphire Substrates with Various Pattern Heights

    Directory of Open Access Journals (Sweden)

    Sheng-Fu Yu

    2012-01-01

    Full Text Available The optical and electrical characteristics of InGaN-based blue light-emitting diodes (LEDs grown on patterned sapphire substrates (PSSs with different pattern heights and on planar sapphire by atmospheric-pressure metal-organic chemical vapor deposition were investigated. Compared with planar sapphire, it was found that the LED electroluminescence intensity is significantly enhanced on PSSs with pattern heights of 0.5 (21%, 1.1 (57%, 1.5 (81%, and 1.9 (91% μm at an injected current of 20 mA. The increased light intensity exhibits the same trend in a TracePro simulation. In addition, it was also found that the level of leakage current depends on the density of V-shape defects, which were measured by scanning electron microscopy.

  16. Modified circular velocity law

    Science.gov (United States)

    Djeghloul, Nazim

    2018-05-01

    A modified circular velocity law is presented for a test body orbiting around a spherically symmetric mass. This law exhibits a distance scale parameter and allows to recover both usual Newtonian behaviour for lower distances and a constant velocity limit at large scale. Application to the Galaxy predicts the known behaviour and also leads to a galactic mass in accordance with the measured visible stellar mass so that additional dark matter inside the Galaxy can be avoided. It is also shown that this circular velocity law can be embedded in a geometrical description of spacetime within the standard general relativity framework upon relaxing the usual asymptotic flatness condition. This formulation allows to redefine the introduced Newtonian scale limit in term of the central mass exclusively. Moreover, a satisfactory answer to the galactic escape speed problem can be provided indicating the possibility that one can also get rid of dark matter halo outside the Galaxy.

  17. Controlled planar interface synthesis by ultrahigh vacuum diffusion bonding/deposition

    International Nuclear Information System (INIS)

    Kim, M. J.; Carpenter, R. W.; Cox, M. J.; Xu, J.

    2000-01-01

    An ultrahigh vacuum (UHV) diffusion bonding/deposition instrument was designed and constructed, which can produce homophase and heterophase planar interfaces from a wide array of materials. The interfaces are synthesized in situ by diffusion bonding of two substrates with or without various interfacial layers, at temperatures up to about 1500 degree sign C. Substrate surfaces can be heat treated, ion-beam sputter cleaned, and chemically characterized in situ by Auger electron spectroscopy prior to deposition and/or bonding. Bicrystals can be synthesized by bonding two single-crystal substrates at a specified orientation. Interfacial layers can be deposited by electron beam evaporation and/or sputter deposition in any layered or alloyed combination on the substrates before bonding. The instrument can accommodate cylindrical and/or wafer type specimens whose sizes are sufficient for fracture mechanical testing to measure interface bond strength. A variety of planar interfaces of metals, semiconductors, and ceramics were synthesized. Examples of bonded stainless steel/Ti/stainless steel, Si/Si, and sapphire/sapphire interfaces are presented. (c) 2000 Materials Research Society

  18. Use of contact Nd:YAG sapphire-laser system for performing partial hepatectomy and splenectomy in dogs

    Science.gov (United States)

    Yu, Chibing; Jing, Shujuan; Cai, Huimin; Shao, Lanxing; Zou, Hegui

    1993-03-01

    An Nd:YAG Sapphire laser blade was used for performing hepatectomy and splenectomy in dogs. The results suggest that a laser blade provides a new way to reduce intraoperative bleeding and to minimize tissue damage. In recent years, there have been some reports on performing surgical procedures using a contact Nd:YAG Sapphire laser system. The current animal study was conducted in order to explore the capability of incision and excision of the laser tip, the damage to the tissue, and the recovery course.

  19. Soft Interfaces

    International Nuclear Information System (INIS)

    Strzalkowski, Ireneusz

    1997-01-01

    This book presents an extended form of the 1994 Dirac Memorial Lecture delivered by Pierre Gilles de Gennes at Cambridge University. The main task of the presentation is to show the beauty and richness of structural forms and phenomena which are observed at soft interfaces between two media. They are much more complex than forms and phenomena existing in each phase separately. Problems are discussed including both traditional, classical techniques, such as the contact angle in static and dynamic partial wetting, as well as the latest research methodology, like 'environmental' scanning electron microscopes. The book is not a systematic lecture on phenomena but it can be considered as a compact set of essays on topics which particularly fascinate the author. The continuum theory widely used in the book is based on a deep molecular approach. The author is particularly interested in a broad-minded rheology of liquid systems at interfaces with specific emphasis on polymer melts. To study this, the author has developed a special methodology called anemometry near walls. The second main topic presented in the book is the problem of adhesion. Molecular processes, energy transformations and electrostatic interaction are included in an interesting discussion of the many aspects of the principles of adhesion. The third topic concerns welding between two polymer surfaces, such as A/A and A/B interfaces. Of great worth is the presentation of various unsolved, open problems. The kind of topics and brevity of description indicate that this book is intended for a well prepared reader. However, for any reader it will present an interesting picture of how many mysterious processes are acting in the surrounding world and how these phenomena are perceived by a Nobel Laureate, who won that prize mainly for his investigations in this field. (book review)

  20. Interface Screenings

    DEFF Research Database (Denmark)

    Thomsen, Bodil Marie Stavning

    2015-01-01

    In Wim Wenders' film Until the End of the World (1991), three different diagrams for the visual integration of bodies are presented: 1) GPS tracking and mapping in a landscape, 2) video recordings layered with the memory perception of these recordings, and 3) data-created images from dreams...... and memories. From a transvisual perspective, the question is whether or not these (by now realized) diagrammatic modes involving the body in ubiquitous global media can be analysed in terms of the affects and events created in concrete interfaces. The examples used are filmic as felt sensations...

  1. Epitactical FeAl films on sapphire and their magnetic properties

    International Nuclear Information System (INIS)

    Trautvetter, Moritz

    2011-01-01

    In the presented thesis epitaxial FeAl thin films on sapphire have been prepared by pulse laser deposition (PLD). The thin films deposited at room temperature exhibits ferromagnetism and subsequent annealing is necessary to transform the thin films to paramagnetic B2-phase, where the transition temperature depends on the crystalline orientation of the sapphire substrate. Alternatively, by deposition at higher substrate temperature the B2-phase is obtained directly. However, morphology of the FeAl film is influenced by different growth modes resulting from different substrate temperatures. The paramagnetic FeAl films can then be transformed to ferromagnetic phase by successive ion irradiation. Independent of the ion species used for irradiation, the same universal relation between thin films' coercive fields and irradiation damage is identified. The ion irradiation ferromagnetism can be transformed back to paramagnetism by subsequent annealing. The mutual transition between ferromagnetic and paramagnetic phases has been performed several times and shows full reversibility. The ferromagnetic phase induced by Kr + irradiation exhibits structural relaxation, where the saturate magnetization of FeAl thin film gradually decreases in several days. Later, ion irradiation has been performed selectively on defined areas of the thin film with the help of an unconventional lithography technique. The subsequent thin film is composed of ordered hexagonal array of ferromagnetic nano-cylinders separated by a paramagnetic matrix, suggesting a promising system for magnetic data storage. (orig.)

  2. AFM imaging and fractal analysis of surface roughness of AlN epilayers on sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Dallaeva, Dinara, E-mail: dinara.dallaeva@yandex.ru [Brno University of Technology, Faculty of Electrical Engineering and Communication, Physics Department, Technická 8, 616 00 Brno (Czech Republic); Ţălu, Ştefan [Technical University of Cluj-Napoca, Faculty of Mechanical Engineering, Department of AET, Discipline of Descriptive Geometry and Engineering Graphics, 103-105 B-dul Muncii Street, Cluj-Napoca 400641, Cluj (Romania); Stach, Sebastian [University of Silesia, Faculty of Computer Science and Materials Science, Institute of Informatics, Department of Biomedical Computer Systems, ul. Będzińska 39, 41-205 Sosnowiec (Poland); Škarvada, Pavel; Tománek, Pavel; Grmela, Lubomír [Brno University of Technology, Faculty of Electrical Engineering and Communication, Physics Department, Technická 8, 616 00 Brno (Czech Republic)

    2014-09-01

    Graphical abstract: - Highlights: • We determined the complexity of 3D surface roughness of aluminum nitride layers. • We used atomic force microscopy and analyzed their fractal geometry. • We determined the fractal dimension of surface roughness of aluminum nitride layers. • We determined the dependence of layer morphology on substrate temperature. - Abstract: The paper deals with AFM imaging and characterization of 3D surface morphology of aluminum nitride (AlN) epilayers on sapphire substrates prepared by magnetron sputtering. Due to the effect of temperature changes on epilayer's surface during the fabrication, a surface morphology is studied by combination of atomic force microscopy (AFM) and fractal analysis methods. Both methods are useful tools that may assist manufacturers in developing and fabricating AlN thin films with optimal surface characteristics. Furthermore, they provide different yet complementary information to that offered by traditional surface statistical parameters. This combination is used for the first time for measurement on AlN epilayers on sapphire substrates, and provides the overall 3D morphology of the sample surfaces (by AFM imaging), and reveals fractal characteristics in the surface morphology (fractal analysis)

  3. High-rate sputter deposition of NiAl on sapphire fibers

    Energy Technology Data Exchange (ETDEWEB)

    Reichert, K.; Martinez, C.; Cremer, R.; Neuschuetz, D. [Lehrstuhl fuer Theoretische Huettenkunde, RWTH Aachen, Aachen (Germany)

    2002-07-01

    Once the fiber-matrix bonding has been optimized to meet the different requirements during fabrication and operation of the later composite component, sapphire fiber reinforced NiAl will be a potential candidate to substitute conventional superalloys as structural material for gas turbine blades. To improve the composite fabrication process, a direct deposition of the intermetallic matrix material onto hBN coated sapphire fibers prior to the consolidation of the fiber-matrix composite is proposed. It is believed that this will simplify the fabrication process and prevent pore formation during the diffusion bonding. In addition, the fiber volume fraction can be quite easily adjusted by varying the NiAl coating thickness. For this, a high-rate deposition of NiAl is in any case necessary. It has been achieved by a pulsed DC magnetron sputtering of combined Al-Ni targets with the fibers rotating between the two facing cathodes. The obtained nickel aluminide coatings were analyzed as to structure and composition by means of X-ray (GIXRD) as well as electron diffraction (RHEED) and X-ray photoelectron spectroscopy (XPS), respectively. The morphology of the NiAl coatings was examined by SEM. (orig.)

  4. Single phase semipolar (11 anti 22) GaN on (10 anti 10) sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Ploch, S.; Stellmach, J.; Schwaner, T.; Frentrup, M.; Wernicke, T.; Pristovsek, M.; Kneissl, M. [Institute of Solid States Physics, (Germany); Park, J.B.; Niermann, T.; Lehmann, M. [Institute of Optics and Atomic Physics, TU Berlin, Hardenbergstr. 36, 10623 Berlin (Germany)

    2011-07-01

    InGaN quantum well based light emitters grown on (0001) GaN suffer from poor quantum efficiencies with increasing indium mole fraction due to strong polarization fields along the polar crystal orientation. This effect can be greatly reduced by growing on semi- and non-polar GaN orientations. Semipolar (11 anti 22) GaN layers were deposited by metalorganic vapour phase epitaxy on (10 anti 10) sapphire. After sapphire substrate nitridation at 1000 C, a GaN nucleation layer was deposited at high temperature, followed by the deposition of 1.5 nm thick GaN buffer layers. The samples show predominantly (11 anti 22) orientation with a small fraction of (10 anti 13) oriented domains. With increasing nitridation layer thickness the (10 anti 13) phase is suppressed leading to a very smooth surface morphology (rms roughness < 4nm). PL measurements show dominant basel plane stacking fault (BSF) I{sub 1} luminescence without any other defects. Transmission electron microscopy measurements reveal a high BSF density. The FWHM of the X-ray diffraction rocking curve measurements of the (1122) reflection decreases to 1193 arcsec and 739 arcsec along [1 anti 100] and [11 anti 23] respectively with increasing nucleation temperature. Using high temperature nucleation smooth and homogeneous (11 anti 22) phase GaN layers have been obtained.

  5. Origin for the shape of Au small crystals formed inside sapphire by ion implantation

    International Nuclear Information System (INIS)

    Ohkubo, M.; Hioki, T.

    1989-01-01

    In ion-implanted oxides, precipitation is usually formed except the case of forming solid solution. The precipitation comprises the metallic particles of implanted atoms, the oxide of implanted atoms, the metal of matrix elements, the compound of implanted atoms and matrix and so on. In particular, the metallic particles of implanted atoms are frequently faceted. From the facets, the equilibrium shape of crystals can be imagined. The equilibrium shape is determined so that the surface free energy is to be minimized. However, the shape of the metallic particles precipitated inside oxides should not be such equilibrium shape because they come in contact with foreign crystals. As the result, in the precipitation phenomena induced by ion implantation, the crystal structures of precipitated particles and substrates, the crystallographic relation between two crystals, interfacial energy and so on must be taken in consideration. In this paper, the report is made on the shape of the metallic gold particles formed inside sapphires by ion implantation that it was caused by only the crystal habit of sapphires regardless of the above-mentioned complexity. (K.I.)

  6. The density and compositional analysis of titanium doped sapphire single crystal grown by the Czocharlski method

    Science.gov (United States)

    Kusuma, H. H.; Ibrahim, Z.; Othaman, Z.

    2018-03-01

    Titanium doped sapphire (Ti:Al2O3) crystal has attracted attention not only as beautiful gemstones, but also due to their applications as high power laser action. It is very important crystal for tunable solid state laser. Ti:Al2O3 crystals have been success grown using the Czocharlski method with automatic diameter control (ADC) system. The crystals were grown with different pull rates. The structure of the crystal was characterized with X-Ray Diffraction (XRD). The density of the crystal was measurement based on the Archimedes principle and the chemical composition of the crystal was confirmed by the Energy Dispersive X-ray (EDX) Spectroscopy. The XRD patterns of crystals are showed single main peak with a high intensity. Its shows that the samples are single crystal. The Ti:Al2O3 grown with different pull rate will affect the distribution of the concentration of dopant Ti3+ and densities on the sapphire crystals boules as well on the crystal growth process. The increment of the pull rate will increase the percentage distribution of Ti3+ and on the densities of the Ti:Al2O3 crystal boules. This may be attributed to the speed factor of the pull rate of the crystal that then caused changes in the heat flow in the furnace and then causes the homogeneities is changed of species distribution of atoms along crystal.

  7. Morphological Evolution of a-GaN on r-Sapphire by Metalorganic Chemical Vapor Deposition

    International Nuclear Information System (INIS)

    Sang Ling; Liu Jian-Ming; Xu Xiao-Qing; Wang Jun; Zhao Gui-Juan; Liu Chang-Bo; Gu Cheng-Yan; Liu Gui-Peng; Wei Hong-Yuan; Liu Xiang-Lin; Yang Shao-Yan; Zhu Qin-Sheng; Wang Zhan-Guo

    2012-01-01

    The morphological evolution of a-GaN deposited by metalorganic chemical vapor deposition (MOCVD) on r-sapphire is studied. The influences of V/III ratio and growth temperature on surface morphology are investigated. V-pits and stripes are observed on the surface of a-GaN grown at 1050°C and 1100°C, respectively. The overall orientation and geometry of V-pits are uniform and independent on the V/III molar ratio in the samples grown at 1050°C, while in the samples grown at 1100°C, the areas of stripes decrease with the adding of V/III ratio. We deduce the origin of V-pits and stripes by annealing the buffer layers at different temperatures. Because of the existence of inclined (101-bar1) facets, V-pits are formed at 1050°C. The (101-bar1) plane is an N terminated surface, which is metastable at higher temperature, so stripes instead of V-pits are observed at 1100°C. Raman spectra suggest that the growth temperature of the first layer in the two-step process greatly affects the strain of the films. Hence, to improve the growth temperature of the first layer in the two-step method may be an effective way to obtain high quality a-GaN film on r-sapphire. (condensed matter: structure, mechanical and thermal properties)

  8. The Prescribed Velocity Method

    DEFF Research Database (Denmark)

    Nielsen, Peter Vilhelm

    The- velocity level in a room ventilated by jet ventilation is strongly influenced by the supply conditions. The momentum flow in the supply jets controls the air movement in the room and, therefore, it is very important that the inlet conditions and the numerical method can generate a satisfactory...

  9. Multidisc neutron velocity selector

    International Nuclear Information System (INIS)

    Rosta, L.; Zsigmond, Gy.; Farago, B.; Mezei, F.; Ban, K.; Perendi, J.

    1987-12-01

    The prototype of a velocity selector for neutron monochromatization in the 4-20 A wavelength range is presented. The theoretical background of the multidisc rotor system is given together with a description of the mechanical construction and electronic driving system. The first tests and neutron measurements prove easy handling and excellent parameters. (author) 6 refs.; 7 figs.; 2 tabs

  10. Museets interface

    DEFF Research Database (Denmark)

    Pold, Søren

    2007-01-01

    Søren Pold gør sig overvejelser med udgangspunkt i museumsprojekterne Kongedragter.dk og Stigombord.dk. Han argumenterer for, at udviklingen af internettets interfaces skaber nye måder at se, forstå og interagere med kulturen på. Brugerne får nye medievaner og perceptionsmønstre, der må medtænkes i...... tilrettelæggelsen af den fremtidige formidling. Samtidig får museets genstande en ny status som flygtige ikoner i det digitale rum, og alt i alt inviterer det til, at museerne kan forholde sig mere åbent og eksperimenterende til egen praksis og rolle som kulturinstitution....

  11. Effects of annealing temperature and duration on the morphological and optical evolution of self-assembled Pt nanostructures on c-plane sapphire.

    Science.gov (United States)

    Sui, Mao; Li, Ming-Yu; Kunwar, Sundar; Pandey, Puran; Zhang, Quanzhen; Lee, Jihoon

    2017-01-01

    Metallic nanostructures (NSs) have been widely adapted in various applications and their physical, chemical, optical and catalytic properties are strongly dependent on their surface morphologies. In this work, the morphological and optical evolution of self-assembled Pt nanostructures on c-plane sapphire (0001) is demonstrated by the control of annealing temperature and dwelling duration with the distinct thickness of Pt films. The formation of Pt NSs is led by the surface diffusion, agglomeration and surface and interface energy minimization of Pt thin films, which relies on the growth parameters such as system temperature, film thickness and annealing duration. The Pt layer of 10 nm shows the formation of overlaying NPs below 650°C and isolated Pt nanoparticles above 700°C based on the enhanced surface diffusion and Volmer-Weber growth model whereas larger wiggly nanostructures are formed with 20 nm thick Pt layers based on the coalescence growth model. The morphologies of Pt nanostructures demonstrate a sharp distinction depending on the growth parameters applied. By the control of dwelling duration, the gradual transition from dense Pt nanoparticles to networks-like and large clusters is observed as correlated to the Rayleigh instability and Ostwald ripening. The various Pt NSs show a significant distinction in the reflectance spectra depending on the morphology evolution: i.e. the enhancement in UV-visible and NIR regions and the related optical properties are discussed in conjunction with the Pt NSs morphology and the surface coverage.

  12. Comprehensive strain and band gap analysis of PA-MBE grown AlGaN/GaN heterostructures on sapphire with ultra thin buffer

    Energy Technology Data Exchange (ETDEWEB)

    Mahata, Mihir Kumar; Ghosh, Saptarsi; Jana, Sanjay Kumar; Bag, Ankush; Kumar, Rahul [Advanced Technology Development Center, Indian Institute of Technology, Kharagpur, 721302 (India); Chakraborty, Apurba; Biswas, Dhrubes [Department of Electronics and Electrical Communication Engineering, Indian Institute of Technology, Kharagpur, 721302 (India); Mukhopadhyay, Partha [Rajendra Mishra School of Engineering Entrepreneurship, Indian Institute of Technology, Kharagpur, 721302 (India)

    2014-11-15

    In this work, cluster tool (CT) Plasma Assisted Molecular Beam Epitaxy (PA-MBE) grown AlGaN/GaN heterostructure on c-plane (0 0 0 1) sapphire (Al{sub 2}O{sub 3}) were investigated by High Resolution X-ray Diffraction (HRXRD), Room Temperature Raman Spectroscopy (RTRS), and Room Temperature Photoluminescence (RTPL). The effects of strain and doping on GaN and AlGaN layers were investigated thoroughly. The out-of-plane (‘c’) and in-plane (‘a’) lattice parameters were measured from RTRS analysis and as well as reciprocal space mapping (RSM) from HRXRD scan of (002) and (105) plane. The in-plane (out-of plane) strain of the samples were found to be −2.5 × 10{sup −3}(1 × 10{sup −3}), and −1.7 × 10{sup −3}(2 × 10{sup −3}) in GaN layer and 5.1 × 10{sup −3} (−3.3 × 10{sup −3}), and 8.8 × 10{sup −3}(−1.3 × 10{sup −3}) in AlGaN layer, respectively. In addition, the band structures of AlGaN/GaN interface were estimated by both theoretical (based on elastic theory) and experimental observations of the RTPL spectrum.

  13. Comprehensive strain and band gap analysis of PA-MBE grown AlGaN/GaN heterostructures on sapphire with ultra thin buffer

    International Nuclear Information System (INIS)

    Mahata, Mihir Kumar; Ghosh, Saptarsi; Jana, Sanjay Kumar; Bag, Ankush; Kumar, Rahul; Chakraborty, Apurba; Biswas, Dhrubes; Mukhopadhyay, Partha

    2014-01-01

    In this work, cluster tool (CT) Plasma Assisted Molecular Beam Epitaxy (PA-MBE) grown AlGaN/GaN heterostructure on c-plane (0 0 0 1) sapphire (Al 2 O 3 ) were investigated by High Resolution X-ray Diffraction (HRXRD), Room Temperature Raman Spectroscopy (RTRS), and Room Temperature Photoluminescence (RTPL). The effects of strain and doping on GaN and AlGaN layers were investigated thoroughly. The out-of-plane (‘c’) and in-plane (‘a’) lattice parameters were measured from RTRS analysis and as well as reciprocal space mapping (RSM) from HRXRD scan of (002) and (105) plane. The in-plane (out-of plane) strain of the samples were found to be −2.5 × 10 −3 (1 × 10 −3 ), and −1.7 × 10 −3 (2 × 10 −3 ) in GaN layer and 5.1 × 10 −3 (−3.3 × 10 −3 ), and 8.8 × 10 −3 (−1.3 × 10 −3 ) in AlGaN layer, respectively. In addition, the band structures of AlGaN/GaN interface were estimated by both theoretical (based on elastic theory) and experimental observations of the RTPL spectrum

  14. Multidisk neutron velocity selectors

    International Nuclear Information System (INIS)

    Hammouda, B.

    1992-01-01

    Helical multidisk velocity selectors used for neutron scattering applications have been analyzed and tested experimentally. Design and performance considerations are discussed along with simple explanation of the basic concept. A simple progression is used for the inter-disk spacing in the 'Rosta' design. Ray tracing computer investigations are presented in order to assess the 'coverage' (how many absorbing layers are stacked along the path of 'wrong' wavelength neutrons) and the relative number of neutrons absorbed in each disk (and therefore the relative amount of gamma radiation emitted from each disk). We discuss whether a multidisk velocity selector can be operated in the 'reverse' configuration (i.e. the selector is turned by 180 0 around a vertical axis with the rotor spun in the reverse direction). Experimental tests and calibration of a multidisk selector are reported together with evidence that a multidisk selector can be operated in the 'reverse' configuration. (orig.)

  15. Structural properties, crystal quality and growth modes of MOCVD-grown AlN with TMAl pretreatment of sapphire substrate

    KAUST Repository

    Sun, Haiding; Wu, Feng; Altahtamouni, Talal Mohammed Ahmad; Alfaraj, Nasir; Li, Kun; Detchprohm, Theeradetch; Dupuis, Russell; Li, Xiaohang

    2017-01-01

    The growth of high quality AlN epitaxial films relies on precise control of the initial growth stages. In this work, we examined the influence of the trimethylaluminum (TMAl) pretreatment of sapphire substrates on the structural properties, crystal quality and growth modes of heteroepitaxial AlN films on (0001) sapphire substrates. Without the pretreatment, the AlN films nucleated on the smooth surface but exhibited mixed crystallographic Al- (N-) polarity, resulting in rough AlN film surfaces. With increasing the pretreatment time from 1 to 5 s, the N-polarity started to be impeded. However, small islands were formed on sapphire surface due to the decompostion of TMAl. As a result, small voids became noticeable at the nucleation layer (NL) because the growth started as quasi three-dimensional (3D) but transformed to 2D mode as the film grew thicker and got coalesced, leading to smoother and Al-polar films. On the other hand, longer pretreatment time of 40 s formed large 3D islands on sapphire, and thus initiated a 3D-growth mode of the AlN film, generating Al-polar AlN nanocolumns with different facets, which resulted into rougher film surfaces. The epitaxial growth modes and their correlation with the AlN film crystal quality under different TMAl pretreatments are also discussed.

  16. Using a novel spectroscopic reflectometer to optimize a radiation-hardened submicron silicon-on-sapphire CMOS process

    International Nuclear Information System (INIS)

    Do, N.T.; Zawaideh, E.; Vu, T.Q.; Warren, G.; Mead, D.; Do, N.T.; Li, G.P.; Tsai, C.S.

    1999-01-01

    A radiation-hardened sub-micron silicon-on-sapphire CMOS process is monitored and optimized using a novel optical technique based on spectroscopic reflectometry. Quantitative measurements of the crystal quality, surface roughness, and device radiation hardness show excellent correlation between this technique and the Atomic Force Microscopy. (authors)

  17. Patterning of light-extraction nanostructures on sapphire substrates using nanoimprint and ICP etching with different masking materials.

    Science.gov (United States)

    Chen, Hao; Zhang, Qi; Chou, Stephen Y

    2015-02-27

    Sapphire nanopatterning is the key solution to GaN light emitting diode (LED) light extraction. One challenge is to etch deep nanostructures with a vertical sidewall in sapphire. Here, we report a study of the effects of two masking materials (SiO2 and Cr) and different etching recipes (the reaction gas ratio, the reaction pressure and the inductive power) in a chlorine-based (BCl3 and Cl2) inductively coupled plasma (ICP) etching of deep nanopillars in sapphire, and the etching process optimization. The masking materials were patterned by nanoimprinting. We have achieved high aspect ratio sapphire nanopillar arrays with a much steeper sidewall than the previous etching methods. We discover that the SiO2 mask has much slower erosion rate than the Cr mask under the same etching condition, leading to the deep cylinder-shaped nanopillars (122 nm diameter, 200 nm pitch, 170 nm high, flat top, and a vertical sidewall of 80° angle), rather than the pyramid-shaped shallow pillars (200 nm based diameter, 52 nm height, and 42° sidewall) resulted by using Cr mask. The processes developed are scalable to large volume LED manufacturing.

  18. Sapphire: a better material for atomization and in situ collection of silver volatile species for atomic absorption spectrometry

    Czech Academy of Sciences Publication Activity Database

    Musil, Stanislav; Matoušek, Tomáš; Dědina, Jiří

    2015-01-01

    Roč. 108, JUN (2015), s. 61-67 ISSN 0584-8547 R&D Projects: GA ČR GA14-23532S Grant - others:GA AV ČR(CZ) M200311202 Institutional support: RVO:68081715 Keywords : silver * volatile species generation * sapphire tube atomizer Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.289, year: 2015

  19. Dispersion Free Doped and Undoped AlGaN/GaN HEMTs on Sapphire and SiC Substrates

    NARCIS (Netherlands)

    Kraemer, M.C.J.C.M.; Jacobs, B.; Kwaspen, J.J.M.; Suijker, E.M.; Hek, A.P. de; Karouta, F.; Kaufmann, L.M.F.; Hoskens, R.C.P.

    2004-01-01

    We present dispersion free pulsed current voltage (I-V) and radio frequency (RF) power results of undoped and doped AlGaN/GaN HEMTs on sapphire and SiC substrates. The most significant processing step leading to these results is the application of a reactive ion etching (RIE) argon (Ar) plasma

  20. Heteroepitaxial growth of CuInS2 thin films on sapphire by radio frequency reactive sputtering

    International Nuclear Information System (INIS)

    He, Y.B.; Kriegseis, W.; Meyer, B.K.; Polity, A.; Serafin, M.

    2003-01-01

    Direct heteroepitaxial growth of uniform stoichiometric CuInS 2 (CIS) thin films on sapphire (0001) substrates has been achieved by radio frequency reactive sputtering. X-ray ω-2θ scans reveal that the sputtered layers grow in a (112) orientation with a chalcopyrite structure. A rocking curve full width at half maximum of about 0.05 deg. (180 arc sec) for the (112) peak demonstrates a nearly perfect out-of-plane arrangement of CIS (112) parallel sapphire (0001). X-ray diffraction Phi scans further illustrate an excellent in-plane ordering of CIS [1-bar10] parallel sapphire (101-bar0). The sputtered thin CIS epilayers had a smooth surface with a typical root-mean-square roughness of about 3.3 nm as evaluated by atomic force microscopy. The epitaxial growth of tetragonal CIS on hexagonal sapphire provides evidence that heteroepitaxial growth may be realized between structures of different symmetry, such as films of cubic or tetragonal structures on hexagonal substrates or vice versa

  1. 78 FR 56691 - Sapphire Power Marketing LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...

    Science.gov (United States)

    2013-09-13

    ... Power Marketing LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for... Sapphire Power Marketing LLC's application for market-based rate authority, with an accompanying rate... submission of protests and interventions in lieu of paper, using the FERC Online links at http://www.ferc.gov...

  2. Broadband single-transverse-mode fluorescence sources based on ribs fabricated in pulsed laser deposited Ti: sapphire waveguides

    NARCIS (Netherlands)

    Grivas, C.; May-Smith, T.C.; Shepherd, D.P.; Eason, R.W.; Pollnau, Markus; Jelinek, M.

    2004-01-01

    Active rib waveguides with depths and widths varying from 3 to 5 μm and from 9 to 24 μm, respectively, have been structured by $Ar^{+}$-beam etching in pulsed laser deposited Ti:sapphire layers. Losses in the channel structures were essentially at the same levels as the unstructured planar waveguide

  3. Performance of Ar+-milled Ti:Sapphire rib waveguides as single transverse-mode broadband fluorescence sources

    NARCIS (Netherlands)

    Grivas, C.; Shepherd, D.P.; May-Smith, T.C.; Eason, R.W.; Pollnau, Markus; Crunteanu, A.; Jelinek, M.

    2003-01-01

    Rib waveguides have been fabricated in pulsed-laser-deposited Ti:sapphire layers using photolithographic patterning and subsequent Ar+-beam milling. Fluorescence output powers up to 300 W have been observed from the ribs following excitation by a 3-W multiline argon laser. Mode intensity profiles

  4. Intracavity doubling of CW Ti:sapphire laser to 392.5 nm using BiBO-crystal

    DEFF Research Database (Denmark)

    Mortensen, Jesper Liltorp; Thorhauge, Morten; Tidemand-Lichtenberg, Peter

    2005-01-01

    In this work we present results obtained for intra-cavity frequency-doubling of a 785 nm CW Ti:sapphire laser utilising BiBO as the non-linear crystal. Intracavity doubling offers several advantages compared to extra-cavity doubling, such as no need to couple to an external resonance cavity...

  5. Distinct crystallinity and orientations of hydroxyapatite thin films deposited on C- and A-plane sapphire substrates

    Science.gov (United States)

    Akazawa, Housei; Ueno, Yuko

    2014-10-01

    We report how the crystallinity and orientation of hydroxyapatite (HAp) films deposited on sapphire substrates depend on the crystallographic planes. Both solid-phase crystallization of amorphous HAp films and crystallization during sputter deposition at elevated temperatures were examined. The low-temperature epitaxial phase on C-plane sapphire substrates has c-axis orientated HAp crystals regardless of the crystallization route, whereas the preferred orientation switches to the (310) direction at higher temperatures. Only the symmetric stretching mode (ν1) of PO43- units appears in the Raman scattering spectra, confirming well-ordered crystalline domains. In contrast, HAp crystals grown on A-plane sapphire substrates are always oriented toward random orientations. Exhibiting all vibrational modes (ν1, ν3, and ν4) of PO43- units in the Raman scattering spectra reflects random orientation, violating the Raman selection rule. If we assume that Raman intensities of PO43- units represent the crystallinity of HAp films, crystallization terminating the surface with the C-plane is hindered by the presence of excess H2O and OH species in the film, whereas crystallization at random orientations on the A-plane sapphire is rather promoted by these species. Such contrasting behaviors between C-plane and A-plane substrates will reflect surface-plane dependent creation of crystalline seeds and eventually determine the orientation of resulting HAp films.

  6. Structural properties, crystal quality and growth modes of MOCVD-grown AlN with TMAl pretreatment of sapphire substrate

    KAUST Repository

    Sun, Haiding

    2017-08-08

    The growth of high quality AlN epitaxial films relies on precise control of the initial growth stages. In this work, we examined the influence of the trimethylaluminum (TMAl) pretreatment of sapphire substrates on the structural properties, crystal quality and growth modes of heteroepitaxial AlN films on (0001) sapphire substrates. Without the pretreatment, the AlN films nucleated on the smooth surface but exhibited mixed crystallographic Al- (N-) polarity, resulting in rough AlN film surfaces. With increasing the pretreatment time from 1 to 5 s, the N-polarity started to be impeded. However, small islands were formed on sapphire surface due to the decompostion of TMAl. As a result, small voids became noticeable at the nucleation layer (NL) because the growth started as quasi three-dimensional (3D) but transformed to 2D mode as the film grew thicker and got coalesced, leading to smoother and Al-polar films. On the other hand, longer pretreatment time of 40 s formed large 3D islands on sapphire, and thus initiated a 3D-growth mode of the AlN film, generating Al-polar AlN nanocolumns with different facets, which resulted into rougher film surfaces. The epitaxial growth modes and their correlation with the AlN film crystal quality under different TMAl pretreatments are also discussed.

  7. Influence of interface properties on fracture behaviour of concrete

    Indian Academy of Sciences (India)

    Interface; concrete; bond strength; fracture toughness; stiffness; ductility. 1. Introduction .... behaviour of concrete using sandwich, and direct rock-mortar compact specimens under mode I and mode II ... pulse velocity technique. 4.2 Geometry of ...

  8. Dielectric haloscopes: sensitivity to the axion dark matter velocity

    Energy Technology Data Exchange (ETDEWEB)

    Millar, Alexander J.; Redondo, Javier; Steffen, Frank D., E-mail: millar@mpp.mpg.de, E-mail: jredondo@unizar.es, E-mail: steffen@mpp.mpg.de [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany)

    2017-10-01

    We study the effect of the axion dark matter velocity in the recently proposed dielectric haloscopes, a promising avenue to search for well-motivated high mass (40–400 μeV) axions. We describe non-zero velocity effects for axion-photon mixing in a magnetic field and for the phenomenon of photon emission from interfaces between different dielectric media. As velocity effects are only important when the haloscope is larger than about 20% of the axion de Broglie wavelength, for the planned MADMAX experiment with 80 dielectric disks the velocity dependence can safely be neglected. However, an augmented MADMAX or a second generation experiment would be directionally sensitive to the axion velocity, and thus a sensitive measure of axion astrophysics.

  9. Characterization of local hydrophobicity on sapphire (0001) surfaces in aqueous environment by colloidal probe atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wada, Tomoya; Yamazaki, Kenji; Isono, Toshinari; Ogino, Toshio, E-mail: ogino-toshio-rx@ynu.ac.jp

    2017-02-28

    Highlights: • Local hydrophobicity of phase-separated sapphire (0001) surfaces was investigated. • These surfaces are featured by coexistence of hydrophilic and hydrophobic domains. • Each domain was characterized by colloidal probe atomic force microscopy in water. • Both domains can be distinguished by adhesive forces of the probe to the surfaces. • Characterization in aqueous environment is important in bio-applications of sapphire. - Abstract: Sapphire (0001) surfaces exhibit a phase-separation into hydrophobic and hydrophilic domains upon high-temperature annealing, which were previously distinguished by the thickness of adsorbed water layers in air using atomic force microscopy (AFM). To characterize their local surface hydrophobicity in aqueous environment, we used AFM equipped with a colloidal probe and measured the local adhesive force between each sapphire domain and a hydrophilic SiO{sub 2} probe surface, or a hydrophobic polystyrene one. Two data acquisition modes for statistical analyses were used: one is force measurements at different positions of the surface and the other repeated measurement at a fixed position. We found that adhesive force measurements using the polystyrene probe allow us to distinctly separate the hydrophilic and hydrophobic domains. The dispersion in the force measurement data at different positions of the surface is larger than that in the repeated measurements at a fixed position. It indicates that the adhesive force measurement is repeatable although their data dispersion for the measurement positions is relatively large. From these results, we can conclude that the hydrophilic and hydrophobic domains on the sapphire (0001) surfaces are distinguished by a difference in their hydration degrees.

  10. Structural disorder in sapphire induced by 90.3 MeV xenon ions

    International Nuclear Information System (INIS)

    Kabir, A.; Meftah, A.; Stoquert, J.P.; Toulemonde, M.; Monnet, I.; Izerrouken, M.

    2010-01-01

    In our previous work , we have evidenced, using RBS-C, two effects in the aluminium sublattice of sapphire irradiated with 90.3 MeV xenon ions: a partial disorder creation that saturates at ∼40% followed above a threshold fluence by a highly disordered layer appearing behind the surface. In this work, by RBS-C analysis of the oxygen sublattice, we have observed only one regime of partial disorder creation that saturates at ∼60% in tracks of cross-section double of that found for the aluminium sublattice. Complementary analysis by X-ray diffraction shows that the lattice strain increases with the fluence until a maximum is reached about 7.5 x 10 12 ions/cm 2 . For higher fluences, strain decreases first indicating a little stress relaxation in the material and tends afterwards, to remain constant. This stress relaxation is found to be related to the aluminium sublattice high disorder.

  11. Properties of grazing-incidence pulsed Ti:sapphire laser oscillator

    International Nuclear Information System (INIS)

    Tamura, Koji

    2008-03-01

    A pulsed operation of a grazing-incidence double-grating Ti:sapphire laser oscillator that consists of a gain medium, back mirror, and a pair of gratings, was studied. A stable single-longitudinal-mode operation was achievable. From the calculation of the optical path trajectories, it can be explained by the increased beam walk-off from the gain medium by the introduction of the second grating compared with the conventional single-grating grazing-incidence cavity geometry. The improved spectral property was also explained by the calculations of increased dispersion. The results indicate that the oscillator configuration was useful for the applications which require stable mode operation and narrow linewidth such as the high resolution spectroscopy or the laser isotope separation. (author)

  12. Design of patterned sapphire substrates for GaN-based light-emitting diodes

    International Nuclear Information System (INIS)

    Wang Hai-Yan; Lin Zhi-Ting; Han Jing-Lei; Zhong Li-Yi; Li Guo-Qiang

    2015-01-01

    A new method for patterned sapphire substrate (PSS) design is developed and proven to be reliable and cost-effective. As progress is made with LEDs’ luminous efficiency, the pattern units of PSS become more complicated, and the effect of complicated geometrical features is almost impossible to study systematically by experiments only. By employing our new method, the influence of pattern parameters can be systematically studied, and various novel patterns are designed and optimized within a reasonable time span, with great improvement in LEDs’ light extraction efficiency (LEE). Clearly, PSS pattern design with such a method deserves particular attention. We foresee that GaN-based LEDs on these newly designed PSSs will achieve more progress in the coming years. (topical review)

  13. The sapphire backscattering monochromator at the Dynamics beamline P01 of PETRA III

    Energy Technology Data Exchange (ETDEWEB)

    Alexeev, P., E-mail: pavel.alexeev@desy.de [Deutsches Elektronen-Synchrotron DESY (Germany); Asadchikov, V. [Russian Academy of Sciences, A.V. Shubnikov Institute of Crystallography (Russian Federation); Bessas, D. [European Synchrotron Radiation Facility (France); Butashin, A.; Deryabin, A. [Russian Academy of Sciences, A.V. Shubnikov Institute of Crystallography (Russian Federation); Dill, F.-U.; Ehnes, A.; Herlitschke, M. [Deutsches Elektronen-Synchrotron DESY (Germany); Hermann, R. P.; Jafari, A. [JARA-FIT, Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI (Germany); Prokhorov, I. [Kaluga Branch of Shubnikov Institute of Crystallography RAS, Research Center for Space Materials Science (Russian Federation); Roshchin, B. [Russian Academy of Sciences, A.V. Shubnikov Institute of Crystallography (Russian Federation); Röhlsberger, R.; Schlage, K.; Sergueev, I.; Siemens, A.; Wille, H.-C., E-mail: hans.christian.wille@desy.de [Deutsches Elektronen-Synchrotron DESY (Germany)

    2016-12-15

    We report on a high resolution sapphire backscattering monochromator installed at the Dynamics beamline P01 of PETRA III. The device enables nuclear resonance scattering experiments on Mössbauer isotopes with transition energies between 20 and 60 keV with sub-meV to meV resolution. In a first performance test with {sup 119}Sn nuclear resonance at a X-ray energy of 23.88 keV an energy resolution of 1.34 meV was achieved. The device extends the field of nuclear resonance scattering at the PETRA III synchrotron light source to many further isotopes like {sup 151}Eu, {sup 149}Sm, {sup 161}Dy, {sup 125}Te and {sup 121}Sb.

  14. Narrow linewidth operation of the RILIS titanium: Sapphire laser at ISOLDE/CERN

    CERN Document Server

    Rothe, S; Wendt, K D A; Fedosseev, V N; Kron, T; Marsh, B A

    2013-01-01

    A narrow linewidth operating mode for the Ti:sapphire laser of the CERN ISOLDE Resonance Ionization Laser Ion Source (RILIS) has been developed. This satisfies the laser requirements for the programme of in-source resonance ionization spectroscopy measurements and improves the selectivity for isomer separation using RILIS. A linewidth reduction from typically 10 GHz down to 1 GHz was achieved by the intra-cavity insertion of a second (thick) Fabry-Perot etalon. Reliable operation during a laser scan was achieved through motorized control of the tilt angle of each etalon. A scanning, stabilization and mode cleaning procedure was developed and implemented in LabVIEW. The narrow linewidth operation was confirmed in a high resolution spectroscopy study of francium isotopes by the Collinear Resonance Ionization Spectroscopy experiment. The resulting laser scans demonstrate the suitability of the laser, in terms of linewidth, spectral purity and stability for high resolution in-source spectroscopy and isomer select...

  15. Microstructure of nitrides grown on inclined c-plane sapphire and SiC substrate

    International Nuclear Information System (INIS)

    Imura, M.; Honshio, A.; Miyake, Y.; Nakano, K.; Tsuchiya, N.; Tsuda, M.; Okadome, Y.; Balakrishnan, K.; Iwaya, M.; Kamiyama, S.; Amano, H.; Akasaki, I.

    2006-01-01

    High-quality (112-bar 0) GaN layers with atomically flat surface have been grown on a precisely offset-angle-controlled (11-bar 02) sapphire substrate by metal-organic vapor phase epitaxy (MOVPE). Insertion of AlGaN layer between underlying AlN layer and GaN was found to improve crystalline quality of upper GaN layer. In addition, a combination of high growth condition followed and epitaxial lateral overgrowth has been employed for the growth of GaN and this helped in reducing the dislocation density in the resultant layers. GaN and AlN were grown on (303-bar 8) SiC substrates by MOVPE and sublimation methods, respectively. The crystal orientation of GaN and AlN could be just aligned to that of the substrate. Microstructure analysis of the layers was also carried out by transmission electron microscopy

  16. Preparation and structural properties of YBCO films grown on GaN/c-sapphire hexagonal substrate

    Energy Technology Data Exchange (ETDEWEB)

    Chromik, S., E-mail: stefan.chromik@savba.sk [Institute of Electrical Engineering, SAS, Dubravska cesta 9, 84104 Bratislava (Slovakia); Gierlowski, P. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Spankova, M.; Dobrocka, E.; Vavra, I.; Strbik, V.; Lalinsky, T.; Sojkova, M. [Institute of Electrical Engineering, SAS, Dubravska cesta 9, 84104 Bratislava (Slovakia); Liday, J.; Vogrincic, P. [Department of Microelectronics, Slovak Technical University, Ilkovicova 3, 81219 Bratislava (Slovakia); Espinos, J.P. [Instituto de Ciencia de Materiales de Sevilla, Avda Americo Vespucio 49, 41092 Sevilla (Spain)

    2010-07-01

    Epitaxial YBCO thin films have been grown on hexagonal GaN/c-sapphire substrates using DC magnetron sputtering and pulsed laser deposition. An MgO buffer layer has been inserted between the substrate and the YBCO film as a diffusion barrier. X-ray diffraction analysis indicates a c-axis oriented growth of the YBCO films. {Phi}-scan shows surprisingly twelve maxima. Transmission electron microscopy analyses confirm an epitaxial growth of the YBCO blocks with a superposition of three a-b YBCO planes rotated by 120 deg. to each other. Auger electron spectroscopy and X-ray photoelectron spectroscopy reveal no surface contamination with Ga even if a maximum substrate temperature of 700 deg. C is applied.

  17. Intensity Noise Transfer Through a Diode-pumped Titanium Sapphire Laser System

    DEFF Research Database (Denmark)

    Tawfieq, Mahmoud; Hansen, Anders Kragh; Jensen, Ole Bjarlin

    2017-01-01

    higher RIN than a setup with only a single nonlinear crystal. The Ti:S is shown to have a cut-off frequency around 500 kHz, which means that noise structures of the pump laser above this frequency are strongly suppressed. Finally, the majority of the Ti:S noise seems to originate from the laser itself......In this paper, we investigate the noise performance and transfer in a titanium sapphire (Ti:S) laser system. This system consists of a DBR tapered diode laser, which is frequency doubled in two cascaded nonlinear crystals and used to pump the Ti:S laser oscillator. This investigation includes...... electrical noise characterizations of the utilized power supplies, the optical noise of the fundamental light, the second harmonic light, and finally the optical noise of the femtosecond pulses emitted by the Ti:S laser. Noise features originating from the electric power supply are evident throughout...

  18. Femtosecond laser micromachining of sapphire capillaries for laser-wakefield acceleration

    Energy Technology Data Exchange (ETDEWEB)

    Messner, Philipp; Delbos, Niels Matthias; Maier, Andreas R. [CFEL, Center for Free-Electron Laser Science, 22607 Hamburg (Germany); University of Hamburg, Institute of Experimental Physics, 22761 Hamburg (Germany); Calmano, Thomas [University of Hamburg, Institute of Experimental Physics, 22761 Hamburg (Germany)

    2015-07-01

    Laser-plasma accelerator are promising candidates to provide ultra-relativistic electron beams for compact light sources. One factor that limits the achievable electron beam energy in a laser plasma accelerator is the Rayleigh length of the driver laser, which dictates the length over which the electron beams can effectively be accelerated. To overcome this limitation lasers can be guided in a capillary waveguide to extend the acceleration length beyond the Rayleigh length. The production of waveguide structures on scales, that are suitable for plasma acceleration is very challenging. Here, we present experimental results from waveguide machining in sapphire crystals using a Clark MXR CPA 2010 laser with a wavelength of 775nm, 1KHZ repetition rate and a pulse duration of 160 fs. We discuss the effects of different parameters like energy, lens types, writing speed and polarisation on the size and shape of the capillaries, and compare the performance of different parameter sets.

  19. Mid-IR absorption sensing of heavy water using a silicon-on-sapphire waveguide.

    Science.gov (United States)

    Singh, Neetesh; Casas-Bedoya, Alvaro; Hudson, Darren D; Read, Andrew; Mägi, Eric; Eggleton, Benjamin J

    2016-12-15

    We demonstrate a compact silicon-on-sapphire (SOS) strip waveguide sensor for mid-IR absorption spectroscopy. This device can be used for gas and liquid sensing, especially to detect chemically similar molecules and precisely characterize extremely absorptive liquids that are difficult to detect by conventional infrared transmission techniques. We reliably measure concentrations up to 0.25% of heavy water (D2O) in a D2O-H2O mixture at its maximum absorption band at around 4 μm. This complementary metal-oxide-semiconductor (CMOS) compatible SOS D2O sensor is promising for applications such as measuring body fat content or detection of coolant leakage in nuclear reactors.

  20. Characterization of barium strontium titanate thin films on sapphire substrate prepared via RF magnetron sputtering system

    Science.gov (United States)

    Jamaluddin, F. W.; Khalid, M. F. Abdul; Mamat, M. H.; Zoolfakar, A. S.; Zulkefle, M. A.; Rusop, M.; Awang, Z.

    2018-05-01

    Barium Strontium Titanate (Ba0.5Sr0.5TiO3) is known to have a high dielectric constant and low loss at microwave frequencies. These unique features are useful for many electronic applications. This paper focuses on material characterization of BST thin films deposited on sapphire substrate by RF magnetron sputtering system. The sample was then annealed at 900 °C for two hours. Several methods were used to characterize the structural properties of the material such as X-ray diffraction (XRD) and atomic force microscopy (AFM). Field emission scanning electron microscopy (FESEM) was used to analyze the surface morphology of the thin film. From the results obtained, it can be shown that the annealed sample had a rougher surface and better crystallinity as compared to as-deposited sample.

  1. Mode-locked Ti:sapphire laser oscillators pumped by wavelength-multiplexed laser diodes

    Science.gov (United States)

    Sugiyama, Naoto; Tanaka, Hiroki; Kannari, Fumihiko

    2018-05-01

    We directly pumped a Ti:sapphire laser by combining 478 and 520 nm laser diodes to prevent the effect of absorption loss induced by the pump laser of shorter wavelengths (∼450 nm). We obtain a continuous-wave output power of 660 mW at a total incident pump power of 3.15 W. We demonstrate mode locking using a semiconductor saturable absorber mirror, and 126 fs pulses were obtained at a repetition rate of 192 MHz. At the maximum pump power, the average output power is 315 mW. Shorter mode-locked pulses of 42 and 48 fs were respectively achieved by Kerr-lens mode locking with average output powers of 280 and 360 mW at a repetition rate of 117 MHz.

  2. Improving InGaN-LED performance by optimizing the patterned sapphire substrate shape

    International Nuclear Information System (INIS)

    Huang Xiao-Hui; Liu Jian-Ping; Fan Ya-Ming; Kong Jun-Jie; Yang Hui; Wang Huai-Bing

    2012-01-01

    The epitaxial growths of GaN films and GaN-based LEDs on various patterned sapphire substrates (PSSes) with different values of fill factor (f) and slanted angle (θ) are investigated in detail. The threading dislocation (TD) density is lower in the film grown on the PSS with a smaller fill factor, resulting in a higher internal quantum efficiency (IQE). Also the ability of the LED to withstand the electrostatic discharge (ESD) increases as the fill factor decreases. The illumination output power of the LED is affected by both θ and f. It is found that the illumination output power of the LED grown on the PSS with a lower production of tan θ and f is higher than that with a higher production of tan θ and f. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  3. Interfaces habladas

    Directory of Open Access Journals (Sweden)

    María Teresa Soto Sanfiel

    2012-04-01

    Full Text Available Este artículo describe y piensa al fenómeno de las Interfaces habladas (IH desde variados puntos de vista y niveles de análisis. El texto se ha concebido con los objetivos específicos de: 1.- procurar una visión panorámica de aspectos de la producción y consumo comunicativo de las IH; 2.- ofrecer recomendaciones para su creación y uso eficaz, y 3.- llamar la atención sobre su proliferación e inspirar su estudio desde la comunicación. A pesar de la creciente presencia de las IF en nues-tras vidas cotidianas, hay ausencia de textos que las caractericen y analicen por sus aspectos comunicativos. El trabajo es pertinente porque el fenómeno significa un cambio respecto a estadios comunica-tivos precedentes con consecuencias en las concepciones intelectuales y emocionales de los usuarios. La proliferación de IH nos abre a nue-vas realidades comunicativas: hablamos con máquinas.

  4. Advances in Trace Element “Fingerprinting” of Gem Corundum, Ruby and Sapphire, Mogok Area, Myanmar

    Directory of Open Access Journals (Sweden)

    F. Lin Sutherland

    2014-12-01

    Full Text Available Mogok gem corundum samples from twelve localities were analyzed for trace element signatures (LA-ICP-MS method and oxygen isotope values (δ18O, by laser fluorination. The study augmented earlier findings on Mogok gem suites that suggested the Mogok tract forms a high vanadium gem corundum area and also identified rare alluvial ruby and sapphire grains characterised by unusually high silicon, calcium and gallium, presence of noticeable boron, tin and niobium and very low iron, titanium and magnesium contents. Oxygen isotope values (δ18O for the ruby and high Si-Ca-Ga corundum (20‰–25‰ and for sapphire (10‰–20‰ indicate typical crustal values, with values >20‰ being typical of carbonate genesis. The high Si-Ca-Ga ruby has high chromium (up to 3.2 wt % Cr and gallium (up to 0. 08 wt % Ga compared to most Mogok ruby (<2 wt % Cr; <0.02 wt % Ga. In trace element ratio plots the Si-Ca-Ga-rich corundum falls into separate fields from the typical Mogok metamorphic fields. The high Ga/Mg ratios (46–521 lie well within the magmatic range (>6, and with other features suggest a potential skarn-like, carbonate-related genesis with a high degree of magmatic fluid input The overall trace element results widen the range of different signatures identified within Mogok gem corundum suites and indicate complex genesis. The expanded geochemical platform, related to a variety of metamorphic, metasomatic and magmatic sources, now provides a wider base for geographic typing of Mogok gem corundum suites. It allows more detailed comparisons with suites from other deposits and will assist identification of Mogok gem corundum sources used in jewelry.

  5. Generation of continuous-wave single-frequency 1.5 W 378 nm radiation by frequency doubling of a Ti:sapphire laser.

    Science.gov (United States)

    Cha, Yong-Ho; Ko, Kwang-Hoon; Lim, Gwon; Han, Jae-Min; Park, Hyun-Min; Kim, Taek-Soo; Jeong, Do-Young

    2010-03-20

    We have generated continuous-wave single-frequency 1.5 W 378 nm radiation by frequency doubling a high-power Ti:sapphire laser in an external enhancement cavity. An LBO crystal that is Brewster-cut and antireflection coated on both ends is used for a long-term stable frequency doubling. By optimizing the input coupler's reflectivity, we could generate 1.5 W 378 nm radiation from a 5 W 756 nm Ti:sapphire laser. According to our knowledge, this is the highest CW frequency-doubled power of a Ti:sapphire laser.

  6. Examples of Vector Velocity Imaging

    DEFF Research Database (Denmark)

    Hansen, Peter M.; Pedersen, Mads M.; Hansen, Kristoffer L.

    2011-01-01

    To measure blood flow velocity in vessels with conventional ultrasound, the velocity is estimated along the direction of the emitted ultrasound wave. It is therefore impossible to obtain accurate information on blood flow velocity and direction, when the angle between blood flow and ultrasound wa...

  7. Interface waves propagating along tensile fractures in dolomite

    International Nuclear Information System (INIS)

    Roy, S.; Pyrak-Nolte, L.J.

    1995-01-01

    Elastic interface waves have been observed in induced tensile fractures in dolomite rock cores. Multiscaling wavelet analysis distinguishes the interface wave from bulk shear waves, quantifies the interface wave spectral content, and determines the arrival time of peak energy. The dominant seismic energy is concentrated in the slow interface wave, with little or no detectable energy in the fast wave. As stress across the fracture increases, the slow interface wave velocity increases, and the frequency of the spectral peak shifts to higher frequencies. The shear dynamic specific stiffness of the fracture was calculated from the peak energy arrival time as a function of stress. 13 refs., 5 figs., 1 tab

  8. Frequency-doubled DBR-tapered diode laser for direct pumping of Ti:sapphire lasers generating sub-20 fs pulses

    DEFF Research Database (Denmark)

    Müller, André; Jensen, Ole Bjarlin; Unterhuber, Angelika

    2011-01-01

    For the first time a single-pass frequency doubled DBR-tapered diode laser suitable for pumping Ti:sapphire lasers generating ultrashort pulses is demonstrated. The maximum output powers achieved when pumping the Ti:sapphire laser are 110 mW (CW) and 82 mW (mode-locked) respectively at 1.2 W...... of pump power. This corresponds to a reduction in optical conversion efficiencies to 75% of the values achieved with a commercial diode pumped solid-state laser. However, the superior electro-optical efficiency of the diode laser improves the overall efficiency of the Ti:sapphire laser by a factor > 2....... The optical spectrum emitted by the Ti:sapphire laser when pumped with our diode laser shows a spectral width of 112 nm (FWHM). Based on autocorrelation measurements, pulse widths of less than 20 fs can therefore be expected....

  9. Frequency-doubled DBR-tapered diode laser for direct pumping of Ti:sapphire lasers generating sub-20 fs pulses.

    Science.gov (United States)

    Müller, André; Jensen, Ole Bjarlin; Unterhuber, Angelika; Le, Tuan; Stingl, Andreas; Hasler, Karl-Heinz; Sumpf, Bernd; Erbert, Götz; Andersen, Peter E; Petersen, Paul Michael

    2011-06-20

    For the first time a single-pass frequency doubled DBR-tapered diode laser suitable for pumping Ti:sapphire lasers generating ultrashort pulses is demonstrated. The maximum output powers achieved when pumping the Ti:sapphire laser are 110 mW (CW) and 82 mW (mode-locked) respectively at 1.2 W of pump power. This corresponds to a reduction in optical conversion efficiencies to 75% of the values achieved with a commercial diode pumped solid-state laser. However, the superior electro-optical efficiency of the diode laser improves the overall efficiency of the Ti:sapphire laser by a factor > 2. The optical spectrum emitted by the Ti:sapphire laser when pumped with our diode laser shows a spectral width of 112 nm (FWHM). Based on autocorrelation measurements, pulse widths of less than 20 fs can therefore be expected.

  10. Characteristics of a Ti:sapphire laser pumped by a Nd:YAG laser and its analysis. Nd:YAG laser reiki Ti:sapphire laser no dosa tokusei to sono kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Okada, T.; Masumoto, J.; Mizunami, T.; Maeda, M.; Muraoka, K. (Kyushu Univ., Fukuoka (Japan). Faculty of Engineering)

    1991-06-29

    Although Ti: Sapphire expects of a possibility of being a light source much superior to a dye laser having been used as a wavelength variable laser for spectral analyses, it has a limitation that it does not oscillate directly in the visible and ultraviolet regions. In order to develop a light source that is synchronizable over ultraviolet-near infrared regions, by means of combining a Ti: Sapphire laser of a high peak power, comprising an oscillator and a multistage amplifier, with a non-linear frequency conversion method for harmonic generation and Raman conversion, a prototype Ti:Sapphire laser that is excited by YAG laser second harmonic, and that synchronizes with a prism was fabricated, and its operational characteristics were investigated. As a result, an output energy of 35.6 mJ at a maximum was obtained at a wavelength of 773 nm against an excitation energy of 129 mJ, a conversion efficiency of 38.2% was obtained against the absorption energy of the crystals, and a continuous synchronism was achieved over 750 to 900 nm. 4 refs., 9 figs., 1 tab.

  11. Crystal Structure and Ferroelectric Properties of ε-Ga2O3 Films Grown on (0001)-Sapphire.

    Science.gov (United States)

    Mezzadri, Francesco; Calestani, Gianluca; Boschi, Francesco; Delmonte, Davide; Bosi, Matteo; Fornari, Roberto

    2016-11-21

    The crystal structure and ferroelectric properties of ε-Ga 2 O 3 deposited by low-temperature MOCVD on (0001)-sapphire were investigated by single-crystal X-ray diffraction and the dynamic hysteresis measurement technique. A thorough investigation of this relatively unknown polymorph of Ga 2 O 3 showed that it is composed of layers of both octahedrally and tetrahedrally coordinated Ga 3+ sites, which appear to be occupied with a 66% probability. The refinement of the crystal structure in the noncentrosymmetric space group P6 3 mc pointed out the presence of uncompensated electrical dipoles suggesting ferroelectric properties, which were finally demonstrated by independent measurements of the ferroelectric hysteresis. A clear epitaxial relation is observed with respect to the c-oriented sapphire substrate, with the Ga 2 O 3 [10-10] direction being parallel to the Al 2 O 3 direction [11-20], yielding a lattice mismatch of about 4.1%.

  12. An All-Solid-State High Repetiton Rate Titanium:Sapphire Laser System For Resonance Ionization Laser Ion Sources

    Science.gov (United States)

    Mattolat, C.; Rothe, S.; Schwellnus, F.; Gottwald, T.; Raeder, S.; Wendt, K.

    2009-03-01

    On-line production facilities for radioactive isotopes nowadays heavily rely on resonance ionization laser ion sources due to their demonstrated unsurpassed efficiency and elemental selectivity. Powerful high repetition rate tunable pulsed dye or Ti:sapphire lasers can be used for this purpose. To counteract limitations of short pulse pump lasers, as needed for dye laser pumping, i.e. copper vapor lasers, which include high maintenance and nevertheless often only imperfect reliability, an all-solid-state Nd:YAG pumped Ti:sapphire laser system has been constructed. This could complement or even replace dye laser systems, eliminating their disadvantages but on the other hand introduce shortcomings on the side of the available wavelength range. Pros and cons of these developments will be discussed.

  13. In situ observation of Ag-Cu-Ti liquid alloy/solid oxide interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Durov, O.V. [Frantsevich Institute for Problems of Materials Science of NASU, 3 Krzhyzhanovsky Street, Kiev 142, 03680 (Ukraine)], E-mail: avdu@ukr.net; Krasovskyy, V.P. [Frantsevich Institute for Problems of Materials Science of NASU, 3 Krzhyzhanovsky Street, Kiev 142, 03680 (Ukraine)

    2008-11-15

    In situ investigation methods are a very interesting means for understanding high-temperature interface processes. A method of direct observation of the interactions between transparent materials (Al{sub 2}O{sub 3}, SiO{sub 2}, CaF{sub 2}) and metal melts was elaborated. For the Ag-36.65 at.%Cu-8.15 at.%Ti/sapphire system, the formation of a dark compound at the interface was observed to occur at high temperature. This result does not confirm the conclusion of a neutron spectroscopy study which indicated that titanium oxides form at the interface only during solidification of the alloy. Interactions of the same alloy with SiO{sub 2} and CaF{sub 2} were also considered.

  14. Influences of oxygen gas flow rate on electrical properties of Ga-doped ZnO thin films deposited on glass and sapphire substrates

    International Nuclear Information System (INIS)

    Makino, Hisao; Song, Huaping; Yamamoto, Tetsuya

    2014-01-01

    The Ga-doped ZnO (GZO) films deposited on glass and c-plane sapphire substrates have been comparatively studied in order to explore the role of grain boundaries in electrical properties. The influences of oxygen gas flow rates (OFRs) during the deposition by ion-plating were examined. The dependences of carrier concentration, lattice parameters, and characteristic of thermal desorption of Zn on the OFR showed common features between glass and sapphire substrates, however, the Hall mobility showed different behavior. The Hall mobility of GZO films on glass increased with increasing OFR of up to 15 sccm, and decreased with further increasing OFR. On the other hand, the Hall mobility of GZO films on c-sapphire increased for up to 25 sccm. The role of grain boundary in polycrystalline GZO films has been discussed. - Highlights: • Ga-doped ZnO films were deposited on glass and c-sapphire by ion-plating. • The epitaxial growth on c-sapphire was confirmed by X-ray diffraction. • Dependence of Hall mobility showed different tendency between glass and sapphire. • Grain boundaries influence transport properties at high O 2 gas flow rate

  15. Changing of micromorphology of silicon-on-sapphire epitaxial layer surface at irradiation by subthreshold energy X-radiation

    CERN Document Server

    Kiselev, A N; Skupov, V D; Filatov, D O

    2001-01-01

    The morphology of silicon-on-sapphire epitaxial layer surface after pulse irradiation by the X-rays with the energy of <= 140 keV is studied. The study on the irradiated material surface is carried out by the methods of the atomic force microscopy and ellipsometry. The average roughness value after irradiation constitutes 7 nm. The change in the films surface microrelief occurs due to reconstruction of their dislocation structure under the action of elastic waves, originating in the X radiation

  16. Unusual ruby-sapphire transition in alluvial megacrysts, Cenozoic basaltic gem field, New England, New South Wales, Australia

    Science.gov (United States)

    Sutherland, Frederick L.; Graham, Ian T.; Harris, Stephen J.; Coldham, Terry; Powell, William; Belousova, Elena A.; Martin, Laure

    2017-05-01

    Rare ruby crystals appear among prevailing sapphire crystals mined from placers within basaltic areas in the New England gem-field, New South Wales, Australia. New England ruby (NER) has distinctive trace element features compared to those from ruby elsewhere in Australia and indeed most ruby from across the world. The NER suite includes ruby (up to 3370 ppm Cr), pink sapphire (up to 1520 ppm Cr), white sapphire (up to 910 ppm) and violet, mauve, purple, or bluish sapphire (up to 1410 ppm Cr). Some crystals show outward growth banding in this respective colour sequence. All four colour zones are notably high in Ga (up to 310 ppm) and Si (up to 1820 ppm). High Ga and Ga/Mg values are unusual in ruby and its trace element plots (laser ablation-inductively coupled plasma-mass spectrometry) and suggests that magmatic-metasomatic inputs were involved in the NER suite genesis. In situ oxygen isotope analyses (secondary ion mass spectrometry) across the NER suite colour range showed little variation (n = 22; δ18O = 4.4 ± 0.4, 2σ error), and are values typical for corundum associated with ultramafic/mafic rocks. The isolated NER xenocryst suite, corroded by basalt transport and with few internal inclusions, presents a challenge in deciphering its exact origin. Detailed consideration of its high Ga chemistry in relation to the known geology of the surrounding region was used to narrow down potential sources. These include Late Palaeozoic-Triassic fractionated I-type granitoid magmas or Mesozoic-Cenozoic felsic fractionates from basaltic magmas that interacted with early Palaeozoic Cr-bearing ophiolite bodies in the New England Orogen. Other potential sources may lie deeper within lower crust-mantle metamorphic assemblages, but need to match the anomalous high-Ga geochemistry of the New England ruby suite.

  17. Micro-Structured Sapphire Fiber Sensors for Simultaneous Measurements of High-T and Dynamic Gas Pressure in Harsh Environments

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Hai [Clemson Univ., SC (United States); Tsai, Hai-Lung [Missouri Univ. of Science and Technology, Rolla, MO (United States); Dong, Junhang [Univ. of Cincinnati, OH (United States)

    2014-09-30

    This is the final report for the program “Micro-Structured Sapphire Fiber Sensors for Simultaneous Measurements of High Temperature and Dynamic Gas Pressure in Harsh Environments”, funded by NETL, and performed by Missouri University of Science and Technology, Clemson University and University of Cincinnati from October 1, 2009 to September 30, 2014. Securing a sustainable energy economy by developing affordable and clean energy from coal and other fossil fuels is a central element to the mission of The U.S. Department of Energy’s (DOE) National Energy Technology Laboratory (NETL). To further this mission, NETL funds research and development of novel sensor technologies that can function under the extreme operating conditions often found in advanced power systems. The main objective of this research program is to conduct fundamental and applied research that will lead to successful development and demonstration of robust, multiplexed, microstructured silica and single-crystal sapphire fiber sensors to be deployed into the hot zones of advanced power and fuel systems for simultaneous measurements of high temperature and gas pressure. The specific objectives of this research program include: 1) Design, fabrication and demonstration of multiplexed, robust silica and sapphire fiber temperature and dynamic gas pressure sensors that can survive and maintain fully operational in high-temperature harsh environments. 2) Development and demonstration of a novel method to demodulate the multiplexed interferograms for simultaneous measurements of temperature and gas pressure in harsh environments. 3) Development and demonstration of novel sapphire fiber cladding and low numerical aperture (NA) excitation techniques to assure high signal integrity and sensor robustness.

  18. Quadrupolar interactions in non-cubic crystal and related extra heat capacities. Possible effects on a sapphire bolometer

    Energy Technology Data Exchange (ETDEWEB)

    Bassou, M. [Tunis Univ. (Tunisia)]|[CEA/DSM/DRECAM/SPEC, Gif-wur-Yvette (France); Rotter, M. [Karlova Univ., Prague (Czech Republic)]|[CEA/DSM/DRECAM/SPEC, Gif-wur-Yvette (France); Bernier, M. [CEA/DSM/DRECAM/SPEC, Gif-wur-Yvette (France); Chapellier, M. [CEA/DSM/DRECAM/SPEC, Gif-wur-Yvette (France)

    1996-02-11

    It is shown that in a non-cubic crystal, the extra heat capacity due to quadrupolar interaction of nuclear spins >1/2 could be much bigger than the phonon heat capacity when the temperature decreases. The possible coupling between quadrupolar and phonon heat reservoir via paramagnetic impurities is stressed. A NMR experiment done on sapphire is presented with an evaluation of the coupling between the two reservoirs and its consequence on the performance of the bolometer. (orig.).

  19. Quadrupolar interactions in non-cubic crystal and related extra heat capacities. Possible effects on a sapphire bolometer

    International Nuclear Information System (INIS)

    Bassou, M.; Rotter, M.; Bernier, M.; Chapellier, M.

    1996-01-01

    It is shown that in a non-cubic crystal, the extra heat capacity due to quadrupolar interaction of nuclear spins >1/2 could be much bigger than the phonon heat capacity when the temperature decreases. The possible coupling between quadrupolar and phonon heat reservoir via paramagnetic impurities is stressed. A NMR experiment done on sapphire is presented with an evaluation of the coupling between the two reservoirs and its consequence on the performance of the bolometer. (orig.)

  20. Characterization and growth mechanism of nonpolar and semipolar GaN layers grown on patterned sapphire substrates

    International Nuclear Information System (INIS)

    Okada, Narihito; Tadatomo, Kazuyuki

    2012-01-01

    Nonpolar and semipolar GaN layers with markedly improved crystalline quality can be obtained by selective-area growth from the sapphire sidewalls of patterned sapphire substrates (PSSs). In this paper, we review the crystalline qualities of GaN layers grown on PSSs and their growth mechanism. We grew semipolar {1 1 −2 2} and {1 0 −1 1} GaN layers on r- and n-PSSs. The crystalline qualities of the GaN layers grown on the PSSs were higher than those of GaN layers grown directly on heteroepitaxial substrates. To reveal the growth mechanism of GaN layers grown on PSSs, we also grew various nonpolar and semipolar GaN layers such as m-GaN on a-PSS, {1 1 −2 2} GaN on r-PSS, {1 0 − 1  1} GaN on n-PSS, m-GaN on c-PSS and a-GaN on m-PSS. It was found that the nucleation of GaN on the c-plane-like sapphire sidewall results in selective growth from the sapphire sidewall, and nonpolar or semipolar GaN can be obtained. Finally, we demonstrated a light-emitting diode fabricated on a {1 1 −2 2} GaN layer grown on an r-PSS. (paper)

  1. A phase stabilized and pulse shaped Ti:Sapphire oscillator-amplifier laser system for the LCLS rf photoinjector

    International Nuclear Information System (INIS)

    Kotseroglou, T.; Alley, R.; Clendenin, J.; Fisher, A.; Frisch, J.

    1998-04-01

    The authors have designed a laser system for the Linac Coherent Light Source rf photoinjector consisting of a Ti:Sapphire oscillator and 2 amplifiers using Chirped Pulse Amplification. The output after tripling will be 0.5 mJ tunable UV pulses at 120 Hz, with wavelength around 260 nm, pulsewidth of 10 ps FWHM and 200 fs rise and fall times. Amplitude stability is expected to be 1% rms in the UV and timing jitter better than 500 fs rms

  2. Crystal growth velocity in deeply undercooled Ni-Si alloys

    Science.gov (United States)

    Lü, Y. J.

    2012-02-01

    The crystal growth velocity of Ni95Si5 and Ni90Si10 alloys as a function of undercooling is investigated using molecular dynamics simulations. The modified imbedded atom method potential yields the equilibrium liquidus temperatures T L ≈ 1505 and 1387 K for Ni95Si5 and Ni90Si10 alloys, respectively. From the liquidus temperatures down to the deeply undercooled region, the crystal growth velocities of both the alloys rise to the maximum with increasing undercooling and then drop slowly, whereas the athermal growth process presented in elemental Ni is not observed in Ni-Si alloys. Instead, the undercooling dependence of the growth velocity can be well-described by the diffusion-limited model, furthermore, the activation energy associated with the diffusion from melt to interface increases as the concentration increases from 5 to 10 at.% Si, resulting in the remarkable decrease of growth velocity.

  3. Development of an optimal velocity selection method with velocity obstacle

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Geuk; Oh, Jun Ho [KAIST, Daejeon (Korea, Republic of)

    2015-08-15

    The Velocity obstacle (VO) method is one of the most well-known methods for local path planning, allowing consideration of dynamic obstacles and unexpected obstacles. Typical VO methods separate a velocity map into a collision area and a collision-free area. A robot can avoid collisions by selecting its velocity from within the collision-free area. However, if there are numerous obstacles near a robot, the robot will have very few velocity candidates. In this paper, a method for choosing optimal velocity components using the concept of pass-time and vertical clearance is proposed for the efficient movement of a robot. The pass-time is the time required for a robot to pass by an obstacle. By generating a latticized available velocity map for a robot, each velocity component can be evaluated using a cost function that considers the pass-time and other aspects. From the output of the cost function, even a velocity component that will cause a collision in the future can be chosen as a final velocity if the pass-time is sufficiently long enough.

  4. Growth of vertically oriented InN nanorods from In-rich conditions on unintentionally patterned sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Terziyska, Penka T., E-mail: pterziy1@lakeheadu.ca [Semiconductor Research Laboratory, Department of Electrical Engineering, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1 (Canada); Butcher, Kenneth Scott A. [Semiconductor Research Laboratory, Department of Electrical Engineering, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1 (Canada); MEAglow Ltd., Box 398, 2400 Nipigon Road, Thunder Bay, ON P7C4W1 (Canada); Rafailov, Peter [Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia (Bulgaria); Alexandrov, Dimiter [Semiconductor Research Laboratory, Department of Electrical Engineering, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1 (Canada); MEAglow Ltd., Box 398, 2400 Nipigon Road, Thunder Bay, ON P7C4W1 (Canada)

    2015-10-30

    Highlights: • Vertical InN nanorods are grown on selective areas of sapphire substrates. • In metal droplets nucleate on the sharp needle apexes on the selective areas. • The preferred orientation and the growth direction of the nanorods are (0 0 0 1). • The nanorods grow from the supersaturated indium melt on their tops. - Abstract: Vertically oriented InN nanorods were grown on selective areas of unintentionally patterned c-oriented sapphire substrates exhibiting sharp needles that preferentially accommodate In-metal liquid droplets, using Migration Enhanced Afterglow (MEAglow) growth technique. We point out that the formation of AlN needles on selected areas can be reproduced intentionally by over-nitridation of unmasked areas of sapphire substrates. The liquid indium droplets serve as a self-catalyst and the nanorods grow from the supersaturated indium melt in the droplet in a vertical direction. X-ray diffraction measurements indicate the presence of hexagonal InN only, with preferred orientation along (0 0 0 1) crystal axis, and very good crystalline quality. The room temperature Raman spectrum shows the presence of the A{sub 1}(TO), E{sub 2}(high) and A{sub 1}(LO) phonon modes of the hexagonal InN.

  5. Green-diode-pumped femtosecond Ti:Sapphire laser with up to 450 mW average power.

    Science.gov (United States)

    Gürel, K; Wittwer, V J; Hoffmann, M; Saraceno, C J; Hakobyan, S; Resan, B; Rohrbacher, A; Weingarten, K; Schilt, S; Südmeyer, T

    2015-11-16

    We investigate power-scaling of green-diode-pumped Ti:Sapphire lasers in continuous-wave (CW) and mode-locked operation. In a first configuration with a total pump power of up to 2 W incident onto the crystal, we achieved a CW power of up to 440 mW and self-starting mode-locking with up to 200 mW average power in 68-fs pulses using semiconductor saturable absorber mirror (SESAM) as saturable absorber. In a second configuration with up to 3 W of pump power incident onto the crystal, we achieved up to 650 mW in CW operation and up to 450 mW in 58-fs pulses using Kerr-lens mode-locking (KLM). The shortest pulse duration was 39 fs, which was achieved at 350 mW average power using KLM. The mode-locked laser generates a pulse train at repetition rates around 400 MHz. No complex cooling system is required: neither the SESAM nor the Ti:Sapphire crystal is actively cooled, only air cooling is applied to the pump diodes using a small fan. Because of mass production for laser displays, we expect that prices for green laser diodes will become very favorable in the near future, opening the door for low-cost Ti:Sapphire lasers. This will be highly attractive for potential mass applications such as biomedical imaging and sensing.

  6. Ultrasensitive label-free detection of DNA hybridization by sapphire-based graphene field-effect transistor biosensor

    Science.gov (United States)

    Xu, Shicai; Jiang, Shouzhen; Zhang, Chao; Yue, Weiwei; Zou, Yan; Wang, Guiying; Liu, Huilan; Zhang, Xiumei; Li, Mingzhen; Zhu, Zhanshou; Wang, Jihua

    2018-01-01

    Graphene has attracted much attention in biosensing applications for its unique properties. Because of one-atom layer structure, every atom of graphene is exposed to the environment, making the electronic properties of graphene are very sensitive to charged analytes. Therefore, graphene is an ideal material for transistors in high-performance sensors. Chemical vapor deposition (CVD) method has been demonstrated the most successful method for fabricating large area graphene. However, the conventional CVD methods can only grow graphene on metallic substrate and the graphene has to be transferred to the insulating substrate for further device fabrication. The transfer process creates wrinkles, cracks, or tears on the graphene, which severely degrade electrical properties of graphene. These factors severely degrade the sensing performance of graphene. Here, we directly fabricated graphene on sapphire substrate by high temperature CVD without the use of metal catalysts. The sapphire-based graphene was patterned and make into a DNA biosensor in the configuration of field-effect transistor. The sensors show high performance and achieve the DNA detection sensitivity as low as 100 fM (10-13 M), which is at least 10 times lower than prior transferred CVD G-FET DNA sensors. The use of the sapphire-based G-FETs suggests a promising future for biosensing applications.

  7. High Transparent and Conductive TiO2/Ag/TiO2 Multilayer Electrode Films Deposited on Sapphire Substrate

    Science.gov (United States)

    Loka, Chadrasekhar; Moon, Sung Whan; Choi, YiSik; Lee, Kee-Sun

    2018-03-01

    Transparent conducting oxides attract intense interests due to its diverse industrial applications. In this study, we report sapphire substrate-based TiO2/Ag/TiO2 (TAT) multilayer structure of indium-free transparent conductive multilayer coatings. The TAT thin films were deposited at room temperature on sapphire substrates and a rigorous analysis has been presented on the electrical and optical properties of the films as a function of Ag thickness. The optical and electrical properties were mainly controlled by the Ag mid-layer thickness of the TAT tri-layer. The TAT films showed high luminous transmittance 84% at 550 nm along with noteworthy low electrical resistance 3.65 × 10-5 Ω-cm and sheet resistance of 3.77 Ω/square, which is better are than those of amorphous ITO films and any sapphire-based dielectric/metal/dielectric multilayer stack. The carrier concentration of the films was increased with respect to Ag thickness. We obtained highest Hackke's figure of merit 43.97 × 10-3 Ω-1 from the TAT multilayer thin film with a 16 nm thick Ag mid-layer.

  8. Airborne particulate concentration during laser hair removal: A comparison between cold sapphire with aqueous gel and cryogen skin cooling.

    Science.gov (United States)

    Ross, Edward V; Chuang, Gary S; Ortiz, Arisa E; Davenport, Scott A

    2018-04-01

    High concentrations of sub-micron nanoparticles have been shown to be released during laser hair removal (LHR) procedures. These emissions pose a potential biohazard to healthcare workers that have prolonged exposure to LHR plume. We sought to demonstrate that cold sapphire skin cooling done in contact mode might suppress plume dispersion during LHR. A total of 11 patients were recruited for laser hair removal. They were treated on the legs and axilla with a 755 or 1064 nm millisecond-domain laser equipped with either (i) cryogen spray (CSC); (ii) refrigerated air (RA); or (iii) contact cooling with sapphire (CC). Concentration of ultrafine nanoparticles <1 μm were measured just before and during LHR with the three respective cooling methods. For contact cooling (CC), counts remained at baseline levels, below 3,500 parts per cubic centimeter (ppc) for all treatments. In contrast, the CSC system produced large levels of plume, peaking at times to over 400,000 ppc. The CA cooled system produced intermediate levels of plume, about 35,000 ppc (or about 10× baseline). Cold Sapphire Skin cooling with gel suppresses plume during laser hair removal, potentially eliminating the need for smoke evacuators, custom ventilation systems, and respirators during LHR. Lasers Surg. Med. 50:280-283, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  9. MOVPE of InN films on GaN templates grown on sapphire and silicon(111) substrates

    International Nuclear Information System (INIS)

    Jamil, Muhammad; Arif, Ronald A.; Ee, Yik-Khoon; Tong, Hua; Tansu, Nelson; Higgins, John B.

    2008-01-01

    This paper reports the study of MOVPE of InN on GaN templates grown on sapphire and silicon(111) substrates. Thermodynamic analysis of MOVPE of InN performed using NH 3 as nitrogen source and the experimental findings support the droplet-free epitaxial growth of InN under high V/III ratios of input precursors. At a growth pressure of 500 Torr, the optimum growth temperature and V/III ratio of the InN film are 575-650 C and >3 x 10 5 , respectively. The surface RMS roughness of InN film grown GaN/sapphire template is ∝0.3 nm on 2 μm x 2 μm area, while the RMS roughness of the InN film grown on GaN/Si(111) templates is found as ∝0.7 nm. The X-ray diffraction (XRD) measurement reveals the (0002) texture of the InN film on GaN/sapphire template with a FWHM of 281 arcsec of the InN(0002) ω rocking curve. For the film grown on GaN/Si template under identical growth conditions, the XRD measurements show the presence of metallic In, in addition to the (0002) orientation of InN layer. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. The active control devices of the size of products based on sapphire measuring tips with three degrees of freedom

    Science.gov (United States)

    Leun, E. V.; Leun, V. I.; Sysoev, V. K.; Zanin, K. A.; Shulepov, A. V.; Vyatlev, P. A.

    2018-01-01

    The article presents the results of the calculation of the load capacity of the active control devices (ACD) sapphire tip, which showed nearly 30-fold margin of safety to shock loads and experimental researches in mechanical contact with 5 cogs cutter 15 mm in diameter rotating with a frequency of 1000 rpm, which confirmed the calculations, determined the surface roughness Rz of the contact area of no more than 0.15 μm. Conditions have been created for recording without distortion of the image through a sapphire tip in contact with the processed article. A ACD design with new functionality is proposed: with one, two and three degrees of freedom of the sapphire tip and allows measuring the taper of the article and measurements on the chord. It is shown that with the implementation of their fixed head like the frame of the gyroscope with the rotations around the axes OY and OZ. It is shown that the rotation of the tip around the axis OX can be replaced more convenient for the implementation of the angular offset of the transferred image due to rotation of the output end of the flexible optical waveguide relative to the input. This makes it possible to reduce the "blurring of the image" during registration of the fast moving product profile when the slope of the recorder lines coincides with the slope of the edges of the image elements of the selected moving elements of the article.

  11. The nucleation of HCl and Cl{sub 2}-based HVPE GaN on mis-oriented sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Bohnen, Tim; Dreumel, Gerbe W.G. van; Enckevort, Willem J.P. van; Ashraf, Hina; Jong, Aryan E.F. de; Hageman, Paul R.; Vlieg, Elias [IMM, Radboud University, Nijmegen (Netherlands); Weyher, Jan L. [Institute of High Pressure Physics, Polish Academy of Sciences, Warsaw (Poland)

    2010-07-15

    The nucleation of both classic HCl-based and novel Cl{sub 2{sup -}} based HVPE GaN on mis-oriented sapphire substrates was investigated. The use of Cl{sub 2}in HVPE increases the growth rate by a factor of 4-5 and strongly reduces the parasitic deposition, allowing for the growth of much thicker wafers than HCl-based HVPE. Morphological SEM surface studies of the HCl-based HVPE sample surface show that at 600 C a nanocrystalline layer is deposited on the sapphire. During the subsequent annealing phase, the morphology changes to a {mu}m-sized island structure. During overgrowth at 1080 C, the islands coalesce. Small voids or pinholes are then formed in between the coalescing GaN islands. These pinholes lead to numerous pits on the surface of the GaN at thicknesses of 5 {mu}m. The pits disappear during continued overgrowth and can no longer be found on the surface, when the GaN film reaches a thickness of 45 {mu}m. This particular coalescence mechanism also applies to Cl{sub 2}-based HVPE GaN on sapphire (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Gas Gun Studies of Interface Wear Effects

    Science.gov (United States)

    Jackson, Tyler; Kennedy, Greg; Thadhani, Naresh

    2011-06-01

    The characteristics of interface wear were studied by performing gas gun experiments at velocities up to 1 km/s. The approach involved developing coefficients of constitutive strength models for Al 6061 and OFHC-Cu, then using those to design die geometry for interface wear gas gun experiments. Taylor rod-on-anvil impact experiments were performed to obtain coefficients of the Johnson-Cook constitutive strength model by correlating experimentally obtained deformed states of impacted samples with those predicted using ANSYS AUTODYN hydrocode. Simulations were used with validated strength models to design geometry involving acceleration of Al rods through a copper concentric cylindrical angular extrusion die. Experiments were conducted using 7.62 mm and 80 mm diameter gas guns. Differences in the microstructure of the interface layer and microhardness values illustrate that stress-strain conditions produced during acceleration of Al through the hollow concentric copper die, at velocities less than 800 m/s, result in formation of a layer via solid state alloying due to severe plastic deformation, while higher velocities produce an interface layer consisting of melted and re-solidified aluminum.

  13. Efficient evaluation of epitaxial MoS2 on sapphire by direct band structure imaging

    Science.gov (United States)

    Kim, Hokwon; Dumcenco, Dumitru; Fregnaux, Mathieu; Benayad, Anass; Kung, Yen-Cheng; Kis, Andras; Renault, Olivier; Lanes Group, Epfl Team; Leti, Cea Team

    The electronic band structure evaluation of two-dimensional metal dichalcogenides is critical as the band structure can be greatly influenced by the film thickness, strain, and substrate. Here, we performed a direct measurement of the band structure of as-grown monolayer MoS2 on single crystalline sapphire by reciprocal-space photoelectron emission microscopy with a conventional laboratory ultra-violet He I light source. Arrays of gold electrodes were deposited onto the sample in order to avoid charging effects due to the insulating substrate. This allowed the high resolution mapping (ΔE = 0.2 eV Δk = 0.05 Å-1) of the valence states in momentum space down to 7 eV below the Fermi level. The high degree of the epitaxial alignment of the single crystalline MoS2 nuclei was verified by the direct momentum space imaging over a large area containing multiple nuclei. The derived values of the hole effective mass were 2.41 +/-0.05 m0 and 0.81 +/-0.05 m0, respectively at Γ and K points, consistent with the theoretical values of the freestanding monolayer MoS2 reported in the literature. HK acknowledges the french CEA Basic Technological Research program (RTB) for funding.

  14. Thermal plasma fabricated lithium niobate-tantalate films on sapphire substrate

    International Nuclear Information System (INIS)

    Kulinich, S.A.; Yoshida, T.; Yamamoto, H.; Terashima, K.

    2003-01-01

    We report the deposition of LiNb 1-x Ta x O 3 (0≤x≤1) films on (001) sapphire substrates in soft vacuum using a radio frequency thermal plasma. The growth rate, crystallinity, c-axis orientation, and surface roughness were examined as functions of substrate temperature, precursor feed rate, and substrate surface condition. The film Nb/Ta ratio was well controlled by using an appropriate uniform mixture of lithium-niobium and lithium-tantalum alkoxide solutions. The epitaxy and crystallinity of the films were much improved when the film growth rate was raised from 20 to 180-380 nm/min, where the films with the (006) rocking curve full width at half maximum values as low as 0.12 deg. -0.2 deg. could be produced. The film roughness could be reduced by using a liquid precursor with higher metal concentrations, achieving the root-mean-square value on the order of 5 nm. The refractive indices of the films are in good correspondence with their composition and crystallinity

  15. Optical properties tailoring by high fluence implantation of Ag ions on sapphire

    International Nuclear Information System (INIS)

    Marques, C.; Silva, R.C. da; Wemans, A.; Maneira, M.J.P.; Kozanecki, A.; Alves, E.

    2006-01-01

    Optical and structural properties of single crystalline α-Al 2 O 3 were changed by the implantation of high fluences of Ag ions. Colourless transparent (101-bar 0) sapphire samples were implanted at room temperature with 160keV silver ions and fluences up to 1x10 17 Agcm -2 . Surface amorphization is observed at the fluence of 6x10 16 Agcm -2 . Except for the lower fluences (below 6x10 16 Agcm -2 ) the optical absorption spectra reveal the presence of a band peaking in the region 450-500nm, depending on the retained fluence. This band has been attributed to the presence of silver colloids, being thus 1x10 16 Agcm -2 below the threshold for colloid formation during the implantation. Annealing in oxidizing atmosphere promotes the recrystallization along with segregation of Ag followed by loss through evaporation. Recrystallization is retarded for annealing in reducing atmosphere and the Ag profile displays now a double peak structure after evaporation. Playing with the implantation fluence, temperature and annealing atmosphere controllable shifts of the position and intensity of the optical bands in the visible were achieved

  16. Surface-Energy-Anisotropy-Induced Orientation Effects on RayleighInstabilities in Sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Santala, Melissa; Glaeser, Andreas M.

    2006-01-01

    Arrays of controlled-geometry, semi-infinite pore channels of systematically varied crystallographic orientation were introduced into undoped m-plane (10{bar 1}0) sapphire substrates using microfabrication techniques and ion-beam etching and subsequently internalized by solid-state diffusion bonding. A series of anneals at 1700 C caused the breakup of these channels into discrete pores via Rayleigh instabilities. In all cases, channels broke up with a characteristic wavelength larger than that expected for a material with isotropic surface energy, reflecting stabilization effects due to surface-energy anisotropy. The breakup wavelength and the time required for complete breakup varied significantly with channel orientation. For most orientations, the instability wavelength for channels of radius R was in the range of 13.2R-25R, and complete breakup occurred within 2-10 h. To first order, the anneal times for complete breakup scale with the square of the breakup wavelength. Channels oriented along a <11{bar 2}0> direction had a wavelength of {approx} 139R, and required 468 h for complete breakup. Cross-sectional analysis of channels oriented along a <11{bar 2}0> direction showed the channel to be completely bounded by stable c(0001), r{l_brace}{bar 1}012{r_brace}, and s{l_brace}10{bar 1}1{r_brace} facets.

  17. Mosaic Structure Characterization of the AlInN Layer Grown on Sapphire Substrate

    Directory of Open Access Journals (Sweden)

    Engin Arslan

    2014-01-01

    Full Text Available The 150 nm thick, (0001 orientated wurtzite-phase Al1−xInxN epitaxial layers were grown by metal organic chemical vapor deposition on GaN (2.3 µm template/(0001 sapphire substrate. The indium (x concentration of the Al1−xInxN epitaxial layers was changed as 0.04, 0.18, 0.20, 0.47, and 0.48. The Indium content (x, lattice parameters, and strain values in the AlInN layers were calculated from the reciprocal lattice mapping around symmetric (0002 and asymmetric (10–15 reflection of the AlInN and GaN layers. The mosaic structure characteristics of the AlInN layers, such as lateral and vertical coherence lengths, tilt and twist angle, heterogeneous strain, and dislocation densities (edge and screw type dislocations of the AlInN epilayers, were investigated by using high-resolution X-ray diffraction measurements and with a combination of Williamson-Hall plot and the fitting of twist angles.

  18. Atomic Step Formation on Sapphire Surface in Ultra-precision Manufacturing

    Science.gov (United States)

    Wang, Rongrong; Guo, Dan; Xie, Guoxin; Pan, Guoshun

    2016-01-01

    Surfaces with controlled atomic step structures as substrates are highly relevant to desirable performances of materials grown on them, such as light emitting diode (LED) epitaxial layers, nanotubes and nanoribbons. However, very limited attention has been paid to the step formation in manufacturing process. In the present work, investigations have been conducted into this step formation mechanism on the sapphire c (0001) surface by using both experiments and simulations. The step evolutions at different stages in the polishing process were investigated with atomic force microscopy (AFM) and high resolution transmission electron microscopy (HRTEM). The simulation of idealized steps was constructed theoretically on the basis of experimental results. It was found that (1) the subtle atomic structures (e.g., steps with different sawteeth, as well as steps with straight and zigzag edges), (2) the periodicity and (3) the degree of order of the steps were all dependent on surface composition and miscut direction (step edge direction). A comparison between experimental results and idealized step models of different surface compositions has been made. It has been found that the structure on the polished surface was in accordance with some surface compositions (the model of single-atom steps: Al steps or O steps). PMID:27444267

  19. Solid state dewetting and stress relaxation in a thin single crystalline Ni film on sapphire

    International Nuclear Information System (INIS)

    Rabkin, E.; Amram, D.; Alster, E.

    2014-01-01

    In this study, we deposited a 80 nm thick single crystalline Ni film on a sapphire substrate. Heat treatment of this film at 1000 °C followed by slow cooling resulted in the formation of faceted holes, star-like channel instabilities and faceted microwires. The ridges at the rims of faceted holes and channels exhibited a twinning orientation relationship with the rest of the film. A sub-nanometer-high hexagonal topography pattern on the surface of the unperturbed film was observed by atomic force microscopy. No such pattern was observed on the top facets of isolated Ni particles and hole ridges. We discuss the observed dewetting patterns in terms of the effects of Ni surface anisotropy and faceting on solid state dewetting. The hexagonal pattern on the surface of the unperturbed film was attributed to thermal stress relaxation in the film via dislocations glide. This work demonstrates that solid state dewetting of single crystalline metal films can be utilized for film patterning and for producing hierarchical surface topographies

  20. N-polar InGaN-based LEDs fabricated on sapphire via pulsed sputtering

    Science.gov (United States)

    Ueno, Kohei; Kishikawa, Eiji; Ohta, Jitsuo; Fujioka, Hiroshi

    2017-02-01

    High-quality N-polar GaN epitaxial films with an atomically flat surface were grown on sapphire (0001) via pulsed sputtering deposition, and their structural and electrical properties were investigated. The crystalline quality of N-polar GaN improves with increasing film thickness and the full width at half maximum values of the x-ray rocking curves for 0002 and 101 ¯ 2 diffraction were 313 and 394 arcsec, respectively, at the film thickness of 6 μ m . Repeatable p-type doping in N-polar GaN films was achieved using Mg dopant, and their hole concentration and mobility can be controlled in the range of 8 × 1016-2 × 1018 cm-3 and 2-9 cm2V-1s-1, respectively. The activation energy of Mg in N-polar GaN based on a temperature-dependent Hall measurement was estimated to be 161 meV, which is comparable to that of the Ga-polar GaN. Based on these results, we demonstrated the fabrication of N-polar InGaN-based light emitting diodes with the long wavelength up to 609 nm.

  1. N-polar InGaN-based LEDs fabricated on sapphire via pulsed sputtering

    Directory of Open Access Journals (Sweden)

    Kohei Ueno

    2017-02-01

    Full Text Available High-quality N-polar GaN epitaxial films with an atomically flat surface were grown on sapphire (0001 via pulsed sputtering deposition, and their structural and electrical properties were investigated. The crystalline quality of N-polar GaN improves with increasing film thickness and the full width at half maximum values of the x-ray rocking curves for 0002 and 101¯2 diffraction were 313 and 394 arcsec, respectively, at the film thickness of 6μm. Repeatable p-type doping in N-polar GaN films was achieved using Mg dopant, and their hole concentration and mobility can be controlled in the range of 8 × 1016–2 × 1018 cm−3 and 2–9 cm2V−1s−1, respectively. The activation energy of Mg in N-polar GaN based on a temperature-dependent Hall measurement was estimated to be 161 meV, which is comparable to that of the Ga-polar GaN. Based on these results, we demonstrated the fabrication of N-polar InGaN-based light emitting diodes with the long wavelength up to 609 nm.

  2. Sapphire capillaries for laser-driven wakefield acceleration in plasma. Fs-laser micromachining and characterization

    International Nuclear Information System (INIS)

    Schwinkendorf, Jan-Patrick

    2012-05-01

    Plasma wakefields are a promising approach for the acceleration of electrons with ultrahigh (10 to 100 GV/m) electric fields. Nowadays, high-intensity laser pulses are routinely utilized to excite these large-amplitude plasma waves. However, several detrimental effects such as laser diffraction, electron-wake dephasing and laser depletion may terminate the acceleration process. Two of these phenomena can be mitigated or avoided by the application of capillary waveguides, e.g. fabricated out of sapphire for longevity. Capillaries may compensate for laser diffraction like a fiber and allow for the creation of tapered gas-density profiles working against the dephasing between the accelerating wave and the particles. Additionally, they offer the possibility of controlled particle injection. This thesis is reporting on the set up of a laser for fs-micromachining of capillaries of almost arbitrary shapes and a test stand for density-profile characterization. These devices will permit the creation of tailored gas-density profiles for controlled electron injection and acceleration inside plasma.

  3. A sapphire monolithic differential accelerometer as core sensor for gravity gradiometric geophysical instrumentation

    Directory of Open Access Journals (Sweden)

    F. Mango

    2006-06-01

    Full Text Available Gradiometric gravimetry is a survey technique widely used in geological structure investigation. This work demonstrates the feasibility of a new class of low frequency accelerometers for geodynamics studies and space applications. We present the design features of a new low noise single-axis differential accelerometer; the sensor is suitable to be used in a Gravity Gradiometer (GG system for land geophysical survey and gravity gradient measurements. A resolution of 1 Eötvös (1 Eö=10?9s?2 at one sample per second is achievable in a compact, lightweight (less than 2 kg portable instrument, operating at room temperature. The basic components of the sensor are two identical rigidly connected accelerometers separated by a 15-cm baseline vector and the useful signal is extracted as the subtraction of the two outputs, by means of an interferometric microwave readout system. The structure will be engraved in a monocrystal of sapphire by means of Computer-Numerically-Controlled (CNC ultrasonic machining: the material was chosen because of its unique mix of outstanding mechanical and dielectric properties.

  4. Infrared Reflectance Analysis of Epitaxial n-Type Doped GaN Layers Grown on Sapphire.

    Science.gov (United States)

    Tsykaniuk, Bogdan I; Nikolenko, Andrii S; Strelchuk, Viktor V; Naseka, Viktor M; Mazur, Yuriy I; Ware, Morgan E; DeCuir, Eric A; Sadovyi, Bogdan; Weyher, Jan L; Jakiela, Rafal; Salamo, Gregory J; Belyaev, Alexander E

    2017-12-01

    Infrared (IR) reflectance spectroscopy is applied to study Si-doped multilayer n + /n 0 /n + -GaN structure grown on GaN buffer with GaN-template/sapphire substrate. Analysis of the investigated structure by photo-etching, SEM, and SIMS methods showed the existence of the additional layer with the drastic difference in Si and O doping levels and located between the epitaxial GaN buffer and template. Simulation of the experimental reflectivity spectra was performed in a wide frequency range. It is shown that the modeling of IR reflectance spectrum using 2 × 2 transfer matrix method and including into analysis the additional layer make it possible to obtain the best fitting of the experimental spectrum, which follows in the evaluation of GaN layer thicknesses which are in good agreement with the SEM and SIMS data. Spectral dependence of plasmon-LO-phonon coupled modes for each GaN layer is obtained from the spectral dependence of dielectric of Si doping impurity, which is attributed to compensation effects by the acceptor states.

  5. Neutron irradiation of sapphire for compressive strengthening. II. Physical properties changes

    Energy Technology Data Exchange (ETDEWEB)

    Regan, Thomas M. E-mail: thomas_regan@uml.edu; Harris, Daniel C. E-mail: harrisdc@navair.navy.mil; Blodgett, David W.; Baldwin, Kevin C.; Miragliotta, Joseph A.; Thomas, Michael E.; Linevsky, Milton J.; Giles, John W.; Kennedy, Thomas A.; Fatemi, Mohammad; Black, David R.; Lagerloef, K. Peter D

    2002-01-01

    Irradiation of sapphire with fast neutrons (0.8-10 MeV) at a fluence of 10{sup 22}/m{sup 2} increased the c-axis compressive strength and the c-plane biaxial flexure strength at 600 deg. C by a factor of {approx}2.5. Both effects are attributed to inhibition of r-plane twin propagation by damage clusters resulting from neutron impact. The a-plane biaxial flexure strength and four-point flexure strength in the c- and m-directions decreased by 10-23% at 600 deg. C after neutron irradiation. Neutron irradiation had little or no effect on thermal conductivity, infrared absorption, elastic constants, hardness, and fracture toughness. A featureless electron paramagnetic resonance signal at g=2.02 was correlated with the strength increase: This signal grew in amplitude with increasing neutron irradiation, which also increased the compressive strength. Annealing conditions that reversed the strengthening also annihilated the g=2.02 signal. A signal associated with a paramagnetic center containing two Al nuclei was not correlated with strength. Ultraviolet and visible color centers also were not correlated with strength in that they could be removed by annealing at temperatures that were too low to reverse the compressive strengthening effect of neutron irradiation.

  6. Sapphire capillaries for laser-driven wakefield acceleration in plasma. Fs-laser micromachining and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Schwinkendorf, Jan-Patrick

    2012-08-15

    Plasma wakefields are a promising approach for the acceleration of electrons with ultrahigh (10 to 100 GV/m) electric fields. Nowadays, high-intensity laser pulses are routinely utilized to excite these large-amplitude plasma waves. However, several detrimental effects such as laser diffraction, electron-wake dephasing and laser depletion may terminate the acceleration process. Two of these phenomena can be mitigated or avoided by the application of capillary waveguides, e.g. fabricated out of sapphire for longevity. Capillaries may compensate for laser diffraction like a fiber and allow for the creation of tapered gas-density profiles working against the dephasing between the accelerating wave and the particles. Additionally, they offer the possibility of controlled particle injection. This thesis is reporting on the set up of a laser for fs-micromachining of capillaries of almost arbitrary shapes and a test stand for density-profile characterization. These devices will permit the creation of tailored gas-density profiles for controlled electron injection and acceleration inside plasma.

  7. Slow rupture of frictional interfaces

    Science.gov (United States)

    Bar Sinai, Yohai; Brener, Efim A.; Bouchbinder, Eran

    2012-02-01

    The failure of frictional interfaces and the spatiotemporal structures that accompany it are central to a wide range of geophysical, physical and engineering systems. Recent geophysical and laboratory observations indicated that interfacial failure can be mediated by slow slip rupture phenomena which are distinct from ordinary, earthquake-like, fast rupture. These discoveries have influenced the way we think about frictional motion, yet the nature and properties of slow rupture are not completely understood. We show that slow rupture is an intrinsic and robust property of simple non-monotonic rate-and-state friction laws. It is associated with a new velocity scale cmin, determined by the friction law, below which steady state rupture cannot propagate. We further show that rupture can occur in a continuum of states, spanning a wide range of velocities from cmin to elastic wave-speeds, and predict different properties for slow rupture and ordinary fast rupture. Our results are qualitatively consistent with recent high-resolution laboratory experiments and may provide a theoretical framework for understanding slow rupture phenomena along frictional interfaces.

  8. Control rod velocity limiter

    International Nuclear Information System (INIS)

    Cearley, J.E.; Carruth, J.C.; Dixon, R.C.; Spencer, S.S.; Zuloaga, J.A. Jr.

    1986-01-01

    This patent describes a velocity control arrangement for a reciprocable, vertically oriented control rod for use in a nuclear reactor in a fluid medium, the control rod including a drive hub secured to and extending from one end therefrom. The control device comprises: a toroidally shaped control member spaced from and coaxially positioned around the hub and secured thereto by a plurality of spaced radial webs thereby providing an annular passage for fluid intermediate the hub and the toroidal member spaced therefrom in coaxial position. The side of the control member toward the control rod has a smooth generally conical surface. The side of the control member away from the control rod is formed with a concave surface constituting a single annular groove. The device also comprises inner and outer annular vanes radially spaced from one another and spaced from the side of the control member away from the control rod and positioned coaxially around and spaced from the hub and secured thereto by spaced radial webs thereby providing an annular passage for fluid intermediate the hub and the vanes. The vanes are angled toward the control member, the outer edge of the inner vane being closer to the control member and the inner edge of the outer vane being closer to the control member. When the control rod moves in the fluid in the direction toward the drive hub the vanes direct a flow of fluid turbulence which provides greater resistance to movement of the control rod in the direction toward the drive hub than in the other direction

  9. Velocity Dispersions Across Bulge Types

    International Nuclear Information System (INIS)

    Fabricius, Maximilian; Bender, Ralf; Hopp, Ulrich; Saglia, Roberto; Drory, Niv; Fisher, David

    2010-01-01

    We present first results from a long-slit spectroscopic survey of bulge kinematics in local spiral galaxies. Our optical spectra were obtained at the Hobby-Eberly Telescope with the LRS spectrograph and have a velocity resolution of 45 km/s (σ*), which allows us to resolve the velocity dispersions in the bulge regions of most objects in our sample. We find that the velocity dispersion profiles in morphological classical bulge galaxies are always centrally peaked while the velocity dispersion of morphologically disk-like bulges stays relatively flat towards the center--once strongly barred galaxies are discarded.

  10. PREFACE: Water at interfaces Water at interfaces

    Science.gov (United States)

    Gallo, P.; Rovere, M.

    2010-07-01

    This special issue is devoted to illustrating important aspects and significant results in the field of modeling and simulation of water at interfaces with solutes or with confining substrates, focusing on a range of temperatures from ambient to supercooled. Understanding the behavior of water, in contact with different substrates and/or in solutions, is of pivotal importance for a wide range of applications in physics, chemistry and biochemistry. Simulations of confined and/or interfacial water are also relevant for testing how different its behavior is with respect to bulk water. Simulations and modeling in this field are of particular importance when studying supercooled regions where water shows anomalous properties. These considerations motivated the organization of a workshop at CECAM in the summer of 2009 which aimed to bring together scientists working with computer simulations on the properties of water in various environments with different methodologies. In this special issue, we collected a variety of interesting contributions from some of the speakers of the workshop. We have roughly classified the contributions into four groups. The papers of the first group address the properties of interfacial and confined water upon supercooling in an effort to understand the relation with anomalous behavior of supercooled bulk water. The second group deals with the specific problem of solvation. The next group deals with water in different environments by considering problems of great importance in technological and biological applications. Finally, the last group deals with quantum mechanical calculations related to the role of water in chemical processes. The first group of papers is introduced by the general paper of Stanley et al. The authors discuss recent progress in understanding the anomalies of water in bulk, nanoconfined, and biological environments. They present evidence that liquid water may display 'polymorphism', a property that can be present in

  11. Measurement of sound velocity profiles in fluids for process monitoring

    International Nuclear Information System (INIS)

    Wolf, M; Kühnicke, E; Lenz, M; Bock, M

    2012-01-01

    In ultrasonic measurements, the time of flight to the object interface is often the only information that is analysed. Conventionally it is only possible to determine distances or sound velocities if the other value is known. The current paper deals with a novel method to measure the sound propagation path length and the sound velocity in media with moving scattering particles simultaneously. Since the focal position also depends on sound velocity, it can be used as a second parameter. Via calibration curves it is possible to determine the focal position and sound velocity from the measured time of flight to the focus, which is correlated to the maximum of averaged echo signal amplitude. To move focal position along the acoustic axis, an annular array is used. This allows measuring sound velocity locally resolved without any previous knowledge of the acoustic media and without a reference reflector. In previous publications the functional efficiency of this method was shown for media with constant velocities. In this work the accuracy of these measurements is improved. Furthermore first measurements and simulations are introduced for non-homogeneous media. Therefore an experimental set-up was created to generate a linear temperature gradient, which also causes a gradient of sound velocity.

  12. Effect of Interface Nanotexture on Light Extraction of InGaN-Based Green Light Emitting Diodes

    International Nuclear Information System (INIS)

    Yao-Bo, Pan; Sheng-Li, Qi; Hao, Fang; Guo-Yi, Zhang; Mao-Sheng, Hao

    2010-01-01

    We report the enhancement of the light extraction of InGaN-based green light emitting diodes (LEDs) via the interface nanotexturing. The texture consists of high-density nanocraters on the surface of a sapphire substrate with an in situ etching. The width of nanocraters is about 0.5 μm and the depth is around 0.1 μm. It is demonstrated that the LEDs with interface texture exhibit about a 27% improvement in luminance intensity, compared with standard LEDs. High power InGaN-based green LEDs are obtained by using the interface nanotexture. An optical ray-tracing simulation is performed to investigate the effect of interface nanotexture on light extraction. (cross-disciplinary physics and related areas of science and technology)

  13. On linear relationship between shock velocity and particle velocity

    International Nuclear Information System (INIS)

    Dandache, H.

    1986-11-01

    We attempt to derive the linear relationship between shock velocity U s and particle velocity U p from thermodynamic considerations, taking into account an ideal gas equation of state and a Mie-Grueneisen equation of state for solids. 23 refs

  14. Sodium Velocity Maps on Mercury

    Science.gov (United States)

    Potter, A. E.; Killen, R. M.

    2011-01-01

    The objective of the current work was to measure two-dimensional maps of sodium velocities on the Mercury surface and examine the maps for evidence of sources or sinks of sodium on the surface. The McMath-Pierce Solar Telescope and the Stellar Spectrograph were used to measure Mercury spectra that were sampled at 7 milliAngstrom intervals. Observations were made each day during the period October 5-9, 2010. The dawn terminator was in view during that time. The velocity shift of the centroid of the Mercury emission line was measured relative to the solar sodium Fraunhofer line corrected for radial velocity of the Earth. The difference between the observed and calculated velocity shift was taken to be the velocity vector of the sodium relative to Earth. For each position of the spectrograph slit, a line of velocities across the planet was measured. Then, the spectrograph slit was stepped over the surface of Mercury at 1 arc second intervals. The position of Mercury was stabilized by an adaptive optics system. The collection of lines were assembled into an images of surface reflection, sodium emission intensities, and Earthward velocities over the surface of Mercury. The velocity map shows patches of higher velocity in the southern hemisphere, suggesting the existence of sodium sources there. The peak earthward velocity occurs in the equatorial region, and extends to the terminator. Since this was a dawn terminator, this might be an indication of dawn evaporation of sodium. Leblanc et al. (2008) have published a velocity map that is similar.

  15. 16 CFR 23.23 - Misuse of the words “ruby,” “sapphire,” “emerald,” “topaz,” “stone,” “birthstone,” “gemstone,” etc.

    Science.gov (United States)

    2010-01-01

    ... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Misuse of the words âruby,â âsapphire,â... PEWTER INDUSTRIES § 23.23 Misuse of the words “ruby,” “sapphire,” “emerald,” “topaz,” “stone,” “birthstone,” “gemstone,” etc. (a) It is unfair or deceptive to use the unqualified words “ruby,” “sapphire...

  16. Interface Simulation Distances

    Directory of Open Access Journals (Sweden)

    Pavol Černý

    2012-10-01

    Full Text Available The classical (boolean notion of refinement for behavioral interfaces of system components is the alternating refinement preorder. In this paper, we define a distance for interfaces, called interface simulation distance. It makes the alternating refinement preorder quantitative by, intuitively, tolerating errors (while counting them in the alternating simulation game. We show that the interface simulation distance satisfies the triangle inequality, that the distance between two interfaces does not increase under parallel composition with a third interface, and that the distance between two interfaces can be bounded from above and below by distances between abstractions of the two interfaces. We illustrate the framework, and the properties of the distances under composition of interfaces, with two case studies.

  17. Introduction to vector velocity imaging

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Udesen, Jesper; Hansen, Kristoffer Lindskov

    Current ultrasound scanners can only estimate the velocity along the ultrasound beam and this gives rise to the cos() factor on all velocity estimates. This is a major limitation as most vessels are close to perpendicular to the beam. Also the angle varies as a function of space and time making ...

  18. Railgun armature velocity improvement, SBIR phase 2

    Science.gov (United States)

    Thurmond, Leo E.; Bauer, David P.

    1992-08-01

    Railgun hypervelocity performance has not been repeatably demonstrated at velocities over 6 km/s. A significant performance limiting phenomena is the formation of secondary current paths in parallel with the main projectile accelerating plasma. A confined plasma armature technique was developed to prevent secondary armature formation. Confinement prevents loss of ionized material from the plasma armature and thereby prevents formation of a low rail-to-rail conductance. We controlled pressure in the confined armature via controlled venting through ports in the rails. Railgun tests with the confined armature show that sealing at the rail-confinement vessel interface is critical and difficult to achieve. Our tests show that during low seal leakage operation secondaries are prevented. However, maintaining good seal for the entire launch is very difficult.

  19. Global catalog of earthquake rupture velocities shows anticorrelation between stress drop and rupture velocity

    Science.gov (United States)

    Chounet, Agnès; Vallée, Martin; Causse, Mathieu; Courboulex, Françoise

    2018-05-01

    Application of the SCARDEC method provides the apparent source time functions together with seismic moment, depth, and focal mechanism, for most of the recent earthquakes with magnitude larger than 5.6-6. Using this large dataset, we have developed a method to systematically invert for the rupture direction and average rupture velocity Vr, when unilateral rupture propagation dominates. The approach is applied to all the shallow (z earthquakes of the catalog over the 1992-2015 time period. After a careful validation process, rupture properties for a catalog of 96 earthquakes are obtained. The subsequent analysis of this catalog provides several insights about the seismic rupture process. We first report that up-dip ruptures are more abundant than down-dip ruptures for shallow subduction interface earthquakes, which can be understood as a consequence of the material contrast between the slab and the overriding crust. Rupture velocities, which are searched without any a-priori up to the maximal P wave velocity (6000-8000 m/s), are found between 1200 m/s and 4500 m/s. This observation indicates that no earthquakes propagate over long distances with rupture velocity approaching the P wave velocity. Among the 23 ruptures faster than 3100 m/s, we observe both documented supershear ruptures (e.g. the 2001 Kunlun earthquake), and undocumented ruptures that very likely include a supershear phase. We also find that the correlation of Vr with the source duration scaled to the seismic moment (Ts) is very weak. This directly implies that both Ts and Vr are anticorrelated with the stress drop Δσ. This result has implications for the assessment of the peak ground acceleration (PGA) variability. As shown by Causse and Song (2015), an anticorrelation between Δσ and Vr significantly reduces the predicted PGA variability, and brings it closer to the observed variability.

  20. Diffraction imaging and velocity analysis using oriented velocity continuation

    KAUST Repository

    Decker, Luke

    2014-08-05

    We perform seismic diffraction imaging and velocity analysis by separating diffractions from specular reflections and decomposing them into slope components. We image slope components using extrapolation in migration velocity in time-space-slope coordinates. The extrapolation is described by a convection-type partial differential equation and implemented efficiently in the Fourier domain. Synthetic and field data experiments show that the proposed algorithm is able to detect accurate time-migration velocities by automatically measuring the flatness of events in dip-angle gathers.

  1. Weight of Production of Emeralds, Rubies, Sapphires, and Tanzanite from 1995 Through 2005

    Science.gov (United States)

    Yager, Thomas R.; Menzie, W. David; Olson, Donald W.

    2008-01-01

    U.S. Geological Survey (USGS) historically has not attempted to report comprehensive world production of gemstones on a country basis. This was because estimation of gemstone production is inherently difficult due to the fragmentary nature of the industry, the lack of governmental oversight or reporting in many countries where colored gemstones are mined, and the wide variation in quality between individual gemstones. Unlike diamonds, which, with the exception of the alluvial stones of West Africa, are mainly produced by large international mining companies and evaluated, cut, and marketed through a highly developed pricing structure and complex commercial arrangements, colored gemstones are mainly mined by individuals or small companies and have less developed evaluation and marketing arrangements. The trading centers for colored gems are smaller and less well known than the diamond centers. Colored gemstones, like alluvial diamonds, have the potential to be used to fund civil conflicts and other illegal activities, and because trade in colored gemstones is less organized than that of diamonds, they offer less opportunity for effective regulation of their trade. And, like diamond, until the recent advent of the Kimberley Process no generally accepted estimates of colored gemstone production globally or by producing country have existed. The present paper is a first attempt to develop production statistics for the three precious gems -emeralds, rubies, and sapphires - and tanzanite tanzanite, a semi-precious gem. The data consist of the weight of production of each of the gemstones from 1995 through 2005. Preliminary data on the weights of gemstone production were presented as a poster session at the Gemological Institute of America's Gemological Research Conference in San Diego, CA, in 2006, and as a published abstract (Yager, 2006) in an attempt to gather response to the estimates. The USGS continues to welcome information and suggestions that would improve the

  2. The growth and characterization of well aligned RuO2 nanorods on sapphire substrates

    International Nuclear Information System (INIS)

    Chen, C C; Chen, R S; Tsai, T Y; Huang, Y S; Tsai, D S; Tiong, K K

    2004-01-01

    Self-assembled and well aligned RuO 2 nanorods (NRs) have been grown on sapphire (SA) substrates via metal-organic chemical vapour deposition (MOCVD), using bis(ethylcyclopentadienyl)ruthenium as the source reagent. The surface morphology, structural, and spectroscopic properties of the as-deposited NRs were characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected-area electron diffractometry (SAD), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and micro-Raman spectroscopy. FESEM micrographs reveal that vertically aligned nanorods (NRs) were grown on SA(100), while the NRs on the SA(012) were grown with a tilt angle of ∼ 35 degrees from the normal to the substrates. TEM and SAD measurements showed that the RuO 2 NRs with square cross-section have the long axis directed along the [001] direction. The XRD results indicate that the RuO 2 NRs are (002) oriented on SA(100) and (101) oriented on SA(012) substrates. A strong substrate effect on the alignment of the RuO 2 NRs growth has been demonstrated and the probable mechanism for the formation of these NRs has been discussed. XP spectra show the coexistence of higher oxidation state of ruthenium in the as-grown RuO 2 NRs. Micro-Raman spectra show the red-shift and peak broadening of the RuO 2 signatures with respect to that of the bulk counterpart which may be indicative of a phonon confinement effect for these NRs

  3. Radial velocity asymmetries from jets with variable velocity profiles

    International Nuclear Information System (INIS)

    Cerqueira, A. H.; Vasconcelos, M. J.; Velazquez, P. F.; Raga, A. C.; De Colle, F.

    2006-01-01

    We have computed a set of 3-D numerical simulations of radiatively cooling jets including variabilities in both the ejection direction (precession) and the jet velocity (intermittence), using the Yguazu-a code. In order to investigate the effects of jet rotation on the shape of the line profiles, we also introduce an initial toroidal rotation velocity profile. Since the Yguazu-a code includes an atomic/ionic network, we are able to compute the emission coefficients for several emission lines, and we generate line profiles for the Hα, [O I]λ6300, [S II]λ6716 and [N II]λ6548 lines. Using initial parameters that are suitable for the DG Tau microjet, we show that the computed radial velocity shift for the medium-velocity component of the line profile as a function of distance from the jet axis is strikingly similar for rotating and non-rotating jet models

  4. Brain–muscle interface

    Indian Academy of Sciences (India)

    2011-05-16

    May 16, 2011 ... Clipboard: Brain–muscle interface: The next-generation BMI. Radhika Rajan Neeraj Jain ... Keywords. Assistive devices; brain–machine interface; motor cortex; paralysis; spinal cord injury ... Journal of Biosciences | News ...

  5. Occurrence and elimination of in-plane misoriented crystals in AlN epilayers on sapphire via pre-treatment control

    International Nuclear Information System (INIS)

    Wang Hu; Xiong Hui; Wu Zhi-Hao; Yu Chen-Hui; Tian Yu; Dai Jiang-Nan; Fang Yan-Yan; Zhang Jian-Bao; Chen Chang-Qing

    2014-01-01

    AlN epilayers are grown directly on sapphire (0001) substrates each of which has a low temperature AlN nucleation layer. The effects of pretreatments of sapphire substrates, including exposures to NH 3 /H 2 and to H 2 only ambients at different temperatures, before the growth of AlN epilayers is investigated. In-plane misoriented crystals occur in N-polar AlN epilayers each with pretreatment in a H 2 only ambient, and are characterized by six 60°-apart peaks with splits in each peak in (101-bar 2) phi scan and two sets of hexagonal diffraction patterns taken along the [0001] zone axis in electron diffraction. These misoriented crystals can be eliminated in AlN epilayers by the pretreatment of sapphire substrates in the NH 3 /H 2 ambient. AlN epilayers by the pretreatment of sapphire substrates in the NH 3 /H 2 ambient are Al-polar. Our results show the pretreatments and the nucleation layers are responsible for the polarities of the AlN epilayers. We ascribe these results to the different strain relaxation mechanisms induced by the lattice mismatch of AlN and sapphire. (interdisciplinary physics and related areas of science and technology)

  6. Transfer-free graphene synthesis on sapphire by catalyst metal agglomeration technique and demonstration of top-gate field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Miyoshi, Makoto, E-mail: miyoshi.makoto@nitech.ac.jp; Arima, Yukinori; Kubo, Toshiharu; Egawa, Takashi [Research Center for Nano Device and Advanced Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Mizuno, Masaya [Research Center for Nano Device and Advanced Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Soga, Tetsuo [Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

    2015-08-17

    Transfer-free graphene synthesis was performed on sapphire substrates by using the catalyst metal agglomeration technique, and the graphene film quality was compared to that synthesized on sputtered SiO{sub 2}/Si substrates. Raman scattering measurements indicated that the graphene film on sapphire has better structural qualities than that on sputtered SiO{sub 2}/Si substrates. The cross-sectional transmission microscopic study also revealed that the film flatness was drastically improved by using sapphire substrates instead of sputtered SiO{sub 2}/Si substrates. These quality improvements seemed to be due the chemical and thermal stabilities of sapphire. Top-gate field-effect transistors were fabricated using the graphene films on sapphire, and it was confirmed that their drain current can be modulated with applied gate voltages. The maximum field-effect mobilities were estimated to be 720 cm{sup 2}/V s for electrons and 880 cm{sup 2}/V s for holes, respectively.

  7. Transfer-free graphene synthesis on sapphire by catalyst metal agglomeration technique and demonstration of top-gate field-effect transistors

    International Nuclear Information System (INIS)

    Miyoshi, Makoto; Arima, Yukinori; Kubo, Toshiharu; Egawa, Takashi; Mizuno, Masaya; Soga, Tetsuo

    2015-01-01

    Transfer-free graphene synthesis was performed on sapphire substrates by using the catalyst metal agglomeration technique, and the graphene film quality was compared to that synthesized on sputtered SiO 2 /Si substrates. Raman scattering measurements indicated that the graphene film on sapphire has better structural qualities than that on sputtered SiO 2 /Si substrates. The cross-sectional transmission microscopic study also revealed that the film flatness was drastically improved by using sapphire substrates instead of sputtered SiO 2 /Si substrates. These quality improvements seemed to be due the chemical and thermal stabilities of sapphire. Top-gate field-effect transistors were fabricated using the graphene films on sapphire, and it was confirmed that their drain current can be modulated with applied gate voltages. The maximum field-effect mobilities were estimated to be 720 cm 2 /V s for electrons and 880 cm 2 /V s for holes, respectively

  8. Garbage collector interface

    OpenAIRE

    Ive, Anders; Blomdell, Anders; Ekman, Torbjörn; Henriksson, Roger; Nilsson, Anders; Nilsson, Klas; Robertz, Sven

    2002-01-01

    The purpose of the presented garbage collector interface is to provide a universal interface for many different implementations of garbage collectors. This is to simplify the integration and exchange of garbage collectors, but also to support incremental, non-conservative, and thread safe implementations. Due to the complexity of the interface, it is aimed at code generators and preprocessors. Experiences from ongoing implementations indicate that the garbage collector interface successfully ...

  9. Microcomputer interfacing and applications

    CERN Document Server

    Mustafa, M A

    1990-01-01

    This is the applications guide to interfacing microcomputers. It offers practical non-mathematical solutions to interfacing problems in many applications including data acquisition and control. Emphasis is given to the definition of the objectives of the interface, then comparing possible solutions and producing the best interface for every situation. Dr Mustafa A Mustafa is a senior designer of control equipment and has written many technical articles and papers on the subject of computers and their application to control engineering.

  10. Fractals control in particle's velocity

    International Nuclear Information System (INIS)

    Zhang Yongping; Liu Shutang; Shen Shulan

    2009-01-01

    Julia set, a fractal set of the literature of nonlinear physics, has significance for the engineering applications. For example, the fractal structure characteristics of the generalized M-J set could visually reflect the change rule of particle's velocity. According to the real world requirement, the system need show various particle's velocity in some cases. Thus, the control of the nonlinear behavior, i.e., Julia set, has attracted broad attention. In this work, an auxiliary feedback control is introduced to effectively control the Julia set that visually reflects the change rule of particle's velocity. It satisfies the performance requirement of the real world problems.

  11. Southern high-velocity stars

    International Nuclear Information System (INIS)

    Augensen, H.J.; Buscombe, W.

    1978-01-01

    Using the model of the Galaxy presented by Eggen, Lynden-Bell and Sandage (1962), plane galactic orbits have been calculated for 800 southern high-velocity stars which possess parallax, proper motion, and radial velocity data. The stars with trigonometric parallaxes were selected from Buscombe and Morris (1958), supplemented by more recent spectroscopic data. Photometric parallaxes from infrared color indices were used for bright red giants studied by Eggen (1970), and for red dwarfs for which Rodgers and Eggen (1974) determined radial velocities. A color-color diagram based on published values of (U-B) and (B-V) for most of these stars is shown. (Auth.)

  12. Subsonic leaky Rayleigh waves at liquid-solid interfaces.

    Science.gov (United States)

    Mozhaev, V G; Weihnacht, M

    2002-05-01

    The paper is devoted to the study of leaky Rayleigh waves at liquid-solid interfaces close to the border of the existence domain of these modes. The real and complex roots of the secular equation are computed for interface waves at the boundary between water and a binary isotropic alloy of gold and silver with continuously variable composition. The change of composition of the alloy allows one to cross a critical velocity for the existence of leaky waves. It is shown that, contrary to popular opinion, the critical velocity does not coincide with the phase velocity of bulk waves in liquid. The true threshold velocity is found to be smaller, the correction being of about 1.45%. Attention is also drawn to the fact that using the real part of the complex phase velocity as a velocity of leaky waves gives only approximate value. The most interesting feature of the waves under consideration is the presence of energy leakage in the subsonic range of the phase velocities where, at first glance, any radiation by harmonic waves is not permitted. A simple physical explanation of this radiation with due regard for inhomogeneity of radiated and radiating waves is given. The controversial question of the existence of leaky Rayleigh waves at a water/ice interface is reexamined. It is shown that the solution considered previously as a leaky wave is in fact the solution of the bulk-wave-reflection problem for inhomogeneous waves.

  13. Interface magnons. Magnetic superstructure

    International Nuclear Information System (INIS)

    Djafari-Rouhani, B.; Dobrzynski, L.

    1975-01-01

    The localized magnons at an interface between two Heisenberg ferromagnets are studied with a simple model. The effect of the coupling at the interface on the existence condition for the localized modes, the dispersion laws and the possible occurrence of magnetic superstructures due to soft modes are investigated. Finally a comparison is made with the similar results obtained for interface phonons [fr

  14. Water at Interfaces

    DEFF Research Database (Denmark)

    Björneholm, Olle; Hansen, Martin Hangaard; Hodgson, Andrew

    2016-01-01

    The interfaces of neat water and aqueous solutions play a prominent role in many technological processes and in the environment. Examples of aqueous interfaces are ultrathin water films that cover most hydrophilic surfaces under ambient relative humidities, the liquid/solid interface which drives...

  15. User Interface History

    DEFF Research Database (Denmark)

    Jørgensen, Anker Helms; Myers, Brad A

    2008-01-01

    User Interfaces have been around as long as computers have existed, even well before the field of Human-Computer Interaction was established. Over the years, some papers on the history of Human-Computer Interaction and User Interfaces have appeared, primarily focusing on the graphical interface e...

  16. Graphical Interfaces for Simulation.

    Science.gov (United States)

    Hollan, J. D.; And Others

    This document presents a discussion of the development of a set of software tools to assist in the construction of interfaces to simulations and real-time systems. Presuppositions to the approach to interface design that was used are surveyed, the tools are described, and the conclusions drawn from these experiences in graphical interface design…

  17. Optical-fiber interferometer for velocity measurements with picosecond resolution

    International Nuclear Information System (INIS)

    Weng Jidong; Tan Hua; Wang Xiang; Ma Yun; Hu Shaolou; Wang Xiaosong

    2006-01-01

    The conventional Doppler laser-interference velocimeters are made up of traditional optical elements such as lenses and mirrors and will generally restrict its applications in multipoint velocity measurements. By transfering the light from multimode optical fiber to single-mode optical fiber and using the currently available conventional telecommunications elements, the authors have constructed a velocimeter called all-fiber displacement interferometer system for any reflector. The unique interferometer system is only made up of fibers or fiber-coupled components. The viability of this technique is demonstrated by measuring the velocity of an interface moving at velocity of 2133 m/s with 50 ps time resolution. In addition, the concept of optical-fiber mode conversion would provide a way to develop various optical-fiber sensors

  18. Sound Velocity in Soap Foams

    International Nuclear Information System (INIS)

    Wu Gong-Tao; Lü Yong-Jun; Liu Peng-Fei; Li Yi-Ning; Shi Qing-Fan

    2012-01-01

    The velocity of sound in soap foams at high gas volume fractions is experimentally studied by using the time difference method. It is found that the sound velocities increase with increasing bubble diameter, and asymptotically approach to the value in air when the diameter is larger than 12.5 mm. We propose a simple theoretical model for the sound propagation in a disordered foam. In this model, the attenuation of a sound wave due to the scattering of the bubble wall is equivalently described as the effect of an additional length. This simplicity reasonably reproduces the sound velocity in foams and the predicted results are in good agreement with the experiments. Further measurements indicate that the increase of frequency markedly slows down the sound velocity, whereas the latter does not display a strong dependence on the solution concentration

  19. Settling velocities in batch sedimentation

    International Nuclear Information System (INIS)

    Fricke, A.M.; Thompson, B.E.

    1982-10-01

    The sedimentation of mixtures containing one and two sizes of spherical particles (44 and 62 μm in diameter) was studied. Radioactive tracing with 57 Co was used to measure the settling velocities. The ratio of the settling velocity U of uniformly sized particles to the velocity predicted to Stokes' law U 0 was correlated to an expression of the form U/U 0 = epsilon/sup α/, where epsilon is the liquid volume fraction and α is an empirical constant, determined experimentally to be 4.85. No effect of viscosity on the ratio U/U 0 was observed as the viscosity of the liquid medium was varied from 1x10 -3 to 5x10 -3 Pa.s. The settling velocities of particles in a bimodal mixture were fit by the same correlation; the ratio U/U 0 was independent of the concentrations of different-sized particles

  20. Parasitic lasing suppression in large-aperture Ti:sapphire amplifiers by optimizing the seed–pump time delay

    International Nuclear Information System (INIS)

    Chu, Y X; Liang, X Y; Yu, L H; Xu, L; Lu, X M; Liu, Y Q; Leng, Y X; Li, R X; Xu, Z Z

    2013-01-01

    Theoretical and experimental investigations are carried out to determine the influence of the time delay between the input seed pulse and pump pulses on transverse parasitic lasing in a Ti:sapphire amplifier with a diameter of 80 mm, which is clad by a refractive index-matched liquid doped with an absorber. When the time delay is optimized, a maximum output energy of 50.8 J is achieved at a pump energy of 105 J, which corresponds to a conversion efficiency of 47.5%. Based on the existing compressor, the laser system achieves a peak power of 1.26 PW with a 29.0 fs pulse duration. (letter)

  1. Complementary analyses on the local polarity in lateral polarity-inverted GaN heterostructure on sapphire (0001) substrate

    International Nuclear Information System (INIS)

    Katayama, Ryuji; Kuge, Yoshihiro; Onabe, Kentaro; Matsushita, Tomonori; Kondo, Takashi

    2006-01-01

    The fabrication of the lateral polarity-inverted GaN heterostructure on sapphire (0001) using a radio-frequency-plasma-enhanced molecular beam epitaxy is demonstrated. Its microscopic properties such as surface potentials, piezoelectric polarizations, and residual carrier densities were investigated by Kelvin force microscopy and micro-Raman scattering. The inversion from Ga polarity to N polarity in a specific domain and its higher crystal perfection had been unambiguously confirmed by these complementary analyses. The results were also fairly consistent with that of KOH etching, which suggests the applicability of these processes to the fabrication of photonic nanostructures

  2. Effect of sapphire substrate nitridation on the elimination of rotation domains in ZnO epitaxial films

    International Nuclear Information System (INIS)

    Ying Minju; Du Xiaolong; Mei Zengxia; Zeng Zhaoquan; Zheng Hao; Wang Yong; Jia Jinfeng; Zhang Ze; Xue Qikun

    2004-01-01

    The rotation domain structures in ZnO films grown on sapphire substrates under different pre-treatment conditions have been investigated by in situ reflection high-energy electron diffraction and ex situ x-ray diffraction (XRD). It was found that by appropriate nitridation treatment, forming a thin AlN film on the substrate, the rotation domains in ZnO films could be completely suppressed, and a full width at half maximum of only 180 arcsec was observed in the (0 0 0 2) reflection of XRD rocking curves. The mechanisms for the elimination of rotation domains in the ZnO films are discussed

  3. Single mode operation in a pulsed Ti:sapphire laser oscillator with a grazing-incidence four-mirror cavity

    CERN Document Server

    Ko, D K; Binks, D J; Gloster, L A W; King, T A

    1998-01-01

    We demonstrate stable single mode operation in a pulsed Ti:sapphire laser oscillator with a novel grazing-incidence four-mirror coupled cavity. This cavity consists of a grating, a gain medium, and four mirrors and, therefore, has a four-arm interferometer configuration. Through the interferometric effect, we could suppress the adjacent modes and obtain stable single mode operation with a bandwidth of < 200 MHz. We also have developed a general analysis of the laser modes and the threshold conditions for configuration and the experimental results agree well with the theoretical predictions.

  4. Quantization of interface currents

    Energy Technology Data Exchange (ETDEWEB)

    Kotani, Motoko [AIMR, Tohoku University, Sendai (Japan); Schulz-Baldes, Hermann [Department Mathematik, Universität Erlangen-Nürnberg, Erlangen (Germany); Villegas-Blas, Carlos [Instituto de Matematicas, Cuernavaca, UNAM, Cuernavaca (Mexico)

    2014-12-15

    At the interface of two two-dimensional quantum systems, there may exist interface currents similar to edge currents in quantum Hall systems. It is proved that these interface currents are macroscopically quantized by an integer that is given by the difference of the Chern numbers of the two systems. It is also argued that at the interface between two time-reversal invariant systems with half-integer spin, one of which is trivial and the other non-trivial, there are dissipationless spin-polarized interface currents.

  5. Water at Interfaces.

    Science.gov (United States)

    Björneholm, Olle; Hansen, Martin H; Hodgson, Andrew; Liu, Li-Min; Limmer, David T; Michaelides, Angelos; Pedevilla, Philipp; Rossmeisl, Jan; Shen, Huaze; Tocci, Gabriele; Tyrode, Eric; Walz, Marie-Madeleine; Werner, Josephina; Bluhm, Hendrik

    2016-07-13

    The interfaces of neat water and aqueous solutions play a prominent role in many technological processes and in the environment. Examples of aqueous interfaces are ultrathin water films that cover most hydrophilic surfaces under ambient relative humidities, the liquid/solid interface which drives many electrochemical reactions, and the liquid/vapor interface, which governs the uptake and release of trace gases by the oceans and cloud droplets. In this article we review some of the recent experimental and theoretical advances in our knowledge of the properties of aqueous interfaces and discuss open questions and gaps in our understanding.

  6. Online Wavelet Complementary velocity Estimator.

    Science.gov (United States)

    Righettini, Paolo; Strada, Roberto; KhademOlama, Ehsan; Valilou, Shirin

    2018-02-01

    In this paper, we have proposed a new online Wavelet Complementary velocity Estimator (WCE) over position and acceleration data gathered from an electro hydraulic servo shaking table. This is a batch estimator type that is based on the wavelet filter banks which extract the high and low resolution of data. The proposed complementary estimator combines these two resolutions of velocities which acquired from numerical differentiation and integration of the position and acceleration sensors by considering a fixed moving horizon window as input to wavelet filter. Because of using wavelet filters, it can be implemented in a parallel procedure. By this method the numerical velocity is estimated without having high noise of differentiators, integration drifting bias and with less delay which is suitable for active vibration control in high precision Mechatronics systems by Direct Velocity Feedback (DVF) methods. This method allows us to make velocity sensors with less mechanically moving parts which makes it suitable for fast miniature structures. We have compared this method with Kalman and Butterworth filters over stability, delay and benchmarked them by their long time velocity integration for getting back the initial position data. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  7. Properties of the generation of radiation in the near infrared part of the spectrum with a sapphire crystal laser having radiation-induced color centers

    International Nuclear Information System (INIS)

    Voitovich, A.P.; Grinkevich, V.E.; Kononov, V.A.; Kromskii, G.I.

    1986-01-01

    This paper investigates the spectral stability of the color centers in sapphire and the energy of lasers in which the active elements were colored with various techniques. Color centers were produced by neutron irradiation. The absorption spectra of the color centers are shown. The transformation of the spectra shows that the mutual conversions of color centers takes place during the thermal annealing of the sapphire; most of the color centers formed have luminescence. Generation or radiation with a tunable frequency was obtained in the case of transverse or quasi-longitudinal excitation by a ruby laser. The results show that ways for increasing the stability of the energy generated by a sapphire laser with color centers can be found

  8. Structural characterization of AgGaTe{sub 2} layers grown on a- and c-sapphire substrates by a closed space sublimation method

    Energy Technology Data Exchange (ETDEWEB)

    Uruno, Aya; Usui, Ayaka [Department of Electrical Engineering and Bioscience, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Kobayashi, Masakazu [Department of Electrical Engineering and Bioscience, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, 2-8-26 Nishiwaseda, Shinjuku, Tokyo 169-0051 (Japan)

    2014-07-15

    AgGaTe{sub 2} layers were grown on a- and c-plane sapphire substrates by a closed space sublimation method with varying the source temperature. Grown films were evaluated by θ -2θ and pole figure measurements of X-ray diffraction. AgGaTe{sub 2} layers were grown to have strong preference for the (103) orientation. However, it was cleared the Ag{sub 5}Te{sub 3} was formed along with the AgGaTe{sub 2} when the layer was grown on c-plane sapphire. The orientation of the film was analyzed by using the pole figure, and resulted in AgGaTe{sub 2} without Ag{sub 5}Te{sub 3} layers could be grown on a-plane sapphire. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. A Novel Method for Measurements of the Penetration Depth of MgB2 Superconductor Films by Using Sapphire Resonators with Short-Circuited Parallel Plates

    International Nuclear Information System (INIS)

    Jung, Ho Sang; Lee, J. H.; Cho, Y. H.; Lee, Sang Young; Seong, W. K.; Lee, N. H.; Kang, W. N.

    2009-01-01

    We introduce a measurement method that enables to measure the penetration depth(λ) of superconductor films by using a short-ended parallel plate sapphire resonator. Variations in the (λof MgB 2 films could be measured down to the lowest temperature using a sapphire resonator with a YBa 2 Cu 3 O 7-x film at the bottom. A model equation of λλ 0 [1-(T/T c ) τ ] -1/2 for MgB 2 films appeared to describe the observed variations of the resonant frequency of the sapphire resonator with temperature, with λ 0 , τ and T c used as the fitting parameters.

  10. Improvement in light-output efficiency of near-ultraviolet InGaN-GaN LEDs fabricated on stripe patterned sapphire substrates

    International Nuclear Information System (INIS)

    Lee, Y.J.; Hsu, T.C.; Kuo, H.C.; Wang, S.C.; Yang, Y.L.; Yen, S.N.; Chu, Y.T.; Shen, Y.J.; Hsieh, M.H.; Jou, M.J.; Lee, B.J.

    2005-01-01

    InGaN/GaN multi-quantum wells near ultraviolet light-emitting diodes (LEDs) were fabricated on a patterned sapphire substrate (PSS) with parallel stripe along the sapphire direction by using low-pressure metal-organic chemical vapor deposition (MOCVD). The forward- and reverse-bias electrical characteristics of the stripe PSS LEDs are, respectively, similar and better than those of conventional LEDs on sapphire substrate. The output power of the epoxy package of stripe PSS LED was 20% higher than that of the conventional LEDs. The enhancement of output power is due not only to the reduction of dislocation density but also to the release of the guided light in LEDs by the geometric shape of the stripe PSS, according to the ray-tracing analysis

  11. The effect of a slight mis-orientation angle of c-plane sapphire substrate on surface and crystal quality of MOCVD grown GaN thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seong-Woo; Suzuki, Toshimasa [Nippon Institute of Technology, 4-1 Gakuendai, Miyashiro, Saitama, 345-8501 (Japan); Aida, Hideo [NAMIKI Precision Jewel Co. Ltd., 3-8-22 Shinden, Adachi-ku, Tokyo, 123-8511 (Japan)

    2004-09-01

    The effect of a slight mis-orientation of c-plane sapphire substrate on the surface morphology and crystal quality of GaN thin films grown by MOCVD has been investigated. The mis-orientation angle of vicinal c-plane sapphire substrate was changed within the range of 0.00(zero)-1.00(one) degree, and the experimental results were compared with those on just angle (zero degree) c-plane sapphire substrate. The surface morphology and crystal quality were found to be very sensitive to mis-orientation angle. Consequently, the mis-orientation angle was optimized to be 0.15 . (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Shape-changing interfaces:

    DEFF Research Database (Denmark)

    Rasmussen, Majken Kirkegård; Pedersen, Esben Warming; Petersen, Marianne Graves

    2015-01-01

    Shape change is increasingly used in physical user interfaces, both as input and output. Yet, the progress made and the key research questions for shape-changing interfaces are rarely analyzed systematically. We review a sample of existing work on shape-changing interfaces to address these shortc......Shape change is increasingly used in physical user interfaces, both as input and output. Yet, the progress made and the key research questions for shape-changing interfaces are rarely analyzed systematically. We review a sample of existing work on shape-changing interfaces to address...... these shortcomings. We identify eight types of shape that are transformed in various ways to serve both functional and hedonic design purposes. Interaction with shape-changing interfaces is simple and rarely merges input and output. Three questions are discussed based on the review: (a) which design purposes may...

  13. Nonlinear Displacement Discontinuity Model for Generalized Rayleigh Wave in Contact Interface

    Energy Technology Data Exchange (ETDEWEB)

    Kim, No Hyu; Yang, Seung Yong [Korea University of Technology and Education, Cheonan (Korea, Republic of)

    2007-12-15

    Imperfectly jointed interface serves as mechanical waveguide for elastic waves and gives rise to two distinct kinds of guided wave propagating along the interface. Contact acoustic nonlinearity (CAN) is known to plays major role in the generation of these interface waves called generalized Rayleigh waves in non-welded interface. Closed crack is modeled as non-welded interface that has nonlinear discontinuity condition in displacement across its boundary. Mathematical analysis of boundary conditions and wave equation is conducted to investigate the dispersive characteristics of the interface waves. Existence of the generalized Rayleigh wave(interface wave) in nonlinear contact interface is verified in theory where the dispersion equation for the interface wave is formulated and analyzed. It reveals that the interface waves have two distinct modes and that the phase velocity of anti-symmetric wave mode is highly dependent on contact conditions represented by linear and nonlinear dimensionless specific stiffness

  14. Nonlinear Displacement Discontinuity Model for Generalized Rayleigh Wave in Contact Interface

    International Nuclear Information System (INIS)

    Kim, No Hyu; Yang, Seung Yong

    2007-01-01

    Imperfectly jointed interface serves as mechanical waveguide for elastic waves and gives rise to two distinct kinds of guided wave propagating along the interface. Contact acoustic nonlinearity (CAN) is known to plays major role in the generation of these interface waves called generalized Rayleigh waves in non-welded interface. Closed crack is modeled as non-welded interface that has nonlinear discontinuity condition in displacement across its boundary. Mathematical analysis of boundary conditions and wave equation is conducted to investigate the dispersive characteristics of the interface waves. Existence of the generalized Rayleigh wave(interface wave) in nonlinear contact interface is verified in theory where the dispersion equation for the interface wave is formulated and analyzed. It reveals that the interface waves have two distinct modes and that the phase velocity of anti-symmetric wave mode is highly dependent on contact conditions represented by linear and nonlinear dimensionless specific stiffness

  15. Anisotropic diffusion of volatile pollutants at air-water interface

    Directory of Open Access Journals (Sweden)

    Li-ping Chen

    2013-04-01

    Full Text Available The volatile pollutants that spill into natural waters cause water pollution. Air pollution arises from the water pollution because of volatilization. Mass exchange caused by turbulent fluctuation is stronger in the direction normal to the air-water interface than in other directions due to the large density difference between water and air. In order to explore the characteristics of anisotropic diffusion of the volatile pollutants at the air-water interface, the relationship between velocity gradient and mass transfer rate was established to calculate the turbulent mass diffusivity. A second-order accurate smooth transition differencing scheme (STDS was proposed to guarantee the boundedness for the flow and mass transfer at the air-water interface. Simulations and experiments were performed to study the trichloroethylene (C2HCl3 release. By comparing the anisotropic coupling diffusion model, isotropic coupling diffusion model, and non-coupling diffusion model, the features of the transport of volatile pollutants at the air-water interface were determined. The results show that the anisotropic coupling diffusion model is more accurate than the isotropic coupling diffusion model and non-coupling diffusion model. Mass transfer significantly increases with the increase of the air-water relative velocity at a low relative velocity. However, at a higher relative velocity, an increase in the relative velocity has no effect on mass transfer.

  16. Linear flow dynamics near a T/NT interface

    Science.gov (United States)

    Teixeira, Miguel; Silva, Carlos

    2011-11-01

    The characteristics of a suddenly-inserted T/NT interface separating a homogeneous and isotropic shear-free turbulence region from a non-turbulent flow region are investigated using rapid distortion theory (RDT), taking full account of viscous effects. Profiles of the velocity variances, TKE, viscous dissipation rate, turbulence length scales, and pressure statistics are derived, showing very good agreement with DNS. The normalized inviscid flow statistics at the T/NT interface do not depend on the form of the assumed TKE spectrum. In the non-turbulent region, where the flow is irrotational (except within a thin viscous boundary layer), the dissipation rate decays as z-6, where z is distance from the T/NT interface. The mean pressure exhibits a decrease towards the turbulence due to the associated velocity fluctuations, consistent with the generation of a mean entrainment velocity. The vorticity variance and dissipation rate display large maxima at the T/NT interface due to the existing inviscid discontinuities of the tangential velocity, and these maxima are quantitatively related to the thickness of the viscous boundary layer (VBL). At equilibrium, RDT suggests that the thickness of the T/NT interface scales on the Kolmogorov microscale. We acknowledge the financial support of FCT under Project PTDC/EME-MFE/099636/2008.

  17. Highly efficient and reliable high power LEDs with patterned sapphire substrate and strip-shaped distributed current blocking layer

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Shengjun [School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072 (China); State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Yuan, Shu; Liu, Yingce [Quantum Wafer Inc., Foshan 528251 (China); Guo, L. Jay [Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109 (United States); Liu, Sheng, E-mail: victor_liu63@126.com [School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072 (China); Ding, Han [State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2015-11-15

    Graphical abstract: - Highlights: • TEM is used to characterize threading dislocation existing in GaN epitaxial layer. • Effect of threading dislocation on optical and electrical of LEDs is discussed. • Strip-shaped SiO{sub 2} DCBL is designed to improve current spreading performance of LEDs. - Abstract: We demonstrated that the improvement in optical and electrical performance of high power LEDs was achieved using cone-shaped patterned sapphire substrate (PSS) and strip-shaped SiO{sub 2} distributed current blocking layer (DCBL). We found through transmission electron microscopy (TEM) observation that densities of both the screw dislocation and edge dislocation existing in GaN epitaxial layer grown on PSS were much less than that of GaN epitaxial layer grown on flat sapphire substrate (FSS). Compared to LED grown on FSS, LED grown on PSS showed higher sub-threshold forward-bias voltage and lower reverse leakage current, resulting in an enhancement in device reliability. We also designed a strip-shaped SiO{sub 2} DCBL beneath a strip-shaped p-electrode, which prevents the current from being concentrated on regions immediately adjacent the strip-shaped p-electrode, thereby facilitating uniform current spreading into the active region. By implementing strip-shaped SiO{sub 2} DCBL, light output power of high power PSS-LED chip could be further increased by 13%.

  18. Air-void embedded GaN-based light-emitting diodes grown on laser drilling patterned sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hao; Li, Yufeng; Wang, Shuai; Feng, Lungang; Xiong, Han; Yun, Feng, E-mail: fyun2010@mail.xjtu.edu.cn [Key Laboratory of Physical Electronics and Devices of Ministry of Education and Shaanxi Provincial Key Laboratory of Photonics and Information Technology, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Solid-State Lighting Engineering Research Center, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Su, Xilin [Shaanxi Supernova Lighting Technology Co., Ltd., Xi’an, Shaanxi 710075 (China)

    2016-07-15

    Air-void structure was introduced in GaN-based blue light-emitting diodes (LED) with one-step growth on periodic laser drilling patterned sapphire substrate, which free of any photolithography or wet/dry etching process. The influence of filling factors (FF) of air-void on crystal quality and optical performance were investigate. Transmission electron microscopy images and micro-Raman spectroscopy indicated that the dislocation was bended and the partially compressed strain was released. When FF was 55.43%, compared with the LED structure grown on flat sapphire substrate, the incorporation of air-void was observed to reduce the compressed stress of ∼20% and the luminance intensity has improved by 128%. Together with the simulated reflection intensity enhancement by finite difference time-domain (FDTD) method, we attribute the enhanced optical performance to the combined contribution of strong back-side light reflection of air-void and better GaN epitaxial quality. This approach provides a simple replacement to the conventional air-void embedded LED process.

  19. Formation of metal nanoparticles of various sizes in plasma plumes produced by Ti:sapphire laser pulses

    International Nuclear Information System (INIS)

    Chakravarty, U.; Naik, P. A.; Mukherjee, C.; Kumbhare, S. R.; Gupta, P. D.

    2010-01-01

    In this paper, an experimental study on generation of nanoparticle various sizes using Ti:sapphire laser pulses, is reported. Nanoparticle formation in plasma plumes of metals like silver and copper, expanding in vacuum, has been studied using stretched pulses of 300 ps duration [subnanoseconds (sub-ns)] from a Ti:sapphire laser. It has been compared with the nanoparticle formation (of the same materials) when compressed pulses of 45 fs duration were used under similar focusing conditions. Nanoparticle formation is observed at intensities as high as 2x10 16 W/cm 2 . The structural analysis of the nanoparticle deposition on a silicon substrate showed that, using 45 fs pulses, smaller nanoparticles of average size ∼20 nm were generated, whereas on using the sub-ns pulses, larger particles were produced. Also, the visible light transmission and reflection from the nanoparticle film of Ag on glass substrate showed surface plasmon resonance (SPR). The SPR curves of the films of nanoparticles deposited by femtosecond pulses were always broader and reflection/transmission was always smaller when compared with the films formed using the sub-ns pulses, indicating smaller size particle formation by ultrashort pulses. Thus, it has been demonstrated that variation in the laser pulse duration of laser offers a simple tool for varying the size of the nanoparticles generated in plasma plumes.

  20. Growth and characterization of polar and nonpolar ZnO film grown on sapphire substrates by using atomic layer deposition

    International Nuclear Information System (INIS)

    Kim, Ki-Wook; Son, Hyo-Soo; Choi, Nak-Jung; Kim, Jihoon; Lee, Sung-Nam

    2013-01-01

    We investigated the electrical and the optical properties of polar and nonpolar ZnO films grown on sapphire substrates with different crystallographic planes. High resolution X-ray results revealed that polar c-plane (0001), nonpolar m-plane (10-10) and a-plane (11-20) ZnO thin films were grown on c-plane, m- and r-sapphire substrates by atomic layer deposition, respectively. Compared with the c-plane ZnO film, nonpolar m-plane and a-plane ZnO films showed smaller surface roughness and anisotropic surface structures. Regardless of ZnO crystal planes, room temperature photoluminescence spectra represented two emissions which consisted of the near bandedge (∼ 380 nm) and the deep level emission (∼ 500 nm). The a-plane ZnO films represented better optical and electrical properties than c-plane ZnO, while m-plane ZnO films exhibited poorer optical and electrical properties than c-plane ZnO. - Highlights: • Growth and characterization of a-, c- and m-plane ZnO film by atomic layer deposition. • The a-plane ZnO represented better optical and electrical properties than c-plane ZnO. • The m-plane ZnO exhibited poorer optical and electrical properties than c-plane ZnO

  1. 5-nJ Femtosecond Ti3+:sapphire laser pumped with a single 1 W green diode

    Science.gov (United States)

    Muti, Abdullah; Kocabas, Askin; Sennaroglu, Alphan

    2018-05-01

    We report a Kerr-lens mode-locked, extended-cavity femtosecond Ti3+:sapphire laser directly pumped at 520 nm with a 1 W AlInGaN green diode. To obtain energy scaling, the short x-cavity was extended with a q-preserving multi-pass cavity to reduce the pulse repetition rate to 5.78 MHz. With 880 mW of incident pump power, we obtained as high as 90 mW of continuous-wave output power from the short cavity by using a 3% output coupler. In the Kerr-lens mode-locked regime, the extended cavity produced nearly transform-limited 95 fs pulses at 776 nm. The resulting energy and peak power of the pulses were 5.1 nJ and 53 kW, respectively. To our knowledge, this represents the highest pulse energy directly obtained to date from a mode-locked, single-diode-pumped Ti3+:sapphire laser.

  2. Velocity distribution in snow avalanches

    Science.gov (United States)

    Nishimura, K.; Ito, Y.

    1997-12-01

    In order to investigate the detailed structure of snow avalanches, we have made snow flow experiments at the Miyanomori ski jump in Sapporo and systematic observations in the Shiai-dani, Kurobe Canyon. In the winter of 1995-1996, a new device to measure static pressures was used to estimate velocities in the snow cloud that develops above the flowing layer of avalanches. Measurements during a large avalanche in the Shiai-dani which damaged and destroyed some instruments indicate velocities increased rapidly to more than 50 m/s soon after the front. Velocities decreased gradually in the following 10 s. Velocities of the lower flowing layer were also calculated by differencing measurement of impact pressure. Both recordings in the snow cloud and in the flowing layer changed with a similar trend and suggest a close interaction between the two layers. In addition, the velocity showed a periodic change. Power spectrum analysis of the impact pressure and the static pressure depression showed a strong peak at a frequency between 4 and 6 Hz, which might imply the existence of either ordered structure or a series of surges in the flow.

  3. Velocity Estimate Following Air Data System Failure

    National Research Council Canada - National Science Library

    McLaren, Scott A

    2008-01-01

    .... A velocity estimator (VEST) algorithm was developed to combine the inertial and wind velocities to provide an estimate of the aircraft's current true velocity to be used for command path gain scheduling and for display in the cockpit...

  4. Diffusion between evolving interfaces

    International Nuclear Information System (INIS)

    Juntunen, Janne; Merikoski, Juha

    2010-01-01

    Diffusion in an evolving environment is studied by continuous-time Monte Carlo simulations. Diffusion is modeled by continuous-time random walkers on a lattice, in a dynamic environment provided by bubbles between two one-dimensional interfaces driven symmetrically towards each other. For one-dimensional random walkers constrained by the interfaces, the bubble size distribution dominates diffusion. For two-dimensional random walkers, it is also controlled by the topography and dynamics of the interfaces. The results of the one-dimensional case are recovered in the limit where the interfaces are strongly driven. Even with simple hard-core repulsion between the interfaces and the particles, diffusion is found to depend strongly on the details of the dynamical rules of particles close to the interfaces.

  5. User interface support

    Science.gov (United States)

    Lewis, Clayton; Wilde, Nick

    1989-01-01

    Space construction will require heavy investment in the development of a wide variety of user interfaces for the computer-based tools that will be involved at every stage of construction operations. Using today's technology, user interface development is very expensive for two reasons: (1) specialized and scarce programming skills are required to implement the necessary graphical representations and complex control regimes for high-quality interfaces; (2) iteration on prototypes is required to meet user and task requirements, since these are difficult to anticipate with current (and foreseeable) design knowledge. We are attacking this problem by building a user interface development tool based on extensions to the spreadsheet model of computation. The tool provides high-level support for graphical user interfaces and permits dynamic modification of interfaces, without requiring conventional programming concepts and skills.

  6. Complex Interfaces Under Change

    DEFF Research Database (Denmark)

    Rosbjerg, Dan

    The hydrosphere is dynamic across the major compartments of the Earth system: the atmosphere, the oceans and seas, the land surface water, and the groundwater within the strata below the two last compartments. The global geography of the hydrosphere essentially depends on thermodynamic and mechan...... these interfaces and interfaced compartments and processes. Climate, sea-level, oceanographic currents and hydrological processes are all affected, while anthropogenic changes are often intense in the geographic settings corresponding to such interfaces....... and mechanical processes that develop within this structure. Water-related processes at the interfaces between the compartments are complex, depending both on the interface itself, and on the characteristics of the interfaced compartments. Various aspects of global change directly or indirectly impact...

  7. Sound velocity of tantalum under shock compression in the 18–142 GPa range

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Feng, E-mail: xifeng@caep.cn; Jin, Ke; Cai, Lingcang, E-mail: cai-lingcang@aliyun.com; Geng, Huayun; Tan, Ye; Li, Jun [National Key Laboratory of Shock Waves and Detonation Physics, Institute of Fluid Physics, CAEP, P.O. Box 919-102 Mianyang, Sichuan 621999 (China)

    2015-05-14

    Dynamic compression experiments of tantalum (Ta) within a shock pressure range from 18–142 GPa were conducted driven by explosive, a two-stage light gas gun, and a powder gun, respectively. The time-resolved Ta/LiF (lithium fluoride) interface velocity profiles were recorded with a displacement interferometer system for any reflector. Sound velocities of Ta were obtained from the peak state time duration measurements with the step-sample technique and the direct-reverse impact technique. The uncertainty of measured sound velocities were analyzed carefully, which suggests that the symmetrical impact method with step-samples is more accurate for sound velocity measurement, and the most important parameter in this type experiment is the accurate sample/window particle velocity profile, especially the accurate peak state time duration. From these carefully analyzed sound velocity data, no evidence of a phase transition was found up to the shock melting pressure of Ta.

  8. Refinement by interface instantiation

    DEFF Research Database (Denmark)

    Hallerstede, Stefan; Hoang, Thai Son

    2012-01-01

    be easily refined. Our first contribution hence is a proposal for a new construct called interface that encapsulates the external variables, along with a mechanism for interface instantiation. Using the new construct and mechanism, external variables can be refined consistently. Our second contribution...... is an approach for verifying the correctness of Event-B extensions using the supporting Rodin tool. We illustrate our approach by proving the correctness of interface instantiation....

  9. Universal computer interfaces

    CERN Document Server

    Dheere, RFBM

    1988-01-01

    Presents a survey of the latest developments in the field of the universal computer interface, resulting from a study of the world patent literature. Illustrating the state of the art today, the book ranges from basic interface structure, through parameters and common characteristics, to the most important industrial bus realizations. Recent technical enhancements are also included, with special emphasis devoted to the universal interface adapter circuit. Comprehensively indexed.

  10. Cosmic string induced peculiar velocities

    International Nuclear Information System (INIS)

    van Dalen, A.; Schramm, D.N.

    1987-02-01

    We calculate analytically the probability distribution for peculiar velocities on scales from 10h -1 to 60h -1 Mpc with cosmic string loops as the dominant source of primordial gravitational perturbations. We consider a range of parameters βGμ appropriate for both hot (HDM) and cold (CDM) dark matter scenarios. An Ω = 1 CDM Universe is assumed with the loops randomly placed on a smooth background. It is shown how the effects can be estimated of loops breaking up and being born with a spectrum of sizes. It is found that to obtain large scale streaming velocities of at least 400 km/s it is necessary that either a large value for βGμ or the effect of loop fissioning and production details be considerable. Specifically, for optimal CDM string parameters Gμ = 10 -6 , β = 9, h = .5, and scales of 60h -1 Mpc, the parent size spectrum must be 36 times larger than the evolved daughter spectrum to achieve peculiar velocities of at least 400 km/s with a probability of 63%. With this scenario the microwave background dipole will be less than 800 km/s with only a 10% probability. The string induced velocity spectrum is relatively flat out to scales of about 2t/sub eq//a/sub eq/ and then drops off rather quickly. The flatness is a signature of string models of galaxy formation. With HDM a larger value of βGμ is necessary for galaxy formation since accretion on small scales starts later. Hence, with HDM, the peculiar velocity spectrum will be larger on large scales and the flat region will extend to larger scales. If large scale peculiar velocities greater than 400 km/s are real then it is concluded that strings plus CDM have difficulties. The advantages of strings plus HDM in this regard will be explored in greater detail in a later paper. 27 refs., 4 figs., 1 tab

  11. Angle independent velocity spectrum determination

    DEFF Research Database (Denmark)

    2014-01-01

    An ultrasound imaging system (100) includes a transducer array (102) that emits an ultrasound beam and produces at least one transverse pulse-echo field that oscillates in a direction transverse to the emitted ultrasound beam and that receive echoes produced in response thereto and a spectral vel...... velocity estimator (110) that determines a velocity spectrum for flowing structure, which flows at an angle of 90 degrees and flows at angles less than 90 degrees with respect to the emitted ultrasound beam, based on the received echoes....

  12. Electromagnetic Interface Testing Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Electromagnetic Interface Testing facilitysupports such testing asEmissions, Field Strength, Mode Stirring, EMP Pulser, 4 Probe Monitoring/Leveling System, and...

  13. Automatic discrimination of bubbles and slugs in two-phase gas-liquid flow and measurement of the respective velocities

    International Nuclear Information System (INIS)

    Fitremann, J.M.; Guilpin, C.; Postaire, J.

    1976-01-01

    The measurement of the interface velocity in a two-phase gas-liquid flow is a difficult problem, owing to the dispersion of the velocity components of individual bubbles, gas-slugs, droplets, waves, etc. An entirely automatic method is presented, it gives the velocity of slugs and bubbles independently, by discrimination of local phase probe signals into a 'slug' signal and a 'bubble' signal feeding a shape-recognition program. Both discriminated void fractions are also calculated by the apparatus [fr

  14. ROTATIONAL VELOCITIES FOR M DWARFS

    International Nuclear Information System (INIS)

    Jenkins, J. S.; Ramsey, L. W.; Jones, H. R. A.; Pavlenko, Y.; Barnes, J. R.; Pinfield, D. J.; Gallardo, J.

    2009-01-01

    We present spectroscopic rotation velocities (v sin i) for 56 M dwarf stars using high-resolution Hobby-Eberly Telescope High Resolution Spectrograph red spectroscopy. In addition, we have also determined photometric effective temperatures, masses, and metallicities ([Fe/H]) for some stars observed here and in the literature where we could acquire accurate parallax measurements and relevant photometry. We have increased the number of known v sin i values for mid M stars by around 80% and can confirm a weakly increasing rotation velocity with decreasing effective temperature. Our sample of v sin is peak at low velocities (∼3 km s -1 ). We find a change in the rotational velocity distribution between early M and late M stars, which is likely due to the changing field topology between partially and fully convective stars. There is also a possible further change in the rotational distribution toward the late M dwarfs where dust begins to play a role in the stellar atmospheres. We also link v sin i to age and show how it can be used to provide mid-M star age limits. When all literature velocities for M dwarfs are added to our sample, there are 198 with v sin i ≤ 10 km s -1 and 124 in the mid-to-late M star regime (M3.0-M9.5) where measuring precision optical radial velocities is difficult. In addition, we also search the spectra for any significant Hα emission or absorption. Forty three percent were found to exhibit such emission and could represent young, active objects with high levels of radial-velocity noise. We acquired two epochs of spectra for the star GJ1253 spread by almost one month and the Hα profile changed from showing no clear signs of emission, to exhibiting a clear emission peak. Four stars in our sample appear to be low-mass binaries (GJ1080, GJ3129, Gl802, and LHS3080), with both GJ3129 and Gl802 exhibiting double Hα emission features. The tables presented here will aid any future M star planet search target selection to extract stars with low v

  15. 3D Crustal Velocity Structure Model of the Middle-eastern North China Craton

    Science.gov (United States)

    Duan, Y.; Wang, F.; Lin, J.; Wei, Y.

    2017-12-01

    Lithosphere thinning and destruction in the middle-eastern North China Craton (NCC), a region susceptible to strong earthquakes, is one of the research hotspots in solid earth science. Up to 42 wide-angle reflection/refraction deep seismic sounding (DSS) profiles have been completed in the middle-eastern NCC, we collect all the 2D profiling results and perform gridding of the velocity and interface depth data, and build a 3D crustal velocity structure model for the middle-eastern NCC, named HBCrust1.0, using the Kriging interpolation method. In this model, four layers are divided by three interfaces: G is the interface between the sedimentary cover and crystalline crust, with velocities of 5.0-5.5 km/s above and 5.8-6.0 km/s below. C is the interface of the upper and lower crust, with velocity jump from 6.2-6.4 km/s to 6.5-6.6 km/s. M is the interface between the crust and upper mantle, with velocity 6.7-7.0 km/s at the crust bottom and 7.9-8.0 km/s on mantle top. Our results show that the first arrival time calculated from HBCust1.0 fit well with the observation. It also demonstrates that the upper crust is the main seismogenic layer, and the brittle-ductile transition occurs at depths near interface C. The depth of interface Moho varies beneath the source area of the Tangshan earth-quake, and a low-velocity structure is found to extend from the source area to the lower crust. Based on these observations, it can be inferred that stress accumulation responsible for the Tangshan earthquake may have been closely related to the migration and deformation of the mantle materials. Comparisons of the average velocities of the whole crust, the upper and the lower crust show that the average velocity of the lower crust under the central part of the North China Basin (NCB) in the east of the craton is obviously higher than the regional average, this high-velocity probably results from longterm underplating of the mantle magma. This research is founded by the Natural Science

  16. Noise measurements on NbN thin films with a negative temperature resistance coefficient deposited on sapphire and on SiO2

    NARCIS (Netherlands)

    Leroy, G.; Gest, J.; Vandamme, L.K.J.; Bourgeois, O.

    2007-01-01

    We characterize granular NbNx thin cermet films deposited on either sapphire substrate or on SiO2 and compare the 1/f noise at 300 K and 80 K. The films were characterized with an impedance analyzer from 20 Hz to 1 MHz and analyzed as a resistor R in parallel with a capacitor C. The calculated noise

  17. Demonstration of frequency control and CW diode laser injection control of a titanium-doped sapphire ring laser with no internal optical elements

    Science.gov (United States)

    Bair, Clayton H.; Brockman, Philip; Hess, Robert V.; Modlin, Edward A.

    1988-01-01

    Theoretical and experimental frequency narrowing studies of a Ti:sapphire ring laser with no intracavity optical elements are reported. Frequency narrowing has been achieved using a birefringent filter between a partially reflecting reverse wave suppressor mirror and the ring cavity output mirror. Results of CW diode laser injection seeding are reported.

  18. Synthesis of high quality graphene on capped (1 1 1) Cu thin films obtained by high temperature secondary grain growth on c-plane sapphire substrates

    Science.gov (United States)

    Kim, Youngwoo; Moyen, Eric; Yi, Hemian; Avila, José; Chen, Chaoyu; Asensio, Maria C.; Lee, Young Hee; Pribat, Didier

    2018-07-01

    We propose a novel growth technique, in which graphene is synthesized on capped Cu thin films deposited on c-plane sapphire. The cap is another sapphire plate which is just laid upon the Cu thin film, in direct contact with it. Thanks to this ‘contact cap’, Cu evaporation can be suppressed at high temperature and the 400 nm-thick Cu films can be annealed above 1000 °C, resulting in (1 1 1)-oriented grains of millimeter size. Following this high temperature annealing, graphene is grown by chemical vapor deposition during the same pump-down operation, without removing the contact cap. The orientation and doping type of the as-grown graphene were first studied, using low energy electron diffraction, as well as high resolution angle-resolved photoemission spectroscopy. In particular, the orientation relationships between the graphene and copper thin film with respect to the sapphire substrate were precisely determined. We find that the graphene sheets exhibit a minimal rotational disorder, with ~90% of the grains aligned along the copper high symmetry direction. Detailed transport measurements were also performed using field-effect transistor structures. Carrier mobility values as high as 8460 cm2 V‑1 s‑1 have been measured on top gate transistors fabricated directly on the sapphire substrate, by etching the Cu film from underneath the graphene sheets. This is by far the best carrier mobility value obtained to date for graphene sheets synthesized on a thin film-type metal substrate.

  19. Interface, a dispersed architecture

    NARCIS (Netherlands)

    Vissers, C.A.

    1976-01-01

    Past and current specification techniques use timing diagrams and written text to describe the phenomenology of an interface. This paper treats an interface as the architecture of a number of processes, which are dispersed over the related system parts and the message path. This approach yields a

  20. Icinga Monitoring System Interface

    CERN Document Server

    Neculae, Alina Georgiana

    2014-01-01

    The aim of this project is to develop a web interface that would be used by the Icinga monitoring system to manage the CMS online cluster, in the experimental site. The interface would allow users to visualize the information in a compressed and intuitive way, as well as modify the information of each individual object and edit the relationships between classes.

  1. Verden som interface

    DEFF Research Database (Denmark)

    2007-01-01

    Oversættelse af Peter Weibels tekst "The World as Interface" i Passepartout # 27. Interfacekulturens æstetik. Udgivelsesdato: 28.04.07......Oversættelse af Peter Weibels tekst "The World as Interface" i Passepartout # 27. Interfacekulturens æstetik. Udgivelsesdato: 28.04.07...

  2. Ecological Interface Design

    DEFF Research Database (Denmark)

    Vicente, Kim J.; Rasmussen, Jens

    1992-01-01

    A theoretical framework for designing interfaces for complex human-machine systems is proposed. The framework, called ecological interface design (EID), is based on the skills, rules, knowledge taxonomy of cognitive control. The basic goal of EID is twofold: first, not to force processing...

  3. Engineering Musculoskeletal Tissue Interfaces

    Directory of Open Access Journals (Sweden)

    Ece Bayrak

    2018-04-01

    Full Text Available Tissue engineering aims to bring together biomaterials, cells, and signaling molecules within properly designed microenvironments in order to create viable treatment options for the lost or malfunctioning tissues. Design and production of scaffolds and cell-laden grafts that mimic the complex structural and functional features of tissues are among the most important elements of tissue engineering strategy. Although all tissues have their own complex structure, an even more complex case in terms of engineering a proper carrier material is encountered at the tissue interfaces, where two distinct tissues come together. The interfaces in the body can be examined in four categories; cartilage-bone and ligament-bone interfaces at the knee and the spine, tendon-bone interfaces at the shoulder and the feet, and muscle-tendon interface at the skeletal system. These interfaces are seen mainly at the soft-to-hard tissue transitions and they are especially susceptible to injury and tear due to the biomechanical inconsistency between these tissues where high strain fields are present. Therefore, engineering the musculoskeletal tissue interfaces remain a challenge. This review focuses on recent advancements in strategies for musculoskeletal interface engineering using different biomaterial-based platforms and surface modification techniques.

  4. Adaptive user interfaces

    CERN Document Server

    1990-01-01

    This book describes techniques for designing and building adaptive user interfaces developed in the large AID project undertaken by the contributors.Key Features* Describes one of the few large-scale adaptive interface projects in the world* Outlines the principles of adaptivity in human-computer interaction

  5. Interface colloidal robotic manipulator

    Science.gov (United States)

    Aronson, Igor; Snezhko, Oleksiy

    2015-08-04

    A magnetic colloidal system confined at the interface between two immiscible liquids and energized by an alternating magnetic field dynamically self-assembles into localized asters and arrays of asters. The colloidal system exhibits locomotion and shape change. By controlling a small external magnetic field applied parallel to the interface, structures can capture, transport, and position target particles.

  6. Subwavelength engineered fiber-to-chip silicon-on-sapphire interconnects for mid-infrared applications (Conference Presentation)

    Science.gov (United States)

    Alonso-Ramos, Carlos; Han, Zhaohong; Le Roux, Xavier; Lin, Hongtao; Singh, Vivek; Lin, Pao Tai; Tan, Dawn; Cassan, Eric; Marris-Morini, Delphine; Vivien, Laurent; Wada, Kazumi; Hu, Juejun; Agarwal, Anuradha; Kimerling, Lionel C.

    2016-05-01

    The mid-Infrared wavelength range (2-20 µm), so-called fingerprint region, contains the very sharp vibrational and rotational resonances of many chemical and biological substances. Thereby, on-chip absorption-spectrometry-based sensors operating in the mid-Infrared (mid-IR) have the potential to perform high-precision, label-free, real-time detection of multiple target molecules within a single sensor, which makes them an ideal technology for the implementation of lab-on-a-chip devices. Benefiting from the great development realized in the telecom field, silicon photonics is poised to deliver ultra-compact efficient and cost-effective devices fabricated at mass scale. In addition, Si is transparent up to 8 µm wavelength, making it an ideal material for the implementation of high-performance mid-IR photonic circuits. The silicon-on-insulator (SOI) technology, typically used in telecom applications, relies on silicon dioxide as bottom insulator. Unfortunately, silicon dioxide absorbs light beyond 3.6 µm, limiting the usability range of the SOI platform for the mid-IR. Silicon-on-sapphire (SOS) has been proposed as an alternative solution that extends the operability region up to 6 µm (sapphire absorption), while providing a high-index contrast. In this context, surface grating couplers have been proved as an efficient means of injecting and extracting light from mid-IR SOS circuits that obviate the need of cleaving sapphire. However, grating couplers typically have a reduced bandwidth, compared with facet coupling solutions such as inverse or sub-wavelength tapers. This feature limits their feasibility for absorption spectroscopy applications that may require monitoring wide wavelength ranges. Interestingly, sub-wavelength engineering can be used to substantially improve grating coupler bandwidth, as demonstrated in devices operating at telecom wavelengths. Here, we report on the development of fiber-to-chip interconnects to ZrF4 optical fibers and integrated SOS

  7. Subcritical crack growth along polymer interfaces

    Science.gov (United States)

    Gurumurthy, Charavana Kumara

    2000-10-01

    The adhesion characteristics have been investigated for a polyimide (PI)/model epoxy (ME) interface that is important for microelectronic applications. The fracture toughness (G*c) of this interface has been measured using an asymmetric double cantilever beam (ADCB) technique. The G*c is low, 10-25 J/m 2, and is sensitive to the mechanical phase angle psi. A modified ADCB setup has been used to measure the subcritical crack growth velocity v due to the stress-assisted water attack (SAWA) at various relative humidities (RH) and temperatures (T) as a function of its driving force (the strain energy release rate) G*. The threshold G* decreases remarkably. Above the threshold log v rises linearly with √ G* (a hydrolysis controlled regime) but then enters a regime where the crack velocity is almost independent of √G*, i.e., v = v* (a transport controlled regime). A model for SAWA has been developed based on thermally-activated kinetics for hydrolysis of the ester covalent bonds that bridge from one side to the other of the interface. A new technique has been developed for the determination of the fatigue crack growth under thermal (T) and hydro-thermal (HT) conditions as a function of the range in the strain energy release rate (DeltaG). Under T-fatigue, the fatigue crack growth per unit temperature cycle (da/dN) increases as a power of DeltaG, i.e., a Paris law relationship holds. The HT da/dN measured is higher than da/dN under T-fatigue conditions and has been successfully modeled as a summation of two components: (a) the da/dN due to T-fatigue and (b) the da/dN due to the SAWA along the interface for a given T-cycle. A surface modification procedure that converts a thin interpenetrated by a solvent cast ME is used to strengthen ME/PI interface. The G* c increases with the interpenetration distance w. Increasing w also improves the resistance of the PI/ME interface to SAWA with the threshold G* increasing and the water transport controlled velocity (v

  8. Quantifying Heterogeneities in Soil Cover and Weathering in the Bitterroot and Sapphire Mountains, Montana: Implications for Glacial Legacies and their Morphologic Control on Soil Formation

    Science.gov (United States)

    Benjaram, S. S.; Dixon, J. L.

    2017-12-01

    To what extent is chemical weathering governed by a landscape's topography? Quantifying chemical weathering in both steep rocky landscapes and soil-mantled landscapes requires describing heterogeneity in soil and rock cover at local and landscape scales. Two neighboring mountain ranges in the northern Rockies of western Montana, USA, provide an ideal natural laboratory in which to investigate the relationship between soil chemical weathering, persistence of soil cover, and topography. We focus our work in the previously glaciated Bitterroot Mountains, which consist of steep, rock-dominated hillslopes, and the neighboring unglaciated Sapphire Mountains, which display convex, soil-mantled hillslopes. Soil thickness measurements, soil and rock geochemistry, and digital terrain analysis reveal that soils in the rock-dominated Bitterroot Mountains are only slightly less weathered than those in the Sapphire Mountains. However, these differences are magnified when adjusted for rock fragments at a local scale and bedrock cover at a landscape scale, using our newly developed metric, the rock-adjusted chemical depletion fraction (RACDF) and rock-adjusted mass transfer coefficient (RA τ). The Bitterroots overall are 30% less weathered than the Sapphires despite higher mean annual precipitation in the former, with an average rock-adjusted CDF of 0.38 in the postglacial Bitterroots catchment and 0.61 in the nonglacial Sapphire catchment, suggesting that 38% of rock mass is lost in the conversion to soil in the Bitterroots, whereas 61% of rock mass is lost in the nonglaciated Sapphires. Because the previously glaciated Bitterroots are less weathered despite being wetter, we conclude that the glacial history of this landscape exerts more influence on soil chemical weathering than does modern climate. However, while previous studies have correlated weathering intensity with topographic parameters such as slope gradient, we find little topographic indication of specific controls

  9. Improved crystalline quality of AlN epitaxial layer on sapphire by introducing TMGa pulse flow into the nucleation stage

    Science.gov (United States)

    Wu, Hualong; Wang, Hailong; Chen, Yingda; Zhang, Lingxia; Chen, Zimin; Wu, Zhisheng; Wang, Gang; Jiang, Hao

    2018-05-01

    The crystalline quality of AlN epitaxial layers on sapphire substrates was improved by introducing trimethylgallium (TMGa) pulse flow into the growth of AlN nucleation layers. It was found that the density of both screw- and edge-type threading dislocations could be significantly reduced by introducing the TMGa pulse flow. With increasing TMGa pulse flow times, the lateral correlation length (i.e. the grain size) increases and the strain in the AlN epilayers changes from tensile state to compressive state. Unstrained AlN with the least dislocations and a smooth surface was obtained by introducing 2-times TMGa pulse flow. The crystalline improvement is attributed to enhanced lateral growth and improved crystalline orientation by the TMGa pulse flow.

  10. Femtosecond resolution timing jitter correction on a TW scale Ti:sapphire laser system for FEL pump-probe experiments.

    Science.gov (United States)

    Csatari Divall, Marta; Mutter, Patrick; Divall, Edwin J; Hauri, Christoph P

    2015-11-16

    Intense ultrashort pulse lasers are used for fs resolution pump-probe experiments more and more at large scale facilities, such as free electron lasers (FEL). Measurement of the arrival time of the laser pulses and stabilization to the machine or other sub-systems on the target, is crucial for high time-resolution measurements. In this work we report on a single shot, spectrally resolved, non-collinear cross-correlator with sub-fs resolution. With a feedback applied we keep the output of the TW class Ti:sapphire amplifier chain in time with the seed oscillator to ~3 fs RMS level for several hours. This is well below the typical pulse duration used at FELs and supports fs resolution pump-probe experiments. Short term jitter and long term timing drift measurements are presented. Applicability to other wavelengths and integration into the timing infrastructure of the FEL are also covered to show the full potential of the device.

  11. Photoluminescence characteristics of low indium composition InGaN thin films grown on sapphire by metalorganic chemical vapor deposition

    International Nuclear Information System (INIS)

    Feng, Z.C.; Liu, W.; Chua, S.J.; Yu, J.W.; Yang, C.C.; Yang, T.R.; Zhao, J.

    2006-01-01

    The wavelength shifts in the photoluminescence (PL) from low indium composition (∼ 3%) InGaN epitaxial thin films, grown on sapphire substrates by metalorganic chemical vapour deposition, has been studied by a combination of experiment and theory. As temperature increases from 6 K, the PL peak energy red-shifts very slightly first, then blue-shifts to reach a maximum at near 100 K, and red-shifts again till room temperature. This unique PL behaviour, indicating the existence of the phase separation, is interpreted qualitatively from the spatial variation of band structure due to the In-compositional fluctuation. Theoretical calculation, based upon a model involving the band-tail states in the radiative recombination, explains the experimental data successfully

  12. High-quality single crystalline NiO with twin phases grown on sapphire substrate by metalorganic vapor phase epitaxy

    Directory of Open Access Journals (Sweden)

    Kazuo Uchida

    2012-12-01

    Full Text Available High-quality single crystalline twin phase NiO grown on sapphire substrates by metalorganic vapor phase epitaxy is reported. X-ray rocking curve analysis of NiO films grown at different temperatures indicates a minimum full width at half maximum of the cubic (111 diffraction peak of 0.107° for NiO film grown at as low as 550 °C. Detailed microstructural analysis by Φ scan X-ray diffraction and transmission electron microscopy reveal that the NiO film consists of large single crystalline domains with two different crystallographic orientations which are rotated relative to each other along the [111] axis by 60°. These single crystal domains are divided by the twin phase boundaries.

  13. High-phase-purity zinc-blende InN on r-plane sapphire substrate with controlled nitridation pretreatment

    International Nuclear Information System (INIS)

    Hsiao, C.-L.; Wu, C.-T.; Hsu, H.-C.; Hsu, G.-M.; Chen, L.-C.; Liu, T.-W.; Shiao, W.-Y.; Yang, C. C.; Gaellstroem, Andreas; Holtz, Per-Olof; Chen, C.-C.; Chen, K.-H.

    2008-01-01

    High-phase-purity zinc-blende (zb) InN thin film has been grown by plasma-assisted molecular-beam epitaxy on r-plane sapphire substrate pretreated with nitridation. X-ray diffraction analysis shows that the phase of the InN films changes from wurtzite (w) InN to a mixture of w-InN and zb-InN, to zb-InN with increasing nitridation time. High-resolution transmission electron microscopy reveals an ultrathin crystallized interlayer produced by substrate nitridation, which plays an important role in controlling the InN phase. Photoluminescence emission of zb-InN measured at 20 K shows a peak at a very low energy, 0.636 eV, and an absorption edge at ∼0.62 eV is observed at 2 K, which is the lowest bandgap reported to date among the III-nitride semiconductors

  14. Temperature dependence of InN growth on (0001) sapphire substrates by atmospheric pressure hydride vapor phase epitaxy

    International Nuclear Information System (INIS)

    Kumagai, Yoshinao; Adachi, Hirokazu; Otake, Aya; Higashikawa, Yoshihiro; Togashi, Rie; Murakami, Hisashi; Koukitu, Akinori

    2010-01-01

    The temperature dependence of InN growth on (0001) sapphire substrates by atmospheric pressure hydride vapor phase epitaxy (HVPE) was investigated. N-polarity single-crystal InN layers were successfully grown at temperatures ranging from 400 to 500 C. The a and c lattice constants of InN layers grown at 450 C or below were slightly larger than those of InN layers grown above 450 C due to oxygen incorporation that also increased the carrier concentration. The optical absorption edge of the InN layer decreased from above 2.0 to 0.76 eV when the growth temperature was increased from 450 to 500 C. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. On-Line Self-Calibrating Single Crystal Sapphire Optical Sensor Instrumentation for Accurate and Reliable Coal Gasifier Temperature Measurement

    Energy Technology Data Exchange (ETDEWEB)

    Kristie Cooper; Gary Pickrell; Anbo Wang

    2005-11-01

    This report summarizes technical progress April-September 2005 on the Phase II program ''On-Line Self-Calibrating Single Crystal Sapphire Optical Sensor Instrumentation for Accurate and Reliable Coal Gasifier Temperature Measurement'', funded by the Federal Energy Technology Center of the U.S. Department of Energy, and performed by the Center for Photonics Technology of the Bradley Department of Electrical and Computer Engineering at Virginia Tech. The outcome of the first phase of this program was the selection of broadband polarimetric differential interferometry (BPDI) for further prototype instrumentation development. This approach is based on the measurement of the optical path difference (OPD) between two orthogonally polarized light beams in a single-crystal sapphire disk. The objective of this program is to bring the sensor technology, which has already been demonstrated in the laboratory, to a level where the sensor can be deployed in the harsh industrial environments and will become commercially viable. Due to the difficulties described on the last report, field testing of the BPDI system has not continued to date. However, we have developed an alternative high temperature sensing solution, which is described in this report. The sensing system will be installed and tested at TECO's Polk Power Station. Following a site visit in June 2005, our efforts have been focused on preparing for that field test, including he design of the sensor mechanical packaging, sensor electronics, the data transfer module, and the necessary software codes to accommodate this application.. We are currently ready to start sensor fabrication.

  16. The Java Legacy Interface

    DEFF Research Database (Denmark)

    Korsholm, Stephan

    2007-01-01

    The Java Legacy Interface is designed to use Java for encapsulating native legacy code on small embedded platforms. We discuss why existing technologies for encapsulating legacy code (JNI) is not sufficient for an important range of small embedded platforms, and we show how the Java Legacy...... Interface offers this previously missing functionality. We describe an implementation of the Java Legacy Interface for a particular virtual machine, and how we have used this virtual machine to integrate Java with an existing, commercial, soft real-time, C/C++ legacy platform....

  17. Operator interface for vehicles

    Science.gov (United States)

    Bissontz, Jay E

    2015-03-10

    A control interface for drivetrain braking provided by a regenerative brake and a non-regenerative brake is implemented using a combination of switches and graphic interface elements. The control interface comprises a control system for allocating drivetrain braking effort between the regenerative brake and the non-regenerative brake, a first operator actuated control for enabling operation of the drivetrain braking, and a second operator actuated control for selecting a target braking effort for drivetrain braking. A graphic display displays to an operator the selected target braking effort and can be used to further display actual braking effort achieved by drivetrain braking.

  18. The interface effect

    CERN Document Server

    Galloway, Alexander R

    2013-01-01

    Interfaces are back, or perhaps they never left. The familiar Socratic conceit from the Phaedrus, of communication as the process of writing directly on the soul of the other, has returned to center stage in today's discussions of culture and media. Indeed Western thought has long construed media as a grand choice between two kinds of interfaces. Following the optimistic path, media seamlessly interface self and other in a transparent and immediate connection. But, following the pessimistic path, media are the obstacles to direct communion, disintegrating self and other into misunderstanding

  19. The computer graphics interface

    CERN Document Server

    Steinbrugge Chauveau, Karla; Niles Reed, Theodore; Shepherd, B

    2014-01-01

    The Computer Graphics Interface provides a concise discussion of computer graphics interface (CGI) standards. The title is comprised of seven chapters that cover the concepts of the CGI standard. Figures and examples are also included. The first chapter provides a general overview of CGI; this chapter covers graphics standards, functional specifications, and syntactic interfaces. Next, the book discusses the basic concepts of CGI, such as inquiry, profiles, and registration. The third chapter covers the CGI concepts and functions, while the fourth chapter deals with the concept of graphic obje

  20. RadVel: The Radial Velocity Modeling Toolkit

    Science.gov (United States)

    Fulton, Benjamin J.; Petigura, Erik A.; Blunt, Sarah; Sinukoff, Evan

    2018-04-01

    RadVel is an open-source Python package for modeling Keplerian orbits in radial velocity (RV) timeseries. RadVel provides a convenient framework to fit RVs using maximum a posteriori optimization and to compute robust confidence intervals by sampling the posterior probability density via Markov Chain Monte Carlo (MCMC). RadVel allows users to float or fix parameters, impose priors, and perform Bayesian model comparison. We have implemented real-time MCMC convergence tests to ensure adequate sampling of the posterior. RadVel can output a number of publication-quality plots and tables. Users may interface with RadVel through a convenient command-line interface or directly from Python. The code is object-oriented and thus naturally extensible. We encourage contributions from the community. Documentation is available at http://radvel.readthedocs.io.

  1. Influence of interface scattering on shock waves in heterogeneous solids

    International Nuclear Information System (INIS)

    Zhuang Shiming; Ravichandran, Guruswami; Grady, Dennis E.

    2002-01-01

    In heterogeneous media, the scattering due to interfaces between dissimilar materials play an important role in shock wave dissipation and dispersion. In this work the influence of interface scattering effect on shock waves was studied by impacting flyer plates onto periodically layered polycarbonate/6061 aluminum, polycarbonate/304 stainless steel and polycarbonate/glass composites. The experimental results (using VISAR and stress gauges) indicate that the rise time of the shock front decreases with increasing shock strength, and increases with increasing mechanical impedance mismatch between layers; the strain rate at the shock front increases by about the square of the shock stress. Experimental and numerical results also show that due to interface scattering effect the shock wave velocity in periodically layered composites decreases. In some cases the shock velocity of a layered heterogeneous composite can be lower than that of either of its components

  2. User interface development

    Science.gov (United States)

    Aggrawal, Bharat

    1994-01-01

    This viewgraph presentation describes the development of user interfaces for OS/2 versions of computer codes for the analysis of seals. Current status, new features, work in progress, and future plans are discussed.

  3. Natural gesture interfaces

    Science.gov (United States)

    Starodubtsev, Illya

    2017-09-01

    The paper describes the implementation of the system of interaction with virtual objects based on gestures. The paper describes the common problems of interaction with virtual objects, specific requirements for the interfaces for virtual and augmented reality.

  4. Pattern formation at interfaces

    CERN Document Server

    Maier, Giulio; Nepomnyashchy, Alexander

    2010-01-01

    Applying modern nonlinear stability theory to problems of continuous media mechanics in the presence of interfaces, this text is relevant to materials science, chemical engineering, and heat transfer technologies, as well as to reaction-diffusion systems.

  5. Universal quantum interfaces

    International Nuclear Information System (INIS)

    Lloyd, Seth; Landahl, Andrew J.; Slotine, Jean-Jacques E.

    2004-01-01

    To observe or control a quantum system, one must interact with it via an interface. This article exhibits simple universal quantum interfaces--quantum input/output ports consisting of a single two-state system or quantum bit that interacts with the system to be observed or controlled. It is shown that under very general conditions the ability to observe and control the quantum bit on its own implies the ability to observe and control the system itself. The interface can also be used as a quantum communication channel, and multiple quantum systems can be connected by interfaces to become an efficient universal quantum computer. Experimental realizations are proposed, and implications for controllability, observability, and quantum information processing are explored

  6. Scalable coherent interface

    International Nuclear Information System (INIS)

    Alnaes, K.; Kristiansen, E.H.; Gustavson, D.B.; James, D.V.

    1990-01-01

    The Scalable Coherent Interface (IEEE P1596) is establishing an interface standard for very high performance multiprocessors, supporting a cache-coherent-memory model scalable to systems with up to 64K nodes. This Scalable Coherent Interface (SCI) will supply a peak bandwidth per node of 1 GigaByte/second. The SCI standard should facilitate assembly of processor, memory, I/O and bus bridge cards from multiple vendors into massively parallel systems with throughput far above what is possible today. The SCI standard encompasses two levels of interface, a physical level and a logical level. The physical level specifies electrical, mechanical and thermal characteristics of connectors and cards that meet the standard. The logical level describes the address space, data transfer protocols, cache coherence mechanisms, synchronization primitives and error recovery. In this paper we address logical level issues such as packet formats, packet transmission, transaction handshake, flow control, and cache coherence. 11 refs., 10 figs

  7. Introduction to interfaces 3

    DEFF Research Database (Denmark)

    Mortensen, Lars Boje; Høgel, Christian; Borsa, Paolo

    2017-01-01

    The Editors introduce Issue No. 3 of Interfaces: A Journal of Medieval European Literatures, dedicated to "Rediscovery and Canonization: The Roman Classics in the Middle Ages," and offer a general overview of the matter and contents of the contributions.......The Editors introduce Issue No. 3 of Interfaces: A Journal of Medieval European Literatures, dedicated to "Rediscovery and Canonization: The Roman Classics in the Middle Ages," and offer a general overview of the matter and contents of the contributions....

  8. Faraday instability at foam-water interface.

    Science.gov (United States)

    Bronfort, A; Caps, H

    2012-12-01

    A nearly two-dimensional foam is generated inside a Hele-shaw cell and left at rest on its liquid bath. The system is then vertically shaken and, above a well-defined acceleration threshold, surface waves appear at the foam-liquid interface. Those waves are shown to be subharmonic. The acceleration threshold is studied and compared to the common liquid-gas case, emphasizing the energy dissipation inside the foam. An empirical model is proposed for this energy loss, accounting for the foam characteristics such as the bubble size but also the excitation parameter, namely the linear velocity.

  9. High temperature interface superconductivity

    International Nuclear Information System (INIS)

    Gozar, A.; Bozovic, I.

    2016-01-01

    Highlight: • This review article covers the topic of high temperature interface superconductivity. • New materials and techniques used for achieving interface superconductivity are discussed. • We emphasize the role played by the differences in structure and electronic properties at the interface with respect to the bulk of the constituents. - Abstract: High-T_c superconductivity at interfaces has a history of more than a couple of decades. In this review we focus our attention on copper-oxide based heterostructures and multi-layers. We first discuss the technique, atomic layer-by-layer molecular beam epitaxy (ALL-MBE) engineering, that enabled High-T_c Interface Superconductivity (HT-IS), and the challenges associated with the realization of high quality interfaces. Then we turn our attention to the experiments which shed light on the structure and properties of interfacial layers, allowing comparison to those of single-phase films and bulk crystals. Both ‘passive’ hetero-structures as well as surface-induced effects by external gating are discussed. We conclude by comparing HT-IS in cuprates and in other classes of materials, especially Fe-based superconductors, and by examining the grand challenges currently laying ahead for the field.

  10. MER SPICE Interface

    Science.gov (United States)

    Sayfi, Elias

    2004-01-01

    MER SPICE Interface is a software module for use in conjunction with the Mars Exploration Rover (MER) mission and the SPICE software system of the Navigation and Ancillary Information Facility (NAIF) at NASA's Jet Propulsion Laboratory. (SPICE is used to acquire, record, and disseminate engineering, navigational, and other ancillary data describing circumstances under which data were acquired by spaceborne scientific instruments.) Given a Spacecraft Clock value, MER SPICE Interface extracts MER-specific data from SPICE kernels (essentially, raw data files) and calculates values for Planet Day Number, Local Solar Longitude, Local Solar Elevation, Local Solar Azimuth, and Local Solar Time (UTC). MER SPICE Interface was adapted from a subroutine, denoted m98SpiceIF written by Payam Zamani, that was intended to calculate SPICE values for the Mars Polar Lander. The main difference between MER SPICE Interface and m98SpiceIf is that MER SPICE Interface does not explicitly call CHRONOS, a time-conversion program that is part of a library of utility subprograms within SPICE. Instead, MER SPICE Interface mimics some portions of the CHRONOS code, the advantage being that it executes much faster and can efficiently be called from a pipeline of events in a parallel processing environment.

  11. Lectures on random interfaces

    CERN Document Server

    Funaki, Tadahisa

    2016-01-01

    Interfaces are created to separate two distinct phases in a situation in which phase coexistence occurs. This book discusses randomly fluctuating interfaces in several different settings and from several points of view: discrete/continuum, microscopic/macroscopic, and static/dynamic theories. The following four topics in particular are dealt with in the book. Assuming that the interface is represented as a height function measured from a fixed-reference discretized hyperplane, the system is governed by the Hamiltonian of gradient of the height functions. This is a kind of effective interface model called ∇φ-interface model. The scaling limits are studied for Gaussian (or non-Gaussian) random fields with a pinning effect under a situation in which the rate functional of the corresponding large deviation principle has non-unique minimizers. Young diagrams determine decreasing interfaces, and their dynamics are introduced. The large-scale behavior of such dynamics is studied from the points of view of the hyd...

  12. Touchfree medical interfaces.

    Science.gov (United States)

    Rossol, Nathaniel; Cheng, Irene; Rui Shen; Basu, Anup

    2014-01-01

    Real-time control of visual display systems via mid-air hand gestures offers many advantages over traditional interaction modalities. In medicine, for example, it allows a practitioner to adjust display values, e.g. contrast or zoom, on a medical visualization interface without the need to re-sterilize the interface. However, when users are holding a small tool (such as a pen, surgical needle, or computer stylus) the need to constantly put the tool down in order to make hand gesture interactions is not ideal. This work presents a novel interface that automatically adjusts for gesturing with hands and hand-held tools to precisely control medical displays. The novelty of our interface is that it uses a single set of gestures designed to be equally effective for fingers and hand-held tools without using markers. This type of interface was previously not feasible with low-resolution depth sensors such as Kinect, but is now achieved by using the recently released Leap Motion controller. Our interface is validated through a user study on a group of people given the task of adjusting parameters on a medical image.

  13. Interface evaluation for soft robotic manipulators

    Science.gov (United States)

    Moore, Kristin S.; Rodes, William M.; Csencsits, Matthew A.; Kwoka, Martha J.; Gomer, Joshua A.; Pagano, Christopher C.

    2006-05-01

    The results of two usability experiments evaluating an interface for the operation of OctArm, a biologically inspired robotic arm modeled after an octopus tentacle, are reported. Due to the many degrees-of-freedom (DOF) for the operator to control, such 'continuum' robotic limbs provide unique challenges for human operators because they do not map intuitively. Two modes have been developed to control the arm and reduce the DOF under the explicit direction of the operator. In coupled velocity (CV) mode, a joystick controls changes in arm curvature. In end-effector (EE) mode, a joystick controls the arm by moving the position of an endpoint along a straight line. In Experiment 1, participants used the two modes to grasp objects placed at different locations in a virtual reality modeling language (VRML). Objective measures of performance and subjective preferences were recorded. Results revealed lower grasp times and a subjective preference for the CV mode. Recommendations for improving the interface included providing additional feedback and implementation of an error recovery function. In Experiment 2, only the CV mode was tested with improved training of participants and several changes to the interface. The error recovery function was implemented, allowing participants to reverse through previously attained positions. The mean time to complete the trials in the second usability test was reduced by more than 4 minutes compared with the first usability test, confirming the interface changes improved performance. The results of these tests will be incorporated into future versions of the arm and improve future usability tests.

  14. Total internal reflection effect on gyrotropic interface

    Science.gov (United States)

    Glushchenko, Alexander G.; Glushchenko, Eugene P.; Zhukov, Sergey V.

    2018-02-01

    This article considers the physical features of total internal reflection at gyrotropic and isotropic interfaces for two cases: electrical gyrotropy (plasma) and magnetic gyrotropy (ferrite). It is shown that the plasma magnetization may lead to the formation of the total internal reflection effect, which does not occur in isotropic plasma. The threshold values of the magnetic field, which are necessary for the total internal reflection effect, are determined. The total internal reflection effect on a ferrite-dielectric interface for waves emanating from different angles is observed in various frequency ranges and magnetization fields. The study points out the possibility of changing the total internal reflection angle value in large limits due to a change in the external magnetic field magnitude. The calculation results of the total internal reflection angle dependence on the external magnetic field magnitude are presented. The formulas are elaborated for calculating the total internal reflection angles of different interfaces for gyrotropic and isotropic media. The generalized formulas are defined for calculating the Doppler effect in the gyrotropic media. The study demonstrates how the velocity of the media interface affects the limiting angle of total internal refection.

  15. Velocity distribution of fragments of catastrophic impacts

    Science.gov (United States)

    Takagi, Yasuhiko; Kato, Manabu; Mizutani, Hitoshi

    1992-01-01

    Three dimensional velocities of fragments produced by laboratory impact experiments were measured for basalts and pyrophyllites. The velocity distribution of fragments obtained shows that the velocity range of the major fragments is rather narrow, at most within a factor of 3 and that no clear dependence of velocity on the fragment mass is observed. The NonDimensional Impact Stress (NDIS) defined by Mizutani et al. (1990) is found to be an appropriate scaling parameter to describe the overall fragment velocity as well as the antipodal velocity.

  16. Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives: Synthesis and the effects on chemical mechanical polishing (CMP) performances of sapphire wafers

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Tingting; Lei, Hong, E-mail: hong_lei2005@aliyun.com

    2017-08-15

    Highlights: • The novel Nd{sup 3+}-doped colloidal SiO{sub 2} abrasives were synthesized by seed-introduced method. • The Nd{sup 3+}-doped colloidal SiO{sub 2} abrasives exhibited lower Ra and higher MRR on sapphire during CMP. • The cores SiO{sub 2} were coated by the shells (SiO{sub 2}, Nd{sub 2}Si{sub 2}O{sub 7} and Nd(OH){sub 3}) via chemical bonds and hydrogen bonds. • XPS analysis revealed the solid-state chemical reaction between Nd{sup 3+}-doped colloidal SiO{sub 2} abrasives and sapphire during CMP. - Abstract: Abrasive is one of the most important factors in chemical mechanical polishing (CMP). In order to improve the polishing qualities of sapphire substrates, the novel Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives were prepared by seed-induced growth method. In this work, there were a series of condensation reactions during the synthesis process of Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives and the silica cores were coated by shells (which contains SiO{sub 2}, Nd{sub 2}Si{sub 2}O{sub 7} and Nd(OH){sub 3}) via chemical bonds and hydrogen bonds in the Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives, which made the composite abrasives’ core-shell structure more sTable Scanning electron microscopy (SEM) showed that Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives were spherical and uniform in size. And the acting mechanisms of Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives on sapphire in CMP were investigated. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) analysis and X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the solid-state chemical reactions between the shells (which contained SiO{sub 2}, Nd{sub 2}Si{sub 2}O{sub 7} and Nd(OH){sub 3}) of Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives and the sapphire occurred during the CMP process. Furthermore, Nd{sup 3+}-doped colloidal SiO{sub 2} composite abrasives exhibited lower surface roughness and

  17. Electron velocity and momentum density

    International Nuclear Information System (INIS)

    Perkins, G.A.

    1978-01-01

    A null 4-vector eta + sigma/sub μ/based on Dirac's relativistic electron equation, is shown explicitly for a plane wave and various Coulomb states. This 4-vector constitutes a mechanical ''model'' for the electron in those staes, and expresses the important spinor quantities represented conventionally by n, f, g, m, j, kappa, l, and s. The model for a plane wave agrees precisely with the relation between velocity and phase gradient customarily used in quantum theory, but the models for Coulomb states contradict that relation

  18. Studying the instantaneous velocity field in gas-sheared liquid films in a horizontal duct

    Science.gov (United States)

    Vasques, Joao; Tokarev, Mikhail; Cherdantsev, Andrey; Hann, David; Hewakandamby, Buddhika; Azzopardi, Barry

    2016-11-01

    In annular flow, the experimental validation of the basic assumptions on the liquid velocity profile is vital for developing theoretical models of the flow. However, the study of local velocity of liquid in gas-sheared films has proven to be a challenging task due to the highly curved and disturbed moving interface of the phases, small scale of the area of interrogation, high velocity gradients and irregular character of the flow. This study reports on different optical configurations and interface-tracking methods employed in a horizontal duct in order to obtain high-resolution particle image velocimetry (PIV) data in such types of complex flows. The experimental envelope includes successful measurements in 2D and 3D waves regimes, up to the disturbance wave regime. Preliminary data show the presence of complex structures in the liquid phase, which includes re-circulation areas below the liquid interface due to the gas-shearing action, together with non-uniform transverse movements of the liquid phase close to the wall due to the presence of 3D waves at the interface. With the aid of the moving interface-tracking, PIV, time-resolved particle-tracking velocimetry and vorticity measurements were performed.

  19. Phase formation and strain relaxation of Ga2O3 on c-plane and a-plane sapphire substrates as studied by synchrotron-based x-ray diffraction

    Science.gov (United States)

    Cheng, Zongzhe; Hanke, Michael; Vogt, Patrick; Bierwagen, Oliver; Trampert, Achim

    2017-10-01

    Heteroepitaxial Ga2O3 was deposited on c-plane and a-plane oriented sapphire by plasma-assisted molecular beam epitaxy and probed by ex-situ and in-situ synchrotron-based x-ray diffraction. The investigation on c-plane sapphire determined a critical thickness of around 33 Å, at which the monoclinic β-phase forms on top of the hexagonal α-phase. A 143 Å thick single phase α-Ga2O3 was observed on a-plane sapphire, much thicker than the α-Ga2O3 on c-plane sapphire. The α-Ga2O3 relaxed very fast in the first 30 Å in both out-of-plane and in-plane directions as measured by the in-situ study.

  20. Instrument for measuring flow velocities

    International Nuclear Information System (INIS)

    Griffo, J.

    1977-01-01

    The design described here means to produce a 'more satisfying instrument with less cost' than comparable instruments known up to now. Instead of one single turbine rotor, two similar ones but with opposite blade inclination and sense of rotation are to be used. A cylindrical measuring body is carrying in its axis two bearing blocks whose shape is offering little flow resistance. On the shaft, supported by them, the two rotors run in opposite direction a relatively small axial distance apart. The speed of each rotor is picked up as pulse recurrence frequency by a transmitter and fed to an electronic measuring unit. Measuring errors as they are caused for single rotors by turbulent flow, profile distortion of the velocity, or viscous flow are to be eliminated by means of the contrarotating turbines and the subsequently added electronic unit, because in these cases the adulterating increase of the angular velocity of one rotor is compensated by a corresponding deceleration of the other rotor. The mean value then indicated by the electronic unit has high accurancy of measurement. (RW) [de

  1. Environmental materials and interfaces

    International Nuclear Information System (INIS)

    1991-11-01

    A workshop that explored materials and interfaces research needs relevant to national environmental concerns was conducted at Pacific Northwest Laboratory. The purposes of the workshop were to refine the scientific research directions being planned for the Materials and Interface Program in the Molecular Science Research Center (MSRC) and further define the research and user equipment to the included as part of the proposed Environmental and Molecular Science Laboratory (EMSL). Three plenary information sessions served to outline the background, objectives, and status of the MSRC and EMSL initiatives; selected specific areas with environmentally related materials; and the status of capabilities and facilities planned for the EMSL. Attention was directed to four areas where materials and interface science can have a significant impact on prevention and remediation of environmental problems: in situ detection and characterization of hazardous wastes (sensors), minimization of hazardous waste (separation membranes, ion exchange materials, catalysts), waste containment (encapsulation and barrier materials), and fundamental understanding of contaminant transport mechanisms. During all other sessions, the participants were divided into three working groups for detailed discussion and the preparation of a written report. The working groups focused on the areas of interface structure and chemistry, materials and interface stability, and materials synthesis. These recommendations and suggestions for needed research will be useful for other researchers in proposing projects and for suggesting collaborative work with MSRC researchers. 1 fig

  2. Application of Vectors to Relative Velocity

    Science.gov (United States)

    Tin-Lam, Toh

    2004-01-01

    The topic 'relative velocity' has recently been introduced into the Cambridge Ordinary Level Additional Mathematics syllabus under the application of Vectors. In this note, the results of relative velocity and the 'reduction to rest' technique of teaching relative velocity are derived mathematically from vector algebra, in the hope of providing…

  3. Questions Students Ask: About Terminal Velocity.

    Science.gov (United States)

    Meyer, Earl R.; Nelson, Jim

    1984-01-01

    If a ball were given an initial velocity in excess of its terminal velocity, would the upward force of air resistance (a function of velocity) be greater than the downward force of gravity and thus push the ball back upwards? An answer to this question is provided. (JN)

  4. Balance velocities of the Greenland ice sheet

    DEFF Research Database (Denmark)

    Joughin, I.; Fahnestock, M.; Ekholm, Simon

    1997-01-01

    We present a map of balance velocities for the Greenland ice sheet. The resolution of the underlying DEM, which was derived primarily from radar altimetery data, yields far greater detail than earlier balance velocity estimates for Greenland. The velocity contours reveal in striking detail......, the balance map is useful for ice-sheet modelling, mass balance studies, and field planning....

  5. Interfacing Sensors To Micro Controllers

    KAUST Repository

    Norain, Mohamed

    2018-01-01

    This lecture will cover the most common interface and interface techniques between sensors and microcontrollers. The presentation will introduce the pros and cons of each interface type including analogue, digital and serial output sensors. It will also cover the basic required electronics knowledge to help you in selecting and designing your next sensor to microcontroller interface.

  6. Interfacing Sensors To Micro Controllers

    KAUST Repository

    Norain, Mohamed

    2018-01-15

    This lecture will cover the most common interface and interface techniques between sensors and microcontrollers. The presentation will introduce the pros and cons of each interface type including analogue, digital and serial output sensors. It will also cover the basic required electronics knowledge to help you in selecting and designing your next sensor to microcontroller interface.

  7. Development of laser diode-pumped high average power solid-state laser for the pumping of Ti:sapphire CPA system

    Energy Technology Data Exchange (ETDEWEB)

    Maruyama, Yoichiro; Tei, Kazuyoku; Kato, Masaaki; Niwa, Yoshito; Harayama, Sayaka; Oba, Masaki; Matoba, Tohru; Arisawa, Takashi; Takuma, Hiroshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    Laser diode pumped all solid state, high repetition frequency (PRF) and high energy Nd:YAG laser using zigzag slab crystals has been developed for the pumping source of Ti:sapphire CPA system. The pumping laser installs two main amplifiers which compose ring type amplifier configuration. The maximum amplification gain of the amplifier system is 140 and the condition of saturated amplification is achieved with this high gain. The average power of fundamental laser radiation is 250 W at the PRF of 200 Hz and the pulse duration is around 20 ns. The average power of second harmonic is 105 W at the PRF of 170 Hz and the pulse duration is about 16 ns. The beam profile of the second harmonic is near top hat and will be suitable for the pumping of Ti:sapphire laser crystal. The wall plug efficiency of the laser is 2.0 %. (author)

  8. Structural and electronic properties of InN epitaxial layer grown on c-plane sapphire by chemical vapor deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Barick, Barun Kumar, E-mail: bkbarick@gmail.com; Prasad, Nivedita; Saroj, Rajendra Kumar; Dhar, Subhabrata [Department of Physics, Indian Institute of Technology, Bombay, Mumbai 400076 (India)

    2016-09-15

    Growth of InN epilayers on c-plane sapphire substrate by chemical vapor deposition technique using pure indium metal and ammonia as precursors has been systematically explored. It has been found that [0001] oriented indium nitride epitaxial layers with smooth surface morphology can be grown on c-plane sapphire substrates by optimizing the growth conditions. Bandgap of the film is observed to be Burstein–Moss shifted likely to be due to high background electron concentration. It has been found that the concentration of this unintentional doping decreases with the increase in the growth temperature and the ammonia flux. Epitaxial quality on the other hand deteriorates as the growth temperature increases. Moreover, the morphology of the deposited layer has been found to change from flat top islands to faceted mounds as the flow rate of ammonia increases. This phenomenon is expected to be related to the difference in surface termination character at low and high ammonia flow rates.

  9. XPS and ToF-SIMS analysis of natural rubies and sapphires heat-treated in a reducing (5 mol% H 2/Ar) atmosphere

    Science.gov (United States)

    Achiwawanich, S.; James, B. D.; Liesegang, J.

    2008-12-01

    Surface effects on Mong Hsu rubies and Kanchanaburi sapphires after heat treatment in a controlled reducing atmosphere (5 mol% H 2/Ar) have been investigated using advanced surface science techniques including X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Visual appearance of the gemstones is clearly affected by the heat treatment in a reducing atmosphere. Kanchanaburi sapphires, in particular, exhibit Fe-containing precipitates after the heat treatment which have not been observed in previous studies under an inert atmosphere. Significant correlation between changes in visual appearance of the gemstones and variations in surface concentration of trace elements, especially Ti and Fe are observed. The XPS and ToF-SIMS results suggest that; (1) a reducing atmosphere affects the oxidation state of Fe; (2) dissociation of Fe-Ti interaction may occur during heat treatment.

  10. XPS and ToF-SIMS analysis of natural rubies and sapphires heat-treated in a reducing (5 mol% H{sub 2}/Ar) atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Achiwawanich, S. [Department of Physics, La Trobe University, VIC 3086 (Australia); Centre for Materials and Surface Science, La Trobe University, VIC 3086 (Australia); James, B.D. [Centre for Materials and Surface Science, La Trobe University, VIC 3086 (Australia); Department of Chemistry, La Trobe University, VIC 3086 (Australia); Liesegang, J. [Department of Physics, La Trobe University, VIC 3086 (Australia); Centre for Materials and Surface Science, La Trobe University, VIC 3086 (Australia)], E-mail: J.Liesegang@latrobe.edu.au

    2008-12-30

    Surface effects on Mong Hsu rubies and Kanchanaburi sapphires after heat treatment in a controlled reducing atmosphere (5 mol% H{sub 2}/Ar) have been investigated using advanced surface science techniques including X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Visual appearance of the gemstones is clearly affected by the heat treatment in a reducing atmosphere. Kanchanaburi sapphires, in particular, exhibit Fe-containing precipitates after the heat treatment which have not been observed in previous studies under an inert atmosphere. Significant correlation between changes in visual appearance of the gemstones and variations in surface concentration of trace elements, especially Ti and Fe are observed. The XPS and ToF-SIMS results suggest that; (1) a reducing atmosphere affects the oxidation state of Fe; (2) dissociation of Fe-Ti interaction may occur during heat treatment.

  11. N-polar GaN/AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistor formed on sapphire substrate with minimal step bunching

    Science.gov (United States)

    Prasertsuk, Kiattiwut; Tanikawa, Tomoyuki; Kimura, Takeshi; Kuboya, Shigeyuki; Suemitsu, Tetsuya; Matsuoka, Takashi

    2018-01-01

    The metal-insulator-semiconductor (MIS) gate N-polar GaN/AlGaN/GaN high-electron-mobility transistor (HEMT) on a (0001) sapphire substrate, which can be expected to operate with lower on-resistance and more easily work on the pinch-off operation than an N-polar AlGaN/GaN HEMT, was fabricated. For suppressing the step bunching and hillocks peculiar in the N-polar growth, a sapphire substrate with an off-cut angle as small as 0.8° was introduced and an N-polar GaN/AlGaN/GaN HEMT without the step bunching was firstly obtained by optimizing the growth conditions. The previously reported anisotropy of transconductance related to the step was eliminated. The pinch-off operation was also realized. These results indicate that this device is promising.

  12. User interface design considerations

    DEFF Research Database (Denmark)

    Andersen, Simon Engedal; Jakobsen, Arne; Rasmussen, Bjarne D.

    1999-01-01

    and output variables. This feature requires special attention when designing the user interface and a special approach for controlling the user selection of input and output variables are developed. To obtain a consistent system description the different input variables are grouped corresponding......When designing a user interface for a simulation model there are several important issues to consider: Who is the target user group, and which a priori information can be expected. What questions do the users want answers to and what questions are answered using a specific model?When developing...... the user interface of EESCoolTools these issues led to a series of simulation tools each with a specific purpose and a carefully selected set of input and output variables. To allow a more wide range of questions to be answered by the same model, the user can change between different sets of input...

  13. Workshop on Interface Phenomena

    CERN Document Server

    Kreuzer, Hans

    1987-01-01

    This book contains the proceedings of the first Workshop on Interface Phenomena, organized jointly by the surface science groups at Dalhousie University and the University of Maine. It was our intention to concentrate on just three topics related to the kinetics of interface reactions which, in our opinion, were frequently obscured unnecessarily in the literature and whose fundamental nature warranted an extensive discussion to help clarify the issues, very much in the spirit of the Discussions of the Faraday Society. Each session (day) saw two principal speakers expounding the different views; the session chairmen were asked to summarize the ensuing discussions. To understand the complexity of interface reactions, paradigms must be formulated to provide a framework for the interpretation of experimen­ tal data and for the construction of theoretical models. Phenomenological approaches have been based on a small number of rate equations for the concentrations or mole numbers of the various species involved i...

  14. High-bandwidth memory interface

    CERN Document Server

    Kim, Chulwoo; Song, Junyoung

    2014-01-01

    This book provides an overview of recent advances in memory interface design at both the architecture and circuit levels. Coverage includes signal integrity and testing, TSV interface, high-speed serial interface including equalization, ODT, pre-emphasis, wide I/O interface including crosstalk, skew cancellation, and clock generation and distribution. Trends for further bandwidth enhancement are also covered.   • Enables readers with minimal background in memory design to understand the basics of high-bandwidth memory interface design; • Presents state-of-the-art techniques for memory interface design; • Covers memory interface design at both the circuit level and system architecture level.

  15. An Approach to Interface Synthesis

    DEFF Research Database (Denmark)

    Madsen, Jan; Hald, Bjarne

    1995-01-01

    Presents a novel interface synthesis approach based on a one-sided interface description. Whereas most other approaches consider interface synthesis as optimizing a channel to existing client/server modules, we consider the interface synthesis as part of the client/server module synthesis (which...... may contain the re-use of existing modules). The interface synthesis approach describes the basic transformations needed to transform the server interface description into an interface description on the client side of the communication medium. The synthesis approach is illustrated through a point...

  16. Photoluminescence studies of ZnO thin films on R-plane sapphire substrates grown by sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Su [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Gimhae, Gyungnam 621-749 (Korea, Republic of); Nam, Giwoong; Kim, Soaram [Department of Nano Engineering, Inje University, Gimhae, Gyungnam 621-749 (Korea, Republic of); Kim, Do Yeob [Holcombe Department of Electrical and Computer Engineering, Center for Optical Materials Science and Engineering Technologies, Clemson University, Clemson, SC 29634 (United States); Lee, Dong-Yul [LED R and D team, Samsung Electronics Co. Ltd., Yongin 446-711 (Korea, Republic of); Kim, Jin Soo [Research Center of Advanced Materials Development (RCAMD), Division of Advanced Materials Engineering, Chonbuk National University, Jeonju, Chonbuk 561-756 (Korea, Republic of); Kim, Sung-O [Holcombe Department of Electrical and Computer Engineering, Center for Optical Materials Science and Engineering Technologies, Clemson University, Clemson, SC 29634 (United States); Kim, Jong Su [Department of Physics, Yeungnam University, Gyeongsan, Gyeongsangbuk-do 712-749 (Korea, Republic of); Son, Jeong-Sik [Department of Visual Optics, Kyungwoon University, Gumi, Gyeongsangbuk-do 730-850 (Korea, Republic of); Leem, Jae-Young, E-mail: jyleem@inje.ac.kr [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Gimhae, Gyungnam 621-749 (Korea, Republic of)

    2012-10-15

    Zinc oxide (ZnO) thin films on R-plane sapphire substrates were grown by the sol-gel spin-coating method. The optical properties of the ZnO thin films were investigated using photoluminescence. In the UV range, the asymmetric near-band-edge emission was observed at 300 K, which consisted of two emissions at 3.338 and 3.279 eV. Eight peaks at 3.418, 3.402, 3.360, 3.288, 3.216, 3.145, 3.074, and 3.004 eV, which respectively correspond to the free exciton (FX), bound exciton, transverse optical (TO) phonon replica of FX recombination, and first-order longitudinal optical phonon replica of FX and the TO (1LO+TO), 2LO+TO, 3LO+TO, 4LO+TO, and 5LO+TO, were obtained at 12 K. From the temperature-dependent PL, it was found that the emission peaks at 3.338 and 3.279 eV corresponded to the FX and TO, respectively. The activation energy of the FX and TO emission peaks was found to be about 39.3 and 28.9 meV, respectively. The values of the fitting parameters of Varshni's empirical equation were {alpha}=4 Multiplication-Sign 10{sup -3} eV/K and {beta}=4.9 Multiplication-Sign 10{sup 3} K, and the S factor of the ZnO thin films was 0.658. With increasing temperature, the exciton radiative lifetime of the FX and TO emissions increased. The temperature-dependent variation of the exciton radiative lifetime for the TO emission was slightly higher than that for the FX emission. - Highlights: Black-Right-Pointing-Pointer ZnO thin films on R-plane sapphire substrates were grown by sol-gel method. Black-Right-Pointing-Pointer Two emission peaks at 3.338 and 3.279 eV were observed at 300 K Black-Right-Pointing-Pointer Activation energies of the two peaks were 39.3 and 28.9 meV,respectively. Black-Right-Pointing-Pointer Exciton radiative lifetime of the two peaks increased with increasing temperature.

  17. Hybrid Ti:Sapphire / KrF laser facility GARPUN for combined subpicosecond/nanosecond laser-matter interaction studies

    International Nuclear Information System (INIS)

    Zvorykin, V.D.; Ionin, A.A.; Konyashcenko, A.V.; Levchenko, A.O.; Krokhin, O.N.; Mesyats, G.A.; Molchanov, A.G.; Rorulev, M.A.

    2006-01-01

    Complete test of publication follows. Hybrid laser facility consisting of Ti:Sapphire front end, 3ω converter, and e-beam-pumped large-aperture KrF amplifiers is under construction to generate combined sub-picosecond/nanosecond pulses in UV spectral range at 248-nm wavelength. This is a part of the Petawatt excimer laser project started at P.N. Lebedev Physical Institute. In comparison with commonly used solid-state chirped-pulse amplifiers (CPA), KrF amplifiers have following advantages: (i) low-density gaseous matter with three orders of magnitude lower non-linear refraction index has a small value of B-integral and negligible pulse distortion; (ii) short radiation lifetime τ r = 6 ns of the upper laser level of KrF(B-X) transition (with accounting for collisions τ c ∼ 2 ns), that means the population inversion is recovered each 2 ns during the pumping time, which is typically τ p ≥ 100 ns for technical reasons. Thus, it might be possible eliminating of very costly large-aperture compressor gratings and to amplify both short τ sh c and long τ long ≥ τ c pulses in the same amplifiers, as a short pulse does not affect the gain during the most of pumping. This gives a unique opportunity for realization of fast-ignition scheme in Inertial Confinement Fusion using large-scale KrF drivers. The Ti:Sapphire front end 'Start 248M' currently operates with the following parameters: rep rate 10 Hz, pulse energy and duration at fundamental wavelength (744 nm) > 8 mJ and 0.5 mJ and 0.4 mJ, 740 nm) and multi-pass amplifier (10 Hz, > 15 mJ, 740 nm), both pumped by 2ω pulsed Lotis LS-2134 Nd:YAG laser (10 Hz, 10 ns, 532 nm) with distributed energies of 5 and 70 mJ, two-gratings compressor, and 3ω converter with two BBO crystals and total efficiency 8%. EMG 150MSC Lambda Physik KrF laser is used afterwards to generate ns pulses and to amplify fs pulses in its two separate discharge chambers. Two e-beam pumped KrF amplifiers Berdysh and GARPUN with active volumes 10

  18. Critical velocities in He II for independently varied superfluid and normal fluid velocities

    International Nuclear Information System (INIS)

    Baehr, M.L.

    1984-01-01

    Experiments were performed to measure the critical velocity in pure superflow and compare to the theoretical prediction; to measure the first critical velocity for independently varied superfluid and normal fluid velocities; and to investigate the propagation of the second critical velocity from the thermal counterflow line through the V/sub n/,-V/sub s/ quadrant. The experimental apparatus employed a thermal counterflow heater to adjust the normal fluid velocity, a fountain pump to vary the superfluid velocity, and a level sensing capacitor to measure the superfluid velocity. The results of the pure superfluid critical velocity measurements indicate that this velocity is temperature independent contrary to Schwarz's theory. It was found that the first critical velocity for independently varied V/sub n/ and V/sub s/ could be described by a linear function of V/sub n/ and was otherwise temperature independent. It was found that the second critical velocity could only be distinguished near the thermal counterflow line

  19. Vision-Based Interfaces Applied to Assistive Robots

    Directory of Open Access Journals (Sweden)

    Elisa Perez

    2013-02-01

    Full Text Available This paper presents two vision-based interfaces for disabled people to command a mobile robot for personal assistance. The developed interfaces can be subdivided according to the algorithm of image processing implemented for the detection and tracking of two different body regions. The first interface detects and tracks movements of the user's head, and these movements are transformed into linear and angular velocities in order to command a mobile robot. The second interface detects and tracks movements of the user's hand, and these movements are similarly transformed. In addition, this paper also presents the control laws for the robot. The experimental results demonstrate good performance and balance between complexity and feasibility for real-time applications.

  20. Adhesive joint evaluation by ultrasonic interface and lamb waves

    Science.gov (United States)

    Rokhlin, S. I.

    1986-01-01

    Some results on the application of interface and Lamb waves for the study of curing of thin adhesive layers were summarized. In the case of thick substrates (thickness much more than the wave length) the interface waves can be used. In this case the experimental data can be inverted and the shear modulus of the adhesive film may be explicitly found based on the measured interface wave velocity. It is shown that interface waves can be used for the study of curing of structural adhesives as a function of different temperatures and other experimental conditions. The kinetics of curing was studied. In the case of thin substrates the wave phenomena are much more complicated. It is shown that for successful measurements proper selection of experimental conditions is very important. This can be done based on theoretical estimations. For correctly selected experimental conditions the Lamb waves may be a sensitive probe of adhesive bond quality and may be used or cure monitoring.

  1. Computational analysis of acoustic transmission through periodically perforated interfaces

    Directory of Open Access Journals (Sweden)

    Rohan E.

    2009-06-01

    Full Text Available The objective of the paper is to demonstrate the homogenization approach applied to modelling the acoustic transmission on perforated interfaces embedded in the acoustic fluid. We assume a layer, with periodically perforated obstacles, separating two half-spaces filled with the fluid. The homogenization method provides limit transmission conditions which can be prescribed at the homogenized surface representing the "limit" interface. The conditions describe relationship between jump of the acoustic pressures and the transversal acoustic velocity, on introducing the "in-layer pressure" which describes wave propagation in the tangent directions with respect to the interface.This approach may serve as a relevant tool for optimal design of devices aimed at attenuation of the acoustic waves, such as the engine exhaust mufflers or other structures fitted with sieves and grillages. We present numerical examples of wave propagation in a muffler-like structure illustrating viability of the approach when complex 3D geometries of the interface perforation are considered.

  2. Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors

    Directory of Open Access Journals (Sweden)

    Keisuke Iwano

    2016-10-01

    Full Text Available We investigate the optical transmittances of ion-irradiated sapphire crystals as potential vacuum ultraviolet (VUV to near-infrared (NIR window materials of fusion reactors. Under potential conditions in fusion reactors, sapphire crystals are irradiated with hydrogen (H, deuterium (D, and helium (He ions with 1-keV energy and ∼ 1020-m-2 s-1 flux. Ion irradiation decreases the transmittances from 140 to 260 nm but hardly affects the transmittances from 300 to 1500 nm. H-ion and D-ion irradiation causes optical absorptions near 210 and 260 nm associated with an F-center and an F+-center, respectively. These F-type centers are classified as Schottky defects that can be removed through annealing above 1000 K. In contrast, He-ion irradiation does not cause optical absorptions above 200 nm because He-ions cannot be incorporated in the crystal lattice due to the large ionic radius of He-ions. Moreover, the significant decrease in transmittance of the ion-irradiated sapphire crystals from 140 to 180 nm is related to the light scattering on the crystal surface. Similar to diamond polishing, ion irradiation modifies the crystal surface thereby affecting the optical properties especially at shorter wavelengths. Although the transmittances in the VUV wavelengths decrease after ion irradiation, the transmittances can be improved through annealing above 1000 K. With an optical transmittance in the VUV region that can recover through simple annealing and with a high transparency from the ultraviolet (UV to the NIR region, sapphire crystals can therefore be used as good optical windows inside modern fusion power reactors in terms of light particle loadings of hydrogen isotopes and helium.

  3. Natural User Interfaces

    OpenAIRE

    Câmara , António

    2011-01-01

    Dissertação de Mestrado em Engenharia Informática apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra This project’s main subject are Natural User Interfaces. These interfaces’ main purpose is to allow the user to interact with computer systems in a more direct and natural way. The popularization of touch and gesture devices in the last few years has allowed for them to become increasingly common and today we are experiencing a transition of interface p...

  4. Interfacing to accelerator instrumentation

    International Nuclear Information System (INIS)

    Shea, T.J.

    1995-01-01

    As the sensory system for an accelerator, the beam instrumentation provides a tremendous amount of diagnostic information. Access to this information can vary from periodic spot checks by operators to high bandwidth data acquisition during studies. In this paper, example applications will illustrate the requirements on interfaces between the control system and the instrumentation hardware. A survey of the major accelerator facilities will identify the most popular interface standards. The impact of developments such as isochronous protocols and embedded digital signal processing will also be discussed

  5. Virtual interface environment workstations

    Science.gov (United States)

    Fisher, S. S.; Wenzel, E. M.; Coler, C.; Mcgreevy, M. W.

    1988-01-01

    A head-mounted, wide-angle, stereoscopic display system controlled by operator position, voice and gesture has been developed at NASA's Ames Research Center for use as a multipurpose interface environment. This Virtual Interface Environment Workstation (VIEW) system provides a multisensory, interactive display environment in which a user can virtually explore a 360-degree synthesized or remotely sensed environment and can viscerally interact with its components. Primary applications of the system are in telerobotics, management of large-scale integrated information systems, and human factors research. System configuration, research scenarios, and research directions are described.

  6. After Rigid Interfaces

    DEFF Research Database (Denmark)

    Troiano, Giovanni Maria

    (1) a user study with a prototype of an elastic, deformable display, and (2) a user study of deformable interfaces for performing music. The first study reports a guessability study with an elastic, deformable display where 17 participants suggested fitting gestures for 29 tasks, including navigation......, Transformation, Adaptation and Physicalization. In synthesis, the work presented in this thesis shows (1) implications of usefulness for deformable interfaces and how their new input modalities can redefine the way users interact with computers, and (2) how a systematic understanding of conventional design...

  7. Interface or Interlace?

    DEFF Research Database (Denmark)

    Hansen, Lone Koefoed; Wamberg, Jacob

    2005-01-01

    Departing from an analysis of the computer's indeterminate location between medium and machine, this paper problematises the idea of a clear-cut interface in complex computing, especially Augmented Reality. The idea and pratice of the interface is derived from the medium as a representational...... surface and thus demands the overview of an autonomous consciouness. Instead we introduce the term interlace, a mingling of representational and physical levels, thus describing the computer's ambiguous blending of imaginary and real. The proposition is demonstrated through analysis of different recent...

  8. CAMAC to GPIB interface

    International Nuclear Information System (INIS)

    Naivar, F.J.

    1978-01-01

    A CAMAC module developed at the Los Alamos Scientific Laboratory allows any device conforming to the GPIB standard to be connected to a CAMAC system. This module incorporates a microprocessor to control up to 14 GPIB-compatible instruments using a restricted set of CAMAC F-N-A commands. The marriage of a device-independent bus (IEEE Standard 488-1975) to a computer-independent bus (IEEE Standard 583-1975) provides a general method for interfacing a system of programmable instruments to any computer. This module is being used to interface a variety of interactive devices on a control console to a control computer

  9. Nonlinear optics at interfaces

    International Nuclear Information System (INIS)

    Chen, C.K.

    1980-12-01

    Two aspects of surface nonlinear optics are explored in this thesis. The first part is a theoretical and experimental study of nonlinear intraction of surface plasmons and bulk photons at metal-dielectric interfaces. The second part is a demonstration and study of surface enhanced second harmonic generation at rough metal surfaces. A general formulation for nonlinear interaction of surface plasmons at metal-dielectric interfaces is presented and applied to both second and third order nonlinear processes. Experimental results for coherent second and third harmonic generation by surface plasmons and surface coherent antiStokes Raman spectroscopy (CARS) are shown to be in good agreement with the theory

  10. X-ray characterization of CdO thin films grown on a-, c-, r- and m-plane sapphire by metalorganic vapour phase-epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Zuniga-Perez, J.; Martinez-Tomas, C.; Munoz-Sanjose, V. [Departamento de Fisica Aplicada y Electromagnetismo, Universitat de Valencia, C/Dr. Moliner 50, 46100 Burjassot (Spain)

    2005-02-01

    CdO thin films have been grown on a-plane (11 anti 20), c-plane (0001), r-plane (01 anti 12) and m-plane (10 anti 10) sapphire substrates by metalorganic vapour-phase epitaxy (MOVPE). The effects of different substrate orientations on the structural properties of the films have been analyzed by means of X-ray diffraction, including {theta}-2{theta} scans, pole figures and rocking curves. (111), (001) and (110) orientations are found on a-, r-, and m-sapphire respectively, while films deposited on c-plane exhibit an orientation in which no low-index crystal plane is parallel to the sample surface. The recorded pole figures have allowed determining the epitaxial relationships between films and substrates, as well as the presence or absence of extended defects. The rocking curves indicate that high quality thin films, in terms of tilt and twist, can be obtained on r-, c- and m-plane sapphire, while further improvement is needed over the a-orientation. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. X-ray characterization of CdO thin films grown on a-, c-, r- and m-plane sapphire by metalorganic vapour phase-epitaxy

    International Nuclear Information System (INIS)

    Zuniga-Perez, J.; Martinez-Tomas, C.; Munoz-Sanjose, V.

    2005-01-01

    CdO thin films have been grown on a-plane (11 anti 20), c-plane (0001), r-plane (01 anti 12) and m-plane (10 anti 10) sapphire substrates by metalorganic vapour-phase epitaxy (MOVPE). The effects of different substrate orientations on the structural properties of the films have been analyzed by means of X-ray diffraction, including θ-2θ scans, pole figures and rocking curves. (111), (001) and (110) orientations are found on a-, r-, and m-sapphire respectively, while films deposited on c-plane exhibit an orientation in which no low-index crystal plane is parallel to the sample surface. The recorded pole figures have allowed determining the epitaxial relationships between films and substrates, as well as the presence or absence of extended defects. The rocking curves indicate that high quality thin films, in terms of tilt and twist, can be obtained on r-, c- and m-plane sapphire, while further improvement is needed over the a-orientation. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Self-assembled growth and structural analysis of inclined GaN nanorods on nanoimprinted m-sapphire using catalyst-free metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kyuseung; Chae, Sooryong; Jang, Jongjin; Min, Daehong; Kim, Jaehwan; Nam, Okhyun, E-mail: ohnam@kpu.ac.kr [Convergence Center for Advanced Nano Semiconductor (CANS), Department of Nano-Optical Engineering, Korea Polytechnic University, Siheung, 15073 (Korea, Republic of)

    2016-04-15

    In this study, self-assembled inclined (1-10-3)-oriented GaN nanorods (NRs) were grown on nanoimprinted (10-10) m-sapphire substrates using catalyst-free metal-organic chemical vapor deposition. According to X-ray phi-scans, the inclined GaN NRs were tilted at an angle of ∼57.5° to the [10-10]{sub sapp} direction. Specifically, the GaN NRs grew in a single inclined direction to the [11-20]{sub sapp}. Uni-directionally inclined NRs were formed through the one-sided (10-11)-faceted growth of the interfacial a-GaN plane layer. It was confirmed that a thin layer of a-GaN was formed on r-facet nanogrooves of the m-sapphire substrate by nitridation. The interfacial a-GaN nucleation affected both the inclined angle and the growth direction of the inclined GaN NRs. Using X-ray diffraction and selective area electron diffraction, the epitaxial relationship between the inclined (1-10-3) GaN NRs and interfacial a-GaN layer on m-sapphire substrates was systematically investigated. Moreover, the inclined GaN NRs were observed to be mostly free of stacking fault-related defects using high-resolution transmission electron microscopy.

  13. Automated quantification of apoptosis in B-cell chronic lymphoproliferative disorders: a prognostic variable obtained with the Cell-Dyn Sapphire (Abbott) automated hematology analyzer.

    Science.gov (United States)

    Fumi, M; Martins, D; Pancione, Y; Sale, S; Rocco, V

    2014-12-01

    B-chronic lymphocytic leukemia CLL, a neoplastic clonal disorder with monomorphous small B lymphocytes with scanty cytoplasm and clumped chromatin, can be morphologically differentiated in typical and atypical forms with different prognosis: Smudge cells (Gumprecht's shadows) are one of the well-known features of the typical CLL and are much less inconsistent in other different types CLPD. Abbott Cell-Dyn Sapphire uses the fluorescence after staining with the DNA fluorochrome propidium iodide for the measurement of nucleated red blood cells (NRBCs) and nonviable cells (FL3+ cell fraction): We have studied the possible correlation between presence and number of morphologically identifiable smudge cells on smears and the percentage of nonviable cells produced by Cell-Dyn Sapphire. 305 blood samples from 224 patients with B-cell lymphoproliferative disorders and 40 healthy blood donors were analyzed by CBC performed by Cell-Dyn Sapphire, peripheral blood smear, and immunophenotype characterization. FL3+ fraction in CLPD directly correlated with the percentage of smudge cells and is significantly increased in patients with typical B-CLL. This phenomenon is much less evident in patients with atypical/mixed B-CLL and B-NHL. In small laboratories without FCM and cytogenetic, smudge cells%, can be utilized as a preliminary diagnostic and prognostic tool in differential diagnosis of CLPD. © 2014 John Wiley & Sons Ltd.

  14. Broadband dielectric characterization of sapphire/TiOx/Ba₀.₃Sr₀.₇TiO₃ (111)-oriented thin films for the realization of a tunable interdigitated capacitor.

    Science.gov (United States)

    Ghalem, Areski; Ponchel, Freddy; Remiens, Denis; Legier, Jean-Francois; Lasri, Tuami

    2013-05-01

    A complete microwave characterization up to 67 GHz using specific coplanar waveguides was performed to determine the dielectric properties (permittivity, losses, and tunability) of sapphire/TiOx/Ba0.3Sr0.7TiO3 (BST) (111)-oriented thin films. To that end, BaxSr1-xTiO3 thin films were deposited by RF magnetron sputtering on sapphire (0001) substrate. To control the preferred (111) orientation, a TiOx buffer layer was deposited on sapphire. According to the detailed knowledge of the material properties, it has been possible to conceive, fabricate, and test interdigitated capacitors, the basic element for future microwave tunable applications. Retention of capacitive behavior up to 67 GHz and a tunability of 32% at 67 GHz at an applied voltage of 30 V (150 kV/cm) were observed. The Q-factor remains greater than 30 over the entire frequency band. The possibility of a complete characterization of the material for the realization of high-performance interdigitated capacitors opens the door to microwave device fabrication.

  15. Transport near slippery interfaces

    NARCIS (Netherlands)

    Haase, A. Sander

    2016-01-01

    Some surfaces exhibit wall slip, meaning that a owing uid has a velocity relative to that surface. This leads to increased advection in the direct vicinity of the wall. As this directly a ects the rate of transport at larger scales, slippery surfaces have a potentially important application in

  16. Space as interface

    DEFF Research Database (Denmark)

    Lykke-Olesen, Andreas

    2006-01-01

    multiple projects spanning over fields such as tangible user interfaces, augmented reality, and mobile computing, a conceptual framework characterizing camera-based mixed interaction spaces is developed. To show the applicability of the framework, it is deployed on one of the presented cases and discussed...

  17. The Liquid Vapour Interface

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage

    1985-01-01

    In this short review we are concerned with the density variation across the liquid-vapour interface, i.e. from the bulk density of the liquid to the essentially zero density of the vapour phase. This density variation can in principle be determined from the deviation of the reflectivity from...

  18. Photochemistry at Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Eisenthal, Kenneth B [Columbia Univ., New York, NY (United States)

    2015-02-24

    We have advanced our capabilities to investigate ultrafast excited state dynamics at a liquid interface using a pump to excite molecules to higher electronic states and then probe the subsequent time evolution of the interfacial molecules with femtosecond time delayed vibrational SFG.

  19. Is the interface OK?

    Digital Repository Service at National Institute of Oceanography (India)

    Suresh, T.

    When a peripheral device fails, software methods can be initially resorted to before the usual hardware test procedures are used. A test program is presented here that allows various peripherals, inter-faced to a Norsk Data computer, to be tested...

  20. Evolution of Self-Assembled Au NPs by Controlling Annealing Temperature and Dwelling Time on Sapphire (0001).

    Science.gov (United States)

    Lee, Jihoon; Pandey, Puran; Sui, Mao; Li, Ming-Yu; Zhang, Quanzhen; Kunwar, Sundar

    2015-12-01

    Au nanoparticles (NPs) have been utilized in a wide range of device applications as well as catalysts for the fabrication of nanopores and nanowires, in which the performance of the associated devices and morphology of nanopores and nanowires are strongly dependent on the size, density, and configuration of the Au NPs. In this paper, the evolution of the self-assembled Au nanostructures and NPs on sapphire (0001) is systematically investigated with the variation of annealing temperature (AT) and dwelling time (DT). At the low-temperature range between 300 and 600 °C, three distinct regimes of the Au nanostructure configuration are observed, i.e., the vermiform-like Au piles, irregular Au nano-mounds, and Au islands. Subsequently, being provided with relatively high thermal energy between 700 and 900 °C, the round dome-shaped Au NPs are fabricated based on the Volmer-Weber growth model. With the increased AT, the size of the Au NPs is gradually increased due to a more favorable surface diffusion while the density is gradually decreased as a compensation. On the other hand, with the increased DT, the size and density of Au NPs decrease due to the evaporation of Au at relatively high annealing temperature at 950 °C.

  1. Time-resolved photoemission micro-spectrometer using higher-order harmonics of Ti:sapphire laser

    International Nuclear Information System (INIS)

    Azuma, J.; Kamada, M.; Kondo, Y.

    2004-01-01

    Full text: A new photoemission spectrometer is under construction for the photoemission microscopy and the time-resolved pump- probe experiment. The higher order harmonics of the Ti:sapphire laser is used as the light source of the VUV region in this system. Because the fundamental laser is focused tightly into the rare gas jet to generate the higher order harmonics, the spot size of the laser, in other words, the spot size of the VUV light source is smaller than a few tens of micrometer. This smallness of the spot size has advantage for the microscopy. In order to compensate the low flux of the laser harmonics, a multilayer-coated schwaltzshild optics was designed. The multilayers play also as the monochromatic filter. The spatial resolution of this schwaltzshild system is found to be less than 1 micrometer by the ray-tracing calculations. A main chamber of the system is equipped with a time-of-flight energy analyzer to improve the efficiency of the electron detection. The main chamber and the gas chamber are separated by a differential pumping chamber and a thin Al foil. The system is designed for the study of the clean surface. It will be capable to perform the sub-micron photoemission microscopy and the femto-second pump-probe photoemission study for the various photo-excited dynamics on clean surfaces

  2. Preparation and modification of VO2 thin film on R-sapphire substrate by rapid thermal process

    Science.gov (United States)

    Zhu, Nai-Wei; Hu, Ming; Xia, Xiao-Xu; Wei, Xiao-Ying; Liang, Ji-Ran

    2014-04-01

    The VO2 thin film with high performance of metal-insulator transition (MIT) is prepared on R-sapphire substrate for the first time by magnetron sputtering with rapid thermal process (RTP). The electrical characteristic and THz transmittance of MIT in VO2 film are studied by four-point probe method and THz time domain spectrum (THz-TDS). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and search engine marketing (SEM) are employed to analyze the crystalline structure, valence state, surface morphology of the film. Results indicate that the properties of VO2 film which is oxidized from the metal vanadium film in oxygen atmosphere are improved with a follow-up RTP modification in nitrogen atmosphere. The crystallization and components of VO2 film are improved and the film becomes compact and uniform. A better phase transition performance is shown that the resistance changes nearly 3 orders of magnitude with a 2-°C hysteresis width and the THz transmittances are reduced by 64% and 60% in thermal and optical excitation respectively.

  3. Growth modes of InN (000-1) on GaN buffer layers on sapphire

    International Nuclear Information System (INIS)

    Liu Bing; Kitajima, Takeshi; Chen Dongxue; Leone, Stephen R.

    2005-01-01

    In this work, using atomic force microscopy and scanning tunneling microscopy, we study the surface morphologies of epitaxial InN films grown by plasma-assisted molecular beam epitaxy with intervening GaN buffer layers on sapphire substrates. On smooth GaN buffer layers, nucleation and evolution of three-dimensional InN islands at various coverages and growth temperatures are investigated. The shapes of the InN islands are observed to be predominantly mesalike with large flat (000-1) tops, which suggests a possible role of indium as a surfactant. Rough GaN buffer layers composed of dense small GaN islands are found to significantly improve uniform InN wetting of the substrates, on which atomically smooth InN films are obtained that show the characteristics of step-flow growth. Scanning tunneling microscopy imaging reveals the defect-mediated surface morphology of smooth InN films, including surface terminations of screw dislocations and a high density of shallow surface pits with depths less than 0.3 nm. The mechanisms of the three-dimensional island size and shape evolution and formation of defects on smooth surfaces are considered

  4. Front Surface Tandem Filters using Sapphire (Al2O3) Substrates for Spectral Control in thermophotovoltaic Energy Conversion Systems

    International Nuclear Information System (INIS)

    T Rahmlow, Jr.; J Lazo-Wasem; E Gratrix; P Fourspring; D DePoy

    2005-01-01

    Front surface filters provide an effective means of improving thermophotovoltaic (TPV) system efficiency through spectral control of incident radiant energy. A front surface filter reflects the below band gap photons that can not be converted by the TPV cell back towards the high temperature radiator and allows convertible above band gap photons to pass through the filter into the TPV cell for conversion to electricity. The best spectral control efficiency to date has been demonstrated by front surface, tandem filters that combine an interference filter and an InPAs layer (plasma filter) in series. The InPAs material is a highly doped, epitaxially grown layer on an InP substrate. These tandem filter designs have been fabricated with energy and angle weighted spectral efficiencies of 76% for TPV cells with a 2.08(micro)m (0.6eV) band gap [1]. An alternative to the InPAs layer on an InP substrate is an Al 2 O 3 (sapphire) substrate. The use of Al 2 O 3 may increase transmission of above band gap photons, increase the mechanical strength of the tandem filter, and lower the cost of the tandem filter, all at the expense of lower spectral efficiency. This study presents design and fabrication results for front surface tandem filters that use an Al 2 O 3 substrate for 2.08(micro)m band gap TPV cells

  5. Eu{sup 3+} activated GaN thin films grown on sapphire by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Perea-Lopez, Nestor; Tao, Jonathan H. [Materials Science and Engineering Program, University of California at San Diego, La Jolla, CA 92093 (United States); McKittrick, Joanna [Materials Science and Engineering Program, University of California at San Diego, La Jolla, CA 92093 (United States); Department of Mechanical and Aerospace Engineering, University of California at San Diego, La Jolla, CA 92093 (United States); Talbot, Jan B. [Materials Science and Engineering Program, University of California at San Diego, La Jolla, CA 92093 (United States); Department of Nanoengineering, University of California at San Diego, La Jolla, CA 92093 (United States); Raukas, M.; Laski, J.; Mishra, K.C. [OSRAM SYLVANIA Central Research, Beverly, MA 01915-1068 (United States); Hirata, Gustavo [CCMC-UNAM, Km. 107 Carretera Tijuana-Ensenada, C. P. 22800 Ensenada Baja California (Mexico)

    2008-07-01

    By means of pulsed laser deposition, polycrystalline thin films of GaN doped with Eu{sup 3+} were grown on sapphire. The PLD target was formed in three steps. First, stoichiometric amounts of Ga{sub 2}O{sub 3} and Eu{sub 2}O{sub 3} were dissolved in nitric acid, which produces Ga{sub (1-x)}Eu{sub x} (NO{sub 3}){sub 3}. Next, the nitrates were oxidized in a tubular furnace with O{sub 2} flow forming Ga{sub 2(1-x)}Eu{sub 2x}O{sub 3}. Finally, the oxide powder was flushed with anhydrous ammonia to produce the desired nitride product: Ga{sub (1-x)}Eu{sub x}N. Film growth was done in a stainless steel vacuum chamber partially filled with N{sub 2} (400 mTorr). For the deposit, the 3{sup rd} harmonic of a Nd:YAG laser ({lambda}=355 nm) was focused on the surface of the target. After deposition, annealing in NH{sub 3} was required to produce films with pure GaN hexagonal phase. The luminescence of the film was characterized by photo- and cathodoluminescence. In addition, the chemical and structural properties were analyzed by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Preparation and modification of VO2 thin film on R-sapphire substrate by rapid thermal process

    International Nuclear Information System (INIS)

    Zhu Nai-Wei; Hu Ming; Xia Xiao-Xu; Wei Xiao-Ying; Liang Ji-Ran

    2014-01-01

    The VO 2 thin film with high performance of metal–insulator transition (MIT) is prepared on R-sapphire substrate for the first time by magnetron sputtering with rapid thermal process (RTP). The electrical characteristic and THz transmittance of MIT in VO 2 film are studied by four-point probe method and THz time domain spectrum (THz-TDS). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and search engine marketing (SEM) are employed to analyze the crystalline structure, valence state, surface morphology of the film. Results indicate that the properties of VO 2 film which is oxidized from the metal vanadium film in oxygen atmosphere are improved with a follow-up RTP modification in nitrogen atmosphere. The crystallization and components of VO 2 film are improved and the film becomes compact and uniform. A better phase transition performance is shown that the resistance changes nearly 3 orders of magnitude with a 2-°C hysteresis width and the THz transmittances are reduced by 64% and 60% in thermal and optical excitation respectively. (interdisciplinary physics and related areas of science and technology)

  7. Investigation of diamond wheel topography in Elliptical Ultrasonic Assisted Grinding (EUAG) of monocrystal sapphire using fractal analysis method.

    Science.gov (United States)

    Wang, Qiuyan; Zhao, Wenxiang; Liang, Zhiqiang; Wang, Xibin; Zhou, Tianfeng; Wu, Yongbo; Jiao, Li

    2018-03-01

    The wear behaviors of grinding wheel have significant influence on the work-surface topography. However, a comprehensive and quantitative method is lacking for evaluating the wear conditions of grinding wheel. In this paper, a fractal analysis method is used to investigate the wear behavior of resin-bonded diamond wheel in Elliptical Ultrasonic Assisted Grinding (EUAG) of monocrystal sapphire, and a series of experiments on EUAG and conventional grinding (CG) are performed. The results show that the fractal dimension of grinding wheel topography is highly correlated to the wear behavior, i.e., grain fracture, grain pullout, and wheel loading. An increase in cutting edge density on the wheel surface results in an increase of the fractal dimension, but an increase in the grain pullout and wheel loading results in a decrease in the fractal dimension. The wheel topography in EUAG has a higher fractal dimension than that in CG before 60 passes due to better self-sharpening behavior, and then has a smaller fractal dimension because of more serious wheel loadings after 60 passes. By angle-dependent distribution analysis of profile fractal dimensions, the wheel surface topography is transformed from isotropic to anisotropic. These indicated that the fractal analysis method could be further used in monitoring of a grinding wheel performance in EUAG. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Channel Temperature Determination for AlGaN/GaN HEMTs on SiC and Sapphire

    Science.gov (United States)

    Freeman, Jon C.; Mueller, Wolfgang

    2008-01-01

    Numerical simulation results (with emphasis on channel temperature) for a single gate AlGaN/GaN High Electron Mobility Transistor (HEMT) with either a sapphire or SiC substrate are presented. The static I-V characteristics, with concomitant channel temperatures (T(sub ch)) are calculated using the software package ATLAS, from Silvaco, Inc. An in-depth study of analytical (and previous numerical) methods for the determination of T(sub ch) in both single and multiple gate devices is also included. We develop a method for calculating T(sub ch) for the single gate device with the temperature dependence of the thermal conductivity of all material layers included. We also present a new method for determining the temperature on each gate in a multi-gate array. These models are compared with experimental results, and show good agreement. We demonstrate that one may obtain the channel temperature within an accuracy of +/-10 C in some cases. Comparisons between different approaches are given to show the limits, sensitivities, and needed approximations, for reasonable agreement with measurements.

  9. Optogenetic activation of neocortical neurons in vivo with a sapphire-based micro-scale LED probe

    Directory of Open Access Journals (Sweden)

    Niall eMcAlinden

    2015-05-01

    Full Text Available Optogenetics has proven to be a revolutionary technology in neuroscience and has advanced continuously over the past decade. However, optical stimulation technologies for in vivo need to be developed to match the advances in genetics and biochemistry that have driven this field. In particular, conventional approaches for in vivo optical illumination have a limitation on the achievable spatio-temporal resolution. Here we utilize a sapphire-based microscale gallium nitride light-emitting diode (µLED probe to activate neocortical neurons in vivo. The probes were designed to contain independently controllable multiple µLEDs, emitting at 450 nm wavelength with an irradiance of up to 2 W/mm2. Monte-Carlo stimulations predicted that optical stimulation using a µLED can modulate neural activity within a localized region. To validate this prediction, we tested this probe in the mouse neocortex that expressed channelrhodopsin-2 (ChR2 and compared the results with optical stimulation through a fiber at the cortical surface. We confirmed that both approaches reliably induced action potentials in cortical neurons and that the µLED probe evoked strong responses in deep neurons. Due to the possibility to integrate many optical stimulation sites onto a single shank, the µLED probe is thus a promising approach to control neurons locally in vivo.

  10. Indentation-Induced Mechanical Deformation Behaviors of AlN Thin Films Deposited on c-Plane Sapphire

    International Nuclear Information System (INIS)

    Jian, Sh.R.; Juang, J.Y.

    2012-01-01

    The mechanical properties and deformation behaviors of AlN thin films deposited on c-plane sapphire substrates by helicon sputtering method were determined using the Berkovich nano indentation and cross-sectional transmission electron microscopy (XTEM). The load-displacement curves show the 'pop-ins' phenomena during nano indentation loading, indicative of the formation of slip bands caused by the propagation of dislocations. No evidence of nano indentation-induced phase transformation or cracking patterns was observed up to the maximum load of 80 mN, from either XTEM or atomic force microscopy (AFM) of the mechanically deformed regions. Instead, XTEM revealed that the primary deformation mechanism in AlN thin films is via propagation of dislocations on both basal and pyramidal planes. Furthermore, the hardness and Young's modulus of AlN thin films estimated using the continuous contact stiffness measurements (CSMs) mode provided with the nanoindenter are 16.2 GPa and 243.5 GPa, respectively.

  11. Development of Auto-Seeding System Using Image Processing Technology in the Sapphire Crystal Growth Process via the Kyropoulos Method

    Directory of Open Access Journals (Sweden)

    Churl Min Kim

    2017-04-01

    Full Text Available The Kyropoulos (Ky and Czochralski (Cz methods of crystal growth are used for large-diameter single crystals. The seeding process in these methods must induce initial crystallization by initiating contact between the seed crystals and the surface of the melted material. In the Ky and Cz methods, the seeding process lays the foundation for ingot growth during the entire growth process. When any defect occurs in this process, it is likely to spread to the entire ingot. In this paper, a vision system was constructed for auto seeding and for observing the surface of the melt in the Ky method. An algorithm was developed to detect the time when the internal convection of the melt is stabilized by observing the shape of the spoke pattern on the melt material surface. Then, the vision system and algorithm were applied to the growth furnace, and the possibility of process automation was examined for sapphire growth. To confirm that the convection of the melt was stabilized, the position of the island (i.e., the center of a spoke pattern was detected using the vision system and image processing. When the observed coordinates for the center of the island were compared with the coordinates detected from the image processing algorithm, there was an average error of 1.87 mm (based on an image with 1024 × 768 pixels.

  12. Workflow User Interfaces Patterns

    Directory of Open Access Journals (Sweden)

    Jean Vanderdonckt

    2012-03-01

    Full Text Available Este trabajo presenta una colección de patrones de diseño de interfaces de usuario para sistemas de información para el flujo de trabajo; la colección incluye cuarenta y tres patrones clasificados en siete categorías identificados a partir de la lógica del ciclo de vida de la tarea sobre la base de la oferta y la asignación de tareas a los responsables de realizarlas (i. e. recursos humanos durante el flujo de trabajo. Cada patrón de la interfaz de usuario de flujo de trabajo (WUIP, por sus siglas en inglés se caracteriza por las propiedades expresadas en el lenguaje PLML para expresar patrones y complementado por otros atributos y modelos que se adjuntan a dicho modelo: la interfaz de usuario abstracta y el modelo de tareas correspondiente. Estos modelos se especifican en un lenguaje de descripción de interfaces de usuario. Todos los WUIPs se almacenan en una biblioteca y se pueden recuperar a través de un editor de flujo de trabajo que vincula a cada patrón de asignación de trabajo a su WUIP correspondiente.A collection of user interface design patterns for workflow information systems is presented that contains forty three resource patterns classified in seven categories. These categories and their corresponding patterns have been logically identified from the task life cycle based on offering and allocation operations. Each Workflow User Interface Pattern (WUIP is characterized by properties expressed in the PLML markup language for expressing patterns and augmented by additional attributes and models attached to the pattern: the abstract user interface and the corresponding task model. These models are specified in a User Interface Description Language. All WUIPs are stored in a library and can be retrieved within a workflow editor that links each workflow pattern to its corresponding WUIP, thus giving rise to a user interface for each workflow pattern.

  13. Coalescence dynamics of mobile and immobile fluid interfaces

    KAUST Repository

    Vakarelski, Ivan Uriev

    2018-01-12

    Coalescence dynamics between deformable bubbles and droplets can be dramatically affected by the mobility of the interfaces with fully tangentially mobile bubble-liquid or droplet-liquid interfaces expected to accelerate the coalescence by orders of magnitudes. However, there is a lack of systematic experimental investigations that quantify this effect. By using high speed camera imaging we examine the free rise and coalescence of small air-bubbles (100 to 1300 μm in diameter) with a liquid interface. A perfluorocarbon liquid, PP11 is used as a model liquid to investigate coalescence dynamics between fully-mobile and immobile deformable interfaces. The mobility of the bubble surface was determined by measuring the terminal rise velocity of small bubbles rising at Reynolds numbers, Re less than 0.1 and the mobility of free PP11 surface by measuring the deceleration kinetics of the small bubble toward the interface. Induction or film drainage times of a bubble at the mobile PP11-air surface were found to be more than two orders of magnitude shorter compared to the case of bubble and an immobile PP11-water interface. A theoretical model is used to illustrate the effect of hydrodynamics and interfacial mobility on the induction time or film drainage time. The results of this study are expected to stimulate the development of a comprehensive theoretical model for coalescence dynamics between two fully or partially mobile fluid interfaces.

  14. Determination of velocity correction factors for real-time air velocity monitoring in underground mines

    OpenAIRE

    Zhou, Lihong; Yuan, Liming; Thomas, Rick; Iannacchione, Anthony

    2017-01-01

    When there are installations of air velocity sensors in the mining industry for real-time airflow monitoring, a problem exists with how the monitored air velocity at a fixed location corresponds to the average air velocity, which is used to determine the volume flow rate of air in an entry with the cross-sectional area. Correction factors have been practically employed to convert a measured centerline air velocity to the average air velocity. However, studies on the recommended correction fac...

  15. Angle dependence of Andreev scattering at semiconductor-superconductor interfaces

    DEFF Research Database (Denmark)

    Mortensen, Asger; Flensberg, Karsten; Jauho, Antti-Pekka

    1999-01-01

    We study the angle dependence of the Andreev scattering at a semiconductor-superconductor interface, generalizing the one-dimensional theory of Blonder, Tinkham, and Klapwijk (BTK),An increase of the momentum parallel to the interface leads to suppression of the probability of Andreev reflection...... and increase of the probability of normal reflection. We show that in the presence of a Fermi velocity mismatch between the semiconductor and the superconductor the angles of incidence and transmission are related according to the well-known Snell's law in optics. As a consequence there is a critical angle...

  16. Characteristic wave velocities in spherical electromagnetic cloaks

    International Nuclear Information System (INIS)

    Yaghjian, A D; Maci, S; Martini, E

    2009-01-01

    We investigate the characteristic wave velocities in spherical electromagnetic cloaks, namely, phase, ray, group and energy-transport velocities. After deriving explicit expressions for the phase and ray velocities (the latter defined as the phase velocity along the direction of the Poynting vector), special attention is given to the determination of group and energy-transport velocities, because a cursory application of conventional formulae for local group and energy-transport velocities can lead to a discrepancy between these velocities if the permittivity and permeability dyadics are not equal over a frequency range about the center frequency. In contrast, a general theorem can be proven from Maxwell's equations that the local group and energy-transport velocities are equal in linear, lossless, frequency dispersive, source-free bianisotropic material. This apparent paradox is explained by showing that the local fields of the spherical cloak uncouple into an E wave and an H wave, each with its own group and energy-transport velocities, and that the group and energy-transport velocities of either the E wave or the H wave are equal and thus satisfy the general theorem.

  17. Easy-to-use interface

    International Nuclear Information System (INIS)

    Blattner, D O; Blattner, M M; Tong, Y.

    1999-01-01

    Easy-to-use interfaces are a class of interfaces that fall between public access interfaces and graphical user interfaces in usability and cognitive difficulty. We describe characteristics of easy-to-use interfaces by the properties of four dimensions: selection, navigation, direct manipulation, and contextual metaphors. Another constraint we introduced was to include as little text as possible, and what text we have will be in at least four languages. Formative evaluations were conducted to identify and isolate these characteristics. Our application is a visual interface for a home automation system intended for a diverse set of users. The design will be expanded to accommodate the visually disabled in the near future

  18. Geotail observations of FTE velocities

    Directory of Open Access Journals (Sweden)

    G. I. Korotova

    2009-01-01

    Full Text Available We discuss the plasma velocity signatures expected in association with flux transfer events (FTEs. Events moving faster than or opposite the ambient media should generate bipolar inward/outward (outward/inward flow perturbations normal to the nominal magnetopause in the magnetosphere (magnetosheath. Flow perturbations directly upstream and downstream from the events should be in the direction of event motion. Flows on the flanks should be in the direction opposite the motion of events moving at subsonic and subAlfvénic speeds relative to the ambient plasma. Events moving with the ambient flow should generate no flow perturbations in the ambient plasma. Alfvén waves propagating parallel (antiparallel to the axial magnetic field of FTEs may generate anticorrelated (correlated magnetic field and flow perturbations within the core region of FTEs. We present case studies illustrating many of these signatures. In the examples considered, Alfvén waves propagate along event axes away from the inferred reconnection site. A statistical study of FTEs observed by Geotail over a 3.5-year period reveals that FTEs within the magnetosphere invariably move faster than the ambient flow, while those in the magnetosheath move both faster and slower than the ambient flow.

  19. Reciprocally-Rotating Velocity Obstacles

    KAUST Repository

    Giese, Andrew

    2014-05-01

    © 2014 IEEE. Modern multi-agent systems frequently use highlevel planners to extract basic paths for agents, and then rely on local collision avoidance to ensure that the agents reach their destinations without colliding with one another or dynamic obstacles. One state-of-the-art local collision avoidance technique is Optimal Reciprocal Collision Avoidance (ORCA). Despite being fast and efficient for circular-shaped agents, ORCA may deadlock when polygonal shapes are used. To address this shortcoming, we introduce Reciprocally-Rotating Velocity Obstacles (RRVO). RRVO generalizes ORCA by introducing a notion of rotation for polygonally-shaped agents. This generalization permits more realistic motion than ORCA and does not suffer from as much deadlock. In this paper, we present the theory of RRVO and show empirically that it does not suffer from the deadlock issue ORCA has, permits agents to reach goals faster, and has a comparable collision rate at the cost of performance overhead quadratic in the (typically small) user-defined parameter δ.

  20. High velocity impact experiment (HVIE)

    Energy Technology Data Exchange (ETDEWEB)

    Toor, A.; Donich, T.; Carter, P.

    1998-02-01

    The HVIE space project was conceived as a way to measure the absolute EOS for approximately 10 materials at pressures up to {approximately}30 Mb with order-of-magnitude higher accuracy than obtainable in any comparable experiment conducted on earth. The experiment configuration is such that each of the 10 materials interacts with all of the others thereby producing one-hundred independent, simultaneous EOS experiments The materials will be selected to provide critical information to weapons designers, National Ignition Facility target designers and planetary and geophysical scientists. In addition, HVIE will provide important scientific information to other communities, including the Ballistic Missile Defense Organization and the lethality and vulnerability community. The basic HVIE concept is to place two probes in counter rotating, highly elliptical orbits and collide them at high velocity (20 km/s) at 100 km altitude above the earth. The low altitude of the experiment will provide quick debris strip-out of orbit due to atmospheric drag. The preliminary conceptual evaluation of the HVIE has found no show stoppers. The design has been very easy to keep within the lift capabilities of commonly available rides to low earth orbit including the space shuttle. The cost of approximately 69 million dollars for 100 EOS experiment that will yield the much needed high accuracy, absolute measurement data is a bargain!

  1. Group Velocity for Leaky Waves

    Science.gov (United States)

    Rzeznik, Andrew; Chumakova, Lyubov; Rosales, Rodolfo

    2017-11-01

    In many linear dispersive/conservative wave problems one considers solutions in an infinite medium which is uniform everywhere except for a bounded region. In general, localized inhomogeneities of the medium cause partial internal reflection, and some waves leak out of the domain. Often one only desires the solution in the inhomogeneous region, with the exterior accounted for by radiation boundary conditions. Formulating such conditions requires definition of the direction of energy propagation for leaky waves in multiple dimensions. In uniform media such waves have the form exp (d . x + st) where d and s are complex and related by a dispersion relation. A complex s is required since these waves decay via radiation to infinity, even though the medium is conservative. We present a modified form of Whitham's Averaged Lagrangian Theory along with modulation theory to extend the classical idea of group velocity to leaky waves. This allows for solving on the bounded region by representing the waves as a linear combination of leaky modes, each exponentially decaying in time. This presentation is part of a joint project, and applications of these results to example GFD problems will be presented by L. Chumakova in the talk ``Leaky GFD Problems''. This work is partially supported by NSF Grants DMS-1614043, DMS-1719637, and 1122374, and by the Hertz Foundation.

  2. Feasibility of using ultrasonic pulse velocity to measure the bond between new and old concrete

    Directory of Open Access Journals (Sweden)

    Fareed Hameed Majeed

    2017-11-01

    Full Text Available Connecting new and old concrete is required in many practical situations, such as repairing, strengthening or extending existing reinforced concrete buildings or members. In addition to using this technique at construction joints. It is obvious the practical difficulties to measure the bond attained at the interface surface between the new and old concrete. Doing the destructive shear test at the interface surface is not an option in most practical cases due to its destructive character. So, this paper aims to study the feasibility of using the nondestructive ultrasonic pulse velocity to evaluate the bond attained at the interface surface between new and old concrete. An experimental work has been done to 24 specimens of normal and high strength concrete, with and without using an epoxy bonding agent at the interface that connect the two materials. The results of experiments clearly shown that this method can be used to evaluate the acquired bond between the new and old concrete.

  3. Physical modelling of interactions between interfaces and turbulence; Modelisation physique des interactions entre interfaces et turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Toutant, A

    2006-12-15

    The complex interactions between interfaces and turbulence strongly impact the flow properties. Unfortunately, Direct Numerical Simulations (DNS) have to entail a number of degrees of freedom proportional to the third power of the Reynolds number to correctly describe the flow behaviour. This extremely hard constraint makes it impossible to use DNS for industrial applications. Our strategy consists in using and improving DNS method in order to develop the Interfaces and Sub-grid Scales concept. ISS is a two-phase equivalent to the single-phase Large Eddy Simulation (LES) concept. The challenge of ISS is to integrate the two-way coupling phenomenon into sub-grid models. Applying a space filter, we have exhibited correlations or sub-grid terms that require closures. We have shown that, in two-phase flows, the presence of a discontinuity leads to specific sub-grid terms. Comparing the maximum of the norm of the sub-grid terms with the maximum of the norm of the advection tensor, we have found that sub-grid terms related to interfacial forces and viscous effect are negligible. Consequently, in the momentum balance, only the sub-grid terms related to inertia have to be closed. Thanks to a priori tests performed on several DNS data, we demonstrate that the scale similarity hypothesis, reinterpreted near discontinuity, provides sub-grid models that take into account the two-way coupling phenomenon. These models correspond to the first step of our work. Indeed, in this step, interfaces are smooth and, interactions between interfaces and turbulence occur in a transition zone where each physical variable varies sharply but continuously. The next challenge has been to determine the jump conditions across the sharp equivalent interface corresponding to the sub-grid models of the transition zone. We have used the matched asymptotic expansion method to obtain the jump conditions. The first tests on the velocity of the sharp equivalent interface are very promising (author)

  4. Evaluation of interlayer interfacial stiffness and layer wave velocity of multilayered structures by ultrasonic spectroscopy.

    Science.gov (United States)

    Ishii, Yosuke; Biwa, Shiro

    2014-07-01

    An ultrasonic evaluation procedure for the interlayer interfacial normal stiffness and the intralayer longitudinal wave velocity of multilayered plate-like structures is proposed. Based on the characteristics of the amplitude reflection spectrum of ultrasonic wave at normal incidence to a layered structure with spring-type interlayer interfaces, it is shown that the interfacial normal stiffness and the longitudinal wave velocity in the layers can be simultaneously evaluated from the frequencies of local maxima and minima of the spectrum provided that all interfaces and layers have the same properties. The effectiveness of the proposed procedure is investigated from the perspective of the sensitivity of local extremal frequencies of the reflection spectrum. The feasibility of the proposed procedure is also investigated when the stiffness of each interface is subjected to small random fluctuations about a certain average value. The proposed procedure is applied to a 16-layered cross-ply carbon-fiber-reinforced composite laminate. The normal stiffness of resin-rich interfaces and the longitudinal wave velocity of plies in the thickness direction evaluated from the experimental reflection spectrum are shown to be consistent with simple theoretical estimations.

  5. Computing discharge using the index velocity method

    Science.gov (United States)

    Levesque, Victor A.; Oberg, Kevin A.

    2012-01-01

    Application of the index velocity method for computing continuous records of discharge has become increasingly common, especially since the introduction of low-cost acoustic Doppler velocity meters (ADVMs) in 1997. Presently (2011), the index velocity method is being used to compute discharge records for approximately 470 gaging stations operated and maintained by the U.S. Geological Survey. The purpose of this report is to document and describe techniques for computing discharge records using the index velocity method. Computing discharge using the index velocity method differs from the traditional stage-discharge method by separating velocity and area into two ratings—the index velocity rating and the stage-area rating. The outputs from each of these ratings, mean channel velocity (V) and cross-sectional area (A), are then multiplied together to compute a discharge. For the index velocity method, V is a function of such parameters as streamwise velocity, stage, cross-stream velocity, and velocity head, and A is a function of stage and cross-section shape. The index velocity method can be used at locations where stage-discharge methods are used, but it is especially appropriate when more than one specific discharge can be measured for a specific stage. After the ADVM is selected, installed, and configured, the stage-area rating and the index velocity rating must be developed. A standard cross section is identified and surveyed in order to develop the stage-area rating. The standard cross section should be surveyed every year for the first 3 years of operation and thereafter at a lesser frequency, depending on the susceptibility of the cross section to change. Periodic measurements of discharge are used to calibrate and validate the index rating for the range of conditions experienced at the gaging station. Data from discharge measurements, ADVMs, and stage sensors are compiled for index-rating analysis. Index ratings are developed by means of regression

  6. Vector blood velocity estimation in medical ultrasound

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Gran, Fredrik; Udesen, Jesper

    2006-01-01

    Two methods for making vector velocity estimation in medical ultrasound are presented. All of the techniques can find both the axial and transverse velocity in the image and can be used for displaying both the correct velocity magnitude and direction. The first method uses a transverse oscillation...... in the ultrasound field to find the transverse velocity. In-vivo examples from the carotid artery are shown, where complex turbulent flow is found in certain parts of the cardiac cycle. The second approach uses directional beam forming along the flow direction to estimate the velocity magnitude. Using a correlation...... search can also yield the direction, and the full velocity vector is thereby found. An examples from a flow rig is shown....

  7. Algorithms for estimating blood velocities using ultrasound

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    2000-01-01

    Ultrasound has been used intensively for the last 15 years for studying the hemodynamics of the human body. Systems for determining both the velocity distribution at one point of interest (spectral systems) and for displaying a map of velocity in real time have been constructed. A number of schemes...... have been developed for performing the estimation, and the various approaches are described. The current systems only display the velocity along the ultrasound beam direction and a velocity transverse to the beam is not detected. This is a major problem in these systems, since most blood vessels...... are parallel to the skin surface. Angling the transducer will often disturb the flow, and new techniques for finding transverse velocities are needed. The various approaches for determining transverse velocities will be explained. This includes techniques using two-dimensional correlation (speckle tracking...

  8. Safety Parameters Graphical Interface

    International Nuclear Information System (INIS)

    Canamero, B.

    1998-01-01

    Nuclear power plant data are received at the Operations Center of the Consejo de Seguridad Nuclear in emergency situations. In order to achieve the required interface and to prepare those data to perform simulation and forecasting with already existing computer codes a Safety Parameters Graphical Interface (IGPS) has been developed. The system runs in a UNIX environment and use the Xwindows capabilities. The received data are stored in such a way that it can be easily used for further analysis and training activities. The system consists of task-oriented modules (processes) which communicate each other using well known UNIX mechanisms (signals, sockets and shared memory segments). IGPS conceptually have two different parts: Data collection and preparation, and Data monitorization. (Author)

  9. Politics at the interface

    DEFF Research Database (Denmark)

    Kannabiran, Gobinaath; Petersen, Marianne Graves

    2010-01-01

    At the birth of participatory design, there was a strong political consciousness surrounding the design of new technology, the design process in particular, establishing a rich set of methods and tools for user-centered design. Today, the term design has extended its scope of concern beyond...... the process of design and into how users interact with the designed product on a day-to-day basis. This paper is an attempt to call to attention the need for a new set of methods, attitudes and approaches, along with the existing, to discuss, analyze and reflect upon the politics at the interface....... By presenting a critical analysis of two design cases, we elicit the importance of such an agenda and the implications for design in doing so. We use the Foucauldian notion of power to analyze the power relationships in these two cases and to articulate the politics at the interface. We conclude by emphasizing...

  10. Urban Sound Interfaces

    DEFF Research Database (Denmark)

    Breinbjerg, Morten

    2012-01-01

    This paper draws on the theories of Michel de Certeau and Gaston Bachelard to discuss how media architecture, in the form of urban sound interfaces, can help us perceive the complexity of the spaces we inhabit, by exploring the history and the narratives of the places in which we live. In this pa......This paper draws on the theories of Michel de Certeau and Gaston Bachelard to discuss how media architecture, in the form of urban sound interfaces, can help us perceive the complexity of the spaces we inhabit, by exploring the history and the narratives of the places in which we live....... In this paper, three sound works are discussed in relation to the iPod, which is considered as a more private way to explore urban environments, and as a way to control the individual perception of urban spaces....

  11. The technical supervision interface

    CERN Document Server

    Sollander, P

    1998-01-01

    The Technical Control Room (TCR) is currently using 30 different applications for the remote supervision of the technical infrastructure at CERN. These applications have all been developed with the CERN made Uniform Man Machine Interface (UMMI) tools built in 1990. However, the visualization technology has evolved phenomenally since 1990, the Technical Data Server (TDS) has radically changed our control system architecture, and the standardization and the maintenance of the UMMI applications have become important issues as their number increases. The Technical Supervision Interface is intended to replace the UMMI and solve the above problems. Using a standard WWW-browser for the display, it will be inherently multi-platform and hence available for control room operators, equipment specialists and on-call personnel.

  12. Virtual button interface

    Science.gov (United States)

    Jones, J.S.

    1999-01-12

    An apparatus and method of issuing commands to a computer by a user interfacing with a virtual reality environment are disclosed. To issue a command, the user directs gaze at a virtual button within the virtual reality environment, causing a perceptible change in the virtual button, which then sends a command corresponding to the virtual button to the computer, optionally after a confirming action is performed by the user, such as depressing a thumb switch. 4 figs.

  13. Noise at the Interface

    DEFF Research Database (Denmark)

    Prior, Andrew

    2011-01-01

    The notion of noise occupies a contested territory, in which it is framed as pollution and detritus even as it makes its opposite a possibility - noise is always defined in opposition to something else, even if this ‘other’ is not quite clear. This paper explores noise in the context of ‘the...... interface’ asking what its affordances as an idea may contribute to our understanding of interface. I draw historically on information theory in particular to initiate this exploration....

  14. Remote determination of the velocity index and mean streamwise velocity profiles

    Science.gov (United States)

    Johnson, E. D.; Cowen, E. A.

    2017-09-01

    When determining volumetric discharge from surface measurements of currents in a river or open channel, the velocity index is typically used to convert surface velocities to depth-averaged velocities. The velocity index is given by, k=Ub/Usurf, where Ub is the depth-averaged velocity and Usurf is the local surface velocity. The USGS (United States Geological Survey) standard value for this coefficient, k = 0.85, was determined from a series of laboratory experiments and has been widely used in the field and in laboratory measurements of volumetric discharge despite evidence that the velocity index is site-specific. Numerous studies have documented that the velocity index varies with Reynolds number, flow depth, and relative bed roughness and with the presence of secondary flows. A remote method of determining depth-averaged velocity and hence the velocity index is developed here. The technique leverages the findings of Johnson and Cowen (2017) and permits remote determination of the velocity power-law exponent thereby, enabling remote prediction of the vertical structure of the mean streamwise velocity, the depth-averaged velocity, and the velocity index.

  15. Planning and User Interface Affordances

    National Research Council Canada - National Science Library

    St. Amant, Robert

    1999-01-01

    .... We identify a number of similarities between executing plans and interacting with a graphical user interface, and argue that affordances for planning environments apply equally well to user interface environments...

  16. Middle cerebral artery blood velocity during running

    DEFF Research Database (Denmark)

    Lyngeraa, Tobias; Pedersen, Lars Møller; Mantoni, T

    2013-01-01

    for eight subjects, respectively, were excluded from analysis because of insufficient signal quality. Running increased mean arterial pressure and mean MCA velocity and induced rhythmic oscillations in BP and in MCA velocity corresponding to the difference between step rate and heart rate (HR) frequencies....... During running, rhythmic oscillations in arterial BP induced by interference between HR and step frequency impact on cerebral blood velocity. For the exercise as a whole, average MCA velocity becomes elevated. These results suggest that running not only induces an increase in regional cerebral blood flow...

  17. Demonstration of a Vector Velocity Technique

    DEFF Research Database (Denmark)

    Hansen, Peter Møller; Pedersen, Mads M.; Hansen, Kristoffer L.

    2011-01-01

    With conventional Doppler ultrasound it is not possible to estimate direction and velocity of blood flow, when the angle of insonation exceeds 60–70°. Transverse oscillation is an angle independent vector velocity technique which is now implemented on a conventional ultrasound scanner. In this pa......With conventional Doppler ultrasound it is not possible to estimate direction and velocity of blood flow, when the angle of insonation exceeds 60–70°. Transverse oscillation is an angle independent vector velocity technique which is now implemented on a conventional ultrasound scanner...

  18. On whistler-mode group velocity

    International Nuclear Information System (INIS)

    Sazhin, S.S.

    1986-01-01

    An analytical of the group velocity of whistler-mode waves propagating parallel to the magnetic field in a hot anisotropic plasma is presented. Some simple approximate formulae, which can be used for the magnetospheric applications, are derived. These formulae can predict some properties of this group velocity which were not previously recognized or were obtained by numerical methods. In particular, it is pointed out that the anisotropy tends to compensate for the influence of the electron temperature on the value of the group velocity when the wave frequency is well below the electron gyrofrequency. It is predicted, that under conditions at frequencies near the electron gyrofrequency, this velocity tends towards zero

  19. Velocity measurement of conductor using electromagnetic induction

    International Nuclear Information System (INIS)

    Kim, Gu Hwa; Kim, Ho Young; Park, Joon Po; Jeong, Hee Tae; Lee, Eui Wan

    2002-01-01

    A basic technology was investigated to measure the speed of conductor by non-contact electromagnetic method. The principle of the velocity sensor was electromagnetic induction. To design electromagnet for velocity sensor, 2D electromagnetic analysis was performed using FEM software. The sensor output was analyzed according to the parameters of velocity sensor, such as the type of magnetizing currents and the lift-off. Output of magnetic sensor was linearly depended on the conductor speed and magnetizing current. To compensate the lift-off changes during measurement of velocity, the other magnetic sensor was put at the pole of electromagnet.

  20. Conduction velocity of antigravity muscle action potentials.

    Science.gov (United States)

    Christova, L; Kosarov, D; Christova, P

    1992-01-01

    The conduction velocity of the impulses along the muscle fibers is one of the parameters of the extraterritorial potentials of the motor units allowing for the evaluation of the functional state of the muscles. There are no data about the conduction velocities of antigravity muscleaction potentials. In this paper we offer a method for measuring conduction velocity of potentials of single MUs and the averaged potentials of the interference electromiogram (IEMG) lead-off by surface electrodes from mm. sternocleidomastoideus, trapezius, deltoideus (caput laterale) and vastus medialis. The measured mean values of the conduction velocity of antigravity muscles potentials can be used for testing the functional state of the muscles.